JP2023097437A - Method of producing chemically strengthened glass, chemically strengthened glass, cover glass, and display device - Google Patents

Abstract

To provide a method of producing chemically strengthened glass with which residue derived from ZrO2 or the like on the glass surface is reduced.SOLUTION: In the method of producing chemically strengthened glass, preparing a glass, chemically strengthening the glass, and alkali-treating the glass obtained by the chemical strengthening are performed in this order, wherein the glass contains at least one of metallic oxides selected from the group consisting of ZrO2, TiO2, Y2O3, SnO2, and the alkali treatment is performed using an aqueous alkaline solution containing a chelating agent, wherein the amount of precipitation formation of metals constituting the metal oxide, measured under specific conditions using the aqueous alkaline solution containing the chelating agent, is 20% or less of that using an aqueous alkaline solution without the chelating agent.SELECTED DRAWING: None

Description

The present invention relates to a method for producing chemically strengthened glass and chemically strengthened glass. The present invention also relates to a cover glass and a display device having the chemically strengthened glass.

In recent years, chemically strengthened glass has been used as cover glass for various display devices, and further improvement in strength is required. For example, Patent Literature 1 discloses improving the surface strength of a glass plate by chemically strengthening the glass by immersing it in a potassium nitrate molten salt.

Further, Patent Document 2 discloses a method of chemically strengthening glass using a specific molten salt, followed by treatment with an acid and an alkali. As a result, the surface strength of the glass is remarkably improved without polishing or etching the glass surface with hydrofluoric acid or the like after the chemical strengthening treatment. This is because the high-density compressive stress layer formed by chemical strengthening treatment has a low-density layer on the outermost layer, and part or all of it is removed by alkali treatment, thereby increasing the surface strength. is improved.

The chemically strengthened glass obtained by such chemical strengthening treatment is not limited to small display devices such as digital cameras and mobile phones, but can be used for display devices such as car navigation systems for vehicles. It is also suitable for cover glasses comprising

Japanese special table 2013-516387 International Publication No. 2015-008763

However, when the chemically strengthened glass contains components of ZrO ₂ , TiO ₂ , Y ₂ O ₃ , SnO ₂ (hereinafter sometimes simply referred to as “ZrO ₂ etc.”), in the process of obtaining the chemically strengthened glass It has been found that the alkaline treatment causes appearance defects such as unevenness when used as a cover glass. It has been found that this is due to the generation of residues derived from ZrO ₂ and the like on the surface of the chemically strengthened glass after the alkali treatment.

It is difficult to visually confirm the presence of residues derived from ZrO ₂ and the like on the surface of chemically strengthened glass. However, the presence of the residue is an anti-reflection (AR; Anti Reflection) layer formation, anti-glare (AG; Anti Glare) processing, antifouling (AFP: Anti Finger Print) layer formation and other decorative treatments for chemically strengthened glass. Therefore, the presence or absence of optical unevenness during the above-described decorating treatment can be used as an indicator of the presence of residue.

Accordingly, an object of the present invention is to provide a method for producing chemically strengthened glass in which residue derived from ZrO ₂ and the like on the glass surface is reduced, and chemically strengthened glass with less residue. Another object of the present invention is to provide a cover glass having such a chemically strengthened glass, and to provide a display device including the cover glass.

The present inventors have found that when an alkaline aqueous solution containing a specific chelating agent is used in the alkali treatment after the glass is chemically strengthened, ZrO ₂ etc. present on the surface of the resulting chemically strengthened glass The present invention was completed based on the finding that the amount of the residue derived from this method can be greatly reduced.

That is, one aspect of the method for producing chemically strengthened glass according to the present invention is as follows.
Preparing a glass, chemically strengthening the glass, and alkali-treating the glass obtained by the chemical strengthening treatment are sequentially performed, and the glass is composed of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and Chemically strengthened glass containing at least one metal oxide selected from the group consisting of SnO ₂ , wherein the alkali treatment is performed using an alkaline aqueous solution containing a chelating agent, and the chelating agent satisfies the following conditions 1 to 3: manufacturing method.
(Condition 1) 1 mL of an acid solution having an ion concentration of 1 mol/L of the metal constituting the metal oxide and an alkaline chemical solution so that the total number of ligand fields is 1.5 times the number of moles of the metal. 100 mL of an alkaline aqueous solution containing the chelating agent with adjusted concentration is prepared. The amount (g) of precipitated metal is measured when 1 mL of the acid solution is added to 100 mL of the alkaline aqueous solution containing the chelating agent.
(Condition 2) Prepare 1 mL of an acid solution in which the ion concentration of the metal constituting the metal oxide is 1 mol/L, and 100 mL of an alkaline aqueous solution that is the same alkaline chemical solution as in Condition 1 and does not contain a chelating agent. do. The amount (g) of precipitated metal is measured when 1 mL of the acid solution is added to 100 mL of the alkaline aqueous solution containing no chelating agent.
(Condition 3) The amount of precipitates measured under Condition 1 is 20% or less of the amount of precipitates measured under Condition 2.

Another aspect of the method for producing chemically strengthened glass according to the present invention is as follows.
Preparing a glass, chemically strengthening the glass, and alkali-treating the glass obtained by the chemical strengthening treatment are sequentially performed, and the glass is composed of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and containing at least one metal oxide selected from the group consisting of _SnO2 , and the alkali treatment is performed using an alkaline aqueous solution containing a chelating agent, the chelating agent being pentetic acid, tartaric acid, gluconic acid, etidronic acid and apple A method for producing a chemically strengthened glass containing at least one selected from the group consisting of acids.

Furthermore, one aspect of the chemically strengthened glass according to the present invention is as follows.
At least one selected from the group consisting of Zr, Ti, Y, and Sn, an alkali metal, and Al, when comparing the molar ratios of the contents of the elements represented by {(Zr + Ti + Y + Sn) / Al}, Chemically strengthened glass, wherein the ratio of the molar ratio on the surface to the molar ratio on the base composition is 5 to 300%.

According to the method for manufacturing chemically strengthened glass according to the present invention, it is possible to reduce residues derived from ZrO ₂ and the like on the surface of chemically strengthened glass. As a result, it is possible to obtain an excellent chemically strengthened glass that is practically free from optical unevenness. Moreover, the chemically strengthened glass according to the present invention can provide an excellent cover glass for a display device, a display device having such a cover glass, and the like.

Although the present invention will be described in detail below, the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention.

<Method for manufacturing chemically strengthened glass>
The method for manufacturing chemically strengthened glass according to this embodiment includes the following steps in order.
(Step a) a step of preparing glass;
(Step b) a step of chemically strengthening the glass; and (e) a step of alkali-treating the glass obtained by the chemical strengthening.

Moreover, the manufacturing method may further include the following step c and step d.
(Step c) a step of washing the glass;
(Step d) A step of acid-treating the glass obtained by the chemical strengthening treatment.

The glass of step a contains at least one metal oxide selected from the group consisting of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and SnO ₂ .

The alkali treatment in step e is performed using an alkali aqueous solution containing a chelating agent.
In one embodiment, the chelating agent satisfies conditions 1 to 3 below.
(Condition 1) 1 mL of an acid solution having an ion concentration of 1 mol/L of the metal constituting the metal oxide and an alkaline chemical solution so that the total number of ligand fields is 1.5 times the number of moles of the metal. 100 mL of an alkaline aqueous solution containing the chelating agent with the adjusted concentration is prepared. The amount (g) of precipitated metal is measured when 1 mL of the acid solution is added to 100 mL of the alkaline aqueous solution containing the chelating agent.
(Condition 2) Prepare 1 mL of an acid solution in which the ion concentration of the metal constituting the metal oxide is 1 mol/L, and 100 mL of an alkaline aqueous solution that is the same alkaline chemical solution as in Condition 1 above and does not contain a chelating agent. do. The amount (g) of precipitated metal is measured when 1 mL of the acid solution is added to 100 mL of the alkaline aqueous solution containing no chelating agent.
(Condition 3) The precipitation amount measured under the condition 1 is 20% or less of the precipitation amount measured under the condition 2.

In one embodiment, the chelating agent in the alkaline aqueous solution containing the chelating agent is at least one selected from the group consisting of pentetic acid, tartaric acid, gluconic acid, etidronic acid and malic acid.

Hereinafter, the manufacturing method according to this embodiment will be described step by step.

(Step a) Step of Preparing Glass The glass used in this embodiment contains at least one metal oxide selected from the group consisting of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and SnO ₂ . Other compositions are not particularly limited as long as they are glasses that are usually subjected to chemical strengthening treatment. For example, when the ions to be ion-exchanged in the subsequent step b of chemical strengthening treatment are alkali metal ions, the glass preferably further contains alkali metal oxides.

The alkali metal oxide contained in the glass is preferably at least one oxide selected from the group consisting of lithium, sodium and potassium, more preferably at least one oxide of lithium and sodium, and further an oxide of sodium. preferable.

The metal oxide contained in the glass is a component that can remain as a residue on the surface of the chemically strengthened glass after the glass is chemically strengthened and alkali treated. This residue derived from ZrO ₂ and the like causes optical unevenness when forming an AR layer, AG processing, or forming an AFP layer on chemically strengthened glass.

Such optical unevenness is particularly noticeable when the total content of ZrO ₂ , TiO ₂ , Y ₂ O ₃ , and SnO ₂ is 0.01% or more in terms of mol% based on oxides. . That is, in order to solve the problem of the present invention, the total content is preferably 0.01% or more, more preferably 0.05% or more, and further preferably 0.1% or more. , more preferably 0.3% or more, and particularly preferably 0.5% or more. On the other hand, if the residual component is too large, optical unevenness will still occur even if the residual amount is reduced compared to the conventional case. From the practical viewpoint of suppressing the occurrence of optical unevenness, the total content is preferably 5% or less, more preferably 3% or less, and even more preferably 2.5% or less.

Among the metal oxides that can become residues, ZrO ₂ is a component that increases the surface compressive stress (CS) due to ion exchange during chemical strengthening treatment, and may be contained. When ZrO ₂ is contained, the content is preferably 0.1% or more, more preferably 0.5% or more, and still more preferably 1% or more in terms of mol % based on the oxide. On the other hand, in order to suppress devitrification during melting and improve the quality of chemically strengthened glass, the content of _ZrO2 is preferably 5% or less, more preferably 3% or less, and particularly preferably 2.5%. It is below.

Among the metal oxides that can become residues, TiO ₂ is a component that suppresses the change in color tone of the glass due to solarization and may be contained. When TiO ₂ is included, the content is preferably 0.01% or more, more preferably 0.03% or more, still more preferably 0.05% or more, and particularly preferably 0.05% or more, in terms of mol% based on the oxide. is 0.1% or more. On the other hand, in order to suppress devitrification during melting, the content of TiO ₂ is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.2% or less.

Among the metal oxides that can become residues, Y ₂ O ₃ is a component that increases the surface compressive stress of the chemically strengthened glass and decreases the crystal growth rate, so it may be contained. When Y ₂ O ₃ is included, the content is preferably 0.1% or more, more preferably 0.2% or more, still more preferably 0.5% or more, particularly preferably 0.5% or more, in terms of mol% based on the oxide. is greater than or equal to 0.8%, typically greater than or equal to 1%. On the other hand, if the Y ₂ O ₃ content is too high, it becomes difficult to increase the compressive stress layer during the chemical strengthening treatment. Therefore, the content of Y ₂ O ₃ is preferably 5% or less, more preferably 3% or less, still more preferably 2% or less, and particularly preferably 1.5% or less.

Among the metal oxides that can become residues, SnO ₂ may be contained for the purposes of adjusting refractive index characteristics, improving meltability, suppressing coloration, improving transmittance, clarifying, and improving chemical durability. . When SnO ₂ is contained, the content is preferably 0.01% or more, more preferably 0.03% or more, and still more preferably 0.05% or more in terms of mol % based on oxides. On the other hand, too much SnO ₂ tends to cause devitrification and coloration. Therefore, the SnO ₂ content is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.2% or less.

From the viewpoint of corrosion resistance, the glass preferably contains at least one of ZrO ₂ and TiO ₂ among the metal oxides that can become residues.

As described above, the glass in the present embodiment may contain a component that allows residues derived from ZrO ₂ or the like to remain on the glass surface after chemical strengthening treatment and alkali treatment. That is, various compositions can be used as long as they have compositions that can be molded and strengthened by chemical strengthening treatment. Specific examples include aluminosilicate glass, soda lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.
The glass may be commercially available or independently manufactured.

A more specific composition of the glass used as the chemically strengthened glass is not particularly limited, but examples thereof include the following. The composition of the glass to be chemically strengthened and the base composition of the chemically strengthened glass subjected to the chemical strengthening treatment and the alkali treatment can be regarded as the same. This is because the composition of the portion of the chemically strengthened glass having tensile stress is the base composition, and the portion has the same composition as the glass before the chemical strengthening treatment. Therefore, in this specification, the composition of the glass refers to the composition of the glass before chemical strengthening treatment, or the base composition of the chemically strengthened glass, that is, the intermediate layer that is the inner part than the chemically strengthened compressive stress layer means the composition of

(i) Contents in terms of mol % based on oxides are SiO ₂ : 50 to 80%, Al ₂ O ₃ : 2 to 25%, Li ₂ O: 0 to 20%, Na ₂ O: 0 to 18 %, K ₂ O: 0-10%, MgO: 0-15%, CaO: 0-5%, and ZrO ₂ : 0-5%, and ZrO ₂ , TiO ₂ , Y ₂ O ₃ , and Glasses having a total SnO ₂ content of 0.01% or more.
(ii) Contents in terms of mol % based on oxides are SiO ₂ : 50 to 74%, Al ₂ O ₃ : 1 to 10%, Na ₂ O: 6 to 14%, K ₂ O: 3 to 11 %, MgO: 2-15%, CaO: 0-6%, and ZrO ₂ : 0-5%, the total content of SiO ₂ and Al ₂ O ₃ is 75% or less, Na ₂ O and K ₂ The total content of O is 12-25%, the total content of MgO and CaO is 7-15%, and the total content of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and SnO ₂ is 0. A glass that is greater than or equal to .01%.
(iii) Contents in terms of mol % based on oxides are SiO ₂ : 68 to 80%, Al ₂ O ₃ : 4 to 10%, Na ₂ O: 5 to 15%, K ₂ O: 0 to 1 %, MgO: 4-15%, and ZrO ₂ : 0-1%, and the total content of ZrO ₂ , TiO ₂ , Y ₂ O ₃ , and SnO ₂ is 0.01% or more.
(iv) Contents in terms of mol% based on oxides are SiO ₂ : 67 to 75%, Al ₂ O ₃ : 0 to 4%, Na ₂ O: 7 to 15%, K ₂ O: 1 to 9 %, MgO: 6-14% and ZrO ₂ : 0-1.5%, the total content of SiO ₂ and Al ₂ O ₃ is 71-75%, the content of Na ₂ O and K ₂ O is The total is 12 to 20%, the content of CaO is less than 1% when it is contained, and the total content of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and SnO ₂ is 0.01% Glass that is more than that.
(v) Contents in terms of mol % based on oxides are SiO ₂ : 50 to 80%, Al ₂ O ₃ : 2 to 25%, Li ₂ O: 0.1 to 20%, Na ₂ O: 0 .1-18%, K ₂ O: 0-10%, MgO: 0-15%, CaO: 0-5%, P ₂ O ₅ : 0-5%, B ₂ O ₃ : 0-5%, ZrO ₂ : 0 to 5%, TiO ₂ : 0 to 1%, and Y ₂ O ₃ : 0 to 5%, and the total content of ZrO ₂ , TiO ₂ , Y ₂ O ₃ , and SnO ₂ is Glass that is 0.01% or more.

Commercially available glass may be used as the glass in the present embodiment, and the manufacturing method is not particularly limited when it is manufactured. For example, the desired frit is put into a continuous melting furnace, the frit is preferably heated and melted at 1500 to 1600 ° C., clarified, fed to a forming apparatus, the molten glass is formed into a plate, and slowly cooled. It can be manufactured by

Various methods can be adopted for molding the glass. For example, various forming methods such as a down-draw method, a float method, a roll-out method, and a press method can be employed. Examples of the down-draw method include an overflow down-draw method, a slot-down method, a redraw method, and the like.

Although the thickness of the glass is not particularly limited, it is usually preferably 5 mm or less, more preferably 3 mm or less, in order to effectively perform the chemical strengthening treatment. When used as a cover glass for an in-vehicle display device such as a car navigation system, the thickness of the glass is preferably 0.2 mm or more, more preferably 0.8 mm or more, and still more preferably 1 mm or more, from the viewpoint of strength.

The shape of the glass is not particularly limited. For example, glass of various shapes such as a flat plate shape having a uniform plate thickness, a shape having a curved surface on at least one of the front surface and the back surface, and a three-dimensional shape having a bent portion or the like can be used.
Further, when used as a cover glass for an in-vehicle display device such as car navigation, the length of the short side is, for example, 50 mm or more and 500 mm or less, preferably 100 mm or more and 300 mm or less, and the length of the long side is, for example, 50 mm. 1500 mm or more, preferably 100 mm or more and 1200 mm or less.

(Step b) Step of chemically strengthening the glass In step b, the glass prepared in step a is chemically strengthened.

The chemical strengthening treatment is a treatment for forming a surface layer in which compressive stress remains due to ion exchange, that is, a compressive stress layer, on the glass surface.
Specifically, by ion exchange at a temperature below the glass transition point, alkali metal ions with a small ionic radius on the glass surface are replaced with alkali metal ions with a larger ionic radius. For example, in the case of ion exchange of alkali metal ions, Li ions on the glass surface are replaced with Na ions or K ions, and Na ions on the glass surface are replaced with K ions. This ion exchange changes the composition of the glass surface and forms a compressive stress layer with a high density on the glass surface. This densification of the glass surface generates compressive stress, which strengthens the glass.

In fact, the density of chemically strengthened glass gradually increases from the intermediate layer existing in the center of the glass, that is, the outer edge of the bulk, toward the surface of the compressive stress layer. has no sharp boundary where the density changes abruptly. The term "intermediate layer" as used herein refers to a layer that exists in the center of the glass and is sandwiched between compressive stress layers. Unlike the compressive stress layer, this intermediate layer is a layer in which ions are not exchanged.

One aspect of the chemical strengthening treatment method will be described below, but the present invention is not limited to this.
The chemical strengthening treatment is preferably carried out by bringing the glass into contact with molten salt. The molten salt preferably contains a nitrate, more preferably a nitrate containing alkali metal ions.
The nitrate preferably contains other alkali metal ions having a larger ionic radius than the alkali metal ions contained in the glass. For example, when the glass contains at least one of Li ions and Na ions, potassium nitrate ( _KNO3 ) are more preferred. In that case, it is more preferable that the glass contains Na ions.

By bringing glass into contact with molten salt containing potassium nitrate, ion exchange occurs between Li ions on the glass surface and Na ions in the molten salt, and between Na ions on the glass surface and K ions in the molten salt. do. Thereby, a high-density compressive stress layer is formed on the surface layer of the glass.

The method of bringing the glass into contact with the molten salt includes a method of coating the glass with a paste-like molten salt, a method of spraying an aqueous solution of the molten salt onto the glass, and a method of immersing the glass in a salt bath of the molten salt heated to the melting point or higher. etc. is possible. Among them, the method of immersing in molten salt is preferable.

The molten salt is preferably an inorganic salt having a melting point below the strain point of the glass to be chemically strengthened. The strain point of glass is usually about 500 to 600.degree.
For example, since the melting point of potassium nitrate is 330° C., an inorganic salt containing potassium nitrate is in a molten state below the strain point of glass, and can be easily handled in the operating temperature range. Therefore, it is preferable to perform the chemical strengthening treatment using a molten salt containing potassium nitrate. The content of potassium nitrate in the molten salt is preferably 50% by mass or more.

The molten salt preferably contains a flux in addition to a nitrate such as potassium nitrate from the viewpoint of increasing the strength of the chemically strengthened glass.
Flux has the property of cutting the network of glass represented by Si--O--Si bonds. Since the temperature at which the chemical strengthening treatment is performed is as high as several hundred degrees Celsius, if the covalent bond between the Si—O of the glass is moderately broken at that temperature, hydrogen will form Si— in the bond network of Si—O—Si. It enters in the form of OH and forms a low density layer on the surface of the glass. The strength of the chemically strengthened glass is increased by removing this low-density layer by alkali treatment, which will be described later. The low-density layer is formed in a very small region of the surface layer of the compressive stress layer formed by the chemical strengthening treatment, and is a very thin layer compared to the thickness of the compressive stress layer.

The flux preferably contains at least one selected from the group consisting of carbonates, hydrogen carbonates, phosphates, and hydroxides, and more preferably contains at least one carbonate. More specifically, _{K2CO3 , Na2CO3} , _{KHCO3 , NaHCO3} , _{K3PO4 , Na3PO4 ,} KOH, NaOH _{, Li2CO3 , Rb2CO3 , Cs2CO3} , MgCO ₃ , CaCO ₃ , and BaCO ₃ are more preferred, and K ₂ CO ₃ , Na ₂ CO ₃ , KHCO ₃ , NaHCO ₃ , Li ₂ CO ₃ , Rb ₂ CO ₃ , Cs ₂ CO ₃ , More preferably, it contains at least one selected from MgCO ₃ , CaCO ₃ and BaCO ₃ .

In addition to the type of flux, the degree of breakage of covalent bonds of glass such as Si--O--Si bonds can also be adjusted by the composition of the glass and the chemical strengthening treatment conditions such as the temperature and time of the chemical strengthening treatment. It is considered preferable to appropriately adjust these conditions so that one or two of the four covalent bonds extending from Si are broken.

For example, in the case of a molten salt using K ₂ CO ₃ as a flux, if the flux content in the molten salt is 0.1 mol% or more and the chemical strengthening treatment temperature is 350 to 500° C., the chemical strengthening treatment time is 1 minute to 10 hours is preferred, 5 minutes to 8 hours is more preferred, and 10 minutes to 4 hours is even more preferred.

The amount of the flux added is preferably 0.1 mol % or more, more preferably 0.5 mol % or more, more preferably 1 mol % or more, and particularly preferably 2 mol % or more, from the viewpoint of surface hydrogen concentration control. From the viewpoint of productivity, it is preferable that the solubility of each flux is not higher than the saturation solubility of each flux. Adding too much flux may lead to corrosion of the glass. For example, when K ₂ CO ₃ is used as a flux, the amount added is preferably 24 mol % or less, more preferably 12 mol % or less, and particularly preferably 8 mol % or less.

The molten salt may contain other chemical species in addition to the nitrate and the flux as long as the effects of the present invention are not impaired. Other chemical species include, for example, alkali chlorides and alkali borates such as sodium chloride, potassium chloride, sodium borate and potassium borate. These may be added singly or in combination of multiple types.

In addition, although the details will be described later, the chemically strengthened glass obtained by the chemical strengthening treatment has a hydrogen concentration Y in the region of the depth X from the outermost surface, where X = 0.1 to 0.4 (μm), the following relational expression (I) is preferably satisfied.
Y=aX+b (I)
[The meaning of each symbol in Formula (I) is as follows.
Y: Hydrogen concentration (converted to H ₂ O, mol/L)
X: depth from the top surface of the glass (μm)
a: -0.45 or more and 0.01 or less b: 0.01 or more and 0.40 or less]

Means for controlling a and b in the above relational expression (I) include, for example, changing flux concentration, sodium concentration, temperature, time, etc. in the chemical strengthening treatment.

As the control of a and b, when changing the Na concentration in the molten salt in the chemical strengthening treatment, the Na concentration is preferably 500 ppm by weight or more, more preferably 1000 ppm by weight or more. It is more preferable that the Na concentration in the molten salt is 2000 ppm by weight or more, because the low-density layer is easily deepened by the acid treatment step d described below. There is no particular upper limit to the Na concentration, and it is permissible until the desired surface compressive stress (CS) is obtained.

As the control of a and b, when changing the dew point temperature in the chemical strengthening treatment, it is preferable to increase the amount of water vapor and perform ion exchange in an atmosphere with a dew point temperature of 20° C. or higher. The dew point temperature is more preferably 30°C or higher, more preferably 40°C or higher, particularly preferably 50°C or higher, and most preferably 60°C or higher. Moreover, the dew point temperature is preferably lower than the temperature of the inorganic salt (molten salt) for ion exchange.

The dew point temperature should be within the above range at least in the vicinity of the interface of the molten salt, and the vicinity of the interface means the atmosphere in the region 200 mm or less from the interface of the molten salt. Dew point temperature can be measured by a Vaisala DRYCAP® DMT346 dew point transducer. The dew point temperature in this specification is a value when it is assumed that equilibrium is established between the molten salt and the atmosphere in the vicinity of the interface of the molten salt.

The dew point temperature can be adjusted by introducing water vapor, and conventionally known methods and gases can be used for the method of introducing water vapor and the gas used.

(Step c) Step of cleaning the glass After performing the chemical strengthening treatment in step b, the glass is cleaned as necessary.
The order and number of times of performing the step c are not particularly limited, and for example, it may be performed after at least one of the steps a, b, d and e. Further, for example, when a specific process is repeatedly performed, such as performing a treatment combining process d and process e multiple times, process d, process c, process e, process c, process d . . . Additionally, step c may be performed as appropriate between specific steps.

Industrial water, deionized water, etc. are used for cleaning the glass. Among them, ion-exchanged water is preferred.
The washing conditions vary depending on the washing solution used, but when ion-exchanged water is used, washing at 0 to 100° C. is preferable from the viewpoint of completely removing adhering salts.

In the cleaning process, the chemically strengthened glass is immersed in a tank containing deionized water, etc., the surface of the glass plate is exposed to running water, and the cleaning solution is sprayed onto the surface of the glass plate using a shower. etc., various methods can be applied.

(Step d) Step of acid-treating glass obtained by chemical strengthening treatment Step d is preferably performed between step b and step e. Moreover, the treatment combining the steps d and e may be performed twice or more, and the step c may be performed between the steps d and e during the combined treatment. Furthermore, step c may be carried out between steps e and d when the treatment combining steps d and e is carried out again.

By the acid treatment in step d, a low-density layer is formed on the glass surface by altering the surface layer of the compressive stress layer. This low-density layer is formed when Na or K leaks from the outermost surface of the compressive stress layer, called leaching, and H enters and replaces it.

In the acid treatment step, the chemically strengthened glass is brought into contact with an acid. Specifically, for example, the chemically strengthened glass is immersed in an acidic solution, whereby Na and K on the surface of the chemically strengthened glass are replaced with H.

The solution used in the acid treatment step is not particularly limited as long as it is acidic, and may have a pH of less than 7. Moreover, the acid used may be a weak acid or a strong acid. Specifically, acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, oxalic acid, carbonic acid and citric acid are preferred. These acids may be used alone or in combination.

The temperature at which the acid treatment is performed is preferably 100° C. or less, although it varies depending on the type and concentration of the acid used and the time.
Although the time for acid treatment varies depending on the type, concentration, and temperature of the acid used, it is preferably 10 seconds or longer, more preferably 1 minute or longer, preferably 5 hours or shorter, and 2 hours or shorter, from the viewpoint of productivity. is more preferred.
Although the concentration of the solution used for the acid treatment varies depending on the type of acid used, time, and temperature, it is preferable that the concentration is less likely to cause corrosion of the container, specifically 0.1% by mass to 20% by mass.

Since the low-density layer is removed by the alkali treatment in step e described later, the thicker the low-density layer, the easier it is to remove the glass surface. Therefore, the thickness of the low-density layer varies depending on the depth of cracks and latent scratches on the glass surface, but is preferably 5 nm or more, more preferably 20 nm or more, and even more preferably 80 nm or more from the viewpoint of the glass surface removal amount. By removing cracks and latent flaws on the surface of the glass, which cause a decrease in strength in the chemically strengthened glass, higher surface strength of the chemically strengthened glass can be achieved. In step b, by introducing water vapor and performing ion exchange at a high dew point temperature, the thickness of the low-density layer can be increased, for example, 300 nm or more.
Although the upper limit of the thickness of the low-density layer is not particularly limited, it is usually 2000 nm or less.
The thickness of the low-density layer can be controlled by the flux concentration, sodium concentration, temperature, time, water vapor amount, etc. in the step b of the chemical strengthening treatment.

The density of the low-density layer is lower than the density of the region deeper than the ion-exchanged compressive stress layer, ie, the bulk, from the viewpoint of glass surface removability.

The thickness of the low-density layer is obtained from the period (Δθ) measured by X-ray-reflectometry (XRR).
The density of the low density layer is determined by the critical angle (θc) measured by XRR.
Incidentally, it is also possible to simply observe the cross section of the glass with a scanning electron microscope (SEM) to confirm the formation of the low-density layer and the thickness of the layer.

(Step e) Step of Alkali-treating Glass Obtained by Chemical Strengthening After the step b, the glass is alkali-treated as the step e after the steps c and d if necessary. When the step e is performed after the step d, it is preferable to perform the alkali treatment of the step e after the step c of cleaning the glass after the step d.
Further, after the alkali treatment of step e, it is preferable to go through the step of cleaning the glass of step c.

Alkaline treatment is a treatment method for removing the surface layer of the chemically strengthened glass surface by bringing the chemically strengthened glass into contact with an alkaline aqueous solution, which is a basic solution. For example, when the step d of acid treatment is performed, such removal becomes remarkable. That is, part or all of the low-density layer formed by the acid treatment is removed.
The amount of surface layer removed can be controlled by the conditions of the alkaline treatment. If at least a part of the surface layer is removed, the effect of improving the strength can be obtained. is more preferably removed.

By performing alkali treatment, chemically strengthened glass _with excellent strength can be obtained by removing the surface _layer as described above. It was found that the derived residue was generated on the surface of the chemically strengthened glass.

Although the details of the residue are not clear, the following is considered.
ZrO ₂ contained in the glass is naturally contained in the chemically strengthened glass after chemical strengthening treatment, and exists not only in the bulk but also on its surface. ZrO ₂ present on the surface is susceptible to the external environment, and Zr is chemically stable. For example, in a basic alkaline aqueous solution for alkali treatment, it is assumed that it becomes a hydroxide and remains on the surface of the chemically strengthened glass without being completely removed, and tends to become a residue.
On the other hand, when alkali treatment is performed using an alkaline aqueous solution containing a specific chelating agent, the chelating agent tends to associate with Zr, which is a metal component that can cause residue, and as a result, Zr(OH) ₄ etc. precipitation as a solid can be suppressed. As a result, we believe that chemically strengthened glass with less residue can be obtained.

It was found that metal oxides such as TiO ₂ , Y ₂ O ₃ , and SnO ₂ other than ZrO ₂ also generate residues derived from the respective metal oxides when alkali treatment is performed, as with _ZrO 2 .

From the viewpoint of further reducing the residue amount, it is preferable to repeat the step of acid treatment in step e and the step of alkali treatment in step e after the alkali treatment in step e. That is, it is preferable to carry out a treatment combining the acid treatment of step d and the alkali treatment of step e two or more times. On the other hand, from the viewpoint of productivity, the number of times of performing the above-described combined treatments is preferably 3 or less.

Therefore, in the method for manufacturing chemically strengthened glass according to the present embodiment, an alkaline aqueous solution containing a specific chelating agent is used for the alkaline treatment.
In one embodiment of the alkaline aqueous solution containing a chelating agent, the chelating agent satisfies conditions 1 to 3 below.
(Condition 1) 1 mL of an acid solution having a metal ion concentration of 1 mol/L, and the chelating agent whose concentration is adjusted with an alkaline chemical solution so that the total number of ligand fields is 1.5 times the number of moles of the metal. Prepare 100 mL of an alkaline aqueous solution containing The amount (g) of precipitated metal is measured when 1 mL of the acid solution is added to 100 mL of the alkaline aqueous solution containing the chelating agent.
(Condition 2) 1 mL of an acid solution having a metal ion concentration of 1 mol/L and 100 mL of an alkaline aqueous solution containing no chelating agent, which is the same alkaline solution as in Condition 1 above, are prepared. The amount (g) of precipitated metal is measured when 1 mL of the acid solution is added to 100 mL of the alkaline aqueous solution containing no chelating agent.
(Condition 3) The precipitation amount measured under the condition 1 is 20% or less of the precipitation amount measured under the condition 2.

The amounts of precipitated metals measured under conditions 1 and 2 above were used to simulate the effect of reducing residues derived from ZrO2 and the like in an alkaline aqueous solution containing a chelating agent without using glass containing _{ZrO2 and} the like. can be used as a valid verification. That is, as described above, the amount of precipitation of metals constituting metal oxides such as ZrO ₂ measured under condition 1 is defined as [A], and the amount is measured under condition 2 using an alkaline aqueous solution that does not contain a chelating agent. When [B] is the amount of precipitated metal that constitutes a metal oxide such as ZrO ₂ , if [A] is lower than [B], it can be considered that the residue derived from ZrO ₂ etc. is reduced. , As shown in Condition 3 above, if [A] is 20% or less of [B], it can be said that the residue derived from ZrO ₂ and the like in the chemically strengthened glass can be sufficiently reduced. [A] is preferably 10% or less of [B], more preferably 5% or less, and the lower the better.

Chelating agents generally have different properties depending on the steric structure such as the length of coordinating arms, the chelate stability constant, and the like. However, the chelating agent in the present embodiment cannot be explained by any one of the above properties alone, and it is considered that these properties are comprehensively and complexly intertwined and may or may not produce an effect.
For example, in the case of glass containing ZrO ₂ as a metal oxide, a chelating agent that satisfies the above conditions 1 to 3 with respect to the amount of precipitated Zr, that is, a chelating agent that makes [A] 20% or less of [B] include, for example, pentetic acid, tartaric acid, gluconic acid, etidronic acid, malic acid. On the other hand, although details will be described later, succinic acid, triethylenetetraminehexaacetic acid (TTHA), oxalic acid, ethylenediaminetetraacetic acid (EDTA), ethylenediaminehydroxyethyltriacetic acid (HEDTA), dihydroxyethylglycine (DHEG), and citric acid In both cases, the above [A] for Zr was 80% or more of [B].

As described above, there is a large difference in whether or not the effects of the present invention are exhibited even with chelating agents that have been used as equivalents in the past. Therefore, in the present embodiment, whether or not the chelating agent exhibits the effects of the present invention is determined by comparing the metal precipitation amounts measured under Conditions 1 and 2 above.

Examples of the acid contained in the acid solution used in Conditions 1 and 2 include HNO ₃ , HCl, H ₂ SO ₄ and the like. Among them, HNO ₃ is preferable from the viewpoint of low corrosiveness to SUS (stainless steel) containers.
The acid concentration in the acid solution is preferably 1 to 20% by mass, more preferably 4% by mass or more, and more preferably 15% by mass or less.
The pH of the acid solution is preferably 0 to 3, more preferably 0.1 or more, and more preferably 2 or less. One type of acid is usually used in the acid solution, but the use of two or more types is not excluded.

The base contained in the alkaline aqueous solution used in Condition 1 and Condition 2 is preferably sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, or the like. Among them, sodium hydroxide and potassium hydroxide are more preferable from the viewpoint of simulating the environment when actually chemically strengthened glass is subjected to alkali treatment. One type of base is usually used in the alkaline aqueous solution, but the use of two or more types is not excluded.

The concentration of the base in the alkaline aqueous solution varies depending on the chelating agent used, the type of base, time, and temperature, but from the viewpoint of removability of the glass surface layer, it is preferably 0.1% by mass or more, more preferably 0.4% by mass or more. , more preferably 1.0% by mass or more, and preferably 20% by mass or less.

The pH of the alkaline aqueous solution may be above 7, and _a weak base or a strong base may be used. 1 or more is preferable, 11 or more is more preferable, and 12 or more is still more preferable.

The temperature at which the alkali treatment is performed varies depending on the type, concentration, and time of the chelating agent and base used, but from the viewpoint of preventing corrosion of the glass, it is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher. Also, the temperature is preferably 100° C. or lower, more preferably 80° C. or lower, and even more preferably 60° C. or lower.

The time for the alkali treatment varies depending on the type, concentration, and temperature of the chelating agent and base used, but from the viewpoint of productivity, it is preferably 10 seconds or longer, more preferably 1 minute or longer, and preferably 5 hours or shorter. Two hours or less is more preferable.

In one embodiment of the alkaline aqueous solution containing a chelating agent, the chelating agent is at least one selected from the group consisting of pentetic acid, tartaric acid, gluconic acid, etidronic acid and malic acid. Moreover, when the glass contains ZrO ₂ as a metal oxide, the chelating agent is preferably at least one selected from the group consisting of tartaric acid, gluconic acid, etidronic acid and malic acid. These chelating agents may be used in the form of salts such as pentetate, tartrate, gluconate, etidronate and malate.
When these chelating agents are used, the type of base in the alkaline aqueous solution, the concentration of the base, the pH of the alkaline aqueous solution, and the temperature and time for the alkaline treatment are preferably the same as those described above.

Pentetic acid is diethylenetriaminepentaacetic acid, a chelating agent commonly referred to as DTPA. Tartaric acid is 2,3-dihydroxybutanedioic acid. Gluconic acid is (2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanoic acid. Etidronic acid is 1-hydroxyethane-1,1-diphosphonic acid, a chelating agent called HEDP. Malic acid is 2-hydroxybutanedioic acid.

The concentration of the chelating agent in the alkaline aqueous solution containing the chelating agent varies depending on the type of chelating agent, but in the form of a salt composed of the chelating agent acid and metal ions, it is generally preferably 0.1% by mass or more, 0.5% by mass or more is more preferable, and 1% by mass or more is even more preferable.
A chelating agent other than the chelating agent described above may be added to the alkaline aqueous solution containing the chelating agent as long as the effects of the present invention are not impaired. However, when other chelating agents are contained, the above-mentioned "concentration of chelating agents in alkaline aqueous solution containing chelating agents" does not include the concentration of the other chelating agents, but is distinguished.
In one aspect of the other chelating agent, the amount of precipitation of metals constituting metal oxides such as _ZrO2 measured under Condition 1 above is measured under Condition 2 above using an alkaline aqueous solution that does not contain a chelating agent. It is a chelating agent that accounts for more than 20% of the amount of precipitated metal that constitutes a metal oxide such as ZrO ₂ , that is, a chelating agent that does not satisfy condition 3 above. Yet another aspect of other chelating agents are chelating agents that do not fall within the group consisting of pentetic acid, tartaric acid, gluconic acid, etidronic acid and malic acid.

Alkali treatment is a treatment for removing the surface layer of glass that has been chemically strengthened. Some or all of it is removed by alkali treatment.
Regardless of the presence or absence of the acid treatment in step d, if the chemically strengthened glass containing ZrO ₂ or the like is treated with alkali, a residue derived from ZrO ₂ is generated. By performing the treatment, the generation of such residue can be reduced. Moreover, when the acid treatment of the step d is performed, the effect of reducing the residue due to the alkali treatment using the alkaline aqueous solution containing the chelating agent can be further obtained. In addition, when a molten salt containing a nitrate containing alkali metal ions and a flux is used for the chemical strengthening treatment in step b, there is a tendency for the generation of residues due to the alkali treatment to increase, whereas the alkali aqueous solution contains the chelate By adding an agent and performing alkali treatment, the effect of reducing such residues can be further obtained. Furthermore, when the molten salt is used in step b and the acid treatment in step d is further performed, the tendency of the generation of residues to increase is more pronounced. If the treatment is performed, the effect of reducing the residue can be further obtained.

The effect of reducing residues derived from ZrO ₂ and the like can be determined by comparing chemically strengthened glasses manufactured under the same conditions except for the presence or absence of a chelating agent in the alkaline aqueous solution used for the alkaline treatment. Chemically strengthened glass obtained by performing alkali treatment with an alkaline aqueous solution containing a chelating agent on the amount of residue present on the surface of chemically strengthened glass obtained by performing alkali treatment with an alkaline aqueous solution containing no chelating agent. The amount of residue present on the surface is preferably 90% or less, more preferably 85% or less. In addition, in the chemical strengthening treatment of step b, if a nitrate containing alkali metal ions and a molten salt containing a specific flux are used, and acid treatment is further performed as step d, the amount of residue generated by the alkali treatment is large. When an alkaline aqueous solution containing a chelating agent is used for the alkali treatment, it is also possible to make it 60% or less of the case where the alkaline treatment is carried out with an alkaline aqueous solution containing no chelating agent.

The amount of residue derived from ZrO ₂ and the like present on the surface of the chemically strengthened glass is determined by X-ray photoelectron spectroscopy (XPS). can be measured by analyzing Since the amount of residue generated varies depending on the composition of the glass, in the present embodiment, the amount of metal elements forming the residue normalized using the amount of Al ₂ O ₃ that forms the glass skeleton is measured.
That is, when the chemically strengthened glass contains Al ₂ O ₃ , the content of elements present on the surface of the chemically strengthened glass is normalized by Al, and Zr / Al, Ti / Al, Y / Al, Sn / Al Find the ratio for each. The amount of residue can be estimated by comparing the content ratio with the parent composition of the chemically strengthened glass, that is, the glass composition before the chemical strengthening treatment.

Each of the above ratios is a ratio for _each element that is the source of the residue on the surface. is normalized by Al. When comparing the molar ratio of the content of the elements represented by this {(Zr + Ti + Y + Sn) / Al}, if the ratio of the molar ratio on the surface to the molar ratio in the parent composition of the chemically strengthened glass is 300% or less , It is preferable that the amount of residue derived from ZrO ₂ etc. on the surface is sufficiently reduced compared to conventional chemically strengthened glass, more preferably 200% or less, further preferably 180% or less, and even more preferably 165% or less.
Although the lower limit of the molar ratio is not particularly limited, it is usually 5% or more, preferably 50% or more, and more preferably 75% or more.
When the molar ratio is within the above range, even if the surface of the chemically strengthened glass is subsequently subjected to AR treatment or AG treatment, optical unevenness does not pose a practical problem.

According to the manufacturing method according to the present embodiment, chemically strengthened glass with a small amount of residue derived from ZrO ₂ and the like on the surface can be obtained.

<Chemical strengthened glass>
Since the chemically strengthened glass obtained by the manufacturing method according to the present embodiment has a small amount of residue on the surface, even if it is subjected to AR processing or AG processing, optical unevenness does not pose a practical problem. For this reason, it is also suitable for items having a certain size and thickness, such as a cover glass for a display device such as a car navigation system for a vehicle.

The base composition of the chemically strengthened glass is the same as the composition of the glass described in (Step a) in <Production method of chemically strengthened glass>, and the preferred embodiments are also the same.

The amount of residue derived from ZrO ₂ and the like on the surface of the chemically strengthened glass is the same as the amount of residue described in (step e) in <Production method of chemically strengthened glass>, and the preferred embodiment is also the same.

For chemically strengthened glass, a straight line obtained by linearly approximating the profile of hydrogen concentration Y with respect to depth X from the outermost surface at X=0.1 to 0.4 μm preferably satisfies the following relational expression (I).
Y=aX+b (I)
[In the formula (I), Y is the hydrogen concentration (converted to H ₂ O, mol/L), X is the depth from the outermost surface of the glass (μm), a is −0.45 to 0.01, and b is 0.45 to 0.01. 01 to 0.40. ]

When the hydrogen concentration in the glass is high, hydrogen enters the Si--O--Si bond network of the glass in the form of Si--OH, breaking the Si--O--Si bond. It is thought that when the hydrogen concentration in the glass is high, the Si--O--Si bonds are broken in many parts, chemical defects are likely to be generated, and the strength is lowered.

The above relational expression (I) holds true in a region of depth X=0.1 to 0.4 (μm) from the outermost surface of the chemically strengthened glass. The thickness of the compressive stress layer formed by ion exchange depends on the degree of chemical strengthening, but is usually formed in the range of 5-90 μm. The penetration depth of hydrogen into the glass depends on the diffusion coefficient, temperature and time, and the amount of penetration of hydrogen is affected by the amount of water in the atmosphere. The hydrogen concentration in the chemically strengthened glass after the chemical strengthening treatment is highest at the outermost surface and gradually decreases toward the deep portion (bulk) where no compressive stress layer is formed. The above relational expression (I) defines the degree of decrease, but since the moisture concentration may change due to deterioration over time at the outermost surface (X = 0 μm), the near surface is considered to have no effect. It is assumed to hold in the [region of X=0.1 to 0.4 (μm)].

In formula (I), a is the slope that defines the degree of decrease in hydrogen concentration. The range of a is preferably -0.45 to 0.01, more preferably -0.40 to -0.05, and still more preferably -0.35 to -0.10.
In formula (I), b corresponds to the hydrogen concentration on the outermost surface (X=0 μm). The range of b is preferably 0.01 to 0.40, more preferably 0.05 to 0.38, still more preferably 0.10 to 0.36.

It is generally believed that the reduction in glass strength is caused by the extension of microcracks present on the glass surface due to mechanical pressure from the outside. The more Si—OH rich the glass structure at the tip of the crack, the easier the crack extends [Won-Taek Han et al. , "Effect of residual water in silica glass on static fatigue", Journal of Non-Crystalline Solids, 127, (1991) 97-104].
Assuming that the tip of the crack is exposed to the atmosphere, the amount of Si—OH at the tip of the crack is presumed to show a positive correlation with the hydrogen concentration on the outermost surface of the glass. Therefore, b corresponding to the hydrogen concentration on the outermost surface is preferably in the range shown above.

The penetration depth of hydrogen is highly likely to change depending on the chemical strengthening treatment conditions, but if it does not change, it corresponds to b corresponding to the hydrogen concentration on the outermost surface and the slope that defines the degree of decrease in hydrogen concentration. A negative correlation appears in a. Therefore, a is preferably in the range shown above.

The chemically strengthened glass hydrogen concentration profile (H ₂ O concentration, mol/L) in this specification is a profile measured under the following analysis conditions.
Secondary Ion Mass Spectrometry (SIMS) is used to measure the hydrogen concentration profile of the chemically strengthened glass. A standard sample with a known hydrogen concentration is required to obtain a quantitative hydrogen concentration profile by SIMS.

A method for preparing a standard sample and a method for quantifying the hydrogen concentration are described below.
1) Cut out a part of the chemically strengthened glass to be measured.
2) A region of 100 μm or more is removed from the surface of the cut chemically strengthened glass by polishing or chemical etching. Both sides are removed. That is, the thickness of the removed portion on both sides is 200 μm or more. This removal-treated chemically strengthened glass is used as a standard sample. 3) Infrared spectroscopy (IR) was performed on the standard sample, and the absorbance height A ₃₅₅₀ of the peak top near 3550 cm ^-1 of the IR spectrum and the absorbance height A ₄₀₀₀ (baseline) of 4000 cm ^-1 were measured. demand. 4) Measure the plate thickness d (cm) of the standard sample using a plate thickness measuring instrument such as a micrometer. 5) With reference to Document A below, the infrared practical absorption coefficient ε _pract [L / (mol cm)] of H ₂ O of chemically strengthened glass is set to 75, and the hydrogen concentration of the standard sample is calculated using the following formula (II) (Converted to H ₂ O, mol/L) is obtained.
Hydrogen concentration of standard sample=(A ₃₅₅₀ −A ₄₀₀₀ )/(ε _pract ·d) Formula (II)
Literature A) S. Ilievski et al. , Glastech. Ber. Glass Sci. Technol. , 73 (2000) 39.

The chemically strengthened glass to be measured and the standard sample with a known hydrogen concentration obtained by the above method were simultaneously transported into the SIMS apparatus, and measured in order to obtain the depth profile of the intensity of ¹ H ^- and ³⁰ Si ^- . get. ^{The 30} Si ^- profile is then subtracted from the ¹ H ^- profile to obtain the depth profile of the ^{1 H-} / ³⁰ Si ^- intensity ratio. The average ¹ H ⁻ / ³⁰ Si ⁻ intensity ratio in the region from 0.1 μm to 0.4 μm in depth was calculated from the depth direction profile of ^{the 1} H ⁻ / ³⁰ Si ⁻ intensity ratio of the standard sample. Concentration and calibration curve is created so as to pass through the origin (calibration curve with standard sample of 1 level). Using this calibration curve, ^{the 1} H ⁻ / ³⁰ Si ⁻ intensity ratio on the vertical axis of the profile of the chemically strengthened glass to be measured is converted into hydrogen concentration. Thereby, the hydrogen concentration profile of the chemically strengthened glass to be measured is obtained. The SIMS and IR measurement conditions are as follows.

(SIMS measurement conditions)
Apparatus: ADEPT1010 manufactured by ULVAC-Phi
Primary ion species: Cs ⁺
Acceleration voltage of primary ions: 5 kV
Primary ion current value: 500 nA
Incident angle of primary ions: 60° with respect to the normal to the sample surface
Primary ion raster size: 300×300 μm ²
Secondary ion polarity: Negative secondary ion detection area: 60×60 μm ² (4% of primary ion raster size)
ESA Input Lens: 0
Use of neutralization gun: Yes Method of converting horizontal axis from sputter time to depth: Analysis The depth of the crater is measured by a stylus profilometer (Dektak 150 manufactured by Veeco) to determine the sputter rate of primary ions. . This sputter rate is used to convert the horizontal axis from sputter time to depth.
Field Axis Potential at ¹ H ^- Detection: Optimal values may vary from instrument to instrument. The value is set with care by the measurer so that the background is sufficiently cut.

(IR measurement conditions)
Apparatus: Thermo Fisher Scientific Nic-plan/Nicolet 6700 Resolution: 8 cm ^-1 Accumulation: 64 Detector: TGS detector

In order to derive the relational expression (I) from the hydrogen concentration profile (H ₂ O concentration, mol/L) of the chemically strengthened glass measured under the above analysis conditions, first, the depth from the outermost surface of the chemically strengthened glass X = 0.1 ~ Linear approximation is performed on the profile of the hydrogen concentration Y in the region of 0.4 (μm). The equation of the approximate straight line thus obtained is defined as relational expression (I).

<Cover glass>
The cover glass according to the present embodiment has the chemically strengthened glass obtained by the above <chemically strengthened glass manufacturing method> or the chemically strengthened glass described in the above <chemically strengthened glass>, and covers the front surface of a display device or the like. It may be used as a cover glass.

An antireflection (AR; Anti Reflection) layer and an antifouling (AFP: Anti Finger Print) layer may be formed on at least one main surface of the chemically strengthened glass. The antifouling layer may be formed directly on the main surface of the chemically strengthened glass, but when an antireflection layer is formed, it is more preferably formed on the antireflection layer.
At least one main surface of the chemically strengthened glass may be subjected to antiglare (AG; Anti Glare) processing.
By using the above-described chemically strengthened glass, a cover glass practically free from optical unevenness can be obtained even if decorative treatments such as antireflection layer, antifouling layer, and antiglare treatment are applied.

The AR layer is made of, for example, a metal oxide layer, and preferably has a structure in which a plurality of metal oxide layers having different refractive indices are laminated.
The AR layer preferably has a structure in which a high refractive index layer having a refractive index of 1.9 or more at a wavelength of 550 nm and a low refractive index layer having a refractive index of 1.6 or less at a wavelength of 550 nm are alternately laminated. . The number of layers of each of the low refractive index layer and the high refractive index layer is not limited, but the number of each layer is, for example, 1 to 6 layers.

The material of the high refractive index layer is preferably one or more whose main component is, for example, silicon nitride, titanium oxide, niobium oxide, tantalum oxide, and zirconium oxide. Furthermore, among these materials, silicon nitride, niobium oxide, and tantalum oxide are more preferable, and niobium oxide is particularly preferable, from the viewpoint of productivity and refractive index.
The material of the low refractive index layer preferably contains, for example, silicon oxide or silicon oxide doped with aluminum.

The AFP layer is made of, for example, a fluorine-containing compound, preferably a fluoroorganosilicon compound.
AG processing refers to imparting antiglare properties by forming unevenness on the main surface of chemically strengthened glass or by forming a layer including unevenness on the main surface of chemically strengthened glass.

A display device according to the present embodiment includes the cover glass. Such a display device may be used, for example, as an in-vehicle display device such as a car navigation system, a smart phone, a personal computer, and the like.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these. Examples 1, 3, 5 and 7 to 12 are examples, and examples 2, 4 and 6 are comparative examples.

<Evaluation 1 of chelating agent>
A chelating agent contained in an alkaline aqueous solution used for chemically strengthened glass was investigated.
First, as an acid solution, an aqueous solution of nitric acid with a concentration of 0.01 mol/L was prepared, and 1 mL of acid solution was prepared by dissolving Zr therein so that the ion concentration of Zr was 1 mol/L. Next, as an alkaline aqueous solution, an aqueous solution containing 55.6 μL of a 48% sodium hydroxide aqueous solution was prepared, and a chelating agent was added thereto at a concentration such that the total number of ligand fields was 1.5 times the number of moles of Zr. 100 mL of an alkaline aqueous solution was prepared. Chelating agents include succinic acid, triethylenetetraminehexaacetic acid (TTHA), oxalic acid, ethylenediaminetetraacetic acid (EDTA), ethylenediaminehydroxyethyltriacetic acid (HEDTA), dihydroxyethylglycine (DHEG), citric acid, pentetic acid (DTPA). , tartaric acid, gluconic acid, etidronic acid (HEDP), and malic acid were added in the form of a salt consisting of a chelating agent acid and a metal ion. Table 1 shows the specific amount of the chelating agent to be added. As a reference, 100 mL of an alkaline aqueous solution was prepared in the same manner except that the chelating agent was not included.
1 mL of the acid solution was added to 100 mL of each of the alkaline aqueous solutions, and the precipitate of Zr produced was collected and weighed to obtain the amount of precipitate of Zr. As a reference, an alkaline aqueous solution was prepared by dissolving EDTA in an amount of 10 times and 100 times the amount of the chelating agent, that is, at a concentration where the total number of ligand fields is 15 times and 150 times the number of moles of Zr. Then, the amount of precipitated Zr was obtained in the same manner.
Table 1 shows the amount of precipitated Zr when an alkaline aqueous solution containing each chelating agent is used, with the amount of Zr precipitated when an acid solution is added to an alkaline aqueous solution containing no chelating agent, assuming that the amount of precipitated Zr is 100%. .

<Evaluation 2 of chelating agent>
As an acid solution, an aqueous solution of nitric acid with a concentration of 0.01 mol/L was prepared, and 1 mL of an acid solution was prepared by dissolving Ti so that the ion concentration of Ti was 1 mol/L. Next, an aqueous solution containing 55.6 μL of a 48% sodium hydroxide aqueous solution was prepared as an alkaline aqueous solution, and a chelating agent was added thereto at a concentration such that the total number of ligand fields was 1.5 times the number of moles of Ti. 100 mL of an alkaline aqueous solution was prepared. Two types of chelating agents, ethylenediaminetetraacetic acid (EDTA) and gluconic acid, were added in the form of a salt composed of the chelating agent acid and metal ions. Table 2 shows the specific amount of the chelating agent to be added. As a reference, 100 mL of an alkaline aqueous solution was prepared in the same manner except that the chelating agent was not included.
1 mL of the acid solution was added to 100 mL of each of the alkaline aqueous solutions, and the precipitate of Ti produced was collected and weighed to obtain the amount of Ti precipitate produced.
Table 2 shows the amount of precipitated Ti when an alkaline aqueous solution containing each chelating agent is used, with the amount of Ti precipitated when an acid solution is added to an alkaline aqueous solution containing no chelating agent, assuming that the amount of Ti precipitated is 100%. .

From the results in Table 1, it was found that there is a large difference in the amounts of metal precipitates produced, even among chelating agents that have been used as equivalents, without being significantly distinguished in the past. Chelating agents generally have different properties depending on the steric structure such as the length of coordinating arms, the chelate stability constant, and the like. On the other hand, it was found that the above results cannot be explained by any one of these characteristics, and that all characteristics are comprehensively and complexly intertwined, and the effect may or may not be produced.
Pentetic acid (DTPA), tartaric acid, gluconic acid, etidronic acid (HEDP), and malic acid all gave excellent results in which the amount of metal precipitated was 20% or less of the reference, and conditions 1 to 3 above were obtained. The result was fulfilled.
In particular, when comparing EDTA with DTPA, which is known to be similar to EDTA in both physical and chemical properties, the amount of Zr precipitated in EDTA is 96.3% of the reference, and is only 3.7%. %, whereas the amount of Zr precipitate generated when using DTPA was 9.0% of the reference, and it was found that as much as 91% of precipitation could be suppressed. . Also, even if the amount of EDTA added was 10 times and 100 times excessive, the amount of precipitation was 90.2% and 71.6% of the reference, respectively, and the precipitation suppression effect of DTPA was not achieved at all. .

<Example 1>
As step a, _SiO2 64.4%, _Al2O3 8.0%, _{Na2O 12.5} %, _K2O 4.0%, MgO 10.5, expressed in mol% based on oxides. %, CaO 0.1%, SrO 0.1%, BaO 0.1%, and ZrO ₂ 0.5%.
Next, in step b, potassium nitrate was added to a SUS (stainless steel) cup and heated to 450° C. with a mantle heater to prepare a molten salt. After preheating the aluminosilicate glass prepared in step a to 200 to 400° C., it was immersed in molten salt at 450° C. for 90 minutes for ion exchange treatment, and then cooled to around room temperature for chemical strengthening treatment. The obtained chemically strengthened glass was subjected to the washing step c by washing with water.
Next, as step e, an alkaline aqueous solution obtained by adding 0.1% by weight of sodium gluconate as a chelating agent to 0.4% by weight of sodium hydroxide aqueous solution is prepared in a beaker, and the temperature is adjusted to 40° C. using a water bath. did The chemically strengthened glass obtained in the above step c was immersed in the alkaline aqueous solution for 3 minutes to carry out an alkali treatment. After that, as step c, after washing with pure water several times, it was dried by air blow.
As described above, the chemically strengthened glass of Example 1 was obtained.

<Example 2>
A chemically strengthened glass of Example 2 was obtained in the same manner as in Example 1 except that the alkali treatment in step e and the subsequent washing in step c were not performed.

For the chemically strengthened glass of Example 1, the molar ratio of the contents of the elements represented by {(Zr+Ti+Y+Sn)/Al} in the glass surface composition and the glass matrix composition was calculated by the following method.
Next, the ratio of Zr, etc. on the glass surface to the glass matrix composition was calculated by dividing the molar ratio in the surface composition of the glass by the molar ratio in the glass matrix composition. This value is hereinafter referred to as the "surface ratio of Zr, etc.", and it is a value that can be used as a measure of the amount of residue derived from ZrO ₂ and the like.

(Method for calculating {(Zr+Ti+Y+Sn)/Al} in surface composition of glass)
The surface composition of the glass was measured by X-ray photoelectron spectroscopy (hereinafter referred to as XPS). For the measurement, ESCA5500 manufactured by ULVAC-Phi was used, and the measurement was performed under the conditions of a pass energy of 93.9 eV, an energy step of 0.8 eV/step, and a detection angle (the angle between the sample surface and the detector) of 45°. rice field.
Analysis software MultiPak was used for the analysis of the obtained wide spectrum. The Shirley method was applied to subtract the spectral background. Si (2p), Al (2p), Na (1s), K (2p), Mg (1s), Zr (3d), Sn (3d5), Ti (2s), Y (3d5) O (1s) as peaks ) was used to calculate the surface composition (unit: atomic %), and then the value (molar ratio) of {(Zr+Ti+Y+Sn)/Al} normalized by Al was determined.

(Method for calculating {(Zr+Ti+Y+Sn)/Al} in glass mother composition)
A region of 100 μm or more was removed from the surface of the chemically strengthened glass by chemical etching with hydrofluoric acid to expose the region inside the glass, and then the composition was measured by XPS. The conditions of XPS and the calculation method of {(Zr+Ti+Y+Sn)/Al} were the same as the conditions and calculation method described in the above (Method of calculating {(Zr+Ti+Y+Sn)/Al} in the glass surface composition).

As a result, when the value of the surface ratio of Zr etc. on the chemically strengthened glass surface of Example 2 is 1, the value of the surface ratio of Zr etc. on the chemically strengthened glass surface of Example 1 is 0.83. Only by adding the chelating agent to the alkaline aqueous solution, the residue derived from ZrO ₂ and the like on the surface was reduced by 15% or more.

<Example 3>
As step a, an aluminosilicate glass having the same composition and dimensions as in Example 1 was prepared.
Next, in step b, a 435° C. molten salt of potassium nitrate containing 6 mol % of potassium carbonate and 2000 ppm by weight of sodium was prepared in a SUS (stainless steel) cup. After preheating the aluminosilicate glass prepared in step a to 200 to 400° C., it was immersed in molten salt at 435° C. for 120 minutes for ion exchange treatment, and then cooled to around room temperature for chemical strengthening treatment. The obtained chemically strengthened glass was subjected to the washing step c by washing with water.
Next, as step d, a 6% by weight nitric acid (HNO ₃ ) aqueous solution was prepared in a beaker, and the temperature was adjusted to 40° C. using a water bath. The chemically strengthened glass was immersed in the nitric acid aqueous solution for 3 minutes for acid treatment. After that, as step c, after washing with pure water several times, it was dried by air blow.
Next, as step e, an alkaline aqueous solution obtained by adding 0.1% by weight of sodium gluconate as a chelating agent to 0.4% by weight of sodium hydroxide aqueous solution is prepared in a beaker, and the temperature is adjusted to 40° C. using a water bath. did The acid-treated glass was immersed in the alkaline aqueous solution for 3 minutes to carry out alkali treatment. After that, as step c, after washing with pure water several times, it was dried by air blow. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 80 nm per side relative to the glass after step a.
As described above, the chemically strengthened glass of Example 3 was obtained.

<Example 4>
A chemically strengthened glass of Example 4 was obtained in the same manner as in Example 3, except that a 0.4% by weight sodium hydroxide aqueous solution containing no chelating agent was used for the alkali treatment in step e. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 79 nm per side relative to the glass after step a.

For the chemically strengthened glasses of Examples 3 and 4, the values of the surface ratios of Zr and the like were measured using X-ray photoelectron spectroscopy (XPS) (ESCA5500 manufactured by Ulvac-Phi) in the same manner as described above. asked.
As a result, when the surface ratio of Zr, etc. in Example 4 was 1, the surface ratio of Zr, etc. on the surface of the chemically strengthened glass of Example 3 was 0.08. Further, as specific values, the surface ratio of Zr, etc. in Example 3 was 147%, while the surface ratio of Zr, etc. in Example 4 was 1880%.
In the chemically strengthened glass of Example 4, the amount of Zr, etc. in the surface composition of the glass is more than 18 times greater than that in the base composition, and the residue derived from ZrO ₂ etc. is very large. On the other hand, as in Example 3, only by adding a specific chelating agent to the alkaline aqueous solution in the alkali treatment, the surface ratio of Zr or the like is 0.08 when the chelating agent is not added, that is, less than 10%. As a result, it was suggested that the residue derived from ZrO ₂ and the like on the surface is extremely reduced.
In addition, the surface ratio of Zr etc. in the chemically strengthened glass obtained in Example 3 is 300% or less, and it can be said that the residue derived from ZrO ₂ etc. on the surface is sufficiently reduced. Even when the antireflection layer was formed on the surface of the glass, no optical unevenness that would pose a practical problem occurred.

<Example 5>
The chemically strengthened glass of Example 5 was obtained in the same manner as in Example 3 except that an alkaline aqueous solution obtained by adding 1% by weight of sodium gluconate as a chelating agent to a 4% by weight sodium hydroxide aqueous solution was used for the alkali treatment in step e. Obtained. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 95 nm per side relative to the glass after step a.

<Example 6>
A chemically strengthened glass of Example 6 was obtained in the same manner as in Example 5, except that a 4% by weight sodium hydroxide aqueous solution containing no chelating agent was used for the alkali treatment in step e. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 82 nm per side relative to the glass after step a.

For the chemically strengthened glasses of Examples 5 and 6, the surface ratio values of Zr and the like were determined in the same manner as in Example 1.
As a result, when the value of the surface ratio of Zr etc. in Example 6 is 1, the value of the surface ratio of Zr etc. in Example 5 is 0.50. As a result, the residue derived from ZrO ₂ and the like on the surface was reduced to half. Further, as specific values, the surface ratio of Zr, etc. in Example 5 was 188%, while the surface ratio of Zr, etc. in Example 6 was 374%.
In addition, the surface ratio of Zr and the like in the chemically strengthened glass obtained in Example 5 is 300% or less, and it can be said that the residue derived from ZrO ₂ and the like on the surface is sufficiently reduced. Even when the antireflection layer was formed on the surface of the glass, no optical unevenness that would pose a practical problem occurred.

<Example 7>
In step b, the procedure was the same as in Example 5, except that potassium nitrate containing 6 mol% of potassium carbonate and 4000 ppm by weight of sodium was used as the molten salt, and that the dew point of the atmosphere during the chemical strengthening treatment was controlled to 55 ° C. Thus, the chemically strengthened glass of Example 7 was obtained. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 532 nm per side relative to the glass after step a.

<Example 8>
In step b, the procedure was the same as in Example 3, except that potassium nitrate containing 6 mol% of potassium carbonate and 4000 ppm by weight of sodium was used as the molten salt, and that the dew point of the atmosphere during the chemical strengthening treatment was controlled to 55 ° C. Thus, the chemically strengthened glass of Example 8 was obtained. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 552 nm per side relative to the glass after step a.

For the chemically strengthened glasses of Examples 7 and 8, the surface ratio values of Zr and the like were determined in the same manner as in Example 1.
As a result, the specific values of the surface ratio of Zr etc. were 125% in Example 7 and 131% in Example 8, both of which were 300% or less, and the residue derived from ZrO ₂ etc. on the surface was sufficiently reduced. rice field.

<Example 9>
The composition of step a is _SiO2 64.4%, _Al2O3 10.5%, _Na2O 16.0%, _{K2O 0.6} %, MgO 8.3%, and ZrO2 _0.2 %. An aluminosilicate glass B having a thickness of 2 mm was prepared.
Next, in step b, potassium nitrate containing 6 mol % of potassium carbonate and 6000 ppm by weight of sodium was added to a cup made of SUS (stainless steel) and heated to 435° C. with a mantle heater to prepare a molten salt. After preheating the aluminosilicate glass prepared in step a to 200 to 400° C., it was immersed in molten salt at 435° C. for 120 minutes for ion exchange treatment, and then cooled to around room temperature for chemical strengthening treatment. The obtained chemically strengthened glass was subjected to the washing step c by washing with water.
Next, as step d, a 6% by weight nitric acid (HNO ₃ ) aqueous solution was prepared in a beaker, and the temperature was adjusted to 40° C. using a water bath. The chemically strengthened glass was immersed in the nitric acid aqueous solution for 3 minutes for acid treatment. After that, as step c, after washing with pure water several times, it was dried by air blow.
Next, in step e, an alkaline aqueous solution was prepared in a beaker by adding 1% by weight of sodium gluconate as a chelating agent to a 4% by weight sodium hydroxide aqueous solution, and the temperature was adjusted to 40° C. using a water bath. The chemically strengthened glass obtained in the above step c was immersed in the alkaline aqueous solution for 3 minutes to carry out an alkali treatment. After that, as step c, after washing with pure water several times, it was dried by blowing air to obtain a chemically strengthened glass of Example 9. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 100 nm per side relative to the glass after step a.

<Example 10>
A chemically strengthened glass of Example 10 was obtained in the same manner as in Example 7 except that the concentration of the sodium hydroxide aqueous solution in step e was 0.4% by weight and the concentration of sodium gluconate was 0.1% by weight. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 83 nm per side relative to the glass after step a.

For the chemically strengthened glasses of Examples 9 and 10, the surface ratio values of Zr and the like were determined in the same manner as in Example 1.
As a result, the specific values of the surface ratio of Zr etc. were 39% in Example 9 and 107% in Example 10, both of which were 300% or less, and the residue derived from ZrO ₂ etc. on the surface was sufficiently reduced. rice field.

<Example 11>
A chemically strengthened glass of Example 11 was obtained in the same manner as in Example 9 except that in the step a, the dew point of the atmosphere was controlled to 55° C. and then the chemical strengthening treatment was performed. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 441 nm per side relative to the glass after step a.

<Example 12>
Except that in step a, chemical strengthening treatment was performed after controlling the dew point of the atmosphere to 55 ° C., and the concentration of the sodium hydroxide aqueous solution in step e was 0.4% by weight and the concentration of sodium gluconate was 0.1% by weight. obtained the chemically strengthened glass of Example 11 in the same manner as in Example 9. The surface of the chemically strengthened glass after undergoing steps b to e was removed by 435 nm per side relative to the glass after step a.

For the chemically strengthened glasses of Examples 11 and 12, the surface ratio values of Zr and the like were determined in the same manner as in Example 1.
As a result, the specific values of the surface ratio of Zr etc. were 32% in Example 11 and 37% in Example 12, both of which were 300% or less, and the residue derived from ZrO ₂ etc. on the surface was sufficiently reduced. rice field.

<Hydrogen concentration profile>
For the chemically strengthened glasses of Examples 5, 7, 9, and 11, the hydrogen concentration profile was measured by the method described above, and the relational expression (I) represented by Y=aX+b was derived. Y in the relational expression (I) is the hydrogen concentration (converted to H ₂ O, mol/L) in the region of depth X from the outermost surface, and X indicating the depth from the outermost surface is 0.1 to 0.4 μm. is. Table 3 shows the values of a and b in relational expression (I).

Although the present invention has been described in detail and 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 Japanese Patent Application No. 2021-212957 filed on December 27, 2021, the contents of which are incorporated herein by reference.

Claims (16)

preparing the glass
chemically strengthening the glass, and alkali-treating the glass obtained by the chemical strengthening, in this order;
The glass contains at least one metal oxide selected from the group consisting of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and SnO ₂ ,
The alkali treatment is performed using an aqueous alkali solution containing a chelating agent,
The method for producing chemically strengthened glass, wherein the chelating agent satisfies the following conditions 1 to 3.
(Condition 1) 1 mL of an acid solution having an ion concentration of 1 mol/L of the metal constituting the metal oxide and an alkaline chemical solution so that the total number of ligand fields is 1.5 times the number of moles of the metal. 100 mL of an alkaline aqueous solution containing the chelating agent with adjusted concentration is prepared. The amount (g) of precipitated metal is measured when 1 mL of the acid solution is added to 100 mL of the alkaline aqueous solution containing the chelating agent.
(Condition 2) Prepare 1 mL of an acid solution in which the ion concentration of the metal constituting the metal oxide is 1 mol/L, and 100 mL of an alkaline aqueous solution that is the same alkaline chemical solution as in Condition 1 and does not contain a chelating agent. do. The amount (g) of precipitated metal is measured when 1 mL of the acid solution is added to 100 mL of the alkaline aqueous solution containing no chelating agent.
(Condition 3) The amount of precipitates measured under Condition 1 is 20% or less of the amount of precipitates measured under Condition 2. preparing the glass
chemically strengthening the glass, and alkali-treating the glass obtained by the chemical strengthening, in this order;
The glass contains at least one metal oxide selected from the group consisting of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and SnO ₂ ,
The alkali treatment is performed using an aqueous alkali solution containing a chelating agent,
The method for producing chemically strengthened glass, wherein the chelating agent is at least one selected from the group consisting of pentetic acid, tartaric acid, gluconic acid, etidronic acid and malic acid. The chemical strengthening according to claim 1 or 2, wherein the content of the chelating agent in the alkaline aqueous solution containing the chelating agent is 0.1% by mass or more in the form of a salt composed of an acid and a metal ion that is a chelating agent. A method of making glass. The method for producing chemically strengthened glass according to any one of claims 1 to 3, wherein the glass obtained by the chemical strengthening treatment is acid-treated between the chemical strengthening treatment and the alkali treatment. 5. The method for producing chemically strengthened glass according to claim 4, wherein a treatment combining said acid treatment and then said alkali treatment is performed two or more times. The chemical strengthening treatment is performed by bringing the glass into contact with molten salt,
6. The molten salt according to any one of claims 1 to 5, wherein the molten salt contains nitrates containing alkali metal ions, and at least one flux selected from the group consisting of carbonates, hydrogencarbonates, phosphates and hydroxides. 2. The method for producing the chemically strengthened glass according to item 1. The flux is _K2CO3 , _{Na2CO3 , KHCO3 , NaHCO3 , K3PO4 , Na3PO4} , KOH, NaOH, _{Li2CO3 , Rb2CO3 , Cs2CO3 ,} The method for producing chemically strengthened glass according to claim 6, comprising at least one selected from the group consisting of _MgCO3 , _CaCO3 , and _BaCO3 . The method for producing chemically strengthened glass according to any one of claims 1 to 7, wherein the metal oxide contains at least one of ZrO ₂ and TiO ₂ . The content of the glass in terms of mol% based on the oxide is
_SiO2 : 50-80%,
Al ₂ O ₃ : 2-25%,
Li ₂ O: 0-20%,
_Na2O : 0-18%,
_K2O : 0-10%,
MgO: 0-15%,
CaO: 0-5%, and ZrO ₂ : 0-5%,
The method for producing chemically strengthened glass according to any one of claims 1 to 8, wherein the total content of ZrO ₂ , TiO ₂ , Y ₂ O ₃ and SnO ₂ is 0.01% or more. Zr, Ti, Y, and at least one selected from the group consisting of Sn, an alkali metal, and Al,
When comparing the molar ratios of the contents of the elements represented by {(Zr + Ti + Y + Sn) / Al}, the ratio of the molar ratio on the surface to the molar ratio in the mother composition is 5 to 300%. Chemically strengthened glass. . The chemically strengthened glass according to claim 10, wherein the hydrogen concentration Y in the region of depth X from the outermost surface of the glass satisfies the following relational expression (I) when X = 0.1 to 0.4 (μm).
Y=aX+b (I)
The meaning of each symbol in formula (I) is as follows.
Y: Hydrogen concentration (converted to H ₂ O, mol/L)
X: depth from the top surface of the glass (μm)
a: -0.45 or more and 0.01 or less b: 0.01 or more and 0.40 or less The content in mol% display based on the oxide is
_SiO2 : 50-80%,
Al ₂ O ₃ : 2-25%,
Li ₂ O: 0-20%,
_Na2O : 0-18%,
_K2O : 0-10%,
MgO: 0-15%,
CaO: 0-5%, and ZrO ₂ : 0-5%,
The chemically strengthened glass according to _claim 10 or 11, wherein the total content of _ZrO2 , _TiO2 , _Y2O3 and _SnO2 is 0.01% or more. The chemically strengthened glass according to any one of claims 10 to 12;
and an antireflection layer formed on at least one main surface of the chemically strengthened glass. 14. The cover glass according to claim 13, wherein at least one of said main surfaces is antiglare processed. The cover glass according to claim 13 or 14, further comprising an antifouling layer formed on at least one of said main surfaces or said antireflection layer. A display device comprising the cover glass according to any one of claims 13 to 15.