JP2551118B2 - Magneto-optical disk medium and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] With respect to a magneto-optical disk, a magneto-optical recording layer is provided for the purpose of realizing both excellent adhesion and flatness and preventing deterioration of recording and reproducing characteristics due to moisture permeation. In a magneto-optical disk medium supported on a substrate, a film made of nitrogen oxide of at least one metal selected from the group consisting of Zr, Ti, Nb, Ta and V is provided between the magneto-optical recording layer and the substrate and in the magneto-optical recording layer. It is configured to be provided above.

TECHNICAL FIELD The present invention relates to a magneto-optical disk and a method for manufacturing the same,
More specifically, it relates to a magneto-optical disk using a substrate such as plastic or glass and a method for manufacturing the same.

[Prior Art] In a conventional magneto-optical disk, a glass substrate has been used as a substrate in terms of characteristics such as warpage and stability of recording / reproducing characteristics. However, glass substrates are expensive,
Also, since there is a risk of cracking, plastic materials have recently begun to be used for substrates.

Since plastic substrates have problems in terms of the above characteristics, as a countermeasure against this, oxide materials such as TiO ₂ and TiO, or Si
It has been proposed to apply an oxide material such as ₃ N ₄ or AlN to a plastic substrate as a base film.

[Problems to be Solved by the Invention] According to the study by the present inventors, even if a film of an oxide material is directly formed on a substrate such as a plastic, its adhesion is weak.
Under the atmospheric environment where the magneto-optical disk is used, the underlying oxide film peels off from the substrate together with the magneto-optical recording layer, while the nitride film has too strong adhesion to the substrate, so the substrate warps, It was found to significantly deform the substrate. Furthermore, since the above oxide materials and nitride materials do not have excellent moisture permeability, they are used as protective films for the magneto-optical recording layer to protect the magneto-optical recording layer from moisture in the atmosphere. Even if it does, a sufficient moisture permeation preventive effect cannot be obtained. Similarly, even if these materials are used as the base protective film, in the case of a plastic substrate, a sufficient effect of preventing moisture permeation from the plastic substrate side cannot be obtained, and the recording / reproducing characteristics eventually deteriorate with time. Therefore, the present invention solves the drawbacks that a nitride protective film having a high adhesion in a magneto-optical disk is likely to warp, and an oxide protective film that does not cause a warp has a weak adhesion, resulting in excellent adhesion and flatness. It is intended to realize both of them and prevent deterioration of recording and reproducing characteristics due to moisture permeation over time.

[Means for Solving the Problems] A magneto-optical disk medium according to the present invention is a magneto-optical disk medium in which a magneto-optical recording layer is supported by a substrate.
A film made of nitrogen oxide of at least one metal of the group consisting of Nb, Ta and V is provided between the magneto-optical recording layer and the substrate and on the magneto-optical recording layer.

 Hereinafter, the constitution of the present invention will be described in detail.

Hereinafter, the film provided on the magneto-optical recording layer is referred to as an upper protective film. The film provided between the magneto-optical recording layer and the substrate is hereinafter referred to as a base protective film.

The upper protective film has an effect of mainly blocking moisture from the atmosphere from permeating the magneto-optical film. On the other hand, the undercoat protective film has the effect of adhering the magneto-optical film to the substrate of plastic or the like and blocking the magneto-optical film from moisture from the substrate of plastic or the like.

The magneto-optical disk medium of the present invention has a simple structure when both the upper protective film and the lower protective film are made of the same material, but it is also within the scope of the present invention that both protective films are made of different materials. The upper protective film preferably has a thickness of 80 to 120 nm, and the lower protective film preferably has a thickness of 80 to 120 nm. The lower limit value and the upper limit value are determined for the following reasons. That is, if the thickness is less than the lower limit, the effect of each protective film is small, while if the thickness of the upper protective film exceeds the upper limit, the laser transmission efficiency decreases,
Even if the thickness of the base protective film exceeds the upper limit value, the effect is not particularly increased and the economical efficiency is lowered. The preferred thickness is 80 for both protective films
~ 100 nm.

In the present invention, the laminated structure of substrate / underlying protective film / magneto-optical recording layer / upper protective film is most preferred, and nitrogen oxide is most preferably ZrON. However, if the effect of the present invention is not impaired and a defect such as warpage is not caused, a film of a laminated material other than the present invention can be additionally formed. For example, SiO ₂ , SiON or the like may be laminated between the underlayer protective film or the upper protective film and the magneto-optical recording layer.

A 1.2 mm thick polycarbonate, acrylic, or APO substrate is usually used for the plastic substrate.

The above-mentioned upper protective film and lower protective film can be used not only on the plastic substrate but also on the glass-2P substrate.

As a method of manufacturing the above-mentioned upper and lower protective films, a sputtering method is preferable in terms of film composition and thickness uniformity.

Further, two specific sputtering methods are possible: a vacuum sputtering method and a sputtering method utilizing a reaction by an atmospheric gas.

In the vacuum sputtering method, sputtering is performed in a vacuum using a target made of a nitrogen oxide of at least one metal selected from the group consisting of Zr, Ti, Nb, Ta and V. Is provided between the magneto-optical recording layer and the plastic substrate and on the magneto-optical recording layer. In this method, the composition of the target is
It is preferable to adjust such that the nitride is 50 to 99 mol% and the oxide is the balance. If the amount of nitride is less than 50 mol%, the adhesion will be reduced.

On the other hand, when the nitride content exceeds 99 mol%, the laminated film is liable to warp and the moisture permeability is deteriorated, so the above composition is preferable. This target is prepared, for example, by mixing powder of zirconium nitride and powder of zirconium oxide and firing. It is natural that the target may be prepared by preparing nitrogen oxide of zirconium as a compound in advance and firing it. The nitrogen oxide in the present invention is selected from compounds or mixtures as described above, and is a substance containing N and O in the protective film. Next, the degree of vacuum in the vacuum atmosphere in which sputtering film formation is performed is not particularly limited, but 10 ^-1 Torr to several Torr is preferable. When the degree of vacuum is less than this lower limit, it becomes difficult to discharge. If the upper limit is exceeded, the sputtering efficiency will decrease. Therefore, the degree of vacuum in the above range is preferable.

In the sputtering method utilizing the reaction with the atmosphere, various targets and atmospheres can be adopted as long as the sputtered material reacts with nitrogen and / or oxygen.

As a preferable sputtering method, a target made of a nitride or oxide of at least one metal selected from the group consisting of Zr, Ti, Nb, Ta and V is used in an oxygen atmosphere (in the case of a nitride target) or in a nitrogen atmosphere ( In the case of an oxide target), a film made of nitrogen oxide of at least one metal is provided between the magneto-optical recording layer and the plastic substrate and on the magneto-optical recording layer.

In this method, as an oxide of Ti, TiO, TiO ₂ O ₃ , T
i ₂ O _{5 and the} like, Nb oxide, NbO, Nb ₂ O _{5 and the} like, Ta oxide, TaO and TaO _{2 and the} like, V oxide and V ₂ O _{5 and the} like are used as targets. can do. Further, TiN, etc. is used as a Ti nitride, and ZrN, etc. is used as a Nb for Zr.
, NbN, etc. can be used as targets, the Ta nitride can be TaN, etc., and the V nitrides can be VN, etc. The target oxide (nitride) reacts with nitrogen gas (oxygen gas) in the chamber of the sputtering apparatus to form nitrogen oxide on the substrate.

(Function) Although oxides generally have different degrees of adhesion, since they have poor adhesion to plastics, the oxide film deposited on the plastics is easily peeled off from the plastic substrate. Therefore, if nitrogen or nitride is added to this oxide to slightly nitrid it, the adhesion is improved.

Nitride has good adhesion to plastic, but when laminated with a plastic substrate, the stress in the in-plane direction of the film is too strong, which causes a problem of deforming the substrate. Therefore, by adding oxygen or oxide to this nitride, the adhesion is not impaired and the substrate is not deformed.

As described above, nitrogen or the like added to the oxide film enhances the adhesion, but does not cause the warp of the substrate, while oxygen or the like added to the nitride film does not reduce the adhesion and prevents the warp of the substrate. Therefore, according to the present invention, the drawbacks of oxide or nitride alone films are eliminated, and a base protective film and a top protective film having only the excellent properties of each film are provided.

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

〔Example〕

In the following examples, a peeling test as shown in FIG. 2 was carried out in order to investigate the adhesion between the base film and the substrate.
Cut the base film into a grid pattern as shown in the figure to make 100 squares, adhere the tape to this, and peel off the tape. to decide.

In order to examine the warp, a test as shown in FIG. 3 was conducted. That is, the plastic substrate on which the upper protective film and the lower protective film are formed is placed on the table and the substrate is deformed (sledding).
The change with time was examined by an acceleration test at 80 ° C. The measurement was based on the method of measuring the amount of warp at the edge of the substrate as shown in FIG.

In order to investigate the protective effect against moisture permeation, the C / N was measured by leaving the plastic substrate on which the upper and lower protective films were formed in the air at 85 ° C and 90% RH.

 The C / N measurement conditions were as follows.

Rotation speed 900 rpm Frequency 1.0 MHz Linear velocity 4.0 mW / S Recording magnetic field 300 Oe Example 1 The target used in this example is ZrN as a mother phase and ZrO.
₂ was added and a sintered target was used.

Using this target, the top and bottom protective film (ZrON) of the magneto-optical disk was formed. As the substrate, a polycarbonate resin substrate (PC) having a thickness of 1.2 mm and a diameter of 5 inches was used. The structure of the disc was as follows.

PC substrate / ZrON base protection film (thickness 80 nm) / TbFeCo (thickness 90
nm) / ZrON top protective film (thickness: 80 nm) The results of the test are shown in Table 1 for the peeling test, Fig. 1 for the warpage, Fig. 3 for the protective effect against moisture permeation, and Table 2 for the disk characteristics.
, Respectively.

Example 2 In this example, the same treatment as in Example 1 was performed using a target obtained by adding TiO ₂ to a mother phase of TiN and sintering the target.

Example 3 In this example, the same treatment as in Example 1 was performed using a target obtained by adding Nb ₂ O ₅ to NbN as a mother phase and sintering it.

Example 4 In this example, the same treatment as in Example 1 was performed using a target obtained by adding HfO ₂ to HfN as a mother phase and sintering the target.

Comparative Example 1 In this comparative example, the same treatment as in Example 1 was performed using a target obtained by sintering ZrO ₂ .

Comparative Example 2 In this comparative example, the same treatment as in Example 1 was performed using a target obtained by sintering SiO ₂ .

Comparative Example 3 In this comparative example, the same treatment as in Example 1 was performed using a target obtained by sintering Si ₃ N ₄ .

Figure 4 shows the change in C / N with time due to the acceleration test. From this, it is understood that when the oxide alone and the nitride alone are used as the upper and lower protective films, the C / N deteriorates due to moisture permeability, but the nitrogen oxide does not deteriorate the C / N.

The embodiment of the present invention described above has (a) no peeling of the protective film and has the same adhesiveness as Si ₃ N ₄ (Table 1),
(B) has no deformation like Si ₃ N ₄ (Fig. 1), (c)
There is no deterioration due to moisture permeability like oxides and nitrides (Fig. 4), and (d) disk characteristics are Zr as shown in Table 2.
No difference is seen with the protective film of O ₂ .

Example 5 The film forming method in this example was a method in which 100% ZrO ₂ was used as a target and sputtering was performed in a 100% nitrogen atmosphere to deposit ZrON on the substrate.

The substrate is the same polycarbonate resin (PC) as in Example 1.
Was used. The disc structure was the same as in Example 1.

The results of the test are shown in Table 3 for the peeling test, Fig. 1 for the warpage, Fig. 3 for the protective effect against moisture permeation, and Table 2 for the disk characteristics.
, Respectively. The effect of protecting against warpage and moisture permeation obtained in this example was the same as that in Example 1, so the results are shown in the same figure as Example 1.

Example 6 In this example, 100% TiO ₂ was used as a target in Example 5
The same treatment was carried out.

Example 7 In this example, 100% Nb ₂ O ₅ was used as a target in Example 5.
The same treatment was carried out.

Example 8 In this example, 100% HfO ₂ was used as a target in Example 5
The same treatment was carried out.

Similar results were obtained even when Ar + N ₂ mixed gas was used instead of 100% N ₂ atmosphere.

(Effects of the Invention) As described above, the magneto-optical disk medium of the present invention in which nitrogen oxide is provided as the upper / lower protective film has excellent moisture permeation resistance and little warpage. Further, even though the plastic substrate is used, it has a performance equal to or higher than that of the magneto-optical disk using the glass substrate, so that the plasticization of the substrate is surely advanced.

[Brief description of drawings]

FIG. 1 is a graph showing the change over time of the warp amount of the magneto-optical disk, FIG. 2 is an explanatory diagram of the peel test, FIG. 3 is a graph showing the amount of warp of the substrate, and FIG. 4 is a graph showing the change over time of C / N. Is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuyo Maeda 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (56) References JP-A-60-193150 (JP, A) JP-A-61- 22458 (JP, A)

Claims (8)

(57) [Claims] 1. A magneto-optical disk medium having a magneto-optical recording layer supported on a substrate, wherein a film made of nitrogen oxide of at least one metal selected from the group consisting of Zr, Ti, Nb, Ta and V is formed. A magneto-optical disk medium provided between the magneto-optical recording layer and the substrate and on the magneto-optical recording layer. 2. A method of manufacturing a magneto-optical disk medium having a magneto-optical recording layer supported on a substrate, wherein 50 to 99 mol% of at least one metal selected from the group consisting of Zr, Ti, Nb, Ta and V. Is sputtered in a vacuum using a target composed of a nitride and the balance being an oxide of nitrogen oxide, and a film of the nitrogen oxide of at least one metal is formed between the magneto-optical recording layer and the substrate. A method for manufacturing a magneto-optical disk medium, which is provided on the magneto-optical recording layer. 3. The magneto-optical device according to claim 2, wherein the target is a target obtained by mixing zirconium nitride powder and zirconium oxide powder and firing the mixture, or a target obtained by firing a nitrogen oxide compound of zirconium. Disk medium manufacturing method. 4. The target is a target obtained by adding ZrO ₂ to a mother phase of ZrO ₂ and sintering, a target obtained by adding TiN to a mother phase of TiO ₂ and sintering, and a target of NbN being added to a mother phase of Nb ₂ O _5. The method for producing a magneto-optical disk medium according to claim 2, wherein the target is a sintered target or a target obtained by adding HfO ₂ to a mother phase of HfN and sintering the target. 5. A method for manufacturing a magneto-optical disk medium supported on a substrate of a magneto-optical recording layer, wherein a target made of a nitride selected from TiN, ZrN, NbN, TaN and VN is used in an oxygen atmosphere. A film made of sputtered nitrogen oxide is provided between the magneto-optical recording layer and the substrate and on the magneto-optical recording layer, or TiO, Ti ₂ O ₃ , Ti ₂ O ₅ , NbO, Nb ₂ O. ₅ , TaO, TaO ₂ , V
Sputtering in a nitrogen atmosphere using a target made of an oxide selected from ₂ O ₅ to provide a film made of a nitrogen oxide between the magneto-optical recording layer and the substrate and on the magneto-optical recording layer. A method of manufacturing a magneto-optical disk medium characterized by the above. 6. A ZrON film is formed by sputtering ZrO ₂ as a target in a nitrogen atmosphere, or a TiON film is formed by sputtering as TiO ₂ as a target in a nitrogen atmosphere, or Nb ₂ O is formed as a target. 6. The HbON film is formed by sputtering ₅ in a nitrogen atmosphere to form an NbON film or by using HfO ₂ as a target in a nitrogen atmosphere.
A method for manufacturing the magneto-optical disk medium described. 7. The method for manufacturing a magneto-optical disk medium according to claim 5, wherein the nitrogen atmosphere is a 100% N ₂ atmosphere or a mixed gas atmosphere of an inert gas and N ₂ . 8. The method for manufacturing a magneto-optical disk medium according to claim 7, wherein the inert gas is Ar.