JP3435272B2 - Information recording medium, recording method and recording apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal obtained by FM-modulating an analog code such as video and audio by a recording beam such as a laser beam, digital data such as computer data, facsimile signals and digital audio signals. The present invention relates to an information recording medium capable of recording information in real time, a recording method, and a recording device. In particular, the present invention relates to a disc-shaped recording medium using a rewritable phase change type optical recording film.

[0002]

2. Description of the Related Art A recording / erasing method for a rewritable recording film uses, for example, a recording film for a phase change type optical disk capable of high-speed erasing that can be crystallized in a time substantially equal to a laser irradiation time for recording. In some cases, the power of one energy beam was changed between at least two levels, both higher than the read power level, that is, at least between a high power level and an intermediate power level. This method has an advantage that new information is recorded while erasing existing information, that is, so-called overwriting (rewriting by overwriting) is possible. When this phase change type optical disk is rewritten a number of times, the recording information signal is repeatedly irradiated with a laser beam at a high power level.

In particular, in a region near the pre-formatted portion, the probability that VFO, recording marks, etc. will be repeatedly recorded at the same location is high, and therefore local film thickness change is likely to occur due to the flow of the recording film. . As a method of improving this problem, as described in Japanese Patent Laid-Open No. 3-150725, there is a method of randomly shifting the data write start position every time data is rewritten or every suitable number of times. As a result, the positions where the marks are formed can be dispersed appropriately, and the rewriting characteristics are also improved.

[0004]

Even if information is recorded on the phase-change type optical disk by using the above-mentioned conventional technique, the asymmetry of the temperature distribution in the laser beam causes the entire area to be rewritten many times. The flow of the recording film will occur. Therefore, the film thickness becomes non-uniform in the recording area. In particular, one of the film thicknesses is thicker at the beginning and end of the recording area and the other is thinner, or the thickness of the recording film changes, or the film thickness at the center of the recording area is thicker and the film at the beginning and end portions is thicker. The film thickness changes as the thickness decreases. Due to such a change in the film thickness, there is a problem that the reproduced signal waveform is distorted, and the region where the waveform distortion is generated becomes wider as the number of times of rewriting increases.

Further, in a rewritable digital video disc or the like, there is a possibility that mark edge recording in which information is provided at both ends (edges) of a recording mark is used for high density recording. In the case of such mark edge recording method,
Since long marks are repeatedly recorded, deterioration due to flow becomes more remarkable. If one of the beginning and end is thick and one is thin, the flow may be stopped by adjusting the film thickness of the lower protective layer, etc., but the center is thick and both ends are thin. In this case, it is difficult to deal with it by adjusting the recording film composition and film thickness.

An object of the present invention is to solve the above problems in the prior art, and to provide an information recording medium, a recording method and a recording apparatus capable of surely obtaining a reproduction signal corresponding to a recording information signal. .

[0007]

In the present invention, a recording medium in which information can be recorded or rewritten by irradiation with laser light is used. This recording medium has a pre-formatted area in which information such as a track address is previously formed as recording marks due to uneven pits or phase changes. In addition to this preformatted area, a recording area such as a gap area, a VFO or SYNC area, and a data area is secured. Further, dummy areas are provided on at least one of the front and back of the recording area.
The VFO area may be made longer and a part of the VFO area may be used instead of the previous dummy area. In addition, a buffer area is provided in contact with the dummy area to allow the recording area to expand and contract due to motor rotation jitter. Here, one of the purposes of providing the above-mentioned dummy area is that the reproduced signal waveform distortion is VFO even if the recording film flows due to a large number of rewritings.
This is to prevent the information in the data area that has to be actually read from being damaged in the SYNC area, the SYNC area, the dummy area, or the buffer area. Furthermore, it is preferable that the dummy area is longer than the maximum shift width of the write start position of the recording information signal. Further, it is preferable to add a bit string (data part postamble) according to a predetermined rule in front of the dummy area so that the ratio of the mark and the space is not reversed.

As described above, in the present invention, the light beam is applied to the recording area to record or rewrite information in the area. Here, by recording dummy data that does not substantially carry information at the end of the recording area where the signal reproduction characteristics deteriorate due to aging due to the irradiation of the light beam, it is possible to ensure information even with aging. It can be recorded and reproduced.

Recording is performed using a signal in which a dummy signal is added to at least one of the front side and the rear side of a target recording information signal such as VFO, SYNC and data. When it is added to one side, the rear side is preferable. In this case, a dummy signal is mainly recorded in the dummy area. Then, the average energy of the laser beam during the recording of the dummy signal is made smaller than the average energy during the recording of the target recording information signal, so that the film thickness change due to the flow of the recording film due to the rewriting many times is relaxed in the dummy area. You can That is, the flowing recording film is not moved suddenly but gradually moved. As a result, the region where the film thickness changes can be narrowed, and the loss of recording capacity can be minimized.

At the time of reproduction, only the reproduction signal waveform of the recording area corresponding to the target recording information signal is reproduced.
As a result, the reproduced signal waveform is slightly distorted due to the flow in the dummy area where a dummy signal is recorded and a part of the buffer area, but there is no influence of the flow in the recording area where the target signal is recorded. A reproduced signal corresponding to the target recorded information signal can be obtained.

Further, even if the number of times of rewriting increases, a large distortion is unlikely to occur in the reproduced signal waveform from the recorded information signal.
When the flow occurs from the center toward both ends, the width of the film thickness change region at the terminal end tends to be wider, so that the capacity loss can be effectively reduced only by providing the dummy region at the terminal end with the buffer effect. Here, as a method of reducing the average energy of the laser beam during dummy signal recording,
For example, a signal with a single frequency may be used as a dummy signal and the duty ratio of this signal may be adjusted to reduce it.

In the case of the mark edge recording method, the average duty ratio is about 50%, so the duty ratio of the dummy signal may be 50% or less. Duty ratio of at least part of the dummy signal is 10% or more and 40%
The following is more preferable. It is particularly preferable if it is 20% or more and 30% or less. The average energy in the laser beam during recording of the dummy signal may be reduced stepwise or continuously by adjusting the duty ratio of the dummy signal stepwise or continuously. Alternatively, the recording power may be changed.

By randomly shifting the writing start of the recording information signal for rewriting, the degree of distortion of the reproduced signal waveform due to flow can be reduced. In this case, if the maximum shift width is made longer than the dummy signal to be added, an error will occur in the VFO, SYNC area and data area due to flow, so it is preferable to make it shorter than the dummy signal. However, if it is too short, the effect of adding the dummy becomes small, so the maximum shift width is preferably about 1/20 to 1/2 of the length of the dummy signal.

In the present invention, a recording medium in which information regarding the pattern of the dummy signal is recorded on the recording medium in advance is used. For example, such information may be recorded in the control track portion of the recording medium.

As the recording film used in the present invention, a crystal-amorphous phase change optical recording film capable of high-speed crystallization, a recording film utilizing a change between amorphous-amorphous, a crystal system or crystal grains. A crystal-crystal phase change recording film such as a change in diameter and a magneto-optical recording film are preferable, but other recording films may be used. In particular, Ge-
A recording film using a phase change such as an Sb-Te based recording film or an Ag-In-Sb-Te based recording film may be used. Also,
CrTe or A, which has a higher melting point than the main component material in the recording film
It is preferable to use a recording film having a high melting point material such as g ₂ Te added thereto, a recording medium having two reflective layers, or the like, because the change in the recording film thickness due to flow can be further suppressed.

Recording according to the present invention includes a laser light source, an optical system, an automatic focusing (AF) means, a tracking means, a reproduction signal detecting means, a control track reading means,
A recording medium on which information regarding a pattern of a dummy signal to be added to at least one of before and after a recording information signal is previously recorded on a recording medium, means for rotating or moving the recording medium, and laser light from the laser light source. Means for condensing on the recording medium, signal modulating means for converting a signal to be recorded into a modulation code, means for adding a dummy signal to at least one of before and after a recording information signal, recording waveform corresponding to the recording code Of the laser light reflected from the recording medium, a recording waveform generation means for generating a recording start position, a recording start position control means for randomly shifting the recording start position, a laser driving means for driving the laser light source by the recording waveform. A means for converting the intensity change into an electric signal, a binary conversion means for converting the electric signal into a binary waveform, and a dummy signal portion To means it can be realized by a recording apparatus having a means for the signal of the information by decoding the binary signal.

Further, the present invention is not limited to the disk shape,
It can also be applied to other forms of recording media such as cards.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below.

Example 1 FIG. 1 is a structural sectional view of a disk used in this example. First, on a polycarbonate substrate 1 for continuous servo having a diameter of 5 inches and a thickness of 0.6 mm, a ZnS film having a thickness of about 125 nm was first formed by a magnetron sputtering method.
It was formed -SiO ₂ dielectric layer layer 2. Next, ZnS-Si
A recording film 3 of Cr ₅ Ge ₂₀ Sb ₂₀ Te ₅₅ is formed on the O ₂ dielectric layer 2.
Was formed to a thickness of about 30 nm. ZnS-Si on this
The O ₂ dielectric layer 4 was formed to a film thickness of about 20 nm. Furthermore,
After forming the Si layer 5 with a thickness of about 100 nm on this,
The Al-Ti alloy reflective layer 6 was formed to a thickness of about 100 nm. These films were sequentially formed in the same sputtering device. After that, an ultraviolet curable resin layer 7 was applied on this, and then a hot-melt adhesive 8 was used to adhere and adhere to the protective plate 9. Here, instead of the protective plate 9, by closely adhering the polycarbonate substrate 1 to another substrate formed from the ultraviolet curable resin layer 7, a laminated disk having a recording capacity of 2 times can be obtained.

FIG. 2 shows an example of the sector format of the substrate used in this embodiment. There is a pre-formatted area 10 in which information such as a sector address and a track address is previously formed as uneven pits.
In addition to the read-only preformat area 10, a recording area 14 in which recording (including rewriting) such as a gap area 11, a VFO, a SYNC area 12 and a data area 13 is ensured. The recording area 14 is provided in the groove portion. Further, in this embodiment, dummy areas 15 and 16 are provided before and after the recording area. Further, after the dummy area 16 on the rear side of the recording area, a buffer area 17 for coping with rotation jitter is also provided. In the dummy areas 15 and 16, even if the recording film flows due to a large number of times of rewriting, in the area on the front side of the recording area, the reproduced signal waveform distortion due to the flow causes the dummy area 1 on the front side.
5, the reproduced signal waveform distortion due to the flow remains in the rear dummy area 16 in the area on the rear side of the recording area, and the data area 13 that must be actually read out.
It works to prevent the information in your computer from being damaged. Here, the dummy areas 15 and 16 are longer than the maximum shift width of the write start position of the recording signal, and the rear dummy area 16 in which the change in the recording film thickness due to the flow is large is the front dummy area 15
Have been longer than. In some cases, the dummy region for suppressing the flow may be either the front side or the rear side. It is more effective to use only the rear side.

Recording may be performed by using a signal in which a dummy signal is added to at least one of the front side and the rear side of a target recording information signal such as VFO, SYNC and data, but in the present embodiment, a dummy signal is used as an example. 500 Tw (1
Tw: 90 ns) was added to both sides of the recorded information signal. Further, in this embodiment, the recording start position was randomly shifted within the range of 15 Tw. In this case, a dummy signal is mainly recorded in the dummy area. Further, the average energy of the dummy signal is made smaller than the average energy of the target recording information signal in order to alleviate the flow of the recording film due to a large number of rewritings. That is, the mark formation probability does not suddenly become 0 from 50% at the start and end of the recording laser irradiation area, but becomes 0 gradually. Actually, a single frequency (recording pulse period: 10T
The signal of w) was used as a dummy signal, for example, the mark of 3 Tw and the space of 7 Tw were repeated to reduce the duty ratio of this signal. A signal having the same duty ratio and having one cycle that is an integral multiple of 1 byte may be used.

In the case of recording by the mark edge recording method, when the average energy when recording is performed at a single frequency is substituted, the duty ratio becomes almost the same as 50%, so the duty ratio of the dummy signal is 50%. %, The duty ratio of the disk used in this example was reduced to about 30% because the recording film flows from the center toward the recording start end portion and the recording end portion by a large number of rewritings. At this time, the duty ratio is 10% or more and 40%
If it is below, the effect of adding a dummy is large, but the effect is particularly large in the case of 20% or more and 30% or less. As a result, the flow of the recording film can be significantly eased, and the recording power margin is expanded. The average energy of the laser beam during dummy signal recording may be reduced stepwise or continuously.

In the control track portion of the disk used in this embodiment, information on the pattern of the dummy signal (for example, the pattern in which the average recording mark length recorded by the dummy signal is shorter than the average space length between the recording marks) , Information such as a pattern having a single frequency) is recorded in advance as concave and convex pits, and recording is performed according to this information. When the rewriting was performed many times by changing the shift width of the recording start position variously, the writing start position of the recording information signal was set to 1 /
By randomly shifting in the range of about 20 to 1/2, the reproduced signal waveform distortion due to the flow could be reduced.
In addition, Ge containing no high melting point material such as CrTe
In the -Sb-Te-based phase change recording film and the Ag-In-Sb-Te-based phase change recording film, the flow suppression effect was obtained by using such a recording waveform to which the dummy signal was added, but CrTe and A recording film to which a high melting point material such as Ag ₂ Te is added is preferable because it has a large recording power margin for relaxing the flow.

FIG. 3 shows an example of a block diagram of a recording / reproducing system in the recording / reproducing apparatus of this embodiment. First, at the time of recording, an original signal (information) to be recorded is input to the modulator 18 and converted into a modulation code to be used. The control data recorded on the recording medium is read, and the dummy data generated based on the control data is added to the code string of the data to be recorded. Then, a recording waveform corresponding to the target recording code is generated by the recording waveform generator 19 and output as recording pulse signals of various powers. Then, a recording start position controller 20 for randomly shifting the recording start position
After that, the laser driver 21 modulates the drive current of the semiconductor laser 22 and condenses and irradiates the laser light on the rotating disk 24 through the optical system of the optical head 23 to form a recording mark. To do. During reproduction, a change in the intensity of the laser light reflected from the target address on the disk 24 is reflected by the light receiver 2.
5 is taken in and converted into an electric signal. Then, this electric signal is input to the waveform equalizer 27 through the reproduction signal amplifier 26. The signal output from the waveform equalizer 27 is converted into a binary waveform. Finally, after passing through the circuit 28 from which the dummy signal portion has been deleted, the binary signal becomes a data bit string (information) by the discriminator 29 and the decoder 30.

In the present embodiment, an example of the continuous servo system is shown, but the sample servo system also provided similar effects.

Embodiment 2 FIG. 4 shows an example of the sector format of the substrate used in this embodiment. There is a pre-formatted area 10 'in which information such as a sector address and a track address is previously formed as uneven pits. In addition to the read-only preformat area 10 ', a recording area 14' in which recording (including rewriting) such as the gap area 11 ', the VFO or SYNC area 12', and the data area 13 'is ensured. The recording area 14 'is provided in the groove portion. In this embodiment, dummy areas 15 'and 16' are provided before and after the recording area. Further, after the dummy area 16 'on the rear side of the recording area, a buffer area 17' for coping with rotation jitter is also provided. In the dummy areas 15 ′ and 16 ′, even if the recording film flows due to a large number of times of rewriting, in the area on the front side of the recording area, the reproduced signal waveform distortion due to the flow stays up to the front dummy area 15 ′. In the area on the rear side of the recording area, the reproduced signal waveform distortion due to the flow stays up to the rear dummy area 16 ', and the information in the data area 13' that must be actually read is prevented from being damaged.

Here, the dummy areas 15 'and 16' are made longer than the maximum shift width of the write start position of the recording signal, and the rear dummy area 1 in which the change in the recording film thickness due to the flow is large.
6'is longer than the dummy region 15 'on the front side. In some cases, the dummy region for suppressing the flow may be either the front side or the rear side. It is more effective to use only the rear side. Furthermore, in the present embodiment, a bit string (data part postamble) is added according to a predetermined rule before the dummy data to be recorded in the rear dummy area 16 'so that the ratio of the mark to the space is not reversed.

Recording can be performed by using a signal in which a dummy signal is added to at least one of the front side and the rear side of the target recording information signal such as VFO, SYNC and data, but in the present embodiment, the effect of the dummy can be easily understood. In order to do so, dummy signals were added to both sides of the recording information signal for a time of 500 Tw (1 Tw: 90 ns).

Further, in this embodiment, the recording start position is set to 15
Random shift was performed within the range of Tw. In this case, a dummy signal is mainly recorded in the dummy area. Further, the average energy of the dummy signal is made smaller than the average energy of the target recording information signal in order to alleviate the flow of the recording film due to a large number of rewritings. That is, the mark formation probability does not suddenly become 0 from 50% at the start and end of the recording laser irradiation area, but becomes 0 gradually. Actually, a signal having a single frequency (recording pulse period: 10 Tw) is used as a dummy signal, and, for example,
Repeating 3Tw mark and 7Tw space,
The duty ratio of this signal was reduced. A signal having the same duty ratio and having one cycle that is an integral multiple of 1 byte may be used. When recording with the mark edge recording method,
When replaced with the average energy when recording is performed at a single frequency, the duty ratio is almost the same as 50%, so the duty ratio of the dummy signal is preferably 50% or less, but the disk used in this embodiment is The duty ratio was reduced to about 30% because the recording film flows from the center toward the recording start end portion and the recording end portion by a large number of rewritings. At this time, if the duty ratio is 10% or more and 40% or less, the effect of adding the dummy is great, but 20% or more and 30% or more.
The effect was particularly large in the case of not more than%. As a result, the flow of the recording film can be significantly eased, and the recording power margin is expanded. The average energy of the laser beam during dummy signal recording may be reduced stepwise or continuously.

In the dummy signal recording pattern, the ratio of the length of the recording mark to the length of the space between the recording marks is important. However, when the dummy signal pattern is recorded by the mark edge recording method, when the pattern is described by an array of 1s and 0s, if it is wrong to start with a recording mark or a space, the recording mark and the space are separated. The length ratios of all are reversed. For example, the end of the user data before the dummy signal may end with a mark or end with a space.Therefore, if the signal pattern to be written in the dummy area is continued as it is, the ratio of the recording mark to the space will be the reverse of the desired ratio. It can happen. Therefore, a bit string is added to the beginning of the dummy signal or the end of the data according to a predetermined rule so that the ratio of the mark to the space is not reversed.

An example of the bit string (data part postamble 31) added to FIG. 5 is illustrated (in this embodiment, the data part postamble 31 and the dummy data 32 are called dummy signals). That is, it is checked whether the end of the user data ends with a mark or a space, and by adding data corresponding thereto, the record mark and the space of the dummy signal are prevented from being reversed. It is more preferable that the user data added above does not violate the rules of the data signal modulation method.
The method shown in FIG. 5 is such.

In the control track portion of the disk used in this embodiment, information on the pattern of the dummy signal (for example, a pattern in which the average recording mark length recorded by the dummy signal is shorter than the average space length between the recording marks) , Information such as a pattern having a single frequency) is recorded in advance as concave and convex pits, and recording is performed according to this information.

FIG. 6 shows an example of the format. For recording dummy data patterns on control tracks
It is Divide the dummy data area into two, for example, FIGS. 6 (a)
As shown in, the length of the mark formed in the former part of the two is 4 bits and the space is 4 Tw.
Bit, how many times this mark and space pair is repeated is shown by the following 8 bits, and then the length of the mark formed in the latter part of the two divided parts, the length of the space, and the number of repetitions are 8 bits. , 16 bits in total. Therefore, 4 bytes represent all the patterns in the dummy area. The entire dummy area may be a single repeating pattern, or may be divided into three or more. If there are three or more, the required space on the control track is larger than 4 bytes.

As another example, as shown in FIG. 6B, the arrangement of the marks and spaces in the former part of the dummy area divided into two is the same as the relationship between the data in the data part and the recording marks and spaces. Then, the array of 1s and 0s is represented by 2 bytes, and the array of marks and spaces after the division into 2 may be similarly represented by the array of 1s and 0s in the subsequent 2 bytes. Also in this case, the space required for the control track when the area is divided into two is 4 bytes. When the number of divisions is three or more, the required space on the control track is larger than 4 bytes, as in the above example. Also,
When the rewriting is performed a number of times by changing the shift width of the recording start position variously, the writing start position of the recording information signal is randomly shifted within the range of about 1/20 to 1/2 of the dummy signal. The reproduced signal waveform distortion due to the flow could be reduced. In addition, a Ge-Sb-Te-based phase change recording film or A containing no high melting point material such as CrTe.
Even in the g-In-Sb-Te phase change recording film, the flow suppression effect was obtained by using the recording waveform to which the dummy signal was added, but a high melting point material such as CrTe or Ag ₂ Te was added. The above recording film is preferable because it has a large recording power margin for alleviating the flow.

The disk and the recording / reproducing apparatus used in this embodiment are substantially the same as those in the first embodiment.

[0036]

According to the present invention, a recording medium having a dummy area in at least one of the recording areas is used, and a dummy signal of the optimum pattern described in the control track is added to at least one of before and after the recording information signal. By recording information with the signal, even if the dummy area is narrow, the recording area is not affected by the flow of the recording film due to a large number of rewritings, so that the target recorded information can be reliably reproduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a disk structure according to an embodiment.

FIG. 2 is a plan view showing an example of a sector format in the embodiment.

FIG. 3 is a configuration block diagram of an information recording apparatus used in the embodiment.

FIG. 4 is a plan view showing an example of a sector format in the embodiment.

FIG. 5 is a plan view showing an arrangement example of a data part postamble and dummy data in the embodiment.

FIG. 6 is a plan view showing a pattern recording example of a dummy signal in the example.

[Explanation of symbols]

1 polycarbonate substrate 2 ZnS-SiO ₂ dielectric layer 3 recording film _{(Cr 5 Ge 20 Sb 20 Te} 55) 4 ZnS-SiO 2 dielectric layer 5 Si reflective layer 6 AlTi alloy reflective layer 7 UV-curable resin protective layer 8 hotmelt Adhesive layer 9 Protective plate 10, 10 'Preformatted area 11, 11' Gap area 12, 12 'VFO and SYNC area 13, 13' Data area 14, 14 'Recording area 15, 15' Front dummy area 16, 16 ' Rear dummy area 17, 17 'Buffer area 18 for dealing with rotation jitter Modulator 19 Recording waveform generator 20 Recording start position controller 21 Laser driver 22 Semiconductor laser 23 Optical head 24 Disk 25 Light receiver 26 Playback signal Amplifier 27 Waveform equalizer 28 Dummy signal remover 29 Discriminator 30 Decoder 31 Data part postamble 32 Me data.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Motoyasu Terao               1-280, Higashikoigokubo, Kokubunji, Tokyo                 Central Research Laboratory, Hitachi, Ltd. (72) Inventor, J. Miyamoto               1-280, Higashikoigokubo, Kokubunji, Tokyo                 Central Research Laboratory, Hitachi, Ltd. (72) Inventor Hiroyuki Minemura               1-280, Higashikoigokubo, Kokubunji, Tokyo                 Central Research Laboratory, Hitachi, Ltd. (72) Inventor Akemi Hirotsune               1-280, Higashikoigokubo, Kokubunji, Tokyo                 Central Research Laboratory, Hitachi, Ltd.                (56) Reference JP-A-8-7276 (JP, A)                 JP 7-211001 (JP, A)                 JP-A-7-262566 (JP, A)                 JP-A-8-180410 (JP, A)                 JP 9-35276 (JP, A)                 JP-A-4-153919 (JP, A)

Claims (2)

(57) [Claims] 1. An information recording method for recording information on a recording medium having a phase change recording film by irradiation with an energy beam, wherein a dummy signal is added before and after the recording information signal, and the recording information is recorded. The dummy signal on the rear side of the signal is longer than the dummy signal on the front side of the recording information signal, the recording start position of the recording information signal is randomly shifted, and the maximum shift width of the shift is the front side of the recording information signal. And a length shorter than the length of the rear dummy signal, wherein a postamble is added between the recording information signal and the rear dummy signal to record information. 2. The information recording method according to claim 1, wherein the postamble has a pattern depending on whether the end of the recording information signal is a mark or a space.