JPS5956228A - Production for disc original - Google Patents

Abstract

PURPOSE:To form a signal groove or a groove for grinding a reproducing stylus with an accurate width in the circumferential direction of a disc original even for the vertical face deflection of the disc, by condensing a laser light and converting it to a parallel light having the same width as the groove and irradiating a photosensitive layer with this parallel light to process it. CONSTITUTION:A laser light 28 is irradiated to a photoresist film 23 of an original 22 through a convex lens 26 and a concave lens 27. Since the concave lens 27 has the focus in the position coinciding with a focus (f) of the convex lens 26, the laser light 28 is converted to a parallel light 28b. The width of the light is made equal to a width W of the groove for grinding. Consequently, the width W of a spiral groove 24 for grinding is constant even in case of the vertical face deflection of the original 22.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a reproduction needle for a video disc or an audio disc.
The present invention relates to a disk master manufacturing method for manufacturing a polishing disk for polishing a disk playback stylus, or a video disk or audio disk on which signals are recorded, particularly for manufacturing the master.

[Background technology of the invention]

Conventionally, objects to be polished, such as playback needles of video disc players, have been polished by inserting the tip of the playback needle into a conical shape, for example, into a circumferential spiral groove formed on the top surface of a rotating polishing plate. As the needle is inserted, the opening edge of the groove, that is, the back of the groove, is brought into contact with the tapered surface of the cone, and the rolling abrasion between the regenerating needle and the polishing machine causes it to be polished to the same size as the width of the groove. ing. Finally, it is processed to have the same cross-sectional shape as the groove. In other words, the object to be polished, including the video and audio playback hooks, slides in the grooves on the top surface of the polishing machine, comes into contact with the shoulder areas of the grooves, and is gradually polished at the shoulder areas. It is designed so that it can be finished to the predetermined dimensions. Therefore, the width of the groove is a major factor in determining the finished dimensions of the object to be polished.

By the way, the above-mentioned polishing disk is formed by first creating a master disk and then going through a predetermined process.

A photosensitive layer such as a photoresist film is formed on the surface of this master disc, and by irradiating this photosensitive layer with a laser beam, the grooves that will become the base of the polished grooves are cut into a spiral shape. created by Conventionally, as shown in Fig. 1, a laser beam emitted in advance is once focused on a focal point f using a convex lens 1, and the focused beam slightly in front of the focal point f is irradiated onto the disk surface as a circular spot of a predetermined area. The photoresist film 2 was cut to form polishing grooves 3 in the photoresist film 2. Therefore, the groove width W of this polishing groove 3 changes depending on the spot width of the laser beam focused by the convex lens 1, and by keeping the distance from the convex lens 1 to the master 4 at a predetermined distance, polishing with a constant width can be achieved. A groove 3 for use is formed. Here, FIG. 1 is a cross-sectional view showing a master 4 placed on a rotating body 6 rotated by a rotating shaft 5. As shown in FIG.

In addition, as described above, in order to form grooves on the top surface of the disk using a laser beam, as shown in FIG. 2, signal grooves called pits are cut on the top surface of the disk 5 using a laser beam. There are cases.

In this case, the laser is, for example, an argon laser 6
The laser beam 7 is divided into a main ray 9 and a sub-light beam 10 by a half mirror 8, and the intensity of the principal ray 9 is modulated by an information signal 12 in an optical modulator 11, while the sub-light beam 10 In the optical modulator 13, the intensity of light is changed by the tracking signal 14, and respective outputs are obtained. Both main and sub beams 9 and 10 are modulated by the respective optical modulators 12 and 13, and the intensity of the light changes.
After the beams are again collected in one place by the half mirror 15, they are focused onto the disk 5 by the objective lens 16, and a signal groove is cut on the disk 5. A large number of discs for actual use are press-produced based on the master disc on which the grooves are formed.

[Problems with conventional technology]

However, forming the polishing grooves 3 and the like on the master disk 4 using the conventional method described in FIG. 1 poses the following problems.

That is, conventionally, the photoresist film 2 is cut with a focused beam before converging at the focal point f to form the polishing groove 3, and the groove width W of the polishing groove 3 is smaller than the convex lens of the master 4. It is set in a distance relationship with respect to 1. That is, when the master 4 approaches the convex lens 1, a wide groove 3 is formed, and when the master 4 moves away from the convex lens 1, the groove width W of the groove 3 becomes narrow. Therefore, this master 4
In any case, if there is no vertical wobbling in Figure 3 (
If there is even a slight surface deviation from the normal state shown in (a), the upper surface of this master 4 will differ in its approach to the focal point f, as shown in FIGS. 3 (b) and (c), and as a result, the polishing groove 3 The groove width W along the circumferential direction of the disk is shown in FIG. 4 (b).
There was a problem in that W2 fluctuated as shown in Figures 1 and 4 (c). That is, FIG. 4(B) shows the polishing groove 3 formed when the surface of the master 4 is tilted upward, and its width W1 is larger than the normal width W, and FIG. The width W2 of the polishing groove 3 that is formed when the surface runs out is smaller than the normal width W.

This problem is caused by the fact that even if the above-mentioned surface runout is small, it not only has a large influence as an error on the groove width W, but also requires extremely high precision, such as the playback needle of a video disc player. In the case of objects to be polished, this can lead to large errors in the finish.

For this reason, it is conceivable to correct the groove width W of the polishing groove 3 using an autofocus mechanism or the like. In this case, the position of the convex lens 1 is adjusted to be closer to or closer to the master 4 based on the measurement results, but the correction tends to be delayed, resulting in a problem with followability, and the polishing groove is always normal. It is difficult to form 3.

In addition, this problem can be solved by the disk 5 as shown in Figure 2 above.
A similar problem occurred when cutting grooves for signal recording on the top.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and is designed to ensure that the signal groove or the groove for polishing the playback needle formed on the master disk is formed with an accurate width in the circumferential direction even with respect to the surface runout of the disk. The purpose of the present invention is to provide a method for manufacturing a master disk.

[Summary of the invention]

In the present invention, when cutting a photosensitive layer laminated on a disk with a laser beam to form a spiral signal groove or a groove for polishing a reproduction needle, the laser beam is focused, and the laser beam after the focus is transferred to the laser beam. A signal groove or a polishing groove with a regular width is formed by converting into a parallel light beam having the same width as the groove width, and irradiating the parallel light beam onto the photosensitive layer to process the photosensitive layer. This is how it was done.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings from FIG. 5 onwards.

Fig. 5 is a sectional view showing the first embodiment of the present invention, and Fig. 6 is an explanatory diagram showing the embodiment shown in Fig. 5, and shows the groove width of the polishing groove formed on the master disc with surface wobbling. be.

In these figures, reference numeral 21 is a glass plate that is a component of the master 22, and a photosensitive layer 23 (referred to as a photoresist film) coated with, for example, photoresist is laminated on the upper surface of the glass plate 21. This master disc 22 is placed on a rotating body 33 and is rotated by rotationally driving the rotary body 30, and a laser beam 28 is irradiated from above onto the photoresist film 23 of the master disc 22 that is rotationally driven. is configured to be This laser beam 28 passes through a convex lens portion and a concave lens 27 disposed on the optical path in front of the focal point f of the convex lens 26 to the master 22.
The photoresist film 23 of is irradiated. However, this concave lens 27 is different from the convex lens 2.
It is interposed in the section between the focal point f of the convex lens 26 and the optical axis thereof is the same as that of the convex lens 26, so that the focal point position coincides with the focal point f of the convex lens 26.

In the above configuration, the master 22 rotates with the rotation of the rotating body 30, and the photoresist film 22 of the master 22 in the rotating state
A laser beam 28 is irradiated toward. This laser beam 28 is focused by the convex lens 26 and attempts to be focused at the focal point f of the convex lens 26. Since there is a concave lens 27 between this focal point f and the convex lens 26, in this embodiment, when the convergent light beam 28a reaches the center line 27a of the concave lens 21, it is bent and becomes a parallel light beam 28b.
The focused light beam 28a at the time when it reaches this center line 27a
The width of the light beam is made equal to the polishing groove width W.

Therefore, the focused light beam 2 passing on the center line 27a
By setting the width of the light beam 8a to a predetermined width, it is possible to form a polishing groove 24 in the photoresist film 23 with a groove width corresponding to the type of regenerating needle.

This setting involves selecting a ray section from the convex lens 26 to its focal point f, placing the concave lens 27 at a predetermined position, and
The focal point of this concave lens 27 may be selected to be the focal position of the convex lens 26.

The parallel light rays 28b thus obtained are irradiated onto the photoresist film 23 with a width equal to the groove width W of the polishing grooves 24 (or signal grooves) formed on the master 22, so even if the master 22 has vertical surface fluctuation. Even if there is, the groove width W of the polishing groove 24 is a spiral groove with a constant width. FIG. 6 is a diagram for explaining this, and FIG. 6 (a) shows a state where there is no surface wobbling on the master 22, and FIG. 6 (b) shows a state where there is surface wobbling that rises upward. FIG. 6(c) shows a state where there is downward surface wobbling. In any of the above cases, a constant groove width W can be obtained by using the parallelized light beam 28b of the present invention.

Note that the laser beam 28, the convex lens 26, and the concave lens 2
The configuration 7 gradually moves integrally in the radial direction of the master disc 22 as the master disc 22 rotates. As a result, the polishing groove 23 is formed in the photoresist film 23 as a spiral groove having a constant width from the starting end to the ending end.

Further, the focal point f of the convex lens 26 on the master 22 side may be set at a position passing through the master 22.

Furthermore, the parallel light rays 28b can also be obtained by optical means that uses the convex lens 25 in addition to the concave lens 27. FIG. 7 shows a second embodiment showing the method in this case, and the same reference numerals are used for the same components as those in FIG. 5. In the embodiment shown in FIG.
A second convex lens (hereinafter referred to as a second convex lens) is interposed between the focal point f of the first convex lens 26 and the master 22. In this case as well, parallel light beams 28b whose beam width is equal to the groove width W can be obtained from the second convex lens 2) on the photoresist film 23, and uniform spiral polishing grooves 24 or signal grooves are formed. It is something.

Further, FIG. 8 shows a third embodiment of the present invention. In this embodiment, a correction mask 29 is interposed between the concave lens 27 of the first embodiment and the master 22 to correct the width of the parallel light beam 28a for cutting the photoresist film 23.

This correction mask 29 is formed of a suitably thick metal mask, and has a square hole 31 (or a circular hole) having the same width as the groove width W of the polishing groove 24. This square hole 31 has a square or rectangular shape. Therefore, even if the parallel line 28a is not the same size as the groove width W of the polishing groove 24 and is wider than the groove width W of the polishing groove 24, the rectangular hole of the correction mask 29 As long as the width of the polishing groove 31 is made to match the groove width W of the polishing groove 24, this polishing groove accurately draws a spiral groove having the groove width W using the corrected parallel light rays 28b. Further, this correction mask 29 can also be interposed in the parallel beam section between the second convex lens 5 and the master n in the second embodiment.

In the above explanation, the case where the polishing grooves 24 for polishing the object to be polished are formed on the upper surface of the master disc 22 has been explained, but the present invention can also be applied to the case where signal grooves are formed on the disc for reproduction. Of course, it can be applied.

〔Effect of the invention〕

As explained above, according to the present invention, an optical means for collimating the focused light beam is interposed between the optical means for converging the laser beam and the master, and the photoresist film of the master is coated with the parallel light. Since the polishing grooves or signal grooves are formed by cutting, even if the master disk has surface fluctuations, the width of the irradiated surface of this parallel beam will always be the same as the width of this parallel beam, resulting in a uniform There is an advantage that a spiral groove can be formed.

[Brief explanation of drawings]

Figure 1 is an explanatory cross-sectional diagram showing the case of forming abrasive grooves on a master disc using the conventional method, Figure 2 is an explanatory diagram of cutting signal grooves on a video disc, and Figure 3 is an explanatory diagram of the case where the disc is subject to surface wobbling. An explanatory diagram to explain the inconvenience when this occurs,
FIG. 4 is an explanatory diagram showing changes in groove width caused by the disadvantages in FIG. 3, FIG. 5 is an explanatory diagram showing the first embodiment of the present invention, and FIG. 6 is an explanatory diagram showing groove widths made uniform by the present invention. FIG. 7 is an explanatory diagram showing a second embodiment of the present invention, and FIG. 8 is an explanatory diagram showing a third embodiment of the present invention. 21...Glass plate, 22...Master disk, 23...Photoresist film, 24...Signal groove or polishing structure, 25, 26...Convex lens, 27...Concave lens, 28...Laser beam, 28a...Focused light beam, 28b...Parallel light beam, 29...
Correction mask, 30...Rotating body, Representative Patent Attorney Noriyuki Norihiko (and 1 other person) Figure 3 (, A) (B) Figure 4 (A) (B) 44 (C) (C) 5 Figure 6 (A) (B) (C) Figure 7

Claims (1)

[Claims] (1) A master disk on which a photosensitive layer is laminated is driven to rotate, and a laser beam focused by an optical means that focuses light is irradiated onto the photosensitive layer of the master disk to form a spiral signal groove or a groove for polishing a reproduction needle. In this method, an optical means for collimating the focused light beam is interposed between the optical means for focusing the laser beam and the master disk, and the focused laser beam is A method for manufacturing a disk master, characterized in that the light beam is made into a parallel beam having a width approximately equal to the groove width of the signal groove or the reproduction needle polishing groove.