# US 2017/0283307 A1 · High-hardness transparent glass ceramic and preparation method therefore

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- Number: US 2017/0283307 A1
- Document ID: US20170283307A1
- Status: Published application
- Kind: A1
- Application number: 15/514,023
- Filed: 2015-09-22
- Published: 2017-10-05
- Earliest claimed: 2014-11-19
- Assignees: Cdgm Glass Co., Ltd
- Applicants: Cdgm Glass Co., Ltd
- Inventors: Baoping YUAN; Tianlai YU; Xuejian SU
- Web page: https://patentgrep.com/patent/US20170283307A1

## CPC

- C03C 10/0045: {containing SiO2, Al2O3 and MgO as main constituents}
- C03B 32/02: Thermal crystallisation, e.g. for crystallising glass bodies into glass-ceramic articles {(C03B27/012 takes precedence)}
- C03C 3/085: containing an oxide of a divalent metal
- C03C 3/095: containing rare earths
- C03C 3/097: containing phosphorus, niobium or tantalum
- C03C 2204/00: Glasses, glazes or enamels with special properties
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES

## Abstract

A high-hardness transparent glass ceramic and a preparation method therefor, wherein the components by weight percentage include: 55.0%-70.0% of SiO2, 15.0%-20.0% of Al2O3, 0%-10.0% of MgO, and 0%-12.5% of ZnO, necessarily including one of MgO or ZnO, and the crystallized glass thereof contains microcrystals of spinel crystal. In the present invention, a suitable precursor glass is subjected to thermal treatment, and microcrystals are separated from the glass substrate by crystallization, producing a glass ceramic having a Moh's hardness greater than 7 and a visible-light transparency rate greater than 80% through 1 mm of the glass. The glass ceramic of the invention overcomes the problem that ordinary optical glass is easy to be scratched. The present glass ceramic can be served as protective face for mobile phones, protective glass for optical instruments and in communications equipment, substrate for magnetic disks, LCD panel, or protective glass for other optoelectronic devices.

## Claims

### Claim 1

A high-hardness transparent glass ceramic, wherein the components by weight percentage include: 55.0%-70.0% of SiO2, 15.0%-20.0% of Al2O3, 0-10.0% of MgO, and 0-12.5% of ZnO, necessarily including one of MgO or ZnO, and the crystallized glass thereof contains microcrystals of spinel crystal.

### Claim 2 (depends on 1)

The high-hardness transparent glass ceramic according to claim 1, further including: 0-10.0% of ZrO2; 0-2.0% of P2O5; 0-7.0% of TiO2; 0-1.5% of Sb2O3; 0-0.5% of CeO2; 0-2.0% of Na2O; 0-2.0% of K2O; 0-2.0% of Y2O3; 0-1.0% of La2O3.

### Claim 3 (depends on 1)

The high-hardness transparent glass ceramic according to claim 1, including: 4-10.0% of MgO and/or 4-12.5% of ZnO.

### Claim 4 (depends on 1)

The high-hardness transparent glass ceramic according to claim 1, wherein the Moh's hardness of the glass is greater than 7, and the visible-light transparency rate is greater than 80% through 1 mm.

### Claim 5

A preparation method for a high-hardness transparent glass ceramic, comprising the following steps:
(a) Batching
Weighing raw materials based on the weight ratio, and then pouring into a mixer, and finally mixing uniformly to obtain a glass precursor material;
(b) Smelting
feeding the above glass precursor material into a smelting furnace for melting and clarification at high temperature, dissolving the glass precursor material into a high temperature glass stock solution while removing bubbles and foreign matters from the high temperature glass stock solution;
(c) Molding and annealing
roughly annealing the molten and molded high temperature glass stock solution at a certain tapping temperature;
(d) Thermal treatment
Placing the above roughly annealed glass into a high temperature furnace for thermal treatment, and then generating microcrystal of spinel crystal in the glass after thermal treatment, so as to obtain the high-hardness glass ceramic provided by the present invention.

### Claim 6 (depends on 5)

The preparation method for a high-hardness transparent glass ceramic according to claim 5, wherein, with regard to the raw material in step (a), MgO, Na2O and K2O are introduced in the form of carbonate or nitrate or sulfate, and other components are introduced in the form of oxide.

### Claim 7 (depends on 5)

The preparation method for a high-hardness transparent glass ceramic according to claim 5, wherein the melting in step (b) is: at 1550-1600° C., and lasting for 4-8 h; the clarifying is: at 1600-1650° C., and lasting for 4-10 h.

### Claim 8 (depends on 5)

The preparation method for a high-hardness transparent glass ceramic according to claim 5, wherein the tapping temperature in step (c) is 1500-1600° C.; the molding is resulted by cooling in a hot die, or a float process or a profiling process.

### Claim 9 (depends on 8)

The preparation method for a high-hardness transparent glass ceramic according to claim 8, wherein the hot die refers to making sure that the die temperature is 100-200° C. during molding; the cooling means blowing and cooling the pre-heated die when the high temperature molten glass is poured into the die.

### Claim 10 (depends on 5)

The preparation method for a high-hardness transparent glass ceramic according to claim 5, wherein the thermal treatment in step (d) comprises a crystal nucleus precipitation stage and a microcrystal growth stage; at the crystal nucleus precipitation stage, the temperature is required to be 650-800° C. and the time of duration to be 1-4 h; at the microcrystal growth stage, the temperature is required to be 850-1000° C., and the time of duration to be 0.5-4 h.

### Claim 11 (depends on 2)

The high-hardness transparent glass ceramic according to claim 2, including: 4-10.0% of MgO and/or 4-12.5% of ZnO.

### Claim 12 (depends on 2)

The high-hardness transparent glass ceramic according to claim 2, wherein the Moh's hardness of the glass is greater than 7, and the visible-light transparency rate is greater than 80% through 1 mm.