JP2801296B2 - Method for manufacturing magneto-optical recording medium - Google Patents

Description

The present invention relates to a method for manufacturing a magneto-optical recording medium.

[Prior Art] A magneto-optical recording medium capable of erasing and rewriting information generally has a structure in which a protective film, a magnetic film having perpendicular magnetic anisotropy, and a protective film are laminated in this order on a transparent substrate. Alternatively, it has a structure in which a reflective film is further laminated on the above-mentioned upper protective film. As a material for forming the magnetic film, an amorphous alloy of a rare earth element and a transition metal is preferable. For example, an alloy such as TbFeCo, NdDyFeCo, and GdTbFe is used. The magneto-optical recording medium having the above structure has a problem that the Kerr rotation angle is about 1 degree and the magneto-optical effect is small.

In order to solve the above problems, a transition metal layer such as Fe and Co and a noble metal layer such as Cu, Au, Pt, and Pd are alternately laminated in a thickness of 1 to 200 ° in a large number, Or TbFe
A magneto-optical recording medium with a composition modulation film having perpendicular magnetic anisotropy was developed by laminating a number of rare earth transition metal alloy layers such as SiO2 and dielectric layers such as SiO alternately with the same thickness. ing. The magneto-optical recording medium including the composition modulation film in which the transition metal layers and the noble metal layers are alternately stacked has a large magneto-optical effect particularly for light having a short wavelength, and enables high-density recording.

The light irradiated to record, reproduce, or erase information on the magneto-optical recording medium provided with the composition modulation film is irradiated at the interface between the transition metal layer and the noble metal layer or the rare earth transition metal alloy layer and the dielectric material constituting the composition modulation film. Multiple reflections occur at the interface with the body layer. Due to the interference effect due to multiple reflection, the Kerr rotation angle of the magneto-optical recording medium is significantly enhanced.
The Kerr rotation angle of a magneto-optical recording medium including a magnetic film composed of a composition modulation film of Fe and SiO reaches a maximum of 25 degrees.

Conventionally, the composition modulation film uses two targets having a composition corresponding to the composition of the above-mentioned two layers, and forms two shutters disposed between the two targets and the transparent substrate. It is formed by performing a sputtering method that alternately opens and closes according to the conditions.

[Problems to be Solved by the Invention] In order for a magneto-optical recording medium having a composition modulation film to have a large Kerr rotation angle, the two layers having different compositions constituting the composition modulation film must be separated at the interface between the two layers. It is necessary that a region where the composition is mixed (hereinafter, referred to as a mixed region) is narrow.

When forming a composition modulation film by the conventional sputtering method, in order to narrow the mixing area, after closing the shutter of one target, the shutter of the other target must be opened at a sufficient interval. Therefore, the film formation rate of the composition modulation film is low. Further, since dust is generated by opening and closing the shutter, a defect such as a pinhole may be generated in the obtained composition modulation film.

An object of the present invention is to provide a method capable of mass-producing a magneto-optical recording medium having a composition modulation film.

[Means for Solving the Problems] According to the present invention, the above object is achieved by forming two or more layers having different compositions alternately with a film thickness in the range of 1 to 200 °. In a method for manufacturing a magneto-optical recording medium having a composition modulation film having a property and a transparent substrate, two targets having compositions corresponding to the compositions of the two layers described above are used and placed so as to face the targets. A method for manufacturing a magneto-optical recording medium, characterized in that the composition modulation film is formed by performing a sputtering method of performing planetary rotation of the transparent substrate thus rotated so that the number of rotations is at least five times the number of revolutions. This is achieved by providing. Here, the composition modulation film is formed of two layers of a transition metal layer and a noble metal layer, or is formed of two layers of a rare earth transition metal alloy layer and a dielectric layer.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples.

FIG. 1 is a schematic plan view showing the relationship between a transparent substrate and two targets when forming a composition modulation film according to the present invention. According to the present invention, the transparent substrate 1 attached to the chamber base of the chamber is revolved around the point O ₂ while revolving around the point O ₁ , so that the number of revolutions is at least five times the number of revolutions. Rotate the planet so that it becomes. In the present invention, the rotation speed is preferably at least 10 times the revolution speed, the rotation speed is in the range of 5 to 20 rpm, and the revolution speed is suitably in the range of 0.5 to 2 rpm. is there.

Two targets 2 and 3 having a composition corresponding to the composition of the two layers constituting the composition modulation film face the transparent substrate 1 and are placed on a track on which the transparent substrate 1 revolves so as to be separated from each other. Sputter power is applied to each of the two targets. It is necessary to determine the sputter power according to the composition of the target.For example, it is preferable to apply an RF sputter power of 150 to 250 W to the SiO target, and to apply a DC sputter power of 70 to 130 W to the TbFe alloy target. preferable. It is preferable to provide a partition plate between the two targets in that the mixing region in the composition modulation film can be narrowed.

FIG. 2 shows a schematic sectional view of an example of the magneto-optical recording medium obtained by the present invention. The magneto-optical recording medium has a structure in which a protective film 4, a composition modulation film 5 having perpendicular magnetic anisotropy, and a protective film 6 are sequentially laminated on a transparent substrate 1. The composition modulation film 5 is formed by alternately laminating 5 to 20 layers of a transition metal layer such as Fe and Co and a noble metal layer such as Cu, Au, Pt and Pd, or a rare earth transition metal alloy layer such as TbFe. And a dielectric layer of SiO or the like are preferably alternately laminated in a range of 5 layers or more and 20 layers or less. The film thickness of each of the above-mentioned layers is in the range of 1 to 200 °, and more preferably in the range of 6 to 10 °.

The film formation rate of the composition modulation film in the present invention is 50 to 100 ° /
min, which is higher than the film forming rate in the conventional sputtering method.

Materials for forming the above protective film include SiN, AlN, AlSi
It is preferable to use N or the like, and the film thickness is 300 to 1600.
It is preferable to be within the range of Å. The protective film can be formed by a magnetron sputtering method, a reactive sputtering method, or the like.

As the above transparent substrate, a polycarbonate resin substrate,
An amorphous polyolefin resin substrate, a polymethyl methacrylate resin substrate, a glass substrate, or the like is used.

[Effects of the Invention] According to the present invention, a method capable of mass-producing a magneto-optical recording medium having a composition modulation film is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing the relationship between a transparent substrate and two targets when forming a composition modulation film according to the present invention, and FIG. 2 is a schematic cross section of an example of a magneto-optical recording medium obtained by the present invention. FIG. 1 ... Transparent substrate, 2,3 ... Target, 5 ... Composition modulation film.

Claims (1)

(57) [Claims] 1. A magneto-optical device comprising a composition modulation film having perpendicular magnetic anisotropy and a transparent substrate, wherein two or more layers having different compositions are alternately laminated with a film thickness in the range of 1 to 200 °. In the method for manufacturing a recording medium, the composition modulation film may be composed of two layers of a transition metal layer and a noble metal layer, or may be composed of two layers of a rare earth transition metal alloy layer and a dielectric layer. Using two targets having compositions corresponding to the composition of the two layers described above, the transparent substrate placed so as to face the target is planetary-rotated so that the number of revolutions is five times or more the number of revolutions. A method for manufacturing a magneto-optical recording medium, comprising forming the composition modulation film by performing a sputtering method.