JPH07287873A - Optical disk substrate, manufacturing method therefor and optical disk device - Google Patents

Abstract

PURPOSE:To obtain an excellent transferred pattern by eliminating a narrow region since guide grooves do not exist on both adjacent sides in the radial direction of an irregular pattern. CONSTITUTION:In an optical disk substrate on which a first guide groove 22-1 of an optical disk is formed, an irregular pattern is formed in the radial position different from that of the guide groove on the surface of the substrate and a light reflection film or a recording film is formed on the pattern, the first guide groove 22-1 does not exist on both adjacent sides in the radial direction of the irregular pattern and a second guide groove 22-2 exists on both adjacent sides in the circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to substrates for read-only type optical disks such as CD-ROMs and write-once, reversible type optical disks, and is intended to improve the quality thereof. In particular, the present invention relates to a substrate manufacturing technique suitable for an optical disc having a narrow track pitch that supports high-density recording.

[0002]

2. Description of the Related Art Optical discs include a read-only type and a readable / writable type. The former includes a laser disk (LD) and a compact disk (CD), which are currently mass-produced. In addition to the above, there are CD-ROMs, CD-Is, DV-Is, and the like as multimedia media in the read-only type optical discs, and these are about to develop greatly in the future. In particular, there are great expectations for optical discs as electronic publication media. The latter includes recording forms represented by magneto-optical and phase change optical disks. As a means for manufacturing these optical disks, a nickel stamper is first formed from a master by an electroforming process, and a nickel stamper is used for injection molding, or a pattern is transferred onto a flat substrate with an ultraviolet curable resin, so-called 2P.
Discs were manufactured in large quantities by the law. This master is manufactured as follows. A so-called cutting is performed by applying a photoresist to a thickness of about 140 nanometers on a glass substrate having a thickness of about 10 mm by spin coating and exposing the photoresist with a laser beam having a signal modulated. For cutting, the modulation signal is concentric or spiral, and along a track with a track pitch of 1.6 μm, in the case of a substrate other than a read-only board, a preformatted signal representing the data recording address and the timing clock is recorded in various places on the master disc. is doing. Further, a guide groove for recording and reproducing laser light is recorded on almost the entire usage area of the master. In the case of a read-only optical disc, information pits are recorded on the entire surface.

The shape of the completed preformat and laser light guide groove is as follows. That is, in a substrate other than a reproduction-only substrate, there are guide grooves all around and there are pits in places.

[0004]

In order to increase the recording density of an optical disc, there are methods such as circumferential recording density so-called linear density improvement or high track density reduction of radial track pitch. In order to realize these, in a drive device, it is necessary to shorten the wavelength to miniaturize the light spot diameter. It is necessary to improve the transferability of the track pitch. High quality,
In the present state of the art, an injection molding method using a polycarbonate resin is generally used as a low-cost optical disk substrate manufacturing method.
This method has a problem in transferability in a narrow area, and a narrow area between the continuous guide groove and the concavo-convex pattern is apt to cause transfer failure, resulting in a decrease in optical disk yield and signal deterioration.

An object of the present invention is, as described above, when the track pitch (in the present invention, the pitch in the radial direction of the second guide groove portion) is narrowed, it is used for recording addresses of data of good quality and for timing. An optical disk substrate and an optical disk device for obtaining a high-quality tracking error signal for guiding an optical head of an optical disk drive device and a signal for counting the number of tracks, and an optical disk device.

[0006]

In order to achieve these objects, in the present invention, there is no first guide groove on both sides in the radial direction of the concavo-convex pattern, and between the circumferential concavo-convex pattern and the concavo-convex pattern. The second guide groove is provided.

That is, the features of the present invention are as follows: (1) The first guide groove of the optical disc and the concavo-convex pattern are formed at radial positions different from the guide groove on the surface of the substrate, and the light reflection film or the recording film is formed thereon. In the optical disc substrate
In the optical disc substrate, there is no guide groove on both sides in the radial direction of the concavo-convex pattern, and there are second guide grooves on both sides in the circumferential direction.

(2) The optical path difference in reflection between the second guide groove portion and the flat portion between the second guide groove portions described in (1) above is between λ / 8 and λ / 2 of the laser wavelength used. Is preferred. This is because the track cross count is not hindered within this range.

(3) The track cross signal is excellent even when the radial pitch of the second guide groove portions described in (1) above is 1.2 μm or less.

(4) The radial width of the second guide groove is
There may be two or more types.

(5) It is preferable to set the shapes of the first and second guide grooves so that the polarities of the tracking error signals by the first guide groove and the second guide groove are mutually inverted. (6) It is preferable that the depth of the concavo-convex pattern in the second guide groove region is the same as the depth of the first guide groove or the second guide groove.

Further, according to the present invention, (7) a step of applying a photosensitive material on the surface of the substrate, and exposing the surface with guide groove information of the optical disk, address information such as sector marks, or intensity-modulated laser light. And a step of forming a concave-convex pattern and a first guide groove and a second guide groove in accordance with the exposure by a developing process, and a step of producing a transfer master from the master, In a method of manufacturing an optical disk substrate having a resin surface on which the concavo-convex pattern and the first guide groove and the second guide groove are transferred from this master mold, the concavo-convex pattern does not have guide grooves on both sides in the radial direction. The optical disk substrate manufacturing method is characterized in that the pattern is formed such that the second guide groove exists on the circumference of the same radius as the pattern.

Further, according to the present invention, (8) a concave-convex pattern is formed on the substrate surface at the first guide groove of the optical disk and at a radial position different from the guide groove, and a light reflection film or a recording film is formed thereon. In the optical disc substrate, there is no guide groove on both sides in the radial direction of the concavo-convex pattern, and there are second guide grooves on both sides in the circumferential direction.
An optical disk device having an optical head and an actuator for driving the optical head, and an optical disk having means for making the polarity of a tracking deviation signal in the second guide groove area the same as that of the first guide groove area. There is a feature in the device. (9) A concave / convex pattern for changing the physical state of the detected light is provided within a range that the light spot can reach within the response time of tracking control after entering the second guide groove area described in (8), and this is detected. It is preferable to have a means for inverting the polarity of the tracking error signal.

[0014]

The optical disk substrate manufactured by the above means is
There is no narrow area that is disadvantageous to injection molding, and it is possible to provide a knack track pitch optical disk substrate at a high speed in a large amount at a low cost. In addition, since the tracking error signal and the signal for reproducing light that crosses the track can be reliably obtained, the reliability of track following and head access is improved.

[0015]

【Example】

Example 1 An example of the present invention will be described below with reference to the drawings. FIG. 1 shows the concept of an optical system in an optical disk master cutting device. Argon laser 1 (manufactured by Spectra Physics Inc .; wavelength 458 nm, output; 100 mW)
The light from was changed its direction of travel by 90 degrees by the mirror 2 and was split by the semi-transparent mirror 3 into two lights of approximately equal intensity.
The light (light A) reflected by the semi-transparent mirror 3 passes through an AO (Akast Optics) modulator 4 for intensity modulation, changes its traveling direction by the mirror 2, is reflected by the semi-transparent mirror 3, and is first reflected by the semi-transparent mirror 3. It is combined with the light (light B) split by the transparent mirror 3.
On the other hand, the light B, after passing through the semitransparent mirror 3, is reflected by the mirror 2 and has an AO (Akast Optics) modulator 4 for intensity modulation.
Through the semitransparent mirror 3 and is combined with the above-mentioned light A. After that, the light A and the light B pass through almost the same optical axis and pass through the lens 5 for condensing the light, and are narrowed down as two spots on the surface of the master 6 arranged near the focal point. Format circuit for AO (Akast Optics) modulator 4
An electric signal modulated into a desired signal is sent from 10, and the laser light is switched according to the electric signal to obtain a predetermined master. The master 6 is a positive type photoresist 8 (Shipley Company; AZ135) on a glass substrate 7 having a thickness of 10 mm.
0 etc.) was spin coated to a thickness of 210 nm.
This master is rotated by a rotary motor 9 at a speed of 600 rpm.

FIG. 2 shows the positional relationship of the light spots on the master when the cutting laser light is viewed from directly above. The concavo-convex pattern 31 and the second guide groove 22-2 are exposed by the spot S1, and the first guide groove 22-1 is exposed by the spot S2 to form respective shapes on the resist surface. The first guide groove does not exist laterally in the radial direction of the concavo-convex pattern. Further, a second guide groove narrower than the radial width of the concavo-convex pattern exists between the concavo-convex patterns in the circumferential direction. By doing so, the reproduction signal output is different between the concavo-convex pattern and the second guide groove, and the respective signals can be distinguished.

FIG. 3 is a view of the surface of the optical disk substrate as viewed from directly above. Further, the depth of the second guide groove is set so that the tracking servo signal processing can be performed similarly to the signal from the first guide groove having a depth λ / 8, that is, the signal from the first guide groove. It is deeper than the first guide groove so as not to conflict with each other in terms of polarity. The depth referred to here is the depth of the cross-sectional shape of the groove or the concavo-convex pattern converted into a rectangular shape having the same cross-sectional area. In the case of a rectangular groove, the amplitude of the tracking signal increases when the groove depth is λ / 8, becomes 0 at λ / 4, and reverses the polarity at the same amplitude as λ / 8 at 3λ / 8. Therefore, the polarity inversion due to the difference in the position of the guide groove can be canceled by dividing the depth of the first guide groove and the depth of the second guide groove into grooves deeper than λ / 4 or shallower. By the way, here, the depth 3 is deeper than the concavo-convex pattern representing the clock pit 32 with the depth λ / 4 and the address pit 21 such as the sector mark.
It was set to λ / 8.

FIG. 4 shows a cross-sectional view of each portion of A, B and C in FIG. The depths of the first and second guide grooves may be the same. In this case, polarity reversal can be prevented by the method described below. Further, the second guide groove is not formed in the region where the first guide groove exists. However, this is not absolute, and there may be some overlapping areas. However, the track cross count must be within the range. It goes without saying that it may be applied to a form such as a CD-ROM in which the first guide groove does not exist at all.

When the depths of the first guide groove and the second guide groove are made to coincide with each other, it is not necessary to change the depth and the manufacturing process is simplified, but the positional relationship between the guide grooves makes it easy. As can be seen, the error signal for the track shift of the light spot is inverted. That is, in FIG. 3, tracking control is performed so that spots are arranged between the grooves in the first guide groove area, while control is performed on the groove in the second guide groove area. Will be needed. On the other hand, after the light spot enters the second guide groove area, an uneven pattern for detecting the second guide groove area is provided within a range that can be reached within the response time of tracking control. . For example, FIG. 5 shows an example of a signal when an uneven pattern is provided for that purpose.
2 RF (Radio Frequency) signals corresponding to the total light amount detection signal
Value, sample hold (S
/ H) signal to ON. The end of the region is detected when a predetermined time has elapsed by counting the clock signal, and the S / H signal is turned off.

FIG. 6 shows a block diagram of the tracking signal inversion control by this signal. The detection circuit 63 detects the amount of light received by the optical head so that the RF signal 65 and the TES signal (Tracking Error Sig
nal) 66, and the area detection circuit 67 detects the S / H signal 68
To get Furthermore, the polarity reversing circuit 69 allows the S / H signal 68 and TES
From the signal 66, when the S / H signal 68 is OFF, the TES signal 66 is output as a through signal, and when the S / H signal 68 is HIGH, the non-polarized TES signal 610 without polarity inversion can be obtained by inverting and outputting the signal. From this, the tracking servo circuit 611 outputs an actuator drive signal 612, and the actuator in the optical head 62 is driven by this signal.

Further, in this way, by arranging the second guide groove regions continuously in the radial direction within the disk,
Cross-track counting for access control can also be performed accurately. Since the intensity of the total reflected light quantity along the track crossing becomes extremely small on the groove, it is
The polarities of the guide groove area and the groove crossing signal are reversed. However, if the second guide groove area is continuously arranged, the spot always crosses the head of the area, so that the above S / H signal is obtained. By applying this not only to the TES signal but also to the groove crossing signal, it is possible to realize highly accurate track counting by combining both. To reverse the polarity of the groove crossing signal, the groove depths of the first guide groove and the second guide groove are set to λ /
This is an effective method even when there is no inversion of the tracking error signal because it occurs even if it is divided by 4 and deeper or shallower.

In this way, stampers and replicas are produced by a normal process from a master completed by exposing and developing a pattern having a track pitch of 1.2 μm, and a reflective film of aluminum, titanium, etc. is attached to the replica substrate, and a track cross signal is produced. The access performance including the level, the tracking performance in which the optical head follows the first guide groove, and the like were evaluated. In the former case, the track cross signal has heretofore disappeared in some places in the concavo-convex pattern portion, and the target track may not be reached. However, in the case of the present invention in which the second guide groove was formed, the target track could be reliably reached. Also for the latter, tracking control could be stably performed in the area of the uneven pattern by the second guide groove. Normally, when there is no guide groove, it is possible to hold the spot position in the area with the guide groove immediately before that and reproduce the signal, but in this case, the length of the area is so small that the track deviation can be ignored. So the area is limited to a short range. On the other hand, in the present invention, since tracking control can be performed stably even in the uneven pattern area, it is not necessary to limit the length of the area and it can be used for the uneven pattern area as data such as so-called partial ROM.

<Embodiment 2> The cutting method in the above embodiment was mainly described with respect to a method using two laser beams, but the present invention is not limited to this, and a single laser beam can be used. The optical system shown in FIG.
A master having the above structure can be produced. FIG. 5 is basically similar to FIG. 1, except that there is no light A and instead an AO light deflector is inserted after the AO modulator 11 to deflect the light in the radial direction by half the track pitch. I am trying. By doing so, the light quantity of the spot is increased, and the master can be produced at high speed, and the master can be completed in a short time. Further, even if spot miniaturization is performed by a method of losing light quantity such as super-resolution, the master can be completed with the conventional rotation and processing time. Further, even in a substrate having no second guide groove on the side of the concavo-convex pattern and having a second guide groove overlapping the concavo-convex pattern, the optical head incorporated in the optical disk device has a tracking servo function in the first guide groove region. Therefore, even if it enters the area without the first guide groove, there is no particular problem in signal recording / reproduction by maintaining the previous servo state.

<Third Embodiment> FIG. 7 is a view showing the surface of an optical disk substrate showing a third embodiment of the present invention. The second guide groove described in the first embodiment is provided on both sides in the circumferential direction of the pit of the concave-convex pattern 31, and the wide groove 22 is provided on the extension in the circumferential direction.
―3 is provided. The wide groove 22-3 can be easily formed by moving light in the radial direction at high speed in the optical deflector 11 of FIG. 5 by the radial width of the wide groove 22-3. A record erasable signal 51 is recorded in the wide groove 22-3. Here, the uneven pattern 31, the second guide groove 22-2,
The depth of the wide groove 22-3 is unified to λ / 8.

[0025]

INDUSTRIAL APPLICABILITY In a narrow area such as between the concave-convex pattern on the surface of the optical disk substrate and the guide groove, injection transfer failure is likely to occur. However, according to the present invention, there is no guide groove on both sides in the radial direction of the concave-convex pattern. A good transfer pattern can be obtained without the above-mentioned narrow area. In addition, since there is no guide groove on both sides of the pit in the radial direction, the track cross signal may not be output originally, but there is a second guide groove between the circumferential concave-convex pattern and the concave-convex pattern. Therefore, the optical head was able to reach the target track.

[0026]

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an optical system in an optical disc master cutting device.

FIG. 2 is a spot arrangement diagram on a master in a cutting device.

FIG. 3 is a plan view showing a relative positional relationship between a guide groove and an uneven pattern.

FIG. 4 is a sectional view of each part in FIG.

FIG. 5 is a signal time chart diagram in the second groove region.

FIG. 6 is a configuration diagram of a tracking servo polarity reversing device.

FIG. 7 is a conceptual diagram of an optical system in an optical disc master cutting device.

FIG. 8 is a plan view showing a relative positional relationship between a groove and an uneven pattern according to a third embodiment.

[Explanation of symbols]

1 ... Argon laser, 2 ... Mirror, 3 ... Semi-transparent mirror, 4 ... AO
Modulator, 5 ... Lens, 6 ... Master, 8 ... Substrate, 9 ... Rotation motor, 10 ... Format circuit, 11 ... AO optical deflector, 21 ...
Address pits, 31 ... Concavo-convex pattern, 32 ... Clock pits, 51 ... Record erasable signal, 61 ... Optical disk, 62 ... Optical head, 63 ... Signal detection circuit, 64 ... Detection signal, 65 ... RF signal,
66 ... TES signal, 67 ... Area detection circuit, 68 ... S / H signal, 69 ... Polarity inversion circuit, 610 ... Non-polarity inversion TES signal, 611 ... Tracking servo circuit, 612 ... Actuator drive signal.

Front page continuation (72) Inventor Shinkichi Horigo 1-280 Higashi Koikeku, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Yumiko Anza 1-280 Higashi Koikeku, Kokubunji City, Tokyo Inside Hitachi Research Laboratory (72) Inventor Toshie Sasaki 1-280 Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (9)

[Claims] 1. An optical disk substrate having a first guide groove of an optical disk and a concave / convex pattern formed on a surface of the substrate at a radial position different from that of the guide groove, and a light reflection film or a recording film formed on the concave / convex pattern. An optical disk substrate characterized in that there is no guide groove on both sides in the radial direction, and there is a second guide groove on both sides in the circumferential direction. 2. An optical path difference in reflection between the second guide groove portion and a flat portion between the second guide groove portions is between λ / 8 and λ / 2 of a laser wavelength used. The optical disc substrate according to claim 1. 3. The radial pitch of the second guide groove portion is 1.
The optical disc substrate according to claim 1, wherein the optical disc substrate has a thickness of 2 μm or less. 4. The optical disk substrate according to claim 1, wherein the second guide groove has two or more radial widths. 5. The first and second guide groove shapes are set so that the polarities of the tracking error signals by the first guide groove and the second guide groove are inverted from each other. 5. The optical disk substrate according to any one of 1 to 4. 6. The optical disk substrate according to claim 5, wherein the depth of the concavo-convex pattern in the second guide groove region is the same as the depth of the first guide groove or the second guide groove. 7. A step of applying a photosensitive material on the surface of a substrate, a step of exposing the surface with address information such as guide groove information of an optical disk or sector marks, or intensity-modulated laser light, and a developing treatment. A step of forming an optical disk master having a concave-convex pattern and a step of forming a first guide groove and a second guide groove in accordance with exposure, a step of manufacturing a transfer master from the master, and the concave-convex pattern from the master. And a method of manufacturing an optical disk substrate having a resin surface on which the first guide groove and the second guide groove are transferred, the guide groove does not exist on both sides in the radial direction of the concavo-convex pattern, and the concavo-convex pattern has the same radius circle. A method of manufacturing an optical disk substrate, characterized in that a pattern is formed so that a second guide groove is present in the optical disk substrate. 8. An optical disk substrate having a first guide groove of an optical disk and a concave / convex pattern formed on a surface of the substrate at a radial position different from that of the guide groove, and a light reflection film or a recording film formed on the concave / convex pattern. In an optical disk device having an optical disk substrate having no guide grooves on both sides in the radial direction and second guide grooves on both sides in the circumferential direction, an optical head, and an actuator for driving the optical head, The optical disk device, which has means for setting the polarity of the tracking deviation signal in the guide groove area to the signal having the same polarity as that of the first guide groove area. 9. An uneven pattern for changing the physical state of the detected light is provided within a range that the light spot can reach within the response time of tracking control after entering the second guide groove area, and tracking is performed by detecting this. 9. The optical disk device according to claim 8, further comprising means for inverting the polarity of the error signal.