JP2004178751A - Optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk having a uniform protective layer, in the optical disk wherein recording and/or reproduction of an information signal are performed by irradiating an information signal part with a laser beam from the protective layer side. <P>SOLUTION: The optical disk is so constituted that the information signal part 2 which is so constituted that the information signal can be recorded and/or reproduced by irradiating the laser beam, and the protective layer 3 covering at least the information signal part 2 are successively laminated on a principal surface of a substrate 1 having a center hole 1a. The substrate 1 has a circular protrusion 1b with the center hole 1a as the center between the center hole 1a and a clamping region. A resin dropped between the protrusion 1b and the clamping region is applied on at least the information signal part 2 by a spin coat method, and a light transmissible sheet 3b is stuck to the substrate 1 by using the applied resin to form the protective layer 3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical disc, and more particularly to an optical disc suitable for application to an optical disc on which information signals are recorded and / or reproduced by irradiating a laser beam from a side provided with a protective layer for protecting an information signal portion. It is.
[0002]
[Prior art]
In recent years, optical disks have been required to have higher recording densities. Therefore, a next-generation high-density optical disk having a protective layer having a thickness of 0.1 mm on a reflective film or a recording layer provided on a substrate has been proposed. In this optical disc, blue-violet laser light is condensed by an objective lens having a high NA (for example, 0.85), and the condensed laser light is irradiated from the protective layer side to a reflective film or a recording layer. Recording and / or reproduction of the information signal is performed.
[0003]
The following method has been proposed as a method for manufacturing this next-generation high-density optical disk.
(1) A sheet in which a pressure-sensitive adhesive is uniformly applied (for example, 20 μm in thickness) to one surface of a light-transmitting sheet (for example, 80 μm in thickness) having a controlled thickness is produced, and this sheet is punched into an annular shape. And a method of manufacturing an optical disk in which the substrate is superimposed on a substrate and bonded by applying pressure (hereinafter, referred to as a first optical disk manufacturing method).
(2) A method for manufacturing an optical disk in which an ultraviolet-curable resin is applied by spin coating on a reflective film or a recording layer provided on a substrate, and a light-transmitting sheet is attached to the substrate with the ultraviolet-curable resin (hereinafter referred to as a second optical disk). This is referred to as an optical disk manufacturing method).
[0004]
Meanwhile, in an optical disc such as a CD (Compact Disc) or a DVD (Digital Versatile Disc or Digital Video Disc), the optical discs are adjacent to each other between the clamping area and the reflective film or the recording layer when the optical discs are stacked and stocked in the manufacturing process. Protrusions are provided to prevent the optical disks from contacting each other (for example, see Patent Documents 1 and 2). The projection is provided on a surface to be irradiated with the laser beam (hereinafter, referred to as a reading surface). If projections are provided on the opposite surface to be printed, the projections may cause bleeding of printing, poor printing riding, and breakage of the screen.Therefore, projections are provided on the reading surface side. ing.
[0005]
[Patent Document 1]
JP-A-10-106044
[Patent Document 2]
JP 2000-293902 A
Therefore, it has been considered to provide such projections on next-generation high-density optical disks. However, in the next-generation high-density optical disk, unlike an optical disk such as a CD or a DVD, printing is performed on the substrate side instead of the protective layer side. This is because, as described above, in the next-generation high-density optical disk, recording and / or reproduction of an information signal is performed by irradiating a laser beam from the side on which the protective layer is formed.
[0008]
Therefore, it is conceivable that a projection is provided on the side on which the protective layer is formed. As a method of manufacturing the optical disk, use of the above-described method of manufacturing the second optical disk has been studied. Here, the second optical disk manufacturing method is used because the first optical disk manufacturing method has the following problems.
[0009]
(A) A light-transmitting sheet coated with a pressure-sensitive adhesive is generally delivered as a roll having a length of 100 m or more. Therefore, it is required to control the thickness over a length of 100 m or more, but it is difficult to uniformly apply a pressure-sensitive adhesive to one surface of the light-transmitting sheet with such a length. is there. For this reason, it is costly to manufacture a light-transmitting sheet on which a pressure-sensitive adhesive is uniformly applied, which leads to an increase in the manufacturing cost of an optical disk.
(B) When bonding the light transmissive sheet to the substrate, bubbles are mixed between the light transmissive sheet and the substrate.
[0010]
[Problems to be solved by the invention]
However, using the above-described second optical disc manufacturing method, a next-generation high-density optical disc in which protrusions are provided between a clamping area and a reflective film or a recording layer, as in an optical disc such as a CD or a DVD. When an optical disc is manufactured, there is a problem that the thickness of the adhesive layer becomes uneven as described below.
[0011]
a) When the ultraviolet curable resin is dropped on the outer peripheral side from the protrusion, the thickness of the adhesive layer in a section (for example, a section of 10 mm) at a predetermined distance from the drop position of the ultraviolet curable resin to the outer peripheral side becomes uneven.
b) When the ultraviolet curable resin is dropped on the inner peripheral side from the protrusion, radial uneven coating is generated on the adhesive layer by the protrusion.
[0012]
Therefore, an object of the present invention is to provide an optical disc having a uniform protective layer in a next-generation high-density optical disc having a projection for preventing adjacent optical discs from contacting each other when optical discs are stacked and stocked. It is in.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the first invention of the present application discloses a method in which one main surface of a substrate having an opening in a central portion includes:
An information signal unit configured to be able to record and / or reproduce an information signal by irradiating a laser beam;
A protective layer covering at least the information signal portion is sequentially laminated,
In an optical disc on which information signals are recorded and / or reproduced by irradiating a laser beam to the information signal portion from the protective layer side,
The substrate has, between the opening and the clamping region, an annular protrusion centered on the opening or three or more protrusions on the circumference centered on the opening, and the protective layer has the protrusion and the clamping region. An optical disc characterized by being formed by applying at least an information signal portion with a resin dropped during the spin coating method, and bonding a light transmitting sheet to a substrate with the applied resin. .
[0014]
According to the present invention, since the substrate has between the opening and the clamping region an annular projection centering on the opening or three or more projections on a circumference centering on the opening, the projection and the clamping are provided. A resin for attaching the sheet to the substrate can be dropped between the ping region and the ping region.
[0015]
The second invention of the present application is directed to one principal surface of a substrate having an opening in a central portion,
An information signal unit configured to be able to record and / or reproduce an information signal by irradiating a laser beam;
A protective layer covering at least the information signal portion is sequentially laminated,
In an optical disc on which information signals are recorded and / or reproduced by irradiating a laser beam to the information signal portion from the protective layer side,
The substrate has, between the opening and the clamping region, an annular projection centering on the opening or three or more projections on a circumference centering on the opening,
An optical disc, wherein the protective layer is formed by applying a resin dropped between the protrusion and the clamping region on at least the information signal portion by a spin coating method and curing the resin.
[0016]
According to the present invention, since the substrate has between the opening and the clamping region an annular projection centering on the opening or three or more projections on a circumference centering on the opening, the projection and the clamping are provided. A resin for forming a protective layer between the ping region and the ping region can be dropped.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of an optical disk according to an embodiment of the present invention. As shown in FIG. 1, the optical disc has an annular shape in which a center hole 1a is formed in the center. An annular projection 1b centered on the center hole 1a is provided on one main surface of the optical disk on which the laser beam is irradiated. In the vicinity of the center hole 1a of the optical disk, a clamping area (not shown) for mounting the optical disk on the spindle motor is set.
[0018]
Further, as shown in FIG. 1, the optical disc according to the embodiment is configured by sequentially laminating an information signal section 2 and a protective layer 3 on one main surface of a substrate 1. The optical disc according to this embodiment is an optical disc (for example, a Blu-ray Disc) on which information signals are recorded and / or reproduced by irradiating the information signal unit 2 with a laser beam from the protective layer 3 side. is there.
[0019]
FIG. 2 shows an example of the size of each part of the optical disc according to the embodiment of the present invention. The diameter (diameter) of the optical disk is selected to be, for example, 120 mm. The diameter (diameter) of the center hole 1a of the optical disc is selected to be, for example, 15 mm. The thickness of the optical disk is selected to be, for example, 1.2 mm. The thickness of the substrate 1 is selected to be, for example, 1.1 mm. The thickness of the protective layer 3 is selected to be, for example, 0.1 mm. The height of the protrusion 1b is selected to be 0.05 mm to 0.2 mm, for example, 0.1 mm based on the surface of the optical disk on which the laser beam is irradiated. The clamping area is, for example, an area defined by a diameter of 23 mm or more and 33 mm or less.
[0020]
The substrate 1 has an annular shape, and has irregularities formed on one main surface. As a material of the substrate 1, for example, polycarbonate (PC), acrylic, or polyolefin is used.
[0021]
An annular projection 1b centering on the center hole 1a is formed on the surface of the substrate 1 on which the information signal portion 2 is formed. The protrusions 1b are for preventing adjacent disks from contacting each other when the optical disks are stacked, and between the center hole 1a and the clamping area, for example, a diameter of 15 mm to 23 mm, preferably a diameter of 15 mm to 23 mm. It is formed in an area of 18 mm to 22 mm. Note that the shape of the protrusion 1b is not limited to this example, and three or more protrusions may be formed on a circumference centered on the center hole 1a.
[0022]
The information signal section 2 is for recording and / or reproducing information signals by irradiating a laser beam through the protective layer 3. Specifically, when the optical disc is of a read-only type, a reflective film made of metal is selected as the information signal portion 2, and when the optical disc is of a write-once type, at least a film made of an organic dye material is provided. When the recording layer is selected and is of a rewritable type, a recording layer having at least a film made of a magneto-optical material or a film made of a phase change material is selected.
[0023]
The protective layer 3 is configured by sequentially laminating an adhesive layer 3a and a light transmitting sheet 3b on the information signal section 2. The adhesive layer 3a is formed by curing an ultraviolet curable resin applied on the information signal section 2. The thickness of the adhesive layer 3a is selected to be, for example, 20 μm. The material of the adhesive layer 3a is not limited to an ultraviolet-curable resin, and may be a resin other than an ultraviolet-curable resin.
[0024]
The light transmissive sheet 3b has a planar annular shape as in the substrate 1. As the material of the light-transmitting sheet 3b, a material that satisfies at least optical characteristics capable of transmitting laser light used for recording and / or reproducing information signals is selected, and for example, polycarbonate or polyolefin is selected. The thickness of the light transmitting sheet 3b is selected to be, for example, 80 μm. The thickness of the light transmitting sheet 3b is determined in consideration of the wavelength of the laser beam used for recording and / or reproducing the information signal and the desired thickness of the protective layer 3.
[0025]
Next, a manufacturing process of the optical disc according to the embodiment of the present invention will be described with reference to FIG. First, as shown in FIG. 3A, after a substrate 1 having one main surface formed with concavities and convexities is formed by injection molding, an information signal portion 2 is formed on one main surface having concavities and convexities. For example, when the optical disk is a read-only type, a reflection film is formed on one main surface of the substrate 1 by sputtering. The projection 1b is formed, for example, when the substrate 1 is molded by an injection molding device (not shown). Specifically, the protrusion 1b is formed by a groove formed in the mold insert. The mold nest is provided inside the inner diameter hole of the stamper on the stamper mounting side.
[0026]
Next, as shown in FIG. 3B, the nozzle 10 is moved so that the ultraviolet curable resin is dropped between the projection 1b and the clamping area (for example, at a position having a radius of 11 mm). Then, the ultraviolet curable resin 11 is dropped from the nozzle 10 while rotating the substrate 1. As a result, the ultraviolet curable resin 11 is applied between the protrusion 1b and the clamping area in an annular shape centering on the center hole 1a.
[0027]
Next, as shown in FIG. 3C, the substrate 1 is rotated at a high speed. As a result, the ultraviolet curable resin 11 applied between the protrusion 1b and the clamping region spreads from the inner peripheral side to the outer peripheral side, and the ultraviolet curable resin 11 is uniformly applied on the information signal unit 2.
[0028]
Finally, as shown in FIG. 3D, the light-transmitting sheet 3b is bonded to the substrate 1 with the ultraviolet-curing resin 11 uniformly applied on the information signal portion 2, and the ultraviolet rays are irradiated on the light-transmitting sheet 3b side, for example. Irradiates the ultraviolet curable resin. Thus, a desired protective layer 3 is formed on the substrate 1.
[0029]
The inventor measured the thickness of the protective layer 3 of the optical disk according to the embodiment manufactured as described above and the thickness of the protective layer of the conventional optical disk, and compared the measurement results. Here, in the optical disc according to the embodiment, the dropping position of the ultraviolet curable resin for forming the adhesive layer 3a is a position with a radius of 11 mm, and in the conventional optical disc, the dropping of the ultraviolet curable resin for forming the adhesive layer is performed. The position is a position with a radius of 20 mm.
[0030]
FIG. 4 shows the measurement results of the thickness of the protective layer of the conventional optical disk. FIG. 5 shows a measurement result of the thickness of the protective layer 3 using the optical disc according to the embodiment of the present invention. As shown in FIG. 4, in the conventional optical disk, the thickness of the protective layer becomes non-uniform in the range of 10 mm from the dropping position toward the outer peripheral side, and in the region of 20 mm or more from the dropping position toward the outer peripheral side. Is gradually increased. On the other hand, from FIG. 5, in the optical disk according to this embodiment, the thickness of the protective layer monotonically increases in the range of about 5 mm from the dropping position toward the outer circumference, and the area of 5 mm or more from the dropping position toward the outer circumference. It can be seen that the thickness of the protective layer becomes substantially uniform.
[0031]
According to the embodiment of the present invention, the following effects can be obtained.
Since the substrate 1 has an annular protrusion 1b centered on the center hole 1a between the center hole 1a and the clamping region, an ultraviolet curable resin serving as an adhesive layer 3a between the protrusion 1b and the clamping region. Can be dropped. Therefore, the uniformity of the protective layer 3 on the information signal section 2 can be improved as compared with a conventional optical disc.
[0032]
In addition, it is possible to prevent a plurality of pieces from being taken out from the pole after stocking. Further, since the projection 1b is provided on the reading surface of the optical disk, it is possible to prevent adjacent optical disks from contacting each other when the optical disks are overlaid.
[0033]
As described above, one embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.
[0034]
For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as needed.
[0035]
Further, the present invention may be applied to an optical disk in which a protective layer 3 is formed by applying an ultraviolet curable resin onto at least the information signal section 2 by spin coating and curing the resin.
[0036]
【The invention's effect】
As described above, according to the present invention, the resin for bonding the sheet to the substrate can be dropped between the protrusion and the clamping area. Therefore, the uniformity of the protective layer can be improved as compared with the conventional optical disc.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a configuration of an optical disc according to an embodiment of the present invention.
FIG. 2 is a sectional view showing an example of the size of each part of the optical disc according to one embodiment of the present invention.
FIG. 3 is a sectional view showing a manufacturing process of the optical disc according to the embodiment of the present invention.
FIG. 4 is a graph showing a measurement result of a film thickness of a protective layer of the optical disc according to the embodiment of the present invention.
FIG. 5 is a graph showing a measurement result of a thickness of a protective layer of a conventional optical disc.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate, 1a ... Center hole, 1b ... Protrusion, 2 ... Information signal part, 3 ... Protective layer, 3a ... Adhesive layer, 3b ... Light transmissive sheet, 10 nozzle, 11 ultraviolet curable resin

Claims (4)

On one main surface of the substrate having an opening in the center,
An information signal unit configured to be able to record and / or reproduce an information signal by irradiating a laser beam;
A protection layer covering at least the information signal portion is sequentially laminated,
An optical disc in which recording and / or reproduction of an information signal is performed by irradiating the information signal portion with a laser beam from the protective layer side,
The substrate has, between the opening and the clamping region, an annular protrusion centered on the opening or three or more protrusions on a circumference centered on the opening, and the protective layer has the protrusion and the protrusion. It is formed by applying a resin dropped between the clamping area and at least the information signal portion by a spin coating method, and bonding a light transmitting sheet to the substrate with the applied resin. An optical disc characterized by the following. 2. The optical disk according to claim 1, wherein the protrusion is formed in a range of 15 mm to 23 mm in diameter. On one main surface of the substrate having an opening in the center,
An information signal unit configured to be able to record and / or reproduce an information signal by irradiating a laser beam;
A protection layer covering at least the information signal portion is sequentially laminated,
An optical disc in which recording and / or reproduction of an information signal is performed by irradiating the information signal portion with a laser beam from the protective layer side,
The substrate has between the opening and the clamping region an annular projection centering on the opening or three or more projections on a circumference centering on the opening,
An optical disc, wherein the protective layer is formed by applying a resin dropped between the protrusion and the clamping region on at least the information signal portion by a spin coating method and curing the resin. 4. The optical disk according to claim 3, wherein the protrusion is formed in a range from 15 mm to 23 mm in diameter.

Images