JPH02156445A - Magneto-optical recording medium and production thereof - Google Patents

Abstract

PURPOSE:To produce the magneto-optical recording medium having excellent reliability and reading-out performance and good recording sensitivity by forming coating films, at least one of which contains at least Si, C, N, and H as the constituting elements. CONSTITUTION:A substrate 1 consists of glass, etc., and a 1st protective film 2 is interposed between the substrate 1 and a magnetic film to commonly provide a Kerr enhancement effect and a protective function. The magnetic film 3 is, for example, an RE-TM film of a TbFeCo system and a 2nd protective film 4 is a back protective film having a protective function. This coating film contains at least the Si, N, C and H as the constituting elements and the content of the C atom is over 30atomic% and <=60atomic% of the constituting elements excluding the H. Since the C atoms are incorporated into the coating film, the affinity of the coating film and the substrate is improved and since the adhesive property is improved, the generation of peeling and cracking of the coating film is suppressed. The adhesive property of the coating film and the substrate is improved and the decrease of stresses is possible particularly when the atomic content of the C is over 30atomic% and <=60atomic%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magneto-optical recording medium, and more particularly to a coating film laminated on a substrate together with a magneto-optical recording magnetic film.

(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 has excellent writing speed and repeat durability. 1 has been done.

By the way, the magneto-optical Si magnetic film (hereinafter simply referred to as a magnetic film) of this magneto-optical type optical recording medium may include, for example, a rare earth-transition metal thin film (hereinafter referred to as RET-1 film) or an MnB1 thin film. Conventionally, methods using RE-TM crotches have been proposed, and among these, those using RE-TM crotches have excellent overall characteristics. However, these films have the disadvantage of poor corrosion resistance, and due to corrosion, they cause deterioration such as changes in coercive force, decrease in Kerr rotation angle, and occurrence of pitting corrosion. to noise
This leads to a decrease in ratlo) and an increase in the nipping rate.

As a countermeasure against this problem, it is known to improve the corrosion resistance by forming a coating film on both sides or 11 sides of the magnetic film.

When the above ms film is provided on the light incident side of the magnetic film, it can have a Kerr effect enhancement effect that increases the Kerr rotation angle of the magnetic film. It is necessary that the refractive index of the crotch is large. On the other hand, magneto-optical recording media have a structure in which a synthetic resin, glass, etc. is used as a substrate, and a magnetic film and a coating film are provided on this. It is desired that it has good affinity with the substrate and magnetic film,
In particular, when synthetic resin such as polycarbonate or acrylic resin is used as a substrate, it has good compatibility with the substrate and magnetic film.
It is strongly required that oxygen, moisture, etc. contained in or transmitted through the substrate do not pass therethrough. Furthermore, when a protective film is provided on the light incident side of the magnetic film, it must be sufficiently transparent to allow incident light to reach the magnetic film.

Conventionally, SiO, Al
Oxides such as 2O3 or AIN.

Nitrides such as Si3N4 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.

In other words, magneto-optical recording media using oxides such as SiO and Al2O3 have the disadvantage that the oxides release oxygen, making it easy to oxidize rare earth metals, which tends to cause deterioration of the characteristics of the RE-TM film. Those using SiN have a problem of lacking stability against moisture, and those using SiN have a drawback of poor adhesion to the substrate and peeling.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned prior art, and provides a method for coating a magnetic film with a coating film that has the function of protecting the magnetic film from corrosion or enhancing the Kerr effect. The purpose of this invention is to provide a magneto-optical recording medium.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the inventors of the present invention have carried out extensive studies and found that 114 of the magnetic film in a magneto-optical recording medium
The present inventors have discovered a coating film that has the function of protecting against food or enhancing the Kerr effect, and have completed the present invention.

That is, the present invention provides a magneto-optical recording medium comprising a magneto-optical recording magnetic film and a coating film for protecting the magnetic film and/or enhancing the Kerr effect on the front and back surfaces of the substrate, which The present invention relates to a magneto-optical recording medium and a method for manufacturing the same, characterized in that at least one of the coating films contains at least Si, C, N, and H as constituent elements.

Examples of the magnetic film in the magneto-optical recording medium of the present invention include the above-mentioned M n Bi yarn material or RE-TM film. In addition, as a RE-TM film, Tb
FeCo-based film or GdFeCo.

GdTbFe, TbCo, TbDyFeCo.

Examples include NdDyFeCo and DyFeCo. Furthermore, other recording materials using recording materials that are subject to deterioration due to monomers and moisture in plastic, or moisture from the outside, such as WORM (write onc
It is also applicable to all chalcogens etc. for e read many).

A transparent substrate such as polycarbonate, glass, or Epoquine resin can be used as the substrate, and the shape of the SiA medium can be a general disk shape, or a card, tape, sheet, drum, or other arbitrary shape. may be adopted.

The coating film in the magneto-optical recording medium of the present invention is interposed between the magnetic film and the substrate in order to obtain at least one of the effects of force effect enhancement and the function of protecting the magnetic film from corrosion etc. Further, for the purpose of protecting the magnetic film from corrosion etc., it is coated on the back surface of the magnetic film. For example, if the magnetic film is R
In the case of an E-TM film or a MnBi-based film, the crotch inserted between the substrate and the magnetic film satisfies the above two effects.

The magneto-optical recording medium of the present invention is one in which a coating film containing H containing the above-mentioned constituent elements is laminated on both the front and back sides of a magnetic film, or one in which a coating film containing the above-mentioned constituent elements is laminated on both the front and back surfaces of a magnetic film, and one in which the coating film is formed only on one side of the hostile film and no coating is applied on the other side. Alternatively, it includes those covered with other films.

A characteristic element of the magneto-optical recording medium of the present invention is that the coating film contains at least Si and N as constituent elements.

It contains four of C and H.

The inclusion of C atoms in the coating film improves the affinity between the coating film and the substrate and improves adhesion, thereby suppressing peeling and cracking of the coating film. In particular, when the C atom content of the coating film is more than 30 atomic % and less than 60 atomic %, the adhesion between the coating film and the substrate is improved and stress can be reduced. Further, it is thought that the bonding between Si and H binds the dangling bonds of Si, improving transparency, and furthermore, the inclusion of hydrogen in the coating film improves affinity with the substrate. The basic framework of the above coating film is stable S
It is constructed from i-N and Si-C bonds, and is chemically stable and excellent in blocking oxygen and moisture.

The coating film of the magneto-optical recording medium of the present invention contains at least four constituent elements, St, N, C, and H, and the transparency of the coating film is improved by the presence of hydrogen. There is. However, when the hydrogen content is high, the refractive index decreases, so obtaining a high refractive index while maintaining transparency is one of the key points in providing the coating film with the Kerr effect enhancement function. According to the present invention, there is provided a magneto-optical recording medium that has a coating film suitable for Kerr effect enhancement that has high transparency and a large refractive index because hydrogen is appropriately introduced into the coating film. You can get rid of it.

When the coating film in the medium of the present invention is inserted between the substrate and the magnetic film, the thickness of the coating film is set to 60 to 10 (l n
m is preferable, and when the coating film is used as a back protection for magnetic 11/J, the coating film is preferably 50 to 150 nm, for example, because if it is too thin, the protective effect will decrease and if it is too thick, the film formation time will be longer. It is preferable to set it as approximately.

In the method for manufacturing the magneto-optical recording medium of the present invention, in particular, as a method for forming a coating film, for example, metal silicon is used as a target and ammonia and hydrocarbon gas (preferably methane gas) are used as an inert gas, or ammonia and hydrocarbon gas (preferably methane gas) are used as an inert gas. One example is a reactive sputtering method using a mixture of methane gas) and hydrogen gas. Furthermore, CVD (cheI
It can also be formed by a vapor deposition method.

When forming a coating film by reactive sputtering, there are no particular restrictions on the equipment used, but low temperature production is required when using a resin substrate, and when heating a glass substrate, etc., there is no temperature rise due to sputtering. Since this is preferable, J! A magnetron device is particularly preferably used because it is easy to control temporary humidity and temperature and has a high formation rate. Preliminary evacuation during sputtering is preferably performed to as high a vacuum as possible to eliminate the influence of residual gas.

Metallic silicon may be used as the target, or several 96 impurities may be included. In addition, the sputtering gas pressure is 0.15 to IPa, and the proportion of ammonia gas is 2 to 4.
0%, hydrocarbon gas or hydrogen gas percentage is 7-40%
It is preferable that

By producing the coating film in this manner, it is possible to mass-produce the coating film, and a coating film with strong packing properties can be obtained.

(Example) The present invention will be described below based on embodiments with reference to the drawings.

FIG. 1 is a diagram showing an outline of an embodiment of a magneto-optical recording medium in terms of its thickness cross section, and in this diagram, 1 indicates a transparent substrate made of glass, polymethyl methacrylate, polycarbonate, etc. . A groove (not shown) for tracking guidance is formed in this substrate.

Reference numeral 2 denotes a first coating film interposed between the substrate 1 and the magnetic film for both Kerr effect enhancement and protection functions, and the magnetic film 3 is, for example, a TbFeCo-based RE-TM film.

4 is a second (back) protective film having a protective function.

The magneto-optical recording medium of the present invention is formed by forming the first protective film 1 and the second protective film 4 into a coating film having characteristics of the constituent elements, for example.

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, and these two layers are, for example, a SiO2 film 6 that has a protective effect and a ZnS film that has a Kerr effect enhancement effect. It can be formed as a membrane 7. 8
9 is a magnetic film, and 9 is a back protection film.

Examples 1-8. Comparative Example 1 Characteristic characteristics of the coating film of the magneto-optical recording medium of the present invention were determined by 7I.
In order to determine I11, a coating film according to the present invention and a coating film not according to the present invention for comparison were formed to a thickness of about 240 nm on quartz glass, a circular cover glass, and an n-type silicon wafer substrate.

Note that the coating film in the magneto-optical recording medium of the present invention was sample 1.
- 8 (corresponding to Examples 1 to 8 respectively) and sample 9, which was coated with a magneto-optical recording medium of the present invention and a coating film having different constituent elements for comparison.
(corresponding to Comparative Example 1).

The coating film was formed using a high frequency power source (frequency 13.56 MHz).
) and a two-pole magnetron sputtering device (CFS-4ES Toku 111 Seisakusho) equipped with a DC power source, metal silicon was set up as a target, and preliminary exhaust 2X10-'P was used.
The substrate was rotated at 2 Or pm without heating, and the introduced gas was formed by high-frequency sputtering at a power of 300 W under the conditions shown in Table 1.

The composition of the film formed on the silicon wafer was determined by EPMA (
clcstron prove m1cro anal
Table 1 shows the results of quantification using tli.ysis).

From Table 1, if the amount of methane gas introduced exceeds 2 seconds, C
4) The atomic content a exceeds 30 atomic %.

Further, FIG. 3 shows the film formation rate of the films of Samples 1 to 9 determined using a stylus film thickness meter versus the C atom content.

The figure shows that the film formation rate is higher when C atoms are included;
It is about 1.7 to 2 times as large as the 5iNI 1% of sample 9, and it can be seen that the C atom content in particular has a large value of 50 at % or more. This high deposition rate can contribute to shortening the time for producing media.

The infrared transmission spectrum of the coating film of sample 4 formed on a silicon wafer substrate was calculated by Fourier transform infrared luminosity (JIR
-100 manufactured by JEOL Ltd.). The results are shown in FIG. Note that the results are shown after correcting the absorption of the silicon wafer as the substrate. 2170cm from the same figure
Absorption due to a 5i-H bond was observed near 1 and an N-H bond was observed near 1160 cm', indicating that the film contained H.

FIG. 5 shows the results of measuring the refractive index of a film formed on a silicon wafer using an ellipsometer with respect to the C atom content. From the figure, it can be seen that the refractive index of the coating film used in the magneto-optical recording medium of the present invention is 1.9 or more, and the function of Kerr effect enhancement can be expected. In addition, the transmittance of the protective films 1 to 9 formed on the quartz glass substrate (wavelength 830
nm) using a spectrophotometer, all showed a transmittance of 90% or more.

FIG. 6 shows the stress value calculated from the change in the amount of warpage of the cover glass when a film is formed on the circular cover glass with respect to the C atom content. It can be seen from the figure that the stress decreases as the C atom content increases, and particularly when the C atom content exceeds 30 atom %, the stress becomes extremely small.

From this, it is expected that peeling off of the coating film and generation of cracks can be suppressed by using a coating film with a C atom content of more than 30 at% among the coating films used in the magneto-optical recording medium of the present invention. I know it will happen.

Examples 9-13. Comparative Example 2.3 Magneto-optical recording media with the configuration shown in Figure 1 (Samples 10 to 15)
) on a polycarbonate substrate (diameter 13cm, thickness 1
．． 2mm disc, with 1.6μm pitch guide groove (groove width 0
．． 6 μm) on top of 75 nm thick Tb Fe C
o Magnetic film 3 and this magnet 24 G4.5 1
1.5 A protective film according to the present invention was laminated on the front and back surfaces with a protective film sandwiched therebetween.

The magneto-optical recording medium was manufactured using the sputtering apparatus described above, with the weight film being formed by high frequency sputtering and the magnetic film being formed by direct current sputtering in accordance with the following.

The protective film was formed under the conditions shown in Table 2. Sample 10-1
5 (each corresponding to Examples 9 to 13 and Comparative Example 2), the thickness of the protective film 2 was 85 nm, and the thickness of the back protective film 4 was 10 nm.
It was set to 100n constant. Further, in sample 16 (corresponding to comparative example 3), the protective film 2 was not provided, and the back protective film 4 was formed under the conditions of sample 15, and the film thickness was 1100 nm.

Further, the magnetic film was formed by direct current sputtering using TbFeCo as a target under the same conditions as above.

5. Validity Test 1 The density of the film was evaluated for the magneto-optical recording media with the above acid f of '110 to '15.

The density Δp1 method is based on a knife on the surface of the back protective film.
100 rnm square gobanme were made, cellophane tape was pasted thereon, and then peeled off.The number of pieces remaining on the substrate was calculated, and the average value of 10 measurements was calculated. The results are shown in Table 3. From the same table, the adhesion of the protective film is much better than that of the SiN film, and the adhesion of the coating film is improved by increasing the C atom content in the film, especially when it exceeds 30 at%. I understand that.

Table 3 Evaluation Test 2 The recording and reproducing characteristics of the magneto-optical recording media of Samples 10 to 16 above were measured using a drive device.

The specifications of the drive device used were: wavelength; 830 nm;
The NA of the lens is 0.5, and the measurement conditions are linear velocity; 4
m/s, external magnetic field; 5000e, recording frequency;
IMHz, duty ratio: 50%, read power +0.
It was set to 8mW.

0.211'L recording power in the range of 3mW to 8mW
Recording was performed at intervals of XV, and the C/NU and optimum recording power when the second harmonic was the lowest were determined. Table 4 shows the results.
Shown below.

In this evaluation test, the C/N value for all samples 10 to 15 was 4 to 4 compared to sample 1'416, which did not have an enhancement film.
It has improved by 5dB. C/N of the magneto-optical recording medium of the present invention
Although the value is large due to the function of Kerr effect enhancement, it can be seen that particularly samples 11 and 12 with a C atom content of 50 atomic % or more have a large C/N 1lfi. Therefore, it was found that the Kerr effect enhancement function of the protective film according to the present invention is sufficient.

It was also found that the optimum recording sensitivity was improved in samples 10 to 15 compared to sample 16, which did not have a film for effect enhancement. It can be seen that it is improved. Therefore, it can be seen that the magneto-optical recording medium of the present invention has excellent recording sensitivity.

Table 4 Furthermore, for detailed comparison of recording sensitivity, the linear velocity and recording frequency were adjusted to keep the recording bit length constant at 1.4 μm for the media of Sample 10 (Example 9) and Sample 15 (Comparative Example 2). The relationship between linear velocity and optimal recording sensitivity was determined by changing the linear velocity. The drive device and duty ratio used were the same as above, and the recording power was varied at 0.2 mW intervals in the range of 3 to 10 mW, and the recording power at which the second harmonic was the lowest was determined as the optimum recording sensitivity. The results are shown in FIG.

From the figure, it can be seen that the medium of the present invention has superior recording sensitivity by about 1 to 1.5 mW compared to the medium coated with a SiN coating film, and the difference between the two widens as the linear velocity increases.

Even after holding for 2,000 hours, no change was observed when observed with the naked eye, but cracks in the circumferential direction were observed when observed using an optical microscope. In addition, the magneto-optical recording medium of Samples 10, 11, and 12 did not suffer from cracking, peeling, or pitting even after being held for 2,000 hours.

In addition, since pitting corrosion did not occur and the reflectance did not change,
It can be seen that the protective film according to the present invention has low stress and excellent adhesion, suppressing the occurrence of cracks and peeling, and is also excellent in blocking moisture and oxygen.

Evaluation Test 3 The magneto-optical recording media of Samples 10 to 15 above were heated at 65°C, 90% l
(It was maintained in an Iλ·1 humidity atmosphere and its state was observed.

In the magneto-optical recording medium provided with the SiN film of Sample 15 (Comparative Example 2), cracks occurred in the film in the circumferential direction after being held for 300 hours. The durability of the magneto-optical recording medium of the present invention is determined by the above-mentioned difference in adhesion and the stress value of the medium provided with the coating film of sample 13.14 with a C atom gold platinum content of 30 atomic % or less. In other words, the coating film in the medium of the present invention is made more flexible and has less stress due to the bonding of Si and H, the bonding of N and H, and the dangling bonds of St and N being bonded by H. It is thought that cracks and peeling occur due to improved adhesion and thinning.

(Effects of the Invention) As described above, the magneto-optical recording medium of the present invention is characterized by its coating film, which has low stress and excellent adhesion between the 2JIM and the magnetic film. I of magneto-optical recording film
i4 protection from eclipse and/or magneto-optical enhancement, resulting in excellent reliability and readability. Furthermore, the magneto-optical recording medium of the present invention has excellent recording sensitivity.

1: Substrate ~ Figure 1

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing an outline of the structure of the magneto-optical recording medium that is the subject of the present invention, and Figure 3 shows the deposition rate of the thin films of samples 1 to 9 with respect to the C content of the film. FIG. Figure 4 is a diagram showing the infrared transmission spectrum of Sample 1 formed on a silicon wafer, Figure 5 is a diagram showing the refractive index of Samples 1 to 9 relative to the C content of the film, and Figure 6 is a diagram of the sample. A diagram showing the stress of films 1 to 9 versus C content, Figure 7 is sample 1.
FIG. 3 is a diagram showing the relationship between the linear velocity and the optimum recording sensitivity of media of 0 and 15. 5 ~ Figure 2 Figure 3 C content/atom 0/. Figure 5 C content/atom 0/. Figure 6 C content/atom''/e Figure 7 Linear velocity/m, s'1

Claims (4)

[Claims] (1) A magneto-optical recording medium comprising a magneto-optical recording magnetic film and a coating film for protecting the magnetic film and/or enhancing the Kerr effect being laminated on the front and back surfaces of the magneto-optical recording magnetic film on a substrate, the above-mentioned coating At least one of the films includes at least Si, C,
A magneto-optical recording medium characterized by containing N and H as constituent elements. (2) The C atom content of the coating film is 30% of the constituent elements excluding H.
The magneto-optical recording medium according to claim 1, wherein the content is greater than 60 atom % and less than 60 atom %. (3) The coating film is formed by reactive sputtering using metallic silicon as a target in an atmosphere containing an inert gas, ammonia gas, and a hydrocarbon gas. The method for producing a magneto-optical recording medium according to item 1 or 2. (4) The coating film is formed by reactive sputtering using metallic silicon as a target in an atmosphere containing an inert gas, ammonia gas, hydrocarbon gas, and hydrogen gas. A method for producing a magneto-optical recording medium according to item 1 or 2.