Zinc phthalocyanine-Organic photoconductive film

We are studying a new imaging device that may be suitable for palm-size HDTV broadcasting cameras. A key device for such an advanced system is organic photoconductive film. Our goal is the realization of an imaging device (Figure 1a) that utilizes layered organic photoconversion films, each of which will absorb only a specific wavelength of light (blue, green, or red), with an anticipated result of a dramatic reduction in camera size. This article describes zinc phthalocyanine, a material sensitive to red wavelength light.

What is zinc phthalocyanine?

Zinc phthalocyanine is an organic material that is formed when a zinc atom bind at the center of an organic molecule called a phthalocyanine ring (Figure 2). Organic materials with metal atoms (Zn, Cu, etc.) bound at the center of a phthalocyanine ring are collectively called phthalocyanine. Since phthalocyanine absorbs mainly red light, not light in green or blue, it has an appearance similar to the color of cyanogen (blue green), which is a complementary color of red. One familiar application is in the long lasting paint (pigment) used for the blue of the Shinkansen bullet train. Its property of efficiently generating a charge based on the amount of absorbed light (photoconversion) has led to it being used as a photoreceptor material for copier machines. An anticipated future application is advanced solar batteries.

World's first: HDTV shoot using organic photoconductive film

We took note of the fact that zinc phthalocyanine absorbs red light especially well, and are pursuing its use in the development of an organic photoconductive film for the color red. Approximately four years after fundamental experiments began, and after thorough research to enhance photoconversion efficiency and picture resolution, we can now record HDTV video signals (red color only) by using organic photoconductive film (Figure 3). This achievement is a big step toward the realization of a broadcast-quality palm-size HDTV camera system. Our future research will focus on developing organic photoconductive films with sensitivities to green and blue light. We will also work to improve the transparent circuit to read out the signals from layered organic films, with a view toward building a palm-size HDTV camera for broadcasting.