GLASS, STRENGTHENED GLASS, AND METHOD FOR MANUFACTURING STRENGTHENED GLASS

Abstract

A glass of the present invention includes as a glass composition, in terms of mass %, 50% to 75% of SiO.sub.2, 1% to 30% of Al.sub.2O.sub.3, 0% to 25% of B.sub.2O.sub.3, 0% to 10% of Li.sub.2O, 0.01% to 20% of Na.sub.2O, 0% to 10% of K.sub.2O, 0.0001% to 0.1% of Fe.sub.2O.sub.3, 0.00001% to 0.01% of Cr, 0.00001% to 0.01% of Ni, and 0.0001% to 0.5% of TiO.sub.2.

Claims

1. A glass, comprising as a glass composition, in terms of mass %, 50% to 75% of SiO.sub.2, 1% to 30% of Al.sub.2O.sub.3, 0% to 25% of B.sub.2O.sub.3, 0% to 10% of Li.sub.2O, 0.01% to 20% of Na.sub.2O, 0% to 10% of K.sub.2O, 0.0001% to 0.1% of Fe.sub.2O.sub.3, 0.00001% to 0.01% of Cr, 0.00001% to 0.01% of Ni, and 0.0001% to 0.5% of TiO.sub.2.

2. The glass according to claim 1, wherein the glass comprises as the glass composition, in terms of mass %, 50% to 75% of SiO.sub.2, 1% to 30% of Al.sub.2O.sub.3, 0% to 10% of B.sub.2O.sub.3, 0% to 10% of Li.sub.2O, 3% to 20% of Na.sub.2O, 0.001% to 10% of K.sub.2O, 0% to 8% of ZrO.sub.2, 0% to 10% of P.sub.2O.sub.5, 0.0001% to 0.1% of Fe.sub.2O.sub.3, 0.00001% to 0.01% of Cr, 0.00001% to 0.01% of Ni, and 0.0001% to 0.5% of TiO.sub.2.

3. The glass according to claim 1, wherein the glass comprises as the glass composition, in terms of mass %, 60% to 75% of SiO.sub.2, 1% to 15% of Al.sub.2O.sub.3, 1% to 25% of B.sub.2O.sub.3, 0% to 10% of Li.sub.2O, 1% to 15% of Na.sub.2O, 0.001% to 5% of K.sub.2O, 0% to 10% of CaO, 0% to 5% of BaO, 0% to 5% of ZnO, 0.0001% to 0.1% of Fe.sub.2O.sub.3, 0.00001% to 0.01% of Cr, 0.00001% to 0.01% of Ni, and 0.0001% to 0.1% of TiO.sub.2.

4. The glass according to claim 1, wherein the glass comprises as the glass composition, in terms of mass %, 65% to 75% of SiO.sub.2, 5% to 15% of Al.sub.2O.sub.3, 1% to 15% of B.sub.2O.sub.3, 0% to 5% of Li.sub.2O, 1% to 15% of Na.sub.2O, 0.001% to 5% of K.sub.2O, 0% to 10% of CaO, 0% to 5% of BaO, 0.0001% to 0.1% of Fe.sub.2O.sub.3, 0.00001% to 0.01% of Cr, 0.00001% to 0.01% of Ni, and 0.0001% to 0.1% of TiO.sub.2.

5. The glass according to claim 1, wherein the glass has a content of SnO.sub.2 of from 0 mass % to 3.0 mass % in the glass composition.

6. The glass according to claim 1, wherein the glass has a content of Cl of from 0.001 mass % to 0.3 mass % in the glass composition.

7. The glass according to claim 1, wherein the glass has a content of SO.sub.3 of from 0 mass % to 0.3 mass % in the glass composition.

8. The glass according to claim 1, wherein the glass has a shape selected from the group consisting of a sheet shape, a tube shape, and a rod shape.

9. The glass according to claim 1, wherein the glass has an external transmittance at a wavelength of 550 nm and a thickness of 0.55 mm of 90% or more.

10. The glass according to claim 1, wherein the glass has an external transmittance at a wavelength of 400 nm and a thickness of 0.55 mm of 85% or more.

11. The glass according to claim 1, wherein the glass has a chromaticity (X,Y) in xy chromaticity coordinates (C light source, sheet thickness 1 mm conversion) within a range of (0.3090 to 0.3120, 0.3150 to 0.3180).

12. The glass according to claim 1, wherein the glass is used for any one of a window glass for a vehicle, a cover glass of an interior panel for a vehicle, a cover glass for a CMOS sensor package, a cover glass for a LED package, a cover glass for a wireless communication device, a glass for a pharmaceutical container, a glass for a laboratory device, or a glass for supporting a semiconductor.

13. A tempered glass, comprising a compressive stress layer on a surface thereof, wherein the tempered glass comprises the glass of claim 1.

14. The tempered glass according to claim 13, wherein the tempered glass has a compressive stress value of from 200 MPa to 1,500 MPa on an outermost surface thereof.

15. The tempered glass according to claim 13, wherein the compressive stress layer has a depth of layer of from 5 μm to 100 μm.

16. A method of manufacturing a tempered glass, comprising melting and forming a glass batch containing a waste tempered glass to provide a glass, and then subjecting the glass to ion exchange treatment to provide a tempered glass.

17. The method of manufacturing a tempered glass according to claim 16, wherein a ratio of the waste tempered glass in the glass batch is from 0.1 mass % to 100 mass %.

18. The method of manufacturing a tempered glass according to claim 16, wherein the waste tempered glass comprises, as a glass composition, in terms of mass %, 50% to 75% of SiO.sub.2, 1% to 30% of Al.sub.2O.sub.3, 0% to 25% of B.sub.2O.sub.3, 0% to 10% of Li.sub.2O, 0.01% to 20% of Na.sub.2O, 0% to 10% of K.sub.2O, 0% to 0.3% of Cl, and 0% to 0.3% of SO.sub.3.

19. The method of manufacturing a tempered glass according to claim 16, wherein the waste tempered glass has a particle size D.sub.50 of from 1 μm to 100 μm.

20. The method of manufacturing a tempered glass according to claim 16, the method further comprising adding, as a glass raw material, one kind or two or more kinds selected from the group consisting of an alkali metal sulfate, an alkali metal chloride, stannic oxide, and antimony trioxide into the glass batch.

21. The method of manufacturing a tempered glass according to claim 16, the method further comprising adding, as a glass raw material, a nitrate raw material into the glass batch.

22. The method of manufacturing a tempered glass according to claim 21, wherein a cation of the nitrate raw material is an alkali metal ion or an alkaline earth metal ion.

23. The method of manufacturing a tempered glass according to claim 22, wherein the alkali metal ion is one kind or two or more kinds selected from the group consisting of a lithium ion, a sodium ion, and a potassium ion.

24. The method of manufacturing a tempered glass according to claim 22, wherein the alkaline earth metal ion is a strontium ion and/or a barium ion.

Description

EXAMPLES

[0080] The present invention is hereinafter described based on Examples. The present invention is by no means limited to the following Examples.

[0081] Examples (Sample Nos. 1 to 24) of the present invention are shown in Tables 1 and 2. Sample Nos. 1 to 23 are obtained by melting and forming a glass batch containing a waste tempered glass to provide a glass, and then subjecting the resultant to ion exchange treatment. Sample No. 24 is obtained by, after melting and forming of a glass batch containing a waste tempered glass are performed to provide a glass, subjecting the glass to crystallization treatment, and then subjecting the resultant crystallized glass to ion exchange treatment. Glass compositions of the waste tempered glasses used in Examples are shown in Tables 3 and 4. Those waste tempered glasses are each a waste tempered glass recovered from a cover glass for a smartphone, an ample tube, a glass for a building material, or a cover glass for an image pickup element, which is commercially available (Sample Nos. 25 to 49).

TABLE-US-00001 TABLE 1 mass % No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 SiO.sub.2 61.400 61.300 61.300 58.400 66.100 66.910 Al.sub.2O.sub.3 17.800 17.900 17.900 12.900 14.000 5.280 B.sub.2O.sub.3 0.600 0.600 0.600 0.000 2.500 20.600 Li.sub.2O 0.010 0.010 0.010 0.100 0.010 0.800 Na.sub.2O 14.500 14.500 14.400 14.400 13.400 2.340 K.sub.2O 2.020 2.050 2.140 5.640 0.600 1.590 MgO 3.050 3.020 2.980 1.990 3.000 0.000 CaO 0.024 0.078 0.120 2.030 0.000 0.550 SrO 0.000 0.007 0.014 0.000 0.000 0.000 BaO 0.013 0.017 0.013 0.014 0.000 1.140 ZnO 0.000 0.000 0.000 0.000 0.000 0.000 Y.sub.2O.sub.3 0.000 0.000 0.000 0.000 0.000 0.000 P.sub.2O.sub.5 0.000 0.000 0.000 0.000 0.000 0.000 ZrO.sub.2 0.001 0.012 0.017 4.460 0.000 0.000 Sb.sub.2O.sub.3 0.000 0.000 0.000 0.000 0.000 0.000 SnO.sub.2 0.350 0.330 0.340 0.000 0.350 0.000 Cl 0.037 0.036 0.046 0.016 0.046 0.080 F 0.000 0.000 0.000 0.000 0.000 0.710 SO.sub.3 0.000 0.003 0.005 0.027 0.003 0.000 Fe.sub.2O.sub.3 0.004 0.006 0.007 0.0220 0.0050 0.0005 Cr 0.00004 0.00006 0.00006 0.00014 0.00013 0.00004 Ni 0.00013 0.00008 0.00005 0.00005 0.00002 0.00008 TiO.sub.2 0.002 0.002 0.002 0.0290 0.0020 0.0005 Ratio (mass %) of waste tempered 0.1 50 80 98 77 15 glass in glass batch Average particle diameter D.sub.50 30 5,000 90 93 33 1,000 (μm) of waste tempered glass No. of waste glass used 25 25 25 26 27 28 External transmittance 92 92 92 92 92 92 (%) at 550 nm External transmittance 91 91 91 91 91 91 (%) at 400 nm Chromaticity X 0.3107 0.3104 0.3102 Unmeasured Unmeasured Unmeasured Chromaticity Y 0.3168 0.3162 0.3165 Unmeasured Unmeasured Unmeasured CS (MPa) 1,060 1,055 1,077 1,024 856 543 DOL (μm) 41 40 39 38.8 28 3 mass % No. 7 No. 8 No. 9 No. 10 No. 11 No. 12 SiO.sub.2 70.800 69.000 69.000 66.600 72.200 64.500 Al.sub.2O.sub.3 6.020 5.800 5.800 8.300 7.070 16.300 B.sub.2O.sub.3 12.300 10.200 10.200 9.700 10.900 0.000 Li.sub.2O 0.000 0.000 0.000 0.000 0.000 0.000 Na.sub.2O 6.460 10.700 10.700 11.100 5.860 13.800 K.sub.2O 1.120 0.006 0.005 0.002 1.950 0.150 MgO 0.050 0.000 0.000 0.000 0.013 5.100 CaO 0.750 3.100 3.100 3.100 0.720 0.030 SrO 0.040 0.000 0.000 0.000 0.026 0.000 BaO 2.140 0.000 0.000 0.000 1.190 0.000 ZnO 0.000 0.900 0.900 0.900 0.000 0.000 Y.sub.2O.sub.3 0.000 0.000 0.000 0.000 0.000 0.000 P.sub.2O.sub.5 0.000 0.000 0.000 0.000 0.000 0.000 ZrO.sub.2 0.080 0.000 0.000 0.000 0.000 0.070 Sb.sub.2O.sub.3 0.097 0.000 0.000 0.000 0.020 0.000 SnO.sub.2 0.000 0.300 0.300 0.300 0.000 0.000 Cl 0.110 0.005 0.003 0.005 0.080 0.003 F 0.000 0.000 0.000 0.000 0.000 0.000 SO.sub.3 0.000 0.000 0.000 0.000 0.000 0.010 Fe.sub.2O.sub.3 0.0340 0.0022 0.0004 0.0010 0.0097 0.0068 Cr 0.00007 0.00006 0.00001 0.00004 0.00010 0.00005 Ni 0.00010 0.00003 0.00001 0.00002 0.00001 0.00004 TiO.sub.2 0.0110 0.0010 0.0003 0.0010 0.0230 0.0140 Ratio (mass %) of waste tempered 83 51 8 23 91 88 glass in glass batch Average particle diameter D.sub.50 32 95 25 30 21 16 (μm) of waste tempered glass No. of waste glass used 29 30 31 32 36 37 External transmittance 92 92 92 92 92 92 (%) at 550 nm External transmittance 91 91 91 91 91 91 (%) at 400 nm Chromaticity X Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Chromaticity Y Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured CS (MPa) 398 811 811 923 379 1,062 DOL (μm) 9 9 9 12 14 30

TABLE-US-00002 TABLE 2 mass % No. 13 No. 14 No. 15 No. 16 No. 17 No. 18 SiO.sub.2 61.100 60.800 64.700 61.500 62.400 56.600 Al.sub.2O.sub.3 16.800 16.300 16.500 19.700 18.100 24.300 B.sub.2O.sub.3 0.000 0.600 0.000 3.900 0.000 0.000 Li.sub.2O 0.000 0.000 0.000 0.000 4.840 2.810 Na.sub.2O 15.400 14.100 14.900 13.200 5.630 10.000 K.sub.2O 0.920 3.640 0.000 0.010 2.160 0.014 MgO 5.350 3.580 3.500 1.500 1.950 0.000 CaO 0.016 0.520 0.060 0.030 0.240 0.023 SrO 0.000 0.000 0.000 0.000 0.000 0.000 BaO 0.000 0.000 0.000 0.000 0.000 0.000 ZnO 0.000 0.000 0.000 0.000 0.000 1.400 Y.sub.2O.sub.3 0.000 0.000 0.000 0.000 1.890 0.000 P.sub.2O.sub.5 0.000 0.000 0.000 0.000 0.000 4.700 ZrO.sub.2 0.330 0.000 0.020 0.000 2.420 0.007 Sb.sub.2O.sub.3 0.000 0.000 0.000 0.000 0.000 0.000 SnO.sub.2 0.000 0.480 0.360 0.190 0.000 0.080 Cl 0.004 0.012 0.004 0.015 0.004 0.011 F 0.000 0.000 0.000 0.000 0.000 0.000 SO.sub.3 0.037 0.003 0.003 0.002 0.064 0.001 Fe.sub.2O.sub.3 0.0060 0.0120 0.0070 0.0110 0.005 0.009 Cr 0.00004 0.00015 0.00009 0.00001 0.00011 0.00009 Ni 0.00004 0.00009 0.00012 0.00011 0.00050 0.00003 TiO.sub.2 0.0047 0.0049 0.0082 0.0056 0.15 0.011 Ratio (mass %) of waste tempered 71 81 82 46 99.9 83 glass in glass batch Average particle diameter D.sub.50 19 29 45 500 7 23 (μm) of waste tempered glass No. of waste glass used 38 39 40 41 42 43 External transmittance 92 92 92 92 92 92 (%) at 550 nm External transmittance 91 91 91 91 91 91 (%) at 400 nm Chromaticity X Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Chromaticity Y Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured CS (MPa) 1,140 886 1,068 980 970 993 DOL (μm) 30 33.8 33.1 34 9.8 26.7 mass % No. 19 No. 20 No. 21 No. 22 No. 23 No. 24 SiO.sub.2 56.800 52.200 68.600 61.500 62.200 67.880 Al.sub.2O.sub.3 25.100 27.500 4.630 16.600 17.300 22.280 B.sub.2O.sub.3 0.000 0.100 0.000 0.000 0.000 0.100 Li.sub.2O 3.640 3.100 0.000 0.000 0.000 3.800 Na.sub.2O 7.460 7.200 15.600 12.500 14.900 0.680 K.sub.2O 0.730 0.600 0.330 4.210 1.970 0.010 MgO 0.200 0.300 9.000 3.780 2.360 1.230 CaO 0.016 0.000 1.670 0.025 0.028 0.020 SrO 0.000 0.000 0.005 0.000 0.000 0.000 BaO 0.000 0.000 0.000 0.000 0.003 0.000 ZnO 0.000 0.000 0.000 0.000 0.000 0.000 Y.sub.2O.sub.3 0.000 0.000 0.000 0.000 0.000 0.000 P.sub.2O.sub.5 5.710 8.800 0.007 0.011 0.002 0.390 ZrO.sub.2 0.016 0.000 0.016 1.010 0.910 2.590 Sb.sub.2O.sub.3 0.000 0.000 0.000 0.000 0.000 0.000 SnO.sub.2 0.100 0.100 0.000 0.220 0.000 1.180 Cl 0.004 0.050 0.030 0.010 0.009 0.010 F 0.000 0.000 0.000 0.000 0.000 0.000 SO.sub.3 0.001 0.000 0.200 0.002 0.001 0.002 Fe.sub.2O.sub.3 0.048 0.007 0.013 0.005 0.006 0.009 Cr 0.00008 0.00006 0.00003 0.00001 0.00002 0.00001 Ni 0.00001 0.00002 0.00015 0.00013 0.00025 0.00001 TiO.sub.2 0.01 0.003 0.012 0.003 0.002 0.020 Ratio (mass %) of waste tempered 73 42 81 44 53 40 glass in glass batch Average particle diameter D.sub.50 18 37 30 48 16 15 (μm) of waste tempered glass No. of waste glass used 44 45 46 47 49 48 External transmittance 92 92 92 92 92 91 (%) at 550 nm External transmittance 91 91 91 91 91 87 (%) at 400 nm Chromaticity X Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Chromaticity Y Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured Unmeasured CS (MPa) 1,021 1,094 781 921 1,001 1,174 DOL (μm) 25.7 24.5 17.6 40.8 45.2 7.0

TABLE-US-00003 TABLE 3 mass % No. 25 No. 26 No. 27 No. 28 No. 29 No. 30 No. 31 No. 32 No. 33 No. 34 No. 35 No. 36 SiO.sub.2 61.5 58.4 66.1 66.9 70.8 69.0 69.0 69.0 69.0 69.0 66.6 72.2 Al.sub.2O.sub.3 18.0 12.9 14.0 5.3 6.0 5.8 5.8 5.8 5.8 5.8 8.3 7.1 B.sub.2O.sub.3 0.5 0.0 2.5 20.6 12.3 10.2 10.2 10.2 10.2 10.2 9.7 10.9 Li.sub.2O 0.0 0.1 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Na.sub.2O 14.5 14.4 13.4 2.3 6.5 10.7 10.7 10.7 10.7 10.7 11.1 5.9 K.sub.2O 2.0 5.6 0.6 1.6 1.1 0.0 0.0 0.0 0.0 0.0 0.0 2.0 MgO 3.0 2.0 3.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 CaO 0.1 2.0 0.0 0.6 0.8 3.1 3.1 3.1 3.1 3.1 3.1 0.7 SrO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 BaO 0.0 0.0 0.0 1.1 2.1 0.0 0.0 0.0 0.0 0.0 0.0 1.2 ZnO 0.0 0.0 0.0 0.0 0.0 0.9 0.9 0.9 0.9 0.9 0.9 0.0 Y.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 P.sub.2O.sub.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 ZrO.sub.2 0.0 4.5 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Sb.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SnO.sub.2 0.3 0.0 0.4 0.0 0.0 0.3 0.3 0.3 0.3 0.3 0.3 0.0 CS (MPa) 930 781 750 543 398 811 811 811 811 811 923 379 DOL (μm) 46 48 33 3 9 9 9 9 9 9 12 14

TABLE-US-00004 TABLE 4 mass % No. 37 No. 38 No. 39 No. 40 No. 41 No. 42 No. 43 No. 44 No. 45 No. 46 No. 47 No. 48 No. 49 SiO.sub.2 64.5 61.1 60.8 64.7 61.5 64.9 57.9 57.0 52.2 68.5 61.7 67.9 62.5 Al.sub.2O.sub.3 16.3 16.8 16.3 16.5 19.7 18.1 23.9 25.1 27.5 4.6 16.8 22.3 17.4 B.sub.2O.sub.3 0.0 0.0 0.6 0.0 3.9 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 Li.sub.2O 0.0 0.0 0.0 0.0 0.0 4.8 2.8 3.6 3.1 0.0 0.0 3.7 0.0 Na.sub.2O 13.8 15.4 14.1 14.9 13.2 5.3 10.0 7.5 7.2 15.6 12.3 0.7 14.8 K.sub.2O 0.2 0.9 3.6 0.0 0.0 0.2 0.0 0.7 0.6 0.3 4.1 0.0 2.0 MgO 5.1 5.4 3.6 3.5 1.5 2.0 0.0 0.2 0.3 9.0 3.8 1.3 2.4 CaO 0.0 0.0 0.5 0.1 0.0 0.2 0.0 0.0 0.0 1.7 0.0 0.0 0.0 SrO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 BaO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 ZnO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Y.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.0 1.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 P.sub.2O.sub.5 0.0 0.0 0.0 0.0 0.0 0.0 5.2 5.7 8.8 0.0 0.0 0.4 0.0 ZrO.sub.2 0.1 0.3 0.0 0.0 0.0 2.5 0.0 0.0 0.0 0.0 1.0 2.6 0.9 Sb.sub.2O.sub.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SnO.sub.2 0.0 0.0 0.5 0.4 0.2 0.0 0.1 0.1 0.1 0.0 0.2 1.1 0.0 CS (MPa) 875 800 743 834 850 700 815 774 800 800 942 300 1,013 DOL (μm) 25 50 39 53 39 15 15 15 15 25 46 110 45

[0082] As described below, each sample shown in Tables 1 and 2 was produced. First, a waste tempered glass was coarsely pulverized into a size of 5 mm or less, and was then pulverized with a commercially available glass pulverization apparatus, such as a ball mill or a jet mill, so as to have a predetermined particle diameter, to thereby prepare a powdered waste tempered glass. An average particle diameter D.sub.50 of each powder was measured with a commercially available laser diffraction particle size distribution analyzer or a known mesh sieve. Subsequently, a composition of the waste tempered glass after pulverization was analyzed, and then a waste glass, an oxide raw material, a nitrate raw material, and a carbonate raw material in the tables were mixed with each other so as to have a glass composition in the tables. Thus, a glass batch was produced. Next, the glass batch was melted in a continuous melting furnace, and the resultant molten glass was formed into a glass sheet. Subsequently, the resultant glass sheet was subjected to cut processing into a size of 200 mm×200 mm×0.55 mm.

[0083] Each resultant sample was evaluated for the glass composition, the transmittance, and the chromaticity.

[0084] The external transmittance is a value measured at an optical path length of 0.55 mm, and is a value measured with UV-3100PC manufactured by Shimadzu Corporation.

[0085] The chromaticity is a value calculated from a transmittance curve measured with UV-3100PC manufactured by Shimadzu Corporation in conformity with JIS Z8722:2009.

[0086] Subsequently, both surfaces of the glass sheet were subjected to optical polishing, and ion exchange treatment was performed by immersing the glass sheet in a KNO.sub.3 molten salt at 430° C. for 4 hours. After the ion exchange treatment, the surfaces of each sample were washed.

[0087] After that, the compressive stress value (outermost surface) and the depth of layer of the compressive stress layer on the surface were calculated based on the number of interference fringes observed with a surface stress meter (FSM-6000 manufactured by Orihara Industrial Co., Ltd.) and intervals therebetween. In the calculation, the refractive index and the optical elastic constant of each sample were set to 1.50 and 30 [(nm/cm)/MPa], respectively. The compressive stress value (outermost surface) and the depth of layer of the compressive stress layer on the surface of each sample shown in Tables 3 and 4 were also calculated by the same method.

[0088] As apparent from Tables 1 and 2, each of Sample Nos. 1 to 24 has a waste tempered glass introduced into the glass batch, but the transmittance of the resultant glass sheet is high. Thus, it is conceived that recycling of the waste tempered glass can be promoted.

INDUSTRIAL APPLICABILITY

[0089] The glass and the tempered glass of the present invention can be applied to, for example, a window glass for a vehicle, a cover glass of an interior panel for a vehicle, a cover glass for a CMOS sensor package, a cover glass for a LED package, a cover glass for a wireless communication device, a glass for a pharmaceutical container, a glass for a laboratory device, or a glass for supporting a semiconductor.