LEAD-FREE OPTICAL GLASS OF THE HARD FLINT AND LANTHANUM HARD FLINT POSITION

Abstract

The lead-free optical glass can be used in the fields of imaging, sensor technology, microscopy, medical technology, digital projection, photolithography, laser technology, wafer/chip technology, as well as of telecommunications, optical communication engineering and optics/lighting in the automotive sector. It has a refractive index nd of 1.82≦nd≦2.00 and/or an Abbe number vd of 18≦vd≦28 with good chemical stability, excellent crystallization stability and the following composition, in wt. based on oxide content, of:

Description

EXAMPLES

Table II contains 13 exemplary embodiments in the preferred composition range, as well as two comparative examples. The examples of the glass according to the invention were produced as follows:

The raw materials for the oxides, preferably the corresponding carbonates, and the phosphate proportion, preferably as complex phosphate, are weighed out, one or more fining agents such as Sb₂O₃ are added and subsequently mixed well. The glass batch is melted at about 1200° C. in discontinuous batch melting equipment, subsequently refined (1250° C.) and homogenized. At a casting temperature of about 1000° C., the glass can be cast and worked to the desired dimensions. In large-volume continuous equipment, experience shows that the temperatures can be reduced by at least about 100 K and the material can be worked by the method of molding close to final geometry, for example precision pressing.

TABLE I
MELTING EXAMPLE OF GLASS BATCH CALCULATED
FOR 100 KG (ACCORDING TO EXAMPLE 4, TABLE II)
	Oxide	wt. %	Raw material	Weigh-in (kg)
	P2O5	22.0	P2O5	9.75
			Ba(H2PO4)2	(see BaO)
	Nb2O5	41.5	Nb2O5	41.56
	Bi2O3	6.0	Bi2O3	6.00
	GeO2	2.0	GeO2	2.00
	BaO	12.5	Ba(H2PO4)2	27.89
	Li2O	1.5	Li2CO3	3.73
	K2O	2.0	K2CO3	2.21
			KNO3	1.07
	Cs2O	2.5	Cs2CO3	2.88
	ZnO	0.5	ZnO	0.50
	TiO2	2.5	TiO2	2.50
	WO3	7.0	WO3	7.00
	Sb2O3	0.5	Sb2O3	0.30
	Sum	100.0		107.39

The properties of the examples of the glass according to the invention obtained in this way are reported in Table 11 as the properties of example 4.

TABLE II
Melting Examples 1-5 (in wt. %)
	Examples
	1	2	3	4	5
P2O5	12.0	14.0	16.0	22.0	30.0
Nb2O5	50.0	48.0	49.0	41.5	35.0
Bi2O3	13.0	11.0	9.0	6.0	6.0
GeO2	6.0	7.0	2.0	2.0	1.0
Li2O			2.0	1.5
Na2O
K2O				2.0
Cs2O				2.5
MgO
CaO		1.5	1.0
SrO			2.0
BaO	7.0	16.5	15.0	12.5	9.0
ZnO			2.0	0.5
TiO2				2.5	5.0
ZrO2
WO3	12.0	2.0	2.0	7.0	14.0
Sb2O3		0.3		0.3
Sum	100.0	100.3	100.0	100.3	100.0
nd [7K/h]	1.9586	1.9344	1.9671	1.9130	1.8877
νd [7K/h]	19.4	21.2	20.0	21.2	20.6
pg·F [7K/h]	0.6474	0.6379	0.6406	0.6363	0.6446
ΔPg·F	337	282	289	280	349
(10−4)[7K/h]
α20-300	8.8	7.9	6.8	7.1	7.9
(10−6 ×
K−1)
Tg (° C.)	496	633	660	596	517
ρ (g/cm3)	4.46	4.42	4.37	4.14	3.99
Melting Examples 6-10 (in wt. %)
	Examples
	6	7	8	9	10
P2O5	32.0	35.0	16.0	20.0	23.0
Nb2O5	33.0	30.0	43.0	37.0	48.0
Bi2O3	2.0	4.0	8.0	7.0	2.0
GeO2	0.5	0.1	1.0	0.5	2.0
Li2O	6.0	4.0
Na2O				1.0
K2O				6.0	1.0
Cs2O					6.0
MgO	1.5
CaO				4.0	6.0
SrO
BaO	16.0	12.0	15.0	16.0	9.0
ZnO				4.0	1.0
TiO2		7.0
ZrO2	5.0		7.0	2.5
WO3	4.0	7.9	10.0	2.0	2.0
Sb2O3	0.3				0.3
Sum	100.3	100.0	100.0	100.0	100.3
nd [7K/h]	1.9194	1.9030	1.9239	1.9780	1.8953
νd [7K/h]	23.0	20.3	23.4	20.5	23.8
Pg·F [7K/h]	0.6155	0.6406	0.6251	0.6324	0.6280
ΔPg·F	133	316	218	249	235
(10−4)[7K/h]
α20-300	6.5	5.4	18.8	10.8	20.7
(10−6 ×
K−1)
Tg (° C.)	632	625	411	479	464
ρ (g/cm3)	4.16	3.78	4.46	4.63	4.31
Melting Examples 11-13 and
Comparative Examples A, B (in wt. %)
	Examples
	11	12	13	A	B
P2O5	27.0	24.0	13.0	14.0	18.0
Nb2O5	40.0	33.0	32.0	37.0	34.9
Bi2O3	4.0	13.0	11.0	5.0	3.0
GeO2	4.0	0.1	2.5	3.0	0.1
Li2O			0.5	0.5
Na2O	0.5	1.5		4.0	6.0
K2O	0.5		1.5	2.5	4.0
Cs2O	4.0		1.0	3.0
MgO				4.0	6.0
CaO			0.5		2.0
SrO		1.0	6.0	4.0
BaO	7.0	16.5	16.0	10.0	17.0
ZnO		5.9	1.5
TiO2		1.0	1.5	3.0	2.0
ZrO2			1.0	4.0
WO3	13.0	4.0	12.0	6.0	7.0
Sb2O3
Sum	100.3	100.0	100.0	100.0	100.0
nd [7K/h]	1.8448	1.8922	1.9694	1.9239	1.8953
νd [7K/h]	23.2	23.3	21.3	23.4	23.8
Pg·F [7K/h]	0.6298	0.6302	0.6353	0.6251	0.6280
ΔPg·F	249	251	272	218	235
(10−4)[7K/h]
α20-300	9.0	9.3	10.5	18.8	20.7
(10−6 ×
K−1)
Tg (° C.)	530	550	416	411	464
ρ (g/cm3)	4.17	4.23	4.49	4.46	4.31

All glass examples 1 to 13 have a SiO₂ content of less than 0.1 wt. % and a content of less than 100 ppm of residues of the metallic crucible materials. They are distinguished by a high crystallization stability and excellent transparency.

The comparative examples A and B have glass compositions, for which, because of a high flux material content outside the composition ranges according to the present invention (the alkali metal oxide content is above 10 wt. %), a homogenous molten mass is indeed obtained, but microscopic devitrification occurs on cooling of the composition, so that a transparent glass ceramic material is generated. Nevertheless measurement of the optical data is possible. The phase transition becomes particularly obvious considering the escalating values for the thermal properties, in this case for example the thermal expansion coefficient.

The glass according to the invention has optical data in common with known optical glasses of this position. It is, however, distinguished by better chemical stability and machinability, lower production costs due to reduced raw material and process costs, sufficient crystallization stability owing to their shortness, and by good environmental friendliness. An adjustment of the crystallization stability and viscosity-temperature profile have been achieved by the glass according to the present invention as shown with examples (Table II) so that further thermal processing (pressing or re-pressing) of the glass is readily possible.

Claims

1. A lead-free optical glass having a composition, in wt. % based on oxide content, of:

2. The glass according to claim 1, which is free of B2O3, free of contamination by SiO2, and/or free of residues from metallic crucible materials.

3. The glass according to claim 1, wherein a sum total amount of TiO2+ZrO2 does not exceed 7 wt. %.

4. The glass according to claim 1, wherein an alkali metal oxide content, defined as a sum total amount of Li2O, Na2O, K2O and Cs2O, is at most 8 wt. % and/or each of said Li2O, Na2O, K2O and Cs2O is present in an amount of up to 6 wt. %.

5. The glass according to claim 1, wherein a sum total amount of MgO, CaO, SrO and ZnO is at most 8 wt. % and/or each of said MgO, CaO, SrO and ZnO is present in an amount of up to 6 wt. %.

6. The glass according to claim 1, containing at most 6 wt. % of aluminium oxide.

7. The glass according to claim 1, containing at most 6 wt. % of zinc oxide.

8. The glass according to claim 1, containing at most 5 wt. % of Ag2O.

9. The glass according to claim 1, containing up to 5 wt. % of a sum total amount of La2O3, Y2O3, Gd2O3, Ta2O5 and Yb2O5.

10. The glass according to claim 1, which is free of Pt and/or SiO2.

11. The glass according to claim 1, containing a fining agent comprising

12. The glass according to claim 1, having a refractive index nd of 1.82≦nd≦2.00 and/or an Abbe number vd of 18≦vd≦28.

13. A method of producing a glass comprising the step of setting up oxidizing conditions in a glass melt from which said glass is formed; wherein said glass has a composition, in wt. % based on oxide content, of:

14. A method of making an optical component comprising a lens, prism, light guide rod, array, optical fiber, gradient component and/or an optical window, said optical component comprising a glass having a composition, in wt. % based on oxide content, of:

15. A method of making an optical part or an optical component for a sensor, microscopy, medical technology, digital projection, telecommunication, optical communications engineering/information transmission, optics/lighting in the automotive sector, photolithography, a stepper, an excimer laser, a wafer, a computer chip, an integrated circuit and/or an electronic device containing said integrated circuit and/or said computer chip, said optical part or said optical component comprising a glass having a composition, in wt. % based on oxide content, of:

16. An optical element comprising a lens, a prism, a light guide rod, an array, an optical fiber, a gradient component and/or an optical window, said optical element comprising a glass having a composition, in wt. % based on oxide content, of:

17. A method of producing an optical element, comprising the step of pressing a glass having a composition, in wt. % based on oxide content, of:

18. An optical part or optical component for imaging, a sensor, microscopy, medical technology, digital projection, telecommunication, optical communications engineering/information transmission, optics/lighting in the automotive sector, photolithography, a stepper, an excimer laser, a wafer, a computer chip, an integrated circuit and/or an electronic device containing said computer chip and/or said circuit, said optical part or said optical component comprising a glass having a composition, in wt. % based on oxide content, of: