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

Abstract

A glass plate, which has a content of total iron as calculated as Fe 2 O 3 of 5 to 50 ppm and a content of Fe 2+ in total iron as calculated as Fe 2 O 3 of from 0.02 to 20 ppm, where 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 contains, as represented by mass percentage based on oxides, from 45 to 80% of SiO 2 , more than 7% and at most 30% of Al 2 O 3 , from 0 to 15% of B 2 O 3 , from 0 to 15% of MgO, from 0 to 10% of CaO, from 0 to 20% of Na 2 O, from 0 to 10% of K 2 O and from 0 to 10% of ZrO 2 .

What is claimed is: 
     
         1 . A glass plate, which has a content of total iron as calculated as Fe 2 O 3  of from 5 to 50 ppm and a content of Fe 2+  in total iron as calculated as Fe 2 O 3  of from 0.02 to 20 ppm,
 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 SiO 2 , more than 7% and at most 30% of Al 2 O 3 , from 0 to 15% of B 2 O 3 , from 0 to 15% of MgO, from 0 to 10% of CaO, from 0 to 20% of Na 2 O, from 0 to 10% of K 2 O and from 0 to 10% of ZrO 2 . 
 
     
     
         2 . The glass plate according to  claim 1 , which has a content of Fe 2+  in total iron as calculated as Fe 2 O 3  of from 0.02 to 9.8 ppm. 
     
     
         3 . The glass plate according to  claim 1 , wherein the composition of the glass plate except for iron substantially comprises, as represented by mass percentage based on oxides, from 60 to 80% of SiO 2 , from 0 to 7% of MgO and from 0 to 15% of Na 2 O. 
     
     
         4 . The glass plate according to  claim 1 , wherein the composition of the glass plate except for iron substantially comprises, as represented by mass percentage based on oxides, from 0 to 0.5% of CaO and from 0 to 0.3% of K 2 O. 
     
     
         5 . The glass plate according to  claim 1 , wherein at least one component selected from the group consisting of CeO 2 , Sb 2 O 3 , SnO 2  and As 2 O 3  is contained, and the total content of such components is at most 0.3% as represented by mass percentage based on oxides. 
     
     
         6 . The glass plate according to  claim 5 , wherein the content of CeO 2  or the content of SnO 2  is at least 0.1%. 
     
     
         7 . The glass plate according to  claim 1 , which has a thickness of from 0.5 to 10 mm. 
     
     
         8 . The glass plate according to  claim 7 , which has a thickness of from 1 to 2.5 mm. 
     
     
         9 . 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 SiO 2 , more than 7% and at most 30% of Al 2 O 3 , from 0 to 15% of B 2 O 3 , from 0 to 15% of MgO, from 0 to 10% of CaO, from 0 to 20% of Na 2 O, from 0 to 10% of K 2 O and from 0 to 10% of ZrO 2 .   
     
     
         10 . The glass plate according to  claim 9 , wherein the composition of the glass plate except for iron substantially comprises, as represented by mass percentage based on oxides, from 60 to 80% of SiO 2 , from 0 to 7% of MgO and from 0 to 15% of Na 2 O. 
     
     
         11 . The glass plate according to  claim 9 , wherein the composition of the glass plate except for iron substantially comprises, as represented by mass percentage based on oxides, from 0 to 0.5% of CaO and from 0 to 0.3% of K 2 O. 
     
     
         12 . The glass plate according to  claim 9 , which has a content of total iron as calculated as Fe 2 O 3  of from 5 to 50 ppm and a content of Fe 2+  in total iron as calculated as Fe 2 O 3  of from 0.02 to 20 ppm. 
     
     
         13 . The glass plate according to  claim 12 , which has a content of Fe 2+  in total iron as calculated as Fe 2 O 3  of from 0.02 to 9.8 ppm. 
     
     
         14 . The glass plate according to  claim 9 , wherein at least one component selected from the group consisting of CeO 2 , Sb 2 O 3 , SnO 2  and As 2 O 3  is contained, and the total content of such components is at most 0.3% as represented by mass percentage based on oxides. 
     
     
         15 . The glass plate according to  claim 14 , wherein the content of CeO 2  or the content of SnO 2  is at least 0.1%. 
     
     
         16 . The glass plate according to  claim 9 , which has a thickness of from 0.5 to 10 mm. 
     
     
         17 . The glass plate according to  claim 16 , which has a thickness of from 1 to 2.5 mm.