JPH0512658A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk generating few errors by forming a dust gathering recessed part intersecting at an acute angle in at least one position to a recording track on the surface of a magnetic layer. CONSTITUTION:Many lines of a recording track part 16 are provided in concentric circular like with the center O of the rotation of a magnetic disk 2 on the first magnetic layer 14a. Then, a continuous circular groove shape recessed part 31 is formed round the center of a point P shifting slightly from the center O of the rotation of the magnetic disk 2. Thus, this groove shape recessed part 31 is intersected at the acute angle theta in one position or more with the recording track part 16. This intersecting angle theta is 0.1-20 degree, preferably, 0.5-10 degree.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk such as a flexible magnetic disk or a hard magnetic disk, and more particularly to a highly reliable magnetic disk with less trouble due to dust.

[0002]

2. Description of the Related Art A flexible magnetic disk is mainly composed of a magnetic layer formed on a non-magnetic substrate made of a synthetic resin film. In order to improve the durability of the magnetic layer in such a magnetic recording medium, the binder, filler, lubricant and the like in the magnetic layer have been optimized.

[0003]

By the way, due to long-term sliding contact between the magnetic disk and the magnetic head device, minute abrasion powder is generated due to abrasion of the magnetic layer and the cleaning sheet. This abrasion powder adheres to the surface of the magnetic disk, but with the rotation of the magnetic disk, it gradually accumulates on the head surface of the magnetic head device, which causes an error when writing or reading information.

In order to solve such a drawback, various proposals have been made to improve the cleaning sheet attached to the inner surface of the cartridge case, for example, to improve the effect of collecting dusts such as abrasion powder. However, the sufficient effect is not obtained.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a highly reliable magnetic disk with few errors.

[0006]

In order to achieve the above object, the present invention provides a magnetic disk having a non-magnetic substrate such as a flexible base film and a magnetic layer formed on the surface of the substrate. And a dust collecting concave portion eccentric to the recording track is formed on the surface of the magnetic layer, and the dust collecting concave portion intersects with the recording track at an acute angle at at least one position. Is.

[0007]

As described above, according to the present invention, since the dust collecting recess is formed directly on the surface of the magnetic layer and the dust collecting recess intersects the recording track at an acute angle, the magnetic disk is When the magnetic head device rotates and travels relatively on the magnetic layer while slidingly contacting, the dust that is trying to accumulate on the magnetic head device is effectively collected in the concave portion, and the head surface is always kept clean. It is possible to provide a highly reliable magnetic disk.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. 1 is an exploded perspective view of a part of a magnetic disk cartridge according to an embodiment, FIG. 2 is an enlarged sectional view of a magnetic sheet,
3 is a plan view of the magnetic disk, FIG. 4 is an enlarged cross-sectional view of the cleaning sheet, and FIG. 5 is an enlarged cross-sectional view of the vicinity of the magnetic head insertion port showing the usage state of the magnetic disc cartridge.
FIG. 6 is an enlarged sectional view near the elastic piece of this magnetic disk cartridge.

As shown in FIG. 1, a magnetic disk cartridge is composed of a cartridge case 1, a flexible magnetic disk 2 rotatably housed therein, and a shutter slidably supported by the cartridge case 1. It is mainly composed of 3 and 3.

The cartridge case 1 is composed of an upper case 1a and a lower case 1b, which are injection-molded with a hard synthetic resin such as ABS resin. An opening 4 for inserting the rotary drive shaft is formed substantially in the center of the lower case 1b, and a rectangular head insertion opening 5 is formed near the opening 4.
The upper case 1a is also provided with a head insertion opening 5 (see FIG. 5). As shown in FIG. 1, in the vicinity of the front surfaces of the upper case 1a and the lower case 1b, a slightly lower concave portion 6 is formed in order to regulate the sliding range of the shutter 3, and an intermediate position of the concave portion 6 is formed. The head insertion port 5 is provided.

As shown in FIGS. 5 and 6, a cleaning sheet 7 is attached to the inner surfaces of the upper case 1a and the lower case 1b by means such as ultrasonic welding. As shown in FIG. 4, the cleaning sheet 7 includes a disk-side nonwoven fabric layer 7a that contacts the magnetic disk 2, a case-side nonwoven fabric layer 7b that contacts the cartridge case 1, a disk-side nonwoven fabric layer 7a, and a case-side nonwoven fabric layer. 7b, and an intermediate nonwoven fabric layer 7c for connecting with 7b.

The disk-side non-woven fabric layer 7a and the case-side non-woven fabric layer 7b are made of rayon fibers alone, so that the front side and the back side are not distinguished from each other. The intermediate nonwoven fabric layer 7c is composed of a mixed layer of rayon fibers and thermoplastic fibers. As the thermoplastic fiber, for example, polyamide, polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylic fiber or the like is used. In addition, a non-woven fabric made of acrylic fiber or polyester fiber alone, or a blended fiber thereof with rayon fiber or the like can be used as the non-woven fabric layers 7a and 7b.

When the magnetic disk cartridge is in use, as shown in FIG. 5, a head core for magnetically reading and writing, and a first magnetic head device 8a including a slider for stably contacting the head core with the magnetic disk are provided. Similarly to the magnetic head device 8a, a second magnetic head device 8b having a head core and a slider is inserted from each of the head insertion ports 5 and 5, and both magnetic head devices 8a and 8b are inserted.
Thus, the magnetic disk 2 rotates while being sandwiched by the magnetic head devices 8a and 8b, and signals are written and read by the magnetic head devices 8a and 8b. Note that the magnetic head device used in the present invention does not necessarily need the above-mentioned slider, and may be only the one that holds the head core in a predetermined shape.

Further, as shown in FIG. 6, an elastic piece 9 formed by bending a plastic sheet such as polyester is attached to the inner surface of the lower case 1b in an inclined state. On the other hand, a protrusion 10 is formed on the inner surface of the upper case 1a at a position facing the elastic piece 9. Therefore, a part of the lower cleaning sheet 7 is lifted by the elastic piece 9, and the lift thereof is slightly pushed down by the protrusion 10 on the upper case 1a side, so that the magnetic disk 2 is lifted by the upper and lower cleaning sheets 7, 7. It is elastically pinched by. Then, as the magnetic disk 2 rotates, the surface of the disk is cleaned by the cleaning sheets 7, 7.

Next, the structure of the magnetic disk 2 will be described. As shown in FIG. 3, the magnetic disk 2 is composed of a disk-shaped flexible magnetic sheet 11 and a center hub 12 inserted into a central hole of the magnetic sheet 11 and welded.

Further, as shown in FIG. 2, the magnetic sheet 11 is composed of a base film 13 made of a transparent polyester film or the like, and magnetic layers 14a and 14b formed on both sides of the base film 13 by coating. ing.

As the base film 13, for example, a synthetic resin film such as polyethylene terephthalate (PET), polyethylene terephthalate (PEN) or polyimide is used.

The magnetic layer 14 includes a ferromagnetic powder, a binder,
It is composed of a mixture of lubricants and reinforcing powders.

Examples of the ferromagnetic powder include α-Fe,
Barium ferrite, Co-Ni, Co-P, γ-Fe
₂ O ₃ , Fe ₃ O ₄ , Co-containing γ-Fe ₂ O ₃ , Co-containing γ-Fe ₃ O ₄ , CrO ₂ , Co, Fe-Ni and the like are used.

Examples of the binder include vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, urethane resins, polyisocyanate compounds, radiation-curable resins, and fibrin-based materials such as nitrocellulose. Resin or the like is used.

Examples of the lubricant include higher fatty acids such as stearic acid and oleic acid, higher fatty acid esters thereof, liquid paraffin, squalane, fluorine resin,
Fluorine oil can be used. The addition rate of the lubricant is 0.1 to 25% by weight, preferably 1 to 10% by weight, based on the magnetic powder.

As the reinforcing powder, for example, aluminum oxide, chromium oxide, silicon carbide, silicon nitride or the like is used. The reinforcing powder is preferably added in an amount of 0.1 to 25% by weight based on the magnetic powder.

The specific composition of the magnetic paint is as follows. Magnetic coating composition example 1 α-Fe 100 parts by weight (Hc: 1850 Oe, saturation magnetization: 135 emu / g average major axis diameter: 0.25 μm, average axis ratio: 8) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 14 1 part by weight Urethane resin 8.5 parts by weight Trifunctional isocyanate compound 5.6 parts by weight Alumina powder (average particle size 0.43 μm) 20 parts by weight Carbon black 2 parts by weight Oleyl oleate 7 parts by weight Cyclohexanone 150 parts by weight Toluene 150 parts by weight

[0024]                             Magnetic paint composition example 2 Barium ferrite 100 parts by weight (Hc: 530 Oe, saturation magnetization: 57 emu / g,   (Average particle size: 0.04 μm) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 11.0 parts by weight Urethane resin 6.6 parts by weight Trifunctional isocyanate compound 4.4 parts by weight Alumina powder (average particle size 0.43 μm) 15 parts by weight Carbon black 2 parts by weight Oleyl oleate 7 parts by weight Cyclohexanone 150 parts by weight 150 parts by weight of toluene

The composition of the above-mentioned magnetic coating composition example 1 or magnetic coating composition example 2 was well mixed and dispersed in a ball mill to prepare a magnetic coating material, and this was coated on both sides of a base film of 75 μm polyethylene terephthalate (PET). The magnetic layer 14 having a surface roughness Ra (0.08 mm cutoff) of 0.01 μm or less was formed by applying a coating to a dry thickness of 0.7 μm, drying and calendering.

The magnetic disk 2 constructed in this way
A continuous or discontinuous groove portion 15 for tracking servo has a width a = 5 μm on the surface of the second magnetic layer 14b.
Then, a large number are formed concentrically at intervals corresponding to the track width = b (for example, 15 μm) by, for example, embossing (see FIG. 7). This tracking servo recess 1
If an example of the overall pattern of 5 is shown, it is formed concentrically with the center of rotation of the magnetic disk 2 as shown in FIG. 3, and as shown in FIG. 3 and FIG. It becomes the track section 16.

The recess 15 is formed by compression with a stamper as described later. As shown in FIG. 8, the recess 15 having an inverted trapezoidal cross section partially bulges up around the recess 15 and therefore the recording track portion. Protrusions 17 having a substantially mountain-shaped cross section are formed on both sides of 16 in a continuous or discontinuous state. In addition, the height between the protrusions 17 is relatively lower than that between the protrusions 17 (however, the recess 1
A lower portion 18 (shallower than the portion) is formed, and this lower portion 18 just faces a magnetic gear (not shown) of the magnetic head device.

FIG. 8 is a chart showing a state in which the surface of the second magnetic layer 14b is measured by a surface roughness meter. As shown in FIG. 8, the shape and height of the protrusion 17 are not necessarily constant. , The cross-sectional shape is mountain-shaped overall, and the lower part 18
It can be seen that are formed at almost the same level.

As shown in the figure, when a reference line L passing through the bottom surface of each lower portion 18 is drawn, the average depth of the recess 15 from the reference line L is 0.01 to 0.5 μm (in the embodiment, About 0.15 μm), and the average height of the protrusions 17 is 0.01 to
0.1 μm (about 0.05 μm in the example), and lower part 1
The average step from the bottom of 8 to the top of the protrusion 17 is 0.01
.About.0.1 .mu.m (about 0.05 .mu.m in the example) is suitable.

FIG. 9 shows the recess 1 for servo tracking.
FIG. 7 is a diagram for explaining a step of forming No. 5. The magnetic disk 2 to which the center hub 12 is attached is set on the base 19. The base 19 has a central hole 2 in the center hub 12.
0 (see FIG. 3) is provided with a projecting guide pin 21, and the magnetic disk 2 is placed on the base 19 by passing the guide pin 21 through the center hole 20 of the center hub 12. The magnetic disk 2 is positioned on the base 19.

A stamper 22 is arranged above the base 19 so as to be vertically movable in parallel therewith. The stamper 22 is guided to move up and down by the guide pin 21 of the base 19. Further, the stamper 22 is formed with a large number of minute projections 23 concentrically for forming the servo tracking recesses 15.

The stamper 22 is lowered from the state shown in FIG. 9 so that the magnetic sheet 11 of the magnetic disk 2 is attached to the base 19 and the stamper 2.
It is sandwiched between the two and a predetermined pressure. As a result, the protrusions 23 formed on the stamper 22 bite into the surface of the second magnetic layer 14b, and as shown in FIG. 8, compression forms the recess 15 having a substantially trapezoidal cross-sectional shape. A part of the magnetic layer 14b is pushed to form the protrusion 17.

The protrusion 17 formed in this manner has a higher filling rate of the magnetic powder, the reinforcing powder and the binder in the magnetic layer than the lower portion 18, and has a large mechanical strength and is less likely to be worn. Becomes

10 and 11 show the magnetic disk 2
FIG. 3 is a diagram for explaining a tracking servo of FIG. As shown in these figures, the first magnetic layer 1 of the magnetic disk 2 is
The first magnetic head device 8b opposite to 4b is integrally mounted with a light emitting element 29, which emits a beam of tracking servo, such as an LED, and a light receiving element 30 which receives reflected light from the magnetic disk 2. Has been.

As shown in FIG. 10, the portions of the first magnetic head device 8b to which the light emitting element 29 and the light receiving element 30 are attached are open toward the magnetic disk 2 side.

Light from the light emitting element 29 is emitted from the second magnetic layer 1
The light is reflected by the bottom of the concave portion 4b of FIG. 4b and the vicinity of the recording track portion 16, and is received by the light receiving element 30 (actually composed of a plurality of detecting elements).

The detection signal 31 from the light receiving element 30 is input to the servo signal calculating section 32 as shown in FIG. 11, and the magnetic head device 8a for the recording track 16 at the present time is inputted.
The shift amount of (8b), in other words, the position correction amount of the magnetic head device 8a (8b) with respect to the recording track 16 is calculated.

At the present time, for example, when the first magnetic head device 8a is used to write, read, or erase information, the servo signal computing section 32 is used.
The position correction control signal 33 thus obtained is input to the head drive control section 34, and the tracking control of the first magnetic head device 8a is performed based on the control signal 33.

On the other hand, when the second magnetic head device 8b is used to write, read, or erase information, the position correction control obtained by the servo signal calculation section 32 is performed. The signal 33 is input to the head drive control unit 34, and based on the control signal 33, the second magnetic head device 8 that moves integrally with the first magnetic head device 8a.
The tracking control of b is performed. In addition, 35 in the figure
Is a drive motor for rotationally driving the magnetic disk 2.

Next, the surface condition of the first magnetic layer 14a will be described mainly with reference to FIGS. This first
The magnetic layer 14a also has a rotation center O of the magnetic disk 2.
(See FIG. 12) A large number of recording track portions 1 concentrically with
6 is provided. As shown in the figure, a large number of continuous circular groove-shaped concave portions 31 are formed around a point P slightly deviated from the rotation center O of the magnetic disk 2. Therefore, the groove-shaped concave portion 31 intersects the recording track portion 16 at one or more positions at an acute angle θ (see FIG. 13). Although only one recording track portion 16 and one concave portion 31 are shown in FIG. 12, a great number of recording track portions 16 and concave portions 31 are actually formed.

The range of the intersection angle θ is 0.1 to 20 degrees, preferably 0.5 to 10 degrees.

As shown in FIG. 9, the recess 31 is formed in the base 1.
A protrusion 32 corresponding to the shape of the recess 31 is provided in advance on the surface of the recess 9, and the recess 31 is formed at the same time when the tracking servo groove 15 is formed by pressing the stamper 22 as described above. be able to.

By thus forming the recess 31 by compression, as in the case of the tracking servo groove-like recess 15, as shown in FIG. 14, the cross-sectional shape becomes an inverted trapezoid and corresponds to the recess 31. Is pushed to the outer periphery of the concave portion 31 and rises to form a protrusion 33 having a mountain-shaped cross section. The density of the protruding portion 33 increases and the mechanical strength increases.

As described above, the concave portion 31 is formed on the recording track 16.
Therefore, the height of the protrusion 33 and the length of the recess 31 in the track width direction directly affect the dropout characteristics.

First, the relationship between the height of the protrusion 33 and the dropout characteristic will be described. When the chevron-shaped protrusions 33 are formed in this manner, the magnetic head device mainly has the protrusions 33.
Contact with. Therefore, the contact area with the magnetic head device is reduced and the contact resistance is reduced, which has the advantage of improving the wear resistance of the magnetic layer. However, if the height of the protruding portion 33 is too high, the distance between the flat portion 34 and the magnetic head device, that is, the spacing loss becomes large, and dropout occurs.

The inventors of the present invention investigated the dropout occurrence state and the average starting torque of the magnetic disk by changing the average height of the protrusion 33 variously, and summarized the results in Table 1 below. In this dropout test, a 2 MB magnetic disk was used, analog recording was performed at a linear recording density of 17 kfci, and an average reproduction output of 60% or less was determined to be a dropout.

In the table, a circle mark indicates that dropout did not occur, and a cross mark indicates that dropout occurred.

[0048]                                   Table 1     Average height of protrusions With or without dropout Average starting torque         (Μm) (g-cm)         0.00 ○ 500         0.01 ○ 280         0.02 ○ 100         0.05 ○ 80         0.10 ○ 80         0.15 x 80

As is apparent from this table, when the average height of the protrusions 33 from the flat surface 34 of the magnetic layer is 0.15 μm or more, dropout is recognized, which is not preferable in terms of characteristics. On the other hand, the average height of the protrusions 33 is 0.01 μm.
If it is less than this, then the adhesion with the magnetic head device is improved, and therefore the average starting torque becomes large. Therefore, in order to prevent dropout from occurring and to keep the average starting torque low, the average height of the protrusions 33 from the flat surface 34 of the magnetic layer is in the range of 0.01 to 0.10 μm, preferably 0. The range is preferably 0.02 to 0.10 μm, and more preferably 0.05 to 0.10 μm.

The average height of the protrusion 33 can be controlled by appropriately adjusting the height of the protrusion 32 for forming the recess 31, the pressure for forming the recess 31, the composition of the magnetic layer 14, and the like. .

Next, the relationship between the total length of the recess 31 in the track width direction and the dropout characteristic will be described. If too many recesses 31 are formed on the recording track portion 16 as described above, the total spacing loss becomes large, which also causes dropout.

In the continuous groove-shaped recess 31 as shown in FIG. 13, the present inventors have variously changed the length c of the recess 31 in the track width direction so that the total length in the track width direction with respect to the track width b ( Tc = c1 + c2 where c1 =
The relationship between the ratio of c2) [(Tc / b) × 100 (%)] and the dropout characteristics was measured, and the results are summarized in Table 2 below. The dropout test was conducted under the same conditions as in Table 1 above.

[0053]                                   Table 2         [(Tc / b) x 100] (%) Presence or absence of dropout                           0 ○                         10 ○                         20 ○                         40 ○                         45 x                         50 x

As is clear from Table 2, when the ratio of the total length (Tc) of the concave portion 31 in the track width direction to the track width b is 45% or more, the spacing loss becomes large and dropout occurs. Therefore, the ratio of the total length (Tc) of the recess 31 in the track width direction to the track width b needs to be restricted to 40% or less.

FIG. 15 is a diagram showing a modification of the recess 31. In the case of this example, the concave portions 31 are not continuous and are individually independent in an appropriate shape such as an elliptical shape (illustrated example), a circle, a triangle, a quadrangle, a polygon, etc. As shown in FIG. 12, the body is eccentric to the rotation center O of the magnetic disk 2 to form a substantially circular shape, and intersects the recording track 16 at an acute angle θ. Even in such a pattern of the concave portions 31, the average height of the protrusions 33 formed by the concave portions 31 is restricted to the range of 0.01 to 0.10 μm, and the track width of the concave portions 31 with respect to the track width b. The ratio of the total length (Tc) in the direction is regulated to 40% or less.

The length (c1, c2) of the recess 31 in the track width direction is 1 to 20 μm, preferably 1 to 5 μm.
Is. If the length of the recess 31 in the track width direction is less than 1 μm, the dust collecting effect is lost, and if it exceeds 20 μm, the output of the recording track portion is reduced.

The depth of the recess 31 is 0.01 to 0.5.
μm, preferably 0.02 to 0.5 μm. Recess 3
If the depth of 1 is less than 0.01 μm, the dust collecting effect is lost, and if it exceeds 0.5 μm, the magnetic disk is deformed when forming the recess 31 and contact with the magnetic head device is insufficient. It is easy to become.

The pitch of the recess 31 is 10 to 300 μm,
It is preferably 50 to 200 μm. When the pitch of the recesses 31 becomes less than 10 μm and the recesses 31 approach each other,
The bulge around the recess 31 becomes large, and the head contact deteriorates. On the other hand, the pitch of the recess 31 is 300 μm.
When it exceeds, the effect of collecting dusts by the recess 31 is reduced.

The amount of eccentricity of the center P of the recess 31 with respect to the rotation center 0 of the magnetic disk 2, that is, the distance between the rotation center O and the center P in FIG. 12 is 5 μm to 1 mm, preferably 5 μm.
It is 0 to 500 μm. If the amount of eccentricity is less than 5 μm, the dust collection effect is small. On the other hand, when the amount of eccentricity exceeds 500 μm, the angle of intersection θ with the recording track becomes large, which reduces the output of the recording track.

In the above embodiment, a continuous groove-shaped recess 15 for tracking servo is formed on one side of the magnetic disk 2, and a dust collecting recess 3 is formed on the other side of the magnetic disk 2.
However, the present invention is not limited to this, and the recesses 31 may be formed on both sides of the magnetic disk 2 if the tracking servo of the magnetic disk 2 is performed by another means.

Next, specific examples and comparative examples of the present invention will be described. (Specific Example 1) The track density is 135 tpi (188 μ)
m), a concentric concavity 31 was formed by a stamper on a 3.5-inch magnetic disk having a track width of 115 μm and a surface roughness Ra of 0.008 μm used at a rotation speed of 300 rpm. The length of the recess 31 in the track width direction is 3 μm, the depth is 0.05 μm, and the pitch is 100 μm.
The eccentric amount of the center P of the concave portion 31 with respect to the rotation center O of the magnetic disk 2 is 100 μm.

(Specific Example 2) Rotation center O of the magnetic disk 2
The specific example 1 is the same as the specific example 1 except that the eccentric amount of the center P of the concave portion 31 is set to 5 μm.

(Specific Example 3) Track density is 1000 tp
i (25 μm), track width 20 μm, rotation speed 900
Concentric concavities 31 formed by a stamper were formed on a 3.5-inch magnetic disk having a surface roughness Ra of 0.005 μm used at rpm. The length of the recess 31 in the track width direction is 1 μm, the depth is 0.02 μm, the pitch is 25 μm, and the eccentric amount of the center P of the recess 31 with respect to the rotation center O of the magnetic disk 2 is 200 μm.

(Specific Example 4) Center of rotation O of the magnetic disk 2
The specific example 3 is the same as the specific example 3 except that the eccentric amount of the center P of the concave portion 31 with respect to 5 μm.

Comparative Example 1 The same as Example 1 except that the recess 31 is not formed in the magnetic disk 2.

Comparative Example 2 The same as Example 2 except that the recess 31 is not formed in the magnetic disk 2. FIG.
Is a diagram showing another embodiment, and in the case of this embodiment, the concave or convex portion 31 which is continuous or discontinuous with respect to the circular recording track portion 16.
Has an oval or other deformed circle.

[0067]

The signals of 500 kHz are recorded on the magnetic disks of Examples 1 and 2 and Comparative Example 1, and the magnetic head device is sequentially moved from the outer track to the inner track and from the inner track to the outer track. The signal was read. 100 magnetic disks were used, 10 hours of head seek were repeated, and the reliability was evaluated by the number of error disks generated during that time. Further, signals of 1.5 MHz were recorded on the magnetic disks of the above-mentioned specific examples 3 and 4 and comparative example 2, and the reliability was evaluated in the same manner.

Each magnetic disk was run for 10 hours,
With the magnetic head device in contact with the magnetic disk 3
The starting torque was measured when the system was left standing for 0 minutes and then restarted. The results of these tests are summarized in Table 3 below.

[0069]                                   Table 3                 Number of error disks (sheets) Average starting torque (g-cm)     Specific example 1 0 43     Specific example 2 144     Comparative Example 1 5 83     Specific Example 3 0 67     Specific Example 4 2 65     Comparative Example 1 13 98

As is clear from this table, in the present invention (specific examples 1 to 4), since the dust is effectively collected by the concave portion formed on the surface of the magnetic layer, the number of error disks is reduced. A small number of highly reliable magnetic disks can be provided.

[Brief description of drawings]

FIG. 1 is a partially exploded perspective view of a magnetic disk cartridge according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a magnetic disk used in the magnetic disk cartridge.

FIG. 3 is a plan view of a magnetic disk used in the magnetic disk cartridge.

FIG. 4 is an enlarged cross-sectional view of a cleaning sheet used for the magnetic disc cartridge.

FIG. 5 is an enlarged cross-sectional view of the vicinity of a magnetic head insertion port showing a usage state of the magnetic disc cartridge.

FIG. 6 is an enlarged cross-sectional view in the vicinity of an elastic piece of the magnetic disc cartridge.

FIG. 7 is a partially enlarged sectional view of a magnetic disk used in the magnetic disk cartridge.

FIG. 8 is a chart showing a surface state of a second magnetic layer of the magnetic disk.

FIG. 9 is a diagram for explaining the recess forming process of the magnetic disk.

FIG. 10 is a diagram for explaining tracking of a magnetic head.

FIG. 11 is a diagram for explaining tracking of a magnetic head.

FIG. 12 is a plan view of the magnetic disk on the first magnetic layer side.

FIG. 13 is an enlarged plan view of the first magnetic layer.

FIG. 14 is a chart showing the surface state of the first magnetic layer.

FIG. 15 is an enlarged plan view showing a modified example of the first magnetic layer.

FIG. 16 is a plan view of a first magnetic layer of a magnetic disk according to another example.

[Explanation of symbols]

1 Cartridge case 2 magnetic disk 8a First magnetic head device 8b Second magnetic head device 11 Magnetic sheet 13 base film 14a First magnetic layer 14b Second magnetic layer 15 Tracking servo recess 16 Recording Track 31 recess 33 Projection 34 Flat surface O Magnetic disk rotation center P Center of recess

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Tottori             Hitachima, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd. (72) Inventor Toshio Doi             Hitachima, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd.

Claims (8)

[Claims] 1. A magnetic disk having a base made of a non-magnetic material and a magnetic layer formed on the surface of the base, wherein at least one recording track is formed on the surface of the magnetic layer.
A magnetic disk characterized in that a dust collecting concave portion intersecting at an acute angle is formed at a point. 2. The magnetic disk according to claim 1, wherein the dust collecting recess is formed in a circular shape eccentric to the recording track. 3. The magnetic disk according to claim 2, wherein the dust collecting recess is continuously formed in a circular shape. 4. The magnetic disk according to claim 2, wherein the dust collecting recess is discontinuous and formed in a substantially circular shape. 5. The magnetic disk according to claim 1, wherein the dust collecting recess has a substantially trapezoidal cross section. 6. The total length in the recording track width direction of the dust collecting recesses intersecting on the recording track is regulated to 40% or less of the recording track width. A magnetic disk characterized by. 7. The magnetic disk according to claim 1, wherein a magnetic layer is formed on both surfaces of the substrate, and the dust collecting recesses are formed on both of the magnetic layers. 8. The magnetic layer according to claim 1, wherein magnetic layers are formed on both surfaces of the substrate, the dust collecting recess is formed in one of the magnetic layers, and the other magnetic layer is adjacent to the recording track. A magnetic disk characterized in that a recess for a tracking servo is formed.