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

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 B 2 O 3 , 3 to 50% of SiO 2 , 5 to 40% of TiO 2 , 1 to 40% of ZnO, 5 to 20% of La 2 O 3 , 0 to 10% of Gd 2 O 3 , 0 to 15% of Nb 2 O 5 , 0 to 10% of ZrO 2 , 0 to 5% of Ta 2 O 5 , 0 to 10% of Bi 2 O 3 , 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 Li 2 O, and 0 to 5% of Na 2 O, optionally containing Sb 2 O 3 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.

1 . An optical glass comprising, by mol %, 
 5 to 50% of B 2 O 3 ,    3 to 50% of SiO 2 ,    5 to 40% of TiO 2 ,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    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 Li 2 O, and    0 to 5% of Na 2 O,    optionally containing Sb 2 O 3  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.    
   
   
       2 . An optical glass comprising, by mol %, 
 5 to 50% of B 2 O 3 ,    3 to 50% of SiO 2 ,    5 to 40% of TiO 2 ,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    0 to 10% of MgO,    0 to 8% of CaO,    0 to 10% of SrO,    0 to 10% of BaO, the content of BaO being less than 13% by weight,    provided that the total content of MgO, CaO, SrO and BaO is 15% by weight or less,    0 to 20% of Li 2 O,    0 to 5% of Na 2 O,    0 to 1% of Sb 2 O 3 ,    and having a refractive index (nd) of over 1.88 and an Abbe's number (vd) of 35 or less.    
   
   
       3 . An optical glass comprising, by mol %, to 50% of B 2 O 3 , 
 3 to 50% Of SiO 2 ,    5 to 40% of TiO 2 ,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    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 less than 6% by weight,    0 to 20% of Li 2 O,    0 to 5% of Na 2 O, and    0 to 1% of Sb 2 O 3 , the amount of Sb 2 O 3  being 1% by weight or less,    and having a refractive index of 1.8 or more and an Abbe's number (vd) of 35 or less.    
   
   
       4 . An optical glass comprising, by mol %, 
 25 to 50% of B 2 O 3 , the content of B 2 O 3  being over 15% by weight,    3 to 50% Of SiO 2 ,    5 to 40% of TiO 2 ,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    0 to 10% of MgO,    0 to 8% of CaO,    0 to 10% of SrO,    0 to 10% of BaO, the content of BaO being less than 13% by weight,    provided that the total content of MgO, CaO, SrO and BaO is less than 15% by weight,    0 to 20% of Li 2 O,    0 to 5% of Na 2 O, and    0 to 1% of Sb 2 O 3 , the amount of Sb 2 O 3  being 1% by weight or less,    and having a refractive index (nd) of 1.8 or more and an Abbe's number (vd) of 35 or less.    
   
   
       5 . An optical glass comprising, by mol %, 
 5 to 50% of B 2 O 3 ,    3 to 50% of SiO 2 ,    5 to 40% of TiO 2 ,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    0 to 10% of MgO,    0 to 8% of CaO,    0 to 10% of SrO,    0 to 10% of BaO, the content of BaO being less than 13% by weight,    provided that the total content of MgO, CaO, SrO and BaO is less than 15% by weight,    2 to 20% of Li 2 O, the content of Li 2 O being over 2% by weight,    0 to 5% of Na 2 O, and    0 to 1% of Sb 2 O 3 , the amount of Sb 2 O 3  being 1% by weight or less,    and having a refractive index (nd) of 1.8 or more and an Abbe's number (vd) of 35 or less.    
   
   
       6 . An optical glass comprising, by mol %, 
 25 to 50% of B 2 O 3 , the content of B 2 O 3  being over 17% by weight,    3 to 50% Of SiO 2 ,    5 to 40% of TiO 2 ,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    0 to 10% of MgO,    0 to 8% of CaO,    0 to 10% of SrO,    0 to 10% of BaO, the content of BaO being less than 13% by weight,    2 to 20% of Li 2 O, the content of Li 2 O being over 2% by weight,    0 to 5% of Na 2 O, and    0 to 1% of Sb 2 O 3 , the amount of Sb 2 O 3  being 1% by weight or less,    and having a refractive index (nd) of 1.8 or more and an Abbe's number (vd) of 35 or less.    
   
   
       7 . An optical glass comprising, by mol %, 
 5 to 50% of B 2 O 3 ,    3 to 50% of SiO 2 ,    12 to 40% of TiO 2 , the content of TiO 2  being over 12% by weight but not more than 30% by weight,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    0 to 10% of MgO,    0 to 8% of CaO,    0 to 10% of SrO,    0 to 10% of BaO, the content of BaO being less than 13% by weight,    provided that the total content of MgO, CaO, SrO and BaO is less than 6% by weight,    0 to 20% of Li 2 O,    0 to 5% of Na 2 O, and    0 to 1% of Sb 2 O 3 , the amount of Sb 2 O 3  being less than 1% by weight,    and having a refractive index (nd) of 1.8 or more and an Abbe's number (vd) of 35 or less.    
   
   
       8 . An optical glass comprising, by mol %, 
 5 to 50% of B 2 O 3 ,    3 to 20% of SiO 2 , the content of SiO 2  being less than 8% by weight,    5 to 40% of TiO 2 ,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    0 to 10% of MgO,    0 to 8% of CaO,    0 to 10% of SrO,    0 to 10% of BaO, the content of BaO being less than 13% by weight,    2 to 20% of Li 2 O, the content of Li 2 O being over 2% by weight,    0 to 5% of Na 2 O, and    0 to 1% of Sb 2 O 3 , the amount of Sb 2 O 3  being 1% by weight or less,    and having a refractive index (nd) of 1.8 or more and an Abbe's number (vd) of 35 or less.    
   
   
       9 . An optical glass comprising, by mol %, 
 5 to 50% of B 2 O 3 ,    3 to 20% of SiO 2 , the content of SiO 2  being less than 8% by weight,    5 to 40% of TiO 2 ,    1 to 40% of ZnO,    5 to 20% of La 2 O 3 ,    0 to 10% of Gd 2 O 3 ,    0 to 15% of Nb 2 O 5 ,    0 to 10% of ZrO 2 ,    0 to 5% of Ta 2 O 5 ,    0 to 10% of Bi 2 O 3 ,    0 to 10% of MgO,    0 to 8% of CaO,    0 to 10% of SrO,    0 to 10% of BaO, the content of BaO being less than 13% by weight,    0 to 20% of Li 2 O,    0 to 5% of Na 2 O, and    0 to 1% of Sb 2 O 3 ,    and having a refractive index (nd) of over 1.88 and an Abbe's number (vd) of 35 or less.    
   
   
       10 . The optical glass of  claim 1 , which contains 1 to 20 mol % of Li 2 O.  
   
   
       11 . The optical glass of  claim 1 , which contains over 27% by weight of La 2 O 3 .  
   
   
       12 . The optical glass of  claim 1 , which contains 16% by weight or less of TiO 2 .  
   
   
       13 . The optical glass of  claim 1 , which contains over 27% by weight of La 2 O 3  and 1 to 20 mol % of Li 2 O.  
   
   
       14 . The optical glass of  claim 1 , wherein the content of CaO is less than 5% by weight.  
   
   
       15 . The optical glass of  claim 1 , which has a sag temperature of 670° C. or lower.  
   
   
       16 . The optical glass of  claim 1 , which is for use in precision press-molding.  
   
   
       17 . A precision press-molding preform formed of the optical glass recited in  claim 15 .  
   
   
       18 . A process for producing a precision press-molding preform formed of a glass, which comprises separating a molten glass from a flowing glass and shaping the molten glass into a preform during cooling of the molten glass, 
 wherein said glass is the optical glass recited in  claim 15 .    
   
   
       19 . An optical element formed of the optical glass recited in  claim 1 .  
   
   
       20 . A process for producing an optical element, which comprises heating a precision press-molding preform formed of a glass and precision press-molding the preform with a press mold, 
 wherein the preform recited in  claim 17  is used as the precision press-molding preform.    
   
   
       21 . A process for producing an optical element, which comprises heating a precision press-molding preform formed of a glass and precision press-molding the preform with a press mold, 
 wherein a preform produced by the process recited in  claim 18  is used as the precision press-molding preform.    
   
   
       22 . The process for producing an optical element as recited in  claim 20 , wherein the press mold and the preform are heated together to precision press-mold the preform with the press mold.  
   
   
       23 . The process for producing an optical element as recited in  claim 20 , wherein the press mold is pre-heated, and the preform is pre-heated separately from the press mold and introduced into the pre-heated press mold to precision press-mold the preform with the press mold.