JP2974555B2 - Magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording information using a laser beam and a magnetic head.

[0002]

2. Description of the Related Art In recent years, magneto-optical recording media have attracted attention as optical recording media capable of erasing and rewriting information.

A conventional magneto-optical recording medium is locally heated by irradiating a laser beam while applying a magnetic field to the magnetic recording layer from the outside, thereby reducing the coercive force of the recording layer. A so-called light modulation method in which information is recorded by changing the direction of magnetization is used. However, this method has a problem in that information cannot be overwritten and information can be rewritten at high speed.

In order to solve such a problem, for example, as described in JP-A-51-107121, a magnetic field applied to a magnetic recording layer is modulated by an information signal, and thereby the recording layer is modulated. A so-called magnetic field modulation method in which information is recorded by changing the direction of magnetization has been proposed.

As a conventional magneto-optical recording system, as shown in FIG. 9, a recording layer 6 having a magneto-optical recording film and a protective layer 7 are sequentially laminated on a substrate 1 as a magneto-optical recording medium. In general, a light source (not shown) is arranged so that a laser beam 92 can be incident on the recording layer via the substrate 1, and a magnetic field generating means 91 is arranged on the protective layer 7 side. However, in a magneto-optical recording medium, in particular, in a magneto-optical recording system of the magnetic field modulation type, the gap h between the protective film 7 of the magneto-optical recording medium and the magnetic head 91 during recording becomes extremely small as shown in FIG. (For example, about 5 μm), it is necessary to reduce the surface roughness of the protective film in order to prevent contact between the magnetic head and the protective film. Contacts with the protective layer Adsorbed phenomenon occurs between them if, since the head crash there is a problem that occurs and by putting a filler in the protective layer conventionally,
A method for preventing the adsorption by appropriately roughening the surface of the protective layer has been proposed. For example, Japanese Patent Application Laid-Open No. 4-64936 discloses a method in which the surface roughness of the protective film is adjusted to 0.01 to 0.05 μm. It describes what you can do. By the way, the center line average roughness ( _Ra ) is generally used as the surface roughness, and this _Ra is different from the floating stability and adsorptivity of the floating magnetic head at room temperature and normal humidity. while indicating correlation between, for example 50 ° C., in the high temperature and high humidity conditions such as 80% RH, the flying stability of R _a is always floating magnetic head, not the measure of prevention of adsorption example Even when _Ra was within the above range, the floating magnetic head and the protective film could not be completely prevented from adsorbing.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has excellent floating stability of a magnetic head even under high temperature and high humidity conditions, and effectively prevents adsorption to a protective film. It is an object of the present invention to provide a magneto-optical recording medium that can be used.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned objects, and as a result, the flying stability and the adsorptivity of the flying magnetic head have been evaluated as the center line as a measure of the surface roughness of the protective film. The present invention was found to have a clear correlation with the average peak height (hereinafter abbreviated as R _pm ), and made the present invention.
The magneto-optical recording medium of the present invention has a magneto-optical recording film on a substrate and has a protective layer on the recording layer. In the magneto-optical recording medium, the surface of the protective layer not facing the recording layer has a surface. And a surface roughness having a center line average peak height of 0.1 μm or more and 0.85 μm or less.

The magneto-optical recording medium of the present invention is a magneto-optical recording medium comprising a recording layer having a substrate and a magneto-optical recording film, the side of the magneto-optical recording medium facing the magnetic field generating means. Surface has a center line average peak height of 0.1 μm or more.
It has a surface roughness of 85 μm or less.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view showing a layer structure of an embodiment of a magneto-optical disk according to the present invention. In FIG. 1, reference numeral 1 denotes a substrate provided with a preformat such as guide grooves and prepits on its surface; The inorganic dielectric thin film, 3 is an amorphous magnetic recording film, 4 is an inorganic dielectric thin film, 5 is a reflective film, and the recording layer 6 is composed of 2 to 5. Reference numeral 7 denotes a protective layer formed on the reflective film of the recording layer 6. The present invention relates to the protective layer 7
Recording layer not facing the side surface of, as the surface roughness of the side of the surface 7a facing the magnetic field generating means of the magneto-optical recording medium in other words, the R _pm is formed on the 0.1μm or 0.85μm or less It is characterized by the following. By setting the R _pm of the surface of the protective layer within the above range, a magneto-optical recording medium having excellent floating stability of the magnetic head even under conditions of high temperature and high humidity and capable of effectively preventing attraction to the protective film of the magnetic head. What you can get.

In the present invention, R _pm is a portion of a measured length L in the direction of the center line (X) from the roughness curve f (x) of the protective layer surface as shown in FIG. Is divided into five equal parts, and the interval between the center line and the straight line passing through the highest peak and parallel to the center line in each of the five equally divided sections is represented by P _n (where n = 1, 2, 3, 4, 5) is a value represented by the following equation.

(R _pm ) = (1/5) × (P ₁ + P ₂ + P
₃ + P ₄ + P ₅₎

Here, the center line (X) of the roughness curve f (x) is defined as the area surrounded by the straight line and the roughness curve when a straight line parallel to the average line of the roughness curve is drawn. It means a straight line that is equal on both sides of the straight line, and the average line of the roughness curve is
In the extracted portion of the roughness curve f (x), it means a straight line parallel to the surface of the protective layer and set so that the sum of squares of the deviation from the line to the roughness curve is minimized. Things.

In the present invention, the measurement length L used for calculating R _pm is preferably 2 to 6 mm.

In the present invention, R _{pm is} 0.1 μm or more and 0.8 μm or less, particularly 0.15 μm or more and 0.75 μm.
The following is preferable in terms of the flying stability of the magnetic head because the coefficient of friction between the magnetic head and the protective layer can be kept sufficiently low even if the linear velocity of the magnetic head with respect to the protective layer decreases, Furthermore, the lower limit of the value of R _pm is set to 0.4 μm.
m, especially 0.5 μm, is preferable because it can prevent the magnetic head from adsorbing to the protective layer surface even under extremely severe conditions such as dew condensation conditions.

Next, as a method of manufacturing a magneto-optical recording medium according to the present invention, Al ₂ O ₃ or Si is formed on a recording layer formed on a substrate by a conventional method, for example, a vapor deposition method or a sputtering method.
It can be manufactured by applying and curing a mixture obtained by mixing and dispersing a filler such as ceramic particles such as O ₂ , TiO ₂ , TiO ₂ , and ZnO or metal particles such as Cu, Ni, and Al in an ultraviolet-curable resin composition. easily 0 by controlling the viscosity and coating method and the like of R _pm particle size and the ultraviolet curable resin composition of the filler in this case the protective layer surface.
It can be in the range of 1 μm to 0.85 μm.

[0017] Further, as another manufacturing method, the surface roughness adhesive or pressure-sensitive adhesive film or sheet having a pre-formed becomes the surface on the recording layer R _pm within 0.1~0.85μm as the like in a method of pasted, the master having R _pm is a pattern of 0.1~0.85μm after applying a photocurable resin composition was pressed against the photocurable resin composition layer on the recording layer And a method of irradiating light to transfer the pattern to the photocurable resin composition layer.

In the present invention, the protective layer 7 is formed by dispersing metal particles or ceramic particles formed by applying a conductive material (Ni, Cu, Au, Ag, Sb, etc.) on the surface of the protective layer. When the surface resistivity of the surface 7a is set to 1 × 10 ¹⁰ Ω / □ or less, it is possible to effectively suppress the electrostatic adsorption between the magnetic head and the protective layer in a low humidity environment.

The protective layer of the present invention has a thickness of 2 to 30.
The range of μm, particularly 5 to 10 μm, is preferable because a sufficient magnetic field can be applied to the recording film while maintaining the protection function of the protection film against external scratches.

As the magneto-optical recording medium according to the present invention,
0.1 to 0.85 and R _pm of the surface 7a of the protective layer 7 to which
Although the configuration of μm has been described, for example,
In the case of a magneto-optical recording medium used in a system in which the arrangement of the magnetic head and the laser beam is reversed from that shown in FIG. 9, the surface of the magneto-optical recording medium facing the magnetic head, that is, the recording of the substrate, The surface on which the layer is not formed may have a structure in which R _pm has a surface roughness of 0.1 to 0.85 μm, or the surface of the substrate on which the recording layer is not formed may have the above-mentioned structure. The surface on the side facing the magnetic head formed in the same manner as described above has an R _pm of 0.1 to 0.8.
It is preferable to adopt a configuration having a protective layer having a surface roughness of 5 μm.

Further, among the constitutions of the magneto-optical recording medium to which the present invention can be applied, there is no particular limitation on the constitution of the recording layer and the material used, and the constitution of the recording layer is not limited to the above constitution. The structure may be such that the body protective film is provided on one side of the magnetic recording film, and the structure may be such that there is no reflective layer.

As the magneto-optical recording film, for example, GdF
e, TbFe, GdTbFe, TbFeCo, GdTb
An amorphous recording layer made of a rare earth element such as FeCo and a transition metal, and the like, and an inorganic dielectric protective film such as S
i ₃ N ₄ , SiO ₂ , ZnS, SiC or the like can be used, and further, aluminum, gold, silver or the like is used as the reflection layer.

In the present invention, the substrate is not particularly limited. For example, the substrate is formed of a polycarbonate resin, an acrylic resin, a polystyrene resin, or a polyolefin resin having a preformat such as a guide groove or a prepit formed on the surface. A substrate having a preformat formed on the surface by the 2P method can also be used. The thickness of the substrate is, for example, 0.3 to 5 m so that dust adhering to the substrate surface does not penetrate the substrate and block the laser beam irradiated to the recording layer.
m, particularly preferably about 0.8 to 1.5 mm.

[0024]

The present invention will be described in more detail with reference to the following examples.

(Example 1) Outer diameter 86 mm, inner diameter 15 m
m, 1000 mm thick Si ₃ N ₄ on a transparent polycarbonate donut-shaped substrate with a thickness of 1.2 mm and TbFe
100% Co, 300% Si ₃ N ₄ and 60 A1
The recording layer was formed by laminating the inorganic dielectric thin film and the magneto-optical recording film sequentially by sputtering so that the angle was 0 °. Next, a polyethylene terephthalate film having a donut shape having a thickness of 6 μm, an outer diameter of 86 mm, and an inner diameter of 28 mm and having a center line average peak height ( R _pm ) of 0.4 μm as a surface roughness of one surface was an A1 film as a recording layer. The A1 film and the other surface of the film were adhered to each other with an adhesive so that a magneto-optical disk was formed as a protective layer.

In this embodiment, the measurement of the center line average peak height on the film surface is a value measured at a measurement length of 4 mm. Conditions at 25 ° C. and 50% RH between the protective layer of the magneto-optical disk thus obtained and the flying magnetic head (condition I)
Was measured as follows when the linear velocity of the disk with respect to the magnetic head was 6.60 m / s.

That is, the disk is placed horizontally on the rotating spindle, and the floating magnetic head is placed on the protective film with a predetermined load (6).
g), the disk is rotated so that the linear velocity of the disk with respect to the magnetic head becomes a predetermined value, and the horizontal force applied to the floating magnetic head at that time is measured using a strain gauge. The ratio to a predetermined load was defined as the friction coefficient. Next, a magneto-optical disk was prepared in exactly the same manner as described above, and the friction between the protective layer of the magneto-optical disk and the flying magnetic head under high-temperature and high-humidity conditions of 50 ° C. and 80% RH (condition II). The coefficient was measured. Table 1 shows the results.

It should be noted the R _pm described above At a present embodiment is the average value of R _pm measured At a 10 arbitrary places of the polyethylene terephthalate film surface.

Each _Rpm is based on Japanese Industrial Standards (JI
S) Measured using a stylus type surface roughness meter (trade name: Handysurf E30A, manufactured by Tokyo Seimitsu Co., Ltd.) based on B0651 at a cutoff value of 0.8 mm.

[0030]

[Table 1]

Next, the attraction force between the protective film and the magnetic head under the conditions I and II of the magneto-optical disk was measured. In the present invention, a floating magnetic head is mounted with a predetermined load (6 g) on a protective film of a disk which is horizontally set, and the maximum force required to lift the magnetic head in the vertical direction is defined as an attraction force. . Table 2 shows the results.

[0032]

[Table 2]

(Examples 2-1 to 2-6) Except that the center line average peak height of the film of the protective layer was changed as shown in Table 3 in the same manner as in Example 1, 2
A total of 12 magneto-optical disks were prepared, and the friction coefficient and the attraction force under the conditions I and II were measured in the same manner as in Example 1.

[0034]

[Table 3]

Comparative Examples 1-1 to 1-5 Each of Examples 2 to 1-5 was prepared in the same manner as in Example 1 except that the center line average peak height of the protective layer film was changed as shown in Table 4.
A total of 10 magneto-optical disks were prepared, and the friction coefficient and the attraction force under the conditions I and II were measured in the same manner as in Example 1.

[0036]

[Table 4]

With respect to the friction coefficients under the conditions I and II of Example 1, Examples 2-1 to 2-6, and Comparative Examples 1-1 to 1-5, the horizontal axis indicates the average height of the center line, and the vertical axis indicates the vertical axis. The results plotted on a graph with the friction coefficient on the axis are shown in FIGS.

Further, the first embodiment, the embodiments 2-1 to 2-
FIG. 5 shows the results of plotting the adsorbing force under conditions I and II of Comparative Example 6 and Comparative Examples 1-1 to 1-5 on a graph in which the horizontal axis represents the center line average mountain height and the vertical axis represents the adsorbing force. And FIG.

FIG. 4 shows that the frictional force between the protective layer of the magneto-optical recording medium disk and the magnetic head under high temperature and high humidity conditions depends on the center line average peak height. 3 and 4, when the average height of the center line is 0.85 μm or less under the normal temperature and normal humidity condition and the high temperature and high humidity condition, the friction coefficient between the protective layer and the magnetic head is 0.1 or less. It can be seen that the head is flying stably.

FIG. 6 shows that the attraction force between the protective layer of the magneto-optical disk and the magnetic head under high temperature and high humidity conditions depends on the center line average peak height, and FIG. 5 and FIG. If the average peak height of the center line is 0.1 μm or more under high temperature and high humidity conditions, the attraction force between the protective layer and the magnetic head is substantially equal to the load on the protective film of the magnetic head, and therefore the magnetic head is attracted to the protective film. It can be seen that no occurrence has occurred.

The magneto-optical disks prepared in Comparative Examples 1-1 and 1-2 were subjected to high temperature and high humidity conditions (condition II).
Coefficient of friction is due not measurable in adsorption to the protective layer surface of the magnetic head, and Tsu or a can shown in FIG.

(Comparative Examples 2-1 to 2-5) In Example 1, the center line average roughness (R) was used as the surface roughness of the protective layer film.
_A magneto-optical disk was prepared in the same manner as in Example 1 except that _a ) was changed as shown in Table 5. However, _Rpm was set to 0.1 μm or less.

[0043]

[Table 5]

With respect to the magneto-optical disks of Comparative Examples 2-1 to 2-5, the attraction force under the conditions I and II was measured in the same manner as in Example 1, and the value was plotted on the abscissa along the center line average roughness. And plotted on a graph with the vertical axis representing the adsorption force.
The results are shown in FIGS. 7 and 8, the center line average roughness shows a correlation with the adsorbability between the protective film and the magnetic head under normal temperature and normal humidity, but no correlation was observed under the high temperature and high humidity conditions.

[0045] Note that the R _a as described above At a present comparative example is an average value of R _a measured At a 10 arbitrary places of the polyethylene terephthalate film surface.

Each _Ra is defined by Japanese Industrial Standards (JI
S) Measured with a stylus-type surface roughness meter (Handy Surf E30A, manufactured by Tokyo Seimitsu Co., Ltd.) based on B0651 at a cutoff value of 0.8 mm.

[0047] (Examples 3-7) in the same manner as in Example 1 R _pm is 0.1μm, 0.4μm, 0.65μm, 0.
Two 75 μm and 0.85 μm magneto-optical disks were each produced.

The coefficient of friction of the magneto-optical disk under the conditions I and II between the protective layer and the magnetic head was determined by setting the linear velocity of the disk to the magnetic head to 3.67 m / s.
The measurement was performed while changing to 4.40 m / s and 5.50 m / s. The measurement was performed in exactly the same manner as in Example 1. Table 6 shows the results.

The evaluation was performed according to the following criteria.

AA: coefficient of friction is 0.05 or less A: coefficient of friction is more than 0.05 and 0.1 or less B: coefficient of friction is more than 0.1 and 0.2 or less C: coefficient of friction is 0.2 Greater than

[0051]

[Table 6]

Next, the attraction force between the protective film and the magnetic head at 60 ° C. and 80% (condition III) and at 70 ° C. and 80% (condition IV) of the magneto-optical disks of Examples 3 to 7 above was used. The measurement was performed in the same manner as described above.

Table 7 shows the evaluation results.

The evaluations in Table 7 are based on the following criteria.

A: 7.0 g or less B: Greater than 7.0 g

[0056]

[Table 7]

[0057]

As described above, as the surface roughness of the protective film, the center line average peak height (R _pm ) is set to be 0.1 μm or more and 0.85 μm or less, so that it can be obtained under high temperature and high humidity conditions. In addition, the flying stability of the flying magnetic head can be maintained, and the attraction between the protective film and the flying magnetic head can be suppressed. Therefore, by measuring R _pm , the flying stability of the flying type magnetic head can be easily improved even under a high temperature and high humidity condition without actually examining the flying stability and the adsorptivity with the actual flying type magnetic head. No adsorption phenomenon occurs,
A high-performance flying magnetic head-compatible magneto-optical recording medium can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of one embodiment of a magneto-optical disk according to the present invention.

FIG. 2 is an explanatory diagram of a center line average mountain height.

FIG. 3 is a graph showing a relationship between a center line average peak height (R _pm ) and a friction coefficient under a condition I.

FIG. 4 is a diagram showing a relationship between a center line average peak height (R _pm ) and a friction coefficient under a condition II.

FIG. 5 is a diagram showing a relationship between a center line average mountain height (R _pm ) and an attraction force under a condition I.

FIG. 6 is a diagram showing the relationship between the center line average peak height (R _pm ) and the attraction force under the condition II.

FIG. 7 is a diagram showing a relationship between center line average roughness (R _a ) and adsorption force under condition I.

FIG. 8 is a graph showing the relationship between the center line average roughness (R _a ) and the attraction force under the condition II.

FIG. 9 is a schematic diagram showing a laser beam and a positional relationship between a magnetic head and a magneto-optical disk when recording information on the magneto-optical disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Inorganic dielectric thin film 3 Amorphous magnetic recording film 4 Inorganic dielectric thin film 5 Reflective film 6 Recording layer 7 Protective layer 91 Magnetic field generating means 92 Laser beam

Claims (8)

(57) [Claims] 1. A magneto-optical recording medium comprising a substrate, a recording layer having a magneto-optical recording film, and a protective layer in this order, wherein the surface of the protective layer not facing the recording layer has a center. A magneto-optical recording medium having a surface roughness having a linear average peak height of 0.1 μm or more and 0.85 μm or less. 2. The magneto-optical recording according to claim 1, wherein the surface of the protective layer on the side not facing the recording layer has a surface roughness having a center line average peak height of 0.1 μm or more and 0.8 μm or less. Medium. 3. The magneto-optical recording medium according to claim 1, wherein the center line average peak height is a value calculated by setting a measured length to 2 to 6 mm with respect to a roughness curve of the protective layer surface. 4. The magneto-optical recording medium according to claim 1, wherein said recording layer has a structure in which an inorganic dielectric film, a magneto-optical recording film, an inorganic dielectric film, and a reflection film are laminated in this order from the substrate side. 5. The magneto-optical recording medium according to claim 1, wherein said magneto-optical recording film comprises an amorphous film of rare earth and transition metal. 6. A magneto-optical recording medium comprising a recording layer having a substrate and a magneto-optical recording film, wherein the surface of the magneto-optical recording medium facing the magnetic field generating means has a center line average peak height. Has a surface roughness of 0.1 μm or more and 0.85 μm or less. 7. The magneto-optical recording medium according to claim 6 , wherein the surface of the magneto-optical recording medium on the side facing the magnetic field generating means has a center line average peak height of 0.1 μm or more and 0.8 μm or less. . 8. The center line average peak height is a value calculated by setting a measured length to 2 to 6 mm with respect to a roughness curve of a surface of the magneto-optical recording medium facing the magnetic field generating means. Item 7. A magneto-optical recording medium according to Item 6 .