Abstract: An alkali-free glass consisting essentially of: SiO2 64 to 76 mol %,  Al2O3 5 to 14 mol %, B2O3 5 to 16 mol %, MgO 1 to 16.5 mol %, CaO 0 to 14 mol %, SrO 0 to 6 mol %, and BaO 0 to 2 mol %.

Abstract: A glass for a data storage medium substrate, which consists essentially of the following components as represented by mol %: SiO2 60 to 72, Al2O3  2 to 9 MgO  3 to 9, CaO  2 to 10, SrO  0 to 15, ZnO  0 to 4, TiO2  0 to 8, ZrO2  0 to 4, Li2O  1 to 12, Na2O  0 to 8, K2O  0 to 5, Y2O3  0 to 5, La2O3  0 to 5, and Li2O + Na2O + K2O  4 to 15, and which has a Young's modulus of at least 85 GPa.

Abstract: A flat speaker device having a flat speaker unit fitted into a through-hole for mounting a speaker of a wall surface board having its back secured to a wall surface leaving a specific spacing therebetween, the flat speaker unit comprising a total-drive type flat speaker comprising a plurality of magnets juxtaposed on a plane and a diaphragm formed from a plurality of projections for respectively covering the plurality of magnets, a speaker frame with a mounting flange mounted on the flat speaker so as to encircle the outer periphery of the flat speaker, rod-like screw members mounted so as to pass through the speaker frame from the front surface towards the back, and swining blades each disposed on the back of the speaker frame with one end threadedly engaged with a respective rod-like screw member and having a length such that when the blade is swung outwardly of a diagonal line of the speaker frame, the tip portion of the blade extends outwardly from the speaker frame.