Photographic materials often contain layers sensitized to different regions of the spectrum, such as red, blue, green, ultraviolet, infrared, X-ray, to name a few. A typical color photographic element contains a layer sensitized to each of the three primary regions of the visible spectrum, i.e., blue, green, and red. Silver halide used in these materials has an intrinsic sensitivity to blue light. Increased sensitivity to blue light, along with sensitivity to green light or red light, is imparted through the use of various sensitizing dyes adsorbed to the silver halide grains. Sensitized silver halide retains its intrinsic sensitivity to blue light.
If, prior to processing, blue light reaches a layer containing silver halide that has been sensitized to a region of the spectrum other than blue, the silver halide grains exposed to the blue light, by virtue of their intrinsic sensitivity to blue light, would be rendered developable. This would result in a false rendition of the image information being recorded by the photographic element. It is therefore a common practice to include in the photographic element a material that filters blue light. This blue-absorbing material can be located anywhere in the element where it is desired to filter blue light. In a color photographic element that has layers sensitized to each of the primary colors, it is common to have the blue-sensitized layer closest to the exposure source and to interpose a blue-absorbing, or yellow, filter layer between the blue-sensitized layer and the green- and red-sensitized layers.
The material most commonly used as a blue-absorbing material in photographic elements is yellow colloidal silver, referred to in the art as Carey Lea silver. It absorbs blue light during exposure and is readily removed during processing, usually during the silver bleaching and fixing steps. Carey Lea silver, however, exhibits unwanted absorption in the green region of the spectrum. Also, silver can be an expensive component of a photographic element.
A number of yellow dye alternatives for Carey Lea silver have been suggested. These include dyes disclosed in U.S. Pat. Nos. 2,538,008, 2,538,009, and 4,420,555, and U.K. Pat. Nos. 695,873 and 760,739. Many of these dyes, although they exhibit the requisite absorption of blue light, also are subject to stain problems. Some dyes are not fully decolorized or removed during photographic processing, thus causing post-processing stain. Other dyes wander into other layers of the element, adversely affecting image quality. Still other dyes react before exposure with other components of the photographic element, such as color couplers, thus causing incubative stain. Therefore, it would be desirable to provide a filter dye for use in photographic elements that absorbs blue light, but does not absorb significant amounts of light in other regions of the spectrum, and exhibits neither incubative nor post-processing stain.
USPTO Backgrounds
USPTO Backgrounds