TW201504165A - Method for reducing warpage of glass substrate by chemical strengthening treatment, and chemically strengthened glass and method for producing same - Google Patents

Abstract

The present invention relates to a method which comprises forming a film having at least one layer on at least a top surface of a glass substrate that is produced by a float method and has a bottom surface and the top surface to thereby reduce the warpage of the glass substrate which can be caused by a subsequent chemical strengthening treatment, wherein the bottom surface is in contact with a molten metal during molding and the top surface is opposed to the bottom surface. In the method, the glass substrate can have a compressive stress layer depth of 20 [mu]m or less when the glass substrate is subjected to a chemical strengthening treatment with potassium nitrate melt at 420 DEG C for 150 minutes, and the film contains at least one of oxides and composite oxides each comprising silicon and has a film thickness of 17 nm or more.

Description

Method for reducing warpage of glass substrate caused by chemical strengthening treatment, chemically strengthened glass and manufacturing method thereof

The present invention relates to a method for reducing warpage of a glass substrate caused by chemical strengthening treatment, a chemically strengthened glass having reduced warpage, and a method for producing chemically strengthened glass with reduced warpage.

In recent years, portable information devices such as personal computers (Personal Computers), smart phones, and e-book readers have become the mainstream with touch panel displays. The touch panel display has a structure in which a touch sensor glass and a cover glass are superposed on a glass substrate for a display, or a structure in which a touch sensor glass and a cover glass are integrated.

For such a portable information device, it is required to be lightweight and thin, and therefore, the cover glass for display protection is also required to be thin.

However, if the thickness of the cover glass is made thin, there is a problem that the strength is lowered, and the cover glass itself is broken due to dropping during use or the like.

Therefore, in order to improve the damage resistance, the conventional cover glass is formed by compressing the float glass produced by the floating method to form a compressive stress layer on the surface, thereby improving the damage resistance of the cover glass.

As a method of chemical strengthening, an ion exchange treatment in which Na ions in the glass are substituted with K ions in the molten salt by immersing the glass plate in the molten salt of KNO ₃ is generally used. In this case, a compressive stress (hereinafter referred to as CS (Compressive Stress)) is generated on the surface of the glass by infiltrating the K ion having an ionic radius larger than that of the Na ion into the network of the glass. Here, the depth of the compressive stress layer generated by chemical strengthening is referred to as Depth of Layer (hereinafter, referred to as DOL).

In the float glass, it is reported that warpage occurs after the chemical strengthening treatment to impair flatness (Patent Document 1). It is considered that the warpage is a compressive stress layer of a glass surface (hereinafter also referred to as a top surface) which is not in contact with molten tin during molding by a floating method, and a glass surface (hereinafter also referred to as a bottom surface) which is in contact with molten tin. The status is different.

In the past, the reason why the top surface of the float glass is different from the state of the bottom surface compressive stress layer is that the molten metal penetrates into the glass surface which is in contact with the molten metal during the float molding (Patent Document 1).

Patent Document 1 discloses that the plate-shaped body produced and processed in a floating manner is not subjected to surface polishing, and is immersed or contacted with Li ions or Na ions or the mixed inorganic salts, and then chemically strengthened. Thereby the above warpage is improved.

Further, in order to reduce the warpage described above, there is a countermeasure for reducing the stress difference between the two surfaces by reducing the compressive stress generated by chemical strengthening, or by the top surface and the bottom surface of the float glass. After the surface heterogeneous layer is removed by a grinding treatment, a polishing treatment, or the like, chemical strengthening is performed, whereby no difference in ion exchange reaction occurs.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Special Publication No. 7-72093

However, in the method described in Patent Document 1, it is necessary to immerse the float glass in the mixed inorganic salt before chemical strengthening, which is complicated. Further, regarding the method of reducing the compressive stress, the strength of the float glass after chemical strengthening is insufficient.

Further, there is a problem in that the method of grinding or polishing the top surface and the bottom surface of the float glass before chemical strengthening to improve productivity, and it is preferable to omit such Grinding treatment or grinding treatment.

Therefore, an object of the present invention is to provide a method for effectively suppressing warpage after chemical strengthening by a simple method, a method for sufficiently improving productivity, a method for producing chemically strengthened glass for suppressing warpage, and a chemically strengthened glass. .

The present inventors have found that by forming at least one film having a specific film thickness on at least the top surface of the glass substrate, the warpage of the float glass after chemical strengthening can be effectively reduced, and the present invention is completed based on the knowledge. .

That is, the present invention is as follows.

A method for reducing warpage of a glass substrate caused by chemical strengthening treatment, which comprises a glass substrate formed by a floating method and having a bottom surface in contact with a molten metal during forming and a top surface on the opposite side of the bottom surface At least one film is formed on at least the top surface to reduce the warpage of the glass substrate caused by the subsequent chemical strengthening treatment, and the glass substrate is subjected to a chemical strengthening treatment at 420 ° C for 150 minutes by a potassium nitrate molten salt. The glass substrate having a layer depth of 20 μm or less and the film contains at least one type of oxide containing cerium and a composite oxide, and has a film thickness of 17 nm or more.

2. The method according to the above item 1, wherein the film has a film density of 1.9 to 2.3 g/cm ³ .

3. The method according to the above item 1 or 2, wherein the glass substrate is used for chemical strengthening treatment with a chemical strengthening temperature of T (unit: K) and a chemical strengthening time of t (unit: hour), and contains SiO ₂ , The mass percentages of SiO ₂ , Al ₂ O ₃ , MgO, CaO, SrO, BaO, ZrO ₂ , Na ₂ O, and K ₂ O are used to represent the content. The dol determined by the following formula is 20 or less, and dol=−0.13× Al ₂ O ₃ -1.88 × MgO - 2.41 × CaO - 1.85 × SrO - 1.35 × BaO - 1.59 × ZrO ₂ + 1.50 × Na ₂ O + 2.42 × K ₂ O - 129359 / T + 9.28 × t ^0.5 + 182.88.

4. The method according to any one of items 1 to 3, wherein the glass substrate is represented by a mass percentage of an oxide standard, and contains 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , and 8 to 22 % of Na ₂ O, 0 to 7% of K ₂ O, 0 to 17% of MgO, 0 to 22% of CaO, 0 to 8% of SrO, 0 to 8% of BaO, and 0 to 5% of ZrO ₂ .

5. The method according to any one of items 1 to 4, wherein the glass substrate is represented by a mass percentage of an oxide standard, and contains 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , and 8 to 22 % of Na ₂ O, 0 to 7% of K ₂ O, 0 to 5% of ZrO ₂ , and in the case of containing at least one of MgO, CaO, SrO and BaO, the content of MgO, CaO, SrO and BaO The total amount is 5 to 25%, and the ratio of the sum of the contents of Na ₂ O to K ₂ O to the content of Al ₂ O ₃ (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 1.5 or more.

6. The method according to the above item 5, wherein the (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 10 or less.

The method according to any one of the preceding claims, wherein the glass substrate contains at least one of CaO, SrO and BaO, and the total content of CaO, SrO and BaO is expressed as a mass percentage based on the oxide. 10%.

The method according to any one of items 1 to 7, wherein the film is a film formed by a normal pressure CVD (Chemical Vapor Deposition) method.

A method for producing a chemically strengthened glass, comprising the steps of: a film forming step for forming by a floating method and having a bottom surface in contact with a molten metal during forming and a top surface on an opposite side of the bottom surface And a glass substrate having a compressive stress layer depth of 20 μm or less when subjected to chemical strengthening treatment at 420 ° C for 150 minutes by potassium nitrate molten salt, at least one film is formed on the top surface of the glass substrate; and a chemical strengthening step is performed. The glass substrate on which the film is formed is subjected to a chemical strengthening treatment, and the film forming step is characterized in that the film forming step includes at least one type of oxide containing cerium and a composite oxide. Forming the above film in a manner of 17 nm or more, and reducing the above The warpage of the above glass substrate in the chemical strengthening step.

10. The method for producing a chemically strengthened glass according to the above item 9, wherein the film is formed so as to have a film density of 1.9 to 2.3 g/cm ³ in the film forming step.

The method for producing a chemically strengthened glass according to the above item 9, wherein the glass substrate contains SiO ₂ and chemical strengthening is performed by setting the chemical strengthening temperature to T (unit: K) in the chemical strengthening step. The time is set to t (unit: hour), and the mass percentages of SiO ₂ , Al ₂ O ₃ , MgO, CaO, SrO, BaO, ZrO ₂ , Na ₂ O, and K ₂ O of the above glass substrate are expressed by the following formula. The obtained dol is treated in a manner of 20 or less, dol=-0.13×Al ₂ O ₃ -1.88×MgO-2.41×CaO-1.85×SrO-1.35×BaO-1.59×ZrO ₂ +1.50×Na ₂ O+ 2.42 x K ₂ O-129359/T+9.28×t ^0.5 +182.88.

The method for producing a chemically strengthened glass according to any one of the preceding claims, wherein the film is formed by a normal pressure CVD method in the film forming step.

A chemically strengthened glass which is formed by a floating method and having a bottom surface which is in contact with a molten metal during molding and a top surface on the opposite side of the bottom surface, and is melted at 420 ° C by potassium nitrate molten salt. In the case of the chemical strengthening treatment, the depth of the compressive stress layer is 20 μm or less, at least one film is formed on the top surface of the glass substrate, and the glass substrate on which the film is formed is chemically strengthened. The film includes at least one or more oxides and composite oxides containing cerium, and has a film thickness of 17 nm or more, and a thickness of from 5 nm from the surface layer of the film to a film thickness from the surface layer of the film after chemical strengthening treatment. The average value (unit: atm%) of the amount of K present at 80% of the position is divided by the average value (unit: atm%) of the amount of K present from the interface between the glass substrate and the film at a depth of 20 nm to 30 nm. The value is 0.2 or more, or the surface of the film from the surface of the film after the chemical strengthening treatment is from 5 nm to the surface layer of the film. The average value (unit: atm%) of the amount of Na present at a position of 80% of the film thickness is divided by the average amount of Na present at a depth of 20 nm to 30 nm from the interface between the glass substrate and the film (unit: atm %) The value obtained is 0.2 or more.

The chemically strengthened glass according to the above item 13, wherein the glass substrate is represented by a mass percentage of an oxide standard, and contains 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , and 8 to 22% of Na. ₂ O, 0 to 7% of K ₂ O, 0 to 17% of MgO, 0 to 22% of CaO, 0 to 8% of SrO, 0 to 8% of BaO, and 0 to 5% of ZrO ₂ .

The chemically strengthened glass according to the above item 13 or 14, wherein the glass substrate is represented by a mass percentage based on an oxide, and contains 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , and 8 to 22%. Na ₂ O, 0 to 7% of K ₂ O, 0 to 5% of ZrO ₂ , and in the case of containing at least one of MgO, CaO, SrO and BaO, the total content of MgO, CaO, SrO and BaO The ratio of the sum of the contents of Na ₂ O to K ₂ O to the content of Al ₂ O ₃ (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 1.5 or more.

The chemically strengthened glass according to the above item 15, wherein the (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 10 or less.

The chemically strengthened glass according to any one of the preceding items, wherein the glass substrate contains at least one of CaO, SrO, and BaO, and the total content of CaO, SrO, and BaO is expressed by mass percentage of the oxide standard. 1~10%.

According to the present invention, by forming at least one film having a specific film thickness on at least the top surface of the glass substrate, the exchange rate of ions between the top surface and the bottom surface can be adjusted, and the difference in ion exchange amount between the top surface and the bottom surface can be reduced. Thereby, even when the compressive stress layer is formed by chemical strengthening, the state of the compressive stress layer of the top surface and the bottom surface can be equalized, so that warping is less likely to occur. Therefore, according to the present invention, even if the polishing treatment before chemical strengthening or the like is simplified or omitted, the warpage of the float glass after chemical strengthening can be reduced, and excellent flatness can be obtained.

1‧‧‧Central slit

2‧‧‧outer slit

4‧‧‧flow path

5‧‧‧Exhaust slit

10‧‧‧Injector

20‧‧‧ glass substrate

Fig. 1 is a graph showing the correlation between the amount of Δ ion exchange of various glasses (the value obtained by subtracting the ion exchange amount of the bottom surface from the ion exchange amount of the top surface) and the Δ warpage amount.

2 is a conceptual diagram of a device for forming a film on a glass substrate by a CVD method.

Fig. 3 is a graph showing the correlation between the amount of warpage of the glass and the film thickness of the SiO ₂ film.

Hereinafter, an embodiment of the present invention will be described in detail.

In the method of the present embodiment, by forming at least one type of film containing ruthenium oxide and composite oxide and having a film thickness of 17 nm or more, the exchange speed of ions between the top surface and the bottom surface can be adjusted to compress the top surface and the bottom surface. The state of the stress layer is equalized. Therefore, it is possible to reduce the warpage of the glass substrate after the chemical strengthening without reducing the compressive stress of the glass substrate or performing the processing such as grinding and polishing before the chemical strengthening treatment.

Further, it is preferred that the film used in the method of the present embodiment has a film density of 1.9 g/cm ³ or more. When the film density of the film is 1.9 g/cm ³ or more, the exchange rate of ions can be further suppressed, and the state of the compressive stress layers on the top surface and the bottom surface can be further balanced.

(glass)

The glass substrate used in the method of the present embodiment is a glass substrate having a compressive stress layer depth of 20 μm or less when subjected to chemical strengthening treatment at 420 ° C for 150 minutes, preferably 18 μm or less, more preferably 16 μm. the following. In addition, when the depth of the compressive stress layer exceeds 20 μm, it becomes difficult to cut the chemically strengthened glass after the chemical strengthening treatment. Therefore, it is preferable to use a glass substrate having a compressive stress layer depth of 20 μm or less under normal chemical strengthening treatment conditions.

The surface compressive stress of the glass substrate used in the method of the present embodiment after the chemical strengthening treatment is preferably 450 MPa or more, and more preferably 500 MPa or more. CS and DOL can be measured using a surface stress meter.

The composition of the glass substrate used in the method of the present embodiment is formed by a floating method, and can be strengthened by a chemical strengthening treatment, and is 420 ° C by a potassium nitrate molten salt. When the depth of the compressive stress layer in the chemical strengthening treatment for 150 minutes is 20 μm or less, various components can be used. Specifically, for example, a glass plate composed of soda-calcium silicate glass can be mentioned.

The thickness of the glass substrate is not particularly limited. However, in order to effectively carry out the following chemical strengthening treatment, it is usually preferably 5 mm or less, more preferably 3 mm or less.

Preferably, the glass substrate used in the method of the present embodiment is used for chemical strengthening treatment with a chemical strengthening temperature of T (unit: K) and a chemical strengthening time of t (unit: hour), and contains SiO ₂ and uses SiO _{2 .} The mass percentages of Al ₂ O ₃ , MgO, CaO, SrO, BaO, ZrO ₂ , Na ₂ O, and K ₂ O indicate that the dol determined by the following formula is 20 or less.

Dol=-0.13×Al ₂ O ₃ -1.88×MgO-2.41×CaO-1.85×SrO-1.35×BaO-1.59×ZrO ₂ +1.50×Na ₂ O+2.42×K ₂ O-129359/T+9.28×t ^0.5 +182.88

The composition of the glass substrate used in the method of the present embodiment is, for example, the composition of the following glass.

(i) expressed as a mass percentage based on oxides, containing 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , 8 to 22% of Na ₂ O, and 0 to 7% of K ₂ O, A total of 5 to 25% of RO (R = Mg, Ca, Sr, Ba), 0 to 5% of ZrO ₂ glass; (ii) expressed by mass percentage of oxide, containing 60 to 80% of SiO ₂ , 0.01~8% Al ₂ O ₃ , 8~22% Na ₂ O, 0~7% K ₂ O, 0~17% MgO, 0~22% CaO, 0~8% SrO , 0 to 8% of BaO, 0 to 5% of ZrO ₂ glass; (iii) expressed by mass percentage of oxide, containing 64 to 77% of SiO ₂ , 0.01 to 7% of Al ₂ O ₃ , 10 ~18% Na ₂ O, 0~5% K ₂ O, 1~10% MgO, 1~12% CaO, 0~5% SrO, 0~5% BaO, 0~3% ZrO ₂ glass; (iv) 60% to 80% SiO ₂ , 0.01 to 8% Al ₂ O ₃ , 8 to 22% Na ₂ O, 0 to 7% by mass percentage K ₂ O, 0 to 5% of ZrO ₂ , and in the case of containing at least one of MgO, CaO, SrO and BaO, the total content of MgO, CaO, SrO and BaO is 5 to 25%, Na ₂ O and a ratio of the sum of the content of K ₂ O to the content of Al ₂ O ₃ (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 1.5 or more; (v) the mass based on the oxide The fraction indicates that it contains 60-80% SiO ₂ , 0.01-8% Al ₂ O ₃ , 8-22% Na ₂ O, 0-7% K ₂ O, 0-5% ZrO ₂ , and In the case of containing at least one of MgO, CaO, SrO and BaO, the total content of MgO, CaO, SrO and BaO is 5 to 25%, the sum of the contents of Na ₂ O and K ₂ O and the ratio of Al ₂ O ₃ a ratio of content (Na ₂ O+K ₂ O)/Al ₂ O ₃ of 1.5 or more and 10 or less; (vi) expressed by mass percentage of oxide, containing 60 to 80% of SiO ₂ , 0.01 to 8 % of Al ₂ O ₃ , 8 to 22% of Na ₂ O, 0 to 7% of K ₂ O, 0 to 5% of ZrO ₂ , and when at least one of MgO, CaO, SrO, and BaO is contained, The total content of MgO, CaO, SrO and BaO is 5 to 25%, and the total content of CaO, SrO and BaO is 1 to 10%, the sum of Na ₂ O and K ₂ O and the content of Al ₂ O ₃ . The ratio of (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 1.5 or more.

The reason why the glass composition is limited to the above range in the glass substrate of the present embodiment will be described below.

SiO ₂ is known as a component which forms a network structure in a glass fine structure, and is a main component of glass. The content of SiO ₂ is 60% or more, preferably 64% or more, more preferably 66% or more, still more preferably 67% or more. Further, the content of SiO ₂ is 80% or less, preferably 77% or less, more preferably 75% or less. When the content of SiO ₂ is 60% or more, it is advantageous in terms of stability or weather resistance of glass. On the other hand, when the content of SiO ₂ is 80% or less, it is advantageous in terms of meltability and formability.

Al ₂ O ₃ is an essential component and has an effect of improving the ion exchange performance in chemical strengthening, and in particular, the effect of increasing CS is large. Al ₂ O _{3 is} also known as a component for improving the weather resistance of glass. Further, it has an effect of suppressing penetration of tin from the bottom surface during the floating molding.

The content of Al ₂ O ₃ is 0.01% or more, preferably 0.2% or more, more preferably 0.5% or more. Further, the content of Al ₂ O ₃ is 8% or less, more preferably 7% or less, further preferably 6% or less, and particularly preferably 5.5% or less. When the content of Al ₂ O ₃ is 0.5% or more, the desired CS value can be obtained by ion exchange, and the effect of suppressing penetration of tin can be obtained. On the other hand, when the content of Al ₂ O ₃ is 8% or less, the devitrification temperature does not increase greatly even when the viscosity of the glass is high, so that it is advantageous in terms of productivity. .

Although the MgO system is not essential, it is preferable to contain the glass by stabilizing the glass and increasing the composition of the CS. The content of MgO is preferably 1% or more, more preferably 2% or more. Further, the content of MgO is preferably 17% or less, more preferably 6% or less, further preferably 5.7% or less, and particularly preferably 5.4% or less. When the content of MgO is 1% or more, the meltability at a high temperature becomes good, and devitrification becomes difficult to occur. On the other hand, when the content of MgO is 17% or less, particularly 6% or less, devitrification can be prevented from occurring, and a sufficient ion exchange rate can be obtained.

Although the CaO system is not essential, it is preferable to contain the glass by stabilizing the glass and increasing the composition of the CS. The content of CaO is preferably 1% or more, more preferably 2% or more. Further, the content of CaO is preferably 22% or less, more preferably 9% or less, further preferably 8.5% or less, and particularly preferably 8.2% or less. When the content of CaO is 1% or more, the meltability at a high temperature becomes good, and devitrification becomes difficult to occur. On the other hand, when the content of CaO is 22% or less, particularly 9% or less, a sufficient ion exchange rate can be obtained, and a desired DOL can be obtained.

Although the SrO and BaO systems are not essential, the glass is further stabilized and the composition of CS is improved. The content of SrO and BaO is preferably 1% or more, more preferably 2% or more. Further, the content of SrO and BaO is preferably 8% or less, more preferably 5% or less, further preferably 3% or less, and particularly preferably 2% or less.

The total content of MgO, CaO, SrO and BaO is preferably 5 to 25%. In the case of less than 5%, there is glass instability or the inability to obtain sufficient CS. Moreover, in the case of more than 25%, there is a tendency that the glass is unstable or does not produce sufficient ion exchange.

Further, in the case of improving the brittleness of the glass, the total content of CaO, SrO and BaO is preferably from 1 to 10%. If it is less than 1%, there is a problem that CS cannot be fully obtained. Moreover, when it exceeds 10%, there is a possibility that the glass becomes too brittle and the strength is lowered.

Although the ZrO ₂ system is not essential, it stabilizes the glass and improves the composition of CS. If the content of ZrO ₂ exceeds 5%, the glass may be destabilized or may not produce sufficient ion exchange. In the case of containing ZrO _{2 ,} it is preferably 5% or less, more preferably 3% or less.

An essential component of the Na ₂ O system has a function of forming a surface compressive stress layer by ion exchange and deepening the DOL. Further, it is a component which lowers the high temperature viscosity and devitrification temperature of the glass and improves the meltability and formability of the glass.

The content of Na ₂ O is 8% or more, preferably 10% or more, more preferably 11% or more. Further, the content of Na ₂ O is 22% or less, preferably 20% or less, more preferably 18% or less. When the content of Na ₂ O is 8% or more, a desired surface compressive stress layer can be formed by ion exchange. On the other hand, when the content of Na ₂ O exceeds 22%, the weather resistance is lowered, which is not preferable.

Although K ₂ O is not an essential component, it has an effect of increasing the ion exchange rate and deepening the DOL, and can be contained within 7%. If it exceeds 7%, the DOL becomes too deep, and a sufficient CS cannot be obtained. It is preferably 5% or less, more preferably 4% or less. Further, a small amount of K ₂ O is suppressed from the effect of infiltration of tin from the bottom surface during the float molding, and therefore it is preferably contained in the case of performing float molding. In this case, the content of K ₂ O is preferably 0.05% or more, more preferably 0.1% or more.

The Al ₂ O ₃ system increases the composition of the high temperature viscosity and the devitrification temperature, and the Na ₂ O and K ₂ O systems lower the composition of the high temperature viscosity and the devitrification temperature. If the ratio of the sum of the contents of Na ₂ O to K ₂ O to the content of Al ₂ O ₃ (Na ₂ O+K ₂ O)/Al ₂ O _{3 is} less than 1.5, the high temperature viscosity is increased and the devitrification temperature is also increased. . Also, there is a possibility that the DOL becomes excessively shallow. (Na ₂ O+K ₂ O)/Al ₂ O _{3 is} preferably 1.5 or more, more preferably 1.8 or more, still more preferably 2 or more. On the other hand, (Na ₂ O+K ₂ O)/Al ₂ O _{3 is} preferably 10 or less, more preferably 8 or less, still more preferably 5 or less.

Although TiO ₂ is not an essential component, it is known that it is present in a large amount in a natural raw material and becomes a color source of yellow. The content of TiO ₂ is preferably 0.2% or less, more preferably 0.13% or less, still more preferably 0.1% or less. If the content of TiO ₂ exceeds 0.2%, there is a case where the glass is yellowed.

Although Fe ₂ O ₃ is not an essential component, it is extremely difficult to set the content to zero because it exists in nature and in various production lines. It is known that Fe ₂ O ₃ in an oxidized state causes coloring of yellow, and FeO in a reduced state causes coloring of blue, and it is known that when the two are balanced, the glass is colored green.

When the glass of this embodiment is used for a display device, a window glass, or a solar cell, it is not preferable for a deep color. The total amount of iron is converted to Fe ₂ O ₃ , and the content thereof is preferably 0.15% or less, more preferably 0.13% or less, still more preferably 0.11% or less.

A clarifying agent for the melting of SO ₃ -based glass. Usually, the content in the glass is one or more of the amount of the raw material input. The content of SO _{3 in} the glass is preferably 0.02% or more, more preferably 0.05% or more, still more preferably 0.1% or more. Further, the content of SO ₃ is preferably 0.4% or less, more preferably 0.35% or less, still more preferably 0.3% or less. When the content of SO ₃ is 0.02% or more, it is possible to sufficiently clarify and suppress bubble defects. On the other hand, when the content of SO ₃ is 0.4% or less, the defects of sodium sulfate generated in the glass can be suppressed.

The composition examples G1 to G18 indicating the mass percentage of the glass used in the method of the present embodiment and the compressive stress CS (unit: MPa) and the compressive stress layer depth DOL (unit: μm) when the chemical strengthening is performed are shown. In Table 1, Table 2.

In the table, (Na ₂ O+K ₂ O)/Al ₂ O ₃ is the ratio of the sum of the contents of Na ₂ O to K ₂ O to the content of Al ₂ O ₃ , and RO is the content of MgO, CaO, SrO and BaO. In total, CaO+SrO+BaO is the total content of CaO, SrO, and BaO, and the strengthening temperature (unit: °C) and strengthening time (unit: h) are those for chemical strengthening, and KNO ₃ is used for chemical strengthening. The concentration of KNO _{3 in} the molten salt (unit: mass%), and dol is the above dol. Further, the remaining component of the molten salt in which the concentration of KNO ₃ is not 100% is NaNO ₃ .

(membrane)

In the method of the present embodiment, at least one film containing at least one of an oxide containing cerium and a composite oxide is formed on at least a top surface of the glass substrate.

The oxide is, for example, an alkali-free oxide such as SiO ₂ or a composite oxide containing an alkali element or an alkaline earth element, but is not limited thereto.

The term "alkali-free oxide" means an oxide containing an element other than an alkali metal element, An oxide or a composite oxide containing one or more elements other than an alkali metal, or a mixed oxide of two or more kinds of oxides and composite oxides, or a laminate of the above oxides or composite oxides.

The alkali-free oxide preferably contains at least one oxide containing an oxide of cerium and a composite oxide.

It may be a film composed only of an oxide, or may contain another compound such as a nitride, a fluoride or a sulfide, and may be combined with any element. It may also be a film which is doped with a lanthanoid element or a lanthanoid element, for example.

The film thickness of the film is 17 nm or more, preferably 30 nm or more, more preferably 34 nm or more, still more preferably 36 nm or more, still more preferably 38 nm or more. When the film thickness is 17 nm or more, the warpage to the top surface side can be improved by the effect of ion exchange inhibition. When the film thickness is thick, the amount of warping displacement is increased as compared with the case where there is no film, and the warpage improving effect is improved. In addition, when the amount of ion exchange on the bottom surface side is large, if the ion exchange blocking effect on the top surface side is increased, warping may occur on the bottom surface side. For example, the film thickness may be 100 nm or less. The amount of warping displacement is suppressed.

The film thickness can be measured by an X-ray reflectance method. The film thickness can be adjusted, for example, by adjusting the concentration of the material gas. The interface between the glass substrate and the film is defined by this measurement.

The film density of the film is preferably 1.90 g/cm ³ or more, more preferably 1.90 to 2.30 g/cm ³ , still more preferably 1.92 to 2.18 g/cm ³ , still more preferably 1.94 to 2.15 g/cm ³ . When the film density is 1.90 g/cm ³ or more, the warpage to the top surface side can be improved by the effect of ion exchange inhibition. In addition, when the amount of ion exchange on the bottom surface side is large, if the ion exchange blocking effect on the top surface side is increased, warpage to the bottom surface side may occur. For example, the film density may be set to 2.30 g/ The amount of warping displacement is suppressed by cm ³ or less.

The film density can be measured by an X-ray reflectance method. The film density can be adjusted, for example, by adjusting the concentration of the material gas.

In the method of the present invention, in order to reduce the warpage of the glass substrate after chemical strengthening, The film is formed on the top surface of the surface which is easily chemically strengthened in the top surface and the bottom surface. The film may be formed on at least one of the top surfaces of the glass substrate, and may be formed only on the top surface or on both the top surface and the bottom surface.

In the case where a film is formed on both the top surface and the bottom surface, the warpage of the glass substrate after chemical strengthening can be reduced by adjusting the film thickness or the film density between the film on the top surface side and the film on the bottom surface side.

The film is preferably 50% or more, more preferably 70% or more, of the surface of the coated glass substrate.

(Method of forming a film)

Examples of the method for forming the film include a CVD method such as a normal pressure CVD method and a plasma CVD method, a sputtering method, a wet coating method, and a vapor deposition method. Among these, from the viewpoint of easily forming a film over a large area, a CVD method is preferred, and a normal pressure CVD method is more preferred.

As a specific method, for example, a case where a film is formed on a glass substrate by a CVD method will be described below based on a schematic diagram shown in FIG. 2 .

The ejector 10 for the atmospheric pressure CVD method is used to supply a gas containing a cerium source and an oxidizing agent to the surface of the glass substrate, and the cerium source and the oxidizing agent are allowed to react on the surface of the glass substrate to obtain a glass substrate on which the film is formed.

That is, it is preferable to heat the gas to be mixed with preferably 0.01 to 10 SLM, preferably 0.01 to 50% by mass, and preferably 1 to 1000 SLM, to 10 to 200 ° C, as shown in Fig. 2 . The central slit 1 is blown, and an oxidizing agent of preferably 0.5 to 2000 SLM and preferably a carrier gas of 1 to 5000 SLM are blown from the outer slit 2 to obtain an oxide containing cerium and a composite oxide film preferably of 17 nm or more. The glass substrate.

The conditions of the flow rate and the temperature are merely examples, and the conditions for coating the oxide containing the cerium and the composite oxide are not limited to these conditions. Furthermore, the SLM is an abbreviation for standard liter per minute.

The gas system flows through the flow path 4 on the substrate 20, and in the exhaust slit 5, the total gas flow rate discharged into the ejector is preferably 1.0 to 20 times. Measuring the temperature of the gas For the flow rate, a hot wire anemometer (for example, manufactured by Kanomax, Climomaster 6543) is used.

Preferably, the glass substrate is heated to preferably 300 to 700 °C. The temperature of the glass substrate can be measured by providing a radiation thermometer just before the gas is blown.

As the source of cerium, for example, SiH ₄ , SiHCl ₃ , SiH ₂ Cl ₂ , SiH ₃ Cl, SiCl ₄ , Si(CH ₃ ) ₂ Cl ₂ , SiBr ₄ , SiI ₄ , SiF ₄ and Si (OC ₂ H _{5 may be} mentioned). _4, etc., but not limited to these.

Examples of the oxidizing agent include O ₂ , O ₃ , NO, NO ₂ , N ₂ O, CO, and CO ₂ .

The carrier gas is preferably a gas which does not react with a helium source and an oxidizing agent at normal temperature, and examples thereof include N ₂ , air, H ₂ , O ₂ , Ne, Xe, CO ₂ , Ar, He, and Kr. They may be used singly or in combination of two or more. Among these, an inert gas such as N ₂ or Ar is preferable.

The membrane can also be a variety of functional membranes. Examples of the functional film include a low reflection film, a heat ray absorbing film, a heat ray reflection film, a UV (ultraviolet) absorbing film, a conductive film, and a glass weathering resistant film, but are not limited thereto. The same function can be imparted to both sides of the glass substrate, and different functions can be imparted.

As a method of imparting the same or different functions to both surfaces of the glass substrate, specifically, for example, in the slow cooling region of the floating method, the surfaces of both surfaces of the glass substrate can be supplied with the same or different functional films. The source and the oxidant were fabricated without changing the glass composition and were fabricated in a single process on a glass substrate having the same or different functions on both sides. According to this method, the functional film can be formed on the glass substrate in a single process in accordance with the usual method for producing a glass substrate, which is very useful as a process which is low in cost and high in productivity.

Since the glass substrate used in this embodiment is formed by the floating method, the glass substrate can be normally conveyed by roll conveyance. In the floating method, a melting furnace having a raw material for melting glass is used, and the molten glass is floated on a molten metal (tin or the like) to form a float of the glass ribbon. A glass substrate is produced by a kiln and a glass manufacturing apparatus for slow cooling of the glass ribbon.

Therefore, when the glass is molded on the molten metal (tin) bath, the glass substrate conveyed on the molten metal bath may be supplied with a vapor source and an oxidizing agent from the side not contacting the metal surface to form a film on the surface of the glass substrate.

In the slow cooling zone after the molten metal (tin) bath, the glass substrate is conveyed by roller conveyance. Here, the slow cooling zone includes not only the inside of the slow cooling furnace but also the portion which is carried out from the molten metal (tin) bath in the floating kiln to the inside of the slow cooling furnace. In the slow cooling zone, the helium source and the oxidant can be supplied from the top surface of the molten metal (tin). Alternatively, the helium source and the oxidant may be supplied from the bottom surface of the molten metal (tin).

Further, a glass substrate having a film formed on the surface thereof can be produced by a combination of a CVD method, a spray method, a roll coating method, a flow coating method, and the like by a glass manufacturing technique by a floating method. In this case, a film containing a germanium source and an oxidant may be supplied from a surface that does not contact the molten metal (tin) or a surface (top surface) that does not contact the roll to form a film on the glass substrate, and may be appropriately formed. A liquid is supplied to form a film on the glass substrate.

In the method of the present embodiment, a multilayer structure of a plurality of layers having different physical properties on the surface layer of the glass substrate may be formed. As a method of forming a multilayer structure of a plurality of layers having different physical properties on a surface layer of a glass substrate, specifically, for example, a TiO ₂ film of the first layer is formed on the surface of the glass substrate, and the film is formed on the TiO ₂ film. The second layer of the cerium oxide film is formed into a film, and the SnO ₂ layer of the third layer is formed on the ruthenium dioxide film to obtain a transparent conductive oxide film having a multilayer structure.

(chemical strengthening treatment)

The chemical strengthening treatment can be carried out by a previously known method. Moreover, it is preferable to perform the machining according to the shape of the application, for example, the machining such as cutting, end face machining, and drilling, before the chemical strengthening treatment. Further, the cutting or the like may be performed after the chemical strengthening treatment.

By chemical strengthening treatment, the glass substrate is contacted by immersion or the like to contain a larger a metal ion of a metal salt (eg, K ion) of an ionic radius (eg, K ion), whereby a metal ion of a smaller ionic radius in the glass substrate (typically Na ions or Li ions are replaced by metal ions of larger ionic radii.

The chemical strengthening treatment can be carried out, for example, by immersing the glass plate in a potassium nitrate solution at 300 to 550 ° C for 5 minutes to 20 hours. The ion exchange conditions may be selected in consideration of the viscosity characteristics of the glass, the use, the thickness of the sheet, the tensile stress inside the glass, and the like.

Examples of the molten salt used for the chemical strengthening treatment include basic nitrates such as potassium nitrate, sodium sulfate, potassium sulfate, sodium chloride, and potassium chloride, and basic sulfates and basic chloride salts. These molten salts may be used singly or in combination of plural kinds.

In the present embodiment, the processing conditions of the chemical strengthening treatment are not particularly limited, and the optimum conditions may be selected in consideration of the characteristics of the glass, the molten salt, and the like.

By equalizing the ion exchange amount between the top surface and the bottom surface by the method of the present embodiment, the warpage of the glass after chemical strengthening can be improved. The amount of warpage of the glass can be measured by a contact type surface shape measuring device [for example, Surfcom (trade name) manufactured by Tokyo Fine Industries Co., Ltd.]. The amount of warpage is measured by a contact surface shape measuring device, and after the reference line correction is performed so that the measurement start point and the measurement end point are the same level, the difference between the highest point and the lowest point is measured. It is positive when it is warped toward the top surface, and it is negative when it is warped toward the bottom surface.

The change in the amount of warpage of the glass before and after the chemical strengthening (the amount of warpage of △) was measured by the following formula.

(Formula) △ warpage amount = (the amount of warpage after chemical strengthening) - (the amount of warpage before chemical strengthening)

Δ When the amount of warpage is in the case of a glass having a thickness of 0.7 mm and 50 × 50 mm, it is preferably 15 μm or less, and more preferably 12 μm or less. By setting the amount of Δ warpage to 15 μm or less, it is possible to prevent the occurrence of defects when the metal wiring is patterned on the glass substrate.

Further, the method for producing a chemically strengthened glass according to the present embodiment includes a film forming step of forming the at least one film on a top surface of the glass substrate, and a chemical strengthening step. The above-described chemical strengthening treatment is performed on the glass substrate on which the film is formed. In addition, the glass substrate used in the film formation step is formed by a floating method, and the depth of the compressive stress layer when the chemical strengthening treatment is performed at 420 ° C for 150 minutes by the potassium nitrate molten salt is 20 μm or less. .

The film is formed into a film in the film formation step so as to contain at least one type of oxide containing cerium and a composite oxide and having a film thickness of 17 nm or more. Thereby, it is possible to manufacture a chemically strengthened glass which is less than the warpage of the glass substrate produced in the chemical strengthening step.

Further, the chemically strengthened glass of the present embodiment is formed by forming a film containing at least one type of oxide containing cerium and a composite oxide and having a film thickness of 17 nm or more on a glass substrate, and then performing chemical strengthening treatment. In addition, the glass substrate is formed by a floating method, and the depth of the compressive stress layer when the chemical strengthening treatment is performed at 420 ° C for 150 minutes by a potassium nitrate molten salt is 20 μm or less.

In the chemically strengthened glass of the present embodiment, in the relationship between the film and the glass substrate after the chemical strengthening treatment, the depth from the surface layer of the film in the cross-sectional direction of the glass substrate is 5 nm to the film thickness of the surface layer of the film. The average value of the amount of K at the position of % (set to A _K , unit: atm%) divided by the average of the amount of K from the position where the depth of the substrate is 20 nm to 30 nm from the interface between the glass substrate and the film The value (set to B _K , unit: atm%) is 0.2 or more, or an average value of the amount of Na from the position where the depth of the surface layer of the film is 5 nm to the position where the surface layer of the film is 80% of the film thickness ( Set to A _Na , unit: atm%) divided by the average amount of Na from the position where the depth of the substrate between the glass substrate and the film is 20 nm to 30 nm (set to B _Na , unit: atm %) The value obtained is 0.2 or more. That is, A _K /B _K ≧0.2 or A _Na /B _Na ≧0.2. Further, it is preferably A _K /B _K ≧0.2 and A _Na /B _Na ≧0.2.

In the film on the top surface of the glass substrate before the chemical strengthening treatment, Na and K were hardly present. When the chemical strengthening treatment is started, Na on the glass substrate starts to permeate into the film, and moves to the interface with the potassium nitrate molten salt while performing ion exchange with H. The moved Na is ion exchanged with KNO ₃ and K is infiltrated into the membrane. The side which penetrates into the K side of the film is ion-exchanged with Na or K and moves to the interface between the glass substrate and the film. The moved K is ion-exchanged with Na or K of the glass substrate to infiltrate into the glass substrate, and chemical strengthening treatment can be performed even if the film is formed on the glass substrate.

At this time, since K or Na penetrates into the film, the amount of K which is ion-exchanged with Na of the glass substrate is reduced as compared with the case of no film. Attenuating the chemistry of the glass substrate by setting K or Na in the film to a certain amount with respect to K or Na in the glass substrate, that is, by setting A _K /B _K ≧0.2 or A _Na /B _Na ≧0.2 Strengthen and suppress warpage. In order to enhance the suppression effect of warpage, it is preferably A _K /B _K ≧0.4 or A _Na /B _Na ≧0.4. Further, it is more preferably A _K /B _K ≧ 0.4 and A _Na /B _Na ≧ 0.4.

According to the chemically strengthened glass obtained in the present embodiment, a chemically strengthened glass product having a functional film on the surface of the chemically strengthened glass substrate can be obtained. Examples of such a chemically strengthened glass product include a cover glass display and a touch sensor of a touch panel display provided in a portable information device such as a tablet PC, a notebook PC, a smart phone, and an e-book reader. Cover glass for glass, LCD TVs, and PC monitors. It can also be applied to a glass substrate mounted in a display device or device.

Example

Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited thereto.

(1) Fabrication of float glass

The glass material of the following composition was manufactured by a floating method so that the thickness of the glass material was 0.7 mm, and it was cut into 100*100 mm, and the float glass plate was manufactured.

(Glass material A) expressed by mass%, 71.5% SiO ₂ , 1.8% Al ₂ O ₃ , 13.5% Na ₂ O, 0.26% K ₂ O, 4.64% MgO, 7.83% CaO, 0.03% ZrO ₂

(2) Production of glass substrate

Using the ejector 10 for the atmospheric pressure CVD method, the surface of the float plate glass produced in (1) is supplied with methacryl (SiH ₄ ), oxygen (O ₂ ) in the manner shown in the schematic diagram shown in FIG. _{2 .} The gas is obtained by reacting methane with oxygen on the surface of the glass substrate to obtain a glass substrate on which the SiO ₂ film is formed.

That is, a gas of 100% SiH ₄ mixed with 0.045 SLM and nitrogen gas (N ₂ ) of 53.8 SLM was heated to 580 ° C and blown from the central slit 1 shown in FIG. 2 at a flow rate of 95.9 Ncm/sec, from the outer slit. 2 45 SLM of oxygen and 8.9 SLM of nitrogen were blown at a flow rate of 48.0 Ncm/sec to obtain a glass substrate having a SiO ₂ film of 71 nm.

The gas system flows through the flow path 4 on the substrate 20, and in the exhaust slit 5, two times the total gas flow rate introduced into the ejector is discharged. For measuring the temperature and flow rate of the gas, a hot wire anemometer (manufactured by Kanomax, Climomaster 6543) was used.

As the glass substrate, the above-mentioned glass substrate (thickness: 0.7 mm) containing the glass material A was used. The glass substrate was heated to 580 ° C and conveyed at a speed of 1.96 m/min. The temperature of the glass substrate is measured by providing a radiation thermometer just before the gas is blown.

(3) Determination of film thickness and film density of film of glass substrate

The film thickness and film density of the film formed on the surface of the glass substrate obtained in (2) were measured by an X-ray reflectance method.

(4) Determination of film thickness and density of film on glass substrate

The film thickness and density of the cerium oxide film formed on the surface of the (2) glass substrate were measured by X-ray reflectance (XRR). The analysis conditions are shown below.

. Device: ATX-G manufactured by RIGAKU

. X-ray source: Cu-Kα ray

. X-ray output: 50kV-300mA

. Optical system: Ge (111) asymmetric beam compression optical system

. Slit: S1 = 1 × 10 mm, S2 = 0.1 × 10 mm, RS = 0.2 × 10 mm, GS = 0.2 mm

. Scanning speed: 0.1°/min

. Sampling width: 0.001 °

. Measuring range: 0~2°

. Analytical method: The value obtained by the extended Fourier analysis is set as an initial value, the surface density (membrane density) is calculated from the total reflection angle by the nonlinear least squares fitting method, and the film thickness is calculated from the Fourier transform of the interference pattern.

(5) Chemical strengthening treatment

The glass substrate obtained in (2) was subjected to chemical strengthening treatment at 420 ° C for 150 minutes by a potassium nitrate molten salt.

(6) Determination of the surface stress and the depth of the compressive stress layer

For the chemically strengthened float glass, the average value of the surface stress (CS, in MPa) and the depth of the compressive stress layer (DOL, in μm) were measured. The average value of the surface stress (CS) and the depth of the compressive stress layer were measured using a surface stress meter (FSM-6000LE) manufactured by Ohara. The results are shown in Table 3.

(7) Ion exchange amount (K ₂ O mass%)

The amount of ion exchange after chemical strengthening is quantified by a fluorescent X-ray method. The analysis conditions are shown below.

. Device: ZSX PrimusII manufactured by RIGAKU

. X-ray source: Rh

. X-ray output: 50kV-60mA

. Measuring line: K-Kα

. Filter: OUT

. Attenuator: 1/1

. Slit: S4

. Spectroscopic crystal: LiF (200)

. Detector: PC

. PHA: 100-300

. Crest angle: 136.650°

. Measurement time: 30 seconds

. Quantitative Methods: The standard known K ₂ O mass% relative intensity ratio of the sample of the sample is calculated K ₂ O mass%. The amount of ion exchange was determined by (K ₂ O mass% after chemical strengthening) - (K ₂ O mass % before chemical strengthening). Further, the analysis depth by the value measured by the fluorescent X-ray analysis using K-Kα ray is typically 10 μm, and there is almost no influence of the film on the glass surface.

(8) Calculation of △ warpage amount (calculated value)

A plurality of glass substrates (thickness: 0.7 mm, 50 × 50 mm) containing a glass material A having a different degree of weathering (Na ₂ O concentration) were subjected to chemical strengthening treatment at 420 ° C for 150 minutes, and the amount of △ warpage and the amount of Δ ion exchange were investigated. A graph obtained by the correlation of (K ₂ O mass%) is shown in Fig. 1. As a result, it was found that the amount of Δ warpage has a correlation with the amount of Δ ion exchange. The Δ warpage amount (calculated value) was calculated from the graph shown in Fig. 1 and the Δ ion exchange amount. Here, the amount of Δ ion exchange is obtained by subtracting the ion exchange amount of the bottom surface from the ion exchange amount of the top surface.

(9) Calculation of warpage displacement amount (calculated value)

With respect to the amount of Δ warpage obtained in (8), the amount of warpage with respect to the amount of warpage at this time is calculated based on the amount of Δ warpage when the SiO ₂ film is not formed, that is, the degree of warpage is calculated. The amount of warpage displacement obtained by subtracting the amount of Δ warpage when the SiO ₂ film was not formed was subtracted from the Δ warpage amount of each example, and the curve obtained by investigating the correlation with the film thickness is shown in Fig. 3 . As a result, it was found that the film thickness has a correlation with the amount of warpage displacement.

As shown in Table 3, by suppressing the amount of ion exchange of the top surface by chemically strengthening the glass substrate on which the film of SiO ₂ is formed, the glass substrate can be made to suppress the amount of warpage of the glass substrate before and after chemical strengthening. Displacement. That is, it can be seen that the difference in the amount of ion exchange between the top surface and the bottom surface can be reduced. Further, by reducing the difference in the amount of ion exchange between the top surface and the bottom surface, the amount of change in the direction of suppressing the amount of warpage, that is, the amount of warping displacement, can be increased as compared with the case where the film of SiO ₂ is not formed. Further, it is understood that by controlling the warping displacement amount, the amount of warpage of the Δ, which is the difference in the amount of warpage of the glass substrate before and after chemical strengthening, can be reduced, and the warpage after chemical strengthening can be reduced.

Moreover, as is clear from FIG. 3, in order to generate a force (warpage displacement amount) in which the glass substrate is displaced in the direction opposite to the warpage in the case where the SiO ₂ film is not formed, the film thickness must be 17 nm or more.

From the viewpoint of preventing the occurrence of defects in patterning the metal wiring on the glass substrate, the amount of warpage of Δ is preferably 15 μm or less. Examples 1 and 2 in which a glass substrate containing SiO ₂ (film density: 2.03 g/cm ³ , film density: 2.12 g/cm ³ ) was chemically strengthened on a surface of a glass substrate at a thickness of 71 nm and 97 nm, respectively. △ The amount of warpage (calculated value) is 15 μm or less. On the other hand, a film containing SiO ₂ (film density: 2.08 g/cm ³ ) is formed on the surface of the glass substrate with a film thickness of 33 nm, and chemical strengthening is performed. The Δ warpage amount of Example 4 in which the glass substrate is chemically strengthened in general is more than 15 μm.

Further, as shown in Table 3, in Example 2 in which SiO ₂ was formed into a film of 97 nm, the amount of Δ ion exchange became a negative value. From this result, it is understood that by adjusting the thickness of the film formed on the glass substrate, the amount of ion exchange between the top surface and the bottom surface can be controlled to control the amount of warpage of the glass substrate after chemical strengthening.

Further, as shown in Table 3, the stress values of the faces on which the film was formed in Examples 1, 2, and 3 were compared with Example 4, and as a result, the same stress value was given.

From this result, it is understood that by forming a film containing SiO ₂ having a film thickness of 17 nm or more on at least the top surface of the glass substrate, it is possible to reduce the ion exchange amount difference between the top surface and the bottom surface without reducing the stress caused by chemical strengthening, and to reduce the chemistry. The strengthened glass substrate is warped.

Further, in the chemically strengthened glass of Example 2 in which SiO ₂ was formed into a film of 97 nm, the average value of the amount of Na in the SiO ₂ film and the glass substrate and the average value of the amount of K were measured. The average amounts of Na and K the average amount of the SiO ₂ film in the film represents the concentration of SiO ₂ and based on the present depth from a surface of the SiO ₂ film (surface layer) from the surface of the SiO ₂ film is a film of 5nm to The average concentration of Na and K at 80% of the thickness. The average value of the amount of Na in the glass substrate and the average value of the amount of K represent the concentration of the glass substrate, and are present at an average concentration of Na and K at a depth of 20 nm to 30 nm from the interface between the glass substrate and the SiO ₂ film.

The amounts of Na and K were determined by measuring the concentration profiles of Na and K by X-ray photoelectron spectroscopy. The sputtering ion system uses C ₆₀ ⁺ and the sputtering angle is set to 45 degrees. When the spectrum was acquired, it was set to Pass Energy: 117.4 [eV], Energy Step: 0.50 [eV/step], the measurement angle was set to 75 degrees, and the measurement interval was set to 2 min. The pit depth of the sample after measurement was measured using a Dektak 150 manufactured by ULVAC, and the measurement time was converted to depth. The results of the measurement are shown in Table 4.

From this result, it is understood that a certain amount of Na and K exist in the SiO ₂ film. Therefore, it was confirmed that the chemically strengthened glass substrate of Example 2 is a chemically strengthened glass in which the amount of ion exchange between the top surface and the bottom surface is reduced to reduce warpage.

The present invention has been described in detail with reference to the specific embodiments thereof, and it is understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

In addition, the present application is based on Japanese Patent Application No. 2013-125789, filed on Jun.

Claims (17)

A method for reducing warpage of a glass substrate caused by chemical strengthening treatment, which is at least a glass substrate formed by a floating method and having a bottom surface in contact with the molten metal during molding and a top surface on the opposite side of the bottom surface Forming at least one film on the top surface, and reducing the warpage of the glass substrate caused by the subsequent chemical strengthening treatment, the glass substrate is a compressive stress layer depth by chemical strengthening treatment at 420 ° C for 150 minutes by potassium nitrate molten salt The glass substrate is 20 μm or less, and the film contains at least one type of oxide containing cerium and a composite oxide, and has a film thickness of 17 nm or more. The method of claim 1, wherein the film has a film density of 1.9 g/cm ³ or more. The method of claim 1 or 2, wherein the glass substrate is used for chemical strengthening treatment at a chemical strengthening temperature of T (unit: K), chemical strengthening time t (unit: hour), and contains SiO ₂ , using SiO ₂ The mass percentages of Al ₂ O ₃ , MgO, CaO, SrO, BaO, ZrO ₂ , Na ₂ O and K ₂ O indicate that the dol determined by the following formula is 20 or less, and dol=−0.13×Al ₂ O _{3 -} 1.88 × MgO - 2.41 × CaO - 1.85 × SrO - 1.35 × BaO - 1.59 × ZrO ₂ +1.50 × Na ₂ O + 2.42 × K ₂ O - 129359 / T + 9.28 × t ^0.5 + 182.88. The method of any one of claims 1 to 3, wherein the glass substrate is represented by a mass percentage of an oxide standard, and contains 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , and 8 to 22%. na ₂ O, 0 ~ 7% of K ₂ O, 0 ~ 17% of MgO, 0 ~ 22% of CaO, 0 ~ 8% of SrO, 0 ~ 8% of BaO, 0 ~ 5% of ZrO _2. The method of any one of claims 1 to 4, wherein the glass substrate is represented by a mass percentage of an oxide standard, and contains 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , and 8 to 22%. Na ₂ O, 0 to 7% of K ₂ O, 0 to 5% of ZrO ₂ , and when at least one of MgO, CaO, SrO, and BaO is contained, the total content of MgO, CaO, SrO, and BaO is 5 to 25%, the ratio of the sum of the contents of Na ₂ O to K ₂ O to the content of Al ₂ O ₃ (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 1.5 or more. The method of claim 5, wherein the (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 10 or less. The method according to any one of claims 1 to 6, wherein the glass substrate contains at least one of CaO, SrO and BaO, and the total content of CaO, SrO and BaO is expressed as 1 to 10% by mass based on the oxide. . The method of any one of claims 1 to 7, wherein the film is a film formed by an atmospheric pressure CVD method. A method for producing a chemically strengthened glass, comprising the steps of: forming a film by a floating method and having a bottom surface in contact with a molten metal during forming and a top surface on an opposite side of the bottom surface, and borrowing a glass substrate having a compressive stress layer depth of 20 μm or less when subjected to chemical strengthening treatment at 420 ° C for 150 minutes, and at least one film is formed on the top surface of the glass substrate; and a chemical strengthening step is performed to form a pair The glass substrate having the film is subjected to a chemical strengthening treatment, and the film forming step is characterized in that the film forming step contains at least one type of oxide containing cerium and a composite oxide, and the film thickness is 17 nm or more. The film is formed in such a manner as to reduce the warpage of the glass substrate in the chemical strengthening step. The method for producing a chemically strengthened glass according to claim 9, wherein the film is formed so as to have a film density of 1.9 g/cm ³ or more in the film forming step. The method for producing a chemically strengthened glass according to claim 9 or 10, wherein the glass substrate contains SiO ₂ , and in the chemical strengthening step, the chemical strengthening temperature is set to T (unit: K), and the chemical strengthening time is set to t (unit: hour), the mass percentage of SiO ₂ , Al ₂ O ₃ , MgO, CaO, SrO, BaO, ZrO ₂ , Na ₂ O, and K ₂ O using the above glass substrate is expressed by the following formula The dol is treated in a manner of 20 or less, dol=-0.13×Al ₂ O ₃ -1.88×MgO-2.41×CaO-1.85×SrO-1.35×BaO-1.59×ZrO ₂ +1.50×Na ₂ O+2.42×K ₂ O-129359/T+9.28×t ^0.5 +182.88. The method for producing a chemically strengthened glass according to any one of claims 9 to 11, wherein in the film forming step, the film is formed by an atmospheric pressure CVD method. A chemically strengthened glass which is formed by a floating method and having a bottom surface which is in contact with a molten metal during forming and a top surface on the opposite side of the bottom surface, and is heated at 420 ° C for 150 minutes by molten salt of potassium nitrate. The glass substrate having a depth of the compressive stress layer at the time of the strengthening treatment is 20 μm or less, at least one film is formed on the top surface of the glass substrate, and the glass substrate on which the film is formed is chemically strengthened, and is characterized in that: The film contains at least one type of oxide containing cerium and a composite oxide, and has a film thickness of 17 nm or more, and a thickness of from 5 nm from the surface layer of the film to 80% of the film thickness from the surface layer of the film after chemical strengthening treatment The average value (unit: atm%) of the amount of K present at the position is divided by the average value (unit: atm%) of the amount of K present from the interface between the glass substrate and the film at a depth of 20 nm to 30 nm. The average value of the amount of Na present in the range from 0.2 nm or more after the chemical strengthening treatment to the surface layer of the film from a depth of 5 nm to a film thickness of 80% from the surface layer of the film (unit: Atm%) The value obtained by dividing the average value (unit: atm%) of the amount of Na present from the interface between the glass substrate and the film at a depth of 20 nm to 30 nm is 0.2 or more. The chemically strengthened glass according to claim 13, wherein the glass substrate is represented by a mass percentage of an oxide standard, and contains 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , and 8 to 22% of Na ₂ O. 0 to 7% of K ₂ O, 0 to 17% of MgO, 0 to 22% of CaO, 0 to 8% of SrO, 0 to 8% of BaO, and 0 to 5% of ZrO ₂ . The chemically strengthened glass according to claim 13 or 14, wherein the glass substrate is represented by mass percentage of an oxide standard, and contains 60 to 80% of SiO ₂ , 0.01 to 8% of Al ₂ O ₃ , and 8 to 22% of Na _{2 .} O, 0 to 7% of K ₂ O, 0 to 5% of ZrO ₂ , and in the case of containing at least one of MgO, CaO, SrO and BaO, the total content of MgO, CaO, SrO and BaO is 5~ 25%, the ratio of the sum of the contents of Na ₂ O to K ₂ O to the content of Al ₂ O ₃ (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 1.5 or more. The chemically strengthened glass according to claim 15, wherein the above (Na ₂ O+K ₂ O)/Al ₂ O ₃ is 10 or less. The chemically strengthened glass according to any one of claims 13 to 16, wherein the glass substrate contains at least one of CaO, SrO and BaO, and the total content of CaO, SrO and BaO is expressed as a mass percentage based on the oxide. 10%.