# US 9,434,644 B2 · Cover glass and method for producing cover glass

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- Number: US 9,434,644 B2
- Document ID: US9434644B2
- Status: Granted
- Kind: B2
- Application number: 13/247,627
- Filed: 2011-09-28
- Published: 2012-04-05
- Granted: 2016-09-06
- Earliest claimed: 2010-09-30
- Assignees: AvanStrate Inc.; Hoya Corporation
- Applicants: Akihiro Koyama; Mikiko Morishita; Satoshi Ami; Kazuaki Hashimoto; Tetsuo Takano
- Inventors: Akihiro Koyama; Mikiko Morishita; Satoshi Ami; Kazuaki Hashimoto; Tetsuo Takano
- Web page: https://patentgrep.com/patent/US9434644B2

## CPC

- C03C 21/002: {to perform ion-exchange between alkali ions (C03C21/005 takes precedence)}
- C03C 3/083: containing aluminium oxide or an iron compound
- C03C 3/085: containing an oxide of a divalent metal
- C03C 3/087: containing calcium oxide, e.g. common sheet or container glass
- C03C 15/00: Surface treatment of glass, not in the form of fibres or filaments, by etching (etching or surface-brightening compositions, in general C09K13/00)
- C03C 15/02: for making a smooth surface
- 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

## Abstract

The disclosed cover glass is produced by etching a glass substrate that has been formed by a down-drawing process, and chemically strengthening the glass substrate to provide the glass substrate with a compressive-stress layer on the principal surfaces thereof. The glass substrate contains, as components thereof, 50% to 70% by mass of SiO2, 5% to 20% by mass of Al2O3, 6% to 30% by mass of Na2O, and 0% to less than 8% by mass of Li2O. The glass substrate may also contain 0% to 2.6% by mass of CaO, if necessary. The glass substrate has an etching characteristic in which the etching rate is at least 3.7 μm/minute in an etching environment having a temperature of 22° C. and containing hydrogen fluoride with a concentration of 10% by mass.

## Claims

### Claim 1

A cover glass comprising:
a plate-shaped glass substrate having a compressive-stress layer on principal surfaces thereof,
the glass substrate containing, as components thereof, 50% to 67% by mass of SiO2, 5% to 20% by mass of Al2O3, 10% to 15.4% by mass of Na2O, 0% to 1% by mass of Li2O, 0% to less than 4% by mass of K2O, substantially no CaO, 0% to less than 0.1% by mass of ZrO2, 0% to 1% by mass of TiO2, 0% to 5% by mass of B2O3, and greater than 1% to 15% by mass of MgO,
the ratio of the content of K2O to R2O (K2O/R2O) of the substrate being from 0 to 0.08, and
the ratio of the content of ZrO2 and TiO2 to SiO2 ((ZrO2+TiO2)/SiO2) of the substrate being from 0 to 0.01, and if the content by percentage of the SiO2 is X % by mass and the content by percentage of the Al2O3 is Y % by mass, X-½·Y is 45% to 57.5% by mass.

### Claim 2 (depends on 1)

The cover glass according to claim 1, wherein the compressive-stress layer is formed on an end surface of the cover glass.

### Claim 3 (depends on 1)

The cover glass according to claim 1, wherein the glass substrate has an etching characteristic in which an etching rate is at least 3.7 μm/minute in an etching environment having a temperature of 22° C. and containing hydrogen fluoride with a concentration of 10% by mass.

### Claim 4 (depends on 1)

The cover glass according to claim 1, wherein the glass substrate is formed into a plate-like shape by a down-drawing process.

### Claim 5 (depends on 1)

The cover glass according to claim 1, wherein the glass substrate contains substantially no K2O.

### Claim 6 (depends on 1)

The cover glass according to claim 1, wherein the glass substrate has a strain point of 580° C. or more.

### Claim 7 (depends on 1)

The cover glass according to claim 1, wherein the depth of the compressive stress layer range is 47.7 μm to 90.0 μm.