JP2001357561A - Optical disc and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk with large capacity and a method for manufacturing the optical disk in which high accuracy recording and reproducing can be performed by mounting the disk on the device for high density recording and reproducing with a large numerical aperture of the objective lens. SOLUTION: The optical disk is manufactured by laminating a film type thin disk and an injection molded thick disk with a film adhesive, and recording signals are written on the laminated faces of the disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DVD (digital versatile disk) as a large-capacity recording medium.
More particularly, the present invention relates to a method for manufacturing a large-capacity optical disk manufactured by laminating a plurality of disks having different thicknesses.

[0002]

2. Description of the Related Art Among optical disks currently on the market,
In particular, DVDs have been manufactured by injection molding or injection compression molding. In these manufacturing methods, a single material such as polycarbonate or acrylic resin is filled in a mold to form a disk as a molded substrate having a thickness of about 0.6 mm. At this time, a stamper in which a recording signal (pits or grooves with irregularities) is cut is mounted in the mold, and when the molten resin comes into contact with the stamper and pressure is applied, the signal of the stamper is transferred to a disk. I was Next, a sputtering process for depositing a predetermined metal on the disk is performed. The thus formed disks having a thickness of 0.6 mm are bonded together with a liquid UV curing adhesive. This UV curing adhesive is cured by irradiation with a UV lamp, and an optical disc as a product is manufactured. For example, in an optical disk standardized as DVD 9, gold (Au) or silicon (Si) is vapor-deposited on one disk, and aluminum (Al) is vapor-deposited on the other disk. Was bonded with a UV-curable adhesive to form a product.

FIG. 7 is a side sectional view showing a conventional optical disk manufactured as described above. The disks 100, which are two molded substrates having a thickness of 0.6 mm, are provided with an adhesive layer
0 shows a state in which the sheets are bonded together and molded. FIG.
FIG. 8 is a schematic process diagram showing a method for manufacturing the conventional optical disk shown in FIG. 7. As shown in FIG. 8, a conventional optical disk is manufactured by an injection molding process 120, a sputtering process 130, an adhesive application process 140, a bonding process 150, and a UV curing process 160.

[0004]

In this field, the demand for improving the recording density of optical disks has been increasing year by year. As a measure for improving the recording density, there is a method of reducing the size of a recording signal in a recording medium (the optical disk itself). For example, in the current DVD, the minimum pit has a width of 0.3.
μm, a height of 0.13 μm, and a track pitch of 0.74 μm. However, these sizes are further reduced to improve the recording density of a recording medium. It is predicted to be.

On the other hand, in order to shorten the wavelength of a laser used as a light source, a red laser (having a wavelength of about 65
0 nm) to a blue laser (wavelength: about 400 nm). In order to improve the recording density, there is a method of not only shortening the wavelength of the light source but also reducing the laser beam spot diameter by increasing the numerical aperture (NA) of the objective lens on the drive side. Specifically, the numerical aperture of an objective lens in a general DVD player at present is about 0.6, and a numerical value as large as 0.85 has been reported. .

When the numerical aperture of the objective lens is increased as described above, the laser beam can be narrowed down, and a recording signal of a smaller size can be read. However, if the numerical aperture of the objective lens is increased, the focal length becomes shorter and the depth of focus becomes shallower. Therefore, in a conventional 1.2 mm thick optical disk on which a 0.6 mm thick molded substrate is bonded, a recording signal is written from the objective lens. However, there is a problem that the distance to the surface is too long to read the signal. SUMMARY OF THE INVENTION An object of the present invention is to provide a high-capacity optical disk which is mounted on an apparatus having a high numerical aperture of an objective lens and capable of high-density recording and reproduction, and a high-capacity optical disk and a manufacturing method thereof.

[0007]

An optical disk according to the present invention comprises at least two disks having different thicknesses bonded to each other via a film adhesive, and at least one disk is formed of a resinous film. Have been. The optical disk thus configured is mounted on a device capable of high-density recording and reproduction with a high numerical aperture of the objective lens, and can perform recording and reproduction with high precision.

The method for manufacturing an optical disk according to the present invention comprises the steps of cutting a sheet-like film into a desired disk shape, forming the disk into a disk shape having a desired thickness by injection molding, and transferring a recording signal of a stamper. And depositing a desired metal on the disk to which the recording signal has been transferred,
The method includes a step of attaching a film adhesive to a disk on which a desired metal is deposited, a step of attaching the film to a disk to which the film adhesive is attached, and a step of curing the film adhesive. The method of manufacturing an optical disk configured as described above can provide an optical disk that can be mounted on an apparatus having a high numerical aperture of an objective lens and capable of high-density recording and reproduction and capable of recording and reproduction with high precision.

According to another aspect of the present invention, there is provided a method of manufacturing an optical disk, comprising: cutting a sheet-like film into a desired disk shape; transferring a recording signal of a stamper to the disk-shaped film; Forming a disk having a desired thickness by transferring a recording signal of the stamper, a step of depositing a desired metal on the disc on which the recording signal is transferred, and a step of depositing a desired metal on the disc on which the desired metal is deposited. The method includes a step of attaching a film adhesive, a step of attaching a film to which a recording signal has been transferred to a disk to which the film adhesive has been attached, and a step of curing the film adhesive. The manufacturing method of the optical disk configured as described above can provide a high-capacity optical disk that is mounted on a device capable of high-density recording and reproduction with a high numerical aperture of the objective lens and that can perform recording and reproduction with high precision. Become.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical disk according to the present invention and a method for manufacturing the same will be described. In the following description, a DVD will be described as an example of an optical disk. D
The numerical aperture of the objective lens in the VD player is set to, for example, 0.1.
When using a large value of 85, this DV
The D-reproducer can narrow down the laser, and can read a recording signal of a smaller size. However, when the numerical aperture of the objective lens is increased, the focal length becomes shorter and the depth of focus becomes shallower. For this reason, the numerical aperture of the objective lens is set to 0.
When it is set to 85, the thickness of the disk (the distance from the optical disk surface to the recording signal portion) needs to be 0.1 mm. Therefore, if the total thickness of the optical disk is maintained at 1.2 mm in consideration of compatibility with currently commercially available optical disks, it is necessary to bond two disks having a thickness of 0.1 mm and a thickness of 1.1 mm. A disk having a thickness of 0.6 mm or 1.1 mm can be formed by injection molding.
A disk having a thickness of 20 mm and a thickness of 0.1 mm is difficult to be formed by injection molding, and it is impossible to maintain the plate thickness with high accuracy.

In a conventional manufacturing process for bonding optical disks, a liquid adhesive is applied by spin coating.
Two disks were stuck together. When the numerical aperture of the objective lens is 0.6, the thickness variation of the adhesive layer is ± 10 μm.
Even so, reading is possible because the depth of focus of the objective lens is deep and the recording signal size is large at present. But,
When the numerical aperture of the objective lens is 0.85, the depth of focus becomes shallow, so that the thickness variation of the adhesive layer requires an accuracy of ± 3 μm or less. When disks are bonded by spin coating, a method is used in which the adhesive is applied in the radial direction of the disk using centrifugal force. Since the position is different, the thickness of the adhesive layer is necessarily different at the radial position. Therefore, it has been difficult to maintain the thickness variation of the adhesive layer at ± 3 μm or less by the manufacturing method of applying the adhesive by spin coating.

Therefore, the optical disk of the present invention has a diameter of 0.1 m.
A thin disk and a thick disk having different thicknesses typified by the m thickness and the 1.1 mm thickness are formed with high precision and bonded together with a uniform adhesive layer. Hereinafter, specific examples of an optical disc and a method of manufacturing the same according to the present invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG. 1 shows Embodiment 1 according to the present invention.
FIG. 2 is a side sectional view showing the optical disc of FIG. FIG. 2 shows the first embodiment.
FIG. 7 is a process chart showing a method for manufacturing the optical disk of FIG. As shown in FIG. 1, the optical disk 1 of the first embodiment is formed by laminating a thin disk 7 and a thick disk 8 with a film adhesive 16. In the first embodiment, the optical disc 1
When the total thickness of the thin disk 7 is 1.2 mm, the thickness of the thin disk 7 is calculated by subtracting the thickness of the thick disk 8 (1.1 mm) and the thickness of the adhesive layer from the total thickness (1.2 mm).
A C (polycarbonate) film is selected. For example, if the thickness of the adhesive layer is 30 μm, the P of 70 μm
Select C film. In Example 1, for example, Pure Ace (registered trademark) of Teijin Limited was used as the PC film. This PC film contains gold (A
u) or silicon (Si) is deposited. DVD
Currently, an Au or Si film is used as a semi-reflective semi-transmissive film on the L0 side (the side close to the optical pickup) of the disc. Generally, the PC film is wound in a roll shape. For this reason, in order to continuously deposit on a PC film at low cost, it is preferable to carry out the deposition on a roll-shaped PC film rather than on the cut PC film.

Next, as shown in FIG.
Is deposited on a PC film 9 having a diameter of 120 mm and an inner diameter of 1 mm.
Cut into 5 mm donut shapes. After the film 10 cut into a donut shape is heated to a temperature equal to or higher than the glass transition point, it is put into a mold and pressed by a press machine (pressing step 11). At this time, the film 10 comes into contact with the stamper in the mold of the press machine, and the recording signal of the stamper is transferred.
A thin disk 7 is formed. In order to finally obtain a disk shape having high dimensional accuracy, the film 10 may be cut slightly larger than a predetermined size before being put into a press machine, and may be trimmed again to a predetermined shape after pressing. On the other hand, the thick disk 8 (the thickness is 1.1 mm in the first embodiment) is manufactured by injection molding. This injection molding is performed in the injection molding step 2 in FIG. In the injection molding process 2, a recording signal is transferred to the thick disk 8 simultaneously with molding by a stamper in a mold. Aluminum (Al) is deposited on the thick disk 8 as a reflective film in the sputtering step 3.

Next, an adhesive application step 4 is performed. In the adhesive application step 4, the thin disk 7 and the thick disk 8
For example, if the thickness of the adhesive layer is 30 μm, a film adhesive 16 having a thickness of 30 μm is used as the adhesive. As the film adhesive 16, a thermosetting type, a UV curing type, or the like is commercially available. It is desirable to use a UV-curable film adhesive in order to reduce the productivity and damage to the disc. In the adhesive application step 4, if the film adhesive 16 is held on a flat surface and is attached to the thick disk 8 at a stretch, there is no escape route for air, so that the film adhesive is applied to the thick disk 8 as shown in FIG. Roller 15 from one side
Paste while pushing the air while holding down.

Next, in a bonding step 5, the thin disk 7 is bonded to the thick disk 8 to which the film adhesive 16 has been bonded, while pressing the thin disk 7 from both sides with rollers. After the bonding step, the film adhesive 16 is cured by irradiating a UV lamp (UV curing step 6),
The thin disk 7 and the thick disk 8 are fixed, and the optical disk is manufactured. As a result, an optical disk having a total thickness of 1.2 mm, in which the distance from the disk surface to the recording signal portion is 0.1 mm, is manufactured with high accuracy.

In the first embodiment, the thin disk 7
Is described as having a thickness of 0.07 mm,
The thickness of the thin disk 7 formed of a film is 0.05
It can be formed in the range of mm to 0.4 mm. In the first embodiment, an example in which a UV-curable film adhesive is used as the adhesive has been described. However, a heat-curable film adhesive may be used. Is heated in a furnace or the like.

Embodiment 2 Next, Embodiment 2 showing a method of manufacturing an optical disk according to the present invention will be described with reference to the accompanying drawings. FIG. 3 is a side sectional view showing a vacuum forming step for a thin disk 7 in the method for manufacturing an optical disk according to the second embodiment of the present invention. FIG. 4 is a side view showing an adhesive application step for the thick disk 8 in the optical disk manufacturing method according to the second embodiment. In the manufacturing method of the optical disk of the second embodiment, the manufacturing steps are the same as those of the first embodiment except for the manufacturing steps shown in FIGS.

As in the first embodiment, when the total thickness of the optical disk is 1.2 mm, the thin disk 7 is changed from the total thickness (1.2 mm) to the thickness of the thick disk 8 (1.1 m).
A PC (polycarbonate) film having a thickness obtained by subtracting m) from the thickness of the adhesive layer is selected. For example, if the thickness of the adhesive layer is 30 μm, a PC film of 70 μm is selected. In Example 2, as the PC film,
For example, Pure Ace (registered trademark) of Teijin Limited was used. This PC film contains Au or Si in advance.
Has been deposited.

Next, the PC film on which Au or Si is deposited is cut to a size larger than 120 mm in diameter. The size of the film 10 cut at this time is determined by a sealing frame 13 used when vacuuming is performed in the vacuum forming process.
Larger than the inner diameter of After being heated to a temperature equal to or higher than the glass transition point, the cut film 10 is put into a vacuum forming die shown in FIG. The vacuum molding die into which the film 10 is loaded is depressurized by the vacuum pump 19 after the seal frame 13 is fitted to the base frame 18 and the internal space is sealed. At this time, the film 10 comes into contact with the stamper 12 and the recording signal of the stamper 12 is transferred.

After the completion of the vacuum forming step, the thin disk, which is the film 10 to which the recording signal has been transferred, is again trimmed or trimmed in a mold, and finally has a predetermined size (for example, a diameter of 120 mm). Is formed in a disk shape. On the other hand, since the thick disk 8 (the thickness is 1.1 mm in the second embodiment) is manufactured by injection molding, a recording signal is transferred simultaneously with the injection molding. Al is deposited on the thick disk 8 as a reflection film. As shown in FIG. 4, a film adhesive 16 is attached to the thick disk 8 on which Al is deposited. As shown in FIG. 4, a UV curable adhesive is applied to a protective film 17 by a film adhesive roll 14 so that the film adhesive 16
Is formed, and this film adhesive 16 is
5 is attached to the thick disk 8. At this time,
The pressing roll 15 rolls on the thick disk 8 in the direction of arrow A, and adheres the film adhesive 16 on the thick disk 8 while removing mixed air.

Next, the thin disk 7 is bonded on the thick disk 8 to which the film adhesive 16 has been bonded. After that, the film adhesive 16 is cured by a UV curing process, and the thick disk 8 and the thin disk 7 are bonded together.
An optical disk having a desired shape is manufactured. In the manufacturing method of the second embodiment, in order to improve the transferability of the recording signal from the stamper 12 to the thin disk 7, after the film is put into the mold, the mold temperature is once changed to the glass transition of the PC film material. The temperature is raised to the temperature or higher, and the transfer is performed for about 2 seconds. After the transfer is completed, the mold temperature is lowered to the glass transition temperature or lower, and the mold is cooled. The typical glass transition temperature of the PC film material is between 140 ° C. and 150 ° C.
The temperature was raised from 5 ° C to 160 ° C. When the mold is cooled, the temperature may be set to 140 ° C. or lower. Since the thin disk 7 is thin and has a small heat capacity, the die is immediately cooled by opening the die. Therefore, considering the next shot, it is desirable that the mold temperature during cooling be closer to 140 ° C.

Embodiment 3 Next, Embodiment 3 showing an optical disk according to the present invention will be described with reference to the accompanying drawings. FIG. 5 is a side sectional view showing an optical disc of Embodiment 3 according to the present invention. The optical disc 1A of the third embodiment is a recording medium having a single recording layer, and a recording signal is transferred only to the thick disc 8. Therefore, the thin disk 7A to which the recording signal is not transferred is formed of a PC film material having a predetermined thickness, and is bonded to the thick disk 8.

The optical disk 1A of the third embodiment configured as described above is formed by a manufacturing method without the pressing step 11 in the manufacturing process of FIG. The single-layer optical disc 1A manufactured as described above is mounted on a recording / reproducing apparatus having a high numerical aperture of the objective lens, for example, 0.85, and can perform recording / reproducing with high recording density.

Embodiment 4 Next, Embodiment 4 showing an optical disk according to the present invention will be described with reference to the accompanying drawings. FIG. 6 is a side sectional view showing an optical disc of Embodiment 4 according to the present invention. The optical disc 1B of the fourth embodiment is a recording medium having four recording layers. The recording signal is transferred to both sides of the thick disc 8A, and the thin disc 7B in which the recording signals are transferred to both faces of the thick disc 8A. , 7C are pasted. Therefore, the thickness of the thick disk 8A is 1.0 mm when the total thickness of the optical disk 1B is 1.2 mm.

The thick disk 8A constituting the optical disk 1B of the fourth embodiment configured as described above has a stamper placed up and down in the injection molding step 2 of the manufacturing process of FIG. The recording signal of the stamper is transferred to the printer. In the sputtering process, a desired metal, for example, Al is deposited on both surfaces of the thick disk 8A. In the next adhesive application step, the film adhesive 16 is applied to both surfaces of the thick disk 8A at the same time. The thin disks 7B, 7B are provided on both sides of the thick disk 8A on which the film adhesive 16 is stuck.
C is pasted. Recording signals are respectively transferred to the thin disks 7B and 7C by the pressing step shown in FIG. 2 or the vacuum forming step shown in FIG.

The optical disk 1B of the fourth embodiment has a sandwich structure in which the thick disk 8A is sandwiched between the thin disk 7B and the thin disk 7C, so that reading and writing can be performed from both sides. The four-layer optical disc 1B manufactured in this manner is mounted on a recording / reproducing apparatus having a high numerical aperture of an objective lens, for example, 0.85, and can reliably perform recording / reproducing with a high recording density and have a large capacity. Optical disk.

[0028]

As will be apparent from the detailed description of the embodiments, the present invention has the following effects.
According to the present invention, it is possible to provide a high-capacity optical disk which can be mounted on an apparatus capable of high-density recording and reproduction with a high numerical aperture of an objective lens and perform recording and reproduction with high accuracy, and a method of manufacturing the same. According to the present invention, it is possible to obtain a high-precision, large-capacity optical disk of two-layer recording formed by laminating a thin disk and a thick disk, and it is possible to manufacture such optical disks in large quantities at low cost. .

[Brief description of the drawings]

FIG. 1 is a side sectional view of an optical disc according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing an optical disc of Embodiment 1 according to the present invention.

FIG. 3 is a side sectional view showing a vacuum molding step in a method for manufacturing an optical disk according to a second embodiment of the present invention.

FIG. 4 is a side view showing an adhesive application step in the method for manufacturing an optical disc of Embodiment 2 according to the present invention.

FIG. 5 is a side sectional view of an optical disc according to a third embodiment of the present invention.

FIG. 6 is a side sectional view of an optical disc according to a fourth embodiment of the present invention.

FIG. 7 is a side sectional view of a conventional optical disk.

FIG. 8 is a process chart showing a conventional optical disc manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk 2 Injection molding process 3 Sputtering process 4 Adhesive coating process 5 Laminating process 6 UV curing process 7 Thin disk 8 Thick disk 9 PC film 10 Film 11 Pressing process 12 Stamper 13 Seal frame 14 Film adhesive roll 15 Pressing roll 16 Film adhesive 17 Protective film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Norihide Higaki 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. F term (reference) 5D029 HA05 HA06 JB13 JB33 KB08 RA08 RA38 RA45 RA46 RA49 5D121 AA02 AA07 DD06 EE26 EE27 GG24

Claims (11)

[Claims] 1. An optical disk, wherein at least two disks having different thicknesses are bonded together via a film adhesive, and at least one disk is formed of a resinous film. 2. The optical disk according to claim 1, wherein a recording signal is written on at least one surface of at least two disks facing each other. 3. At least two disks are composed of a thin disk and a thick disk, and a semi-reflective transflective film is formed on a surface of the thin disk on which a recording signal is written, and the recording of the thick disk is performed. 2. The optical disk according to claim 1, wherein a reflection film is formed on a surface on which the signal is written. 4. The optical disk according to claim 1, wherein the thickness of the disk formed of a film is in the range of 0.05 mm to 0.4 mm. 5. A disk having a sandwich structure in which a thick disk is sandwiched between two thin disks, each of which is bonded via a film adhesive, and a recording signal is applied to at least one of the bonded surfaces. The optical disk according to claim 1, wherein the optical disk is written. 6. A step of cutting a sheet-like film into a desired disk shape, a step of forming a disk having a desired thickness by injection molding and transferring a recording signal of a stamper, and a step of transferring the recording signal. A step of depositing a desired metal on the disc; a step of attaching a film adhesive to the disc on which the desired metal is deposited; a step of attaching the film to the disc on which the film adhesive is attached; and curing the film adhesive. A method for manufacturing an optical disk, comprising: 7. A step of cutting a sheet-like film into a desired disk shape, a step of transferring a recording signal of a stamper to the film cut into a disk shape, and forming a disk having a desired thickness by injection molding. Transferring the recording signal of the stamper, depositing a desired metal on the disc on which the recording signal has been transferred, attaching a film adhesive to the disc on which the desired metal has been deposited, and transferring the recording signal. A method for manufacturing an optical disk, comprising: a step of attaching a film to a disk to which a film adhesive is attached; and a step of curing the film adhesive. 8. The method of manufacturing an optical disk according to claim 7, wherein in the step of transferring the recording signal of the stamper to the film cut into a disk shape, the recording signal is transferred by a hot press method or a vacuum forming method. . 9. A step of transferring a recording signal of a stamper to a film cut into a disk shape, wherein a hot pressing method or a vacuum forming method is used, and a hot pressing method is performed at a temperature higher than a glass transition point of a material of the film. 8. The method of manufacturing an optical disk according to claim 7, wherein the recording signal is transferred while holding the mold or the vacuum forming die, and after the transfer, the temperature of the hot press die or the vacuum forming die is lower than the glass transition point. 10. The method of manufacturing an optical disc according to claim 7, wherein a semi-reflective semi-transmissive film is formed on a sheet-like film. 11. The method for manufacturing an optical disk according to claim 6, wherein the film adhesive for bonding the disk and the film is a thermosetting or UV-curable adhesive.