Cyanine dyes

Abstract

Disclosed are novel trimethine cyanine dyes, light absorbents, light-resistant improvers, and optical recording media which comprise the trimethine cyanine dyes. The cyanine dyes exert satisfactory solubility and heat resistance when used in high-density optical recording media.

We claim:  
     
         1 . An optical recording medium, which comprises a trimethine cyanine dye represented by Formula 1 and has a solubility of at least 50 mg/ml in diacetone alcohol at 20° C.:  
       
         
           
           
               
               
           
         
       
       wherein in Formula 1, R 1  and R 2  independently represent an optionally substituted aliphatic hydrocarbon group; Z 1  and Z 2  independently represent an optionally substituted naphthalene ring to form a benzoindolenic ring; and X −  represents an organic metal complex as a counter ion selected from the group consisting of RF 6   − , ClO 4   − , and Sb 6   − .  
     
     
         2 . The optical recording medium of  claim 1 , which is capable of recording information thereon by writing thereon with a laser beam having a wavelength of around 630 to 680 nm.  
     
     
         3 . The optical recording medium of  claim 1 , which has a decomposition point of over 272° C.  
     
     
         4 . The optical recording medium of  claim 1 , which has a reflection efficiency of at least 45%.  
     
     
         5 . The optical recording medium of  claim 1 , which further contains 0.03 to 0.3 mole of a light-resistant improver to one mole of said trimethine cyanine dye.