ISNOG 2014, 19th International Symposium on Non-Oxide and New Optical Glasses, Aug. 24-28th, 2014, Jeju, KOREA

A2-709-1001
Development of high strength chemically strengthened glass
K. Kawamoto, T. Murata, S. Miwa, M. Ohji, H. Yamazaki
Nippon Electric Glass Co., Ltd. 7-1 Seiran 2-Chome. Otsu, Shiga 520-8639, Japankkawamoto@neg.co.jp

ln(ln(1/(1-F)))

Newly developed chemically strengthened glass, T2X-1, is demonstrated. T2X-1 has high strength andexcellent ion-exchange property.
A cover glass is expected to have a deep compressive stress layer and a high compressive stress in order toobtain and to maintain a high fracture strength [1,2]. A 40 m or more compressive stress layer and a 700MPa or
more compressive stress is usually recommended for a cover glass. However, there are two problems, one is along ion-exchange time to create a deep compressive layer and the other is a deterioration of compressive stressin mass production by Na+ contamination in molten KNO3. Therefore, the following two improvements for ion
exchange properties of chemically strengthened glass are requested. One is a fastening of ion-exchange speed.
The other is to keep high compressive stress even in highly Na+ ion contaminated molten KNO3.
The fracture strength, the depth of compressive stress layer (DOL) and the compressive stress value (CS) of
T2X-1 were investigated experimentally and compared with conventional glasses. Glass substrates, 0.7mm
thick T2X-1, CX-01 (conventional Alumino-silicate: AS) and Soda-lime (SL), were used.
Specimens of dimensions 135.4×85.2×0.7mm were ion exchanged and tested by three point bending test.
T2X-1, AS and SL were ion-exchanged in molten KNO3 at 430oC for 4.5, 8 and 1 hours, respectively. Na+concentration in molten KNO3 was 1,000ppm. The figure below shows a Weibull plot of fracture strength ofT2X-1, AS and SL. DOL, CS and fracture strength 15 percentile (B15) of each are also shown. T2X-1 has higher
fracture strength than AS and SL. B15 of T2X-1 was 20% higher than that of conventional Alumino-silicate.
T2X-1, AS and SL were ion exchanged in molten KNO3 at 430oC for 1 to 8 hours. T2X-1 achieved 40 m ofDOL at 3 hours. On the other hand, 6 hours and over 8 hours were necessary for AS and SL, respectively. T2X1
has twice faster ion-exchange speed compared conventional Alkali-alumino-silicate.
T2X-1, AS and SL were ion-exchanged in molten KNO3 at 430oC for 3, 6 and 13 hours, respectively, tocreate about 40 m of DOL. Na+ concentration in molten KNO3 ranged form 0 to 20,000ppm. T2X-1 could keep
CS over 700MPa until 15,000ppm, whereas, AS could keep CS over 700MPa until 4,000ppm. SL could notachieve 700MPa. T2X-1 is durable against the CS deterioration by fourfold more Na+ contamination in molten
KNO3 than conventional Alkali-alumino-silicate.
1.5
1.0
0.5
0.0-0.5-1.0

 T2X-1
DOL: 49m
CS: 860MPa
B15: 720MPa
ٌAlumino-silicate
DOL: 47m
CS: 740MPa
B15: 610MPa
٠ Soda-lime
DOL: 11m
CS: 550MPa-1.5-2.0-2.5-3.0-3.5-4.0
6.2

6.3

6.4

6.5

6.6

6.7

ln()

Fig. 1. Weibull plot of T2X-1, Alumino-silicate and Soda-lime. [MPa] is fracture strength. F is failure probability
calculated by Mean ranks.
References[1] Sinue Gomez et al, “Designing Strong Glass for Mobile Devices”, SID 09 DIGEST, pp1045-1048[2] James J. Price et al, “A Mechanics Framework for Ion-Exchanged Cover Glass with a Deep Compression Layer”, SID 09 DIGEST,
pp1049-1051

20 ∷ISONG 2014∷60