JPH0442452A - Magneto-optical disk and production thereof - Google Patents

Abstract

PURPOSE:To prevent the degradation in recording and reproducing characteristics when a rotating speed is increased by laminating a 1st dielectric layer, a recording layer, a 2nd dielectric layer, and a metallic reflecting layer in this order, setting the thermal conductivity of the 2nd dielectric layer higher than the thermal conductivity of the 1st dielectric layer and setting the thermal conductivity of the metallic reflecting layer higher than the thermal conductivity of the recording layer. CONSTITUTION:The magneto-optical recording layer 11 is constituted by laminating the 1st dielectric layer (enhancement layer) 2, the recording layer 3, the 2nd dielectric layer (inorg. protective layer) 4, and the metallic reflecting layer 5 successively from a transparent substrate 1 side. The thermal conductivity of the 2nd dielectric layer 4 is higher than the thermal conductivity of the 1st dielectric layer 2 and the metallic reflecting layer of the metallic reflecting layer 5 is higher than the thermal conductivity of the recording layer 3. The heat conduction in the film thickness direction of the magneto-optical recording layer 11 is made higher than the thermal conduction in the surface direction, by which the energy of a laser beam is efficiently transmitted in a short period of time to the recording layer 3. The prescribed part of the recording layer 3 is increased in a short period of time in this way even if the rotating speed of the disk is increased. The recording sensitivity is thus improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a magneto-optical disk formed by laminating a plurality of thin films on a substrate and a method for manufacturing the same, and is particularly applicable in fields where high-speed signal transfer is required. Related to magneto-optical disks and their manufacturing method.

(Prior Art) In recent years, among magneto-optical recording media, magneto-optical disks that can be written and read using laser light have been widely used for large-capacity data files.

The layer structure of this magneto-optical disk is glass.

It is known that a dielectric protective layer (also called an enhancement layer), a recording layer, an inorganic protective layer, and a thin film of a metal reflective layer are laminated on a transparent substrate such as plastic by a sputtering method. A layer structure having a multilayered magneto-optical recording layer is preferable because it can increase the phase margin.

In terms of characteristics, the recording layer of a magneto-optical disk is a single layer of an alloy mainly composed of transition metals and rare earth metals, or a thin film mainly composed of transition metals and a thin film mainly composed of rare earth metals. At least two alternately laminated layers with a thickness of 10 people are used. In particular, Tb or Dy is used as the rare earth metal, and F as the transition metal.
A recording layer using e and Co is preferable because it has excellent magnetic properties such as Kerr rotation angle and coercive force, and has excellent overall recording and reproducing properties as disclosed in, for example, JP-A-58-73748. .

By the way, a general problem with optical recording systems, including magneto-optical recording, is that the transfer speed is slower than that of hard disks. As a measure to deal with this problem, increasing the rotation speed of the drive is being considered.

In the past, it was sufficient to design magneto-optical disks on the assumption that the rotational speed of the drive was constant, but in the future, it is necessary to design magneto-optical disks based on the assumption that the rotational speed of the drive is constant. There is an increasing demand for reduced media designs.

In other words, there is a need for a magneto-optical disk that has low linear velocity dependence and can record and erase with the same laser power even when the drive rotational speed increases from low to high speed.

On the other hand, as conventional techniques for improving the recording sensitivity of magneto-optical disks, Japanese Patent Laid-Open Nos. 1-179241 and 1999
-179242 publication and JP-A-82-293541
There is a technology described in the publication No. These technologies are
This shows that the lower the thermal conductivity of the material for the metal reflective film, the higher the recording sensitivity, which is preferable.

(Problem to be solved by the invention) However, these conventional techniques only show the concept of media design under a certain number of rotations, and do not take into account at all the support for high-speed transfer due to high-speed rotation of the drive. do not have. In other words, achieving high rotation speed is essential to solving the slow transfer speed of magneto-optical disks, which is considered a disadvantage over hard disks. It is necessary that recording and erasing can be performed with a laser power of 200 mL, that is, the dependence of the recording sensitivity of the medium on linear velocity must be small, and the above-mentioned prior art did not take this point into consideration at all.

The present invention was made in view of these circumstances,
It is an object of the present invention to provide a magneto-optical disk that has low linear velocity dependence and can prevent deterioration of recording and reproducing characteristics, especially when the disk rotational speed is made higher than before, and a method for manufacturing the same.

(Means for Solving the Problems) A first magneto-optical disk according to the present invention has a first dielectric layer, a recording layer, a second dielectric layer and a metal reflective layer laminated in this order on a transparent substrate. In the magneto-optical disk, the thermal conductivity of the second dielectric layer is higher than the thermal conductivity of the first dielectric layer, and the thermal conductivity of the metal reflective layer is higher than the thermal conductivity of the recording layer. It is characterized by its large size.

A second magneto-optical disk according to the present invention is characterized in that the metal reflective layer has a thermal conductivity of 0.1 cal/Cm·sIC·1 or more.

Moreover, the manufacturing method of the first magneto-optical disk according to the present invention is as follows:
In a method for manufacturing a magneto-optical disk in which a first dielectric layer, a recording layer 6, a second dielectric layer, and a metal reflective layer are laminated in this order on a transparent substrate using a vacuum film-forming method, the heat of the second dielectric layer is It is characterized in that the conductivity is higher than the thermal conductivity of the first dielectric layer, and the thermal conductivity of the metal reflective layer is higher than the thermal conductivity of the recording layer.

The second manufacturing method of the magneto-optical disk according to the present invention is such that the thermal conductivity of the metal reflective layer is set to 0.1 cal/cm・Set・1.
The present invention is characterized by the above.

(Function) According to the above configuration, the thermal conductivity of the first dielectric layer (enhancement layer), which is the first layer on the light beam incident side, is higher than that of the second dielectric layer (inorganic protective layer), which is the third layer. In addition to increasing the thermal conductivity, the fourth layer, the metal reflective layer, has a higher thermal conductivity than the second layer, the recording layer, to improve heat conduction in the thickness direction of the magneto-optical recording layer. By making this larger than that in the in-plane direction, the energy of the laser beam can be efficiently transmitted to the recording layer within a short time. In magneto-optical disks, when the recording layer is heated to above the Curie point by laser light incident through the transparent substrate, signals are recorded by reversing the magnetization of that region. Since the energy of light can be efficiently transmitted to the recording layer within a short time, even if the disk rotation speed is increased compared to conventional methods in order to increase the signal transfer rate, it is possible to move a predetermined portion of the recording layer in a short time. It can be warmed up.

In addition, the thermal conductivity of the metal reflective layer is 0.1 cal/c■
・If the value is relatively large, such as Sec.1 or more, the heat dissipation characteristics during recording, erasing, etc. can be improved, and heat diffusion in the film thickness direction can be promoted, so that the temperature increase time mentioned above can be further shortened. becomes possible.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the layer structure of a magneto-optical recording layer of a magneto-optical disk according to an embodiment of the present invention. That is, this magneto-optical disk has a magneto-optical recording layer 1 on a transparent disk substrate 1.
1 is formed, and this magneto-optical recording layer 1
1 is a first dielectric layer (enhancement layer) in order from the transparent substrate 1 side; 2. It is formed by laminating a recording layer 3, a second dielectric layer (inorganic protective layer) 4, and a metal reflective layer 5. The thermal conductivity of the second dielectric layer 4 is higher than that of the first dielectric layer 2, and the thermal conductivity of the metal reflective layer 5 is higher than that of the recording layer 3. . Further, the thermal conductivity of the metal reflective layer 5 is 0.1 eal/C1·sec·1 or more, preferably 0.3 cal/c layer·SIC·1. Note that a through hole 6 for chucking is bored in the center of this magneto-optical disk.

FIG. 2 shows a double-sided recording type magneto-optical disk in which two single-plate magneto-optical disks as shown in FIG. 1 are bonded together with an adhesive layer 14 interposed therebetween.

That is, a magneto-optical recording layer 11 is formed on a transparent disk substrate 1, the outer surface of the transparent disk substrate 1 is covered with an organic resin protective layer 12, and the surface of this magneto-optical recording layer 11 is covered with an organic resin protective layer 13. It is made by bonding two single-plate magneto-optical disks with an adhesive layer 14. Recording and playback of signals.

As shown by the arrows in FIG. 2, the laser beam for erasing is made to be incident perpendicularly to the substrate surface from both sides of this magneto-optical disk, and after passing through the substrate 1, it first hits the first dielectric The light will be incident on the body layer 2. In addition, the second
In the figure, the central through hole of the magneto-optical disk is omitted.

Further, the first dielectric layer 2 is an enhancement layer made of a dielectric material for imparting an enhancement effect to the recording layer 3, and is formed to have a thickness of 800 to 1300 nm. Examples of the material of the first dielectric layer 2 include SI Ox,
Dielectrics such as oxides, nitrides and sulfides such as SI Nx , Ta Ox , AJNx and ZnS are used.

Among these, from the viewpoint of optical properties and protective function, nitride of Sl, nitride of A1, or a mixture thereof is preferable.

Further, the recording layer 3 is formed to have a thickness of 200 to 300 layers. This recording layer 3 is preferably an amorphous alloy thin film mainly composed of transition metals and rare earth metals. The transition metal that can be the composition of this recording layer 3 is F.
e, Co, Ni, etc., and rare earth metals such as Tb, Gd,
There are Dy, Ss, Nd, etc. Further, specific examples of the composition of this recording layer 3 include Gd Co, Gd Fe, Tb F
e, Dy Fe, Gd Fe Tb, Tb Fe Nl
, Dy Fe Co.

Tb Fe Ni, Gd Fe Co, Nd Dy
FeC.

etc. Among them, TbFeCo is most preferable because it has a large manufacturing tolerance, and it also contains Cr,
'IN, Ta, Nb, Pt, etc. from 0.5 to 10 at%
, desirably 3 to 8 at%, from the viewpoint of having practically sufficient corrosion resistance.

Further, the second dielectric layer 4 for protecting the recording layer 3 and for enhancing the Kerr effect has a thickness of 200 to 60 mm.
It is formed to a thickness of 0.00 people. This second dielectric layer 4 is an inorganic protective layer, and like the first dielectric layer 4, it is usually a dielectric thin film.

Further, the metal reflective layer 5 is formed to have a thickness of 300 to 1000 layers, more preferably 400 to 800 layers. If the film thickness of the metal reflective layer 5 is less than 300 mm, light will pass through and become crystalline, resulting in a decrease in C/N and 1
000 Å or more is not preferable because the heat capacity increases and the sensitivity decreases as a result. Further, as the metal reflective layer 5, various metals and alloys can be used. For example, AJ, Al-Cu, Al-Tl, Aj-T
a, Nf, N1-Cu, Au, Cu, Cu-
A film of metal such as TI, Cu-Zu, etc. is formed on the inorganic protective layer by a sputtering method. Note that the thermal conductivity of this metal reflective layer 5 is 0.1 (cal/cm・se
c・k) In order to obtain ζ impurity gas elements in these metal thin films, for example, 02. It is desirable to reduce Nz, H2, and Ar as much as possible.

Furthermore, it is desirable that the mechanical properties of the transparent disk substrate 1, particularly the surface contact acceleration and surface contact amount, be reduced so that recording, reproduction, and erasing can be performed effectively even during high-speed rotation. As the material of this substrate 1, polycarbonate, polymethyl methacrylate, epoxy resin, glass, etc. are used. Among these, resin substrates such as polycarbonate, polymethyl methacrylate, and epoxy resin are preferred in terms of cost, and polycarbonate is particularly preferred since it has advantages such as relatively low water absorption and high glass transition temperature.

By the way, as mentioned above, in the magneto-optical disk of this embodiment, the thermal conductivity of the second dielectric layer 4 is higher than that of the jli11 dielectric layer 2, and the thermal conductivity of the metal reflective layer 5 is higher than that of the recording layer 3. The thermal conductivity of these first
Dielectric layer 2. The thermal conductivity of the second dielectric layer 4, the recording layer 3, and the metal reflective layer 5 is, for example, 0.03 cal/c's.
ec4.0.07cal/cm+s@c-, 0.
12cal/cm・sec・k and 0.25cal
/cm・sec・beast. As a result, the energy of the laser beam incident on the magneto-optical recording layer is transmitted faster in the thickness direction of the disk than in the surface direction of the disk, and is efficiently transmitted to the recording layer 3. Further, the metal reflective layer 5
The thermal conductivity of the disc is set to a relatively high value of 1.1 cal/tm Therefore, the energy of the laser beam can be transmitted to the recording layer 3 more efficiently.

Next, a method for manufacturing the above-mentioned magneto-optical disk will be explained.

A polycarbonate substrate 1 having a diameter of 130 m and a thickness of 1.2 mm and having a guide groove provided on one side is set on a rotating substrate holder of a sputtering apparatus. Argon gas is introduced into the sputtering chamber, and the gas pressure is set at 5 sTorr.

Next, the first dielectric layer 2 is first formed by magnetron sputtering. Next, by supplying power to two metal targets and performing binary simultaneous sputtering at an Ar gas pressure of 1 mTorr, two of the recording layers 3 were formed on the tJS1 dielectric layer 2.
Form to a thickness of 50 people. Next, a second layer is placed on this recording layer 3.
A dielectric layer 4 is formed to a thickness of 450 mm at a gas pressure of 5 m Torr.Furthermore, a metal reflective layer 5 is formed thereon to a thickness of 500 mm at a gas pressure of 1 m Torr.

Thereafter, an ultraviolet curable resin is applied onto the magneto-optical recording layer to a thickness of 2 μm using a spin code method, and cured by irradiation with ultraviolet rays to form an organic resin protective layer.

The two single disks thus formed are pasted together with the sides without the magneto-optical recording layer facing outward, and a hot melt adhesive is applied onto the organic resin protective layer and adhesive is applied under pressure. Let's do it.

Note that the magneto-optical disk of the present invention and its manufacturing method are not limited to those of the above-described embodiments, and can be modified in various other ways. For example, the magneto-optical disk does not necessarily have to be a double-sided recording type, but may be a single-sided recording type.

Hereinafter, regarding the magneto-optical disk of the present invention, Example a,
This will be further explained by comparing the sensitivities of magneto-optical disks b, c, and d with those of comparative examples.

Example-a Diameter 110m5 with guide groove provided on one side by injection molding
A polycarbonate substrate with a thickness of 1.2 mm was set on a rotating substrate holder of a sputtering apparatus, and argon gas was introduced into the sputtering chamber to set the gas pressure to 1 Torr.

Then, a thin film of 5INX with a thickness of 1100 mm was first formed as a first dielectric layer on the substrate by magnetron sputtering.

Then, by applying electric power to the Fe Co Cr alloy target and the Tb target, Tb 1sFe bsCoBC is deposited on the first dielectric layer by binary simultaneous sputtering.
A recording layer having a composition r6 was formed to a thickness of 250 mm.

After that, a second dielectric layer of A-Si is formed on the recording layer.
A thin film of Nx was deposited to a thickness of 400.

Furthermore, as a metal reflective layer on top of that, Ai) -TI(Tl
lat%) to a thickness of 500 nm, thereby forming a first dielectric layer and a recording layer on the substrate.

A four-layer magneto-optical recording layer consisting of a second dielectric layer and a metal reflective layer was formed.

After that, the above-mentioned ultraviolet curing resin made by Dainippon Ink Co., Ltd.
5D-17 was applied to a thickness of 2 μm using a spin cord method and cured by irradiation with ultraviolet rays to provide an organic resin protective layer.

Under similar conditions, another magneto-optical disk with the magneto-optical recording layer and the organic resin protective layer provided on one side of the substrate was prepared.
I created one. Hot melt adhesive #XW-18 manufactured by Toagosei Kagaku Co., Ltd. is applied onto the organic resin protective layer that covers the magneto-optical recording layer of each disk, and both disks are bonded together under pressure via this adhesive. Sample A of a double-sided recording type magneto-optical disk was prepared.

Separately, the thermal conductivity of each layer constituting the magneto-optical recording layer is
Thin film thermal conductivity measuring device (PIT-1) manufactured by Shinku Riko Co., Ltd.
When measured, the following measured values were obtained.

First dielectric layer; SiN+, s 0.03cal/
cs/stC/k recording layer; TbPeCoCr
0.12cal/cs-sec4 second dielectric layer;
Ao SiNx 0.07cal /cs・5ec4
Metal reflective layer; Aj-TI 0.25cal/cm
・s! c4 Example-b In contrast to Example-a, the second dielectric layer was AJNX and 40
Sample B of a double-sided recording type magneto-optical disk was prepared under the same conditions as in Example-a, except that the film was formed to a thickness of 0.0 mm.

The thermal conductivity of each layer is: First dielectric layer; SiN+, s 0.03 cal
/cm・uc・k Recording layer; TbPeCoCr
0.12cal/cm・sec・k second dielectric layer;
AJNx 0.22cal/cm+ttt-
Metal reflective layer; AJ-Tl 0.25cal/c
It was s+scc+1.

Example-C In Example-a, the first dielectric layer was formed as AJSION to a thickness of 1100 mm, and the second dielectric layer was formed as 5 IN.
Example-a except that the film was formed to a thickness of 400 mm as x
Sample C of double-sided recording type magneto-optical disk under the same conditions as
It was created.

The thermal conductivity of each layer is: First dielectric layer; AJSlON 0.01 cal
/cm+s! cek recording layer; TbFeCoCr
0.12cal/cm・s! Second dielectric layer on c+; 5iN1, 30.03cal/cm・5tc
ek metal reflective layer; AJ! -TI 0.25cal
/ls+・uc*.

Example-d In Example-a, the first dielectric layer is SIN.

Except that the second dielectric layer was formed to a thickness of 1100 mm as 5INo.a, and the thickness of 400 mm was formed as the second dielectric layer.
Sample D of a double-sided recording type magneto-optical disk was prepared under the same conditions as in Example-a.

The thermal conductivity of each layer is: 1st dielectric layer; 5IN1.30.03cal/c
m*sec・k recording layer: TbPeCoCr
0.12cal/1m・stt・k second dielectric layer;
5INo, s 0.06cal /c1sec・k
Metal reflective layer; AJ-Ti G, 25cal/cm
e@! It was on c+.

Comparative Example Compared to Example-8, the second dielectric layer was 5INx and 40
Sample X of a double-sided recording type magneto-optical disk was prepared under the same conditions as in Example-a, except that the film was formed to a thickness of 0.0 mm.

The thermal conductivity of each layer is: First dielectric layer; SiNx 0.03ca! /c
tsec・k recording layer: TbFeCoCr 0
．． 12cal/cts! c・k second dielectric layer; 5
ING, s 0.03cal/cm・5ec4
Metal reflective layer; Al2-TIG, 25cal/c
It was masecak.

For each sample of the magneto-optical disk obtained as above, the minimum recording laser power (Pth) at which the C/N can exceed 40 dB is determined as the recording sensitivity (sV),
In addition, the dependence of the recording sensitivity on linear velocity was evaluated in FIG.

As is clear from FIG. 3, Examples a and b.

Samples A, B, C, and D based on samples c and d have lower linear velocity dependence than sample It can also be used as a variable rotation speed type magneto-optical disk.

(Effects of the Invention) As explained above, according to the magneto-optical disk and the manufacturing method thereof of the present invention, the relationship of thermal conductivity between each layer in the magneto-optical recording layer is defined and Since the heat conduction is good, the energy of the laser beam can be efficiently transmitted to the recording layer within a short time, and recording sensitivity can be improved. This makes it possible to respond to faster disk rotational speeds and faster transfer rates.

In addition, the thermal conductivity of the metal reflective layer is 0.1 cal/cm・s.
If the value is set to a relatively large value of ee.1 or more, thermal diffusion in the thickness direction of the magneto-optical recording layer can be promoted, so that the recording sensitivity can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the layer structure of the magneto-optical recording layer of a magneto-optical disk according to an embodiment of the present invention, and FIG. 2 is a double-sided recording type made by laminating two magneto-optical disks shown in FIG. 1. FIG. 3, which is a schematic cross-sectional view showing a magneto-optical disk, is a graph showing the dependence of recording sensitivity on linear velocity for the magneto-optical disk according to the example and the magneto-optical disk according to the comparative example. 1... Transparent disk substrate 2... First dielectric layer 3.
...Recording layer 4...Second dielectric layer 5...
Metal reflective layer 11... magneto-optical recording layer 14...
Adhesive layer Figure 1 June 1991

Claims (4)

[Claims] (1) In a magneto-optical disk in which a first dielectric layer, a recording layer, a second dielectric layer, and a metal reflective layer are laminated in this order on a transparent substrate, the thermal conductivity of the second dielectric layer is A magneto-optical disk characterized in that the thermal conductivity of the first dielectric layer is higher than that of the first dielectric layer, and the thermal conductivity of the metal reflective layer is higher than the thermal conductivity of the recording layer. (2) The thermal conductivity of the metal reflective layer is 0.1 cal/cm.
2. The magneto-optical disk according to claim 1, wherein the magneto-optical disk is set to sec.k or more. (3) In a method for manufacturing a magneto-optical disk in which a first dielectric layer, a recording layer, a second dielectric layer and a metal reflective layer are laminated in this order on a transparent substrate using a vacuum film-forming method, the second dielectric layer A magneto-optical disk characterized in that the thermal conductivity of the layer is higher than the thermal conductivity of the first dielectric layer, and the thermal conductivity of the metal reflective layer is higher than the thermal conductivity of the recording layer. manufacturing method. (4) The thermal conductivity of the metal reflective layer is 0.1 cal/cm.
4. The method for manufacturing a magneto-optical disk according to claim 3, characterized in that: -sec.k or more.