Glass plate for display device, plate glass for display device and production process thereof

Abstract

A process for producing a plate glass for a display device having a thickness of at most 1.5 mm by a float process, wherein the plate glass comprises, as represented by mole percentage based on the following oxides, from 67 to 75% of SiO2, from 0 to 4% of Al2O3, from 7 to 15% of Na2O, from 1 to 9% of K2O, from 6 to 14% of MgO and from 0 to 1.5% of ZrO2, has a total content of SiO2 and Al2O3 of from 71 to 75%, has a total content Na2O+K2O of Na2O and K2O of from 12 to 20%, and has a content of CaO of less than 1% if contained.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a glass plate for e.g. a cover glass or a glass substrate of a display device, typically a mobile device such as a cell phone or a personal digital assistance (PDA) or a small display device such as a touch panel, a plate glass used for production of such a glass plate, a process for producing such a plate glass, a cover glass and a display device.[0003]2. Discussion of Background[0004]In recent years, for mobile devices such as cell phones and PDA, use of a cover glass (protective glass) for protecting a display and improving appearance, is increasing.[0005]Weight reduction and thickness reduction are required for such portable digital devices. Therefore, a cover glass used for protecting a display is also required to be thin. However, if the thickness of the cover glass is made to be thin, the strength is lowered, and if a display device is dropped at a time of using or carrying it, th...

AI Technical Summary

Benefits of technology

[0042]According to the present invention, a thin plate glass for a display device, with which chipping is less likely to occur at the time of glass processing, and which is capable of chemical tempering treatment, can be obtained. Further, it is possible to produce such a thin plate glass by a float process.

[0043]Further, a glass plate and a cover glass for a display device, with which a decrease in the strength due to chipping at the time of glass processing before chemical tempering treatment is less likely to occur, and the possibility of destruction of glass by itself at the time of use is reduced, can be obtained.

Problems solved by technology

However, if the thickness of the cover glass is made to be thin, the strength is lowered, and if a display device is dropped at a time of using or carrying it, the cover glass itself may sometimes be broken.

Therefore, there is a problem that the cover glass cannot accomplish the original object to protect display devices.

If the air quenching tempering method is applied to a thin glass plate, the temperature difference between the surface and the inside tends not to arise, and it is thereby difficult to form a compressive stress layer, and the desired property of high strength cannot be obtained.

Accordingly, when a plate glass for a cover glass is processed to form a glass plate for a cover glass, it is subjected to a complicated process such as drilling or scribing a curve to be formed into a glass plate having a final shape in many cases.

If chipping occurs when such a plate glass (so-called raw plate glass) is processed, latent flaws are also formed at the same time.

However, in a case where a glass plate which has remaining latent flaws which have been formed at the same time as chipping by processing is chemically tempered, if the latent flaws are so deep that they are beyond the compressive stress layer, the improvement in the strength of the glass plate may be insufficient.

Further, if the latent flaws are present in an interior tensile stress layer of glass, cracks may expand by themselves and the glass may voluntarily break.

Further, in a case where chemical tempering treatment is carried out while glass dust formed by chipping is attached to the surface of the glass plate, only that portion is not tempered and may cause a drawback such as a dent or warpage.

That is, the chipping may cause a product failure other than the latent flaws, which may lead to a decrease in the strength.

In a case where such a large substrate is processed, as the one side tends to be long, formation of deep latent flaws is highly possible.

Further, as the substrate gets larger, it is heavier and is likely to bend, and the probability of breakage from the latent flaws tends to be high.

Accordingly, the probability of chipping is increased by the increase in size of the substrate, and the breakage failure of glass may be increased in the substrate processing step.

Such problems due to the chipping are more serious due to an increase in the demand for a reduction in the thickness of a cover glass accompanying need for weight saving of e.g. mobile devices.

That is, if the thickness of a cover glass is reduced form 2 mm to 1 mm, the strength is reduced to one quarter, and the above-described problems are more serious.