CN110891912A

CN110891912A - Glass for chemical strengthening and chemically strengthened glass

Info

Publication number: CN110891912A
Application number: CN201880046870.9A
Authority: CN
Inventors: 李清; 大原盛辉; 秋叶周作
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2017-07-18
Filing date: 2018-07-12
Publication date: 2020-03-17
Also published as: WO2019017278A1

Abstract

The purpose of the present invention is to provide a glass for chemical strengthening which has a thermal expansion coefficient of the same degree as that of a conventional soda-lime glass and a high-temperature viscosity of the same degree as that of the conventional soda-lime glass, and which can achieve high strength by chemical strengthening treatment. The present invention relates to a glass for chemical strengthening having a specific composition and an average linear thermal expansion coefficient of 75X 10 in the range of 50 ℃ to 350 ℃^‑7/K～95×10^‑7/K。

Description

Glass for chemical strengthening and chemically strengthened glass

Technical Field

The present invention relates to chemically strengthened glass.

Background

Chemically strengthened glass is widely used as cover glass for information equipment having a touch panel display, and the like. Chemically strengthened glass is glass obtained by forming a compressive stress layer on the surface of glass by ion exchange treatment. The properties of chemically strengthened glass are generally expressed in terms of surface Compressive Stress (CS) and Depth of Compressive stress (DOL).

When a conventional soda-lime glass is subjected to chemical strengthening treatment, a chemically strengthened glass having a compressive stress CS of 400MPa to 600MPa and a compressive stress depth DOL of about 6 μm to about 10 μm is obtained. However, such glass may have insufficient strength depending on the application.

Therefore, in order to improve the strength of chemically strengthened glass, aluminosilicate glass which is easily ion-exchanged has been developed. When the aluminosilicate glass is subjected to chemical strengthening treatment, for example, a chemically strengthened glass having a CS of 700MPa to 850MPa and a DOL of 20 μm to 100 μm is obtained. However, aluminosilicate glass has high viscosity at high temperature, and thus has poor productivity.

Thus, an Al is proposed₂O₃Soda-lime glass having a higher content than conventional soda-lime glass and having high ion exchange performance like aluminosilicate glass (see patent document 1).

Documents of the prior art

Patent document

Patent document 1: international publication No. 2014/122934

Disclosure of Invention

Problems to be solved by the invention

The glass described in patent document 1 contains Al in a larger amount than the conventional soda-lime glass₂O₃And has high-temperature viscosity equivalent to that of conventional soda-lime glass. This is considered to be due to the high content of the alkali metal oxide. Specifically, the Na content is 18 to 24 mass%₂O, and therefore a coefficient of thermal expansion of 95X 10^-7More than K. That is, the thermal expansion coefficient is larger than that of the conventional soda-lime glass. Therefore, when used in place of the conventional soda-lime glass, there is a problem that dimensional variation occurs due to temperature changeTo a problem of (a).

The purpose of the present invention is to provide a glass for chemical strengthening which has a thermal expansion coefficient of the same degree as that of a conventional soda-lime glass and a high-temperature viscosity of the same degree as that of the conventional soda-lime glass, and which can achieve high strength by chemical strengthening treatment.

Means for solving the problems

The present invention provides a glass for chemical strengthening, which is represented by mass percentage based on oxides and contains: 62 to 68 percent of SiO₂7 to 12 percent of Al₂O₃15 to 18 percent of Na₂O, 0 to 2 percent of K₂O, 7 to 12 percent of MgO, 0 to 2 percent of CaO, and 0.1 to 2 percent of ZrO₂15 to 18% of total alkali metal oxide and 7 to 14% of total alkaline earth metal oxide, wherein the chemical strengthening glass has an average coefficient of thermal expansion CTE of 75 x 10 within a temperature range of 50 to 350 DEG C^-7/K～95×10^-7and/K. The present invention also provides a chemically strengthened glass obtained from the above glass for chemical strengthening.

Effects of the invention

According to the present invention, a glass for chemical strengthening having a thermal expansion coefficient similar to that of a conventional soda-lime glass and a high-temperature viscosity similar to that of the conventional soda-lime glass can be obtained, and a high strength can be obtained by chemical strengthening treatment. Further, a chemically strengthened glass having a thermal expansion coefficient similar to that of conventional soda-lime glass and a high-temperature viscosity similar to that of conventional soda-lime glass can be obtained.

Detailed Description

The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented within a range not departing from the gist of the present invention. In the present specification, the term "%" means "% by mass" and "to" means not less than the lower limit and not more than the upper limit.

The chemical strengthening glass (untreated glass) of the present embodiment contains, as represented by mole percentage based on oxides: 62 to 68 percent of SiO₂7 to 12 percent of Al₂O₃15 to 18 percent of Na₂O, 0 to 2 percent of K₂O, 7 to 12 percent of MgO, 0 to 2 percent of CaO, and 0.1 to 2 percent of ZrO₂. Here, the glass for chemical strengthening is a glass that can be ion-exchanged and is suitable for chemical strengthening treatment.

The composition of the untreated glass will be described below.

SiO₂Is a component constituting the network structure of the glass, and SiO₂Is an essential component. To ensure the stability and weatherability of the glass, SiO₂The content of (b) is 62% or more, preferably 63% or more, and more preferably 63.5% or more. SiO for lowering the melting temperature of glass and thereby enabling an improvement in productivity₂The content of (b) is 68% or less, preferably 67% or less, more preferably 66% or less, and further preferably 65% or less.

Al₂O₃Is a component for improving the ion exchange performance during the chemical strengthening treatment, and is used for increasing the surface compressive stress CS and Al after the chemical strengthening treatment₂O₃The content of (b) is 7% or more, preferably 8% or more, more preferably 8.5% or more, and further preferably 9% or more. In the case of producing the glass by the float method, Al₂O₃When the content of (b) is 7% or more, it is preferable because tin can be prevented from entering the glass from the float furnace during float forming.

In addition, Al is used for lowering the devitrification temperature of the glass and facilitating the forming₂O₃The content of (b) is 12% or less, preferably 11% or less, more preferably 10% or less, and further preferably 9% or less.

Na₂O is a component for forming a surface compressive stress layer by ion exchange at the time of chemical strengthening treatment, and Na₂O is an essential component. To increase the surface compressive stress CS and increase the depth DOL, Na of the compressive stress after chemical strengthening₂The content of O is 15% or more, preferably 16% or more, and more preferably 16.5% or more. To maintain the weatherability of the glass, Na₂The content of O is 18% or less, preferably 17.5% or less.

K₂O is not an essential component, but K may be contained in an amount of at most 2% in order to increase the ion effect rate during the chemical strengthening treatment and increase the depth DOL of the compressive stress after the chemical strengthening treatment₂And O. In the presence of K₂In the case of O, K is used to obtain the above-mentioned effects₂The content of O is preferably 0.1% or more, more preferably 0.3% or more. K₂When the content of O is too large, the surface compressive stress CS after chemical strengthening is not easily increased. In addition, the thermal expansion coefficient may increase. K₂The content of O is preferably 1.5% or less, more preferably 1% or less, and further preferably 0.7% or less.

Selected from the group consisting of Li₂O、Na₂O and K₂The alkali metal oxide in the group consisting of O improves the meltability of the glass and increases the thermal expansion coefficient. Therefore, their total amount is 15% to 18%. In order to reduce the thermal expansion coefficient, 17.5% or less is preferable.

Na₂O and K₂The total amount of O is preferably 15% to 18%, more preferably 17.5% or less.

In order to improve the chemical strengthening property and the meltability, Al is preferable₂O₃、ZrO₂And Na₂Al in total of O content₂O₃+ZrO₂+Na₂O is much. Al (Al)₂O₃+ZrO₂+Na₂O is preferably 24.5% or more, more preferably 25% or more, further preferably 25.5% or more, and particularly preferably 26% or more. On the other hand, Al₂O₃+ZrO₂+Na₂When O is large, devitrification and chemical durability are deteriorated. In addition, brittleness is deteriorated. Al (Al)₂O₃+ZrO₂+Na₂O is preferably 31% or less, more preferably 29% or less, further preferably 28.5% or less, and particularly preferably 28% or less.

In the alkali metal oxides, Li₂O tends to reduce the surface compressive stress CS after chemical strengthening, and therefore the content thereof is preferably less than 1%, more preferably 0.1% or less, and preferably Li is not contained₂O。

MgO is a component for improving the stability of glass, tends to improve ion exchange performance for chemical strengthening, and contains 7% or more of MgO. In order to obtain a sufficient effect, the content of MgO is preferably 7.5% or more, and more preferably 8% or more. When the content of MgO is too large, the glass is easily devitrified, or the ion exchange rate in the chemical strengthening treatment is lowered. In order to obtain stability and chemical strengthening treatment characteristics of the glass, the content of MgO is 12% or less, preferably 11% or less, more preferably 10% or less, and further preferably 9% or less.

CaO is not an essential component, but may be contained in an amount of at most 2% in order to reduce the high-temperature viscosity of the glass. When CaO is excessive, the glass is easily devitrified and ion exchange is inhibited in the chemical strengthening treatment. The content of CaO is preferably 1% or less, more preferably 0.5% or less.

MgO, CaO, SrO and BaO are collectively called alkaline earth metal oxides, and are components that lower the high-temperature viscosity of the glass and facilitate melting, and the total content of the alkaline earth metal oxides is 7% or more. The total amount of the alkaline earth metal oxide is 14% or less, preferably 12% or less, more preferably 10% or less, and still more preferably 9% or less, in order to suppress devitrification and increase the ion exchange rate.

In order to increase the surface compressive stress CS after chemical strengthening, at least 0.1% of ZrO is contained₂Preferably, it contains ZrO in an amount of 0.5% or more₂More preferably, at least 1% of ZrO₂。ZrO₂When the content of (A) is too large, there is a possibility that the liquidus temperature T of the glass may be too high_LBecomes too high. For maintaining the stability of the glass, ZrO₂The content of (b) is 2% or less, preferably 1.5% or less, and more preferably 1% or less.

The untreated glass may contain other components within a range not impairing the object of the present invention. The content of the other components is preferably 4% or less in total, more preferably 1% or less in total, and further preferably 0.5% or less in total. Examples of such other components are described below.

For example, sulfate, chloride, fluoride, or the like may be appropriately contained as a fining agent at the time of melting.

In addition, Fe may be contained₂O₃. Due to the large amount of Fe existing in nature₂O₃Therefore, it is difficult to make the content zero, and Fe is usually contained in an amount of 0.005% or more₂O₃. Due to Fe₂O₃Produces a blue or green coloration, so that Fe is added in the case where it is desired to suppress the coloration₂O₃The content of (b) is preferably 1% or less, more preferably 0.2% or less.

May contain TiO₂. Due to TiO₂Yellow coloration is produced, and therefore TiO is used for suppressing the coloration₂The content of (b) is preferably 1% or less, more preferably 0.5% or less, and further preferably 0.2% or less.

In order to improve the meltability of the glass, ZnO may be contained in an amount of at most 2%. However, when glass is formed by the float method, ZnO is reduced in the float furnace, and defects are likely to occur in the product, and therefore, it is preferable that ZnO is not contained.

The untreated glass has an average coefficient of thermal expansion CTE in the range of 50 ℃ to 350 ℃ of 75X 10^-7/K～95×10^-7The CTE of chemically strengthened glass is also the same. Since the CTE is about the same as that of the conventional soda-lime glass, when the glass is used in place of the conventional soda-lime glass, dimensional variation is not easily generated even when the temperature is changed, and handling is easy. The average coefficient of thermal expansion CTE is preferably 94.5X 10^-7and/K is less than or equal to. In addition, the average coefficient of thermal expansion CTE is preferably 80X 10^-7More preferably 85X 10,/K or more^-7More than K.

When the glass transition temperature Tg of the untreated glass is 560 ℃ or higher, it is preferable from the viewpoint of heat resistance. When the untreated glass is used after being bent, the glass transition temperature Tg of the untreated glass is more preferably 570 ℃ or higher from the viewpoint of easily obtaining a desired shape.

The viscosity of the glass reaches 10²Temperature T at dPa · s₂Preferably 1530 ℃ or lower. Temperature T₂Is one of the indexes of the manufacturing characteristics of glass, and is a standard of the temperature required for melting the glass raw material. Temperature T₂More preferably 1525 ℃ or lower. Typically, 1460 ℃ or higher.

The viscosity of the glass reaches 10⁴Temperature T at dPa · s₄Preferably 1130 ℃ or lower. Temperature T₄One of the indices of the glass production characteristics is the temperature at which the glass is formed. Temperature T for improving glass manufacturing efficiency₄More preferably 1120 ℃ or lower, and still more preferably 1100 ℃ or lower. Temperature T₄If the amount is too low, the glass may be easily devitrified during the forming. To prevent devitrification during forming, T₄Preferably 1000 ℃ or higher, more preferably 1040 ℃ or higher, and still more preferably 1060 ℃ or higher.

Temperature T₄Relative to the temperature T of the liquid phase_LWhen the amount is too low, devitrification is likely to occur during glass forming. Thus, the temperature T₄Temperature T of liquid phase_LDifference of difference T₄-T_LPreferably-50 ℃ or higher, more preferably-30 ℃ or higher, and still more preferably-10 ℃ or higher. In the case of using the float method in glass forming, T₄-T_LPreferably 0 ℃ or higher, more preferably 10 ℃ or higher, and still more preferably 20 ℃ or higher.

The shape of the untreated glass is not particularly limited, but is preferably a plate shape from the viewpoint of facilitating chemical strengthening treatment. As a method for forming the sheet-like article, a known method such as a float method or a fusion method can be used. A large-sized glass sheet with high precision can be efficiently obtained by the float method, and is particularly preferable. The thickness of the plate when formed into a plate shape is not particularly limited, and is, for example, 0.15mm to 6 mm. When the thickness is 1.3mm or more, for example, the chemical strengthening may be performed after the physical strengthening. The plate thickness in this case is preferably 1.5mm or more, more preferably 1.8mm or more. The thickness when used for a laminated glass described later is, for example, 1.1mm or less, preferably 0.8mm or less, and more preferably 0.5mm or less.

The untreated glass may be used after being formed into a flat plate shape and then bent. When bending, a flat plate-shaped glass is heated and bent using a mold or the like. The bent glass may be laminated to form a laminated glass.

The chemically strengthened glass is obtained by subjecting the untreated glass to a chemical strengthening treatment.

The chemical strengthening treatment is a treatment in which alkali metal ions in the glass and alkali metal ions in the molten salt are ion-exchanged by a method such as immersing the glass plate in a molten salt containing alkali metal ions having a large ionic radius. A compressive stress layer is formed on the surface of the glass by ion exchange between alkali metal ions having a small ionic radius in the glass and alkali metal ions having a large ionic radius in the molten salt.

As a method of the chemical strengthening treatment, for example, a glass plate is immersed in a molten potassium nitrate salt at 330 to 550 ℃ for 5 minutes to 20 hours. The treatment conditions for chemical strengthening are appropriately selected in consideration of the thermal characteristics, the application, the shape, and the like of the glass.

Examples of the molten salt used for the chemical strengthening treatment include: potassium nitrate, cesium nitrate, silver nitrate, potassium sulfate, potassium chloride, and the like. These molten salts may be used alone, or a plurality of molten salts may be used in combination. In addition, sodium salt may be added for adjusting chemical strengthening property.

The chemically strengthened glass preferably contains one or more ions selected from the group consisting of potassium ions, cesium ions, rubidium ions, and silver ions in the surface layer. The inclusion of these ions generates compressive stress on the surface. In addition, when silver ions are contained, antibacterial properties can be imparted.

The chemically strengthened glass has a compressive stress layer on the surface. The surface compressive stress CS is preferably 700MPa or more. The chemically strengthened glass has a large surface compressive stress and is not broken even by a strong tensile stress.

The depth DOL of the compressive stress of the chemically strengthened glass is preferably 12 μm or more, more preferably 13 μm or more, still more preferably 15 μm or more, and particularly preferably 17 μm or more. Since chemically strengthened glass is easily broken when damage exceeding the depth of DOL occurs, it is preferable that DOL is large in order to prevent breakage. On the other hand, when DOL is too large, cutting of the chemically strengthened glass becomes difficult. In order to cut the chemically strengthened glass, DOL is preferably 40 μm or less, and more preferably 35 μm or less.

The surface compressive stress and the depth of compressive stress can be measured by using a surface stress meter.

The use of the chemically strengthened glass is not particularly limited. For example, the present invention can be used for a protective glass for a portable display such as a mobile phone including a smartphone and a tablet terminal, a protective glass for an instrument, a protective glass for a cooking utensil, a lighting device, a showcase, or the like. Further, the glass is also suitable for use in a double glazing for buildings and houses, and a solar cell substrate.

The chemically strengthened glass of the present invention is also suitable as a laminated glass for use in automobiles and the like. When used for laminated glass, untreated glass may be bent and then strengthened and bonded. Further, two chemically strengthened glass plates may be bonded, or the chemically strengthened glass plate may be bonded to another glass plate. The untreated glass sheet may also be adhered.

Examples

Examples 1 to 19 are examples, and examples 20 to 24 are comparative examples. Glasses of examples 1 to 17, 23 and 24 were produced by the following methods. Examples 18 to 22 are calculation examples.

The usual glass raw materials were appropriately selected to obtain SiO in tables 1 to 3₂～ZrO₂The glass composition shown in the column by mass percentage was prepared by charging a platinum crucible with a glass raw material prepared so as to obtain about 900g of glass, melting the glass raw material in an electric furnace maintained at about 1600 ℃ for 4 hours, and homogenizing the molten glass.

A glass block was obtained by the following method: the resulting molten glass was poured into a mold, held at a temperature higher than the respective glass transition temperatures Tg by about 50 ℃ for 1 hour, and then cooled to around room temperature at a cooling rate of 1K/min. The obtained glass block was cut, ground, and mirror-polished to obtain a glass plate (glass for chemical strengthening) of 40mm × 40mm × 1 mmt.

Further, the specific gravity, coefficient of thermal expansion CTE, glass transition temperature Tg, temperature T were measured by the method described later using the remaining glass gob as far as possible₂、T₄And temperature of liquid phaseT_L. The numerical values shown in parentheses are estimated values, and the blank column indicates no evaluation. The results are shown in tables 1 to 3.

The obtained glass plate was immersed in a molten salt containing 97.8% potassium nitrate and 2.2% sodium nitrate at 425 ℃ for 2.5 hours, thereby obtaining a chemically strengthened glass. For the obtained chemically strengthened glass, the surface compressive stress CS and the depth of compressive stress DOL were measured using a surface stress meter (FSM-6000) manufactured by yokuwa corporation. In this case, the numerical values shown in parentheses are estimated values. The results are shown in tables 1 to 3.

Other evaluation methods are described below.

(coefficient of thermal expansion CTE and glass transition temperature Tg)

The average thermal expansion coefficient in the range of 50 to 350 ℃ was measured at a temperature rising rate of 5K/min based on JIS R1618(2002) using a thermal expansion meter (TD5000SA) manufactured by BRUKER AXS. The glass transition temperature Tg was determined from the obtained thermal expansion curve.

(specific gravity)

The specific gravity was measured by the archimedes method.

(T₂And T₄)

T₂And T₄Determined on the basis of ISO7884-2(1987) using a rotary viscometer.

(temperature of liquid phase T_L)

The glass was pulverized using a mortar to obtain glass particles of 2mm to 4 mm. The glass particles were arranged in a platinum boat and kept in a temperature gradient furnace for 24 hours. After cooling, the presence or absence of crystal precipitation was observed by a microscope. The maximum value of the temperature at which the crystallized glass particles are arranged is defined as T_L。

TABLE 1

TABLE 2

TABLE 3

As shown in tables 1 to 3, examples 1 to 19 as examples have thermal expansion coefficients and high-temperature viscosities similar to those of conventional soda lime glass, and high strength was obtained by chemical strengthening treatment.

On the other hand, examples 20 to 22 as comparative examples have a large content of alkali metal oxide and a large thermal expansion coefficient. Further, example 23 as a comparative example is an example of aluminosilicate-based chemically strengthened glass, and it is known that: due to Al₂O₃Large content, therefore T₂And T₄High, there is a difficulty in productivity. This glass obtained high CS and very large DOL by chemical strengthening, but was difficult to cut after strengthening because DOL was too large.

In addition, example 24 as a comparative example is an example of a conventional soda-lime-based chemically strengthened glass, and Al is used for the reason₂O₃Since the content is small, CS and DOL after the strengthening are small, and the performance as a strengthened glass is insufficient.

The present invention has been described in detail with reference to the specific embodiments, but it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. The present application is based on japanese patent application published on 7/18/2017 (japanese patent application 2017-. In addition, all references cited are incorporated into this application in their entirety.

Industrial applicability

The chemically strengthened glass obtained from the glass for chemical strengthening of the present invention can be suitably used for a display device, particularly a cover glass of a touch panel display. Further, the glass is also suitable for use in a double glazing for buildings and houses, and a solar cell substrate.

Claims

1. A glass for chemical strengthening, which comprises, in mass percent based on oxides:

62 to 68 percent of SiO₂、

7 to 12 percent of Al₂O₃、

15 to 18 percent of Na₂O、

0% -2% of K₂O、

7 to 12 percent of MgO,

0 to 2 percent of CaO,

0.1% -2% of ZrO₂，

The total amount of alkali metal oxide is 15-18%,

the total amount of the alkaline earth metal oxide is 7 to 14 percent,

the glass for chemical strengthening has an average linear thermal expansion coefficient of 75X 10 in the range of 50 to 350 DEG C^-7/K～95×10^-7/K，

The alkali metal oxide is selected from Li₂O、Na₂O and K₂O, and the alkaline earth metal oxide is one or more selected from the group consisting of MgO, CaO, SrO and BaO.

2. The glass for chemical strengthening as claimed in claim 1, wherein Na is represented by mass percentage based on oxide₂O and K₂The total content of O is 15 to 18 percent.

3. The glass for chemical strengthening as claimed in claim 1 or 2, wherein Al is represented by mass percentage based on oxide₂O₃、ZrO₂And Na₂The total content of O is 25% or more.

4. The glass for chemical strengthening as claimed in any one of claims 1 to 3, wherein the glass viscosity of the glass for chemical strengthening is 10²Temperature T at dPa · s₂At 1530 ℃ or lower.

5. The glass for chemical strengthening as claimed in any one of claims 1 to 4, wherein the glass viscosity of the glass for chemical strengthening is 10⁴Temperature T at dPa · s₄Below 1130 ℃.

6. The glass for chemical strengthening as claimed in any one of claims 1 to 5, wherein the glass for chemical strengthening is a float glass.

7. A chemically strengthened glass obtained from the glass for chemical strengthening according to any one of claims 1 to 6.

8. The chemically strengthened glass according to claim 7, wherein the chemically strengthened glass has a surface compressive stress of 700MPa or more.

9. The chemically strengthened glass according to claim 7 or 8, wherein the chemically strengthened glass has a compressive stress depth of 12 μm or more.