Chemically strengthened glass, and electronic device housing
The present invention relates to a chemically strengthened glass having a thickness of t (unit: μm) and a relative permittivity of 7.0 or less at 20° C. and a frequency of 10 GHz, in which a value of Z determined by the following formula is 0.65 or more, where S1 is an entropy function calculated from an amount of alkali ions in a center portion of the glass, S2 is an entropy function calculated from an average amount of alkali ions from a glass surface to a depth of 0.05t, and X (unit: MPa) is an average value of a compressive stress in a region from the glass surface to the depth of 0.05t: Z=(S2−S1)×10+X/1000.
1 . A chemically strengthened glass having a thickness of t (unit: μm) and a relative permittivity of 7.0 or less at 20° C. and a frequency of 10 GHz, and
having a base composition comprising, in terms of molar percentage based on oxides:
10% or less of Al 2 O 3 ;
2% or less of K 2 O;
3% or less of MgO; and
14% or more of Li 2 O and/or Na 2 O in total,
wherein a value of Z determined by the following formula is 0.65 or more and a value of S1 is 0.2 or less, where S1 is an entropy function calculated from an amount of alkali ions in a center portion of the glass, S2 is an entropy function calculated from an average amount of alkali ions from a glass surface to a depth of 0.05t, and X (unit: MPa) is an average value of a compressive stress in a region from the glass surface to the depth of 0.05t:
Z =( S 2− S 1)×10+ X/ 1000,
provided that an entropy function S is calculated by the following formula from [Li 2 O], [Na 2 O], and [K 2 O] which are contents of Li 2 O, Na 2 O, and K 2 O respectively in terms of molar percentage based on oxides, and in the formula, when [Li 2 O], [Na 2 O], and [K 2 O] are zero, the entropy function S is 1×10 −4 :
S=−[Li 2 O]/([Li 2 O]+[Na 2 O]+[K 2 O])log([Li 2 O]/([Li 2 O]+[Na 2 O]+[K 2 O]))−[Na 2 O]/([Li 2 O]+[Na 2 O]+[K 2 O])log([Na 2 O]/([Li 2 O]+[Na 2 O]+[K 2 O]))−[K 2 O]/([Li 2 O]+[Na 2 O]+[K 2 O])log([K 2 O]/([Li 2 O]+[Na 2 O]+[K 2 O])), and
a content of Li ions after the chemical strengthening at the depth of 0.05t from the glass surface is greater than or equal to 4.1 mol %.
2 . The chemically strengthened glass according to claim 1 , wherein a value of (S2−S1) obtained by subtracting the entropy function S1 from the entropy function S2 is 0.04 or more.
3 . The chemically strengthened glass according to claim 1 , having a dielectric loss tangent of 0.02 or less at 20° C. and a frequency of 10 GHz.
4 . The chemically strengthened glass according to claim 1 , wherein the base composition comprises in terms of molar percentage based on oxides:
40% to 80% of SiO 2 ;
0% to 20% of B 2 O 3 ;
1% to 10% of Al 2 O 3 ; and
14% to 30% of Li 2 O and/or Na 2 O in total.
5 . The chemically strengthened glass according to claim 1 , having a surface compressive stress value CS 0 of 300 MPa or more.
6 . The chemically strengthened glass according to claim 1 , having an internal chemical strengthening stress CS 0.05t at a depth of 0.05t from the glass surface of 75 MPa or more,
wherein the thickness t is 300 μm or more.
7 . The chemically strengthened glass according to claim 1 , having a depth of a compressive stress layer DOL of 70 μm or more,
wherein the thickness t is 350 μm or more.
8 . The chemically strengthened glass according to claim 1 , being a lithium aluminosilicate glass,
wherein the base composition comprises, in terms of molar percentage based on oxides:
40% to 70% of SiO 2 ;
7.5% to 10% of Al 2 O 3 ; and
5% to 25% of Li 2 O.
9 . The chemically strengthened glass according to claim 1 , wherein the thickness t is 100 μm or more and 2000 μm or less.
10 . The chemically strengthened glass according to claim 1 , being a glass ceramic.
11 . The chemically strengthened glass according to claim 1 , having a dielectric loss tangent of 0.018 or less at 20° C. and a frequency of 10 GHz.
12 . An electronic device housing comprising the chemically strengthened glass according to claim 1 .