JPH08221807A - Optical recording medium and its production - Google Patents

Abstract

PURPOSE: To obtain an optical recording medium which has sufficient welding strength and is free from the warpage of a substrate and the degradation in double refraction and a production method thereof. CONSTITUTION: A hub 5 having a welding rib 6 is ultrasonically welded to the substrate 2 formed with a recording layer, etc., 3. This optical recording medium is so formed that the relation of the following equation holds between the height L of the welding rib of the hub and an ultrasonic welding depth D: 0.12mm3D<=(L-0.05mm).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium in which a hub capable of magnet clamping is ultrasonically welded and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a method of fixing an optical recording medium to a turntable of a drive unit, a mechanical clamp method for mechanically fixing the medium and a medium having a hub at the center of a substrate are used to form a metal portion of the hub. A magnet clamp system has been proposed in which the magnet is fixed and supported by a permanent magnet provided on the drive unit side. Of these two methods, the magnet clamp method is becoming popular because it can be easily attached to and detached from the drive unit and the apparatus can be downsized, and the ISO standard also adopts this method.

As a magnet clamp type hub,
There are metal hubs made entirely of metal, or resin-made composite hubs made by insert-molding metal plates. As the composite hub, there are an adhesive type that is fixed to the substrate with an adhesive and an ultrasonic type that is fixed to the substrate by ultrasonic welding. Conventional techniques relating to a method of fixing a hub to a substrate by ultrasonic waves are described in, for example, Japanese Utility Model Publication No. 5-31721, Japanese Patent Application Laid-Open No. 62-192945, Japanese Patent Publication No. 6-3678. Compared to the adhesive type, the ultrasonic type can reduce the tact time of hub attachment, downsize the device, and reduce the cost, and the reliability that the initial welding strength does not deteriorate over time. Is excellent at.

FIG. 2 is a schematic sectional view showing a general composite hub used as this ultrasonic type. As shown in this figure, the ultrasonic type hub 5 has a convex shape and has an appropriate height L (see the enlarged view of FIG. 2).
The rib 6 for welding having the above is arranged concentrically with the center hole 8 of the hub at the flange portion of the hub.

3A and 3B are schematic sectional views showing a general hub attachment process by ultrasonic welding. First,
As shown in FIG. 3A, the hub 5 is vacuum-sucked to the ultrasonic horn 9 having the positioning pin 10, and the disk-shaped substrate 2 is formed.
Get closer to. Then, as shown in FIG. 3B, the horn 9 is ultrasonically oscillated while the rib 6 and the substrate 2 are in contact with each other.
As a result, the resin in the portion to be welded is heated by frictional heat and melted, and the hub 6 is welded to the substrate 2.

[0006]

However, in the method of ultrasonically welding the hub to the substrate, the welding strength is sometimes insufficient and the hub may be removed in the driving device. In some cases, although the welding strength is sufficient, problems such as warpage of the substrate and deterioration of birefringence may be adversely affected to the recording / reproducing characteristics.

The present invention has been made in order to solve the above-mentioned problems of the prior art, has sufficient welding strength, is free from warpage of the substrate and deterioration of birefringence, and has high reliability and recording / reproducing characteristics. It is an object of the present invention to provide an excellent optical recording medium and a manufacturing method thereof.

[0008]

The optical recording medium of the present invention comprises:
In an optical recording medium in which a hub having welding ribs is ultrasonically welded to a substrate on which at least a recording layer is formed, the following formula (a) is provided between the welding rib height L and the ultrasonic welding depth D of the hub. It is characterized by the relationship of.

0.12 mm ≦ D ≦ (L−0.05 mm) (a) Further, the manufacturing method of the optical recording medium of the present invention is the same as the above formula (a).
It is characterized in that ultrasonic welding is performed so that the above relationship holds.

[0010]

According to the present invention, the ultrasonic welding is performed by selecting the hub and adopting the welding conditions such that the relationship between the height L of the welding rib of the hub and the ultrasonic welding depth D satisfies the above-mentioned specific expression (a). It was found that the degree of can be made very suitable.

[0011]

1 is a schematic sectional view showing an embodiment of an optical recording medium of the present invention. In this embodiment, a sputter layer 3 including at least a magneto-optical recording layer is formed on an optically transparent substrate 2.
Is formed and is covered with a protective layer 4 to form a disk-shaped magneto-optical recording medium 1. A hub 5 having a welding rib 6 is ultrasonically welded to the center hole of the medium 1, and the hub 5 has a structure capable of a magnet clamp method. Then, the relationship of the expression (a) is established between the welding rib height L of the hub 5 and the ultrasonic welding depth D (see the enlarged view of FIG. 1).

In the present invention, the hub used in the conventional ultrasonic welding can be used as the hub 5 without limitation. For example, as shown in FIG. 2, it is a resin composite hub insert-molded so that the hollow metal disk 7 is located in the center hole 8 of the hub, and it is concentric with the center hole 8 of the hub. A hub having a rib 6 for welding that protrudes in the shape of a collar in the flange can be preferably used. As the resin material forming the hub 5, any material that can be ultrasonically welded can be used without limitation, and for example, the same resin material as the material of the substrate can be preferably used. Specific examples include polycarbonate resin, acrylic resin, polyolefin resin and the like.

In the present invention, the rib height L (see the enlarged view of FIG. 1 and the enlarged view of FIG. 2) may be appropriately determined as desired within a range satisfying the above expression (a). The rib height L is always 0.17 mm in order to satisfy the above formula (a).
That is all. The rib height L is 0.2 to 0.35 mm.
It is desirable to be within the range. If lower than 0.2 mm, welding depth D
The range tends to be too narrow, and if it exceeds 0.35 mm, it tends to be difficult to form a hub.

In the present invention, as the material for forming the substrate 2, all materials that can be used as a substrate for an optical recording medium, such as polycarbonate resin, acrylic resin, and polyolefin resin, can be used.

In the present invention, the ultrasonic welding process may be performed in the same manner as the conventional process except that the ultrasonic welding is performed so as to satisfy the above formula (a). For example, FIG.
As shown in (b), the hub 5 may be vacuum-sucked to the ultrasonic horn 9, and the horn 9 may be ultrasonically oscillated while the rib 6 and the substrate 2 are in contact with each other.

The distance between the hub 5 and the substrate 2 is determined by the descending amount of the ultrasonic horn 9, and the welding depth (D: see the enlarged view of FIG. 1) can be determined. This welding depth D is too shallow,
If the above formula (a) is not satisfied, sufficient welding strength cannot be obtained, and the problem arises that the hub is removed in the drive device. On the other hand, when the welding depth D is too deep and does not satisfy the above formula (a), the welding strength is sufficient, but there is a problem that the warp or birefringence of the substrate deteriorates and the recording / reproducing characteristics are adversely affected. Occurs. In the present invention, when a hub having welding ribs of a certain height L is used, the ultrasonic horn 9 is simply lowered by paying attention to the welding depth D so as to satisfy the formula (a). And ultrasonic welding can be performed well.

In the present invention, the welding depth D means the total welding depth including the holding depth, as will be concretely shown in the examples below. Here, the holding depth is the depth that is welded during the holding time after the ultrasonic oscillation is stopped. In addition, other ultrasonic welding conditions (for example, horn pressure,
The frequency, oscillation time, etc.) may be appropriately determined as desired.

Hereinafter, the present invention will be described in more detail with reference to more specific examples.

Example 1 A magneto-optical recording medium 1 having the structure shown in FIG. 1 was produced as follows.

First, an Si ₃ N ₄ underlayer, a TbFeCo recording layer, and a Si ₃ N ₄ interference layer were formed on a disc-shaped polycarbonate substrate 2 having a diameter of 86 mm by using a sputtering apparatus.
A sputter layer 3 consisting of four Al reflection layers was formed, and subsequently an ultraviolet curable resin was coated as a protective layer 4.

Next, the welding rib height (L) is 0.27 m.
Welding depth (WD) 170 of the H.m. hub 5 [made by Kato Spring Co., Ltd.] using a hub attaching machine [made by Ultrasonic Industry Co., Ltd., trade name OD ³ auto alignment welder]
Welded with a thickness of μm. As a result, the total welding depth (D) is 206 μm (holding depth 36 μm).

With respect to the magneto-optical recording medium thus manufactured, the change in warp before and after hub attachment (at the radius of 40 mm where the largest change) and the birefringence change (at the radius of 24 mm where the largest change) were measured. . The results are shown in Table 1.
Shown in The welding strength is measured by Tensilon (trade name)
Using a tester, the magneto-optical recording medium 1 was placed on a receiving jig 11 as shown in FIG.

<Example 2-1 to Example 2-4> The total welding depth (D) is 120 μm, 140 μm, 170 μm.
A magneto-optical recording medium was produced in the same manner as in Example 1 except that the thickness was changed to m and 220 μm. The evaluation results are also shown in Table 1.

<Comparative Example 1-1 to Comparative Example 1-3> Total welding depth (D) is 80 μm, 100 μm, 240 μm.
A magneto-optical recording medium was prepared in the same manner as in Example 1 except that the above was changed. The evaluation results are also shown in Table 1.

<Example 3-1 to Example 3-2> Example 1 except that the welding rib height (L) was set to 0.20 mm and the total welding depth (D) was changed to 120 μm and 150 μm. Similarly, a magneto-optical recording medium was produced. The evaluation results are also shown in Table 1.

<Comparative Example 2-1 to Comparative Example 2-3> The total welding depth (D) is 80 μm, 100 μm, 170 μm.
A magneto-optical recording medium was produced in the same manner as in Example 3-1 to Example 3-2 except that the above was changed. The evaluation results are also shown in Table 1.

[0027]

[Table 1] As is clear from the results in Table 1, the magneto-optical recording media of the examples satisfying the above formula (a) have practically no problems in welding strength, warpage, and birefringence change, and good results were obtained. On the other hand, in the magneto-optical recording medium of the comparative example which does not satisfy the above formula (a), the welding strength is so low as to be a practical problem, or the values of changes in warpage and birefringence are a practical problem. It has become.

FIG. 5 and FIG. 6 are graphs in which the results of Table 1 are organized.

FIG. 5 shows the relationship between the total welding depth D and the welding strength. It is clearly understood from this graph that when the value of D exceeds 120 μm, a welding strength of 30 kgf or more, which is a level that causes no practical problem, is obtained.

FIG. 6 shows the relationship between L-D (corresponding to the distance between the flange portion of the hub and the substrate), the change in the warp, and the change in the birefringence. When the value of LD is small, the warpage and the change of birefringence (double pass) are large, and the value of LD is 50 μm.
From the graph, it can be clearly seen that the above results in a change in birefringence of 5 nm or less and a change in warp of 30 μm or less, which are practically problem-free.

[0031]

As described above, according to the present invention, it is possible to prevent the ultrasonically welded hub from coming off, and the warp and deterioration of birefringence of the disk due to the hub attachment. Therefore, an optical recording medium having high reliability and excellent recording / reproducing characteristics can be manufactured with high productivity and at low cost.

Also, from the viewpoint that ultrasonic welding can be favorably carried out as a method for fixing the hub to the substrate, the tact time for hub attachment can be shortened, the apparatus can be downsized, and the initial welding strength does not deteriorate over time. Etc. are also excellent.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an optical recording medium of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a composite hub used as an ultrasonic type.

FIG. 3 is a schematic cross-sectional view illustrating a hub attachment process by ultrasonic welding.

FIG. 4 is a diagram schematically showing the relationship between a sample and a jig when measuring the welding strength in Examples and Comparative Examples.

FIG. 5 is a graph showing the relationship between total welding depth D and welding strength in Examples and Comparative Examples.

FIG. 6 is a graph showing the relationship between changes in warpage and changes in birefringence in Examples and Comparative Examples.

[Explanation of symbols]

 1 Magneto-optical recording medium 2 Substrate 3 Sputtering layer 4 Protective layer 5 Hub 6 Welding rib 7 Metal plate 8 Hub central hole 9 Ultrasonic horn 10 Ultrasonic horn positioning pin 11 Receiving jig 12 Jig for pressure compressor

Claims (3)

[Claims] 1. An optical recording medium in which a hub having welding ribs is ultrasonically welded to a substrate on which at least a recording layer is formed, wherein the hub has a welding rib height L and an ultrasonic welding depth D. An optical recording medium having the relationship of the following expression (a). 0.12 mm ≤ D ≤ (L-0.05 mm) (a) 2. The optical recording medium according to claim 1, wherein the hub is a resin composite hub insert-molded so that a metal plate is located in a central hole portion. 3. A method of manufacturing an optical recording medium, comprising the step of ultrasonically welding a hub having welding ribs to a substrate having at least a recording layer formed thereon, wherein the welding rib height L and the ultrasonic welding depth D of the hub are provided. And a method of manufacturing an optical recording medium, characterized in that ultrasonic welding is performed so that the relationship of the following formula (a) is established. 0.12 mm ≤ D ≤ (L-0.05 mm) (a)