JP2507000B2 - Optical disc master - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical disc master used when manufacturing an optical disc.

2. Description of the Related Art As an optical disc master, a master such as glass whose surface is polished is generally used. However, when a groove having a V-shaped cross section (hereinafter abbreviated as V groove) is formed on the master in advance and used, the V groove is formed by machining, so that a master such as copper is used as the master for the optical disc. Used.

When forming the V-groove, a metal master is finished to a flat surface with a maximum average roughness Rmax of about 0.5 μm using a Borley lathe or the like, and then the V-groove is cut with a V-shaped cutting tool.

The optical disc master is coated with a photoresist on a V-grooved metal master, exposed to light with laser light whose intensity is modulated by an information signal to be recorded, and developed to form a shape corresponding to the photosensitivity. Further, it is created by digging a metal by an ion milling method or the like.

A spin coating method is generally used to apply the photoresist. In the spin coating method, the entire area where the host resist is applied is applied with a thickness of several mm (this is called pre-coating), and then the master disk is rotated at a speed of several hundreds to several thousands of revolutions per minute and the photoresist is applied. To a constant thickness (this is called final coating).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention When a metal such as copper having a V groove is used as an optical disc master, the photoresist overflows to the inner peripheral side of the region where the V groove is formed in pre-coating when applying the photoresist. There is. In this case, when the final coating is performed, the photoresist is difficult to flow because the surface is rough on the inner peripheral side of the region where the V groove is formed, and uneven coating of the photoresist occurs radially from the portion where the photoresist overflows toward the outer peripheral side. There is a problem that it will end up.

Further, in order to prevent the photoresist from overflowing from the region where the V groove is formed in the pre-coating, the photoresist may be applied from the outermost side to the outer side by about several mm from the innermost circumference of the region where the V groove is formed. In this case, there arises a problem that a few mm from the innermost circumference of the region where the V groove is formed is wasted.

It is an object of the present invention to provide an optical disc master that solves the above-mentioned conventional problems.

Means for Solving the Problems The present invention is directed to a region in which a groove having a V-shaped cross section is formed on a master made of a metal such as copper, and an inner circumference in contact with the region in which the groove having a V-shaped cross section is formed. This is accomplished by forming mirrored areas on the sides, etc.

Action In the optical disc master of the present invention, the inner peripheral side of the region where the V groove is formed is mirror-finished. Therefore, even if the photoresist overflows to the inner peripheral side during pre-coating, the photoresist easily flows and the final coating is performed. Even coating unevenness does not occur. Further, the photoresist can be applied to the entire region where the V groove is formed.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of the surface of an embodiment of the optical disc master of the present invention.

In the figure, 1 is a region in which a V groove is formed, and 2 is a region in which the surface is mirror finished.

The master, which is made of metal such as copper, is also finished on a flat surface with a maximum average roughness Rmax of about 0.5 μm or less using a Borley lathe, both front and back surfaces. This is to enable vacuum chucking when applying a photoresist or irradiating a laser beam to record a signal.

Next, a tool with a curved tip (R tool) on the surface
Finish with a mirror. For example, the maximum average roughness is set to about 0.02 μm by using a cutting tool having a radius of 0.2 μm. in this case,
If it is not R bit, even if the maximum average roughness is 0.02 μm or less, it does not become a mirror surface and the photoresist does not easily flow, so there is no effect of eliminating uneven coating of the photoresist.

The area to be mirror finished is on the inner peripheral side of the area where the V groove is formed.
An area with a width of about 5 mm is sufficient. This is because the photoresist overflowing from the region in which the V-groove is formed does not have to stop in the mirror-finished region and reach the rough region of the inner peripheral surface.

The region to be mirror finished may have a width of about 1 mm, but in this case, it is not desirable because the photoresist should hardly overflow from the region where the V groove is formed to the inner peripheral side when the photoresist is applied. This is because there is a possibility that the photoresist may overflow beyond the mirror-finished area to the rough surface area, resulting in uneven coating.

Further, even if the area to be mirror finished is 10 mm or more in width, no particular inconvenience occurs. However, considering the time and effort required to finish the mirror surface, it is not desirable to widen the width of the region for finishing the mirror surface more than necessary.

To form a mirror-finished region in contact with the V-groove-formed region, the V-groove is formed after the V-groove-finished region is previously mirror-finished as shown in FIG. It can be easily realized.

The V groove is formed by using a V-shaped cutting tool having a V-shaped tip.

The outer peripheral side of the V-groove-formed region of the optical disc master usually has a rough surface area in contact with the V-groove-formed area, and the rough surface area is higher. Therefore, the photoresist accumulates at the boundary between the region where the V groove is formed and the rough surface at the time of final coating, and the photoresist becomes thicker in the region where the V groove is formed with a width of several mm from this boundary. However, there is a drawback that this part cannot be used. As shown in FIGS. 3 and 4, this disadvantage can be eliminated by providing a mirror-finished region on the outer peripheral side in contact with the V-groove-formed region. The width of the mirror-finished region is about 5 mm, but it is not inconvenient if it is wider than that. In addition, in FIG.
FIG. 3 is a cross-sectional view of an outer peripheral portion of an optical disc master.

At the time of final coating, the photoresist accumulates at the boundary with the rough surface area, and even if the photoresist becomes thick with a width of a few mm from this boundary, the thicker area is the mirror finished area and the V-shaped groove. It does not affect the area where the mark was formed. At the boundary between the V-groove-formed region and the mirror-finished region, the photoresist easily flows in the mirror-finished region, so that the photoresist does not accumulate at this boundary and the inner circumference of the boundary is reduced. The photoresist is not thickened on the side. Therefore, by providing a mirror-finished region in contact with the V-groove-formed region, the V-groove-formed region can be used up to the outermost circumference.

An optical disc is required to record a signal having a certain amount of information. This is accomplished by forming grooves over a constant width with a constant groove pitch and utilizing the entire grooved area. However, in the conventional optical disk master, the inner and outer circumferences of the grooved area are several mm.
It was difficult to record the signal with a certain amount of information because it was not possible to use this part. As shown in FIG. 5, by providing mirror-finished regions on the inner and outer peripheral sides of the V-groove-formed region, the photoresist can be uniformly applied to the entire V-groove-formed region. , The entire area where the V-groove is formed can be used.
This makes it possible to easily record a signal having a certain amount of information on the optical disc master.

When a mirror-finished area is provided on the inner and outer peripheral sides of the V-groove-formed area, as shown in FIG. When finished, it is not necessary to set the R bit for finishing the mirror surface twice on the inner circumference side and the outer circumference side, and it is possible to expect the effect that the V groove will be finished neatly.

This is considered to be because the mirror surface finish stabilizes the cutting resistance applied to the V bit when the V groove is formed using the V bit.

EFFECTS OF THE INVENTION In the optical disk master of the present invention, by providing a mirror-finished region in contact with the V-groove-formed region, the photoresist can be uniformly applied to the entire V-groove-formed region. The entire formed area can be used.

[Brief description of drawings]

FIG. 1 is a plan view of an optical disc master having a V groove formed region and a mirror finished region according to an embodiment of the present invention, and FIG. 2 is an optical disc master showing the mirror finished region of the present invention. FIG. 3 is an enlarged schematic view of a cross-section on the outer peripheral side of the region in which the V-groove of the present invention is formed, and FIGS. 4 and 5 show the region in which the V-groove of the present invention is formed and a mirror surface. Plan view of an optical disc master having a defined area, No. 6
The figure is a schematic view of an optical disc master showing a mirror finishing area of the present invention. 1 ... V grooved area 2 ... Mirror-finished area 3 ... Master disk made of metal such as copper 4 ... V-groove planned area

Claims (4)

(57) [Claims] 1. An optical disk master having an area in which a V-shaped groove is formed in a cross section, wherein the V-shaped groove is formed on the inner peripheral side of the area in which the V-shaped groove is formed. An optical disk master, which has a mirror-finished area in contact with a given area. 2. An optical disk master having an area having a V-shaped groove in cross section, wherein the V-shaped groove is formed on the outer peripheral side of the area having the V-shaped groove. An optical disk master having a mirror-finished area in contact with the area. 3. An optical disk master having an area in which a V-shaped groove is formed in a cross section, wherein the V-shaped groove is formed on an inner peripheral side and an outer peripheral side of the area in which the V-shaped groove is formed. An optical disk master, which has a mirror-finished area in contact with the area in which is formed. 4. An optical disk master having an area in which a V-shaped groove is formed in a cross section, and a mirror surface from about several millimeters of the area where the V-shaped groove is to be formed to about several millimeters of the outer peripheral side. An optical disk master, wherein V-shaped grooves are formed after finishing.