JP3271779B2 - Optical disc and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk and a method for manufacturing the same. INDUSTRIAL APPLICABILITY The present invention can be effectively used for an optical disc having a light absorbing layer containing a dye as a main component, particularly, a write-once optical compact disc.

[0002]

2. Description of the Related Art A light absorbing layer containing a dye as a main component is provided directly or via an underlayer on a disk substrate which is formed of a molding resin and has information pits and / or guide grooves formed on the surface side in advance. In an optical disk in which a metal reflective film is further provided on the light absorbing layer, the disk substrate is most excellent in mass productivity when formed by injection molding using a molding resin as a material and a stamper. In addition, spin coating is suitable for forming the light absorbing layer.

[0003] In an optical disk in which a light absorption layer is provided by spin coating on a disk substrate formed by injection molding as described above, recording and reproducing characteristics are likely to be different between the inner and outer peripheral sides of the optical disk. There was a problem.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an optical disk having uniform characteristics in a recording area and a method of manufacturing the same.

[0005]

As shown in FIG. 1 (b), an optical disk according to the present invention has a structure in which a light absorbing layer 12 is provided on the surface side of a disk substrate 10, and the light absorbing layer 12 is further provided on the light absorbing layer 12.
A structure in which a metal reflective film 14 having a uniform thickness is provided "is defined as a basic structure (claim 1). The disk substrate 10 is made of a molding resin, the light absorbing layer 12 contains a pigment as a main component ,
Ru is formed on the court. On the surface side (the side on which the light absorbing layer 12 is formed) of the disk substrate 10, "information pits and / or guide grooves" are formed in advance. Light absorbing layer 12
May be formed directly on the disk substrate 10, but FIG.
As shown in (c), the disk substrate 10 and the light absorbing layer 12
And an underlayer 11 having a uniform thickness.
Further, the undercoat layer 13 having a uniform thickness can be interposed between the metal reflection film 14 and the light absorption layer 12.

Further, as shown in FIG. 1D, a protective film 14 having a uniform thickness can be provided on the metal reflective film 14 (claim 2).

A feature common to the optical disks according to the first and second aspects is that, as shown in FIG.
The depth of the information pits and / or guide grooves 10A formed on the surface side of the light absorbing layer 12 gradually increases from the inner circumference side to the outer circumference side. The depth of the concave portion 12A formed corresponding to the guide groove 10A is substantially uniform. "

According to a third aspect of the present invention, there is provided a method of manufacturing an optical disk according to the first aspect, wherein the unevenness corresponding to the information pits and / or the guide grooves is changed from the inner circumference toward the outer circumference. Using a stamper formed so as to gradually increase the depth of the concave portion, a molding resin substrate disk is formed by injection molding, and a base layer having a uniform thickness is formed directly on the surface of this substrate disk or after forming a dye layer. Light-absorbing layer mainly composed of is formed by spin coating
Then , a metal reflective film having a uniform thickness is formed on the light absorbing layer directly or after forming a subbing layer having a uniform thickness by vapor deposition or sputtering. "

An optical disk according to claim 2, wherein the optical disk formed by this method is "coated with an ultraviolet curable resin on the metal reflective film and cured by irradiation with ultraviolet light to form a protective film having a uniform thickness". (Claim 4).

The recording and / or reproducing light beam is irradiated from the surface of the substrate disk on the side opposite to the side where the information pits and / or the guide grooves are formed.

[0011]

When a substrate disk made of a molded resin is formed by injection molding using a stamper having irregularities corresponding to information pits and / or guide grooves, the transferability of the irregularities of the stamper is closer to the center of the stamper. High and tends to decrease as the distance from the center increases. For this reason, when the depth of the concave and convex portions of the stamper is constant, the depth of the "information pits and / or guide grooves" transferred and formed on the disk substrate surface increases from the center of the disk substrate toward the peripheral portion. Tend to be “gradually shallower”.

When the light absorbing layer is formed on the disk substrate by spin coating, the light absorbing layer is formed so as to fill the "information pits and / or guide grooves" on the surface of the disk substrate. And / or a concave portion following the guide groove is formed. However, during coating, the centrifugal force acting on the light-absorbing layer material increases as the distance from the center of the disk substrate increases. Easy to fill. The effect unique to spin coating and the effect unique to injection molding are that the closer the information pits and / or guide grooves transferred / formed on the disk substrate surface are to the periphery of the disk substrate, the more likely they are to be shallower. Acting synergistically, the depth of the light absorbing film surface is
The closer to the outer peripheral side of the optical disk, the more easily it becomes “shallow”, which causes non-uniform recording and reproduction characteristics.

Therefore, in the present invention, injection is performed by using a "stamper in which irregularities corresponding to information pits and / or guide grooves are formed so that the depth of the concave portion gradually increases from the inner peripheral side toward the outer peripheral side." By molding, the depth of the information pits and / or guide grooves transferred / formed on the surface of the molded resin substrate disk is gradually increased from the inner peripheral side toward the outer peripheral side. By spin-coating the light absorbing layer directly or after forming an underlayer having a uniform thickness on the surface, the "overfilling of the concave portion in the peripheral portion" due to the above-described action peculiar to the spin coating can be performed on the information pit and / or the guide groove. This is offset by the increase in the depth, and “the depth of the concave portion on the surface side of the light absorbing layer is made substantially uniform”.

If the depth of the concave and convex concave portions of the stamper is appropriately selected so as to be closer to the peripheral portion, a disk substrate having information pits and / or guide grooves adjusted to a desired depth can be obtained. Even if a light absorbing layer having a uniform thickness is formed on such a disc substrate by a coating method other than spin coating, for example, by dipping or the like, the recording / reproducing characteristics are the same as in the present invention. Note that an optical disk that does not fluctuate can be realized.

[0015]

EXAMPLES Specific examples will be described below. Claim 4
According to the method described above, the optical disk of claim 2 is a "write-once type".
Manufactured optical compact discs.

A photoresist was applied to the surface of a glass disk having a diameter of 250 mm, and pattern exposure according to "information pits and / or guide grooves" was performed by laser beam exposure in a region of 22.35 mm to 59 mm from the center. At that time, the relative intensity of the laser beam was changed as shown by a graph line 3A-1 in FIG. After pattern exposure, development is performed to remove the photoresist on the exposed part,
A Ni thin film was formed on the remaining photoresist by sputtering, and this Ni thin film was used as an electrode to Ni electroforming to form a nickel layer. Thereafter, the nickel layer was peeled off from the glass disk, and the remaining photoresist was removed to obtain a “stamper”. This stamper has “irregularities corresponding to information pits and / or guide grooves”, and the depth of the concave portions of the irregularities gradually increases from the inner peripheral side toward the outer peripheral side.

Using this stamper, a polycarbonate disk substrate was formed by injection molding. The diameter of the disk substrate is 120 mm, and the radius: 22.35 mm-
"Information pits and / or guide grooves" are transcribed and formed in the area of 59 mm, and have a depth from the inner peripheral side toward the outer peripheral side as shown by a graph line 3A-2 in FIG. It is getting deeper.

A solution of 2,2,3,3-tetrafluoropropanol to which 5% by weight of ethylene glycol monomethyl ether acetate is added is a cyanine dye having a structural formula shown in FIG. 1.5 wt% is dissolved to form a coating solution, and this coating solution is spin-coated on the surface of the disk substrate to about 1300 ° C.
The light absorbing layer having a thickness of 3 mm was formed.

On this light absorbing layer, Au is sputter-deposited to a thickness of about 800 ° to form a metal reflection film, and an ultraviolet curable resin is further applied thereon and cured by irradiation with ultraviolet light to have a thickness of 3 μm. A protective film was used.

The recording area of the write-once optical compact disc thus obtained, ie, diameter: 44.7 to 118 mm
The information is written in the area of No. 2, wavelength: 782 nm, N.I. A:
A reproduction power of 0.
5mw, linear velocity: then play at 1.3m / s, "information pitch
When the reflectivity (Itop) of the portion " g and / or guide groove" was measured, the reflectivity in the recording area became constant as shown by the graph line 3A-3 in FIG. 3C. This means that the recording / writing on the optical compact disc of this embodiment is
This means that the reproduction characteristics do not vary depending on the location in the recording area.

For comparison, a disk substrate formed by a stamper formed by keeping the relative intensity of the laser beam in exposing the photoresist layer constant as shown by a graph line 3B-1 in FIG. The depth of the formed information pits and / or guide grooves is gradually reduced from the inner peripheral side to the outer peripheral side of the disk substrate as shown by a graph line 3B-2 in FIG. In a comparative optical compact disk in which a light absorbing layer, a metal reflective film and a protective film are formed on the disk substrate in the same manner as in the above embodiment, the reflectance in the recording area is represented by a graph line 3B in FIG. As shown in -3, the density gradually increased from the inner peripheral side to the outer peripheral side of the optical disk, and the characteristics in the recording area were not uniform.

[0022]

As described above, according to the present invention, a novel optical disk and a method for manufacturing the same can be provided. Since the optical disk of the present invention is configured as described above, the characteristics of recording and reproduction are stable in the recording area, and mass production can be carried out with good mass productivity and low cost by a combination of injection molding and spin coating as in the prior art.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the features and structure of an optical disc according to the present invention.

FIG. 2 is a diagram showing a structural formula of a main component dye of a light absorbing layer in an example.

FIG. 3 is a diagram illustrating an example.

[Explanation of symbols]

10 Disc substrate 10A Information pit and / or
Or guide groove 11 underlayer 12 light absorbing layer
12A Depression on the surface of light absorbing layer 14 Metal reflective film 15 Protective film

Continuation of the front page (56) References JP-A-62-245544 (JP, A) JP-A-1-315042 (JP, A) JP-A-3-295041 (JP, A) JP-A-4-274038 (JP) JP-A-63-222327 (JP, A) JP-A-1-181129 (JP, U)

Claims (4)

(57) [Claims] An optical system comprising a dye as a main component directly or via an underlayer having a uniform thickness on a disk substrate formed of a molding resin and having information pits and / or guide grooves formed on the surface side in advance. An absorption layer is provided by spin coating ,
A metal reflective film having a uniform thickness is provided on the light absorbing layer directly or via an undercoat layer having a uniform thickness, and the depth of information pits and / or guide grooves formed on the disk substrate surface side is reduced. Is gradually deeper from the inner peripheral side toward the outer peripheral side, and on the light absorbing layer surface side,
An optical disc characterized in that the depth of the recess corresponding to the information pit and / or the guide groove is substantially uniform. 2. A write-once optical disc, wherein a protective film having a uniform thickness is provided on the metal reflection film of the optical disc according to claim 1. 3. The method for manufacturing an optical disk according to claim 1, wherein the concaves and convexes corresponding to the information pits and / or the guide grooves gradually increase the depth of the concave from the inner peripheral side to the outer peripheral side. Using a stamper formed in the above, a molded resin substrate disk is formed by injection molding, and an underlayer of uniform thickness is formed directly on this substrate disk or after spinning the light-absorbing layer mainly composed of dye. A method for manufacturing an optical disk, comprising: forming a coating, forming a subbing layer having a uniform thickness directly on the light absorbing layer, or forming a metal reflecting film having a uniform thickness by vapor deposition or sputtering. 4. A method for manufacturing an optical information disk according to claim 2, wherein an ultraviolet curing resin is applied on the metal reflection film of the optical disk formed by the method according to claim 3, and cured by irradiation with ultraviolet light. A method for manufacturing an optical disk, comprising: forming a protective film on the optical disk.