JP2001126336A - Magneto-optical disk and recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an outside diameter smaller and thickness smaller and to suppress the inclination arising in an information recording region during recording and reproducing. SOLUTION: This magneto-optical disk has the annular information recording region and a holding region which is disposed on the inner peripheral side of the information recording region and is used to be held by a disk rotational drive mechanism 11 on a recording and reproducing device 10 side. The magneto-optical disk 1 is so formed that f<=6439×t3/(d1-d2)2 holds when the pressing force of pressing the magnetic head 19 on the recording and reproducing device 10 side to the information recording region is defined as (f) (gf), the outside diameter as d1 (mm), the outside diameter in the holding region as d2 (mm) and the thickness of a disk substrate as (t) (mm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magneto-optical disc on which information is recorded and reproduced, and a recording and reproducing apparatus for recording and reproducing information on and from the magneto-optical disc.

[0002]

2. Description of the Related Art A magneto-optical disk capable of recording and reproducing information is known as an information recording medium. This type of magneto-optical disk is capable of recording and reproducing information at a relatively high speed, and can be used for information recording media such as a read-only type, a recordable type, and a rewritable type. Therefore, it is widely used for business use and consumer use.

[0003] As read-only recording media, for example, compact discs and video discs have become widespread.
As a rewritable recording medium, for example, a magneto-optical disk is widely used. Rewritable recording media are generally
A recording film composed of various functional films is formed on a disk-shaped disk substrate, and a transparent substrate having light transmissivity for protecting the recording film is formed.

In a magneto-optical disk, a recording film is formed by forming a perpendicular magnetic film made of a rare earth-transition metal crystal alloy such as a TbFeCo alloy as a functional film on a disk substrate.

[0005] When recording and reproducing information, this type of magneto-optical disk is irradiated with light such as laser light from the transparent substrate side. When information is recorded on the magneto-optical disk, the coercive force of the perpendicular magnetization film in the region irradiated with the laser beam is reduced, and a magnetic field is externally applied to the region where the coercive force is reduced. Information is recorded by reversing the direction of magnetization of the region. When reading / reproducing information recorded on the magneto-optical disk by a laser beam according to the direction and length of magnetization of an arbitrary region of the recording film, the linearly polarized laser beam is reflected on the surface of the perpendicular magnetization film. It utilizes the Kerr effect, in which the polarization direction is sometimes rotated in different directions with the direction of the magnetization.

[0006] When recording and reproducing information, the magneto-optical disk is rotated in a state where the center of the main surface is rotated. The magneto-optical disk has a center hole,
It is held by a disk rotation drive mechanism on the recording / reproducing apparatus side and is rotationally driven by a spindle motor of the disk rotation drive mechanism.

[0007]

The above-mentioned magneto-optical disk is required to have a higher recording density, and the numerical aperture (NA) of an objective lens for irradiating the magneto-optical disk with a laser beam is desired. When the value of () is increased, coma aberration which occurs when a laser beam which is to be perpendicularly incident on the recording surface of the magneto-optical disk is inclined relative to the recording surface is likely to occur. Coma is
It increases in proportion to the cube of the numerical aperture of the objective lens and the thickness of the disk substrate, which is the thickness of the light transmitting layer of the magneto-optical disk.

For this reason, in a magneto-optical disk, generally, by reducing the thickness of the disk substrate,
It has been considered to reduce coma. In a magneto-optical disk, reducing the thickness of the disk substrate is also effective from the viewpoint of suppressing birefringence.

However, the magneto-optical disk has a problem that it is difficult to secure the mechanical rigidity of the disk itself by reducing the thickness of the disk substrate. In particular, in the case of a magneto-optical disk, since magneto-optical recording is performed by magnetic field modulation, the magnetic circuit is applied to the recording film at a very short distance from the point that the magnetic field generated by the magnetic circuit for applying the magnetic field to the recording film is effectively used. It is necessary to arrange in.

Therefore, in a recording / reproducing apparatus for recording / reproducing information on / from a magneto-optical disk, a magnetic head is mounted on a surface opposite to a surface irradiated with laser light with a magneto-optical disk interposed therebetween. It is configured such that it is constantly contacted by being pressed with a pressing force, or is floated by a small amount by an air current generated by rotation of the magneto-optical disk. The magnetic head applies a certain load to the magneto-optical disk even when the magnetic head is in contact with the recording surface of the magneto-optical disk and when the magnetic head flies a very small amount on the recording surface.

A magneto-optical disk may be warped in the radial direction (radial direction) of an information recording area due to a force acting in a direction pressing the magneto-optical disk as described above. Laser light applied to the magneto-optical disk is not perpendicularly incident on the recording surface of the disk substrate. For this reason, the reflected light from the magneto-optical disk does not return accurately to the objective lens and the light receiving section, and coma aberration occurs, which causes a problem that a servo signal is shifted and information is not accurately recorded / reproduced. is there.

Accordingly, the present invention provides a magneto-optical disk and an information recording / reproducing apparatus for a magneto-optical disk capable of reducing the outer diameter of the disk and reducing the thickness of the disk so as to suppress the inclination occurring in the information recording area during recording / reproduction to an allowable amount or less. An object of the present invention is to provide a recording / reproducing apparatus capable of improving the reliability of the recording / reproducing operation of the present invention.

[0013]

In order to achieve the above-mentioned object, a magneto-optical disk according to the present invention comprises a ring-shaped information recording area and a recording / reproducing apparatus provided on the inner peripheral side of the information recording area. Holding area for holding by the means. This magneto-optical disk has a pressing force f for pressing the magnetic head on the recording / reproducing apparatus side against the information recording area.
(Gf), the outer diameter is d ₁ (mm), and the outer diameter of the holding area is d.
₂ (mm), the thickness of the disk substrate is t (mm), and f ≦ 6439 × t ³ / (d ₁ −d ₂ ) ² is established.

The magneto-optical disk constructed as described above has
The inclination caused by the pressing force of the magnetic head pressed against the information recording area is suppressed to an allowable amount or less. Therefore, according to the magneto-optical disk, the reliability of the recording / reproducing operation is improved. Note that the thickness of the disk substrate is the thickness of the light transmitting layer through which the beam light applied to the information recording area is transmitted.

The recording / reproducing apparatus according to the present invention comprises an annular information recording area and a holding area provided on the inner peripheral side of the information recording area for holding by the holding means of the recording / reproducing apparatus. It is configured to record and reproduce information on a magneto-optical disk. In this recording / reproducing apparatus, the pressing force for pressing the magnetic head against the information recording area of the magneto-optical disk is f (gf), the outer diameter is d ₁ (mm), and the outer diameter of the holding area is d ₂ (mm). , The thickness of the disk substrate is t (m
m), and a magneto-optical disk formed so as to satisfy f ≦ 6439 × t ³ / (d ₁ −d ₂ ) ² is used as an information recording medium.

In the recording / reproducing apparatus configured as described above, when recording / reproducing information on / from the magneto-optical disk, the pressing force of the magnetic head pressed against the information recording area of the magneto-optical disk is set to a predetermined upper limit or less. By setting, the tilt generated in the magneto-optical disk is suppressed. Therefore, according to the recording / reproducing apparatus, the reliability of the recording / reproducing operation is improved. Note that the thickness of the disk substrate is the thickness of the light transmitting layer through which the beam light applied to the information recording area is transmitted.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of the present invention will be described with reference to the accompanying drawings.

The magneto-optical disk according to the present invention has a center hole in the center of the information recording area, and the periphery of the center hole is substantially held by a disk rotation drive mechanism on the recording / reproducing apparatus side. An annular holding area is provided. The center hole of the magneto-optical disk is provided with a metal center hub to be held by the disk rotation drive mechanism.

Generally, when the magneto-optical disk is pressed by the magnetic head of the recording / reproducing apparatus located at the outermost periphery, the deflection amount and inclination (disk skew) at the irradiation position of the laser beam irradiated from the optical pickup. Is the largest.

That is, when the magnetic head is pressed to the outermost periphery of the information recording area of the magneto-optical disk, the entire disk is bent as shown by performing a linear analysis by the finite element method in FIG. .

The amount of deflection V generated on the magneto-optical disk
And the slope T are as follows: V = A × f (d ₁ −d ₂ ) ³ / t ³ (μm) (Equation 1) T = B × f (d ₁ −d ₂ ) ³ / t ³ = 3 × B × f (d ₁ −d ₂ ) ³ / t ³ (mrad) (Equation 2) However, A and B are almost replaced by a constant relationship determined by the disk material and shape.

For example, if the outer diameter d ₁ of the magneto-optical disk is 40
mm to 64 mm, the outer diameter d ₂ of the holding area is 13 mm to 1
7 mm, the outermost information recording area when the thickness t of the disk substrate, which is the thickness of the transmission layer through which the laser light applied to the information recording area of the magneto-optical disk is transmitted, is 0.4 mm to 0.8 mm. Is calculated by a simulation based on the finite element method, and the constants A and B in Expressions 1 and 2 are obtained from the calculation results. A = 0.00007 B = 0.00021

In the simulation, polycarbonate is used as a disc material, and each of the above equations 1 and 2 is proportional to the reciprocal of the modulus of longitudinal elasticity.
E ₁ a longitudinal elastic coefficient of polycarbonate, if the longitudinal elastic coefficient of the disc material and _{E 2, A = 0.00007 × (} E 1 / E 2) B = 0.00021 × (E 1 / E 2) is satisfied I do.

Next, the relationship between the outer diameter d ₁ of the magneto-optical disk and the inclination due to the pressing force of the magnetic head will be described with reference to the drawings. In FIGS. 2, 3, 4, 5, and 6, the horizontal axis indicates the pressing force (gf) of the magnetic head, and the horizontal axis indicates the tilt (mrad) of the magneto-optical disk. Also,
In each figure, the thickness t of the magneto-optical disk is 1.2 m.
m, 1.0mm, 0.8mm, 0.6mm, 0.4mm
Are shown by curves A, B, C, D, and E, respectively.

When the outer diameter d _{1 of the} magneto-optical disk is 64 mm, as shown in FIG. 2, the inclination generated in the magneto-optical disk decreases as the thickness t of the magneto-optical disk decreases.

Similarly, the outer diameter d _{1 of the} magneto-optical disk is 55
3, 4, 5, and 6, similarly, the inclination occurring in the magneto-optical disk depends on the thickness t of the disk substrate of the magneto-optical disk. It becomes smaller as it is made thinner.

The skew in the tangential direction (hereinafter, referred to as tangential skew) and the radial skew in the radial direction (hereinafter, referred to as radial skew) of the information recording area of the magneto-optical disk, and the jitter of the reproduced signal. The change will be described with reference to the drawings. 7 and 8, the horizontal axis represents the disk skew (mrad), and the vertical axis represents the jitter (%). 7 and 8
Where the wavelength of the laser beam is λ, the position of the groove in the information recording area by λ / 8, the position of the land by λ / 8, the position of the groove by 3λ / 8, and the land by 3λ / 8 Are shown by curves F, G, H, and I, respectively.

As shown in FIGS. 7 and 8, the jitter of the reproduced signal increases as the disk skew increases, and there is a difference depending on the recording / reproducing system of the magneto-optical disk, but the tangential skew and the radial skew are different. The allowable amount is about ± 10 to 15 mrad.

As the material used for the disk substrate of the magneto-optical disk, not only polycarbonate but also various resin materials can be considered. Currently applied materials are:
Single and composite materials available, with a longitudinal modulus of 1.8-
It is about 3.0 GPa. Polycarbonate has a longitudinal elastic modulus of about 2.2 GPa.

Using these longitudinal elastic moduli, the above equation 2
Is calculated from the following equation: 0.00021 × (2.2 / 3.0) ≦ B ≦ 0.000
21 (2.2 / 1.8) Therefore, it is necessary to satisfy the range of 0.000154 ≦ B ≦ 0.000257.

The amount of deflection by the magnetic head is 1.0 mrad
When the above is allowed, from Expression 2 described above, 1.0 = B × 0.4 (d ₁ −d ₂ ) ² / t ³ ...

[0032] Each of formulas 3, the lower limit value of the thickness t of the disc substrate from the equation 4 (mm) _{^{is, 3 √ {(d 1 -d}} 2) 2/16234} ≦ t ≦ 3 √ {(d 1 -d ₂₎ it is necessary to satisfy ^2/9728} ... formula 5.

Therefore, when the range of the upper limit value f of the pressing force of the magnetic head is determined by Equation 5 in consideration of the above-described conditions, the bending amount of the magneto-optical disk caused by the magnetic head is allowed to be 1.0 rad. , 1.0 = B × f (d ₁ −d ₂ ) ² / t ³ 1.0 / {B × (d ₁ −d ₂ ) ² / t ³ } = f, and the upper limit B of Bmax = 0.000257, By the lower limit value Bmin of B = 0.000154, 1.0 / {0.000257 × (d ₁ −d ₂ ) ² / t ³ } ≦ f ≦ 1.0 / {0.000154 × (d ₁₋ d ₂ ) ² / t ³ ｝ Accordingly, as the range of the upper limit value f of the pressing force of the magnetic head, the range of 3891 × t ³ / (d ₁ −d ₂ ) ² ≦ f ≦ 6439 × t ³
/ (D ₁ −d ₂ ) ² This gives, for example, when d ₁ = 64 mm, d ₂ = 17 mm and t = 0.6, 0.4 ≦ f ≦ 0.6 d ₁ = 55 mm, d ₂ = 15 mm , T = 0.5, 0.3 ≦ f ≦ 0.5 d ₁ = 50 mm, d ₂ = 15 mm, t = 0.6, 0.7 ≦ f ≦ 1.1 d ₁ = 50 mm, When d ₂ = 15 mm and t = 0.6, 0.4 ≦ f ≦ 0.7 d ₁ = 40 mm, d ₂ = 15 mm, and when t = 0.5, 0.8 ≦ f ≦ 1.3. This is within the range of the upper limit f of the pressing force of the magnetic head. Then, the magneto-optical disk according to the present invention is formed such that the above-described equations hold.

Next, the lower limit of the pressing force of the magnetic head will be briefly described. In the above-described magnetic head, the slider member is supported by a support arm made of, for example, ceramics or a resin material via the slider member. The contact area of the slider member with the magneto-optical disk is determined by the flying height, pressing force and the like in the case of a flying magnetic head. The flying height of the magnetic head is generally set to about 5 μm to 10 μm in order to prevent interference such as projections on the coating surface of the surface of the magneto-optical disk and to minimize the height.
In order to determine the flying height of the magnetic head, the linear velocity and the rotation speed of the magneto-optical disk are required as factors.

Also in the case of a sliding type magnetic head, taking into account sliding friction generated between the magneto-optical disk and the magnetic head,
The pressing force is set roughly. However, the pressing force of the magnetic head and the action of the slider member have a predetermined range. In particular, even when the pressing force is smaller than the predetermined value, the tilting state and the height direction when the magnetic head is mounted. In an environment where other conditions such as the positional deviation of the optical disk and the conditions for covering the surface of the magneto-optical disk are uniform, there may be no problem in the operational function.

The area of the slider member is determined as described above, but there is almost no difference in the thickness in the flying height direction, and the slider member is formed to have a minimum size in terms of mechanism. From the above, the mass of the slider member itself can be substantially determined from conditions such as the pressing force. When the slider member is made of a general material, the slider member has a pressing force of 2 gf and a pressure of 0.2 gf.
It is about 0.015 g with a pressure of 0.5 gf and a pressure of 0.5 gf.

Therefore, the mass M (g) of a general slider member is expressed by the following equation: M = 0.023f + 0.003 (Equation 6) where f is a standard pressing force (gf ).

By the way, the recording / reproducing apparatus is required to operate normally even when a certain degree of impact is applied as a condition for the recording / reproducing operation. The recording / playback device is actually
When the magnetic head is moved away from the surface of the magneto-optical disk due to an impact applied while the magnetic head is being driven, a sufficient magnetic field required to record the information is generated when the magnetic head is moved away from the surface of the magneto-optical disk. It cannot be applied to the recording area, making it difficult to record information accurately. The recording system of the recording / reproducing device electrically stores the information to be recorded in a storage means such as a memory in order to prevent a temporary abnormal operation due to a large short-time impact, so that the recording seems to be performed normally. Although such a configuration may be adopted, practical considerations require mechanical considerations against impacts that are difficult to cope with such a configuration.

Therefore, in general, the recording / reproducing apparatus is designed so that the mechanical operation is not adversely affected even when an impact of about 10 G is externally applied as a design guide. . The recording / reproducing apparatus requires a minimum pressing force of about 10 times the weight of the slider member in order to prevent the magnetic head from being separated from the magneto-optical disk due to an impact.

From the above equation 6, the minimum pressing force fmin is obtained by fmin = 10 × M = 0.23f + 0.03 (Equation 7).

From the above equation (7), when the upper limit is 2 gf, the lower limit is 0.5 gf, the upper limit is 1 gf, the lower limit is 0.26 gf, and the upper limit is 0.5 gf. When the lower limit is 0.15 gf and the upper limit is 0.2 gf, the lower limit is 0.08 gf.

Next, as shown in FIG. 9, a recording / reproducing apparatus 10 using the above-described magneto-optical disk 1 as an information recording medium includes a disk rotation drive mechanism 11 for rotating the magneto-optical disk 1 and a magneto-optical disk 1 And a recording / reproducing mechanism 12 for recording / reproducing information to / from the device.

As shown in FIG. 9, the disk rotation drive mechanism 11 has a disk table 15 on which the magneto-optical disk 1 is mounted, and a spindle motor 16 for driving the disk table 15 to rotate. The disk table 15 is provided with a magnet 17 for holding the center hub of the magneto-optical disk 1 by suction.

The recording / reproducing mechanism 12 is, for example, shown in FIGS.
As shown in FIG. 1 and FIG. 11, an optical pickup 18 for reproducing information on the magneto-optical disk 1, a magnetic head 19 for recording information on the magneto-optical disk 1, and an optical pickup 18 and the magnetic head 19 are mounted on the magneto-optical disk. 1
And a feed mechanism 20 for moving in the radial direction.

The optical pickup 18 comprises an optical system 21 having an objective lens 22 for focusing a laser beam on an information recording area of the magneto-optical disk 1 as shown in FIGS.
And an objective lens driving unit 23 that drives and displaces the objective lens 22 in two axial directions. The objective lens driving unit 23 drives the objective lens 22 biaxially, a lens holder 24 supporting the objective lens 22, a support mechanism (not shown) for supporting the lens holder 24 movably in biaxial directions. And a displaceable magnetic circuit 25.

The magnetic head 19 is shown in FIGS.
As shown in FIG. 1, the objective lens 22 of the optical pickup 18
, And is supported by the distal end of the support arm 27, and the base end of the support arm 27 is supported by the feed mechanism 20. And the magnetic head 19
Is pressed against the information recording area of the magneto-optical disk 1 within the range of the above-described upper limit f of the pressing force due to the rigidity of the support arm 27.

The feed mechanism 20 includes a support base 28 for supporting the optical pickup 18, a pair of guide shafts 29, 29 for movably supporting the support base 28, and a support base 28 having a diameter of the magneto-optical disk 1. And an electromagnetic circuit 30 that moves linearly in the direction. The support base 28 has a support arm 2
7 is fixedly attached thereto. The electromagnetic circuit 30 includes a yoke 31, a magnet 32, a driving coil 3
3 and so on.

The recording / reproducing apparatus 10 configured as described above
The operation of recording and reproducing information on and from the magneto-optical disk 1 will be described.

The recording / reproducing apparatus 10 drives the magneto-optical disk 1 mounted on the disk table 15 of the disk rotation drive mechanism 11 and rotates the magneto-optical disk 1.
The magnetic head 19 is pressed with a predetermined pressing force against the information recording area. The recording / reproducing apparatus 10 is configured such that the optical pickup 18 and the magnetic head 19
The information recording area is moved to a predetermined position in the radial direction of the information recording area to record and reproduce information. According to the recording / reproducing apparatus 10, the occurrence of tilt due to the bending caused by the magnetic head 19 pressed against the information recording area of the magneto-optical disk 1 is suppressed.

As described above, when the diameter of the magneto-optical disk 1 according to the present invention is reduced, the disk substrate can be reliably set to an appropriate thickness. For this reason, according to the magneto-optical disk 1, the tilt caused by the magnetic head 19 pressed against the information recording area can be suppressed to an allowable amount or less.

Further, the recording / reproducing apparatus 10 according to the present invention
During recording and reproduction on the magneto-optical disk 1, the magnetic head 19 pressed against the information recording area of the magneto-optical disk 1 can suppress the tilt due to the bending generated on the magneto-optical disk 1 to an allowable value or less. Therefore, according to the recording / reproducing apparatus 10, the reliability of the information recording / reproducing operation for the magneto-optical disk 1 can be improved.

[0052]

As described above, according to the magneto-optical disk of the present invention, during recording and reproduction, the tilt caused by the magnetic head pressed against the information recording area can be suppressed to an allowable value or less.

Further, according to the recording / reproducing apparatus of the present invention, during recording / reproducing on the magneto-optical disk, the tilt generated on the magneto-optical disk by the magnetic head pressed against the information recording area of the magneto-optical disk is equal to or less than an allowable amount. Can be suppressed. Therefore, according to this recording / reproducing device,
The reliability of the information recording / reproducing operation for the magneto-optical disk can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the bending that occurs in a magneto-optical disk according to the present invention.

FIG. 2 shows the magneto-optical disk having an outer diameter of 64 mm.
FIG. 6 is a diagram showing a relationship between a pressing force and a tilt by the magnetic head when the relation is set as follows.

FIG. 3 shows the magneto-optical disk having an outer diameter of 55 mm.
FIG. 6 is a diagram showing a relationship between a pressing force and a tilt by the magnetic head when the relation is set as follows.

FIG. 4 shows the magneto-optical disk having an outer diameter of 50 mm.
FIG. 6 is a diagram showing a relationship between a pressing force and a tilt by the magnetic head when the relation is set as follows.

FIG. 5 is a diagram showing an outer diameter of the magneto-optical disk of 45 mm.
FIG. 6 is a diagram showing a relationship between a pressing force and a tilt by the magnetic head when the relation is set as follows.

FIG. 6 shows an outer diameter of the magneto-optical disk of 40 mm.
FIG. 6 is a diagram showing a relationship between a pressing force and a tilt by the magnetic head when the relation is set as follows.

FIG. 7 is a diagram showing a change in jitter due to tangential skew in the magneto-optical disk.

FIG. 8 is a diagram showing a change in jitter due to radial skew in the magneto-optical disk.

FIG. 9 is a perspective view showing a recording / reproducing apparatus according to the present invention.

FIG. 10 is a plan view for explaining a magnetic head of the recording / reproducing apparatus.

FIG. 11 is a longitudinal sectional view illustrating the magnetic head.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 magneto-optical disk, 10 recording / reproducing device, 11 disk rotation drive mechanism, 19 magnetic head

Claims (2)

[Claims] 1. A magnetic head on the recording / reproducing apparatus side, comprising: an annular information recording area; and a holding area provided on an inner peripheral side of the information recording area for holding by a holding means on the recording / reproducing apparatus side. Is f (gf), the outer diameter is d ₁ (mm),
The outer diameter of the holding area is d ₂ (mm), the thickness of the disk substrate is t (mm), and f ≦ 6439 × t ³ / (d ₁ −d ₂ ) ² is formed. A magneto-optical disk characterized by the following. 2. A method for transmitting information to a magneto-optical disk having an annular information recording area and a holding area provided on an inner peripheral side of the information recording area and held by holding means on a recording / reproducing apparatus side. In the recording / reproducing apparatus for recording / reproducing, the pressing force for pressing the magnetic head against the information recording area of the magneto-optical disk is f (gf), and the outer diameter is d ₁ (m
m), the outer diameter of the holding area is d ₂ (mm), the thickness of the disk substrate is t (mm), and f ≦ 6439 × t ³ / (d ₁ −d ₂ ) ² is satisfied. A recording / reproducing apparatus characterized in that the magneto-optical disk is used as an information recording medium.