阅读说明：本技术 熔融盐组合物的寿命延长方法、化学强化玻璃的制造方法、玻璃助剂和玻璃的原材料 (Method for extending life of molten salt composition, method for producing chemically strengthened glass, glass auxiliary agent, and raw material for glass ) 是由 今北健二 相泽治夫 藤原祐辅 于 2020-04-20 设计创作，主要内容包括：本发明涉及熔融盐组合物的寿命延长方法,其包含向在化学强化用玻璃的化学强化处理中使用的熔融盐组合物中添加玻璃助剂的工序,其中,以氧化物基准的质量％计,玻璃助剂中的SiO-(2)和Al-(2)O-(3)的含量的合计为60％以上。(The present invention relates to a method for prolonging the life of a molten salt composition, which comprises a step of adding a glass auxiliary agent to a molten salt composition used for chemical strengthening treatment of a glass for chemical strengthening, wherein SiO in the glass auxiliary agent is contained in an amount of mass% based on an oxide 2 And Al 2 O 3 The total content of (a) is 60% or more.)

1. A method for prolonging the life of a molten salt composition, which comprises a step of adding a glass auxiliary agent to a molten salt composition used for chemical strengthening treatment of a glass for chemical strengthening,

SiO in the glass auxiliary agent in mass percent based on oxide₂And Al₂O₃The total content of (a) is 60% or more.

2. The molten salt composition according to claim 1, wherein SiO in the glass auxiliary agent is in mass% on an oxide basis₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O is 95% or more.

3. The molten salt composition according to claim 2, wherein Li in the glass auxiliary agent is contained in an amount of Li in mass% based on an oxide₂O content is 3% or less, and Na₂The content of O is more than 5%.

4. The molten salt composition according to claim 2, wherein Li in the glass auxiliary agent is contained in an amount of Li in mass% based on an oxide₂O content is 3% or less, and K₂The content of O is more than 5%.

5. The method for extending the life of the molten salt composition according to any one of claims 1 to 4, wherein the water content of the glass auxiliary agent is 5% or less.

6. The molten salt composition according to any one of claims 1 to 5, wherein the glass auxiliary agent has a plate shape.

7. The molten salt composition according to any one of claims 1 to 5, wherein the glass auxiliary agent is in the form of particles.

8. The molten salt composition according to any one of claims 1 to 7, wherein the chemical strengthening glass contains 1% or more of Li in mass% on an oxide basis₂O。

9. The molten salt composition according to any one of claims 1 to 8, wherein the chemical strengthening glass contains Na in an amount of 1% by mass or more based on an oxide₂O。

10. The method for extending the life of the molten salt composition according to any one of claims 1 to 9, wherein the molten salt composition contains a nitrate.

11. The molten salt composition according to any one of claims 1 to 10, wherein,

the method for extending the lifetime of a molten salt composition further comprises a step of removing the glass auxiliary agent having absorbed Li and/or Na from the molten salt composition, the step being performed within 24 hours from the step of adding the glass auxiliary agent to the molten salt composition.

12. A method for producing a chemically strengthened glass, comprising:

a step of immersing a glass auxiliary agent in a molten salt composition so that the glass auxiliary agent absorbs Li and/or Na contained in the molten salt composition, wherein SiO in the glass auxiliary agent is contained in an amount of mass% based on an oxide₂And Al₂O₃The total content of (A) is more than 60%;

a step of removing the glass auxiliary agent having absorbed Li and/or Na from the molten salt composition;

a step of producing a glass for chemical strengthening using the glass auxiliary agent taken out as a material; and

and a step of subjecting the glass for chemical strengthening to a chemical strengthening treatment.

13. The method for producing a chemically strengthened glass according to claim 12, wherein SiO in the glass auxiliary is in mass% on an oxide basis₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O is 95% or more.

14. A glass auxiliary agent for prolonging the life of a molten salt composition used in a chemical strengthening treatment of glass by absorbing Li ions and/or Na ions contained in the molten salt composition,

SiO in the glass auxiliary agent in mass percent based on oxide₂And Al₂O₃The total content of (a) is 60% or more.

15. The glass additive according to claim 14, wherein SiO in the glass additive is in mass% on an oxide basis₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O is 95% or more.

16. A raw material for glass, wherein the raw material for glass is glass, and SiO in the glass is calculated by mass% based on oxides₂、Na₂O and Li₂The total content of O is 95% or more, and Li₂O and Na₂The total content of O is 15% or more.

Technical Field

The present invention relates to a method for prolonging the life of a molten salt composition, a method for producing chemically strengthened glass, a glass auxiliary agent, and a raw material for glass.

Background

As protective glass for displays of portable terminals such as smartphones, glass having drop strength is required, and chemically strengthened glass having a high surface compressive stress value (CS) and a large depth of layer (DOL) is actively developed.

In the chemical strengthening treatment, the glass for chemical strengthening is immersed in the molten salt composition, and alkali metal ions having a small ionic radius in the glass for chemical strengthening are exchanged with alkali metal ions having a large ionic radius in the molten salt composition, whereby a compressive stress layer is formed on the surface of the glass for chemical strengthening, thereby obtaining the glass for chemical strengthening. If the molten salt composition after this treatment contains a sufficient amount of alkali metal ions having a large ionic radius, the molten salt composition can be reused as it is for chemical strengthening treatment of a new glass for chemical strengthening. However, the amount of ions having a large ionic radius in the molten salt composition is reduced and the amount of ions having a small ionic radius is increased by the chemical strengthening treatment, and therefore the number of times of use of the molten salt composition is limited.

In order to increase the number of times the molten salt composition is used, that is, to extend the life of the molten salt composition, a technique of adding an additive (auxiliary agent) to the molten salt composition is known. For example, patent document 1 discloses a technique of adding a Li-absorbing glass for chemical strengthening to a molten salt composition.

Patent document 2 discloses the following technique: na salt and K salt of different anions are added to the molten salt composition, and by reaction with them, ions having a small ionic radius in the molten salt composition are discharged out of the system as solid precipitates.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4410354

Patent document 2: japanese patent laid-open publication No. 2013-67555

Non-patent document

Non-patent document 1: kyokurang et al, "New glass and physical Properties thereof", first edition, Kabushiki Kaisha institute of systems and services, 8 month and 20 days in 1984

Disclosure of Invention

Problems to be solved by the invention

However, the Li absorbing glass described in patent document 1 and the Na salt and the K salt of the different anions described in patent document 2 react with water in the molten salt composition, and there is a problem that the pH of the molten salt composition increases. When the pH rises, OH^-The network of glass is cut to form precipitates on the surface of the glass, and the transparency of the glass is lowered. In recent years, in particular, in applications such as protective glass for displays of portable terminals, chemically strengthened glass is required to have a strength significantly higher than that of conventional glass, and the amount of ion exchange in chemical strengthening treatment is significantly larger than that of conventional glass such as glass for magnetic recording media described in patent document 1, for example. As the amount of ion exchange increases, chemical strengthening time is also required to be shortened, and strengthening at a higher temperature is required to shorten the strengthening time. The higher the temperature, the more significant the breaking of the glass network due to the increase in pH and the accompanying decrease in transparency of the glass, and therefore an auxiliary agent which is less likely to increase in pH than conventional Li absorbents is required.

In view of the above circumstances, an object of the present invention is to provide a method for prolonging the life of a molten salt composition, which can suppress an increase in pH of the molten salt composition.

It is another object of the present invention to provide an auxiliary agent used in the method for prolonging the life of the molten salt composition.

Further, the present invention aims to provide a method for producing chemically strengthened glass and a glass material, which can reduce production costs.

Means for solving the problems

That is, a method for prolonging the life of a molten salt composition of the present invention, which comprises applying the molten salt composition to a glass for chemical strengthening to be used in a chemical strengthening treatment of the glass for chemical strengtheningA step of adding a glass auxiliary agent to the molten salt composition, wherein SiO in the glass auxiliary agent is contained in an amount of mass% based on the oxide₂And Al₂O₃The total content of (a) is 60% or more.

In one embodiment of the method for prolonging the life of the molten salt composition of the present invention, the SiO in the glass auxiliary agent is in mass% on an oxide basis₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O may be 95% or more.

In one embodiment of the method for prolonging the life of the molten salt composition of the present invention, Li in the glass auxiliary agent is in mass% on an oxide basis₂The content of O may be 3% or less, and Na₂The content of O may be 5% or more.

In one embodiment of the method for prolonging the life of the molten salt composition of the present invention, Li in the glass auxiliary agent is in mass% on an oxide basis₂The content of O may be 3% or less, and K₂The content of O may be 5% or more.

In one embodiment of the method for prolonging the life of the molten salt composition of the present invention, the water content of the glass auxiliary may be 5% or less.

In one embodiment of the method for prolonging the life of the molten salt composition of the present invention, the glass auxiliary agent may be in the form of a plate.

In one embodiment of the method for prolonging the life of the molten salt composition of the present invention, the glass auxiliary agent may be in the form of particles.

In one embodiment of the method for prolonging the lifetime of the molten salt composition of the present invention, the chemical strengthening glass may contain 1% or more of Li in mass% based on oxides₂O。

In one embodiment of the method for prolonging the life of the molten salt composition of the present invention, the chemical strengthening glass may contain Na in an amount of 1% or more by mass on an oxide basis₂O。

In one embodiment of the method for prolonging the life of a molten salt composition of the present invention, the molten salt composition may contain a nitrate.

One embodiment of the method for prolonging the lifetime of a molten salt composition of the present invention further comprises a step of removing the glass auxiliary agent having absorbed Li and/or Na from the molten salt composition, and the step can be performed within 24 hours from the step of adding the glass auxiliary agent to the molten salt composition.

The method for producing chemically strengthened glass of the present invention comprises: a step of immersing the glass auxiliary agent in the molten salt composition so that the glass auxiliary agent absorbs Li and/or Na contained in the molten salt composition, wherein SiO in the glass auxiliary agent is in mass% based on oxides₂And Al₂O₃The total content of (A) is more than 60%; a step of removing the glass additive having absorbed Li and/or Na from the molten salt composition; a step of producing a glass for chemical strengthening using the glass auxiliary agent taken out as a material; and a step of subjecting the glass for chemical strengthening to a chemical strengthening treatment.

In one embodiment of the method for producing a chemically strengthened glass of the present invention, SiO in the glass auxiliary agent is in mass% based on an oxide₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O may be 95% or more.

The glass auxiliary agent of the present invention is used for prolonging the life of a molten salt composition used for chemical strengthening treatment of glass by absorbing Li ions and/or Na ions contained in the molten salt composition, wherein SiO in the glass auxiliary agent is contained in a mass% on an oxide basis₂And Al₂O₃The total content of (a) is 60% or more.

In one embodiment of the glass auxiliary of the present invention, SiO in the glass auxiliary is in mass% based on an oxide₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O may be 95% or more.

The glass of the present invention is made of glass as a raw material and is based on oxideIn% by weight, SiO in the glass₂、Na₂O and Li₂The total content of O is 95% or more, and Li₂O and Na₂The total content of O is 15% or more.

Effects of the invention

The method for prolonging the life of a molten salt composition of the present invention can suppress an increase in the pH of the molten salt composition.

Detailed Description

The method for extending the lifetime of the molten salt composition, the method for producing a chemically strengthened glass, and the glass auxiliary agent according to the present invention will be described below in detail with reference to embodiments, but the present invention is not limited to the following embodiments, and can be implemented by being arbitrarily modified within a range not departing from the gist of the present invention.

In the present specification, "%" in the content of glass components means mass% based on oxides.

In the present specification, when a range of numerical values is expressed by using "-" it means a range including numerical values described before and after the range as a lower limit value and an upper limit value.

In the present specification, "chemically strengthened glass" refers to glass after being subjected to a chemical strengthening treatment, and "glass for chemical strengthening" refers to glass before being subjected to a chemical strengthening treatment.

< glass auxiliary >

First, the glass auxiliary of the present embodiment will be explained. The glass auxiliary agent of the present embodiment is a glass auxiliary agent for reducing the concentration of small alkali metal ions contained in a molten salt composition used for chemical strengthening treatment of a glass for chemical strengthening, and increasing the concentration of large alkali metal ions to prolong the life of the molten salt composition. In the case where the molten salt composition is used for Li-Na exchange and/or Li-K exchange, the small alkali metal is Li, and in the case where the molten salt composition is used for Na-K exchange, the small alkali metal is Na. Further, in the case where the molten salt composition is used for Li-Na exchange, the large alkali metal is Na, and in the case where the molten salt composition is used for Li-K exchange and/or Na-K exchange, the large alkali metal is K.

SiO in the glass auxiliary of the present embodiment is in mass% based on oxides₂And Al₂O₃The total content of (c) is 60% or more. In addition, SiO in the glass auxiliary of the present embodiment₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O is preferably 95% or more.

The glass auxiliary of the present embodiment is in a glass state, SiO₂With Al₂O₃The total amount of (b) is 60% or more, so that the reaction with water in the molten salt is small, and the increase in pH of the molten salt composition can be suppressed. SiO of the glass auxiliary of the present embodiment₂With Al₂O₃The total amount of (A) is preferably 65% or more.

From inhibition by OH^-In view of the reduction in transparency of the glass, the pH of the molten salt composition to which the glass auxiliary agent of the present embodiment is added is preferably substantially neutral. Specifically, the pH of the molten salt composition after the addition of the glass auxiliary agent is preferably less than 7.9, more preferably 7.5 or less, and still more preferably 7.0 or less. The molten salt composition to which the glass auxiliary is added usually has a pH of 5.0 or more.

In addition, when the glass auxiliary of the present embodiment is SiO in the glass composition₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂When the total content of O is 95% or more, the effect of extending the life of the molten salt composition is particularly high, and elution of ions which inhibit chemical strengthening is particularly small, as described below, and therefore, the total content is preferable.

When the glass auxiliary agent is added to the molten salt composition containing small alkali metal ions, the ions of the large alkali metal in the glass auxiliary agent are exchanged (ion-exchanged) with the ions of the small alkali metal in the molten salt composition, the ions of the small alkali metal in the molten salt composition are absorbed by the glass auxiliary agent, and the ions of the large alkali metal in the glass auxiliary agent are released into the molten salt composition, thereby prolonging the life of the molten salt composition.

As a result of extensive studies, the present inventors have found that a glass containing an oxide containing an element having an atomic number of less than 20 as a main component, more specifically SiO₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The glass containing O as a main component has an excellent effect of prolonging the life of the molten salt. That is, it is found that the glass has an effect of absorbing ions of a small alkali metal in the molten salt composition and releasing ions of a large alkali metal to extend the life of the molten salt composition. Further, it is found that since ions which inhibit chemical strengthening are not easily eluted in the molten salt composition, the compressive stress value caused by chemical strengthening is not easily decreased. When the glass auxiliary agent contains a large amount of an element having an atomic number of 20 or more, the life prolonging effect of the molten salt composition is considered to be small for the following reason.

First, ions having a valence of 3 or 5 act as a network modifier for the glass auxiliary, but ions having a large size and an atomic number of greater than 20 are difficult to move in the Si skeleton, and when such elements are present, the movement of alkali metal ions in the glass auxiliary is inhibited, and thus the ion exchange amount is reduced.

Further, the 2-valent ions such as CaO and SrO do not significantly reduce the ion exchange amount of the glass auxiliary, but when eluted in the molten salt composition, they stay on the surface of the glass to be chemically strengthened, and hinder the chemical strengthening treatment. Therefore, even if a glass auxiliary agent containing a large amount of 2-valent ions is added to the molten salt composition, the life of the molten salt composition is not prolonged. Non-patent document 1 also discloses that ions such as CaO and SrO interfere with the chemical strengthening treatment.

Therefore, in order to ensure an excellent effect of extending the life of the molten salt, it is preferable that SiO, which is a component containing an element having an atomic weight of less than 20, be used as the glass auxiliary agent of the present embodiment₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O is set to 95% or more. In addition, the present embodimentSiO of glass auxiliary₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O is more preferably 96% or more, and still more preferably 98% or more, and the upper limit is not particularly limited, and may be 100%.

Preferred ranges of the contents of these components will be described below.

The optimum composition of the glass auxiliary can be roughly classified into two types according to the method of use. One is a composition in which chemical durability is prioritized over a small amount of alkali metal ion absorbed and a large amount of alkali metal ion released, that is, an ion exchange amount. Since the molten salt composition has excellent chemical durability, the reaction with water in the molten salt composition is reduced, and the increase in pH of the molten salt composition is suppressed. Therefore, more additives than ever can be added to the molten salt composition, and the life prolonging effect is improved compared with ever. On the other hand, there is also a composition in which the ion exchange amount is prioritized over chemical durability. By increasing the amount of ion exchange per unit amount of the auxiliary agent, the life prolonging effect is improved as compared with the conventional one. In addition, the above 2 examples are listed, but intermediate compositions thereof may be used.

Further, the optimum composition of the glass auxiliary agent varies depending on whether the small alkali metal ion to be ion-exchanged is Li or Na. The following description will be made in detail.

(first composition)

First, a preferable range of the composition of the glass auxiliary (hereinafter, also referred to as "first composition") in which chemical durability is prioritized when the small alkali metal ion is Li will be described.

SiO₂Is a component constituting the skeleton of the glass auxiliary.

In order to increase the stability of the glass auxiliary, the SiO of the glass auxiliary of the first composition₂The content of (b) is preferably 52% or more, more preferably 54% or more, and still more preferably 57% or more.

On the other hand, SiO as the glass auxiliary of the first composition is used for improving the meltability of the glass auxiliary₂In an amount ofPreferably 95% or less, more preferably 92% or less, and still more preferably 90% or less.

Na₂O is an indispensable component for Li-Na ion exchange.

Na as glass auxiliary agent of first composition for increasing ion exchange amount₂The content of O is preferably 5% or more, more preferably 9% or more, and further preferably 11% or more.

On the other hand, in Na₂When the content of O is excessive, chemical durability tends to be deteriorated. Na of glass auxiliary agent of first composition giving priority to chemical durability₂The content of O is preferably 25% or less, more preferably 22% or less, and further preferably 20% or less.

Al₂O₃Is a component that inhibits ion exchange of alkali metal ions, but is also a component that improves chemical durability. Al of glass auxiliary of first composition₂O₃The content of (b) may be 0%, but the glass auxiliary of the first composition may contain Al within a range in which the effects of the present invention are exerted₂O₃。

The glass auxiliary agent of the first composition contains Al₂O₃In the case of (3), Al is preferred₂O₃Relative to Na₂Proportion of O content (Al)₂O₃/Na₂O) is small, for example, preferably 2.0 or less, more preferably 1.5, and further preferably 1.1 or less. Al (Al)₂O₃The content of (b) is preferably 40% or less, more preferably 30% or less, and further preferably 20% or less.

To obtain sufficient chemical durability, SiO₂With Al₂O₃The total amount of (a) is preferably 65% or more, more preferably 70% or more, and still more preferably 75% or more. On the other hand, to increase the amount of ion exchange, SiO₂With Al₂O₃The total amount of (a) is preferably 95% or less, more preferably 92% or less, and still more preferably 90% or less.

P₂O₅、B₂O₃Although not essential, may be included in the glass of the first compositionIn the adjuvant. When the content of these components is too large, chemical durability is liable to deteriorate, and therefore the content of each of these components is preferably 10% or less, more preferably 5% or less, and further preferably 2% or less. The lower limit of the content of these components is not particularly limited, and may be 0%, but for the purpose of improving the meltability of the glass, it is preferably 0.1% or more, more preferably 0.5% or more, and still more preferably 1.0% or more.

MgO、K₂O, although not an indispensable component, may be contained in the glass auxiliary of the first composition. When the content of these components is too large, chemical durability is liable to deteriorate, and therefore the content of each of these components is preferably 15% or less, more preferably 10% or less, and further preferably 7% or less. The lower limit of the content of these components is not particularly limited, and may be 0%, but for the purpose of improving the meltability of the glass, it is preferably 1% or more, more preferably 3% or more, and still more preferably 5% or more.

In addition, when a large amount of Li is contained in the glass auxiliary₂In the case of O, ion exchange between Na ions in the glass auxiliary and Li ions in the molten salt is difficult to occur. Therefore, in order to ensure a sufficient amount of ion exchange in the glass auxiliary of the first composition, it is preferable to use Li₂The content of O is set to 3% or less. Li of glass auxiliary agent of first composition₂The content of O is more preferably 2% or less, and still more preferably 1% or less.

In addition, Li to the glass auxiliary of the first composition₂The lower limit of the content of O is not particularly limited, and may be 0%.

(second composition)

Next, a preferable range of the composition of the glass auxiliary (hereinafter, also referred to as "second composition") in which chemical durability is prioritized in the case where the small alkali metal ion is Na will be described. The glass auxiliary having the second composition can be ion-exchanged not only with Na as a small alkali metal ion but also with Li as a small alkali metal ion.

With respect to SiO₂、P₂O₅、B₂O₃Since MgO is the same as the first composition, the description thereof will be omitted.

Known as K₂O is an essential component for Na-K ion exchange and also contributes to K-Li ion exchange.

K of glass auxiliary agent of second composition for increasing ion exchange amount₂The content of O is preferably 5% or more, more preferably 9% or more, and further preferably 11% or more.

On the other hand, in K₂When the content of O is excessive, chemical durability tends to be deteriorated. K of glass auxiliary agent of second composition with priority on chemical durability₂The content of O is preferably 28% or less, more preferably 20% or less, and further preferably 16% or less.

Al₂O₃Is a component that inhibits ion exchange of alkali metal ions, but is also a component that improves chemical durability. Al of glass auxiliary of second composition₂O₃The content of (b) may be 0%, but the glass auxiliary of the second composition may contain Al within a range in which the effects of the present invention are exerted₂O₃。

The glass auxiliary agent of the second composition contains Al₂O₃In the case of (3), Al is preferred₂O₃In relation to K₂Proportion of O content (Al)₂O₃/K₂O) is small, for example, preferably 2.0 or less, more preferably 1.5, and further preferably 1.1 or less. Al (Al)₂O₃The content of (b) is preferably 40% or less, more preferably 30% or less, and further preferably 20% or less.

To obtain sufficient chemical durability, SiO₂With Al₂O₃The total amount of (a) is preferably 65% or more, more preferably 70% or more, and still more preferably 75% or more. On the other hand, to increase the amount of ion exchange, SiO₂With Al₂O₃The total amount of (a) is preferably 95% or less, more preferably 92% or less, and still more preferably 90% or less.

Li₂O is a component that exchanges Na ions in the molten salt composition. However, Li₂O-rich glass additive in absorption meltingWhen Na ions in the molten salt composition are melted, Li ions are released into the molten salt composition. Li ions in the molten salt composition have an effect of shortening the life of the molten salt composition, and are therefore not preferable components. Therefore, Li of the glass auxiliary of the second composition is preferable₂The content of O is small, specifically, Li being a glass auxiliary of the second composition₂The content of O is preferably 3% or less, more preferably 1.5% or less, and further preferably 0.5% or less. The glass auxiliary of the second composition may not contain Li₂O。

In addition, when a large amount of Na is contained in the glass auxiliary₂In the case of O, ion exchange between K ions in the glass auxiliary and Na ions in the molten salt composition hardly occurs. Therefore, in order to ensure a sufficient amount of ion exchange in the glass auxiliary agent of the second composition, Na is preferably added₂The content of O is set to 30% or less. Na of glass auxiliary agent of second composition₂The content of O is more preferably 25% or less, and still more preferably 20% or less. On the other hand, when a large amount of Na is contained in the glass auxiliary₂In the case of O, Na ions in the glass auxiliary agent may be ion-exchanged with Li ions in the molten salt composition, thereby extending the life of the molten salt composition. When the ion exchange between Li ions in the molten salt composition and Na ions in the glass auxiliary agent and the ion exchange between Na ions in the molten salt composition and K ions in the glass composition are both aimed, Na ions in the glass auxiliary agent of the second composition₂The O content is preferably 2% or more, more preferably 5% or more, and further preferably 10% or more.

Na for glass auxiliary agent of second composition₂The lower limit of the O content is not particularly limited, and may be 0%.

(third composition)

Next, a preferable range of the composition of the glass auxiliary (hereinafter, also referred to as "third composition") in which the ion exchange amount is prioritized when the small alkali metal ion is Li will be described.

SiO₂Is a component constituting the skeleton of the glass auxiliary.

SiO of glass auxiliary agent with third composition for improving stability of glass₂The content of (b) is preferably 55% or more, more preferably 60% or more, and further preferably 65% or more.

On the other hand, SiO, which is a glass auxiliary agent of the third composition, is used for improving the meltability of the glass₂The content of (b) is preferably 75% or less, more preferably 73% or less, and further preferably 69% or less.

Na₂O is an indispensable component for Li-Na ion exchange.

Na as glass auxiliary agent of third composition for increasing ion exchange amount₂The content of O is preferably 20% or more, more preferably 25% or more, and further preferably 30% or more.

On the other hand, in Na₂When the content of O is excessive, chemical durability tends to be deteriorated. Na of glass auxiliary agent of third composition₂The content of O is preferably 45% or less, more preferably 40% or less, and further preferably 35% or less.

Al₂O₃Is a component that interferes with ion exchange of alkali metal ions, and is also a component that improves chemical durability. Al of glass auxiliary of third composition₂O₃The content of (b) is preferably 0%, but the glass auxiliary of the third composition may contain Al within a range in which the effects of the present invention are exhibited₂O₃。

The glass auxiliary agent in the third composition contains Al₂O₃In the case of (3), Al is preferred₂O₃Relative to Na₂Proportion of O content (Al)₂O₃/Na₂O) is small, and is preferably 0.3 or less, more preferably 0.2, and further preferably 0.1 or less.

To obtain sufficient chemical durability, SiO₂With Al₂O₃The total amount of (a) is preferably 60% or more, more preferably 65% or more. On the other hand, to increase the amount of ion exchange, SiO₂With Al₂O₃The total amount of (a) is preferably 80% or less, more preferably 75% or less, and still more preferably 70% or less.

P₂O₅、B₂O₃Although not an essential component, the composition is,but may be included in the glass auxiliary of the third composition. When the content of these components is too large, chemical durability is liable to deteriorate, and therefore the content of each of these components is preferably 10% or less, more preferably 5% or less, and further preferably 2% or less. The lower limit of the content of these components is not particularly limited, and may be 0%, but for the purpose of improving the meltability of the glass, it is preferably 0.1% or more, more preferably 0.5% or more, and still more preferably 1.0% or more.

MgO、K₂O is not an indispensable component, but may be contained in the glass auxiliary of the third composition. When the content of these components is too large, chemical durability is liable to deteriorate, and therefore the content of each of these components is preferably 10% or less, more preferably 5% or less, and further preferably 3% or less. The lower limit of the content of these components is not particularly limited, and may be 0%, but for the purpose of improving the meltability of the glass, it is preferably 0.1% or more, more preferably 0.5% or more, and still more preferably 1% or more.

In addition, when a large amount of Li is contained in the glass auxiliary₂In the case of O, ion exchange between Na ions in the glass auxiliary and Li ions in the molten salt is difficult to occur. Therefore, in order to ensure a sufficient amount of ion exchange in the glass auxiliary of the third composition, it is preferable to use Li₂The content of O is set to 3% or less. Li of glass auxiliary agent of third composition₂The content of O is more preferably 2% or less, and still more preferably 1 or less.

In addition, Li to glass auxiliary of third composition₂The lower limit of the content of O is not particularly limited, and may be 0%.

(fourth composition)

Next, a preferable range of the composition of the glass auxiliary (hereinafter, also referred to as "fourth composition") in which the ion exchange amount is prioritized when the small alkali metal ion is Na is described. The glass auxiliary having the fourth composition can be ion-exchanged not only with Na as a small alkali metal ion but also with Li as a small alkali metal ion.

With respect to SiO₂、P₂O₅、B₂O₃Since MgO has the same composition as the third component, the description thereof is omitted.

Known as K₂O is an essential component for Na-K ion exchange and also contributes to K-Li ion exchange.

K of glass auxiliary agent of fourth composition for increasing Na absorption₂The content of O is preferably 20% or more, more preferably 25% or more, and further preferably 30% or more.

On the other hand, in K₂When the content of O is excessive, chemical durability tends to be deteriorated. K of glass auxiliary agent of fourth composition₂The content of O is preferably 45% or less, more preferably 40% or less, and further preferably 35% or less.

Al₂O₃Is a component that inhibits ion exchange of alkali metal ions, but is also a component that improves chemical durability. Al of glass auxiliary of fourth composition₂O₃The content of (b) may be 0%, but the glass auxiliary agent of the fourth composition may contain Al within a range in which the effects of the present invention are exerted₂O₃。

The glass auxiliary agent in the fourth composition contains Al₂O₃In the case of (3), Al is preferred₂O₃In relation to K₂Proportion of O content (Al)₂O₃/K₂O) is small, and is preferably 0.3 or less, more preferably 0.2, and further preferably 0.1 or less.

To obtain sufficient chemical durability, SiO₂With Al₂O₃The total amount of (a) is preferably 60% or more, more preferably 65% or more. On the other hand, to increase the amount of ion exchange, SiO₂With Al₂O₃The total amount of (a) is preferably 80% or less, more preferably 75% or less, and still more preferably 70% or less.

Li₂O is a component that exchanges Na ions in the molten salt composition. However, when Li is used₂When the glass auxiliary agent containing much O absorbs Na ions in the molten salt composition, Li ions are released into the molten salt composition. Li ions in molten salt compositions having shortened molten salt combinationsLife of the substance, therefore Li₂O is not a preferred component. Therefore, Li of the glass auxiliary of the fourth composition₂The smaller the content of O, the more preferable is, specifically, Li₂The content of O is preferably 3% or less, more preferably 1.5% or less, and further preferably 0.5% or less. The glass auxiliary of the fourth composition may not contain Li₂O。

In addition, when a large amount of Na is contained in the glass auxiliary₂In the case of O, ion exchange between K ions in the glass auxiliary and Na ions in the molten salt composition hardly occurs. Therefore, in order to secure a sufficient amount of ion exchange in the glass auxiliary agent of the fourth composition, Na is preferably added₂The content of O is set to 30% or less. Na of glass auxiliary agent of fourth composition₂The content of O is more preferably 25% or less, and still more preferably 20% or less. On the other hand, when a large amount of Na is contained in the glass auxiliary₂In the case of O, Na ions in the glass auxiliary agent may be ion-exchanged with Li ions in the molten salt composition, thereby extending the life of the molten salt. When the ion exchange between the Li ions in the molten salt composition and the Na ions in the glass auxiliary agent and the ion exchange between the Na ions in the molten salt composition and the K ions in the glass composition are aimed at the same time, Na of the glass auxiliary agent of the fourth composition₂The content of O is preferably 2% or more, more preferably 5% or more, and further preferably 10% or more.

Na for glass auxiliary agent of fourth composition₂The lower limit of the O content is not particularly limited, and may be 0%.

Next, other components will be described. The other components are similarly described in the case where chemical durability is prioritized, in the case where the ion exchange amount is prioritized, in the case where the small ion is Li ion, and in the case where the small ion is Na ion.

The glass auxiliary of the present embodiment may contain other components within a range in which the effects of the present invention are exhibited. For example, the glass auxiliary of the present embodiment may contain N, F, S, Cl or the like.

As described above, the total content of the elements having an atomic weight of 20 or more in the glass auxiliary of the present embodiment is preferably small, preferably 5% or less, more preferably 3% or less, and still more preferably 1% or less. Examples of the element having an atomic weight of 20 or more include Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, La, Gd, Ca, Sr, Ba, Zr, Ta, W, and the like.

Specific compositions of the glass auxiliary of the present embodiment include, for example, the following compositions (a) and (B).

Composition (A)

A glass auxiliary, comprising, in mass% on an oxide basis:

52 to 90 percent of SiO₂、

0 to 40% of Al₂O₃、

Less than 15% of MgO,

K of 15% or less₂O、

Less than 3% Li₂O、

5 to 25 percent of Na₂O、

Less than 10% of B₂O₃And, and

p of 10% or less₂O₅，

The total content of the above oxides is 95% or more, and SiO₂With Al₂O₃The total content of (A) is 65-95%.

Composition (B)

A glass auxiliary, comprising, in mass% on an oxide basis:

55 to 75 percent of SiO₂、

20 to 45 percent of Na₂O、

0.3 or less of Al₂O₃/Na₂O、

Less than 10% of MgO,

K of 10% or less₂O、

Less than 3% Li₂O、

Less than 10% of B₂O₃And, and

p of 10% or less₂O₅，

SiO₂With Na₂The total content of O is 95% or more, and SiO₂With Al₂O₃The total content of (A) is 60-80%.

In order to further suppress an increase in pH of the molten salt composition, the water content of the glass auxiliary agent of the present embodiment is preferably low, preferably 5% or less, more preferably 1% or less, and further preferably 0.1% or less.

The shape of the glass auxiliary agent of the present embodiment is not particularly limited, and may be, for example, a plate shape, a flake shape, or a granular shape (powder shape), and may be other shapes. When the glass auxiliary agent is in the form of a plate, it is preferable because it can be easily taken out from the molten salt composition. When the glass auxiliary is plate-shaped, the thickness is preferably 0.3mm or more, more preferably 0.5mm or more, and still more preferably 1.0mm or more. When the thickness is too large, the alkali metal ion absorption amount decreases, and therefore the thickness is preferably 5.0mm or less. The plate thickness is more preferably 3.0mm or less, and still more preferably 2.0mm or less.

On the other hand, when the glass auxiliary is in the form of particles, the workability is excellent, and therefore it is preferable. When the glass auxiliary is in the form of particles, the particle diameter is preferably 0.3mm or more, more preferably 0.5mm or more, and still more preferably 1.0mm or more. On the other hand, when the particle diameter is too large, the alkali metal ion absorption amount decreases, and therefore the particle diameter is preferably 5.0mm or less. The particle diameter is more preferably 3.0mm or less, and still more preferably 2.0mm or less. In the present specification, the particle diameter means an average diameter of particles.

< method for prolonging life of molten salt composition >

Next, a method for extending the life of the molten salt composition according to the present embodiment (hereinafter, also simply referred to as "the method for extending the life of the present embodiment" or "the method of the present embodiment") will be described. The method for extending the lifetime of a molten salt composition according to the present embodiment includes a step of adding the glass auxiliary according to the present embodiment to the molten salt composition used for the chemical strengthening treatment of glass.

According to the method for prolonging the life of a molten salt composition of the present embodiment, it is possible to suppress an increase in pH of the molten salt composition and sufficiently prolong the life of the molten salt composition.

The method for extending the lifetime of the present embodiment may be performed during the chemical strengthening treatment or may be performed during the period in which the chemical strengthening treatment is not performed. That is, the glass auxiliary agent may be added to the molten salt composition in which the chemical strengthening glass is immersed, or the glass auxiliary agent may be added to the molten salt composition in which the chemical strengthening glass is not immersed.

When the glass auxiliary agent is added, the glass auxiliary agent can be spread in a strengthening furnace, or placed in a box body and taken out, or poured into a box (カセット) of strengthened glass as a part of glass. When a case is used, it is preferable to use a case having a net structure so that the molten salt is brought into contact with the auxiliary. In addition, when the case is fixed in the cartridge, the auxiliary agent can be easily replaced at the time of taking out and putting in the chemically strengthened cartridge, and therefore, it is preferable.

In addition, since the ion exchange amount of the glass auxiliary added to the molten salt composition gradually decreases and the life prolonging effect of the molten salt composition decreases, in this case, it is preferable to take out the glass auxiliary from the molten salt composition. That is, the life extension method of the present embodiment preferably includes a step of taking out the glass auxiliary agent having absorbed small alkali metals (Li and/or Na) from the molten salt composition.

In order to improve the productivity of the chemically strengthened glass, the life extension method of the present embodiment is preferably performed in a short time. Therefore, in the method of the present embodiment, the step of taking out the glass auxiliary agent having absorbed a small alkali metal from the molten salt composition is preferably performed within 24 hours, more preferably within 10 hours, and even more preferably within 5 hours from the step of adding the glass auxiliary agent to the molten salt composition. In order to sufficiently prolong the molten salt composition in a short time as described aboveLifetime, preferably SiO₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂A glass auxiliary agent with a total content of O of more than 95%.

In the method for extending the lifetime of the present embodiment, the amount of the glass auxiliary agent to be added to the molten salt composition is not particularly limited, and may be appropriately adjusted depending on the total amount of the molten salt composition, the content of small alkali metal ions, the desired treatment time, and the like.

The temperature of the molten salt composition in the life extension method of the present embodiment may be a temperature at which the exchange of the small alkali metal ions in the molten salt composition and the large alkali metal ions in the glass auxiliary is performed, and is preferably 350 ℃ or more, more preferably 400 ℃ or more, and further preferably 420 ℃ or more, from the viewpoint of promoting the ion exchange. In view of the decomposition of the molten salt, the temperature of the molten salt composition is preferably 500 ℃ or lower, more preferably 475 ℃ or lower, and still more preferably 460 ℃ or lower.

The molten salt composition whose lifetime is extended by the method of the present embodiment may contain large alkali metal ions (Na ions and/or K ions), and the type thereof is not particularly limited, and usually contains a nitrate salt (sodium nitrate and/or potassium nitrate).

A glass for chemical strengthening which is chemically strengthened by a molten salt composition having a prolonged life by the method of the present embodiment will be described.

Glass for chemical strengthening as long as it contains Li₂O and/or Na₂Any glass may be used as long as it has a composition that can be strengthened by forming or chemical strengthening treatment. Examples of the glass for chemical strengthening include: aluminosilicate glass, soda-lime glass, borosilicate glass, lead glass, alkali barium glass, aluminoborosilicate glass, and the like. Specifically, for example, a glass containing 50 to 80% of SiO in terms of mole percentage based on oxides can be used as the glass for chemical strengthening₂2 to 25 percent of Al₂O₃0.1 to 20 percent of Li₂O、0.1 to 18 percent of Na₂O, 0 to 10% of K₂O, 0-15% MgO, 0-5% CaO, 0-5% P₂O₅0 to 5% of B₂O₃0 to 5% of Y₂O₃And 0 to 5% of ZrO₂。

In order to obtain a chemically strengthened glass having a high CS, a large DOL, and particularly a high strength by a chemical strengthening treatment, it is preferable to use a glass for chemical strengthening containing a large amount of small alkali metal to increase the amount of ion exchange at the time of chemical strengthening. Small alkali metals (Li) of glass for chemical strengthening which is chemically strengthened with molten salt composition having a prolonged lifetime by the method of the present embodiment₂O and/or Na₂O) may be 1% or more, 3% or more, or 5% or more, for example.

The thickness and shape of the glass for chemical strengthening are not particularly limited. The glass for chemical strengthening may have various shapes such as a flat plate shape having a uniform plate thickness, a shape having a curved surface at least on the front surface or the back surface, and a three-dimensional shape having a curved portion or the like, or may be subjected to shape processing according to the application, for example, mechanical processing such as cutting, end surface processing, and hole forming. Specific examples of the shape of the glass for chemical strengthening include a plate shape having a thickness of 0.3mm to 2.0 mm.

< method for producing chemically strengthened glass >

Next, a method for producing a chemically strengthened glass according to the present embodiment (hereinafter, also referred to as "the production method according to the present embodiment") will be described. The method for producing a chemically strengthened glass according to the present embodiment is a method for producing a chemically strengthened glass by recovering a glass auxiliary agent used in the method for prolonging the life of the molten salt composition, and using the recovered glass auxiliary agent as a material.

That is, the method for producing chemically strengthened glass of the present embodiment includes: a step of immersing the glass auxiliary agent in the molten salt composition so that the glass auxiliary agent absorbs small alkali metals (Li and/or Na) contained in the molten salt composition, wherein SiO in the glass auxiliary agent is contained in the molten salt composition in a mass% based on an oxide₂And Al₂O₃Sum of contents ofCalculated as more than 60 percent; a step of removing the glass auxiliary agent having absorbed small alkali metals (Li and/or Na) from the molten salt composition; a step of producing a glass for chemical strengthening using the glass auxiliary agent taken out as a material; and a step of subjecting the glass for chemical strengthening to a chemical strengthening treatment. In the above production method, SiO in the glass auxiliary agent is in mass% based on oxides₂、Al₂O₃、Na₂O、P₂O₅、B₂O₃MgO and K₂The total content of O is preferably 95% or more.

In the method for extending the lifetime of the molten salt composition according to the present embodiment, the small alkali metal ions that have moved from the glass for chemical strengthening into the molten salt composition are absorbed by the glass auxiliary agent, and the large alkali metal ions are released from the glass auxiliary agent into the molten salt composition. Therefore, the glass auxiliary agent after use (hereinafter also referred to as "used glass auxiliary agent") in the method for extending the life of the molten salt composition according to the present embodiment contains a large amount of small alkali metal. By using the used glass auxiliary agent as a material for a chemically strengthened glass, the amount of an expensive Li material or Na material can be reduced, and therefore, a chemically strengthened glass, and further a chemically strengthened glass, can be obtained at low cost.

In the step of causing the glass auxiliary agent to absorb the small alkali metal (Li and/or Na) contained in the molten salt composition, the glass auxiliary agent is added to the molten salt composition so that the glass auxiliary agent absorbs the small alkali metal contained in the molten salt composition. The detailed description is not repeated as in the description of the life prolonging method of the present embodiment.

The step of taking out the glass auxiliary agent having absorbed small alkali metals (Li and/or Na) from the molten salt composition in the manufacturing method of the present embodiment is the same as the step of taking out the glass auxiliary agent having absorbed small alkali metals (Li and/or Na) from the molten salt composition in the lifetime extension method of the present embodiment described above.

The method for producing the glass for chemical strengthening in the step of producing the glass for chemical strengthening using the glass auxiliary taken out (used glass auxiliary) as a material is not particularly limited, and examples thereof include the following methods: according to a desired composition, another glass material is appropriately mixed and melted with the used glass auxiliary agent, and the mixture is put into a continuous melting furnace, heated, melted, and clarified, and then supplied to a forming apparatus, and then the molten glass is formed into a sheet shape and slowly cooled. As a method of forming molten glass into a plate shape, for example, a float method is cited.

The used glass auxiliary agent is preferably made of SiO₂、Al₂O₃、MgO、Na₂O、K₂O、Li₂O、ZrO₂、TiO₂、ZnO、B₂O₃、P₂O₅And the like contained in the glass for chemical strengthening. When the used glass auxiliary contains a component not contained in the chemical strengthening glass, it is difficult to use the used glass auxiliary as a raw material (raw material) of the chemical strengthening glass. When the used glass auxiliary is used as a raw material for a glass for chemical strengthening, it is preferable that the kind of components (the number of components) contained in the used glass auxiliary is small. When the amount of the component is increased, the process of mixing with other glass materials becomes complicated when used as a raw material, and a burden is imposed on the process. For example, SiO is preferable as the composition of the glass auxiliary after use as the raw material of the glass for chemical strengthening₂、Na₂O、Li₂Glass containing 95% or more of total O. Na (Na)₂O and Li₂The total content of O is preferably 15% or more, more preferably 20% or more, and still more preferably 25% or more.

The chemical strengthening treatment method in the step of subjecting the glass for chemical strengthening to chemical strengthening treatment is also not particularly limited, and the type, temperature, treatment time, and the like of the molten salt composition to be used may be appropriately adjusted according to the desired compressive stress distribution.

Examples

Hereinafter, examples of the present invention will be specifically described, but the present invention is not limited thereto. In the examples, "ppm" means "mass ppm".

< production of glass auxiliary >

(glasses 1 and 2)

Glass sheets of the compositions shown in the columns of glasses 1 and 2 of table 1 were produced by the float process. The resulting glass plate was pulverized and classified, and particles which passed through a 2mm mesh but not through a 1mm mesh were collected to obtain granular glasses 1 and 2.

(glass 3 to 8)

Raw materials were prepared according to the compositions of glasses shown in glasses 3 to 8 in table 1, and the glass was melted by heating at 1600 to 1700 ℃ for 30 minutes, then the glass obtained by quenching with a rolling mill (rolout machine) was crushed and classified in the same manner as glass 1, to obtain granular glasses 3 to 8.

In the present specification, the shape of the glass obtained by rapid cooling using a rolling mill is referred to as "sheet shape", and the shape of the glass after classification is referred to as "granular shape".

(glass 9 to 13)

Sheet-like and granular glasses 9 to 13 were obtained by the same production method as that for glasses 3 to 8, using raw materials prepared in accordance with the compositions shown in glasses 9 to 13 in Table 2.

The water content of the obtained glass auxiliary was measured using a heat drying type moisture meter (manufactured by A & D, MS-70).

TABLE 1

TABLE 2

In experimental examples 1 to 14, the Li absorption effect was examined. Experimental examples 1, 4 to 9, and 12 to 14 are examples, and experimental examples 2, 3, 10, and 11 are comparative examples.

< Experimental example 1 >

(first chemical strengthening treatment Process)

The Li concentration (3000 p) was adjusted to an amount shown in the column of "Li before addition" in Table 3pm) is little blended with LiNO₃600g of NaNO₃Heated to 380 ℃ to melt it.

Using this molten salt composition, a sheet of "glass A" described later having a thickness of 0.6mm was immersed at 380 ℃ for 1 hour to obtain a chemically strengthened glass.

The stress distribution of the obtained chemically strengthened glass was measured using a measuring machine SLP1000 manufactured by kyowski ltd, which applied scattered light photoelasticity manufactured by kyowski ltd. CS, DOL are read from the resulting stress profile. The results are shown in the column "CS before addition" and "DOL before addition" in table 3.

(step of adding glass auxiliary)

The molten salt composition was added with the particulate glass 4 in an amount of 5 mass% based on the molten salt composition, and the mixture was held at 410 ℃ for 3 hours. Then, the molten salt composition is cooled and solidified.

The content of Li contained in the cured salt was measured by wet analysis. The measurement results are shown in the column "Li amount after addition" in table 2. Further, the Li trapping amount was calculated by subtracting the post-addition Li amount from the pre-addition Li amount. The results are shown in the column of "Li trapping amount" in table 3.

In addition, 2g of the cured salt was added to 20mL of pure water, and the pH was measured. The measurement results are shown in the column "pH of fortified salt" in table 3.

(second chemical strengthening treatment Process)

The cured salt was heated again to 380 ℃ and a sheet of "glass A" having a thickness of 0.6mm was immersed for 1 hour, whereby a chemically strengthened glass was obtained.

The stress distribution of the obtained chemically strengthened glass was measured using the SLP 1000. And reading CS and DOL according to the obtained stress distribution. The results are shown in the "CS after addition" column and the "DOL after addition" column of table 3.

(glass for chemical strengthening)

As the glass for chemical strengthening, a glass having the following composition in mol% based on oxides was used.

GlassA：SiO₂ 66.2％、Al₂O₃ 11.2％、Li₂O 10.4％、Na₂O 5.6％、K₂O1.5％、MgO 3.1％、CaO 0.2％、ZrO₂ 1.3％、Y₂O₃ 0.5％

And (3) glass B: SiO 2₂ 64.4％、Al₂O₃ 8.0％、Na₂O 12.5％、K₂O 4.0％、MgO10.5％、CaO 0.1％、SrO 0.1％、BaO 0.1％、ZrO₂ 0.5％

< Experimental examples 2 and 3 >

The same treatments and measurements as in experimental example 1 were carried out using glasses 7 and 8. The results are shown in table 3.

TABLE 3

< Experimental examples 4 to 11 >

The properties of glasses 1 to 8 as Li absorbents were examined by the same procedure as in experimental examples 1 to 3, and the results are shown in Table 4. The amount of the glass additive added was set to 17 mass% with respect to the molten salt. The temperature and time for immersing the glass auxiliary were set to 450 ℃ and 48 hours. Other test conditions were the same as in examples 1 to 3.

TABLE 4

< Experimental example 12 >

The characteristics of the granular and flaky glass 4 as a Li absorbent were examined according to the same procedure as in experimental example 1, and the results are shown in table 5. The amount of the glass additive added was set to 5 mass% with respect to the molten salt, and the time for immersing the Li absorber was changed from 12 hours to 96 hours. The dipping temperature was set to 450 ℃ for the granular glass auxiliary and 410 ℃ for the flaky glass auxiliary. The Li trapping amount and the pH of the molten salt after adding the glass auxiliary agent are shown in table 5.

TABLE 5

< Experimental example 13 >

The characteristics of the granular and flaky glass 4 as a Li absorbent were examined in accordance with the same procedure as in experimental example 12, and the results are shown in table 6. The glass auxiliary agent was immersed at 410 ℃ for 48 hours while changing the amount of the glass auxiliary agent within the range of 1.15 to 5 mass%. The Li trapping amount and the pH of the molten salt after adding the glass auxiliary agent are shown in table 6. The moisture content of the sheet-like glass 4 was measured, and as a result, the water content was 0.16.

TABLE 6

< Experimental example 14 >

Table 7 shows the CS and DOL before and after the addition of the glass auxiliary agent when the "glass a" is strengthened and the glass auxiliary agent is added according to the same procedure as in experimental example 1. LiNO was added in a small amount to give a Li concentration (3000ppm)₃600g of NaNO₃The glass was melted at 380 ℃ and the resulting melt was used as a molten salt, and the thickness of "glass A" was 0.55 mm. In the first and second chemical strengthening treatment steps, the "glass a" is strengthened by immersion in a molten salt at 410 ℃ for 4 hours. The glass additive was immersed in the molten salt composition at 410 ℃ for 24 hours using the particulate glass 11 as the glass additive. The conditions other than these were the same as in experimental example 1.

TABLE 7

	Experimental example 14
		Glass auxiliary agent composition	Glass 11
Glass additive shape	Granular form
		Glass auxiliary agent content (%)	0.65
CS (MPa) before addition	187
		DOL (μm) before addition	106
CS (MPa) after addition	226
		DOL (μm) after addition	104
pH of fortified salt	6.0
		Amount of Li (ppm) before addition	3000
Amount of Li (ppm) after addition	2001
		Li Capture amount (ppm)	999

According to table 3, in experimental examples 2 and 3, the pH increased after the addition of the glass auxiliary agent. On the other hand, in experimental example 1, even after the addition of the glass auxiliary, the pH was within the preferable range of less than 7.9, and was substantially neutral. In addition, in experimental examples 2 and 3, although the effect of reducing Li in the molten salt by adding the glass assistant was observed, CS after adding the glass assistant was slightly lower than CS before adding the glass assistant. It is considered that the multivalent ions eluted from the glass auxiliary agent act as ions that inhibit chemical strengthening. DOL did not change significantly before and after addition of the glass auxiliary.

In table 4 in which the addition amount of the glass auxiliary agent was further increased to extend the glass auxiliary agent impregnation time, in experimental examples 10 and 11, the pH after the addition of the glass auxiliary agent was further increased. On the other hand, in experimental examples 4 to 9, although the amount of the glass auxiliary added was large, the pH after addition was in a preferable range of less than 7.9 and was neutral among all the glass auxiliary. In all examples, the Li absorption effect was confirmed, and in experimental examples 4, 7, 8, and 9, the CS was confirmed to be significantly increased by the addition of the glass auxiliary agent.

In tables 5 and 6, the granular glass auxiliary agent (Li absorber) and the flaky glass auxiliary agent (Li absorber) were compared using glass 4, and table 5 changed the immersion time with the addition amount fixed, and table 6 changed the addition amount with the strengthening time fixed. In either table, there was no large difference in the Li trapping amount between the granular glass and the flaky glass. In addition, in all experiments, the pH after addition was essentially neutral.

In addition, according to Table 7, in Experimental example 14, NaNO was added by adding glass 11₃Li in the molten salt is reduced and CS after addition is increased. The pH of the molten salt after the addition was neutral.

< Experimental examples 15 to 18 >

In experimental examples 15 to 18, the Na absorption effect was examined. Experimental examples 15 to 17 are examples, and experimental example 18 is a comparative example.

(first chemical strengthening treatment Process)

NaNO was added in a small amount to give a Na concentration (5400ppm) in the amount shown in the column of "Na amount before addition" in Table 8₃KNO of 600g₃Heated to 380 ℃ to melt it.

Using the molten salt composition, a sheet of "glass B" having a thickness of 2.0mm was immersed at 435 ℃ for 1 hour, thereby obtaining a chemically strengthened glass.

The stress distribution of the obtained chemically strengthened glass was measured by using a measuring machine FSM6000LE manufactured by yokugaku corporation. And reading CS and DOL according to the obtained stress distribution. The results are shown in the column "CS before addition" and "DOL before addition" in table 8.

(step of adding glass auxiliary)

9 to 12% by mass of a granular or flaky glass is added to the molten salt composition in an amount of 5% by mass of the molten salt composition, and the mixture is held at 435 ℃ for 24 hours. The composition, shape and water content of the glass auxiliary used are shown in Table 8.

Then, the molten salt composition was cooled and solidified, and the Na content in the solidified salt was measured by wet analysis. The measurement results are shown in the column "Na amount after addition" in table 8. Further, the Na trapping amount was calculated by subtracting the Na amount after addition from the Na amount before addition. The results are shown in the column "Na trapping amount" in Table 8.

In addition, 2g of the cured salt was added to 20mL of pure water, and the pH was measured. The measurement results are shown in the column "pH of fortified salt" in Table 8.

(second chemical strengthening treatment Process)

The cured salt was heated again to 435 ℃ and a sheet of "glass B" having a thickness of 2.0mm was immersed for 1 hour, thereby obtaining a chemically strengthened glass.

The stress distribution of the obtained chemically strengthened glass was measured using FSM6000LE described above. And reading CS and DOL according to the obtained stress distribution. The results are shown in the "CS after addition" column and the "DOL after addition" column of table 8.

TABLE 8

	Experimental example 15	Experimental example 16	Experimental example 17	Experimental example 18
					Glass auxiliary agent composition	Glass 9	Glass 10	Glass 11	Glass 12
Glass additive shape	Sheet-like shape	Sheet-like shape	Granular form	Sheet-like shape
					Glass auxiliary agent content (%)	1.75	1.46	0.65	-
CS (MPa) before addition	761	-	-	-
					DOL (μm) before addition	26	-	-	-
CS (MPa) after addition	765	763	778	790
					DOL (μm) after addition	25	26	25	25
pH of fortified salt	6.2	5.4	6.0	8.7
					Na amount (ppm) before addition	5400	-	-	-
Na amount (ppm) after addition	4653	5310	4550	3528
					Na Capture amount (ppm)	747	90	850	1872

According to Table 8, the Na absorption effect was confirmed by adding glass aids 9 to 12. However, in experimental example 18, the pH increased after the addition of the glass auxiliary agent. On the other hand, in experimental examples 15 to 17, the pH after adding the glass auxiliary agent was within a preferable range of less than 7.9 and was substantially neutral.

Although the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. The present application is based on the japanese patent application filed on 26.4.2019 (japanese patent application 2019-086234), the content of which is incorporated in the present application by reference.