JPH0750038A - Manufacture of master optical disc - Google Patents

Abstract

PURPOSE:To manufacture a master optical disc which facilitates accurate tracking control in such a manner that signal bits of adjacent tracks are alternately different. CONSTITUTION:A first photoresist thin film 2 is formed on a glass substrate 1, a first laser beam 3 is continuously applied to the first photoresist thin film 2 and the part of the first photoresist thin film 2 to which the first laser beam 3 is applied is removed to form a trench 4. A metal thin film 6 is formed on the glass substrate 5 on which the trench is formed and the part of the metal thin film 6 which is formed on the remaining first photoresist thin film 2 is removed with the first photoresist thin film 2 to leave a spiral metal thin film 6. Further, a second photoresist thin film 7 is formed on the glass substrate 5 on which the spiral metal thin film 6 is formed. A second laser beam 8 is applied to the spiral metal thin film 6 and to the space between the adjacent spiral thin films 6 with tracking to record signals and the part of second photoresist thin film 7 to which the second laser beam is applied is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disc master in which information is stored at a high density.

[0002]

2. Description of the Related Art In order to increase the density of optical discs, it has been considered to shorten the wavelength of a reproducing laser and increase the NA of an objective lens, but at present, the wavelength is 670 nm and the NA is 0.6.
Is a limit, and there are some known methods that do not rely on shorter wavelengths or higher NA.

As one of them, there is a method, as disclosed in Japanese Patent Laid-Open No. 54-136303, which alternately changes the depth of signal bits in adjacent tracks. The reflected light is received by a detector that is divided into two photodetector units, and the sum signal of the two photodetector units is used to reproduce the signal bit string of one depth.
If the difference signal of these two photodetection sections is used for reproduction of the other signal bit string, crosstalk from adjacent tracks is small, and it is possible to narrow the pitch and increase the density.

A method of manufacturing an optical disc master of this system will be described with reference to FIGS. Once it is necessary to prepare a substrate on which uneven grooves are formed,
As shown in (a), the photoresist 1 is formed on the glass substrate 11.
2 is applied and the photoresist 1 is applied as shown in FIG.
2 is continuously irradiated with a laser beam 13 and then developed as shown in FIG. 2C to remove the photoresist 12 at the irradiation portion of the laser beam 13. Furthermore, FIG.
As shown in (d), a groove 14 is formed in the glass substrate 11 by a reactive ion etching method using CHF ₃ gas, and then the photoresist 12 is removed as shown in FIG. 2 (e). Next, the glass substrate 1 on which the concave and convex grooves 14 are formed
2 is coated again with a photoresist 16 as shown in FIG. 2 (f), and a laser beam 17 is radiated while tracking in and between the grooves as shown in FIG. 2 (g) to record a signal, After development, the photoresist 16 in the recording portion is shown in FIG.
By removing as shown in (h), an optical disk master having signal bits 18 and 19 having different depths in and between the grooves can be obtained.

[0005]

However, the above-mentioned conventional method for manufacturing an optical disk master has the following problems.

That is, the refractive index of the photoresist is about 1.
7. Since the refractive index of glass is about 1.5, which is not so different,
The reflectance at the boundary between the glass and the photoresist is 0.4%, which is very small. When the photoresist 16 is applied to the glass substrate 15 in which the groove is formed, the tracking signal from the groove is extremely small, and the tracking control cannot be accurately performed when the signal is recorded on the master. In order to solve the above-mentioned conventional problems, it is an object of the present invention to provide a method for manufacturing an optical disc master that enables accurate tracking control when recording a signal on the master.

[0007]

In order to achieve the above object, a method of manufacturing an optical disk master according to the present invention comprises forming a first photoresist thin film on a glass substrate, and applying a first laser beam to the first photoresist thin film. Continuously irradiate the
The first photoresist in the portion irradiated with the laser beam is removed to form a groove, a metal thin film is formed on the glass substrate on which the groove is formed, and the remaining metal on the first photoresist thin film is formed. The thin film is removed together with the first photoresist to leave the metal thin film in a spiral shape, and a second photoresist thin film is further formed thereon, and a second laser beam is applied onto the spiral metal thin film and between the metal thin films. An optical disc master in which signal bits having different depths are formed in adjacent tracks by a method of irradiating while tracking to record a signal and removing the second photoresist thin film in the portion irradiated with the second laser beam. Is to be manufactured.

[0008]

Since the spiral metal thin film is formed on the glass substrate by the above method, the boundary between the metal and the photoresist has a high reflectance, and even if the second photoresist is applied, the tracking signal from the groove is not generated. It is large enough to enable accurate tracking control when recording signals on the master.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing an optical disk master according to an embodiment of the present invention will be described below with reference to the drawings.

1 (a) to 1 (h) showing a method for manufacturing an optical disk master according to this embodiment, a first photoresist thin film 2 is formed on a glass substrate 1 (see FIG. 1).
(A)), 1st laser beam 3 is continuously irradiated from the 1st photoresist thin film 2 (FIG. 1 (b)), and it develops and the groove | channel 4 is formed (FIG. 1 (c)). A metal thin film 6 is formed on the substrate 5 in which the groove 4 is formed (FIG. 1D), and the metal thin film 6 on the first photoresist thin film 2 is removed together with the first photoresist thin film 2 to remove the metal thin film. 6 is left in a spiral shape (FIG. 1 (e)), a second photoresist thin film 7 is formed thereon again (FIG. 1 (f)), and a second laser beam 8 is applied to the spiral thin metal film 6. The signal is recorded by irradiating on and between the above and tracking (FIG. 1 (g)). Then, by developing, signal bit strings 9 and 10 having different depths on the metal thin film 6 and between the metal thin films 6 can be manufactured (FIG. 1).
(H)).

As shown in FIG. 1E, the remaining first photoresist thin film 2 is dissolved in a solvent, and the metal thin film 6 on the first photoresist thin film 2 is simultaneously removed to form a spiral metal thin film 6. In order to make the first photoresist thin film 2 easily dissolved in the solvent,
The first photoresist thin film 2 must be in contact with the solvent, and the thickness of the first photoresist thin film 2 should be thicker than the metal thin film 6. Further, it is preferable that the metal thin film 6 does not adhere to the end surface of the groove 4 formed in the first photoresist thin film 2, and a thin film forming method such as an ion beam sputtering method having high directivity is adopted.

The metal thin film 6 formed on the glass substrate 1 needs to have high adhesion to the glass substrate 1, and as such a substance, there is chromium or the like.

An organic solvent such as acetone is used to dissolve the first photoresist thin film 2. However, the metal thin film 6
When forming a film, the first photoresist thin film 2 may be deteriorated by heat and may not dissolve in an organic solvent. Even in that case, it can be easily dissolved with a strong acid such as sulfuric acid. If a noble metal such as gold is used as the metal thin film 6, the metal thin film 6 can be left without being dissolved in strong acid. Generally, a noble metal such as gold has low adhesion to glass, but if formed by a sputtering method while being assisted by an ion beam such as argon, the adhesion is improved.

[0014]

As is apparent from the above description, according to the method of manufacturing an optical disc master of the present invention, a photoresist thin film is formed on a glass substrate having grooves formed therein, and signals are recorded between the grooves. Even in such a case, the tracking signal from the groove is large and accurate tracking control can be performed, so that a high-density optical disc master can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an optical disc master for explaining a method for manufacturing an optical disc master according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of an optical disc master for explaining a method of manufacturing a conventional optical disc master.

[Explanation of symbols]

 1 Glass Substrate 2 First Photoresist Thin Film 3 First Laser Beam 4 Groove 5 Groove Formed Glass Substrate 6 Metal Thin Film 7 Second Photoresist Thin Film 8 Second Laser Beam 9, 10 Signal Bit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kishi Shunho 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toshiki Miyamoto, 1006 Kadoma, Kadoma City Osaka Prefecture (72) Inventor Shinya Abe, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A step of forming a first photoresist thin film on a glass substrate, a step of continuously irradiating the first photoresist thin film with a first laser beam, and a step of applying the first laser beam A step of removing the first photoresist thin film in the irradiated portion to form a groove, a step of forming a metal thin film on the glass substrate in which the groove is formed, and a step of forming a groove on the remaining first photoresist thin film. A step of removing the metal thin film together with the first photoresist thin film to leave the metal thin film in a spiral shape; a step of further forming a second photoresist thin film on the metal thin film; and a step of applying a second laser beam to the spiral metal. A process of irradiating while tracking the thin film and between the spiral metal thin films to record a signal, and removing the second photoresist thin film in the portion irradiated with the second laser beam, the signal is recorded. The method for manufacturing a master optical disc mainly the step of forming a bit, to form a different signal bit sequences in depth in adjacent tracks. 2. The method for producing an optical disk master according to claim 1, wherein the thickness of the first photoresist thin film is thicker than the thickness of the metal thin film. 3. The method for producing an optical disk master according to claim 1, wherein the precious metal thin film is formed by a sputtering method while being assisted by an ion beam.