Kabushiki Kaisha Ohara

Ohara, Inc.

Susumu Uehara

Koji Shimizu

Yasuo Ochi

Jie Fu

Shinya Mashiko

Kiyoyuki Momono

An optical glass having optical constants of a refractive index (nd) of 1.78 or over, an Abbe number (&#x3bd;d) of 30 or below, and a partial dispersion ratio (&#x3b8;g, F) of 0.620 or below comprises SiOand NbOas essential components, wherein an amount of NbOin mass % is more than 40%. The optical glass further comprising, in mass % on oxide basis, less than 2% of KO and one or more oxides selected from the group consisting of BO, TiO, ZrO, WO, ZnO, SrO, LiO and NaO wherein a total amount of SiO, BO, TiO, ZrO, NbO, WO, ZnO, SrO, LiO and NaO is more than 90% and TiO/(ZrO+NbO) is less than 0.32.

Optical glass

Provided is an optical glass having optical constants, a refractive index (n) of more than 1.9 and an Abbe number (&#x3bd;d) of not more than 38, having a small partial dispersion ratio and capable of being produced from inexpensive materials. The optical glass has a partial dispersion ratio (&#x3b8;g, F) of at most 0.615, and contains, as indispensable ingredients, BO, LaO, TiO, NbOand TaO, wherein the ratio, as % by mass, of TiO/NbOis at most 0.26 and GeO/NbOis at most 0.38. The optical glass contains, in terms of % by mass, the following ingredients: and 

An optical glass having a refractive index (nd) within a range from 1.825 to 1.870, an Abbe number (&#x3bd;d) within a range from 22 to less than 27, a transformation temperature (Tg) within a range from 530&#xb0; C. to 585&#xb0; C. and an mean coefficient of linear thermal expansion (&#x3b1;) within a range from 80&#xd7;10&#xb0; C.to 103&#xd7;10&#xb0; C., comprising SiO, TiO, NbOand LiO and being substantially free of a Pb compound.

An optical glass having refractive index (nd) exceeding 1.85, Abbe number (&#x3bd;d) of 36 or over, comprising SiO, BO, LaO, GdO, TaOand LiO as essential components, being free of Pb and As components, and having glass transition temperature (Tg) of 630&#xb0; C. or below.

An optical glass of the present invention has optical constants of a refractive index (nd) within a range from 1.75 to 1.85 and an Abbe number (&#x3bd;d) within a range from 35 to 45, comprises SiOand BOas essential components and one or more components selected from the group consisting of ZrO, NbO, TaOand WO, has a glass transition temperature (Tg) of 580&#xb0; C. or below and has weathering resistance (surface method) of Class 1 or Class 2.

An optical glass has optical constants of a refractive index (nd) within a range from 1.73 to less than 1.80 and an Abbe number (&#x3bd;d) within a range from 43 to 55, comprises SiO, BO, YO, LaO, ZnO and LiO as essential components, is substantially free of lead component, arsenic component and fluorine component, has a ratio of SiO/BOof 0.30 to 1.55 and a ratio of YO/LaOof 0.15 to 1.00, and has a glass transition temperature (Tg) of 620&#xb0; C. or below.

An optical glass has a low glass transition temperature (Tg) and optical constants in which a refractive index (n) is in the range of from 1.70 to less than 1.74 and an Abbe number (&#x3bd;) is between 40 and 45 (excluding 40 and 45), has a content of SiOis 17% by mass or less, a glass transition temperature (Tg) is 540&#xb0; C. or less, and a weathering resistance (surface-method) in Class 1 or 2, and has excellent chemical durability, particularly weathering resistance (surface-method) and is appropriate for precision mold press forming.

An optical glass having a refractive index (nd) within a range from 1.825 to 1.870, an Abbe number (&#x3bd; d) within a range from 22 to less than 27, a transformation temperature (Tg) within a range from 530&#xb0; C. to 585&#xb0; C. and an mean coefficient of linear thermal expansion (&#x3b1;) within a range from 80&#xd7;10&#xb0; C.to 103&#xd7;10&#xb0; C., comprising SiO, TiO, NbOand LiO and being substantially free of a Pb compound.

An optical glass having a refractive index (nd) and Abbe number (&#x3bd;d) within a range enclosed with a border line consisting of straight lines connecting point A (nd being 1.75 and &#x3bd;d being 50.0), point B (nd being 1.80 and &#x3bd;d being 46.0), point C (nd being 1.80 and &#x3bd;d being 50.0) and point D (nd being 1.75 and &#x3bd;d being 56.0) in the order of the point A, the point B, the point C, the point D and the point A in x-y rectangular coordinates in which x coordinate represents Abbe number (&#x3bd;d) and y coordinate represents refractive index (nd), including refractive index (nd) and Abbe number (&#x3bd;d) on the border line except for the straight line connecting the point A with the point D and the straight line connecting the point B with the point C, containing, as essential components, SiO, BO, LaO, GdO, LiO and F, and being substantially free of AsO.

An optical glass having a refractive index (n) and an Abbe number (v) which are within an area surrounded by the straight lines which are drawn by connecting point A (n=1.835, v=46.5), point B (n=1.90, v=40.0), point C (n=1.90, v=35.0) and point D (n=1.835, v=38.0) in a sequence of A, B, C, D and A as border lines in x-y coordinates shown in FIG., in which X-axis is the Abbe number (v) and Y-axis is the refractive index (n), the area including the border line. The optical glass has low glass transition temperature (Tg), and suitable for precision mold pressing.

An optical glass suitable for precision mold pressing has a refractive index (nd) of 1.88 or over and an Abbe number (&#x3bd; d) within a range from 22 to 28, comprises, in mass %, and has a glass transition point (Tg) within a range from 500&#xb0; C. to 580&#xb0; C. The optical glass preferably has a yield point (At) within a range from 550&#xb0; C. to 640&#xb0; C.

An optical glass has optical constants which are an refractive index (nd) of 1.70&#x2013;1.75 and an Abbe number (vd) of 45.0&#x2013;54.0; a glass transformation temperature (Tg) of 500&#x2013;580&#xb0; C. The glass has the following composition in mass percent of: SiOmore than 5&#x2013;15%; BO20-less than 30%; a total amount of SiO+BOmore than 25&#x2013;40%; LaOmore than 21-less than 30%; YOmore than 5&#x2013;15%; GdO0-less than 10%; ZrO1&#x2013;8%; NbO0.1&#x2013;5%; TaOmore than 5&#x2013;12%; a total amount of ZrO+NbO+TaO7&#x2013;20%; ZnO 0&#x2013;10%; CaO 0&#x2013;10%; SrO 0&#x2013;5%; BaO 0&#x2013;10%; a total amount of ZnO+CaO+SrO+BaO 5&#x2013;15%; LiO 1&#x2013;8%; SbO0&#x2013;1%; and AsO0&#x2013;1%. The glass is substantially free of YbOand AlO. Devitrification is not generated when the optical glass is kept at a temperature of 920&#xb0; C. for two hours.

An optical glass having a refractive index (n) and an Abbe number (v) which are within an area surrounded by the straight lines which are drawn by connecting point A (n=1.835, v=46.5), point B (n=1.90, v=40.0), point C, (n=1.90, v=35.0) and point D (n=1.835, v=38.0) in a sequence of A, B, C, D and A as border lines in x-y coordinates shown in FIG., in which X-axis is the Abbe number (v) and Y-axis is the refractive index (n), the area including the border line. The optical glass has low glass transition temperature (Tg), and suitable for precision mold pressing. The optical glass which has the refractive index (n) and Abbe number (v) within the above-described area, where the area includes the border lines, has the composition of SiO&#x2014;BO&#x2014;LaO&#x2014;GdO&#x2014;LiO&#x2014;F system, the transition temperature (Tg) of 550 to 650&#xb0; C., and is free from lead, cadmium, thorium, YO, POand TeO.

There is provided an optical glass suitable for mold pressing having optical constants of a refractive index (n) within a range from 1.60 to 1.69 and Abbe number (&#x3bd;) within a range from 35 to 45, having a glass transition point (Tg) within a range from 300&#xb0; C. to 500&#xb0; C., being free from devitrification when the optical glass is held at a temperature which is higher by 100&#xb0; C. than the glass transition point (Tg) for 30 minutes, comprising in mass % on oxide basis: and being free from LaO, TiO, TaOand PbO.

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Sagamihara, Japan

Susumu Uehara