JP2004014046A - Manufacturing method of multilayer optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a substrate for transfer to be easily pilled off from the side of a disk substrate. <P>SOLUTION: A signal layer 12 is deposited on irregularity information 11c preliminarily formed on one surface of the disk substrate 11, a peeling layer 22 is deposited on irregularity information 21c preliminarily formed on one surface of the substrate 21 having diameter D2 of circumference 21b larger than diameter D1 of circumference 11b of the disk substrate 11, a second light transmission layer 13B by transparent ultraviolet cured resin is deposited on the peeling layer 22 and furthermore, the substrate 21 is peeled from the side of the disk substrate 11 as attaching the peeling layer 22 on the substrate 21 after adhering the second light transmission layer 13B on the side of the substrate 21 via a first light transmission layer 13A by a transparent adhesive agent dropped on the signal layer 12 on the side of the disk substrate 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, a signal layer is formed in multiple layers on one side of a thick disk substrate, and, among the multilayered signal layers, on the outermost signal layer farthest from the disk substrate in the stacking direction. The present invention relates to a method for manufacturing a multi-layer optical disc, wherein a thin transparent cover layer is formed on a substrate, and a laser beam is incident from the transparent cover layer toward each signal layer.
[0002]
[Prior art]
In general, an optical disc records information signals such as video information, audio information, and computer data at a high density on spirally or concentrically formed tracks on a disc-shaped disc substrate, and records recorded tracks. It is frequently used because a desired track can be accessed at high speed during reproduction.
[0003]
At this time, optical disks can be roughly classified into a read-only type and a recording / reproducing type. Here, the read-only type optical disk converts an information signal into a digital pit row with concave pits and convex lands, and this pit row is spirally or concentrically formed on a disk-shaped transparent disk substrate. Further, a metal reflection film and a protective film are sequentially formed on the pit row, and a signal layer of the pit row having the metal reflection film formed thereon is formed only for reproduction.
[0004]
On the other hand, in the recording / reproducing type optical disk, concave grooves and convex lands are alternately formed in advance in a spiral or concentric manner on a disk-shaped transparent disk substrate. A recording film, a metal reflection film, and a protective film are sequentially formed thereon, and a signal layer formed of grooves and lands on which the recording film is formed is formed so as to be recordable and reproducible.
[0005]
The read-only type optical disk uses a laser beam for reproduction emitted from an optical pickup, which is movably provided in the optical disk device in the radial direction of the optical disk, via an objective lens, from a laser beam incident surface of the disk substrate to a signal layer. , And the return light reflected from the signal layer is detected by a photodetector in the optical pickup and reproduced.
[0006]
On the other hand, a recording / reproducing type optical disk has a recording laser beam emitted through an objective lens from an optical pickup provided movably in a radial direction of the optical disk in the optical disk apparatus, and a signal layer from a laser beam incident surface of the disk substrate to a signal layer. And the signal layer is recorded with this laser beam, and then the recorded signal layer is reproduced with the reproduction laser beam in the same manner as described above.
[0007]
Among the above optical discs, a CD (Compact Disc) containing music information, a CD-ROM (CD-Read Only Memory) containing computer data, and a recordable / reproducible CD-R capable of recording an information signal only once. (CD-Recordable), DVD (Digital Versatile Disc) capable of recording video information and audio information which is digitized and compressed by increasing the recording capacity by 6 to 8 times as compared with CD, and recording / reproducing which can record an information signal only once. Possible DVD-R (DVD-Recordable), recordable / reproducible DVD-RW (DVD-Recordable) capable of recording information signals a plurality of times, DVD-RAM (DVD-Random Access Memory) or DVD-Writable ), Etc., it is already widely used.
[0008]
On the other hand, recently, the outer dimensions are almost the same as those of existing CDs and existing DVDs, and information signals can be recorded and / or reproduced at an ultra-high density compared to DVDs. Ultra-high density having a recording capacity of about 15 GB to 25 GB is available. The development of optical discs is being actively pursued.
[0009]
Here, in order to increase the recording capacity of the optical disc, it is generally necessary to reduce the spot diameter of the laser beam. The spot diameter of the laser beam depends on the laser wavelength, the numerical aperture (NA) of the objective lens, and the like. caused by. At this time, if the numerical aperture (NA) of the objective lens is increased, the aberration tends to increase with respect to the tilt of the optical disk, and the influence of the tilt angle (Tilt) of the optical disk increases. Since this aberration is proportional to the thickness from the laser beam incident surface to the signal layer on the disk substrate and (NA) ³ , when increasing the NA of the objective lens, the distance from the laser beam incident surface to the signal layer is increased. The aberration can be reduced by reducing the thickness.
[0010]
As described above, in the case of an ultra-high-density optical disk, use a laser beam having a wavelength of about 400 nm and use an objective lens having a numerical aperture (NA) of about 0.7 to 0.85. Thus, the thickness from the laser beam incident surface to the signal layer on the disk substrate is approximately 0.1 mm to 0.2 mm. In an ultra-high-density optical disk, a signal layer on a disk substrate has an information signal recorded with a track pitch of 0.32 μm, a minimum recording length of 0.14 μm to 0.17 μm, and a 2T modulation signal. The coding method is called 1,7PP, and a method obtained by improving the (1,7) RLL coding method is used.
[0011]
By the way, an ultra-high-density multi-layer optical disc capable of further increasing the recording capacity of an ultra-high-density optical disc by multiplying a signal layer on a disc substrate has been studied. A new manufacturing method for manufacturing a high-density two-layer type optical disc is described in a preliminary book page 312 of the International Symposium on Optical Memory 2001, Oct 16-19, Taipei, Taiwan, held in Taiwan in the fall of 2001. 12 and 13 are disclosed.
[0012]
FIG. 12 is a diagram schematically illustrating an ultra-high-density two-layer optical disc in a conventional example.
[0013]
As shown in FIG. 12, the conventional ultra-high-density two-layer optical disc 100 uses a blue laser beam with a wavelength of 405 nm and an objective lens with a numerical aperture (NA) of 0.85. When the outer dimensions of the thick disk substrate 101 are formed in a disk shape of 120 mm, the recording capacity of the signal layer per layer is about 25 GB, and the recording capacity is doubled by making this signal layer into two layers. It was done.
[0014]
That is, the disk substrate 101 having a large thickness of about 1.1 mm has a center hole 101a having a diameter of 15 mm and an outer periphery 101b having a diameter of 120 mm. Concavo-convex information 101c, which is formed as a stamp, is formed by injection molding. Further, a second signal layer 102 having a metal reflection film is formed on the unevenness information 101c of the disk substrate 101.
[0015]
Further, a second light-transmitting layer (transparent adhesive layer) 103A made of a transparent adhesive using a transparent ultraviolet curable resin is provided on the second signal layer 102, and a second substrate on a transfer substrate 111 (FIG. 13) described later is formed. By bonding the light transmitting layer 103B, the light transmitting layer 103 is formed to have a thickness of about 30 μm including the first and second light transmitting layers 103A and 103B.
[0016]
After the unevenness information 103B1 is transferred onto the second light transmitting layer 103B of the light transmitting layer 103 by the unevenness information 111c shown in FIG. 13B described later, the semi-transparent information is transferred onto the unevenness information 103B1. A first signal layer 104 having a reflective film is formed.
[0017]
Further, a transparent cover layer 105 composed of a transparent adhesive layer 105A and a transparent resin cover sheet 105B is formed on the first signal layer 104 with a reduced thickness, and the laser beam incident surface (= surface) of the transparent resin cover sheet 105B is formed. ) To the bonding surface located between the first light transmitting layer (transparent adhesive layer) 103A and the second light transmitting layer 103B is set to about 0.1 mm.
[0018]
The transparent resin cover sheet 105B side of the transparent cover layer 105 is the laser beam incident side.
[0019]
With the above-described configuration, when the laser beam incident from the transparent cover layer 105 side passes through the semi-transmissive reflective film of the first signal layer 104 and further reaches the second signal layer 102 through the light transmission layer 103. Can record an information signal on the second signal layer 102 at a very high density, or reproduce a recorded information signal at a very high density.
[0020]
When a laser beam incident from the transparent cover layer 105 side is reflected by the semi-transmissive reflection film of the first signal layer 104, an information signal is recorded on the first signal layer 104 at an ultra high density, or In addition, a recorded information signal can be reproduced at a very high density.
[0021]
Therefore, the above-described second signal layer 102 of the upper layer and the first signal layer 104 of the lower layer provide an ultra-high-density two-layer optical disc 100 in the conventional example.
[0022]
Next, a case of manufacturing the above-described conventional high-density two-layer optical disc 100 will be described with reference to FIGS.
[0023]
FIGS. 13 (a) to 13 (e) are views schematically showing a manufacturing process for manufacturing an ultra-high-density two-layer optical disc in a conventional example.
[0024]
First, as shown in FIG. 13A, a thick disk substrate 101 is prepared. The disk substrate 101 has a center hole diameter of 15 mm, an outer diameter of 120 mm, and a substrate thickness of about 1.1 mm using a polycarbonate resin or the like, and is provided with a stamper (not shown) mounted in an injection molding machine. On one surface of the disk substrate 101, the unevenness information 101c is transferred in a state of being etched in an uneven shape. Further, a second signal layer 102 having a metal reflection film is formed on the unevenness information 101c of the disk substrate 101.
[0025]
Further, as shown in FIG. 13B, the transfer substrate 111 side is prepared. The transfer substrate 111 has a center hole having a diameter of 15 mm and an outer diameter of 120 mm using, for example, a transparent polycarbonate resin. One of the transfer substrates 111 is provided by a stamper (not shown) mounted in an injection molding machine. Is transferred in a state where the unevenness information 111c is carved in an uneven shape. The second light transmitting layer 103B is formed on the unevenness information 111c of the transfer substrate 111 using a transparent ultraviolet curable resin.
[0026]
Next, as shown in FIG. 13C, the disk substrate 101 side and the transfer substrate 111 side are covered with a first light transmitting layer (transparent adhesive layer) 103A made of a transparent adhesive using a transparent ultraviolet curable resin. Glue. Specifically, a transparent adhesive using a transparent ultraviolet curable resin is dropped on the second signal layer 102 on the disk substrate 101 side, and a first light transmitting layer (transparent adhesive layer) 103A made of the transparent adhesive is used. By bonding the second light transmitting layer 103B on the transfer substrate 111 side through the substrate, the light transmitting layer 103 including the first and second light transmitting layers 103A and 103B is formed with a thickness of about 30 μm. At this time, when the disk substrate 101 side and the transfer substrate 111 side are bonded with a transparent adhesive, a metal reflective film is necessarily formed on the second signal layer 102 on the disk substrate 101 side in order to cure the transparent adhesive. Therefore, the metal reflective film blocks the ultraviolet rays when the ultraviolet rays are irradiated. On the other hand, since a metal reflection film is not formed on the transparent transfer substrate 111 side, when ultraviolet light is irradiated from the transparent transfer substrate 111 side, the ultraviolet light is transmitted through the first light transmission layer 103B through the first light transmission layer 103B. Since the light reaches the layer (transparent adhesive layer) 103A, the first light transmitting layer (transparent adhesive layer) 103A can be cured.
[0027]
Next, as shown in FIG. 13D, the transfer substrate 111 is separated from the disk substrate 101 in the state shown in FIG. 13C. As a result, in a state where the unevenness information 111c of the transfer substrate 111 is transferred as the unevenness information 103B1 on the second light transmitting layer 103B, the second light transmitting layer 103B is placed on the second signal layer 102 on the disk substrate 101 side. One light transmission layer (transparent adhesive layer) 103A is adhered.
[0028]
Next, as shown in FIG. 13E, a first signal layer 104 and a transparent resin cover layer 105 are sequentially formed on the light transmitting layer 103 on the disk substrate 101 side. Specifically, a first signal layer 104 having a semi-transmissive reflective film is formed on the unevenness information 103B1 of the second light transmitting layer 103B adhered to the disk substrate 101, and a transparent layer is formed on the first signal layer 104. A thin transparent resin cover sheet 105B is bonded via a transparent adhesive layer 105A made of a transparent adhesive using an ultraviolet curable resin, and the thickness of the transparent adhesive layer 105A and the transparent resin cover sheet 105B is about 0.1 mm. Is formed. Then, the total thickness when the transparent resin cover sheet 105B is bonded to the disk substrate 101 side is approximately 1.2 mm, and the ultra-high density two-layer type optical disk 100 in the conventional example is completed.
[0029]
[Problems to be solved by the invention]
By the way, in manufacturing the ultra-high density two-layer type optical disc 100 in the conventional example as described above, the disc substrate 101 side and the transfer substrate 111 side are adhered to each other as shown in FIG. When the transfer substrate 111 is gradually peeled from the outer periphery toward the inner periphery from the 101 side, when the disk substrate 101 side and the transfer substrate 111 side are bonded, the outer diameter of the two substrates 101 and 111 becomes smaller. Since the same is applied, the transparent adhesive to be the first light transmitting layer (transparent adhesive layer) 103A wraps around and attaches to the outer peripheral end surface of the transfer substrate 111, so that the second light transmission The layer 103B remains adhered, the second light transmitting layer 103B cannot be peeled off from the transfer substrate 111, and defects occur in the outer peripheral portion of the two-layer optical disc 100, resulting in quality and reliability. Two-layer type optical disc 100 is caused a problem such as are made poor.
[0030]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and a first invention is to form a signal layer in multiple layers on one surface side of a thick disk substrate, and to form a multilayer among the signal layers. A thin transparent cover layer is formed on the outermost signal layer farthest from the disc substrate in the stacking direction, and a laser beam is directed from the transparent cover layer side toward each signal layer. In the method for manufacturing the configured multilayer optical disc,
A first step of forming a signal layer on unevenness information previously formed on one surface of the disk substrate;
A second step of forming a release layer on unevenness information formed in advance on one surface of the transfer substrate having an outer diameter larger than the outer diameter of the disk substrate;
A third step of forming a second light transmission layer made of a transparent ultraviolet curable resin on the release layer on the transfer substrate side;
A fourth step of bonding the second light transmitting layer on the transfer substrate side to the signal layer on the disk substrate side via a first light transmitting layer made of an adhesive;
The transfer substrate is peeled off from the disk substrate while the transfer layer is still attached to the transfer substrate, and the unevenness information on the transfer substrate side is formed on the second light transmitting layer shifted to the disk substrate side. A fifth step of exposing the transferred unevenness information,
A sixth step of forming a signal layer on the unevenness information of the second light transmitting layer shifted to the disk substrate side;
A seventh step of repeating the above-described second to sixth steps using another transfer substrate to further multiply a signal layer on the disk substrate side as necessary;
An eighth step of forming the thin transparent cover layer on the outermost signal layer of the signal layers multilayered on the disk substrate side. It is.
[0031]
Further, in the second invention, the signal layer is formed in multiple layers on one surface side of the thick disk substrate, and the signal layer which is the most distant from the disk substrate in the stacking direction among the multilayered signal layers. Forming a thin transparent cover layer on the outermost signal layer, a method for manufacturing a multilayer optical disc configured to make a laser beam incident from the transparent cover layer side toward the signal layer of each layer,
A first step of forming a signal layer on unevenness information previously formed on one surface of the disk substrate;
A second step of forming a first light transmitting layer of a transparent ultraviolet curable resin on the signal layer on the disk substrate side;
A third step of forming a release layer on unevenness information formed in advance on one surface of the transfer substrate having an outer diameter larger than the outer diameter of the disk substrate;
A transparent adhesive is dropped on the first light transmitting layer on the disk substrate side, and the uneven information formed on one surface of the transfer substrate on the second light transmitting layer by the transparent adhesive is peeled off. A fourth step of transferring through the layer;
Fifth, exposing the transfer substrate from the disk substrate side while exposing the transfer substrate with the release layer attached thereto, exposing the unevenness information transferred onto the second light transmitting layer on the disk substrate side. Steps and
A sixth step of forming a signal layer on the unevenness information of the second light transmitting layer on the disk substrate side;
A seventh step of repeating the above-described second to sixth steps using another transfer substrate to further multiply a signal layer on the disk substrate side as necessary;
An eighth step of forming the thin transparent cover layer on the outermost signal layer of the signal layers multilayered on the disk substrate side. It is.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of a method for manufacturing a multilayer optical disk according to the present invention will be described below with reference to FIGS. 1 to 11 with reference to <double-layer optical disk>, <multi-layer optical disk manufacturing method>, <three-layer optical disk>, The details will be described in the order of <four-layer optical disc> and <method of manufacturing multilayer optical disc of modified example>.
[0033]
The method for manufacturing a multilayer optical disk according to the present invention is a partial improvement on the method for manufacturing an ultra-high-density two-layer optical disk in the conventional example described above with reference to FIGS. Although the manufacturing process of a multilayer optical disk is basically the same as the conventional one, in particular, a signal layer is formed on the unevenness information formed on one surface of the disk substrate, and the diameter is larger than the outer diameter of the disk substrate. A release layer is formed on the uneven information formed on one surface of the transfer substrate having an outer diameter, and a second light transmission layer made of a transparent ultraviolet curable resin is formed on the release layer. After bonding the second light transmitting layer on the transfer substrate side via the first light transmitting layer with the transparent adhesive dropped on the signal layer on the substrate side, the transfer substrate is attached with the release layer attached to the transfer substrate. When peeling from the disk substrate side, transfer The outer dimensions of the substrate are formed to be slightly larger than the outer dimensions of the disk substrate, and the outer peripheral portion of the second light transmitting layer formed on the transfer substrate side is improved so as to improve the peeling performance. The information on the unevenness of the second light transmitting layer formed on the substrate side can be reliably transferred to the disk substrate side. The method of manufacturing a multilayer optical disk according to the present invention is applicable not only to a two-layer optical disk but also to a multilayer optical disk having two or more layers.
[0034]
<Dual-layer optical disk>
Before describing the method for manufacturing a multilayer optical disk according to the present invention, a two-layer optical disk manufactured by applying this manufacturing method will be described with reference to FIG.
[0035]
FIG. 1 is a diagram schematically illustrating a two-layer optical disk manufactured by applying the method of manufacturing a multilayer optical disk according to the present invention.
[0036]
As shown in FIG. 1, a two-layer type optical disk 10 manufactured by applying the method for manufacturing a multilayer optical disk according to the present invention has a thick disk-shaped disk substrate 11 on one side in a manner similar to the conventional one. The signal layers 12, 14 are formed in two layers, and the thickness of the two signal layers 12, 14 is thin on the outermost signal layer 14 farthest from the disk substrate 11 in the laminating direction. The transparent cover layer 15 is formed so that a laser beam is incident on the signal layers 12 and 14 from the transparent cover layer 15 side.
[0037]
The above-described two-layer type optical disk 10 uses a blue laser beam having a wavelength of about 400 nm and an objective lens having a numerical aperture (NA) of 0.7 to 0.85 to form a thick disk substrate 11. When the external dimensions are formed to 120 mm, the recording capacity of the signal layer per layer is about 25 GB, and the recording capacity is doubled by making this signal layer into two layers.
[0038]
That is, in the above-described two-layer type optical disk 10, the disk substrate 11 having a large thickness of about 1.1 mm has a center hole 11a having a diameter of 15 mm and an outer periphery 11b having a diameter of 120 mm. Concavo-convex information 11c consisting of an embossed mark is formed in advance on one surface of the substrate 11 by injection molding, and a ring-shaped groove 11d is formed in the center hole 11a on the innermost peripheral side of one surface of the disk substrate 11. It is pre-formed concentrically with a shallow depth. At this time, the unevenness information 11c engraved on one surface of the disk substrate 11 indicates that a pit row formed by concave pits and convex lands when viewed from the non-recording / reproducing surface side of the disk in the case of a read-only type. On the other hand, in the case of the recording / reproducing type, a concave groove and a convex land are formed on the disk substrate 11 in a spiral shape when viewed from the non-recording / reproducing surface side of the disk. Alternatively, they are formed alternately and concentrically in advance.
[0039]
A ring-shaped groove 11d formed on the innermost peripheral side of one surface of the disk substrate 11 is formed by dropping a transparent adhesive made of a transparent ultraviolet curable resin onto the second signal layer 12 as described later. This is to prevent the transparent adhesive from extending toward the center hole 11a when the light transmitting layer (transparent adhesive layer) 13A is formed.
[0040]
Further, a second signal layer 12 having a metal reflection film is formed on the unevenness information 11c of the disk substrate 11. At this time, the second signal layer 12 formed on the unevenness information 11c of the disk substrate 11 is a read-only type in which only a metal reflection film such as aluminum is formed on a pit row. In the case of the recording / reproducing type, a metal reflection film and a recording film are formed on a concave groove and a convex land in the above order.
[0041]
In addition, a transfer substrate 21 (FIG. 2B) described later via a first light transmitting layer (transparent adhesive layer) 13A made of a transparent adhesive using a transparent ultraviolet curable resin on the second signal layer 12 is used. By bonding the second light transmitting layer 13B formed of a transparent ultraviolet curable resin on the release layer 22, the light transmitting layer 13 including the first and second light transmitting layers 13A and 13B has a thickness of about 20 to 30 μm. It is formed with a film thickness.
[0042]
In the light transmitting layer 13, the unevenness information 13A1 and the ring-shaped convex portion 13A2 are transferred onto the inner first light transmitting layer 13A by the unevenness information 11c and the ring-shaped groove 11d of the disk substrate 11, and the outer second light-transmitting layer 13A. The unevenness information 13B1 and the ring-shaped convex portion 13B2 are transferred onto the light transmitting layer 13B by the unevenness information 21c and the ring-shaped groove 21d of the transfer substrate 21 (FIG. 2B) described later.
[0043]
Further, the first signal layer 14 having a semi-transmissive metal reflection film is formed on the unevenness information 13B1 on the second light transmission layer 13B side and on the ring-shaped protrusion 13B2.
[0044]
Further, a transparent cover layer 15 composed of a transparent adhesive layer 15A and a transparent resin cover sheet 15B is formed on the first signal layer 14 with a reduced thickness. In this embodiment, unlike the conventional example, a transparent resin layer 15A is provided. The distance from the laser beam incident surface (= surface) of the cover sheet 15B to the bonding surface located between the second signal layer 12 and the first light transmitting layer 13A is set to about 0.1 mm.
[0045]
The transparent resin cover sheet 15B side of the transparent cover layer 15 is the laser beam incident side, and a second layer number is given in advance to the second signal layer 12 on the inner peripheral side, and Since the first layer number is assigned to the first signal layer 14 on the inner peripheral side in advance, the laser beam incident from the transparent resin cover sheet 15B side focuses each signal layer 12, 14 according to the layer number. Control.
[0046]
Here, the reason why the distance from the laser beam incident surface of the transparent resin cover sheet 15B to the rear second signal layer 12 is set in advance will be described. For example, if the distance from the laser beam incident surface of the transparent resin cover sheet 15B to the rear side second signal layer 12 is preset to, for example, 100 μm (= 0.1 mm), the thickness of the light transmission layer 13 is about 20 μm to 30 μm. If there is, the distance from the laser beam incident surface of the transparent resin cover sheet 15B to the first signal layer 14 on the near side is naturally shorter than 100 μm and about 70 μm to 80 μm.
[0047]
Although FIG. 1 shows a case where the signal layer is formed into two layers, considering the case where the signal layer is further formed into a plurality of layers as well as two layers as described later, the laser beam incident on the transparent resin cover sheet 15B is considered. A method in which the distance from the surface to the innermost signal layer in the stacking direction is set in advance, and the distance from the laser beam incident surface to each signal layer is gradually shortened as each signal layer becomes closer to the front. Is taking. Therefore, since the thickness of the transparent cover layer 15 is fixed so as to be equivalent to the distance from the laser beam incident surface of the transparent resin cover sheet 15B to the innermost signal layer, when designing the objective lens in the optical pickup, The objective lens can be designed to reduce aberrations in accordance with the distance to the innermost signal layer. On the other hand, although the spherical aberration that occurs when the objective lens is focused on each of the signal layers on the front side increases, the increase in the spherical aberration is from the laser beam incident surface of the transparent resin cover sheet 15B to each of the signal layers on the front side. Can be corrected by reducing the frame circumference difference with respect to the tilt due to the warpage of the disk as the distance becomes shorter, and the effect that the signal quality from each signal layer becomes the same even if the signal layers are multilayered is obtained. It is clear that setting the distance from the laser beam incident surface of the transparent resin cover sheet 15B to the innermost signal layer in the stacking direction in advance is an effective method.
[0048]
With the above-described configuration, when the laser beam incident from the transparent cover layer 15 side passes through the semi-transparent metal reflective film of the first signal layer 14 and further passes through the light transmission layer 13 and reaches the second signal layer 12 Focusing on, it is possible to record an information signal on the second signal layer 12 at a very high density, or to reproduce a recorded information signal at a very high density.
[0049]
Focusing on the case where the laser beam incident from the transparent cover layer 15 side is thermally absorbed by the semi-transmissive metal reflective film of the first signal layer 14 during recording or reflected during reproduction, the first signal layer It is possible to record an information signal at an ultra-high density on the recording medium 14, or to reproduce a recorded information signal at an ultra-high density.
[0050]
Therefore, the two-layer type optical disc 10 having an extremely high density is obtained by the above-mentioned upper second signal layer 12 and the above-mentioned lower first signal layer 14.
[0051]
<Manufacturing method of multilayer optical disk>
A method for manufacturing a multilayer optical disk according to the present invention will be described in the order of steps with reference to FIGS.
[0052]
FIGS. 2A and 2B are longitudinal sectional views when a disk substrate and a transfer substrate are manufactured in the method for manufacturing a multilayer optical disk according to the present invention.
FIGS. 3A and 3B are longitudinal cross-sectional views of a method of manufacturing a multilayer optical disk according to the present invention, in which films are formed on the disk substrate side and the transfer substrate side, respectively.
FIGS. 4A and 4B are longitudinal sectional views of a method of manufacturing a multilayer optical disk according to the present invention, in which a disk substrate side and a transfer substrate side are bonded.
FIG. 5 is a longitudinal sectional view of a method of manufacturing a multilayer optical disk according to the present invention, in which the first light transmitting layer is cured by a transparent adhesive with ultraviolet light when the disk substrate side and the transfer substrate side are bonded;
FIG. 6 is a vertical cross-sectional view of the method for manufacturing a multilayer optical disk according to the present invention, in which the transfer substrate is separated from the disk substrate while the transfer substrate is provided with the release layer.
FIG. 7 is a longitudinal sectional view when the outer periphery of the second light transmitting layer adhered to the disk substrate side is cut by a cutter in the method for manufacturing a multilayer optical disk according to the present invention;
FIG. 8 is a vertical cross-sectional view of a method of manufacturing a multilayer optical disk according to the present invention, in which a first signal layer is formed on a second light transmission layer adhered to a disk substrate side;
FIG. 9 is a longitudinal sectional view of a method of manufacturing a multilayer optical disc according to the present invention, in which a transparent cover layer is formed on the first signal layer on the disc substrate side to complete a two-layer optical disc.
[0053]
(First step)
As shown in FIGS. 2A and 2B, in the first step, a thick disk substrate 11 and a transfer substrate 21 are manufactured.
[0054]
First, the thick disk substrate 11 shown in FIG. 2A is formed using a polycarbonate resin or the like so that the diameter of the center hole 11a is 15 mm, the diameter D1 of the outer periphery 11b is 120 mm, and the substrate thickness T1 is approximately 1.1 mm. The unevenness information 11c is preliminarily transferred to one surface of the disk substrate 11 in a state of being etched in an uneven shape by a stamper (not shown) attached in the injection molding machine. A ring-shaped groove 11d is formed concentrically along the center hole 11a.
[0055]
At this time, the concavo-convex information 11c formed on one surface of the disk substrate 11 is spirally or concentrically formed at a track pitch of about 0.32 μm, for example, in a range of 42 mm to 117 mm in diameter. Furthermore, when the unevenness information 11c is formed in a read-only type, the pit depth is in the form of a pit row of about 0.08 μm. On the other hand, when the unevenness information 11c is formed in a recording / reproducing type, the groove depth is increased. It takes the form of a groove having a height of about 0.02 μm and a land extending between the grooves. Further, the ring-shaped groove 11d formed at the innermost peripheral portion on one surface of the disk substrate 11 is formed in a concave shape with a depth of about 0.1 mm over a range of 19 mm to 20 mm in diameter, for example.
[0056]
On the other hand, the transfer substrate 21 shown in FIG. 2B uses a transparent substrate material having a light transmittance of 50% or more, preferably 70% or more with respect to ultraviolet rays. Resin, acrylic resin, amorphous polyolefin resin, styrene resin, quartz glass, soda-lime glass, borosilicate glass and the like are used.
[0057]
The transfer substrate 21 is formed such that the diameter of the center hole 21a is slightly larger than the diameter 15mm of the center hole 11a of the disk substrate 11, and the diameter D2 of the outer periphery 21b is equal to the diameter D1 (= 120 mm), the substrate thickness T2 is formed to be approximately 1.2 mm, and unevenness information is formed on one surface of the transfer substrate 21 by a stamper (not shown) mounted in an injection molding machine. 21c is preliminarily transferred in an unevenly carved state, and a ring-shaped groove 21d is preliminarily formed in the innermost peripheral portion along the center hole 21a.
[0058]
At this time, the diameter D2 of the outer periphery 21b of the transfer substrate 21 is formed to be slightly larger than the diameter D1 of the outer periphery 11b of the disk substrate 11 differently from the related art, so that the transfer substrate 21 is Although the diameter D2 of the outer periphery 21b of the transfer substrate 21 may be 121 mm or more, it is set to 130 mm as described above in this embodiment.
[0059]
The substrate thickness T2 of the transfer substrate 21 may be 0.6 mm or more, but in this embodiment, it is set to approximately 1.2 mm as described above. In particular, increasing the substrate thickness T2 of the transfer substrate 21 to about 1 mm to 2 mm reduces the undulation on one surface of the transfer substrate 21, which is desirable. However, if the substrate thickness T2 of the transfer substrate 21 is increased to 3 mm or more, a large force is required to warp the transfer substrate 21 at the time of peeling, and the efficiency decreases, which is not desirable.
[0060]
Similarly to the disk substrate 11, the unevenness information 21c formed on one surface of the transfer substrate 21 has a spiral or concentric shape with a track pitch of about 0.32 μm over a range of 42 mm to 117 mm in diameter, for example. When formed into a read-only type, it takes the form of a pit row, while when formed into a record / reproduce type, it takes the form of grooves and lands, but as described below. When the unevenness information 21c is shifted to the disk substrate 11 side via the second light transmission layer 13B, the rotation direction of the unevenness information 21c of the transfer substrate 21 is set in advance so as to match the rotation direction of the unevenness information 11c of the disk substrate 11. It is set on the stamper side (not shown).
[0061]
Similarly to the disk substrate 11, the ring-shaped groove 21d formed on one surface of the transfer substrate 21 at the innermost peripheral portion has a depth of about 0.1 mm over a range of 19 mm to 20 mm in diameter, for example. It is formed in a concave shape.
[0062]
(2nd process)
As shown in FIGS. 3A and 3B, in the second step, a film is formed on each of the disk substrate 11 side and the transfer substrate 21 side.
[0063]
First, as shown in FIG. 3A, a second signal layer 12 having a metal reflection film is formed on the unevenness information 11c formed on one surface of the disk substrate 11. At this time, in the case of the read-only type, the second signal layer 12 formed on the unevenness information 11c of the disk substrate 11 has only a metal reflection film such as aluminum formed on the pit row. In the case of the type, a metal reflective film such as aluminum and a recording film in which a silicon oxide transparent film, a tellurium-based phase change recording film, and a silicon oxide transparent film are laminated on the concave groove and the convex land are formed in the above order. are doing. In the case of the recording / reproducing type, since the recording film is a phase change recording type, it is necessary to carry out an initialization process using a laser beam to crystallize the formed tellurium-based phase change recording film. desirable. This is because, after the recording film is formed, the film surface is initialized in a state where the film surface is less likely to be contaminated by dust and dirt in the air, so that a recording film having good recording characteristics can be obtained. Incidentally, the initialization processing of the recording film in the second signal layer 12 can be performed after a fifth step described later is completed.
[0064]
Next, as shown in FIG. 3B, a peeling layer 22 having a thickness of about 5 nm to 50 nm is formed on the unevenness information 21c formed on one surface of the transfer substrate 21 for the purpose of improving peeling. ing.
[0065]
Further, an ultraviolet curable resin is dropped on the release layer 22 to form the second light transmission layer 13B with a thickness of about 10 μm. At this time, the other surface opposite to the one surface of the transfer substrate 21 is mounted on a rotary table (not shown), and while the rotary table is rotated, an ultraviolet curable resin is dropped on the release layer 22 and rotated. The table is rotated at a high speed, and the ultraviolet curing resin is applied to a desired thickness. Then, when the applied ultraviolet curable resin is cured by irradiating it with ultraviolet light, it becomes the second light transmitting layer 13B. It is preferable that the thickness of the second light transmitting layer 13B is about 5 μm to about 10 μm, and in the embodiment, it is about 10 μm. If the thickness of the second light transmitting layer 13B is to be formed to be thinner than 5 μm, the rotary table must be rotated for a long time, resulting in a decrease in production efficiency. On the other hand, if the second light transmitting layer 13B is formed to have a thickness of more than 10 μm, the thickness of the ultraviolet curable resin is different between the inner peripheral portion and the outer peripheral portion of the disk after the ultraviolet curing resin is stretched by the rotating table. Not so desirable.
[0066]
When the second light transmitting layer 13B is formed on the release layer 22, the UV curable resin forms the concave / convex information 13B1 complementary to the concave / convex information 21c of the transfer substrate 21, and the UV curable resin is Since it enters the ring-shaped groove 21d of the transfer substrate 21 formed at the innermost peripheral portion via the release layer 22, a ring-shaped convex portion 13B2 complementary to the ring-shaped groove 21d is formed. Since the ultraviolet curable resin is temporarily dammed by the ring-shaped groove 21d before entering the center hole 21a of the transfer substrate 21, the ultraviolet curable resin does not adhere to the center hole 21a of the transfer substrate 21. After applying the cured resin, there is ample time to cure and the production efficiency is improved. Then, when the second light transmitting layer 13B of the transfer substrate 21 is shifted to the disk substrate 11 side as described later, the above-mentioned ring-shaped convex portion 13B2 can be used as a projection for positioning when forming the cover layer. Also occurs.
[0067]
The above-mentioned peeling layer 22 desirably has good adhesion to the transfer substrate 21. Specifically, gold, chromium, nickel, silicon, silicon carbide or nitride, oxide, or the like is formed into a thin film. By doing so, the film has light transmittance, and is controlled to a thickness through which ultraviolet rays can be transmitted in a third step described later. At this time, if the release layer 22 is too thin, such as 1 nm or 2 nm, the film will not be uniform, and some portions of the film will not be formed, and the second light transmitting layer 13B will be transferred as described in a later step. The peel strength to the second light transmitting layer 13B is different between the part where the peeling layer 22 is formed and the part where the peeling layer 22 is not formed when peeling from the transfer substrate 21. The layer 13B is inconvenient because it does not fulfill its original purpose of correctly transferring to the disk substrate 11 side. Therefore, a thickness of 5 nm or more is desirable to achieve the purpose. On the other hand, when the thickness of the peeling layer 22 is increased to 100 nm, the surface shape of the film after the formation of the second light transmitting layer 13B may not accurately represent the unevenness information 21c of the transfer substrate 21 or may cause The adhesiveness between the transfer substrate 21 and the release layer 22 deteriorates due to the intra-film stress, and the second light transmission layer 13B formed at the time of peeling of the second light transmission layer 13B described in a later step becomes a release layer. Since the entire object 22 is peeled off and the irregularity information 21c of the transfer substrate 21 is correctly transferred to the disk substrate 11 side by the second light transmitting layer 13B, the original purpose is not achieved, so that a uniform film is formed. And the film thickness is preferably as thin as possible. At this time, since the appropriately selected release layer 22 can maintain its effect even in a plurality of transfer and release steps under an appropriately selected thickness, a large number of transfer substrates 21 are prepared. There is no need to perform this, and an effect of improving the manufacturing efficiency also occurs.
[0068]
(3rd step)
As shown in FIGS. 4A and 4B, in the third step, the disk substrate 11 side and the transfer substrate 21 side are bonded with a transparent adhesive using an ultraviolet curable resin.
[0069]
In the third step, the center hole 11a of the disk substrate 11 is fitted to the center spindle 31a of the rotary table 31 as shown in FIG. When placed on the turntable 31, the second signal layer 12 formed on one surface side faces upward. In this state, the turntable 31 is rotated and a transparent adhesive using a transparent ultraviolet curable resin is applied. It is dropped on the second signal layer 12. Then, when the transparent adhesive is uniformly stretched on the second signal layer 12, the turntable 31 is stopped. Thereafter, the transfer layer 21 is formed from above the disk substrate 11 with the release layer 22 formed on one surface of the transfer substrate 21 and the second light transmitting layer 13B formed on the release layer 22 facing downward. The center hole 21a of the substrate 21 is fitted to the center spindle 31a of the rotary table 31, and the second light transmitting layer 13B of the transfer substrate 21 is placed on the second signal layer 12 of the disk substrate 11 by the first light using a transparent adhesive. When bonding is performed via the transmission layer (transparent adhesive layer) 13A, the light transmission layer 13 of the first light transmission layer 13A and the second light transmission layer 13B is integrally formed as shown in FIG. 4B. .
[0070]
Further, when the first light transmitting layer 13A made of the transparent adhesive is formed on the second signal layer 12, the ultraviolet curable resin enters the ring-shaped groove 11d of the disk substrate 11 formed at the innermost peripheral portion, and the disk is formed. Before entering the center hole 11a of the substrate 11, it is temporarily blocked by the ring-shaped groove 11d, so that the ultraviolet curing resin does not adhere to the center hole 11a of the disk substrate 11, and after the application of the ultraviolet curing resin, until the curing. This allows more time and improves production efficiency.
[0071]
At this time, as the transparent adhesive, a urethane acrylate resin, an epoxy acrylate resin, a urethane methacrylate resin, an epoxy methacrylate resin, or the like is used, and a photopolymerization initiator is added to each of these resins so as to be cured by ultraviolet rays.
[0072]
As described above, since the second light transmission layer 13B is formed in advance to about 10 μm, the thickness of the light transmission layer 13 including the first and second light transmission layers 13A and 13B is 20 μm to It is about 30 μm.
[0073]
At this time, as described above, since the outer diameter of the transfer substrate 21 is larger than the outer diameter of the disk substrate 11, the outer peripheral portion of the transfer substrate 21 protrudes from the outer peripheral portion of the disk substrate 11.
[0074]
In addition, the center spindle 31a of the rotary table 31 is arranged so that the center hole 11a of the disk substrate 11 and the center hole 11a of the transfer substrate 21 concentrically coincide with each other. By making the diameter 5 μm to 10 μm smaller than the diameter of 21a, the two substrates 11 and 21 can be overlapped with each other so that the eccentricity is reduced, and the height of the center spindle 31a is attached. The thickness is set slightly higher than the thickness of the two substrates 11 and 21 to be combined.
[0075]
As described above, when the two substrates 11 and 21 are stacked and placed on the turntable 31 in this order, ultraviolet rays can be irradiated through the transfer substrate 21 at the time of curing the adhesive in the fourth step described below.
[0076]
(4th process)
As shown in FIG. 5, in the fourth step, when the disk substrate 11 side and the transfer substrate 21 side are bonded with a transparent adhesive using an ultraviolet curable resin, the first light transmitting layer of the transparent adhesive is irradiated with ultraviolet rays. (Transparent adhesive layer) 13A is cured.
[0077]
In the fourth step, when the disk substrate 11 is placed on the rotary table 31 and the transfer substrate 21 is bonded onto the disk substrate 11 with a transparent adhesive using an ultraviolet curable resin, the rotary table 31 is rotated. By irradiating the ultraviolet lamp 32 from above the transfer substrate 21 with the ultraviolet light from the ultraviolet lamp 32, the transfer substrate 21, the release layer 22 having light transmittance, and the second light transmission layer 13B are separated. Since the light passes through the first light transmitting layer (transparent adhesive layer) 13A sequentially, the first light transmitting layer 13A can be cured by the transparent adhesive. Then, after the transparent adhesive is hardened, the rotation of the turntable 31 is stopped, and the two substrates 11 and 21 bonded to each other are removed from the turntable 31.
[0078]
Although the first light transmitting layer 13A is described as being made of a transparent adhesive using an ultraviolet curable resin, the present invention is not limited to this, and other materials (e.g., a material having a similar adhesive function) may be used. = Other adhesives).
[0079]
Other adhesives suitable for the present invention include transparent double-sided PSA sheets. This transparent double-sided pressure-sensitive adhesive sheet is one in which release sheets are provided on both sides of the pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive sheets do not adhere to each other during handling, which is preferable because the efficiency of the work process increases. Further, since the transparent double-sided pressure-sensitive adhesive sheet has no thickness variation with respect to the sheet thickness, for example, it is easy to set the range of variation to about ± 1 μm with respect to the sheet thickness of 20 μm. It is preferable to accurately control the thickness of the transmission layer 13.
[0080]
At this time, in the case of using a transparent double-sided pressure-sensitive adhesive sheet, first, a pressure-sensitive adhesive sheet from which one side of the release sheet has been peeled off is attached to the second light transmitting layer 13B of the transfer substrate 21 using a rotating roller or the like. Thereafter, the release sheet on the opposite side of the adhesive sheet stuck on the second light transmitting layer 13B of the transfer substrate 21 is peeled off, and the opposite side of the adhesive sheet is placed in the vacuum chamber on the second signal layer 12 of the disk substrate 11. Paste on. At this time, it is preferable that the degree of vacuum in the vacuum chamber is 100 Pa or less, since air bubbles are not involved in the adhesive sheet during bonding. Then, after bonding the second signal layer 12 of the disk substrate 11 and the second light transmitting layer 13B of the transfer substrate 21 via a pressure-sensitive adhesive sheet in a vacuum, in order to remove microbubbles remaining at 10 μm or less, Pressure degassing is performed in an autoclave (= pressurized heater) of 5 atm (5 × 10 ⁵ Pa) or less. By doing so, the microbubbles disappear, and the effect of obtaining the light transmitting layer 13 with a small thickness error occurs.
[0081]
As a material of this transparent pressure-sensitive adhesive sheet, for example, ethylene vinyl acetate copolymer, chlorinated polyolefin, butadiene styrene copolymer and the like have a strong adhesive force. This is preferable because it does not peel off from the light transmitting layer 13B.
[0082]
(Fifth step)
As shown in FIG. 6, in the fifth step, the disc substrate 11 side and the transfer substrate 21 side are bonded with a transparent adhesive using an ultraviolet curable resin, and then the transfer substrate 21 is left with the release layer 22 attached thereto. The transfer substrate 21 is peeled off from the disk substrate 11 side. By doing so, the release layer 22 can be reused many times.
[0083]
Here, as described above, the outer diameter D2 of the outer periphery of the transfer substrate 21 is slightly larger than the outer diameter D1 of the disk substrate 11, and the release layer 22 is formed on the unevenness information 21c of the transfer substrate 21. Therefore, by deflecting the outer peripheral portion of the transfer substrate 21, the second light transmitting layer 13B formed on the release layer 22 of the transfer substrate 21 is surely separated from the outer peripheral portion toward the inner peripheral portion. Can be.
[0084]
When the transfer substrate 21 is peeled from the disk substrate 11 side, the diameter D2 of the outer periphery 21b of the transfer substrate 21 is formed to be larger than the diameter D1 of the outer periphery 11b of the disk substrate 11; The separation performance of the transfer substrate 21 is improved even when the release layer 22 is formed on the surface of the transfer substrate 21 alone. The peeling performance is further improved.
[0085]
When the transfer substrate 21 is peeled off from the disk substrate 11 while the transfer layer 21 is still attached to the transfer substrate 21, the second light transmitting layer 13B on the transfer substrate 21 side becomes the second signal on the disk substrate 11 side. The first light transmitting layer (transparent adhesive layer) 13A is adhered to the layer 12 via the first light transmitting layer (transparent adhesive layer) 13A, and the surface of the second light transmitting layer 13B is complementary to the unevenness information 21c of the transfer substrate 21. The certain concavo-convex information 13B1 and the ring-shaped protrusion 13B2 complementary to the ring-shaped groove 21d of the transfer substrate 21 are reliably transferred and exposed. At this time, the outer peripheral portion of the second light transmitting layer 13 </ b> B shifted from the transfer substrate 21 to the disk substrate 11 protrudes from the outer peripheral portion of the disk substrate 11.
[0086]
In this state, if the recording film (tellurium-based phase change recording film) in the second signal layer 12 formed for recording and reproduction in the second step has not been initialized, the recording film It is preferable that the (tellurium-based phase-change recording film) is subjected to an initialization process using a laser beam to crystallize the formed recording film. When the initialization process is performed in the fifth step, since the light transmitting layer 13 is formed on the recording film, there is an effect of preventing the recording film from being changed by heat at the time of initialization, and good recording characteristics are obtained. Can be obtained.
[0087]
(Sixth step)
As shown in FIG. 7, in the sixth step, the outer peripheral portion of the second light transmission layer 13 </ b> B shifted to the disk substrate 11 side is deleted by the cutter 33 along the outer peripheral diameter of the disk substrate 11.
[0088]
(Seventh step)
As shown in FIG. 8, in the seventh step, the first signal layer 14 having a semi-transmissive metal reflection film is formed on the second light transmission layer 13B shifted to the disk substrate 11 side.
[0089]
In the seventh step, the first signal layer 14 is formed on the unevenness information 13B1 and the ring-shaped protrusion 13B2 of the second light transmitting layer 13B shifted to the disk substrate 11 side. At this time, the first signal layer 14 formed on the concavo-convex information 13B1 has only a semi-transparent metal reflective film such as gold formed on the pit row in the case of the read-only type, while In this case, a semi-transmissive metal reflection film such as gold, a transparent silicon oxide film, a tellurium-based phase change recording film, and a recording film having a transparent silicon oxide film laminated on the concave groove and the convex land are formed in this order. are doing. At this time, the semi-transmissive metal reflection film of the first signal layer 14 has a property of transmitting 30% to 50% of the incident laser beam.
[0090]
In the case of the recording / reproducing type, since the recording film of the first signal layer 14 is a phase change recording type, the recording film is initialized by using a laser beam, and the formed tellurium-based phase change recording film is crystallized. It is desirable to make it. A desirable reason is that in the seventh step, the recording film in the first signal layer 14 is subjected to an initialization process, so that the recording film is initialized before the contamination of the recording film surface by dust and air proceeds after the formation of the recording film. Since the processing can be performed, there is an effect that a recording film having good recording characteristics can be obtained.
[0091]
(Eighth step)
As shown in FIG. 9, in the eighth step, a thin transparent cover layer 15 is formed on the first signal layer 14 formed on the thick disk substrate 11 side.
[0092]
In the eighth step, a thin transparent resin cover sheet 15B having a thickness of about 0.09 μm is prepared in advance. By setting the diameter of the center hole 15B1 to 20 mm, the transparent resin cover sheet 15B has a diameter of 19 mm at the innermost periphery of the second light transmitting layer 13B shifted to the disk substrate 11 side in the center hole 15B1. The ring-shaped protrusions 13B2 projecting over a diameter of 20 mm can be concentrically fitted and aligned, and the outer diameter of the transparent resin cover sheet 15B is set to 119 mm, which is slightly smaller than the outer diameter of the disk substrate 11. are doing. At this time, since the outer diameter of the transparent resin cover sheet 15B is slightly smaller than the outer diameter of the disk substrate 11, even if a hand or the like touches the outer peripheral portion of the transparent resin cover sheet 15B while handling the disk, the transparent resin cover sheet 15B can be prevented from peeling off, and a highly reliable transparent cover layer 15 can be obtained.
[0093]
Then, the surface opposite to the one surface of the thick disk substrate 11 is placed again on a rotating table (not shown), and a transparent signal is formed on the first signal layer 14 on the disk substrate 11 while rotating the rotating table. A transparent adhesive using an ultraviolet curable resin is dropped. Then, when the transparent adhesive is uniformly stretched on the first signal layer 14, the turntable 31 is stopped. Thereafter, the ring-shaped convex portion 13B2 is fitted into the center hole 15B1 of the prepared transparent resin cover sheet 15B, and the transparent resin cover sheet 15B is irradiated with ultraviolet rays via the transparent resin cover layer 15A made of a transparent adhesive. The transparent resin cover layer 15A having a thickness of about 0.01 mm and the transparent resin cover sheet 15B having a thickness of about 0.09 mm are adhered on the first signal layer 14 to form a thin transparent resin cover having a thickness of about 0.1 mm. Layer 15 is formed. Then, the total thickness when the transparent resin cover sheet 15B is adhered to the disk substrate 11 side is approximately 1.2 mm, and the super-high-density two-layer optical disk 10 is completed. At this time, the transparent resin cover sheet 15B side of the transparent cover layer 15 is the laser beam incident side.
[0094]
Note that a method may be used in which the transparent resin cover layer 15 made of a transparent adhesive is repeatedly formed a plurality of times so as to be about 0.1 mm without using the thin transparent resin cover sheet 15B of about 0.09 mm. At this time, if only the liquid UV-curable resin is used to form a film having a thickness of about 0.1 mm and then the UV-curable resin is cured, the ring-shaped convex formed at the innermost peripheral portion described above may be used. Since the height of the portion 13B2 is about 0.1 mm, it is possible to prevent the ultraviolet curable resin from flowing into the center hole 11a of the disk substrate 11 by the ring-shaped convex portion 13B2.
[0095]
The ultra-high-density two-layer type optical disk 10 manufactured in this way has few defects in the unevenness information of the outer peripheral portion of the disk substrate 11 and the first signal layer 14 and has a high quality.
[0096]
<Three-layer type optical disk>
FIG. 10 is a diagram schematically illustrating a three-layer optical disk manufactured by applying the method for manufacturing a multilayer optical disk according to the present invention.
[0097]
The three-layer type optical disc 30 shown in FIG. 10 has a third signal layer 32 having a metal reflective film, a light transmitting layer 33, and a semi-transmitting layer on one surface of a disc substrate 31 having a thickness of approximately 1.1 mm. The second signal layer 34 having a metal reflection film, the light transmission layer 35, and the first signal layer 36 having a semi-transmission metal reflection film are formed in the order described above, and the third, second, and second layers are formed. A thin transparent cover layer 37 having a thickness of approximately 0.1 mm is formed on the outermost first signal layer 36 farthest from the disk substrate 31 in the stacking direction among the one signal layers 32, 34, and 36, The overall thickness is about 1.2 mm, and the transparent cover layer 37 side is the laser beam incident side.
[0098]
At this time, the second signal layer 34 and the first signal layer 36 formed on the disk substrate 31 are formed on separate transfer substrates by applying the above-described method for manufacturing a multilayer optical disk according to the present invention. The film is formed after the respective unevenness information is transferred to the disk substrate 31 side by the second light transmitting layer.
[0099]
Then, an information signal is recorded on the third signal layer 32, the second signal 34, and the first signal layer 36 at an ultra-high density with a laser beam incident from the transparent cover layer 37, or the recorded information signal is super-high-density. Regenerating to density.
[0100]
As described above, when the signal layer is multilayered on the disc substrate side, the second light transmitting layers are formed using a plurality of transfer substrates having different unevenness information, and then each second light transmitting layer is formed. A signal layer is formed on each of the second light transmitting layers by moving to the disk substrate side, and further on the outermost signal layer farthest from the disk substrate in the stacking direction among the multilayered signal layers. If a transparent cover layer having a small thickness is formed, multilayering is possible.
[0101]
<Four-layer optical disk>
FIG. 11 is a diagram schematically illustrating a four-layer optical disk manufactured by applying the method of manufacturing a multilayer optical disk according to the present invention.
[0102]
The four-layer type optical disc 30 shown in FIG. 11 has a second signal layer 42 having a metal reflection film, a light transmission layer 43, and a half on one surface side of a first disc substrate 41 having a thickness of about 0.5 mm. The first signal layer 44 having a transmission metal reflective film is formed in the above-described order, and the second signal layer 42, 44 is farthest from the first disk substrate 41 in the stacking direction. On the outermost first signal layer 44, a thin transparent cover layer 45 having a thickness of about 0.1 mm is formed.
[0103]
On the other hand, a fourth signal layer 47 having a metal reflection film, a light transmission layer 48, and a third signal layer having a semi-transmission metal reflection film are provided on one surface side of a second disc substrate 46 having a thickness of about 0.5 mm. 49 are formed in the above order, and on the outermost third signal layer 49 of the fourth and third signal layers 47, 49, which is farthest from the second disk substrate 46 in the laminating direction. A transparent cover layer 50 having a thickness as small as about 0.1 mm is formed. Then, the other surfaces of the first and second disk substrates 41 and 46, which are opposite to the respective one surfaces, are adhered to each other via a transparent adhesive layer 51 made of a transparent adhesive using an ultraviolet curable resin. The total thickness of the whole is approximately 1.2 mm, and the transparent cover layers 45 and 50 on both sides are on the laser beam incident side.
[0104]
At this time, the first signal layer 44 formed on the first disk substrate 41 and the third signal layer 49 formed on the second disk substrate 46 are formed by the above-described method for manufacturing a multilayer optical disk according to the present invention. Is applied, and the unevenness information formed on the respective separate transfer substrates is transferred to the first disk substrate 41 side and the second disk substrate 46 side by the second light transmitting layer, and then the film is formed.
[0105]
Then, an information signal is recorded at an extremely high density on the second signal layer 42 and the first signal 44 on the first disk substrate 41 side by the laser beam incident from the transparent cover layer 45, or the recorded information signal is overwritten. While reproducing at high density, an information signal is recorded at an ultra-high density on the fourth signal layer 47 and the third signal 49 on the second disk substrate 46 by a laser beam incident from the transparent cover layer 505, or The recorded information signal is reproduced at a very high density.
[0106]
<Method of Manufacturing Multi-Layer Optical Disk of Modification>
In the above-described method for manufacturing a multilayer optical disk, the signal layer 12 is formed on the unevenness information 11c formed on one surface of the disk substrate 11 when forming the signal layer on one surface of the disk substrate. The release layer 22 is formed on the unevenness information 21c formed on one surface of the transfer substrate 21 having a diameter D2 of the outer circumference 21b larger than the diameter D1 of the outer circumference 11b of the disk substrate 11, and the release layer 22 is formed on the release layer 22. A second light transmitting layer 13B made of a transparent ultraviolet curable resin is formed, and further via a first light transmitting layer (transparent adhesive layer) 13A made of a transparent adhesive dropped on the signal layer 12 on the disk substrate 11 side. After the second light transmitting layer 13B on the transfer substrate 21 side is bonded, the transfer substrate 21 is peeled off from the disk substrate 11 with the release layer 22 still attached to the transfer substrate 21. Conversely, the signal layer 12 is formed on the unevenness information 11c formed on one surface of the disk substrate 11, and the first light transmission layer 13A made of a transparent ultraviolet curable resin is formed on the signal layer 12, and The release layer 22 is formed on the unevenness information 21c formed on one surface of the transfer substrate 21 having a diameter D2 of the outer periphery 21b larger than the diameter D1 of the outer periphery 11b of the disk substrate 11; A transparent adhesive is dropped on the first light transmitting layer 13A, and the unevenness information 21c formed on one surface of the transfer substrate 21 on the second light transmitting layer 13B by the transparent adhesive is applied via the release layer 22. After the transfer, the transfer substrate 21 may be deformed so as to be separated from the disk substrate 11 while the transfer substrate 21 has the release layer 22 attached thereto.
[0107]
In other words, although the process for forming the signal layer into multiple layers by partially modifying the method of manufacturing a multilayer optical disk is omitted, the signal layer is formed on the uneven information formed on one surface of the disk substrate. A first step of forming a film, a second step of forming a first light transmission layer of a transparent ultraviolet curable resin on the signal layer on the disk substrate side, and a step of forming an outer diameter larger than the outer diameter of the disk substrate. A third step of forming a release layer on the unevenness information formed on one surface of the transfer substrate, and dropping a transparent adhesive on the first light-transmitting layer on the disk substrate side. A step of transferring the unevenness information formed on one surface of the transfer substrate onto the second light transmitting layer via the release layer, and transferring the transfer substrate to the disk substrate with the release layer attached to the transfer substrate. From the disk substrate side A fifth step of exposing the unevenness information transferred onto the light transmitting layer, a sixth step of forming a signal layer on the unevenness information of the second light transmitting layer on the disk substrate side, and another transfer substrate And the above-described second to sixth steps are repeated to further increase the number of signal layers as necessary on the disk substrate side. This may be the eighth step of forming a thin transparent cover layer on the outer signal layer.
[0108]
In the above description, a method of manufacturing a multilayer optical disk having a disk substrate 11 having a diameter of 12 cm has been described. However, the present invention is not limited to this, and is applicable to a disk substrate 11 having a diameter of 5 cm or 8 cm. Needless to say.
[0109]
【The invention's effect】
In the method for manufacturing a multilayer optical disk according to the present invention described in detail above, according to the first aspect, when the signal layer is multilayered on one surface side of the disk substrate, the signal layer is formed in advance on one surface of the disk substrate. Forming a signal layer on the concavo-convex information, and, while forming a release layer on concavo-convex information formed in advance on one surface of the transfer substrate having a larger outer diameter than the outer diameter of the disk substrate, A second light transmitting layer made of a transparent ultraviolet curable resin is formed on the release layer, and a second light transmitting layer on the transfer substrate side is formed on the signal layer on the disk substrate via a first light transmitting layer made of an adhesive. When the transfer substrate was peeled from the disk substrate side with the release layer attached to the transfer substrate after bonding the transmission layer, the outer diameter of the transfer substrate was formed to be larger than the outer diameter of the disk substrate, in particular. So, film formation on transfer substrate The second light transmitting layer can be reliably peeled from the outer peripheral part toward the inner peripheral part, so that the unevenness information of the transfer substrate can be complemented on the second light transmitting layer transferred to the disk substrate side. The related unevenness information can be reliably transferred without any defect.
[0110]
According to the second aspect of the present invention, when the signal layer is multilayered on one surface side of the disk substrate, the signal layer is formed on the unevenness information formed in advance on one surface of the disk substrate, and the signal layer is formed. Forming a first light transmitting layer of a transparent ultraviolet curable resin on the layer, and forming the first light transmitting layer on the surface of the transfer substrate having a larger outer diameter than the outer diameter of the disk substrate on the unevenness information formed in advance on one surface of the transfer substrate; A release layer was formed, and a transparent adhesive was dropped on the first light transmitting layer on the disk substrate side, and formed on one surface of the transfer substrate on the second light transmitting layer made of the transparent adhesive. After transferring the unevenness information via the release layer, when the transfer substrate is peeled off from the disk substrate side with the release layer attached to the transfer substrate, the diameter of the outer periphery of the transfer substrate is particularly adjusted to the outer circumference of the disk substrate. Because it was formed larger than the diameter of The transfer substrate can be reliably peeled from the outer peripheral portion toward the inner peripheral portion as it is, whereby the unevenness complementary to the unevenness information of the transfer substrate is formed on the second light transmitting layer on the disk substrate side. Information can be reliably transferred without defects.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a two-layer optical disc manufactured by applying a method of manufacturing a multilayer optical disc according to the present invention.
FIGS. 2A and 2B are longitudinal sectional views when a disk substrate and a transfer substrate are respectively manufactured in the method for manufacturing a multilayer optical disk according to the present invention.
3 (a) and 3 (b) are longitudinal sectional views when films are formed on the disk substrate side and the transfer substrate side, respectively, in the method for manufacturing a multilayer optical disk according to the present invention.
FIGS. 4A and 4B are longitudinal cross-sectional views when a disc substrate side and a transfer substrate side are bonded in a method for manufacturing a multilayer optical disc according to the present invention.
FIG. 5 is a longitudinal sectional view of a method of manufacturing a multilayer optical disk according to the present invention, in which the first light transmitting layer is cured with a transparent adhesive by ultraviolet rays when the disk substrate side and the transfer substrate side are bonded.
FIG. 6 is a vertical cross-sectional view when the transfer substrate is peeled off from the disk substrate side with the release layer attached to the transfer substrate in the method for manufacturing a multilayer optical disk according to the present invention.
FIG. 7 is a longitudinal sectional view when the outer periphery of the second light transmitting layer adhered to the disk substrate side is cut by a cutter in the method for manufacturing a multilayer optical disk according to the present invention.
FIG. 8 is a longitudinal sectional view when a first signal layer is formed on a second light transmitting layer adhered to the disk substrate side in the method for manufacturing a multilayer optical disk according to the present invention.
FIG. 9 is a longitudinal sectional view of a method of manufacturing a multilayer optical disk according to the present invention, in which a transparent cover layer is formed on the first signal layer on the disk substrate side to complete a two-layer optical disk.
FIG. 10 is a diagram schematically illustrating a three-layer optical disc manufactured by applying the method of manufacturing a multilayer optical disc according to the present invention.
FIG. 11 is a diagram schematically illustrating a four-layer optical disk manufactured by applying the method of manufacturing a multilayer optical disk according to the present invention.
FIG. 12 is a diagram schematically illustrating an ultra-high-density two-layer optical disc in a conventional example.
13 (a) to 13 (e) are views schematically showing a manufacturing process for manufacturing an ultra-high-density two-layer type optical disc in a conventional example.
[Explanation of symbols]
10 ... two-layer type optical disc,
11: disk substrate, 11a: center hole, 11b: outer periphery, 11c: unevenness information,
11d: ring-shaped groove,
12 ... second signal layer,
13: light transmitting layer, 13A, 13B: first and second light transmitting layers,
13A1... Unevenness information, 13A2.
13B1 ... unevenness information, 13B2 ... ring-shaped convex part,
14 ... first signal layer,
15: transparent cover layer, 15A: transparent adhesive layer, 15B: transparent resin cover sheet, 21: transfer substrate, 21a: center hole, 21b: outer periphery, 21c: unevenness information,
21d: ring-shaped groove,
30 ... three-layer type optical disc,
31: disk substrate, 32: third signal layer, 33: light transmitting layer,
34, a second signal layer, 35, a light transmitting layer, 36, a first signal layer, 37, a transparent cover layer,
40 ... 4-layer type optical disc,
41: disk substrate, 42: second signal layer, 43: light transmitting layer, 44: first signal layer, 45: transparent cover layer,
46: disk substrate, 47: fourth signal layer, 48: light transmitting layer, 49: third signal layer, 50: transparent cover layer, 51: adhesive layer.

Claims (2)

A signal layer is formed in multiple layers on one surface side of a thick disk substrate, and a thickness is formed on the outermost signal layer farthest from the disk substrate in the stacking direction among the multilayered signal layers. Forming a thin transparent cover layer, a method for manufacturing a multilayer optical disc configured to allow a laser beam to be incident from the transparent cover layer side toward the signal layer of each layer,
A first step of forming a signal layer on unevenness information previously formed on one surface of the disk substrate;
A second step of forming a release layer on unevenness information formed in advance on one surface of the transfer substrate having an outer diameter larger than the outer diameter of the disk substrate;
A third step of forming a second light transmission layer made of a transparent ultraviolet curable resin on the release layer on the transfer substrate side;
A fourth step of bonding the second light transmitting layer on the transfer substrate side to the signal layer on the disk substrate side via a first light transmitting layer made of an adhesive;
The transfer substrate is peeled off from the disk substrate while the transfer layer is still attached to the transfer substrate, and the unevenness information on the transfer substrate side is formed on the second light transmitting layer shifted to the disk substrate side. A fifth step of exposing the transferred unevenness information,
A sixth step of forming a signal layer on the unevenness information of the second light transmitting layer shifted to the disk substrate side;
A seventh step of repeating the above-described second to sixth steps using another transfer substrate to further multiply a signal layer on the disk substrate side as necessary;
An eighth step of forming the thin transparent cover layer on the outermost signal layer of the signal layers multilayered on the disk substrate side. . A signal layer is formed in multiple layers on one surface side of a thick disk substrate, and a thickness is formed on the outermost signal layer farthest from the disk substrate in the stacking direction among the multilayered signal layers. Forming a thin transparent cover layer, a method for manufacturing a multilayer optical disc configured to allow a laser beam to be incident from the transparent cover layer side toward the signal layer of each layer,
A first step of forming a signal layer on unevenness information previously formed on one surface of the disk substrate;
A second step of forming a first light transmitting layer of a transparent ultraviolet curable resin on the signal layer on the disk substrate side;
A third step of forming a release layer on unevenness information formed in advance on one surface of the transfer substrate having an outer diameter larger than the outer diameter of the disk substrate;
A transparent adhesive is dropped on the first light transmitting layer on the disk substrate side, and the uneven information formed on one surface of the transfer substrate on the second light transmitting layer by the transparent adhesive is peeled off. A fourth step of transferring through the layer;
Fifth, exposing the transfer substrate from the disk substrate side while exposing the transfer substrate with the release layer attached thereto, exposing the unevenness information transferred onto the second light transmitting layer on the disk substrate side. Steps and
A sixth step of forming a signal layer on the unevenness information of the second light transmitting layer on the disk substrate side;
A seventh step of repeating the above-described second to sixth steps using another transfer substrate to further multiply a signal layer on the disk substrate side as necessary;
An eighth step of forming the thin transparent cover layer on the outermost signal layer of the signal layers multilayered on the disk substrate side. .

Images