JPH05151632A - Magneto-optical disk - Google Patents

Abstract

PURPOSE:To decrease the vacuum-suction and the friction coefft. of a flying head by forming a protective layer whose surface is roughened by a simple process without using a stamper. CONSTITUTION:In a magneto-optical disk A-1 which is successively laminated with an optical recording layer 2a and a protective layer 3a on a main surface of a substrate 1, the protective layer 3a forms a two-layer structure which is successively laminated with layers incorporating fillers in an insulator layer, and also the surface roughness of the protective layer 3a is 1-100nm Ra in the central line mean roughness. Thus floating characteristics of a flying head are improved. Also the corrosion of the optical recording layer 2a is prevented, and further the sticking of the flying head is prevented.

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 in which an optical recording layer and a protective layer are sequentially laminated on one main surface of a substrate.

[0002]

2. Description of the Related Art At present, magneto-optical discs are widely used for music and images for consumer use.
Further, for example, a WO type magneto-optical disk has begun to be used as an external storage device of a computer or an information processing device for data. In addition, you can read and write as many times as you like
W-type magneto-optical disks are also being developed. These are generally used by sequentially stacking an optical recording layer and a protective layer on a substrate.

Recently, the average particle size of the protective layer of a magneto-optical disk is
It has been reported that 0.7 μm of alumina particles and a stearic acid-based lubricant are added (Page 923 (Presentation number of 37th Joint Symposium on Applied Physics)
29a-G-9) etc.). Also, using a stamper with a frosted surface, transfer the pattern of the resin onto the optical recording layer,
It has also been reported that a protective layer having a roughened surface is formed by transfer (page 922 of the aforementioned proceedings (lecture number 29a-G-8)).
Etc.).

Both of the above reports relate to a so-called magnetic field modulation recording type magneto-optical disk, and have been proposed in particular to solve the problems of abrasion and peeling of the protective layer due to friction with a flying head for recording information. .. The reason for adding alumina to the protective layer is to increase the strength of the protective layer and prevent its abrasion and peeling. Further, the reason why the surface of the protective layer is roughened by the stamper is to prevent the flying head from sticking to the protective layer and enable the flying head to fly smoothly from the magneto-optical disk.

However, the addition of alumina to the protective layer does not change the coefficient of friction with the head, so it is conceivable to add a lubricant, but if this is done, the hardness of the protective layer will decrease, There is a problem that reliability is lowered. In addition, the transfer of the protective layer by the stamper has a problem that the production of the stamper and the transfer of the resin are complicated and the production process is significantly complicated.

[0006]

An object of the present invention is to eliminate the use of the stamper or the like, to form a roughened protective layer in a simple process, and further to reduce the vacuum adsorption and friction coefficient of the flying head. It is an object to provide a magneto-optical disk.

[0007]

The magneto-optical disk of the present invention is a magneto-optical disk in which an optical recording layer and a protective layer are sequentially laminated on one main surface of a substrate, wherein the protective layer comprises an insulating layer and a filler. It is characterized in that it has a two-layer structure in which the contained layers (filler-containing layers) are sequentially laminated, and the surface roughness of the protective layer is 1 to 100 nmRa in terms of center line average roughness.

Here, the optical recording layer means a layer having a multilayer structure including at least a magneto-optical recording layer. A material having electrical insulation may be used for the insulating layer, and for example, a resin layer or an inorganic dielectric layer can be used.
Used in seed layers or layers of more than one species.

[0009]

In general, when the filler is in contact with the optical recording layer, the redox reaction between the filler and the optical recording layer causes corrosion due to the oxidation of the optical recording layer. Further accelerates the oxidation.

However, according to the magneto-optical disk of the present invention, since the insulating layer is interposed between the filler-containing layer which is the upper layer of the protective layer and the optical recording layer, corrosion of the optical recording layer is prevented as much as possible. be able to. Moreover, if the filler-containing layer is made electrically conductive, it can also be prevented from charging.

Further, by appropriately roughening the surface of the protective layer, sticking of the flying head can be prevented as much as possible and good flying can be realized. That is, when the center line average roughness of the protective layer surface is less than 1 nmRa, the coefficient of static friction with the flying head disk is large, and the vacuum adsorption of the flying head occurs, which damages the protective layer of the disk when the flying head floats and lands. However, if the surface roughness is higher than 100 nmRa, the flying head will not fly even if the disk rotates at a specified speed, and the protective layer of the disk will be damaged, reducing reliability. It turned out to be optimal.

The interposition of the insulating layer can prevent the occurrence of birefringence abnormality on the read surface side of the disk at the position where the filler of the filler-containing layer is present. That is, since only the resin shrinks when the resin containing the filler is cured, the filler may exert an external force on the substrate at this time, but the interposition of the insulating layer can avoid this. It should be noted that the lower layer of the filler-containing layer can be expected to have a buffering effect by forming it as a resin layer, and it has been found by research by the present inventors that this thickness is preferably about 2 μm or more.

Further, when the present invention is applied to a laminated magneto-optical disk, it is possible to improve the familiarity between the hot melt adhesive used for bonding and the protective layer and improve the reliability of the bonding. it can.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail with reference to the drawings. In the magneto-optical disk A-1 shown in FIG. 1, an optical recording layer 2a is formed on a main surface of a substrate 1 (having a thickness of 1.2 mm) made of a resin such as polycarbonate by sputtering, and a protective layer 3a is further formed by spin coating. It was formed.

Here, the optical recording layer 2a is composed of a first dielectric layer of amorphous yttrium sialon (thickness of about 100 nm), amorphous.
A Gd-Dy-Fe-based magneto-optical recording layer (about 20 nm thick), a second dielectric layer of amorphous yttrium sialon (about 30 nm thick), and a reflective layer of metallic aluminum (about 100 nm thick) were sequentially laminated. It is a thing. Other materials used for the first and second dielectric layers include silicon nitride, aluminum nitride, silicon carbide, cadmium sulfide, titanium nitride, zinc sulfide, magnesium fluoride, cadmium oxide, and bismuth oxide, either alone or in combination. be able to. As the material of the reflective layer, Cr, Ti, Cu, Ag, SUS, etc. can be used alone or in combination. Further, especially as the material of the magneto-optical recording layer, in addition to Gd-Dy-Fe system, for example, Gd-Dy-Fe, G
d-Tb-Fe, Tb-Fe-Co, Dy-Fe-Co, Gd-Tb-Dy-Fe, Gd-Tb-Fe-Co,
Tb-Dy-Fe-Co, Gd-Dy-Fe-Co, Nd-Gd-Dy-Fe, Nd-Dy-Fe-Co, Nd
A wide variety of alloy systems such as -Gd-Dy-Fe-Co system can be used.

The protective layer 3a comprises an insulating layer 4 as a lower layer and a filler-containing layer 5 as an upper layer. The insulating layer 4 is a urethane acrylate-based UV curable resin (manufactured by Dainippon Ink and Chemicals; The product name SD-301) is applied and formed to a thickness of about 10 μm. Here, as the material of the insulator layer 4, any material having electrical insulation may be used, and in addition to the above materials, examples of the resin include acrylic resin, epoxy resin, polyester resin, acrylic ester resin, and urethane acryl. A UV-curable type, a thermosetting type, an anaerobic-curing type, a moisture-curing type such as a system, a polyether type, or a silicon type can be used. Further, as the inorganic material, silicon nitride, aluminum nitride, silicon carbide, cadmium sulfide, titanium nitride, zinc sulfide, magnesium fluoride, cadmium oxide,
Dielectric materials such as bismuth oxide can be used as one kind or as a mixture of two or more kinds, and these mixtures may have a multilayer structure. The flying head and the optical recording layer 2
Since the distance from a is actually about 25 μm or less, the thickness of the insulator layer 4 is optimally 2 to 24 μm, preferably 4 to 15 μm for reliability in organic materials such as resin. If the thickness of the inorganic material is less than 0.05 μm, reliability cannot be obtained. If the thickness is more than 0.5 μm, the warp of the disk is increased, so the thickness is set to 0.05 to 0.5 μm.

On the other hand, the filler-containing layer 5 is composed of an acrylic acid ester type ultraviolet curable resin (manufactured by Dainippon Ink and Chemicals;
SnO ₂ with an average particle size of about 0.15 μm added to the product name SD-17)
It is formed by coating the above-mentioned filler to a thickness of about 0.15 μm. Here, the filler 6 is made of Sb-added SnO ₂ system or the like, but it does not have to be electrically conductive and may be SiO ₂ or Al ₂ O.
Insulating ceramics such as ₃ , Si ₃ N ₄ , SiC, CdS, ZnS, and SiO may be used. Further, it may be a conductive ceramic or the like, for example, ITO (In ₂ O _{3 with} SnO ₂ added), Sb ₂ O ₃ , Ir
_{O 2, MoO 2, NbO 2} , PtO 2, RuO 2, WO oxides such as _2, MoC, N
Carbides such as bC, TaC, TiC, and WC, and nitrides such as NbN, Ta ₂ N, TiN, ZrN, and VN can also be antistatic, and may be used alone or in combination with the above-mentioned insulating filler.

The magneto-optical disk B-1 shown in FIG.
On the main surface of the substrate 1 made of the same material as the magneto-optical disk A-1, the first dielectric layer of amorphous yttrium sialon (about
75 nm thick), amorphous Gd-Dy-Fe-based magneto-optical recording layer (about 100 nm
Optical recording layer 2 formed by sequentially sputtering (thickness)
b, and a protective layer 3b is further provided thereon. An amorphous yttrium sialon insulator layer 7 is formed by sputtering as the lower layer of the protective layer 3b, and the upper layer is the magneto-optical disk A-1. The filler-containing layer 5 is formed in the same manner as in.

The magneto-optical disk C-1 shown in FIG. 3 is a comparative example, and the protective layer 3a in the magneto-optical disk A-1 is used.
Instead of the above, only the filler-containing layer 5 as the upper layer is provided to form the protective layer 3c.

Next, these magneto-optical disks A-1, B-1, C-1
Approximately 1000 at normal temperature and humidity and 80 ℃, 90% RH
Table 1 shows the results of measuring the error rate (bit error rate; hereinafter abbreviated as BER) of the recording bit before and after inputting the time.
Shown in.

[0021]

[Table 1]

As is clear from Table 1, the magneto-optical disk
Corrosion occurred in C-1 and the BER deteriorated.
No corrosion occurred at -1, B-1 and no change in BER was observed before and after the environmental test. Thus, the presence of the insulating layer in the lower layer prevented corrosion of the optical recording layer.

Further, when the reading surface side of these samples was observed with an optical microscope, as shown in Table 2, in C-1 without the lower layer, birefringence abnormality occurred on the reading surface side, and the lower layer was an inorganic material. Even B-1 had a slight birefringence anomaly on the reading surface side. On the other hand, it was found that in A-1 in which the lower layer is resin, no birefringence abnormality was observed when the thickness of the lower resin layer was 2 μm or more.

[0024]

[Table 2]

Next, in the same manner as in Samples A-1, B-1, and Sample A-1, coating thicknesses of the filler-containing layer 5 and the average particle diameter of the filler 6 were changed to form A-2 to A. Table 3 shows the results of obtaining the optimum surface roughness for -9.

[0026]

[Table 3]

Here, the content of the filler 6 in the resin of the filler-containing layer 5 is about 6 wt%. Further, Sample A-6 is the one in which about 6 wt% of SiO ₂ filler having an average particle size of 0.65 μm is further added to Filler 6, and Sample A-9 has no filler in the upper layer. The surface roughness was measured with a stylus type surface roughness meter. Also, measure the coefficient of dynamic friction and the coefficient of static friction of the surface of the protective layer against the flying head with a friction measuring device, and use the same friction measuring device to measure the disk rotation speed when the flying head floats. The number was measured. Mn-Z for flying head
n Ferrite flying head was used. The surface roughness represents the average value of the centerline average roughness (Ra, measurement length = 0.2 mm) along the diameter direction of the magneto-optical disk, and the filler 6
Indicates the average particle size of the filler.

In all of the above samples, when the filler 6 is added, the surface roughness is increased and the coefficient of friction is decreased as compared with the sample A-9 which is not added. Samples A-1 to A-5 have an appropriate surface roughness of 1 to 10
Since it has 0 nmRa, the flying head crashes at a disk rotation speed of 1800 rpm or less and good results are obtained. Further, in Sample B-1, even when the lower layer was an inorganic film, the same characteristics as in Sample A-1 were obtained, and in Sample A-6, similar characteristics were obtained even when an insulating filler was added.

On the other hand, since the surface roughness of sample A-8 was large, the flying head could not be fully floated up, and a crash occurred even when the disk rotation speed exceeded 1800 rpm. From the above, the surface roughness to prevent such a crash is 1
It was found that ~ 100 nmRa is good, and preferably 1-80 nmRa.

Next, the average particle size of the filler 6 is about 0.65 μm.
Table 4 shows the result of obtaining the optimum value of the concentration of the filler in the upper layer of the protective layer with the coating thickness being about 0.6 μm.

[0031]

[Table 4]

As is clear from Table 4, when the concentration of the filler is 3 wt% or less, the surface roughness sharply decreases and becomes less than 1 nmRa, which is a problem, and when the concentration of the filler exceeds 40 wt%, the viscosity becomes large. It was found that the spin coat was too high to be possible. Then, it was found that the preferable concentration of the filler 6 is 3 to 40 wt%, and more preferably 3 to 30 wt% for keeping the coating thickness constant and maintaining an appropriate surface roughness.

The surface roughening on the surface of the protective layer in the above-described embodiment is not limited to the magneto-optical disk of the magnetic field modulation recording system, and for example, in the so-called bonded magneto-optical disk of the optical modulation system, the bonding is performed. It is also possible to improve the familiarity between the adhesive agent such as hot melt used and the protective layer, and to improve the bonding strength, and it is possible to carry out appropriate modification within the scope not departing from the gist of the present invention.

[0034]

As described above, according to the magneto-optical disk of the present invention, the protective layer has a two-layer structure in which the insulating layer and the layer containing the filler are sequentially laminated, and the surface of the protective layer is formed. Since the centerline average roughness is 1 to 100 nmRa, the roughened protective layer can be formed by a simple method such as spin coating without using a stamper. Also,
By appropriately roughening the surface of the protective layer, sticking of the flying head is prevented as much as possible, and by making the protective layer conductive, dust and other substances are prevented from adhering, and by preventing static electricity, flying It is possible to prevent the head from adsorbing and realize a good flying operation of the flying head.

Further, by using a resin layer as the lower layer, a buffering effect on the upper layer can be provided, and by setting the thickness of the lower layer to 2 μm or more, birefringence abnormality can be prevented as much as possible. It is possible to provide a highly reliable magneto-optical disk.

Further, when the present invention is applied to a laminated type magneto-optical disk, the familiarity between the adhesive such as hot melt for laminating and the protective layer is improved, and the reliability of the laminating is improved. be able to.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a magneto-optical disk A-1 according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a magneto-optical disk B-1 according to an embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of a magneto-optical disk C-1 of a comparative example.

[Explanation of symbols]

1 ... Substrate 2a, 2b ...
.Optical recording layers 3a, 3b, 3c ... Protective layers 4, 7 ...
・ Insulator layer 5 ・ ・ ・ Filler-containing layer 6 ・ ・ ・ Filler A-1, B-1, C-1 ・ ・ ・ Magneto-optical disk

Claims (3)

[Claims] 1. A magneto-optical disk in which an optical recording layer and a protective layer are sequentially laminated on one main surface of a substrate, wherein the protective layer has a two-layer structure in which an insulating layer and a layer containing a filler are sequentially laminated. And a surface roughness of the protective layer as a centerline average roughness of 1 to 100 nmRa. 2. The protective layer comprising the insulator layer and a layer containing a filler is formed of a lower resin layer and an upper resin layer containing a filler.
The magneto-optical disk described in. 3. The magneto-optical disk according to claim 2, wherein the lower resin layer has a thickness of 2 μm or more.