JPH02177035A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve medium performance and durability by forming a transparent dielectric layer of a specific composite oxide. CONSTITUTION:The transparent dielectric layer consists of the oxide of at least either of In or Sn and Bi and the refractive index is required to be >=2.0, more preferably >=2.10. The content of the Bi is preferably >=6at.%, more preferably >=12at.% in the case of using this layer as a light interference layer. The refractive index improves if nitrogen is incorporated into this composite oxide and the content thereof is preferably in a several to 40at.% range. The method for producing the composite oxide is preferably a sputtering method and above all, sputtering with a gaseous mixture composed of Ar and N2. A material which allows recording and reproducing by a magneto-optical effect is preferable as the magneto-optical recording layer and the transparent substrate is preferably a polycarbonate resin. The transparent dielectric layer 2 consisting of the composite oxide, a thin transparent metallic film layer 3 consisting of a titanium alloy film, and the magneto-optical recording layer 4 are constituted in this order on the high-polymer resin substrate 1. The excellent medium performance and durability are obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to an optical recording medium on which information is recorded, reproduced, erased, etc. using light such as a laser. More specifically, a magneto-optical recording layer made of a metal thin film with the direction of easy magnetization perpendicular to the film surface is formed on a transparent substrate, and is suitable for magneto-optical recording in which information is recorded and reproduced by the magneto-optic effect. , relates to an optical recording medium with excellent medium performance and environmental resistance.

[Prior Art] Among optical recording media, magneto-optical recording media have been eagerly awaited for practical use as high-density, large-capacity, and rewritable information recording media.

As the recording layer of the above-mentioned magneto-optical recording medium, for example, TbFe described in JP-A-52-31703, JP-A-58
There have already been many proposals, such as TbFeCo described in Japanese Patent No. 73746. However, one of the magneto-optical properties of these materials is a Kerr rotation angle of 0.3 to 0.
Extremely small at 5°, CNR when playing back recorded signals
There is a problem that the (Carrier to No. 1se Ratio) is low. At the same time, most of these materials have problems in terms of durability, such as being susceptible to corrosion such as oxidation. Therefore, in order to solve these problems, a transparent dielectric layer is provided between the substrate and the recording layer as a protective layer that also serves as an optical interference layer.
It has been proposed to improve the err rotation angle and at the same time prevent the diffusion of gases such as oxygen from the substrate side. Such a transparent dielectric layer includes Si:+N4,
Ai! It is said that it is preferable to use nitrides such as N, HgFz, ZnS, hexafluorides, FiA oxides, and the like.

By the way, among these, ZNS, Si3N4, and AI! are said to have excellent environmental resistance. After conducting a series of studies on N, etc., we found that the film forming speed was slow, the distortion in the film was large, and especially when a multilayer film was formed on a plastic substrate, there were problems such as peeling along the groups during environmental tests. It was found that there was a problem with durability in addition to oxidation resistance.

In addition, regarding the improvement of the Kerr rotation angle, since the refractive index is about 2.0 in both cases, even if multiple reflections of light are used, the limit is to increase the Kerr rotation angle to about O55 to O17 degrees.
There are also problems that cannot be addressed with various specifications. Therefore, from a practical standpoint, it is considered that further improvements are needed in terms of both of these points, particularly in terms of improving the Kerr rotation angle and improving durability.

[Object of the Invention] The present invention was made in view of the current situation, and an object of the present invention is to provide an optical recording medium with high medium performance and good durability by improving the transparent dielectric layer. Specifically, by making the dielectric layer of the recording medium so that its refractive index can be adjusted over a wide range at a relatively high level, it is possible to create a medium that meets various specifications, and it is also possible to use magneto-optical recording media. The first objective is to increase the Kerr rotation angle and improve media performance. In addition, by making the dielectric layer have low internal stress and good adhesion, it prevents warping of the medium, cracking and peeling due to deterioration of the interface between the substrate and the dielectric layer, and at the same time prevents defects such as pinholes. The second objective is to suppress the
The purpose of

[Configuration 2 of the invention] The above objects are achieved by the invention as follows.

That is, the present invention provides an optical recording medium having a transparent dielectric layer as a protective layer and/or an optical interference layer, wherein the transparent dielectric layer is an amorphous composite oxide of 81 and at least one of In or SO. This is an optical recording medium characterized by the following.

The above-mentioned present invention was made as follows.

In other words, for example, when indium oxide, tin oxide, or a mixture thereof is used as a dielectric layer in a magneto-optical recording medium, it has high adhesion to a transparent substrate, and there is no cracking or peeling observed in a high-temperature, high-humidity environment resistance test. Although it has the advantage that it does not occur at all, due to the low refractive index, Ke due to multiple reflections of light
Since the effect of improving the rr rotation angle is small and the effect of confining the laser light during simultaneous recording is small, there is a drawback that the recording sensitivity of the medium is low. Therefore, we focused on elements with a high refractive index as oxides, and added Tn or /
When we investigated ways to improve the oxides of Sn and Sn, we found that the oxides obtained by adding 8j were surprisingly amorphous films, and the internal stress was similar to that of each class oxide film of the constituent metal elements. It is ideal as a transparent dielectric layer for optical recording media because its refractive index can be adjusted over a wide range to a high level of 2.0 or higher depending on the amount of 31 added, and its adhesive properties are on the same level as In or SO oxides. This was done after discovering that it has properties close to those of .

Furthermore, since indium oxide, tin oxide, or a mixture thereof in the conventional examples described above has high electrical conductivity, the thermal conductivity contributed by electrons is high, and when recording, the bits are The disadvantage is that the shape is distorted. However, it has been found that by adding the above-mentioned 81, the electrical conductivity is lost, the thermal conductivity can be reduced by a large 50%, and the disturbance of the recorded bit shape can be suppressed.

In view of the above, the composite oxide of the present invention is an oxide of at least one of In or Sn and Bi, and may be an amorphous one that has no grain boundaries and is advantageous in terms of noise level, corrosion resistance, gas barrier properties, etc. It has been confirmed that even if the content of Bi is as small as 1 at % or less, it becomes amorphous, and when used as a mere protective layer, there is no particular restriction on the content. However, if you want to obtain a large optical interference effect, specifically the effect of improving the Kerr rotation angle of magneto-optical recording and the effect of confining laser light, the refractive index should be 2.0 or more, more preferably 2.0 or more.
．． It is said that Bi content is required to be 10 or more, and when used as such an optical interference layer, the Bi content is 6 at% or more, and even 12 at%.
At% or more is preferable. Note that with these contents, the thermal conductivity is also greatly reduced, and it is also possible to suppress disturbances in the recording bit shape.

On the other hand, when the Bi content increases, the adhesive force with a polymer substrate etc. decreases, and the durability of the medium as a whole decreases. In addition, if the Bi content is too large, the refractive index becomes too high and the medium reflectance decreases, potentially lowering the detection sensitivity of the recording/reproducing device.

From this point of view, the Bi content should be 50 at% or less, and even 40 at%.
At% or less is preferable.

In addition, when nitrogen is included in the above composite oxide, it has the effect of improving the refractive index, as is clear from the study example, and it is preferable to include nitrogen, but as the nitrogen content increases, the aforementioned adhesive strength decreases. There is a tendency to From this point of view, the nitrogen content is preferably in the range of several at% to 40 at%.

Note that the above-mentioned complex oxide of the present invention includes the above-mentioned Bi,
It goes without saying that elements other than In, sn, o, and N may also be included on the order of impurities.

As a method for manufacturing the composite oxide film of the present invention, various thin film forming methods such as a known vacuum evaporation method, a PVD method such as a sputtering method, or a CVD method can be applied. However, as an optical recording medium, it is preferable to produce the optical recording medium under conditions that have particularly high adhesion to a plastic substrate in order to avoid peeling that occurs during a high temperature, high humidity environment resistance test. For this purpose, a sputtering method is preferred. Among these, sputtering with a mixed gas of Ar and N2 is preferable in terms of stable operation since it causes fewer abnormal discharges.

By the way, as mentioned above, the optical recording medium of the present invention uses the composite oxide as a protective layer or an optical interference layer, and it is clear from the spirit of the present invention that other configurations are not particularly limited. For example, it can be applied to optical recording media of various known optical recording methods, such as a light reflective recording layer, a phase change optical recording layer, and a magneto-optical recording layer.

However, because of the above-mentioned properties of the composite oxide of the present invention, particularly in that a large optical interference effect can be obtained, it can be particularly advantageously applied to magneto-optical recording media. Examples of magneto-optical recording media include the following.

In other words, the magneto-optical recording layer is one that can be recorded and reproduced by the magneto-optical effect. Specifically, the magneto-optical recording layer has an easy magnetization direction perpendicular to the film surface and can be created based on the magneto-optic effect by creating arbitrary reversal magnetic domains. A magnetic metal thin film that can record and reproduce information.
For example, FeTbCo alloy based on FeTb alloy, FeTb
Various known materials can be used, such as Gd alloy, NdDyFeCo alloy, FB-Nd alloy, amorphous alloy film of rare earth metal and transition metal such as Fe-Pr and Fe-Ce, or garnet film. Among these, the present invention is effective for amorphous alloy films of rare earth metals and transition metals that are easily oxidized.

As the material of the transparent substrate, polymer resins such as polycarbonate resin, acrylic resin, epoxy resin, 4-methyl-pentene resin, or copolymers thereof, or glass can be used. Among them, polycarbonate resin is preferably used in terms of mechanical strength, weather resistance, heat resistance, and moisture permeability.

By the way, as mentioned above, the composite oxide of the present invention has excellent properties in terms of adhesiveness, internal stress of the film, gas barrier properties, etc., and can be used for magneto-optical recording using transparent polymer substrates such as polycarbonate resin. Particularly effective in media. In this configuration, it is preferable in terms of oxidation resistance and moisture permeation resistance to further provide a transparent metal thin film layer made of metallic titanium or a metallic titanium alloy between the composite oxide film and the magneto-optical recording film. From the viewpoint of acid resistance, it is preferable that the element to be combined in the titanium alloy is at least one metal selected from the group of Cr, Ti, and Re. The film thickness of this metallic titanium or metallic titanium alloy must be 50 Å or less from the viewpoint of recording and reproduction, and the CNR of the medium must be
The thickness is preferably 20 Å or less in terms of increasing the .

As described above, the present invention provides a transparent dielectric layer made of the above-mentioned composite oxide and a transparent metal film layer made of the above-mentioned titanium or titanium alloy film on a polymer resin substrate.

This effect is remarkable in a magneto-optical recording medium having the magneto-optical recording layers in this order.

It should be noted that the magneto-optical recording medium described above can be applied to any of the well-known configurations, including a configuration in which a back protective layer is provided on the side opposite to the substrate of the magneto-optical recording layer, and a double-sided medium in which media with these configurations are bonded together. .

Known configurations for providing the back protective layer include an inorganic protective layer made of dielectric material, metal, etc., an organic protective layer made of organic resin such as photosensitive resin, lamination of transparent flat plates, and combinations thereof. There is.

The dielectric protective layer is preferably made of a material with few cracks or pinholes, such as AeN or MgFz, in order to prevent oxygen and H2O from entering the magneto-optical recording layer from the film surface.

ZnS, CeF+, AffiF3 3NaF, Si3
N4, Sin.

5iOz, Zrz 03. Nitride such as In203.5n02, fluoride, oxide, or a mixture thereof can be used. In particular, the composite oxide of at least one element of In or Sn and Bi according to the present invention is suitable as such a protective layer because it does not cause peeling or cracking in a durability test.

It also prevents oxygen present at the interface between the magneto-optical recording layer and the dielectric protective layer made of the above-mentioned composite oxide, or free or incompletely bound oxygen in the oxide protective layer itself, from entering the magneto-optical recording layer. In order to further suppress this, it is preferable to provide a barrier layer made of a metallic titanium film or the aforementioned titanium alloy film with a thickness of 50 Å or less between the magneto-optical recording layer and the dielectric protective layer. The thickness of this barrier layer made of metallic titanium or metallic titanium alloy is preferably 20 Å or less from the viewpoint of sensitivity during recording.

When using a metal film protective layer as the back surface protective layer, Ai
, Cu, Au, Ag, Si, Ti, Cr,
A metal film made of Ta, Re, Zr, or an alloy thereof can be applied, but in order to reduce heat diffusion from the laser beam spot during recording, a material with low thermal conductivity, such as ri, cr, ra, Re, or Metal films made of alloys of these are particularly preferred. The above-mentioned inorganic protective layer can be produced by a known vacuum evaporation method, sputtering method, or the like.

Furthermore, as the back surface protective layer, an organic protective layer can be used as described above. As such an organic substance protective layer, various known photosensitive resins can be used, and it can be formed by a coating method or the like. Note that it is preferable to use the organic protective layer in combination with the above-mentioned inorganic protective layer so that the inorganic protective layer is in contact with the recording layer. The back surface protective layer may be a combination of the above protective layers. Note that the back surface protective layer is preferably provided so as to cover at least the side surfaces of the recording layer.

Note that it is clear from the characteristics thereof that the various protective layers described above can be applied to optical recording media other than magneto-optical recording media, such as phase-change type optical recording media.

The effects of the above-described present invention are as follows.

In magneto-optical recording media that use a transparent plastic substrate and provide a transparent dielectric film between the substrate and the magneto-optical recording layer in order to increase the Kerr rotation angle due to film surface reflection, as mentioned above, the typical dielectric film is Conventional example Sin, Ai'N, S
When ite disks are constructed using i3N4, ZnS, etc., the Kerr rotation angle of these media is 0.5 to 0.7°.
, and K due to the effect of multiple reflections of light in the dielectric layer
It cannot be said that the improvement in the err rotation angle is still sufficient. this is,
This is believed to be because the refractive index N of each of the dielectrics mentioned above is as small as about 1.9 to 2.0.

In general, when durability tests were conducted on magneto-optical disks using these conventional dielectric materials under high temperature, high humidity and/or heat cycles, it was observed that the disks cracked and the magneto-optical properties rapidly deteriorated. .

This is mainly due to peeling of the dielectric film at the interface of the plastic substrate.

On the other hand, in the above structure, the above-mentioned In is added to the transparent dielectric layer.
In the magneto-optical disk of the present invention using a composite oxide film of at least one of Sn and Bi, the Kerr rotation angle is 0.9.
It is possible to greatly increase the angle by ~1.1°, and at the same time,
No peeling or cracking occurs due to deterioration at the interface with the plastic substrate. This means that the refractive index N of the composite oxide film is 2.0 to 2.
．． You can choose from a large level of 4, and also In or/and S.
This is thought to be due to the fact that the characteristics of the oxide of n are maintained and the affinity with organic polymer resin substrates such as polycarbonate substrates is high.

These effects not only improve the performance of the medium, but also are particularly effective against long-term stability under normal environments, heat cycles, and heat shock.

Furthermore, the causes of noise generated during recording, playback, and erasing of media include light scattering and disturbance of recorded bits caused by crystal grain boundaries in conventional crystalline dielectric films, but the above-mentioned complex Since the dielectric film is amorphous and has low thermal conductivity, there is almost no such scattering or disturbance, and compared to the conventional magneto-optical disk described above, noise during recording and reproduction can be reduced. Understood.

It is clear that the effects of the present invention described above are not limited to magneto-optical recording media, but can be similarly achieved in known optical recording media such as phase change type two-reflection type.
Therefore, the present invention is widely applicable to optical recording media. As described above, the present invention makes a significant contribution to improving the characteristics, including the durability, of optical recording media, especially magneto-optical recording media.

The present invention will be explained below based on experimental examples and examples for understanding the characteristics of the above-mentioned composite dielectric.

[Experimental example] At least one of In and Sn, which is the basis of the present invention, and Bi
Composite oxides and nitrogen-containing oxides were prepared and evaluated as follows by changing the orange content of Bi.

Experimental Examples 1 to 7 A slide glass with a length of 76 mm, a width of 26 mm, and a thickness of 111'1 m.

A 3-target high-frequency magnetron sputtering device (ANELHA
! Fix it in a wooden vacuum chamber (model 5PF-4308), and
x 10−+T.

Exhaust until rr.

Next, Ar10z mixed gas <02:VOI%) was introduced into the vacuum chamber, and the pressure was increased to 10m Torr.
2. The gas flow rate was adjusted. Diameter 100 as a target
mm.

A disk with a thickness of 5 mm, the composition is BixIn, 5n201
00-(X, +y+z) (X, V, Z G, in atomic %).

(x, y, z) is (34,6,O), (2B,
12. O), (20,20,O), (12°28.
0), (6,34,0), (22,14,4),
7 consisting of an oxide sintered body with each composition of (22, 4, 14)
Types were used as appropriate. Discharge power ioow, discharge frequency 1
High frequency sputtering was performed at 3.56 MHz, and Table 1
Composite oxide film with the composition shown in the film composition column (
A BiInSnO film) was deposited to a thickness of about 100 m.

First, the refractive index of the thin film with respect to light with a wavelength of 830 nm was determined using a sample deposited on a Si wafer.

As a measuring device, an automatic ellipsometer DNA-0LW manufactured by Mizojiri Optical Co., Ltd. was used. The results are shown in the refractive index column of Table 1.

Next, the internal stress of the thin film was determined using a sample deposited on a thin glass plate. For measurement, TENCORINSTI
? Made by UHENTS, stylus type surface roughness meter alpha-st
The amount of warpage was measured when a length of 2 mm was scanned with a stylus using EP200, and the internal stress σ was determined. The results are shown in the internal stress column of Table 1.

Additionally, using samples deposited on glass slides,
The crystalline state was measured. For measurement, Rigaku IIU powerful X
Linear diffraction device HIGHPOWERUNIT) IODEL
D-3F was used. The results are shown in the column of crystalline state in Table 1.

Experimental Examples 8 to 14 As in Experimental Examples 1 to 7, a slide glass with a length of 78 mm, a width of 26 mm, and a thickness of 1 mm, a Si wafer with a thickness of 1 mm and a square of 1 cm, and a thin plate glass (18 mm in diameter x 0.0 mm in thickness) were prepared.
A three-target high-frequency magnetron sputtering device (ANELVA (manufactured by IL, model 5PF-4308)
The tube was fixed in a vacuum chamber and evacuated to 4 x tO-7 tons orr.

Ar/Nz mixed gas (N2:
A nitrogen-containing composite oxide film (BiInSnON film) having the composition shown in the film composition column of Table 1 was prepared under the same conditions as in Experimental Examples 1 to 7 except that 30Vo 1%) was used.
People piled up. The refractive index, internal stress σ, and crystal state were measured in exactly the same manner as in Experimental Examples 1 to 7.

The results are shown in Table 1.

Experimental example 15 Same as experimental examples 1 to 7, length 76 mm, width 26 mm
.

A slide glass with a thickness of imm, a 1 cm square Si wafer with a thickness of 1 mm, and a thin plate glass (a disk with a diameter of t8 mm and a thickness of 0.7 mm) were fixed in the sputtering apparatus used in Experimental Examples 1 to 7, and a 4 x 10 -7 Torr.

"60In40" as a target (subscript number is atomic%)
An Ar10z mixed gas (Oz: loVOI%) was used as the sputtering gas. DC reactive sputtering was performed at a discharge voltage of 400 V and a current of 0.5 A, and the composition was "24In1606".
A composite oxide film of 0 (subscript number is atomic %) was deposited.

The refractive index and internal stress σ were determined in exactly the same manner as in Experimental Examples 1 to 7.
And the crystal state was measured. The results are shown in Table 1.

Experimental Example 16.17 For comparison, conventional xn2 Q3 films and Bi2O3 films were prepared and evaluated as follows.

The length was 76 mm and the width was 26 m in exactly the same manner as in Experimental Examples 1 to 7.
m, 1mm thick slide glass, 1cm thick for 1 city
Square S1 wafer and thin glass (diameter 18mm+x
A disk with a thickness of 0.1 mm) was fixed in a vacuum chamber of a 3-target high-frequency magnetron sputtering device (Anelva II, 5PF-43 leaf type), and
Exhaust until

In2O3 sintered body as target, B! Inz 03111.inz 0311. Biz 03 films each 100
OA (7) thickness was multiplied. The refractive index, internal stress σ, and crystal state were measured in exactly the same manner as in Experimental Examples 1 to 7. The results are shown in Table 1.

Experimental Examples 1 to 7 and 15 according to the present invention and Experimental Example 1 of the conventional example
6, the refractive index of the composite oxide film can be adjusted over a wide range to a high level of 2.0 or more depending on the Bi content, and the internal stress σ is significantly reduced compared to In203 regardless of the Bi content. I understand. Furthermore, the internal stress of the composite oxide is smaller than that of the 8i203 film of Experimental Example 17, which is a conventional example, and this is thought to be obtained by the synergistic effect of the mixture of Bi and In and/or Sn. From these points, it is thought that if this composite oxide is used as a dielectric layer of a magneto-optical recording medium, the laser light confinement effect will be improved, and recording sensitivity and CNR will be improved. Furthermore, it can be expected to have the effect of suppressing the occurrence of defects such as peeling and cracking.

Furthermore, as shown in Experimental Examples 8 to 14, by further incorporating nitrogen into this composite oxide, it was possible to further improve the refractive index.

Furthermore, as is clear from Experimental Examples 16 and 17, the conventionally known B! z 03. The intermediate thin film of Ir1203 is a thin film having a crystalline state. On the other hand, as is clear from Experimental Examples 1 to 15, the composite oxide film according to the present invention was surprisingly found to be in an amorphous state.

Therefore, it is thought to have the effect of reducing media noise, such as scattering of laser light during recording/reproduction by crystal grain boundaries and disturbance of bit shape due to non-uniformity of heat conduction during bit formation.

[Example] A magneto-optical disk using the composite oxide of the above-mentioned experimental example as an optical interference layer and/or a protective layer was prepared, and the effects of the present invention were confirmed.

Examples 1 to 7 Magneto-optical recording media having the configuration shown in FIG. 1 were produced and evaluated as follows. In the figure, 1 is a substrate, 2 is a dielectric layer, 3 is a transparent metal thin film layer, 4 is a recording layer, and 5 is a back image 3 layer.

A disk with a diameter of 130 mm and a thickness of 1.2 mm, 1.6
Polycarbonate resin with groups of μm pitch (
The disk substrate 1 of the PC is fixed in a vacuum chamber of a three-target high-frequency magnetron sputtering device (Model 5PF-430H manufactured by ANELVA), and the vacuum chamber is evacuated to 4.times.10@-7 Torr. In addition, during film formation, the substrate 1 has a concentration of 15 pp
Rotated at m.

Next, in the same manner as in Experimental Examples 1 to 7 described above, transparent dielectric layers 2 made of composite oxides having different 81 contents were formed. That is, the target is a disk with a diameter of iomm and a thickness of 5 mm, and the composition is BixIn, 5n70100.
-(x+y+z) (X, y' are atomic %).

(X, V, Z) is (34,6,0), (28,1
2,0), (20,20,0), (12°28,
O), (6,34,0), (22,14,4),
Seven types of oxide sintered bodies having the respective compositions (22, 4, 14) were appropriately prepared, and these were sequentially attached to the sputtering apparatus to form films under the following conditions. First, ^r102 mixed gas (02: I VO +%) was introduced into the vacuum chamber, and the flow rate of the Ar10z mixed gas was adjusted so that the pressure was 10 m Torr. Next, high frequency sputtering was performed at a discharge power of 100 W and a discharge frequency of 13.56 MHz to deposit a composite oxide film having the composition and thickness shown in Table 2 as the dielectric layer 2. Here, each film thickness is a value that maximizes the figure of merit FR·θk (R: medium reflectance, err rotation angle second to θ) optically determined from the refractive index N of the dielectric layer 2. At the same time, the CNR was set to a value that maximized when the dielectric film thickness was changed in an actual medium.

Next, a target of “80” was used as the transparent metal thin film layer 3.
20 alloy (the subscript indicates the composition (atomic %)), and the sputtering gas was changed from Ar10z to pure Ar (5N
About 15 people deposited a T1Cr alloy film under the same discharge conditions as described above except for the following.

Next, a target of Tb23Fe6 was used as the magneto-optical recording layer 4.
．． A disk of COB alloy (the suffix indicates the composition (atomic %)) was used, and 1bFeC was used under the same discharge conditions as the RICR alloy film.
About 400 people deposited o-alloy films.

Further, a target of Tta was used as the backside protective layer 5.

Return to Cr2o and T' i C under the same discharge conditions as above.
Approximately 500 people deposited r-alloy films.

In the above order, each B1-containing composite oxide is used as a transparent dielectric layer, and the other components are the same as those shown in FIG. 1.
/ [BixIn, Sri□0100-(x+y+z
) ] A magneto-optical disk having a laminated structure of /T1Cr/TbFeCo/T1Cr was obtained.

The measurement results of the Kerr rotation angle of this magneto-optical disk (laser wavelength λ: 633 nm) are shown in the Kerr rotation angle column of Table 2. Next, the CNR of this disk was measured.

For measurements, magneto-optical recording and reproducing equipment @ (Nakamichi 083-100) was used.
0 to taoorpm)
Recording, playback, and erasing were performed at a position with a rotation radius of 30 mm.

Signal reproduction was performed with a laser power of 0.8 mW.

The optimum laser power during recording was determined to be a value that maximizes the difference between the first and second harmonics during signal reproduction. The frequency of the signal was set to IMH2. The optimum laser power for each medium is shown in the column of recording power in Table 2. The applied magnetic field during recording and erasing is 500Qe (Oersted). The evaluation results of the CNR and noise level of the medium are shown in the CNR and noise level columns of Table 2. The noise level was expressed in units of dam, which indicates the absolute level with 1- as a reference.

When the surfaces of these disks were observed, no defects such as pinholes, peeling, or cracks were observed.

Next, these disks were left in a high temperature and high humidity atmosphere of 80° C. and 85% RH for 1000 hours. Thereafter, when the Kerr rotation angle, the optimum laser power during recording, and the CNR noise level were measured, no changes were observed at all compared to the measurement results before being left. Furthermore, no defects such as pinholes, peeling, or cracks on the medium surface were observed.

Examples 8 to 14 Magneto-optical disks having the structure shown in FIG. 1 in which the transparent dielectric layer 2 was made of the same nitrogen-containing composite oxide as in Experimental Examples 8 to 14 were prepared and evaluated as follows.

A disk with a diameter of 1301111+1 and a thickness of 1.2mm,
A disk substrate 1 of polycarbonate resin (PC>) having groups of 1.6/l pitch was fixed in exactly the same sputtering apparatus as used in Examples 1 to 7 under exactly the same conditions.

As a sputtering gas when forming dielectric layer 2 ^
Ar/Nz mixed gas (N2: 30
Sputtering was performed under exactly the same conditions as in Examples 1 to 7, except that the dielectric layer 2 was
PC/[8! XInySnz(o
loo-a Na) 100-(x+y+z) 1/
A magneto-optical disc with a laminated structure of T i Cr/TbFeCo/T i Cr was obtained.

Note that the film thickness of the dielectric layer 2 was set in the same manner as in Examples 1 to 7.

As in Examples 1 to 7, Kerr rotation angle, recording power, C
NR and noise level were measured. The results are shown in Examples 8 to 14 in Table 2.

When the surfaces of these disks were observed, no defects such as pinholes, peeling, cracks, etc. were observed.

Next, these disks were left in a high temperature and high humidity atmosphere of 80° C. and 85% RH for 1000 hours. When the Kerr rotation angle, optimum laser power during recording, CNR, and noise level were measured after that, no changes were observed at all compared with the measurement results before leaving as in Examples 1 to 7. Furthermore, no defects such as pinholes, peeling, or cracks on the medium surface were observed.

Example 15 A magneto-optical disk having the structure shown in FIG. 1 in which the transparent dielectric layer 2 was made of the same composite oxide as in Experimental Example 15 was prepared and evaluated in the following manner.

A disk with a diameter of 13h+m and a thickness of 1.2mm, 1.6μ
Polycarbonate resin (P
The disk substrate of C) was fixed in exactly the same sputtering apparatus as used in Examples 1 to 7 under exactly the same conditions.

The composite oxide film of dielectric layer 2 was formed in the same manner as in Experimental Example 15 described above. In other words, as a target [”
An alloy target of 60In40 (subscript number is atomic%) was used, and the sputtering gas was Ar1.
A 0z mixed gas (02: 10Vo1%) was used. DC reactive sputtering was performed at a voltage of 400 V and a current of 0.5 A during discharge to form a composite oxide film of about 720 layers having the same composition as in Experimental Example 15 as dielectric layer 2, 24In16060 (subscript number is atomic %). Note that this film thickness was set in the same manner as in Examples 1 to 7.

Hereinafter, sputtering was carried out under exactly the same conditions as in Examples 1 to 7.
C/Bi241016060/T1Cr/TbFeCo
A magneto-optical disk having a laminated structure of /T1Cr was obtained.

Kerr rotation angle and recording power CN as in Examples 1 to 7
R. The noise level was measured. The results are shown in Example 15 in Table 2.

When I observed the surface of this disc, I found that there were no pinholes or peeling.
No defects such as cracks were observed.

Next, this disk was left in a high temperature, high humidity atmosphere of 80° C. and 85% RH for 1000 hours. When the Kel'r rotation angle, optimum laser power during recording, CNR, and noise level were measured after that, no changes were observed at all compared to the measurement results before leaving as in Examples 1 to 7. Furthermore, no defects such as pinholes, peeling, or cracks on the medium surface were observed.

Comparative Example For comparison purposes, a magneto-optical disk having the structure shown in FIG. 1 using the conventional Inz 03 as the transparent dielectric layer 2 was prepared and evaluated as follows.

A disc with a diameter of 130mm and a thickness of 1.2mm, 1.6μ
Polycarbonate resin (P
The disk substrate of C) was fixed in exactly the same sputtering apparatus as used in Examples 1 to 7 under exactly the same conditions.

The In20:l film of dielectric layer 2 was molded to a thickness of 800 mm using an In203 sintered body as a target in exactly the same manner as in Experimental Example 16, and the other layers were formed in the same manner as in Experimental Example 16.
Sputtering was performed under exactly the same conditions as in Example 7, and the dielectric layer was Ir1z Owl, and the other configurations were the same as in Examples 1 to 1.
A magneto-optical disk having a laminated structure of Cr/FeCo/Cr was obtained. In addition, the film thickness of the Inz 0wl film is from Example 1 to
I set it up in the same way as 7.

As in Examples 1 to 7, Kerr rotation angle, recording power, C
NR and noise level were measured. The results are shown in the column of Comparative Example in Table 2 before standing.

When the surface of this medium was observed, no defects such as pinholes, peeling, cracks, etc. were observed.

Next, this medium was left in a high temperature, high humidity atmosphere at 80° C. and 85% RH for 100 hours. The subsequent Kerr rotation angle, optimum laser power during recording, CNR, and noise level were measured. The results are shown in the column of Comparative Examples in Table 2 after standing. It can be seen that the Kerr rotation angle, recording sensitivity, CNR, and noise level have all deteriorated compared to before being left unused. In addition, pinholes were observed on the medium surface.

Example 16 A magneto-optical recording medium having the configuration shown in FIG. 2 and having a metal reflective layer that also utilizes the Hu-Lovey effect was prepared and evaluated in the following manner. In Figure 2, 1°2.3.4 is the first
As shown in the figure, 5a and 5b are back protective layers, and 6 is a metal reflective layer.

A disk with a diameter of 130mm and a thickness of 1.2n+m, 1.6
Polycarbonate resin with groups of μm pitch (
A disk substrate of PC) was fixed in exactly the same sputtering apparatus as used in Examples 1 to 7 under exactly the same conditions.

First, a nitrogen-containing composite oxide film was formed as the dielectric layer 2 in the following manner. Ar/N, + mixed gas (N2:30
Vo 1%) was introduced into the vacuum chamber, and the pressure was 10 m Tor.
The flow rate of the Ar/N2 mixed gas was adjusted so that r.

The target used was a sintered target having a diameter of 100 mm, a thickness of 5 mm, and a composition of 8!2oIn1asro2060 (subscripts are atomic %). Discharge power ioow
, high frequency sputtering was performed at a discharge frequency of 13.56 MH2 to form dielectric layer 2 of "20"183'205
About 500 people deposited a nitrogen-containing oxide film with a composition of ON10. This film thickness was set in the same manner as in Examples 1-7.

Next, the sputtering gas was changed from Ar/Nz to pure Ar (5
Sputtering was performed under the same discharge conditions as above, replacing the target with two alloy targets having the compositions "60" 30Re10° and Nd5 DV15TbB Fe60CO12 (subscripts are atomic %) instead of N). The metal thin film layer 3 shown in FIG.
．． Magneto-optical recording layer 4. As the back metal protective layer 5a, T1C
15 people each for rRe, NdDyTbFeCo, and T1CrRe.

It was deposited at a film thickness of 200 and 15.

The target was returned to the Bf20InIBSn2060 sintered target on which the composite oxide film of dielectric layer 2 had been formed, and under exactly the same discharge conditions as dielectric layer 2, B1In5nO
About 200 people deposited the back dielectric protective layer 5b made of N.

Finally, the target is coated with the metal thin film layer 3 and the back metal thin film 1.
The T'60"30RelO alloy target used for forming 1i5a was returned to, and approximately 500 T i CrRe films were deposited as the metal reflective layer 6 under exactly the same discharge conditions as the metal thin film layer 3.

When the reflectance of this medium to 830 nm laser light was examined, it was found to be 13%. Furthermore, when the noise level was measured, it was confirmed that the noise level was as low as -59 dBm.

Examples 1 to 16. From the and comparative examples, I related to the present invention
By using a composite oxide thin film of 81 and at least one of n and Sn as a dielectric layer, magneto-optical recording with improved Kerr rotation angle, recording sensitivity, CNR, and reduced noise level as expected from its characteristics. It turns out that the medium can be realized. As shown in Experimental Examples 1 to 15, the above composite oxide increases the refractive index of the dielectric layer, which improves the optical interference effect, specifically the laser light confinement effect, and increases the Kerr rotation angle. , recording sensitivity,
It was confirmed that an improvement in CNR can be achieved. Also,
The composite oxide thin films of the transparent dielectric layers of Examples 1 to 16 were in an amorphous state as shown in Experimental Examples 1 to 7.

Therefore, compared to films made of crystalline Inz 03 or Bi2O3 alone, there is less disturbance in the bit shape due to scattering of laser light by crystal grain boundaries during recording and reproduction and non-uniformity of heat conduction during bit formation, and the noise level is reduced. Although a reduction is expected, it was confirmed in Examples 1 to 16 and the comparative example that the noise level was large as expected, and specifically, it was confirmed that the noise level could be reduced by 2 dBm or more.

Further, as shown in Examples 8 to 14, it was found that the above-mentioned effects were further improved by using a composite oxide containing nitrogen.

Furthermore, the composite oxide films of Examples 1 to 16 were prepared in Experimental Examples 1 to 1.
5, the Inz 03 film of the comparative example (Experimental Example 1)
Compared to 6), the internal stress is significantly reduced. For this reason, even when accelerated deterioration tests were conducted under high temperature and high humidity conditions, no peeling or cracking due to the internal stress of the film occurred, and it was found that this had a great effect on improving durability.

The significance of the present invention has been demonstrated above.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of Examples 1 to 15 and a comparative example, and FIG. 2 is a sectional view showing the structure of Example 16. 1: Substrate, 2: Dielectric layer, 3: Metal thin film layer. 4: Recording layer, 5.5a, 5b: Back protective layer, 6: Metal reflective layer

Claims (1)

[Claims] 1. An optical recording medium having a transparent dielectric layer as a protective layer and/or an optical interference layer, wherein the transparent dielectric layer is an amorphous composite oxide of Bi and at least one of In or Sn. An optical recording medium characterized by: 2. A transparent dielectric layer made of the above composite oxide, a transparent metal thin film layer made of a Ti film or an alloy film of Ti and at least one of Re, Cr, and Ta, and a non-containing layer of rare earth metals and transition metals on a transparent polymer substrate. 2. The optical recording medium according to claim 1, comprising magneto-optical recording layers made of crystalline alloy films in this order. 3. The optical recording medium according to claim 1 or 2, wherein the composite oxide is a nitrogen-containing oxide containing nitrogen. 4. The optical recording medium according to claim 3, wherein the nitrogen content of the nitrogen-containing oxide is 40 at% or less.