Photomagnetic disc

Abstract

Abstract PURPOSE:To offer a both-side photomagnetic disc where the thickness is nearly the same as a one side disc and the track roundness of both sides is coincident completely by providing symmetrically an optomagnetic recording medium on a transparent base plate having a spiral track guide groove while clipping a reflecting film. CONSTITUTION:Layers 2, 6 made of the same kind of optomagnetic recording medium film, layers 3, 5 made of the same kind of dielectric film, a layer 4 made of metallic reflecting film, and a layer 7 made of transparent high polymer protecting film are formed on a transparent high-polymer base plate 1 having the spiral track guide groove, the film thickness of the layers 2, 6 is taken as 100-300Angstrom , the film thickness of the layers 3, 5 is taken as 800-1,200Angstrom , and the film thickness of the layer 7 is taken as >=1.5mum. In taking the depth of the track guide groove to 1/8 of the wavelength of laser light, the recessed part viewed from the incident direction of the laser light is sensed as a dark part and the projected part is sensed as a light part, and the recording of information is brought to the said dark part. In this case, the part being the light part viewed from the surface is the dark part viewed from the rear side, then the recording of the information to the rear side is brought to the dark part when viewed from the front side.

Inventors

• 👤 Tadao Iwaki
• 👤 忠雄 岩城

Bibliographic Details