JPS6331045A - Manufacture of master disk having concentric circular groove - Google Patents

Abstract

PURPOSE:To form a concentric circuit guide groove high in dimensional accuracy with a comparatively simple manufacturing equipment by making the relative shifting of a substrate and an optical system into an equal speed continuous motion, shifting an optical beam in the reverse direction with the movable mechanism of a recording head only by the shifting part of the substrate or the optical system, and forming a concentric circular groove. CONSTITUTION:For the starting of recording, an AO modulator 2 is turned on and exposure is started simultaneously when a rotating synchronizing signal is generated. Simultaneously, a signal is added to a track coil, control is executed so that the distance of the position of an optical beam on a substrate 5 and the rotating center can be always constant, the light axis is shifted in the direction reverse to the shifting direction of the substrate, a locus draws a circular and the exposure is executed. Next, simultaneously when the second rotating synchronizing signal is generated, the AO modulator is turned off, the exposure is stopped and the recording for one groove is completed. Simultaneously, a track coil driving signal is turned off and the recording head is returned to the original position. Next, only one circumferential part is awaited as it is. Next, simultaneously when the third synchronizing signal is generated, the AO modulator and the track coil driving signal are turned on and the exposure of the second groove is started. The action during the exposure is executed in the same way as the first groove. The above-mentioned action is repeated and the recording of the concentric circular groove is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a guide groove master for an optical disc.

(Prior Art and Problems) A recordable optical disc that can be recorded and reproduced by a user usually has a guide groove formed therein for positioning the recording/reproducing head. There are two types of guide grooves: spiral and concentric. Of these, the spiral groove can be formed by exposing a rotating substrate or an optical system including a recording head while moving at a constant speed. On the other hand, since the guide grooves of the concentric grooves are not continuous, relative movement of the recording head and the substrate and exposure cannot be performed simultaneously and continuously. A conventional method for forming concentric grooves will be described below with reference to the drawings.

FIG. 3 is an operation timing chart in a conventional concentric groove forming method. In Fig. 3, (dl is a rotation synchronization signal of one pulse per one rotation of the board, (el is ^0(Acou
sto-optical) modulator or EO (Ele
(ctro-optical) on/off signal of the recording light by the modulator (optical modulator drive signal), (f) shows the drive signal of the motor for moving the substrate or optical system. Next, this operation will be explained. For the sake of simplicity, we will explain a method in which the relative movement between the substrate and the optical system is performed by moving the substrate, but the operating principle is exactly the same in the method of moving the optical system.First, the substrate rotates at a constant speed, When the moving motor is stopped and a synchronization signal is generated, the optical modulator is turned on to start exposure, and the exposure is stopped at the same time as the next synchronization signal is generated to complete the exposure for one round.Next. Immediately after the exposure stops, the moving motor is started to move the substrate by one pitch, and the movement is completed before the third synchronization signal is generated.

Next, as soon as the third synchronization signal is received, exposure starts,
At the same time as the fourth synchronization signal is received, exposure is stopped and exposure for one round is completed. As described above, concentric grooves can be formed by alternately performing substrate movement and exposure. In addition,
If the rotation speed of the substrate is too fast (if the movement cannot be completed within one cycle, the movement is performed by one pitch in two or three turns.In the conventional method of forming concentric grooves described above, the moving motor A step motor or a DC servo motor is used for this purpose, but since either type of motor operates intermittently, it is easily affected by the meshing accuracy of moving parts (compared to the case of spiral groove formation, which operates continuously). The pitch accuracy of concentric grooves formed by the conventional method is about ±0.08 μm.
Step motors are not suitable for forming spiral grooves because their constant velocity during continuous operation is lower than that of DC servo motors. - On the other hand, DC servo motors have the drawbacks of poor responsiveness to intermittent motion, the need for expensive length measuring devices such as a ladder length measuring device, and a complicated structure for high-precision positioning. have That is, it is difficult to form grooves with high precision no matter which motor is used.

(Means for Solving the Problems) The present invention was made in view of the drawbacks of the prior art, and its purpose is to create a concentric groove original plate that can form concentric guide grooves with high dimensional accuracy using a relatively simple manufacturing device. The purpose is to provide a manufacturing method.

The present invention forms concentric grooves by making the relative movement between the substrate and the optical system a constant continuous movement, and moving the light beam in the opposite direction by the movement of the recording head by the amount of movement of the substrate or the optical system. It is characterized by

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

FIG. 1 is a block diagram of a groove original manufacturing apparatus applied to the present invention. In Fig. 1, 1 is a recording Ar laser, 2 is an AO laser
3 is a mirror, 4 is a recording head, 5 is a glass substrate, 6 is a motor for rotating the substrate, 7 is an air slide, 8 is a ball screw, and 9 is a DC servo motor for moving the substrate.

The recording head 4 includes a focus control mechanism using a semiconductor laser, and is also equipped with a movement mechanism in the trunk direction like a known optical disk recording/reproducing head, and by applying a signal to a track drive coil, the radius of the substrate can be adjusted. It is possible to move the optical axis in this direction. Next, an operation method when producing a concentric groove original using this production apparatus will be described.

FIG. 2 is an operation timing diagram when forming concentric grooves using this apparatus. In Figure 2, (a) is a rotation synchronization signal of one pulse for each rotation of the substrate, (crest) is the on/off signal of the laser beam by the ^0 transformer (AO modulator drive signal), and (C) is the rotation synchronization signal of one pulse for each rotation of the substrate. The drive signal to the track coil of the recording head is shown. The substrate rotates at a constant speed and generates a rotation synchronization signal (a) of one pulse for each rotation. On the other hand, the substrate moving mechanism also operates continuously at a constant speed, and its speed is such that it advances by one pitch for every two rotations of the substrate. First, to start recording, the AO modulator is turned on and exposure is started at the same time as the rotation synchronization signal is generated.

At the same time, a signal is applied to the trunk coil, and while controlling the distance between the position of the light beam on the board and the center of rotation of the board to be always constant, the optical axis is moved in the opposite direction to the direction in which the board moves, and the trajectory is Expose while drawing a perfect circle. Next, at the same time as the second rotation synchronization signal is generated, the AO modulator is turned off to stop exposure and complete the recording of one groove. At the same time, the track coil drive signal is also turned off and the recording head is returned to its original position. That is, the recording head comes to a position two pitches ahead of the recorded groove. Next, only the rotation and movement of the substrate remains in operation for one revolution. Next, at the same time as the third synchronization signal is generated, the AO modulator and the track coil drive signal are turned on, and exposure of the second grain groove is started.

The operation during exposure is the same as for the first grain groove. By repeating the above operations and recording a predetermined number of grooves, recording of concentric grooves is completed. It goes without saying that in this apparatus, if continuous exposure is performed without using a mechanism for moving the recording head in the track direction, recording of spiral grooves is also possible.

Next, more specific embodiments of the present invention will be described. 1100mm photoresist is applied to the glass substrate using a spin code.
The substrate was coated to a thickness of n, and then the substrate was mounted on the above manufacturing apparatus and concentric grooves were recorded.

The rotation speed of the substrate is 900 rpm, and the moving speed of the substrate is 12μ.
m/sec, that is, the groove pinch setting value was 1.6 μm. A concentric groove original plate was obtained by developing the substrate on which recording had been completed. The groove pitch of the concentric groove original plate thus obtained was measured. Measurements were performed using an optical microscope on 100 continuous lines in a total of 12 directions every 30° in the radial direction of the substrate. As a result, the average value of the groove pitch in any direction was 1.6 μl, and the variation was ±0.03 μm or less.

Similar measurements were performed on a groove original plate in which a 1.6 μm pinch spiral groove was formed using a conventional manufacturing device with a similar configuration, and the pitch variation was ±0.
It was 0.03 μm or less.

As a result, it has been found that it is possible to form a concentric groove original plate, which has been considered difficult in the past, with the same accuracy as a spiral groove original plate.

(Effects of the Invention) As explained above, according to the method for manufacturing a concentric groove original plate of the present invention, the rotation and movement of the substrate are continuous operations at a constant speed, and the movement of the optical axis is controlled by a drive signal to the track coil of the recording head. Since this is done by adding , there is an advantage that concentric grooves with high dimensional accuracy can be formed with a relatively simple manufacturing device. Further, according to the groove original manufacturing apparatus according to the present invention, it is possible to form a spiral groove, and there is an advantage that the spiral groove can also be formed with high dimensional accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a grooved original manufacturing apparatus of the present invention, FIG. 2 is an operation timing diagram for explaining the method of manufacturing a concentric grooved original of the present invention, and FIG. 3 is a diagram of a conventional concentric grooved original. FIG. 3 is an operation timing chart for explaining the manufacturing method. 1...Ar laser 2...AO modulator 3.
...Mirror 4...Recording pad 5...Glass substrate 6...Substrate rotation motor 7...
Air slide 8...Ball screw 9...Motor for board movement Patent applicant Nippon Telegraph and Telephone Corporation Figure 1 l-4i size 2-AOllvi11# 3-11 mirror 4--π rhyme head F. 5-m- is the last 5-6----board original n-circle moge 7--1 air slide 8--1 wood-ru-binji q-11 buri rare am so-ge Figure 2

Claims (1)

[Claims] 1. In a method of forming grooves on a rotating optical disk substrate using a light beam, a predetermined groove is formed during two rotations of the substrate by relative movement of the rotating substrate and an optical system including a recording head. While moving at a constant speed equal to the pitch of A control signal for moving the recording head is applied to expose the recording head so that the trajectory draws a perfect circle, and in the next revolution, the exposure is stopped and the recording head is returned to its original position, and the recording head is moved between the substrate and the recording head by a predetermined pitch. After relatively moving the optical system, by repeating the exposure operation using the above method in the next round, two parts of the substrate are exposed.
A method for manufacturing a concentric groove original plate, characterized in that one concentric guide groove is formed for each rotation. 2. The method for manufacturing a concentric groove original according to claim 1, wherein the optical system is fixed and the substrate is moved in the relative movement of the substrate and the optical system. 3. The method for manufacturing a concentric groove original plate according to claim 1, wherein the relative movement of the substrate and the optical system involves fixing the center of the substrate and moving the optical system.