JP3219398B2 - Optical information recording medium and recording / reproducing method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk, an optical card, and the like for recording and reproducing information using a laser beam.
The present invention relates to an optical information recording medium such as an optical tape and a recording / reproducing method using the same.

[0002]

2. Description of the Related Art Conventionally, as an optical information recording medium, a groove (guide groove) having a depth of about 1/8 of the wavelength of recording / reproducing light is formed on the surface of a transparent disk substrate, and a gap between these grooves is formed. It is known that a prepit array is formed on a land, and a light absorbing / reflective recording film recordable with a laser condensing beam is provided thereon. In this recording medium, the focused laser beam is diffracted by the diffraction effect of the groove,
A track shift is detected by detecting the distribution of the reflected light, and tracking control is performed based on the detected track shift to read uneven pre-pit information or form a recording pit on the recording film in association with the pre-pit information.

However, in such an optical information recording medium, only one of a groove and a land can be used for tracking.
It has been difficult to increase the information recording density. In other words, tracking can be performed in grooves or lands by simply reversing the polarity of tracking,
If the pre-pit row exists only on the land as described above, it is not possible to form an additional recording pit in association with the information of the pre-pit because the pre-pit on which the address information and the like are recorded cannot be read out by tracking the groove. There was a drawback, and it was not possible to increase the information recording density.

The present applicant has proposed a novel optical information recording medium in Japanese Patent Application Laid-Open No. 4-195939 in order to solve such a problem. As shown in FIG. 1, this recording medium has tracking grooves 3 and pre-pits 4.
(Hereinafter referred to as a pre-pit row), and when the groove interval (track pitch) is P, the center line of the pre-pit row is shifted to the right or left by approximately P / 4 from the center line of the groove. It is characterized by being formed as described above. This recording medium has an optical recording film (not shown) having a light absorbing / reflecting property on an information recording surface, and the optical recording film is irradiated with a laser condensed beam 6 to form a groove 2 or a land. While tracking the middle of 3,
The pre-pit train is reproduced, and information is recorded based on the reproduced pre-pit train. In the drawing, 1 is a disk substrate,
5 is a recording pit.

[0005]

However, as a result of further study, the optical information recording medium proposed in the above publication and the recording / reproducing method using the same have room for improvement in the following points. I understand. (1) In the recording medium, as shown in FIG. 1, since the pre-pit row is located between the groove and the land, the shape of the pre-pit becomes asymmetric, and when tracking between the groove and the land, a push-pull signal is generated. , An offset voltage is generated. Therefore, it is difficult to accurately track along the pre-pit row. (2) As described above, the shape of the pre-pit is asymmetric and has a considerably complicated cross-sectional shape. Therefore, when a polycarbonate substrate (hereinafter, referred to as a PC substrate) manufactured by an injection molding method is used as the substrate of the recording medium, the prepit shape of the stamper cannot be accurately transferred at the time of manufacturing the substrate. As a result, it is possible that erroneous reproduction of preformat information composed of a pre-pit row may occur due to a transfer failure, and that information cannot be accurately recorded in a data area composed of grooves and lands adjacent to the pre-pit row. There is a problem. (3) Further, as shown in FIG. 1, since the groove exists adjacent to the pre-pit, the amount of reflected light is greatly reduced as compared with the case where the pre-pit exists alone. As a result, there is a problem that the signal amplitude of a pre-pit train optically obtained from the pre-pits using a laser condensed beam is small.

[0006] The present invention has been made in view of the above-mentioned problems of the prior art, and has the following objects. (i) Tracking and recording in both groove and land
An optical information recording medium that can be reproduced. When reproducing preformat information composed of prepits existing in the recording medium, a crosstalk signal from an adjacent track is reduced and a push-pull signal is generated. To provide an optical information recording medium capable of eliminating an offset voltage, and to have a preformat configuration capable of accurately detecting the position of a preformat area. (ii) To accurately track a data area composed of grooves and lands, and to be able to perform a tracking servo capable of accurately reproducing and demodulating preformat information composed of a prepit string. (iii) The tracking servo can be switched accurately and with good timing in the data area and the preformat area.

[0007]

According to the present invention, there is provided an optical information recording medium having a tracking groove and a pre-pit row, wherein the pitch of the groove is P, The column is formed so that its center line is shifted to the right or left by approximately P / 4 from the center line of the groove, and no groove is formed in the preformat area formed by the prepit row. An optical information recording medium characterized by having a preformat mark composed of a mirror mark portion having no groove and no prepit in a preformat area composed of a prepit row. Further, according to the present invention, in the above-described configuration, the pre-format area having the same pattern of the pre-pit row is provided on the center line of the groove and the center line of the land in the pre-format area formed of the pre-pit row. Is provided. Further, according to the present invention, using the optical information recording medium,
When reproducing a data area composed of grooves or lands, the laser focused beam is scanned on the center line of the groove or land while applying tracking servo, and when reproducing a preformatted area composed of prepit rows, the data area is reproduced. Remove the tracking servo near the point where it switches to the preformat area from
After shifting the focused laser beam to the center of the pre-pit row,
Scanning while applying the tracking servo again, then remove the tracking servo near the switching from the preformat area to the data area, shift the focused laser beam to the center of the groove or land, and then scan while applying the tracking servo Records characterized by
A playback method is provided. Further, according to the present invention, when reproducing a data area composed of a groove or a land by using the optical information recording medium, the laser focused beam is scanned on the center line of the groove or the land while applying tracking servo. When reproducing the preformat area composed of the prepit row, remove the tracking servo near the point where the data area is switched to the preformat area, shift the laser focused beam to the center of the prepit row, and do not apply the tracking servo. Recording / reproducing method, in which the laser beam is shifted to the center of the groove or land near the switching from the preformat area to the data area, and then scanning is performed while applying tracking servo. Is done. Further, according to the present invention, when reproducing a data area composed of a groove or a land by using the optical information recording medium, the laser focused beam is scanned on the center line of the groove or the land while applying tracking servo. When reproducing a preformat area composed of a series of prepits, the tracking servo is removed near the point where the data area is switched to the preformat area, and the laser beam is scanned in a fixed state on the center line of the groove or land. Next, there is provided a recording / reproducing method characterized in that scanning is performed while applying tracking servo again near the switching of the preformat area to the data area. Further, according to the present invention, in the above-described method, a preformat mark provided in the preformat area is optically detected using a laser condensing beam, and a header area in the preformat is detected from a signal of the preformat mark. The recording / reproducing method is characterized in that the position of the tracking servo is estimated and the tracking servo is switched on / off.

Hereinafter, the present invention will be described in detail. First, an optical information recording medium according to the present invention will be described. FIG. 2 is a partial perspective sectional view showing an optical information recording medium according to the present invention, and FIG. 3 is a plan view of the same. In these figures, 1 is a disk substrate, 2 is a land, 3 is a groove, 4
Denotes a prepit, 5 denotes a recording pit, 6 denotes a laser condensed beam, and 7 denotes a light absorption / reflection recording layer. As shown in the figure, a groove 3 and a land 2, which are areas for recording and reproducing information, and a row of prepits 4 including address information of each data are formed on the surface of the medium. When the groove interval (track pitch) is P, the center line of the pre-pit row is arranged to be shifted by P / 4 from the center line of the groove 3, and the center line of the land 2 is adjacent to the land 2. The grooves are arranged so as to be located between the center lines of the grooves. Also, no groove exists in a preformat area (including address information) composed of prepit strings.

The shapes of the grooves 3 and the pre-pits 2 are defined by the values of the groove signal characteristics optically obtained by using the laser beam 6. FIGS. 4A to 4D respectively show the relationship between the groove shape and the groove level, the relationship between the groove shape and the land level, the relationship between the groove shape and the push-pull signal used for tracking, the pre-pit shape and the pre-pit amplitude. This shows the relationship. In the optical information recording medium of the present invention, in order to record information on the groove 3 and the land 2, the groove level in the unrecorded state (the intensity of the reflected light when the laser focused beam 6 scans the center line of the groove 3). ) And the land level (reflected light intensity when the laser condensed beam 6 scans the center line of the land 2) are preferably as close as possible. If the difference between the groove level and the land level is large, the recording pit C
This is because there is a difference in / N.

From FIGS. 4A and 4B, the groove shape is 0.1 × (2n + 1) λ ≦ Dg ≦ 0.2 × (2n + 1)
It can be seen that when λ, 0.38 ≦ Wg / BD ≦ 0.56 is satisfied, a state where the groove level and the land level are almost equal can be obtained. Here, Dg is the phase depth of the groove, Wg is the half value groove width with respect to the groove depth, and BD is the beam diameter (1 / e ²⁾ of the laser focused beam for recording / reproducing.
), Λ is the wavelength of the laser focused beam, n = 0, 1,
The parameters indicating the groove shape are defined as shown in FIG. According to the groove shape satisfying the above condition, as shown in FIG.
Thus, a push-pull signal value of 7 is obtained, and the output signal value has no problem in tracking servo.

The shape of the pre-pits is desirably such that the phase depth Dp of the pre-pits is substantially equal to the phase depth Dg of the groove in view of the stamper manufacturing method (see Examples described later). The pre-pit shape is 0.1 × (2n + 1) λ
≦ Dp ≦ 0.2 × (2n + 1) λ, 0.19 ≦ Wp / B
It is desirable to satisfy D ≦ 0.44. Here, Wp is a half value groove width with respect to the depth of the prepit, and a parameter indicating the shape of the prepit is defined as shown in FIG.
According to the prepit having a shape satisfying the above conditions, FIG.
As shown in (d), the pre-pit amplitude is 0.2 to 0.6.
Is obtained, and a numerical value having no problem in signal reproduction is obtained.

In the optical information recording medium of the present invention, a pre-pit format mark may be provided in a pre-format area composed of a pre-pit row. This pre-pit format mark can be composed of a mirror mark portion where no groove and pre-pit exist, or a pre-pit row of the same pattern provided on the center line of the groove and the center line of the land. This preformat mark will be described in detail in the following description of the recording / reproducing method.

Next, a recording / reproducing method for the optical information recording medium will be described. FIGS. 6A and 6B show the scanning trajectory of the laser focused beam when recording / reproducing on / from the optical information recording medium of the present invention. FIG. 6A shows the case where the groove 3 is recorded and reproduced, and FIG. 6B shows the case where the land 2 is recorded and reproduced. In the groove 3 or land 2 which is an area for recording / reproducing information, the laser condensed beam scans on each center line of the groove 3 or land 2, respectively. The laser focused beam scans on the line. This is because unless the laser condensed beam scans the center line of the recording pits in the data area or the pre-pits in the pre-format area, stable recording pit or pre-pit signals cannot be obtained, and accurate signal reproduction cannot be performed. As described above, in order to align the focused laser beam on the center line of the pre-pit row in the pre-format area with good timing, it is necessary to accurately detect the position of the pre-format area. For this,
The optical information recording medium of the present invention is provided with a preformat mark (hereinafter referred to as PFM) which is a mark indicating the presence of the preformat in the preformat area. It is desirable that this PFM can be accurately detected even without tracking servo. The reason is that when reproducing the data area of a certain address, it is necessary to remove the tracking servo and seek. If the PFM cannot be detected accurately even with this tracking servo removed, the tracking servo must be applied again immediately after the seek. This is because the laser condensed beam cannot be shifted in the preformat region.

FIGS. 7A and 7B show a preformat configuration employed in the present invention in order to accurately detect a PFM even when tracking servo is not applied. In FIG. 7A, the PFM is constituted by a mirror mark having no groove 3 and no pre-pit 2. According to this mirror mark, a constant mirror level output can be obtained regardless of the presence or absence of the tracking servo, so that the PFM can be accurately detected without applying the tracking servo. In FIG. 7B, the PFM is arranged so that the interval between the pit rows is P / 2 and the center line of each pre-pit row is the same as the center line of the groove 3 and the land 2. The pre-pit rows of the PFM formed on each of the tracks have the same pattern. In this case, since the crosstalk signal from the adjacent track is large in the prepit amplitude obtained from the PFM, a stable signal amplitude can be obtained without applying the track servo. Therefore,
With this preformat configuration, it is possible to accurately detect the position of the preformat area without applying a tracking servo.

When the eccentricity of the optical information recording medium is large, it is necessary to perform tracking servo to the center of the pre-pit row. In order to accurately scan the center of the groove, land and pre-pit row with the laser converging beam. The operation of moving the laser focused beam to the center of the pre-pit row becomes a problem.

FIG. 8 shows the data area composed of the groove 3 and the land 2 and the waveform of the push-pull signal in the area. FIG. 9 shows the preformat area composed of the pre-pit row and the waveform of the push-pull signal in the area. It is shown. As shown in FIG. 9, since the center line of the pre-pit row is shifted by P / 4 with respect to the groove 3, the sine waveform of the push-pull signal is shifted by .pi. / 2 compared with the case of FIG. ing. Therefore, when the laser focused beam 6 enters the pre-pit row from the groove 3 with the tracking servo applied, the push-pull signal changes from 0 to -Vofs'. When the tracking servo is applied, the objective lens is driven so that the push-pull signal becomes 0 in response to the change of the push-pull signal. At this time, the tracking of the laser focused beam 6 may return to the pre-pit row to be scanned, but the laser focused beam may be shifted to a pre-pit row adjacent to the pre-pit row to be scanned. In order to prevent such a problem from occurring, according to the present invention, the tracking servo is removed at the end of the data area composed of the groove and the land, and the laser focused beam is shifted by P / 4 onto the center line of the pre-pit row. At the same time as the start of the pre-pit train, the tracking servo is applied again. According to this method, the tracking servo can be accurately returned to the center line of the pre-pit row without being affected by the change of the push-pull signal when entering the pre-pit row from the groove. In addition, since the change of the push-pull signal described above occurs when the tracking is switched from the pre-pit train to the groove, the tracking servo is removed at the end of the pre-pit train and the laser focused beam is shifted by P / 4 to the center line of the groove. Apply the tracking servo with the start of the groove. FIG. 10 shows a timing chart of this tracking switching.

The tracking switching is specifically performed as follows. Regenerate the circuit Rf signal (sum signal)
The PFM is detected by the PFM decoder, and a PFM window signal A is generated. A header window signal B is generated from the PFM window signal A, and a preformat window signal C is generated using the PFM window signal A and the header window signal B. From the combination of the delay circuit of the PFM window signal A, a tracking servo ON / OFF switching signal D for releasing the tracking servo before and after the preformat is generated. Further, in order to shift the focused laser beam by P / 4 before and after the pre-pit row, it is necessary to apply a voltage corresponding to Vofs or −Vofs shown in FIG. 8 to the objective lens driving actuator. Therefore, a voltage corresponding to Vofs and −Vofs in FIG. 8 is sampled and held, and a track offset signal E is generated from the voltage signal and the tracking servo ON / OFF switching signal D. The above timing chart is shown in FIG.
0 is shown. FIG. 11 is a circuit block diagram for generating the signals (A to E) shown in the timing chart of FIG.

FIG. 12 is a circuit block diagram for performing tracking servo in the recording / reproducing method of the present invention. In this tracking servo circuit, the above-mentioned signal D is used for switching the tracking servo ON / OFF, and a track offset signal E is added to the actuator for driving the objective lens in order to shift the focused laser beam by P / 4. Configuration. In the optical information recording medium of the present invention, since it is necessary to record information on the groove and the land, FIG. 12 includes a land (L) / groove (G) tracking polarity switching circuit. The L / G tracking polarity switching is performed by a signal from a host controller of a drive that controls recording / reproduction as necessary. Divided standardized by dividing by the PP signal output instead of the push-pull signal (abbreviated as PP in the figure) used for tracking servo
A push-pull signal (hereinafter abbreviated as DPP) may be used. By using this DPP, it is possible to remove disturbance factors such as a change in the reflectivity of the optical information recording medium and a change in the light amount of the laser diode, and to reliably apply the tracking servo.

On the other hand, if the eccentricity of the optical information recording medium is so small as to be negligible in one preformat area, there is no need to apply tracking servo in the preformat area. In this case, using the preformat window signal C of FIG.
N / OFF switching may be performed. FIG. 13 shows a timing chart when the tracking servo is turned on / off using the preformat window signal C. In the header area, the offset voltage Vofs is applied to the actuator for driving the objective lens while the tracking servo is turned off in order to scan the laser focused beam substantially on the center line of the pre-pit row. FIG. 14 is a circuit block diagram for generating the track offset signal E 'with good timing. FIG. 15 is a circuit block diagram using the signal C of FIG. 13 as a tracking servo signal and the signal E ′ of FIG. 13 as a track offset signal with respect to FIG.

If the eccentricity of the optical information recording medium is so small as to be negligible within one preformat area, the track offset signal E 'in FIG. 13 may always be set to 0 (V). That is, this means that the laser focused beam scans not on the center line of the pre-pit row but on the center line of the groove or land. FIG. 16 shows the manner in which the laser beam is scanned over the center line of the groove or land and the preformat information composed of the prepit rows is reproduced. In this case, the peak hold circuit and the track offset pulse generation circuit in FIG. 14 are unnecessary, and the input of the E ′ signal is unnecessary in FIG. The amplitude of the prepit reproduced in the state of FIG. 16 is smaller by about 10% than the amplitude of the prepit reproduced in the state of FIGS. 6A and 6B. This is because the signal is reproduced in a state where the laser condensed beam is shifted by P / 4 with respect to the center line of the pre-pit row. However, in the optical information recording medium of the present invention, a sufficiently large pre-pit amplitude is obtained, so that even if the pre-pit amplitude is reduced by about 10%, no problem occurs in signal reproduction.

Next, a method of manufacturing a stamper for manufacturing a substrate of the optical information recording medium having the above configuration and a master exposure apparatus will be described. Normally, a PC substrate transferred from a mold called a stamper by an injection molding method is used for the uneven shape of the substrate of the optical information recording medium. FIG. 17 shows a general manufacturing flowchart of this stamper. FIG. 17 (a)
Is a spin-coated photoresist on a glass disc (hereinafter, this glass disc with photoresist is referred to as a resist master). While rotating the resist master, a concentric or spiral Ar + laser beam is scanned to form a latent image on the photoresist (FIG. 17B). Next, the latent image is developed to form an uneven pattern on the photoresist (FIG. 17C). Next, a Ni sputtered film is formed as a conductive film on the photoresist surface (FIG. 17D). Next, this resist master with a Ni film is laminated by electroforming to a thickness of about 0.3 mm (FIG. 17E). Next, the Ni electroformed plate is polished, the inner and outer diameters required for molding are processed, and washing such as removal of the photoresist is performed to complete the Ni stamper (FIG. 17 (f)). The PC substrate transferred from the Ni stamper by the injection molding method has an inverted shape of the concavo-convex shape of the stamper, and has substantially the same shape as the concavo-convex shape formed on the photoresist surface (FIG. 1).
7 (g)).

FIG. 7 shows an example using an Ar + laser focused beam.
FIG. 18 is a block diagram of an optical system of a master exposure machine for a photoresist master exposure machine (hereinafter, referred to as a master exposure machine) for forming grooves, lands, and pre-pit rows in the photoresist of FIG. 2 shows a timing chart for controlling the Ar + laser focused beam. The features of the optical system of the master exposure apparatus shown in FIG. 18 are as follows: (1) One Ar + laser focused beam is used to form a groove and a prepit array; and (2) The groove is formed continuously. When irradiating the beam and forming a pre-pit row, a signal modulator 23 for irradiating / cutting the beam in accordance with the pattern of the pre-pit row is provided. (3) A groove and a pre-pit having different groove widths are formed. Light intensity modulator 25 for changing the light intensity of the beam by each groove.
And (4) having an optical deflector 27 for deflecting the beam to form different grooves and pre-pit rows on the center line.

As shown in the timing chart for controlling the condensed Ar + laser beam in FIG. 19, the signal given to the signal modulator (hereinafter, referred to as DA / O) 23 has the groove and the groove shown in FIG. ON, O according to the pre-pit row
FF switches. Light intensity modulator (hereinafter referred to as A A / O)
Signal applied to 25, the input voltage is set to V ₁ was when exposing the groove, the input voltage is set to V ₂ when exposing the pre-pit. Since the voltage V ₁ is larger set than the voltage V _2, the light intensity Pg of the laser beam focused upon the results exposing the groove, the laser beam focused by the light intensity Pp to be used during the exposure of the pre-pit
(V ₁ > V ₂ ⇒Pg> Pp). Signal applied to the optical deflector (hereinafter W A / O hereinafter) 27 is set to 2.5 (V) when exposing the groove, the input voltage is set to W ₁ when exposing the pre-pit. According to the voltage value input to the WA / O 27, the condensed Ar + laser beam is deflected on the photoresist surface. The difference between the input voltages W ₁ and 2.5 (V), as the position of the Ar + laser beam focused on the photoresist surface, is set to P / 4 (W-2.5 ( V) →
(P / 4 beam position difference).

Further, it is also possible to form the grooves, lands and pre-pit rows shown in FIG. 9A on a photoresist master using two Ar + laser focused beams.
FIG. 20 is a block diagram of an optical system of a master exposure machine using the two Ar + laser focused beams, and FIG. 21 is a timing chart for controlling the Ar + laser focused beam. Things. In these figures, the same elements as those in FIGS. 18 and 19 are denoted by the same reference numerals. The feature of this optical system is that it has a half mirror 35 for splitting a beam 1 for exposing a groove and a beam 2 for exposing a pre-pit.
DA / O23 for intermittently forming grooves, AA / O25 for adjusting light intensity, and WA / for setting the interval between beam 1 and beam 2 on the photoresist surface to P / 4. In the optical system of beam 2 having O, DA / O 37 for modulating the signal of the condensed Ar + laser beam in accordance with the pattern of the prepit row.
And an A / O 38 for adjusting the light intensity.

In the timing chart of FIG. 21, in each of the beam 1 and the beam 2, the signal O applied to each DA / O according to the groove or the pre-pit is determined.
N / OFF is switched, and each A A / O is adjusted according to the light intensity required when exposing a groove or pre-pit.
Set the voltage to be applied to

FIG. 22 shows the grooves in FIG.
5 is a timing chart for forming a land, a PFM, and a prepit row in a header area on a photoresist master. Also in this case, the optical system of the master exposure machine shown in FIG. 20 is used. The difference from the case of FIG. 7A is that the pre-pit row of the PFM is located on each center line of the groove and the land. Beams 1 and 2 are DA / Os 23 and 37 according to the pattern of the groove or prepit.
Signal modulation is applied. Further, in the beam 1, it is necessary to form grooves and pre-pits having different groove widths, so that the light intensity of the beam 1 is switched in a pre-format area composed of a groove area and a pre-pit row.
The voltages V ₁ and V ₂ are switched and input to O25. The light intensity of the beam 2, the voltage V ₃ to A A / O38 to be the same as the pre-pit shape formed by the beam 1 is set. The interval between the beam 1 and the beam 2 on the photoresist surface is set to P / 2 in the groove and the PFM portion. In order to shift the prepit row by P / 4 with respect to the center of the groove, WA / O27 is used in the groove. 2.5 (V)
Is set, and the voltage W1 (V) is set in the pre-pit row.

[0027]

Next, an example of manufacturing an optical information recording medium according to the present invention will be described. In this embodiment, as preformat information, the ISO standard format (90 mm: ISO / IEC) of a magneto-optical disk of 90 mm and 130 mm is used.
10090, 130 mm: ISO / IEC DIS10
089), and a magneto-optical disk was produced as follows.

First, a photoresist master was prepared by the method shown in FIG. 17 under the following conditions. <Preparation conditions of photoresist master> Glass substrate Plate thickness 6 mm, φ250 mm Photoresist OFPR800 (manufactured by Tokyo Ohka) dilute viscosity 2 cp to 60% with thinner Film formation Spin coating method First rotation 150 rpm, 20 sec Second rotation 400-450 rpm , 90 sec Pre-bake 90 ° C., 30 min Master exposure Table rotation speed 300 rpm Exposure amount at r = 30 mm Groove 4.0 mW Pre-pit 2.0 mW Developer DE-3 (manufactured by Tokyo Ohka) 33% dilution Spin development Method Development 500 rpm, 60 sec Pure water rinse 500 rpm, 180 sec drying 1000 rpm, 30 sec post bake 130 ° C., 30 min

The optical system configuration of the master exposure machine used the one-beam exposure optical system shown in FIG. The track pitch is P = 1.6
μm, and the interval between the groove and the center line of the pre-pit row was P / 4 = 0.4 μm. Ar + laser wavelength is 45
7.9 nm, NA of the objective lens is 0.9, and DA
/ O, A A / O and WA A / O are input to ISO
The one encoded according to the standard format was used. Further, the groove shapes of the grooves and prepits manufactured under the above conditions were as follows. Groove Dg = 900-1000 (Å), Wg =
0.7-0.8 (μm) Pre-pit Dp = 900-1000 (Å), Wp =
0.3 to 0.4 (μm) The groove and the prepit had the same groove depth, and the depth was the same as the photoresist film thickness applied to the photoresist master. As shown in FIGS. 17 (a) and 17 (b), the grooves and prepits had trapezoidal cross-sectional shapes. Since the light intensity distribution of the Ar + laser condensed beam has a Gaussian distribution, when a groove having a groove depth smaller than the photoresist film thickness is formed, it is only V-shaped or U-shaped. The cross-sectional shape of the groove or prepit is V
In the case of a letter or U-shape, good recording / reproducing signals on the optical information recording medium cannot be obtained, so that the groove and the prepit have to be trapezoidal in cross section. For this reason, in this embodiment, the cross-sectional shape of the groove is trapezoidal.

Using the photoresist master prepared as described above, a stamper was prepared by the method shown in FIG. 17 under the following conditions. <Stamper fabrication conditions> Sputtered film Ni DC sputtered film thickness about 500 (Å) Electroforming Electroforming liquid Ni sulfamate After electroforming Plate thickness about 0.3 mm Polishing Polishing Surface roughness Rmax 0.3 μm or less

[0031] Using the stamper prepared above, to prepare a PC substrate by injection molding, Al on that substrate, ZnSiO ₂ as a dielectric layer, TbFeCo as the recording film, as ZnSiO _2, reflective film as a dielectric layer, Further, a UV curable resin film was laminated as a protective layer to produce a magneto-optical disk. Here, an example of manufacturing a magneto-optical disk has been described. However, the present invention is not limited to this, and a write-once optical recording medium using a cyanine dye, a phthalocyanine dye, and a naphthalocyanine dye, or a phase-change optical recording medium using GeSbTe or the like. The present invention is also applicable to the optical recording medium described above.

Next, the result of recording information on the magneto-optical disk produced above and reproducing the recorded information will be described. Recording was performed by a conventional method, and reproduction was performed under the following conditions. <Reproduction conditions> Pickup (PU) Semiconductor laser wavelength 780 nm,
Objective lens NA = 0.5 Reproduction laser power Approx. 1.0 mW Disk rotation speed 1800 rpm In this embodiment, tracking servo is applied in the data area composed of grooves and lands, and tracking servo is applied in the prepit area composed of prepits. Played without. In the preformat area, reproduction was performed without shifting the focused laser beam to the center of the prepit row. When the data is reproduced on the groove, the trajectory of the laser beam focused on the data area and the header area including the preformat information (constituted by the pre-pit string) is as shown in FIG. An ODF (Offset Detection Flag) composed of a mirror surface was used as a PFM for detecting the position of the preformat area (FIG. 25).
reference). A tracking servo ON / OFF switching signal C was obtained from the ODF detection signal by the same means as in FIG. 14 (see FIG. 24). Based on the signal C, the tracking servo switching between the data area and the preformat area was performed using the tracking servo circuit having the tracking servo block diagram shown in FIG. The reproduction on the land was performed as shown in FIG. In this case, FIG.
7, the L / G tracking polarity was simply switched.

The measurement results of each signal of the header section measured above are shown below. At the time of reproduction on a groove (in the case of FIG. 23) Groove level Ig / (I ₁ + I ₂ ) a = 0.6 to 0.7 Sector mark Ism / (I ₁ + I ₂ ) a = 0.5 to 0.6 VFO Ivfo / (I ₁ + I ₂ ) a = 0.3 to 0.4 ・ Reproduction on land (in the case of FIG. 24) Land level Il / (I ₁ + I ₂ ) a = 0.55 to 0.65 Sector mark Ism / (I ₁ + I ₂ ) a = 0.5 to 0.6 VFO Ivfo / (I ₁ + I ₂ ) a = 0.3 to 0.4 Further, the center of the prepit array is scanned and scanned with a laser beam. The magnitude of the signal amplitude of the sector mark and the VFO is Ism / (I ₁ + I ₂ ) a = 0.55 to 0.65,
Ivfo = 0.34 to 0.43, and it was confirmed that the signal amplitude was reduced only by about 10% in this embodiment.

If the optical information recording medium of this embodiment is used for recording / reproducing as described above, the recording capacity can be doubled as compared with the conventional one because of the advantage of recording on both the groove and the land. Since the track pitch of the groove and the prepit row can be made sufficiently large with respect to the reproduction beam diameter, the preformat information can be accurately reproduced without deterioration of the preformat signal due to the crosstalk signal.

[0035]

According to the present invention, the following remarkable effects can be obtained due to the above-mentioned structure. (1) Since one set of data tracks of a groove and a land shares one pre-pit row, the information recording density can be improved, and the data track exists in the pre-format area rather than the recording pit density recorded in the data area. Since the density of prepits can be reduced, the reproduction reliability of preformat information is high. Also, since the laser focused beam has a preformat configuration in which the signal amplitude fluctuation is small even if it is not located at the center of the track to be reproduced, a signal indicating the position of the preformat area regardless of the presence or absence of the tracking servo. Can be detected. (2) Since the tracking servo state is switched between a data area composed of grooves and lands and a preformat area composed of prepit rows, the center line of the prepit row is shifted by P / 4 from the center line of the groove. As a result, it is possible to realize a tracking servo that prevents the deviation of the track servo and the jump of the track to an adjacent track. (3) Since a signal output indicating the position of the preformat area can be obtained by using an optical information recording medium having a preformat mark, tracking for accurately switching the tracking servo state in the preformat area can be obtained from this signal output. A servo switching signal can be generated.

[Brief description of the drawings]

FIG. 1 is a partial perspective sectional view showing a configuration of an optical information recording medium proposed by the present applicant previously.

FIG. 2 is a partial perspective sectional view showing a configuration of an optical information recording medium according to the present invention.

FIG. 3 is a plan view of the medium of FIG. 2;

FIG. 4 is a diagram showing a relationship between a groove shape and a groove level, a relationship between a groove shape and a land level, a relationship between a groove shape and a push-pull signal used for tracking, and a relationship between a prepit shape and a prepit amplitude. .

FIG. 5 is a diagram showing definitions of parameters indicating shapes of prepits and grooves.

FIG. 6 is a diagram showing a scanning trajectory of a laser focused beam during recording / reproduction.

FIG. 7 is an explanatory diagram of a preformat configuration.

FIG. 8 is an explanatory diagram of a preformat region including a groove and a land, and a waveform of a push-pull signal in the region.

FIG. 9 is an explanatory diagram of a preformat area including a prepit string and a waveform of a push-pull signal in the area.

FIG. 10 is a timing chart of signals used for tracking switching.

FIG. 11 is a circuit block diagram for generating signals used for tracking switching.

FIG. 12 is a block diagram showing a tracking servo circuit used in the present invention.

FIG. 13 is a timing chart when the tracking servo is switched on / off using a preformat window signal C;

FIG. 14 shows a track offset signal E ′ with good timing.
FIG. 3 is a circuit block diagram for generating a.

15 uses the preformat window signal C of FIG. 13 as a tracking servo signal and the signal E ′ of FIG. 13 as a track offset signal with respect to the circuit of FIG.
FIG. 6 is a circuit block diagram when using the.

FIG. 16 is an explanatory diagram of reproduction of preformat information.

FIG. 17 is an explanatory diagram of a method for producing a PC board by injection molding.

FIG. 18 is a block diagram of an optical system of a master exposure machine.

FIG. 19 is a timing chart for controlling an Ar + laser focused beam.

FIG. 20 is a block diagram of an optical system of a master exposure machine using two Ar + laser focused beams.

FIG. 21 is an operation timing chart when the master exposure machine of FIG. 20 is used.

FIG. 22 is another operation timing chart when the master exposure machine of FIG. 20 is used.

FIG. 23 is an explanatory diagram of a trajectory scanned by a laser condensed beam in a header area in the embodiment.

FIG. 24 is an explanatory diagram of a trajectory scanned by a laser condensed beam on a land in the embodiment.

FIG. 25 shows ON / OFF of the tracking servo in the embodiment.
It is explanatory drawing of OFF switching.

FIG. 26 is a circuit block diagram for obtaining an ON / OFF switching signal C of a tracking servo.

FIG. 27 is a block diagram of a tracking servo circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Disc substrate 2 Land 3 Groove 4 Pre-pit 5 Recording pit 6 Laser condensing beam 7 Light absorption / reflection recording layer P Groove interval (track pitch) 23, 37 Signal modulator (DA / O) 25, 38 Light intensity modulator (A A / O) 27 Optical deflector (W A / O) 35 Half mirror

Claims (6)

(57) [Claims] 1. An optical information recording medium having a tracking groove and a pre-pit row, wherein the center line of the pre-pit row is left and right by approximately P / 4 from the center line of the groove, where P is an interval between the grooves. No groove is formed in the preformat area formed of the pre-pit row formed so as to be shifted to any one side, and further, the groove and the pre-pit are formed in the preformat area formed of the pre-pit row. An optical information recording medium having a preformat mark including a mirror mark portion that does not exist. 2. A preformat area having a same pattern formed of a prepit line on a center line of a groove and a center line of a land in a preformat area formed by a prepit line. Optical information recording medium. 3. When reproducing a data area composed of a groove or a land by using the optical information recording medium according to claim 1 or 2, a laser beam is focused on the center line of the groove or the land by a tracking servo. When reproducing while prescanning the preformat area consisting of the prepit array, remove the tracking servo near the switch from the data area to the preformat area, shift the laser focused beam to the center of the prepit array, and then Scan while applying the tracking servo, then remove the tracking servo near the switch from the preformat area to the data area, shift the focused laser beam to the center of the groove or land,
A recording / reproducing method wherein scanning is performed while applying a tracking servo. 4. When reproducing a data area composed of a groove or a land by using the optical information recording medium according to claim 1 or 2, a laser beam is focused on the center line of the groove or the land by a tracking servo. When reproducing the pre-format area consisting of the pre-pit row while scanning, remove the tracking servo near the switch from the data area to the pre-format area, shift the laser focused beam to the center of the pre-pit row, and then perform tracking. Scan without servo,
Next, a recording / reproducing method characterized in that a laser focused beam is shifted to the center of a groove or a land in the vicinity of switching from a preformat area to a data area, and then scanning is performed while applying tracking servo. 5. When reproducing a data area composed of a groove or a land by using the optical information recording medium according to claim 1 or 2, a laser beam is focused on the center line of the groove or the land by a tracking servo. When reproducing the pre-format area consisting of pre-pit rows while scanning, remove the tracking servo near the switch from the data area to the pre-format area, and fix the laser focused beam on the center line of the groove or land. A recording / reproducing method characterized in that scanning is performed while tracking servo is applied again in the vicinity of the switching from the preformat area to the data area. 6. A preformat mark provided in the preformat area is optically detected by using a laser condensed beam, and a position of a header area in the preformat is estimated from a signal of the preformat mark to perform tracking. The recording / reproducing method according to any one of claims 3 to 5, wherein servo ON / OFF switching is performed.