JP2001312840A - Surface readout type optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface readout type optical recording medium excellent in recording/reproducing characteristics and head floating characteristic. SOLUTION: This surface readout type optical recording medium has at least a reflection layer, a recording layer and a protection layer layered on a substrate in this order. Such an alloy is used as the reflection layer, as is obtained by adding 0.1-10.0 atomic % at least one element selected from rare earth elements, Zr, Hf, Nb, Ta, Mo, W, Re, Ru, Os, Rh, Ir, Pd, Pt, Au and Ag to Al.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable surface-reading type optical recording medium, in particular, a surface-reading type magneto-optical recording medium for recording, reproducing and erasing information by using a laser beam and a magnetic field, or a laser beam alone. The present invention relates to a surface reading type phase change type recording medium for recording, reproducing and erasing information.

[0002]

2. Description of the Related Art Optical recording media are portable recording media capable of large-capacity, high-density recording, and have been in demand as rewritable media for recording large-capacity files and moving images of computers accompanying the recent increase in multimedia. Is rapidly increasing.

A magneto-optical recording medium is generally formed by forming a multilayer film including a recording layer on a transparent disk-shaped substrate such as plastic.
Recording and erasing are performed by irradiating a laser while applying a magnetic field, and reproduction is performed by reflected light of the laser. Conventionally, the recording method is
So-called optical modulation recording, in which recording is performed by applying a fixed magnetic field in the opposite direction after erasing by applying a fixed magnetic field, has been the main focus.In recent years, a magnetic field modulation method that modulates a magnetic field according to a recording pattern while irradiating a laser, Attention has been paid to a method capable of performing recording (direct overwrite) in one rotation and accurately recording even at a high recording density.

Further, a phase change recording method utilizing a reversible phase change between a crystalline phase and an amorphous phase can be directly overwritten and has recently been used.

[0005] Conventionally, a laser for recording / reproducing has been irradiated onto a recording film through a substrate. Recently, so-called near-field optical recording has been used as a means for increasing the density of recording / reproducing by bringing an optical head close to the recording film. (Appl.
Phys. Lett. 68, p. 141 (199
6)). In this recording method, Solid Immersi
By using an onLens (hereinafter abbreviated as SIL) head to reduce the laser beam spot size, the recording limit is shorter than the conventional recording limit (／ λ / 2NA: NA is the numerical aperture of the objective lens) determined by the laser wavelength (λ) of the light source. Reproduction with marks is possible, and recording and reproduction with an ultra-high recording density can be realized.

In this near-field optical recording, it is necessary to bring the optical head close to the recording medium (up to 100 nm). Therefore, instead of irradiating the recording film with a laser beam through the substrate as in a conventional optical recording medium, the substrate is not moved. A method is used in which a recording film is directly irradiated with a laser beam without passing through. That is,
In a conventional optical recording medium, the structure of the recording film is generally substrate / first protective layer / recording layer / second protective layer / reflection layer, whereas in near-field optical recording, the substrate / reflection layer is used. / First
A recording / reproducing operation is performed by irradiating a laser beam from the film surface side as a film structure having the reverse structure of the protective layer / recording layer / second protective layer (surface reading type recording).

Recently, a surface recording method in which recording and reproduction are performed by irradiating a laser through a protective coating layer on a thin film with a lens NA of 1 or less has been proposed (JM).
agn. Soc. Jpn. 68, S1, p. 269 (1
999)).

In the near-field optical recording, a floating slider head is often used to bring the recording film and the SIL head close to each other. However, the distance between the head and the recording medium is very short due to the reversed film structure. (~ 0.1μ
m), there is the same problem of the interface between the head and the recording medium as the hard disk drive (head crash etc.). In addition, there is a problem of CNR reduction due to the surface properties of the thin film.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to
An object of the present invention is to provide an optical recording medium for surface-reading type optical recording having a film structure of a reverse structure to that of a conventional one having a high R and excellent head flying characteristics.

[0010]

Means for Solving the Problems The present inventors have made intensive studies in view of the above-mentioned situation, and as a result, have found that a surface read-out layer having at least a reflective layer, a recording layer and a protective layer laminated on a substrate in this order. -Type optical recording media, Al is rare earth,
Zr, Hf, Nb, Ta, Mo, W, Re, Ru, O
By forming an alloy in which at least one element selected from s, Rh, Ir, Pd, Pt, Au and Ag is added in a range of 0.1 atomic% to 10.0 atomic% as the reflective layer,
NR and head flying property are improved, and when Al alloy is expressed as Al _1-XY A _{X BY} , A is at least one element selected from rare earth metals, and B is Ti, Zr, H
f, V, Nb, Ta, Cr, Mo or W, at least one element selected from the group consisting of 0.001 ≦ X, 0.0
The present inventors have found that the use of an Al alloy satisfying the range of 01 ≦ Y and X + Y ≦ 0.1 as the reflection film improves the CNR and the head flying property improving effect, and has completed the present invention.

That is, the surface-reading optical recording medium of the present invention is a surface-reading type optical recording medium comprising at least a reflective layer, a recording layer, and a protective layer laminated on a substrate in this order, wherein Al is a rare earth element, Zr, or Hf. , Nb, Ta, M
o, W, Re, Ru, Os, Rh, Ir, Pd, Pt,
An alloy in which at least one element selected from Au and Ag is added in a range of 0.1 atomic% to 10.0 atomic% is used as the reflective layer.

Furthermore, a surface reading type optical recording medium of the present invention, at least a reflective layer on the substrate, the surface reading type optical recording medium which the recording layer and the protective layer are laminated in this order, an Al alloy Al _1-XY When expressed as A _{X BY} ,
Is at least one element selected from rare earth metals, B is at least one element selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo or W, and 0.00
Al in the range of 1 ≦ X, 0.001 ≦ Y, X + Y ≦ 0.1
It is characterized in that an alloy is used as a reflection film.

Hereinafter, the present invention will be described in more detail.

FIG. 1 is a partial cross-sectional view of an embodiment of a surface read type optical recording medium according to the present invention. A reflective layer 12, a recording layer 13, and a protective layer 14 are laminated on a substrate 11.

The substrate 11 is not particularly limited as long as it satisfies the characteristics of a medium substrate such as mechanical characteristics.
Glass, polycarbonate, amorphous polyolefin, engineering plastic, or the like can be used.

The reflective layer 12 is made of a rare earth (IIIa)
Group), Zr, Hf, Nb, Ta, Mo, W, Re, R
at least one element selected from u, Os, Rh, Ir, Pd, Pt, Au and Ag in an amount of 0.1 atomic% to 1 atomic%;
An alloy added in an amount of 0.0 at%, preferably 0.5 to 5 at%, having a thickness of 20 nm or more and 100 nm or less;
Preferably, it is preferably formed with a film thickness of 30 to 80 nm.

Here, preferable elements to be added to Al include Zr, Ta, Pt and Pd. Further, at least one element selected from Sc, Y and a lanthanoid is also preferable, and more preferably a lanthanoid element, specifically, Gd, Dy, Nd or Sm.

When the Al alloy is expressed as Al _1-XY A _{X BY} , A is at least one selected from rare earth metals.
Seed element, B is Ti, Zr, Hf, V, Nb, Ta, C
r, at least one element selected from Mo or W, and 0.001 ≦ X, 0.001 ≦ Y, X + Y ≦ 0.
It is preferable that the alloy in the range of 1 is used as the reflective film. In the Al alloy, the rare earth element A is preferably a lanthanoid, and the element B is preferably Zr, Ta, W, or the like.

By adding the above-described elements to Al, the surface roughness of the film is reduced, noise is reduced, and CNR is improved. When the rare earth metal is added, the noise reduction effect tends to be larger. It is also considered that the head flying characteristics are improved by increasing the hardness of the film by adding the element.

If the thickness is less than 20 nm, the effect as a reflective layer may be small, and if it is more than 100 nm, the surface roughness may increase, noise may increase, and the CNR may decrease. If the added amount of the added element is too large, the recording sensitivity becomes too high and becomes impractical. Therefore, the upper limit of the added amount is preferably about 10.0 atomic%. Further, a metal film may be formed between the substrate 11 and the reflective layer 12 for improving adhesion and corrosion resistance.

The recording layer 13 may be any material as long as it has perpendicular magnetization and a large coercive force. TbFeCo or a material mainly composed of TbFeCo is particularly preferred because it has a large coercive force. The coercive force of the recording layer is preferably as large as possible in order to stably retain recorded information, but is preferably 5 kOe or more for a magneto-optical recording medium for near-field magneto-optical recording. Further, a phase change recording medium utilizing a reversible phase change between a crystalline phase and an amorphous phase can be used as the recording layer. In this case, since heat generated in the recording layer is large, it is preferable to form a protective layer between the reflective layer 12 and the recording layer 13.

The protective layer 14 is made of SiN, AlN, SiAl
It is made of a transparent dielectric such as ON, Ta ₂ O ₅ , or a mixed material of ZnS and SiO ₂ . In order to improve the flying characteristics of the slider head, the protective layer 14 may be a laminate of a transparent dielectric layer and a diamond-like carbon (DLC) solid lubricating layer obtained by adding hydrogen or nitrogen to carbon. Furthermore, by forming a liquid lubricating layer of an extremely thin perfluoropolyether or the like thereon by a method such as a dip pulling method, the flying characteristics of the slider head are further improved.

In addition to the above-described structure, the surface-reading type optical recording medium of the present invention has a structure in which a dielectric is formed on the reflective layer 12 and a recording layer is formed thereon. Layers can be stacked and a recording layer can be formed thereon for use.

The above underlayer, reflective layer, recording layer, protective layer,
For forming the solid lubricating layer, a vacuum thin film forming technique such as a vacuum evaporation method or a sputtering method can be used.

In the surface-reading optical recording medium of the present invention, by forming a protective coating layer made of an acrylic UV curable resin or the like after forming the protective layer 14, the surface-reading type optical recording medium for an optical system having an NA of 1 or less is formed. It can also be used as a recording medium. For forming the protective coating layer, a vacuum thin film forming technique, a dip pulling method, a spin coating method, or the like can be used.

[0026]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples.

(Example 1) A medium for surface reading type magneto-optical recording having a structure as shown in FIG. 2 was manufactured. A 50 nm thick Al film is formed as a reflective layer 22 on a polycarbonate substrate 21 having a guide groove with a track pitch of 0.45 μm.
_{A 0.986} Zr _0.014 alloy film was formed by placing a Zr chip on an Al target and sputtering. Tb on this
_A recording layer 23 made of _0.20 (Fe _0.76 Co _0.20 Ta _0.04 ) _0.80 was formed to a thickness of 20 nm by DC sputtering. Furthermore, a protective layer 24 made of SiN is further
The solid lubricating layer 25 made of diamond-like carbon (DLC) was formed to a thickness of 230 nm by reactive DC sputtering using a Si target in a mixed atmosphere of N ₂ and N _2.
Was formed in a mixed atmosphere of 15 nm by a reactive RF sputtering method using a C target. After forming the DLC layer,
A perfluoropolyether-based lubricating layer 26 was applied to a thickness of 1 nm by a pull-up method to manufacture a magneto-optical recording medium.

Example 2 A surface read type magneto-optical recording medium was manufactured in the same manner as in Example 1. However, in this embodiment, the reflection layer 22 is made of Al _0.986 Ta _0.014 , Al _0.981 P
t _0.019 , Al _0.98 Pd _0.02 , Al _0.98 Mo _0.02 , Al
_A surface read type magneto-optical recording medium was manufactured by changing the _{values to 0.98} W _0.02 and Al _0.98 Au _0.02 , respectively.

Example 3 A surface read type magneto-optical recording medium was manufactured in the same manner as in Example 1. However, in this embodiment, the reflection layer 22 is made of Al _0.981 Gd _0.019 , Al _0.98 Dy
_The surface readout type magneto-optical recording medium was manufactured by changing to _0.02 , Al _0.98 Nd _0.02 and Al _0.98 Sm _0.02 , respectively.

Example 4 A surface read type magneto-optical recording medium was manufactured in the same manner as in Example 1. However, in this embodiment, the reflection layer 22 is made of Al _0.98 Gd _0.01 Zr _0.01 , Al
_{0.98 Nd 0.01 Ta 0. 01, Al} 0.98 Sm 0.01 W 0.01 and was manufactured surface reading type magneto-optical recording medium by changing respectively.

Example 5 A surface read type magneto-optical recording medium was manufactured in the same manner as in Example 1. However, in this embodiment, a substrate having a track pitch of 0.55 μm is used,
After the formation of the DLC layer, a protective coating layer made of an acrylic ultraviolet curable resin is formed to a thickness of 10 μm by a spin coating method, and thereafter, a lubricating layer of a perfluoropolyether is applied to a thickness of 1 nm by a pull-up method to obtain a surface readout type. A magneto-optical recording medium was manufactured.

Comparative Example 1 A medium for surface reading type magneto-optical recording having a structure as shown in FIG. 3 was manufactured. An Al film having a thickness of 50 nm was formed as a reflective layer 32 by a DC sputtering method on a polycarbonate substrate 31 provided with a guide groove having a track pitch of 0.45 μm. Tb on this
_A recording layer 33 of _0.20 (Fe _0.76 Co _0.20 Ta _0.04 ) _0.80 was formed to a thickness of 20 nm by DC sputtering. Furthermore, a protective layer 34 made of SiN is further
The solid lubricating layer 35 made of diamond-like carbon (DLC) was formed to a thickness of 230 nm by reactive DC sputtering using a Si target in a mixed atmosphere of N ₂ and N _2.
In a mixed atmosphere of 15 nm by a reactive RF sputtering method using a C target. After forming the DLC layer,
A perfluoropolyether-based lubricating layer 36 was applied to a thickness of 1 nm by a pull-up method to manufacture a magneto-optical recording medium.

The recording / reproducing characteristics shown below were measured for the surface readout type magneto-optical recording media of Examples 1 to 4 and Comparative Example 1.

A magneto-optical recording medium is set on a spindle and the medium is rotated at a linear velocity of 10 m / s. A slider SIL head having a laser wavelength of 680 nm and an effective numerical aperture of 1.2 was levitated to a height of 100 nm on the thin film surface, and the recording layer was heated to a temperature higher than the Curie temperature by irradiating a laser in a pulsed manner. Is recorded at 16.7 MHz (mark length: 0.30 μm). Here, the coil magnetic field at the time of recording was set to 150 Oe. The CNR was measured while changing the recording power, and the value at which the CNR was saturated was taken as the CNR value of the sample. The reproduction power is 0.8 mW.

Further, the following glide tests were performed on the surface readout type magneto-optical recording media of Examples 1 to 4 and Comparative Example 1.

A magneto-optical recording medium is set on a spindle and rotated. Introduction Waffle burnishing head (Glide Height, Flying Height: 25 nm)
Is used to seek once between a radius of 20 to 60 mm. Next, the disk is sought by a glide head with a piezo element (Flying Height: 50 nm, manufactured by Glide Height Co., Ltd.), and the voltage value induced in the piezo element is monitored. Hits with a voltage value of 500 mV or more are counted as hits. Very good hit count 0-2, 3-5
Is good, 6 to 9 is slightly good, and 10 or more is bad.

Table 1 shows CNR measurement results and glide test results. × is bad in the glide test result,
Fair indicates good, Good indicates good, and Good indicates very good.

The samples of the examples were compared with those of the comparative example in CN.
It can be seen that both the R and the head flying property are improved.

The recording characteristics of the surface read type magneto-optical recording medium of Example 5 were measured using a slider head having an optical system with a laser wavelength of 680 nm and an effective numerical aperture of 0.8. A good SNR value of 23 dB was obtained at 0.4 μm, and it was confirmed that the medium could be used as an overcoated surface readout type magneto-optical recording medium.

[0040]

[Table 1]

[0041]

According to the present invention, rare earth, Zr,
Hf, Nb, Ta, Mo, W, Re, Ru, Os, R
By using an alloy containing at least one element selected from the group consisting of h, Ir, Pd, Pt, Au, and Ag in a range of 0.1 to 10.0 atomic% as the reflective layer, or changing the Al alloy to Al _1- when expressed as _XY a _X B _Y, at least one element a selected from rare earth metals, B is Ti, Zr,
At least one element selected from Hf, V, Nb, Ta, Cr, Mo or W, 0.001 ≦ X, 0.001
By using an Al alloy that satisfies ≦ Y and X + Y ≦ 0.1 as the reflective film, it is possible to obtain an excellent surface-read type optical recording medium having improved recording / reproducing characteristics, CNR, head flying characteristics, and the like.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a structure of an example of a surface read type optical recording medium of the present invention.

FIG. 2 is a partial cross-sectional view showing the structure of the first embodiment of the present invention.

FIG. 3 is a partial sectional view showing the structure of Comparative Example 1 of the present invention.

[Explanation of symbols]

 11, 21, 31: Substrate 12, 22, 32: Reflective layer 13, 23, 33: Recording layer 14, 24, 34: Protective layer 25, 35: Solid lubricating layer 26, 36: Lubricating layer

Claims (4)

[Claims] 1. A surface-reading optical recording medium comprising a substrate, on which at least a reflective layer, a recording layer and a protective layer are laminated in this order, wherein Al is rare earth, Zr, Hf, Nb, T
a, Mo, W, Re, Ru, Os, Rh, Ir, Pd,
A surface-reading type optical recording medium, wherein an alloy to which at least one element selected from Pt, Au and Ag is added in a range of 0.1 atomic% to 10.0 atomic% is used as a reflective layer. 2. The element added to Al is at least one element selected from Sc, Y and lanthanoids.
The surface-reading type optical recording medium according to claim 1. 3. In a surface-reading type optical recording medium having at least a reflective layer, a recording layer, and a protective layer laminated in this order on a substrate, when A _{1 -XYA X} B _Y is used, A is a rare earth metal. At least one selected element, B is T
i, Zr, Hf, V, Nb, Ta, Cr, Mo or W
At least one element selected from the group consisting of 0.001
A surface-reading type optical recording medium, wherein an alloy satisfying ≦ X, 0.001 ≦ Y, and X + Y ≦ 0.1 is used as a reflective film. 4. The reflective layer has a thickness of not less than 20 nm and not more than 100 nm.
4. The method according to claim 1, wherein:
Item 4. A surface-reading type optical recording medium according to Item 1.