JPH0316048A - Magneto-optical recording medium and production thereof - Google Patents

Abstract

PURPOSE:To obtain the large magneto-optical effect without generating the corrosion of a magneto-optical recording film by using Si, N and H as constituting elements to form the coating films laminated and constituted together with the magneto-optical recording film. CONSTITUTION:The coating films 2, 4 are laminated together with the magneto- optical recording film 3 on the front and rear surfaces on a substrate 1. At least either of the constituting films is formed of the Si, N and H as its constituting elements. The coating films 2, 4 made of the Si, N and H as the constituting elements have the function to increase a Kerr effect and the function to protect the magnetic film 3 against corrosion. The magneto-optical recording medium formed in such a manner obviates the corrosion of the magnetic film 3, has the large magneto-optical effect and has the excellent reading performance, recording sensitivity and reliability as well.

Description

Detailed Description of the Invention (Industrial Application 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. be.

(Prior Art) Among optical recording media, there are phase change type, photochromic type, magneto-optical type media, etc. as conventionally known rewritable type media that can be written and erased. Among these rewritable types, the magneto-optical type is attracting attention because it has excellent writing speed and repeat durability.

By the way, the magneto-optical recording magnetic film (hereinafter simply referred to as a magnetic film) of this magneto-optical optical recording medium is made of, for example, a rare earth-transition metal thin! Films using I (hereinafter referred to as RE-TM film) or MnB i-based thin films have been proposed in the past, and among these, films using RE-TM films have excellent overall characteristics. However, these magnetic films have the disadvantage of poor corrosion resistance, and corrosion of the magnetic film causes deterioration such as a change in coercive force, a decrease in the rotation angle per force, and the occurrence of pitting corrosion. N value (carrier to
This leads to a decrease in noise rate (1o) and an increase in error rate. As a countermeasure against this problem, it is known to form a coating film on both or one side of the magnetic film to improve the corrosion resistance of the magnetic film.

In addition, when the above coating film is laminated on the light incident surface of the magnetic film (hereinafter referred to as the surface of the magnetic film as appropriate), it can have the function of increasing the Kerr effect by increasing the Kerr rotation angle of the magnetic film. However, for this purpose, it is necessary to increase the refractive index of the coating film.

Furthermore, magneto-optical recording media have a structure in which a substrate such as alloy resin or glass is provided with a magnetic film and a coating film, and the coating film is chemically stable and free from oxygen and moisture. It is desired that the material be shielded and have good compatibility with the substrate and magnetic film. In particular, when synthetic resin such as polycarbonate or acrylic resin is used as a substrate, it is strongly required that it has good affinity with the substrate and magnetic film and that oxygen, moisture, etc. contained in or passing through the substrate do not permeate. be done. Furthermore, when a coating film is provided on the surface of a magnetic film, it must be sufficiently transparent to allow incident light to reach the magnetic film.

In addition, there is a demand for magneto-optical recording media to operate at higher speeds in order to increase the information transfer rate. Therefore, a magneto-optical recording medium is required that can record with lower light intensity, that is, has good recording sensitivity.

Conventionally, SiO 2 ,1 has been used as a coating film having at least one of the functions of protecting the magnetic film and increasing the Kerr effect.
0 and other oxides, p. ．． n N, S is N
23 nitrides such as 4 etc. have been reported. However, the following drawbacks have been pointed out to magneto-optical recording media in which the above-mentioned coating film is laminated together with a magnetic film. That is, SiO SAn
Magneto-optical recording media using oxides such as ) 203 as coating films have the disadvantage that the oxides release oxygen, which makes the magnetic film easy to oxidize, resulting in characteristic deterioration. On the other hand, since AIN lacks stability against moisture, magneto-optical recording media using it as a coating film are susceptible to moisture, and Sl8N4 has the disadvantage of poor adhesion to the substrate and peeling. be.

As described above, conventional magneto-optical recording media do not meet the above-mentioned requirements, and furthermore, they have the problem of insufficient sensitivity for high-speed operation.

(Problems to be Solved by the Invention) The object of the present invention was to provide a light beam that does not cause corrosion of the magnetic film, has a large Kerr effect, and has excellent writing sensitivity. Our goal is to provide magnetic recording media.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have found that a coating with a function of protecting a magnetic film from corrosion or increasing the Kerr effect in a magneto-optical recording medium is provided. They discovered a coating film and completed the present invention. That is, the present invention is a magneto-optical recording medium which is constructed by laminating a magneto-optical recording magnetic film and a coating film on the surface and/or back surface of the substrate on a substrate, the above-mentioned film 1! A magneto-optical recording medium and a method for manufacturing the same, characterized in that at least one of the films is a coating film containing St, N, and H as constituent elements. The present invention will be explained in detail below.

Examples of the magnetic film in the magneto-optical recording medium of the present invention include the above-mentioned MnBi-based material or RE-TM film. Among these, TbFeC is used as the RE-TM film.
o-based films, GdFeCo, GdTbFe, TbCo, T
Examples include films such as bDyFeCo, NdDyFeCo, and DyFeCo. Furthermore, other recording materials using recording materials that are subject to deterioration due to monomers and moisture in plastics, or moisture from the outside, such as WO
R M (write once read many
), it is obvious that it is applicable to all chalcogens, etc. In addition, glass, polycarbonate, epoxy, or other resin substrates can be used as the substrate, and the recording medium can be of any shape, such as a general disk shape, a card, tape, sheet, drum, etc. can be done.

The coating film containing Si, N, and H as constituent elements used in the magneto-optical recording medium of the present invention has the function of increasing the force-strength effect. The C/N value of the magneto-optical recording medium thus obtained is improved, and the read performance is improved.

Also covered above! ! Since the film has the function of protecting the magnetic film from corrosion, magneto-optical recording is 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). The magnetic film of the medium is protected from corrosion,
This improves the reliability of the magneto-optical recording medium. Furthermore, the above 1! ! When the film is laminated on the surface and/or back surface of the magnetic film, the resulting magneto-optical recording medium has good recording sensitivity.

The reason 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 is not clear, but it may be due to the constituent elements in the coating film or their combinations. It is possible that In other words, bonds between Si atoms and H atoms and between N atoms and H atoms occur in the coating film, and as a result, bonds between dangling bonds between St atoms and N atoms occur, improving transparency and improving the coating film. H inside
It is thought that the inclusion of atoms improves the affinity between the coating film and the substrate. Furthermore, the reason why the recording sensitivity of the magneto-optical recording medium using the above-mentioned coating film is good is that the Si atoms and N atoms in the coating film partially combine with the middle atoms, and the molecular structure of the coating film is improved. It is thought that this is because the network structure becomes a partially cut structure, which lowers the thermal conductivity of the coating film. This means that among the above coating films,
Especially in the infrared region 3350±50cm, 2200±50c
Those that have absorption at m-' and -1 and 850±50 cm-' are transparent;
This is inferred from the fact that it has excellent adhesion to the substrate, thermal conductivity, etc., making it preferable. Note that each of the above absorptions is N-
This shows that H bonds, St-H bonds, and Si-N bonds are contained in the coating film.

Incidentally, the content of H atoms in the coating film containing Si, N and H as constituent elements used in the present invention is preferably from 1.0×10 2 to 1.0×3 10 23 per 10 2 . If more than this,
There is a risk that the coating film becomes a bolus and is easily destroyed, that read errors are more likely to occur in magneto-optical recording media, and that the C/N value decreases. 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 tends to deteriorate, and the recording sensitivity of the magneto-optical recording medium tends to deteriorate. In addition, the more preferable H atom content is 5.5% per coating film IC:tn3. 5 from OX1021. There are 1022 OX.

Further, it is preferable that the N atom content of the coating film is 10 atomic % or more; if it is less than this, the absorption of light by '81H may increase and the obtained Kerr effect may be reduced. Note that the upper limit of the N atom content of the coating film is preferably about 60 atomic % from the viewpoint of ease of shaping the coating film.

Further, in the magneto-optical recording medium of the present invention, the thickness of the coating film is not particularly limited, but for example, in order to use it for the purpose of increasing the Kerr effect, it is preferably set to a thickness in the range of 50 to 150 nm. When used only for the purpose of corrosion protection of the magnetic film, it is preferable to set the thickness to 30 to 200 layers. In either case, if the coating is too thick, the coating time will be long, and if the coating is too thin, the effect of the coating 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 with Si, N, and H as its constituent elements is
Using metallic silicon as a target, argon gas, nitrogen gas, and hydrogen gas are used as sputtering gases. The shape can be formed by sputtering using a gas mixed with ammonia gas. In addition, the above-mentioned coating film can also be coated with C under an atmosphere of silane gas, nitrogen gas, or hydrogen gas.
V D (chemica!vapor depos
Although magnetic films can also be formed by the sputtering method, it is preferable to use the sputtering method from the viewpoint of device compatibility and the fact that the rise in substrate temperature is small. . Although there are no particular restrictions on the sputtering equipment that can be used to manufacture the magneto-optical recording medium of the present invention, a magnetron equipment is particularly preferably used because it is easy to control the substrate temperature and has a high film forming speed. be done. Furthermore, si
, N, and H as constituent elements, it is best to perform preliminary evacuation before sputtering to as high a vacuum as possible to eliminate the influence of residual gas, and ensure that the total sputter gas during sputtering is 0. .15~1. It is preferable to use OPa. Further, when ammonia gas is used, the proportion of ammonia gas in the sputtering gas is preferably 5 to 40% by volume.

The content of H atoms or N atoms in the coating film can be adjusted by appropriately adjusting the amount of nitrogen gas, hydrogen gas, or ammonia gas mixed in the sputtering gas used. Furthermore, even if the metal silicon used as the target contains several percent of impurities, the resulting coating film will not be affected in any way.

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

(Example) The present invention will be described below 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 the magneto-optical recording medium of the present invention in its thickness section. In this example, reference numeral 1 denotes a transparent substrate made of glass, polymethyl methacrylate, polycarbonate, etc., and a hole (not shown) for tracking guidance is formed on this substrate. Further, light is irradiated through the substrate 1 to perform recording or reading. 2 is a coating film laminated on the surface of the magnetic film interposed between the substrate 1 and the magnetic film (hereinafter referred to as a surface coating film)
3 indicates a magnetic film made of, for example, a TbFeCo-based RE-TM film. Furthermore, 4 indicates a coating film laminated on the back side of the magnetic film (hereinafter referred to as the back coating film), and in this example, both the surface coating film 2 and the back coating fflllllJ are S.
Cover 1 whose constituent elements are L, N and H! ! Consists of a membrane. The thickness of each film is 30 to 120 nm for the magnetic film 3, 50 to 120 nm for the surface coating film 2, and 50 to 120 nm for the magnetic film 3.
is formed at about 70 to 110 rv. Note that the magneto-optical recording medium of the present invention has a surface coating film 2 and a back coating film 8! Either one of the films 4 may be composed of a coating other than a coating film containing St, N, and H as constituent elements.

FIG. 2 is a diagram showing an outline of another embodiment of the magneto-optical recording medium in its thickness section. In this example, the coating film between the substrate 5 and the magnetic film 8 is formed in two layers. These two layers can be composed of a SiO 2 film 6 and a ZnS film 7. The SiO 2 H 6 is formed to a thickness of about 10 to 100 nm for the purpose of protecting the magnetic film 8 from corrosion, and the ZnS film 7 is formed by the Kerr effect. For the purpose of increasing the thickness, 50 to 1 2 O
n! It is formed to about 8. In addition, the back coating film 9 is made of Si
, N and H as constituent members.

In addition to the embodiments described above, 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 a magnetic film. Such magneto-optical recording media have a reflective film made of, for example, aluminum, titanium, chromium, or a reflective metal or alloy, with a thickness of about 20 to 100 nm, on the back side of the magnetic film. The light incident on the disk is reflected, and recording and reproduction are performed using this reflected light. In such a reflective magneto-optical recording medium of the present invention, the above-mentioned coating film is laminated on the surface and/or back surface of the magnetic film, and the thickness of this coating film is determined by the thickness of the coating film laminated on the surface of the magnetic film. In this case, it is preferable to set the thickness to 70 to 150 nm, and the thickness of the magnetic film is set to about 10 to 50 nm. Furthermore, when a coating film containing St, N, and H as constituent elements is laminated on the back surface of the magnetic film, it is preferable that this coating film has a function of increasing the Faraday effect, and for this purpose, it is necessary to ffllll! The thickness of l is 10~80n
It is preferable to set it to m.

Examples 1 to 9 In order to measure the characteristics of the 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, n-type silicon wafer substrate. about 110 to 1
The thickness was 40 nm.

The coating film was made using a two-pole magnetron scattering device (CFS-
4ES (manufactured by Tokuda Seisakusho) was used to set up metal silicon as a target, and pre-exhaust 2-O
'P-a or less, and while rotating the substrate at 20 rpm without heating, a power of 300 was applied by high-frequency sputtering.
It was formed using W and the gases shown in Table 1 were introduced as sputtering gases.

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

It can be seen 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.

Table 1 In addition, the infrared absorption spectrum of the coating film formed on the silicon wafer was measured using a Fourier transform infrared photometer (J'lR-10
0 (manufactured by JEOL Ltd.). As a result, 850
(7) Absorption due to Si-N bond was observed near -1, absorption due to N-H bond near 3320CITl-', and absorption due to N-H bond near 2170CI! Absorption due to Si-H bond was observed in the vicinity of 1-', and it was confirmed that the coating film formed in this example contained H. Furthermore, the content of H in the arytenoid membrane was calculated in Journal Op Applied Physics, Vol. 49, p. 2473, 1978 (Journal Op Applied Physics, Vol. 49, p.
of Applied Physics 49.247
3-(197g)), that is, a method using an infrared absorption spectrum. The results are shown in Table 2. In addition, the composition of the film is E P M
A (Electron Probe M1cro^n
lysis). The results are also shown in Table 2. Note that the results of the EPMA group analysis show the group excluding H.

Table 2 In order to compare the characteristics of the coating film, which is a characteristic structure of the magneto-optical recording medium of the present invention, the gases shown in Table 3 were introduced as sputtering gases onto a quartz glass, n-type silicon wafer substrate. 8! in the same manner as in Example 1! A film was formed. In addition, the thickness of the coating film was set to 110 to 140 rv. The refractive index, transmittance, and composition of the coating film obtained were measured in the same manner as in Example 1. The results are shown in Table 3.

Table 3 In addition, the infrared absorption spectrum of the coating film formed on the silicon wafer was measured using a Fourier transform infrared photometer. As a result, it was found that these films did not contain any absorption indicating that they contained H.

Examples 10 to 13 A magneto-optical recording medium having the configuration shown in FIG.
75 on the Jm pitch guide groove (groove width 0.6am)
nm thick Tb Fe Co magnetic 24B4.

5 11.5 Film 3 and a coating film containing Si, N, and H as constituent elements on the surface and back surface of this magnetic film (surface coating film 2 and back coating film 4).
) were manufactured by laminating them.

The magneto-optical recording medium was manufactured using the sputtering apparatus described above, with the coating film being formed by high frequency sputtering and the magnetic film being formed by direct current sputtering. Covered'I! The formation of the i film was performed in Example 3 (Example 10) and Example 4 (Example 11).
), Example 7 (Example 12) The experiments were carried out under the same conditions as those employed in Example 8 (Example 13). The thickness of the surface coating film 2 is 85nffi, and the thickness of the back coating film 4 is 10.
It was set to 0 nm. Furthermore, magnetic 1f! I3 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 shapes and conditions of the surface coating H2 and the back coating film 4 were changed. The shape and strength of the surface coating film 2 and the back coating film 4 are based on the conditions adopted in Comparative Example 1 (Comparative Example 3) and Comparative Example 2 (Comparative Example 4).
The test was carried out under the same conditions as those employed in . Further, as Comparative Example 5, a magneto-optical recording medium was manufactured which did not include the surface coating film 2 and had only the back coating film 4 with a film thickness of 10 On- as a coating film. At this time, the formation of the backside coating @4 was carried out under the conditions adopted 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 recording power was measured using a drive device.

The specifications of the drive device used were: wavelength; NA of 830I1 lens; 0.5. In addition, the measurement conditions were to change the linear velocity and recording frequency so that the recording bit length was 1.4jm.
Recording power is 0.2mW in the range of 3Ilw to 10mW.
Recording was performed at different intervals, and the optimum recording power when the second harmonic was the lowest was determined.

Other measurement conditions were: external magnetic field; 5000e. Duty ratio: 50%, read power: 0.8 ■V. The results of Example 10.11 are shown in FIG. 3, and the results of Example 12.
The results of No. 13 are shown in FIG. 4, and the results of Comparative Examples 3 and 4 are shown in FIG. From FIGS. 3 to 5, it can be seen that the magneto-optical recording medium of the present invention has excellent recording sensitivity.

Next, the magneto-optical recording media shown in Examples 10 to 13 and Comparative Example 3.4 were maintained in an atmosphere of 65° C. and 90% relative humidity, and their conditions were observed and changes in reflectance were measured.

The change in reflectance of the magneto-optical recording medium of Example 10.11 is shown in the sixth example.
FIG. 7 shows the change in reflectance of the magneto-optical recording medium of Example 12.13, and FIG. 8 shows the change in reflectance of the magneto-optical recording medium of Comparative Example 3.4. The magneto-optical recording medium of Comparative Example 3.4 cracked after being held for about 400 to 500 hours.
Reflectance decreased. On the other hand, 1! whose constituent elements are SL, N, and H! The magneto-optical recording medium of the present invention using a film is 150
Even after holding for 0 hours, no cracks or pitting corrosion occurred, and almost no change in reflectance was observed, indicating that the product had excellent reliability. Further, from this fact, the coating film containing Si, N, and H as the constituent elements used as the coating film in the magneto-optical recording medium of the present invention! The membrane was found to be excellent at 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. In other words, since the coating film used in the present invention contains H atoms, it has improved affinity with the substrate, and the difference in durability of the magneto-optical recording medium is due to the increased adhesion. it is conceivable that. Furthermore, the coating film used in the above examples has Si-H bonds, Si-N
Due to the presence of bonds, the film is more flexible and has less stress, which, together with the above-mentioned improved adhesion, prevents cracks and t! I
This is thought to be due to the fact that separation is less likely to occur.

Next, the recording and reproducing 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 were: wavelength 830cm, lens NA: 0.5, and measurement conditions: linear velocity 4m/s, external magnetic field: 50000e. Recording frequency: I MHz duty ratio: 50%, read par'7-; 0. cmW, and the measurement was performed using a recording power of 3
Recording was performed at intervals of 0.21 in the range from +aW to cmW, and the C/N value when the second harmonic was the lowest was determined. The results are shown in Table 4.

Table 4 From the results of the above-mentioned recording and reproducing measurements, it was found that the coating film used in the magneto-optical recording medium of the present invention has a sufficient function of increasing the force-strength effect.

(Effects of the Invention) As described above, the magneto-optical recording medium of the present invention has Si,
A coating film containing N and H as constituent elements is provided to protect the magneto-optical recording film and/or increase the Kerr effect, and this magneto-optical recording medium is free from corrosion of the magnetic film and is It has a large magneto-optical effect and has excellent read performance, recording sensitivity, and reliability.

1,5...Substrate 3, 8...Magnetic film 6...SlO2III

Claims (8)

[Claims] (1) A magneto-optical recording medium formed by laminating a coating film on the surface and/or back surface of a magneto-optical recording magnetic film on a substrate, wherein at least one of the coating films includes Si, N, and A magneto-optical recording medium comprising a coating film containing H as a constituent element. (2) The H atom content of the coating film whose constituent elements are Si, N, and H is 1.0 x 10^2 per 1 cm^3 of the coating film.
2. The magneto-optical recording medium according to claim 1, wherein the number of the magneto-optical recording medium is ^1 to 1.0 x 10^2^3. (3) Claim (1) characterized in that the N atom content of the coating film whose constituent elements are Si, N, and H is 10 at % or more (however, the composition excludes H atoms). or the first (
2) The magneto-optical recording medium according to item 2). (4) The coating film whose constituent elements are Si, N and H has an infrared range of 3350±50cm^-^1, 2200±50cm^-
The magneto-optical recording medium according to any one of claims (1) to (3), characterized in that it has absorption at ^1 and 850±50 cm^-^1. (5) Sputtering is performed using metallic silicon as a target and a mixed gas of argon gas, nitrogen gas, and hydrogen gas as sputtering gas, and Si, N, and H
2. The method of manufacturing a magneto-optical recording medium according to claim 1, further comprising forming a coating film containing as a constituent element. (6) A claim characterized in that sputtering is performed using metallic silicon as a target and a mixed gas of argon gas and ammonia gas as a sputtering gas to form a coating film containing Si, N, and H as constituent elements. A method for manufacturing a magneto-optical recording medium according to item (1). (7) Sputtering is performed using metallic silicon as a target and a mixed gas of argon gas, ammonia gas, and hydrogen gas as sputtering gas, and Si, N
2. The method of manufacturing a magneto-optical recording medium according to claim 1, further comprising forming a coating film containing H and H as constituent elements. (8) Sputtering is performed using metallic silicon as a target and a mixed gas of argon gas, ammonia gas, and nitrogen gas as sputtering gas, and Si, N
2. The method of manufacturing a magneto-optical recording medium according to claim 1, further comprising forming a coating film containing H and H as constituent elements.