JP4174151B2 - optical disk - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disc, relates to the optical disc to form a coating film such as protective film, in particular by spin coating onto the substrate.
[0002]
[Prior art]
In recent years, research on a large-capacity optical information recording / reproducing system has been promoted toward a recording device or the like replacing an external storage device of a computer or a home video tape recorder. As an information recording medium for this recording / reproducing system, fine irregularities corresponding to information are provided on the surface of a disk-shaped transparent substrate, and various functional films such as a recording film and a reflective film are laminated on the transparent substrate. There is known an optical disc on which a protective film is formed for protecting the liquid from moisture, oxygen, dust and the like in the atmosphere.
[0003]
As a method for applying a photocurable resin onto the optical disk substrate, the optical disk substrate is attached to a turntable, and a liquid photocurable resin is dropped and supplied in an annular shape to the inner periphery of the optical disk substrate. The spin coat method in which a protective film is formed by casting a photocurable resin by casting it outward in the radial direction by centrifugal force is commonly used because of high production efficiency and low production cost.
[0004]
FIG. 4 is a cross-sectional view of a conventional optical disk in which a protective film 33 is formed on an optical disk substrate 31 by spin coating. In the figure, reference numeral 31a denotes a central hole portion of the substrate 31, 31b denotes one main surface of the substrate 31, and 32 denotes a mark of a claw for pressing the inner peripheral stamper. As shown in the figure, a protective film 33 is formed from the inner peripheral portion side to the outer peripheral portion side of one main surface 31b of the substrate 31.
[0005]
[Problems to be solved by the invention]
However, when the protective film 33 is formed by this spin coating method, the inner peripheral side of the optical disk substrate 31 is thinner than the outer peripheral side as shown in FIG. 4, and the thickness of the protective film 33 is not uniform in the radial direction. As described above, when the thickness of the protective film 33 is not uniform, there is a problem in that the condensed spot causes aberration during recording / reproduction by the optical pickup, and an error occurs due to deterioration of the recording / reproduction signal.
[0006]
An object of the present invention is to provide an optical disc capable of solving such drawbacks of the prior art and forming a coating film with a uniform film thickness.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an optical disc in which a coating such as a protective film is formed on an optical disc substrate by spin coating, and an annular protrusion adjacent to the inner peripheral portion of the coating is formed on the optical disc substrate. It is characterized by providing.
[0010]
The present invention is configured as described above, and when the coating film is formed by spin coating, since the optical disk substrate is provided with a protrusion, the coating film constituent material is not evenly distributed on the outer peripheral side of the optical disk substrate and is substantially uniform. It can be cast to form a coating film having a uniform thickness as a whole.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an optical disk according to an embodiment, which is intended for a phase change optical disk or an optical-magnetic disk, for example.
[0013]
An optical disk substrate 1 according to the present embodiment is a disc-shaped transparent substrate having a circular hole 1a into which a spindle portion of a motor serving as a rotation shaft is inserted at the center, and is used as an information signal on one main surface 1b of the substrate 1. Corresponding fine irregularities (not shown) are formed. As the material of the substrate 1, plastic materials such as polycarbonate resin and polyolefin resin are used. Various functional films (not shown) such as a recording film and a reflective film are laminated on one main surface 1b of the substrate 1, and further, a protective film for protecting the various functional films from moisture and oxygen in the atmosphere. 3 is formed.
[0014]
At this time, an annular protrusion 2 is previously formed integrally with the substrate 1 at a position slightly outside in the radial direction from the hole 1a on the substrate 1 and inside a recording area (not shown) of the substrate 1; The protrusion 2 has a trapezoidal cross-sectional shape in which the inner peripheral surface and the outer peripheral surface are inclined to each other, and the protective film 3 is formed starting from the outer peripheral surface. Therefore, in the completed optical disc, the inner peripheral portion of the protective film 3 is adjacent to the outer peripheral surface of the protrusion 2. For example, when the outer diameter of the substrate 1 is 120 mm, the inner diameter of the hole 1a is 15 mm, and the thickness 3a of the protective film 3 is 0.1 mm, the thickness 2a of the protrusion 2 is 0.1 mm or more, that is, the protrusion 2 The thickness 2a is preferably equal to or greater than the thickness 3a of the protective film 3. In the present embodiment, as shown in FIG. 1, the thickness 2a of the protrusion 2 is designed to be slightly higher than the thickness 3a of the protective film 3 (thickness 2a> thickness 3a).
[0015]
2A and 2B are explanatory views showing a method for forming the protective film 3. The turntable 12 can be rotated by a rotation mechanism (not shown) such as a motor, and the rotation speed and rotation time are controlled. The substrate 1 is mounted on the turntable 12 by a detachable robot and fixed by an air suction mechanism (both not shown). First, the substrate 1 is rotated at a low speed by the turntable 12, and the photocurable resin 4 having fluidity is dropped from the nozzle 11 over about one turn while being in contact with the outer peripheral surface 2b of the protrusion 2 as shown in FIG. The As the photocurable resin 4, for example, an acrylic ultraviolet curable resin or the like is used.
[0016]
Next, the other portions are masked so that only the photocurable resin 4 outside the outer peripheral surface 2b is exposed, and the photocurable resin 4 is exposed and precured. Then, by rotating the substrate 1 at a high speed, the precured photocurable resin 4 is thinly cast toward the outer peripheral side of the substrate 1 by centrifugal force [see FIG.
[0017]
Since the photocurable resin 4 rotates and stretches while adsorbing to the substrate 1 due to the presence of the protrusions 2 and the surface tension of the precuring and the photocurable resin 4 itself during this high-speed rotation, it extends from the innermost periphery to the outer periphery. Uniform film thickness. Next, the entire surface of the coating is uniformly irradiated with light for exposure and cured to form the protective film 3.
[0018]
FIG. 3 is a cross-sectional view of the main part of a mold 20 for injection molding the substrate 1, and the configuration and the method for manufacturing the substrate 1 will be described. The substrate 1 is formed by injecting and filling molten resin such as polycarbonate resin into the cavity 301 of the mold 20. The stamper 22 is fixed to the fixed-side mirror member 25 by an inner periphery stamper retainer 21, a stamper inner periphery suction air circuit 24, and an outer periphery stamper retainer 23. Concavities and convexities formed as information on the surface of the stamper 22 are transferred to one main surface 1 b of the substrate 1 by injection molding of the substrate 1.
[0019]
The cab ring 27 is movably incorporated in the movable mirror surface member 26 to form the outer peripheral portion of the substrate 1. A cut punch 29 for punching out the hole 1a of the substrate 1 and an ejector 28 for taking out the substrate are provided at the center of the movable mirror member 26.
[0020]
Since the mold 20 integrally molds the protrusion 2 of the substrate 1, an annular recess 21 a is formed in the inner peripheral stamper presser 21. Reference numeral 25 a denotes a central portion of the fixed-side mirror member 25.
[0021]
Although the case where the protective film is formed has been described in the above embodiment, the present invention is not limited to this. For example, when forming another coating film such as a recording layer containing an organic dye such as a cyanine dye. Is also applicable.
[0022]
In the above-described embodiment, the protrusion is integrally formed with the substrate. However, it is also possible to insert-mold an annular body or a cylindrical body made of metal or the like into the base to form a protrusion protruding from the substrate. However, it is desirable to select a material having good wettability with respect to the material for forming the protective film or the recording layer to be spin-coated as the material for forming the protrusion.
[0023]
In the above-described embodiment, the case where a coating film is formed in one layer has been described. However, the coating film may be formed in two or more layers. In this case, the height of the protruding portion is designed to be greater than the total thickness of the coating films to be laminated. Good.
[0024]
【The invention's effect】
The present invention is configured as described above, and when the coating film is formed by spin coating, since the optical disk substrate is provided with a protrusion, the coating film constituent material is not evenly distributed on the outer peripheral side of the optical disk substrate and is substantially uniform. It can be cast to form a coating film having a uniform thickness as a whole.
[0026]
From the above, the present invention can provide an optical disc having a uniform quality and having a uniform thickness as a whole, and having a stable quality.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an optical disc according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a protective film forming method according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view of a main part of an injection mold for a substrate according to an embodiment of the present invention.
FIG. 4 is a cross-sectional view of a conventional optical disc.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical disk board | substrate 1a Circular hole 1b One main surface 2 of board | substrate 1 Projection part 2a Thickness of projection part 3 Protective film 3a Thickness of protective film 4 Photocurable resin 11 Nozzle 12 Turntable 20 Injection mold 21 Inside Peripheral stamper holder 21a Concave portion 22 of inner stamper holder 21 Stamper 23 Outer stamper holder 24 Stamper inner suction air circuit 25 Fixed side mirror member 25a Fixed side mirror member central part 26 Movable side mirror member 27 Cavity 28 Ejector 301 Cavity

Claims (4)

  An optical disk in which a coating film is formed on an optical disk substrate by spin coating, wherein the optical disk substrate is provided with an annular protrusion adjacent to the inner periphery of the coating film.   2. The optical disk according to claim 1, wherein the height of the protrusion is equal to or greater than the film thickness of the coating film.   2. The optical disc according to claim 1, wherein the protrusion is formed integrally with the optical disc substrate.   2. The optical disk according to claim 1, wherein the coating film is a protective film.

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