JP2925795B2 - Method of manufacturing magneto-optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magneto-optical disk, and more particularly to a technique for improving magnetic field sensitivity and environmental resistance.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 7 and 8, a magneto-optical disk is formed on a glass substrate and a transparent plastic substrate 1 such as polycarbonate or polymethyl methacrylate.
N, Si ₃ N ₄ , AlN, Al ₂ O ₃ , Y ₂ O ₃ , SiO ₂ ,
A protective film 2 made of ZnS or the like (hereinafter referred to as a base protective film), a magnetic film 3 made of an amorphous alloy of a rare earth-transition metal such as TbFe or TbFeCo, SiN, Si
_{3 N 4, AlN, Al 2} O 3, Y 2 O 3, SiO 2, a protective film made of ZnS or the like 2 (hereinafter, referred to as upper base protective film), Al,
A reflective film made of a material having a high reflectivity such as Au or Ag is formed by sputtering or vacuum vapor deposition, and the film-formed surface is spin-coated using an ultraviolet-curable resin or the like by resin coating 5 by screen printing or the like. Coated .

[0003]

One of the performance requirements for a magneto-optical disk is long-term environmental reliability.

[0004] The performance of a magneto-optical disk is degraded by the external environment. Mainly, the recording sensitivity with respect to the power of the laser beam changes, and accordingly, the carrier-to-noise ratio (hereinafter, referred to as CNR) decreases.

Another performance required of a magneto-optical disk is a magnetic field sensitivity at the time of data writing.

The magnetic field sensitivity indicates the degree of writing (magnetization reversal) of the magneto-optical disk (magnetic film) with respect to the intensity of the external magnetic field. The higher the magnetic field sensitivity, the better the writing is possible with a small magnetic field. I do.

As one method of improving the magnetic field sensitivity, a method of changing the composition ratio of the material constituting the magnetic film 3 is considered. In this method, it is necessary to replace the material of the magnetic film or to change other characteristics ( The dynamic characteristics such as the recording sensitivity and the static characteristics such as the Kerr rotation angle also change, and there is a problem that the original recording / reproducing characteristics may not be maintained.

Therefore, an object of the present invention is to provide a method of manufacturing a magneto-optical disk capable of improving the magnetic field sensitivity without changing the composition of the magnetic film and improving the environmental resistance for a long time. It is in.

[0009]

SUMMARY OF THE INVENTION Therefore, in order to achieve the above-mentioned object, the present invention provides a method for manufacturing a magneto-optical disk in which a disk-shaped protective film is formed and then a magnetic film is formed. Before film formation, the surface of the protective film is irradiated with ultraviolet rays in advance.
It is a thing. In addition, per unit area of this UV irradiation
Is 3 mW · Hr / cm ² or less.
You.

Further, the present invention provides a method for manufacturing a magnetic recording medium , comprising the steps of:
In addition, an upper protective film is formed, or the surface of the magnetic film is formed.
Forming an upper protective film and a reflective film in this order on the surface, or
Or an upper protective film and a reflective film on the surface of the magnetic film.
And then coat the surface of the reflective film with a protective resin
This is another feature.

[0011]

According to the present invention, the surface of the underlying protective film is irradiated with ultraviolet rays.
By improving the magnetic field sensitivity and environmental resistance
Is improving.

[0012] Integrated time per unit area of ultraviolet irradiation
Is preferably 3 mW · Hr / cm ² or less.

According to the above method, the above-mentioned problem is solved because the composition of the magnetic film is not changed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.
This will be described with reference to FIGS. FIG.
Not directly related to the present invention, but helps to improve magnetic field sensitivity
Flowchart showing an example of a method for manufacturing a magneto-optical disk
FIG. 2 shows a change in the recording laser power according to FIG.
FIG. 3 shows the carrier-to-noise ratio (CNR) according to FIG.
FIG. 4 is a diagram showing a change in Bia during recording according to FIG.
A diagram showing a change in a reproduction level of a carrier with respect to an s magnetic field intensity.
It is. FIG. 5 is a flowchart showing one embodiment of the manufacturing method of the present invention.
FIG. 6 is a chart showing the bias at the time of recording according to FIG.
FIG. 7 is a diagram showing a change in a carrier reproduction level with respect to a magnetic field strength.
is there.

[0015] Figure 1 is all SANYO which sequentially show an example of a process for forming the magneto-optical disk having a reflective film, after forming the lower ground protective film, sputter etching the surface of the underlying protective film processes There is a feature in that is added . Shimoho
FIGS. 2 and 3 show the improvement in environmental resistance obtained by sputter etching of the protective film.

In FIG. 2, the horizontal axis represents a temperature of 70 ° C. and a relative humidity of 90.
%, And the vertical axis shows the ratio of the optimum recording laser power to the initial value. Both are 100
Until the time, but increasing the recording sensitivity is observed, a magneto-optical disk was subjected to sputter etching of the lower fabric protective film,
The change is small and hardly changes after 100 hours. On the other hand, in the case of the conventional magneto-optical disk, the initial recording sensitivity greatly increases, and further increases after 100 hours.

In FIG. 3, the horizontal axis represents a temperature of 70.degree.
%, The vertical axis represents the carrier-to-noise ratio (C
NR). CNR of conventional magneto-optical disk against to decreases over time, decrease in CNR is slight in the magneto-optical disk was subjected to sputter etching of the lower fabric protective film.

Next, FIG. 4 shows the improvement of the magnetic field sensitivity in terms of the reproduction level of a carrier (hereinafter, referred to as C) with respect to the Bias magnetic field strength at the time of recording. The sample shown here is
38W · Hr / m without underlayer protective film sputter etching
Is a ² of two kinds. From the figure, it can be seen that the carrier rises when the bias magnetic field intensity is lower in the case with sputter etching than in the case without sputter etching, and the magnetic field sensitivity is improved.

Thus, in the manufacturing process of the magneto-optical disk,
Before applying sputter etching to the underlayer protective film.
To suppress the change in recording sensitivity and improve the magnetic field sensitivity
But the magnetic field sensitivity is the same as in sputter etching.
As a method that can be expected to improve the
There are external irradiation, the main of the present invention in the ultraviolet irradiation method
There are features.

FIG. 5 is a schematic diagram showing an ultraviolet ray irradiation on the underlayer protective film.
In the projection method, a film forming process of a magneto-optical disk having a reflective film is shown in order. In addition to the conventional process shown in FIG. 7, the present invention adds a process of irradiating the surface of the underlying protective film with ultraviolet light (UV) after forming the underlying protective film.

FIG. 6 shows the resulting improvement in magnetic field sensitivity. The samples shown in the figure are of two types, that is, no UV irradiation of the underlying protective film and a UV irradiation of 2.2 mW · Hr / cm ² . From the figure, it can be seen that the rising gradient of the carrier wave (C) is steeper with UV irradiation than with no UV irradiation, and the magnetic field sensitivity is improved.

[0022]

As described above, according to the method of manufacturing a magneto-optical disk of the present invention, after forming the undercoat protection film , the undercoat protection film is formed.
Since the surface of the protective film is irradiated with ultraviolet rays,
Irradiation sharpens the rising slope of the carrier wave,
As a result, the magnetic field sensitivity is improved, and good writing is possible with a small magnetic field.
It is possible to adjust the composition ratio of the materials constituting the conventional magnetic film.
It is necessary to change the magnetic film material as in the method of changing
Or other characteristics, such as dynamic characteristics such as recording sensitivity and power.
-Static characteristics such as the rotation angle have changed, and
It is not impossible to maintain the raw characteristics,
Excellent, such as improved environmental reliability
It has the effect .

[Brief description of the drawings]

FIG. 1 shows a sputter etch on a protective underlayer of a magneto-optical disk .
5 is a flowchart illustrating an example of a manufacturing method for performing a pitting process .

FIG. 2 is a diagram showing a change in recording laser power according to FIG. 1;

FIG. 3 is a diagram illustrating a change in a carrier-to-noise ratio (CNR) according to FIG. 1;

FIG. 4 is a diagram showing a change in a reproduction level of a carrier with respect to a Bias magnetic field intensity during recording according to FIG. 1;

FIG. 5 shows an embodiment of a method for manufacturing a magneto-optical disk according to the present invention.
Is a flowchart showing a manufacturing process according to the first embodiment.

6 is a diagram showing a change in the reproduction level of a carrier wave with respect to the Bias magnetic field strength during recording according to FIG. 5;

FIG. 7 is a flowchart illustrating an example of a conventional method for manufacturing a magneto-optical disk .

8 is an enlarged partial cross-sectional view of the magneto-optical disk according to FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Protective film 3 Magnetic film 4 Reflective film 5 Resin coat

Continuation of the front page (72) Inventor Junji Kawasaki 1-4-4 Shiromi, Chuo-ku, Osaka City, Osaka Prefecture In-house examiner, NEC Home Electronics Co., Ltd. Yutaka Nakamura (56) References JP-A-1-118236 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G11B 11/10 541

Claims (5)

(57) [Claims] (1) A protective film and a magnetic film are formed on a disk-shaped substrate.
In the method for manufacturing a magneto-optical disk having a film, the magnetic film
A process for irradiating the surface of the protective film with ultraviolet light before forming the film . 2. The integral of the ultraviolet irradiation per unit area.
^{2. The} method according to claim 1 , wherein the time is 3 mW · Hr / cm ² or less . 3. An upper protective film is further provided on the surface of the magnetic film.
3. The method for manufacturing a magneto-optical disk according to claim 1, wherein the film is formed . 4. An upper protective film on the surface of the magnetic film,
3. A film is formed in the order of a reflection film.
The manufacturing method of the magneto-optical disk described in the above . 5. An upper protective film on the surface of the magnetic film,
The film is formed in the order of the reflective film, and the surface of the reflective film is made of protective resin.
The method for manufacturing a magneto-optical disk according to claim 1, wherein the magnetic disk is coated with the magnetic disk.