Disk Unit
In the case of a disk with a high NA which enables high-density recording, since the coma aberration increases as the numerical aperture, NA, increases, a disk protective layer needs to be thin very much, and a damage or scratch imparted to a surface of the disk affects largely the record and reproduction of data. An object of the invention is to reduce the generation of damage to a storage disk due to a collision between a lens holder or an objective lens and the storage disk. With a view to attaining the object, according to the invention, a longitudinal direction of a protector 11 provided on a holder is made substantially parallel to a straight line which connects the rotational center of a motor with the center of an objective member.
1 . A disk unit having:
an objective lens for focusing light on the storage disk;
a holder for holding the objective member;
a protector for protecting the storage disk from a damage; and
a motor for rotationally driving the storage disk, wherein
an arrangement of the protector is substantially parallel to a hypothetical straight line between a rotational center of the motor and an optical axis of the objective lens.
2 . The disk unit as set forth in claim 1 , wherein the protector is provided on both sides of the objective member.
3 . The disk unit as set forth in claim 1 , wherein a cross section of the protector taken widthwise has a shape which protrudes towards the storage disk.
4 . The disk unit as set forth in claim 3 , wherein a cross section of the protector taken widthwise has a shape which contains partially an arc.
5 . The disk unit as set forth in claim 1 , wherein the protector is disposed at a position which lies on the holder except for an area defined as lying further upstream in a rotational direction and radially closer to a rotational center of the storage disk than the objective lens.
6 . The disk unit as set forth in claim 1 , wherein the protector is made up of a protective member which is formed on a base material which makes up the holder.
7 . The disk unit as set forth in claim 6 , wherein a protective member forming portion where the protective member is formed is provided by altering a height of the base material which makes up the holder.
8 . The disk unit as set forth in claim 7 , wherein the protective member forming portion has a straight or curved groove which passes through substantially a center of the protective member forming portion when viewed from a storage disk side.
9 . The disk unit as set forth in claim 1 , wherein two pairs of the protector is provided on both sides of the objective lens.
10 . A disk unit for recording or reproducing an information on a storage disk having:
a light source for emitting short-wavelength light;
an objective lens for focusing light from the light source on the storage disk;
a light receiving unit for receiving light from the light source;
a holder for holding the objective member;
a protector for protecting the storage disk from a damage;
a base for holding the holder in such a manner as to move freely in a radial direction of a storage disk; and
a motor provided on the base for rotationally driving the storage disk, wherein
an arrangement of the protector is substantially parallel to a hypothetical straight line between a rotational center of the motor and an optical axis of the objective lens.
11 . The disk unit as set forth in claim 6 , wherein the protective member is a protective member for protecting at least the storage disk and has a tensile stress at 100% stretch of 0.49 kgf/mm 2 or smaller.
12 . The disk unit as set forth in claim 6 , wherein the protective member has a breaking strength of 0.43 kgf/mm 2 or larger.
13 . The disk unit as set forth in claim 6 , wherein the protective member results from a polymerization of at least urethane acrylate and a monomer.
14 . The disk unit as set forth in claim 13 , wherein the protective member results from a polymerization of 5 to 10 percent by weight of the urethane acrylate and the monomer.
15 . The disk unit as set forth in claim 13 , wherein the monomer contains 0.1 to 5 percent by weight of diacrylate monomer and 90 percent by weight of monomer which has a molecular weight of 150 to 500 and an annular construction.
16 . The disk unit as set forth in claim 14 , wherein the monomer contains 0.1 to 5 percent by weight of diacrylate monomer and 90 percent by weight of monomer which has a molecular weight of 150 to 500 and an annular construction.
17 . The disk unit as set forth in claim 13 , wherein the protective member is a polymer having at least a hydroxyl group.
18 . The disk unit as set forth in claim 17 , wherein the protective member is a polymer having at least one of a hydroxy-based acrylate monomer and a hydroxy-based methacrylate monomer.
19 . The disk unit as set forth in claim 17 , wherein the lens holder has a base material which holds the protective member, and the base material contains a liquid crystal polymer.
20 . A disk unit for recording or reproducing an information on a storage disk having:
an objective lens for focusing light on the storage disk;
a holder for holding the objective lens; and
a protector for preventing the storage disk from contacting with the objective lens or the holder, wherein
the protector is so arranged that the width of the protector in a rotational direction of the storage disk is minimized.