JP2001291289A - Method for reproducing stamper for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reproducing a stamper for an optical disk so that reproduced signals almost equal to the reproduced signals of the optical disk can be obtained, and to check the recording state in the stamper stage. SOLUTION: Signals are reproduced from the stamper 7 for the manufacture of an optical disk by irradiating the stamper 7 with laser light 13S of wavelength λ/n through an object lens 14S having the numerical aperture NA/n, wherein n is the refractive index of the resin substrate of the optical disk, λis the wavelength of the laser light to reproduce signals through the resin, and NA is the numerical aperture of the object lens which converges the laser light to irradiate the resin substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reproducing method for inspecting an optical disk stamper used for manufacturing an optical disk.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view showing a manufacturing process of an optical disk. First, a glass substrate 1 whose surface is polished and cleaned is prepared (a). A photoresist 2 is applied to the glass substrate 1 by spin coating and dried (b). Exposure beam 3 modulated by the signal to be recorded
As a result, a latent image of pits or grooves is selectively formed in the photoresist layer 2 (c). Thereafter, by exposing and developing the photoresist layer 2, a master master 4 is prepared (d).

A nickel conductive film 5 is formed on the master master 4 by sputtering (e), and a nickel plating layer 6 is formed on the master master 4 by nickel electroforming (f).
Then, by removing the master master 4 from the nickel plating layer 6, a nickel stamper 7 is formed. The replica disk (resin substrate) 8 is completed by attaching the stamper 7 to a mold and molding a resin such as polycarbonate using the mold. Further, a reflective film and a protective film are sequentially formed on the signal surface of the replica disk 8 to complete the optical disk.

FIG. 3 is an explanatory diagram showing a configuration of a conventional optical disk reproducing system. The optical disk 9 has a reflective film 11 made of aluminum or the like and a protective film 12 made of an ultraviolet curable resin formed on a signal surface of a resin substrate 10 in this order.
When reproducing the optical disk 9, the laser beam 13 having the wavelength λ is focused by the objective lens 14 having the numerical aperture NA, and reaches the signal surface through the resin substrate 10 having the refractive index n.
Here, the laser beam 13 focused by the objective lens 14 and applied to the signal surface of the optical disk 9 is reflected as it is on the surface without pits as shown and returns to the detector, but has a pit. On the surface, the irradiated laser light is diffracted by the pits and goes out of the field of view of the objective lens 14, and only a part of the incident laser light returns to the detector. That is, the intensity of the light returning to the detector is modulated by the pit, and the reproduced signal is detected using the modulated pit.

FIG. 2 is an explanatory view showing the structure of a conventional optical disk stamper reproducing system. The stamper 7 for an optical disk is a master for producing the replica disk 8 as described above, and has a signal reading surface that is not covered with a transparent resin substrate. Conventional stamper 7
Is basically performed by using a pickup for reproducing an optical disk. A laser beam 13 having a wavelength λ is focused by an objective lens 14 having a numerical aperture of NA, and is irradiated on a signal surface of a stamper 7. At this time, the optical disk 9
A glass plate 15 for correcting aberration of laser light having a refractive index n equivalent to the resin substrate 10 and a thickness equivalent to
The laser light condensed by the objective lens 14 is
The signal surface is radiated via the.

[0006]

When the stamper 7 is reproduced by the conventional method shown in FIG. 2, when compared with the reproduction of the optical disk shown in FIG. 3, the signal surface is on the resin substrate having the refractive index n. There is a difference between whether or not they are in contact with each other, so that the signal obtained when the stamper 7 is reproduced by the above-described conventional method is different from the signal obtained when the optical disk is reproduced.

That is, in reproducing the optical disk 9, as shown in FIG. 3, the signal surface has a resin substrate 10 having a refractive index n.
The wavelength λ of the laser light incident on the resin substrate 10 is converted to λ / n, and the laser light having the wavelength λ / n is reproduced. On the other hand, in the reproduction of the stamper 7, since the signal surface is in contact with the atmosphere as shown in FIG. 2, the wavelength conversion of the laser light does not occur, and the reproduction is performed with the laser light of the wavelength λ. Due to this difference in the reproduction wavelength, the signal surface is reproduced with a different phase, and as a result, a difference occurs in the amount of reflected light.

As described above, according to the conventional stamper reproducing method, the reproduction signal of the optical disk created from the stamper cannot be accurately confirmed by reproducing the stamper. Therefore, it is not possible to check whether there is any defect in the recording state at the stamper stage, and to confirm the correct recording state, it is necessary to create a replica disk from the stamper once. It took time and there was a problem in productivity.

The present invention has been proposed in order to solve the above problems, and provides a method of reproducing a stamper for an optical disk capable of obtaining a reproduction signal equivalent to a reproduction signal of an optical disk. An object of the present invention is to improve the productivity by making it possible to confirm the recording state at a stage.

[0010]

To achieve the above object, a method for reproducing an optical disk stamper according to the present invention comprises:
When the refractive index of the resin substrate of the optical disk is n, the wavelength of the laser light for reproducing a signal through the resin substrate is λ, and the numerical aperture of the objective lens for focusing the laser light irradiated on the resin substrate is NA, the wavelength Irradiates a laser beam of approximately λ / n to a stamper for producing the optical disc through an objective lens having a numerical aperture of NA / n, and reproduces a signal from the stamper.

According to this, by setting the reproduction conditions of the optical disk stamper to be equivalent to the reproduction conditions of the optical disk (replica disk), the signal when reproducing the stamper is equivalent to the signal when reproducing the optical disk. become,
By reproducing the stamper, the recording state of the optical disc formed from the stamper can be confirmed.

[0012]

FIG. 1 is an explanatory view showing a reproducing system of a stamper for an optical disk according to an embodiment of the present invention. The optical disk stamper 7 according to the present embodiment is manufactured by the above-described conventional manufacturing process, and has a signal groove 7a formed by recording a signal surface 7 'on the surface.

The method of reproducing the optical disk stamper 7 produced as described above will be described. The refractive index of the resin substrate in the optical disk produced from the stamper 7 is n, and the resin substrate is used for reproducing the signal of this optical disk through the resin substrate. Assuming that the wavelength of the laser light to be emitted is λ and the numerical aperture of the objective lens that focuses the laser light is NA, in FIG.
The wavelength λs of the laser beam 13S is set to λs ≒ λ / n, and the numerical aperture of the objective lens 14S is set to NA / n. The laser beam is irradiated to a stamper 7 for producing the optical disc, and a signal is reproduced from the stamper 7.

Here, in the case of reproducing an optical disk, as shown in FIG.
The wavelength conversion is performed on the laser beam 13 having the wavelength λ, and the laser beam 13 is reproduced by the laser beam having the wavelength approximately λ / n. On the other hand, in the reproduction of the optical disk stamper 7 according to the embodiment of the present invention, since there is no resin substrate having the refractive index n, the reproduction is performed by the laser beam 13S having the wavelength of λ / n. The wavelength of the reproduction laser light is substantially the same, and no phase difference occurs in the detection signal.

In FIG. 1, since the spot diameter d of the laser beam 13S irradiated on the signal surface 7 'is proportional to the wavelength / numerical aperture, d = λs / (NA / n) ≒ (λ / n )
/ (NA / n) ≒ λ / NA, which is almost the same as the reproduction of the optical disk 9 shown in FIG. Furthermore, by making the laser beam incident pattern on the objective lens equivalent to that in the case of the reproduction optical system of the optical disk, the reproduction signal obtained from the stamper 7 can be made equivalent to the reproduction signal obtained from the optical disk.

As described above, according to the method of reproducing the stamper for an optical disk in the embodiment, the wavelength and spot diameter of the reproduced laser beam and the pattern of the laser beam incident on the objective lens are respectively equivalent to those in the case of reproducing the optical disk. Thus, a reproduction signal of the optical disk stamper compatible with the reproduction signal of the optical disk can be obtained.

As a specific example, in the case of a CD, the wavelength λ of the laser beam for reproducing the CD is 780 nm, the refractive index n of the resin substrate (made of polycarbonate) is 1.55, and the numerical aperture NA of the objective lens used is 0 .45, the laser beam 13S shown in FIG. 1 has a wavelength of λs = 780 / 1.55 = 503 nm in order to reproduce the stamper for producing the CD under the reproducing condition equivalent to the reproducing condition of the CD. Objective lens 14
The numerical aperture of S is NA / n = 0.45 / 1.55 = 0.29
Becomes

With reference to FIG. 5, an optical disk manufacturing process including a stamper inspection process employing the optical disk stamper reproducing method of the present invention will be described. First, a glass substrate 1 whose surface is polished and cleaned is prepared, a photoresist is applied to the glass substrate 1 by a spin coating method, and dried (A). On the other hand, signal recording is performed by selectively forming latent images of pits and grooves in the photoresist layer using an exposure beam modulated by a signal to be recorded (B). After that, the master layer 4 is exposed by developing the photoresist layer (C).
Is created.

The master master 4 is coated with a conductive film of nickel by sputtering (D), and a nickel plating layer 6 is formed on the master master 4 by nickel electroforming (E).
Thus, a nickel stamper 7 is created.

The stamper 7 is reproduced by the above-mentioned reproducing method (F), and it is confirmed whether or not the obtained reproduced signal is equivalent to the signal reproduced from the optical disk finally produced. (G). Here, if the reproduced signal is defective, the stamper 7 is re-created from the master master 4 through the above-described steps again, or the master master 4 is created again from the signal recording step (B). hand,
From there, the stamper 7 is created again. When a proper signal is confirmed in the reproduction signal confirmation step (G), the stamper 7 is attached to a mold, and a resin such as polycarbonate is molded using the mold to form a replica disk (resin substrate). Create 8.

According to the manufacturing process of the optical disk, the quality of the stamper 7 can be confirmed by directly obtaining a reproduction signal. Compared with the method of the judgment, the time until the judgment result is obtained can be greatly shortened, whereby the productivity can be improved.

[0022]

Since the present invention is configured as described above,
According to the method of reproducing an optical disk stamper of the present invention, a reproduction signal equivalent to the reproduction signal of the optical disk can be obtained by reproducing the stamper, and the recording state can be confirmed at the stage of the stamper. As a result, a defect in the recording state can be found before forming a replica, and productivity can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method of reproducing an optical disk stamper according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a conventional reproducing method of an optical disk stamper.

FIG. 3 is an explanatory diagram showing a configuration of an optical disc reproduction system.

FIG. 4 is an explanatory diagram showing a manufacturing process of the optical disc.

FIG. 5 is an explanatory view showing a manufacturing process of an optical disk employing the method of reproducing an optical disk stamper according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Photoresist, photoresist layer 3 Exposure beam 4 Master master 5 Nickel conductive film 6 Nickel plating layer 7 Stamper 7a Signal groove part 8 Replica disk 9 Optical disk 9a Signal groove part 10 Resin substrate 11 Reflective film 12 Protective film 13, 13S laser Light 14, 14S Objective lens 15 Resin plate

Claims (1)

[Claims] 1. The refractive index of a resin substrate of an optical disk is n, the wavelength of a laser beam for reproducing a signal through the resin substrate is λ,
When the numerical aperture of the objective lens that focuses the laser light applied to the resin substrate is NA, the laser light having a wavelength of approximately λ / n is formed through the objective lens with the numerical aperture of NA / n to produce the optical disc. And reproducing a signal from the stamper by irradiating the stamper with the stamper.