JPS6028049A - Optothermomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having an improved magnetooptic effect and corrosion resistance by forming a recording layer consisting of a thin magnetic film in which the compsn. ratio of specific additives to an amorphous magnetic material is changed on a base side and the opposite side thereof on the base plate and making the coercive force on both sides different. CONSTITUTION:A curing type silicone resin is coated on a glass base plate 1 and is dried to form a heat insulating layer 2. ZrO2 is then deposited thereon by evaporation with an electron beam or the like to form an anti-reflecting layer 3 and thereafter magnetic layers 4a, 4b consisting of different compsns. formed by contg. >=1 kind among Ge, Si, Ti, Co, Cr and Ni as additives in an amorphous magnetic material such as GdTbFe having a large Kerr rotating angle and low Curie point are formed thereon in this order. For example, (Fe76 Gd12Tb12)80Co20 is used for the layer 4a and Fe76Gd12Tb12 for the layer 4b. SiO as a protection layer 5 is then deposited by evaporation on the layer 4b and a glass base plate 7 for protection is provided via an adhesive layer 6 on the layer 5. The high-sensitivity recording medium having 50-1,000Oe coercive force on the base plate 1 side and 1,000-4,000Oe on the opposite side thereof is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in a magneto-optical recording medium that is used in magneto-optical memories, magnetic recording, display elements, etc. and can be read using magneto-optic effects such as the magnetic Kerr effect or the Faraday effect. .

Conventionally, Mnn1, MnCuB have been used as photothermal magnetic recording media.
Polycrystalline thin films such as GdC01GdFe, TbFe
, DyFe, GdTbFq'rbnype1GdF
Amorphous thin films such as 6CO1TbFeCo and GdTbCQ, and single crystal thin films such as GdIG are known.

Among these thin films, there are various issues such as film formability when manufacturing large-area thin films at temperatures near room temperature, writing efficiency for writing signals with small photothermal energy, and S/N ratio of written signals (for reading). Recently, the amorphous thin film is considered to be excellent for use in photothermal magnetic recording media, taking into consideration the readout efficiency of GdTbFe.In particular, GdTbFe has a large Kerr rotation angle and is Since it has a single point, it is ideal for photothermal magnetic recording media.If ni, ae, co, etc. are added to these amorphous magnetic materials, an even greater magneto-optical effect can be obtained, but the Curie point increases and the recording sensitivity decreases. There is a disadvantage that the value decreases.

In addition, amorphous magnetic materials such as GdTbFe generally have poor corrosion resistance and are corroded in a humid atmosphere, resulting in deterioration of magnetic properties. Si
Although the corrosion resistance is improved by adding elements such as , Cr, and Ti, there is still a drawback that the Curie point increases and the recording sensitivity decreases.

In order to eliminate these drawbacks, K has conventionally provided a protective layer on the recording magnetic layer made of an amorphous magnetic material, or created an air sandwich structure or a bonded structure in which the recording magnetic layer is sealed with an inert gas. Disk-shaped photothermal magnetic recording media have been proposed.

An object of the present invention is to provide a photothermal magnetic recording medium with excellent magneto-optic effects and good recording sensitivity.

This objective is achieved by the following photothermal magnetic recording medium.

In a photothermal magnetic recording medium in which a magnetic thin film recording layer and, if necessary, an auxiliary layer are provided on a substrate, the magnetic thin film recording layer is made of an amorphous magnetic material containing at least one kind of additive, and the substrate side of the recording layer is and a photothermal magnetic recording medium characterized in that the composition ratio of the additive to the entire magnetic material is changed on the opposite side to make the coercive force different.

The coercive force of the magnetic thin film recording layer is Sθ~10000 on the substrate side.
It is particularly preferred that θ is 10θ0−+θθ00θ on the opposite side.

Furthermore, it is particularly preferable to contain at least one of elements such as Co, Bi, Cr, ce, Si, Ti, and Ni.

Here, the amorphous magnetic thin film is usually composed of a rare earth element group such as ca, 'rb, Dy, etc. and a transition metal element group such as Fe, Co, etc., and each is sputtered to a film thickness θθ/~0 using a high frequency sputtering device. .2 μm thick.

The present invention can be applied to a photothermal magnetic recording medium having an air sandwich structure or a bonded structure. In addition, between the writing side substrate and the photothermal magnetic recording layer, a heat insulating layer such as an organic resin, a layer made of a dye or pigment that is transparent to the light used and has a high refractive index when formed, or a layer made of a Ti ,cr,
Metals such as zn, Al, and Si! ? ,,-ha'rio
A protective layer made of an oxide such as , IAI, O, , sio, I cr2o3 can be formed. Also,
It is possible to provide various auxiliary layers such as a layer on which index marks and tracking marks are written, or to use a write-side substrate whose surface is processed to be porous. Recording layer-
The adhesive layer for bonding the protective substrate and the attached substrate is Diana [Ryoe Chemical ■], Coal Top [Nippon Kako Paper ■],
V, P, M (Nihon Kagaku Sangyo ■), Ferroguard [Ronco Laboratories, Inc., USA], Zelasto [Ocean Liquefied Gas]
, Anticorrosion layer containing volatile rust preventive agent such as Killes Guard [Nippon Kagaku Sangyo ■], Metal Guard [Mobil Oil ■], Ruston [Tobi Chemical Co., Ltd.], C, R, C, Dialate [Ryoe Chemical Co., Ltd.] ■An anticorrosion layer containing an oil-soluble rust preventive agent such as A
Metal fine powder containing layer containing metal fine powder such as L, Sn, Zn, Ti, Cr, MgO, BaO, CaO, Al,
Q,, CaCl2゜KOH, NaOH, Ca5Q1-
A desiccant-containing layer containing a desiccant such as % O, Sin, -xi(, O, P2O, activated alumina, Mg(CIO,), ZnBr, etc., 2.'I, O-trimethylpyridine.

Sodium dimethylglycine, Tris (can also be replaced with a hydroxy-containing layer).

The photothermal magnetic recording medium of the present invention has excellent magneto-optic effects and can improve recording sensitivity by forming the recording layer so that the coercive force differs between the substrate side and the opposite side. Furthermore,
Additives in the recording layer are ce and si.

When added to elements such as Ti, the magneto-optical effect improves, and
Corrosion resistance can also be improved.

EXAMPLES The present invention will be specifically described below with reference to Examples.

Example/ A photothermal magnetic recording medium having the structure shown in FIG. 1 was manufactured as follows.

Diameter/20■, thickness l! TM flat glass as a substrate, and on it, a curable silicone resin (product name: SR-Col110 Resin, manufacturer: Toray Silicone Co., Ltd.) was applied using a spinner coating machine to a dry film thickness of 0.3 μm. It was coated and dried at 750°C for 2 hours to form a heat insulating layer. Next, an antireflection layer 3 was formed by depositing ZROT to a thickness of θ/μm by electron beam heating using a vacuum deposition apparatus. Next, the first layer tIa of the magnetic thin film recording layer is formed by sputtering using a high frequency sputtering device.
a, 6cd, 2Tb+2)811co, film thickness θ03
The film was formed in μm. The coercive force was adjusted to /300e. As the co-layer pb of the magnetic thin film recording layer, F876Gd,! A film of Tb,2 was formed to a film thickness of θθS μm. The coercive force was adjusted to 3θ000e. Further, as a protective layer S, sio was deposited to a thickness of θ μm by electron beam heating using a vacuum deposition apparatus. This was bonded to a protective glass substrate 7 using an adhesive layer B to produce a photothermal magnetic recording medium.

In order to evaluate the magneto-optic effect of this photothermal magnetic recording medium, the Kerr rotation angle was measured. Furthermore, in order to evaluate the recording sensitivity and read efficiency, the quality of the SA ratio was determined by measuring the bias magnetic field required for recording at the recording frequency SMH2 and by analyzing the waveform of the reproduced signal.

Recording was performed using the following device. The optical head used had a semiconductor laser (g20 nm) with an output of /SmW as a light source, could irradiate the surface of the recording layer as a minute spot of ~72 μmO, and had an electromagnet that could apply a magnetic field perpendicular to the recording layer. photothermal magnetic recording medium /gθθr
The recording layer was rotated at pm to uniformly magnetize the recording layer, and a laser was pulsed to perform pit recording by changing the frequency at a duty of 50%. In addition, a bias magnetic field was applied using electromagnetic force. For reading and reproducing, an IMW semiconductor laser was used as a light source, and the recording layer was irradiated for the recording time, and the reflected light was detected by a detector via a polarizer.The photothermal magnetic recording medium was also kept at a constant temperature of 45°C and a relative humidity of 3%. A corrosion resistance test was conducted for 00 hours in a humidity chamber, and the change in Kerr rotation angle was determined as a ratio to the initial value. For comparison, the magnetic thin film recording layer did not have a laminated structure, and Fe76G (i,, Tb1., coercive force/left 00b, adjusted to coercive force 30,000e) was used (Ff37+1aa, 'rb,
) Two types of photothermal magnetic recording media manufactured in the same manner as in Example 1 were also tested at the same time, except that a recording layer of sn ao 2° was formed to a thickness θ/ttm. The results are shown in Table 1.

As is clear from Table 1, rare earths with different coercive forces...
A photothermal magnetic recording medium that has a recording layer with a layered structure of amorphous magnetic thin films of transition metals has a larger magneto-optic effect than a photothermal magnetic recording medium that has a single layered recording layer, and can be used at high frequencies. Can record signals.

As the first layer pa of the magnetic thin film recording layer, the coercive force/! ;
Adjusted to 00e (Fe1. Ga,, Tb,,
) so Bi, and 300 as the second layer lIb.
A photothermal magnetic recording medium was manufactured in the same manner as in Example except that FB, Gd, Tb, adjusted to 00e were formed. The magneto-optic effect, recording sensitivity, and read efficiency of this photothermal magnetic recording medium were evaluated in the same manner as in Example. For comparison, F 876 ca, whose magnetic thin film recording layer did not have a laminated structure and whose coercive force was adjusted to 3000 oe.
rb129 coercive force/! ; Adjusted to 00e ( F'e7
A photothermal magnetic recording medium of the same type as in Example 1 was also tested at the same time, except that the recording layer of a act, 'rb, )ao B12Q was formed to a thickness of θ/μm. The results are shown in Table 1.

As is clear from Table 1, photothermal magnetic recording media that have a recording layer with a laminated structure of amorphous magnetic thin films made of rare earth-transition metals with different coercive forces are better than photothermal magnetic recording media that have a recording layer with a single layer structure. It has a greater magneto-optical effect than magnetic recording media, and can record higher frequency signals.

x... This shows a case where a noise pattern appears before recording bits are formed when a bias magnetic field is applied for recording.

The Kerr rotation angle was measured from a transparent substrate (glass) and the measurement wavelength was g 20 nm.

Change in Kerr rotation angle...Himio side 3 relative to initial value A photothermal magnetic recording medium having a magnetic thin film recording layer having the laminated structure shown in Table 2 was manufactured in the same manner as in Example. The magneto-optical effect, recording sensitivity, and read efficiency of these photothermal magnetic recording media were evaluated in the same manner as in Examples. In addition, these photothermal magnetic recording media are 45'C1 relative humidity port]
A corrosion resistance test was conducted for 500 hours in a constant temperature and humidity chamber, and changes in the Kerr rotation angle were measured. For comparison, the magnetic thin film recording layer did not have a laminated structure and the coercive force of Fe76Gd1□Tb12 was adjusted to 300 oooe, coercive force/! ;Adjusted to Ooe (Fe76 Gd12 Tb12)8o
Adjusted to G”2o + anti-magnetic cuff 300e (Fe76
Gd12 'rb1□)8n S12゜, coercive force/,!
;Adjusted to 00e (Fe7. Gd, 2'rb, 2
) Seven types of photothermal magnetic recording media manufactured in the same manner as in Example 1 were also tested at the same time, except that the recording layer of so T12Q was formed to a thickness of θ/μm. The results are shown in Table 2.

As is clear from Table 2, photothermal magnetic recording media with a recording layer of a laminated structure of amorphous magnetic thin films of rare earth-transition metals with different coercive forces are better than photothermal magnetic recording media with a recording layer of a single layer structure. It has a greater magneto-optical effect than magnetic recording media, and can record higher frequency signals. Besides, Ni, Cr, ce
Corrosion resistance is improved by adding elements such as , Si, and Ti.

×...A bias magnetic field is applied for recording.
If a noise pattern appears before recording pits are formed, the Kerr rotation angle changes... Ratio to the initial value In the above embodiment, the recording layer is a laminated structure of two layers with different coercive forces. However, these layers only control the incorporation of additives;
It can be formed continuously in the same device, resulting in excellent productivity. Further, the present invention is not limited to a laminated structure, and it is also possible to form a photothermal magnetic recording medium in which the composition of the magnetic material of the recording layer changes continuously from the substrate side to the opposite side. An example of this is shown below.

Example q A photothermal magnetic recording medium having the structure shown in the first article was produced as follows.

A flat glass plate with a diameter of 20 cm and a thickness of 15 cm was used as a substrate, and a curable silicone resin (product name: 5R-2
10 resin, Manufacturer: Tone Silicone Co., Ltd.)
was applied using a spinner coater to a dry film thickness of O8 μm, and dried at /kO°C for 2 hours to form a heat insulating layer λ. Next, using a VC vacuum evaporation apparatus, ZrO2 is deposited to a film thickness of θ/μm by electron beam heating to form a reflective layer 3. Next, a magnetic thin film recording layer was formed using a high frequency sputtering device. Iron (Fe) was used as the target for Suno (Tsutaring), and cobalt (Co) was mask-deposited using a vacuum evaporation method to a thickness of 4 tpm so as to occupy 20% of the area.Next, on this target The chip area ratio of gadolinium (ad) and terbium (Tb) was set on the target so that the area ratio (Te(Fe76ca12'rb12)) was 8°cQ2o. Pressure is /θ T
After evacuation to a value of Orr, argon gas was flowed to adjust the value to kX/OTorr, and sputtering was performed. At first, leave the shutter closed for 300 seconds.
Power was applied to press batter for 2e minutes.

Next, the shutter was opened once and sputtering was continued for 10 minutes. The coercive force was set to /300e on the surface of the substrate and 30,000e on the opposite side. Furthermore, as a protective layer S
iO was deposited to a film thickness of θ μm by electron beam heating using a vacuum evaporation apparatus. This was bonded to a protective glass substrate 7 using an adhesive layer B to produce a photothermal magnetic recording medium. The composition of the prepared medium was analyzed as follows. When the magnetic thin film formed under the conditions of the example was examined by fluorescent X-ray analysis and chemical analysis, the presence of cobalt (CO) element was confirmed. Furthermore, when the surface of the magnetic thin film forming the interface ψ with the left side of the protective layer was examined by electron spectroscopy, it was found that cobalt (CO
) elements were not detected. From the above results, it was found that the cobalt element was distributed near the interface with the heat insulating layer and had already disappeared by the time the film formation was completed. This magneto-optical recording medium was evaluated in the same manner as in Example. Further, similar to Example 1, a corrosion resistance test was conducted at 6%° C. and 5% relative humidity.

These results are shown in Table 3.

In the above examples, ce, si, etc. were used as additives, but other additives such as N1. Cr or the like can also be used.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams showing the structure of the photothermal magnetic recording medium of the present invention, respectively. /, 7...Glass substrate...Insulating layer 3...Antireflection layer +, +a, gb...Magnetic thin film recording layer 9'...・Interface q between magnetic thin film recording layer, protective layer and ′
'...Interface S between the magnetic thin film recording layer and the heat insulating layer...
...Protective layer 6...Adhesive layer Patent applicant Canon Co., Ltd. Figure 1 Figure 2

Claims (1)

[Scope of Claims] (]) A photothermal magnetic recording medium in which a magnetic thin film recording layer and, if necessary, an auxiliary layer are provided on a substrate, wherein the magnetic thin film recording layer is amorphous (containing at least one type of additive). A photothermal magnetic recording medium characterized in that the recording layer is made of a highly magnetic material, and has a different composition ratio of the additive to the entire magnetic material on the substrate side and the opposite side of the recording layer, thereby making the coercive force different. The coercive force of the magnetic thin film recording layer is 30 on the substrate side.
~/0000e 1000~11000 on the other side
0θ. The photothermal magnetic recording medium according to claim 1. (3) The @ additive is Ge, Sj-, Ti-, Co, B
2. The photothermal magnetic recording medium according to claim 1, comprising at least seven of i, Cr, and Ni.