JP2528173B2 - Optical recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical recording medium for recording / reproducing / erasing information by using light from a laser or the like. More specifically, it is suitable for magneto-optical recording in which a magneto-optical recording layer made of a metal thin film having an easy magnetization direction in a direction perpendicular to the film surface is formed on a transparent substrate and information is recorded and reproduced by the magneto-optical effect. , An optical recording medium having excellent medium performance and environmental resistance.

[Prior Art] Among optical recording media, magneto-optical recording media are expected to be put to practical use as rewritable information recording media with high density and large capacity.

Many proposals have already been made for the recording layer of the above-described magneto-optical recording medium, such as TbFe described in Japanese Patent Laid-Open No. 52-31703 and TbFeCo described in Japanese Patent Laid-Open No. 58-73746. However, these materials have one of its magneto-optical properties,
rr) The rotation angle is extremely small at 0.3 to 0.5 °, and there is a problem that the CNR (Carrier to Noise Ratio) at the time of reproducing the recorded signal is low. At the same time, most of these materials also have a problem in terms of durability in that they are 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, and the Kerr rotation angle is improved by utilizing the optical interference effect, that is, multiple reflection of light. At the same time, it has been proposed to prevent diffusion of gas such as oxygen from the substrate side. It is said that such a transparent dielectric layer is preferably formed of a nitride such as Si ₃ N ₄ , AlN, MgF ₂ or ZnS, a fluoride, a sulfide or the like.

By the way, when we examined ZnS, Si ₃ N ₄ , AlN, etc., which are said to have excellent environmental resistance, among them, the film formation rate was slow, and the film had large defects, especially on the plastic substrate. It was found that when a multilayer film was formed on the film, there was a problem such as peeling along the group due to the environmental test, and there was a problem with durability in a different aspect from the oxidation resistance. In addition, with regard to the improvement of the Kerr rotation angle, since the refractive index is about 2.0 in all cases, even if the multiple reflection of light is used, it is 0.5.
There is a problem that it is not possible to meet various specifications because there is a limit to increase to ~ 0.7 °. Therefore, in terms of practical use, it is considered necessary to further improve the cleaning in terms of various points, especially the improvement of the Kerr rotation angle and the improvement of durability.

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical recording medium having improved medium performance and improved durability by improving the transparent dielectric layer. That is,
Specifically, by allowing the dielectric layer of the recording medium to be adjusted in a wide range at a relatively large level, the medium according to various specifications can be realized and the Kerr rotation can be achieved in the magneto-optical recording medium. The first purpose is to increase the angle and improve the medium performance. Further, by making the dielectric layer have a low internal stress and good adhesiveness, warpage of the medium, cracking and peeling due to deterioration of the interface between the substrate and the dielectric layer are prevented, and at the same time defects such as pinholes are generated. The second purpose is to suppress the durability and improve the durability of the entire medium.

[Structure and Action of Invention] The above-mentioned object is achieved by the present invention described below. That is, the present invention is an optical recording medium having a transparent dielectric layer as a protective layer and / or an optical interference layer, wherein the optical recording medium is a transparent polymer layer, the transparent dielectric layer, the Ti film or the Ti and R layers.
A transparent metal thin film layer made of an alloy film of at least one of e, Cr, and Ta, and a magneto-optical recording layer made of an amorphous alloy film of a rare earth metal and a transition metal are provided in this order, The optical recording medium is characterized in that the body layer is an amorphous composite oxide containing at least one of In and Sn, Bi and nitrogen.

The present invention described above has been made as follows. That is, for example, when indium oxide, tin oxide, or a mixture thereof is used as a dielectric layer in a magneto-optical recording medium, the adhesion to a transparent substrate is high, and cracks or peeling at high temperature and high humidity environment resistance test occur at all. It has the advantage that it does not exist, but due to its low refractive index, it is
Since the effect of improving the Kerr rotation angle is small and the effect of confining the laser beam at the time of recording is small, the recording sensitivity of the medium is low. Therefore, focusing on an element having a high refractive index as an oxide, and examining the improvement of In or / and Sn oxide by the addition of the element, the oxide obtained by adding Bi is surprisingly non- It is a crystalline film, its internal stress is smaller than that of each single oxide film of its constituent metal elements, and its refractive index can also be adjusted over a wide range at a high level of 2.0 or more by the addition amount of Bi, and also the adhesiveness is In or It was made by discovering that it has characteristics close to ideal as a transparent dielectric layer of an optical recording medium, which is about the same as Sn oxide.

Furthermore, since the above-described conventional indium oxide, tin oxide, or a mixture thereof has a high electric conductivity, it has a high thermal conductivity to which electrons contribute, and at the time of recording, due to thermal diffusion from the portion to be recorded, the bit There is a drawback that the shape is disturbed. However, it has been found that by adding Bi described above, the electrical conductivity is lost, the thermal conductivity can be significantly reduced, and the disorder of the recording bit shape can be suppressed.

From the above point of view, the complex oxide relating to the present invention is an oxide of at least one of In and Sn and Bi, and is an amorphous one which has no grain boundary and is advantageous in terms of noise level, corrosion resistance, gas barrier property, etc. It has been confirmed that even if the Bi content is as small as 1 at% or less, it becomes amorphous, and when it is used as a simple protective layer, the content is not particularly limited.
However, in order to obtain a large optical interference effect, specifically, a Kerr rotation angle improving effect of magneto-optical recording and a laser light confining effect, it is said that a refractive index of 2.0 or more, more preferably 2.10 or more is required, When used as such a light interference layer, the Bi content is preferably 6 at% or more, more preferably 12 at% or more. It should be noted that if these contents are included, the thermal conductivity is greatly reduced, and the disorder of the recording bit shape can be suppressed.

On the other hand, when the Bi content increases, the adhesive force with the polymer substrate and the like decreases, and the durability of the medium as a whole decreases. On the other hand, if the Bi content is too high, the refractive index becomes too high, and the medium reflectance decreases, possibly lowering the detection sensitivity of the recording / reproducing apparatus. From this point, the Bi content is 50 at
% Or less, more preferably 40 at% or less.

On top of that, the inclusion of nitrogen in the above composite oxide has the effect of improving the refractive index as is clear from the study examples.
It is preferable to contain nitrogen, but if the nitrogen content increases, the above-mentioned adhesive strength tends to decrease. From this point, the nitrogen content is preferably in the range of several at% to 40 at%.

Incidentally, the above composite oxide of the present invention, the above Bi, In,
It goes without saying that elements other than Sn, O and N may be included in the impurity order.

As the method for producing the complex oxide film of the present invention, a known vacuum deposition method, PVD method such as sputtering method, or C
Various thin film forming methods such as the VD method can be applied. However, the optical recording medium is preferably manufactured under the condition that the adhesiveness to the plastics substrate is particularly large in order not to cause peeling which occurs in the high temperature and high humidity environment resistance test. For this purpose, the sputtering method is preferable. Of these, sputtering with a mixed gas of Ar and N ₂ is preferable in terms of stable operation with less abnormal discharge.

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

However, since the characteristics of the complex oxide of the present invention described above, particularly a large optical interference effect, can be obtained, it can be advantageously applied to a magneto-optical recording medium. Examples of the magneto-optical recording medium include the following.

That is, the magneto-optical recording layer is one that can be recorded and reproduced by the magneto-optical effect, and specifically, it has an easy magnetization direction in a direction perpendicular to the film surface and creates an arbitrary reversal domain so that the magneto-optical effect is generated. A magnetic metal thin film capable of recording and reproducing information, for example, FeTb alloy-based FeTbCo alloy, FeTbGd alloy, NdDyFe
Various known materials such as Co alloy, Fe-Nd alloy, amorphous alloy film of rare earth metal such as Fe-Pr, Fe-Ce and transition metal, or garnet film can be applied. Above all, the present invention is effective for an amorphous alloy film of a rare earth metal and a transition metal which are easily oxidized.

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

By the way, as described above, the composite oxide of the present invention has adhesiveness,
The film has excellent properties such as internal stress and gas barrier property, and is particularly effective in a magneto-optical recording medium using a transparent polymer substrate such as a polycarbonate resin.
Further, in this structure, it is preferable to further provide a transparent metal thin film layer made of metal titanium or a metal titanium alloy between the composite oxide film and the magneto-optical recording film in terms of oxidation resistance and moisture permeation resistance. The element to be combined as the titanium alloy is preferably at least one metal selected from the group consisting of Cr, Ta and Re from the viewpoint of acid resistance. The film thickness of this metal titanium or metal titanium alloy needs to be 50 Å or less from the viewpoint of recording / reproducing, and is preferably 20 Å or less from the viewpoint of further increasing the CNR of the medium.

As described above, the present invention comprises, on a polymer resin substrate, a transparent dielectric layer made of the above composite oxide, a transparent metal thin film layer made of the above titanium or titanium alloy film, and a magneto-optical recording layer in this order. The effect is remarkable in the magneto-optical recording medium having the structure.

The magneto-optical recording medium described above has a configuration in which a back surface protective layer is provided on the opposite side of the magneto-optical recording layer from the substrate, as is known.
Further, all the configurations such as a double-sided medium in which the mediums having these configurations are attached can be applied.

Known configurations for providing the back surface protective layer include an inorganic protective layer made of a dielectric material or metal, an organic protective layer made of an organic resin such as a photosensitive resin, and further a transparent flat plate bonded together, or a combination thereof. There is.

The dielectric protective layer, in order to prevent oxygen and of H ₂ O from entering from the film surface to the magneto-optical recording layer, less material is preferably a crack or a pin _{hole, AlN, MgF 2, ZnS,} CeF 3, AlF 3 · 3NaF, S
A nitride such as i ₃ N ₄ , SiO, SiO ₂ , Zr ₂ O ₃ , In ₂ O ₃ or SnO ₂ , a fluoride, an oxide, or a mixture thereof can be applied. In particular, the above-described composite oxide of at least one element of In or Sn and Bi of the present invention is suitable as such a protective layer because it does not cause peeling or cracking in the durability test.

In addition, oxygen existing 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 bonded oxygen of the oxide protective layer itself may enter the magneto-optical recording layer. In order to suppress further, it is preferable to provide a barrier layer composed of a titanium metal film or a titanium alloy film having a film thickness of 50 Å or less between the magneto-optical recording layer and the dielectric protective layer. The film thickness of the 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 protective layer as the back surface protective layer, Al, C
A metal film made of u, Au, Ag, Si, Ti, Cr, Ta, Re, Zr or alloys of these can be applied, but the thermal conductivity is small in order to reduce heat diffusion from the laser beam spot during recording. A metal film made of a material, that is, Ti, Cr, Ta, Re, or an alloy thereof is particularly preferable. The above inorganic protective layer can be produced by a known vacuum deposition method, sputtering method, or the like.

Further, as the back surface protective layer, the organic material protective layer can be used as described above. As the organic protective layer, various known photosensitive resins can be applied and can be formed by a coating method or the like. The organic protective layer is preferably used 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 respective protective layers. The back surface protective layer is preferably provided so as to cover at least the side surface of the recording layer.

It is apparent from the characteristics and the like that the various protective layers described above can be applied to, for example, a phase change type optical recording medium other than the magneto-optical recording medium.

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

In a magneto-optical recording medium in which a transparent plastic substrate is used and a transparent dielectric layer is provided between the substrate and the magneto-optical recording layer in order to increase the Kerr rotation angle due to film surface reflection, as described above, a typical dielectric film is used. When a disk is constructed by using the conventional SiO, AlN, Si ₃ N ₄ , ZnS, etc., the Kerr rotation angle of these media is 0.5 to 0.7 °, which is due to the effect of multiple reflection of light in the dielectric layer. The improvement in the Kerr rotation angle is not yet sufficient. It is considered that this is because the refractive index N of each dielectric is as small as 1.9 to 2.0. Furthermore, when a magneto-optical disk using these conventional dielectrics was subjected to a durability test by high temperature and high humidity and / or heat cycle, it was observed that cracks were introduced into the disk and the magneto-optical characteristics were rapidly deteriorated. This is mainly due to peeling of the dielectric film at the interface of the plastic substrate.

On the other hand, the transparent dielectric layer having the above-mentioned configuration has the above-mentioned I
In the magneto-optical disk of the present invention using at least one of n and Sn and a Bi composite oxide film, the Kerr rotation angle can be greatly increased to 0.9 to 1.1 °, and at the same time, at the interface with the plastic substrate. No peeling or cracking due to deterioration. This can be selected at a large level such that the refractive index N of the composite oxide film is 2.0 to 2.4, the characteristics of the oxide of In and / or Sn are maintained, and the affinity with an organic polymer resin substrate such as a polycarbonate substrate is maintained. It seems that it is big. These effects not only improve the performance of the medium, but are particularly effective for long-term stability under normal environment, heat cycle, and heat shock.

Further, as a cause of noise generated at the time of recording / reproducing / erasing of a medium, in a conventional dielectric film having a crystal structure, light scattering and disorder of a recording bit due to its crystal grain boundary are mentioned. Since the dielectric film is amorphous and has a low thermal conductivity, there is almost no such scattering and disturbance, and noise during recording / reproduction can be reduced as compared with the above-mentioned conventional magneto-optical disk. all right.

It is apparent that the above-described effects of the present invention are not limited to the magneto-optical recording medium and can be similarly exerted in well-known optical recording media such as phase change type and reflection type. Is widely applicable to optical recording media. As described above, the present invention makes a great contribution to the improvement of the characteristics including the durability of the magneto-optical recording medium among the optical recording media.

Hereinafter, the present invention will be described based on experimental examples and examples for grasping the characteristics of the above-mentioned composite dielectric.

[Experimental Example] A composite oxide of at least one of In and Sn and Bi, which is the basis of the present invention, and a nitrogen-containing oxide were prepared and evaluated in the following manner while changing the content of Bi.

Examples 1 to 7 Length 76 mm, Width 26 mm, Thickness 1 mm Slide Glass, Thickness 1 mm
Then, a 1 cm square Si wafer and a thin glass plate (diameter 18 mm × thickness 0.1 mm disk) were fixed in the vacuum chamber of a 3-target high frequency magnetron sputtering device (SPF-430H manufactured by Anelha Co., Ltd.) and 4 × 10. Exhaust to ^-7 Torr.

Next, an Ar / O ₂ mixed gas (O ₂ : Vol%) was introduced into the vacuum chamber, and the Ar / O ₂ gas flow rate was adjusted so that the pressure was 10 m Torr. As a target, a disk with a diameter of 100 mm and a thickness of 5 mm,
When the composition is Bi _x In _y Sn _z O _{100- (x + y + z)} (x, y, z is atomic%), (x, y, z) is (34,6,0), (28,12 , 0) (20,20,0)
(12,28,0), (6,34,0), (22,14,4), (22,4,14)
Seven kinds of oxide sintered bodies of each composition were used appropriately. High-frequency sputtering was performed at a discharge power of 100 W and a discharge frequency of 13.56 MHz to deposit about 1000 liters of a composite oxide film (BiInSnO film) having the composition shown in the film composition column of Table 1.

First, using a sample deposited on a Si wafer,
The refractive index of the thin film for 830 nm light was determined. As the measuring device, an automatic ellipsometer DHA-OLW 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 the sample deposited on the thin glass plate. TENCOR INSTRUMENTS for measurement
The internal stress σ was obtained by measuring the amount of warpage when a 2 mm length scan was performed with a stylus using a stylus type surface roughness meter alpha-step 200 manufactured by K.K. The results are shown in the column of internal stress in Table 1.

Furthermore, the crystalline state was measured using the sample deposited on the slide glass. Rigaku Denki Co., Ltd. for measurement
A strong X-ray diffractometer manufactured by HIGH POWER UNIT MODEL D-3F was used. The results are shown in the crystalline state column of Table 1.

Examples 8 to 14 Similar to Examples 1 to 7, a slide glass having a length of 76 mm, a width of 26 mm, and a thickness of 1 mm, a 1 mm-thick Si wafer of 1 cm square and a thin plate glass (diameter 18 mm × thickness 0.1 mm disk) ) Is a high-frequency magnetron sputtering device with three targets (Anelva Co., Ltd.)
(Made by SPF-430H) and evacuated to 4 × 10 ^-7 Torr.

Ar / N ₂ mixed gas (N ₂ : 30Vol
%) Under exactly the same conditions as in Experimental Examples 1 to 7
About 1000Å of nitrogen-containing composite oxide film (BiInSnON film) having the composition shown in the column of the film composition of was deposited. Experimental Examples 1 to 7
The refractive index, internal stress σ, and crystalline state were measured in exactly the same manner as in. The results are shown in Table 1.

Experimental Example 15 As in Experimental Examples 1 to 7, length 76 mm, width 26 mm, thickness 1 m
A slide glass of m, a 1 mm-thick 1 cm square Si wafer and a thin glass plate (diameter 18 mm × thickness 0.1 mm disk) were fixed in the sputtering apparatus used in Experimental Examples 1 to 7, and 4 × 10 ⁻⁷ Torr
Exhaust until

An alloy target of Bi ₆₀ In ₄₀ (subscript is atomic%) was used as the target, and Ar was used as the sputtering gas.
An / O ₂ mixed gas (O ₂ : 10 Vol%) was used. Discharge voltage 400
DC reactive sputtering was performed at V and current of 0.5 A, and the composition was Bi
₂₄ In ₁₆ O ₆₀ (Supplemental figures are atomic%) complex oxide film 1000 Å
Was deposited.

The refractive index, σ of internal stress, and crystalline state were measured in exactly the same manner as in Experimental Examples 1 to 7. The results are shown in Table 1.

Experimental Examples 16 and 17 For comparison, In ₂ O ₃ film and Bi ₂ O ₃ film of the conventional example were prepared and evaluated as follows.

Exactly the same as Experimental Examples 1 to 7, length 76 mm, width 26 mm, thickness
Vacuum of 1-mm slide glass, 1-mm-thick 1 cm-square Si wafer and thin glass (18 mm in diameter x 0.1 mm-thick disk) for high-frequency magnetron sputtering equipment with 3 targets (Anerva Corp., SPF-430H type) Fixed in the tank, 4 × 10 ^-7
Exhaust to Torr.

An In ₂ O ₃ film and a Bi ₂ O ₃ film were prepared under exactly the same conditions as in Experimental Examples 1 to 7 except that In ₂ O ₃ sintered body and Bi ₂ O ₃ sintered body were used as targets.
Each of the _three films was deposited to a thickness of about 1000Å. The refractive index, internal stress σ, and crystalline state were measured in exactly the same manner as in Experimental Examples 1 to 7. The results are shown in Table 1.

From Experimental Examples 1 to 7 and 15 according to the present invention and Experimental Example 16 of the conventional example, the composite oxide film has a refractive index of 2. due to the content of Bi.
It was found that the internal stress σ can be adjusted over a wide range at a high level of 0 or more, and that the internal stress σ is significantly reduced compared to In ₂ O ₃ regardless of the Bi content. Furthermore, the internal stress of the composite oxide is smaller than the internal stress of the Bi ₂ O ₃ film of Experimental Example 17 of the conventional example, which is considered to be obtained by the synergistic effect of mixing Bi with In or / and Sn. From these points, it is considered that when this composite oxide is used as the dielectric layer of the magneto-optical recording medium, the confinement effect of laser light is improved, and the recording sensitivity and CNR are improved. Further, the effect of suppressing the occurrence of defects such as peeling and cracks can be expected.

Further, as shown in Experimental Examples 8 to 14, by further containing nitrogen in this composite oxide, the refractive index could be further improved.

Further, as is clear from Experimental Examples 16 and 17, the conventionally known single thin films of Bi ₂ O ₃ and In ₂ O ₃ are thin films having a crystalline state. On the other hand, as is clear from Experimental Examples 1 to 15, it was found that the composite oxide film according to the present invention is surprisingly in an amorphous state. Therefore, it is considered to have an effect of reducing medium noise such as scattering of laser light by crystal grain boundaries at the time of recording / reproducing, and small disorder of the bit shape due to non-uniformity of heat conduction during bit formation.

[Examples and Comparative Examples] Magneto-optical disks having the composite oxide of the above-mentioned experimental example as an optical interference layer and / or a protective layer were prepared, and the effects of the present invention were confirmed.

Comparative Examples 1 to 7 The magneto-optical recording medium having the structure shown in FIG. 1 was prepared 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 surface protective layer.

A disk with a diameter of 130 mm and a thickness of 1.2 mm, and a polycarbonate resin (PC) disk substrate 1 having a 1.6 μm pitch group in a vacuum chamber of a 3-target high frequency magnetron sputtering device (SPF-430H manufactured by Anerva Corp.). Then, evacuate to 4 × 10 ^-7 Torr. The substrate 1 was rotated at 15 rpm during film formation.

Next, in the same manner as in the above-mentioned Experimental Examples 1 to 7, the transparent dielectric layer 2 made of complex oxides having different Bi contents was formed. That is, the target is a disk with a diameter of 100 mm and a thickness of 5 mm, and the composition is Bi _x In _y Sn _z O _{100- (x + y + z)} (x, y, z is atomic%), (x, y, z ) Is (34,6,0), (28,12,0)
(20,20,0) (12,28,0), (6,34,0), (22,14,4),
Seven kinds of (22,4,14) oxide sintered bodies having respective compositions were appropriately prepared, and these were sequentially attached to the sputtering apparatus to form a film under the following conditions. First, Ar / O ₂ mixed gas (O ₂ : 1Vol
%) Into the vacuum chamber and Ar to a pressure of 10 m Torr.
The flow rate of the / O ₂ mixed gas was adjusted. Then, discharge power 100W,
High frequency sputtering was performed at 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 figure of merit optically determined from the refractive index N of the dielectric layer 2. (R: medium reflectance, θk: Kerr rotation angle) is the maximum value, and at the same time, the CNR is also the maximum when the film thickness of the dielectric is changed in the actual medium.

Then, as the transparent metal thin film layer 3, the target was Ti ₈₀ Cr.
Approximately 15 Å of TiCr alloy film was deposited under the same discharge conditions as above, except that a disc of ₂₀ alloys (subscripts indicate composition (atomic%)) was added and the sputtering gas was pure Ar (5N) rather than Ar / O _2. did.

Next, as the magneto-optical recording layer 4, the target was Tb ₂₃ Fe ₆₉ Co ₈
(Additional numbers indicate composition (atomic%))
About 400 liters of TbFeCo alloy film was deposited under the same discharge conditions as the alloy film.

Further, the target was returned to Ti ₈₀ Cr ₂₀ as the back surface protective layer 5, and a TiCr alloy film was deposited at about 500 Å under the same discharge conditions as described above.

PC / [B as shown in Fig. 1 with the same structure except that the complex oxides of each Bi content were used as transparent dielectric layers in the above order.
A magneto-optical disk having a laminated structure of i _x In _y Sn _z O _{100- (x + y + z)} ] / TiCr / TbFeCo / TiCr was obtained.

The measurement results of the kerr rotation angle (laser wavelength λ: 633 nm) of this magneto-optical disk are shown in the column of Kerr rotation angle in Table 2. Next, the CNR of this disc was measured. A magneto-optical recording / reproducing device (Nakamichi OMS-1000 Type III) was used for the measurement, and the disc was rotated at 1800 rpm to record / reproduce at a radius of 30 mmR.
It was erased. Signal reproduction was performed with a laser power of 0.8 mW. The optimum laser power at the time of recording was determined to be a value that maximizes the difference between the first harmonic and the second harmonic at the time of signal reproduction. The frequency of the signal was 1 MHz. The optimum laser power of each medium is shown in the recording power column of Table 2. The applied magnetic field during recording / erasing is 500 Oe (oersted). The CNR and noise level evaluation results of the medium are shown in the column of CNR and noise level in Table 2. The noise level is shown in units of dbm, which is an absolute level based on 1 mW.

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

Next, these disks were left for 1000 hours in a high temperature and high humidity atmosphere of 80 ° C. and 85% RH. After that, when the Kerr rotation angle, the optimum laser power during recording, and the CNR noise level were measured, no change was observed compared with the measurement results before standing. In addition, the occurrence of defects such as pinholes, peeling and cracks on the medium surface was not observed at all.

Examples 1 to 7 Magneto-optical disks having the structure shown in FIG. 1 in which the same nitrogen-containing composite oxide as in the above-described Experimental Examples 8 to 14 was used as the transparent dielectric layer 2 were prepared and evaluated as follows.

A disk substrate 1 of a polycarbonate resin (PC) having a diameter of 130 mm and a thickness of 1.2 mm and having a groove with a pitch of 1.6 μm was placed in the same sputtering apparatus as that used in Comparative Examples 1 to 7 under exactly the same conditions. Fixed

As a sputtering gas when forming the dielectric layer 2
Sputtering was performed under exactly the same conditions as in Comparative Examples 1 to 7 except that Ar / N ₂ mixed gas (N ₂ : 30 Vol%) was used instead of Ar / O ₂ , and each layer was formed to form the dielectric layer 2 exposed. Consisting of a nitrogen-containing complex oxide having the film composition and film thickness shown in 2,
Others are the same as those in Examples 1 to 7 and shown in FIG.
/ [Bi _x In _y Sn _z (O _100-a N _a ) _{100- (x + y + z)} ] / TiCr / TbFeCo /
A magneto-optical disk having a laminated structure of TiCr was obtained.

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

Similar to Comparative Examples 1 to 7, Kerr rotation angle, recording power, CN
The R and noise levels were measured. The results are shown in Example 1 of Table 2.
~ 7.

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

Next, these disks were left for 1000 hours in a high temperature and high humidity atmosphere of 80 ° C. and 85% RH. After that, the Kerr rotation angle, the optimum laser power during recording, the CNR, and the noise level were measured, and as with Comparative Examples 1 to 7, no change was observed as compared with the measurement results before standing. In addition, the occurrence of defects such as pinholes, peeling and cracks on the medium surface was not observed at all.

Comparative Example 8 A magneto-optical disk having the structure shown in FIG. 1 in which the same complex oxide as in Experimental Example 15 was used as the transparent dielectric layer 2 was prepared and evaluated as follows.

A disk substrate of a polycarbonate resin (PC) having a diameter of 130 mm and a thickness of 1.2 mm and having a groove of 1.6 μm pitch was fixed in the same sputtering apparatus as that used in Comparative Examples 1 to 7 under exactly the same conditions. .

The composite oxide film of the dielectric layer 2 was formed in the same manner as in Experimental Example 15 described above. That is, Bi ₆₀ as a target
An alloy target of In ₄₀ (subscript number is atomic%) was used, and the sputtering gas at that time was an Ar / O ₂ mixed gas (O
_2: 10Vol%) was used. At discharge voltage 400V, current 0.5A,
DC reactive sputtering was performed to form, as the dielectric layer 2, about 720 Å of a composite oxide film having the same composition as in Experimental Example 15, Bi ₂₄ In ₁₆ O ₆₀ (subscripts are atomic%). The film thickness was set similarly to Comparative Examples 1-7. Hereinafter, sputtering was performed under exactly the same conditions as in Comparative Examples 1 to 7, the dielectric layer 2 was the above composite oxide, and the other configurations were exactly the same as those in Comparative Examples 1 to 7, PC shown in FIG. / Bi ₂₄ In ₁₆ O ₆₀ / TiCr / Tb
A magneto-optical disk having a laminated structure of FeCo / TiCr was obtained.

Similar to Comparative Examples 1 to 7, Kerr rotation angle, recording power, CNR,
The noise level was measured. The results are shown in Comparative Example 8 in Table 2.

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

Next, this disk was left for 1000 hours in a high temperature and high humidity atmosphere of 80 ° C. and 85% RH. After that, the Kerr rotation angle, the optimum laser power during recording, the CNR, and the noise level were measured, and as with Comparative Examples 1 to 7, no change was observed compared with the measurement results before standing. In addition, the occurrence of defects such as pinholes, peeling and cracks on the medium surface was not observed at all.

Comparative Examples 9 to 10 For comparison, a magneto-optical disk having the structure shown in FIG. 1 in which In ₂ O ₃ of the conventional example was used as the transparent dielectric layer 2 was prepared and evaluated for comparison.

A disk substrate of a polycarbonate resin (PC) having a diameter of 130 mm and a thickness of 1.2 mm and having a groove of 1.6 μm pitch was fixed in the same sputtering apparatus as that used in Comparative Examples 1 to 7 under exactly the same conditions. .

The In ₂ O ₃ film of the dielectric layer 2 was formed to a thickness of 800 Å using the In ₂ O ₃ sintered body as a target in exactly the same manner as in the above-described Experimental Example 16, and the other layers were formed in Comparative Examples 1 to 1. Sputtering was carried out under exactly the same conditions as in No. 7, the dielectric layer was In ₂ O ₃ , and the other constitutions were the same as in Comparative Examples 1 to 7, PC / In ₂ O ₃ / TiCr / TbFeCo shown in FIG. A magneto-optical disk having a laminated structure of / TiCr was obtained. The film thickness of the In ₂ O ₃ film was set in the same manner as in Comparative Examples 1 to 7.

Similar to Comparative Examples 1 to 7, Kerr rotation angle, recording power, CN
The R and noise levels were measured. The results are shown in Comparative Example 9 in Table 2.
Column.

Observation of this medium surface revealed no defects such as pinholes, peeling and cracks.

Next, this medium is heated to 80 ° C, 85% RH in a high temperature and high humidity atmosphere at 1000
Left for hours. After that, the Kerr rotation angle and the optimum laser power during recording, CNR, and noise level were measured. Table 2 shows the results
The column of Comparative Example 10 is shown. It can be seen that the Kerr rotation angle, recording sensitivity, CNR, and noise level have all deteriorated compared to before leaving. In addition, pinholes were found on the medium surface.

Example 8 A magneto-optical recording medium having a structure shown in FIG. 2 provided with a metal reflective layer that also utilizes the Faraday effect was prepared and evaluated as follows. In FIG. 2, 1, 2, 3, and 4 are the same as in FIG. 1, 5a and 5b are backside protective layers, and 6 is a metal reflective layer.

A disk substrate of a polycarbonate resin (PC) having a diameter of 130 mm and a thickness of 1.2 mm and having a groove of 1.6 μm pitch was fixed in the same sputtering apparatus as that used in Comparative Examples 1 to 7 under exactly the same conditions. .

First, a nitrogen-containing composite oxide film was formed as the dielectric layer 2 as follows. Ar / N ₂ mixed gas (N ₂ : 30Vol%) was introduced into the vacuum chamber, and the flow rate of the Ar / N ₂ mixed gas was adjusted so that the pressure was 10 m Torr. 100m diameter as target
A sintered body target having a disc size of 5 mm and a thickness of 5 mm and a composition of Bi ₂₀ In ₁₈ Sn ₂ O ₆₀ (subscripts are atomic%) was used. High-frequency sputtering was performed at a discharge power of 100 W and a discharge frequency of 13.56 MHz to deposit about 500 liters of a nitrogen-containing oxide film having a composition of Bi ₂₀ In ₁₈ Sn ₂ O ₅₀ N ₁₀ as the dielectric layer 2. This film thickness is from Comparative Example 1
It was set in the same manner as 7.

Next, the sputtering gas was changed from Ar / N ₂ to pure Ar (5N), and Ti ₆₀ Cr ₃₀ Re ₁₀ and Nd ₅ Dy ₁₅ Tb ₈ F were used as targets.
Using two kinds of alloy targets with a composition of e ₆₀ Co ₁₂ (subscripts are atomic%), under the same discharge conditions as above, the targets were exchanged for sputtering, and the metal thin film layer shown in FIG. 3, magneto-optical recording layer 4, as the backside metal protective layer 5a, TiCrRe, NdDyTbFeCo, TiCrRe in the order of 15Å, 200
It was deposited with a film thickness of Å, 15Å.

The target was returned to the sintered body target of Bi ₂₀ In ₁₈ Sn ₂ O _{60 on} which the complex oxide film of the dielectric layer 2 was formed, and the back surface dielectric protective layer made of BiInSnON under the same discharge conditions as the dielectric layer 2. About 200Å of 5b was deposited.

Finally, the target was returned to the Ti ₆₀ Cr ₃₀ Re ₁₀ alloy target used for forming the metal thin film layer 3 and the back surface metal thin film layer 5a, and the metal reflection layer 6 was formed under the same discharge conditions as the metal thin film layer 3.
As a TiCrRe film, about 500 Å was deposited.

When the reflectance of this medium with respect to a laser beam of 830 nm was examined, it was 13%. Also, when the noise level was measured, it was confirmed to be a low noise level of −59 dBm.

From Examples 1 to 8 and Comparative Examples 1 to 10, by using at least one of In and Sn according to the present invention and a complex oxide thin film of Bi as a dielectric layer, the Kerr rotation as expected from the characteristics is obtained. It was found that it is possible to realize a magneto-optical recording medium with improved corners, recording sensitivity, CNR, and reduced noise level. This is because, as shown in Experimental Examples 1 to 15, the composite oxide increases the refractive index of the dielectric layer, which improves the optical interference effect, specifically the laser light confinement effect, and the kerr rotation angle. It was confirmed that the recording sensitivity and CNR could be improved. In addition, the composite oxide thin films of the transparent dielectric layers of Examples 1 to 7 and Comparative Examples 1 to 8 are Experimental Examples 1 to 15
It is in an amorphous state as shown in. Therefore, In
Compared to a film of ₂ O ₃ or Bi ₂ O ₃ alone, there is less scattering of the laser light due to crystal grain boundaries during recording / reproduction and less disorder of the bit shape due to non-uniform heat conduction during bit formation, reducing the noise level. Are expected, but Examples 1-8 and Comparative Examples 1-10
As expected, the noise level is high, specifically 2 dBm
It has been confirmed that the above can be reduced.

Further, as shown in Examples 1 to 7, it was found that the above-mentioned effects were further improved by using a composite oxide further containing nitrogen.

Moreover, as shown in Experimental Examples 1 to 15, the complex oxide films of Examples 1 to 7 and Comparative Examples 1 to 8 had a remarkable internal stress as compared with the In ₂ O ₃ film of the comparative example (Example 16). Has fallen to.
Therefore, it was found that even when an accelerated deterioration test under high temperature and high humidity was performed, peeling and cracking due to internal stress of the film did not occur at all, and the durability was greatly improved.

 As described above, the significance of the present invention has been shown.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of Examples 1 to 7 and Comparative Examples 1 to 10, and FIG. 2 is a structure of Example 8. 1: Substrate, 2: Dielectric layer, 3: Metal thin film layer, 4: Recording layer, 5, 5a, 5b: Backside protective layer, 6: Metal reflective layer

Claims (2)

(57) [Claims] 1. An optical recording medium having a transparent dielectric layer as a protective layer and / or a light interference layer, the optical recording medium comprising a transparent polymer layer, a Ti film or Ti and Re, C on a transparent polymer substrate.
A transparent metal thin film layer formed of an alloy film of at least one of r and Ta, and a magneto-optical recording layer formed of an amorphous alloy film of a rare earth metal and a transition metal in this order, wherein the transparent dielectric layer Is an amorphous composite oxide containing at least one of In and Sn, Bi and nitrogen, and an optical recording medium. 2. The nitrogen content of the nitrogen-containing oxide is 40 at%
The optical recording medium according to claim 1, wherein: