Crystal glass having refractive index higher than 1.53 without a content of compounds of lead, barium and arsenic
This invention relates to a crystal glass having a refractive index higher than 1.53 and a high mechanical strength, free of any content of compounds of lead, barium and arsenic and guaranteeing maximum safety for health, which consists in that it comprises by weight: 55-70% SiO 2 , 0.05-3.5% Li 2 O, 2-15% Na 2 O, more than 3% and less than 5% or more than 15% and less than 19% K 2 O, 5 to 10% CaO, more than 1% and less than 4% or more than 7% and less than 8% ZnO, 0.1-3.5% B 2 O 3 , 0.1-3.5% Al 2 O 3 , 0.1-3.5% TiO 2 , less than 3.5% ZrO 2 , 0.05-1.5% Gd 2 O, 3 0.05-1% P 2 O 5 , 0.1-1% Sb 2 O 3 .
1. Crystal glass having a refractive index higher than 1.53 free of any content of compounds of lead, barium and arsenic, comprising by weight:
55-70%
SiO 2 ,
0.05-3.5%
Li 2 O,
2-15%
Na 2 O,
more than 3% and less than 5% or more than
K 2 O,
15% and less than 19%
5 to 10%
CaO,
more than 1% and less than 4% or more than
ZnO,
7% and less than 8%
0.1-3.5%
B 2 O 3 ,
0.1-3.5%
Al 2 O 3 ,
0.1-3.5%
TiO 2 ,
less than 3.5%
ZrO 2 ,
0.05-1.5%
Gd 2 O 3 ,
0.05-1%
P 2 O 5
0.1-1%
Sb 2 O 3 .
2. The crystal glass according to claim 1 , comprising by weight 0.05 to 0.8 wt % Gd 2 O 3 and 0.05 to 0.8% P 2 O 5 and the Gd 2 O 3 /P 2 O 5 ratio is at least equal to 1:1.
3. The crystal glass according to claim 1 , comprising by weight 0.05 to 0.15 wt % Gd 2 O 3 and 0.1 to 0.8% P 2 O 5 and the Gd 2 O 3 /P 2 O 5 ratio is at least equal to 1:2.
4. The crystal glass according to claim 1 , comprising by weight 0.1 wt % Gd 2 O 3 and 0.2 to 0.8% P 2 O 5 and the Gd 2 O 3 /P 2 O 5 ratio is at least equal to 1:2.
5. The crystal glass according to claim 1 , wherein it is clarified and discoloured by usual clarifying and discolouring components and/or mixtures thereof in the usual concentrations.
6. The crystal glass according to claim 1 , comprising by weight:
67.066
SiO 2
0.850
Li 2 O
8.199
Na 2 O
4.802
K 2 O
8.202
CaO
2.401
ZnO
2.900
B 2 O 3
2.499
Al 2 O 3
2.040
TiO 2
0.100
Gd 2 O 3
0.401
P 2 O 5
0.540
Sb 2 O 3 .
7. The crystal glass according to claim 1 , comprising by weight:
63.173
SiO 2
0.541
Li 2 O
2.797
Na 2 O
15.406
K 2 O
8.503
CaO
2.005
ZnO
2.008
B 2 O 3
2.481
Al 2 O 3
1.941
TiO 2
0.102
Gd 2 O 3
0.503
P 2 O 5
0.540
Sb 2 O 3 .
8. The crystal glass according to claim 1 , comprising by weight:
59.125
SiO 2
2.149
Li 2 O
11.397
Na 2 O
3.490
K 2 O
7.188
CaO
7.711
ZnO
3.071
B 2 O 3
0.430
Al 2 O 3
2.082
Ti0O 2
2.082
Zr0O 2
0.103
Gd 2 O 3
0.701
P 2 O 5
0.471
Sb 2 O 3 .