DE596513C - Optical glass with a refractive index over 1.60 - Google Patents

Description

GERMAN EMPIRE

19 JUN. 1934

ISSUED MAY 3, 1934

REICH PATENT OFFICE

PATENT LETTERING

M 596513 CLASS 32 b GROUP l

Jenaer Glaswerk Schott & Gen. in Jena

Optical glass with a refractive index greater than 1.60

Patented in the German Empire on November 6, 1930

It is known that glasses with a refractive index above 1.60 can be produced by increasing the lead oxide content at the expense of the content of silicic acid and monovalent metal 1-oxides (alkalis). In the case of such glasses, however, the increase in the refractive index is linked to a considerable increase in color dispersion. Thus Bleioxydgläser have n _D = 1.60 v = the value 38, those having n _D = 1.75 ν the value = 28, so it falls even with an increase DES n _D 0.015 to d ν ^as one unit. Glasses in which the lead oxide is partially or completely replaced by antimony oxide (Sb ₂ O ₁ ) show a similar behavior. It is also known that glasses with a refractive index above 1.60 and a "." Color dispersion can be achieved by ao the content of lead oxide and antimony oxide in whole or in part by divalent oxides,. such as Ba O, Sr O, Ca O, Mg O, Zn O, replaced. ' However, since part of the SiO _{s is} expediently replaced by trivalent oxides, such as B ₂ O ₃ or Al ₂ O ₃ , in order to reduce the tendency of such glasses to crystallize, the SiO ₂ content is reduced to a greater or lesser extent, which means an increase in acid solubility (sensitivity to stains) ■ 30 of the glasses produced is associated.

. It has now been shown that glasses with a relatively high silicic acid content with weight values above 1.60 and a color dispersion that is smaller than with correspondingly refractive lead-antimony glasses can be produced if the alkaline earth oxide content (BeO, MgO, CaO, SrO, BaO), optionally in addition to monovalent, other divalent and trivalent oxides, at least 10 "/" and introduces up to 20% titanium oxide (TiO ₂ ) into the glass. With a titanium oxide content of 25 ° / ₀ and above, or a germanium oxide content of 27 ° _{) 0} , glasses of high refraction have already been obtained, but then the color dispersion also increases to such an extent that the glasses become like lead-antimony in their connection between the refractive index and color dispersion glasses behave. also occurs when a content of titanium oxide of 25 ° / ₀ because of the inevitable contamination by iron oxide has a yellow to brown coloration of the glass one. on the other hand requires only a go old of far less than 20 ° ₍ ' _o Ti O ₂ , in order to reduce the acid solubility (sensitivity to stains) of the glass very strongly. It is advisable to let the content of bivalent oxides and antimony oxide together amount to at least 35% in the new glasses in order to achieve a too high titanium content and thus an approximation of the color dispersion to that of the lead-antimony glasses when a high refraction is achieved to avoid.

The titanium oxide content in the new glasses can be partially replaced by thorium oxide (ThO ₂ ), hafnium oxide (HfO ₂ ), zirconium oxide (ZrO ₂ ) or a mixture of them. Germanium oxide (GeO ₂ ) and tin oxide (SnO ₂ ) also have a similar effect.

The following table shows four examples of the new glasses:

SiO, 32.0 32.0 32.0 32.0

B ₂ O ₃ .... ■. 8.0 8.0 8.0 7.5

Al ₂ O ₃ - - - - 0.5

Na ₂ O .... 0.2 - - -

CaO ...... 10.0 10.0 10.0 10.0

BaO 43.5 37.2 37.2 36.2

ZnO 3.0 3.0 3.0 2.0

PbO .... 0.3 3.5 6; 5. 0.3

Sb ₂ O ₃ ... - 3.0 - -

TiO. 2, s 3.0 3.0 rr, o

As ₂ O ₃ 0.5 0.3 0.3 0.5

η ο 1.658 1.668 ι , 6 / i 1.696

ν 5i, 4 48, o 47.3 42.0

Claims (2)

Patent claims: That there is at least io / ₀ to alkaline earth oxides, optionally in addition to monovalent, other divalent and trivalent oxides, and titanium oxide containing 1. An optical glass having a refractive index above 1.60, characterized in that silica, ° up to the level of 20 ° / _0th 2. Optical glass according to claim 1, characterized in that it contains at least 35 ° / _{0 of} ^{bivalent oxides and antimony oxide together 1 men.}