| 摘要 |
A main cartridge body unit reduced in size and thickness. To this end, the main cartridge body unit includes a disc-shaped recording medium 5, a main cartridge body unit 6 including an upper plate 21 and a lower plate 22, both of a metal material, forming a plate pair, and an intermediate frame 23, recording and/or reproducing apertures 24, 25 formed in the main cartridge body unit 6 for exposing a portion of a recording area of the disc-shaped recording medium 5 to outside across the inner and outer rims of the disc-shaped recording medium, and a shutter member 61 provided for linear movement within the inside of the main cartridge body unit 6 for opening/closing the recording and/or reproducing aperture. The intermediate frame 23 is sandwiched between the upper and lower plates 21, 22. The disc-shaped recording medium is housed in the main cartridge body unit 6.
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