JPH07169125A - Magneto-optical disk and its production - Google Patents

Abstract

PURPOSE:To inexpensively produce a magneto-optical disk having high sensitivity to a magnetic field and high reliability and a magneto-optical disk having high sensitivity to a magnetic field and satisfactory stability of reproduction. CONSTITUTION:A 1st dielectric film 4, a recording film 5 of a rare earth element-transition element alloy and a 2nd dielectric film 6 are successively formed on a transparent substrate 2 and an intermediate film 9 is interposed between the films 5, 6 to obtain a magneto-optical disk. The 2nd dielectric film 6 contains at least one kind of metallic element and nitrogen. When a Ti, Cr or Nb film is formed in 1 to 28Angstrom thickness as the intermediate film 9, the sensitivity of the disk to a magnetic field and the reliability are improved. When a Co or Ni film is formed in 1 to 18Angstrom thickness as the film 9, the sensitivity of the disk to a magnetic field and the stability of reproduction are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk and a method for manufacturing the same.

[0002]

2. Description of the Related Art Optical discs are receiving attention as a large capacity information carrying medium. Among them, there are magnetic field modulation type magneto-optical disks, which are expected to be applied to data files and the like. In the magnetic field modulation method, a laser beam is irradiated from the optical head to the recording film of the disk in a DC manner to raise its temperature, and at the same time, a modulated magnetic field is emitted from a magnetic head arranged on the opposite side of the optical head. Recording is performed by applying it to the recording film. Therefore, overwrite recording is possible with this method.

Recently, a magneto-optical disk (mini disk) of a magnetic field modulation system capable of recording / reproducing at a low linear velocity equivalent to a compact disk (1.2 to 1.4 m / s) has been put into practical use. There is. This magneto-optical disk can share a drive with a read-only optical disk of a standard conforming to CD. Although the magneto-optical disk drive device is considered to be used as a portable type, in this case, it is required to reduce power consumption. However, the magnetic field modulation type magneto-optical disk requires a recording magnetic head in addition to the optical head, which generally increases power consumption. Therefore, a disc having a high magnetic field sensitivity and capable of recording in a low magnetic field is desired. If the recording is possible in a low magnetic field, the power consumption will be small, and the battery can be made small. Furthermore, the number of coil windings of the magnetic head can be reduced, which is advantageous in designing the magnetic head.

However, conventional magneto-optical disks, such as I
An SO-compliant 3.5-inch magneto-optical disk generally requires a recording magnetic field of 200 Oe or more to obtain a sufficient C / N. On the other hand, in the above-mentioned mini disk, it is desirable to suppress the recording magnetic field to 100 Oe or less, preferably 80 Oe or less in order to suppress power consumption, and it is necessary to obtain C / N of 46 dB or more with such a weak magnetic field strength. . Further, in the future, it is desired to obtain a C / N of 46 dB or more at a recording magnetic field strength of 60 Oe.

Further, since minidiscs are emphasized for outdoor use, they are required to have higher resistance to high temperature and high humidity. On the other hand, since minidiscs are also beginning to be used as data discs for computers, it is required to further improve data integrity.

Japanese Unexamined Patent Publication (Kokai) No. 4-313835 discloses that in a method of manufacturing a magneto-optical recording medium, at least a rare earth-transition metal alloy thin film and a dielectric film are sequentially formed on a substrate,
After depositing the rare earth-transition metal alloy thin film, the substrate is held in an atmosphere of a discharge state containing at least oxygen gas or a gas of a compound containing oxygen as a constituent element. It is said that a high C / N can be obtained under a recording magnetic field. However, as is well known, rare earths are extremely oxidizable materials, and according to the experiments by the present inventors, it is extremely difficult to control the gas (CO ₂ etc.) of a compound containing oxygen as a constituent element to an appropriate amount. It was difficult to stably obtain the desired characteristics. Further, if oxygen is contained in the magnetic layer of the rare earth-transition metal alloy, the reliability may be adversely affected.

In addition to this, "Recording field sensitivity
of magneto-optical disks usingvery thin exchange-c
`` upled films '' (Ichitani et al., J.Magn.Soc.Jpn., Vo
In l.17, Supplement No.S1 (1993), pp.196-200}, by using a laminated film of GdFeCo and TbFeCo as a recording film, a high magnetic field sensitivity suitable for a magnetic field modulation system can be obtained. However, this method increases man-hours and it is difficult to reduce costs.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a magneto-optical disk having high magnetic field sensitivity and high reliability, and a magneto-optical disk having high magnetic field sensitivity and good reproduction stability at low cost. The purpose is to do.

[0009]

Such an object is achieved by any of the following constitutions (1) to (7). (1) A first dielectric film, a recording film of a rare earth element-transition element alloy, and a second dielectric film are provided in this order on a transparent substrate, and between the recording film and the second dielectric film. An intermediate film, the second dielectric film contains at least one metal element and nitrogen, the intermediate film is formed of Ti, Cr or Nb, and the intermediate film has a thickness of 1 to 1. 28 A magneto-optical disk. (2) A first dielectric film, a recording film of a rare earth element-transition element alloy, and a second dielectric film are provided in this order on a transparent substrate, and between the recording film and the second dielectric film. Has an intermediate film, the second dielectric film contains at least one metal element and nitrogen, the intermediate film is formed of Co or Ni, and the intermediate film has a thickness of 1 to 18 A. Is a magneto-optical disk. (3) The above (1) or (wherein the second dielectric film is a metal nitride or a mixture containing at least one of a metal oxide, a carbide and a sulfide in addition to the metal nitride. 2) Magneto-optical disk. (4) The magneto-optical disk according to any one of (1) to (3) above, wherein the recording film, the intermediate film, and the second dielectric film are formed by a sputtering method. (5) The magneto-optical disk according to (4) above, wherein the second dielectric film is formed by a reactive sputtering method. (6) The above (1) to having a reflective film on the second dielectric film.
The magneto-optical disk according to any one of (5). (7) A method for manufacturing the magneto-optical disk according to any one of (1) to (6) above, wherein the intermediate film is formed by a sputtering method in a rare gas atmosphere. .

[0010]

In the present invention, an intermediate film is provided between the recording film and the second dielectric film. This intermediate film is formed by depositing a predetermined metal, and the metal element contained in the intermediate film is different from the metal element contained in the adjacent second dielectric film.

This intermediate film has an action of suppressing mutual diffusion of the second dielectric film constituent element and the recording film constituent element, and by this action, the recording film near the interface with the second dielectric film. The deterioration of the magnetic characteristics is suppressed, and the C / N in recording under a low magnetic field is improved. The deterioration of the magnetic properties of the recording film near the interface with the second dielectric film is considered to be due to nitrogen atoms diffusing from the second dielectric film into the recording film when the second dielectric film is formed. Further, when the second dielectric film is formed by the reactive sputtering method, atoms and ions derived from the reactive gas (especially nitrogen gas) damage the recording film, and C / N in recording under a low magnetic field. However, such damage can be prevented by providing an intermediate film.

If the intermediate film is formed of Ti, Cr, or Nb, deterioration is small even when stored under adverse conditions such as high temperature and high humidity, and a highly reliable magneto-optical disk can be obtained. To be

If the intermediate film is made of Co or Ni, the stability during reproduction becomes good. As described above, minidiscs are required to save power, and therefore, it is necessary to improve sensitivity to an applied magnetic field and laser light. However, on the other hand, when the mini disk is used as a data disk for a computer, it is necessary to prevent information once recorded from being erroneously erased by a magnetic field or heating from the outside. In the present invention, if the intermediate film is formed of Co or Ni, for example, even if a magnetic field is applied from the outside while irradiating the reproducing laser beam, it is difficult to erase information, and therefore stable. Playback is possible.

Incidentally, Japanese Patent Laid-Open No. 5-258368 discloses, "On a substrate, an interference layer, a recording layer made of a rare earth-transition metal amorphous alloy, and a heat made of a metal or semiconductor having a film thickness in the range of 10 to 30 A. A magneto-optical recording medium characterized in that a conductive layer, a dielectric layer and a reflective layer are sequentially laminated. The heat-conducting layer of this magneto-optical recording medium is similar to the intermediate film of the present invention in that it is made of metal and has a thickness. However, in the publication, specific examples of the heat-conducting layer include: Al, Ag, Au,
Cu, Si, and graphite, which are different from the present invention.
That is, when the heat conducting layer material specifically shown in the publication is used, the improvement of reliability and the stability of reproduction according to the present invention cannot be realized. Further, since the publication does not describe a specific value of C / N at an external magnetic field strength of 100 Oe or less, it cannot be said that the magnetic field sensitivity improving effect is also exemplified.

Further, in the above-mentioned Japanese Patent Laid-Open No. 4-313835, a substrate on which a magnetic film is formed is treated with oxygen gas or a compound gas containing oxygen at 1.6 × 10 ⁻⁵ to 1 × 10 ⁻³ To.
By holding in an atmosphere of discharge state including about rr,
There is a description that a layer having a composition containing oxygen is formed on the magnetic film and it is presumed that this layer prevents the elements (N, N ^+, etc.) derived from the dielectric film from being mixed into the magnetic film. The invention described in the publication is similar to the present invention in that nitrogen is prevented from being mixed into the magnetic film, but as described above, the method of holding the magnetic film in an atmosphere of a discharge state containing oxygen gas, etc. It is difficult to stably obtain the desired characteristics.

Further, in Japanese Patent Publication No. 5-32816,
After the recording layer is formed, the target for the recording layer is sputtered in an oxygen-containing atmosphere or the oxide target is sputtered to have a thickness of 30 to 100 A and a thickness of 0.1 to 20 A.
Proposals have been made to form corrosion resistant layers containing atomic% oxygen atoms. This proposal is intended to prevent the corrosion of the recording layer, and the publication does not describe C / N. The effect of the present invention cannot be realized by a method of forming a film on the recording layer by sputtering in an oxygen-containing atmosphere or sputtering using an oxide target like the method described in the publication.

Further, Japanese Patent Laid-Open No. 4-252443 proposes to prevent the corrosion of the recording film by modifying the surface of the recording film with oxygen plasma. In the example of the publication, oxygen gas is introduced to perform reactive sputter etching,
A modified oxide film with a thickness of about 50 A is formed. There is a statement in the same publication that a C / N of 47 dB was obtained, but 100 O
There is no description about the improvement of C / N under a low magnetic field of e or less. Even with this method, the effect of the present invention cannot be realized.

In the present invention, unlike these conventional methods, since the intermediate film is formed by sputtering in a rare gas, a high C / N can be stably obtained under a low magnetic field.

Japanese Unexamined Patent Publication (Kokai) No. 2-297738 discloses "SiO on a plastic molded disk having air permeability.
₂ , oxides such as Al ₂ O ₃ or AlN, Si ₃ N ₄
In the magneto-optical medium, a protective layer made of a nitride such as the above is formed, a magneto-optical recording film layer is formed on the protective layer, and the same protective layer as described above is further formed on the recording layer. An optical disc for recording information is disclosed in which an intermediate layer of Ti or Zr is formed between each layer and the recording layer.
The intermediate layer described in the publication is provided to prevent permeation of water vapor and oxygen by the getter action. In the publication,
It is described that the thickness of the intermediate layer is preferably 30 A or more in order to effectively prevent permeation, and it is set to 50 to 100 A in the examples.

Further, Japanese Patent Laid-Open No. 61-115258 discloses that "RE is one or more elements selected from rare earth elements and TM is one or more elements selected from transition metal elements, and RE-TM system is used. In a magneto-optical recording medium having an alloy amorphous film as a recording layer, a layer made of at least one metal selected from Ti, Cr and Al is deposited as a surface layer on the amorphous film. "There is disclosed a magneto-optical recording medium. In the example of the publication, a metal protective film having a thickness of 100 nm is provided as a surface layer. The publication does not disclose the range of the thickness of the metal protective film. This metal protective film serves as a getter of oxygen and prevents oxygen from entering the recording layer. The publication does not disclose further formation of a dielectric film on the surface layer.

Further, in Japanese Patent Laid-Open No. 2-96951,
"In a magneto-optical recording medium having at least a metal protective layer as a protective layer, the metal protective layer is made of a titanium alloy of one or more elements M and Ti selected from the group consisting of Re, Cr and Ta." A recording medium is disclosed. The publication describes that this metal protective layer has a function of suppressing entry of oxygen, nitrogen, fluorine, moisture, etc. from the dielectric film into the recording layer. In the example of the publication, a titanium alloy film having a thickness of about 15 A is provided between the dielectric layer on the substrate side and the magneto-optical recording layer, and titanium having a thickness of about 500 A is provided on the magneto-optical recording layer. An alloy film is formed. Further, in the comparative example of the publication,
A titanium film having a thickness of about 500 A is formed on the magneto-optical recording layer. However, this publication does not disclose the thickness range of the titanium alloy film or titanium film formed on the magneto-optical recording layer.

The intermediate layer and the metal protective layer disclosed in each of these publications are for preventing invasion of oxygen, moisture and the like into the recording layer, and therefore, 30 to 1000 A is applied on the recording layer.
It is required to be formed to a thickness of. On the other hand, in the present invention, the provision of the intermediate film on the recording film is for improving the magnetic field sensitivity, and the effect of improving the magnetic field sensitivity is remarkably reduced when the thickness is 30 A or more.

In addition to this, Japanese Patent Laid-Open No. 62-43848 discloses "Underlayer consisting of a soft magnetic layer which induces strain anisotropy which increases the coercive force of a perpendicular magnetization film on a non-magnetic substrate. A magneto-optical recording medium in which a perpendicular magnetic film mainly composed of a rare earth and a transition metal is formed via the above, and a soft magnetic film is further formed on the perpendicular magnetic film is disclosed. The soft magnetic film described in this publication stabilizes the written magnetic domain by closing the magnetic flux generated from the perpendicular magnetization film. In the example of the publication, Fe having a thickness of 20 A is formed above and below the perpendicular magnetization film.
The film is formed, but the dielectric film is not formed. The publication does not disclose the thickness range of the soft magnetic film formed on the perpendicular magnetization film.

[0024]

Specific Structure The specific structure of the present invention will be described in detail below.

FIG. 1 shows an example of the structure of the magneto-optical disk of the present invention. In the figure, the magneto-optical disk 1 has a first dielectric film 4, a recording film 5, a second dielectric film 6, a reflective film 7 and a protective coat 8 on the surface of a transparent substrate 2, 5
An intermediate film 9 is provided between the first dielectric film 6 and the second dielectric film 6.

When performing recording and reproduction on the magneto-optical disk of the present invention, the optical head is located on the back surface side (lower side in the figure) of the transparent substrate 2 and is irradiated with laser light through the transparent substrate. For the transparent substrate, glass, polycarbonate, acrylic resin, amorphous polyolefin, styrene resin, or other transparent resin is used.

The first dielectric film 4 and the second dielectric film 6
Has an effect of improving C / N and preventing corrosion of the recording film. The thickness of the first dielectric film is about 40 to 200 nm, and the thickness of the second dielectric film is about 10 to 100 nm. The first dielectric film is preferably composed of one of metal nitrides, oxides, carbides and sulfides, or a mixture containing two or more of these. The second dielectric film is preferably a metal nitride or a mixture containing at least one of a metal oxide, a carbide and a sulfide in addition to the metal nitride. In this case, the metal is Si,
Al, Zn, or a material obtained by adding La, Ce, Nd, Y or the like to these is preferable. Further, N is preferably 30 to 100 atom% in the total of O, C and S. With such a configuration of the second dielectric film, high magnetic field sensitivity and high C / N can be obtained, and deterioration of the recording film is reduced. Each dielectric film contains at least one metal element, but the combination thereof is not particularly limited. The constituent elements of the first dielectric film and the second dielectric film do not have to be the same.

Information is magnetically recorded on the recording film 5 by a modulated heat beam or a modulated magnetic field, and the recorded information is reproduced by magnetic-optical conversion. The magneto-optical disk of the present invention is usually applied to a magnetic field modulation method. Recording film 5
Is an alloy containing a rare earth element and a transition element.
The rare earth element is preferably at least one element selected from Tb, Dy, Nd, Sm, Pr and Ce, and the transition element preferably contains Fe and further contains Co. Specifically the content of each element, the required Curie temperature, coercive force, when may be suitably determined in accordance with the reproduction characteristic and the like, but the atomic ratio to the rare earth element and R was R _A Fe _B Co _C, Usually, it is preferable that 10 ≦ A ≦ 35, 55 ≦ B ≦ 75, 3 ≦ C ≦ 15, and A + B + C = 100. Further, in addition to these elements, various elements such as Cr and Ti may be added if necessary, but the content of these additional elements in the recording film is preferably 12 atomic% or less. . As the additional element, Cr and / or Ti is particularly preferable, and it is preferable that these elements are contained in a total amount of 1 to 10 atomic%. As a specific composition, for example, Tb-Fe-Co
Or Tb-Fe-Co-Cr, Tb-Fe-Co-T
i, Tb-Fe-Co-Cr-Ti, Dy-Tb-Fe
-Co, Nd-Dy-Fe-Co, etc. are mentioned. The layer thickness of the recording film 5 is usually about 10 to 100 nm.

The intermediate film 9 is formed of Ti, Cr or Nb, or Co or Ni. When the intermediate film is formed of Ti, Cr or Nb, a magneto-optical disk with excellent reliability can be obtained.
When Co or Ni is deposited, a magneto-optical disk having excellent reproduction stability can be obtained.

The lower limit of the thickness of the intermediate film is 1 A, preferably 2 A. The upper limit of the thickness is Ti, Cr or N.
b is 28 A, preferably 18 A, more preferably 8 A, and Co or Ni is an intermediate film, 18 A, preferably 10 A, more preferably 9 A.
A. By adjusting the thickness of the intermediate film to 80,
It is possible to obtain a sufficient C / N of 46 dB or more at a low magnetic field strength of Oe or less. If the intermediate film is too thin, the C / N when recorded in a low magnetic field will be significantly low.
The load on the magnetic head increases and power consumption increases.
If the intermediate film is too thick, the effect of improving C / N under a low magnetic field will be significantly reduced.

In the present specification, the thickness of each film is calculated from the sputtering rate and the sputtering time. The sputter rate used to calculate the film thickness is calculated from this thickness and the sputter time by performing spattering for a long time under the same conditions as the actual film formation to form a thick film and then measuring its thickness. .

The intermediate film is a film formed of a metal, for example, a film formed by sputtering a metal target as described later. For example, elemental analysis in the vicinity of the intermediate film was performed by Auger electron spectroscopy. In this case, an element contained in the dielectric film, an element contained in the recording film, or impurities such as argon, oxygen, and nitrogen contained in the atmosphere when forming each film are usually detected. Since the intermediate film is extremely thin, the ratio of elements that have penetrated from the dielectric film to the intermediate film by diffusion in the intermediate film is relatively high compared to other mixed elements, but the present invention also includes such cases. . Since the thickness of the intermediate film is calculated from the sputtering rate and the sputtering time, it is considered that the intermediate film may not be substantially formed into a film if the thickness is as thin as about 1 to 2 A. But,
If the film forming operation is performed so that a film having a thickness of 1 to 2 A is calculated, C /
The N improvement effect is sufficiently realized.

It is preferable to use a sputtering method for forming the dielectric film. The effects of the present invention are realized regardless of whether the ordinary sputtering method or the reactive sputtering method is used. Note that a dielectric film containing oxygen and nitrogen such as a dielectric film containing La, Si, O and N (LaSiON film) is usually formed by a sputtering method, but an oxide target is used in an atmosphere containing nitrogen. Can also be formed by a reactive sputtering method. The amount of N in the film is 15
The present invention is particularly effective when the second dielectric film is formed under the condition of at least atomic%.

The intermediate film is formed in a rare gas atmosphere,
Although oxygen is not introduced into the vacuum chamber, usually, a very small amount of oxygen remains in the vacuum chamber. Therefore, when elemental analysis is performed by Auger electron spectroscopy or the like, oxygen is detected near the intermediate film even when the dielectric film does not contain an oxide. Depending on the method of forming the intermediate film, the oxygen content may slightly increase near the interface between the intermediate film and the recording film. In the present invention, even in such a case, the maximum oxygen content in the vicinity of the interface is preferably 25 atom% or less, more preferably 20 atom% or less. By suppressing the maximum value of the oxygen content to be low, the reliability and the repetition durability are improved, and the high C / N can be stably obtained even in the recording under the high magnetic field and the high temperature. On the other hand, if the oxygen content is too high, the rare earth elements in the recording film are selectively oxidized and the coercive force of the recording film is low, so when recording in a high magnetic field or high temperature, adjacent tracks Are easily affected. Although the present invention aims to obtain a high C / N in recording under a low magnetic field, when used as a recording medium, it is necessary to guarantee high characteristics even in recording under a high magnetic field.

In order to suppress the mixing of oxygen into the film, it is preferable to make the ultimate pressure of the vacuum chamber as low as possible. However, if the oxygen content is in the above range, sufficient performance can be obtained. It is sufficient that the ultimate pressure is 1 × 10 ⁻⁴ Pa or less.

In addition to these, the sputtering conditions are not particularly limited, and the known ordinary conditions may be used.

The reflective film 7 is not essential, but it is preferably provided for improving C / N. The material forming the reflective film 7 is Au, Ag, Pt, Al, Ti, Cr, Ni, C.
Metals such as o, alloys thereof, or compounds thereof are preferable. The reflective film 7 is preferably formed by a sputtering method. The layer thickness of the reflective film 7 is 30
It is preferably about 200 nm.

The protective coat 8 is a resin film provided to protect the sputtered laminated film up to the reflective film 7. The resin forming the protective coat 8 is not particularly limited, but a cured product of a radiation curable compound is preferable. The radiation-curable compound preferably has an acrylic group,
A coating film containing this and a photopolymerization sensitizer or an initiator,
It is preferable to form a protective coat by curing with ultraviolet rays or electron beams. The thickness of the protective coat 8 is usually 1 to 30.
μm, preferably 2 to 20 μm. If the film thickness is too thin, it becomes difficult to form a uniform film and the durability becomes insufficient. On the other hand, if it is too thick, it tends to cause cracks due to shrinkage during curing and warp of the disk.

A transparent hard coat 3 may be formed on the back surface of the transparent substrate 2 as shown in the figure. The material and thickness of the hard coat may be similar to those of the protective coat 8. It is preferable to impart antistatic properties to the hard coat, for example, by adding a surfactant. The hard coat may be provided not only on the main surface of the disk but also on the outer peripheral side surface or the inner peripheral side surface of the disk.

[0040]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

On the transparent substrate, the first dielectric film, the recording film,
An intermediate film, a second dielectric film, a reflective film and a protective coat were sequentially formed under the conditions shown below to prepare magneto-optical disk samples shown in the following tables.

<Transparent Substrate> The transparent substrate has an outer diameter of 64 mm,
A disc-shaped polycarbonate resin plate having an inner diameter of 11 mm and a thickness of 1.2 mm was used.

<First Dielectric Film> 5.0 × 1 in the vacuum chamber
After reducing the pressure to 0 ^-5 Pa or less, reactive magnetron sputtering was performed using Si as a target while flowing Ar gas and N ₂ gas in a vacuum chamber to form a first dielectric film. The conditions for sputtering were: input power: 1 kW, sputtering gas pressure: 0.1 Pa, Ar gas flow rate: 31 SCCM, N ₂ gas flow rate: 19 SCCM. The thickness of the first dielectric film was 60 nm.

<Recording Film> After forming the first dielectric film, the inside of the vacuum chamber was decompressed again to 5.0 × 10 ⁻⁵ Pa or less, and Ar gas was flown into the vacuum chamber while the Tb—Fe—Co system was formed. Magnetron sputtering is performed with the alloy as the target, and Tb-F
A recording film containing e-Co as a main component was formed. The conditions for sputtering were: input power: 1 kW, sputtering gas pressure: 0.2 Pa, Ar gas flow rate: 98 SCCM. The thickness of the recording film was 20 nm. The composition of the recording film was Tb _20.0 Fe _70.0 Co _7.0 Cr _3.0 in atomic ratio.

<Intermediate film> After forming the recording film, the inside of the vacuum chamber was decompressed again to 5.0 × 10 ^-5 Pa or less, and magnetron sputtering was performed by using the target shown in Table 1 while flowing Ar gas into the vacuum chamber. Was performed to form an intermediate film. The conditions for sputtering were: input power: 400 W, sputtering gas pressure: 0.1 Pa, Ar gas flow rate: 40 SCCM. The thickness of the interlayer film is shown in each table. A sample without an intermediate film was also prepared.

<Second Dielectric Film> After forming the intermediate film, the pressure inside the vacuum chamber was reduced to 5.0 × 10 ⁻⁵ Pa or less, and the second dielectric film was formed by the sputtering method using the targets shown in each table. A body membrane was formed. What is described as Si (N) in the column of the target of each table is that the reactive magnetron sputtering was performed using the Si target while flowing the Ar gas and the N ₂ gas in the vacuum chamber. The conditions for this reactive sputtering were: input power: 1 kW, sputtering gas pressure: 0.1 Pa, Ar gas flow rate: 31 SCCM, N ₂ gas flow rate: 19 SCCM. The thickness of the second dielectric film was 20 nm.

<Reflective Film> After forming the second dielectric film, the pressure inside the vacuum chamber is reduced to 5.0 × 10 ⁻⁵ Pa or less again, and Ar gas is flown into the vacuum chamber while the Al alloy is used as a magnetron target. Sputtering was performed to form a reflective film. The conditions for sputtering were: input power: 750 W, sputtering gas pressure: 0.15 Pa, Ar gas flow rate: 10 SCCM. The thickness of the reflective film was 60 nm.

<Protective Coat> A coating film of the following composition for polymerization was formed by spin coating, and the coating film was irradiated with ultraviolet rays to be cured. The average thickness after curing was about 5 μm.

Composition for Polymerization Oligoester acrylate (Molecular weight 5,000) 50 parts by weight Trimethylolpropane triacrylate 50 parts by weight Acetophenone photopolymerization initiator 3 parts by weight

On each magneto-optical disk sample thus obtained, an EFM 3T signal was recorded at an external magnetic field strength (Hex) shown in each table at a linear velocity of 1.28 m / s, and MD evaluation by Sony Tektronix was performed. C / N was measured using system MJ-6100. The results are shown in each table.

The reliability of the samples in Table 1 was evaluated. The reliability was evaluated by storing the sample in an environment of 90 ° C. and 85% RH and the storage time until the block error rate increased to twice the initial value. The results are shown in Table 1.

Further, with respect to the samples shown in Table 2, the stability of reproduction was evaluated. First, for each sample, a linear velocity of 1.2
A 3T signal was recorded at 8 m / s and an external magnetic field strength of 100 Oe. Next, under the condition that an external magnetic field of 200 Oe was applied at a temperature of 70 ° C., one track was reproduced 1 × 10 ⁶ times at a linear velocity of 1.28 m / s, and the C / N reduction amount from the initial reproduction was increased. The maximum reproduction power at which is less than 2 dB was obtained. The results are shown in Table 2.
Shown in. The higher the maximum reproduction power, the less likely it is to be erroneously erased at the time of reproduction, resulting in superior data integrity.

Some of the comparative samples are shown in Table 1 and Table 2.
It was described in duplicate with.

[0054]

[Table 1]

[0055]

[Table 2]

From the above results, the effect of the present invention is clear. As mentioned above, a mini disc is recorded under a low magnetic field of 100 Oe or less, preferably 80 Oe or less.
A C / N of dB or more is desired, but in the sample of the present invention having an intermediate film formed by depositing a predetermined metal in a predetermined thickness, 80 Oe
In each case, a C / N of 46.0 dB or more was obtained, and in particular, when the thickness of the interlayer film was less than 10 A, an extremely high C / N was obtained.

Then, as shown in Table 1, Cr, T
The sample of the present invention having an intermediate film in which i or Nb is formed to a predetermined thickness is compared with a comparative sample having an Al intermediate film.
Highly reliable. Further, as shown in Table 2, the sample of the present invention having the intermediate film formed by depositing Co or Ni to a predetermined thickness has better reproduction stability than the comparative sample having the Al intermediate film.

Next, the oxygen content near the intermediate film was measured by Auger electron spectroscopy. First, after removing the protective coat of each sample, put each sample in the vacuum container of Auger electron spectroscopy equipment and evacuate it for 24 hours to reduce the pressure in the container to 7.0 × 10 ^-10 Torr and further evacuate it. While continuing, the element distribution was measured in the thickness direction by Auger electron spectroscopy. The conditions for Auger electron spectroscopy are: electron gun acceleration voltage: 5 kV, electron gun irradiation current: 500 nA.
The accelerating voltage of the ion gun was 2 kV, the incident angle of argon ions was 58.9 degrees, and the amount of elements was measured while etching with argon ions in the thickness direction by intermittent etching (one etching time of 45 seconds). The etching rate is 13.2 A / min for the second dielectric film and 1 for the recording film.
It was 2.2 A / min. As a result, oxygen peaks were observed near the interface between the intermediate film and the recording film of each sample, but the oxygen content at these peaks was 21 atomic% or less.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a configuration example of a magneto-optical disk of the present invention.

[Explanation of symbols]

 1 Magneto-optical disk 2 Transparent substrate 3 Hard coat 4 First dielectric film 5 Recording film 6 Second dielectric film 7 Reflective film 8 Protective coat 9 Intermediate film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyasu Inoue 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation

Claims (7)

[Claims] 1. A transparent substrate having a first dielectric film, a recording film of a rare earth element-transition element alloy and a second dielectric film in this order, and a recording film and a second dielectric film. A second dielectric film contains at least one metal element and nitrogen, the intermediate film is formed of Ti, Cr or Nb, and the intermediate film has a thickness of Magneto-optical disk of 1-28 A. 2. A transparent substrate having a first dielectric film, a recording film of a rare earth element-transition element alloy, and a second dielectric film in this order, and a recording film and a second dielectric film. A second dielectric film contains at least one metal element and nitrogen, and the intermediate film is formed of Co or Ni. 18 A magneto-optical disk. 3. The first dielectric film is a metal nitride or a mixture containing at least one of a metal oxide, a carbide and a sulfide in addition to the metal nitride. 2 magneto-optical disk. 4. The magneto-optical disk according to claim 1, wherein the recording film, the intermediate film and the second dielectric film are formed by a sputtering method. 5. The magneto-optical disk according to claim 4, wherein the second dielectric film is formed by a reactive sputtering method. 6. The magneto-optical disk according to claim 1, further comprising a reflective film on the second dielectric film. 7. A method of manufacturing a magneto-optical disk according to claim 1, wherein the intermediate film is formed by a sputtering method in a rare gas atmosphere.