JP2003091868A - Optical disk and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk having a multi-layered structure and capable of being manufactured in high productivity with respect to the optical disk wherein a plurality of recording layers or signal layers are laminated and recording or reproduction is performed to respective layers by changing the focal position of a laser beam. SOLUTION: In the optical disk 1 wherein the signal layer 3 is formed on at least one surface of a disk substrate 2 and at least one new signal layer 7 is formed on the signal layer 3 via an intermediate layer 10 to form the multi-layered structure 4 and recording and reproduction of data are performed to at least two signal layers, the intermediate layer is constituted of a UV curing resin layer 6 and an adhesive sheet layer 5 and a rugged shape or a guide groove for constituting a recording signal of data is formed at the UV curing resin layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer optical disc in which a plurality of recording layers or signal layers are laminated and recording or reproducing is performed by changing the focal position of a laser beam.

[0002]

2. Description of the Related Art An optical disc in which a plurality of recording layers or signal layers are laminated and recording or reproduction is performed by changing the focal position of a laser beam, that is, in the case of a multilayer optical disc, As an intermediate layer between the signal layer and another recording layer or signal layer, conventionally, U
A V resin layer is used.

For example, a laminated DVD dual-layer disc is formed by laminating two disc substrates each having a signal layer or a recording layer on one side thereof to form an intermediate layer.

However, in the method of laminating two disk substrates described above to form a multi-layer structure, the intermediate layer itself does not have an uneven shape or a guide groove serving as a signal layer.
It is impossible to stack more layers.

Further, when the signal layer is formed of an ultraviolet curable polymer or an ultraviolet curable resin, the uneven shape or the like to be the signal layer is transferred using a stamper. At this time,
A stamper and a disk substrate are filled or coated with the above ultraviolet curable polymer or ultraviolet curable resin between them,
After bonding, it will be irradiated with ultraviolet rays to be cured.

Since the ultraviolet rays are emitted from the stamper or the disk substrate side, it is necessary that either one of them is able to transmit the ultraviolet rays.

However, it is very difficult to form a transparent stamper which transmits ultraviolet rays, and further, the productivity is remarkably reduced. Further, when an attempt is made to cure by irradiating ultraviolet rays from the disk substrate side, there is a problem that the material used for the signal layer is limited or the film thickness cannot be increased. Further, there is also a problem that the transmittance of ultraviolet rays decreases depending on the number of layers.

[0008]

In view of the above problems, the present invention provides an optical disc in which a plurality of recording layers or signal layers are laminated and recording or reproducing is performed by changing the focal position of a laser beam. An object of the present invention is to provide an optical disc having a multi-layer structure with good properties.

[0009]

In order to solve the above problems, the optical disc of the present invention has a signal layer formed on at least one surface of a disc substrate, and a new signal layer is formed on the signal layer via an intermediate layer. In an optical disc in which at least one layer is laminated to form a multi-layer structure, and data is recorded or reproduced on two or more signal layers, the intermediate layer is composed of an ultraviolet curable resin layer and an adhesive sheet layer. The ultraviolet curable resin layer is formed with a concavo-convex shape or a guide groove forming a data recording signal.

Therefore, it is possible to improve the productivity of a multi-layered optical disc in which a plurality of recording layers or signal layers are laminated and the focal position of the laser beam is changed to perform recording or reproduction respectively.

Further, in the optical disc manufacturing method of the present invention, a signal layer is formed on at least one surface of the disc substrate, and at least one new signal layer is formed on the signal layer via an intermediate layer.
In an optical disk manufacturing method in which a multilayer structure is formed by stacking layers, and data is recorded or reproduced in two or more signal layers, an intermediate layer is previously formed with a stamper uneven shape or a guide groove. The ultraviolet curable resin layer on which is transferred is bonded to a disk substrate with a pressure-sensitive adhesive sheet.

Therefore, it is possible to improve the productivity of a multi-layered optical disc in which a plurality of recording layers or signal layers are laminated and the focal position of the laser beam is changed to perform recording or reproduction respectively.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the optical disk of the present invention and a method of manufacturing the same will be described below with reference to the accompanying drawings.

First, the basic structure of the multilayer structure of the optical disk of the present invention will be described.

That is, as shown in FIG.
Has a structure in which a lower signal layer 3 such as an uneven shape and a guide groove is provided on at least one surface of the disk substrate 2, and a multilayer structure 4 is further laminated thereon.

In the structure for each layer of the multilayer structure 4, the pressure-sensitive adhesive sheet layer 5 is provided on the lower signal layer 3, the ultraviolet curing resin (UV resin) layer 6 is provided thereon, and the upper signal is provided thereon. The layer 7 is laminated, and an optically transparent cover layer 8 is laminated on the uppermost layer.

The concave-convex shape or the guide groove of the lower signal layer 3 and the upper signal layer 7 is formed by coating the UV resin 6a on the stamper and curing it in advance, and then using an adhesive sheet to form a disc. It is attached to the substrate 2 or the like. According to this method, it is not necessary to allow the disc substrate 2 or the stamper to transmit ultraviolet rays, and a multilayer optical disc having two or more layers can be easily produced.

Next, a method of manufacturing the optical disc 1 having the above-mentioned multilayer structure 4 will be described.

That is, as shown in FIG. 2, a reflective film or a reversible or irreversible recording thin film is formed on a disc substrate 2 having a spiral or concentric concavo-convex shape or a guide groove. The lower signal layer 3 is formed by forming a film (step A), and the pressure-sensitive adhesive sheet 5a is attached thereon, whereby the adhesive sheet layer 5 is formed (step B).

The upper signal layer 7 is formed by transferring this with another UV resin 6a from another stamper 9 on which the same concavo-convex shape or guide groove is formed. That is, the UV resin layer 6 is formed by applying the UV resin 6a on the stamper 9 and irradiating it with ultraviolet rays to cure it (step C).

After that, the side of the disk substrate 2 on which the pressure-sensitive adhesive sheet 5a is bonded is pressure-bonded to the stamper 9 to be bonded and peeled off, whereby the intermediate layer 10 is formed by the adhesive sheet layer 5 and the UV resin layer 6. Is formed (step D), and the upper signal layer 7 is formed by the reflective film or the recording film further formed on the intermediate layer 10 (step E).

In step D, the pressure sensitive adhesive sheet 5a can be attached to the stamper 9 side. In the case of further stacking, the above steps B to E are repeated a desired number of times.

Finally, an optically transparent cover layer 8 is formed on the upper signal layer 7 to complete the multilayer optical disc 1 (step F). The cover layer 8 has a role as a protective layer for the respective layers therebelow, particularly the upper signal layer 7, and a function for reducing the influence of dust and scratches during recording and reproduction.

Recording and reproduction on the optical disc 1 are performed by irradiating a laser beam from the cover layer 8 side.

In the optical disc 1, each signal layer 3
And 7 are stacked in the vertical direction (the thickness direction of the optical disc 1 or the irradiation direction of the recording / reproducing laser beam),
By changing the focal position of the objective lens of the recording / reproducing apparatus, recording / reproducing is performed only on a specific signal layer.

As for the returning light from other signal layers which are not the object of recording / reproducing, since the signal layers are separated by the thickness of the intermediate layer 11, they are out of focus and cannot be efficiently returned to the light receiver. , Its effects can be avoided.

Therefore, it is important that the thickness of the intermediate layer 10 is 10 times or more the depth of focus of the objective lens of the recording / reproducing apparatus. This depth of focus is determined by the laser wavelength and the numerical aperture of the lens. For example, at a wavelength of 633 nm, the numerical aperture is 0.
When it is 85, it becomes 2.8 μm.

The pressure-sensitive adhesive sheet layer 5 and the UV resin layer 6 constituting the intermediate layer 10 can be formed if the film thicknesses are 5 μm and 0.1 μm or more, respectively, and the ratio of the film thickness is not limited. Absent. However, since the UV resin layer 6 is generally harder than the pressure-sensitive adhesive sheet layer 5, stress is likely to occur, and thus the optical disc 1 is easily warped. Further, since the transmittance when using a laser in the ultraviolet region to the blue region is low, it is desirable that the intermediate layer 10 be as thin as possible.

According to the method of manufacturing the optical disk 1 described above, when the intermediate layer 10 is formed, the UV resin 6a is applied onto the stamper 9 and then cured as it is.
Compared with the conventional method of directly bonding a stamper and a disk (disk substrate), the disk is less susceptible to warpage and undulation, and the intermediate layer 10 can have a uniform film thickness. Further, the unevenness of the film thickness of the pressure-sensitive adhesive sheet layer 5 is about plus / minus 5%, and moreover, the film thickness can be a disk substrate.

The reflectance of each of the signal layers 3 and 7 is
It is necessary to adjust the number of layers of the multilayer structure 4 and the reflectance, transmittance, absorptance, etc. of each layer. When it is desired to make the intensities of the returned light from the respective signal layers uniform, it is possible to increase the reflectance of each signal layer in order from the laser beam incident side. However, this limits the direction in which recording and reproduction are performed (the direction in which the laser beam is emitted).

The signal layers 3 and 7 do not have to be the same film, and can be combined with a reflective film composed of pits or the like or a reversible or irreversible recording film so as to be read only (read only), It is also possible to manufacture an optical disc in which various signal layers such as rewritable (write-once) and rewritable (write-once) are mixed.

Further, a film having wavelength selectivity may be combined with each of the signal layers 3 and 7, etc. For example, if a red transmissive and blue reflective film is used for the upper multilayer structure, the lower multilayer structure can be recorded and reproduced by a red laser, and the upper multilayer structure can be manufactured as a disc that can be recorded and reproduced by a blue laser. Become.

Specific structures of various optical disks in consideration of the multilayer structure produced by the above manufacturing method are shown below.

That is, as shown in FIG. 3, in an optical disc 1A having a thin cover layer 8 represented by a so-called DVR, a multi-layer structure 4 is provided on a disc substrate 2 and, finally, for protecting it. The cover layer 8 is provided. Therefore, recording / reproduction is performed from the cover layer 8 side, as indicated by the arrow indicating the laser beam irradiation direction.

As shown in FIG. 4, if the multilayer structures 4 and 4 are provided on both sides of the disk substrate 2, respectively, a double-sided recording / reproducing type optical disk 1B is formed as indicated by the arrow of the laser beam irradiation direction. .

Further, as shown in FIG. 5, in the existing single-plate optical disk (for example, CD) 1C, in order to record / reproduce from the disk substrate 2 side, as shown by the arrow in the laser beam irradiation direction. Instead of the cover layer, a layer for protecting the signal layer of the multilayer structure 4, for example, an ultraviolet curable resin or the like is applied to form the protective layer 11, so that a double-sided configuration is not possible.

Further, in the case of a so-called DVD or the like that is of a bonded type, two types of structures are conceivable for the optical disc for recording and reproducing from one side.

That is, as shown in FIG. 6, one of the above-mentioned bonded type optical discs for recording / reproducing from one side is a disc substrate 2 on which a multilayer structure 4 is formed and a disc substrate on which a signal layer is not formed. 12 is an optical disc 1D having a structure in which 12 and 12 are bonded together. In the optical disc 1D, when recording / reproducing is performed by irradiating a laser beam from the side of the disc substrate 2 having the multi-layer structure 4, the disc substrate 12 having no signal layer has the same material and thickness as the multi-layer structure 4. It need not be the same as the disc substrate 2 and need not be optically transparent (transmit a laser beam).

Recording and reproduction from the disk substrate 12 side are also possible. In this case, for example, the multilayer structure 4 may be formed on the polycarbonate disk substrate 2 and the glass disk substrate 12 may be bonded thereto.

As shown in FIG. 7, the other one of the above-mentioned bonded type optical discs for recording / reproducing from one side is formed with two disc substrates 2 each having a multilayer structure 4 and a multilayer structure 4 formed thereon. The optical disc 1E is configured to be bonded on the surface on the opposite side, and the bonding layer 13 serving as an optical intermediate layer so that a laser beam is irradiated from one side to perform recording / reproduction on all signal layers. .

Furthermore, as shown in FIG. 8, a bonded type optical disc 1F for recording / reproducing from both sides of the disc.
In the same manner as the optical disc 1E, the multilayer structure 4
Two disc substrates 2 each having a multi-layer structure 4 are attached to each other on the surface on which the multi-layer structure 4 is formed, and the attachment layer 13 is used as an intermediate layer. A laser beam is irradiated from both sides of the disk substrate 2 to perform recording and reproduction from the respective disk substrate 2 sides.

Finally, the process of producing an optical disc having a thin cover layer 8, for example, the above-mentioned optical disc 1A will be described more specifically.

That is, as shown in FIG.
As the material, a polycarbonate pit having a diameter of 120 mm and a thickness of 1.2 mm, to which the pit shape has been transferred in advance by injection molding, is used. Then, as the lower signal layer 3, a reflection film made of aluminum having a thickness of 60 nm is formed by sputtering.
Form (Step A).

Incidentally, as the material of the disk substrate 2, a thermoplastic resin, a thermosetting resin, a glass 2P disk substrate or the like can be considered in addition to the above. Further, when recording / reproducing is not performed from the side of the disk substrate 2, the disk substrate 2 does not need to be optically transparent, and may have uneven refractive index or birefringence.

Next, a urethane acrylic UV resin 6a is dropped on the stamper 9 and spin coated (3000r).
pm for 30 seconds) to ensure uniform thickness. At this time, the thickness of the UV resin 6a was 2 μm.
After that, the UV resin 6a is cured by irradiating the UV resin 6a with a mercury lamp or a halogen lamp for 5 seconds (step C).

A pressure-sensitive adhesive sheet 5a having a thickness of 25 μm is attached to the disc substrate 2 (step B). As shown in FIG. 9, a large number of the pressure-sensitive adhesive sheets 5a are arranged on a polyethylene sheet mount (conveying sheet) 15 in a state in which a protective cover 14 is affixed to a pre-punched disc. And is bonded to the disk substrate 2 by pressure bonding with a pad made of silicon rubber described later (step B).

As shown in FIG. 10, the pressure-sensitive adhesive sheet 5a is pressure-bonded to the disk substrate 2 by the pad 16 made of silicon rubber, and then the carrier sheet 15 is peeled off (step D). When bubbles are present in the pressure-sensitive adhesive sheet 5a, a pressure defoaming process (for example, leaving it in compressed air of 10 atm for several tens of minutes) is performed.

Then, as the upper signal layer 7, 20 to 4 are used.
An aluminum film is formed by sputtering while adjusting the transmittance with a film thickness of 0 nm (step E).

At this time, the thickness of the intermediate layer 10 composed of the adhesive sheet layer 5 and the UV resin layer 6 is 27 μm,
The film thickness unevenness was plus / minus 2 μm or less.

Then, steps B to E are repeated again to form the intermediate layer 10 and a new signal layer 17 on the upper signal layer 7 to form a three-layer structure of signal layers.

Finally, the cover layer 8 has a thickness of 70 μm.
m polycarbonate plate 18 is attached (step F). That is, as shown in order in FIG. 11, after the UV resin 6a is applied on the signal layer 17 in a circular pattern, a polycarbonate plate 18 is installed, and for example, 500
By rotating for 30 seconds at 0 rpm, the signal layer 1
The UV resin 6a between the polycarbonate plate 7 and the polycarbonate plate 18 is thinly and uniformly extended, and then the UV resin 6a is cured by irradiating ultraviolet rays, whereby the optical disk 1A is formed.

As described above, in the optical disc of the present invention and the manufacturing method thereof, it is possible to form two or more layers, which makes it possible to easily provide a large-capacity optical disc with good productivity. Become.

Further, since the unevenness of the thickness of the intermediate layer 10 is uniform, it becomes possible to form an optical disc having a multi-layer structure suitable for high NA and high speed recording / reproducing.

Further, by changing the laminated signal layers to various ones, it becomes possible to provide an optical disk in which read-only, write-at-once and rewritable are mixed.

Further, by changing the wavelength of the laser beam, it is possible to give a selective control to an arbitrary signal layer to be recorded and reproduced.

It should be noted that the specific shapes and structures of the respective parts shown in the above-mentioned embodiments are merely examples of specific embodiments for carrying out the present invention, and the techniques of the present invention can be realized by these. The scope should not be limitedly interpreted.

[0057]

As described above, in the optical disc of the present invention, the signal layer is formed on at least one surface of the disc substrate, and at least one new signal layer is laminated on the signal layer via the intermediate layer. Thus, in an optical disc having a multi-layer structure and recording or reproducing data in or from two or more signal layers, the intermediate layer is composed of an ultraviolet curable resin layer and an adhesive sheet layer, and the ultraviolet curable resin layer is Is
Since the concavo-convex shape or the guide groove forming the data recording signal is formed, it is possible to easily form two or more layers, and it is possible to easily provide a large-capacity optical disk with good productivity. it can.

Further, in the method for manufacturing an optical disc of the present invention, a signal layer is formed on at least one surface of the disc substrate, and at least one new signal layer is formed on the signal layer via an intermediate layer.
In an optical disk manufacturing method in which a multilayer structure is formed by stacking layers, and data is recorded or reproduced in two or more signal layers, an intermediate layer is previously formed with a stamper uneven shape or a guide groove. Since the ultraviolet-curable resin layer on which is transferred is attached to the disk substrate with a pressure-sensitive adhesive sheet,
Since more layers can be easily formed, a large-capacity optical disk can be easily provided with good productivity.

According to the second aspect of the present invention, the cover layer is formed on the multi-layer structure and the signal layer is recorded / reproduced by using the cover layer as the light transmitting layer. It can be easily provided with good productivity.

According to the third aspect of the present invention, since the multi-layer structure is formed on both sides of the disk substrate, the capacity can be increased as compared with the case of one side.

In the invention described in any one of claims 5 to 7, the disk substrates having the multilayer structure are bonded to each other, and the layer formed by the bonding is used as an intermediate layer to form one side of the disk. Since the recording / reproducing is performed on all the signal layers, the capacity can be further increased as compared with the case where the multilayer structure has one side.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a multilayer structure of an optical disc according to the present invention.

FIG. 2 is a diagram schematically showing a method for manufacturing an optical disc of the present invention.

3 schematically shows a specific embodiment of the optical disc of the present invention together with FIGS. 4 to 8. This diagram shows a multi-layer structure of a thin cover layer and one side of the disc, and recording from the cover layer side. It is a figure which shows the structure of the optical disk which was made to reproduce.

FIG. 4 is a diagram showing a structure of an optical disc having a thin cover layer and a multilayer structure on both sides of the disc, and recording and reproducing are performed from both sides of the disc.

FIG. 5 is a diagram showing a structure of an optical disc having a protective layer made of an ultraviolet curable resin for protecting a signal layer and a multi-layer structure of one side of the disc, and recording / reproducing is performed from the disc substrate side.

FIG. 6 is a diagram showing a structure of an optical disc of a laminated type, which has a multi-layered structure on one side of the disc and can perform recording and reproduction from either side of both sides of the disc.

FIG. 7 is a diagram showing a structure of an optical disc of a laminated type, which has a multi-layer structure on both sides of the disc and can perform recording and reproduction from either side of both sides of the disc.

FIG. 8 is a diagram showing a structure of an optical disc of a laminated type having a multi-layered structure on both sides of the disc, and recording and reproducing are performed from both sides of the disc.

FIG. 9 is a diagram showing a supply form of a pressure-sensitive adhesive sheet in the optical disc manufacturing method of the present invention.

FIG. 10 is a view showing a step of bonding the pressure-sensitive adhesive sheet supplied by the supply mode shown in FIG. 9 to a disk substrate.

FIG. 11 is a diagram showing a step of forming a cover layer in the optical disc manufacturing method of the present invention.

[Explanation of symbols]

1 ... Optical disc, 2 ... Disc substrate, 3 ... Signal layer, 4 ...
Multilayer structure, 5 ... Adhesive sheet layer, 5a ... Pressure sensitive adhesive sheet, 6 ... UV curable resin layer, 7 ... Signal layer, 8 ... Cover layer, 10 ... Intermediate layer, 17 ... Signal layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiyuki Kashiwagi             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F term (reference) 5D029 JB06 JB32 RA04 RA27                 5D121 AA01 AA07 DD03 EE21 FF11                       FF20 GG02

Claims (8)

[Claims] 1. A signal layer is formed on at least one surface of a disk substrate, and at least one new signal layer is laminated on the signal layer via an intermediate layer to form a multilayer structure, and two or more layers are formed. In the optical disc configured to record or reproduce data on or from the signal layer, the intermediate layer includes an ultraviolet curable resin layer and an adhesive sheet layer, and the ultraviolet curable resin layer constitutes a data recording signal. An optical disc having an uneven shape or a guide groove. 2. The optical disc according to claim 1, wherein a cover layer is formed on the multilayer structure, and the cover layer is used as a light transmitting layer for recording and reproducing the signal layer. 3. The optical disc according to claim 1, wherein a multilayer structure is formed on both sides of the disc substrate. 4. The optical disk according to claim 2, wherein a multilayer structure is formed on both surfaces of the disk substrate. 5. A disc substrate having a multi-layer structure is adhered to each other, and the layer formed by the lamination is used as an intermediate layer so that recording and reproduction can be performed from one side of the disc to all signal layers. The optical disc according to claim 1, which has been recorded. 6. A disc substrate provided with a multi-layered structure is adhered to each other, and a layer formed by the lamination is used as an intermediate layer so that recording and reproduction can be performed from one side of the disc to all signal layers. The optical disc according to claim 2, which has been recorded. 7. A disc substrate having a multi-layer structure is attached to each other, and a layer formed by the attachment is used as an intermediate layer so that recording and reproduction can be performed from one side of the disc to all signal layers. The optical disc according to claim 3, which has been recorded. 8. A multilayer structure is formed by forming a signal layer on at least one surface of a disk substrate, and stacking at least one new signal layer on the signal layer via an intermediate layer to form a multilayer structure. In the method for manufacturing an optical disc for recording or reproducing data on or from the signal layer, the intermediate layer is pressure-sensitive adhesive with an ultraviolet curable resin layer to which the uneven shape of the stamper or the guide groove is transferred in advance. A method for manufacturing an optical disc, characterized in that the optical disc is constructed by bonding the sheet to a disc substrate.