Glass plate, light guide plate unit, planar light-emitting device, and liquid crystal display device

A glass plate, which has an effective optical path length of from 25 to 200 cm and an average internal transmittance in the visible region of at least 80% and a chromaticity Y of tristimulus values in the XYZ colorimetric system as defined in JIS Z8701 (Appendix) of at least 93%, under the effective optical path length,

• wherein the effective optical path length is a distance from an edge surface from which light enters the glass plate to an edge surface on the opposite side, and
• the composition of the glass plate except for iron substantially comprises, as represented by mass percentage based on oxides, from 45 to 80% of SiO2, more than 7% and at most 30% of Al2O3, from 0 to 15% of B2O3, from 0 to 15% of MgO, from 0 to 10% of CaO, from 0 to 20% of Na2O, from 0 to 10% of K2O and from 0 to 10% of ZrO2.