Hitachi Maxell, Limited

Susumu Shibasaki

Osamu Ishizaki

Tsuyoshi Maro

Kunio Wakai

Tatsuo Araki

Hiroyuki Hirata

Masashi Yoshimura

Makoto Aihara

Hideki Komiya

Hiroyuki Ohta

Shuji Seki

A method of producing an optical element, in which a first and a second die are cooperated with each other so as to press-mold a material in order to produce an optical element including a lens portion, the first die has a circular cross-sectional shape, and the second die defines therein an interior space having a polygonal cross-sectional shape with respect to the direction of die-fastening, the first die is adapted to enter into the interior space of the second die in the direction of die-fastening in the interior space so to press-mold the material in order to form the lens surface while the material is bulged out through gaps between the first die and the second die around the lens surface whereby forming protrusions. An optical element and a mold assembly for an optical element are also provided.

Production method of optical element, optical element forming mold and optical element

A recording disk comprises a substrate including a plastic material, and an overlay arranged over the substrate and including a recording substance for recording therein an information, and a radially-outer periphery of the overlay is received within a radially-outer periphery of the substrate as seen in an axial direction of the recording disk.

Recording disk and producing method therefor

A method of and an apparatus for making a magnetic recording tape, which is free from wrinkles formed thereon, by the use of a vapor deposition technique. A length of tape reeled on a supply reel is taken up by a take-up reel after having passed through a deposition station where it is movably turned around a cylindrical drum. In one aspect, the difference in tension between two different portions of the tape moving between the drum and the take-up reel and on respective sides of a tensioning roll forming a part of at least one tension control mechanism is adjusted to a value not greater than 10N/mm.sup.2. In another aspect, a charge eraser is employed and installed in the vicinity of the drum for removing an electrostatic charge built up in the tape being moved from the drum onto the take-up reel. In a further aspect, the cylindrical drum is used having its outer peripheral surface roughened to a ten-point average surface roughness of not smaller than 0.1 .mu.m.

Method of a making magnetic recording medium

Growing community of inventors

Ibaraki, Japan

Susumu Shibasaki