Organic write once media is developed for the Blu-ray disc format, namely, a system comprising a blue wavelength laser diode of 405 nm and a high numerical aperture (NA) lens of 0.85. The first generation Blu-ray disc format employs phase change media. Thus, the organic write once media was designed with a reflectivity modulation scheme in order to retain compatibility. A very simple layer structure is proposed, SiO2/Dye/SiO2 without any metal reflective layer, and the media showed sufficient modulation amplitude and signal quality. The optical constants before and after the recording were measured to clarify the recording mechanism, and the result matched well with the readout waveform in the optical disc system. The measured jitter level after random pattern recording at a density of 23.3 GB per disc was 6.7% using a limit equalizer, which satisfies the Blu-ray disc format.