ZrO2-based interface films realizing a dual-layer phase-change optical disk utilizing a blue-violet laser

A ZrO2-based dielectric material shows superior properties for interface films of phase-change optical disks, in particular, when utilizing a blue-violet laser. i) The ZrO2-based film possesses a high transparency at a wavelength of 405 nm, ii) it has a superior adhesiveness with phase-change recording films, and iii) it shows no crystallization or decomposition below 1000 degrees C, as shown by temperature-programmed desorption (TPD) measurement. The film was adopted for interface films of a semitransparent recording layer (L1) that was located on the laser-incident side of a dual-layer optical disk, and a high optical transmittance of more than 50% and a large reflectivity contrast of more than 0.8 were realized. By dynamic evaluation based on the Blu-ray Disc Format version 1.0, the obtained jitter measured with limit equalizer (LEQ jitter) was 6.7% and the cycle number was more than 10,000, whereas those of the reference disk using conventional GeN-based interface films were 7.3% and 2000, respectively. From the optical and thermal simulation, the maximum temperature in the interface film located on the laser-incident side of L1 was around 700 degrees C.