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

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, B 2 O 3 , La 2 O 3 , Gd 2 O 3 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.

1 . An optical glass comprising, as essential components, B 2 O 3 , La 2 O 3 , Gd 2 O 3  and ZnO and having 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.  
     
     
         2 . An optical glass comprising, by mol %,  
       
         
           
                 
                 
               
                     
                 
                     
                 
                   15-45%  
                   B 2 O 3 , 
                 
                   5-20% 
                   La 2 O 3 , 
                 
                   1-20% 
                   Gd 2 O 3 , 
                 
                   10-45%  
                   ZnO, 
                 
                   0-15% 
                   WO 3 , 
                 
                   0-10% 
                   Ta 2 O 5 , 
                 
                   0-10% 
                   Nb 2 O 5 , 
                 
                   0-20% 
                   TiO 2 , 
                 
                   0-20% 
                   SiO 2 , 
                 
                   0-15% 
                   Li 2 O, 
                 
                   0-10% 
                   Na 2 O, 
                 
                   0-10% 
                   K 2 O, 
                 
                   0-10% 
                   MgO, 
                 
                   0-10% 
                   CaO, 
                 
                   0-10% 
                   SrO, 
                 
                   0-10% 
                   BaO 
                 
                   0-8%  
                   Y 2 O 3 , 
                 
                   0-8%  
                   Yb 2 O 3 , 
                 
                     
                 
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
         provided that the total content of La 2 O 3 , Gd 2 O 3 , Y 2 O 3  and Yb 2 O 3  is 10 to 30%,  
         
           
             
                   
                   
                 
                       
                   
                       
                   
                     0-10% 
                     ZrO 2 , 
                   
                     0-10% 
                     Bi 2 O 3 , and 
                   
                     0-1%  
                     Sb 2 O 3 , 
                   
                       
                   
                       
                   
               
                  
                  
                 
                 
                  
                  
                  
                  
                  
                 
              
             
           
         
         and having 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.  
       
     
     
         3 . An optical glass comprising, by mol %,  
       
         
           
                 
                 
               
                     
                 
                     
                 
                   15-45% 
                   B 2 O 3 , 
                 
                    5-20% 
                   La 2 O 3 , 
                 
                    1-20% 
                   Gd 2 O 3 , 
                 
                   10-45% 
                   ZnO, 
                 
                    0-15% 
                   WO 3 , 
                 
                    0-10% 
                   Ta 2 O 5 , 
                 
                    0-10% 
                   Nb 2 O 5 , 
                 
                    0-20% 
                   TiO 2 , 
                 
                    0-20% 
                   SiO 2 , 
                 
                    0-15% 
                   Li 2 O, 
                 
                    0-10% 
                   Na 2 O, 
                 
                    0-10% 
                   K 2 O, 
                 
                    0-10% 
                   MgO, 
                 
                    0-10% 
                   CaO, 
                 
                    0-10% 
                   SrO, 
                 
                    0-10% 
                   BaO 
                 
                   0-8% 
                   Y 2 O 3 , 
                 
                   0-8% 
                   Yb 2 O 3 , 
                 
                     
                 
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
         provided that the total content of La 2 O 3 , Gd 2 O 3 , Y 2 O 3  and Yb 2 O 3  is 10 to 30%,  
         
           
             
                   
                   
                   
                 
                       
                       
                   
                       
                       
                   
                       
                     0-less than 0.5% 
                     ZrO 2 , 
                   
                       
                     0-10% 
                     Bi 2 O 3 , and 
                   
                       
                     0-1% 
                     Sb 2 O 3 , 
                   
                       
                       
                   
                       
                       
                   
               
                  
                  
                 
                 
                  
                  
                  
                  
                  
                 
              
             
           
         
         and having a refractive index (nd) of over 1.86, an Abbe's number (νd) of 35 to less than 39.5 and a glass transition temperature (Tg) of 630° C. or lower.  
       
     
     
         4 . A precision press-molding preform, which is formed of the optical glass recited in  claim 1 .  
     
     
         5 . A process for the production of a precision press-molding preform, which comprises separating a molten glass gob having a predetermined weight from a molten glass flowing out of a pipe, and shaping the glass gob into a preform formed of the optical glass recited in  claim 1 .  
     
     
         6 . A process for the production of a precision press-molding preform, which comprises forming a shaped glass from a molten glass and processing said shaped glass to produce a preform formed of the optical glass recited in  claim 1 .  
     
     
         7 . An optical element formed of the optical glass recited in  claim 1 .  
     
     
         8 . A process for the production of an optical element, which comprises heating the preform recited in  claim 4  and precision press-molding the preform.  
     
     
         9 . A process for the production of an optical element, which comprises heating the preform produced by the process recited in  claim 5  and precision press-molding the preform.  
     
     
         10 . The process for the production of an optical element as recited in  claim 8 , wherein a press mold and the preform are heated together and the preform is precision press-molded with said press mold.  
     
     
         11 . The process for the production of an optical element as recited in  claim 8 , wherein the preform pre-heated separately from a press mold is introduced into the press mold pre-heated, and the preform is precision press-molded.