DD142703A1 - ALKALIFREIES, LEAD-RESISTANT, OPTICAL GLASS HIGH QUANTITY AND RELATIVELY LOW DENSITY - Google Patents

Description

12082 -ι-

Title of the invention

Alkali free, leaded, high refractive index, relatively low density optical glass

Field of application of the invention

The invention relates to glass compositions having a high refractive index, a low dispersion and a low specific weight. The glasses are suitable both for use in scientific instrument construction, in which a low use of optical systems is desired, as well as for the production of eyeglass lenses for the heavily defective. Likewise, the glasses according to the invention can be used for producing photographic lenses which have improved light intensity and a high correction rate.

Characteristic of the known technical solution

Glass compositions for ophtalmic purposes with a relatively high refractive index (n ^ greater than 1.65), an Abbe number approximately equal to 40 and a density less than or equal to 3 »2 g cm ^J have been made known from the systems OaO-Al ₂ O ₃ - TiO ₂ -SiO ₂ using ZrO ₂ , ITb ₂ Oc and alkali oxides, mainly Li ₂ O, as further constituents (French Patent No. 2 313 328).

CaO-ZnO-ZrO ₂ -B ₂ O ₃ -SiO ₂ (Japanese Patent 074 129 (1975))

MgO-CaO-B ₂ O - SiO ₂ using ITb, O _n -, TiO ₂ and others as oxides (Japanese Patent 079 141 (1976))

CaO-La ₂ O - O? 1O ₂ -B ₂ Oo-SiO ₂ , wherein the content of B ₂ O ^ is more than 30% by weight, of SiO ₂ 0-15% by weight and of La ₂ O ₃ IQ-15% by weight (US Pat. Patent No. 4 057 4-35).

Object of the invention

The object of the present invention is an alkali-free optical glass, high refractive index and relatively low density, which has only relatively small amounts of titanium dioxide, no rare and expensive raw materials needed to achieve the value-determining properties, so that a low-cost production is made possible, a good crystallization resistance and weatherability to v / eist and is suitable for continuous melt,

Explanation of _ι jfesens of the invention

The object of the invention is to produce alkali-free, lead-containing glasses, which by their optical properties

Refractive index n ^ ₈ 1.68-1.72 and

Abbe number v _A = 38-46 and a density J> =: 3 | 2 g cia ~ - ^{> are} characterized "According to the invention, this object is achieved in that the glass compositions of

SiO ₂ 20-30 wt %

B ₂ O ₃ 10 »wt 25th%

CaO 15 - 45 wt%.

SiO ₂ 3-15 wt.%

PbO 1-10%, %

MgO 0-3 % by weight

ZnO

BaO

O - 10 weight " % O - 10 Ge W ₀ % O - 4 Ge ν / 9 % Θ - 10 devi, % O »5 Gew o %

consist

It was found that

- By the addition of lead oxide erfindungsgeiaäßen glasses are stable to crystallization;

the glasses according to the invention have a good weathering resistance

- a variety of methods for hot forming can be applied;

- By the non-use of alkali oxides and the use of high concentrations of calcium oxide, the realization of the desired crushing and Abbe number, and the relatively low density is achieved;

~ the titanium dioxide content is kept comparatively low;

- No rare and expensive raw materials must be used to achieve the value-determining properties and thus a cost-effective production is possible.

Exemplary embodiment

The preparation of a glass mass of 2 kg from a composition according to the invention is possible according to the following information:

component % By weight raw material e i η ζ uv / ie ge nde Quantity (fO SiO ₂ 25.3 silica flour 507.0 B ₂ O ₃ 19.5 Boric acid H ^ BO ^ 695.0 CaO 25.1 calcium carbonate 918.7 TiO ₂ 10.1 Titanium dioxide 203.6 PbO 7.8 Red Lead 159.3 Al ₂ O 3.6 Aluminiumhydrο- 112.0 dioxide BaO 8.6 barium 295.0

The calculated raw materials are weighed in and mixed with Cremer.ge.sats. The mixture is melted for 1 to 2 hours at 1520 to 1620 IC. Thereafter, the temperature of the melt usa f 0 to 80 Z. is increased to the

Melt the melt for about 1 hour. Subsequently, 1.5 to 2 hours at a temperature which is between melting and refining temperature, homogenized to process the melt then su. The production of the Glaseo by means of a continuous process is possible

The table contains examples of glasses according to the invention and their properties (in% by weight).

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Claims (2)

S β » 1 «Alkali-free, lead-containing, optical borosilicate glasses with refractive indices n, = 1 _? 68 to 1.72, Abbe numbers v, = 38 to 46 ^, and specific gravities less than or equal to 3 _f 2 g cra * "2, characterized in that they consist of (Gev /,%): 2. Glasses according to item 1, which furthermore may contain oxides for the modification of the optical and physical properties - (% by weight):