GLASS SUBSTRATE FOR MAGNETIC DISK AND MAGNETIC DISK

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United States of America Patent

SERIAL NO

15442051

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Abstract

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A magnetic-disk glass substrate has a circular center hole a pair of main surfaces and an edge surface. The edge surface has a side wall surface and chamfered surfaces interposed between the side wall surface and the main surfaces, and a roundness of an edge surface on an outer circumferential side is 1.5 μm or less. Also, a midpoint A between centers of two least square circle respectively derived from outlines in a circumferential direction respectively obtained at two positions spaced apart by 200 μm in a substrate thickness direction on the side wall surface on the outer circumferential side, and centers B and C respectively derived from a respective one of two chamfered surfaces on the outer circumferential side in the substrate thickness direction, are located such that a sum of respective distances between A and B, and A and C, is 1 μm or less.

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Patent Owner(s)

Patent OwnerAddress
HOYA CORPORATION6-10-1 NISHI-SHINJUKU SHINJUKU-KU TOKYO 1608347 ?1608347

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Inventor(s)

Inventor Name Address # of filed Patents Total Citations
TAKAHASHI, Takeyoshi Tokyo, JP 12 73
TAMAKI, Masanori Tokyo, JP 15 286
UEDA, Masaaki Yokohama-shi, JP 67 1312

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