JP2005302224A5 - - Google Patents

Description

Master exposure method and information recording disk

  The present invention relates to a master exposure method and an information recording disc, and more specifically, produced by a master exposure method for exposing a wobble pattern while causing an exposure beam to meander in the radial direction of the master for the information recording disc, and the master exposure method thereof. The present invention relates to an information recording disc manufactured using a master disc.

  In the field of optical discs, it is required to increase the pitch of recording marks formed on the optical disc and to reduce the track pitch as the information density increases. However, as the information density increases, the influence of the reproduction signal obtained from the recording mark on the spot diameter of the reproduction beam increases. For example, in a region where the spot diameter of the reproduction beam is larger than the shortest recording mark length, when a predetermined recording mark is reproduced, a part of the information of the recording mark adjacent in the track direction is also reproduced by interference. (Intersymbol interference). As a result, problems such as degradation of the quality of the reproduction signal occur. In order to prevent intersymbol interference, the relationship between the reproduction beam spot size and the recording mark size is such that the reproduction signal amplitude changes linearly with respect to the recording mark size at a predetermined reproduction beam spot size ( Hereinafter, it is desirable to stop in a region where the reproduction signal is also referred to as linearity.

  In general, when an optical disk is produced in large quantities, a predetermined pattern (physical pattern such as a groove, pit, or recording information) is formed on a substrate by injection molding using a stamper. The stamper is manufactured through a method such as development / plating after applying a photosensitive resist to the glass master, exposing it with a condensing laser device (cutting device) or the like. At that time, irregularities (pits, continuous grooves, etc.) corresponding to a predetermined pattern exposed by the cutting device are formed on the stamper surface. In such a mastering process, the portable information of the information recording mark can be recorded as a pattern in which the pits, continuous grooves, or pit rows meander. In this case, since the information recording by the meandering pattern can be formed integrally with the groove, the secondary information related to the security of the optical disc may be recorded by the meandering pattern. Furthermore, information (address information or the like) for additionally recording on the optical disc can be recorded in a meandering pattern during exposure of the master. The exposure of the cutting device in such a mastering process is performed precisely in an environment where the temperature and humidity are controlled with a high degree of cleanness, but a mark (meandering pattern) that is smaller than the convergent light diameter of the focused laser (exposure beam) is formed. However, it is difficult to ensure the linearity of the reproduction signal with respect to the recording mark length, and the recording density is determined by the convergent light diameter of the focused laser.

JP 2002-237039 A JP-A-9-288824

By the way, in recent years, high-density recording is required in a format for recording information using a meandering pattern. In the following, problems in high-density recording of meander patterns will be described.

When exposing a predetermined meandering pattern on the master, if the meandering period included in the meandering pattern is constant, the deflection operation of the single exposure beam 10 is repeated at the same period as shown in FIG. 11) Since the meandering pattern 13 is exposed, the trajectory of the meandering pattern 13 actually formed by the mastering process is all uniform. However, the meandering period T in FIG. 1 is a predetermined information recording mark unit such as a clock period at the time of information recording.

When the meandering pattern 13 is exposed with the exposure beam 10, the deflection drive signal for driving the exposure beam 10 is switched to a rectangular wave shape with a predetermined meandering period T as shown in FIG. However, actually, the locus of the meandering pattern exposed by the exposure beam 10 is as shown in FIG. 1B due to the limitation of the operating speed of the deflector and the operating speed of the driver for driving the deflector to deflect. This is not the same rectangular pattern as the deflection drive signal. Therefore, as shown in FIG. 1B, the length in the track direction of the region where the deflection amount of the meandering pattern 13 actually formed in the mastering process is maximum is the region where the deflection amount of the deflection drive signal is maximum. Shorter than the length (meandering period T). In the following, an area length of 1/2 or more of the maximum deflection amount of the meander pattern is referred to as an effective recording mark length. The effective recording mark length is also shorter than the length (meandering period T) of the region where the deflection amount of the deflection drive signal is maximum, as shown in FIG. When using a deflector and a deflection driver that faithfully operate the deflection drive signal and using an exposure beam that can be regarded as a point, an ideal meander pattern corresponding to the deflection drive signal can be realized. Since the exposure beam has a finite spread and the operation speed of the deflector is also limited, a meandering pattern 13 different from the deflection drive signal waveform is formed as shown in FIG.

Further, when a stamper is manufactured from a master on which such a meandering pattern 13 is formed and a wobble groove corresponding to the meandering pattern 13 is formed on the substrate by injection molding using the stamper, the stamper is formed on the master on the substrate. A wobble groove similar to the meandering pattern is formed. Therefore, in the following description, the meander pattern of FIG. 1B will be described as a wobble groove pattern formed on the substrate. In that case, the meandering pattern 13 is called a wobble groove 13. Similarly, in the description of FIGS. 2 to 4 to be described later, a meander pattern is described as a wobble groove pattern formed on the substrate as appropriate.

When the reproduction light 100 is scanned in the direction of the arrow 12 in FIG. 1 in the wobble groove 13 formed on the optical disk in a meandering pattern as shown in FIG. 1, the reproduction signal from the wobble groove 13 is detected. As shown in (), a reproduction signal having a constant amplitude is obtained.

On the other hand, as shown in FIG. 2, when a plurality of meandering periods are included in the meandering pattern of a predetermined track, the linearity of the meandering period of the deflection drive signal with respect to the effective recording mark length is lost. Specifically, as shown in FIG. 2, the effective recording mark length of the area exposed at the meandering period 2T is at least twice the effective recording mark length of the area exposed at the meandering period T. It becomes. That is, if the meandering cycle of the deflection drive signal is different, the effective recording mark length is different from that of the meandering cycle. This is mainly due to the fact that the meandering cycle of the meandering pattern is shortened with the high density recording of information, the deflection operation time of the exposure beam is sufficient for the exposure time required for forming the recording mark (meandering pattern). This is because it disappears. Therefore, the smaller the meander period, the shorter the effective recording mark length, and the smaller the area of the deflection area (recording mark area) that contributes to information reproduction in the reproduction light spot. As a result, the shorter the meander cycle, the smaller the reproduction signal from the recording mark area formed by the meander pattern. Therefore, when a plurality of meandering periods are included in the meandering pattern of a predetermined track, there arises a problem that a difference occurs in the amplitude value of the reproduction signal depending on the meandering period. For example, as shown in FIG. 2B, when a wobble pattern having a plurality of meandering cycles (T and 2T) is included in a wobble groove of a predetermined track, as shown in FIG. The reproduction signal obtained from the region T has a smaller amplitude than the reproduction signal obtained from the region having the meandering period 2T. That is, the linearity (uniformity) of the reproduction signal with respect to the change of the meandering cycle is deteriorated.

In addition, when the meandering cycle of the meander pattern is shortened due to the high density recording of information, the diameter of the reproduction light has a finite size. Interference is likely to occur, resulting in a problem that the linearity of the reproduction signal with respect to the meandering cycle cannot be ensured. For example, as shown in FIG. 2, the reproduction signal of the wobble pattern is detected by scanning the wobble groove 23 formed of the meandering pattern having a plurality of meandering periods (T and 2T) with the reproduction light 100 in the direction of the arrow 12. Then, when the reproducing light 100 is present on the recording mark area B having the meandering period 2T, the reproducing light 100 contains almost only information on the meandering period 2T, but is reproduced on the recording mark area A having the meandering period T. When the light 100 is present, the reproduction light 100 includes a part of a recording mark adjacent to the track direction (such as an inclined portion of a wobble pattern). Therefore, when the information of the recording mark area A having the meandering period T in the wobble groove 23 is reproduced, not only the information of the recording mark area A to be reproduced but also a part of the information of the recording mark area adjacent in the track direction is together. Will play. That is, in the wobble pattern as shown in FIG. 2, when reproducing the information in the recording mark area having the meandering period T, intersymbol interference is likely to occur, and the amplitude of the reproduction signal obtained from the recording mark area having the meandering period T is As shown in FIG. 2C, the amplitude is smaller than the amplitude of the reproduction signal obtained from the recording mark area having the meandering period 2T. Intersymbol interference as described above is more likely to occur as the meander period becomes shorter as information is recorded at higher density.

Actually, when information is recorded in the meandering pattern, it is deflected and recorded at various meandering periods. Therefore, the degradation of the linearity of the effective recording mark length with respect to the meandering period and the deterioration of the linearity of the reproduced signal due to intersymbol interference limit the resolution of the reproduced signal. Further, if the reproduction signal from the meandering pattern becomes small, the signal-to-noise ratio (S / N) also becomes small, the jitter characteristic for the recording mark formed by the meandering pattern deteriorates, and the reproduction error rate increases. Therefore, there is a need for meandering pattern correction means for correcting a deviation in linearity of a reproduction signal with respect to a change in meandering cycle that occurs as information density increases. In particular, effective meandering pattern correction means for reducing the meander period in the linear recording direction (track direction) and reducing the track pitch in the radial direction is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is an optical disc master exposure method in which information is recorded in a wobble groove meander pattern, and reproduction that occurs with an increase in information recording density. An object of the present invention is to provide a master exposure method optimal for high-density recording by correcting signal linearity deterioration.

According to the first aspect of the present invention, in the master exposure method for exposing the meandering pattern while causing the exposure beam to meander in the radial direction of the master, the meandering in the radial direction of the exposure beam according to the meandering cycle of the meandering pattern. A master exposure method characterized by changing the amount is provided.

In the master exposure method according to the first aspect of the present invention, it is preferable that the meandering pattern includes a plurality of meandering cycles, and the plurality of meandering cycles is an integral multiple of a predetermined information recording mark unit. Here, the predetermined information recording mark unit refers to a reference unit for determining the length of a recording mark when information is encoded and recorded. In general, since the length of a recording mark recorded on a medium is set to an integral multiple of the recording clock, the predetermined information recording mark unit is also preferably an integral multiple of the recording clock.

Conventionally, the optical system of a master exposure apparatus (cutting apparatus) has been devised to reduce the diameter of the exposure beam as much as possible. However, the beam diameter of the reproduction light used at the time of reproduction is generally an exposure used in the master exposure apparatus. It is larger than the beam diameter. Therefore, as described above, when the wobble groove meander period becomes smaller as the information density increases, the linearity of the reproduction signal with respect to the change of the meander period cannot be ensured.

Generally, ensuring the linearity of a reproduction signal with respect to a recording mark in an area where information is densified is the same as improving the jitter of the reproduction signal. Therefore, the deterioration of the linearity of the reproduction signal can be evaluated by the jitter of the reproduction signal. It is known that the jitter of the reproduction signal is improved to some extent by compensating the size of the recording mark. Compensating the size of the recording mark and exposing the master disk is a method of exposing the pit pattern by compensating the pit size, that is, compensating the pit size by changing the exposure amount of the exposure beam. The method is known. However, this method cannot be applied to a recording mark in which information is recorded by a meandering pattern. Since recording with a meandering pattern meanders a continuous groove or pit row and assigns information to the meandering pattern, the size of the meandering pattern (eg meandering period) even if the exposure amount is corrected when the groove is formed. Cannot be improved. Further, since the length of the meandering pattern is continuous as a groove, the length of the meandering pattern cannot be adjusted by the exposure amount.

Therefore, in the master exposure method according to the first aspect of the present invention, when a predetermined meandering pattern is formed by irradiating the master with an exposure beam, the exposure beam master radial direction depends on the meandering cycle of the meandering pattern. By changing the amount of meandering, the deterioration of the linearity of the reproduction signal with respect to the change of the meandering period as described above is corrected.

An example of a master exposure method according to the first aspect of the present invention is shown in FIG. In the master exposure method according to the first aspect of the present invention, as shown in FIG. 3A, the meandering amounts a2 and b2 of the single exposure beam 10 when the meandering pattern having the meandering period T is exposed are changed to the meandering period 2T. The meandering amounts a1 and b1 when exposing the meandering pattern are made larger. In the example of FIG. 3, meandering amounts a1 and b1 when exposing a meandering pattern with a meandering period 2T are the same as in the conventional example shown in FIG. As a result, the meandering pattern 33 actually formed on the master by the mastering process has a meandering amount in the meandering period T region larger than the meandering amount in the meandering period 2T region, as shown in FIG.

When a reproduction signal is detected by irradiating the reproduction light 100 having the same spot size as the example of FIG. 2 onto the wobble groove 33 on the optical disk manufactured from the master having the meandering pattern as shown in FIG. Since the meandering amount of the recording mark area B with the meandering period 2T is the same as that of the conventional example of FIG. 2, a reproducing signal with the same amplitude as that of FIG. 2 is detected from the recording mark area B with the meandering period 2T.

On the other hand, in the recording mark area A having the meandering period T, the amount of meandering is larger than that in the conventional example of FIG. 2, so the area of the deflection area (recording mark area to be reproduced) contributing to information reproduction in the reproduction light 100 is increased. And the radial distance from the recording mark area adjacent in the track direction also increases, so that the area of the adjacent recording mark area in the reproduction light 100 also decreases. That is, by increasing the meandering amount of the recording mark area having the meandering period T, the area of the recording mark area to be reproduced in the reproduction light is increased and the influence of intersymbol interference is reduced. As a result, in the present invention, the deterioration of the amplitude of the reproduction signal obtained from the recording mark area having the meandering period T is suppressed, and the reproduction signal obtained from the recording mark area having the meandering period T is reproduced in the conventional example shown in FIG. It becomes larger than the amplitude of the signal. Therefore, in the example of FIG. 3, by adjusting the amount of meandering of the exposure beam when exposing the meandering pattern with the meandering period T during exposure of the master, as shown in FIG. 3C, regardless of the meandering period. A reproduction signal having a constant amplitude can be obtained. That is, in the master exposure method according to the first aspect of the present invention, it is possible to improve the deterioration of the linearity of the reproduction signal with respect to the change in the meandering cycle that occurs with the increase in the information recording density as described above.

According to the second aspect of the present invention, in the master exposure method for exposing the meandering pattern while meandering the exposure beam in the radial direction of the master, when exposing the meandering pattern of the predetermined track with the exposure beam, There is provided a master exposure method characterized in that the amount of meandering in the radial direction of the exposure beam is changed in accordance with the meandering pattern of adjacent tracks.

In the master exposure method according to the second aspect of the present invention, when the meandering pattern of the predetermined track is exposed according to the phase relationship between the meandering pattern of the predetermined track and the meandering pattern of the track adjacent to the predetermined track. It is preferable to change the meandering amount of the exposure beam.

The master exposure method according to the second aspect of the present invention is a master exposure method that corrects fluctuations in the reproduction signal that occur when the meandering pattern differs from track to track. An example is shown in FIG.

In the example shown in FIG. 4, as shown in FIG. 4B, the case where the patterns of the meandering pattern 43 and the meandering pattern 44 of the adjacent track are different is shown. As shown in FIG. 4B, the meandering pattern 43 is a pattern with a constant meandering period T, and the meandering pattern 44 of the track adjacent to the meandering pattern 43 is a pattern including the meandering periods T and 2T. When the meandering pattern differs between adjacent tracks, as shown in FIG. 4B, the recording mark area formed in the meandering pattern 43 and the recording mark area formed in the meandering pattern 44 adjacent thereto in the track direction The phase relationship (distance between recording marks in the radial direction) differs depending on the position in the track. Specifically, as shown in FIG. 4 (b), an area having the same phase as the recording mark area of the adjacent track and the radial distance from the recording mark of the adjacent track is the same as the track pitch (FIG. 4 (b)). ) In the meander pattern 43), an area where the distance from the recording mark of the adjacent track is larger than the track pitch (area Y in the meander pattern 43 in FIG. 4B), and recording of the adjacent track A region where the distance from the mark becomes narrower than the track pitch (region Z in the meander pattern 43 in FIG. 4B) is generated.

Usually, since the exposure beam used for exposure of the master has a Gaussian beam waveform, when exposing the meandering pattern, an area outside the effective diameter (for example, the range indicated by the beam 10 in FIG. 4) is also exposed. Therefore, exposure is also performed to some extent between the meandering patterns (between tracks). The exposure amount (hereinafter also referred to as cross exposure amount) differs depending on the distance between the recording marks in the radial direction (recording marks formed in a meandering pattern). Therefore, when the track pitch is narrowed as the information recording density is increased, the influence of the cross exposure amount on the actually formed meander pattern is increased. For example, in a region where the distance between the recording marks in the radial direction is short like the region Z ′ in FIG. 4, the cross exposure amount increases, and conversely, between the recording marks in the radial direction like the region Y ′ in FIG. The cross exposure amount decreases in an area where the distance is long. Therefore, after exposing the meandering pattern 44 and exposing the meandering pattern 43 with an exposure beam having the same meandering amount, the cross exposure amount in the regions Y ′ and Z ′ in FIG. 4 is not the intended exposure amount. In the regions Y and Z in the meandering pattern 43, a desired meandering pattern (dotted line 40 in FIG. 4) cannot be obtained.

When a reproduction signal is detected from a wobble groove formed with an unintended meandering pattern (not shown) as described above, an area having a short distance from the recording mark of the adjacent track, such as area Z in meandering pattern 43 in FIG. 4 is larger than the reproduction signal obtained from the region X in the meandering pattern 43 in FIG. 4, and the recording signal of the adjacent track as in the region Y in the meandering pattern 43 in FIG. Since the reproduction signal obtained from the far distance area is smaller than the reproduction signal obtained from the area X in the meandering pattern 43 in FIG. 4, the amplitude of the reproduction signal is not uniform in the track direction. This is because the groove width in the track direction is partially different depending on the amount of cross exposure.

In the master exposure method according to the second aspect of the present invention, in order to solve the above problem, when exposing a meandering pattern of a predetermined track, a deflector is used according to the state (phase, etc.) of the meandering pattern of an adjacent track. The deflection level of the modulation signal to be driven, that is, the amount of meandering of the exposure beam is changed. At this time, the meandering amount of the exposure beam is adjusted so that the amplitude of the reproduction signal obtained from the predetermined wobble groove is constant regardless of the meandering pattern of the wobble groove of the adjacent track.

The master exposure method according to the second aspect of the present invention will be described in detail with reference to the example of FIG. 4. Regions that are in phase with adjacent tracks, such as region X in meander pattern 43 in FIG. In this case, the deflection amount of the deflection drive signal (the meandering amount of the exposure beam) does not need to be specifically corrected, but the distance from the recording mark of the adjacent track as in the region Z in the meandering pattern 43 in FIG. In the region where the distance is close, the meandering amount a3 of the exposure beam 10 in the region Z is made smaller than the meandering amount a1 in the region X to adjust the amount of cross exposure between the recording marks in the radial direction (region Z ′). In the region Z in the meandering pattern 43 in FIG. 4B, the cross exposure amount is large, so that a sufficient reproduction signal can be obtained even if the exposure beam 10 meandering amount is small, and the amount of meandering necessary for the desired reproduction signal is obtained. A meandering pattern 43 is formed. At this time, the meandering amount a3 of the exposure beam 10 in the region Z is set so that the amplitude of the reproduction signal obtained from the region Z in the meandering pattern 43 is the same as the amplitude of the reproduction signal obtained from the region X in the meandering pattern 43. Adjust as appropriate.

On the other hand, in the region where the distance from the recording mark of the track adjacent in the radial direction is long like the region Y in the meandering pattern 43 in FIG. The amplitude of the reproduction signal obtained from the region Y is adjusted by increasing the area of the deflection region (recording mark region) that contributes to information reproduction by making it larger than the meandering amount b1 in the region X. However, at this time, the meandering amount b3 of the exposure beam 10 is set so that the amplitude of the reproduction signal obtained from the region Y in the meandering pattern 43 is the same level as the amplitude of the reproduction signal obtained from the region X in the meandering pattern 43. Adjust as appropriate. By using the master exposure method according to the second aspect of the present invention as described above, the linearity of the reproduction signal generated due to the phase relationship between the meandering patterns of the tracks adjacent to each other with the high density recording of information is reduced. It becomes possible to correct. In the above example, the method for adjusting the meandering amount of the predetermined track in consideration of the meandering pattern of the track adjacent to one side of the predetermined track has been described, but the present invention is not limited to this. When exposing the serpentine pattern of the predetermined track, the deflection amount of the serpentine pattern of the predetermined track may be adjusted in consideration of the phase relationship between the serpentine pattern of the predetermined track and the serpentine pattern of the track adjacent to both sides of the predetermined track. .

According to the third aspect of the present invention, there is provided a method for manufacturing an information recording disc using a master disc produced by the master exposure method according to the first or second embodiment of the present invention.

According to the fourth aspect of the present invention, in the information recording disc in which the wobble groove having a plurality of meandering periods is formed, the amount of meandering in the radial direction of the wobble groove differs depending on the meandering period of the wobble groove. An information recording disc is provided.

In the information recording disc according to the fourth aspect of the present invention, it is preferable that the wobble groove region formed in the shortest meander period among the plurality of meander periods has the largest radial meander amount.

The information recording disk according to the fourth aspect of the present invention has wobble grooves formed in a meandering pattern as shown in FIG. 3B, and the amplitude of the reproduction signal obtained from the wobble grooves is constant regardless of the meander period. The amount of meandering is adjusted according to the meandering period of each recording mark area. Further, in the optical disc according to the fourth aspect of the present invention, the meandering amount of the recording mark area having the shortest meandering period (the area having the meandering period T in FIG. 3B) is the largest.

According to the fifth aspect of the present invention, in an information recording disc in which a wobble groove having a plurality of meandering periods is formed, a wobble groove pattern of a predetermined track and a wobble groove pattern of a track adjacent to the predetermined track An information recording disc is provided in which the amount of wobbling in the radial direction of the predetermined track varies according to the phase relationship between them.

The information recording disk according to the fifth aspect of the present invention has wobble grooves formed in a meandering pattern as shown in FIG. 4B, and is adjacent to the wobble groove 43 in FIG. 4B. In consideration of the phase relationship with the pattern of the wobble groove 44 of the track, the meandering amount of each recording mark area in the wobble groove 43 is appropriately adjusted so that the amplitude of the reproduction signal obtained from the wobble groove 43 is uniform. .

The information recording disk in the present invention is a disk having a format for recording information in a meandering pattern, and the present invention can be applied to such a disk and the same effect can be obtained. Examples of the information recording disk of the present invention include a read-only optical disk, a write-once optical disk, a phase change optical disk, a magneto-optical disk, and a hybrid (optical assist) recordable disk.

According to the master exposure method according to the first aspect of the present invention, when the meander pattern corresponding to the predetermined wobble groove is exposed, the meandering amount in the radial direction of the exposure beam is changed according to the meander cycle of the meander pattern. Exposure. At that time, by appropriately adjusting the meandering amount of the exposure beam according to the meandering cycle, the amplitude of the reproduction signal obtained from the wobbled groove formed by the meandering pattern can be made constant regardless of the meandering cycle. Therefore, by using the master exposure method according to the first aspect of the present invention, an information recording disk having excellent linearity of a reproduced signal with respect to a change in meandering cycle even if the information recording density in the track direction of the information recording disk is increased. Is obtained.

According to the master exposure method according to the second aspect of the present invention, when the meander pattern corresponding to the predetermined wobble groove is exposed, the meandering amount of the exposure beam of the predetermined track is changed according to the meander pattern of the adjacent track. Let it be exposed. At this time, by appropriately adjusting the meandering amount of the exposure beam, the amplitude of the reproduction signal obtained from the wobble groove formed by the meandering pattern of the predetermined track can be made constant irrespective of the meandering pattern of the adjacent track. Therefore, by using the master exposure method according to the second aspect of the present invention, an information recording disc having excellent linearity of a reproduced signal can be obtained even when the track pitch of the information recording disc is narrowed as the information density is increased. can get.

Hereinafter, the master exposure method of the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the following embodiments, an optical disc master exposure method will be described.

The master exposure method of Example 1 is shown in FIG. FIG. 3A is a diagram showing a change in the deflection drive signal when deflecting a single exposure beam, and FIG. 3B is a schematic diagram of the meander pattern formed in this example. (C) is the figure which showed the reproduction signal obtained from the wobble groove | channel on the optical disk formed in this example. In this example, as shown in FIG. 3B, a meandering pattern 33 including meandering periods T and 2T is formed in each track, and recording marks (meandering patterns) having the same meandering period are formed in the track radial direction. The meandering pattern 33 was formed so that the recording marks recorded by (1) were aligned. In this example, the meandering cycle T is the clock cycle for recording information. The meandering pattern 33 was formed as follows.

First, after a photosensitive resist was applied to a prepared master (such as a glass master), the master was mounted on a cutting device, and a predetermined meandering pattern as shown in FIG. 3B was exposed. At this time, as shown in FIG. 3B, the meandering pattern 33 was formed while meandering the single exposure beam 10 in the direction of the arrow 11 in FIG. 3B.

When the meandering pattern 33 is exposed, the deflection amounts a2 and b2 of the deflection drive signal in the meandering period T region in the meandering pattern 33 are converted into the deflection driving in the meandering period 2T region as shown in FIG. The amount of deflection of the signal is larger than a1 and b1. In this example, for comparison with the conventional example of FIG. 2, the deflection amounts a1 and b1 of the deflection drive signal in the region of the meandering cycle 2T are the deflection driving in the region of the meandering cycle 2T shown in the conventional example of FIG. The amount of polarization of the signal was the same. However, in this example, as will be described later, the master disk is previously set so that the amplitude of the reproduction signal obtained from the recording mark area having the meandering period T is the same as the amplitude of the reproduction signal obtained from the recording mark area having the meandering period 2T. Before exposure, the differences δa (= a2−a1) and δb (=) between the deflection amounts a2 and b2 of the deflection drive signal in the region of the meander cycle T and the deflection amounts a1 and b1 of the deflection drive signal in the region of the meander cycle 2T. b2-b1) was adjusted.

Next, after completion of the exposure, development processing was performed to form irregularities formed in a meandering pattern as shown in FIG. At this time, the meandering pattern actually formed on the master has a meandering amount in a recording mark area (for example, area A in FIG. 3B) having a meandering period T as shown in FIG. It becomes larger than the amount of meandering in the recording mark area (for example, area B in FIG. 3B) having a meandering period of 2T.

Next, a stamper was produced by subjecting the master on which the meandering pattern was formed to a process such as plating in the same manner as in the past. Then, a wobble groove corresponding to a meandering pattern as shown in FIG. 3B was formed on the substrate of the optical disk by injection molding using the produced stamper.

  Note that the differences δa (= a2−a1) and δb between the deflection amounts a2 and b2 of the deflection drive signal in the region of the meandering period T in FIG. 3 and the deflection amounts a1 and b1 of the deflection drive signal in the region of the meandering cycle 2T are shown. A specific setting method of (= b2-b1) is as follows.

First, the meandering pattern with meandering periods T and 2T was exposed by changing the deflection amount of the deflection drive signal. Next, the meandering patterns with meandering periods T and 2T exposed with various deflection amounts were reproduced with a head that is actually used for reproducing the disk, and the change in the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal was measured. Normally, the output level of the reproduction signal obtained from the meandering pattern increases linearly with an increase in the deflection amount of the deflection drive signal regardless of the meandering period, but the slope of the characteristic varies depending on the meandering period. The characteristics of the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal may vary depending on the polarity of the deflection drive signal, that is, the deflection direction (vertical direction in FIG. 3). The characteristics of the output level of the reproduction signal with respect to the deflection amount of the drive signal were measured. That is, in this example, the characteristics of the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal are measured for each deflection direction in the meandering patterns with meandering periods T and 2T.

Next, the deflection amount of the deflection drive signal corresponding to the desired reproduction signal level was obtained from each characteristic obtained by the above measurement. At this time, the deflection amounts a2 and b2 of the deflection drive signal are obtained from the characteristics of the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal for each deflection direction in the meander pattern of the meander cycle T. From the characteristics of the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal for each deflection direction, the deflection amounts a1 and b1 of the deflection drive signal are obtained. The deflection amount of the deflection drive signal is calculated from the deflection amounts a2 and b2 of the deflection drive signal having the meandering period T corresponding to the desired reproduction signal level and the deflection amounts a1 and b1 of the deflection drive signal having the meandering period 2T. Differences δa (= a2−a1) and δb (= b2−b1) were determined.

The wobble groove 33 formed by the exposure method as described above was irradiated with the reproduction light 100 having the same spot size as in FIG. 2 to reproduce the recording mark formed by the wobbling groove 33 meander pattern. The result is shown in FIG. In this example, the amount of meandering in the recording mark area (for example, area B in FIG. 3B) having a meandering period of 2T is the same as in the conventional example of FIG. 2, so the amplitude of the reproduction signal obtained from that area is also The amplitude of the reproduction signal shown in FIG. On the other hand, the amplitude of the reproduction signal obtained from the recording mark area having the meandering period T (for example, the area A in FIG. 3B) is obtained from the recording mark area having the meandering period 2T as shown in FIG. The amplitude of the reproduced signal is the same.

This is due to the following reasons. Since the amount of meandering is increased in the recording mark area having the meandering period T, the recording mark area having the meandering period T spreads in the radial direction, and the area of the recording mark area to be reproduced in the reproducing light 100 is increased. Further, in the recording mark area having the meandering period T, the radial distance between the recording marks adjacent in the track direction is widened, so that the area of the adjacent recording mark area included in the spot 100 of the reproduction light is also reduced. That is, intersymbol interference can be suppressed. By these effects, deterioration of the reproduction signal obtained from the recording mark area having the meandering period T is suppressed.

In this example, as described above, the amplitude of the reproduction signal obtained from the recording mark area having the meandering period T in advance is the same as the amplitude of the reproduction signal obtained from the recording mark area having the meandering period 2T. The difference δa (= a2−a1) and δb (= b2−b1) between the deflection amounts a2 and b2 of the deflection drive signal in the region of 2 and the deflection amounts a1 and b1 of the deflection drive signal in the region of the meandering period 2T are adjusted. As shown in FIG. 3C, a reproduction signal having a constant amplitude was obtained regardless of the meandering period.

By using the master exposure method as described above, a reproduction signal with a constant amplitude can be obtained regardless of the meandering cycle, so correction of deterioration in the linearity of the reproduction signal with respect to the meandering cycle caused by high density recording of the meandering pattern is corrected. can do.

The master exposure method of Example 2 is shown in FIG. FIG. 4A is a diagram showing a change in the deflection drive signal when deflecting the exposure beam, and FIG. 4B is a schematic diagram of the meander pattern formed in this example. ) Is a diagram showing a reproduction signal obtained from the wobble groove 43 formed in this example. In this example, as shown in FIG. 4B, the meandering pattern 43 is formed at a constant meandering period T, and the meandering pattern 44 adjacent to the meandering pattern 43 includes meandering periods T and 2T in the track direction. Formed with a pattern. In this example, the meandering cycle T is the clock cycle during information recording.

If the meandering pattern between adjacent tracks is different as shown in the meandering pattern 43 in FIG. 4B and the meandering pattern 44 adjacent thereto, the meandering pattern 43 and the meandering adjacent thereto as shown in FIG. The phase relationship with the pattern 44 (distance between recording marks in the radial direction) differs depending on the location in the track. Specifically, as in a region X in the meandering pattern 43 in FIG. 4B, the region having the same phase as the meandering pattern 44 and the distance between the recording marks in the radial direction being the same as the track pitch, FIG. b) A region where the radial distance from the recording mark of the adjacent track is larger than the track pitch, such as a region Y in the meander pattern 43 in FIG. 4B, and a region Z in the meander pattern 43 in FIG. As described above, there is a region where the radial distance from the recording mark of the adjacent track is narrower than the track pitch.

When the meandering pattern as shown in FIG. 4 is exposed, as described above, the area between the recording marks (meandering patterns) of tracks adjacent in the radial direction (areas X ′, Y ′ and Z ′ in FIG. 4). ) Cross exposure amount depends on the distance between the recording marks in the radial direction. For example, in a region where the distance between the recording marks in the radial direction is short, such as a region Z ′ in FIG. 4, the cross exposure amount increases, and conversely, between the recording marks in the radial direction as in region Y ′ in FIG. The cross exposure amount decreases in an area where the distance is long. Therefore, when the regions Y and Z in the meander pattern 43 in FIG. 4 are exposed, the polarization amounts a1 and b1 of the deflection drive signal similar to those in the region X in the meander pattern 43 in FIG. 4 are exposed. When the exposure is carried out, the desired meandering pattern 43 cannot be obtained. As a result, when a reproduction signal from a wobble groove formed with an unintended meandering pattern is detected, the amplitude of the reproduction signal is not uniform in the track direction.

In the master exposure method of this example, in order to solve the above problem, for example, when the meander pattern 43 in FIG. 4B is exposed, deflection is performed according to the state (phase, etc.) of the meander pattern 44 of the adjacent track. The deflection level of the modulation signal that drives the detector was changed. Specifically, a meander pattern 43 as shown in FIG. 4B was formed as follows.

First, as in Example 1, a photosensitive resist was applied to a prepared master (such as a glass master), and then the master was mounted on a cutting device to expose a predetermined meandering pattern. At this time, as shown in FIG. 4B, a meandering pattern was formed while meandering the single exposure beam 10 in the direction of the arrow 11 in FIG. 4B.

Further, when exposing the meandering pattern 43, the deflection amount a3 of the exposure beam 10 is set in a region close to the recording mark of the adjacent track, such as the region Z in the meandering pattern 43 in FIG. The exposure was performed by making it smaller than the deflection amount a <b> 1 in the region X in the meandering pattern 43. By adjusting the difference δa ′ (= a1−a3) between the deflection amount a3 of the deflection drive signal in the region Z in the meandering pattern 43 and the deflection amount a1 of the deflection drive signal in the region X in the meandering pattern 43, A desired meandering pattern 43 (pattern indicated by a broken line 41 in FIG. 4B) was formed by adjusting the cross exposure amount between the recording marks in Z. Incidentally, since the cross exposure amount is large in a region where the distance from the recording mark of the adjacent track is close, such as the region Z in the meander pattern 43 in FIG. 4, a sufficient reproduction signal can be obtained even if the exposure beam meander amount is small. Thus, a meandering pattern having a meandering amount necessary for a desired reproduction signal is formed. At this time, however, as will be described later, the amplitude of the reproduction signal obtained from the region Z in the meandering pattern 43 in advance is the same as the amplitude of the reproduction signal obtained from the region X in the meandering pattern 43. The difference δa ′ (= a1−a3) between the deflection amount a3 of the deflection drive signal and the deflection amount a1 of the deflection drive signal in the region X was adjusted. In this example, the deflection amount of the deflection drive signal is not corrected in a region that is in phase with the adjacent track, such as the region X in the meandering pattern 43 in FIG. The exposure was performed with the same deflection amount as that of the deflection drive signal in the meandering period T shown in the example.

On the other hand, in the region where the distance from the recording mark of the adjacent track is long like the region Y in the meandering pattern 43 in FIG. 4B, the deflection amount b3 of the exposure beam 10 is exposed in the region X in the meandering pattern 43. The deflection amount b1 of the beam 10 is made larger. As a result, the area of the recording mark region to be reproduced in the reproduction light was increased, and the amplitude of the reproduction signal obtained from the region Y in the meandering pattern 43 was adjusted. However, at this time, as described later, the region Y is set so that the amplitude of the reproduction signal obtained from the region Y in the meandering pattern 43 in advance and the amplitude of the reproduction signal obtained from the region X in the meandering pattern 43 are the same level. The difference δb ′ (= b3−b1) between the deflection amount b3 of the exposure beam 10 and the deflection amount b1 of the exposure beam 10 in the region X is adjusted.

Next, after completion of the exposure, development processing was performed to form irregularities formed in a meandering pattern as shown in FIG. At this time, the actually formed meandering pattern 43 is a pattern represented by a broken line 41 in FIG. In the region where the distance from the recording mark of the adjacent track is long like the region Y in the meandering pattern 43, the deflection amount of the exposure beam is made larger than the region X in the meandering pattern 43, so that it is actually formed in the region Y. The meandering amount of the meandering pattern is larger than that of the region X, and in the region where the distance from the recording mark of the adjacent track is close, such as the region Z in the meandering pattern 43, the deflection amount of the exposure beam is larger than that of the region X in the meandering pattern 43. Since it was made smaller, the meandering amount of the meander pattern actually formed in the region Z was smaller than that in the region X.

Next, a stamper was manufactured by performing a process such as plating on the master on which the meandering pattern as shown in FIG. Then, a wobble groove corresponding to a meandering pattern as shown in FIG. 4B was formed on the substrate of the optical disk by injection molding using the produced stamper.

  4, the difference δa ′ (= a1−a3) between the deflection amount a3 of the deflection drive signal in the region Z and the deflection amount a1 of the deflection drive signal in the region X and the deflection amount b3 of the exposure beam 10 in the region Y A specific method for setting the difference δb ′ (= b3−b1) from the deflection amount b1 of the exposure beam 10 in the region X is as follows.

First, a situation where the distance from the recording mark of the adjacent track is a predetermined interval as in the area X in FIG. 4B, and the recording mark of the adjacent track as in the area Y in FIG. 4B. And a situation in which the distance from the recording mark of the adjacent track is close as in the region Z in FIG. 4B, and the meander of the meandering period T under each situation. The exposure was performed by changing the deflection amount of the pattern deflection drive signal. Next, the meandering pattern exposed with various deflection amounts was reproduced with a head actually used for reproducing the disk, and the change in the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal was measured. At this time, for the phase state such as the region X, the characteristic of the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal was measured for each deflection direction. On the other hand, for a phase state such as region Y, the output signal characteristics of the reproduction signal with respect to the deflection amount of the deflection drive signal in the direction away from the recording mark of the adjacent track (downward in FIG. 4B) are measured. For the phase state such as the region Z, the output signal characteristics of the reproduction signal with respect to the deflection amount of the deflection drive signal in the direction approaching the recording mark of the adjacent track (upward in FIG. 4B) are measured. did.

Next, the deflection amount of the deflection drive signal corresponding to the desired reproduction signal level was obtained from each characteristic obtained by the above measurement. At this time, from the characteristics of the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal for each deflection direction in the phase state of the region X, the deflection amounts a1 and b1 of the deflection drive signal corresponding to the desired reproduction signal level are obtained. . On the other hand, from the characteristics of the output level of the reproduction signal with respect to the deflection amount of the deflection drive signal in the phase states of the regions Z and Y, the deflection amounts a3 and b3 of the deflection drive signal corresponding to the desired reproduction signal level are obtained, respectively. Differences δa (= a1−a3) and δb (= b3−b1) of the deflection amount of the deflection drive signal from the deflection amounts a1, b1, a3 and b3 of the deflection drive signal corresponding to the desired reproduction signal level thus obtained are obtained. Asked.

A reproduction signal (not shown) having the same spot size as that of the conventional example shown in FIG. 2 is irradiated onto the wobble groove 43 of the optical disk formed by using the exposure method as described above to detect a reproduction signal. The result is shown in FIG. As is apparent from the result of FIG. 4C, the amplitude of the reproduction signal obtained from the wobble groove 43 is constant regardless of the phase relationship between the wobble groove 43 and the wobble groove 44 of the adjacent track.

In the first embodiment, the deflection amounts a2 and b2 of the single exposure beam when forming the meandering pattern with the meandering period T are larger than the deflection amounts a1 and b1 when forming the meandering pattern with the meandering period 2T. Although described, the present invention is not limited to this. Conversely, the deflection amounts a1 and b1 of the single exposure beam when forming a meandering pattern with a meandering period 2T may be smaller than the deflection amounts a2 and b2 when forming a meandering pattern with a meandering period T. Even in such a case, a reproduction signal having a constant amplitude can be obtained regardless of the meandering period by appropriately adjusting the polarization amounts a1 and b1 of the single exposure beam when the meandering pattern having the meandering period 2T is formed. .

In the first and second embodiments, the polarization amounts a1 and b1 of the deflection drive signal of the exposure beam are described as being constant for comparison with the conventional example shown in FIG. 2, but the present invention is not limited to this. In order to obtain a desired reproduction signal, the polarization amounts a1 to a3 and b1 to b3 of the deflection drive signal may be appropriately adjusted.

In the first embodiment, a master exposure method for correcting deterioration in the linearity of a reproduction signal generated when the recording mark pitch in the track direction becomes narrower as the information density is increased. In the second embodiment, The master exposure method for correcting the deterioration in the linearity of the reproduction signal generated when the track pitch becomes narrow as the information density increases has been described. In the master exposure method of the present invention, master exposure may be performed by combining the first and second embodiments. In that case, the deterioration of the linearity of the reproduction signal can be corrected even if the recording mark pitch in the track direction and the track pitch are simultaneously narrowed as the information density increases.

In the first and second embodiments, the master disk exposure method of the optical disk has been described. However, the present invention is not limited to this, and the present invention can be applied to any disk having a format for recording information by a meandering pattern, and similar effects can be obtained. . For example, the master exposure method of the present invention can be applied to a magneto-optical disk having a format for recording information by a meander pattern, a hybrid (optical assist) recordable disk, a dye recording medium, a phase change medium, a patterned medium, and the like. is there.

In the master exposure method shown in the first embodiment, since the amount of exposure beam meandering is changed in accordance with the meandering period of the meandering pattern, the amplitude of the reproduction signal from the wobble groove can be made constant regardless of the meandering period. it can. Therefore, even if the information recording density in the track direction of the optical disk is increased, an optical disk with excellent reproduction signal linearity with respect to the meandering cycle can be obtained.

In the master exposure method shown in the second embodiment, when the meandering pattern of a predetermined track is exposed, the meandering pattern is changed by changing the meandering amount of the exposure beam of the predetermined track according to the meandering pattern of the adjacent track. Thus, the amplitude of the reproduction signal from the wobble groove corresponding to the meandering pattern of the predetermined track can be made constant regardless of the meandering pattern of the adjacent track. Therefore, even if the track pitch of the optical disk is narrowed, an optical disk with excellent reproduction signal linearity can be obtained.

That is, the master exposure method of the present invention is most suitable as a master exposure method for achieving high-density recording on an optical disc having a format for recording information in a meandering pattern. Further, by manufacturing an optical disc using a master disc formed by the master exposure method of the present invention, a higher recording density optical disc can be manufactured.

FIG. 1 is a diagram showing a master exposure method when forming a meandering pattern having a single meander cycle, and FIG. 1A is a diagram showing a change in a deflection drive signal during master exposure. FIG. 1B is a schematic diagram of a meandering pattern, and FIG. 1C is a change diagram of a reproduction signal obtained from a wobble groove formed on a substrate. FIG. 2 is a diagram showing a master exposure method when forming a meandering pattern including a plurality of meandering periods, and FIG. 2A is a diagram showing a change in a deflection drive signal during master exposure. 2 (b) is a schematic view of a meandering pattern, and FIG. 2 (c) is a change diagram of a reproduction signal obtained from a wobble groove formed on the substrate. 3A and 3B are diagrams showing a master exposure method according to the first embodiment, FIG. 3A is a diagram showing a change in a deflection drive signal during master exposure, and FIG. 3B is an outline of a meander pattern. FIG. 3C is a variation diagram of the reproduction signal obtained from the wobble groove formed on the substrate. 4A and 4B are diagrams showing a master exposure method according to the second embodiment. FIG. 4A is a diagram showing a change in a deflection drive signal at the time of master exposure, and FIG. 4B is an outline of a meandering pattern. FIG. 4C is a variation diagram of the reproduction signal obtained from the wobble groove formed on the substrate.

Explanation of symbols

10 Exposure beam
13, 23, 33, 43, 44 Meander pattern
100 Reproducing light