JPH11265536A - Magneto-optical erasure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical erasure method capable of stably erasing information, being hardly affected by frictional heat generate by the sliding of a magneto-optical recording medium and a magnetic field generator. SOLUTION: Through the magneto-optical recording medium 11, an optical head 12a and the magnetic field generator 13 of a contact type are oppositely arranged on both sides of the medium 11. The magnetic field generator 13 consists of a magnetic field generation part (center yoke) 14c not to be in contact with the magneto-optical recording medium 11 and sliding parts (outer side yokes) 14a and 14b to be in contact with the magneto-optical recording medium 11. The magnetic field generation part 14c of the magnetic field generator 13 is positioned on the optical axis A-A of an objective lens 12 provided on the optical head 12a and the sliding parts 14a and 14b of the magnetic field generator 13 are arranged at a part deviating from the optical axis A-A. While the magnetic layer 4 of the magneto-optical recording medium 11 is irradiated with a laser beam 16 from the optical head 12a, a magnetic field is applied by the magnetic field generation part 14c of the magnetic field generator 13 to the laser beam focusing part of the magnetic layer 4 and the information is erased from the magnetic layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for erasing information recorded on a magneto-optical recording medium, and more particularly to a method for erasing a magneto-optical recording medium using a drive device having an optical head and a contact type magnetic field generator. The present invention relates to a method for stabilizing a temperature rise of a magnetic layer when erasing information recorded in a magnetic layer.

[0002]

2. Description of the Related Art For example, a magneto-optical recording medium such as a magneto-optical disk which is put into practical use as an external storage device of a computer has at least a magnetic layer (for example, a rare earth element) on a transparent substrate.
A thin film containing a transition metal amorphous perpendicular magnetic film) is formed, and the magnetic layer is irradiated with a laser beam through a transparent substrate to locally raise the temperature of the magnetic layer to a temperature near or above the Curie temperature. While applying a bias magnetic field to the magnetic layer from the magnetic field generator, the magnetization direction of the magnetic layer is reversibly inverted to record and erase information.

[0003] Magnetic field generators for applying a bias magnetic field to a magnetic layer include a contact type which slides on a magneto-optical recording medium when the medium is driven, and a non-contact type which is held at a position separated from the magneto-optical recording medium. However, in the contact type magnetic field generator, the magnetic field generator can be arranged closer to the magnetic layer, and the distance from the magnetic field generator to the magnetic layer is always almost constant regardless of the surface deflection of the medium. , And is superior to the non-contact type in that stable recording and erasing can be performed with a small magnetic field. On the other hand, the contact type magnetic field generator has a drawback that the thin film of the magneto-optical recording medium is easily damaged by wear or impact.

[0004] In order to solve such disadvantages, conventionally, attempts have been made to improve abrasion resistance and impact resistance of a magneto-optical recording medium. Known examples of this type include those in which a lubricating layer is formed on a thin film as described in, for example, Japanese Patent Application Laid-Open No.
As described in JP-A-43-834 and JP-A-1-227241, there can be mentioned those obtained by forming a polymer sheet or a non-magnetic metal thin plate on a thin film.

[0005]

However, in order to enable the use of a contact-type magnetic field generator for a magneto-optical recording medium, the wear resistance and impact resistance of the magneto-optical recording medium must be improved as in the prior art. However, it is not enough to improve the above, and some means for eliminating the influence of frictional heat generated by sliding between the magneto-optical recording medium and the magnetic field generator is required. That is, when the temperature of the magnetic layer is raised by frictional heat, it becomes difficult to control the temperature of the magnetic layer by irradiating a laser beam, and erroneous recording or erasing of information is likely to occur.

An object of the present invention is to provide a magneto-optical recording method capable of recording information stably without being adversely affected by frictional heat. is there.

[0007]

According to the present invention, in order to achieve the above object, an optical head and a contact-type magnetic field generator are disposed on both sides of a magneto-optical recording medium so as to face each other. And irradiating the magnetic layer of the magneto-optical recording medium with a laser beam from the optical head while driving the magneto-optical recording medium relative to the magnetic field generating apparatus, and irradiating the magnetic layer with the laser beam from the magnetic field generating apparatus. In a magneto-optical erasing method for erasing information recorded on the magnetic layer by applying a magnetic field to a portion, the frictional heat generated by sliding between the magneto-optical recording medium and the contact type magnetic field generator is generated by the magnetic field. The temperature rise of the magnetic layer is controlled by the intensity of the laser beam irradiated from the optical head to the magnetic layer without directly acting on the laser beam irradiated portion of the layer.

As described above, the contact-type magnetic field generating device having the medium sliding portion can arrange the magnetic field generating portion closer to the magnetic layer, and always generate the magnetic field irrespective of the runout of the medium. Since the distance from the portion to the magnetic layer can be kept substantially constant, stable recording, reproduction, erasing, and the like can be performed with a small magnetic field. In addition, when the tip of the magnetic field generator is configured to be in non-contact with the information recording medium, information recording, reproduction,
Since the frictional heat generated by the sliding of the information recording medium and the magnetic field generator does not directly act on the magnetic field application portion where erasing is performed, it is possible to mitigate the adverse effect of the frictional heat on recording, reproducing, erasing, etc. of information. it can. In particular, in a magneto-optical recording medium in which the Curie temperature is low and a delicate temperature control is required for the magnetic layer when recording, reproducing, and erasing information, the temperature control of the magnetic layer by laser beam irradiation becomes easy, and Erroneous recording and erasure are prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a magneto-optical recording medium drive for executing a magneto-optical erasing method according to the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 11 denotes a magneto-optical recording medium, 12 denotes an objective lens that focuses a laser beam for heating on the magneto-optical recording medium 11, and 13 denotes a magnetic field generator that applies a bias magnetic field to the magneto-optical recording medium 11. ing.

The magneto-optical recording medium 11 includes a transparent substrate 2 on which a preformat pattern 1 such as a guide groove for guiding a laser beam spot on one side and a prepit for indicating an address of a recording area is formed. A first enhanced layer 3 carried on the preformat pattern forming surface, a magnetic layer 4 laminated on the first enhanced layer 3,
A second enhancement layer 5 laminated on the magnetic layer 4, a reflection layer 6 laminated on the second enhancement layer 5, a heat insulation layer 7 laminated on the reflection layer 6, and a heat insulation layer 7 laminated on the heat insulation layer 7; And a lubricating layer 9 laminated on the high thermal conductive layer 8.

The transparent substrate 2 is made of a transparent ceramic material such as glass, or a hard transparent resin material such as polycarbonate, polymethyl methacrylate, polymethyl pentene, or epoxy, and is formed into an arbitrary shape such as a disk shape, a card shape, and a tape shape. It is formed. The preformat pattern 1 is formed in a fine uneven shape on the surface of the transparent substrate. Note that the arrangement and the method of forming the preformat pattern 1 are well-known items and have no direct relation to the gist of the present invention, so that the description is omitted.

The first enhancement layer 3 is used to multiple-reflect a signal reproduction beam between the transparent substrate 2 and the magnetic layer 4 to increase the apparent Kerr rotation angle, thereby improving reproduction sensitivity. Is formed of a dielectric material having a higher refractive index of light than that of the transparent substrate 1, such as silicon nitride.

The magnetic layer 4 can be a magnetic layer for magneto-optical recording of any known composition, but a perpendicular magnetic film of a rare earth element-transition metal system is particularly preferable. As the rare-earth element-transition metal-based perpendicular magnetization film, a terbium-iron-cobalt-based alloy formed by a sputtering method is particularly preferable, and a film obtained by adding platinum or niobium to this also provides good results. .

The second enhancement layer 5 prevents the heat of the magnetic layer 4 from diffusing to the reflective layer 6 and protects the magnetic layer 4 from impact, corrosion, and the like. The laser beam transmitted through the magnetic layer 4 is subjected to multiple reflections to improve the reproduction sensitivity by increasing the apparent Kerr rotation angle, and is formed of the same dielectric material as the first enhanced layer 3. Is done.

The reflection layer 6 is for preventing moisture permeation to the magnetic layer 4 and returning the laser beam transmitted through the magnetic layer 4 to the incident side, and is made of, for example, a metal material such as gold or aluminum, or It is formed of an alloy material containing these metal materials as main components and a high-reflectance material such as a so-called silver mirror.

The heat insulating layer 7 is made of, for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyphenylene oxide, polysulfone,
Polyimide, polyamide imide, polyester imide,
The reflective layer 6 and the high heat conductive layer 8 may be bonded to each other by using a vapor-deposited film of a heat-resistant polymer material such as polybenzimidazole, or when the high heat conductive layer 8 is formed of a foil. It can also be formed with an adhesive or a pressure-sensitive adhesive.

The high thermal conductive layer 8 is made of aluminum, copper, tin,
Metallic or non-metallic materials such as silicon, cerium, lanthanum, indium, germanium, lead, bismuth, tellurium, tantalum, scandium, yttrium, titanium, zirconium, cadmium, zinc, selenium, antimony, gallium, magnesium, boron, carbon, Or CeO ₂ , La ₂ O ₃ , SiO, SiO ₂ , In2O
₃ , Al ₂ O ₃ , GeO, GeO ₂ , PbO, SnO, Sn
O ₂ , Bi ₂ O ₃ , TeO ₂ , Ta ₂ O ₅ , Sc ₂ O ₃ , Y
₂ O ₃ , TiO ₂ , ZrO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Cr
₂ O ₃ , WO ₂ , WO ₃ , CdS, ZnS, CdSe, Zn
Se, In ₂ S ₃ , In ₂ Se ₃ , Sb ₂ S ₃ , Sb ₂ Se ₃ ,
Ga ₂ S ₃ , Ga ₂ Se ₃ , GeS, GeSe, GeS
e ₂ , SnS, SnS ₂ , SnSe, SnSe ₂ , Pb
S, PbSe, Bi ₂ Se ₃ , Bi ₂ S ₃ , MgF ₂ , Ce
F ₂ , CaF ₂ , TaN, Si ₃ N ₄ , AlN, BN, Ti
It can be formed using a vapor-deposited film of an alloy or an inorganic compound such as B ₂ , B ₄ C, or SiC, or can be formed using a foil of a substance selected from the above. Further, the high thermal conductive layer 8 can be formed of a polymer material in which a powder or a granular material of a substance selected from the above is dispersed.

The lubricating layer 9 is formed with a lubricant such as hexadecane, butyl stearate, oleic acid, ethyl stearate, stearic acid, octadecylamine, and solid stearic acid. As means for forming the lubricating layer 9,
A method of coating a solvent solution of a lubricant on the surface of the high thermal conductive layer 8, a method of attaching a polymer sheet impregnated with a lubricant to the surface of the high thermal conductive layer 8, polishing the surface of the high thermal conductive layer 8, A method of impregnating the formed fine recesses with a lubricant can be employed.

The objective lens 12 is incorporated in the optical head 12a together with a semiconductor laser (not shown), an optical modulator, an analyzer, and the like. Focus on layer 4. In FIG. 1, the laser beam 1
6 is focused on the preformat pattern 1, it is also possible to focus on a flat portion (land portion) between adjacent preformat patterns 1.

The drive device of this embodiment has a magnetic generator 1
3, a yoke 14 made of a ferromagnetic material
An electromagnet including a coil 15 wound around a part of the yoke 14 is provided. The yoke 14 includes outer yokes 14a and 14b that come into contact with the lubricating layer 9 of the magneto-optical recording medium 11 when the medium is driven, and a center yoke 14c that is not in contact with the magneto-optical recording medium 11. The tip of 14b serves as a medium sliding surface, and the tip of center yoke 14c serves as a portion for generating a recording magnetic field or an erasing magnetic field H. The step s from the distal ends of the outer yokes 14a and 14b to the distal end of the center yoke 14c only needs to be large enough that the distal end of the center yoke 14c does not contact the magneto-optical recording medium 11. On the other hand, this step s
Becomes larger, the magnetic field applied to the magnetic layer 4 decreases.
The thickness is preferably about 50 μm.

As shown in FIG. 1, the magnetic field generator 13 of this embodiment is used by positioning the tip of a center yoke 14c, which is a magnetic field generator, coaxially with the optical axis AA of the objective lens 12. The outer yokes 14a and 14b are used to reduce the influence of frictional heat on the magnetic field application part, as shown in FIG.
As shown in (a), it is preferable that the tip of the center yoke 14c abuts on a position separated from the recording track where the center yoke 14c is located. However, when the thermal conductivity of the magneto-optical recording medium 11 is sufficiently high, When the distance L from the yoke 14c to the outer yoke 14a or 14b is sufficiently long, as shown in FIG. 2B, the center yoke 14c can be brought into contact with the recording track on which the tip is located. .

In the magnetic field generator 13, the center yoke 14c, which is a magnetic field generator, is configured to be in non-contact with the magneto-optical recording medium 11, so that the magneto-optical recording medium 11 and the outer yokes 14a, 14a, as shown in FIG. The frictional heat J generated by sliding with the magnetic recording medium 11b does not directly act on the portion where information is recorded, reproduced, or erased, and the magnetic field generating portion is moved to the magneto-optical recording medium 11.
The effect of frictional heat can be reduced as compared with the case where the sliding is performed. Therefore, the temperature of the magnetic layer 4 can be easily controlled by laser beam irradiation, and erroneous recording and erasure of information can be prevented.

In the above description, the magnetic field generator 13
The outer yokes 14 are provided on both sides of the center yoke 14c.
Although the case where a so-called double yoke type electromagnet provided with a and 14b is provided has been described as an example, as shown in FIG. 3, the outer yoke 14a is provided only on one side of the center yoke (magnetic field generating portion) 14c. A so-called single yoke type electromagnet can also be used.

In the above, the magnetic field generator 13
The description has been given of the case where an electromagnet is used as an example, but other types of magnetic field generating devices such as a magnetic head and a permanent magnet are similarly configured. FIG. 4 shows an embodiment of a magnetic head, in which an I-shaped core 2 made of a magnetic material having a high magnetic permeability is used.
The cores 21 and 22 are wound around a winding window formed by abutting the two cores 21 and 22 with a gap 23 which is a magnetic field generating part formed at the abutting part of the two cores 21 and 22. Magnetic head 25 comprising winding 24
Is attached to the side surface of the slider 26 which is a medium sliding portion. Between the medium facing surface 23a of the gap 23 and the medium sliding surface 26a of the slider 26, a step s equivalent to that shown in the above-described embodiment is provided. It does not come in contact with the medium. In the magnetic head of this embodiment, the magnetic head 25 is arranged on the upstream side in the medium driving direction and the slider 26 is arranged on the downstream side in the medium driving direction in order to reduce the influence of frictional heat generated by the sliding between the slider 26 and the magneto-optical recording medium. It is preferable to use them.

Further, since the present invention relates to a method for erasing information, the magneto-optical recording medium 11 having an arbitrary film structure can be appropriately used regardless of the above embodiment. In the above embodiment, the method of erasing a magneto-optical recording medium has been described. However, the present invention can be applied to a method of erasing a magnetic recording medium.

Hereinafter, experimental examples of the present invention will be shown to clarify the effects of the present invention.

<Experimental Example 1> A first enhanced layer made of SiN and a terbium-iron-cobalt amorphous vertical were placed on a preformat pattern transfer surface of a disc-shaped polycarbonate substrate formed by injection molding. A magnetic layer made of a magnetic film, a second enhanced layer made of SiN, and AlTi
Reflection layer consisting of sequentially laminated by sputtering method,
A number of magneto-optical disks having the same configuration were manufactured. Thereafter, various aluminum foils having different thicknesses were adhered with an adhesive on the reflection layers of the respective magneto-optical disks to produce various magneto-optical disks having a heat insulating layer and a high thermal conductive layer. Finally, a benzene solution of stearic acid was spin-coated on the aluminum foil of each magneto-optical recording medium and dried to produce a magneto-optical disk with a lubricating layer. Also,
As a comparative example, the experimental example 1 was repeated except that the aluminum foil was not bonded and the lubricating layer was not formed.
A magneto-optical disk formed in the same manner as described above was manufactured. Experimental Example recording of information by mounting the magneto-optical disk according to 1 in drive apparatus having a magnetic field generator of FIG. 1, reproduction, an error rate after repeating 10 ⁶ times the erasure, the magneto-optical of the comparative example The disc is mounted on a drive device equipped with a conventional contact-type magnetic field generator, and recording, reproducing, and erasing information can be performed in 10 minutes.
The error rate after repeating ⁶ times was measured, and the relationship between the thickness of the aluminum foil and the error rate was examined. The result is shown in FIG. As is clear from FIG. 5, the magneto-optical disk of Experimental Example 1 had a lower error rate than the magneto-optical disk of Comparative Example, except that the aluminum foil having a thickness of about 54 μm or more was adhered. I have. However,
There is an optimum value for the thickness of the aluminum foil, about 14 to 42.
A magneto-optical disk to which an aluminum foil having a thickness of μm is adhered can maintain an error rate of 1 × 10 ⁷ or less even after information recording, reproduction, and erasure are repeated 10 ⁶ times. Both the magneto-optical disk having a thinner aluminum foil bonded thereto and the magneto-optical disk having a thicker aluminum foil bonded thereto have an increased error rate. This is because it is not possible to obtain a sufficient frictional heat radiation effect unless a certain amount of thick aluminum foil is bonded.
Conversely, as the thickness of the aluminum foil increases, the magnetic field of the magnetic field generator becomes more difficult to transmit.

<Experimental Example 2> An aluminum foil having a thickness of 20 μm was adhered on a reflective layer of a magneto-optical disk manufactured in the same manner as in Experimental Example 1 with an adhesive, and then stearic acid was placed on the aluminum foil. Was spin-coated and dried to produce a magneto-optical disk with a lubricating layer.
The magneto-optical disk according to the experimental example 2 is mounted on various drive devices including the magnetic field generating device of FIG. 1 and having different levels s of the magnetic field generating device to record, reproduce, and read information. Erase was performed and the error rate was measured.
FIG. 6 shows the relationship between the size of the step s and the error rate. As is clear from FIG. 6, providing a slight step s in the magnetic field generator (for example, about 0.1 μm) is effective in improving the error rate, but increasing the step s to 40 μm or more causes the error rate to increase. And the step s is about 52 μm
In this case, the error rate becomes worse than when the magnetic field generator having no step s is used. This is because when the step s becomes excessive, the magnetic field of the magnetic field generator does not reach the magnetic layer.

<Experimental Example 3> The magneto-optical disk according to Experimental Example 1 and the magneto-optical disk according to the comparative example described in the section of Experimental Example 1 were subjected to a temperature of 80 ° C. and a relative humidity of 90% in an environment of 10%.
After 00 hours, the relationship between the thickness of the aluminum foil and the total number of defects was examined. FIG. 7 shows the result. As is apparent from FIG. 7, when an aluminum foil is adhered on the reflective layer, there is a remarkable effect in reducing defects. In particular, when an aluminum foil having a thickness of 1 μm or more is bonded, defects can be minimized. Experimental examples 1 and 3 show that the thickness of the aluminum foil adhered on the reflective layer is preferably 1 to 50 μm.

[0030]

As described above, according to the present invention,
As a magnetic field generator for applying a bias magnetic field to the magnetic layer, a contact-type magnetic field generator including a magnetic field generator that does not contact the magneto-optical recording medium and a medium sliding unit that contacts the magneto-optical recording medium is used. The frictional heat generated by sliding between the magneto-optical recording medium and the contact-type magnetic field generator does not directly act on the laser beam-irradiated portion of the magnetic layer. Since the temperature rise of the magnetic layer is controlled, the temperature rise of the magnetic layer by the laser beam can be easily and reliably controlled, and erroneous recording and erasure of information due to inappropriate temperature rise of the magnetic layer can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a drive device that executes a magneto-optical recording method according to the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of a magnetic field generating unit and a medium sliding unit with respect to a recording track.

FIG. 3 is a side view showing another example of the magnetic field generator.

FIG. 4 is a side view showing still another example of the magnetic field generator.

FIG. 5 is a graph showing a relationship between an aluminum foil thickness and an error rate.

FIG. 6 is a graph showing a relationship between a step of the magnetic field generator and an error rate.

FIG. 7 is a graph showing the relationship between the thickness of an aluminum foil and the total number of defects.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Magneto-optical recording medium 12 Objective lens 13 Magnetic field generator 14 Yoke 14a, 14b Outer yoke 14c Center yoke 15 Coil s Step

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyuki Suzuki 1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell Co., Ltd.

Claims (1)

[Claims] An optical head and a contact-type magnetic field generator are disposed on both sides of a magneto-optical recording medium so as to face each other, and the magneto-optical recording medium is relatively positioned with respect to the optical head and the magnetic field generator. While driving, the optical head irradiates the magnetic layer of the magneto-optical recording medium with a laser beam, and the magnetic field generator applies a magnetic field to the irradiated portion of the laser beam, thereby reading information recorded on the magnetic layer. In the magneto-optical erasing method for performing erasing, frictional heat generated by sliding between the magneto-optical recording medium and the contact type magnetic field generator is not directly applied to a laser beam irradiated portion of the magnetic layer, and the optical head is A magneto-optical erasing method, wherein the temperature rise of the magnetic layer is controlled by the intensity of a laser beam applied to the magnetic layer.