| abstract |
We describe a new category of bridged indicator dyes with absorption in the infrared region of the electromagnetic spectrum. These bridged indicator dyes are useful as light-sensitive, pH-absorbing optical filtering agents in photographic diffusion transfer processes designed to be performed in ambient light, as well as in diffusion transfer products suitable for these methods. Indicator dyes can also be used for titration and other analytical techniques, as well as in products where pH sensitive indicator dyes are used, and where infrared absorption is required. |