FLUORINE-FREE OPTICAL GLASS

Abstract

The present invention relates to lead and fluorine and preferably lithium free optical glasses for the application areas imaging, projection, telecommunications optical communications engineering, mobile drive and/or laser technology with a refractive index of from 1.60≦nd≦1.64 and an Abbe number of from 56≦□d≦64, which glasses have a low transformation temperature, namely less than or equal to 590° C., preferably less than or equal to 585° C., more preferred less than or equal to 570° C., which glasses can still further be produced and handled easily and are stable to crystallization. The glasses according to the invention with the following composition (in weight-% based on the oxides) comprise the following components:

Description

EXAMPLES

The following examples show preferred glasses according to the invention and shall not limit the scope of protection.

Example 1

The raw material is weighed, one or more fining agents like for example Sb₂O₃ are added and the batch is blended subsequently. The batch is molten at 1170° C. in a continuous melting unit, afterwards it is fined (1170° C.) and homogenized. At a casting temperature of 1070° C. the glass can be cast and processed to the desired proportions. In a continuous unit of big volume the temperatures may according to experience be lowered by at least 100 K and the material can be processed in a near-net-shape process.

TABLE 1
melt example for 100 kg calculated glass
(according to example glass 3):
				weight-in quantity
	Oxide	% by weight	raw material	(g)
	P2O5	31.21	P2O5,	423.88
			Ba(H2PO4)2	see below
	B2O3	12.71	H3BO3	22584.99
	Al2O3	5.73	Al(OH)3	8889.06
	BaO	32.15	Ba(H2PO4)2	71755.35
	CaO	11.44	CaCO3	20281.41
	ZnO	5.61	ZnO	5614.98
	Na2O	1.14	NaHCO3	3089.08
	Sb2O3	0.02	Sb2O3	20.07
	sum	100.01		132658.82

Table 2 contains examples for glasses 1 to 9 according to the present invention.

TABLE 2
examples 1 to 9 (specifications in % by weight based on oxides)
	Example
	1	2	3	4	5	6	7	8	9
P2O5	29.48	30.59	31.21	31.21	30.40	31.23	31.57	28.14	27.56
Bi2O3	5.94	1.75
B2O3	11.62	12.46	12.71	12.71	12.49	12.72	12.86	15.13	12.98
Al2O3	6.34	6.58	5.73	5.54	5.63	5.54	5.60	5.72	8.48
Na2O	0.00	0.29	1.14	1.74	1.71	1.74	1.76	1.79	1.17
BaO	30.36	31.52	32.15	32.16	34.48	29.23	29.55	30.17	32.53
SrO						3.98
CaO	10.80	11.21	11.44	11.01	9.76	9.94	10.59	10.81	11.57
ZnO	5.30	5.50	5.61	5.61	5.51	5.61	8.04	8.21	5.67
Sb2O3			0.02	0.02	0.03	0.03	0.03	0.03	0.03
As2O3	0.15	0.10
Σ	100	100	100	100	100	100	100	100	100
Σ RO (R = Ba, Ca, Sr)	41.16	42.73	43.59	43.17	44.24	43.15	40.14	40.98	44.10
Σ RO (R = Ba, Ca, Sr, Zn)	46.46	48.23	49.20	48.78	49.75	48.76	48.18	49.19	49.77
properties
τi (25 mm, 360 nm)	0.629	0.723	0.806	0.817	0.755	0.741	0.759	0.757	0.701
τi (25 mm, 400 nm)	0.927	0.963	0.981	0.986	0.977	0.970	0.975	0.964	0.961
τi (25 mm, 420 nm)	0.948	0.978	0.990	0.994	0.988	0.980	0.986	0.975	0.978
τi (25 mm, 440 nm)	0.956	0.982	0.991	0.996	0.991	0.982	0.988	0.978	0.982
nd (7 K/h)	1.63063	1.61704	1.61210	1.6104	1.61179	1.60889	1.60841	1.60932	1.61213
vd (7 K/h)	56.31	60.72	62.69	62.67	62.49	62.82	62.56	61.59	61.30
Pg,F	0.5519	0.5447	0.5416	0.5422	0.5419	0.5413	0.5416	0.5426	0.5428
ΔPg,F	0.0028	0.0030	0.0032	0.0038	0.0032	0.0031	0.0030	0.0024	0.0021
α(20-300° C.) [10−6/K]	10.01	10.03	10.29	10.46	10.57	10.48	10.12	10.15	10.22
Tg [° C.]	581	576	565	549	554	554	544	542	554
r [g/cm3]	3.575	3.491	3.467	3.449	3.497	3.444	3.430	3.423	3.438
T bei 107,6 dPas [° C.]	672	670	665	653	653	656	642	646	662
ΔT [T(1013 dPas) −	88	90	96	100	95	98	94	100	104
T(107,6 dPas)]

The glasses according to the present invention of examples 1 to 9 show a glass, transition temperature Tg of less or equal to 581° C. (at a metering precision of ±5° C.) and are well workable.

FIG. 1 shows a internal transmittance curve of a glass according to the present invention of example 4.

FIG. 2 shows the viscosity curve of a glass according to the present invention of example 4. The vertical lines show the temperature interval ΔT in which the viscosity of this glass decreases from 10^7.6 to 10¹³ dPas. ΔT in this case is between 653 and 553° C., thus amounts to 100 K.

Claims

1. Lead- and fluorine-free optical glass with a refractive index nd of 1.60≦nd≦1.64 and an Abbe number of 56≦vd≦64, wherein the glass comprises the following composition (in % by weight based on the oxides):

2. Glass according to claim 1 comprising the following composition (in % by weight based on the oxides):

3. Glass according to claim 1 comprising the following composition (in % by weight based on the oxides):

4. Glass according to claim 1 comprising the following composition (in % by weight based on the oxides):

5. Glass according to claim 1 comprising as a fining agent at least one of the following components (in % by weight):

6. Glass according to claim 1 being free of SiO2, Li2O and/or CdO.

7. Use of a glass claim 1 for the areas of application imaging, projection, telecommunication, optical telecommunication engineering, mobile drive and laser technology.

8. Use of a glass according to claim 1 for optical elements.

9. Optical element comprising a glass according to claim 1.

10. Method for the production of an optical element comprising the steps of precise pressing a glass according to claim 1.