JPH03105745A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To produce magneto-optical recording medium at high yield which can be stored for a long time by sintering an intermetallic compd. of rare earth element, transition metal element and element for improving corrosion resistance, with a simple substance of rare earth, simple substance of transition metal, and simple substance of element for improving corrosion resistance to obtain a target of a fine mixture structure. CONSTITUTION:The medium is produced by a sputtering method in which substrates on a tray travel perpendicularly to the longitudinal line of the target. The target for forming the magneto-optical recording layer has a fine mixture structure obtained by sintering an intermetallic compd. of rare earth element, transition metal element and element for improving corrosion resistance, with a simple substance of rare earth, simple substance of transition metal, and simple substance of element for improving corrosion resistance. The proportion of the element for improving corrosion resistance is <=20atm.% and the area of the intermetallic compd. on the sputtering surface is specified to 10 - 40%. By using this targer, the obtd. medium is suitable for mass production and has repeatability with low error rate and high reliability for long-term storage. This magneto-optical recording medium can be produced at high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in a method of manufacturing a magneto-optical recording medium. More specifically, the present invention provides a highly reliable magneto-optical recording medium for long-term storage, consisting of at least a three-layer structure in which a dielectric layer, a magneto-optical recording layer and a dielectric layer are sequentially provided on a substrate. The present invention relates to a method for manufacturing a magneto-optical recording medium that can be easily manufactured and is suitable for mass production.

2. Description of the Related Art Recently, magneto-optical recording media such as magneto-optical disks have been developed as optical recording media on which information can be recorded, reproduced and erased using a light beam. In the magneto-optical recording layer for recording information in this magneto-optical recording medium, alloys such as Mn-Bi have traditionally been used as recording materials, but today alloys such as Fa and Go and transition metals such as Nd and DYSGd have been used as recording materials. ，
Alloys with rare earth elements such as Tb are commonly used.

By the way, optical recording media that utilize reversible phase change are known as optical recording media on which information can be recorded and erased, but optical recording media that utilize magneto-optical effects are optical recording media that utilize phase change. Unlike conventional magnets, recording and erasing are performed only by reversing the direction of magnetization. In other words, when recording on an optical recording medium that utilizes the magneto-optic effect, first, as an initialization process, an external magnetic field is continuously applied to the magnetic material used as the recording layer while irradiating it with a light beam such as a laser to change the magnetization. After aligning the orientation, a light beam is irradiated while applying an external magnetic field in the opposite direction to form or erase the bit, and the same operation as the initialization process is performed.

Since such a process does not involve movement of the thickness, it has the advantage that there is little risk that the recording shoe will be deformed or that the recorded state or erased state will change.

However, in such magneto-optical recording media,
Coatings are usually formed by sputtering from the viewpoint of productivity, but Nd, I1) I%Gd,
Rare earth elements such as Tb and transition metal elements such as FeSCo and Ni have completely different properties in terms of the emission angle distribution by sputtering, making it difficult to control the composition ratio of rare earth elements and transition metal elements. There are drawbacks.

The structure of the sputtering device used for a certain film of this magneto-optical recording medium is that the substrate is opposed to a target; a rotation-revolution method in which the substrate is rotated and revolved to make the film thickness and composition uniform within the disk surface; There is a passing method in which a disk substrate is passed through a tray with the disk substrate facing the target, but in the former method, although it is easy to achieve uniform film thickness and composition, it requires a sputter input for each sputtered film. In addition to having to turn on and off, the substrate is stationary and revolves around the target, making it difficult to obtain reproducibility of film quality.
In addition, there is a risk that the splatter deposits attached to the tray during rotation and revolution may peel off and adhere to the substrate to be coated, resulting in formation of holes in the film, which is undesirable in terms of mass production.

On the other hand, in the latter method, since the tray is passed continuously while facing the target during film formation, it is easy to obtain reproducibility of film quality. Suitable for peeling objects and mass production. However, this method has the disadvantage that it is difficult to control the film thickness and composition, especially the composition, compared to the rotation-revolution method.

As a method to control this structure, NdSDV, Gd. ．． A method has been proposed that uses a rare earth element such as Tb, a transition metal element such as Fe, Co%Ni, and an intermetallic compound of a rare earth element and a transition metal element in a specific ratio. (Unexamined Japanese Patent Publication No. 1983-205556)
In this method, the recording layer to be formed has a uniform composition throughout the film surface and film thickness direction, but contains rare earth elements such as Fe, Nd, and Dy%Gd%Tb, which are easily oxidized. Because it uses

Therefore, it has been desired to establish a method for efficiently manufacturing a magneto-optical recording medium that is mass-producible, allows sufficient control of the film quality of the magneto-optical recording layer, and is highly reliable for long-term storage.

Problems to be Solved by the Invention The present invention, in response to such demands, provides a highly reliable at least three-layer structure for long-term storage, in which a dielectric layer, a magneto-optical recording layer, and a dielectric layer are sequentially provided on a substrate. The purpose of this invention is to provide a method for manufacturing a magneto-optical recording medium that is suitable for mass production and can efficiently manufacture a magneto-optical recording medium consisting of the following.

Means for Solving the Problems As a result of extensive research in order to achieve the above object, the present inventors adopted a substrate passing type sputtering method as a sputtering method, and as a target for a magneto-optical recording layer, Using a material with a specific structure composed of rare earth elements, transition metal elements, and corrosion resistance improving elements, the concentration of the corrosion resistance improving elements was continuously varied in the film thickness direction, increasing the concentration of the corrosion resistance elements at the upper and lower interfaces. By shaping the magneto-optical recording layer,
It was discovered that the object could be achieved, and based on this knowledge, the present invention was completed.

That is, the present invention uses a magneto-optical recording medium consisting of at least three layers, in which a dielectric layer, a magneto-optical recording layer and a dielectric layer are sequentially provided on a substrate, as a sputtering apparatus, and uses a rectangular target and the substrate as the target. Manufactured by a substrate passing sputtering method using a device having a substrate tray that is fixed in a state facing the target, and a transport mechanism that transports the substrate tray at a constant speed perpendicular to the long side of the target. As targets for forming the magneto-optical recording layer, intermetallic compounds of rare earth elements, transition metal elements, and corrosion resistance improving elements, fine particles made by combining rare earth elements, transition metal elements, and corrosion resistance improving elements by sintering are used. has a mixed tissue;
A light source characterized in that the content of the corrosion resistance improving element is 20m% or less, and the ratio of the area occupied by the intermetallic compound on the sputtered surface is in the range of 10 to 40%. A method of manufacturing a magnetic recording medium is provided.

The present invention will be explained in detail below.

The magneto-optical recording medium obtained by the method of the present invention has a structure consisting of at least three layers in which a dielectric layer, a magneto-optical recording layer and a dielectric layer are successively laminated on a substrate. In order to increase the rotation angle, the dielectric layer provided on the magneto-optical recording layer is further coated with Al2, Ni, Cr.
．． ．． A reflective layer made of metal such as Au may also be provided.

In the method of the present invention, by the substrate passing sputtering method,
Magneto-optical recording media are manufactured, and at this time, a sputtering or film device is used that uses a rectangular target and a substrate tray that fixes the substrate facing the target at a constant speed perpendicular to the long side of the target. An apparatus having a conveyance mechanism for conveying is used. An explanatory view of one example of such a sputter coating apparatus is shown in FIG. The substrate 3 is fixed to the substrate tray 2 while facing the target l, and the substrate tray 2 moves in the direction of the arrow.

Also, if the width dT of the target is sufficiently longer than the mounting position width d of the board, d. A relatively uniform sputtering rate can be obtained within this range. The number of boards installed is
In the figure, there are four sheets of 2×2, but depending on the length of the target, 4×4, 6×4, 6×6, etc. can be selected as appropriate.

Furthermore, when the magneto-optical recording medium has a multilayer structure, sputtering chambers may be connected to form multiple chambers.

FIG. 2 is an explanatory view showing an example of a sputter film apparatus in which sputter chambers are connected to form a multi-chamber system, and the symbols in the figure have the same meanings as above.

The substrate of the magneto-optical recording medium is made of materials commonly used for substrates of ordinary recording materials, such as glass, glass or plastic with a polymeric material that is cured by ultraviolet light, acrylic resin, styrene, etc. A transparent substrate made of resin, polycarbonate resin, vinyl acetate resin, vinyl chloride, polyolefin resin, or the like, or a substrate made of opaque material such as aluminum is used.

Address information and grooves for laser beam tracking may be formed on these substrates by methods such as injection molding, the 2P method, and etching.

As the magneto-optical recording layer provided on the substrate, Gds
Tbs Dy%HaSTIIs Nds Sm and E
``It is an alloy of at least one rare earth element selected from among such elements and at least one transition metal element selected from among Fe, Co, N5, etc., which has a high coercive force Hc and a magnetization Ms. An amorphous perpendicularly magnetized film made of a small material is used. For example, T
bFeSGdTbFe, TbFeCo, NdDyF
Preferable examples include 7-element magnetic films such as eCo and TbFeNi. Furthermore, in order to adjust the coercive force Hc, these materials may be laminated to form an exchange coupling film. Among these materials, TbFeCo and NdDyFeCo are especially
is suitable.

Furthermore, these 7-element magnetic films contain Ho, Tn+, Er as rare earth elements within the range that does not impair the above purpose.
Alternatively, S+++ or the like may be added for the purpose of improving the c/N ratio.

In the present invention, the magneto-optical recording layer contains Cr, Tis AQs Hf, Ta for the purpose of improving corrosion resistance.
, V, Nd, In, Zr%PtSRh, Pd, and Au at a rate of 20 atomic % or less.

When forming an alloy thin film consisting of the above rare earth element, transition metal element, and corrosion resistance improving element as a magneto-optical recording layer in a magneto-optical recording medium by a sputtering method, the rare earth element, transition metal element, and corrosion resistance improving element are Method of splicing together from separate targets and Tb containing corrosion resistance improving elements
There is a method of sputtering from a composite alloy target such as FeCo, NdDyFeCo, etc., but since the present invention uses a passing sputtering method, the latter method using a composite alloy target is used from the viewpoint of controllability of the film composition. .

Regarding the structure of this target, special measures are required because there is a large difference in the emission angle of sputtered atoms between rare earth elements, transition metal elements, and corrosion resistance improving elements, as shown below. For example, when sputtering is performed using a target made entirely of an alloy material consisting of an intermetallic compound of rare earth elements and transition metal elements, the amount of rare earth elements and transition metal elements scattered as shown in Figure 3 (a) is As shown in FIG. 3(b), the ratio of rare earth elements increases significantly from directly above the center of the target toward the periphery. Here, FIG. 3(a) is a graph showing an example of the sputter emission angle distribution of rare earth elements and transition metal elements when using the intermetallic compound target, where the solid line indicates the transition metal sputter emission angle distribution, and the dotted line 4 represents the rare earth element sputter emission angle distribution, and 4 represents the intermetallic compound target. Further, FIG. 3(b) is a graph showing an example of the distribution of the rare earth element/transition metal element (RE/TM) atomic ratio from the center of the target when the intermetallic compound target is used.

Under such circumstances, if film is formed by passing through a tray, it is possible to form a recording layer in which the concentration of rare earth elements changes continuously from dark to light to dark in the film thickness direction. .

On the other hand, when sputtering is performed using a target that does not contain intermetallic compounds and is entirely made of sintered material, the tendency is opposite to that described above, as shown in Figure 4 (a), and Figure 4 (l)) As shown in , the proportion of rare earth elements decreases significantly from directly above the center of the target toward the periphery. here,
FIG. 4(a) is a graph showing an example of the sputter emission angle distribution of rare earth elements and transition metal elements when using a target made of the sintered material, and the solid line indicates the transition metal sputter emission angle distribution. The dotted line represents the rare earth element scattering release angle distribution, and 4' represents the target cut out from the sintered material. Moreover, FIG. 4(b) shows rare earth elements/transition metal elements (RE/TM) when using a target made of the sintered material.
) ji (This is a graph showing an example of the distribution of the child ratio from the target center.

Under such circumstances, when film-forming is performed by passing through the tray, the recording layer is formed in which the concentration of the rare earth element changes continuously in the direction of the film thickness from light to dark, in the opposite direction. can be coated with a certain film.

On the other hand, the corrosion resistance improving element has a sputter emission angle distribution similar to that of the transition metal element and exhibits similar behavior. Therefore, as in the present invention, an intermetallic compound of a rare earth element, a transition metal element, and a corrosion resistance improving element, an earth element alone, a transition metal element alone, and a corrosion resistance improving element alone may be used as a magneto-optical recording layer type target. By using a sintered material having a fine mixed structure and appropriately selecting a certain proportion of each part, a magneto-optical recording layer having a continuous structure change in the film thickness direction can be obtained.

Furthermore, in the present invention, the ratio of the area occupied by the intermetallic compound on the sputtering surface of the target is 10 to 10.
Selected within a range of 40%. Thereby, the composition of the corrosion resistance improving element in the magneto-optical recording layer can be continuously changed in the direction of the film thickness, increasing the concentration of the corrosion resistance improving element at the upper and lower interfaces. As a result, the corrosion resistance improving element present at a high concentration at the interface is present in the dielectric layer provided above and below the magneto-optical recorder.
Alternatively, it is partially oxidized by an oxidizing factor passing through the dielectric layer to form a strong passive-like film, which protects the magneto-optical recording layer as well as the dielectric counterfeit.

If the ratio of the area occupied by the intermetallic compound on the sputtered surface of the target is less than 10%, the difference in composition in the film thickness direction will become too large, which may lead to a decrease in recording and reproducing characteristics, especially the C/N ratio. %, the compositional difference in the film thickness direction decreases, and as a result, the concentration of the corrosion resistance improving element at the interface with the dielectric material provided above and below the magneto-optical recording layer becomes low, and the effect of the present invention is not sufficiently achieved. It will no longer be effective.

The dielectric layers provided above and below the magneto-optical recording layer include, for example, SiNx, SiNxOy, SiOxSSiA (2
Nx, SiA(loxNy, kQNx, A(10xN
y. Materials such as ZnS are used. This dielectric layer may be provided by sputtering using the above compound as a target, or may be provided by reactive sputtering using a metal or metalloid such as Si%Af2 as a target.

Effects of the Invention According to the present invention, a magneto-optical recording medium that is highly reliable for long-term storage can be efficiently manufactured using a substrate-passing sputtering method that is suitable for production with high reproducibility and low error occurrence. .

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

Example 1: 130 diameter, 1.211+ thickness, formed by injection molding
A magneto-optical recording medium was prepared using the polycarbon amorphous substrate No. 1 according to the following procedure by the pass-through sputtering method, and the C/N ratio as recording and reproducing characteristics and 80°C as long-term reliability were determined.
The pit error rate (BER) change rate after 1000 hours under 90% RH was measured and compared.

Pass-through sputtering equipment has a distance between substrate targets of 80m+
i. The shape of the target is a rectangle with long sides 460 mm wide x short sides 130 mm wide, and as a tray to oppose the target,
The installation position radius d of the board is 280m+m, and the diameter is 130m.
The structure is such that up to four layers can be formed in succession depending on the structure.

Further, the ends of the trays overlap each other in the membrane, so that when viewed from the target, the trays appear to be membraned as if they were flowing one after the other.

As a target for forming the magneto-optical recording layer, rare earth element T
5 types of TbFeCo composite materials containing 5 at. The proportion of the area occupied by is 0% (Target Soto A),
A 10% target (Target B), a 25% target (Target C), a 40% target (Target D), and a 55% target (Target E) were prepared. Using each target, the composition ratio of recorded slaughter was approximately Tb+s (Feo.
ecoa. +) Filming conditions such as target assembly, sputtering gas pressure, and power were selected so as to yield y1crs.

First, a dielectric layer made of SiNx is placed on the substrate with a thickness of 1000
After forming a film to a thickness of A, using target A, Tb
A magneto-optical recording layer made of FeCo-Cr is formed into a FR film with a thickness of 250 mm, and then a dielectric layer made of SiNx is formed with a thickness of 350 mm.
In addition, a reflective layer made of A12 was formed to a thickness of 600 mm, and a magneto-optical disk with 400 sides of a 100 tray was fabricated.

Next, switch the target A to target B,
Magneto-optical disks with exactly the same layer structure and the same <ioo tray 400 sides were manufactured.

Furthermore, the same number of magneto-optical disks were similarly produced for the target C1 target D1 target E.

Approximately 10 magneto-optical disks produced from each target were arbitrarily extracted in this manner, and the C/N ratio at the optimum sensitivity was measured as the recording and reproducing characteristics, and the average value was determined. Note that the C/N ratio was measured by rotating the substrate at 1800 rpm.
The recording frequency was 3.7 MHz at the innermost circumference (radius 30 mm). The C/N ratio for each target is shown graphically in FIG. From this figure, it can be seen that when the ratio of the area occupied by the intermetallic compound on the sputtering surface of the target becomes less than 10%, the C/N ratio decreases and becomes less than 45 dB.

Next, each sample was placed in an 80° C1 90% RH constant temperature and humidity chamber, and the pit error rate change rate (BER) lo was measured after 1000 hours had elapsed. . / (BER). ((
BER), is the initial pit error rate, (BER)
．． ．． . . is the pit error rate after 1000 hours] was calculated. The results are shown graphically in FIG.

From this figure, it can be seen that the rate of change in pit error rate increases as the proportion of the area occupied by intermetallic compounds on the sputtering surface of the target increases, and this tendency is particularly noticeable when it exceeds 40%.

From the above results, in order for the C/N ratio to be 45 dB or more and for the pit error rate to not increase in high temperature and high humidity acceleration tests, the area ratio occupied by intermetallic compounds on the sputtering surface of the target must be 10 to 40%. It turns out that it is necessary to be within the range of t.

In addition, 100 sides of the magneto-optical disk prepared using target C were arbitrarily cut out, the C/N ratio and the variation in the recording sensitivity obtained at the maximum value of the C/N ratio were determined, and the error rate of the entire surface was determined. As a result of measurement, the maximum and minimum differences in C/N ratio were 1 dB or less, sensitivity variations were 0.5 W or less at some points, and error rates over the entire surface were all 2xio-' or less.

As a result of the above, it has been confirmed that a manufacturing method for magneto-optical recording media that has good long-term storage stability and is highly mass-producible with little variation between media has been established.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of different examples of sputtering or film apparatuses for carrying out the method of the present invention, respectively,
In the figure, numeral 1 is a target, 2 is a substrate tray, and 3 is a substrate. Figures 3 (a) and (b) show an example of the sputter emission angle distribution of rare earth elements and transition metal elements, and a rare earth element/transition metal element (RE/TM) when using a target made of an intermetallic compound, respectively. ) Figure 7, Figure 4(a) and (
b) is an example of the sputter emission angle distribution of rare earth elements and transition metal elements and rare earth element/transition metal element (RE/TM) atoms when using targets made of sintered materials that do not contain intermetallic compounds. Figure 5 is a graph showing an example of the distribution of the ratio from the center of the target, and Figure 6 is a graph showing an example of the relationship between the ratio of the area occupied by intermetallic compounds on the sputtering surface of the target and the C/N ratio. is the ratio of the area occupied by the intermetallic compound on the sputtering surface of the target and the ratio of 1000 at 80'C and 90% RH.
Relationship 1 with the rate of change in pit error rate over time
Figure 2 is a graph showing an example. Figure I

Claims (1)

[Claims] 1. A magneto-optical recording medium consisting of at least three layers, in which a dielectric layer, a magneto-optical recording layer and a dielectric layer are sequentially provided on a substrate, is used as a sputtering device, and a rectangular target and the substrate are connected to the sputtering device. a substrate tray fixed in a state facing the target;
Using a device having a transport mechanism for transporting the substrate tray at a constant speed perpendicular to the long side of the target,
In manufacturing by the substrate passing sputtering method, intermetallic compounds of rare earth elements, transition metal elements, and corrosion resistance improving elements, rare earth elements alone, transition metal elements alone, and corrosion resistance improving elements alone are used as targets for forming the magneto-optical recording layer. It is made of a material that has a fine mixed structure bonded by sintering and has a content of the corrosion resistance improving element of 20 at % or less, and the proportion of the area occupied by the intermetallic compound on the sputtered surface is 10 to 40%. A method for producing a magneto-optical recording medium, characterized in that a magneto-optical recording medium is used. 2 Rare earth elements are Gd, Tb, Dy, Ho, Tm, Nd
, at least one selected from Sm and Er, the transition metal element is at least one selected from Fe, Co and Ni, and the corrosion resistance improving element is Cr, Ti, Al, Hf.
, Ta, V, Nb, In, Zr, Pt, Rh, Pd, and Au.