JP3030713B2 - Magneto-optical recording medium and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magneto-optical recording medium, and more particularly to a magneto-optical recording medium characterized by a coating film laminated on a substrate together with a magneto-optical recording magnetic film. is there.

(Prior Art) Among optical recording media, there are conventionally known media of a phase change type, a photochromic type, a magneto-optical type and the like as rewritable types capable of writing and erasing. Among these rewritable types, the magneto-optical type has attracted attention because of its excellent writing speed and repetition resistance.

Incidentally, a magneto-optical recording magnetic film of the magneto-optical type optical recording medium (hereinafter, this film is simply referred to as a magnetic film) includes, for example, a rare earth-transition metal thin film (hereinafter, referred to as an RE-TM film) or
A device using an MnBi-based thin film has been conventionally proposed, and a device using an RE-TM film has excellent overall characteristics. However, these magnetic films have a drawback of poor corrosion resistance, and change in coercive force, decrease in Kerr rotation angle, deterioration of pitting, etc. due to corrosion of the magnetic film occur. This leads to a decrease in the value (carrier to noise ratio) and an increase in the error rate. As a countermeasure, it is known that a coating film is formed on both surfaces or one surface of the magnetic film to improve the corrosion resistance of the magnetic film.

When the coating film is laminated on the light incident surface of the magnetic film (hereinafter, appropriately referred to as the surface of the magnetic film), a function of increasing the Kerr effect to increase the Kerr rotation angle of the magnetic film can be provided. Therefore, it is necessary to increase the refractive index of the coating film.

Further, the magneto-optical recording medium has a structure in which a synthetic resin or glass is used as a substrate, and a magnetic film and a coating film are provided on the substrate, and the coating film is chemically stable and shields oxygen and moisture. And
It is desired that the substrate and the magnetic film have good affinity. In particular, when a synthetic resin such as polycarbonate or acrylic resin is used for the substrate, it is strongly required that the substrate and the magnetic film have good affinity and that oxygen and moisture contained in the substrate or transmitted through the substrate are not transmitted. Is done. Further, when the coating film is provided on the surface of the magnetic film, it is necessary that the coating film has sufficient transparency so that incident light can sufficiently reach the magnetic film.

In addition, there is a demand for a magneto-optical recording medium to operate at a higher speed in order to increase the transfer rate of information.
Therefore, a magneto-optical recording medium capable of recording with lower light intensity, that is, a medium having good recording sensitivity is required.

Conventionally, oxides such as SiO ₂ and Al ₂ O ₃ and nitrides such as AlN and Si ₃ N ₄ have been reported as coating films having at least one function of protecting the magnetic film and increasing the Kerr effect. . However, the following disadvantages are pointed out in the magneto-optical recording medium in which the above-described coating film is laminated together with the magnetic film. That is,
A magneto-optical recording medium using an oxide such as SiO ₂ or Al ₂ O ₃ as a coating film has a drawback that the oxide releases oxygen, so that the magnetic film is easily oxidized and characteristic deterioration occurs. . On the other hand, since AlN lacks stability to moisture, the magneto-optical recording medium using it as a coating film has a problem that it is weak to moisture, and Si ₃ N ₄ has poor adhesion to a substrate and peels off. There is a disadvantage that.

As described above, conventional magneto-optical recording media do not satisfy the above-mentioned requirements, and furthermore, they have a problem that their sensitivity is insufficient for high-speed operation.

(Problems to be Solved by the Invention) An object of the present invention has been made in view of the above-mentioned prior art, and has a large Kerr effect without causing corrosion of a magnetic film, and a light having excellent writing sensitivity. An object of the present invention is to provide a magnetic recording medium.

(Means for Solving the Problems) The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems, and as a result, the magnetic recording medium having a function of protecting the magnetic film from corrosion or increasing the Kerr effect. The present inventors have found a covering film and completed the present invention. That is, the present invention
A magneto-optical recording medium comprising a substrate and a magneto-optical recording magnetic film and a coating film laminated on the surface and / or back surface thereof, wherein at least one of the coating films comprises Si, N and H. A magneto-optical recording medium comprising a coating film as an element and a method for manufacturing the same. Hereinafter, the present invention will be described in detail.

Examples of the magnetic film in the magneto-optical recording medium of the present invention include the above-described MnBi-based material and RE-TM film. Of these, TbFeCo-based films and GdFeC
Examples of such films include o, GdTbFe, TbCo, TbDyFeCo, NdDyFeCo, and DyFeCo. Further, other recording materials using a recording material which is deteriorated by a monomer or moisture in plastic or moisture from the outside, for example, WORM (write once)
Obviously, it is applicable to all chalcogens for read many). As the substrate, glass or a resin substrate such as polycarbonate or epoxy can be used, and the shape of the recording medium is not only a general disk shape but also a card, tape, sheet, drum or any other shape is adopted. obtain.

Since the coating film containing Si, N and H as constituent elements used in the magneto-optical recording medium of the present invention has a function of increasing the Kerr effect, it is obtained by laminating this coating film on the surface of the magnetic film. The C / N value of the magneto-optical recording medium is improved, and the read performance is improved. Further, since the coating film has a function of protecting the magnetic film from corrosion, it can be obtained by laminating it on the surface of the magnetic film and / or the surface opposite to the light incident side (hereinafter referred to as the back surface of the magnetic film as appropriate). The magnetic film of the magneto-optical recording medium is protected from corrosion, thereby improving the reliability of the magneto-optical recording medium. Furthermore, when the above-mentioned coating film is laminated on the front surface and / or the back surface of the magnetic film, the recording sensitivity of the obtained magneto-optical recording medium is improved. It is not clear why the coating film containing Si, N and H as constituent elements used in the magneto-optical recording medium of the present invention has the above-mentioned function, but it is based on the constituent elements in the coating film or the combination thereof. It is possible that there is. That is, bonds between Si atoms and H atoms and between N atoms and H atoms are generated in the coating film, which causes bonding of dangling bonds between Si atoms and N atoms, thereby improving transparency. It is considered that the inclusion of H atoms in the film improves the affinity between the coating film and the substrate. Furthermore, the fact that the recording sensitivity of a magneto-optical recording medium using the above-mentioned coating film is improved is explained by the fact that Si atoms and N atoms in the coating film are partially bonded to H atoms, and the molecular structure of the coating film is improved. This is considered to be due to the fact that the network structure was partially cut off, which caused the thermal conductivity of the coating film to decrease. This means that, among the above coating films, particularly the infrared region 3350 ± 50 cm ⁻¹ , 2200 ± 50 cm ⁻¹ and 850 ±
Those having an absorption at 50 cm ^-1 are transparent, adhesion to the substrate,
It is inferred that it is excellent in thermal conductivity and the like and is preferable. Note that each of the above absorptions indicates that an N—H bond, a Si—H bond, and a Si—N bond are included in the coating film.

By the way, the content of H atoms in the coating film containing Si, N and H as constituent elements used in the present invention is about 1 cm ³ ,
It is preferably from 1.0 × 10 ²¹ to 1.0 × 10 ²³ . If the amount is larger than this, the coating film becomes porous and the coating film is likely to be broken, or in the case of a magneto-optical recording medium, a reading error is likely to occur, or the C / N value may be reduced. On the other hand, if the content of H atoms is less than the above range, the adhesion of the coating film to the substrate becomes poor,
In a magneto-optical recording medium, the recording sensitivity tends to deteriorate. The more preferable H atom content is 1 cm ³ of the coating film.
Per unit, from 5.0 × 10 ²¹ to 5.0 × 10 ²² pieces. Further, the N atom content of the coating film is preferably 10 atomic% or more, and if less than this, light absorption of the coating film increases,
The car effect obtained may be reduced. The upper limit of the N content of the coating film is preferably about 60 atomic% from the viewpoint of ease of forming the coating film.

Further, in the magneto-optical recording medium of the present invention, the thickness of the skin film is not particularly limited, for example, in order to use for the purpose of increasing the Kerr effect, it is preferable to set the thickness in the range of 50 to 150 nm, magnetic When used only for the purpose of protecting the film from corrosion, the thickness is preferably set to 30 to 200 nm. If both are too thick, the time required for forming the coating film will be long, and if too thin, the effect of the coating film may not be sufficiently obtained.

The magneto-optical recording medium of the present invention can be manufactured by forming each film by, for example, a sputtering method. Among these, the coating film containing Si, N and H as constituent elements is formed by sputtering using metallic silicon as a target and using a mixture of argon gas, nitrogen gas, hydrogen gas and ammonia gas as a sputtering gas. Can be formed. In addition, the above coating film is formed by CVD under silane-based gas, nitrogen gas, or hydrogen gas atmosphere.
(Chemical vapor deposition) can also be formed, but since the magnetic film is usually formed by sputtering, it is necessary to adopt the sputtering method from the viewpoint of the consistency of the apparatus or the point that the rise in the substrate temperature is small. preferable. Further, a sputtering apparatus that can be used when manufacturing the magneto-optical recording medium of the present invention is not particularly limited, but a magnetron apparatus is particularly preferably used in terms of easy control of the substrate temperature and a high film formation rate. . Furthermore, when forming a coating film containing Si, N and H as constituent elements, preliminary exhaust before sputtering is preferably performed as high as possible in order to remove the influence of residual gas,
It is preferable that the total sputtering gas during sputtering be 0.15 to 1.0 Pa. When an ammonia gas is used, the proportion of the ammonia gas in the sputtering gas is preferably 5 to 40% by volume. Note that H in the coating film
The content of atoms or N atoms can be adjusted by appropriately adjusting the mixing amount of nitrogen gas, hydrogen gas or ammonia gas in the sputter gas used. Furthermore, even if metallic silicon used as a target contains several percent of impurities, there is no effect on the obtained coating film.

According to the above-described method for manufacturing a magneto-optical recording medium, mass productivity is improved, and a coating film having good adhesion to a substrate or a magnetic film can be obtained.

(Examples) Hereinafter, the present invention will be described based on embodiments with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a diagram showing an outline of an embodiment of a magneto-optical recording medium of the present invention in a thickness cross section. In this example, 1
Denotes a transparent substrate made of glass, polymethyl methacrylate, polycarbonate, or the like, and a groove (not shown) for tracking guide is formed on this substrate. Also,
Light is irradiated through the substrate 1 to perform recording or reading. Reference numeral 2 denotes a coating film (hereinafter, referred to as a surface coating film) laminated on the surface of the magnetic film interposed between the substrate 1 and the magnetic film. Reference numeral 3 denotes, for example, a TbFeCo-based RE-TM film or the like. 3 shows a magnetic film. Reference numeral 4 denotes a coating film laminated on the back surface of the magnetic film (hereinafter referred to as a back coating film). In this example, both the surface coating film 2 and the back skin film 4 include Si, N and H as constituent elements. Consisting of a coating film. The thickness of the magnetic film 3 is about 30 to 120 nm, the thickness of the surface coating film 2 is about 50 to 120 nm, and the thickness of the back coating film 4 is about 70 to 110 nm. In the magneto-optical recording medium of the present invention, one of the surface coating film 2 and the back skin film 4 is constituted by a coating film other than a coating film containing Si, N and H as constituent elements. There may be.

FIG. 2 is a diagram showing an outline of another embodiment of the magneto-optical recording medium in a thickness cross section. In this example, the substrate 5 and the magnetic film 8
The coating film between them is formed in two layers. These two layers can be composed of a SiO ₂ film 6 and a ZnS film. The SiO ₂ film 6 has a thickness of 10 to 10 mm for the purpose of protecting the magnetic film 8 from corrosion.
The ZnS film 7 is formed to a thickness of about 50 to 120 nm in order to increase the Kerr effect. The back coating film 9 is made of a coating film containing Si, N and H as constituent elements.

The magneto-optical recording medium of the present invention may be of a reflective type in which a reflective film is provided on the back side of the magnetic film, in addition to the above-described embodiments. Such a magneto-optical recording medium has, for example, a reflective film made of aluminum, titanium, chromium, a reflective metal, an alloy, or the like and having a thickness of about 20 to 100 nm on the back side of the magnetic film, and is incident on the magnetic film by the reflective film. Light is reflected, and recording and reproduction are performed by the reflected light. In such a reflection type magneto-optical recording medium of the present invention, the above-mentioned coating film is laminated on the surface and / or the back surface of the magnetic film, and the thickness of the coating film is laminated on the surface of the magnetic film. In this case, the thickness is preferably set to 70 to 150 nm, and the thickness of the magnetic film is set to about 10 to 50 nm. Further, when a coating film containing Si, N and H as constituent elements is laminated on the back surface of the magnetic film, the coating film preferably has a function of increasing the Faraday effect. To 10
Preferably, it is set to ~ 80 nm.

Examples 1 to 9 In order to measure characteristics of a characteristic coating film of the magneto-optical recording medium of the present invention, a coating film containing Si, N and H as constituent elements was formed on a quartz glass or n-type silicon wafer substrate. It was formed to a thickness of about 110-140 nm.

The coating film is set using metallic silicon as a target using a two-pole magnetron sputtering device (CFS-4ES manufactured by Tokuda Seisakusho) having a high frequency power supply (frequency 13.56 MHz) and a DC power supply, and preliminary exhaustion is 2.0 × 10 ^-4 Pa or less. The substrate was formed by high frequency sputtering at a power of 300 W while introducing a gas shown in Table 1 as a sputtering gas while rotating the substrate at 20 rpm without heating.

Table 1 shows the results obtained by measuring the refractive index of the coating film formed on the silicon wafer with an ellipsometer and the transmittance (wavelength 830 nm) of the coating film formed on the quartz glass substrate with a spectrophotometer. Shown in

It is understood that the coating film used in the magneto-optical recording medium of the present invention has sufficient transparency and has a large refractive index of 1.9 or more, so that a good increase in the Kerr effect can be expected.

In addition, the infrared absorption spectrum of the coating film formed on the silicon wafer was measured with a Fourier transform infrared photometer (JIR-100 manufactured by JEOL Ltd.). As a result, in addition to absorption by Si-N bond near 850 cm ^-1 was observed, absorption by N-H bonds in the vicinity 3320 cm ^-1, observed absorption by Si-H bonds in the vicinity 2170 cm ^-1, this embodiment Was confirmed to contain H. Further, the content of H in this coating film was determined by the Journal of Upright.
Physics 49 2473 1978 (Journal of Appli
ed Physics 49, 2473- (1978)), that is, by a method using an infrared absorption spectrum. Table 2 shows the results. In addition, the composition of the coating film
It was measured by EPMA (Electron Probe Micro Analysis). The results are also shown in Table 2. The result of EPMA composition analysis shows the composition excluding H.

Comparative Examples 1 and 2 Gases shown in Table 3 were introduced as sputter gases onto quartz glass and n-type silicon wafer substrates to compare the characteristics of the coating film, which is a characteristic configuration of the magneto-optical recording medium of the present invention. A coating film was formed in the same manner as in Example 1 except that the coating was performed. In addition, the thickness of the coating film was 110 to 140 nm. The refractive index, transmittance, and composition of the obtained coating film were measured in the same manner as in Example 1. Table 3 shows the results.

Further, the infrared absorption spectrum of the coating film formed on the silicon wafer was measured with a Fourier transform infrared photometer. As a result, it was found that these films did not have absorption indicating that H was contained, and thus did not contain H.

Examples 10 to 13 A magneto-optical recording medium having the structure shown in FIG. 1 was placed on a polycarbonate substrate (a disc having a diameter of 13 cm, a thickness of 1.2 mm, and a guide groove having a pitch of 1.6 μm (groove width: 0.6 μm)). 75nm thick Tb ₂₄ Fe
_64.5 Co _11.5 magnetic film 3 and S
It was manufactured by laminating coating films (i.e., surface coating film 2 and back coating film 4) containing i, N, and H as constituent elements.

The magneto-optical recording medium was manufactured using the above-described sputtering apparatus, and the coating film was formed by high-frequency sputtering, and the magnetic film was formed by DC sputtering. The coating film was formed under the same conditions as those used in Example 3 (Example 10), Example 4 (Example 11), Example 7 (Example 12) and Example 8 (Example 13). Was. The thickness of the surface coating film 2 is 85
nm, and the thickness of the back coating film 4 was 100 nm. Further, the magnetic film 3
Was formed using a TbFeCo alloy as a target.

Comparative Examples 3 to 5 Magneto-optical recording media were manufactured in the same manner as in Example 10, except that the conditions for forming the surface coating film 2 and the back coating film 4 were changed. The surface coating film 2 and the back skin film 4 were formed under the same conditions as those used in Comparative Example 1 (Comparative Example 3) and those used in Comparative Example 2 (Comparative Example 4). Further, as Comparative Example 5, a magneto-optical recording medium having no surface coating film 2 and having only the back coating film 4 having a thickness of 100 nm as a coating film was manufactured. The formation of the back coating film 4 at this time was performed under the conditions employed in Comparative Example 2.

Evaluation Test For the magneto-optical recording media manufactured in Examples 10 to 13 and Comparative Examples 3 to 5, the linear velocity dependence of the recording power was measured using a drive device.

The specifications of the drive device used were: wavelength: 830 nm, lens NA: 0.5. The measurement condition is a recording bit length of 1.4μ.
The recording power was changed at intervals of 0.2 mW in the range of 3 mW to 10 mW by changing the linear velocity and the recording frequency so as to obtain the optimum recording power when the second harmonic was lowest.
Other measurement conditions are an external magnetic field; 5000 e, a duty ratio: 50%, and a read power: 0.8 mW. Examples 10, 11
FIG. 3 shows the results of Examples 12 and 13, and FIG. 5 shows the results of Comparative Examples 3 and 4. 3 to 5 that the recording sensitivity of the magneto-optical recording medium of the present invention is excellent.

Next, the magneto-optical recording media shown in Examples 10 to 13 and Comparative Examples 3 and 4 were kept in an atmosphere of 65 ° C. and 90% relative humidity, and the state was observed and the change in reflectance was measured.

FIG. 6 shows the change in the reflectivity of the magneto-optical recording media of Examples 10 and 11, and FIG. 7 shows the change of the reflectivity of the magneto-optical recording media of Examples 12 and 13, and the magneto-optical recording of Comparative Examples 3 and 4. FIG. 8 shows the change in the reflectance of the medium. Cracks occurred in the magneto-optical recording media of Comparative Examples 3 and 4 after being held for about 400 to 500 hours, and the reflectance decreased.
On the other hand, the magneto-optical recording medium of the present invention using a coating film containing Si, N and H as constituent elements does not generate cracks and pits even after being held for 1500 hours, and there is almost no change in reflectance. It turned out to be excellent in reliability. From this, it was found that the coating film containing Si, N and H as constituent elements used as the coating film in the magneto-optical recording medium of the present invention was excellent in blocking moisture and oxygen. The difference in durability between the magneto-optical recording medium of the present invention and the magneto-optical recording medium of the comparative example is considered to be due to the coating film used. That is, since the coating film used in the present invention contains H atoms, the affinity with the substrate is improved, and the increased adhesion is due to the difference in durability of the magneto-optical recording medium. it is conceivable that. Furthermore, the coating film used in the above embodiment is a film that is more flexible and has less stress due to the presence of Si—H bonds and Si—H bonds. It is conceivable that peeling and peeling hardly occur.

Next, the recording and reproduction characteristics of the magneto-optical recording media obtained in Examples 12 and 13 and Comparative Examples 3 to 5 were measured using a drive device. The specifications of the drive device used are wavelength
830 nm, lens NA 0.5, measurement conditions: linear velocity 4 m / s, external magnetic field: 5000 Oe, recording frequency: 1 MHz, duty ratio: 50
%, Read power; 0.8 mW, measurement was 3 mW recording power
The recording was carried out at intervals of 0.2 mW in the range of 8 mW to 8 mW, and the C / N value when the second harmonic became the lowest was obtained. Table 4 shows the results.

From the results of the recording / reproducing measurement, it was found that the coating film used in the magneto-optical recording medium of the present invention had a sufficient function of increasing the Kerr effect.

(Effects of the Invention) As described above, the magneto-optical recording medium of the present invention can
And a coating film comprising H as a constituent element for protecting the magneto-optical recording film and / or increasing the Kerr effect,
This magneto-optical recording medium does not cause corrosion of the magnetic film, has a large magneto-optical effect, and is excellent in read performance, recording sensitivity and reliability.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are views showing an example of the configuration outline of the magneto-optical recording medium of the present invention. FIG. 3 shows the relationship between the linear velocity and the optimum recording power of the magneto-optical recording media of Examples 10 and 11, FIG. 4 shows Examples 12 and 13, and FIG. 5 shows the results of Comparative Examples 3 and 4. FIG. 6 is a graph showing the change in reflectance over time of the magneto-optical recording media of Examples 10 and 11, FIG. 7 is a graph showing Examples 12 and 13, and FIG. In the figure, 1,5 ...... substrate, 2 ...... surface covering film 3, 8 ...... magnetic film, respectively show 4,9 ...... backside coating film 6 ...... SiO ₂ film, 7 ...... ZnS film.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 11/10 521 G11B 11/10 541

Claims (5)

(57) [Claims] 1. A magneto-optical recording medium comprising a magneto-optical recording magnetic film and a coating film laminated on the surface and / or the back surface thereof on a substrate, wherein at least one of the coating films is Si, N
And a coating film containing H as a constituent element.
The atomic content is 10 atomic% or more and 60 atomic% or less (however, H
Composition excluding atoms), the content of H atoms per coating film 1 cm ³
A magneto-optical recording medium comprising 5.0 × 10 ^{21 to} 5.0 × 10 ²² and the coating film having a refractive index of 1.9 to 2.4. 2. A coating film comprising Si, N and H as constituent elements has absorption in infrared regions of 3350 ± 50 cm ⁻¹ , 2200 ± 50 cm ⁻¹ and 850 ± 50 cm ⁻¹ . A magneto-optical recording medium according to the above mode (1). 3. A coating film containing Si, N and H as constituent elements is formed by sputtering using metallic silicon as a target and using a mixed gas of argon gas, nitrogen gas and hydrogen gas as a sputtering gas. The method for manufacturing a magneto-optical recording medium according to claim 1, wherein: 4. A coating film comprising Si, N and H as constituent elements is formed by sputtering using metallic silicon as a target and using a mixed gas of argon gas and ammonia gas as a sputtering gas. The method for manufacturing a magneto-optical recording medium according to claim 1. 5. Sputtering is performed by using metallic silicon as a target and using a mixed gas of argon gas, ammonia gas and hydrogen gas as a sputtering gas.
The method for manufacturing a magneto-optical recording medium according to claim 1, wherein a coating film containing i, N, and H as constituent elements is formed.