JPH01201844A - Formation of master disk for optical disk - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method for producing a master disc for an optical disc, and more particularly to a method for laser exposure of a resist film coated on a glass substrate.

(b) Conventional technology The conventional method for creating guide grooves for optical discs, such as magneto-optical discs and write-once optical discs, is to apply a resist onto a glass substrate, expose the resist film to a laser beam, and develop it. The method used is to create an uneven part in the resist film by doing this, then transfer the uneven part by electroforming to create a stamper, and then transfer the uneven part of the stamper by molding to create a guide groove for the plastic substrate. ing. Recently, the dimensions of this guide groove are being standardized by the ISO standardization committee, and according to the draft standard,
In the case of group tracking, the guide groove has a width of 1.2
-1.3 μm, depth 880-100n, header in which address signals are recorded in advance Some of the pit shapes are 0.3-0.5 μm wide and 80-130n deep from the viewpoint of signal quality.
m. In other words, in the case of group tracking, it is necessary to create wide guide grooves and narrow pits.

(c) Problems to be Solved by the Invention The groove width is mainly determined by the laser spot diameter, and the spot diameter is controlled by the numerical aperture of the objective lens and the intensity of the laser power. While nudging, the intensity is 0.
．． It is not easy to form an exposure zone of 3 to 0.5 .mu.m and a width of 1.2 to 1.3 .mu.m with good contrast using a single laser beam. Therefore, the inventor of the present application has already applied for a method of forming a wide exposure zone by arranging a plurality of laser beams in the radial direction of the disk (Patent Application No. 208948 of 1988).

However, in this method, the exposed zone is formed with high precision and good contrast, but when the laser beam is moved in the disk radial direction, if the amount of movement (pitch) is uneven, the width of the unexposed zone will be causing variations,
When developed, there is a problem that the width of the land corresponding to the unexposed zone becomes uneven and the uniformity of the height of the land is not maintained.

This invention has been made in consideration of the above circumstances, and the resist film is irradiated with a laser beam having a predetermined interval in the radial direction of the previous disk, and an unexposed zone is secured by the interval, so that the laser beam is To provide a method for creating a master master disk for an optical disk, which can obtain a wide exposed zone without changing the width of the unexposed zone even if the pitch changes during movement of the disk.

(d) Means for Solving the Problems This invention provides a method for applying first and second laser beams to the resist film on a substrate in a predetermined direction in the radial direction of the optical disc in the resist film exposure step when creating a master disc for an optical disc. irradiate at the same time with intervals to form first and second exposure zones, respectively;
The two laser beams are moved in the radial direction of the optical disk while maintaining the predetermined interval so that a portion of the laser beams overlap, and the first and second laser beams are irradiated simultaneously, and this operation is repeated sequentially. In this method, a wide exposure zone consisting of a first exposure zone and a second exposure zone is formed while ensuring a non-exposure zone having a width corresponding to the predetermined interval.

(E) Effect Since the first and second laser beams are irradiated simultaneously with a predetermined interval in the radial direction of the optical disk, an unexposed zone with a width determined by the predetermined interval is formed. Also,
Since a portion of the first laser beam that is irradiated next overlaps with a portion of the second exposure zone that has been formed, a wide exposure zone is formed.

(f) Examples The present invention will now be described in detail based on examples shown in the drawings. This invention is not limited by this.

FIG. 1 is a configuration explanatory diagram showing a schematic configuration of a laser optical system applied to an embodiment of the present invention, and l! is a laser device, 12.18 is a beam splitter, 13.19 is a reflector, 14.15 is an optical modulator, 16 is an optical deflector, +7 is 17
It is a two-wavelength plate.

In such a configuration, one laser beam emitted from the laser device 11 is split into two laser beams 4.5 by the splitter 12.

The laser beam 4 that has passed through the optical RtFII device I4 and the optical deflector 16 is reflected by the reflecting mirror 13 and is reflected by the optical modulator 15.
and the laser beam 5 which has passed through the l/2\Il long plate 17 and been reflected by the reflecting mirror 19, is combined again by the beam splitter 18 and enters the objective lens 3.

Figure 2 is a perspective view showing the exposure state of the resist film during the creation of a master disc for optical discs, and Figures 3(a) and 4(a) are partial enlargements showing each step of the exposure work shown in Figure 1. 3(b) and 4(b) are plan views of the master portion corresponding to FIG. 3(a) and FIG. 4(b), respectively. In these figures, l is a disk-shaped glass substrate, 2 is a resist film coated on the glass substrate Vit, 1, and an objective lens 3 for exposure is arranged near the top of the glass substrate l. The laser beam 4.5 is irradiated through the objective lens 3 so that the resist spots focused on the resist film 2 are spaced apart from each other by a constant distance d in the radial direction of the disk-shaped glass substrate l. . 2
When the unexposed zone between the book beams 4.5 is developed, it becomes a land, and when the exposed zone 7.8 exposed by the beam 4.5 is developed, it becomes a group.

As shown in FIG. 3(a), beams 4.5 are irradiated onto the resist film 2 at intervals d in the radial direction of the disk l, and when the glass substrate l is rotated, the beams 4.5 are irradiated onto the resist film 2 as shown in FIG. 3(b). As shown, exposed zones 7.8 are formed on both sides of the unexposed zone 6 having a width d.

Next, the optical system is moved in the radial direction of the substrate l, that is, in the six directions of the arrows, so that the spot of the laser beam 5 overlaps the exposure zone 7 by the distance, and the substrate l is rotated, as shown in FIG. ) As shown in (b), a wide exposed zone 9 is formed by the exposed zone 8 that has partially overlapped with the exposed zone 7, and an exposed zone 71 is formed across a new unexposed zone 6a having a width d. It is formed.

By sequentially repeating these steps, a wide exposure zone is formed in the resist film. Note that the width d of the unexposed zone is controlled by changing the interval between the laser beams 4.5 and is independent of the moving pitch of the optical system, so the width d of the unexposed zone is maintained with high precision. In addition, the width of the wide exposure zone can be adjusted without controlling the output of the laser beam 4.5.
By changing the moving pitch of the optical system, it is possible to widen the laser beam to the sum of the spot diameters of 4.5 laser beams.

FIG. 5(a) is a partial cross-sectional view showing a method of exposing a part of the header of an optical disc master disc, and FIG.
Fig. 6 is an explanatory diagram of the arrangement of the bit exposure section formed in a part of the header, and Fig. 7 is a plan view of the master disc part of a), Fig. 7 is a modulation signal and deflection signal of the laser beam shown corresponding to Fig. 6. This is a time chart.

In these figures, the modulation signal S of the laser beams 4, 5
l, S2 are output and an exposure band 7.8 is formed on the resist film 2.
is formed, the modulated signal S1.
S2 turns OFF and the deflection signal S3 of laser beam 4 turns ON.
Then, the laser beam 4 is deflected to the position 4a as shown in FIG. 5, and the laser beam 4.5 is stopped from entering the objective lens 3. Next, in a period TI-T3, a modulation signal of the laser beam 4 is output, and the resist film 2 is irradiated with the laser beam 4a correspondingly to form an exposure 7a corresponding to a narrow pit in a part of the header. . At this time, the output of the laser beam 4a is slightly reduced and the spot diameter is reduced. At the same time, the beam angle is deflected by the optical deflector 16 which receives the deflection signal S3 so that the beam spot position 1 is located on the extension of the center of the wide exposure zone 9, and the beam is incident on the objective lens 3 as a beam 4a. be done. Then, the deflection signal S3 is turned off again at time t2.
When the modulation signals of the laser beams 4 and 5 are turned on, the laser beam 4.5 enters the objective lens 3 again and the exposure zone 7.8 is exposed to the lens) II! Formed on top of 2.

The above-mentioned interval d between the non-exposure zones can be adjusted with high accuracy by deflecting the laser beam 4 with the optical deflector 16 or by appropriately rotating the reflecting mirror 19. Further, the 1/2 wavelength plate 17 (FIG. 1) is used to change the plane of polarization so that the beams 4 and 5 do not interfere with each other.

(G) Effects of the Invention According to this invention, since the width of the non-exposed zone is maintained with high precision, it is possible to obtain a land with a uniform width and height.
You can create wide groups.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a laser optical system applied to an embodiment of the present invention, Fig. 2 is a perspective view showing the exposure state of a resist film when creating a master disc for an optical disc in an embodiment of the invention; 3(a) and 4(a) are cross-sectional views showing the process of one embodiment shown in FIG. 2, and FIG. 3(b) and FIG. 4(b) are respectively sectional views of FIG. Figure 4 (
FIG. 5(a) is a sectional view showing another process of the embodiment shown in FIG. 2, and FIG. 5(b) is a partial plan view corresponding to FIG.
Partial plan view corresponding to Figure (a), Figure 6 is Figure 3 (a)
〜A layout explanatory diagram showing the arrangement of exposure zones formed by the process shown in FIG. It is a chart.

Claims (1)

[Claims] 1. In the resist film exposure step when creating a master disc for an optical disc, first and second laser beams are irradiated onto the resist film on the substrate at a predetermined interval in the radial direction of the optical disc. and forming first and second exposure zones, respectively, and then exposing the second laser beam so that a portion of the first laser beam overlaps a portion of the second exposure zone.
After moving the laser beam of the book in the radial direction of the optical disc while maintaining the predetermined interval, the first and second laser beams are irradiated, and this operation is sequentially repeated to expose a non-exposed area with a width corresponding to the predetermined interval. A method for producing a master disc for an optical disc, which comprises forming a wide exposure zone consisting of a first and a second exposure zone while ensuring a wide exposure zone.