JPS59198549A - Photomagnetic disc - Google Patents

Abstract

PURPOSE:To offer a both-side photomagnetic disc where the thickness is nearly the same as a one side disc and the track roundness of both sides is coincident completely by providing symmetrically an optomagnetic recording medium on a transparent base plate having a spiral track guide groove while clipping a reflecting film. CONSTITUTION:Layers 2, 6 made of the same kind of optomagnetic recording medium film, layers 3, 5 made of the same kind of dielectric film, a layer 4 made of metallic reflecting film, and a layer 7 made of transparent high polymer protecting film are formed on a transparent high-polymer base plate 1 having the spiral track guide groove, the film thickness of the layers 2, 6 is taken as 100-300Angstrom , the film thickness of the layers 3, 5 is taken as 800-1,200Angstrom , and the film thickness of the layer 7 is taken as >=1.5mum. In taking the depth of the track guide groove to 1/8 of the wavelength of laser light, the recessed part viewed from the incident direction of the laser light is sensed as a dark part and the projected part is sensed as a light part, and the recording of information is brought to the said dark part. In this case, the part being the light part viewed from the surface is the dark part viewed from the rear side, then the recording of the information to the rear side is brought to the dark part when viewed from the front side.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical disk on which information can be recorded, reproduced, and erased using both sides.

Conventionally, magneto-optical disks using transparent polymer substrates having spiral track guide grooves are well known, and magneto-optical disks in which information can be recorded, reproduced and erased using both sides are also well known. Ta. However, when recording, reproducing, and erasing information using both sides of a conventional magneto-optical disk using a spiral transparent polymer substrate, two disks with a magneto-optical recording medium formed on a spiral transparent polymer substrate are used. Since both substrates are used together, the magneto-optical disks produced are thicker, and it requires sophisticated manufacturing technology to match the circularity of the tracks on the two substrates.

The present invention eliminates the drawback that the magneto-optical disk having the above-mentioned spiral track guide groove is thick and that it is difficult to match the track circularity of the front and back surfaces of the magneto-optical disk, and eliminates the disadvantage of conventional single-sided information recording. - The object of the present invention is to provide a magneto-optical disk which has a thickness comparable to that of a magneto-optical disk for reproduction and erasing, and in which the track circularity on the front and back surfaces of the magneto-optical disk completely matches.

The present invention consists of a transparent polymer substrate having a spiral track guide groove, a first layer made of a magneto-optical recording medium film, a second layer made of a dielectric film, a third layer made of an NG metal reflective film, and a third layer made of a dielectric film. a fourth layer consisting of a magneto-optical recording medium film, a fifth layer consisting of a magneto-optical recording medium film,
By manufacturing a magneto-optical disk with a sixth layer made of a transparent polymer protective film, it has the same thickness as a conventional single-sided magneto-optical disk, and the track circularity on the front and back surfaces is perfectly matched. The above problem was solved by doing this.

To explain one embodiment of the magneto-optical disk with track guide grooves according to the present invention, FIG.
2 is a G4TbFe film, 3 is a SiO film, 4 is a Cu reflective film, 5 is a SiO film, 6 is a GdTbFe film, and 7 is a polycarbonate protective film, G'd T b Fe membrane2.
SiO film 3, Cu reflective film 4. SiO film5. GdTb1l
The l'e film 6 was formed using a low-temperature sputtering device, and the thickness of the Cu reflective film was 1oooX. The polycarbonate protective film 7 was formed by a spin code method. By making the depth of the spiral track guide groove of the polycarbonate substrate 1 equal to the depth of the wavelength of the laser beam used for information reproduction, the concave portion when viewed from the direction of incidence of the laser beam is a digital audio As with the case of a disc, the convex portions are perceived as dark areas, while the convex areas are perceived as bright areas. Information is recorded on the magneto-optical disk with track guide grooves according to the present invention in the bright area. At this time, since the portions of the magneto-optical disk that are bright when viewed from the front surface are dark when viewed from the back, information is recorded on the back side in a dark area when viewed from the front.

FIG. 2 shows that in the magneto-optical disk according to the present invention shown in FIG.
2 is a diagram showing the information reproduction sensitivity when the film thickness of the GdTbFe films 2 and 6 is changed as /1 m. In FIG. 2, the relationship between the information reproduction sensitivity and the film thickness of the GdTbFe films 2 and 6 is almost the same in the case of information reproduction from the front side of the magneto-optical disk according to the present invention and the case of information reproduction from the back side. The case of regeneration was used as a representative example. From Figure 2, the film thickness of GdTbFe films 2 and 6 is 100 to 300X.
In this case, the information reproduction sensitivity was 30 dB or more, which was found to pose no practical problem.

FIG. 3 shows the thickness of the GdTbFe films 2 and 6 in the magneto-optical disk according to the present invention shown in FIG. FIG. 7 is a diagram showing the information reproduction sensitivity when the thickness of the polycarbonate protective film 7 is 2 μm, the width of the rack is 2 μm, and the thickness of the 810 films 3 and 5 is changed. In this case as well, since there is no difference in the reproduction sensitivity between the front and back sides of the disc, the reproduction sensitivity on the front side is used as representative. From FIG. 3, it was found that when the thickness of the 810 films 3 and 5 was 800 to 12 ooi, the information reproducing sensitivity was 30 aB or more, and there was no problem in practical use.

FIG. 4 shows the thickness of the GdT1) Fθ films 2 and 6 in the magneto-optical disk according to the present invention shown in FIG.
FIG. 7 is a diagram showing information reproduction sensitivity when the thickness of the S10 films 3 and 5 is 1000^, the track width is 2 μm, and the thickness of the polycarbonate protective film 7 is varied. The solid line in FIG. 4 indicates the sensitivity when information is reproduced from the substrate side, and the broken line indicates the sensitivity when information is reproduced from the protective film side.

As shown in Fig. 4, even if the thickness of the polycarbonate protective film 7 is changed, the information reproducing sensitivity from the substrate side hardly changes, but the information reproducing sensitivity from the protective film side is approximately 1.5 μm thicker than the polycarbonate protective film 7. It was found that it was not possible to obtain 50 aE or more unless the conditions were above.

FIG. 5 shows the film thicknesses of the GdTbFe films 2 and 6 in the magneto-optical disk according to the present invention shown in FIG.
FIG. 3 is a diagram showing the information reproduction sensitivity when the track width is changed with the thickness of the TO films 3 and 5 being 1000XI and the thickness of the polycarbonate protective film 7 being 6 μm. Figure 5 shows that when the track width becomes less than 5 μm, the information reproduction sensitivity decreases rapidly, so in order to achieve the information reproduction sensitivity of 304 films or more, the track width must be 1.2 μm or more. I understand.

As described above, the magneto-optical disk with track guide grooves according to the present invention has a first layer made of a magneto-optical recording medium film, a second layer made of a dielectric film, and a transparent polymer substrate having a spiral track guide groove. A third layer made of a metal reflective film, a fourth layer made of a dielectric film, a fifth layer made of a magneto-optical recording medium film, and a sixth layer made of a transparent polymer protective film are formed. The film thickness of the magneto-optical recording medium is 100 to 3001.
, the thickness of the second layer and the fourth N dielectric film is 800 to 12
00 people, by making the thickness of the transparent polymer protective film of the sixth layer 1.2μ or more, it has the same thickness as a magneto-optical disk for single-sided information recording, playback, and erasing, and has a surface of a magneto-optical disk. This has the effect that it is possible to easily produce a double-sided usable magneto-optical disk in which the track circularity of the back surface and the back surface are completely matched.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional WJ diagram of an embodiment of a magneto-optical disk with track guide grooves according to the present invention, in which 1 is a polycarbonate substrate having a spiral track guide groove, 2 is a GdT
bFe film, 3 is 810 film, 4 is Ou reflective film, 5 is 810
6 is a GdTbFe film, and 7 is a polycarbonate protective film. FIG. 2 shows the magneto-optical disk according to the present invention shown in FIG. 1, in which the thickness of the 810 films 3 and 5 is 1000 mm, the thickness of the polycarbonate protective film 7 is 2 μl, and the track width is 2 μl. 6 is a graph showing the information reproduction sensitivity when changing the film thickness of FIGS. FIG. 3 shows the thickness of the GdTb+Fe films 2 and 6 in the magneto-optical disk according to the present invention shown in FIG.
This is a graph showing the information reproduction sensitivity when the film thickness of the polycarbonate protective film 7 is 2 μm, the track width is 2 μm, and the film thicknesses of the SiO films 3 and 5 are changed. FIG. 4 shows that the film thickness of the G(ITbFe films 2 and 6 is 200') in the magneto-optical disk according to the present invention shown in FIG.
h, ,s 1o film thickness of 3 and 5 is 100oi,
It is a graph showing the information reproduction sensitivity when the track width is 2 μm and the thickness of the polycarbonate protective film 7 is varied. FIG. 5 shows that the film thickness of the GdTbFe films 2 and 6 is 200X in the magneto-optical disk according to the present invention shown in FIG.
S 10 [3 oyohi 5) I [thickness wo 10. OX is a graph showing the information reproduction sensitivity when the thickness of the polycarbonate protective film 7 is set to 3 μm and the width of the tractor is changed. Figure 1/1 Figure 2 GdTbFe film 2 84 of 6 (A) Figure 3 S star side 61 slot 1

Claims (5)

[Claims] (1) A first layer consisting of a magneto-optical recording medium film on a transparent polymer substrate having a spiral track guide groove. A second layer made of a dielectric film, a third layer made of a metal reflective film,
A magneto-optical disk comprising a fourth layer made of a dielectric film, a fifth layer made of a magneto-optical recording medium film, and a sixth layer made of a transparent polymer protective film. (2) The first layer and the fifth layer are formed of the same type of magneto-optical recording medium, and both the first layer and the fifth layer have a film thickness of 100 to 5 ounces. magneto-optical disk. (3) The second layer and the fourth layer are formed of the same type of dielectric material, and the film thickness of both the second layer and the fourth layer is 800 to 120 mm.
0^. The magneto-optical disk according to claim 2. (4) The magneto-optical disk according to claim 3, wherein the 6H transparent polymer protective film has a thickness of 1.5 μm or more. (5) When the wavelength of the laser beam for information reproduction is λ, the depth of the track guide groove on the transparent polymer substrate is λ, and the width of the track is 1.2 μm or more, Claim 6 Magneto-optical disk described.