Lens and process for the production thereof
AssigneeHoya Corporation
InventorsKazutaka Hayashi, Kouichi Satou, Koichiro Shiraishi
Life of this patent
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Abstract
A lens formed of a high-refractivity low-dispersion glass and free of fogging and scorching on its optical-function surface, which is obtained by precision press-molding of an optical glass having a refractive index (nd) of over 1.83, an Abbe's number (νd) of 40 or more and a glass transition temperature (Tg) of 640° C. or lower and containing no Li2O and has one form of a meniscus form, a biconcave form or a plano-concave form.
Claims2
The process for the production of a lens by precision press-molding a glass material, which comprises the steps of
- introducing a glass material formed of an optical glass having a refractive index (nd) of over 1.83, an Abbe's number (vd) of 40 or more and a glass transition temperature (Tg) of 640° C. or lower and containing, by mol %, 20 to 43% of B2O3, 5 to 24% of La2O3 and 22 to 42% of ZnO, as essential components, and optionally 0 to 18% SiO2, and a total content of La2O3, Gd2O3, Y2O3 and Yb2O3 is 10 to 24%, and no Li2O, no PbO and no cadmium into a press mold, softening the glass material by heating and pressing the glass material with a mold comprising a first mold member whose molding surface for forming an optical-function surface of a lens to be obtained is a concave surface or a flat surface and a second mold member whose molding surface is a convex surface,
- cooling said mold until said glass material in said mold comes to have a temperature of a glass transition temperature (Tg) or lower, and
- taking said glass material cooled out of said mold,
- the cooling being carried out in said step of cooling the mold in a manner that the temperature of the first mold member reaches the glass transition temperature (Tg) of said glass material before the temperature of the second mold member.
The process for the production of a lens by precision press-molding a glass material, which comprises introducing a glass material formed of an optical glass having a refractive index (nd) of over 1.83, an Abbe's number (vd) of 40 or more and a glass transition temperature (Tg) of 640° C. or lower and containing, by mol %, 20 to 43% of B2O3, 5 to 24% of La2O3 and 22 to 42% of ZnO, as essential components, and optionally 0 to 18% SiO2, and a total content of La2O3, Gd2O3, Y2O3 and Yb2O3 is 10 to 24%, and no Li2O, no PbO and no cadmium into a press mold,
- softening the glass material by heating and pressing the glass material with a mold comprising a first mold member whose molding surface for forming an optical-function surface of a lens to be obtained has a large curvature radius or paraxial curvature radius and a second mold member whose molding surface has a small curvature radius or paraxial curvature radius,
- the cooling step of cooling said mold until said glass material in said mold comes to have a temperature of the glass transition temperature (Tg) or lower, and
- the step of taking said glass material cooled out of said mold,
- the cooling being carried out in said cooling step in a manner that the temperature of the first mold member reaches the glass transition temperature (Tg) of said glass material before the temperature of the second mold member, thereby to produce a biconcave lens.
Dependencies are inferred from the claim text.