JPH03248342A - Optical disk substrate and its manufacture - Google Patents

Abstract

PURPOSE:To prevent recording film or protective film on an optical disk substrate peeling or corroding by forming the bottom of a pit with a curved surface not making at an acute angle. CONSTITUTION:A first photoresist layer 2 and a second photoresist layer 3 are laminated on a glass master disk G. Exposure is performed by irradiating the layers with a laser beam 4, however, at this time, exposure power by which no exposure of a glass substrate 1 is performed on the pit 5 after performing developing treatment is employed as the exposure power of the laser beam 4. Thereby, the bottom of the pit can be comprised of a moderate cured surface without generating the acute angle. In such a way, it is possible to prevent the recording film and the protective film on the optical disk substrate peeling or corroding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical disc substrate and a method for manufacturing the same, particularly a video disc that is used exclusively for reading information.

The present invention relates to optical disk substrates such as CDs, CD-ROMs, write-once optical disks on which information can be written once upon a time, and rewritable optical disks on which information can be rewritten, and methods for manufacturing the same.

[Conventional technology]

Conventional optical disc substrates are manufactured through the steps shown in FIG.

The following is a step-by-step explanation.

In the glass disk manufacturing process, the surface of the glass disk 1 is polished and cleaned.

(B) In the photoresist coating step, a photoresist 13 is coated on the surface of the glass disk 1, which has been polished and cleaned, and then dried.

In the recording process using laser light, the information to be recorded is irradiated onto the photoresist 13 coated on the glass disk 1 by intensity modulation of the laser light 4, thereby performing exposure (C).

(D) In the developing step, the photoresist 13 is developed. The photoresist 13 in the unexposed portions does not react during the development process, and the photoresist 13 in the areas exposed to the laser beam 4 reacts during the development process to form pits 14. The glass disk made in this way is called a glass master disk.

(E) In the plating process, plating is performed on the glass master disk.

When this plated metal is peeled off, the pits and other irregularities of the glass master disk are reversed and transferred. This is standby 15
That's what it means.

(F) In the molding process, the above-mentioned standber 15 is used to mold an optical disk substrate 16 by transferring a plastic material such as polycarbonate using a technique such as injection molding or by a photopolymer (2P) method. At this time, the unevenness of the stand bar 15 is reversed and transferred, so that the unevenness of the optical disc substrate 16 that is finally formed matches that of the glass master disk.

On the optical disk substrate 16 manufactured as described above, a reflective film, a protective film, a recording film, etc. are formed depending on the use of each optical disk.

FIG. 9 shows an example of a magneto-optical disk using a conventional optical disk substrate 16, in which a groove 19 for operating a tracking servo. An intermediate film 8. Magnetic recording film 9. A protective film 10 is configured. Such a conventional optical disc substrate 16 has pits 17 and grooves 1.
9 is formed with an almost gently curved surface, but pit 17
It has an acute angle portion 18 at the bottom. The acute-angled portion 18 of the optical disc substrate 17 forms an intermediate film 8 formed on the optical disc substrate 16. Recording film 9. This also affects the protective film 10, forming a steep difference.

In an optical disk, if there is a defect or dust that causes a gap in the medium, the recording film or protective film tends to peel off or corrode from that part, and the acute angle portion 18 also tends to peel off or corrode. have

The reason why such an acute angle portion 18 exists on the optical disc substrate 16 is due to the following manufacturing method.

As mentioned above, the conventional optical disc substrate manufacturing process is performed by the steps shown in FIG. FIG. 7 is an enlarged view of FIG. 6(C), and recording is performed by irradiating a laser beam 4 onto a glass master disc, which is composed of a glass disc l coated with a photoresist 11.

When this glass master disk is developed, it becomes as shown in FIG.

Since the glass disk 1 is exposed in the pit 14, an acute angle portion is generated. When an optical disk substrate is produced from this glass master through the (E) plating process and (F) molding process shown in FIG.
8 occurs.

In the (C) laser beam recording process in Figure 6, if the glass disk 1 is irradiated with a weak laser beam for development so as not to be exposed, the edges of the pits become too smooth, making it impossible to obtain the reproduced signal strength. , the information recording density also decreases. Therefore, it is not possible to make the pit edge gentle.

From the above, with the conventional optical disc substrate manufacturing method, it has not been possible to produce an optical disc substrate without creating an acute angle portion in the pit portion.

[Problem to be solved by the invention]

However, such conventional optical disc substrates and their manufacturing methods have the disadvantage that the recording film and protective film are likely to peel off or corrode, resulting in a lack of long-term reliability.

[Means to solve the problem]

(1) The optical disk substrate of the present invention is an optical disk substrate on which information is recorded with or without pits, and the bottoms of the pits are formed as curved surfaces without having acute angles.

(2) The optical disk substrate manufacturing method of the present invention is a method for manufacturing an optical disk substrate in which information is recorded with or without pits, including a glass disk manufacturing step, a photoresist coating step, and a recording step using laser light.

The developing process consists of two plating processes and a molding process, and is constructed by using two or more types of photoresists with different sensitivity characteristics in the photoresist coating process.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a manufacturing process diagram showing an embodiment of the present invention.

The optical disk substrate manufacturing method shown in FIG. 1 differs from the conventional optical disk substrate manufacturing process in the photoresist coating process.
The process consists of two steps: a first photoresist coating process B1 and a second photoresist coating process B2.

FIG. 2 is a diagram showing the glass master disk after the first photoresist coating step B1 and the second photoresist coating step B2 are irradiated with laser light 4 for exposure. A first photoresist layer 2 and a second photoresist layer 3 are laminated on the glass master disk. The sensitivity characteristics of the first photoresist layer 2 and the second photoresist layer 3 are shown in FIG. This is exposed by irradiating the laser beam 4. At this time, the laser beam 4
The exposure power used is such that the glass substrate 1 is not exposed at the pits 5 after the development process, as shown in FIG.

As a result, the bottom of the pit has a gently curved surface without having an acute angle. At this time, since the exposure sensitivity of the second photoresist film 3 is higher than that of the first photoresist film 2, the edges of the pits can be made steep.
Unlike the conventional example, sufficient reproduction signal strength can be obtained, and the recording density of information is not reduced.

From the glass master disk shown in FIG. 4 through the plating step E and molding step F shown in FIG. 1, an optical disk substrate having pits having no acute angles but concave curved surfaces according to the present invention can be produced.

FIG. 5 shows a cross-sectional view of an embodiment of a magneto-optical disk using the optical tiff substrate according to the present invention.

The optical TiSF substrate 7 according to the present invention shown in FIG. 5 has a groove 12 for operating a tracking servo. A pit 11 for recording information such as track and sector addresses is formed, and an intermediate film 8° and a magnetic recording film 9 are formed thereon. A protective film IO is formed. At this time, since the pits 11 of the substrate do not have acute angle portions 18 as shown in FIG. 9, peeling and corrosion of the recording film and protective film will not occur.

〔Effect of the invention〕

The optical disc substrate of the present invention and its manufacturing method can provide a substrate without an acute angle at the bottom of the bit, so that peeling and corrosion of the recording film and protective film will not occur, and long-term reliability can be improved. .

[Brief explanation of drawings]

FIG. 1 is a manufacturing process diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing the glass master disk and laser irradiation state in the recording process shown in FIG. 1, and FIG. 3 is a diagram showing each resist shown in FIG. 2. Figure 4 is a cross-sectional view of the glass master disk after the development process shown in Figure 1. Figure 5 is a sensitivity characteristic diagram of the film. Figure 5 is a diagram showing the sensitivity characteristics of the film. Figure 5 is a cross-sectional view of the glass master disk after the development process shown in Figure 1. A cross-sectional view of a magneto-optical disk, FIG. 6 is a manufacturing process diagram showing an example of the conventional method, FIG. 7 is a cross-sectional view showing a glass master disk and laser irradiation state in the recording process shown in FIG. 6, and FIG. 8 is a diagram showing a state of laser irradiation. A cross-sectional view of the glass master disk after the development process shown in FIG.
FIG. 2 is a cross-sectional view of a magneto-optical disk manufactured using an optical TiSF substrate manufactured through the manufacturing process shown in the figure. G, Gl...Glass master disc, 1...Glass disk, 2...First photoresist layer, 3...
Second photoresist layer, 4... Laser light, 5, 1
1, 14.17...Pit, 6.15...
・Standber, 7.16... Optical disk board, 8
...Intermediate film, 9...Magnetic recording film, lO
...Protective film, 12.19 ...Groove, 13
...Photoresist, 18...Acute angle part,
A... Crow disk manufacturing process, B1... First photoresist coating process, B2... Second photoresist coating process, B... Photoresist coating process, C...
...-Recording process, D...Development process, E...
...Plating process, F...Molding process, 1...Remaining film thickness, ■...Exposure amount.

Claims (2)

[Claims] (1) An optical disc substrate on which information is recorded with or without pits, characterized in that the bottoms of the pits are formed as curved surfaces without having acute angles. (2) A glass disk manufacturing process for manufacturing a glass disk, a photoresist coating process using two or more types of photoresists with different sensitivity characteristics, a recording process for memorizing with laser light, and a developing process for developing the recording. A method for manufacturing an optical disc substrate, comprising: a plating step of plating the recording that appears on the glass disk by development; and a molding step of molding an optical disc using a stamper formed by the plating.