JPH04318344A - Magneto-optical recording medium and driving device thereof - Google Patents

Abstract

PURPOSE:To provide the magneto-optical recording medium which allows the recording, reproducing and erasing of information with the driving device having a magnetic field generator of a contact type. CONSTITUTION:Thin films including at least a magnetic layer 4 are formed on a transparent substrate 2. A high-thermal conductivity layer 8 is provided via a heat insulating layer 7 on the thin films. Further, a lubricating layer 9 is provided on the surface of this high thermal conductivity layer 8. The magnetic field generator having a magnetic field generating surface without having contact with the magneto-optical recording medium is used as the magnetic field generator. For a higher effect, the magnetic field generating surface is disposed to face the position irradiated with a laser beam spot and a medium- sliding surface is disposed off the recording tracks.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a magneto-optical recording medium and a drive device thereof, and in particular, the influence of frictional heat generated by sliding between the magneto-optical recording medium and a magnetic field generator provided in the drive device. Concerning means for eliminating.

0002

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

There are two types of magnetic field generators that apply a bias magnetic field to the magnetic layer: a contact type that slides on the magneto-optical recording medium when the medium is driven, and a non-contact type that is held at a position separated from the magneto-optical recording medium. However, a contact-type magnetic field generator can place the magnetic field generating part closer to the magnetic layer, and the distance from the magnetic field generating part to the magnetic layer is always almost constant regardless of the surface runout of the medium. It 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, contact-type magnetic field generators have the disadvantage that the thin film of the magneto-optical recording medium is easily damaged by wear or impact.

[0004] In order to solve this drawback, conventionally, a lubricant layer is formed on a thin film as described in, for example, Japanese Patent Laid-Open No. 64-42039, and
As described in Japanese Patent No. 4-43834 and Japanese Unexamined Patent Application Publication No. 1-227241, it has been proposed that a polymer sheet or a thin plate of non-magnetic metal is formed on a thin film.

[0005]

[Problem to be Solved by the Invention] In order to enable the use of a contact type magnetic field generator, it is not enough to simply improve the abrasion resistance and impact resistance of the magneto-optical recording medium as in the prior art. , some means is required to eliminate the influence of frictional heat generated by sliding between the magneto-optical recording medium and the magnetic field generator. That is, if the temperature of the magnetic layer is increased due to frictional heat, it becomes difficult to control the temperature of the magnetic layer by laser beam irradiation, and information is more likely to be recorded or erased incorrectly.

The present invention has been made to solve these problems, and provides a magneto-optical recording medium with a structure in which the temperature of the magnetic layer is not raised by frictional heat, and a magnetic field generation structure with a structure in which frictional heat does not act on the recording track. An object of the present invention is to provide a drive device including a device.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a magneto-optical recording medium in which a thin film including at least a magnetic layer is formed on a transparent substrate, and the magnetic layer is formed through the transparent substrate. In a magneto-optical recording medium in which information is recorded and erased by applying a bias magnetic field to the magnetic layer while irradiating the layer with a laser beam, a high heat conductive layer is provided on the thin film via a heat insulating layer, and A lubricating layer was provided on the surface of the conductive layer.

[0008] Regarding the drive device, an optical head that irradiates a laser beam spot onto a magnetic layer via a magneto-optical recording medium and a magnetic field generator that applies a bias magnetic field to the magnetic layer are arranged opposite to each other. In the drive device for a magneto-optical recording medium, the magnetic field generating device is formed with a magnetic field generating part and a medium sliding surface that are not in contact with the magneto-optical recording medium, and the magnetic field generating part is irradiated with the laser beam spot. The medium sliding surface was placed outside the recording track.

[0009]

[Operation] According to the first means, the heat generated by the sliding between the magneto-optical recording medium and the magnetic field generator is diffused in the film surface direction through the high thermal conductivity layer, and is also propagated toward the magnetic layer side by the heat insulating layer. Since this is prevented, the temperature of the magnetic layer is hardly increased due to frictional heat. Therefore, the temperature of the magnetic layer can be easily controlled by laser beam irradiation, and erroneous recording and erasing of information can be prevented. Furthermore, since a lubricating layer is formed on the surface on which the magnetic field generator slides, the wear resistance of the magneto-optical recording medium is improved. Furthermore, since the heat insulating layer, the high thermal conductivity layer, and the lubricating layer are laminated on the magnetic layer, both the impact resistance and corrosion resistance of the magnetic layer are improved.

Further, according to the second means, since the magnetic field generating device does not slide on the recording track where the laser beam spot is accessed and information is recorded, reproduced, and erased, the magneto-optical recording medium and the magnetic field are The frictional heat generated by sliding with the generator does not directly act on the recording track,
The influence of frictional heat can be alleviated compared to the case where the magnetic field generator slides on the recording track. Therefore, similarly to the above, temperature control of the magnetic layer by laser beam irradiation becomes easy, and erroneous recording or erasing of information is prevented.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a main part showing an example of a magneto-optical recording medium according to the present invention, and FIG. 2 is a plan view. As shown in FIG. 1, the magneto-optical recording medium of the present invention includes a transparent substrate 2 on which a preformat pattern 1 such as a guide groove for guiding a laser beam spot and a pre-pit for displaying the address of a recording area is formed on one side. , a first enhancement layer 3 supported on the preformat pattern forming surface of the transparent substrate 2, a magnetic layer 4 laminated on the first enhancement layer 3, and a second enhancement layer 5 laminated on the magnetic layer 4. and the second
A reflective layer 6 laminated on the enhancement layer 5, a heat insulating layer 7 laminated on the reflective layer 6, a high heat conductive layer 8 laminated on the heat insulating layer 7, and a lubricant layer laminated on the high heat conductive layer 8. It is composed of layer 9.

As shown in FIG. 2, 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 has a center hole 2a in the center. It is formed into a disk shape with a desired diameter. As shown in FIG. 2, the preformat pattern 1 is formed in a spiral shape or a concentric circle shape concentric with the center hole 2a. Note that the method for forming the preformat pattern 1 is a well-known matter and is not directly related to the gist of the present invention, so a description thereof will be omitted.

The first enhancement layer 3 multiple-reflects the signal reproduction beam between the transparent substrate 2 and the magnetic layer 4 and increases the apparent Kerr rotation angle, thereby improving reproduction sensitivity. , is formed of a dielectric material such as silicon nitride, which has a higher optical refractive index than the transparent substrate 1 .

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

The second enhancement layer 5 prevents the heat of the magnetic layer 4 from diffusing into the reflective layer 6, protects the magnetic layer 4 from impact and corrosion, and further protects the magnetic layer 4 and the reflective layer 6. The layer is made of the same dielectric material as the first enhancement layer 3, and is made of the same dielectric material as the first enhancement layer 3. be done.

The reflective layer 6 is for preventing moisture permeation into the magnetic layer 4 and for 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 from an alloy material mainly composed of these metal materials, 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, polyfinylene oxide, polysulfone,
Polyimide, polyamideimide, polyesterimide,
It can also be formed with a vapor-deposited film of a heat-resistant polymer material such as polybenzimidazole, or if the high thermal conductive layer 8 is formed of a foil, the reflective layer 6 and the high thermal conductive layer 8 are bonded together. It can also be formed using adhesive or adhesive.

The high thermal conductivity layer 8 is made of aluminum, copper, tin,
Silicon, cerium, lanthanum, indium, germanium, lead, bismuth, tellurium, tantalum, scandium, yttrium, titanium, zirconium, cadmium,
Zinc, selenium, antimony, gallium, magnesium,
Metallic or nonmetallic materials such as boron, carbon, or CeO2, La2O3, SiO, SiO2, In2O
3, Al2O3, GeO, GeO2, PbO, SnO,
SnO2, Bi2O3, TeO2, Ta2O5, Sc2
O3, Y2O3, TiO2, ZrO2, V2O5, Nb
2O5, Cr2O3, WO2, WO3, CdS, ZnS
, CdSe, ZnSe, In2S3, In2Se3,S
b2S3, Sb2Se3, Ga2S3, Ga2Se3,
GeS, GeSe, GeSe2, SnS, SnS2, S
nSe, SnSe2, PbS, PbSe, Bi2Se3
, Bi2S3, MgF2, CeF2, CaF2, TaN
, Si3N4, AlN, BN, TiB2, B4C, Si
It can be formed with a vapor-deposited film of an alloy such as C or an inorganic compound, or it can be formed with a foil of a substance selected from the above. Further, the high thermal conductivity layer 8 can also be formed using a polymeric material in which powder or granules of the substance selected from the above are dispersed.

The lubricating layer 9 is formed using a lubricant such as hexadecane, butyl stearate, oleic acid, ethyl stearate, stearic acid, octadecylamine, solid stearic acid, or the like. As a means for forming the lubricating layer 9,
A method of coating the surface of the high heat conductive layer 8 with a solvent solution of a lubricant, a method of pasting a polymer sheet impregnated with a lubricant on the surface of the high heat conductive layer 8, a method of polishing the surface of the high heat conductive layer 8, A method of impregnating a lubricant into the fine recesses formed can be adopted.

The magneto-optical recording medium of the above embodiment has a reflective layer 6.
A high heat conductive layer 8 is formed on the surface of the reflective layer 7 via a heat insulating layer 7, and a lubricating layer 9 is further formed on this high heat conductive layer 8, so that each of these layers 7 to 9 acts as a protective film for the layers below the reflective layer 6. This improves the abrasion resistance and impact resistance when the magnetic field generator is slid, as well as the corrosion resistance of the magnetic layer. In addition, frictional heat generated by sliding between the magneto-optical recording medium and the magnetic field generator is diffused in the film surface direction through the high heat conduction layer 8, and is prevented from propagating toward the magnetic layer 4 by the heat insulating layer 7. , the temperature of the magnetic layer 4 is hardly increased due to frictional heat. Therefore, the temperature of the magnetic layer can be easily controlled by laser beam irradiation, and erroneous recording and erasing of information can be prevented.

Although the above embodiments have been explained using a disk-shaped magneto-optical recording medium as an example, it is of course applicable to other shapes of magneto-optical recording media such as a card-shaped magneto-optical recording medium.

Further, in the above embodiment, the magneto-optical recording medium has a four-layer structure in which the base of the heat insulating layer 7 includes the first enhancement layer 3, the magnetic layer 4, the second enhancement layer 5, and the reflective layer 6. Although the present invention has been described by way of example, the gist of the present invention is not limited thereto, and can be applied to magneto-optical recording media having any film structure having at least a magnetic layer.

Next, an example of a magneto-optical recording medium drive device according to the present invention will be explained with reference to FIG. In FIG. 3, 11 is a magneto-optical recording medium, 12 is an optical head that irradiates a laser beam spot onto the magnetic layer 4 of the magneto-optical recording medium 11, 13 is a magnetic field generator that applies a bias magnetic field to the magnetic layer 4, and others. Portions corresponding to those in FIG. 1 are labeled with the same reference numerals.

As shown in this figure, the drive device of this example includes a yoke 14 made of a ferromagnetic material and a coil 15 wound around a part of the yoke 14 as a magnetism generator 13. It is equipped with an electromagnet. The yoke 14 protects the lubricant layer 9 of the magneto-optical recording medium 11 when the medium is driven.
It is composed of outer yokes 14a, 14b that are in contact with the magneto-optical recording medium 11, and a center yoke 14c that is not in contact with the magneto-optical recording medium 11. The recording magnetic field or the erasing magnetic field H is generated by the recording magnetic field H. Outer yoke 14a
, 14b to the tip of the center yoke 14c, it is sufficient that the step s is large enough to prevent the tip of the center yoke 14c from coming into contact with the magneto-optical recording medium 11. On the other hand, as this step s increases, the magnetic layer 4
In consideration of this, the size of the step s is preferably about 1 to 50 μm. As shown in FIG. 3, the magnetism generator 13 aligns the tip of the center yoke 14c with the optical axis A-
A, and the outer yokes 14a and 14b are arranged so as to contact the outside of the recording track being accessed by the laser beam 16.

In the drive device of the above embodiment, the center yoke 14c, which is a magnetic field generating section, is configured so as not to be in contact with the magneto-optical recording medium 11, and the outer yokes 14a, 1, which are the sliding surfaces of the medium,
4b is brought into contact with the outside of the recording track, as shown in Fig. 3.
As shown in FIG.
The frictional heat J generated by sliding on the recording track does not directly act on the recording track on which information is recorded, reproduced, and erased, and the amount of frictional heat J is lower than that in the case where the magnetic field generator 13 slides on the recording track. The impact can be mitigated. Therefore, the temperature of the magnetic layer can be easily controlled by laser beam irradiation, and erroneous recording and erasing of information can be prevented.

In the above embodiment, the magnetic field generating device 13 is a so-called double-yoke type electromagnet in which the outer yokes 14a and 14b are provided on both sides of the center yoke 14c. As shown in FIG. 4, it is also possible to use a so-called single-yoke type electromagnet in which an outer yoke 14a is provided only on one side of a center yoke (magnetic field generating portion) 14c.

Further, in the above embodiment, the case where an electromagnet is used as the magnetic field generating device 13 was explained as an example, but the same applies when using other types of magnetic field generating device such as a magnetic head or a permanent magnet. configured.

Experimental examples of the present invention will be shown below to clarify the effects of the present invention. <Experimental Example 1> On the preformat pattern transfer surface of a disc-shaped polycarbonate substrate formed by injection molding,
A first enhancement layer made of SiN and terbium-iron-
A magnetic layer made of a cobalt-based amorphous perpendicular magnetization film and a Si
A second enhancement layer made of N and a reflective layer made of AlTi were sequentially laminated by sputtering to produce a large number of magneto-optical disks with the same configuration. Thereafter, various types of aluminum foils having different thicknesses were bonded with an adhesive onto the reflective layers of the separate magneto-optical disks, thereby producing various types of magneto-optical disks having a heat insulating layer and a highly thermally conductive layer. Finally, a benzene solution of stearic acid was spin-coated onto the aluminum foil of each magneto-optical recording medium and dried to produce a magneto-optical disk with a lubricating layer. Further, as a comparative example, a magneto-optical disk was produced in the same manner as in Experimental Example 1 except that the aluminum foil was not bonded and the lubricant layer was not formed. The error rate after the magneto-optical disk according to Experimental Example 1 was installed in a drive device equipped with the magnetic field generating device shown in FIG. was attached to a drive device equipped with a conventional contact-type magnetic field generator, and the error rate was measured after recording, reproducing, and erasing information was repeated 106 times, and the relationship between the thickness of the aluminum foil and the error rate was determined. Examined. The results are shown in Figure 5.
Shown below. As is clear from FIG. 5, all of the magneto-optical disks of Experimental Example 1 had lower error rates than the magneto-optical disks of the comparative example, except for the one to which aluminum foil with a thickness of approximately 54 μm or more was adhered. There is. However, the thickness of aluminum foil has an optimum value, and a magneto-optical disk to which aluminum foil with a thickness of approximately 14 to 42 μm is bonded will remain at 1× Although it is possible to maintain an error rate of 107 or less, the error rate increases for both a magneto-optical disk to which an aluminum foil thinner than this is bonded and a magneto-optical disk to which an aluminum foil thicker than this is bonded. This is because sufficient frictional heat dissipation effect cannot be obtained unless a certain thickness of aluminum foil is adhered, and conversely, the thicker the aluminum foil is, the more difficult it is for the magnetic field of the magnetic field generator to pass through.

<Experimental Example 2> On the reflective layer of a magneto-optical disk prepared in the same manner as in Experimental Example 1, an aluminum foil with a thickness of 20 μm was adhered with an adhesive, and then stearic acid was applied onto the aluminum foil. A magneto-optical disk with a lubricating layer was prepared by spin-coating a benzene solution and drying it. The magneto-optical disk according to Experimental Example 2 was mounted on various drive devices equipped with the magnetic field generating device shown in FIG. Erasing 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 even a slight step s in the magnetic field generator (for example, about 0.1 μm) is effective in improving the error rate, but when the step s is increased to 40 μm or more, the error rate starts to increase. If the step s is about 52 μm or more, the error rate will be worse than when a magnetic field generator without the step s is used. This is because if the step s becomes too large, the magnetic field of the magnetic field generator will not reach the magnetic layer.

<Experiment Example 3> The magneto-optical disk according to Experiment Example 1 and the magneto-optical disk according to the comparative example explained in the column of Experiment Example 1 were heated for 10 minutes in an environment of a temperature of 80° C. and a relative humidity of 90%.
After 00 hours, the relationship between the thickness of the aluminum foil and the total number of defects was investigated. The results are shown in FIG. As is clear from FIG. 7, adhering aluminum foil onto the reflective layer has a significant effect on reducing defects. In particular, bonding aluminum foil with a thickness of 1 μm or more can reduce defects to the lowest level. From Experimental Examples 1 and 3, it can be seen that the thickness of the aluminum foil bonded onto the reflective layer is preferably 1 to 50 μm.

[0031]

As explained above, the magneto-optical recording medium of the present invention has a heat insulating layer, a highly thermally conductive layer, and a lubricating layer sequentially laminated on the surface of the recording layer, so it has excellent wear resistance, impact resistance, and corrosion resistance. At the same time, frictional heat resistance is improved. Therefore, highly reliable information recording, reproduction, and erasing operations can be performed using a drive device equipped with a contact-type magnetic field generation device.

Further, in the drive device of the present invention, the magnetic field generating section is configured so as not to be in contact with the magneto-optical recording medium, and the sliding surface of the medium is brought into contact with the outside of the recording track. The frictional heat generated by sliding with the device does not directly affect the recording track where information is recorded, reproduced, and erased, and the effect of frictional heat is less than when the magnetic field generating device slides on the recording track. can be alleviated. Therefore, the temperature of the magnetic layer can be easily controlled by laser beam irradiation, and erroneous recording and erasing of information can be prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing an example of a magneto-optical recording medium according to the present invention.

FIG. 2 is a plan view showing an example of a magneto-optical recording medium according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a drive device according to the present invention.

FIG. 4 is an explanatory diagram showing another example of a magnetic field generating device.

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

FIG. 6 is a graph diagram showing the relationship between the level difference and the error rate of the magnetic field generating device.

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

[Explanation of symbols]

1 Preformat pattern 2 Transparent substrate 3 First enhancement layer 4 Magnetic layer 5 Second enhancement layer 6 Reflection layer 7 Heat insulation layer 8 High thermal conductivity layer 9 Lubricant layer 11 Magneto-optical recording medium 12 Optical head 13 Magnetic field generator s Step

Claims (9)

[Claims] 1. A thin film including at least a magnetic layer is formed on a transparent substrate, and information is recorded and erased by applying a bias magnetic field to the magnetic layer while irradiating the magnetic layer with a laser beam through the transparent substrate. 1. A magneto-optical recording medium comprising: a highly thermally conductive layer provided on the thin film via a heat insulating layer; and a lubricant layer provided on the surface of the highly thermally conductive layer. 2. The thin film according to claim 1,
a first enhancement layer formed on the transparent substrate; a magnetic layer laminated on the first enhancement layer; a second enhancement layer laminated on the magnetic layer; and a second enhancement layer laminated on the second enhancement layer. 1. A magneto-optical recording medium comprising a reflective layer. 3. The highly thermally conductive layer according to claim 1, wherein the high thermally conductive layer is made of a foil made of a highly thermally conductive material, and the heat insulating layer is made of an adhesive or a pressure-sensitive adhesive for bonding the thin film and the highly thermally conductive layer. What is claimed is: 1. A magneto-optical recording medium comprising: 4. The method according to claim 1, wherein the high heat conductive layer is made of a vapor deposited film of a high heat conductive material, and the heat insulating layer is made of a vapor deposited film of a polymeric material. Magneto-optical recording medium. 5. The magneto-optical recording medium according to claim 1, wherein the thickness of the highly thermally conductive layer is adjusted to a range of 1 to 50 μm. 6. According to claim 3 or 4, the highly thermally conductive substance is aluminum, copper, tin, silicon, an alloy thereof, or a polymeric material in which powder or granules of these substances are dispersed. A magneto-optical recording medium characterized by: 7. An optical head that irradiates a laser beam spot onto a magnetic layer via a magneto-optical recording medium and a magnetic field generator that applies a bias magnetic field to the magnetic layer are disposed opposite to each other, and In a drive device for a magneto-optical recording medium, the device is configured to slide on the magneto-optical recording medium, and the magnetic field generating device includes a magnetic field generating surface and a medium sliding surface that are not in contact with the magneto-optical recording medium. What is claimed is: 1. A drive device for a magneto-optical recording medium, wherein the magnetic field generating surface is disposed opposite to the irradiation position of the laser beam spot, and the medium sliding surface is disposed outside the recording track. 8. A drive device for a magneto-optical recording medium according to claim 6, wherein a step difference between a medium sliding surface and a magnetic field generating surface of the magnetic field generating device is 50 μm or less. 9. A drive device for a magneto-optical recording medium according to claim 6, wherein the magnetic field generating device is an electromagnet, a magnetic head, or a permanent magnet.