JP2001023253A - Production of disk-like recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-grade laminated disk which does not entail the degradation in mechanical characteristics, such as acceleration in wobbling of surfaces. SOLUTION: Plural disk substrates are previously formed so as to have the external shape and size of the diameter slightly larger than the external shape and size of a magneto-optical disk to be produced in the final in a disk substrate forming stage ST1. The outer periphery sides of the plural disk substrates (first and second disks) formed with recording layers and protective layers in a recording layer and protective layer forming stage ST2 are partly removed in a dish outer periphery cutting stage ST3 and thereafter, the plural disk substrates (first and second disks) are bonded to each other through an adhesive coating application stage ST4 and a pressing stage STATE5, by which the magneto-optical disk is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a disk-shaped recording medium in which a plurality of disk substrates are bonded.

[0002]

2. Description of the Related Art As an optical disk for recording or reproducing information by irradiating a laser beam, a read-only optical disk such as a CD (Compact Disc) and a rewritable optical disk such as a magneto-optical disk and a phase change disk are available. Various optical disks have been put to practical use. Each of these optical discs has a configuration in which a recording layer having a functional film such as a recording film or a reflection film is formed on a transparent substrate made of plastic such as polycarbonate or glass. These optical discs have been widely used because of their excellent mass productivity, low production cost, and relatively stable information recording or reproduction.

By the way, in these optical disks,
In recent years, recording capacity has been actively increased. Under such circumstances, the recording capacity has been dramatically increased while keeping the external dimensions the same as that of a CD, and it has become possible to store data for one movie with the image quality comparable to that of the current television broadcast.
gital Versatile Disc / Digital Video Disc) has been developed and put into practical use.

In order to increase the recording density and increase the recording capacity of this DVD, information is recorded and reproduced using a laser having a shorter wavelength than a laser used for a CD or the like. . In order to increase the recording density and increase the recording capacity of the DVD, two single-plate disks of about half the thickness of a CD or the like are bonded together so that the recording surface is on the inside. The distance between the light incident surface (disk surface) and the recording surface is reduced.

[0005] Here, an example of a manufacturing process of a bonded type disk in which two single-plate disks are bonded like the above-mentioned DVD will be described.

When manufacturing a bonded disk, first, a resin material such as polycarbonate is injection-molded into a disk shape to produce a disk substrate. Here, the disk substrate is manufactured so as to have an outer dimension slightly larger than the outer dimension of the final bonded disk. Specifically, in the case of finally manufacturing a bonded disk having an outer dimension of φ130 mm, the disk substrate is, for example, φ13 mm.
It is made to have an external dimension of 3.4 mm.

Next, two disk substrates manufactured as described above are prepared, and a recording film is formed on one or both main surfaces of the two disk substrates. This recording film is formed, for example, by forming a material of the recording film on the main surface of the disk substrate by a technique such as sputtering.

Next, a protective film is formed on the main surface of the disk substrate on which the recording film has been formed. This protective film, for example,
A radical ultraviolet curable resin or the like is applied on the main surface of the disk substrate on which the recording film is formed, and is formed by being cured by irradiation of ultraviolet light.

Next, an adhesive such as a hot-melt adhesive is applied on the main surface of the disk substrate on which the protective film is formed, for example, by a method such as a roll coating method. Then, the two disk substrates to which the adhesive has been applied are abutted against each other with the main surfaces to which the adhesive has been applied as abutting surfaces, and are bonded by pressing.

Next, the two disk substrates bonded together with an adhesive are mounted on a cutting device. This cutting device cuts and removes an outer peripheral portion of a cutting target by pressing a cutting blade against an outer peripheral end of the mounted cutting target while rotating the mounted cutting target. The outer dimensions of the two disk substrates bonded to each other via the adhesive are set to a predetermined value by cutting and removing the outer peripheral portion by the cutting device. For example, in the above example, φ13
The outer peripheral portion of the disk substrate having an outer dimension of 3.4 mm is cut and removed by this cutting device, thereby obtaining
The external dimensions are set to 30 mm.

Through the above steps, a bonded disc is completed.

[0012]

However, it has been found that some of the bonded disks manufactured through the above-described steps cause deterioration of mechanical characteristics such as deterioration of surface runout acceleration. Was. Information cannot be stably recorded / reproduced on a bonded disc whose mechanical characteristics have deteriorated in this way.

Accordingly, an object of the present invention is to provide a method of manufacturing a disk-shaped recording medium capable of manufacturing a high-quality bonded disc without deteriorating mechanical characteristics such as surface runout acceleration. And

[0014]

The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and as a result, the disk substrate formed by injection molding has a raised portion at the outer peripheral end thereof. In addition, a liquid pool such as an ultraviolet curable resin serving as a protective film may be formed on the outer peripheral edge, and the outer peripheral edge may have a raised shape. When
The unevenness of the stress occurs due to the raised portion of the outer peripheral edge of the disk substrate, and as a result, a small but high-frequency deformation occurs in the manufactured bonded disk, and the acceleration of the surface runout and the like is increased. It has been found that the mechanical properties have been degraded.

The method for manufacturing a disk-shaped recording medium according to the present invention has been devised based on the above knowledge, and has a plurality of disks each having a diameter slightly larger than the outer dimensions of the disk-shaped recording medium to be manufactured. A first step of forming a plurality of disk substrates, a second step of cutting and removing a part of the outer peripheral side of the plurality of disk substrates formed by the first step,
And a third step of bonding a plurality of disk substrates, the portions of which are cut off on the outer peripheral side, using an adhesive.

According to this method of manufacturing a disk-shaped recording medium, the outer peripheral portions of the plurality of disk substrates formed in the first step are cut and removed in the second step. Even if a raised portion is formed at the outer peripheral end of the disk substrate formed in the above, the raised portion of the outer peripheral end of the disk substrate is cut and removed in the second step. .

In a third step, a plurality of disk substrates each having a flat surface from which the protruding portion of the outer peripheral end has been cut and removed is bonded using, for example, an adhesive such as a cation polymerization hardening resin. Will be.

Therefore, according to this method of manufacturing a disk-shaped recording medium, a plurality of disk substrates are uniformly bonded, so that a high-quality disk-shaped recording medium free from deformation can be manufactured. it can.

In the method of manufacturing a disk-shaped recording medium, in the third step, it is desirable to apply an adhesive to the surface of the disk substrate by a screen printing method.
If the adhesive is applied to the surface of the disk substrate by the screen printing method, it is possible to control the application range of the adhesive on the disk substrate surface. Therefore, for example, even if the raised portion at the outer peripheral end of the disk substrate is not completely removed in the second step, the adhesive is not applied to the raised portion, so that the stress at the time of pressing is reduced. Can be minimized.

[0020]

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

Here, an example of manufacturing a magneto-optical disk by applying the present invention will be described.
The present invention is not limited to this example, and can be applied as a method of manufacturing any type of bonded disc.

FIG. 1 shows an example of a magneto-optical disk manufactured by applying the present invention. The magneto-optical disk 1 includes a first disk 5 having a recording layer 3a and a protective layer 4a formed on one main surface of a disk substrate 2a, and a recording layer 3b and a protective layer formed on one main surface of a disk substrate 2b. The second disk 6 on which the protective layer 4b is formed is bonded to the second disk 6 with the protective layers 4a and 4b facing each other and an adhesive layer 7 interposed therebetween.

A disk substrate 2a forming the first disk 5 and a disk substrate 2b forming the second disk 6
Are formed by forming a light-transmitting material into a disk shape. As a material of the disk substrates 2a and 2b,
For example, glass, polycarbonate, acrylic, epoxy resin and the like can be mentioned. Among them, polycarbonate is most commonly used because of its excellent moldability, dimensional stability, low water absorption and the like.

The recording layer 3a of the first disk 5 and the recording layer 3b of the second disk 6 are made of, for example, SiN.
A first dielectric film made of TbFeCo or the like, a recording magnetic film made of TbFeCo or the like, a second dielectric film made of SiN or the like,
A reflective film made of l or the like is sequentially formed on the disk substrates 2a and 2b in the above order by a method such as sputtering. Here, the first and second dielectric films are for preventing the recording magnetic film from being oxidized and for exhibiting the effect of enhancing the magneto-optical signal due to multiple interference.

The protective layers 4a and 4b are for protecting the recording layer 3a of the first disk 5 and the recording layer 3b of the second disk 6, and, for example, have a radical system on the recording layers 3a and 3b. An ultraviolet-curable resin is applied, and the ultraviolet-curable resin is cured by irradiation with ultraviolet rays.

The adhesive layer 7 is for joining the first disk 5 and the second disk 6 to form one magneto-optical disk 1. For example, the first disk 5 and the second disk 6 are formed by a screen printing method or the like. The adhesive applied on the protective layer 4a of the disk 5 and the adhesive applied on the protective layer 4b of the second disk 6 are cured while abutting each other. As an adhesive constituting the adhesive layer 7, for example,
Cationic polymerization cured resins and the like are used.

The cationically polymerizable resin is, for example, an epoxy resin as a main component and is cured by a cationic polymerization using ultraviolet rays. The polymerization reaction of the cationically polymerized cured resin proceeds by a chain reaction mechanism including a start reaction, a growth reaction, and a termination reaction. First, in the initiation reaction, a cation from the initiator reacts with the epoxy group to generate a carbonium cation. Next, in the growth reaction, the carbonium cation serves as an initiator to chain-open and add the epoxy group. Finally, in the termination reaction, the anion from the initiator binds to the terminal of the ring-opened epoxy group to terminate the chain growth.

Here, the steps of manufacturing the magneto-optical disk 1 configured as described above will be described.

As shown in FIG. 2, for example, the magneto-optical disk 1 includes a disk substrate forming step ST1, a recording layer / protective layer forming step ST2, a disk outer circumference cutting step ST3, an adhesive applying step ST4, and a pressing step ST5. It is manufactured through a process.

When manufacturing the magneto-optical disk 1, first,
In the disk substrate forming step ST1, for example, a material such as polycarbonate is formed into a disk shape by injection molding or the like, and disk substrates 2a and 2b are manufactured.

In the disk substrate forming step ST1, the disk substrates 2a and 2b are manufactured so that their outer diameters are slightly larger than the outer diameter of the final magneto-optical disk 1. Keep it. Specifically, when the magneto-optical disk 1 having an outer dimension of φ130 mm is finally manufactured, the disk substrates 2a and 2b are manufactured so as to have an outer dimension of φ133.4 mm, for example.

Next, in a recording layer / protective layer forming step ST2, the recording layers 3a, 3b and the protective layers 4a, 4b are formed on one main surface of the manufactured disk substrates 2a, 2b.

The recording layers 3a and 3b are, for example, a first dielectric film made of SiN or the like, a recording magnetic film made of TbFeCo or the like, a second dielectric film made of SiN or the like, and a reflection made of Al or the like. The film is formed by a technique such as sputtering.
The film is formed by sequentially forming a film on one main surface of the disk substrates 2a and 2b in the above order. Further, the protective layers 4a, 4b
Is, for example, a recording layer 3a formed on one main surface of a disk substrate 2a, 2b with a radical-based ultraviolet curable resin or the like.
After being applied on 3b, the ultraviolet-curable resin is irradiated with ultraviolet rays to be cured.

The first disk 5 and the second disk 6 constituting the magneto-optical disk 1 are manufactured through the above-described disk substrate forming step ST1 and recording layer / protective layer forming step ST2. . In the above description, the case where the magneto-optical disk 1 having the two recording layers 3a and 3b is manufactured has been described as an example. However, when manufacturing the magneto-optical disk having a single recording layer, two disks are used. The recording layer may be formed only on one of the substrates 2a and 2b.

Next, in the disk outer peripheral cutting step ST3, a part of the outer peripheral side of the first disk 5 and the second disk 6 is cut and removed.

When the disk substrates 2a and 2b constituting the first disk 5 and the second disk 6 are formed into a disk shape by injection molding or the like in the disk substrate forming step ST1, for example, the inner peripheral side is formed. A raised portion may be formed at the outer peripheral end due to a variation in the curing speed from the outer peripheral side or the like. When the disk substrates 2a and 2b are formed into a disk shape by injection molding or the like in the disk substrate forming step ST1, molding burrs are formed at the outer peripheral ends thereof, and the outer peripheral ends are in a protruding state. In some cases.

Then, the recording layer 3 is formed on the disk substrates 2a and 2b formed so that the outer peripheral end is raised as described above.
When the first and second disks 5 and 6 are formed by forming the first and second disks 5 and 6, respectively, the protective layers 4a and 4b are provided on the raised outer peripheral ends of the disk substrates 2a and 2b.
The liquid pool of the ultraviolet-curable resin or the like that forms
As shown in (1), the outer peripheral end is further raised.

When the first disk 5 and the second disk 6 whose outer peripheral ends are raised as described above are bonded together by pressing or the like to manufacture the magneto-optical disk 1,
A variation in stress may occur at the time of bonding, and a small but high-frequency deformation may occur in the manufactured magneto-optical disk 1, which may cause deterioration of mechanical characteristics such as deterioration of surface deflection acceleration.

Therefore, in the present invention, before the first disk 5 and the second disk 6 are bonded by a press or the like, in the disk outer peripheral cutting step ST3, the first disk 5 and the second disk 6 are separated. A part of the outer peripheral side is cut to remove the raised portion.

A cutting device 10 as shown in FIG. 4 is used to cut and remove a part of the outer peripheral side of the first disk 5 and the second disk 6. The cutting device 10 includes a pair of disk holding members 11 and 12 for holding the first disk 5 and the second disk 6, and a first disk 5 held by the pair of disk holding members 11 and 12. And a rotation drive motor 13 for rotating the second disk 6 about its center as a rotation center, and an outer peripheral end of the first disk 5 and the second disk 6 rotated by the drive of the rotation drive motor 13. Abut the first disk 5 and the second disk 5
And a cutting blade 14 for cutting the outer peripheral end of the disc 6.

First disk 5 and second disk 6
Is held by a pair of disk holding members 11 and 12 so as to be sandwiched from both sides, and is rotated by driving a rotation drive motor 13. The outer edges of the first disk 5 and the second disk 6 are gradually cut by pressing the cutting blade 14 against the outer edges.

The cutting of the outer peripheral ends of the first disk 5 and the second disk 6 is performed until the outer dimensions of the first disk 5 and the second disk 6 reach a predetermined value. Specifically, for example, when manufacturing the magneto-optical disk 1 having an outer dimension of φ130 mm, in the disk substrate forming step ST1, the disk substrates 2a and 2b are
In the disk outer peripheral cutting step ST3, the outer peripheral ends of the first disk 5 and the second disk 6 are cut until the external dimensions become φ130 mm.

First disk 5 and second disk 6
By cutting the outer peripheral end in the disk outer peripheral cutting step ST3, even when the outer peripheral end has a raised shape, the raised portion is cut and removed.

Next, in the adhesive applying step ST4, the first disk 5 and the second disk
An adhesive is applied on the protective films 4a and 4b of the disk 6 of FIG. The application of the adhesive is desirably performed by a screen printing method. When an adhesive is applied on the protective films 4a and 4b of the first disk 5 and the second disk 6 by the screen printing method, the range of application of the adhesive on the protective films 4a and 4b is easily controlled. Can be. Therefore, for example, in the disk outer peripheral cutting step ST3,
If the raised portions are not completely removed by cutting the outer peripheral ends of the first disk 5 and the second disk 6,
The adhesive can be prevented from being applied to the raised portion. Thereby, the influence of the raised portions remaining at the outer peripheral ends of the first disk 5 and the second disk 6 can be minimized, and the variation in stress during pressing can be minimized.

The adhesive applied to the protective films 4a and 4b of the first disk 5 and the second disk 6 is as follows.
It is desirable to use a cationic polymerization curing resin. This cationic polymerization curable resin can be handled at room temperature and is an adhesive suitable for a screen printing method. Further, as described above, the cationic polymerization curable resin has a characteristic that the polymerization speed and the curing speed are relatively slow because the polymerization and curing proceed by a chain reaction. First disc 5 and second disc 5
When an adhesive having a high curing speed is used for bonding the disks 6, the adhesive hardens from the time the adhesive is applied to the time when the adhesive is bonded.
In some cases, the disc 6 cannot be properly bonded. On the other hand, if an adhesive having a relatively slow curing speed, such as a cationically polymerizable resin, is used, the first disk 5 and the second disk 6 can be securely and appropriately bonded.

Next, the adhesive applied to the protective films 4a and 4b of the first disk 5 and the second disk 6 is
For example, the adhesive is activated by irradiation with ultraviolet rays.

Next, in the pressing step ST5, the first disk 5 with the adhesive applied on the protective layer 4a and the second disk 6 with the adhesive applied on the protective layer 4b are
The protective layers 4a and 4b are pressed against each other via an adhesive and pressed. As a result, the first disk 5 and the second disk 6 are bonded together with the adhesive, and the magneto-optical disk 1 is completed.

Here, the first disk 5 and the second disk 6 are cut at the outer peripheral end in the disk outer peripheral cutting step ST3, so that the raised portions of the outer peripheral end are removed, and the protective layers 4a, The upper surface of 4b is a flat plane. Therefore, in the pressing step ST5, the first disk 5 and the second disk 6 are uniformly bonded over the entire upper surfaces of the protective layers 4a and 4b. In addition, no deformation occurs due to a variation in stress at the time of pressing.

As described above, in the magneto-optical disk 1, the disk substrate forming step ST1, the recording layer / protective layer forming step ST1
2. Disk outer circumference cutting step ST3, adhesive application step ST
4. Since the disc is manufactured through the steps of the pressing step ST5, the disc is manufactured as a high-quality disc on which information can be stably recorded and reproduced without deformation which causes deterioration of mechanical characteristics such as surface runout acceleration. Will be.

[0050]

EXAMPLE In order to confirm the effects of the present invention, a magneto-optical disk was actually manufactured by the above-described method, and a similar magneto-optical disk was manufactured by a conventional method. It was measured.

(Manufacture of Magneto-Optical Disk) First, polycarbonate was injection-molded to have an outer dimension of φ133.4 mm.
4 disk substrates with a pre-groove were prepared. Then, an SiN film and a T
A bFeCo film, a SiN film, and an Al film were sequentially formed by sputtering to form a recording layer. Further, an ultraviolet curable resin was applied on the recording layer, and irradiated with ultraviolet rays to form a protective layer.

At this stage, two of the four disk substrates on which the recording layer and the protective layer were formed were mounted on a cutting device, and the outer peripheral portion was cut until the outer dimensions became φ130 mm. Removal was performed. Then, an adhesive was applied by screen printing on the protective layers of the two disk substrates from which the outer peripheral portions were cut off. As an adhesive,
Sony Chemical Co., Ltd. cationic polymerization curable resin SK-
7000 (trade name) was used. Then, after irradiating the entire surface of the two disk substrates coated with the cation-polymerized curing resin with a metal halide lamp, ultraviolet rays were applied.
Two disk substrates were bonded by a pressure press to complete a magneto-optical disk (Example).

Before the outer peripheral portion is removed by cutting, an adhesive is applied to the remaining two disk substrates of the four disk substrates on which the recording layer and the protective layer are formed. They were applied, irradiated with ultraviolet rays, and pressed under pressure to bond them together. Then, the disk in which the two disk substrates are bonded to each other is mounted on a cutting device, and the outer peripheral portion is cut and removed until the outer dimension becomes φ130 mm.
A magneto-optical disk was completed (Comparative Example).

(Measurement of Surface Runout Acceleration) The surface runout accelerations of the magneto-optical disk of the example manufactured as described above and the magneto-optical disk of the comparative example were measured. The surface deflection acceleration of these magneto-optical disks was measured using a disk mechanical property evaluation device LM-110A (trade name) manufactured by Ono Sokki.
The measurement was performed by setting the laser wavelength to 680 nm and the number of rotations to 1800 rpm. Table 1 shows the results.

[0055]

[Table 1]

From the results shown in Table 1, in the magneto-optical disk (Example) manufactured by applying the present invention, the two disk substrates had their outer peripheral edges cut off and the raised portions were removed. As a result of laminating later, it can be seen that the surface run-out acceleration is suppressed to a low value, and the disc has a high quality.

On the other hand, in the magneto-optical disk (comparative example) manufactured by the conventional manufacturing method, the outer edge is cut off after the two disk substrates are bonded to each other. It can be seen that the quality has decreased.
This is because, when two disk substrates are bonded by a pressure press, a variation in stress occurs because a protruding portion remains at the outer peripheral end of the disk substrate. It is considered that the deformed magneto-optical disk was deformed.

[0058]

According to the method of manufacturing a disk-shaped recording medium according to the present invention, the outer peripheral portions of the plurality of disk substrates formed in the first step are cut and removed in the second step. Even when a raised portion is formed at the outer peripheral end of the disk substrate formed in the first step, the raised portion of the outer peripheral end of the disk substrate is cut and removed in the second step. In a third step, a plurality of disk substrates having a flat surface are bonded using an adhesive.

Therefore, according to this method of manufacturing a disk-shaped recording medium, a plurality of disk substrates are bonded together uniformly, so that a high-quality disk-shaped recording medium free from deformation can be manufactured. it can.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a part of a magneto-optical disk manufactured by applying the present invention.

FIG. 2 is a diagram illustrating a process of manufacturing the magneto-optical disk.

FIG. 3 is an enlarged sectional view showing a state where the outer peripheral end of a first disk or a second disk constituting the magneto-optical disk is raised.

FIG. 4 is a schematic view showing an example of a cutting device for cutting the outer peripheral ends of the first disk and the second disk.

[Explanation of symbols]

1 magneto-optical disk, 2a, 2b disk substrate, 3
a, 3b recording layer, 4a, 4b protective layer, 5 first disk, 6 second disk, 7 adhesive layer, ST1 disk substrate forming step, ST2 recording layer / protective layer forming step, ST3 disk outer peripheral cutting step, ST4 Adhesive application process, ST5 press process

Claims (3)

[Claims] 1. A first step of forming a plurality of disk substrates having a diameter slightly larger than an outer dimension of a disk-shaped recording medium to be manufactured; and a plurality of disk substrates formed by the first step. A second step of cutting and removing a part of the outer peripheral side of the second step; and a third step of bonding a plurality of disk substrates having a part of the outer peripheral side cut and removed in the second step using an adhesive. A method for manufacturing a disk-shaped recording medium, comprising: 2. The method according to claim 1, wherein in the third step, the adhesive is applied to a surface of the disk substrate by a screen printing method. 3. The method according to claim 1, wherein in the third step, a cationically polymerizable resin is used as the adhesive.