JPS63217545A - Production of optical disk - Google Patents

Abstract

PURPOSE:To obtain a master disk formed with recording pits, the bottom of which is parallel with the slope of V-grooves and to produce a disk having high quality of reproduction signals by providing an ion milling stage in a stage for preparing the master disk. CONSTITUTION:A photoresist 8 is formed on a metallic disk 6 formed with the V-grooves and the signals are recorded thereon by a laser; thereafter, the resist is etched. An ion beam 11 is then projected thereto dig down uniformly the metallic part exposed by the etching (ion milling). Then, the metal is uniformly and increasingly dug by the ion milling and the recording pits having the bottom parallel with the slope of the original V-grooves are obtd. The photoresist is thereafter removed and the master disk is obtd. The bottom of the recording pits is paralleled with the slope of the V-grooves if the disk is prepd. by using such master disk. The disk having the high quality of the reproduction signals is thus produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing an optical disc in which information is reproduced by focusing laser irradiation.

2. Description of the Related Art A video disk device in which the radial cross-section of a disk forms a V-shaped groove and uses the slope of the groove as a signal track to provide high-density and high-quality information has been proposed in Japanese Patent Laid-Open No. 60-212836. There is. The V-groove shape and signal pit shape used therein are given in Japanese Patent Laid-Open No. 57-105828 and Japanese Patent Application No. 60-134568. FIG. 6 shows its cross-sectional shape. 1 is a resin substrate made of acrylic or polycarbonate, on which signal pits 2 are formed.

A reflective layer 3 is provided thereon and covered with a protective layer 4. A feature of this signal pit 2 is that the pit bottom surface 6 is parallel to the slope of the V-groove other than the pit.

A conventional disk manufacturing method will be explained using FIG. 6. A soft metal disc 6 such as copper is mechanically cut using a diamond cutting tool 7 with a V-shaped tip (Fig. 6a).
. A photoresist layer 8 is formed on the thus-formed metal disk (FIG. 6B), and a laser 9 is focused and irradiated onto the V-groove slope to record a signal (FIG. 6C).

An example of a method of recording on the slope of a V-groove using a laser is disclosed in Japanese Patent Application Laid-open No. 1983
It is described in the publication No.-155528.

A laser with a wavelength to which the photoresist is not sensitive (e.g. 6
33 Track the bottom or peak of the V-groove with a null HeN6 laser, and at the same time,
The d laser or hr laser is focused and irradiated, modulated according to the information, and recorded.

Problems to be Solved by the Invention Polymer photoresists such as Mu Z1360 (manufactured by Sibley) have high sensitivity and resolution and are suitable for high quality information, but must be formed by coating. Therefore, due to the effects of viscosity and surface tension, it cannot be formed uniformly along the groove shape as shown in Figure 6. Therefore, the shape after etching is as shown in Figure θ d. If you use this master as a stamper and make a replica, you can create a board 1 with the cross-sectional shape shown in Figure 7.
It became 0 and then 1. The cross-sectional shape of the substrate 1 shown in FIG. 6 is very different, and the reproduced signal quality deteriorates.

If a 5e-Ge-based inorganic photoresist that can be formed by sputtering is used, the photoresist layer can be formed uniformly along the V-groove shape. However, these inorganic photoresists have low sensitivity and cannot record high transfer rate information signals in real time.

Means to solve the problem: Form a photoresist on a metal plate with V grooves formed,
After recording the signal with a laser, it is etched. Next, a means is provided for irradiating an ion beam to uniformly dig into the metal parts exposed by etching.

After that, the photoresist is removed and used as the master.

By providing a process of digging with an active ion beam, it is possible to create a master disk in which the bottom surface of the recording bit is parallel to the slope of the V-groove other than the pit.

Examples Example 1 FIG. 1 shows an example of the present invention. The metal disk in the state shown in FIG. 6d is irradiated with an ion beam 11 of argon or the like, and the exposed metal after the photoresist is etched is dug (ion milling). At this time, it is better that the etching rate of the metal by the ion beam is faster than that of the photoresist. For example, if an argon ion beam is made perpendicularly incident on the disk at an ion current density of 1 in/d, the etching rate of copper can be increased to 2 to 3 times that of 1350 mm.

Laser wavelength i780nm used for video discs,
If the refractive index of the substrate 1 is 1.6, the depth of the recording bit should be approximately 130nl11 (Japanese Patent Application No. 134568/1986).
issue). Therefore, the thickness of the thinnest portion of the photoresist layer is 65 nu or more. That is, it is sufficient that the depth is at least half of the depth of the recording pin.

Ion milling uniformly excavates the metal, creating a recording pit with a bottom parallel to the original V-groove slope. FIG. 1 shows a state in which a small amount of photoresist remains.

When the photoresist is removed, a master 12 having a cross-sectional shape as shown in FIG. 2 is obtained, and a substrate made from this by the conventional method thereafter becomes that shown in FIG. 6.

Embodiment 2 A stamper 13 is made by plating a metal such as Ni on a metal disk before recording a signal (Fig. 3). Using this stamper, Even after going through the process,
A master disk 12 having a good shape as shown in FIG. 2 can be made. In this case, the etching rate of Ni by the argon ion beam is comparable to or slightly faster than that of copper, so there is no problem.

Furthermore, by using a stamper in this way, - times of V
By cutting the grooves, it becomes possible to create master discs on which many types of information signals are recorded.

Embodiment 3 Using a metal film 14 formed on a stamper 13 by a sputtering method (FIG. 4), the etching rate of which is faster than that of copper or nickel by an ion beam, the metal film 14 shown in FIGS.
1 and the master disc 12 shown in FIG. 2 can be made even after the steps shown in FIG. Such metals include Pt, Mn%Ge1Au
, Pd5Sn, Ag, and Pb. For example, gold (Au)
When using T-T, the etching rate is 6 for Z1360.
The thinnest thickness of the photoresist layer may be one-fifth or more of the recording bit depth. The reproduction laser wavelength is 7
If it is 80 nm, the thickness may be 26 nm or more, and there is no need to pay attention to the method of applying the photoresist.

Alternatively, a metal plate 6 having a V-groove cut thereon may be directly coated with a metal film 14 such as a groove U. This can be done by selecting the lower cost option between cutting with the diamond bite 7 and manufacturing the stamper 13 by plating.

By going through the ion milling process in a way that exceeds the effects of the invention,
It is possible to manufacture a disk with high reproduction signal quality in which the bottom of the recording bit is parallel to the VrM slope.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a pot explaining the ion milling process of the present invention, FIG. 2 is a cross-sectional view of a master disk obtained by the present invention, and FIG.
The figure is a cross-sectional view showing the stamper manufacturing process used in the second embodiment of the present invention, Figure 4 is a cross-sectional view of a metal disc used in the third embodiment of the present invention, and Figure 6 is a disc with high reproduction signal quality. 6 is a cross-sectional view for explaining a conventional disk manufacturing process, and FIG. 7 is a cross-sectional view of an optical disk manufactured by the conventional method. 2...Signal pit, 6...Metal plate, 8
...Photoresist, 9...Laser, 11...Ion Beu, 12...Master disc. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 5 Figure 6

Claims (2)

[Claims] (1) In a manufacturing method for optical discs in which information is reproduced by focusing laser irradiation, the cross section in the radial direction of the disc is V.
A photoresist layer is formed on a metal plate with concentric or spiral grooves formed thereon, a laser beam is focused on the slope of the V-shaped groove, a signal is recorded, and an ion beam is etched. A method of manufacturing an optical disc by irradiating the metal part exposed by the etching to form a signal pit having a bottom surface parallel to the original slope of the V-shaped groove, and then removing the photoresist and using it as a master disc. (2) At least the surface portion of the metal plate on the side of the V-shaped groove is made of a metal whose etching rate by an ion beam is faster than that of the photoresist, and when the etching rate is multiplied by N, the most of the photoresist layer. 2. The method of manufacturing an optical disk according to claim 1, wherein the thickness of the thin portion is at least 1/N of the depth of the signal pit.