Optical glass, precision press-molding preform, process for producing the preform, optical element and process for producing the element

Inactive Publication Date: 2006-05-18
HOYA CORP
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Benefits of technology

[0194] According to the present invention, there can be obtained an optical glass having a high refractive index and a low sag temperature and having a low-temperature softening property t

Problems solved by technology

Any one of conventional glasses such as TaSF17 has a high glass transition

Method used

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  • Optical glass, precision press-molding preform, process for producing the preform, optical element and process for producing the element

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examples

[0461] The present invention will be more specifically explained with reference to Examples hereinafter. The present invention shall not be limited by these Examples.

[0462] Oxides, hydroxides, carbonates, nitrates, etc., which corresponded to glass components were used as glass raw materials, the glass raw materials were weighed so as to obtain each of compositions shown in Tables 1-1 to 1-5 and fully mixed, and each of mixtures was separately from the others placed in a platinum crucible and melted under heat at a temperature in the range of 1,200 to 1,250° C. in an electric furnace with stirring in atmosphere for 2 to 4 hours. Each homogenized and refined glass melt was separately cast into a 40×70×15 mm mold made from carbon and allowed to cool gradually to its glass transition temperature. Immediately thereafter, each glass was placed in an annealing furnace and annealed around the glass transition temperature for 1 hour. In the furnace, then, each glass was allowed to cool gra...

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Abstract

An optical glass having high refractivity and a low sag temperature and having a low-temperature softening property that enables precision press-molding is provided, and the optical glass contains, by mol %, 5 to 50% of B2O3, 3 to 50% of SiO2, 5 to 40% of TiO2, 1 to 40% of ZnO, 5 to 20% of La2O3, 0 to 10% of Gd2O3, 0 to 15% of Nb2O5, 0 to 10% of ZrO2, 0 to 5% of Ta2O5, 0 to 10% of Bi2O3, 0 to 10% of MgO, 0 to 8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, provided that the total content of MgO, CaO, SrO and BaO is 15% or less, 0 to 20% of Li2O, and 0 to 5% of Na2O, optionally containing Sb2O3 as a refining agent, and having a refractive index (nd) of 1.8 or more and an Abbe's number (vd) of 35 or less.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an optical glass, a precision press-molding preform formed of the above optical glass, a process for producing the preform, an optical element formed of the above optical glass and a process for producing the element. TECHNICAL BACKGROUND [0002] A high-refractivity low-dispersion glass is briskly in high demand as a material for optical elements such as various lenses. As a glass having such optical properties, there are known a heavy tantalum flint glass TaSF17, and the like, which are described in “Glass Composition Handbook” written by Hiroshi OGAWA and Shinei OGAWA and issued by Japan Glass Product Society, 1991, page 106. DISCLOSURE OF THE INVENTION [0003] In recent years, with rapid widespread use of digital cameras, video cameras and the like, glass lenses as parts therefor are much in demand. On the other hand, with an increase in the pixels of the cameras, optical elements such as glass lenses are required to ha...

Claims

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Application Information

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IPC IPC(8): C03C3/095C03C3/068
CPCC03B11/08C03C3/068C03C3/064C03C3/076C03B11/00
Inventor KASUGA, YOSHIKOZOU, XUELU
Owner HOYA CORP
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