JP2507058B2 - Optical disc master and manufacturing method thereof - 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 into a flat surface having a maximum average roughness R _{max of} about 0.5 μm using a Borley lathe or the like, and then the V groove is cut by a V-shaped cutting tool.

The optical disc master is formed by coating photoresist on a V-grooved metal master and exposing it with a laser beam whose intensity is modulated by an information signal to be recorded to cause a phenomenon 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 photoresist is applied to a whole area having a thickness of several mm (this is called pre-coating), and then the master is rotated at a speed of several hundreds to several thousands of revolutions per minute to apply the photoresist. Apply to a uniform 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. In addition, even if the photoresist overflows the entire circumference on the inner circumference side, the thickness of the overflowed photoresist will not be uniform, so if the final coating is performed, the uneven coating of the photoresist will occur radially. To do.

It is an object of the present invention to provide an optical disk master and a method for manufacturing the same that solve the above problems.

Means for Solving the Problems The present invention is an area in which a groove having a V-shaped cross section is formed on the inner peripheral side in contact with an area in which a groove having a V-shaped cross section is formed on a master made of metal such as copper. This is achieved by forming a more depressed area.

In the optical disc master of the present invention, the inner peripheral side of the region having the V groove is recessed from the region having the V groove, so that the photoresist overflowing to the inner peripheral side during precoating is
When the final coating is performed, the coating liquid is uniformly accumulated at the boundary with the region where the V groove is formed, so that radial coating unevenness does not occur.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of an optical disc master of the present invention, and FIG. 2 is an enlarged schematic diagram of a cross section of the optical disc master of the present invention. In the figure, 1 is a region in which the V groove is formed, and 2 is a region depressed from the region in which the V groove is formed.

The master, which is made of metal such as copper, is also finished on both front and back surfaces to a flat surface with a maximum average roughness R _{max of} about 0.5 μm or less using a Borley lathe. This is to enable vacuum chucking when the V groove is formed by cutting or when a signal is recorded by irradiating laser light.

Next, a V-shaped cutting tool having a V-shaped tip (hereinafter abbreviated as V-biting) is cut into the master by several microns or more, and a V groove is formed by overlapping cutting. After forming the V-groove, a cutting process is performed in order to recess the region in contact with the region 1 in which the V-groove is formed, and a depth of about several tens of microns is engraved. Even if the depth of engraving is about 100 microns, there is no particular problem. When the depth of engraving is as shallow as a few microns or less, the photoresist cannot be uniformly accumulated during the final coating, and the effect of eliminating uneven coating cannot be expected. Further, the recessed region 2 may have a width of several mm or more, and may be recessed over the entire inner peripheral side. Since the inner peripheral side of the region 1 in which the V groove is formed is recessed from the region 2 in which the V groove is formed, the photoresist overflowing to the inner peripheral side during the pre-coating forms the V groove during the final coating. Since it uniformly collects at the boundary with the formed area 1, radial coating unevenness does not occur.

When the boundary portion between the region 2 having the V groove formed on the inner peripheral side of the region 1 having the V groove formed therein and the region 1 having the V groove formed therein and the region 1 having the V groove formed is mirror-finished, the photoresist is formed at this boundary portion. Since the photoresist easily flows, the photoresist is accumulated more uniformly on the boundary with the region 1 where the V groove is formed when performing the fanal coating, so that radial uneven coating is less likely to occur.

In order to finish it into a mirror surface, the surface is finished with a bite (R bite) whose tip has a curvature. For example, the tip has a radius of 0.2
The maximum average roughness is set to about 0.02 μm using a μm cutting tool. In this case, the maximum average roughness is 0.02μ unless it is R byte.
Even if it is less than m, it does not become a mirror surface and the photoresist does not easily flow. Further, a region having a width of about a few mm on the outermost peripheral portion of the recessed region 2 on the inner peripheral side of the region 1 in which the V groove is formed is sufficient as the region to be mirror finished. The reason why the photoresist accumulates during the final coating is because it is a region having a width of about several millimeters.

The outer peripheral side of the area 1 in which the V groove of the optical disc master is formed is
As shown in the enlarged schematic view of the cross section in FIG. 3, there is a rough surface area in contact with the V-groove-formed area 1, and the rough surface area is higher. For this reason,
During the final coating, the photoresist accumulates at the boundary between the region 1 where the V-groove is formed and the rough surface, and the photoresist becomes thicker in the region where the V-groove is formed with a width of several mm from this boundary. There is a drawback that parts cannot be used.

As shown in FIG. 4, this defect can be eliminated by contacting the V-groove-formed region 1 and lowering the outer peripheral side from the V-groove-formed region 1. The width of the depressed region 2 is about 5 mm, but it is sufficient if it is wider than that.

Even if the photoresist tries to accumulate at the boundary with the region 1 in which the V groove is formed during the final coating, since the outside of the boundary is recessed from the region 1 in which the V groove is formed, it is easy to reach the recessed region 2. The photoresist does not flow to the region 1 where the V groove is formed, and the photoresist is not accumulated. By providing the region 2 which is in contact with the region 1 in which the V groove is formed and is depressed from the region 1 in which the V groove is formed, the photoresist is uniformly applied to the outermost periphery of the region 1 in which the V groove is formed without thickening,
The region 1 in which the V groove is formed 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 recessing the inner peripheral side and the outer peripheral side in contact with the V-groove-formed region 1 from the V-groove-formed region 1, photoresist is applied to the entire V-groove-formed region 1. It can be applied uniformly, and the entire region 1 in which 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 forming the depressed region 2 in contact with the region 1 in which the V groove is formed, if the V groove is formed after the depression is performed in advance, the V bit is depressed when the V groove is cut from the depressed side. The V-groove cannot be formed well because the tip is chipped or the V-bite is caught on the boundary by receiving a force from only one direction at the boundary with the region 2 thus formed. Further, if the cutting is started from the side that is not depressed, the force applied to the V bit changes when the cutting is finished, and the V groove at the end of the cutting is disturbed. As described above, if it is attempted to form the V-shaped groove after it has been depressed in advance, it is difficult to form the V-shaped groove without disturbance.

In order to form the depressed region 2 in contact with the V-groove-formed region 1, the V-groove is formed first, and then the region 2 contacted with the V-groove-formed region 1 is depressed. It should be processed. With this configuration, the V groove is formed on a flat surface, so that the V groove is not disturbed at the boundary with the region in which the tip of the V bite is damaged or depressed.

When forming a spiral V-shaped groove, the groove is disturbed while the V-bite is being cut into the master at the point where the V-shaped groove is started to be cut. In order to prevent the entire region 1 in which the V groove is formed from being disturbed, the region 1 in which the V groove is formed is made wider than the region 2 in which the V groove is originally desired to be formed, and then the region in which the V groove is originally desired to be formed It may be processed so that the region in contact with is depressed.
Since the V groove is formed in a plane, the V groove is not disturbed at the end of cutting, and even if the V groove is disturbed at the start of cutting, the disturbed portion can be scraped off when it is depressed, so the V groove is formed. The entire area can be made undisturbed.

EFFECTS OF THE INVENTION In the optical disc master of the present invention, by providing a region that is in contact with the region where the V groove is formed and is depressed from the region where the V groove is formed, the photoresist can be uniformly applied to the entire region where the V groove is formed. Therefore, the entire area where the V groove is formed can be used.

[Brief description of drawings]

FIG. 1 is a plan view of an optical disk master having a V groove formed region and a depressed region according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a boundary portion between a region where a V groove is formed and a depressed region of the embodiment, and FIG. 3 is a cross-section on the outer peripheral side of a region where a V groove is formed in a conventional optical disk master. FIG. 4 is an enlarged cross-sectional view, and FIGS. 4 and 5 are plan views of an optical disk master having a V groove formed region and a depressed region according to another embodiment of the present invention. 1 ... V grooved area, 2 ... mirror-finished area, 3 ... master made of metal such as copper.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kishi Shunho 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Mitsuo Fujiwara 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. In-house (72) Inventor Riichi Kozono 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

(57) [Claims] 1. A master disc for an optical disk having a region having a V-shaped groove in cross section, wherein the V-shaped groove is formed on the inner peripheral side in contact with the region in which the V-shaped groove is formed. An optical disc master, which is characterized by being recessed from the formed area. 2. An optical disk master having an area in which a V-shaped groove is formed in cross section, wherein the V-shaped groove on the inner peripheral side in contact with the area in which the V-shaped groove is formed is formed. An optical disc master, characterized in that the boundary between the depressed region and the region in which the V-shaped groove is formed is a mirror surface. 3. An optical disk master having an area in which a V-shaped groove is formed in a cross section, and the V-shaped groove is formed on the outer peripheral side in contact with the area in which the V-shaped groove is formed. A master disc for an optical disc, which is characterized by being recessed from the area. 4. An optical disk master having an area in which a V-shaped groove is formed in a cross section, wherein the inner and outer peripheral sides in contact with the area in which the V-shaped groove is formed are the V-shaped. An optical disk master that is depressed from the area where the groove is formed. 5. After forming a groove having a V-shaped cross section, the V-shaped groove is formed on the inner peripheral side or the outer peripheral side or the inner peripheral side and the outer peripheral side of the region where the V-shaped groove is formed. A method for manufacturing an optical disk master, which is characterized by processing so as to be depressed from the formed area. 6. An inner peripheral side or an outer peripheral side of a V-shaped groove having a cross section formed over a region wider than the originally intended region and then contacting the region where the V-shaped groove is originally intended to be formed. Alternatively, the manufacturing method of the optical disk master is characterized in that the inner peripheral side and the outer peripheral side are processed so as to be depressed from the region where the V-shaped groove is formed.