JPH0757412A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain sufficient reproduced outputs in spite of an increase in capacity by specifying the recording wavelength of the magnetic disk, the thickness of a magnetic layer and the ratio of the height of the build-ups at the peripheral edges of the respective recesses within recess groups which irregularly reflect incident light and the recording wavelength to specific values or below. CONSTITUTION:The magnetic disk 1 is provided with the many recess groups 3 on the surface of the magnetic layer 2 and regularly reflects light when the light is made incident on the surface of the layer 2. The disk irregularly reflects the light and optical tracking servo is performed when the light is made incident on the recess groups 3. The recording wavelength of the disk 1 is specified to <=2mum and the thickness of the magnetic layer 2 to <0.5mum. In addition, the ratio of the height H of the build-ups 4a at the peripheral edges of the respective recesses 4 within recess groups 3 and the recording wavelength is confined to <=0.025. As a result, the degradation in the reproduced output occurring in the build-ups 4a is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk,
More specifically, the present invention relates to a magnetic disk having a high track density and a high storage capacity, which enables good optical tracking servo.

[0002]

2. Description of the Related Art In recent years, in a magnetic disk manufactured by forming a magnetic layer containing magnetic powder on a substrate such as a polyester film and then punching it into a disc shape, information signals are recorded on the surface of the magnetic layer. A large number of concavities that diffusely reflect incident light are provided at predetermined intervals along the track so that an optical tracking servo can be performed to improve the track density.
The capacity has been increased to achieve 1MB.

However, the format capacity is 21 MB.
However, the capacity has not yet been sufficiently increased, and higher recording density is required. For example, a format capacity of 40M is required.
In order to achieve B, it has been attempted to shorten the recording wavelength and reduce the thickness of the magnetic layer.

[0004]

However, in order to achieve the format capacity of 40 MB, when the recording wavelength is set to 2 μm or less and the thickness of the magnetic layer is set to 0.5 μm or less, the stamper is used on the surface of the magnetic layer. When forming a group of recesses by a stamping device, which is a high-pressure press device, large ridges are formed on the periphery of each recess of the group of recesses, and the ridges form a space.
There is a drawback that a single reproduction output cannot be obtained because a single loss increases.

[0005]

The present invention has been made as a result of various studies for overcoming the above problems, and diffuses incident light along a track where an information signal is recorded on the surface of a magnetic layer. In a magnetic disk in which a large number of recesses are provided at a predetermined interval, the recording wavelength is 2 μm or less, the thickness of the magnetic layer is 0.5 μm or less, and the height H of the ridge at the periphery of each recess and the recording wavelength λ are set. By setting the ratio H / λ to 0.025 or less, the ridges at the periphery of each recess in the group of recesses are made small, and the reduction in reproduction output due to the ridges is suppressed, and a magnetic disk having a large capacity is obtained. , So that the necessary reproduction output can be sufficiently obtained.

An example of the magnetic disk of the present invention will be described below with reference to the drawings. In FIGS. 1 to 3, reference numeral 1 denotes a magnetic disk, and a large number of recess groups 3 are provided on the surface of a magnetic layer 2 at predetermined intervals along a track on which an information signal is recorded. The surface of the magnetic layer 2 is mirror-finished so that light is regularly reflected when light is incident, and irregularly reflected when light is incident on a group of recesses 3 composed of innumerable recesses 4. Tracking tracking is performed.

Here, in order to increase the capacity of the magnetic disk 1, it is preferable that the recording wavelength is 2 μm or less. In order to secure sufficient overwriting characteristics at the recording wavelength 2 μm or less, the magnetic layer 2 is formed. The thickness is preferably 0.5 μm or less. For example, in order to achieve a format capacity of 40 MB, it is necessary to shorten the recording wavelength to about 1.8 μm. In order to secure sufficient overwriting characteristics at the recording wavelength of 1.8 μm, the magnetic layer is required. The thickness of 2 should be 0.4 μm.

However, if the thickness of the magnetic layer 2 is 0.5 μm or less, when the recess group 3 is formed on the surface of the magnetic layer by a stamping device, the thickness of the magnetic layer 2 is thin and the holes in the magnetic layer 2 are small. Is less. Therefore, the deformation of the magnetic layer 2 cannot be absorbed by the holes in the magnetic layer 2, and as shown by the dotted line in FIG. 3, large ridges 4b are formed at the periphery of each recess 4, and the recording wavelength is further increased. Is less than 2 μm, the spacing loss becomes large and the reproduction output is significantly deteriorated.

For this reason, after forming the recess groups 3 by a stamping device, the recess groups 3 are brought into contact with a flat plate on the recess groups 3 at a predetermined temperature and a predetermined load for a predetermined time. Recesses 4 formed on the periphery of each recess 4 of the recess group 3
It is preferable to reduce the height H of a so that the relationship with the recording wavelength λ is 0.025 or less in the ratio of H / λ, and the height of the ridges 4a at the periphery of each recess 4 satisfies the relationship. In this case, the reduction in reproduction output due to the protrusion 4a is sufficiently suppressed, and the required reproduction output can be obtained in the magnetic disk having a large track density and a large capacity.

On the other hand, when H / λ is larger than 0.025, the height of the ridge 4a at the periphery of each recess 4 is still high, and the spacing loss becomes large at a recording wavelength of 2 μm or less, so that the necessary reproduction output is obtained. Was not obtained, and the recording wavelength was 2.8.
In a conventional magnetic disk having a magnetic layer thickness of more than 0.7 μm and a thickness of about 0.7 μm, when each recess is formed on the surface of the magnetic layer by a stamping device, the deformation of the magnetic layer due to the formation of the recess causes Since it is absorbed by the holes, a large ridge is not formed on the peripheral edge of the recess, and since the recording wavelength is long, the deterioration of reproduction output does not pose a problem.

The stamping device is used to set the ratio H / λ of the height H of the ridge 4a at the periphery of each recess 4 of the recess group 3 formed on the surface of the magnetic layer 2 to the recording wavelength λ to 0.025 or less. After forming each recess 4 by, the temperature and load when contacting a flat plate on these recesses 4, 90 ~ 100 ℃,
It is preferably in the range of 50 to 60 t and contacted for 3 to 5 seconds.

The magnetic disk 1 of the present invention as described above is
A magnetic coating consisting of magnetic powder, binder resin, organic solvent and other necessary components is coated on a substrate such as polyester film and dried to form a magnetic layer with a thickness of 0.5 μm or less. Then, using a stamping device on the surface of the magnetic layer, a large number of recesses are provided at predetermined intervals along the track on which the information signal is recorded, and then flat plates are further placed on these recesses. The height H of the ridges at the periphery of each recess of the group of recesses and the ratio of the recording wavelength λ H /
It is manufactured by adjusting λ to 0.025 or less.

The magnetic powder used in the magnetic layer is γ
-Fe2 O3 powder, Fe3 O4 powder, Co-containing γ-Fe
2 O3 powder, Co-containing Fe3 O4 powder, CrO2 powder,
Fe powder, Fe-based powder containing elements such as Al, Cr, Mn, Si, and Zn in Fe, Co powder, F
Magnetic powders generally used in magnetic recording media, such as e-Ni powder and barium ferrite powder, are widely included.

As the binder resin, vinyl chloride-
Generally used as a binder resin for magnetic recording media, such as vinyl acetate-based copolymers, fibrin-based resins, polyvinyl butyral-based resins, polyurethane-based resins, polyester-based resins, isocyanate compounds, and radiation-curable resins. Things are widely used.

As the organic solvent, commonly used organic solvents such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, ethyl acetate and toluene may be used alone or in admixture of two or more.

In the magnetic paint, various additives usually used, such as dispersants, abrasives, lubricants,
An antistatic agent or the like may be optionally added and used.

[0017]

EXAMPLES Next, examples of the present invention will be described. Examples 1 to 3, Comparative Examples 1 to 4 Barium ferrite magnetic powder (coercive force 730 oersted) 100 parts by weight VAGH (manufactured by UCC; vinyl chloride-vinyl acetate-vinyl 15 〃 alcohol copolymer) UR8310 (Nippon Polyurethane) Kogyo Co., Ltd .; urethane resin) 10 〃 Coronet L (Nippon Polyurethane Industry Co., Ltd .; trifunctional low content 10 〃 quantity isocyanate compound) HS-500 (Asahi Carbon Co., Ltd .; Carbon Black) 10 〃 Bengala 5 〃 α-alumina 5 〃 Myristic acid 5 〃 Zinc stearate 2 〃 Stearic acid-n-butyl 5 〃 Cyclohexanone 117 〃 Toluene 117 〃 This composition was mixed and dispersed to prepare a magnetic paint. Is coated on both sides of a number of 62 μm thick polyester films with various thicknesses, dried, and then calendered. A treatment was performed to form a magnetic layer.

Then, after punching these into a disk shape,
A large number of recesses are provided on the magnetic layer along a track on which information signals are recorded using a stamping device at predetermined intervals, and a flat plate is placed in each of these recesses at the temperature and load shown in Table 1 below. The magnetic disks of Examples 1 to 3 and Comparative Examples 1 to 4 were made by contacting for 5 seconds. In Table 1 below, Comparative Examples 1, 2, and 3 are those in which the flat plate contact treatment was omitted and recesses were formed on the surface of the magnetic layer.

[0019]

[Table 1]

With respect to the magnetic disks obtained in the respective examples and comparative examples, the height of the ridges at the periphery of the recesses in the recess group was determined by scanning atomic force microscope AFM (manufactured by Toyo Technica).
Then, the ratio H / λ of the height H of the ridge and the recording wavelength λ was determined. The recording wavelength λ was determined for each of 2,8 μm and 1,8 μm. In addition, the outputs at the recording wavelengths of 2,8 μm and 1,8 μm of the magnetic disks obtained in the respective examples and comparative examples were measured, and the output in which the margin was excellent with respect to the error rate was obtained. ), When the output is sufficient margin (○), when the margin is not sufficient margin (△), when the margin is not obtained at all (×) Evaluated as. Table 2 below shows the results.

[0021]

[Table 2]

[0022]

As is clear from Table 2 above, the magnetic disks (Examples 1 to 3) obtained according to the present invention have a better peripheral edge than the magnetic disks obtained in Comparative Examples 1 to 4. Low ridge height and recording wavelength of 2.8μm and 1.8μ
Good output was obtained at any of the values of m, and from this fact, the magnetic disk obtained by the present invention can perform optical tracking servo satisfactorily, and the track density can be increased to achieve storage. It can be seen that the capacity can be remarkably improved and the output characteristics are excellent.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a magnetic disk of the present invention.

FIG. 2 is a partially enlarged sectional perspective view of the magnetic disk shown in FIG.

3 is a partially enlarged cross-sectional explanatory view of a group of recesses shown in FIG.

[Explanation of symbols]

 1 Magnetic Disk 2 Magnetic Layer 3 Recess Group 4 Recess 4a Ridge

Claims (1)

[Claims] 1. A magnetic layer containing magnetic powder is provided on a substrate,
In a magnetic disk in which a large number of recesses that diffusely reflect incident light are provided at predetermined intervals along the track on which information signals are recorded on the surface of the magnetic layer, the recording wavelength λ is 2 μm or less, and the thickness of the magnetic layer is 0.5 μm. A magnetic disk, characterized in that the ratio H / λ of the height H of the ridges at the periphery of each recess in the group of recesses to the recording wavelength λ is 0.025 or less at μm or less.