JPH04286741A - Flat planar information recording carrier - Google Patents

Abstract

PURPOSE:To improve an environmental resistance characteristic without degrading the recording sensitivity and recording and reproducing characteristics of a magneto-optical disk. CONSTITUTION:A ZnS dielectric layer 2, a magneto-optical recording layer 3, a dielectric layer 4 consisting of ZnS or ZnS-SiO2, a reflection film layer 5 consisting of Al-Ti, Al-Cr or Al-Ti-Cr, and a dielectric layer 6 consisting of AlTiON or ZnS-SiO2 are successively laminated on a transparent substrate 1 consisting of glass or plastic, etc., and finally a protective coat layer 7 consisting of a UV curing resin is provided. C/N is improved by a Kerr enhancement effect and high-temp. and high-moisture resistance characteristics are improved by the addition of the Ti and Cr to the Al and by the AlTiON protective layer according to this constitution.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat information recording carrier, such as an optical disk or an optical card, using a rewritable magneto-optical medium capable of high-capacity, high-density recording.

0002

2. Description of the Related Art In recent years, magneto-optical recording media have attracted attention as recording media capable of high-density recording, large-capacity recording, and high-speed access.

FIGS. 7A and 7B show the structure of a conventional magneto-optical disk. As shown in the figure, conventionally, a magneto-optical film 3, which is a recording medium of a magneto-optical disk, is composed of a rare earth-transition metal alloy thin film. However, since this type of alloy thin film is easily oxidized, a structure in which oxidation is prevented by sandwiching dielectric materials on both sides as shown in FIG. 7(A) is employed. As the oxidation-preventing dielectrics 8 and 9 of this magneto-optical film, oxides such as SiO, SiO2, Ta2O5, etc. are used, nitrides such as Si3N4 and AlN, and carbides such as TaC, TiC, etc. are used. has been done. In addition, as a measure to improve the recording and reproducing characteristics, since the Kerr effect of the magneto-optical film itself is small, a first dielectric film 8 is provided on the reproducing surface side of the recording film in order to increase the apparent Kerr rotation angle. The dielectric film on the reproduction surface side of the recording film has a function of protecting the recording medium layer and also has a function of increasing the Kerr effect (Kerr enhancement effect). Furthermore, for the purpose of improving the recording and reproducing characteristics, a structure that also utilizes the light that has passed through the recording layer has been proposed. Realizes the use of light.

[0004] Furthermore, in order to prevent an increase in recording/erasing energy due to heat flow during recording and erasing, some devices have a structure in which a third dielectric layer 9 is sandwiched between the recording film and the reflective film.

[0005]

However, in the conventional structure as described above, there was a problem that the environmental resistance of the optical recording medium layer 3 was poor. For example, when SiO or SiO2 is used as the first dielectric layer 8, there is a problem in that the magneto-optical film is oxidized due to moisture penetrating locally into the dielectric, resulting in pinholes. Also, Ta2O5
, Si3N4, and AlN have a problem in that the internal stress of these dielectric films themselves is large, which causes cracks in the films, through which moisture enters, causing oxidative deterioration of the magneto-optical film. Furthermore, since SiO and SiO2 have a low refractive index, there is a problem in that even if an appropriate film thickness is selected, the Kerr effect cannot be sufficiently increased.

[0006] Furthermore, Al is very effective as a reflective film because a large reflectance can be obtained when a suitable film thickness is applied to the reflective film 10, but Al itself is a metal that corrodes very easily. However, there was a problem in that it was not suitable as a reflective film for recording media that required high reliability.

In the configuration shown in FIG. 1B in which the reflection film 10 is directly attached to the magneto-optical recording film 3, heat is easily diffused within the reflection film, and a large recording power is required. When recording with such a relatively high recording power, the recording pits are deformed into a shape different from that of the recording laser beam, resulting in a decrease in C/N, which poses a problem in that the recording power margin becomes narrow.

[0008] Furthermore, in order to prevent power loss due to heat flow during recording and erasing, in a disc structure in which a dielectric material for thermal insulation is sandwiched between a recording film and a reflective film, the film thickness of the dielectric material is approximately 100 nm. It takes a long time to form a film because it is thick. In addition, the combination of the film thicknesses of the first layer dielectric 8 and the magneto-optical film 3 has a large effect on the optical interference structure, so highly accurate film thickness control is required, resulting in a problem of poor yield during mass production. was there.

[0009] The present invention solves these problems, and aims to provide an information recording carrier that has excellent environmental resistance, high recording sensitivity, and excellent signal recording and reproducing characteristics. .

0010

[Means for Solving the Problem] In order to solve this problem, the present invention provides a ZnS dielectric layer, a rare earth transition metal based magneto-optical recording layer, a very thin ZnS or Dielectric layer consisting of ZnS-SiO2, Al-Ti, Al-Cr or Al-Ti
-Reflective film layer made of Cr, AlTiON or ZnS-
Dielectric layers made of SiO2 are sequentially laminated, and finally a protective coating layer of ultraviolet curable resin is provided.

[0011]

[Operation] With this configuration, a magneto-optical disk medium having good environmental resistance and excellent recording and reproducing characteristics is obtained. That is, since the first ZnS2 layer shown in FIG. 1 has a large refractive index, by selecting an appropriate film thickness, a large Kerr enhancement effect that increases the Kerr rotation angle can be obtained.

[0012] Furthermore, the third dielectric layer 4 has a film thickness of 3 nm or more.
By forming a 30 nm thin ZnS or ZnS-SiO2 layer, the flow of heat from the laser beam irradiated onto the medium during recording, reproduction, and erasing can be partially released from the in-plane direction to the film thickness direction. This makes it possible to widen the range of recording energy irradiated onto the disk, and improve recording/reproducing/erasing characteristics. In addition, the dielectric layer 4 has a thickness of 3 nm to 3 nm.
Since it is extremely thin at 0 nm, the film formation time is short, and the effect on the optical interference structure is very small, so the effect of film thickness variations on the yield during mass production of disks is also very small.

As the fourth layer of metal reflective film 5, it is possible to improve the corrosion resistance of the reflective film itself by adding Ti or Cr to Al, which is inexpensive and has a high reflectance, in order to improve corrosion resistance. can.

Furthermore, by providing a dielectric protective layer 6 as the fifth layer and forming an AlON or ZnS-SiO2 film as the dielectric, a structure is created in which the metal layer that is easily oxidized is not exposed, and reliability of the disk can be established. . Although the sputtered AlN film has a relatively large internal stress, by adding oxygen and causing a reaction, the internal stress is relaxed and a good protective effect can be achieved. Furthermore, when ZnS is formed on a metal layer, it lacks adhesion and a sufficient protective effect cannot be obtained, but by mixing SiO2 with ZnS, the adhesion improves and a good protective effect can be obtained. You will be able to do it.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a magneto-optical disk which is an embodiment of the present invention. On a substrate 1 made of polycarbonate, a ZnS dielectric layer is formed to a thickness of about 80 nm by RF sputtering, and then a magneto-optical recording film layer 3 is made of GdTbF.
A ZnS dielectric layer 4 is formed to a thickness of about 30 nm by DC sputtering using an eCo alloy target, then a ZnS dielectric layer 4 is formed to a thickness of about 10 nm by RF sputtering, and then an Al-Ti reflective film layer is formed. 5 by DC sputtering method.
Finally, an AlTiON protective layer 6 was formed to a thickness of about 100 nm by reactive sputtering using an AlTi alloy target while introducing nitrogen and oxygen. A protective coating layer 7 was applied thereon using an epoxy-based ultraviolet curing resin.

[0016] Note that the magneto-optical recording layer, the Al-Ti reflective layer,
Instead of DC sputtering, RF sputtering may be used to form the AlTiON dielectric layer. Further, when Al-Cr is used as the reflective film, the fifth dielectric protective film may be an AlCrON layer formed by a reactive sputtering method that introduces oxygen and nitrogen using the same target.

FIG. 2 compares the recording/reproducing characteristics A of the magneto-optical disk of this embodiment with the recording/reproducing characteristics B of a disk without the very thin dielectric layer 4 between the recording film 3 and the reflective film 5. show. As shown in the figure, when increasing the recording power,
A remarkable difference appears in the decrease in C/N in the region of 7 mW or more. That is, a thin dielectric layer 4 is placed between the recording layer 3 and the reflective layer 5.
It can be seen that when there is a high power, the C/N decreases little and a wide recording power margin can be obtained even when recording is performed at high power.

FIG. 3 shows the relationship between the thickness of the first ZnS layer 2 and the reflectance of the disk. The reflectance also depends on the magneto-optical recording film thickness and the thickness of the third ZnS4 layer, but when the magneto-optical film thickness is 30 nm and the third ZnS film thickness is 10 nm, the thickness of the first ZnS layer 2 is It can be seen that an appropriate reflectance for the disk can be obtained within the range of 30 nm to 100 nm.

FIG. 4 shows the third ZnS layer 4 or ZnS-
The relationship between the SiO2 film thickness and the reflectance of the disk is shown. For a disk with a first layer ZnS film thickness of 80 nm and a magneto-optical recording film thickness of 30 nm, ZnS-SiO2 is more gradual when the film thickness becomes thicker, but since the reflectance of the disk becomes lower, a thickness of 3 nm to 30 nm is appropriate. It is.

By selecting the combination of the film thicknesses of the first and third dielectric layers, it is possible to control the reflectance of the disk over a wide range. However, considering productivity, film thickness control, yield, etc., good recording and reproducing characteristics can be obtained by making the dielectric layer 4 between the recording film 3 and the reflective film 5 thinner than 30 nm.

FIG. 5 shows the relationship between the Ti content relative to Al in the reflective film 5 and the reflectance of the reflective film 5. In FIG. 5, the reflectance is shown as a percentage of the standard value, and the thickness of the reflective film 5 is 50 nm. When the content of Ti or Cr increases, the reflectance decreases. The decrease in reflectance in the reflective film layer 5 is as follows:
This leads to a decrease in the car enhancement effect, and also
This is not preferable because N becomes small and it becomes difficult to reproduce the recorded signal. In order to satisfy both these recording/reproducing characteristics and the environmental resistance characteristics of the reflective film itself, the content of Ti or Cr relative to Al must be 1 at. % or more and 20at% or less is appropriate.

The fifth protective layer 6 is provided to protect the metal reflective film layer 5 from deterioration due to oxidation, and in order to obtain a sufficient protective effect, the film needs to have a thickness of 50 nm or more. However, when the protective layer 6 is thick, the recording sensitivity decreases in recording/reproducing characteristics, so the thickness of the protective layer 6 is preferably 180 nm or less. Further, the refractive index of the protective layer 6 is AlTi as in this embodiment.
When ON is used, if the value is higher than 2.5, the protective film 6 becomes metallic in nature and becomes susceptible to corrosion.

FIG. 6 shows the results of an environmental resistance test at high temperature and high humidity. As can be seen from the figure, the disk with the above structure has high reliability.

Note that in order to form the fifth protective layer 6,
A ZnS-SiO2 thin film may be formed by a binary simultaneous sputtering method using two targets of ZnS and SiO2. It is possible to use the same ZnS as the target for the first layer. Alternatively, a mixed target of ZnS and SiO2 may be used.

Furthermore, although this embodiment has been explained using a magneto-optical disk as an example, it is also possible to apply the present invention to recording media such as a magneto-optical card or a magneto-optical tape.

[0026]

As is clear from the above description of the embodiments, according to the present invention, a dielectric material ZnS, a rare earth transition metal based magneto-optical recording medium, and a very thin dielectric material ZnS or ZnS-SiO2 are formed on a substrate. , reflective film Al-Ti or Al-C
r, dielectric protective film AlON, ZnS-SiO2 or T
By forming an AlON film containing i,Cr and further applying a protective coating with an ultraviolet curable resin, a magneto-optical disk with excellent recording/reproducing/erasing characteristics and environmental resistance characteristics can be obtained, and the effect is significant. There is something.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a magneto-optical disk according to an embodiment of the present invention.

[Figure 2] Graph showing the relationship between the third layer (between the recording film and the reflective film) ZnS dielectric layer and recording power

[Figure 3] Graph showing the relationship between the film thickness of the first ZnS dielectric layer and the reflectance of the disk

[Figure 4] Graph showing the relationship between the thickness of the third ZnS dielectric layer and the disk reflectance

[Figure 5] Graph showing the relationship between Ti content and reflectance of Al-Ti reflective film

[Figure 6] Elapsed time of high temperature, high humidity environment resistance test and disc B
Graph showing the relationship between ER (bit error rate)

FIG. 7 (A) is a cross-sectional view showing the structure of a conventional magneto-optical disk; (B) is a cross-sectional view showing the structure of a magneto-optical disk in which the same reflective film is provided directly on the magneto-optical recording layer;

[Explanation of symbols]

1　　　　Substrate 2 ZnS dielectric layer 3 Magneto-optical recording layer 5 Al-Ti reflective film layer 6 AlTiON protective film layer 7 Protective coat layer

Claims (9)

[Claims] Claim 1: A first layer consisting of a dielectric film, a second layer consisting of a magneto-optical medium film, a third layer consisting of a dielectric film, and a metal film, on a transparent resin substrate or glass substrate. A flat information recording carrier formed by sequentially laminating a fourth layer and a fifth layer made of a dielectric film. Claim 2: The first layer dielectric is zinc sulfide (ZnS).
The flat information recording carrier according to claim 1, which has a refractive index of 1.9 or more and 2.5 or less, and a film thickness of 30 nm or more and 100 nm or less. 3. The magneto-optical medium of the second layer is a rare earth-transition metal alloy, and the rare earth metal is terbium (Tb).
, gadolinium (Gd) or dysprosium (Dy)
Contains at least one of these, and the transition metal is iron (Fe
), cobalt (Co) or nickel (Ni),
Contains at least one type, has a film thickness of 10 nm or more, 50 nm
2. The flat information recording carrier according to claim 1, which has a diameter of less than m. 4. The third dielectric layer is made of zinc sulfide (ZnS).
) or zinc sulfide (ZnS) and silicon dioxide (SiO2
), the refractive index is 1.8 or more and 2.5 or less, and the film thickness is 3 nm or more and 30 nm or less.
The flat information recording carrier described above. 5. The fourth metal layer is made of aluminum (Al
), titanium (Ti) or chromium (Cr)
The content of Ti, Cr or Ti-Cr relative to Al is 1 at. % or more, 20at.
% or less, and the film thickness is 10 nm or more and 180 nm or less. 6. The fifth dielectric layer is mainly composed of aluminum nitride containing oxygen, and has an upper limit of refractive index of 2.4.
The flat information recording carrier according to claim 1, which has a film thickness of 50 nm or more and 180 nm or less. 7. The fifth dielectric layer is made of zinc sulfide (Zn
S) or zinc sulfide (ZnS) and silicon dioxide (SiO
2), the flat information recording carrier according to claim 1, wherein the upper limit of the refractive index is 2.4, and the film thickness is 50 nm or more and 180 nm or less. 8. The flat information recording carrier according to claim 1, wherein the fifth dielectric layer contains at least one of titanium (Ti) and chromium (Cr). 9. The flat information recording unit according to claim 1, wherein after the first layer to the fifth layer are sequentially formed on the substrate, a protective coating film is formed using an ultraviolet curable resin.