JPH05198032A - Magneto-optical recording method - Google Patents

Abstract

PURPOSE:To improve C/N and stability and to decrease jitters in magneto- optical recording of a magnetic field modulation system using a non-floating type magnetic head. CONSTITUTION:The magneto-optical recording is executed by the magnetic field modulation system by setting the distance between the recording layer 5 of a magneto-optical recording disk 1 and the main magnetic pole 11 of the magnetic head 10, designated as h, and the perpendicular projection area of the main magnetic pole 11 on the main plane of the disk 1 as Ps, to 0.04mm<=h<=0.3mm, Ps<=0.16pimm<2>, 0.4pi<=Ps/h<2=8pi.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of recording on a magneto-optical recording disk using a magnetic field modulation method.

[0002]

2. Description of the Related Art Optical discs have attracted attention as large-capacity information carrying media. Among them, there are magnetic field modulation type magneto-optical recording disks, which are expected to be applied to data files and the like. In the magnetic field modulation method, a laser beam is applied from the optical head to the recording layer of the disk in a DC manner to raise its temperature, and at the same time, a modulated magnetic field is applied from a magnetic head arranged on the side opposite to the optical head. Applied to the recording layer,
Make a record. Therefore, this method enables overwriting recording and is also considered to be applied to a rewritable compact disc or the like.

The magnetic head used in the magnetic field modulation method is, like the magnetic head of a hard disk drive, a floating magnetic head which floats on the disk surface as the disk rotates, and a magnetic head from the disk surface regardless of disk rotation. There is a non-flying type magnetic head arranged at a fixed distance. This non-floating type magnetic head has a fixed type that fixes the head at a fixed distance from the disk surface, and a head that is housed in a slider and is placed on the back side at a fixed distance from the disk sliding surface of the slider. There is a sliding type that slides a slider so that it is located at a certain distance from the surface. With a non-floating magnetic head, a stronger magnetic field can be applied as the distance between the disk and the magnetic head is shorter, but with a fixed magnetic head the distance between the disk and the magnetic head is reduced due to surface wobbling due to warp or distortion of the disk. Since there is a risk of fluctuation and collision, a displacement sensor may be provided to keep the distance constant. On the other hand, in the sliding type, it is easy to keep the disk head distance constant.

Since the non-floating type magnetic head is not affected by the number of revolutions of the disc, it is suitable for a disc used at a low speed such as a compact disc (CD). Also, there are few troubles due to protrusions and adhered matters on the disk surface. In addition, the structure without the displacement sensor has a simple structure and can be manufactured at low cost.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a magnetic field modulation type magneto-optical recording using a non-flying magnetic head.
It is intended to realize C / N and its stability, and to reduce jitter.

[0006]

The above objects are achieved by the present invention described in (1) and (2) below.

(1) A magnetic head having a main magnetic pole and an auxiliary magnetic pole and applying a magnetic field from the main magnetic pole to the magneto-optical recording disk is arranged on one main surface of the magneto-optical recording disk, Assuming that the distance between the recording layer of the magnetic recording disk and the main magnetic pole is h and the perpendicular projection area of the main magnetic pole with respect to the main surface of the magneto-optical recording disk is Ps, 0.04 mm ≦ h ≦ 0.3 mm, Ps ≦ A magneto-optical recording method characterized by performing magneto-optical recording by a magnetic field modulation method, with 0.16π mm ² and 0.4π ≦ Ps / h ² ≦ 8π. (2) The magneto-optical recording method according to (1), wherein the core shape of the magnetic head is a pot type, an E type or a U type.

[0008]

According to the present invention, the size of the main magnetic pole of the magnetic head, the distance between the magnetic head and the disk surface, and the relationship therebetween are maintained as described above, and magneto-optical recording is performed by the magnetic field modulation method.
Thereby, good C / N can be stably obtained, and jitter can be reduced.

[0009]

[Specific Structure] The specific structure of the present invention will be described in detail below.

The present invention is applied to magnetic field modulation type magneto-optical recording. In this method, a magnetic head is usually arranged on the front surface (recording layer side) of a magneto-optical recording disk, and an optical head is arranged on the rear surface of the disk, and laser light of a constant intensity is emitted from the optical head through the substrate to the recording layer. Then, the modulated magnetic field is applied from the magnetic head to the laser spot portion of the recording layer to perform recording. The magnetic head and the optical head have a fixed positional relationship, and they move integrally in the radial direction of the disk to access a predetermined track.

The magnetic head used in the magneto-optical recording method of the present invention has a main magnetic pole and an auxiliary magnetic pole, and applies a magnetic field in a substantially vertical direction from the main magnetic pole to the recording layer of the magneto-optical recording disk. The return magnetic flux from the recording layer returns to the auxiliary magnetic pole. The shape of the core of such a magnetic head is not particularly limited, but a so-called pot type core or anti-type core is preferable. The pot-shaped core and the E-shaped core can efficiently generate a high-frequency magnetic field with a small recording current.

The pot core preferably has the structure shown in FIG. 1 (a). The pot-shaped core 10 shown in FIG. 1A has a cylindrical auxiliary magnetic pole core 12, a cylindrical main magnetic pole core 11, and a disk-shaped back core 13 that magnetically couples these cores. However, the main magnetic pole core 11 extends on the axis of the back core 13. The peripheral side surface of the auxiliary magnetic pole core 12 is provided with a cutout portion for taking out the winding wound around the main magnetic pole core 11. When the magnetic head operates, the temperature of the core rises.However, if the cutout is provided, the hot air inside the core for the auxiliary magnetic pole is discharged from the cutout by the air flow on the surface of the disk. It is possible to suppress the deterioration of the magnetic characteristics due to the rise. Further, in order to reduce the size of the core, it is preferable that the thickness of the auxiliary magnetic pole core is about 1.5 mm or less.

Further, in the present invention, it is preferable to use the E-shaped core shown in FIG. 1 (b) because the electromagnetic conversion characteristics are good, the heat dissipation is good, and the manufacturing is very easy. In the E-shaped core 10 shown in FIG. 1B, a pair of auxiliary magnetic pole cores 12, 1 sandwiching the main magnetic pole core 11 is provided.
2 are provided symmetrically, and these are magnetically coupled by the back core 13. The main magnetic pole core and the auxiliary magnetic pole core have a prismatic shape in the illustrated example, but may have another shape such as a cylindrical shape.

In addition, a core (U-shaped core) having a shape obtained by removing one of the auxiliary magnetic pole cores of the E-shaped core has the same advantages as the E-shaped core and is preferably used in the present invention.

In each of these cores, the upper end surface area (auxiliary magnetic pole area) of the auxiliary magnetic pole core is usually larger than the upper end surface area (main magnetic pole area) of the main magnetic pole core, but sufficient strength is secured. It is preferable to determine the dimensions so that the magnetic flux leakage in the lateral direction can be sufficiently suppressed. The winding is usually wound around the main magnetic pole 11.

Further, in these cores, the upper end surfaces of the main magnetic pole core and the auxiliary magnetic pole core do not need to be flat,
It may be a curved surface if necessary. Further, the main magnetic pole core and the auxiliary magnetic pole core do not have to have a constant cross-sectional area from the back core to the upper end portion, and the cross-sectional area may be gradually reduced from any position between the back core and the upper end portion. Good.
Further, in such a structure in which the cross-sectional area is reduced, the vicinity of the upper end of the main pole core is made of a metal or the like having a higher magnetic permeability and a higher saturation magnetic flux density than the core material. MIG (metal
Similar to the (in-gap) type magnetic head, the strength of the magnetic field applied to the disk can be improved.

These cores are made of various soft magnetic materials such as ferrite and metal, but they are usually made of Mn-Zn ferrite or Ni-Zn ferrite because they have high electric resistivity and good high frequency characteristics. It is preferable to configure. In an ultra-small vase-shaped core used for a magnetic head for magneto-optical recording, a ferrite sintered body is usually processed into a predetermined shape by grinding using ultrasonic waves, resulting in poor mass productivity and low cost. However, the E-shaped core is excellent in mass productivity because it can be manufactured by producing a molded body having a desired core shape and sintering it, or by simply performing a simple grinding process on the sintered body.

In the present invention, in magneto-optical recording of the magnetic field modulation system, as shown in FIG. 3, the distance between the recording layer 5 of the magneto-optical recording disk 1 and the main magnetic pole 11 of the magnetic head is set to h, and magneto-optical recording is performed. When the perpendicular projection area of the main pole 11 with respect to the main surface of the disk 1 is Ps, 0.04 mm ≦ h ≦ 0.3 mm, Ps ≦ 0.16π mm ² , 0.4π ≦ Ps / h ² ≦ 8π, preferably 0. Recording is performed with 4π ≦ Ps / h ² ≦ 6.3π. The recording layer 5 of the illustrated magneto-optical recording disk 1 is formed on the substrate 2, and the protective coat 8 is formed on the recording layer 5.

In this case, the vertical projected area Ps of the main pole 11 with respect to the main surface of the magneto-optical recording disk 1 is a virtual cylinder or conical surface circumscribing the side surface of the winding portion of the main pole core.
It means the cross-sectional area of the cylinder or the cone when the cylinder or the cone is cut along a plane parallel to the disk main surface and including the tip of the main pole core. Therefore, in the E-shaped core of FIG. 1B, the circular area whose diameter is the diagonal of the square pole-shaped main pole 11 is Ps.

By setting Ps to be 0.16 π mm ² or less, the inductance can be reduced, so that the high frequency characteristics become good and high density recording becomes possible. If h is 0.3 mm or less, the C / N change rate according to the change in the distance between the main pole and the disk surface can be suppressed to a small value. If h exceeds 0.3 mm, the magnetic field strength in the recording spot becomes insufficient, while if h is less than 0.04 mm, there is a limit in securing the surface accuracy of the disk surface.
In the sliding type, there is a risk that dust may enter between the main magnetic pole core and the disk when the disk rotates to cause a head crash. Further, in the fixed type, the core for the main magnetic pole may collide with the disk, so that h is more preferably 0.1.
Set to mm or more.

It should be noted that when the magneto-optical recording disk is rotated, disturbances such as surface wobbling and adhesion of dust occur due to warp of the disk and the distance between the main magnetic pole and the disk changes. The distance h is a value that includes a change in distance due to a disturbance such as surface wobbling. Surface runout is usually ± 0.1
It is about mm or less.

When Ps / h ² exceeds the above range, the uniformity of the magnetic field strength in the recording spot on the disk surface is significantly reduced. That is, the magnetic field strength at the edge portion of the recording spot becomes stronger than that at the central portion of the recording spot,
The utilization efficiency of the magnetic field becomes low. In this specification, the recording spot means the inside of a vertically projected image of the main pole on the disk surface.

On the other hand, if Ps / h ² is less than the above range, that is, if Ps becomes too small with respect to the distance h, the attenuation rate of the magnetic field strength increases from the central portion to the edge portion of the recording spot, and the magnetic field of the recording spot increases. The strength becomes insufficient. Further, the rate of change of the magnetic field strength on the disk surface becomes large with respect to the change of the distance h due to the disturbance.

On the other hand, when Ps / h ² is within the above range, the uniformity of the magnetic field in the recording spot is good, so that the tolerance for the deviation between the central position of the recording spot and the central position of the laser spot is high. And the manufacturing and maintenance management of the recording apparatus becomes easy. In addition, since the rate of change of the magnetic field strength on the disk surface corresponding to the change in the distance between the magnetic head and the disk surface can be suppressed to a small value, the main magnetic pole due to disturbances such as surface wobbling of the disk and adhesion of dust to the disk surface The tolerance for the change in the distance from the disc can be increased. If the uniformity of the magnetic field strength in the recording spot is good, a good C / N can be obtained stably, and the rising and falling of the reproduced signal will be good, so lower the jitter. You can

In the present invention, the magnetic field strength at the recording spot is not particularly limited, but normally it is preferably about 100 to 400 Oe. Such a magnetic head 10
Is fixed in a predetermined position by applying a predetermined winding and fixed in a predetermined position, or the main pole surface is located on the back side by a predetermined distance from the sliding surface and then stored in the slider. The slider disk surface may be slid.

The structure of the magneto-optical recording disk used in the present invention is not particularly limited, but a single-sided recording type magneto-optical recording disk is used because the distance between the main magnetic pole of the magnetic head and the disk surface must be extremely short. An example of a single-sided recording type magneto-optical recording disk is shown in FIG.

The magneto-optical recording disk 1 shown in FIG.
A protective layer 4, a recording layer 5, a protective layer 6, a reflective layer 7 and a protective coat 8 are sequentially formed on the surface of the substrate 2. Further, a hard coat 3 is provided on the back surface of the disk, that is, the back surface side of the substrate 2, as required. The hard coat may be formed not only on the main surface of the disk but also on the outer peripheral side surface and the inner peripheral side surface.

The material of the substrate 2 is not particularly limited as long as it is transparent, and glass and various transparent resins are used. As the transparent resin, polycarbonate resin, acrylic resin,
Amorphous polyolefin resins, styrene resins, etc. may be mentioned. Grooves, pits, etc. are formed on the recording layer 5 side of the substrate 2 as needed for tracking and the like.

The transparent hard coat 3 formed on the back side of the substrate 2 may be made of a radiation curable resin similar to the resin constituting the protective coat 8, and the thickness thereof is 1 to 3.
It is preferably 0 μm, particularly preferably 3 to 10 μm. The transmittance of the substrate 2 through the hard coat 3 for recording light and reproducing light is preferably 80% or more, and particularly preferably 85% or more.

The protective layers 4 and 6 have the effects of improving C / N and improving the corrosion resistance of the recording layer 5. The protective layer 4 has a thickness of about 30 to 300 nm, and the protective layer 6 has a thickness of 10 to 50 nm.
It is preferably about nm. These protective layers are preferably composed of an inorganic thin film made of various oxides, carbides, nitrides, sulfides or mixtures thereof. The protective layer is preferably formed by various vapor phase film forming methods such as sputtering, vapor deposition and ion plating, and particularly by sputtering.

An intermediate layer made of various dielectric materials may be provided between the protective layer 4 and the recording layer 5 to improve C / N and corrosion resistance.

Information is magnetically recorded on the recording layer 5 by a modulated magnetic field, and the recorded information is magnetic-optically converted and reproduced. The material of the recording layer 5 is not particularly limited as long as it can perform magneto-optical recording,
An alloy containing a rare earth metal element, particularly an alloy of a rare earth metal and a transition metal, is preferably formed as an amorphous film by sputtering, vapor deposition, ion plating, etc., particularly sputtering. Examples of rare earth metals include Tb,
It is preferable to use one or more of Dy, Nd, Gd, Sm, and Ce. Transition metals include Fe and Co
Is preferred. In this case, the total content of Fe and Co is 65
It is preferably about 85 atomic%. And the balance is substantially a rare earth metal. Specific preferred examples of the composition of the recording layer include TbFeCo, DyTbFeCo, and NdDy.
FeCo, NdGdFeCo, etc. are mentioned. In the recording layer, Cr, Al, and T are contained in the range of 10 atomic% or less.
i, Pt, Si, Mo, Mn, V, Ni, Cu, Zn,
Ge, Au, etc. may be contained. Further, in the range of 10 atomic% or less, Sc, Y, La, Ce, Pr, Pm, S
Other rare earth metal elements such as m, Eu, Ho, Er, Tm, Yb and Lu may be contained. The thickness of the recording layer 5 is usually about 10 to 1000 nm.

The material of the reflective layer 7 is Cu, Au,
Metals such as Ag, Pt, Al, Ti, Cr, Ni and Co,
Alternatively, these alloys or these compounds are preferable. The reflective layer 7 may be formed in the same manner as the recording layer 5. The thickness of the reflective layer 7 is preferably about 30 to 200 nm.

The structure of the optical head used in the present invention is not particularly limited and may be appropriately selected from various optical heads used for ordinary magneto-optical recording, but in magneto-optical recording of the magnetic field modulation system, movement of the optical head is performed. Since the magnetic flux leaked from the actuator for magnetic recording greatly affects the quality of the recording signal, it is preferable to use an optical head provided with a magnetic shielding member for suppressing the magnetic flux leak. As such an optical head, for example, one disclosed in Japanese Patent Application No. 3-1957771 is preferable.

[0035]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

A magnetic head having a pot-shaped core having the structure shown in FIG. 1A was manufactured. The structure of this magnetic head is shown below.

Core material: Mn-Zn ferrite Number of coil turns: 30 turns Inductance: 5 µH Core outer diameter: 5.0 mm Main pole core diameter: 0.5 mm Projected area Ps of main pole (cross-sectional area of main pole core): 0.
0625π mm ²

Further, a magneto-optical recording disk having the structure shown in FIG. 2 was produced. The board has an outer diameter of 86 mm and an inner diameter of 15 m.
A polycarbonate resin having a thickness of 1.2 mm and a thickness of 1.2 mm was used. The hard coat 3 was made of an ultraviolet curable resin and had a thickness after curing of 5 μm. The protective layer 4 was made of SiN _x and had a thickness of 40 nm. The composition of the recording layer 5 is Tb ₂₃ Fe ₇₂ Co ₅
And the thickness was 20 nm. The protective layer 6 had the same composition as the protective layer 4 and had a thickness of 20 nm. The reflective layer 7 was made of Al alloy and had a thickness of 80 nm. The protective coat 8 was made of an ultraviolet curable resin and had a thickness after curing of 5 μm.

Using the above magnetic head and magneto-optical recording disk, the distance h between the main magnetic pole of the magnetic head and the disk
And the relationship between C and N was calculated. The results are shown in Fig. 4. The surface deviation of the disk at the C / N measurement position is ± 15
μm, and C / N shown in FIG. 4 is an average value at the measurement position.

The maximum surface deviation of the magneto-optical recording disk was ± 0.
If 1mm, the average distance between the main pole and the disk is 0.2mm
, H is 0.1 to 0.3 mm, and Ps / h ² is 0.
It becomes 69π-6.25π. In FIG. 4, the C / N at this time is 53.2 to 52.8 dB, and the fluctuation of the C / N is 0.4 dB. On the other hand, when the average distance is 0.3 mm, h is 0.2 to 0.4 mm and Ps / h ² is 0.39π.
It becomes 1.56π. C / N at this time is 53.0 to 5
It is 1.7 dB, and the C / N changes by 1.3 dB.

Since the C / N fluctuation in magneto-optical recording is about 2 dB in total due to the laser diode and due to the temperature characteristic, if the fluctuation due to the above magnetic head is further increased by 1 dB or more, the total is 3 dB or more. Will be. However, if the distance h is set to 0.3 mm or less, a high C / N can be stably obtained even if surface wobbling occurs.
Is clear from.

When the jitter was measured,
An increase in jitter was observed corresponding to a decrease in C / N.

Next, a computer was used to simulate magneto-optical recording based on the configurations of the magnetic head and the magneto-optical recording disk. For the simulation, electromagnetic field analysis software using a finite element method and a finite integration method (MAGNA FIM manufactured by CRC Inc.) was used. However, the diameter of the main pole is 0.3 to 1.2 mm (Ps
= 0.0225π to 0.36π mm ² ).

In this simulation, h = 0.1 mm
For h and 0.2 mm, the magnetic flux density Bc at the center of the recording spot of the disk and the magnetic flux density Be at the edge were examined. Results are shown in FIG.

In the graph of FIG. 5, the axis of abscissas is the diameter φ of the main pole core, and points corresponding to 0.16π mm ² which is the upper limit of Ps are also shown. The vertical axis is (Be-Bc) /
Bc, that is, the nonuniformity of the magnetic flux density in the recording spot.

As is apparent from FIG. 5, when h = 0.2 mm, a substantially uniform magnetic field intensity is obtained in the recording spot, but when h = 0.1 mm, Ps is 0.16 π mm ² (φ =
Even if it is 0.8 mm or less, if Ps / h ² exceeds 8π (φ is about 0.57 mm), the magnetic field strength at the edge of the recording spot becomes strong and the non-uniformity of the magnetic flux density in the recording spot becomes 15 %, The magnetic flux is not effectively used.

Even with an E-shaped core having the same size Ps as described above, the same result was obtained with h of 0.04 to 0.3 mm, Ps of 0.16π mm ² or less, and Ps / h ² of 0.4πρ to 8π. Got The effect of the present invention is clear from the results of the above examples.

[0048]

According to the present invention, in the method of performing the magnetic field modulation type magneto-optical recording, the size of the magnetic head and the positional relationship between the magnetic head and the disk are optimized so that the C / N and its stability can be improved. Can improve
In addition, it is possible to reduce jitter. Further, in the present invention, the uniformity of the magnetic field strength in the recording spot becomes good, so that the recording magnetic field can be effectively utilized and the magnetomotive force applied to the magnetic head can be small.

[Brief description of drawings]

1A and 1B are perspective views respectively showing a core of a magnetic head used for magneto-optical recording of a magnetic field modulation method.

FIG. 2 is a sectional view showing an example of a magneto-optical recording disk used in the present invention.

FIG. 3 is a partial front view showing a relative positional relationship between a magnetic head and an optical recording medium disk.

FIG. 4 shows a distance h between the main magnetic pole of the magnetic head and the disk,
It is a graph which shows the relationship with C / N.

FIG. 5 is a graph showing the relationship between the size of the main pole core of the magnetic head and the non-uniformity of the magnetic flux density in the recording spot.

[Explanation of symbols]

 1 Magneto-optical recording disk 2 Substrate 3 Hard coat 4 Protective layer 5 Recording layer 6 Protective layer 7 Reflective layer 8 Protective coat 10 Core 11 Main magnetic pole core 12 Auxiliary magnetic pole core 13 Back core

Claims (2)

[Claims] 1. A magnetic head having a main magnetic pole and an auxiliary magnetic pole and configured to apply a magnetic field from the main magnetic pole to the magneto-optical recording disk is arranged on one main surface of the magneto-optical recording disk, Assuming that the distance between the recording layer of the recording disk and the main magnetic pole is h and the perpendicular projection area of the main magnetic pole with respect to the main surface of the magneto-optical recording disk is Ps, then 0.04 mm ≦ h ≦ 0.3 mm, Ps ≦ 0 A magneto-optical recording method characterized in that magneto-optical recording is performed by a magnetic field modulation method, with 16 π mm ² and 0.4 π ≤ Ps / h ² ≤ 8 π. 2. The core shape of the magnetic head is a pot type, E type
The magneto-optical recording method according to claim 1, wherein the magneto-optical recording method is a U-type or a U-type.