JP2729308B2 - Magneto-optical recording element and manufacturing method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording element used for a rewritable disk and the like, and relates to a magneto-optical recording element excellent in weather resistance, hardness and environmental resistance, and a method for producing the same. Things.

[Conventional technology and its problems]

In recent years, rewritable magneto-optical recording media has been actively studied, and this recording method uses a focused laser beam to locally heat the medium, thereby writing bits, and utilizing the magneto-optical effect. The characteristic feature is that an amorphous metal magnetized film composed of a rare earth element and a transition metal element is attracting attention as this medium.

Gb, Tb, Dy, etc. are proposed as the rare earth elements, and Fe, Co, etc. are proposed as one transition metal element.At least one of these elements is selected and combined, thereby forming a medium material, for example, GdDyFe, GdTbFe, DyFeCo and the like.

However, such a magnetic medium has a drawback that it is easily oxidized, and as this oxidation proceeds, the medium becomes transparent and the magneto-optical characteristics are degraded.

In order to solve the above problems, it has been proposed to form a protective layer on the magnetic layer to improve oxidation resistance and corrosion resistance.

Metal such as Ti, Cr, Al, Cu, TiO ₂ , SiO,
Dielectric such as SiO ₂ , MgF ₂ , Si ₃ N ₄ or epoxy type,
Acrylic resins and the like are known.

However, the resin protective layer is still unsatisfactory from the knowledge that it completely prevents intrusion of oxygen and moisture, and the metal, as well as the resin, has low hardness,
Therefore, the surface is easily scratched, and the so-called scratch resistance is poor. In particular, when the magnetic field modulation bias magnetic field applying head is brought close to the magnetic layer, the disk surface and the magnetic field applying head come into contact with each other due to the surface runout of the disk substrate or the vibration of the device itself, which may damage the recording bit or the guide track. (This is called a head crash).

Further, the magneto-optical recording element is required to have excellent environmental resistance so as not to lower the recording sensitivity even when the temperature or humidity changes or under severe conditions.

[Object of the invention]

Accordingly, an object of the present invention is to provide a high-performance magneto-optical recording element having high recording sensitivity while preventing corrosion of a magnetic medium.

It is another object of the present invention to provide a highly reliable magneto-optical recording element having improved scratch resistance of a protective layer for a magnetic medium and excellent environmental resistance.

Still another object of the present invention is to eliminate head crash,
An object of the present invention is to provide a magneto-optical recording element suitable for modulating a magnetic field.

[Means for solving the problem]

According to the present invention, an amorphous magnetic layer having an easy axis of magnetization in a direction perpendicular to the film surface on a substrate, and on the magnetic layer, the following formula TiM _x : wherein M represents a nitrogen atom or a carbon atom; Is 0.05
And a magneto-optical recording element having a nonmagnetic protective layer made of a titanium compound having a number of from 0.90 to 0.90.

According to the present invention, there is provided a method for manufacturing a magneto-optical recording element comprising forming an amorphous magnetic layer having an easy axis of magnetization in a direction perpendicular to a film surface on a substrate and a non-magnetic protective layer by vapor phase growth. formula TiM _x expression by reactive sputtering using a target and sputtering gas consisting of a combination of a reactive gas selected from the group consisting of inert gas and nitrogen compound gas and a carbon compound gas onto the magnetic layer made of Wherein M is a nitrogen atom or a carbon atom, and x is a number in the range of 0.05 to 0.90.

 Hereinafter, the present invention will be described in detail.

The present invention provides a non-magnetic protective layer formed of a compound in which a nitrogen atom or a carbon atom is contained in a titanium atom in an atomic ratio smaller than the stoichiometric amount, thereby increasing the C / N ratio of the magneto-optical recording element to a high level. It is based on the finding that the hardness, thermal shock resistance, and corrosion resistance of the element can be improved while maintaining.

The magneto-optical recording element of the present invention can take various shapes such as a card in addition to a disk as a substrate on which a magnetic layer is formed. Hereinafter, a disk substrate will be described in detail.

FIGS. 1 and 2 show a typical layer structure of the magneto-optical recording element of the present invention, in which a magnetic layer 3 is formed on a substrate 1 via an interference layer 2 and the magnetic layer 3 is formed on the magnetic layer 3. titanium compounds such as (hereinafter abbreviated as TiM _x) to form a protective layer 4 made of. Alternatively, as shown in FIG. 2, the interference layer 2 may be omitted from the laminated structure of FIG. If desired, another type of protective layer 5 can be provided on the nonmagnetic protective layer 4.

In the present invention, the composition ratio of nitrogen (N) or carbon (C) atoms to titanium (Ti) atoms in the TiM _x protective layer 4 is set to fall within a range of 0.05 to 0.90, preferably 0.10 to 0.75. It is important to set.

When the atomic composition ratio is less than 0.05, the hardness decreases, and the film forming rate decreases. On the other hand, when it exceeds 0.90, the thermal shock resistance is inferior, or the film forming rate rapidly decreases.

As described above, the composition ratio of Ti atoms to N or C atoms is important in the TiM _x protective layer, but the bonding state between the atoms has not yet been sufficiently elucidated. However, X-ray diffraction analysis confirms that the lower nitride or carbide of titanium exists in an amorphous state or in the form of a mixed crystal of Ti and TiN or TiC.

The thickness of the TiM _x protective layer 4 is 200 to 2000 mm, preferably 6
The angle may be set in the range of 00 to 1000 °, and within this range, a high protective film effect can be realized without lowering the recording sensitivity.

Further, TiM _x protective layer 4 is one in which the main constituent atoms of Ti atoms and N or C atom, does not exclude the inclusion of atoms other than the above atoms. For example, when formed by a reactive sputtering method, a Ti metal is used for the target, but other metals included in the target may be included with the film formation, and these other metals include, for example, A
There are l, Cr, Si, Mn, Mo, V, Zr and the like. These atoms is allowed to be mixed up to 5 atomic% per total TiM _x protective layer.

The non-magnetic protective layer of the present invention is generally 800 to 4000 kg / mm ² ,
In particular, micro Vickers hardness Hv of 1000 to 2000 kg / mm ²
(A load of 50 kg / mm ² ), and the specific resistance value is generally 1 × 10 ^{2 to} 3 × 10 ³ μΩ- _cm , particularly 5 × 1
It is preferably in the range of 0 ^{2 to} 2 × 10 ³ μΩ- _cm .

Nonmagnetic protective layer of the present invention, TiM _x, in addition to _{TiC x, TiO x C y,} T
iO _x N _y , TiN _x C _y , TiO _x N _y C _z , (0.05 ≦ x + y + z ≦ 0.09)
Can consist of:

The magnetic layer is composed of an amorphous perpendicular magnetization film, for example, GdDy
Fe, GdTbFe, TbFeCo, DyFeCo, NdGdDyFe, GdTbDyFe, GdTbFeC
o, TbDyFeCo, GdDyFeCo, NdDyFeCo, etc.

Further, the interference layer 2 is made of a dielectric material and is interposed between the substrate 1 and the magnetic layer 3 to form an enhancement structure, thereby increasing the apparent Kerr rotation angle to increase the figure of merit, and further increasing the laser index. The recording density by light can be improved. The interference layer 2 is made of nitride of Si, Al, Ti, Si
Carbide, Cd, Zn sulfide, Mg fluoride, Al, Ce, Zr, S
It is formed of a material such as an oxide of i, Cd, and Bi.

Further, a glass plate or a plastic plate is used for the substrate 1, and the plastic substrate material includes polycarbonate resin, epoxy resin, polyester resin, acrylic resin and the like.

In the present invention, for example, another protective layer 5 may be laminated on the protective layer 4 shown in these figures without any problem. The protective layer 5 includes a metal layer or a resin layer.
Alternatively, as shown in FIG. 3, two configurations of FIG. 2 are prepared,
This may be bonded via the adhesive layer 5a.

The magneto-optical recording element of the present invention can be formed by thin film forming means, for example, a vacuum deposition method, a sputtering method,
There are an ion plating method, an ion implantation method, a plating method, and the like.

When forming the TiM _x protective layer, any of the thin film forming means described above can be used, but the reactive sputtering method is advantageous because the composition can be easily controlled as desired.

When forming a TiM _x protective layer by this reactive sputtering method, Ti metal is arranged as a target, and argon (Ar) gas, neon (Ne) gas, krypton (Kr) gas or xenon is used as a sputtering gas. (X
e) Use a combination of an inert gas such as a gas and a reactive gas such as a nitrogen compound gas or a carbon compound gas.

As the nitrogen compound, N ₂ , NH ₃ , NO, N ₂ O, NO _{2 and the} like are used, and as the carbon compound gas, a hydrocarbon gas such as methane, ethane, and propane, and an alcohol gas such as methanol and ethanol are used. used. As a matter of course,
Nitrogen gas may be used for lower nitrides, and carbon compound gas may be used for carbides. In addition, a film of a compound containing two or more atoms of O, N, and C can be formed using two or more of these gases.

Other conditions in the reactive sputtering may be known per se. For example, the sputtering pressure is generally in the range of 1 to 50 mTorr, especially 2 to 10 mTorr.

The production method of the present invention generally uses a sputtering apparatus provided with a target for forming an interference layer, a target for forming a magnetic layer, and a titanium metal target.
This is performed by sequentially forming a magnetic layer and a TiM _x non-magnetic protective layer by sputtering. The substrate on which each layer is formed is taken out, and a resin protective layer and the like are formed on the nonmagnetic protective layer.

For the resin protective layer, various materials can be used as long as the material has a low ion permeability.For example, in the case of an ultraviolet curable resin having a low moisture permeability, it is necessary to prevent the penetration of C1 ions and OH ions. Can be said to be desirable. This UV-curable resin includes epoxy, polyester, acrylic, and acrylic urethane resins.

The resin protective layer has a thickness of 0.1 to 50 μm, preferably 2 to 50 μm.
It is desirable to set within the range of 20 μm to 0.1 μm
If it is less than 50%, no improvement in corrosion resistance / corrosion resistance can be expected.
If it exceeds μm, the adhesiveness of the film itself will be reduced and the tendency to peel off will be remarkable.

〔Example〕

 Next, examples of the present invention will be described.

(Example 1) An interference layer (a layer containing silicon nitride as a main component and containing Y atoms, Al atoms, and O atoms in a disk substrate made of carbonate using an inter-frequency three-source magnetron sputtering apparatus, which is a so-called , YSiAlON layer ... layer called yttrium sialon layer)
Further, a GdDyFe perpendicular magnetization film (the atomic composition ratio of this film is (Gy _0.6 Dy _0.4 ) _0.24 Fe _0.76 ) was sequentially formed with a thickness of 325 °. Then, a TiN _x protective layer was continuously formed in the same device at a thickness of 650 ° to manufacture a magneto-optical recording element having the structure shown in FIG.

The deposition condition of this TiN _x protective layer is that the arrival vacuum degree is 10 ^-4 mTorr
And, with a target of Ti metal, input power power of 500W, Ar gas flow rate of 33sccM, sputtering gas pressure of 3mTo
rr, and the N ₂ gas flow rate was variously changed within 10 sccm. The gas exhaust control valve was used to adjust the sputtering gas pressure to 3 mTorr even when introducing N ₂ gas.

In such a case, the atomic composition ratio of the TiN _x protective layer to the N ₂ gas flow rate is as shown in Table 1. This atomic composition ratio is determined by X-ray photoelectron spectroscopy, and is an average value obtained by repeating the experiment five times for each sample.

(Example 2) In this example, when the hardness of each sample shown in (Example 1) was measured with a micro-Vickers hardness tester (load: 50 kg / mm ² ), the result shown in FIG. 4 was obtained.

In FIG. 4, the horizontal axis represents the N ₂ gas flow rate, the vertical axis represents the micro-Vickers hardness Hv, and the measurement plot of this example is ○.

As is evident from the results, a remarkably high hardness characteristic was obtained as compared with Ti metal by only slightly flowing N ₂ gas.

(Example 3) Next, in this example, when the temperature / humidity cycle test was performed on each sample shown in (Example 1) and the C / N ratio was measured, the results shown in Table 2 were obtained. .

C / N ratio is 4m / sec for flux, recording frequency 1MHz, bias magnetic field 2
It was determined under the conditions of 00 Gauss. Since the thickness of the GdDyFe perpendicular magnetization film is set to 325 °, the TiN _x protective layer also functions as a reflection film, and therefore, the C / N ratio varies depending on gloss. The reflection function is generated because the thickness of the magnetic layer is set to about 300 mm.
In the case of 600 mm or more, the reflection function can be ignored.

The temperature and humidity cycle test was repeated 10 times under the conditions based on JIS-C5024, and the evaluation was classified into three stages. The mark ○ indicates that there was almost no change in both appearance and properties, and the mark △ indicates that dot-like corrosion was slightly generated.
This is a case where there is no problem in practical use, and a mark “x” indicates a case where corrosion, blistering of the film, or cracking in the film is remarkable.

As is clear from Table 2, it can be seen that the samples No. 3, No. 4 and No. 5 have excellent environmental resistance by the temperature and humidity cycle test. Samples No. 2 and No. 6 had some point-like corrosion, but did not hinder practical use.

However, sample No. 1 had many spot-like corrosion and film blistering, and samples No. 7 and No. 8 had many radial cracks.

In addition, it can be seen that the sample Nos. 6, 7, and 8 have remarkably small C / N ratios.

(Example 4) In this example, a TiC _x protective layer was formed under the same conditions as in (Example 1) except that CH ₄ gas was used instead of the N ₂ gas used in (Example 1). Table 3 shows the relationship between the CH ₄ gas flow rate and the atomic composition ratio.

(Example 5) Next, in this example, when the hardness was measured for Sample Nos. 1, 2, and 3 shown in (Example 4) in the same manner as in (Example 2), the results shown in FIG. 4 were obtained. Was.

 The mark in the figure indicates a measurement plot of this example.

As is evident from the results, a remarkable high hardness characteristic was obtained as compared with Ti metal by slightly flowing CH ₄ gas.

(Example 6) Next, the sample shown in (Example 4) was subjected to a temperature-humidity cycle test, and the C / N ratio was measured. As a result, the results shown in Table 4 were obtained. The test conditions and measurement conditions are as shown in (Example 3).

As is clear from Table 4, it can be seen that the samples No. 2, No. 3 and No. 4 have excellent environmental resistance by the temperature and humidity cycle test.

Further, the present inventors have combinations of N ₂ gas and CH ₄ gas in addition to the above embodiment, a combination of N ₂ gas and O ₂ gas, by the combination of O ₂ gas and CH ₄ gas, respectively TiNC, TiON, the TiOC It was confirmed that a similar effect could be obtained even if a nonmagnetic protective layer of a compound was formed.

[Effects of the Invention] As described above, according to the magneto-optical recording element of the present invention, the protective layer has a high hardness, and is excellent in environmental resistance.
As a result, a high-performance and highly-reliable element could be provided.

Further, since the magneto-optical recording element of the present invention has the high hardness protective layer as described above, there is no head crash, which is useful for magnetic field modulation.

[Brief description of the drawings]

1, 2 and 3 are sectional views showing the laminated structure of the magneto-optical recording element of the present invention, and FIG. 4 is a diagram showing the hardness of the titanium compound layer with respect to the flow rate of nitrogen gas or methane gas. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Interference layer 3 ... Magnetic layer 4 ... Titanium compound protective layer 5 ... Protective layer

Claims (2)

(57) [Claims] 1. A following formula TiM _x expression amorphous magnetic layer and a magnetic layer having an axis of easy magnetization in a direction perpendicular to the film surface on the substrate, M represents a nitrogen atom or a carbon atom, x is 0.05 A non-magnetic protective layer made of a titanium compound having a number of from 0.90 to 0.90. 2. A method of manufacturing a magneto-optical recording element comprising forming an amorphous magnetic layer having an easy axis of magnetization in a direction perpendicular to the film surface and a nonmagnetic protective layer on a substrate by vapor phase growth, comprising a titanium metal. The following formula TiM _x on the magnetic layer by reactive sputtering using a target and an inert gas and a sputtering gas consisting of a combination of a reactive gas selected from the group consisting of nitrogen compound gas and carbon compound gas: M represents a nitrogen atom or a carbon atom, and x represents a number of 0.05 to 0.90. A method for manufacturing a magneto-optical recording element, comprising forming a nonmagnetic protective layer having a composition of