SILICATE PRODUCT AND STRENGTHENING METHOD THEREOF

Abstract

Provided is a silicate article comprising SiO.sub.2, Al.sub.2O.sub.3, Na.sub.2O, K.sub.2O, MgO and ZrO.sub.2, wherein the content of Al.sub.2O.sub.3 is 15-28 parts by weight, the content of Na.sub.2O is 13-25 parts by weight, the content of K.sub.2O is 6-15 parts by weight, the content of MgO is 7-16 parts by weight, and the content of ZrO.sub.2 is 0.1-5 parts by weight, relative to 100 parts by weight of SiO.sub.2; and M is 5-13, as calculated by the following formula: M=P.sub.1*wt (Na.sub.2O)+P.sub.2*wt (K.sub.2O)+P.sub.3*wt (MgO)+P.sub.4*wt (ZrO.sub.2)P.sub.5*wt (Al.sub.2O.sub.3)*wt (Al.sub.2O.sub.3). In the formula, P.sub.1 has a value of 0.53, P.sub.2 has a value of 0.153, P.sub.3 has a value of 0.36, P.sub.4 has a value of 0.67, and P.sub.5 has a value of 0.018. The invention further provides a method for chemically strengthening the silicate article, wherein the Young's modulus and the surface compressive stress value of the silicate article can be further improved by using an ultrasonic treatment or both an ultrasonic treatment and a microwave treatment during the chemical strengthening process; furthermore, the tendency of the compressive stress value to change with depth and the depth of a layer of compressive stress can be controlled, thereby effectively preventing spontaneous burst, or slow cracking after collision.

Claims

1. A glass composition, comprising SiO.sub.2, Al.sub.2O.sub.3, Na.sub.2O, K.sub.2O, MgO and ZrO.sub.2, wherein the content of Al.sub.2O.sub.3 is 15-28 parts by weight, the content of Na.sub.2O is 13-25 parts by weight, the content of K.sub.2O is 6-15 parts by weight, the content of MgO is 7-16 parts by weight, and the content of ZrO.sub.2 is 0.1-5 parts by weight, relative to 100 parts by weight of SiO.sub.2; and wherein the glass composition has an M value of 5-13, as calculated by the following formula (1):
M=P.sub.1*wt(Na.sub.2O)+P.sub.2*wt(K.sub.2O)+P.sub.3*wt(MgO)+P.sub.4*wt(ZrO.sub.2)P.sub.5*wt(Al.sub.2O.sub.3)*wt (Al.sub.2O.sub.3)(1) wherein wt (Na.sub.2O) represents the part by weight of Na.sub.2O relative to 100 parts by weight of SiO.sub.2, wt (K.sub.2O) represents the part by weight of K.sub.2O relative to 100 parts by weight of SiO.sub.2, wt (MgO) represents the part by weight of MgO relative to 100 parts by weight of SiO.sub.2, wt (ZrO.sub.2) represents the part by weight of ZrO.sub.2 relative to 100 parts by weight of SiO.sub.2, and wt (Al.sub.2O.sub.3) represents the part by weight of Al.sub.2O.sub.3 relative to 100 parts by weight of SiO.sub.2; and wherein P.sub.1 has a value of 0.53, P.sub.2 has a value of 0.153, P.sub.3 has a value of 0.36, P.sub.4 has a value of 0.67, and P.sub.5 has a value of 0.018.

2. The glass composition according to claim 1, wherein the value of M is 6-10, further preferably the value of M is 6.5-9, and further preferably 7-8.

3. The glass composition according to claim 1, wherein the content of Al.sub.2O.sub.3 is 18-25 parts by weight, the content of Na.sub.2O is 17-23 parts by weight, the content of K.sub.2O is 7-12 parts by weight, the content of MgO is 8-14 parts by weight, and the content of ZrO.sub.2 is 0.8-2 parts by weight, relative to 100 parts by weight of SiO.sub.2.

4. The glass composition according to claim 1, wherein said glass composition further comprises a certain amount of SrO, the content of SrO being 0-3 parts by weight, preferably less than 0.6 parts by weight, relative to 100 parts by weight of SiO.sub.2.

5. The glass composition according to claim 1, wherein said glass composition further comprises BaO and CaO, the content of BaO being 0-2 parts by weight, preferably less than 0.5 parts by weight, and the content of CaO being 0-2 parts by weight, preferably less than 0.5 parts by weight, relative to 100 parts by weight of SiO.sub.2.

6. The glass composition according to claim 1, wherein said glass composition has a 10% HF acid/20 C./20 min corrosion amount of less than 38 mg/cm.sup.2.

7. The glass composition according to claim 1, wherein said glass composition has a Young's modulus of higher than 65 GPa, further preferably higher than 75 GPa.

8. A glass plate, characterized in that said glass plate is made from the glass composition according to claim 1.

9. A glass plate, characterized in that said glass plate is made from the glass composition according to claim 1, wherein the ratio of a surface compressive stress value at a depth of 3 m of said glass plate to that at a depth of 7 m, and the thickness of a layer of compressive stress are calculated by the following formula (2), and the resulting value of the crack resistance factor K should be less than 8:
K=Q.sub.1*(x/y).sup.2+Q.sub.2*(x/y)Q.sub.3*d/10(2) wherein x is the surface compressive stress value at a depth of 3 m of the glass plate, and y is the surface compressive stress value at a depth of 7 m of the glass plate, in unit of MPa; and d represents the thickness of a layer of compressive stress, in unit of m; wherein Q.sub.1 has a value of 3.5, Q.sub.2 has a value of 1.8, and Q.sub.3 has a value of 0.12.

10. The glass plate according to claim 9, wherein the value of K is less than 7.7, further preferably less than 7.3.

11. A method for preparing the glass plate according to any one of claims 9 to 10, characterized in that the glass composition according to any one of claims 1 to 7 is manufactured into a plate-shaped article and subjected to chemical strengthening, wherein said chemical strengthening comprises immersing the plate-shaped article in a molten salt of a nitrate, optionally, immersing said plate-shaped article in a molten salt of sodium nitrate (NaNO.sub.3), a molten salt of potassium nitrate (KNO.sub.3), or a mixed molten salt thereof; optionally, first immersing said plate-shaped article in a molten salt of sodium nitrate (NaNO.sub.3) and then immersing in a molten salt of potassium nitrate (KNO.sub.3).

12. The preparation method according to claim 11, wherein during the chemical strengthening, the temperature of the molten salt is 380 C.-450 C., preferably 390 C.-420 C., and more preferably 400 C., and the immersion time is 0.3-9 hours, preferably 1-8 hours, further preferably 2-7 hours, further preferably 3-6 hours, and more preferably 4-5 hours.

13. The preparation method according to claim 12, wherein an ultrasonic treatment is added during the chemical strengthening.

14. The preparation method according to claim 13, wherein the ultrasonic wave in said ultrasonic treatment has an average acoustic energy density of 50-60 W/L and an ultrasonic frequency of 25-40 kHz.

15. The preparation method according to claim 13, wherein the temperature of said ultrasonic treatment is 380 C.-425 C., preferably 390 C.-410 C.; and the treatment time is 10-80 min, preferably 15-50 min, and more preferably 20-40 min.

16. The preparation method according to claim 13, wherein said ultrasonic treatment is carried out at intervals, wherein the time interval between ultrasonic treatments is 1-40 min, preferably 3-35 min, and more preferably 5-20 min; and the ultrasonic treatment time each time is 10-80 min, preferably 15-50 min, and more preferably 20-40 min.

17. The preparation method according to claim 13, wherein while performing the chemical strengthening, microwave radiation is applied to the surface of the glass, preferably performed alternately with the ultrasonic treatment.

18. The preparation method according to claim 17, wherein the frequency range of the microwave is 1.1-6.2 GHz, preferably 2.6-4.6 GHz, more preferably 3.0-4.0 GHz, and most preferably 3.3-3.5 GHz.

19. The preparation method according to claim 17, wherein the duration of application of the microwave is 5-60 min, preferably 10-40 min, and most preferably 12-25 min.

20. The preparation method according to claim 17, wherein the time interval of application of the microwave is 2-30 min, preferably 5-20 min, and more preferably 7-15 min; and the duration of application of the microwave each time is 5-60 min, preferably 10-40 min, and most preferably 12-25 min.

21-22. (canceled)

Description

DETAILED DESCRIPTION OF EMBODIMENTS

[0058] Specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are merely illustration and explanation of the present invention and are not intended to limit the present invention.

[0059] Tables 1 and 2 show the components of glasses and the contents thereof, as well as the process parameters of the preparation of the glass in Examples 1-10 and Comparative Examples 1-5.

[0060] There is no particular limitation on the preparation of molten glass, and hereinafter the preparation steps are described taking Example 1 as an example as follows:

[0061] Appropriate amounts of various raw materials are mixed, placed in a crucible made from platinum and heated to about 1,400 C. to 1,600 C. to melt them, and after being defoamed and homogenized, the mixture is poured into a mould and annealed to obtain a glass block. The glass block is then cut and ground to obtain a glass plate having a thickness of 0.5 mm, and the glass plate is cut into a desired size (65 mm*135 mm).

[0062] The glass plate is immersed in a molten salt of potassium nitrate (KNO.sub.3), wherein the temperature of the molten salt and the immersion time are specifically shown in the table; and the specific parameters for the ultrasonic treatment and the microwave treatment are also detailed in the table.

[0063] The compressive stress S (unit: MPa) and the thickness t (unit: m) of the layer of compressive stress are measured by using methods known in the art.

[0064] Such methods include, but are not limited to, measuring surface stress (FSM) using, for example, FSM-6000 manufactured by Luceo Co., Ltd. (Tokyo, Japan) or a similar commercial instrument, and in the examples and comparative examples in the present invention, the compressive stress and the depth of layer of compressive stress are measured by using FSM-6000 manufactured by Luceo Co., Ltd. (Tokyo, Japan), specifically by means of methods as described in ASTM 1422C-99 entitled Standard Specification for Chemically Strengthened Flat Glass, and as described in ASTM 1279.19779 entitled Standard Test Method for Non-Destructive Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-Strengthened, and Fully Tempered Flat Glass, which are incorporated herein by reference in their entirety. The measurement of surface stress relies on the accurate measurement of stress optical coefficient (SOC), which is related to the birefringence of a stress-induced glass.

[0065] The instrument has the following parameters:

[0066] Measurement range: 0-1000 MPa

[0067] Measurement accuracy: 20 MPa

[0068] Measurement range (depth of layer of stress): 10-100 m

[0069] Accuracy (depth of layer of stress): 5 m

[0070] Light source: High-brightness LED light source produced by Orihara corporation

[0071] Measurement shape: flat glass, 1010 mm or larger

[0072] Prism: size=12*7 mm RI=1.72/590 nm

[0073] During measurement, the two surfaces of the glass plate are subjected to mirror polish, grinding or etching to eliminate 3 m of the surfaces, and after measurement, the glass is further polished, ground or etched by 4 m.

[0074] A falling ball used in a falling ball impact test is made from stainless steel, and has a mass of 130 g and a diameter of 31.5 cm. During testing, the glass is placed on a bakelite plate mould made from a phenolic resin material, as conventionally used in the art, the above-mentioned steel ball is dropped from different heights, and by dropping ball multiple times, a simple average value of the ball drop height at which cracking occurs is calculated, as a crack height.

[0075] With regard to the resistance of the glass to slow cracking, if the glass plate is left to stand, the time consumed for observing the slow cracking thereof is too long; therefore, a glass plate in which a microcrack appears is placed on a vibrator to accelerate the cracking thereof for the purpose of testing. The change in the length of the crack is observed, and the times (min) required for the crack reaching 10 mm, 15 mm and 20 mm are recorded.

[0076] The vibrator may be any commercially available vibrator as long as the same vibrator and operating parameters are used in the examples and comparative examples. For example, a pneumatic vibrator (QSE small environmentally friendly vibrator, such as QSE-20, with a vibration force of 10 N, a frequency of 7-70 Hz, a noise of 25 db, and a working temperature of 10 C. to 70 C.) produced by Yantai JieShun Pneumatic Equipment Manufacturing Co., Ltd is used in the examples and comparative examples in the present invention, and during operation, the flat glass to be tested is placed above the vibrator.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 SiO.sub.2 100 100 100 100 100 100 100 Al.sub.2O.sub.3 17 18 25 25 15 20 22 Na.sub.2O 15 16 22 24 13 14 23 K.sub.2O 7 9 8 8 6 10 7 MgO 8 10 9 7 9 8 9 CaO 0.5 0 0.4 0 0.5 0.1 0.2 ZrO.sub.2 5 3 0.8 0.5 3.2 3 2 BaO 0.5 0.7 0.6 0 0.8 0.9 0.3 SrO 0.5 0 0.6 0 0.7 0.8 0.5 M (P.sub.1 = 0.53, 10.0 9.6 5.4 5.5 9.1 6.6 9.1 P.sub.2 = 0.153, P.sub.3 = 0.36, P.sub.4 = 0.67, and P.sub.5 = 0.018) The surface 689 672 670 660 650 580 560 compressive stress value at a depth of 3 m, S (MPa) The surface 595 580 578 573 560 450 430 compressive stress value at a depth of 7 m, S (MPa) Depth of 37.8 39.2 38.8 38.3 36.7 31.5 30.8 layer of compressive stress, t (m) K (Q.sub.1 = 3.5, 6.3 6.3 6.5 6.7 6.4 7.8 7.9 Q.sub.2 = 1.8, and Q.sub.3 = 0.12) Ultrasonic 55 57 55 50 60 treatment acoustic energy density (W/L) Ultrasonic 30 27 30 25 40 frequency (kHz) Ultrasonic 400 390 420 380 425 treatment temperature ( C.) Ultrasonic 25 20 22 10 8 treatment time (min) Time interval 12 18 15 5 12 (min) Microwave 3.0 3.5 3.3 2.6 3.0 treatment (GHz) Microwave 15 12 17 13 10 treatment time (min) Time interval 10 15 5 (min) Remarks After After After After After ultrasonic ultrasonic ultrasonic ultrasonic ultrasonic treatment, treatment, treatment, treatment, treatment, there is a there is a there is a there is a there is a time interval time interval time interval time interval time interval of 12 min of 18 min of 15 min of 5 min of 12 min before before before before before microwave microwave microwave microwave microwave treatment, treatment, treatment, treatment, treatment, and after the and after the and after the and after the and after the microwave microwave microwave microwave microwave treatment, treatment, treatment, treatment, treatment, the next there is a there is a there is a the next round of time interval time interval time interval round of ultrasonic of 10 min of 15 min of 5 min ultrasonic treatment before the before the before the treatment is carried next round of next round of next round of is carried out. ultrasonic ultrasonic ultrasonic out. treatment. treatment. treatment. Molten salt 420, 4 h 420, 4 h 420, 4 h 400, 4.5 h 400, 4.5 h 410, 3 h 410, 3 h temperature, immersion time Chemical 34 35 32 30 30 36 37 resistance to 10% HF acid/20 C./ 20 min (mg/cm.sup.2) Young's 86.5 89.8 79.8 75.4 74.8 68.4 67.4 modulus (GPa) Average 52 54 53 50 49 42 40 ball drop height at which cracking occurs (cm) (the falling ball has a mass of 130 g, and a diameter of 31.5 cm) Vibration test 19 17 18 16 14 11 10 (the time 31 27 30 26 22 19 20 required 46 39 45 38 37 30 32 for crack reaching 10 mm, 15 mm and 20 mm, respectively (min))

TABLE-US-00002 TABLE 2 Example Example Example Example Comparative Comparative Comparative Comparative 8 9 10 11 Example 1 example 2 example 3 Example 4 SiO.sub.2 100 100 100 100 100 100 100 100 Al.sub.2O.sub.3 20 20 22 22 15 21 20 22 Na.sub.2O 19 19 18 18 24 13 13 17 K.sub.2O 9 9 10 10 9 7 6 6 MgO 10 10 9 9 9 7 8 7 CaO 0 0.6 0.3 0 1 0.6 0.2 0.2 ZrO.sub.2 0.9 0.9 0.7 0.7 3 2 0.6 1 BaO 0 0.7 0.9 0 0.9 0.8 0.9 0.9 SrO 0 1.2 1 0 2 1.0 1.1 1.1 M (P.sub.1 = 0.53, 8.5 8.5 6.0 6.0 15.3 3.9 3.9 4.4 P.sub.2 = 0.153, P.sub.3 = 0.36, P.sub.4 = 0.67, and P.sub.5 = 0.018) The surface 714 690 650 640 560 530 540 590 compressive stress value at a depth of 3 m, S (MPa) The surface 625 608 536 545 400 390 400 445 compressive stress value at a depth of 7 m, S (MPa) Depth of 45.9 44.8 35.8 36.1 22.5 21.5 25.8 28.5 layer of compressive stress, t (m) K (Q.sub.1 = 3.5, 6.1 6.0 6.9 6.5 9.1 8.7 8.5 8.2 Q.sub.2 = 1.8, and Q.sub.3 = 0.12) Ultrasonic 55 56 56 55 55 treatment acoustic energy density (W/L) Ultrasonic 30 32 32 30 30 frequency (kHz) Ultrasonic 400 410 410 400 400 treatment temperature ( C.) Ultrasonic 35 20 25 15 25 treatment time (min) Time interval 10 12 12 10 9 (min) Microwave 3.0 3.5 3.5 3.0 3.0 treatment (GHz) Microwave 15 10 10 20 10 treatment time (min) Time interval 8 9 12 10 8 (min) Remarks After After After After After ultrasonic ultrasonic ultrasonic ultrasonic ultrasonic treatment, treatment, treatment, treatment, treatment, there is a there is a there is a there is a there is a time interval time interval time interval time interval time interval of 10 min of 12 min of 12 min of 10 min of 9 min before before before before before microwave microwave microwave microwave microwave treatment, treatment, treatment, treatment, treatment, and after the and after the and after the and after the and after the microwave microwave microwave microwave microwave treatment, treatment, treatment, treatment, treatment, there is a there is a there is a there is a there is a time interval time interval time interval time interval time interval of 8 min of 9 min of 12 min of 10 min of 8 min before the before the before the before the before the next round of next round of next round of next round of next round of ultrasonic ultrasonic ultrasonic ultrasonic ultrasonic treatment. treatment. treatment. treatment. treatment. Molten salt 420, 5 h 400, 4.5 h 400, 4.5 h 400, 4.5 h 400, 4.5 h 400, 4.5 h 420, 3 h 420, 3 h temperature, immersion time Chemical 32 33 33 30 48 55 47 41 resistance to 10% HF acid/20 C./ 20 min (mg/cm.sup.2) Young's 76.4 75.6 74.8 75 61.7 60.8 62.5 65.5 modulus (GPa) Average 55 57 54 51 30 31 32 36 ball drop height at which cracking occurs (cm) (the falling ball has a mass of 130 g, and a diameter of 31.5 cm) Vibration test 20 21 18 19 4 5 3 8 (the time 35 37 32 33 12 13 13 18 required 48 49 43 44 20 17 21 27 for crack reaching 10 mm, 15 mm and 20 mm, respectively (min))

TABLE-US-00003 TABLE 3 Example Example Example Example Comparative Comparative Comparative 12 13 14 15 Example 5 Example 6 Example 7 SiO.sub.2 100 100 100 100 100 100 100 Al.sub.2O.sub.3 28 18 27 23 14 29 14 Na.sub.2O 25 17 23 17 12 28 6.8 K.sub.2O 15 12 14 11 5 18 18 MgO 11 11 16 15 6 6.5 6.5 CaO 1.5 1.2 0.7 0.8 2.5 2.2 2.8 ZrO.sub.2 0.1 3.8 0.2 0.4 6 7.8 7.8 BaO 0.4 0.2 1.2 1.1 2.2 2.4 2.6 SrO 0.2 0.1 3 1.5 3.2 3.3 3.5 M (P.sub.1 = 0.53, 5.5 11.5 7.1 7.2 9.7 10.0 10.4 P.sub.2 = 0.153, P.sub.3 = 0.36, P.sub.4 = 0.67, and P.sub.5 = 0.018) The surface 685 668 675 670 560 584 566 compressive stress value at a depth of 3 m, S (MPa) The surface 590 577 582 563 418 428 426 compressive stress value at a depth of 7 m, S (MPa) Depth of 36.8 35.2 34.8 38.6 26.6 24.3 25.8 layer of compressive stress, t (m) K (Q.sub.1 = 3.5, 6.4 6.4 6.4 6.6 8.4 8.7 8.3 Q.sub.2 = 1.8, and Q.sub.3 = 0.12) Ultrasonic 55 57 55 50 55 50 57 treatment acoustic energy density (W/L) Ultrasonic 30 27 30 25 30 25 27 frequency (kHz) Ultrasonic 400 390 420 380 400 380 390 treatment temperature ( C.) Ultrasonic 25 20 22 10 20 10 20 treatment time (min) Time interval 12 18 15 5 12 5 18 (min) Microwave 3.0 GHz 3.5 GHz 3.3 GHz 2.6 GHz 3.0 GHz 2.6 GHz 3.5 GHz treatment (GHz) Microwave 15 12 17 13 15 13 12 treatment time (min) Time interval 10 10 15 5 10 5 10 (min) Remarks After After After After After After After ultrasonic ultrasonic ultrasonic ultrasonic ultrasonic ultrasonic ultrasonic treatment, treatment, treatment, treatment, treatment, treatment, treatment, there is a there is a there is a there is a there is a there is a there is a time interval time interval time interval time interval time interval time interval time interval of 12 min of 18 min of 15 min of 5 min of 12 min of 5 min of 18 min before before before before before before before microwave microwave microwave microwave microwave microwave microwave treatment, treatment, treatment, treatment, treatment, treatment, treatment, and after the and after the and after the and after the and after the and after the and after the microwave microwave microwave microwave microwave microwave microwave treatment, treatment, treatment, treatment, treatment, treatment, treatment, the next there is a there is a there is a the next there is a there is a round of time interval time interval time interval round of time interval time interval ultrasonic of 10 min of 15 min of 5 min ultrasonic of 5 min of 10 min treatment before the before the before the treatment before the before the is carried next round of next round of next round of is carried next round of next round of out. ultrasonic ultrasonic ultrasonic out. ultrasonic ultrasonic treatment. treatment. treatment. treatment. treatment. Molten salt 410, 4 h 410, 4 h 410, 4 h 420, 4.5 h 410, 4 h 420, 4 h 420, 4 h temperature, immersion time Chemical 34 35 32 34 41 42 42 resistance to 10% HF acid/20 C./ 20 min (mg/cm.sup.2) Young's 79.1 76.8 79.8 75.4 66.2 65.6 66.8 modulus (GPa) Average 49 44 48 50 38 38 35 ball drop height at which cracking occurs (cm) (the falling ball has a mass of 130 g, and a diameter of 31.5 cm) Vibration test 13 15 13 14 8 6 8 (the time 26 27 28 26 16 15 18 required 38 42 39 38 26 28 28 for crack reaching 10 mm, 15 mm and 20 mm, respectively (min))

[0077] As shown in Tables 1-3, the contents of the various components of the glass compositions and the values of M thereof in Examples 1-5 and 8-15 fall within the ranges of the present invention. In contrast, although the contents of the various components of the glass composition in Comparative Example 4 fall within the ranges of the present invention, the value M thereof is out of the range of the present invention; and although the values of M of the glass compositions in Comparative Example 5-7 fall within the ranges of the present invention, the contents of the various components thereof are out of the ranges of the present invention. In contrast, the glass products in Examples 1-5 and 8-15 are all superior to those in Comparative Examples 4-7 in terms of chemical resistance and Young's modulus, and also superior to those in Comparative Examples 4-7 in terms of the average height at which the glass plate cracks in the falling ball test, and the times required for crack reaching 10 mm, 15 mm and 20 mm, respectively, in the vibration test are longer than those in Comparative Examples 4-7, i.e., having a preferred resistance to slow cracking.

[0078] It can be seen that with respect to the cases where only the contents of the various components in the glass composition satisfy the ranges of the present invention or only the value of M satisfies the range of the present invention, the cases where the contents of the various components and the value of M both satisfy the ranges of the present invention can produce unexpected technical effects in terms of chemical resistance, Young's modulus, and crack resistance of the glass products.

[0079] Furthermore, it can be seen from Tables 1 and 2 that Examples 1-11, in which the contents of various components in the glass compositions satisfy the ranges of the present invention, the values of M satisfy a range of 5-13, and the values of the crack resistance factor K are less than 8, are superior to Comparative Examples 1-4 in terms of the chemical resistance and Young's modulus, and also superior to Comparative Examples 1-4 in terms of the average height at which the glass plate cracks in the falling ball test, and the times required for crack reaching 10 mm, 15 mm and 20 mm, respectively, in the vibration test are longer than those in Comparative Examples 1-4, i.e., having a preferred resistance to slow cracking.

[0080] Further preferably, where the contents of various components satisfy the ranges of the present invention and the value of M satisfies the range of 5-13, if no ultrasonic treatment or ultrasonic and microwave treatment is applied during the chemical strengthening, the performances such as chemical resistance,

[0081] Young's modulus, the height at which the glass plate cracks, times required for crack reaching certain lengths in the vibration test and the like are all inferior to those of a glass plate having been subjected to ultrasonic treatment or ultrasonic and microwave treatment during the chemical strengthening. For details, reference can be made to the data of Example 6 and Example 7, and the values of M therein are respectively 6.6 and 9.1, which satisfy the range of 5-13, but these examples are not subjected to ultrasonic and microwave treatment during the chemical strengthening; consequently, the values of the crack resistance factor K are relatively high, and are 7.8 and 7.9, respectively. The Young's moduli are 68.4 GPa and 67.4 GPa, respectively, which are lower than those in the other samples (Examples 1-5 and 8-11) which have been subjected to ultrasonic and microwave treatment during the chemical strengthening, but also higher than the values in Comparative Examples 1-4; the average heights at which the glass plate cracks in the falling ball test are slightly less than those in Examples 1-5 and 8-11, but higher than those in Comparative Examples 1-4; and the times required for crack reaching certain lengths in the vibration test are also shorter than those in Examples 1-5 and 8-11, but longer than those in Comparative Examples 1-4, that is to say, the resistance to slow cracking is worse than that in Examples 1-5 and 8-11, but superior to that in Comparative Examples 1-4. For Comparative Example 4, the value of M is 4.4, which is not in the range of 5-13, but ultrasonic treatment and microwave treatment are carried out during the chemical strengthening; it can be seen by comparison that the surface compressive stresses values at 3 m and 7 m and the crack resistance factor K are both better than those in Comparative Examples 1-3, the chemical resistance thereof to 10% HF acid/20 C./20 min is 41 mg/cm.sup.2, the Young's modulus is 65.5 GPa, and the ball drop height at which cracking occurs is 36 cm, which are all superior to the corresponding performances in Comparative Examples 1-3. In the vibration test, the times required for the crack reaching 10 mm, 15 mm and 20 mm, respectively, are 8 min, 18 min, and 27 min, respectively, which are all longer than those in Comparative Examples 1-3, that is to say, although the value of M does not satisfy the range of 5-13, the obtained glass plate sample can also have a relatively good resistance to slow cracking if the sample has been subjected to ultrasonic treatment and microwave treatment.

[0082] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments; various simple modifications can be made to the technical solutions of the present invention within the scope of the technical concept of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0083] It is to be further noted that the specific technical features described in the above-mentioned specific embodiments may be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not be further described with regard to various possible combinations.

[0084] In addition, any combination of various embodiments of the present invention may be made as long as the combination does not depart from the concept of the present invention, and such a combination should also be regarded as the disclosure of the present invention.