Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Reexamination Certificate
2002-02-26
2004-11-16
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
C360S098070, C360S098080, C360S099080, C360S099120
Reexamination Certificate
active
06819526
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to information storage disk holding members made of glass-ceramics and an information storage disk drive device using the disk holding members. In this specification, “holding members” mean members for holding an information storage disk in position in an information storage disk drive device and include, for example, a rotor hub in the form of a rotating column for holding one or more information storage disk, a disk supporting plane forming member on which information storage disks are stacked with a predetermined interval, a spacer ring and a shim, and a clamp as a mounting member.
An information storage disk drive device is generally constructed in such a manner that one or more information storage disks and spacer rings are mounted alternately on a rotor hub which is secured fixedly to a rotor shaft and these disks and spacer rings are finally clamped with a shim and a clamp. The holding members such as the rotor hub and spacer rings are normally made of metal materials such as stainless steel and an aluminum alloy. There is, however, an increasing tendency toward using a disk substrate made of glass-ceramics in lieu of the conventional aluminum disk. In this case, use of a metal material for holding members is undesirable because there is a great difference in the coefficient of thermal expansion between the holding members and the substrate and, moreover, there occur distortion, deformation and flash in the course of processing of the holding members. Furthermore, since an aluminum alloy is a soft material, deformation tends to occur during a high speed rotation and, therefore, it cannot cope sufficiently with current requirement for a high density recording.
In this technical field, since a high precision is required for positioning of a head and a medium, a particularly high precision in size is required for component parts of a medium substrate and a disk. For this reason, it is desirable for information storage disk holding members to have as little difference as possible between other component parts of a disk drive device (hereinafter referred to “other drive component parts”) in the coefficient of thermal expansion within a temperature range of an environment in which the drive device is used. It is also desirable for them to have a low dust producing property, a high reliability, a low cost and a good polishing property. There is demand for a more suitable material for information storage disk holding members which satisfies all of these requirements.
As materials for solving these problems, there have been proposed polycrystalline ceramics (Japanese Patent Application Laid-open Publication No. Sho 61-148667 and Japanese Patent Application Laid-open Publication No. Hei 9-44969 etc.) and amorphous glass (Japanese Patent Application Laid-open Publication No. Hei 10-74350 etc.) but satisfactory solution has not been achieved yet.
It is an object of the present invention to provide information storage disk holding members which have solved the above described problems and are capable of coping with a high speed rotation of a disk in conformity with tendencies toward high density recording and high speed transmission of information, increasing mechanical strength for adaptation to mobile uses, having a thermal expansion property matching that of other drive component parts and eliminating defects caused by dissolving out of alkali, and also to provide an information storage disk drive device using these holding members.
BRIEF SUMMARY OF THE INVENTION
As a result of studies and experiments made by the inventors of the present invention for achieving the above described object of the invention, it has been found, which has led to the present invention, that, by heat treating a base glass of a proper composition such as a SiO
2
—Li
2
O—K
2
O—P
2
O
5
—Al
2
O
3
—ZrO
2
glass under proper conditions, glass-ceramics having a high Young's modulus, a low specific gravity, a coefficient of thermal expansion, a high mechanical strength and a low dust producing property and being thereby capable of coping with a high speed rotation of a disk and very suitable for information storage disk holding members, particularly for spacer rings, can be obtained.
As the first aspect of the invention, the invention described in claim
1
is an information storage disk holding member for holding an information storage disk in position, said holding member being made of glass-ceramics in which a crystal phase is dispersed in a glass matrix.
The invention described in claim
2
is an information storage disk holding member as defined in claim
1
wherein specific rigidity (Young's modulus/specific gravity) is not smaller than 37 GPa and specific gravity is not greater than 3.0.
The invention described in claim
3
is an information storage disk holding member as defined in claim
1
wherein Young's modulus is within a range from 95 GPa to 130 GPa and specific gravity is within a range from 2.40 to 2.60.
The invention described in claim
4
is an information storage disk holding member as defined in claim
1
wherein bending strength is within a range from 400 MPa to 800 MPa.
The invention described in claim
5
is an information storage disk holding member as defined in claim
1
wherein the glass-ceramics comprise, as a predominant crystal phase or phases, at least one crystal phase selected from the group consisting of lithium disilicate (Li
2
O□2SiO
2
), &agr;-quartz (&agr;-SiO
2
), &agr;-quartz solid solution (&agr;-SiO
2
solid solution), &agr;-cristobalite (&agr;-SiO
2
) and &agr;-cristobalite solid solution (&agr;-SiO
2
solid solution).
The invention described in claim
6
is an information storage disk holding member as defined in claim
5
wherein the glass-ceramics comprise, as a predominant crystal phase, lithium disilicate.
The invention described in claim
7
is an information storage disk holding member as defined in claim
1
wherein an amount of crystal of lithium disilicate in the glass-ceramics is 3-10 mass % and an average crystal grain diameter of the crystal phase is within a range from 0.01 &mgr;m-0.05 &mgr;m.
The invention described in claim
8
is an information storage disk holding member as defined in claim
1
wherein the glass-ceramics comprise, in mass % on oxide basis,
SiO
2
70-79%
Li
2
O
8-12%
K
2
O
0-4%
MgO
0-less than 2%
ZnO
0-less than 2%
P
2
O
5
1.5-3%
ZrO
2
1.5-7%
Al
2
O
3
3-9%
Sb
2
O
3
+ As
3
O
3
0-2%.
The invention described in claim
9
is an information storage disk holding member as defined in any of claims
1
-
8
wherein coefficient of thermal expansion within a range from −50° C. to +70° C. is within a range from +65×10
−7
/° C. to +130×10
−7
/° C.
As the second aspect of the invention, the invention described in claim
10
is an information storage disk holding member as defined in claim
1
wherein the glass-ceramics comprises, as a predominant crystal phase, &agr;-quartz (&agr;-SiO
2
) or &agr;-quartz solid solution (&agr;-SiO
2
solid solution), an amount of the crystal phase is 3-35 mass %, and an average crystal grain diameter of the crystal phase is not greater than 0.10 &mgr;m.
The invention described in claim
11
is an information storage disk holding member as defined in claim
10
wherein an average crystal grain diameter of the entire predominant crystal phase of the glass-ceramics is not greater than 0.05 &mgr;m.
The invention described in claim
12
is an information storage disk holding member as defined in claim
10
wherein the glass-ceramics are substantially free of PbO.
The invention described in claim
13
is an information storage disk holding member as defined in claim
10
wherein coefficient of thermal expansion within a range from −50° C. to +70° C. is within a range from +95×10
−7
/° C. to +110×10
−7
/° C.
The invention described in claim
Goto Naoyuki
Ishioka Junko
Kataoka Mariko
Nakajima Kousuke
Yagi Toshitaka
Kabushiki Kaisha Ohara
Tupper Robert S.
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