JPH01196752A - Magneto-optical disk and its manufacture - Google Patents

Abstract

PURPOSE:To obtain satisfactory recording and reproducing characteristics by preliminarily coating at least one face of a transparent substrate with an SiO2 film and forming a protective film of a base. CONSTITUTION:At least one face 11 of a transparent substrate 10 is coated with an SiO2 film, and it is preferable that the film thickness is in the range of 2,000-2,000Angstrom , and 1,300-1,500Angstrom film thickness is most preferable. The base protective layer 12, a magneto-optical recording film 13, and a protective layer 14 are formed and laminated on both recording faces of the substrate 10 by sputtering. The film 13 is sandwiched between layers 12 and 14 on both sides. A protective resin layer 15 consisting of an ultraviolet-curing resin or the like is formed on the layer 14. The layer 15 may consist of a transparent acryl, an epoxy resin, a polycarbonate, or the like. Layers 12 and 14 consist of an oxide or nitride like a Y2O3 or an SiN. A material having 1.8-2.2 refractive index is selected as the material of the layer 12 and its film thickness is about 900Angstrom , and the layer 14 protects the surface of the film 13 and has 800-900Angstrom film thickness. Thus, satisfactory recording and reproducing characteristics are obtained and the mass productivity of a magneto-optical disk is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an erasable/rewritable magneto-optical disk, and more particularly, to an erasable/rewritable magneto-optical disk, which prevents warpage and deformation of the substrate and at the same time
The present invention relates to a magneto-optical disk whose aperture is controlled to have a high Kerr rotation angle with good playback efficiency, and a method for manufacturing the same.

2. Description of the Related Art Magneto-optical disks are attracting attention as erasable and rewritable high-density, large-capacity optical memory recording media in various fields such as external memory for computers and optical disk files. This magneto-optical disk has a basic structure in which a magnetic thin film (magneto-optical recording film) having perpendicular anisotropy is formed on a transparent substrate using a thin film forming technique such as sputtering or vacuum evaporation.

Currently, rare earths are the most commonly used materials for magnetic thin films.
Transition metal amorphous alloy films are extremely susceptible to oxidation and deterioration as they are, and have problems in terms of weather resistance and moisture resistance. For this reason, recently, three-layer recording media have been used in which a magneto-optical recording film is sandwiched between two protective layers such as a protective layer/magnetic layer on the surface where the tracking groove is formed. .

Furthermore, as a disk substrate, a plastic (resin) substrate such as PC (polycarbonate) is generally used because it is superior in productivity, cost, and has less risk of damage than a glass substrate.

Problems to be Solved by the Invention When a recording medium with a three-layer structure as described above is soaked on a transparent substrate, the thickness of the entire recording medium becomes approximately 3000A (angstroms), so a resin substrate is used as the disk substrate. When using this method, after a recording film is fabricated by sputtering, etc., the entire 1λ plate may be deformed or warped due to internal stress, etc., and surface wobbling occurs when the disk is rotated during signal recording + fr generation, causing focus and distortion. Tracking servo may not work properly. Therefore, in extreme cases, recording/playback may be hindered.

Therefore, the present inventors have recently proposed to cover the entire disk substrate with a Si02 film to prevent such phenomena.This method increases the mechanical strength and prevents deformation of the disk. Although good results can be obtained against warpage, etc., when layering a protective film on top of the SiO2 film after coating, strict film thickness management and control is required to optimize the film thickness. This makes it extremely troublesome to form a film on a recording medium by sputtering or the like.

In other words, in the above-mentioned three-layer recording medium, if the underlying protective layer is formed of a material with a higher refractive index than the transparent substrate, the apparent magneto-optical Kerr rotation angle θk can be increased, and the Kerr effect can be increased. It is known that enhancement improves C/N, provides good reproduction amplitude, and can greatly contribute to improving reproduction characteristics. However, when such a protective film is formed on a substrate with a SiO2 film interposed, -
In general, the refractive index of SiO2 film is lower than that of transparent substrates such as PC, so depending on the film thickness, the underlying protective film (layer)
A problem arises in that it no longer contributes to Kerr effect enhancement, and the long-awaited protective film ↑) properties cannot be utilized. Therefore, in order to sufficiently prevent deformation and warping of the SiO2 film and the substrate while at the same time not losing the Kerr effect enhancement provided by the protective film, the combination of the SiO2 film and the protective film must be carefully and precisely Film thickness management and control is necessary, and optimizing it is easy! There are many issues that need to be resolved, not f1 issues.

This invention has been proposed in view of the above points, and can prevent deformation, warping, etc. of the resin substrate caused by recording medium film formation, and at the same time effectively utilize the Kerr effect enhancement exerted by the protective film (layer). The purpose is to make it possible for the government to meet the needs of the government and to ensure that it is sufficiently secured.

Means for Solving the Problems In order to achieve the second object, the present invention forms a SiO2 film with a thickness of 1000 to 2000A on at least one surface of a transparent substrate. The SiO2 film can be coated not only on one side of the transparent substrate but also on both sides or the entire surface.

Further, according to the present invention, a 1-SiO2 film is formed on a transparent substrate.
A structure is adopted in which a protective layer having a thickness in the range shown above is formed, and a magneto-optical recording film is formed thereon.

Furthermore, the present invention coats the surface of the transparent resin substrate with a SiO2 film in the range of 1000 to 2000 Å in advance, and then forms a protective layer made of Y203 or the like with a refractive index of 1.8 to 2.2 via the SiO2 film. The gist of this invention is a manufacturing method characterized by forming a magneto-optical recording film thereon. According to the method of the present invention, the SiO2 film can be formed using other coating methods, but it is more preferable to use the LPD method.

Function: When at least one side of the transparent resin substrate, that is, the side of the recording film, is coated with S 10211X to a thickness in the range of 1000 to 2000 Å (angstroms), the mechanical and chemical properties of the substrate, especially the mechanical strength, are significantly improved. Warpage, deformation, etc. of the disk after the medium film formation is suppressed. If a protective film with a refractive index of 1.8 to 2.2 is formed on this SiO2 pattern with a thickness in the range of 10°O to 2000 Å, the Kerr effect enhancement of the protective film will not be lost, but rather it will improve the performance during signal reproduction. , the Kerr rotation angle obtained by l11 from the substrate side becomes approximately the maximum.

Furthermore, a SiO2 film with a thickness of 1000 to 200
It is coated with a film thickness of 0 Å, and Y20 is applied to the 1-
Since a protective film such as No. 3 is formed, the thickness of the protective film, which requires the most time during sputtering, can be relatively thin, and the time required for forming the protective film can be shortened.

In addition, since the substrate is small (and the recording surface side is coated with SiO2 film), it is possible to quickly evacuate the vacuum chamber in the event of a spat, which shortens the evacuation time required before high vacuum is applied. can.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a magneto-optical disk according to the present invention.
Transparent (resin) substrate 1 made of C (polycarbonate) or the like
On the signal recording surface of 0, there are recording tracks and king grooves (pre-groups) (not shown).

It is formed in a spiral shape along the edge.

A SiO2 film 11.11 is coated with a predetermined thickness on both sides of the transparent substrate 10 (in the first illustrated example).As will be described later, this SiO2 film 11 is coated on the substrate by a precipitation method called the LPD method. The surface of base protective layer 1 is coated.The film thickness is selected in the range of 1000 to 2000 Å.Among them, according to experimental examples, base protective layer 1
To maximize the Kerr rotation angle of the laser beam passing through 2,
The most preferable results are obtained in the range of 300 to 1500A.

Transparent substrate 1 coated with SiO211JE11
On the recording surface side of 0, an F base protective layer 12, a magneto-optical recording film 13, and a protective layer 14 are laminated and formed in this order by sputtering. The magneto-optical recording film 13 is sandwiched between the protective layers 12 and 14 from the front and back, and this three-layer structure forms a magneto-optical recording medium. On the protective layer 14, a protective resin layer 15 made of an ultraviolet curable resin or the like is further formed. The protective resin layer 15 serves to reinforce the mechanical strength of the disk. This protective resin layer 15 may be made of transparent acrylic, epoxy resin, polycarbonate, or the like.

The front and back protective layers 12.14 are formed of oxide or nitride materials such as Y2O3 and SiN.

In particular, as the upper protective layer 12, refraction: $n=1°8~
2.2 materials are selected. In fact, h
[Y2O3 with a refractive index n=1.9 was selected as the material for the protective layer 12.14. Of course, other SiN and Al2O3
Even if n is in the range of 1.8 to 2.2, it is not a problem in the present invention (it can be used).

As will be described later, the underlying protective layer 12 is formed to a thickness of about 90 OA, and the surface protective layer 14 is formed to a thickness of approximately 800 to 900 Å to protect the recording film 13 from the surface side. ing.

Next, the first step of coating the SiO2 film 11 on the transparent substrate 10 will be described.

Although SiO2 mock FL can be coated using thin film forming techniques such as the Suhanota method, CVD method, and RT: air deposition method, the present invention uses a method that is superior in terms of film density, ease of film creation, etc. LPD (LiQuid Phase DeI)
A precipitation method called a position method is sometimes adopted.

FIG. 2 shows the principle of the LPD method, and an immersion tank 20 contains an immersion liquid 21 at a temperature of about (room temperature to 40°C). The immersion liquid 21 is obtained by saturating a hydrosilicic acid (H2SiF6) aqueous solution with SiO2 powder (for example, silica gel), and then adding a horic acid aqueous solution (H3BO3). When the transparent substrate 10 is immersed in this solution 21,
The SiO2 film 11 begins to be deposited on the surface of the substrate.

Thus, after a predetermined period of time has elapsed after immersion, ■Si(O
H) Generation of 4-sol ■ Aggregation and gelation of the generated Si(OH) 4 sol Gelation and transport until it is layered on the substrate surface ■ Laminated Si(OH)
The SiO2 film 11 of a predetermined thickness is coated on the surface of the substrate 10 through three stages of condensation and polymerization of the four gels. In that case, the film thickness is in the range of 1000 to 2000 Å as desired, and more preferably controlled to 1300 to 1500 Å. In terms of the increase in the Kerr rotation angle θ, the thickness of this SiO2 film is around 150 OA, which gives the best results from the experimental results.

After the SiO2 film 11 is coated with the above thickness on the surface of the transparent substrate 10, three layers of base protection tank 12/magneto-optical recording film 13/protection tank 14 are sequentially laminated and formed thereon by sputtering method. .

First, Y2O3 (refractive index n=
1.9) A base protective layer 12 is formed, and then a magneto-optical recording film 13 is formed thereon to a thickness of 100 OA. The magneto-optical recording film 13 is made of, for example, TbFe1TbFeCo.
It is made of amorphous magnetic material such as. After the recording film 13 is formed, a protective layer 14 made of Y2O3 is formed on the surface side with a film thickness of 800~
The film is formed to a thickness of 900A. Furthermore, a protective resin layer 15 is formed thereon by a technique such as a spin cord.

As described above, a three-layer magneto-optical recording medium is formed on the transparent substrate 10 by sand-latching with a protective film. When forming this film, at least one surface of the transparent substrate 10, that is, the recording surface side, is coated with 11 layers of SiO2 film, so that the mechanical strength is improved, and after the film is formed on the recording medium, internal stress etc. This prevents the material from deforming or warping. In order to prevent this deformation and warpage, it is more desirable that the entire surface of the transparent substrate 10 be coated with the SiO2 film 11.

However, the effect of preventing warpage and deformation can be sufficiently exerted even on the - side only.

Furthermore, in combination with the SiO2 film 11 and the lower film 1 protective film 12, the film thickness of SiO2Vt:ll is 1 as described above.
Since the film is controlled to be approximately 150 OA in the range of 000 to 2000 Å, the thickness of the protective layer 12 and 14, which takes a relatively long time during sputtering, can be reduced by 9
It can be made relatively thin, on the order of 00A, and the spunter process, that is, the disk manufacturing process, can be carried out at a correspondingly high speed. In addition, the magneto-optical recording medium can be sputtered with T.
A high vacuum of less than orr is required, but since the SiO2 film is placed under 11 layers, it is not a problem even if it is a resin substrate. Reduction of this evacuation time is important, and together with the above-mentioned ability to form a film at high speed when making a protective replica and the resulting improvement in the film formation rate, mass production of optical discs is possible. Sexuality further improves.

The SiO2 film 11 coated on the substrate 10 has a film thickness of approximately 15 cm in thickness so that the Kerr effect enhancement can be effectively achieved in combination with the underlying protective layer 12.
The film is controlled and optimized to 00A, and the base protective layer 12 is made of Y203, and its refractive index is n=1.9 compared to the refractive index n of the PC board 10: 1.58. Good Kerr effect enhancement is provided to the laser light that passes through the protective layer 12. Therefore, during signal reproduction, the Kerr rotation angle Ok of the reproduced signal observed from the substrate 10 side becomes approximately the maximum.

According to an experimental example, when the thickness of the SiO2 film 11 and the refractive index of the protective layer 12 are set to the above-mentioned values, the Kerr rotation angle θ when viewed from the substrate 10 side is set to be larger than 0°6 ( I got it.

FIG. 3 shows that the magneto-optical disk according to the present invention is used to
This graph shows the results of examining the changes in reflectance R and Kerr rotation angle Ok when a signal is reproduced by changing the thickness of the protective layer 12 with respect to the SiO2 film 11, and the thickness of the SiO2 film 11 is The above optimum value was set to 1500A, and the film thickness of the protective tank 12 was changed with respect to this. In FIG. 3, the horizontal axis represents the film thickness (A) of the protective tank 12, and the vertical axis represents the reflectance R (%) and Kerr rotation angle (θk).

As is clear from FIG. 3, the thickness of the SiO2 film 11 is 1
It is fixed at 500A, and the base protection tank 12
When the recorded signal is reproduced by changing the film thickness of the protective tank 12,
When the film thickness is around 90OA, the reflectance R is approximately minimum and the Kerr rotation angle θk is maximum.

The Kerr rotation angle θ at this time is 0.8 or more.

This agrees with what was stated above. Therefore, if a magneto-optical disk is manufactured by setting the thickness of the SiO2 film 11 to 150 OA and the thickness of the protective tank 12 to about 900 Å as described above, it will affect the signal reproduction characteristics. The Kerr rotation angle θ as viewed from the substrate 10 side is maximum, and a value of 0°6 to 1− is obtained. And 5
If the thickness of the io2 film 11 is set to about 1500 A and the substrate 10 is coated in advance, the thickness of the base protection [12] can be made relatively thin in combination with the SiO21Z11.

Note that the above-mentioned results are shown for one experimental example, and according to the experimental results of the present inventor, the thickness of the SiO2 coated on the substrate 10 and the refractive index of the base protection tank 12 are equal to the above-mentioned values. It can be arbitrarily selected within a range and has the same effect within that range.

As is clear from the explanation in ``Advantages of the Invention'', according to the present invention, at least one surface of the transparent substrate is coated with a SiO2 film in advance, and a base ff1N film is formed on it. This eliminates the phenomenon of deformation and warpage of the disk substrate after the recording medium is formed. In addition, the thickness of the SiO2 film was set to 100
It is set in the range of 0 to 2000 people, and the refractive index is 1.
Since protection of 8 to 2.2 is formed, in the combination of the two, the Kerr rotation angle θk at the time of signal reproduction becomes the maximum due to Kerr effect enhancement, and a good reproduction amplitude can be obtained. Therefore, it is possible to provide a good magneto-optical disk with excellent signal recording and reproducing characteristics.

Furthermore, by coating the substrate with a SiO2 film in advance,
The thickness of the protective tank, which requires time to form a film, can be made relatively thin, and the evacuation time during recording medium production can be shortened.
The mass productivity of magneto-optical disks can be improved.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view of the magneto-optical disk according to the present invention, FIG. 2 is a schematic diagram showing the principle of the LPD method applied to the method of the present invention, and FIG. 3 is a diagram showing the use of the magneto-optical disk according to the present invention. FIG. 2 is a graph diagram showing changes in reflectance R and Kerr rotation angle θ with respect to changes in the thickness of the protective film when signals are reproduced. DESCRIPTION OF SYMBOLS 10...Transparent substrate, 11...SiO2 film, 12...Underlying protective film, 13...Magneto-optical recording film, 14.Fist/protective film.

Claims (6)

[Claims] (1) In a magneto-optical disk comprising a magneto-optical recording film having perpendicular magnetic anisotropy formed on a transparent substrate, a SiO2 film with a thickness of 1000 Å to 200 Å is formed on at least one surface of the transparent substrate.
A magneto-optical disk characterized in that it is formed by forming a film with a film thickness of 0 Å. (2) SiO2 film of 1000~200% on both sides of the transparent substrate
Claim (1) characterized in that the film is formed by forming a film in the range of 0 Å.
) described magneto-optical disk. (3) Through the SiO2 film on the transparent substrate, the refractive index is 1.
Claim (1) or (2) characterized in that the protective layer of 8 to 2.2 is formed, and a magneto-optical recording film is formed thereon.
) described magneto-optical disk. (4) A transparent resin substrate is immersed in a dipping solution using the LPD (Liquid Phase Deposition) method, and a SiO2 film of 1000 to 2000 Å is deposited on the surface.
After coating with a refractive index of 1.
1. A method for manufacturing a magneto-optical disk, which comprises forming a protective layer made of an oxide, nitride, etc. of No. 8 to 2.2, and depositing a magneto-optical recording film thereon. (5) Preliminary coating of SiO2 film on the surface of the transparent resin substrate
After coating in the range of ~2000 Å, a protective layer made of Y2O3 or the like with a refractive index of 1.8 to 2.2 is formed on top of the coating, and a magneto-optical recording film is formed on top of the protective layer. Disc manufacturing method. (6) The method for manufacturing a magneto-optical disk according to claim (4), wherein the film thickness of the oxide, nitride, etc. having a refractive index of 1.8 to 2.2 is in the range of 700 to 1200 Å.