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

a technology of optical glass and press molding preform, which is applied in the direction of glass tempering apparatus, instruments, manufacturing tools, etc., can solve the problems of high glass transition temperature of conventional glasses such as tasf17 and nbsf32, and is not suitable for precision press molding. , to achieve the effect of low glass transition temperature, low dispersion, and high refractive index

Inactive Publication Date: 2005-09-08
HOYA CORP
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Benefits of technology

[0022] According to the present invention, there can be obtained an optical glass which has a high refractive index and low dispersion and has a low glass transition temperature and which has the property of being softened at a low te

Problems solved by technology

However, conventional glasses such as TaSF17 and NbSF32 have high glass

Method used

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

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examples

[0109] The present invention will be further explained below with reference to Examples.

[0110] Oxides, hydroxides, carbonates, nitrates, etc., were used as corresponding raw materials of each glass, these raw materials were weighed so that the composition shown in Tables 1 to 3 was obtained after the formation of the glass, and these raw materials were fully mixed. Then, the mixture was poured into a platinum crucible and melted with stirring in an electric furnace in a temperature range of 1,200 to 1,250° C. in atmosphere for 2 to 4 hours. A homogenized and refined glass melt was cast into a 40×70×15 mm mold made of carbon, and a cast glass was gradually cooled to a transition temperature. Immediately thereafter it was placed in an annealing furnace, and annealed at a temperature around the transition temperature for 1 hour, and in the annealing furnace, it was gradually cooled to room temperature. In this manner, optical glasses were obtained. The optical glasses shown in Tables ...

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Abstract

Provided is an optical glass having high-refractivity low-dispersion properties, having a low glass transition temperature and having the property of being softened at a low temperature so that a preform therefrom is precision press-moldable, and the optical glass comprises, as essential components, B2O3, La2O3, Gd2O3 and ZnO and has a refractive index (nd) of over 1.86, an Abbe's number (νd) of less than 35 and a glass transition temperature (Tg) of 630° C. or lower.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an optical glass, a precision press-molding preform formed of the above glass, a process for the production of the preform, an optical element formed of the above optical glass and a process for the production of the optical element. TECHNICAL BACKGROUND [0002] A high-refractivity low-dispersion glass is in great demand as a material for optical elements such as various lenses. As a glass having such optical constants, a dense tantalum flint glass TaSF17 is known, which is described in “Glass Composition Hand Book” (Hiroshi Ogawa and Shin-ei Ogawa, issued by Japan Glass Product Industrial Society, 1991, page 106). [0003] In recent years, with the rapid spread of digital cameras and video cameras, the demand for glass lenses as parts therefor continues to expand. On the other hand, with an increase in the number of pixels of imaging device in digital cameras, optical elements such as glass lenses are required to have high...

Claims

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Application Information

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IPC IPC(8): C03B11/00C03B23/00G02B1/00C03C3/066C03C3/068C03C3/15C03C3/155
CPCC03C3/068C03C3/155C03C3/15A63B37/02A63B69/0046
Inventor HAYASHI, KAZUTAKA
Owner HOYA CORP
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