WO2012126394A1

WO2012126394A1 - AN ALUMINOSILICATE GLASS CONTAINING Li2O AND P2O5 USED FOR CHEMICAL TOUGHENING

Info

Publication number: WO2012126394A1
Application number: PCT/CN2012/072941
Authority: WO
Inventors: Guangjun Zhang; Gerhard Lautenschlaeger; Jose Zimmer; Matthias Baesel
Original assignee: Schott Glass Technologies (Suzhou) Co. Ltd.
Priority date: 2011-03-23
Filing date: 2012-03-23
Publication date: 2012-09-27
Also published as: CN102690059A; CN102690059B

Abstract

The present invention discloses an aluminosilicate glass and a glass ceramics for chemical tempering, specifically a novel aluminosilicate glass comprising Li₂O and P₂O₅ for chemical tempering. The glass of the present invention can have a high ion exchange rate by adding 0.01-8 wt% of P₂O₅. The glass of the present invention comprises 2-6 wt% of Li₂O, which can reduce the glass molten temperature and glass transition temperature. The glass of the present invention has a low glass transition temperature (Tg) of 480-590°C, and a glass hardness of at least 600 Kg/mm. The glass of the present invention has a large depth of the surface compressive layer (DoL) and a high surface compressive stress (CS) after being chemical tempered. After tempering in pure KNO₃, a surface compressive layer of potassium ion can be formed with a DoL of at least 20 μm and a CS of at least 600 MPa. And tempering in mixed salts of KNO₃ and NaNO₃ or a two-step tempering by using KNO₃ and NaNO₃ can form potassium and sodium ion compressive layers at the same time with a DoL of at least 50 μm and a CS of at least 600 MPa. In addition, the aluminosilicate glass of the present invention can be further subjected to thermal treatment to convert to glass ceramics.

Description

Spec if i ca t i on Aluminosilicate Glass Containing Li₂0 and P2O5 Used for Chemical Toughening

TECHNICAL FIELD

The present invention relates to an aluminosilicate glass suitable for chemical tempering, especially relates to an aluminosilicate glass comprising Li₂O and P₂O₅ suitable for chemical tempering. The present application also relates to products made of the chemically tempered glass. The aluminosilicate glass of the present application is suitable for 3D molding, thermal bending, curve hot bending, infrared bending and other thermal shaping techniques. In addition, the present application further relates to glass ceramics obtained by further thermal treatment of the aluminosilicate glass.

BACKGROUND

Cover glasses are normally used in electronic devices, mobile electronic devices such as personal digital assistants, mobile or cell phones, watches, portable PCs, notebook PCs, digital cameras and PDAs; or used as the glass substrate of touch screens and televisions. There is an urgent need for cover glasses having large sizes and/or 3D dimensions. The cover glass is touch-sensitive to users in some applications such as in the cases of easy damage, scratching and deforming. The cover glass must have high strength and be scratching resistance because of frequent touch.

The traditional soda lime glass cannot meet the above requirements, such as the requirements for high strength and scratching resistance.

The aluminosilicate glass has high strength, high hardness, stable chemical resistance, low thermal expansion coefficient, high scratching resistance and impact resistance, and can be used as a cover glass of mobile devices (cell phones, smart phones, tablet PCs, notebook PCs, PDAs). This kind of glass can also be used as a cover glass of immobilized devices (televisions, personal PCs, MTA devices, digital cameras, watches, and industrial displays), a cover glass of touch screens, cover windows, automobiles windows, trains windows, aviation machines windows, substrate of hard disks or substrate materials of solar cells. It is also possible that the glass can be used in the field of white home appliances such as refrigerators and cookers.

The above applications need glasses of high strength and scratching resistance. Such a high strength can be obtained for this kind of glass normally through ion exchange process conducted under a low temperature environment, which is named chemical tempering. The chemical tempering can increase the strength of the glass against scratching and impact so as to avoid cracking. Chemical tempering imparts the glass a surface compressive stress through ion exchange. The simple principle of ion exchange process is that ion exchange is performed in a salt solution such as NaNO₃, KNO₃ or a mixture of NaNO₃ and KNO₃ at a temperature of 350-490°C, where ions having smaller radius in the surface layer of the glass exchange with ions having larger radius in the liquid, for example, the sodium ions in the glass exchange with the potassium ions in a solution, thereby generating a surface compressive stress by the difference in volume of alkaline ions. This process is particularly suitable for a glass having a thickness of 0.5-4 mm. The chemical tempering of glass has the advantages of not causing warpage, having a surface planeness the same as the original glass sheet, as well as increasing the strength and temperature resistance. Such a glass is also suitable for cutting. The strength of the glass can be characterized by CS (surface compressive stress) and DoL (depth of surface compressive layer). A high CS and high DoL are desired in practical applications. A glass having higher strength can be obtained by controlling DoL (surface compressive layer depth) and CS (surface compressive stress) reasonably. The dimensions of the DoL (depth of surface compressive layer) and CS (surface compressive stress) are related to components of the glass, especially the amount of alkali metal in the glass, and also the glass tempering process including the time and temperature for tempering. During chemical tempering, a compressive layer is formed on the surface of the glass. According to ion dispersing theory, the depth of the compressive layer is proportional to the square root of the tempering time. The longer the tempering time is, the deeper the tempered layer is, the smaller the surface compressive stress is, and the larger the central tensile stress is. If the tempering time is too long, the surface compressive stress will decrease because of increase in central tensile stress and looseness in glass structure, and the strength of the glass will not increase but reduce. Therefore, there is an optimal tempering time for striking a balance among the surface compressive stress, the depth of the tempered layer and the central tensile stress, thereby obtaining a glass having an optimal strength. The optimal tempering time varies with the components of the glass, the components of the salt bath and the tempering temperature.

After ion exchange, the compressive stress is formed on the surface of the glass, thus increasing the strength of glass. For the purpose of balancing the compressive stress on the surface of the glass, the tensile stress is formed in glass center, and the tensile stress, if it is too high, will increase the risks of breaking the glass. A bent glass part is more sensitive to the central tensile stress when subjecting to an outside force. Therefore, the central tensile stress must be lower than 50 MPa, preferably 30 MPa, more preferably lower than 20 MPa, and most preferably lower than 15 MPa. The surface compressive stress must be greater than 600 MPa, preferably greater than 700 MPa, and most preferably greater than 800 MPa.

A glass having a CS higher than 600 MPa, a DoL higher than 20 μιη and a glass transition temperature less than 590°C is of interest. However, in the prior art, such as US 3,218,220, US 3,752,729, US 3,900,329, US 4,156,755 and US 5,928,793 has disclosed that sodium ions or potassium ions are used to replace the lithium ions in the lithium aluminosilicate glass; US 3,485,702, US 3,752,729, US 4,055,703 and US 4,015,045 has disclosed that potassium ions are used to replace the sodium ions in the sodium aluminosilicate glass; and the prior art described below cannot satisfy all the above requirements at the same time, and cannot be suitable for tempering in KNO₃, NaNO₃ or the mixed salts of KNO₃ and NaNO₃ or a two-step tempering by use of NaNO₃ and KNO₃. For example, if a lithium aluminosilicate glass is tempered in KNO₃, the DoL will be normally less than 10 μιη, which will restrict the practical use. And as the sodium aluminosilicate glass does not contain Li₂O, the high efficiency ion exchange cannot be achieved in NaNO₃, and thus no desired tempering effects. Further, the sodium aluminosilicate glass has a high melting point and a high glass transition temperature (T_g) as well, which is normally higher than 600^°C , and therefore, such kind of glass cannot be manufactured economically and suitable for 3D precision molding application.

The demand for cover glasses in 3D dimensions, such as a curved surface, is becoming more and more strong. The method of making the 3D shaped cover glasses economically and effectively is pressing, precision molding or thermal bending.

For the purpose of mass production at a lower cost through pressing and precision molding, it is desirable that molds for pressing and precision molding can be used repeatedly. To this end, a glass having an appropriate softening property, i.e., having a proper glass transition temperature (T_g) should be adopted, and the temperature should be maintained as low as possible during pressing and precision molding, thus preventing the mold surface from oxidizing, and minimizing the oxidization of the mold surface.

The upper limit of the temperature determined by the heat resistance temperature of the molds is 700-900°C for molding, and 650-700°C for precision molding. The pressing temperature is preferably lower than 800°C, more preferably lower than 750°C, further preferably lower than 700°C, particularly preferably lower than 650°C, and especially preferably lower than 600°C. Correspondingly, the upper limit of the glass transition point (T_g) is about 550-620°C, preferably < 600°C, particularly preferably < 590°C, especially preferably < 570°C, more preferably < 550°C, and most preferably < 530°C. The lower the glass transition temperature is, the longer the lifetime of the molds is, and the higher the productivity is. The glass transition points (T_g) of glasses currently used for chemical tempering are all higher than 600°C. Therefore, the aluminosilicate glass having a lower T_g is of importance for 3D molding.

The thermal expansion coefficient (CTE) is an important parameter for thermal pressing, precision molding and thermal bending. During thermal pressing, precision molding and thermal bending, CTE should be within an optimal range, normally 3.5-1 l x lO ⁶ K^{" 1}. The mold used in thermal pressing, precision molding or thermal bending of a glass having such a CTE range can be released easily. The glass also has a good thermal shock resistance, which is advantageous for chemical tempering at elevated temperature. Young's modulus is an inherent property of materials, which is a physical measurement used to define the materials' ability against deforming. The bigger the value is, the more difficult the material deforms under the action of outside force. When the glass is intended for the above applications, it is desired that the glass does not generate a large deformation. Therefore, the glass should have a comparatively higher Young's modulus. However, the Young's modulus is low in the currently used glasses that is about 70-73 kN/mm . For glasses used for touch screens and cover windows, a higher Young's modulus value is better to be favorable for protecting applications of elements.

US 4,055,703 describes an alkali aluminum oxide-silica-zirconia glass comprising P₂O₅ that has a rapid ion exchange rate. The surface compressive layer depth and the DoL value increase upon addition of P₂O₅. However, the glass comprises only 0-0.1 wt.% of Li₂O, and such a low content of Li₂O is not sufficient to reduce T_g and the molten temperature of the glass. In addition, the patent suggests use of an amount of P₂O₅ larger than 10 wt.%, but a glass with a higher P₂O₅ content may lead to devitrification. Further, the glass in the patent requires more of ZnO, while the increase in the amount of ZnO may cause crystallization. Moreover, a higher content of P₂O₅ does not benefit the float process.

US 2008/0286548 describes an alkali aluminosilicate glass with a high mechanical property. However, the glass has a higher softening point and T_g and then is not suitable for pressing, precision molding or thermal bending. Such a glass comprises higher than 64 mol% ( > 64 wt% ) of SiO₂, which causes increase in the molten temperature, resulting in an increased viscosity during melting of the glass, and difficulty to expel bubbles with the result of increase in production cost. US 7,524,782 describes a glass comprising Li₂O and P₂O₅. However, the glass has a lower concentration of Na₂O of < 8 wt%. Such a concentration is not sufficient for chemical tempering of a glass. In this sense, the glass cannot be regarded as a good material for chemical tempering. In addition, the glass in the patent has a CTE lower than 3.5 X 10^"6 K^{_ 1}, and is suitable mainly for optical applications accordingly.

US 2005/014626 describes a glass comprising Li₂O and P₂O₅. However, the glass has a lower concentration of Na₂O of < 8 wt%. Such a concentration is not sufficient for chemical tempering of a glass. In addition, the glass in the patent has a CTE lower than 4.1 X 10^"6 K^{" 1}, and then is suitable mainly for optical elements. US 2009/0263226 describes a glass comprising Li₂O-Al₂O₃-SiO₂.

However, the glass has a lower concentration of Na₂O of < 3 wt%. Such a low Na₂O concentration is not sufficient for chemical tempering, particularly tempered in KNO₃. A lower Na₂O concentration reduces the ion exchange efficiency of sodium ions and potassium ions in the glass. Therefore, the glass described in the patent application is not suitable for tempering with KNO₃ or KNO₃/NaNO₃ mixed salts or for a two-step tempering by use of KNO₃ and NaNO₃, but only for tempering with NaNO₃. The Chinese patent application No. 200910301240.4 describes an aluminosilicate glass with a good chemical tempering property and strength. However, the glass has a higher T_g, not suitable for pressing, precision molding or thermal bending. Therefore, the glass is not suitable for 3D molding under low temperatures. The patent application No. 200810147442.3 describes an aluminosilicate glass. However, the glasses in the application comprises 1-5 wt.% of MgO. Generally, an amount of MgO > 1 wt.% may increase the surface tension of the glass, resulting in difficulty in exchange between the glass and alkali metal ions, thereby reducing the ion exchange efficiency. In addition, the glass disclosed in the patent application has a higher T_g. Therefore, the glass is not suitable for pressing, precision molding or thermal bending, and therefore, not for 3D molding under low temperatures.

The patent application No. 200910086806.6 describes an aluminosilicate glass. However, the glass in the patent application also comprises 1-6 wt.% of MgO. An amount of MgO > 1 wt.% may increase the surface tension of the glass, resulting in difficulty in exchange between the glass and alkali metal ions, thereby reducing the ion exchange efficiency. In addition, the glass disclosed in the patent application contains 0-2 wt.% of Li₂O. An amount of Li₂O lower than 2 wt.% is not sufficient to reduce T_g of the glass, and a higher T_g is not suitable for pressing, precision molding or thermal bending, and thus not for 3D molding under a lower temperature either.

JP 2008/072863 describes an aluminosilicate glass comprising Li₂O, Al₂O₃, and SiO₂. However, the glass contains an mount of ZrO₂ greater than 5 wt.%. An excesssive amount of ZrO₂ increases the molten temperature and glass transition temperature, and the tendency to devitrify.

US 2009/0298669 describes an aluminosilicate glass comprising an extremely high amount of MgO. Generally, an amount of MgO > 1 wt.% may increase the surface tension of the glass, resulting in difficulty in exchange between the glass and the alkali metal ions, thereby reducing the ion exchange efficiency.

US 5,928,793 describes an aluminosilicate glass comprising Li₂O mainly for a lamination glass, which is mainly tempered with NaNO₃. The glass disclosed in the patent comprises > 1 wt.% of CaO, and such an amount of CaO can lower the ion exchange efficiency.

There is no glass having a T_g lower than 590°C and at the same time having a hardness higher than 600 Kg/mm , and having a high CS (greater than 600 MP a) and a high DoL (greater than 20 μιη) after chemical tempering in the prior art as yet. The glasses in the prior art may achieve a high DoL as well as a high T_g, which does not satisfy the requirement for 3D molding; or achieve a low T_g as well as a low DoL, which does not satisfy the requirement for a high DoL.

Most of the glass compositions in the prior art have extremely high molten temperature and high glass transition temperature ( T_g ) , and therefore, are not suitable for use in the existing molten and shaping equipment. As such, it is extremely desired to have glass compositions having the following properties: the glass compositions can be chemical tempered in pure KNO₃ or pure NaNO₃, or in mixed salts of KNO₃ and NaNO₃, or tempered in a two-step fashion by use of KNO₃ and NaNO₃ to form a potassium ion surface compressive layer or a sodium ion surface compressive layer, or a potassium ion and sodium ion mixed surface compressive layer, and can be processed under a low molten temperature.

Also, it has a glass transition temperature ( T_g) lower than 590°C and a hardness of at least 600 Kg/mm .

SUMMARY OF THE INVENTION

The inventors of the present invention have found out, through unremitting efforts, that use of the novel glass composition proposed by the inventors of the present invention can overcome the defects in the prior art, i.e., can provide a glass composition having a low T_g, but a high CS and a high DoL, as well as an appropriate hardness.

The first aspect of the present invention is to provide an aluminosilicate glass for chemical tempering, the glass comprises: component wt.%

SiO₂ 50-62.5

Al₂O₃ 16-21

Na₂O 8- < 12

K₂O 0- < 2

MgO 0- < 1

B₂O₃ 0-10

Li₂O > 2-6

ZnO 0-8

CaO 0- < 1

ZrO₂ 0.1-4

TiO₂ 0-4

CeO₂ 0.01- < 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.002-4

P₂0₅/SiO₂ > 0.0016-0.15. The glass has a T_g of 480-590°C, a CTE of 4.5-10xl0^"6 K^{" 1}, and also a hardness of at least 600 Kgf/mm .

In the present invention, the weight percentages of all components are based on the total weight of the composition unless specified otherwise, and the sum of the contents of the components of the composition should be 100%.

The second aspect of the present invention is to provide an aluminosilicate glass for chemical tempering, the glass comprises: component wt.%

SiO₂ 54-62.5

Al₂O₃ 16-19

Na₂O 8.5- < 10

K₂O 0- < 1

MgO 0- < 1

B₂O₃ 0-10

Li₂O 3-6

ZnO 0-6

CaO 0- < 1

ZrO₂ 2.6-4

TiO₂ 0-2

CeO₂ 0.01- < 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

P₂0₅ 1.8-8

SO₃ 0-0.05 Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.17-2

P₂O₅/SiO₂ > 0.016-0.14.

The glass has a T_g of 480-590°C, a CTE of 4.5-10x l0^"6 K^{" 1}, and a hardness of at least 600 Kgf/mm as well. The third aspect of the present invention is to provide an aluminosilicate glass for chemical tempering, the glass comprises:

ponent wt.%

SiO₂ 55-62.5

Al₂O₃ 17-18

Na₂O 9- < 10

K₂O 0-0.08

B₂O₃ 0-10

Li₂O 4-6

ZnO 0-5

CaO 0- < 1

ZrO₂ 3-4

TiO₂ 0-1

CeO₂ 0.01- < 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

P₂0₅ 2-6

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.17-1.5

P₂0₅/SiO₂ 0.017-0.1. The glass has a T_g of 480-590°C, a CTE of 4.5-10x l0^"6 K^{" 1}, and a hardness of at least 600 Kgf/mm as well.

In the aluminosilicate glass for chemical tempering in the present invention, the amount of MgO is 0- < 1 wt.%, and preferably free of MgO.

In the aluminosilicate glass for chemical tempering in the present invention, the amount of K₂O is from 0- < 2 wt.%, preferably from 0- < 1 wt.%, and more preferably from 0-0.8 wt.%.

With respect to the aluminosilicate glass for chemical tempering in the present invention, a potassium ion compressive layer can be formed with a surface compressive layer having a depth of > 20 μιη upon tempering in molten KNO₃.

With respect to the aluminosilicate glass for chemical tempering in the present invention, a potassium ion compressive layer can be formed with a surface compressive layer having a depth of > 30 μιη upon tempering in molten

With respect to the aluminosilicate glass for chemical tempering in the present invention, a potassium ion compressive layer can be formed with a surface compressive layer having a depth of > 35 μιη upon tempering in molten

With respect to the aluminosilicate glass for chemical tempering in the present invention, a potassium ion compressive layer cam be formed with a surface compressive stress of at least 600 MPa upon tempering in molten KNO₃.

With respect to the aluminosilicate glass for chemical tempering in the present invention, a potassium ion compressive layer can be formed with a surface compressive stress of at least 700 MPa upon tempering in molten KNO₃.

With respect to the aluminosilicate glass for chemical tempering in the present invention, a potassium ion compressive layer can be formed with a surface compressive stress of at least 800 MPa upon tempering in molten KNO₃.

With respect to the aluminosilicate glass for chemical tempering in the present invention, a potassium ion compressive layer can be formed with a surface compressive stress of at least 850 MPa upon tempering in molten KNO₃.

With respect to the aluminosilicate glass for chemical tempering in the present invention, a sodium ion compressive layer can be formed with a surface compressive layer having a depth of at least 50 μιη, preferably at least 100 μιη, more preferably at least 150 μιη upon tempering in molten NaNO₃.

With respect to the aluminosilicate glass for chemical tempering in the present invention, a sodium ion compressive layer can be formed with a surface compressive stress of at least 400 MPa upon tempering in molten NaNO₃.

With respect to the aluminosilicate glass for chemical tempering in the present invention, a potassium ion and sodium ion compressive layer can be formed with a surface compressive layer having a depth of at least 50 μιη upon tempering in mixed salts of molten KNO₃ and NaNO₃. With respect to the alumino silicate glass for chemical tempering in the present invention, a potassium ion and sodium ion compressive layer can be formed with a surface compressive stress of at least 600 MPa upon tempering in mixed salts of molten KNO₃ and NaNO₃.

The aluminosilicate glass for chemical tempering in the present invention does not comprise As₂O₃ or Sb₂O₃.

In the aluminosilicate glass for chemical tempering of the present invention, at least one of the following components is used as the refining agent:

CeO₂ 0.01- < 0.2 wt%

F₂ 0-0.5 wt%

SnO₂ 0.01-0.5 wt%.

The glass composition of the present invention can be refined with any method known in the prior art, comprising use of known refining agents, such as antimony oxide, arsine oxide, tin oxide, or refined by combinations of a plurality of refining methods.

In addition, sulphur can be used to produce a refining agent in the present invention, or the vacuum and high temperature refining can be used, too.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the T_g is 500-570°C.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the T_g is 500-550°C. The aluminosilicate glass for chemical tempering of the present application is characterized in that the Young's modulus is greater than 74 kN/mm 2 , preferably greater than 78 kN/mm 2 , and more preferably greater than 82 kN/mm².

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass has a hardness of higher than 650 Kgf/mm after chemical tempering.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass has a hardness of higher than 700 Kgf/mm after chemical tempering.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass has a hardness of higher than 800 Kgf/mm after chemical tempering.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass has a hardness of higher than 550 Kgf/mm and a T_g of 500-570°C after tempering in mixed salts of molten KNO₃ and NaNO₃.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass has a hardness of higher than 600 Kgf/mm and a T_g of 500-570°C after tempering in mixed salts of molten KNO₃ and NaNO₃.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass has a hardness of higher than 700 Kgf/mrri and a T_g of 500-570°C after tempering in mixed salts of molten KNO₃ and NaNO₃.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass is a thin glass with a thickness of less than 9.0 mm.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass is a thin glass with a thickness of less than 5.0 mm.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass is a thin glass with a thickness of less than 4.0 mm.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass is a thin glass with a thickness of less than 2.0 mm.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass is a thin glass with a thickness of less than 1.0 mm.

The aluminosilicate glass for chemical tempering of the present application is characterized in that the glass is a thin glass with a thickness of less than 0.5 mm.

Another aspect of the present invention is to provide an aluminosilicate glass ceramics for chemical tempering, the glass ceramics comprising: component wt.%

SiO₂ 50-62.5

Al₂O₃ 16-21

Na₂O 8- < 12

K₂O 0- < 2

MgO 0- < 1

B₂O₃ 0-10

Li₂O > 2-6

ZnO 0-8

CaO 0- < 1

ZrO₂ 0.1-4

TiO₂ 0-4

CeO₂ 0.01- < 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.002-4

P₂0₅/SiO₂ > 0.0016-0.15.

The glass ceramics has a hardness of higher than 700 Kgf/mm .

The aluminosilicate glass ceramics for chemical tempering present invention comprising:

component wt.% SiO₂ 54-62.5

Al₂O₃ 16-19

Na₂O 8.5- < 10

K₂O 0- < 1

MgO 0- < 1

B₂O₃ 0-10

Li₂O 3-6

ZnO 0-6

CaO 0- < 1

ZrO₂ 2.6-4

TiO₂ 0-2

CeO₂ 0.01- < 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.17-2

P₂0₅/SiO₂ > 0.016-0.14

The glass ceramics has a hardness of higher than 700 Kgf/mm .

The aluminosilicate glass ceramics for chemical tempering of the present invention comprising:

component wt.%

SiO₂ 55-62.5

Al₂O₃ 17-18

Na₂O 9- < 10

K₂O 0-0.8 B₂O₃ 0-10

Li₂O 4-6

ZnO 0-5

CaO 0- < 1

ZrO₂ 3-4

TiO₂ 0-1

CeO₂ 0.01- < 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.17-1.5

P₂0₅/SiO₂ 0.017-0.1.

The glass ceramics has a hardness of higher than 700 Kgf/mm .

The aluminosilicate glass ceramics for chemical tempering of the present invention contains 0- < 1 wt.% of MgO, preferably free of MgO.

The aluminosilicate glass ceramics for chemical tempering contains 0- < 2 wt.% of K₂O, preferably 0- < 1 wt.%, and more preferably 0-0.8 wt.%.

With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion compressive layer can be formed with a surface compressive layer having a depth of > 20 μιη upon tempering in molten KNO₃. With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion compressive layer can be formed with a surface compressive layer having a depth of > 30 μιη upon tempering in molten KNO₃.

With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion compressive layer can be formed with a surface compressive layer having a depth of > 35 μιη upon tempering in molten

With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion compressive layer can be formed with a surface compressive stress of at least 600 MPa upon tempering in molten KNO₃.

With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion compressive layer can be formed with a surface compressive stress of at least 700 MPa upon tempering in molten KNO₃

With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion compressive layer can be formed with a surface compressive stress of at least 800 MPa upon tempering in molten KNO₃.

With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion compressive layer can be formed with a surface compressive stress of at least 850 MPa upon tempering in molten KNO₃.

With respect to the aluminosilicate glass ceramics for chemical tempering, a sodium ion compressive layer can be formed with a surface compressive layer having a depth of at least 50 μιη, preferably at least 100 μπι, more preferably at least 150 μιη upon tempering in molten NaNO₃. With respect to the aluminosilicate glass ceramics for chemical tempering, a sodium ion compressive layer can be formed with a surface compressive stress of at least 400 MPa upon tempering in molten NaNO₃

With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion and sodium ion compressive layers can be formed with a surface compressive layer having a depth of at least 50 μιη upon tempering in molten KNO₃ and NaNO₃.

With respect to the aluminosilicate glass ceramics for chemical tempering, a potassium ion and sodium ion compressive layers can be formed with a surface compressive stress of at least 800 MPa upon tempering in molten KNO₃ and NaNO₃.

With respect to the aluminosilicate glass ceramics for chemical tempering, the depth of the surface compressive layer is at least 50 μιη upon tempering in molten NaNO₃.

The aluminosilicate glass ceramics for chemical tempering in the present application does not contain As₂O₃ or Sb₂O₃.

In the aluminosilicate glass ceramics for chemical tempering of the present application, at least one of the following components is used as a refining agent:

CeO₂ 0.01- <0.2 wt%

0-0.5 wt%

SnO₂ 0.01-0.5 wt%. The glass ceramics composition of the present application can be refined with any method known in the prior art comprising use of known refining agents, such as antimony oxide, arsine oxide, tin oxide, or refined by combinations of a plurality of refining methods.

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics has a hardness of higher than 700 Kgf/mm .

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics has a hardness of higher than 750 Kgf/mm .

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics has a hardness of higher than 800 Kgf/mm .

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics is a thin glass ceramics with a thickness less than 8.0 mm.

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics is a thin glass ceramics with a thickness less than 5.0 mm.

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics is a thin glass ceramics with a thickness less than 4.0 mm.

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics is a thin glass ceramics with a thickness less than 2.0 mm.

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics is a thin glass ceramics with a thickness less than 1.0 mm.

The aluminosilicate glass ceramics for chemical tempering of the present invention is characterized in that the glass ceramics is a thin glass ceramics with a thickness less than 0.5 mm.

A further aspect of the present invention is to provide a method for tempering the glass or glass ceramics of the present invention. The method comprises providing the aluminosilicate glass or the aluminosilicate glass ceramics of the present invention, and is characterized in tempering in molten KNO₃, or in molten NaNO₃, or in mixed salts of molten NaNO₃ and KNO₃ or a two-step tempering by using KNO₃ and NaNO₃.

The method of tempering the glass or the glass ceramics of the present application comprises providing the aluminosilicate glass or the aluminosilicate glass ceramics of the present invention, tempering in a 100% molten KNO₃ salt bath, or in a 100% molten NaNO₃, or in mixed salts of molten NaNO₃ and KNO₃ in different ratios, or in two-step mode by using KNO₃ and NaNO₃, wherein the chemical tempering temperature ranges from 350°C to 490°C, and the treating period of time lasts 1 to 16 hours.

In the method of tempering the glass or the glass ceramics of the present application, the chemical tempering temperature ranges from 370 to 490°C, and the treating period of time lasts from 4 to 16 hours.

In the method of tempering the glass or the glass ceramics of the present application, the chemical tempering temperature ranges from 400 to 480°C, and the treating period of time lasts from 4 to 14 hours.

In the method of tempering the glass or the glass ceramics of the present application, the chemical tempering temperature ranges from 420 to 460°C, and the treating period of time lasts from 6 to 14 hours.

In the method of tempering the glass or the glass ceramics of the present application, the chemical tempering temperature ranges from 370 to 420°C, and the treating period of time lasts from 6 to 8 hours.

The aluminosilicate glass or aluminosilicate glass ceramics according to the present invention can be produced suitably with the float process, the up draw process, the down draw process and the overflow process, particularly with the micro-float production.

The aluminosilicate glass or aluminosilicate glass ceramics can be used for 3D precision molding and thermal bending, wherein the thermal bending can be conducted through infrared heating. For increasing the glass's absorption of infrared radiation, various microcomponents can be doped into the glass, such as oxides or inorganic salts comprising ions such as Yb³⁺, Fe³⁺, Mn²⁺, Cu²⁺, Ni²⁺, V²⁺. The alumino silicate glass comprising Li₂O and P₂O₅ in the present invention has a surface compressive stress ( CS ) of at least 600 MPa, a depth of the surface compressive layer ( DoL) of at least 20 μιη, and a glass thickness of lower than 10 mm. In addition, the glass of the present invention is suitable for production of a thin glass having a thickness lower than 5 mm.

The glass of the present invention is environmental friendly, and is free of As₂O₃ and Sb₂O₃.

The aluminosilicate glass or the aluminosilicate glass ceramics of the present invention can be used for manufacturing cover glasses of cell phones, smart phones, tablet PCs, notebook PCs, PDAs, televisions, personal PCs, MTA machines or industrial displays.

The aluminosilicate glass or the aluminosilicate glass ceramics of the present invention can be further used for manufacturing touch screen cover glasses, cover windows, automobile windows, train windows, aviation machine windows, substrate of hard disks, or substrate of solar cells.

The aluminosilicate glass or aluminosilicate glass ceramics according to the present invention can be further used in the fields of white home appliances, such as for manufacturing refrigerator parts or cookers.

In a further aspect of the present invention, the present invention provides a glass prefabricated article. The glass prefabricated article is characterized in that it is made of the aluminosilicate glass or aluminosilicate glass ceramics according to the present invention.

The present invention also provides a glass article made of the aluminosilicate glass or aluminosilicate glass ceramics according to the present invention.

The glass article according to the present invention can be used as a cover glass of mobile electronic devices and portable devices or a back panel of notebook PCs.

The glass according to the present invention can be used for production of a one dimensional plane cover glass, a touch screen glass, can also be produced as a two and half dimensional or three dimensional cover glass or a touch screen glass. In addition, it is also possible to form various structures on the surface of the glass through thermal pressing, precision molding, thermal bending or combinations of these techniques.

The 3D shaped cover plate and touch control panel glass may have different shapes such as shapes of tray, arc, curved plane and flanging. In addition, the 3D shaped cover plate and touch-control panel glass can be reprocessed, and pattering and drilling can be conducted on the glass.

The 3D shaped cover glass can be used on the front side and rear side of a device, especially the rear side where additional decoration can be applied with organic or inorganic colors through screen printing. Decoration can also be applied to the inside or outside of the cover glass.

An economic method for producing a 3D shaped cover glass is 3D precision molding or thermal bending and the like.

The aluminosilicate glass of the present invention has a high strength, high hardness, stable chemical resistance, low thermal expansion coefficient, and high scratching resistance and impact resistance, and can be suitably used as cover glasses of mobile devices (cell phones, smart phones, tablet PCs, notebook PCs, PDAs). This type of glass can also be used as immovable devices cover glasses (televisions, personal PCs, MTA devices, digital cameras, watches, and industrial displays), touch screen cover glasses, cover windows, automobile windows, train windows, aviation machine windows, or used for making substrate of hard disks or substrate of solar cells. This glass is also suitable for the field of white home appliances, such as for making refrigerator parts or cookers.

DETAILED DESCRIPTION OF THE INVENTION

SiO₂ is the main glass forming material and the single component having the largest proportion in the glass, which can form the strong network structure. P2O5 is also a glass forming material and is characterized in providing the weak network structure. Optimizing of the strong network forming material and the weak network forming material can achieve an optimal ion exchange rate and depth. Therefore, this method can be used to render the glass a high CS (greater than 600 MPa) and a high DoL (greater than 20 μιη) after chemical tempering.

The inventors of the present invention have found out that adding P₂O₅ to a glass may increase the ion exchange property of the glass to go beyond the limit of the original glass system. Particularly, an increased amount of P₂O₅ may increase ion exchange rate and decrease ion exchange time, thereby achieving a deeper depth of the surface compressive stress in a short time. In addition, P₂O₅ can also be used to improve stress point advantageously and exerts a positive influence on molten temperature. However, when P₂O₅ is greater than 8 wt%, chemical resistance and homogenization of the glass will reduce. From the point of view of cost, an excessive amount of P₂O₅ than is necessary is not desired. In the present invention, the amount of P₂O₅ is 0.01-8 wt.%, preferably 1.8-6 wt.%, more preferably 2-6 wt.%.

For the purpose of obtaining a high CS and high DoL, P₂O₅ plays a key role in opening glass structure and increasing dispersing rate.

The glass of the present invention comprises 50-62.5 wt% of SiO₂, preferably 54-62.5 wt%, more preferably 55-62.5 wt%. The glass should comprise a minimum amount of 50 wt% of SiO₂ as a network forming agent. A too small amount of SiO₂ may affect the glass's chemical resistance harmfully, while increasing of the proportion of SiO₂ to more than 62.5 wt% could lead to increase in transition temperature and molten temperature.

Furthermore, in the glass composition of the present invention, the ratio of P₂O₅/SiO₂ should be controlled to keep > 0.0016-0.1 for realizing an optimal glass property, achieving the purpose of the present invention. SiO₂ is the main glass forming material, a single component having the largest proportion in the glass, and the principal component for forming the strong network structure. P₂O₅ is also a glass forming material and can be crystallized in at least four forms. The most common form of polycrystal comprises P₄Oio molecules. Other forms of polycrystal are in polymerized state. However, in various cases, the phosphor atoms are joined by tetrahedral oxygen atoms, wherein one oxygen atom forms a terminal P=O bond. The phosphate glass structure is a layered structure formed by P₆O₆ rings that are connected with each other, not the same as the structure taken by some polysilicate. The character of P₂O₅ is to provide the weak network structure. A very strong silicate network structure does not benefit ion exchange, resulting in reduced ion exchange rate and depth, whereas a very weak phosphate glass network structure may reduce the stability of the glass. Therefore, the proportion and composition of the silicate strong network structure and the phosphate weak network structure should be optimized. When P₂O₅/SiO₂ is < 0.016, a sufficient high DoL cannot be fulfilled, but if P₂O₅/SiO₂ is > 0.15, the glass will start to devitrify, and thus the chemical stability deteriorates. Optimization of the silicate strong network structure and the phosphate weak network structure may greatly improve ion exchange rate and depth. Therefore, P₂O₅/SiO₂ is preferably > 0.016-0.14, more preferably > 0.016-0.15, particularly preferably 0.017-0.1. In some particular embodiments of the present invention, the ratio of P₂O₅/SiO₂ can be 0.0162, 0.0485, 0.05, 0.0631, 0.0808, 0.0715, 0.0956, 0.1 or 0.1181.

The glass of the present invention comprises 2-6 wt% of Li₂O, preferably 3-6 wt.%, more preferably 4-6 wt%, further more preferably 4-5.5 wt%. Li₂O as a flux can reduce T_g of the glass, whereas Li₂O present in an amount higher than the above range will tend to crystallization. Generally speaking, a glass having a higher amount of lithium is apt to generate surface defects during thermal treatment.

Further, the P₂O₅/Li₂O ratio should be controlled to be 0.002-4 in the glass composition of the present invention for optimizing the glass's property, achieving the object of the present invention. Experiments show that when P₂O₅/Li₂O is < 0.002 and P₂O₅/Li₂O is > 4, a high DoL can be obtained, but the glass's T_g cannot decrease effectively when P₂O₅/Li₂O is > 4. When the ratio of P₂O₅/Li₂O is 0.002-4, preferably > 0.17-2.5, more preferably > 0.17-2.0, further more preferably 0.17-1.5, the T_g of the glass can be controlled to be within the range of 480-590°C after chemical tempering, and the glass can have a DoL of at least 20 μιη and a CS of at least 600 MPa at the same time. In the glass composition of the present invention, the ratio of P₂O₅/Li₂O can be 0.2, 0.4, 0.5, 0.6, 0.92, 1, 1.29, 1.38, 1.45, 1.5 or 2 for achieving a better technical effect. In the glass of the present invention, the amount of Al₂O₃ ranges from 16 to 21 wt%, preferably from 16 to 19 wt%, more preferably from 17 to 18 wt%. Al₂O₃ can be used to improve effectively heat resistance, ion exchange property and the Young's modulus of the glass. However, when the amount of Al₂O₃ is increased, the glass will devitrify easily with a reduced thermal expansion coefficient, thus it is hard for the glass to match with other conventional materials during applications. Further, a high Al₂O₃ amount will also lead to enhance high temperature viscosity, which does not benefit production. However, an amount of Al₂O₃ lower than 16 wt% will reduce the Young's modulus and glass strength.

In the glass of the present invention, Na₂O is present as a flux and is also an important factor for ion exchange in chemical tempering. When Na₂O is > 12 wt% in the glass, the chemical resistance the glass will reduce. The glass should have at least 8 wt% of Na₂O for maintaining the molten temperature of the glass above a practical level whereby rendering the glass a considerable ion exchange property. In the present invention, the amount of Na₂O is 8- < 12 wt.%, preferably 8.5- < 10 wt.%, and more preferably 9- < 10 wt.%.

In the glass of the present invention, ZrO₂ is used to improve chemical stability, increase viscosity and hardness and lower thermal expansion coefficient of the glass. In the present invention, the amount of ZrO₂ is 0.1-4 wt%, preferably 2.6-4 wt.%, and more preferably 3-4 wt.%. When the amount of ZrO₂ is > 4 wt%, the glass will crystallize easily. However, if the amount of ZrO₂ is too low, the glass will not have a high chemical stability.

In the glass of the present invention, MgO may reduce the glass's viscosity under a high temperature, and thus improve fusibility and formability, thereby increasing stress point and the Young's modulus. In addition, adding of MgO to the alkali earth metal oxide components will increase the surface tension of the glass. A large surface tension will exert an impact on ion exchange efficiency. It is preferred that the amount of MgO is 0- < lwt%, and free of MgO is more preferred.

In the glass of the present invention, CaO can also be used to reduce the glass's viscosity under a high temperature, thus improving fusibility and formability, thereby increasing stress point and the Young's modulus. Accordingly, it is preferred that the amount of CaO is 0- < 1 wt%. In addition, CaO can be used to improve the glass's anti-devitrification.

The glass of the present invention also comprises SrO with an amount of 0-1 wt.%. However, in some cases, when a very large amount of this component is present, the strength and thermal expansion coefficient of the glass increase and its devitrification deteriorates, increasing the occurrence of cracks. As a result, the depth of the surface compressive layer becomes shallower after ion exchange.

The glass of the present invention comprises 0-10 wt% of B₂O₃. B₂O₃ has the effects of lowering molten temperature, high temperature viscosity and density.

In the glass of the present invention, K₂O is used to lower high temperature viscosity of the glass and thus improve fusibility and shapeability, reducing the occurrence of cracks. In addition, K₂O is also a component for improving devitrification. In the glass composition, an amount of K₂O of 0- < 2 wt% tends to improve the exchange of sodium by potassium. When the amount is higher than 2 wt%, the strength of the glass will be reduced after chemical tempering. In the present invention, the amount of K₂O is preferably 0- < 1 wt%, more preferably 0-0.8 wt.%.

In addition, an amount of Fe₂O₃ benefits the chemical tempering and subsequent thermal bending. Normally, the amount of Fe₂O₃ is controlled to be between 0.06 and 0.12 wt.%, which can speed up the thermal bending treatment of the glass.

The glass of the present invention can comprise a small amount of a conventional refining agent. The total amount of the added refining agents is preferably at most 2.0 wt%, more preferably at most 1.0 wt%. The amount of the refining agents is an additional amount relative to the rest components of the glass, but the added amount should guarantee that the amount of the components of the glass composition is 100 wt%. The glass of the present invention can comprise at least one of the following components as a refining agent (an additional amount wt% relative to the rest components of the glass):

CeO₂ 0.01-0.2%

F₂ 0-0.5%

SnO₂ 0.01-0.5%.

In addition, sulphur can be used to produce a refining agent in the present invention, or the vacuum and high temperature refining can be used, too. The alumino silicate glass for chemical tempering in the present invention is characterized in having a CTE of 4-10x l0^"6 K^{" 1}, while a T_g between 480 and 590°C at the same time, ensuring repeated use of the mold, and inhibiting the surface of the mold from oxidizing so that the mold can be released easily and has an extended lifetime, accordingly. If CTE is higher than lOxlO^"6 K^{" 1}, the thermal shock resistance will be deteriorated, and the glass can be broken easily during high temperature chemical tempering. However, if CTE is lower than 4x10^~6 K^{" 1}, stress will be generated easily, causing adhesion between the glass and the mold.

A T_g higher than 590 ^°C makes pressing, precision mould-pressing or thermal bending of a glass difficult, while if T_g is lower than 480 ^°C , the glass will become unstable. The aluminosilicate glass for chemical tempering in the present invention is characterized in that the glass has the Young's modulus greater than 74 kN/mm 2 , preferably greater than 78 kN/mm 2 , more preferably greater than 82 kN/mm . If the Young's modulus is less than 73 kN/mm , the material tends to be deformed easily under an outside force, increasing the probability to damage the elements inside the article.

However, if the Young's modulus is greater than 74 kN/mm , preferably greater than 78 kN/mm 2 , and more preferably greater than 82 kN/mm 2 , the glass does not produce a significant deformation under the action of an outside force, which can better protect the elements inside the product and prolong the lifetime.

The aluminosilicate glass has a low amount of K₂O and MgO and a high amount of Na₂O. The aluminosilicate glass has a glass transition temperature ( T_g) of lower than 590°C, and a hardness of at least 600 Kg/mm . The glass can be treated by chemical tempering, has very high ion exchange efficiency and a broad range for chemical tempering. The glass can be chemical tempered in pure KNO₃ or pure NaNO₃, or in mixed salts of KNO₃ and NaNO₃, or tempered in a two step way by using KNO₃ and NaNO₃ in order to form a potassium ion surface compressive layer, a sodium ion surface compressive layer, or a mixed ions surface compressive layer of potassium and sodium. The tempered glass can have a depth of the surface compressive layer (DoL) of at least 20 μιη and a surface compressive stress ( CS ) of at least 600 MPa. During shaping of the glass, particularly when the forming of float process is used, viscosity is an important index for the glass. The float process forming requires that the glass have a short solidification time to suit high speed pulling and fast setting. The glass of the present invention has a viscosity of 1.5x 10 3 -8x 106 Pa-S during thermal forming. The temperature difference corresponds to such a viscosity that can be used to characterize the solidification speed of the float glass, i.e., ΔΤ = T₃ (the temperature at which the viscosity is 10 Pa-S) - T₆ (the temperature at which the viscosity is 10⁶ Pa-S). The glass of the present invention has a solidification speed 250-300°C. The solidification speed will be too slow when the temperature is higher than 300°C, which does not benefit increasing the productivity of pulling production for the float process, while the solidification speed will be too fast if the temperature is lower than 250°C, and the pulling cannot be conducted. The glass of the present invention has a viscosity suitable for float process, as well as other production methods such as down-draw process, up-draw process, and overflow process.

In another aspect of the present invention, the aluminosilicate glass comprising Li₂O and P₂O₅ in the present invention can be converted to glass ceramics by thermal treatment. The glass ceramics material has many properties of glass and ceramics. The glass ceramics has an amorphous phase and one or more crystalline phases, and is prepared through so-called "crystal control" relative to spontaneous crystallization, wherein normally the spontaneous crystallization is not desired during preparation of the glass. The glass ceramics generally has 30-90% by volume of crystalline phase, and therefore, can be used to manufacture a series of materials having interesting mechanical properties, such as a glass having an increased strength. The glass ceramics of the present invention is prepared by the method described in examples. The process of production of a glass comprises melting under a high temperature from 1550 to 1600°C to form an aluminosilicate glass comprising Li₂O and P₂O₅, homogenizing and shaping the glass melt, and nucleating and crystallizing under temperatures after annealing to obtain a glass ceramics article having fine crystal particles with homogenous structure. The prepared glass ceramics normally does not have pores.

As a rule, a suitable crystallizing agent such as TiO₂, ZrO₂, HfO₂ or other known components can be used to dope the glass for the purpose of crystallization (forming crystal nucleus), wherein the total amount of the crystallizing agents is up to 5 wt%, preferably up to 3 wt%, and most preferably up to 2 wt%, relative to all the components of the glass. In the present invention, the crystalline phase of the aluminosilicate glass ceramics comprising Li₂O and P₂O₅ has a "high quarts" structure.

Similarly, the aluminosilicate glass ceramics comprising Li₂O and P₂O₅ of the present invention has low contents of K₂O and MgO as the glass ceramics contains Na₂O at a concentration higher than 8 wt% and also contains Li₂O and P₂O₅. Therefore, the glass ceramics has a broad application range for chemical tempering, can be for chemical tempered in pure KNO₃, pure NaNO₃, or in mixed salts of KNO₃ and NaNO₃ or tempered in a two-step fashion by using of KNO₃ and NaNO₃, with the result of very high ion exchange efficiency.

The glass ceramics of the present invention has a thickness less than 8.0 mm, or less than 5.0 mm, preferably less than 4.0 mm, more preferably less than 2.0 mm, particularly preferably less than 1.0 mm and the most preferably less than 0.5 mm.

The glass of the present invention and the glass ceramics made by the glass of the present invention can be chemical tempered in an alkaline salt solution, such as in KNO₃, NaNO₃ or a mixture of NaNO₃ and KNO₃ or tempered in a two-step mode by using KNO₃ and NaNO₃. The time of chemical tempering is generally < 20 h, preferably < 10 h, more preferably < 8 h, and most preferably < 6 h.

The aluminosilicate glass or aluminosilicate glass ceramics according to the present invention has a surface compressive layer and a surface compressive stress ( CS ) after tempering, the surface compressive layer and the surface compressive stress can be a potassium ion surface compressive layer, a sodium ion surface compressive layer, and can also be a mixed ions surface compressive layer of potassium and sodium. After tempering in pure KNO₃, the depth of the surface compressive layer (DoL) is at least 20 μιη, and the CS is at least 600 MPa. After tempering in pure NaNO₃, the DoL is at least 50 μπι and the CS is at least 400 MPa. After tempering in mixed salts of KNO₃ and NaNO₃ or a two-step tempering by using KNO₃ and NaNO₃, the potassium ion compressive layer and the sodium ion compressive layer can be formed at the same time with a depth of of at least 50 μηι and a CS of at least 650 MPa. K₂O makes a contribution to improvement in surface tension and surface hardness, while Na₂O exerts an impact on increasing the depth of the surface compressive layer and improving the scratching resistance. In the mixed ions surface compressive layer of potassium and sodium, the depth of the surface compressive layer (DoL) can be divided into the depth of the sodium ion surface compressive layer and the depth of the potassium ion surface compressive layer, and the ratio of the depth of the potassium ion surface compressive layer (DoL) to the depth of the sodium ion surface compressive layer (DoL) is 0.01-0.5, preferably 0.05-0.3, more preferably

0.1-0.2. The ratio of the depth of the potassium ion surface compressive layer (DoL) to the depth of the sodium ion surface compressive layer (DoL) can be other values such as 0.02, 0.04, 0.08, 0.1, 0.2, 0.3, 0.4 or 0.5. MODE OF CARRYING OUT THE INVENTION

Examples

Table 1 illustrates examples with the preferred component ranges. The glasses in the examples and comparative examples of the present invention are prepared according to the following steps: as starting materials, oxides, hydroxides, carbonates and nitrates, etc. (purchased from Sinopharm Chemical Reagent Co., Ltd., Suzhou, chemical grade) are weighted and mixed, the mixture is put into a platinum crucible and then placed into an electrical oven, thereafter, it is melted at a temperature of 1550-1600°C, and founded in a metal mold made of stainless steel preheated to 400°C, and cooled slowly for the subsequent processing.

The glass transition temperature T_g, the yield point AT (referring to the temperature of the deforming point on the thermal expansion curve) and the thermal expansion coefficient CTE in the present tests are measured on a NETZSCH thermal expansion instrument (NETZSCH DIL402PC). A glass sample is made to have a shape of strip of about 50 mm, and the temperature is elevated from room temperature to the end of the test at a rate of 5 °C/min.

The density of the glass is measured with the Archimedes law. The glass sample is put into a container containing water, the volume of the sample is obtained by measuring accurately the volume change of water in the container. The density is obtained by dividing the volume by the weigh of the sample that can be measured precisely.

Chemical tempering of the sample is conducted with a small lab-scale salt bath oven (having a diameter of 250x250 mm and a depth of 400 mm). The sample is placed on a special anticorrosion stainless steel sample shelf for tempering in NaNO₃ salt bath, KNO₃ salt bath, or in mixed salts of KNO₃ and NaNO₃ , or for a two-step tempering by using KNO₃ and NaNO₃ at a tempering temperature of 70-490°C and tempering for 1-16 hours.

The stress of the glass is measured on FSM6000 and a polarization microscope. The depth of the potassium ion surface compressive layer (DoL) is measured on a glass surface stress instrument FSM6000, and the depth of the sodium ion surface compressive layer (DoL) is measured on a polarization microscope.

K_IC represents the material's ability against fracture, which means the material's ability to prohibit cracks from becoming unstable and from expanding under plane strain, the higher the K_IC is, the larger the breaking stress or the critical fracture size of the crack is, demonstrating that fracture is not easy. The fracture toughness of the present test is measured by standard GB/T 23806-2009. The compositions (wt% based on oxides), density and CET of the glass of the present invention and basic properties of examples 1-8 are summarized in Table 1 , and the results of glass chemical tempering are shown in Table 2.

Table 2 Property of the glass after chemical tempering

Table 3 Examples of glass ceramics.

The glass ceramics described in the examples is prepared according to the followings: as starting materials, oxides, hydroxides, carbonates and nitrates, etc. (purchased from Sinopharm Chemical Reagent Co., Ltd., Suzhou, chemical grade) are weighted and mixed, the mixture is then put into a platinum crucible, and placed into an electrical oven, melted at a temperature of 1550-1600°C, and founded into a clear glass in a metal mold made of stainless steel. The glass is subjected to thermal treatment at 610°C for 8 hours, and further to thermal treatment at 700°C for 10 hours till the glass ceramics is obtained.

The compositions (wt% based on oxides), density and CET of the glass ceramics of the present invention, and basic properties of the examples after chemical tempering are shown in Table 3.

Claims

C l a ims

1. An aluminosilicate glass for chemical tempering, the glass comprises: component wt.%

SiO₂ 50-62.5

Al₂O₃ 16-21

Na₂O 8- <12

K₂O 0- <2

MgO 0- <l

B₂O₃ 0-10

Li₂O > 2-6

ZnO 0-8

CaO 0- <l

ZrO₂ 0.1-4

TiO₂ 0-4

CeO₂ 0.01- 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

P₂0₅ 0.01-8

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.002-4

P₂0₅/SiO₂ > 0.0016-0.15 the glass has a T_g of 480-590°C, a CTE of 4.5-10x l0^"6 K ¹, and a hardness of at least 600 Kgf/mm .

2. The aluminosilicate glass for chemical tempering according to claim 1, the glass comprises:

component wt.%

SiO₂ 54-62.5

Al₂O₃ 16-19

Na₂O 8.5- <10

K₂O 0- <l

MgO 0- <l

B₂O₃ 0-10

Li₂O 3-6

ZnO 0-6

CaO 0- <l

ZrO₂ 2.6-4

TiO₂ 0-2

CeO₂ 0.01- 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

P₂0₅ 1.8-8

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.17-2

P₂0₅/SiO₂ > 0.016-0.14 the glass has a T_g of 480-590°C, a CTE of 4.5-10x l0^"6 K^{" 1}, and a hardness of at least 600 Kgf/mm .

3. The aluminosilicate glass for chemical tempering according to claim 1, the glass comprises: component wt.%

SiO₂ 55-62.5

Al₂O₃ 17-18

Na₂O 9- <10

K₂O 0-0.8

B₂O₃ 0-10

Li₂O 4-6

ZnO 0-5

CaO 0- <l

ZrO₂ 3-4

TiO₂ 0-1

CeO₂ 0.01- 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.17-1.5

P₂0₅/SiO₂ 0.017-0.1 the glass has a T_g of 480-590°C, a CTE of 4.5-10x l0^"6 K^{" 1}, and a hardness of at least 600 Kgf/mm .

4. The aluminosilicate glass for chemical tempering according to any one of claims 1-3, wherein the glass has a T_g of 500-570°C.

5. The aluminosilicate glass for chemical tempering according to any one of claims 1-3, wherein the glass has a T_g of 500-550°C.

6. The aluminosilicate glass for chemical tempering according to any one of claims 1-3, wherein the glass has a CTE of 6- 10x 10^~6 K^{" 1}.

7. The aluminosilicate glass for chemical tempering according to any one of claims 1-3, wherein the glass has a hardness higher than 650 Kgf/mm after being chemical tempered.

8. The aluminosilicate glass for chemical tempering according to any one of claims 1-3, wherein the glass has a hardness higher than 700 Kgf/mm after being chemical tempered.

9. The aluminosilicate glass for chemical tempering according to any one of claims 1-3, wherein the glass has a hardness higher than 750 Kgf/mm after being chemical tempered.

10. The aluminosilicate glass for chemical tempering according to any one of claims 1-3, wherein the glass has a hardness higher than 550 Kgf/mm and a T_g of 500-570°C after being tempered in mixed salts of molten KNO₃ and NaNO₃.

11. An aluminosilicate glass ceramics for chemical tempering, the glass ceramics comprises: component wt.%

SiO₂ 50-62.5

Al₂O₃ 16-21

Na₂O 8- <12

K₂O 0- <2

MgO 0- <l

B₂O₃ 0-10 Li₂O > 2-6

ZnO 0-8

CaO 0- <l

ZrO₂ 0.1-4

TiO₂ 0-4

CeO₂ 0.01- 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.002-4

P₂0₅/SiO₂ > 0.0016-0.15 wherein the glass ceramics has a hardness higher than 700 Kgf/mm .

12. The aluminosilicate glass ceramics for chemical tempering according to claim 1 1, the glass ceramics comprises: component wt.%

SiO₂ 54-62.5

Al₂O₃ 16-19

Na₂O 8.5- <10

K₂O 0- <l

MgO 0- <l

B₂O₃ 0-10

Li₂O 3-6

ZnO 0-6

CaO 0- <l ZrO₂ 2.6-4

TiO₂ 0-2

CeO₂ 0.01- 0.2

F₂ 0-0.5

SnO₂ 0.01-0.5

SrO 0-1

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.17-2

P₂0₅/SiO₂ > 0.016-0.14 wherein the glass ceramics has a hardness higher than 700 Kgf/mm .

13. The aluminosilicate glass ceramics for chemical tempering according to claim 1 1, the glass ceramics comprises: component wt.%

SiO₂ 55-62.5

Al₂O₃ 17-18

Na₂O 9- <10

K₂O 0-0.8

B₂O₃ 0-10

Li₂O 4-6

ZnO 0-5

CaO 0- <l

ZrO₂ 3-4

TiO₂ 0-1

CeO₂ 0.01- 0.2

F₂ 0-0.5 SnO₂ 0.01-0.5

SrO 0-1

P₂0₅ 2-6

SO₃ 0-0.05

Fe₂O₃ 0.06-0.12

P₂O₅/Li₂O 0.17-1.5

P₂0₅/SiO₂ 0.017-0.1 wherein the glass ceramics has a hardness higher than 700 Kgf/mm .

14. The aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-13, wherein the glass ceramics has a hardness higher than 750 Kgf/mm after being chemical tempered.

15. The aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-13, wherein the glass ceramics has a hardness higher than 800 Kgf/mm after being chemical tempered.

16. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein a potassium ion surface compressive layer having a depth of > 20 μιη is formed after being tempered in molten KNO₃.

17. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein a potassium ion surface compressive layer having a depth of > 30 μιη is formed after being tempered in molten KNO₃.

18. The alumino silicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein a potassium ion surface compressive layer having a depth of > 35 μιη is formed after being tempered in molten KNO₃.

19. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 1 1-15, wherein a potassium ion compressive layer having a surface compressive stress of depth of at least

600 Mpa is formed after being tempered in molten KNO₃.

20. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 1 1-15, wherein a potassium ion compressive layer having a surface compressive stress of at least 700 MPa is formed after being tempered in molten KNO₃.

21. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein a potassium ion compressive layer having a surface compressive stress of at least 800 Mpa is formed after being tempered in molten KNO₃.

22. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein a potassium ion surface compressive layer having a depth of at least 850 Mpa is formed after being tempered in molten KNO₃.

23. The alumino silicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 1 1-15, wherein a sodium ion surface compressive layer having a depth of at least 50 μιη, preferably at least 100 μιη, more preferably at least 150 μιη is formed, after being tempered in molten NaNO₃ .

24. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein a potassium ion and sodium ion surface compressive layer having a depth of at least 50 μιη, preferably at least 100 μιη, more preferably at least 150 μιη is formed after being tempered in mixed salts of molten KNO₃ and NaNO₃.

25. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein a potassium ion and sodium ion compressive layer having a surface compressive stress of at least 600 Mpa, preferably at least 800 Mpa, more preferably at least 1000 Mpa are formed after being tempered in mixed salts of molten KNO₃ and NaNO₃.

26. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 1 1-15, the glass or glass ceramics is free of As₂O₃ or Sb₂O₃.

27. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein at least one of the following components is used as a refining agent,

CeO₂ 0.01- <0.2 wt%

0-0.5 wt%

SnO₂ 0.01-0.5 wt%.

28. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein the glass is a thin glass, and the glass ceramics is a thin glass ceramics, with a thickness less than 5.0 mm.

29. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein the glass is a thin glass, and the glass ceramics is a thin glass ceramics, with a thickness less than 4.0 mm.

30. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein the glass is a thin glass, and the glass ceramics is a thin glass ceramics, with a thickness less than 2.0 mm.

31. The aluminosilicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein the glass is a thin glass, and the glass ceramics is a thin glass ceramics, with a thickness less than 1.0 mm.

32. The alumino silicate glass for chemical tempering according to any one of claims 1-10, or the aluminosilicate glass ceramics for chemical tempering according to any one of claims 11-15, wherein the glass is a thin glass, and the glass ceramics is a thin glass ceramics, with a thickness less than 0.5 mm.

33. A method for chemical tempering the glass or the glass ceramics according to any one of the preceding claims, comprising providing the aluminosilicate glass according to any one of claims 1-10, or the aluminosilicate glass ceramics according to any one of claims 11-15, wherein the tempering is conducted in molten KNO₃, or in molten NaNO₃, or in mixed salts of molten NaNO₃ and KNO₃ or in two-step by use of NaNO₃ and KNO₃.

34. The aluminosilicate glass according to any one of claims 1-10, or the aluminosilicate glass ceramics according to any one of claims 11-15, wherein a sodium ion compressive layer and a potassium ion compressive layer are formed after tempering in mixed salts of molten NaNO₃ and KNO₃ or in two-step by use of NaNO₃ and KNO₃, and a ratio of the potassium ion depth of surface compressive layer (DoL) to the sodium ion depth of surface compressive layer (DoL) is 0.01-0.5, preferably 0.05-0.3, more preferably 0.1-0.2.

35. The method according to claim 33 or 34, wherein the chemical tempering is performed at a temperature ranging from 350°C to 490°C for a treating period of time of 1-16 hours.

36. The method according to claim 35, wherein the chemical tempering is performed at a temperature ranging from 350°C to 490°C for a treating period of time of 4-16 hours.

37. The method according to claim 36, wherein the chemical tempering is performed at a temperature ranging from 400°C to 480°C for a treating period of time of 4-14 hours.

38. The method according to claim 37, wherein the chemical tempering is performed at a temperature ranging from 420°C to 460°C for a treating period of time of 6-14 hours.

39. The aluminosilicate glass according to any one of claims 1-10, or the aluminosilicate glass ceramics according to any one of claims 11-15, wherein it can be manufactured through a micro float process.

40. The aluminosilicate glass according to any one of claims 1-10, or the aluminosilicate glass ceramics according to any one of claims 11-15, wherein the aluminosilicate glass or the aluminosilicate glass ceramics is intended for 3D precision molding and thermal bending.

41. Uses of the aluminosilicate glass according to any one of claims

I- 10, or the aluminosilicate glass ceramics according to any one of claims

I I- 15 for manufacturing the cover glass used in cell phones, smart phones, tablet PCs, notebook PCs, PDAs, televisions, personal PCs, MTA machines or industrial displays; or for manufacturing the cover glass used in touch screens, cover windows, windows of automobiles, windows of trains, windows of aviation machines, cover glass of touch screens; or for manufacturing the substrate of hard disks or solar cells; or for manufacturing the parts of white home appliances or cookers.

42. A glass prefabricated article, wherein the glass prefabricated article or the glass ceramics prefabricated article is made of the aluminosilicate glass according to any one of claims 1-10, or the aluminosilicate glass ceramics according to any one of claims 1 1-15.

43. A glass prefabricated article or a glass ceramics prefabricated article, wherein the glass prefabricated article or the glass ceramics prefabricated article has a surface compressive layer, the glass prefabricated article or the glass ceramics prefabricated article has a potassium ion surface compressive layer having the depth of at least 20 μιη or a sodium ion surface compressive layer having the depth of at least 80 μιη, preferably a potassium ion surface compressive layer having the depth of at least 25 μιη or a sodium ion surface compressive having the depth of at least 100 μιη.

44. A glass prefabricated article or a glass ceramics prefabricated article, wherein the glass prefabricated article has a CTE of 4.5-10x l0^"6 K^"1, and a T_g of 480-590^°C , and the glass prefabricated article is suitable for thermal pressing, 3D precision molding and thermal bending.

45. A glass article obtained from the glass prefabricated article according to claim 44.

46. Use of the glass article according to claim 45 for the cover glass of mobile electronic devices and portable devices, or for the back panel of notebook PCs.