JPH07210905A - Magneto-optical disk - Google Patents

Abstract

PURPOSE:To obtain stable sliding performance by forming an overcoating layer with a UV curing resin and internally incorporating the polyether denatured polysiloxane expressed by specific formula into this resin. CONSTITUTION:The overcoating layer is composed of the UV curing resin and the polyether denatured polysiloxane having the molecular structure expressed by formula I is internally incorporated to 'the-overcoating layer. The sliding performance is added to the layer by the polyether denatured polysiloxane. The layer has the sliding performance together with protective performance and both performances are maintained even after preservation in a high-temp. and low-temp. environment and under a high-temp. and high- humidity environment. The polyether denatured polysiloxane has such excellent effect of imparting the sliding performance to the layer and is stably held in and on the UV curing resin and, therefore, its effect is surely maintained even after sliding over many times of a magnetic head and the stable sliding performance is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk suitable for use in a sliding recording system.

[0002]

2. Description of the Related Art In a magneto-optical recording system, a magnetic thin film is partially heated above a Curie point or a temperature compensation point to eliminate the coercive force of this portion and magnetize in the direction of a recording magnetic field applied from the outside. The basic principle is to reverse the direction of the above, and it is being put to practical use in an optical file system, an external storage device of a computer, or a recording device of audio and video information.

As a magneto-optical disk used in this magneto-optical recording system, a recording magnetic layer having a large magneto-optical effect and having an easy axis of magnetization in the direction perpendicular to the film surface on one main surface of a transparent substrate made of polycarbonate or the like. Layer (for example, a rare earth-transition metal alloy amorphous thin film), a reflective layer, and a dielectric layer are laminated to form a recording portion, and in order to prevent corrosion of the recording portion, an ultraviolet curable resin is formed on the recording portion. It is known that an overcoat layer made of, for example, is formed so as to cover the overcoat layer.

By the way, the magneto-optical recording method is roughly classified into an optical modulation method and a magnetic field modulation method. Among them, the magnetic field modulation method is noted because it can be overwritten. For example, the diameter is about 64 mm. The adoption as a recording method for small magneto-optical discs is under consideration.

The above-mentioned magnetic field modulation method writes information in a magnetic thin film by reversing the applied magnetic field at a high speed, and the magnetic field is usually applied by a magnetic head having magnetic field generating means.

In this case, a magnetic head applying a high-speed reversal magnetic field can generate only a very small magnetic field due to various restrictions, and the magnetic head must be as close to the recording magnetic layer as possible.

Therefore, in such a magnetic field modulation method, adoption of a sliding recording method in which a magnetic head is brought into direct contact with the disk surface of a magnetic disk and recording is performed while sliding is being considered. If this sliding recording method is adopted, a sufficient magnetic force can be applied to the recording magnetic layer even with the magnetic head that applies the high-speed reversal magnetic field. Moreover,
The method in which the head floats above the disk surface requires a complicated servo mechanism to keep the distance between the disk surface and the head constant, but the sliding recording method does not require such a servo mechanism. is there. Therefore, it is also advantageous in simplifying and downsizing the device.

[0008]

By the way, in the sliding recording system, the magnetic head is arranged on the side of the overcoat layer of the magneto-optical disk and directly slides on the surface of the overcoat layer. Therefore, it is an important requirement for the magneto-optical disk used in the sliding recording system that the overcoat layer can withstand the sliding of the head.

However, in view of the conventional magneto-optical disk from this point of view, the ultraviolet curable resin layer formed as the overcoat layer in the conventional magneto-optical disk has a large frictional force with respect to the head. For this reason, it is unsuitable for use in the sliding recording system as it is, and it is necessary to further provide a sliding film on the overcoat layer or add sliding performance to the overcoat layer.

In this case, if a sliding film is further provided on the overcoat layer, the number of manufacturing steps is increased and the cost is increased. Therefore, it is more preferable to provide the overcoat layer with sliding performance as well as protection performance. I can say. For example, if an ultraviolet-curing resin that has sliding performance as well as protection performance, or one in which a lubricant is added to the ultraviolet-curing resin is used as the overcoat layer material, an overcoat layer that has sliding performance in almost the same process as the current process. Can be obtained.

However, the ultraviolet curable resin having excellent protection performance has insufficient sliding performance, and if the sliding performance is to be provided, the protection performance is insufficient, and the ultraviolet curing resin has both the protection performance and the sliding performance at the same time. Is rare. Further, even a resin having both properties has a drawback that it deteriorates when left in a high temperature and high humidity environment, and it is difficult to obtain an overcoat layer for sliding recording only with an ultraviolet curable resin.

On the other hand, the lubricant to be added to the UV-curable resin layer has not only excellent lubricity but also good compatibility with the resin, and can slide in an environment of −25 to 70 ° C. Moreover, it is necessary that the sliding performance and the protection performance are maintained even after storage under the environment of -40 to 80 ° C, and there are more severe requirements than the lubricant used in magnetic media (video tape, floppy disk, etc.). Desired. Therefore, organic lubricants such as fatty acid esters, which are usually used as lubricants in magnetic media, do not meet the above requirements and are insufficient, and the selection range of lubricants is limited.

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and has both protection performance and sliding performance, and both performances are high temperature, low temperature environment, high temperature and high humidity. An object of the present invention is to provide a magneto-optical disk that can be maintained even after being stored in an environment.

[0014]

In order to achieve the above object, the magneto-optical disk of the present invention is a magneto-optical disk comprising a transparent substrate on which a recording magnetic layer and an overcoat layer are laminated. The layer is characterized by being made of an ultraviolet curable resin and internally added with a polyether-modified polysiloxane represented by Chemical formula 2.

[0015]

[Chemical 2]

[0016]

In the magneto-optical disk, when the overcoat layer is made of an ultraviolet curable resin, and the polyether-modified polysiloxane having a predetermined molecular structure is internally added to the overcoat layer, the polyether-modified polysiloxane slides. Dynamic performance is added, and sliding performance as well as protection performance is provided, and both performances are maintained even after storage under high temperature and low temperature environments and high temperature and high humidity environments.

Further, the above polyether-modified polysiloxane is excellent in the effect of imparting sliding performance as described above, and
Since it is stably held in the ultraviolet curable resin and on the surface, the effect is reliably maintained even after the magnetic head has been slid many times, and stable sliding performance is obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings.

In the magneto-optical disk of the present invention, as shown in FIG. 1, an optical head 2 and a magnetic head 3 are arranged to face each other with the magneto-optical disk 1 interposed therebetween, and the magnetic head 3 is opposed to the magneto-optical disk 1. It is used in a sliding recording method in which a signal is recorded while sliding.

More specifically, as shown in FIG. 4, the magneto-optical disk 1 is incorporated in a cartridge 21 which can be freely loaded and ejected in a recording / reproducing apparatus, and is opened in the cartridge 21 when recording a signal. A magnetic head for magnetic field modulation recording from a window 22 (window on the disk surface side on which the recording magnetic layer and its protective film are formed) via a supporting member 23 composed of a leaf spring, a gimbal spring, etc. on the disk surface. 3 is arranged, and the magnetic field for recording is generated by the magnetic head 3
Is applied more.

Further, the cartridge 21 also has a window on the surface opposite to the magnetic head 3 with the magneto-optical disk 1 interposed therebetween, and the optical head 2 is arranged so as to face the window. At the time of recording, the optical head 2 irradiates the recording surface of the magneto-optical disc 1 placed in the magnetic field applied by the recording magnetic head 3 with laser light to heat the portion a of the recording surface. As the magneto-optical disk 1 rotates, the irradiation point a
Rapidly cools, and a recording pit having a magnetization direction (perpendicular magnetic recording) corresponding to the direction of the applied magnetic field is formed in the recording magnetic layer. Further, the optical head 2 is also used for reading the binary data recorded by the above method by the Kerr effect, by irradiating the optical head with the irradiation power lower than that during recording.

The optical head 2 never contacts the disk surface, but the magnetic head 3 simplifies the device,
For the purpose of downsizing and power consumption reduction, a method of contacting and sliding on the disk surface may be used at least during recording.

Then, the magneto-optical disk 1 according to the present embodiment.
The recording magnetic layer 5 is laminated on one main surface of the substrate 4, and the surface of the recording magnetic layer 5 is covered with an overcoat layer 6. The overcoat layer 6 serves as the magnetic head 3.
Is slid by.

The substrate 4 is a disk-shaped transparent substrate having a thickness of about 4 mm, and its material is not only plastic materials such as acrylic resin, polycarbonate resin, polyolefin resin, epoxy resin, but also glass and the like. It

The recording magnetic layer 5 is an amorphous magnetic thin film having a direction of easy magnetization in a direction perpendicular to the film surface, and it has excellent magneto-optical characteristics and has a large coercive force at room temperature. Also, it is desirable to have a Curie point near 200 ° C. As a recording material satisfying such a condition, a rare earth-transition metal alloy amorphous thin film or the like can be mentioned.
A bFeCo-based amorphous thin film is suitable. An additional element such as Cr may be added to the recording magnetic layer 5 for the purpose of improving the corrosion resistance.

The overcoat layer 6 is the recording magnetic layer 5.
It is provided to protect the equipment from external shock and to isolate it from atmospheric water and oxygen.

Here, in the magneto-optical disk according to the present embodiment, since recording is performed while the magnetic head 3 slides on the disk surface, the overcoat layer 6 is made of an ultraviolet curable resin and the overcoat layer 6 is formed. A polyether-modified polysiloxane represented by Chemical Formula 2 is internally added to the layer 6 to prevent abrasion due to sliding and ensure the running performance of the magnetic head.

That is, the polyether-modified polysiloxane functions as a lubricant. This polyether modified polysiloxane is chemically inert,
Suitable as a lubricant with a low pour point (melting point) (melting point: <-40 ° C), high thermal decomposition temperature (thermal decomposition temperature:> 200 ° C), a wide variety of viscosities, and a very small viscosity temperature dependency. In addition to having the above characteristics, it has excellent compatibility with the resin and is suitable for internal addition to the resin.

Therefore, by internally adding such a polyether-modified polysiloxane to the overcoat layer, sliding performance is added to the overcoat layer, and the frictional force on the magnetic head is significantly reduced.

The above polyether-modified polysiloxane is preferably ^{one in which} the ether chain of R ^{1 in} Chemical formula 2 is composed of ethylene oxide and / or propylene oxide, and modification of only propylene oxide is particularly preferred.

The ultraviolet curable resin containing such silicone oil may be any of those usually used as the material for the overcoat layer of a magneto-optical disk, since it is excellent in waterproofness. Acrylic UV curable resin is suitable. In addition, the thickness of the overcoat layer is 10 μ from the viewpoint of securing strength and device configuration.
It is about m.

The above is a basic example of the structure of the magneto-optical disk of the present invention. In the magneto-optical disk of the present invention, a silicone oil is formed on the overcoat layer in which the polyether-modified polysiloxane is further added. You may choose to coat it. As a result, for example, when fine dust or the like adhering to the disk surface is wiped off with an alcohol cloth, the polyether-modified polysiloxane internally added is also wiped off and the lubrication performance is prevented from being impaired.

When the silicone oil is top-coated as described above, the polyether-modified polysiloxane in the overcoat layer is 10% by weight or less, and the thickness of the silicone oil to be top-coated is preferably about 70 nm. If the coating thickness of the top coat silicone oil is too thin, the lubricating effect cannot be sufficiently obtained. On the other hand, if it is too thick, the surface becomes sticky and dust or the like is likely to adhere.

As the silicone oil to be top-coated on the UV-curable resin layer, it is not necessary to consider the compatibility with the resin as in the case of internally adding it to the resin. You can use it. The degree of polymerization is preferably about 10 to 50,000.

[0035]

[Chemical 3]

Further, the magneto-optical disk of the present invention, as in the case of a normal magneto-optical disk, has functional layers other than the recording magnetic layer, that is, the dielectric layer 7, as shown in FIG.
8, a reflective layer 9 and the like are provided. For example, the first dielectric layer 7, the recording magnetic layer 5, the second dielectric layer 8 and the reflective layer 9 are provided on the substrate 4.
It is also possible to provide a recording section 10 composed of layers and cover the overcoat layer 6 on the recording section 10.

As the dielectric layers 7 and 8, oxides and nitrides can be used. However, since oxygen in the dielectric may adversely affect the recording magnetic layer 5, nitride is more preferable. Preferably, silicon nitride, aluminum nitride, or the like is suitable as the substance that does not transmit oxygen and moisture and can sufficiently transmit the used laser beam.

The reflective layer 9 is the second dielectric layer 8 described above.
It is preferable to use a high-reflectance film that reflects 70% or more of the laser light at the boundary with the film, and a non-magnetic metal vapor deposition film is preferable. The reflective layer 9 is preferably a good thermal conductor, and aluminum is suitable in consideration of availability and film formation.

Next, a magneto-optical disk having the above structure was actually manufactured, and the effect of internally adding the polyether-modified polysiloxane to the overcoat layer was examined.

First, a recording magnetic layer is formed on a substrate, and an overcoat layer containing silicone oil is formed on the recording magnetic layer to form a magneto-optical disk (Example disk 1).
Was produced. Then, the frictional force of the manufactured magneto-optical disk was measured.

The overcoat layer contains 2% by weight of propylene oxide-modified dimethylpolysiloxane as shown in Chemical formula 4 in polyester / polyfunctional acrylate.
It was formed by adding it, dispersing it well, applying it to a substrate by a spin coating method, and then curing it with a high pressure mercury lamp.

[0042]

[Chemical 4]

The friction force of the overcoat layer was measured by a spin stand under normal temperature environment and high temperature environment (temperature 70 ° C.).
The measurement was carried out under conditions of a low temperature environment (temperature -15 ° C) and after storage in a high temperature and high humidity environment (80 ° C, 95% RH, 100 hr).

As shown in FIG. 3, the spin stand used for the measurement includes a disk table 11, a plastic head 12, a load converter 13, a bridge box 14 having a temperature compensation function, a strain amplifier 15, an A / D converter 16, It is composed of a personal computer 17. In this spin stand, when the disc table 11 on which the disc is placed is rotated, the load is applied to the load converter 13 by the frictional force generated between the disc and the plastic head 12. This load is converted into an electric signal and is converted to bridge box 14, strain amplifier 15, A /
Personal computer 17 through D converter 16
Entered in.

Here, using such a spin stand, the measurement conditions were set to a head pressure of 2 g and a linear velocity of 1.4 m / sec, and the normal temperature environment and the high temperature environment (temperature 70
C.), in a low temperature environment (temperature -15.degree. C.) and after storage in a high temperature and high humidity environment (80.degree. C., 95% RH, 100 h), the frictional force was measured.

For comparison, a magneto-optical disk (comparative example disk 1) in which an organic lubricant diglycerin tetralaurate was added to the overcoat layer instead of silicone oil, and a magneto-optical disk in which isocetyl stearate was added were used. The frictional force was similarly measured for the disk (comparative disk 2) and the magneto-optical disk in which the lubricant was not added to the overcoat layer (comparative example disk 3).

The frictional force of each magneto-optical disk is also shown in Table 1.

[0048]

[Table 1]

As can be seen from Table 1, the disc 1 of the example in which the propylene oxide-modified dimethylpolysiloxane was added as a lubricant to the overcoat layer was compared to the disc 3 of the comparative example in which the lubricant was not added, under normal temperature environment. ,
The frictional force is low in any of the high temperature environment, the low temperature environment, and the high temperature and high humidity environment after storage.

On the other hand, in Comparative Example Disk 1 to which diglycerin tetralaurate was added as a lubricant, the frictional force after storage under normal temperature and high temperature environments and under high temperature and high humidity environment was
Although the value is relatively low, the frictional force is extremely high in a low temperature environment.

The comparative disc 2 containing isocetyl stearate has a comparatively low frictional force in a room temperature environment, but it has a frictional coefficient after being stored in a high temperature environment and a high temperature and high humidity environment. The force was extremely high, and the frictional force was too large to measure in a low temperature environment.

Therefore, in order to obtain good slidability from the low temperature to the high temperature environment and to obtain good slidability even after storage in the hot and humid environment, Conventionally used organic lubricants such as diglycerin tetralaurate and isocetyl stearate have insufficient sliding performance after storage in high-temperature or low-temperature environments, high-temperature and high-humidity environments. Siloxane has been found to be suitable.

[0053]

As is apparent from the above description, in the magneto-optical disk of the present invention, the overcoat layer is composed of an ultraviolet curable resin, and the polyether-modified polysiloxane having a predetermined molecular structure is formed in the overcoat layer. Since the overcoat layer has sliding performance as well as protection performance, both performances are maintained even after storage under high temperature and low temperature environment and high temperature and high humidity environment, and stable sliding performance. Is obtained. Therefore, according to the present invention, it is possible to obtain a practical magneto-optical disk exhibiting a good sliding performance even under a harsh environment and for a sliding recording system.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a first embodiment of a magneto-optical disk of the present invention, together with the schematic structure of a sliding type magneto-optical recording system.

FIG. 2 is a sectional view showing a configuration of a modified example of the magneto-optical disk according to the first embodiment.

FIG. 3 is a schematic diagram showing a configuration of a measuring device for measuring a frictional force of a magneto-optical disk with respect to a head.

FIG. 4 is a perspective view showing a structure of a cartridge having a magneto-optical disk built therein, together with a schematic structure of a sliding type magneto-optical recording system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magneto-optical disk 2 ... Optical head 3 ... Magnetic head 4 ... Substrate 5 ... Recording magnetic layer 6 ... Overcoat layer 7 ... 1st dielectric layer 8 ... ..Second dielectric layer 9 ... Reflective layer

Claims (1)

[Claims] 1. A magneto-optical disk comprising a recording magnetic layer and an overcoat layer laminated on a transparent substrate, wherein the overcoat layer is made of an ultraviolet curable resin, and the polyether-modified polysiloxane represented by Chemical Formula 1 is used. A magneto-optical disk characterized by being internally added. [Chemical 1]