JP2743088B2 - Magneto-optical recording element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a rewritable magneto-optical recording element in which a magnetic medium is a rare earth-transition metal amorphous metal alloy.

[Prior art and its problems]

Recently, rewritable magneto-optical recording elements have been rapidly developed. Although this magnetic medium is an amorphous metal alloy of a rare earth-transition metal, it has been proposed to form a protective layer because the magneto-optical properties are reduced by oxidation.

The present inventors have already proposed a protective layer of titanium oxide in Japanese Patent Application No. 62-218345.

According to the magneto-optical recording element proposed above, the recording sensitivity did not decrease even under changes in temperature and humidity and under severe conditions, and high hardness and high corrosion resistance were obtained.

Incidentally, in the case of the titanium (Ti) -based protective layer as described above, it can be a passivation film having excellent oxidation resistance. However, in order to form the passivation film over a wide area, an amorphous film is preferable. Has been confirmed. For this purpose, oxygen is added as in the above-mentioned proposal, but it is also proposed to add a metalloid semiconductor element such as B, C, and Si.

According to experiments performed by the present inventors, a Ti-based protective layer to which oxygen and a metalloid semiconductor element are added, that is, a chemical formula (Ti
O _α ) M _β ··· M: semi-metallic semiconductor element, α, β: protective layer represented by atomic ratio ... becomes amorphous or mixed crystal state, and cracks are formed in the layer itself. It was confirmed that the film became a dense film that was difficult to enter and formed an excellent protective layer that was easy to form a passivation film.

However, in the case of a magneto-optical disk provided with a (TiO _α ) M _β protective layer, the written recording bit causes a peak shift, thereby reducing the phase margin, thereby increasing the rotation speed of the disk itself and increasing the speed and speed. There is a problem that it is difficult to perform high-density recording.

Accordingly, an object of the present invention is to provide a high-performance and high-reliability magneto-optical recording element in which a film for protecting a magnetic layer becomes a passivation film, has excellent oxidation resistance, and can perform high-speed and high-density recording. .

[Means for solving the problem]

In the magneto-optical recording element of the present invention, an amorphous magnetic layer having an easy axis of magnetization at least in a direction perpendicular to the film surface and a non-magnetic layer mainly composed of titanium oxide and containing a semimetal semiconductor element are formed on the substrate. The non-magnetic layer has a layer configuration in which a first layer region and a second layer region are sequentially laminated.
It is characterized in that the composition of both layer regions is represented by the following formulas (i) and (ii).

First layer region (i) ·· (TiO _α ) M _β 0.03 ≦ α ≦ 0.90 0.03 ≦ β ≦ 0.35 Second layer region (ii) ·· (TiO _γ ) M _ε 1.10 ≦ γ ≦ 1.50 0.05 ≦ ε .Ltoreq.0.35 The magneto-optical recording element of the present invention can take various shapes as a substrate. 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 an optical layer is formed on the magnetic layer 3. A protective layer 4 of a titanium oxide containing a metal semiconductor element (M) is formed.
Alternatively, as shown in FIG. 2, the interference layer 2 may be omitted from the laminated structure of FIG.

The present invention is characterized in that the protective layer 4 has a layer configuration in which the first layer region 4a and the second layer region 4b are sequentially stacked as described above.

The first layer region 4a has a smaller oxygen content ratio than the second layer region 4b, and thus has a dense film quality. As a result, an anti-oxidation film having a good oxygen shielding effect can be obtained. In addition, the second layer region 4b has a lower thermal conductivity than the first layer region 4a, and thus serves as a heat diffusion preventing layer. When high-density recording is performed, clogging occurs at bit intervals. Reduces thermal interference in the media.

When such a two-layer region 4a, 4b is laminated, a protective layer having both an excellent anti-oxidation effect and an excellent anti-heat diffusion effect is obtained, and thus the object of the present invention can be achieved.

Although oxygen is contained in Ti metal in both layer regions 4a and 4b, the second layer region 4b contains more oxygen than the first layer region 4a,
Thereby, more crystals such as TiO and TiO ₂ are generated.

Further, the two-layer regions 4a and 4b further include a metalloid semiconductor element M
(E.g., C, B, Si, Ge, P, As, Se, Sb, Te, Bi) in a predetermined range, thereby promoting stable amorphousization,
And, the formation of the passivation layer is facilitated.

Further, the present inventors have found that the first layer region 4a has the following formula (i):
It has been found that the second layer region 4b is preferably set to the composition formula (ii).

(I) ·· (TiO _α ) M _β 0.03 ≦ α ≦ 0.90 preferably 0.10 ≦ α ≦ 0.40 0.03 ≦ β ≦ 0.35 preferably 0.10 ≦ β ≦ 0.30 (ii) · (TiO _γ ) M _ε 1.10 ≦ γ ≦ 1.50 preferably 0.12 ≦ γ ≦ 1.40 0.05 ≦ ε ≦ 0.35 preferably 0.10 ≦ ε ≦ 0.30 The thickness of the two-layer regions 4a and 4b is determined by a desirable range depending on the atomic composition ratio, The second layer region 4b may be set to have a larger thickness than the first layer region 4a.

According to experiments repeatedly performed by the present inventors, the thickness of the first layer region 4a is set within the range of 50 to 300 °, preferably 100 to 200 °, and the thickness of the second layer region 4b is 300-150
The angle is set to 0 °, preferably in the range of 500 to 800 °.

When the thicknesses of the two layer regions 4a and 4b are set in this manner, the respective oxygen blocking effects and the heat diffusion preventing effects are effectively obtained, and a long-term reliable element having excellent thermal stability is obtained.

The protective layer 4 has Ti, O and M atoms as main constituent atoms, but does not exclude the inclusion of atoms other than the above atoms. For example, when formed by a reactive sputtering method, Ti metal or TiM metal is used for the target, but other metals contained in the target may be included along with the film formation. Al Cr, Si, Mn, Mo, V, Zr and the like. Or sometimes with the thin film forming N ₂ gas remaining in the air is mixed. These atoms are allowed to be mixed up to 5 atomic% in the entire protective layer.

The magnetic layer is composed of an amorphous perpendicular magnetization film, for example, GdDy
Fe, GdTbFe, TbFeCo, DyFeCo, GdTbDyFe, GdTbFeCo, TbDyFeC
o, GdDyFeCo and the like.

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 can be improved by light. This interference layer 2 is made of SiN, AlN, SiC, CdS, TiN,
_{ZnS, MgF 2, Al 2 O} 3, CeO 2, ZrO 2, SiO, SiO 2, CdO, is formed by a material such as Bi ₂ O _3.

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.

The present invention is not limited to the layer configurations shown in FIGS. 1 and 2, and for example, another protective layer may be laminated on the protective layer 4 shown in these figures. The protective layer includes a metal layer or a resin layer. This resin includes epoxy-based, polyester-based, acrylic-based, and acrylic-urethane-based resins. Alternatively, as shown in FIG. 3, two configurations shown in FIG. 2 may be prepared and bonded together via the adhesive layer 5.

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.

In the case of forming the protective layer, any of the thin film forming means described above can be used, but the reactive sputtering method is advantageous in that the desired composition control can be easily performed.

When a protective layer is formed by this reactive sputtering method, a Ti metal or a TiM metal is disposed on a target, and an argon (Ar) gas, a neon (Ne) gas, a krypton (Kr) gas or An inert gas such as xenon (Xe) gas and oxygen gas may be used. In this film forming method, inert gas atoms are inevitably mixed into the protective layer.

〔Example〕

 Hereinafter, embodiments of the present invention will be described.

(Example 1) The present invention relates to a continuous high-frequency magnetron sputtering apparatus (interval between the center of rotation of a substrate and the center of a φ5 target is 14 cm,
According to this apparatus, three reaction chambers are continuously arranged, and the reaction chambers are sequentially formed in each of the reaction chambers. Form a film.

First, a φ130 mm polycarbonate disk substrate is mounted in the first reaction chamber, and an interference layer (consisting of silicon nitride as a main component, Y atom, Al atom and O
A layer containing atoms, which is called an amorphous yttrium sialon layer (amorphous YSiAlON layer).
A film having a thickness of 50 mm is formed, and then, in a second reaction chamber, an amorphous GdDyFeTi perpendicular magnetization film (the atomic composition ratio of this film is ｛Gd _0.65
Dy _0.35 ) _0.24 Fe _0.76 ｝ _0.98 Ti _0.02 ) with a thickness of 600 順次. Then, a TiOC protective layer was formed in the third reaction chamber.

 The conditions for forming the TiOC protective layer are as follows.

Target: A carbon chip mounted on a Ti metal plate Ultimate vacuum: 10 ^-6 mTorr Input power: 600 W Argon gas flow: 33 sccM Sputter gas pressure: 3 mTorr Oxygen gas flow: 10 sccM or less (The oxygen gas was ionized by the ion assist method, and the gas exhaust control valve was adjusted so that the sputtering gas pressure was 3 mTorr even when the oxygen gas was introduced.) The protective layer was formed after the continuous film formation. A UV-curable resin was applied on the substrate, and the resin layer was formed to a thickness of 5 μm to produce a magneto-optical disk.

In addition, when oxygen gas is not introduced in forming the TiOC protective layer, a TiC protective layer can be formed. Further, when a metal disk on which no carbon chip is mounted is used as a target, a protective layer of Ti metal can be formed.

Thus, six types of magneto-optical disks having different atomic composition ratios of the protective layer were produced, and the atomic composition ratios were determined by Esca analysis. The results shown in Table 1 were obtained. This atomic composition ratio is an average value obtained by repeating the measurement five times for each disk.

Further, the internal stress, recording power, and phase margin (amount due to peak shift) of the protective layer of each magneto-optical disk were determined, and a temperature-humidity cycle test was performed. The results shown in Table 1 were obtained. was gotten.

 Each measurement and test method is as follows.

Internal stress The same layer as the above-described protective layer was formed on a glass substrate having a thickness of 75 μm, and the internal stress was determined from the amount of warpage of the substrate after film formation. still,
When the internal stress is a positive value, it indicates a tensile stress, and when the internal stress is a negative value, it indicates a compressive stress.

Recording power For each magneto-optical disk, rotation speed 2400 rpm, frequency 4.9 MHz, duty 25%, bias magnetic field
The optimum recording power at a portion with a radius of γ = 35 mm under the condition of 350 Oe was determined from the secondary high frequency.

Phase Margin On each magneto-optical disk, a signal of a 4192H repetition pattern is recorded under the optimum recording / reproducing condition of the recording power, and the bit error rate (BER) is BER ≦ 1 × 10 ^−6.
The phase margin at the level was determined.

Temperature and humidity cycle test Radius γ = 35 in advance for various magneto-optical disks
mm part, record the initial BER value, then perform a temperature-humidity cycle test (10 cycles) based on JIS-C5024 on the magneto-optical disk to determine the BER value of the same part, and the rate of change Is represented by

When the crystal structures of the protective layers of the four types of magneto-optical disks B, D, E and F were measured by the X-ray diffraction method, the results shown in FIG. 4 were obtained. In addition, in FIG.
a, b, c and d are the magneto-optical disks B, D, E and F, respectively.
And corresponding.

The above measurement was performed by forming the same film as the above-mentioned protective layer on a glass substrate having a thickness of 1.0 mm.

The horizontal axis in FIG. 4 is the scattering activity angle. The vertical axis represents the diffraction intensity, and the scales are the same in all figures. Further, each peak represents Ti, TiO, the presence of TiO _2.

Thus, the following can be seen from the results shown in Table 1 and FIG.

First, as is clear from the results shown in Table 1, the magneto-optical disk D showed the smallest change rate even in the temperature-humidity cycle test, and was three times or less the initial value.

The above results are supported by the results shown in FIG. That is, according to FIG. 2B, the magneto-optical disk D is made of Ti, TiO, TiO ₂
It is recognized that there is a tendency to be amorphous as a whole. Also, according to FIGS. B, c and d, 20 ° <2θ <30
The presence of a halo pattern can be confirmed in ゜, and
The presence of amorphous TiO ₂ is observed by ESCA analysis.

The present inventors consider that the magneto-optical disk D has almost no internal stress in the protective layer, and has obtained excellent durability due to the passivation characteristic inherent to Ti.

Regarding the magneto-optical disks A, B, C, E, and F, corrosion or oxidation of the magnetic layer, cracks in the protective layer, and peeling of the film were observed, though to varying degrees.

Further, the magneto-optical disk E has the largest value of the phase margin, which indicates that it is suitable for high-speed recording. The present inventors believe that the above result is obtained because the thermal conductivity of the protective layer is the lowest, and that the layer is made of TiO ₂ bonds having a lower thermal conductivity than Ti alone.

In addition, the inventors visually observed the surfaces of the magneto-optical disks D and E, and found that both of them had metallic luster.
This is considered to be due to the inclusion of Ti metal.

With respect to the magneto-optical disk F, the surface of the protective layer shows transparency, and the film formation speed is about one digit lower than that of other disks. Therefore, the temperature of the substrate increases due to long-time sputtering. As a result, the substrate was deformed, and as a result, a decrease in C / N was observed. Therefore, it was found that γ> 1.5 could not be adopted.

(Example 2) Next, based on the result of (Example 1), the present inventors combined the respective protective layers of the magneto-optical disks D and E, and formed a two-layer TiO 2 layer.
A C protective layer was formed.

When such a TiOC protective layer is formed, it can be obtained by changing the amount of oxygen gas introduced into the reaction chamber.

Thus, in the magneto-optical disk manufactured in (Example 1), the formation of the first layer region was (TiO _0.23 ) C _0.16 ,
The composition of the layer region is (TiO _1.33 ) C _0.16 , and the thickness of each layer region is changed in various ways. The other layers have the same layer configuration as in (Example 1). As shown, nine types of magneto-optical disks G to 0 were produced. Note that the column of film thickness in the figure represents “thickness of first layer region / thickness of second layer region”.

The phase margins of the various magneto-optical disks thus obtained were measured, and a temperature / humidity cycle test was performed. The results shown in Table 2 were obtained.

As is clear from the table, as a result of the temperature / humidity cycle test of the magneto-optical disks H, I, J, M and N, the rate of increase of the BER with respect to the initial value was 3 times or less, and the phase margin was ±
It was 17 nsec or more, showing excellent durability and good adaptability to high-speed, high-density and high-quality recording.

Thus, it can be seen that the object of the present invention was most advantageously achieved when the thickness of the first layer region was in the range of 50 to 300 ° and the thickness of the second layer region was in the range of 300 to 1500 °.

(Example 3) In forming the same laminated protective layer as in (Example 2),
B, Si, Ge chips are used instead of carbon chips, and other film formation conditions and layer configurations are set to be the same. Thus, the thickness of the first layer region is 200 mm, and the thickness of the second layer region is 200 mm. Various magneto-optical disks P, Q, and R having a thickness of 800 ° and the composition ratios shown in Table 3 were produced.

A temperature-humidity cycle test was performed on these magneto-optical disks, and the phase margin was measured. The results shown in Table 3 were obtained.

As is clear from the results shown in Table 3, excellent durability and good adaptability to high-speed and high-quality recording were exhibited.

In addition, the present inventors have assumed that the above C, B, S
When an experiment similar to that of the present example was performed using P, As, Se, Sb, Te, and Bi in place of each element of i and Ge, it was experimentally confirmed that the effect of the present invention was obtained.

〔The invention's effect〕

As described above, according to the present invention, the protective layer has both an excellent anti-oxidation effect and an excellent effect of preventing thermal diffusion, and as a result, a high-performance and highly-reliable light capable of high-speed and high-density recording. A magnetic recording element could be provided.

[Brief description of the drawings]

1, 2 and 3 are cross-sectional views showing the layer configuration of the magneto-optical recording element of the present invention, and FIGS. 4a, 4b, 4c and 4d are diagrams showing X-ray diffraction charts. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Interference layer 3 ... Magnetic layer 4 ... Protective layer 4a ... 1st layer area 4b ... 2nd layer area

Claims (2)

(57) [Claims] 1. A magneto-optical recording element comprising a substrate and an amorphous magnetic layer having an easy axis of magnetization at least in a direction perpendicular to the film surface and a non-magnetic layer made of titanium oxide. A first layer region and a second layer region are sequentially laminated, and the composition of the first and second layer regions is represented by the following formulas (i) and (ii). Magneto-optical recording element. First layer region (i) ·· (TiO _α ) M _β 0.03 ≦ α ≦ 0.90 0.03 ≦ β ≦ 0.35 Second layer region (ii) ·· (TiO _γ ) M _ε 1.10 ≦ γ ≦ 1.50 0.05 ≦ ε ≦ 0.35 where M represents a metalloid semiconductor element 2. The first layer region has a thickness of 50 to 300 °,
2. The method according to claim 1, wherein the thickness of the second layer region is 300 to 1500 [deg.].
A magneto-optical recording element according to claim 1.