Glass panel resistant to coloring when irradiated with electron rays

A glass panel resistant to coloring when irradiated with electron rays, which has an electrical resistivity of at least 1.times.10.sup.10 ohm-cm and consists essentially of the following glass composition:

• ______________________________________ SiO.sub.2 64-75% by weight Al.sub.2 O.sub.3 1.5-2.0% by weight CaO 6.5-9.0% by weight MgO 0-5.0% by weight Li.sub.2 O 0.5-2.5% by weight Na.sub.2 O 7.0-12% by weight K.sub.2 O 2.1-5.0% by weight SrO + BaO + ZrO.sub.2 0-10% by weight CeO.sub.2 0-0.5% by weight, ______________________________________
• wherein part of the Na ion, in at least the surface layer of the panel region to be irradiated with electron rays, is substituted with K ion by an ion exchange treatment in a K-containing molten salt so that the molar ratio of Na ion and K ion expressed by Na.sub.2 O/(Na.sub.2 O+K.sub.2 O), in at least the glass layer ranging from 0.5 .mu.m to 1.5 .mu.m in depth from the panel surface of said panel region to be irradiated with electron rays, is 0.3-0.75.

A glass panel resistant to coloring when irradiated with electron rays, which has an electrical resistivity of at least 1.times.10.sup.10 ohm-cm and consists essentially of the following glass composition:

• ______________________________________ SiO.sub.2 64-75% by weight Al.sub.2 O.sub.3 1.5-2.0% by weight CaO 6.5-9.0% by weight MgO 0-5.0% by weight Li.sub.2 O 0.5-2.5% by weight Na.sub.2 O 7.0-12% by weight K.sub.2 O 2.1-5.0% by weight SrO + BaO + ZrO.sub.2 0-10% by weight CeO.sub.2 0-0.5% by weight, ______________________________________
• wherein in part of the Na ion, in at least the surface layer of the panel region to be irradiated with electron rays, is substituted with K ion by an ion exchange treatment in a K-containing molten salt so that the molar ratio of Na ion and K ion expressed by Na.sub.2 O/(Na.sub.2 O+K.sub.2 O), in at least the glass layer ranging from 1.5 .mu.m to 3.5 .mu.m in depth from the panel surface of said panel region to be irradiated with electron rays, is 0.3-0.75.

A glass panel resistant to coloring when irradiated with electron rays, which has an electrical resistivity of at least 1.times.10.sup.10 ohm-cm and consists essentially of the following glass composition:

• ______________________________________ SiO.sub.2 64-75% by weight Al.sub.2 O.sub.3 1.5-2.0% by weight CaO 6.5-9.0% by weight MgO 0-5.0% by weight Li.sub.2 O 0.5-2.5% by weight Na.sub.2 O 7.0-12% by weight K.sub.2 O 2.1-5.0% by weight SrO + BaO + ZrO.sub.2 0-10% by weight CeO.sub.2 0-0.5% by weight, ______________________________________
• wherein part of the Na ion, in at least the surface layer of the panel region to be irradiated with electron rays, is substituted with K ion by an ion exchange treatment in a K-containing molten salt so that the molar ratio of Na ion and K ion expressed by Na.sub.2 O/(Na.sub.2 O+K.sub.2 O), in at least the glass layer ranging from 1.5 .mu.m to 6.5 .mu.m in depth from the panel surface of said panel region to be irradiated with electron rays, is 0.3-0.75.

A glass panel resistant to coloring when irradiated with electron rays, which has an electrical resistivity of at least 1.times.10.sup.10 ohm-cm and consists essentially of the following glass composition:

• ______________________________________ SiO.sub.2 64-75% by weight Al.sub.2 O.sub.3 1.5-2.0% by weight CaO 6.5-9.0% by weight MgO 0-5.0% by weight Li.sub.2 O 0.5-2.5% by weight Na.sub.2 O 7.0-12% by weight K.sub.2 O 2.1-5.0% by weight SrO + BaO + ZrO.sub.2 0-10% by weight CeO.sub.2 0-0.5% by weight, ______________________________________
• wherein part of the Na ion, in at least the surface layer of the panel region to be irradiated with electron rays, is substituted with K ion by an ion exchange treatment in a K-containing molten salt, and wherein reduction (.DELTA.T) in transmittance of the panel after irradiation with electron rays as compared with before irradiation is smaller than 40% when the panel is irradiated with electron rays of 10 KV and 40 .mu.A/cm.sup.2 for 100 hours in vacuum and the transmittance after and before irradiation are measured using a light of 400 nm wavelength.

A glass plate for use in a device which is irradiated with electron rays, which has an electrical resistivity of at least 1.times.10.sup.10 ohm-cm and consists essentially of the following glass composition:

• ______________________________________ SiO.sub.2 64-75% by weight Al.sub.2 O.sub.3 1.5-2.0% by weight CaO 6.5-9.0% by weight MgO 0-5.0% by weight Li.sub.2 O 0.5-2.5% by weight Na.sub.2 O 7.0-12% by weight K.sub.2 O 2.1-5.0% by weight SrO + BaO + ZrO.sub.2 0-10% by weight CeO.sub.2 0-0.5% by weight. ______________________________________