Abstract: A glass composition of the present disclosure includes, in wt %, 50?SiO2?56, 20?B2O3?30, 10?Al2O3?20, 3.5?MgO+CaO?10, and 0?R2O?1.0, further includes Fe2O3, and has a permittivity of less than 5.0 at a frequency of 1 MHz. R is at least one element selected from Li, Na, and K. The glass composition of the present disclosure is a low-permittivity glass composition with which the occurrence of fiber breakage during fiber forming can be reduced even when glass fibers to be formed have a small fiber diameter, and the occurrence of defects such as fiber breakage and fluffing during processing of the glass fibers can be reduced.

Abstract: A glass composition of the present disclosure includes, in wt %, 50?SiO2?56, 20?B2O3?30, 10?Al2O3?20, 3.5?MgO+CaO?10, and 0?R2O?1.0, further includes Fe2O3, and has a permittivity of less than 5.0 at a frequency of 1 MHz. R is at least one element selected from Li, Na, and K. The glass composition of the present disclosure is a low-permittivity glass composition with which the occurrence of fiber breakage during fiber forming can be reduced even when glass fibers to be formed have a small fiber diameter, and the occurrence of defects such as fiber breakage and fluffing during processing of the glass fibers can be reduced.

Abstract: A glass composition of the present disclosure includes, in wt %, 50?SiO2?54, 25?B2O3?30, 12?Al2O3?15, 0.5?MgO?1.9, 3.0?CaO?5.5, 0?ZnO?3.5, 0.1?Li2O?0.5, and 0.1?Na2O?0.3, and has a permittivity of less than 5.0 at a frequency of 1 MHz. The glass composition of the present disclosure has a low permittivity. The use of this glass composition can reduce the occurrence of devitrification and the inclusion of bubbles in glass fibers to be formed or in a shaped glass material to be formed even when the glass fibers have a small fiber diameter or the shaped glass material has a small thickness.