JP2598431Y2 - Magneto-optical disk grinding machine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for grinding a magneto-optical disk for removing protrusions on the surface of a resin protective layer of a magneto-optical disk.

[0002]

2. Description of the Related Art As a magneto-optical disk used in a magnetic field modulation recording system using a floating magnetic head, a resin protective layer formed on a magneto-optical recording layer is mixed with a filler to roughen the surface (Japanese Patent Laid-Open Publication No. JP-A-2-40149) or using a stamper with a roughened surface to transfer a pattern to a resin protective layer to roughen the surface (Japanese Patent Laid-Open No. 232/232).
No. 836). These have the effect of preventing the floating magnetic head from adsorbing to the surface of the resin protective layer. Alternatively, the inventors have proposed to provide a protective layer composed of two layers, a lower resin protective layer containing no filler and an upper resin protective layer containing filler (for example, Japanese Patent Application No. 4-224830). .

However, when foreign matters such as dust enter the resin protective layer, local protrusions having a height of 10 μm or more are generated. The projections are generated not only by the inclusion of foreign matter but also by local aggregation of the fillers.
When such protrusions occur, the floating magnetic head and the protrusions come into contact with each other, hindering the flying characteristics and deteriorating the recording characteristics of the magneto-optical disk. In order to remove protrusions on the surface of the resin protective layer, it is conceivable to grind the surface of the protective layer with a grinding device. However, the optimal structure of the grinding apparatus is unknown, and there are problems such as an inadequate grinding structure in which protrusions cannot be sufficiently ground, abnormalities in the birefringence of the substrate during grinding, and fluctuations in the envelope of the disk.

[0004]

[Problems of the Invention] The problems of the present invention are: 1) grinding the protrusion on the surface of the resin protective layer of the magneto-optical disk to a value equal to or less than the flying height of the magnetic head to prevent contact between the floating magnetic head and the magneto-optical disk; And 2) To prevent the occurrence of abnormalities in the envelope fluctuation of the magneto-optical disk due to the occurrence of abnormal birefringence in the substrate during grinding.

[0005]

The present invention relates to a grinding apparatus for cutting out protrusions on the surface of a resin protective layer of a magneto-optical disk. The grinding surface has a plurality of substantially parallel ridges on the grinding surface, and the corners of the edges of the ridges are formed. A grinding head for a magneto-optical disk, characterized in that a grinding head of approximately 90 degrees or less is provided, and an angle between a longitudinal direction of the ridge and a rotation direction of the magneto-optical disk is approximately 20 degrees or less. . The material of the grinding head is, for example, equivalent to the grinding head used in hard disks,
AlTiC, sapphire, diamond or the like is used.

[0006]

In the present invention, the angle between the longitudinal direction of the ridge of the grinding head and the rotation direction of the magneto-optical disk is set to approximately 20 degrees.
Degrees or less. As a result, the height of the protrusions on the surface of the resin protective layer becomes 3 μm or less, which is almost equal to the flying height of the flying magnetic head. In particular, when this angle is set to 15 degrees or less, the height of the projection becomes 3 μm or less, and the height of the projection can be limited to a height equal to or less than the flying height of the flying magnetic head. In the present invention, the angle of the edge of the ridge, that is, the angle between the bottom surface and the side surface of the ridge along the longitudinal direction of the ridge is set to substantially 90 degrees or less. As a result, it is possible to prevent the occurrence of abnormal birefringence on the substrate during grinding, and to prevent an increase in envelope fluctuation of the magneto-optical disk.

[0007]

EXAMPLE A magneto-optical disk was manufactured as follows.
A magneto-optical recording layer was formed on the main surface of the polycarbonate substrate by sputtering, and a resin protective layer was formed by spin coating. The magneto-optical recording layer is a first dielectric layer of yttrium sialon, a magneto-optical recording layer of Gd-Dy-Fe system, a second dielectric layer of yttrium sialon, and A
This is one in which l-type metal reflection layers are sequentially laminated. As the resin protective layer, a filler-free acrylic urethane-based UV-curable resin layer (about 10 μm) and an acrylic UV-curable resin mixed with a SiO2 filler (average particle size of 4 μm) (about 6 μm) are sequentially used. It is a laminated structure, which consists of two layers, a lower layer without filler and an upper layer with filler. Since the SiO2 filler was added to the upper layer, a large number of local protrusions having a height of about 10 to 20 [mu] m were generated on the surface of the resin protective layer. The projections are mainly due to the aggregation of the filler, but similar projections occur when foreign matter such as dust is mixed. The flying height of the flying magnetic head is generally about 3 μm or more, and the height of the projections needs to be 3 μm or less, preferably 3 μm or less. Here, the height of the protrusion means the maximum value of the height of the protrusion when the surface of the resin protective layer is scanned diagonally by a surface roughness meter.

The surface of the resin protective layer was ground by a grinding machine for a magneto-optical disk in order to grind the projections to a height of 3 μm or less. FIG. 3 shows the grinding head used. In the drawing, reference numeral 4 denotes a base of the grinding head 2 and reference numerals 6 and 6 denote a pair of ridges, each of which is linear and parallel to each other. Instead, they may be inclined to each other. Reference numerals 8 and 8 denote warpage portions, which are ridges 6 when viewed from the direction of rotation of the magneto-optical disk.
6 to prevent grinding of the magneto-optical disk at the tips of the ridges 6, 6. Edges 10, 10, 10, 10 are provided on both side surfaces along the longitudinal direction of the ridges 6, 6, respectively. Then, at the edge 10, the protrusion on the surface of the resin protective layer of the magneto-optical disk is ground. The edge 10 may be provided only on one side, not on both sides of the ridge 6.

The angle between the bottom surface and the side surface of the ridge 6 near the edge 10 is defined as θ, and θ is preferably approximately 90 degrees or less.
Here, the angle is set to 90 degrees, which facilitates processing. Next, the angle between the longitudinal direction of the ridge 6, that is, the continuous direction of the edge 10, and the rotation direction of the magneto-optical disk is defined as α. α is less than 20 degrees,
Preferably, it is 15 degrees or less. Reference numeral 12 denotes an arm of the grinding device for slowly moving the grinding head 2 from the outer peripheral side to the inner peripheral side of the magneto-optical disk by a drive mechanism (not shown).

The angle α between the longitudinal direction of the ridge 6 of the grinding head 2 and the direction of rotation of the magneto-optical disk is shown in FIGS. Since the grinding head 2 is small with respect to the magneto-optical disk, the angle α is constant inside the grinding head 2, but when considering the difference of α inside the ridge 6, α is determined based on the center of the ridge 6. Is determined. That is, α is the angle between the tangent to the rotation direction of the magneto-optical disk and the edge 10 at the center of the ridge 6. FIG. 1 shows a case where α is 0 degree, and FIG.
Shows the case when it is not a degree. When the magneto-optical disk rotates in the direction of the arrow in FIG. 1, the protrusion on the surface of the resin protective layer is ground by touching the edge 10 at an extremely small angle. In contrast, FIG.
When α is increased from 0 degree as in the above, the angle at which the projection collides with the edge 10 due to the rotation of the magneto-optical disk increases.

The effect of the angle α on the grinding of the protrusions on the surface of the resin protective layer was examined. A sapphire grinding head is used as the grinding head 2, and four angles of 0 degrees (sample 1), 8 degrees (sample 2), 15 degrees (sample 3), and 25 degrees (sample 4) are used. The grinding result was evaluated by setting the load on No. 2 to 9.8 gf and the number of rotations to 3600 rpm. The degree of envelope fluctuation of the magneto-optical disk before and after grinding was measured, and the effect of grinding was examined. The angle θ formed between the bottom surface and the side surface of the ridge 6 was 90 degrees. Table 1 shows the measurement results.

[0012]

Table 1 Influence sample of angle α Angle α (degree) Projection height (μm) Envelope fluctuation No. Before grinding After grinding Before grinding After grinding 10 16.4 2.4 ○ ○ 28 15.6 2.7 ○ ○ 3 15 16.2 2.9 ○ ○ 425 15.0 3.5 ○ ○ * ○ indicates no problem.

As is evident from Table 1, the degree of the envelope fluctuation was within the range of non-defective products, and the influence of grinding was not observed. As will be described later, what affects the envelope fluctuation is the angle θ formed between the bottom surface and the side surface of the edge 10 of the ridge 6. The effect of the angle α appears on the height of the protrusion, and the smaller the angle α, the more precise the grinding. For example, in Sample 4 in which the angle α is 25 degrees, the protrusion height after grinding is 3.
In the case of the sample 3 having the angle α of 15 degrees, the protrusion height after grinding can be set to 3 μm or less. The flying height of the flying magnetic head is about 3 μm or more, and therefore, the angle α is set to 20 degrees or less, preferably 15 degrees or less.

The effect of the angle θ will be described with reference to FIGS. 4 to 6 show cross sections of the grinding head 2. Angle θ
Is defined as the angle between the bottom surface and the side surface of the ridge 6 in the vicinity of the edge 10 of the ridge 6, and is substantially 90 degrees or less, such as 90 degrees θ in FIG. 4 and an acute angle θ ′ in FIG. Is preferred. Although it is particularly preferable that θ is 90 degrees, which is easy to process, it is difficult to set it strictly to 90 degrees, and may be about 90 degrees or less. As shown in FIGS. 4 and 5, the angle θ is almost 90.
Below the degree, there is no occurrence of abnormal birefringence of the substrate during grinding,
As a result, there is no abnormality in the envelope fluctuation of the magneto-optical disk. On the other hand, if the angle θ ″ is an obtuse angle as in the comparative example of FIG. 6, abnormal birefringence occurs in the substrate during grinding, and abnormal fluctuation in the envelope occurs.

This mechanism will be described with reference to FIGS. In the figure, reference numeral 01 denotes a substrate of a magneto-optical disk, 02 denotes a magneto-optical recording layer, 03 denotes a lower resin protective layer containing no filler, and 04 denotes an upper resin protective layer containing a filler. Then, the magneto-optical disk is rotated as shown by the arrows in FIGS. 7 and 8, and the protrusion of the upper resin protective layer 04 is cut off at the edge 10 along the longitudinal direction of the ridge 6. Here, when the angle θ is substantially 90 degrees or less as shown in FIG. 7, the force applied at the time of grinding the protrusion is only a force parallel to the substrate 01, and no force is applied in a direction perpendicular to the substrate. Therefore, the magneto-optical recording layer 0
Only the protrusions can be ground without applying force to the substrate 2 or the substrate 01. On the other hand, if an obtuse edge is used as shown in FIG.
1 and perpendicular thereto, and a birefringence abnormality occurs in the substrate 01.
When a birefringence abnormality occurs in the substrate 01, an abnormality occurs in envelope fluctuation.

Under the test conditions shown in Table 1, the angle α was set to 0 degree, and the angle θ was changed in the range of 135 to 60 degrees, and the influence on the envelope fluctuation was examined. FIG. 9 shows the results. The result shows the differential voltage signal when the signal of the magneto-optical disk is read by the magnetic head. When θ is 135 degrees or θ is 100 degrees, the noise indicated by the arrow indicates that the envelope fluctuation due to grinding is abnormal. It is. When θ is 100 degrees or 135 degrees, an increase in envelope fluctuation is observed, but when θ is set to about 90 degrees or less, no abnormality in envelope fluctuation is observed. From this, in order to prevent the occurrence of an abnormality in envelope fluctuation, it is necessary to set the angle θ between the bottom surface and the side surface at the edge 10 of the ridge 6 to approximately 90 degrees or less.

[0017]

[Effects of the Invention] In this invention, 1) grinding the protrusions on the surface of the resin protective layer to a height equal to or less than the flying height of the flying magnetic head to improve the flying characteristics of the magneto-optical head; Prevents abnormal occurrence of envelope fluctuation due to birefringence abnormality. As a result, the characteristics of the magneto-optical disk can be improved, and the yield of the magneto-optical disk can be improved by removing protrusions caused by agglomeration of fillers and invasion of foreign matter.

[Brief description of the drawings]

FIG. 1 is a plan view showing a usage state of a grinding head for a magneto-optical disk according to an embodiment.

FIG. 2 is a plan view showing a usage state of the magneto-optical disk grinding head according to the embodiment.

FIG. 3 is a perspective view of a grinding head for a magneto-optical disk according to the embodiment.

FIG. 4 is a sectional view of a grinding head for a magneto-optical disk according to the embodiment.

FIG. 5 is a cross-sectional view of a modified example of a magneto-optical disk grinding head.

FIG. 6 is a cross-sectional view of a conventional grinding head for a magneto-optical disk.

FIG. 7 is a cross-sectional view illustrating a use state of the grinding head for a magneto-optical disk according to the embodiment.

FIG. 8 is a sectional view showing a state of use of a conventional grinding head for a magneto-optical disk.

FIG. 9 is a characteristic diagram showing a relationship between an angle θ between a bottom surface and a side surface of an edge and envelope fluctuation.

[Explanation of Signs] 2 Grinding head for magneto-optical disk 4 Base 6 Ridge 8 Warp 10 Edge 12 Arm α Angle between rotation direction and edge of magneto-optical disk θ Angle between bottom surface and side surface of edge

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 11/10 541 G11B 7/26

Claims (1)

(57) [Scope of request for utility model registration] 1. A grinding device for cutting out a projection on the surface of a resin protective layer of a magneto-optical disk, wherein the grinding surface has a plurality of substantially parallel ridges, and an angle of an edge of the ridge is substantially 90 degrees or less. Wherein the angle between the longitudinal direction of the protrusion and the rotation direction of the magneto-optical disk is set to approximately 20 degrees or less.