JPH0896363A - Format forming method for optical information recording medium - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for forming a format of an optical information recording medium capable of reliably binarizing a reproduced signal even in high density recording while keeping the amplitude of the reproduced signal in a substantially constant range. There is. [Structure] A formatted optical disc is provided with a VFO section in which short pits Ps are successively created one after another and an ID section in which long pits P1 are arranged in advance. When manufacturing a master, short pits are formed with almost normal laser power, whereas long pits are attenuated with a certain inclination from the tip to the end of the pit to be formed, depending on the length. Formed. By forming the pits in this way, the level of the reflected light beam from the long pit string rises, and the threshold level of the reproduced signal can be determined based on the reproduced signal level from the short pit string.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical information recording medium having a preformat, and more particularly to a method of forming a format of an optical information recording medium capable of high density recording.

[0002]

2. Description of the Related Art In an optical information recording medium capable of optically recording information, that is, an optical disk, it is essential to increase the storage capacity, and various methods such as shortening the wavelength of a semiconductor laser have been studied in order to increase the recording density. ing. In order to record at high density, it is necessary to make each recording mark smaller and the interval between marks smaller.
There is a problem that it becomes smaller and the CN ratio deteriorates. So CN
In order to record at a high density without deteriorating the ratio, it is necessary to set the size and depth of each pit to optimum conditions so as to obtain as large an amplitude as possible for each mark.

When recording / reproducing on an optical information recording medium, information is usually managed in units of sectors, and in order to access a predetermined sector, an address signal of the sector or the like is recorded in each sector. A header section is provided, and a predetermined sector is accessed by reading the signal of the header section. As a method of forming the header portion, a method for recording a preformatted signal on a master by a master recording device for creating a master for manufacturing an optical information recording medium and an optical information recording medium manufactured from the master are manufactured, There is a method in which a format signal is recorded in an actual drive device in the same manner as normal information recording. Regarding a method of forming a header portion by irradiating a laser beam at the time of recording on a master disc, various methods of optimally controlling the laser beam so that each pit of the header portion has an optimum shape have been proposed so far.
A method of controlling the diameter of the laser beam in order to optimize the width and depth of the pit (Japanese Patent Laid-Open No. 62-47845),
In addition, the duty ratio and signal level of the pulse corresponding to each pit are used as the signal frequency (Japanese Patent Laid-Open No. 61-59639).
Or a recording radial position (Japanese Patent Laid-Open No. 59-59,
No. 140634).

[0004]

The laser beam is controlled in order to optimize the width and depth of the pits depending on the type of mark in the header portion, but it is sufficient as the track pitch and pit pitch become narrower. The signal amplitude cannot be obtained. The format signal has a VFO section in which the shortest mark is repeated for synchronization, an ID section in which address section data such as a track number / sector number is written, an address mark section indicating that the ID section starts, and the like. Although pits having different heights are mixed, the signal amplitude of each pit varies due to intersymbol interference due to the influence of marks before and after the pit pitch is clogged.

FIG. 8 shows an example of such intersymbol interference that can occur when reproducing the signal of the header section. Figure 8
The reproduced signal of the VFO part, which is followed by the closest pit Ps in (a),
FIG. 8 (b) shows a reproduction signal of a portion (isolated pattern) where a particularly long pit Pl of the ID portion continues. Figure 8
As shown in (a), in the VFO portion, since the closest pits Ps continue, there are many convex portions (lands) between the pits and the pit width becomes somewhat smaller, so the signal level is close to the mirror portion. The reflectance increases to the L4 level, and the reproduction signal is modulated with the amplitude in the range of L2-L4. On the other hand, in the land portion of the isolated pattern of the ID portion, the reproduction beam enters the long pits Pl (a little wider than the shortest pit) in the front and rear, and the reflected light intensity is reduced, so that L1-L3 close to the groove level. The reproduced signal is modulated with an amplitude in a range of about. If the slice level for binarizing the header part is set to the Ls level with the amplitude of the VFO part as a reference, the isolated pattern part of the ID part cannot be binarized. FIG. 9 shows a waveform obtained by actually performing exposure and development using a glass resist plate and observing a reproduced signal. It can be seen from FIG. 9 that binarization using the slice level is difficult because the level of the VFO part is considerably higher than that of the ID part.

In this way, when the slice level is set and the reproduced signal is binarized, if the amplitude varies, the signal cannot be accurately reproduced, and the pit shape control is performed as described above. Although various methods have been studied, there is a problem that the control becomes difficult as the frequency of the signal increases.

The present invention has been made in view of the above-mentioned circumstances, and the amplitude of a reproduced signal is kept within a substantially constant range, and the reproduced signal is surely binarized even in high density recording. It is another object of the present invention to provide a method for forming a format of an optical information recording medium that can achieve the above.

[0008]

According to the present invention, there is provided an exposure step of exposing a format pit row with a light beam modulated by a format signal on a recording medium master disk having a photosensitive layer coated on the surface thereof. The light beam forming level of each pit of the header portion is reduced by a certain inclination from the leading end to the trailing end of the pit corresponding to the length of the pit to be formed to reduce the light intensity. Format formation of an optical information recording medium including an exposure step of exposing a pit row on the top and a step of forming a pit row corresponding to the exposed pit row on a master and manufacturing an optical information recording medium from the master. A method is provided.

Further, according to the present invention, on the optical information recording medium, the clock frequency referred to at the time of recording and reproducing is recorded in the formatted pit string, and the frequency is different for each radial region. In the step of forming a format pit row by condensing the light beam on the optical disk, the level of the light beam forming each pit of the header section according to the frequency corresponding to the format pit row is extended from the front end to the rear end of the pit. Provided is a method for manufacturing an optical information recording medium, which forms a format pit string by reducing the light intensity with a constant inclination.

Further, according to the present invention, in the exposure step of exposing the format pit row with the light beam modulated by the format signal, the recording medium master having the surface of which the light-sensitive layer is coated is exposed. An exposure step of exposing the pit row on the photo-sensitive layer by reducing the pulse width of the light beam forming each pit with a constant coefficient according to the width, and a pit row corresponding to the exposed pit row And a step of manufacturing an optical information recording medium from this master, and a method for forming a format of the optical information recording medium is provided.

Furthermore, according to the present invention, the optical information in which the clock frequency referred to when recording and reproducing the data is recorded in the formatted pit train, and the frequency is different for each region in the radial direction. In the process of forming a format pit row by condensing a light beam on a recording medium, the pulse width of the light beam forming each pit of the header section according to the frequency corresponding to the format pit row is changed according to its width. Provided is a method of manufacturing an optical information recording medium, which is reduced by a constant coefficient to form a format pit string.

[0012]

In the formatted pit string, the level of the reflected light beam from the long pit string rises, and the threshold level of the reproduced signal can be determined based on the reproduced signal level from the short pit string.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for forming a format of an optical recording medium according to the present invention will be described below with reference to the drawings. FIG. 1 shows a master recording apparatus which employs the optical recording medium format forming method of the present invention for forming a groove and a pre-format. In FIG. 1, a laser light source 1 emits a laser beam (for example, Ar laser or Kr laser), and this laser beam is incident on a laser optical axis control system 2 for adjusting an optical axis. This laser optical axis control system 2 enables the laser light source 1 and the like to be adjusted even if the optical axis changes due to temperature changes or the like.
The laser beam is reflected by the mirror 3 and supplied with the E. A beam modulation system 4 including an O modulator modulates the laser beam to an arbitrary signal. That is, in this beam modulation system 4, the laser beam is modulated by the format signal supplied from the format circuit 22. Next, the laser beam can be pinhole or
The beam diameter and the beam shape are adjusted by passing through the beam shaping system 5 including a slit. The beam shape of the laser beam whose shape and the like have been adjusted is confirmed by the beam monitor system 6. The beam is further guided by the mirror 7 and the objective lens 8
Thus, the optical recording master 9 is focused and irradiated, and the groove and the format pattern are recorded on the optical recording master coated with the photoresist.

In the embodiment of the present invention, in the beam modulation system 4, pits P of a short mark and a long mark are formed.
When the s and Pl are formed, the format signal is controlled so that the intensity of the laser beam is relatively increased when the pit Ps of the short mark is formed, and when the pit Pl of the long mark is formed, The intensity of the laser beam is relatively gradually reduced. That is, the light beam intensity is gradually attenuated when the pit Pl having the long mark is formed as compared with the case where the pit Pl having the short mark is formed. The length and width up to are reduced. A method for forming such a pit will be described later in detail with reference to an actual example. Incidentally, E. The O modulator is a high-speed light intensity modulator (M
Hz order), and E. If the bias voltage applied to the O modulator is changed at high speed, the light intensity can be easily changed, and the size of each pit can be controlled.

The recording master, which has been exposed to the laser beam, is subjected to a development process, then an Ag stamper and Ni electroforming, and is processed into a stamper by processing the surface and end portions. Resin molding is performed using a stamper, and a substrate (for example, acrylic resin or polycarbonate resin) of an optical recording medium is manufactured. In a recording type medium, this substrate is provided with a recording layer that undergoes phase change or diffusion alloying by laser irradiation, for example.

In the optical recording medium manufactured in this way, that is, in the optical disc 10 formatted by the M.CAV system, for example, the tracks are arranged in a substantially concentric pattern, and a plurality of tracks are formed in the radial direction. The strip-shaped area, that is, is divided into a plurality of zones and is divided into a plurality of sectors as a unit for recording data along the circumferential direction, and the number of sectors is set to be the same in each zone. For each zone, a data clock having a different specific frequency for reproducing the data from the track belonging to the zone and for recording the data is defined and recorded in advance in the header portion PF of the track. ing. Each sector of each zone of the optical disc 10 is composed of a header portion PF as a pre-formatted area recorded in advance as format information and a data field as a data area in which a user later records information. In the header section, a sector mark section that clearly indicates the start of one sector, a VFO section in which a synchronization code for deriving a data clock is recorded, and a plurality of ID sections in which ID information is recorded are arranged periodically. At the end of the data field, the next sector and data field
A gap region in which no data is written is provided to clarify the boundary with the field. The VFO section, ID information section, and data field are (2-7) modulated data, and are two or seven "0" s inserted between "1" and "1". Then, a pit mark is formed on the optical disc 1 and reproduced. In the ID section, a track number, a sector number and a CRC code are recorded as ID information. In the VFO section, "10010010
A synchronization code such as "0 ..." In which "1" is read at a constant cycle is recorded. These signals are supplied to the data processing circuit as reproduction signals, and in this data processing circuit, ID information as preformat data, that is, address information (track number, sector number, etc.) and The reproduction data is read.

FIG. 2 is a schematic block diagram of an optical recording medium produced as described above, that is, an optical disc drive device for reproducing information from an optical disc. The optical disk 10 is a spindle motor 1 provided in the drive device.
1 is mounted and rotated in a predetermined direction. The light beam emitted from the semiconductor laser 12 is converted into parallel light by the collimator lens 13, only the vibration of the light wave parallel to the incident surface passes through the polarization beam splitter 14, and the light beam is circularly polarized through the λ / 4 wavelength plate 15. After that, the light is focused on the optical disc 10 by the objective lens 16. On the other hand, the optical disc 10
The light beam reflected above changes from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate 15, and the traveling direction thereof is bent by 90 ° by the polarization beam splitter 14. The reflected light beam passes through the detection lens 17 and is incident on the light receiver 18. The received light beam is photoelectrically converted and sent as a feedback signal to the signal processing system 19 and the servo system 20. In the signal processing system 19, recording and reproducing signals are controlled for recording and reproducing, while in the servo system, the positions of the objective lens 16 and the optical disk 10 are adjusted by controlling the current flowing through the drive coil 21, and the tracking servo Focus servo is executed.

The format portion produced on the exposed and developed resist master disc causes a slight difference in the reproduced signal from the actual substrate due to the transferability at the time of producing the stamper and at the time of forming the substrate. It can be considered that the pit shape at the time of development is reflected on the completed recording medium. Therefore,
A resist plate obtained by applying a photoresist to a glass plate having a thickness of 1.2 mm was test-cut, and the reproduced signal was evaluated by the optical disk measuring device described in FIG.

As described above, when forming pits having different mark lengths as shown in FIG. 3 at the time of forming the format, the light intensity is reduced from the front end portion to the rear end portion of the pits at the same rate. (2-7) In an optical disc on which data is recorded and reproduced by the modulation method, pits Ps and Pl
Has 6 lengths from 3T (T: channel clock) to 8T. In the pit Ps with a length of 3T,
The exposure intensity is hardly changed, and a slight change in the exposure intensity hardly changes the length and width of the pit. On the other hand, in the long pit Pl having a length of 7T or 8T, the rear end of the pit is gradually narrowed. In general, the width of the long pit tends to widen with respect to the short pit Ps, and it can be considered that the width of the long pit Pl is appropriately compensated by the change in the exposure intensity.

When a gradient is given to the change of the exposure intensity, whether the isolated pattern of the ID portion can be binarized by using the slice level determined from the signal amplitude in the VFO portion shown in FIG. The result of the judgment is shown in FIG. At this time, recording / reproduction was performed at the inner peripheral position where the disk radius was about 24 mm, and the slope of the change in exposure intensity was examined by the amount of change of the channel clock T with respect to time. As shown in FIG. 4, it was found that accurate binarization was performed when the exposure intensity change P was set to −1.5 to −3.0 (mW / μsec). The X mark in FIG. 4 indicates that the amplitude of the VFO part cannot be sufficiently obtained,
It shows that the slice level has become unstable. That is, it is presumed that this result does not give sufficient light intensity to form the shortest pit Ps having a length of 3T.
In FIGS. 5A, 5B and 5C, the change P of the exposure intensity is −
Models of reproduced signals at three types of 0.3, -2.0, and -10 (mW / μsec) are shown. In FIG. 5A, the slice level defined in the VFO section cannot be used to binarize the reproduced signal in the ID section, and in FIG. 5D, the slice level defined in the VFO section is not stable. Then, it can be seen that the slope P in FIG. 5C is optimum not only for determining the slice level but also for detecting the binarization. Thus, it is understood that it is necessary to determine the exposure intensity in consideration of not only the level of each signal but also the amplitude and the degree of modulation.

[0021] It is necessary to consider the same in the outer periphery where the clock frequency, that is, the channel frequency is high. At the outer circumference, the frequency for reproduction and recording becomes high and the pulse width becomes short, so that the exposure intensity needs to be changed more rapidly. As a result of performing the same experiment on the outer circumference (r = about 40 mm) as on the inner circumference described above, the binarization by the slice level is accurately performed by the change of the exposure intensity about twice the result shown in FIG. It was confirmed.
This change in exposure intensity depends on the photosensitive characteristics of the resist, the characteristics of the cutting device, etc., but it is clear that it is effective in eliminating the binarization error. Also, MCA
In a disc such as V, increasing the amount of change in the exposure amount from the inner circumference to the outer circumference is very effective for stable binarization.

As shown in FIG. 8, the V with the shortest pit continues.
ID in which the signal level of the FO part and many types of pits coexist
There is a difference in signal level between the part and the isolated part, and the level of the isolated pattern part is considerably lowered. Therefore, as shown in FIG. 6B, if the pulse is cut by a width proportional to the length of the pit as shown in FIG. 6A (the hatched portion in FIG. 6A is a cut portion), As is clear from the comparison with FIG. 6A, in the portion sandwiched by the long pits, the interval between the pits increases and the signal level rises. On the other hand, since the shortest pit has a small cutting width, the level before cutting does not largely change, and the level difference between various signals becomes small. The pulse width can be cut easily by putting a format signal generated from the format circuit 22 into a delay circuit and taking an AND with an inversion signal of the cut pulse generated after the detection of the pulse width.

The optical disc medium according to this embodiment is (2
-7) Recording and reproduction are performed by the modulation method, and there are 6 types of pits from 3T to 8T. Actually, as shown in FIG. 6 (b), the reproduced signal when the pulse width is not cut at all and the cut rate (k = 0.25) as shown in FIG. 6 (c).
Differences from the reproduced signal when the pulse width is cut at are shown in FIGS. 7A and 7B, respectively. FIG. 7 (a)
As is clear from the comparison between FIG. 7B and FIG. 7B, cutting the pulse width is sufficient for adjusting the signal level. However, as shown in the model of FIG.
If the cut amount is too large, the signal amplitude may not be sufficient, so it is necessary to select an appropriate k value determined by the photosensitive characteristics of the resist, the characteristics of the cutting device, and the like. If the proportionality constant k determined by the photosensitive characteristics of the resist, the characteristics of the exposure apparatus, and the like is set and obtained in advance, it is possible to obtain an appropriate pit shape even if the exposure conditions change to some extent.

In the above description, the case of formatting by the master disc manufacturing apparatus shown in FIG. 1 has been described.
All or some of the pits of the format may be formed by the recording / reproducing apparatus shown in FIG. In this case, when the recording signal from the signal processing system corresponds to a long pit as is clear from the above description,
It is preprocessed so that the amplitude level decreases at a certain slope. Alternatively, part of the pulse width of the recording signal corresponding to a long pit may be cut.

[0025]

As described above, according to the present invention, since the difference in signal amplitude level between the VFO section and the ID section of the header section of the recording medium becomes small, the signal amplitude of the VFO section is binarized. Even if the slice level is set, no binarization error occurs in the header portion during reproduction, and the reproduction signal is properly binarized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a master recording apparatus that employs a format forming method for an optical information recording medium according to the present invention.

2 is a block diagram showing an optical disk device for writing information on an optical disk manufactured from a master disk manufactured by the master disk recording apparatus shown in FIG. 1 and reproducing information from the optical disk.

3 is a waveform diagram showing a relationship between pits having different lengths formed on the optical disc shown in FIG. 1 and exposure light intensity for forming the pits.

FIG. 4 is a table showing the relationship between the gradient of exposure intensity change and a binarization error.

FIG. 5 is a waveform diagram showing a relationship between a slope of a change in exposure intensity in a formatted VFO portion and an ID portion and a slice level for binarizing a reproduction signal.

FIG. 6 is a waveform diagram showing the relationship between pits of various lengths for formatting and the pulse width of a laser beam pulse for recording.

7A and 7B are waveforms showing a change in a reproduction signal from a pit formed without cutting the pulse width shown in FIG. 6 and a change in a reproduction signal from a pit formed by cutting the pulse width.

FIG. 8 is a waveform diagram showing changes in pits formed by adopting a conventional optical information recording medium format forming method and reproduction signals thereof.

FIG. 9 is a waveform diagram showing changes in the reproduced signal from the pits of the VFO portion and the ID portion formed by using the conventional format forming method for the optical information recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser source 4 ... Beam modulation system 8 ... Objective lens 9 ... Optical recording master 10 ... Optical disk 12 ... Semiconductor laser 13 ... Objective lens 19 ... Signal processing system 20 ... Servo system 22 ... Format circuit Ps, Pl ... Pit

Claims (4)

[Claims] 1. An exposure step for exposing a format pit row with a light beam modulated by a format signal, in which a master for a recording medium having a surface coated with a photo-sensitive layer is exposed to light for forming each pit of a header section. An exposure step of exposing the pit row on the photo-sensitive layer by reducing the light intensity with a constant inclination from the front end to the rear end of the pit corresponding to the length of the pit to be formed. A method of forming a format of an optical information recording medium, comprising: forming a pit row corresponding to the exposed pit row on a master and manufacturing an optical information recording medium from the master. 2. A light beam is recorded on an optical information recording medium in which a clock frequency referred to when recording and reproducing data is recorded in a formatted pit train, and the frequency is different for each radial region. In the process of forming the format pit row by condensing, the level of the light beam forming each pit of the header part is fixed with a constant inclination from the front end to the rear end of the pit according to the frequency corresponding to the format pit row. A method of manufacturing an optical information recording medium in which a light intensity is reduced to form a format pit string. 3. An exposure step for exposing a format pit row with a light beam modulated by a format signal, in which a master for recording medium having a surface coated with a photo-sensitive layer is exposed to light for forming each pit of a header section. An exposure step of exposing the pit train on the photo-sensitive layer by reducing the pulse width of the beam by a constant coefficient according to the width, and forming a pit train corresponding to the exposed pit train on the master. And a method of forming an optical information recording medium format, the method comprising: 4. A light beam is recorded on an optical information recording medium in which a clock frequency referred to when recording and reproducing data is recorded in a formatted pit train, and the frequency is different for each radial region. In the process of forming the format pit row by condensing, the pulse width of the light beam forming each pit of the header part is reduced by a constant coefficient according to the width according to the frequency corresponding to the format pit row. A method of manufacturing an optical information recording medium for forming a format pit string.