U.S. patent application number 11/037041 was filed with the patent office on 2005-06-09 for disk-shaped magnetic recording medium.
This patent application is currently assigned to FUJI PHOTO FILM CO., LTD.. Invention is credited to Endo, Yasushi.
Application Number | 20050122625 11/037041 |
Document ID | / |
Family ID | 19170328 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050122625 |
Kind Code |
A1 |
Endo, Yasushi |
June 9, 2005 |
Disk-shaped magnetic recording medium
Abstract
A disk-shaped magnetic recording medium for use in a small
magnetic disk cartridge, comprising a flexible disk-shaped magnetic
sheet, and a rigid annular member attached to the outer
circumferential edge portion of one side of the magnetic sheet.
Inventors: |
Endo, Yasushi;
(Kanagawa-ken, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
FUJI PHOTO FILM CO., LTD.
|
Family ID: |
19170328 |
Appl. No.: |
11/037041 |
Filed: |
January 19, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11037041 |
Jan 19, 2005 |
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10303902 |
Nov 26, 2002 |
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6863948 |
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Current U.S.
Class: |
360/133 ;
G9B/23.003; G9B/5.294 |
Current CPC
Class: |
G11B 5/825 20130101;
G11B 23/0021 20130101; Y10T 428/219 20150115 |
Class at
Publication: |
360/133 |
International
Class: |
G11B 033/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 2001 |
JP |
359290/2001 |
Claims
1-8. (canceled)
9. A method of forming a disk-shaped magnetic recording medium for
use in a small magnetic disk cartridge, comprising the steps of:
preparing a flexible disk-shaped magnetic sheet; rotating said
magnetic sheet; and forming a rigid annular member on a
circumferential edge portion of said magnetic sheet by hardening
liquid resin formed on said circumferential edge portion with
ultraviolet rays while rotating said magnetic sheet.
10. The method as set forth in claim 9, wherein said liquid resin
is formed on said circumferential edge portion by being dropping on
said circumferential edge portion.
11. The method as set forth in claim 9, wherein said liquid resin
is formed on said circumferential edge portion by being applied to
said circumferential edge portion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a disk-shaped magnetic
recording medium that is rotatably housed in a small magnetic disk
cartridge.
[0003] 2. Description of the Related Art
[0004] To record or reproduce information, a recording medium is
removably loaded in the card slot of electronic equipment such as a
digital still camera, a digital video camera, a laptop personal
computer (PC), etc. Examples of such recording media that have been
put to practical use are a semiconductor memory type, a hard disk
type, an optical disk type, a magnetic disk type (e.g., a floppy
disk type), etc.
[0005] Among these recording media, semiconductor memories are most
widely used because they are easy to handle and have a relatively
large recording capacity. However, they are relatively expensive.
Because of this, in digital cameras employing the semiconductor
memory, the photographed image data is transferred to a PC and
stored, the data is deleted from the memory, and the semiconductor
memory is repeatedly used.
[0006] Although there are hard disks that can store 340 megabytes
(MB) of data or 1 gigabyte (GB) of data, they are also expensive.
Because of this, data is transferred to another device and stored,
and hard disks are repeatedly used.
[0007] Optical disks have a large recording capacity for their
size. For example, an optical disk with a size of 35 mm.times.41
mm.times.11 mm can store 256 MB of data. Optical disks with a
recording capacity of 512 MB are about to be realized. However,
optical disks have the disadvantage that the recording speed is
slow, because the writing time is time-consuming.
[0008] Meanwhile, there are known some magnetic disks (e.g., floppy
disks) of a small size of 50 mm.times.55 mm.times.2 mm. Such a
small magnetic disk can be exchangeably loaded in a disk drive of a
size that can be inserted into the card slot of a PC, etc. However,
the recording capacity is as small as 40 MB and insufficient to
record image data photographed by a camera. In addition, the size
is not suitable for digital cameras.
[0009] With the spread of PCs, digital cameras have spread rapidly
in recent years because of the simplicity of recording, enhancement
in picture quality due to the development of imagers, possibility
of data deletion and transmission, recording capacity size, etc.
However, the method of use is restricted, because recording media
are limited in cost and recording capacity, as described above. For
instance, since recording media are very expensive, a single camera
has only a single recording medium, which is repeatedly used. That
is, when the recording medium is filled with data, the data is
transferred to a PC and deleted from the recording medium as
described above. Because of this, there are cases where the
recording medium is filled up during a trip. In addition, the
recording medium cannot be stored as is, containing data therein,
nor can it be given away to a person.
[0010] Hence, there is a demand for realization of a recording
medium which is large in recording capacity, low in cost, and small
in size so that the data photographed by a digital camera can be
stored as is or given away to a person. In PCs, there is also a
demand for realization of a recording medium which is large in
recording capacity, low in cost, and small in size so that the
medium with stored data can be handed to a person.
[0011] To meet the aforementioned demands, it is contemplated that
the above-described inexpensive small large-capacity recording
medium may comprise a card-type disk drive which is loaded in
electronic equipment such as a PC and a digital camera, and a
magnetic disk cartridge which is loaded in the small disk drive.
That is, it is contemplated that such a magnetic disk cartridge may
include a housing in which a flexible magnetic disk capable of
high-density recording is rotatably housed, and have a recording
capacity of 200 MB or larger. Examples of magnetic recording media
with a high recording density are a recording medium with a thin
metal film formed by vapor deposition, a recording medium with a
thin metal film formed by sputtering, and a recording medium
employing barium ferrite powder or ferromagnetic magnetic powder.
An example of a magnetic recording medium with a high recording
density employing barium ferrite powder is disclosed in U.S. patent
application Ser. No. 10/266584.
[0012] The "magnetic recording medium with a high recording density
employing barium ferrite powder" is a magnetic disk containing
barium ferrite powder in its magnetic layer, and employs a material
capable of a high recording density. The magnetic disk may comprise
a magnetic recording medium disclosed. The magnetic recording
medium has a non-magnetic layer which includes both non-magnetic
powder and a binder, and a magnetic layer which includes both
ferromagnetic powder (which is ferromagnetic metal powder or
hexagonal-system ferrite powder) and a binder. The non-magnetic
layer and the magnetic layer are formed on at least one surface of
a non-magnetic substrate in the recited order. In the non-magnetic
layer, the quantity of carbon black whose average particle diameter
is 10 to 30 nm is 10 to 50 weight parts with respect to 100 weight
parts of the aforementioned non-magnetic powder. The thickness of
the magnetic layer is 0.2 .mu.m or less. According to a
microanalysis by an electron beam, the standard deviation (b) of
the strength of an element with respect to an average strength (a)
resulting from ferromagnetic powder is 0.03.ltoreq. b/a
.ltoreq.0.4. The center plane average roughness Ra of the magnetic
layer is 5 nm or less, and the 10-point average roughness Rz is 40
nm or less. In a magnetic disk employing the above-described
material, information is recorded or reproduced by a magnetic head
such as an MR head capable of a high recording density.
[0013] The above-described magnetic recording medium can realize a
recording capacity of 200 MB or larger, preferably 500 MB or
larger. Therefore, if a still image has 1 MB of data 500 MB or
larger. Therefore, if a still image has 1 MB of data per image, the
magnetic recording medium can store 500 images. In the case of a
motion picture, the magnetic recording medium can store image
contents of about 30 minutes. Thus, the magnetic recording medium
can store a motion picture photographed by a digital camera or a
motion picture transmitted by a portable telephone. As a result,
users can conveniently use the magnetic recording medium.
Furthermore, the magnetic recording medium can be conveniently used
in PCs as an inexpensive large-capacity recording medium. Thus, the
convenience is great.
[0014] Card-type disk drives are employed in electronic equipment
such as PCs, digital cameras, etc. In the case of PCs, as shown in
FIG. 5A, a disk drive 6 is connected electrically with the socket 4
of a card 2 that is inserted in the card slot of a PC. In the case
of small electronic equipment such as a digital camera 3 shown in
FIG. 5B, a disk drive 6 is connected electrically with the socket
of the receiving portion 5 of the camera 3. Therefore, the disk
drive 6 is extremely small in size and has, for example, a length
of 38 to 55 mm, a width of 35 to 51 mm, and a thickness of 3 to 5
mm. A magnetic disk cartridge 8 is inserted into the disk drive 6
through a slot formed in the disk drive 6, and has, for example, a
length and a width of 25 to 36 mm and a thickness of 1 to 3 mm.
[0015] To achieve the above-described high recording density, it is
necessary that a magnetic head touch the magnetic recording medium
stably. In the case where a flexible recording sheet is employed as
the magnetic recording medium, the gap between the magnetic sheet
and the magnet head varies due to the so-called flutter of the
magnetic sheet being rotated. Because of this, there is a problem
that recording-reproduction characteristics will degrade. With a
reduction in the pitch between recording tracks, there is another
problem that the position of a recording track in the radial
direction of the disk will be slightly shifted or fluctuated.
SUMMARY OF THE INVENTION
[0016] The present invention has been made in view of the
above-described circumstances. Accordingly, it is an object of the
present invention to provide a disk-shaped magnetic recording
medium in which a magnetic head can touch a flexible magnetic sheet
stably by preventing the flutter of the flexible magnetic sheet
during rotation. Another object of the invention is to provide a
method of manufacturing the disk-shaped magnetic recording
medium.
[0017] To achieve the aforementioned objects of the present
invention and in accordance with the present invention, there is
provided a first disk-shaped magnetic recording medium for use in a
small magnetic disk cartridge, comprising:
[0018] a flexible disk-shaped magnetic sheet; and
[0019] a rigid annular member attached along the outer
circumferential edge portion of one side of the magnetic sheet.
[0020] In addition, in accordance with the present invention, there
is provided a second disk-shaped magnetic recording medium for use
in a small magnetic disk cartridge, comprising:
[0021] a flexible disk-shaped magnetic sheet; and
[0022] two rigid annular members attached along the outer
circumferential edge portions of both sides of the magnetic
sheet.
[0023] In the first and second magnetic recording media of the
present invention, the aforementioned annular member may be
prefabricated to be of substantially the same outer diameter as the
magnetic sheet and adhesively attached thereto. The aforementioned
two annular members may alternatively be attached to the outer
circumferential edge portions by hardening liquid resin formed on
the outer circumferential edge portions with ultraviolet rays.
[0024] In the first and second magnetic recording media of the
present invention, it is preferable that the aforementioned annular
members be formed from a material whose sliding resistance is low
with respect to an interior wall surface of the magnetic disk
cartridge.
[0025] The first disk-shaped magnetic recording medium of the
present invention may further comprise an annular member coaxially
attached to an inner circumferential portion of one side of the
magnetic sheet. The second disk-shaped magnetic recording medium of
the present invention may further comprise two annular members
coaxially attached to inner circumferential portions of both sides
of the magnetic sheet.
[0026] Further in accordance with the present invention, there is
provided a method of manufacturing a disk-shaped magnetic recording
medium for use in a small magnetic disk cartridge, comprising the
steps of:
[0027] preparing a flexible disk-shaped magnetic sheet;
[0028] rotating the magnetic sheet; and
[0029] forming a rigid annular member on a circumferential edge
portion of the magnetic sheet by administering liquid resin on the
circumferential edge portion while curing said resin with
ultraviolet rays.
[0030] In the above-described method, the aforementioned liquid
resin may be formed on the circumferential edge portion by being
dropping on the circumferential edge portion. The liquid resin may
also be formed on the circumferential edge portion by being coated
on the circumferential edge portion.
[0031] According to the disk-shaped magnetic recording medium of
the present invention, the flexible disk-shaped magnetic sheet is
equipped with the rigid annular member along the outer
circumferential edge portion of the sheet. Therefore, the flutter
of the magnetic sheet being rotated can be minimized by the
centrifugal force of the annular member that occurs during
rotation. As a result, the disk-shaped magnetic recording medium of
the present invention has the advantage that the magnetic heads in
a disk drive can touch both sides of the magnetic disk stably.
[0032] In addition, the presence of the annular member can prevent
the magnetic sheet from contacting the interior wall surface of the
housing of the cartridge. Therefore, even when the cartridge
undergoes vibration during transportation, for instance, the
magnetic sheet can be prevented from contacting the interior
surface and liner of the cartridge housing.
[0033] Furthermore, by coaxially attaching a similar annular member
to the inner circumference of the magnetic recording medium, the
above-described advantages can be further enhanced.
[0034] According to the above-described manufacturing method of the
present invention, the rigid annular member can be formed by
applying liquid ultraviolet-ray hardening resin to the outer
circumferential edge portion of the magnetic sheet while
irradiating ultraviolet rays to the outer circumferential edge
portion, during the rotation of the magnetic sheet. In this way,
the liquid ultraviolet-ray hardening resin applied to the
circumferential edge portion of the magnetic sheet can be applied
uniformly over the entire circumference of the magnetic sheet by
the centrifugal force that results from rotation of the magnetic
sheet. At the same time, the resin can be hardened by irradiation
of ultraviolet rays. As a result, a dynamically balanced rigid
annular member can be formed along the circumferential edge portion
of the magnetic sheet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The present invention will be described in further detail
with reference to the accompanying drawings wherein:
[0036] FIG. 1 is a schematic sectional view showing a magnetic disk
cartridge in which a magnetic recording medium constructed in
accordance with a preferred embodiment of the present invention is
housed;
[0037] FIG. 2 is a perspective view of the magnetic recording
medium shown in FIG. 1;
[0038] FIG. 3 is an exploded perspective view of the magnetic
recording medium shown in FIG. 2;
[0039] FIG. 4 is a diagram used to explain how the magnetic
recording medium is formed; and
[0040] FIGS. 5A and 5B are diagrams showing a small magnetic disk
cartridge on which the present invention is based, and electronic
equipment with a card slot in which a disk drive for the magnetic
disk cartridge is loaded.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0041] Referring now to FIG. 1, there is shown a magnetic disk
cartridge 10 with a housing 12. Within the housing 12, a
disk-shaped magnetic recording medium 13 is rotatably supported.
The magnetic recording medium 13 is constructed of a flexible
magnetic sheet 14. A center core 15 is fixedly attached to the
central portion of the magnetic sheet 14. Annular members 19, 19
are attached to the outer circumferential edge portions of both
sides of the magnetic sheet 14, respectively. When the magnetic
disk cartridge 10 is loaded in a disk drive such as the disk drive
6 shown in FIG. 5, the center core 15 is magnetically attracted and
rotated by a driving member provided in the disk drive 6. The
annular members 19, 19 are preferably formed from a material whose
sliding resistance is low with respect to the interior wall surface
of the housing 12. Note that the magnetic disk cartridge 10 is
equipped with openings (not shown) and a shutter (not shown) that
opens and closes to expose both sides of the magnetic recording
medium 13 through the openings. Since they do not form part of the
present invention, a detailed description of them will not be
given.
[0042] In addition to the above-described outer annular members 19,
19, the magnetic recording medium 13 may be equipped with inner
annular members 19', 19' which are attached to the inner
circumferential portions of both sides of the magnetic sheet 14, as
shown by phantom lines in FIGS. 1 and 2. While the two outer
annular members 19, 19 are attached to both sides of the magnetic
sheet 14, one outer annular member 19 maybe attached to one side of
the magnetic sheet 14.
[0043] The rigid annular member 19 (or 19') can be attached to the
magnetic sheet 14 by an adhesive, etc., as shown in FIG. 3.
[0044] According to the disk-shaped magnetic recording medium 13 of
the preferred embodiment, the flexible disk-shaped magnetic sheet
14 is equipped with the rigid annular member 19 along the outer
circumferential edge portion of the sheet 14. Therefore, the
flutter of the magnetic sheet 14 being rotated can be minimized by
the centrifugal force of the annular member 19 that occurs during
rotation. As a result, the disk-shaped magnetic recording medium 13
of the preferred embodiment has the advantage that the magnetic
heads in the disk drive 6 can touch both sides of the magnetic disk
14 stably. In addition, the presence of the annular member 19 (and
19') can prevent the magnetic sheet 14 from contacting the interior
wall surface of the housing 12 of the cartridge 10. Therefore, even
when the cartridge 10 undergoes vibration during transportation,
for instance, the magnetic sheet 14 can be prevented from
contacting the interior surface and liner of the housing 12.
[0045] FIG. 4 shows a method of forming the rigid annular member 19
along the outer circumferential edge portion of the magnetic sheet
14. In this method, the center core 14 of the magnetic sheet 14 is
first placed on a rotating table 31 and magnetically fixed to the
rotating table 31. Then, the magnetic sheet 14 is rotated. During
the rotation of the magnetic sheet 14, the rigid annular member 19
can be formed by dropping or applying liquid ultraviolet-ray
hardening resin 29 to the outer circumferential edge portion of the
magnetic sheet 14 while irradiating ultraviolet rays to the outer
circumferential edge portion. In this way, the liquid
ultraviolet-ray hardening resin 29 applied to the circumferential
edge portion of the magnetic sheet 14 can be applied uniformly over
the entire circumference of the magnetic sheet 14 by the
centrifugal force that results from rotation of the magnetic sheet
14. At the same time, the resin 29 can be hardened by irradiation
of ultraviolet rays. As a result, the rigid annular member 19
dynamically balanced can be formed along the circumferential edge
portion of the magnetic sheet 14.
[0046] While the present invention has been described with
reference to the preferred embodiment thereof, the invention is not
to be limited to the details given herein, but may be modified
within the scope of the invention hereinafter claimed.
* * * * *