JP2001293959A - Optical recording medium - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To stably record and reproduce information while suppressing a jitter component of a wobble signal to a practically low value while realizing a high recording density. An optical recording medium is provided. SOLUTION: The track pitch of a recording track is set to 1.3.
A material containing a dye represented by the following formula, which is set to not more than μm and has a property suitable for suppressing the jitter component of the wobble signal to a low value, is used as a recording material constituting the recording layer. However, in the formula, R ₁ and R ₂ are nC ₄ H ₉ , nC ₃ H
₇ is an alkyl group selected from _{n-C 5 H 11,} X
^- is an anion (However, ClO ₄ ^- except a.) A.
The anion X ⁻ is a first type selected from PF ₆ ⁻ , BF ₄ ⁻ , and I ⁻

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wobbling groove which is formed along a recording track, and reproduces a wobble signal from the wobbling groove while applying a signal as a change in reflectance of an organic dye-based recording material to the recording track. Relates to an optical recording medium on which is recorded.

[0002]

2. Description of the Related Art As a recording medium for storing information, an optical disk on which information is recorded and reproduced optically has been put to practical use. For such an optical disk, information is recorded and reproduced with the head in a non-contact state, so that there is no problem such as abrasion deterioration of the recording medium. For this reason, optical disks have become widely used as highly reliable recording media.

[0003] Among such optical disks, a so-called heat mode optical disk has been developed as an optical disk on which a user can write information by himself, in which information is written using heat of light applied to the optical disk. I have. As an example, information is recorded by irradiating recording light such as laser light onto an optical disc and forming minute pits on a recording material by heat generated thereby.
A so-called pit formation type optical disk has been put to practical use.

In this pit formation type optical disk,
As a recording material, a chalcogen material mainly containing tellurium (Te) or an organic dye-based material is generally used. These recording materials are characterized by high sensitivity, low noise, and little deterioration over time. In recent years, among these, in particular, organic dye-based materials have been widely used.

As an optical disk using an organic dye material as a recording material, an optical disk (hereinafter referred to as C) used in a so-called compact disk recordable system is used.
It is called DR. ) Has been put to practical use.

This CD-R has a wobbling groove formed along a recording track. here,
The wobbling groove is a guide groove formed so as to meander at a predetermined cycle. The guide groove itself has a signal component by meandering the guide groove. Note that the guide groove is a groove formed along a recording track in order to facilitate tracking servo by, for example, a push-pull method.

In the CD-R, sector information including FM-modulated absolute time information is recorded as a signal (wobble signal) based on the wobbling groove (ATIP: Absolute Time In Pregroove). That is, in a compact disk recordable system using a CD-R as a recording medium, a wobble signal having a carrier of, for example, 22.05 kHz is detected by a recording / reproducing light spot focused on a wobbling groove, and the absolute time is measured. A data string containing information is detected by FM demodulating the signal.

[0008] As described above, in the method of recording sector information including absolute time information as a wobble signal, signals can be recorded continuously. This is advantageous in achieving compatibility between the two. That is, in the method in which the address information is arranged at the head of each sector, the absolute time information and the recording signal are recorded in a time-division manner, and the recorded signal becomes discontinuous. Although it is difficult to achieve compatibility with the read-only optical disc, a method of recording sector information including absolute time information as a wobble signal can easily achieve compatibility with a read-only optical disc.

[0009]

Incidentally, in the above-mentioned optical disc, the recording density is high so that more information can be recorded while keeping the same outer diameter as that of a standardized existing optical disc. Is being actively promoted. For example, in the above-described CD-R, attempts have been made to achieve a recording capacity of 1.0 GB (gigabyte) or more by increasing the recording density.

In consideration of increasing the recording density, it is effective to reduce the track pitch, which is the interval between adjacent recording tracks. However, when the track pitch is reduced, the amount of information leakage from an adjacent recording track increases, and the jitter component of the signal tends to increase.

In an optical disk in which a wobbling groove is formed along a recording track and absolute time information or the like is recorded as a wobble signal, when the track pitch of the recording track is narrowed, the wobbling signal from an adjacent wobbling groove is generated. The leakage amount increases,
The jitter component of the wobble signal also tends to increase. When the jitter component of the wobble signal increases significantly, it becomes difficult to stably recognize time information and the like included in the wobble signal, and as a result, stable recording and reproduction of information may not be performed.

In an optical disk using an organic dye material as a recording material, the jitter characteristic of a wobble signal is as follows.
It greatly depends on the state of the organic dye-based recording material filled in the wobbling groove. In other words,
The jitter characteristic of the wobble signal largely depends on the viscosity and wettability of the coating liquid applied on the substrate when forming the recording layer.

The viscosity, wettability and the like of such a coating solution are determined by the inherent properties of the dye used.
Therefore, if the recording material is formed using a dye having properties suitable for suppressing the jitter component of the wobble signal to a low value, the wobble signal of the wobble signal can be reduced even in an optical disc in which the track pitch is narrowed and the recording density is increased. The jitter component can be suppressed to a practically sufficiently low value.

The present invention has been made in view of the above-mentioned circumstances, and realizes a high recording density while suppressing the jitter component of a wobble signal to a practically sufficiently low value, It is an object of the present invention to provide an optical recording medium capable of performing stable recording and reproduction.

[0015]

An optical recording medium according to the present invention is an optical recording medium in which a signal is recorded on a recording track as a change in reflectance of an organic dye-based recording material. In this optical recording medium, wobbling grooves are formed along the recording tracks, the track pitch of the recording tracks is 1.3 μm or less, and the optical recording medium contains a compound represented by the following chemical formula 2 as the recording material. It is a feature.

[0016]

Embedded image

Where R ₁ and R ₂ are nC ₄ H ₉ , n
Alkyl group selected from _{-C 3 H 7, n-C} 5 H 11, X - is an anion (provided, ClO ₄ ^- excluding.) Is.

In the optical recording medium according to the present invention, since a material containing the compound shown in Chemical Formula 2 is used as a recording material, recording and reproduction can be performed even if the track pitch is reduced to 1.3 μm or less. It is possible to suppress the jitter component of the wobble signal required for the above to a practically sufficiently low value.
Therefore, with this optical recording medium, information recording and reproduction can be performed stably while realizing high recording density.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. Here, an example in which the present invention is applied to a CD-R standardized as a write-once type optical recording medium will be described. However, the present invention is not limited to this example, and may be applied along a recording track. It is widely applicable to optical recording media in which a wobbling groove is formed and a signal is recorded on a recording track as a change in the reflectance of an organic dye-based recording material while reproducing a wobble signal from the wobbling groove.

A CD-R to which the present invention is applied is made of polymethyl methacrylate (PM
MA), polycarbonate (PC), etc.
a disk substrate 1 formed into a disk having a thickness of about 1.2 mm and a thickness of about 1.2 mm, on which a recording layer 2 formed by spin-coating an organic dye-based recording material, which will be described in detail later, is formed. Have been. On this recording layer 2,
For example, gold (Au), silver (Ag), or the like is formed and the reflection film 3 is formed.
The protective layer 4 is formed on the reflective film 3 by spin-coating, for example, an ultraviolet curable resin.

In this CD-R, an area having a diameter of 50 to 116 mm of the disk substrate 1 is set as an information recording area, and at least in the information recording area, meandering as shown in a plan view of a main part in FIG. The wobbling groove 5 serving as a guide groove is formed, for example, in a spiral shape.
A portion corresponding to the wobbling groove 5 of the recording layer 2 is set as a recording track, and a signal (EFM signal) subjected to EFM modulation is recorded on this recording track.

In the CD-R to which the present invention is applied, the track pitch Tp, which is the interval between adjacent recording tracks, is used.
Is set to 1.3 μm or less. That is, the track pitch is 1.6 μm in the standardized existing CD-R.
m, and the recording capacity is about 650 MB (megabytes). On the other hand, in the CD-R to which the present invention is applied, the track pitch Tp is reduced to 1.3 μm or less and the reduction rate of the track pitch Tp is the same. By increasing the linear density (reducing the linear velocity) by a percentage, a recording capacity of 1.0 GB or more is realized.

The wobbling groove 5 is formed so as to meander (wobble) at a predetermined cycle, and the wobbling causes sector information including absolute time information which has been FM-modulated to become ATIP (Absolute Time).
In Pregroove) recorded as a wobble signal.

In the CD-R configured as described above, while the ATIP wobble signal from the wobbling groove 5 is reproduced to obtain the absolute time information, the EFM signal is used as the organic dye-based recording material constituting the recording layer 2. Is recorded on a recording track as a change in the reflectance of the recording medium.

By the way, in the CD-R to which the present invention is applied, the recording material constituting the recording layer 2 is as follows:
A material containing a dye shown in (1) is used.

[0026]

Embedded image

Wherein R ₁ and R ₂ are nC ₄ H ₉ , n
Alkyl group selected from _{-C 3 H 7, n-C} 5 H 11, X - is an anion (provided, ClO ₄ ^- excluding.) Is.

[0028] Here, the counter ion anion X ₁ ^- as is capable of selecting an arbitrary anion, ClO ₄ ^- For reasons such as the following, it is assumed that except this.

All elements undergo a combustion reaction when placed in a peroxide state. However, some elements are molecularized (ionized) without exceeding the energy gap required for combustion. As a typical example of a material that has been molecularized (ionized) without exceeding the energy gap necessary for this combustion, ClO ₄ ⁻ can be cited.

It can be said that the atmosphere in which these molecules (ions) exist is in an environment where combustion is likely to occur. Naturally, reactions involving heat are expected to be more intense than other molecules (atoms, ions).

The reason why the thermal reaction in the dye containing ClO ₄ ^- is particularly violent is mainly due to the above reasons.

When ClO ₄ ^- is selected as the counter ion in the dye shown in Chemical formula ₃ , the thermal reaction becomes too violent, and as a result, the jitter component increases. Therefore,
In the present invention, the above-mentioned ClO ₄ ^- is excluded as a counter ion of the dye shown in Chemical formula ₃ .

Accordingly, specific examples of the counter ion of the dye shown in Chemical Formula 3 include a halogen-based anion and a phosphorus-based anion. In particular, PF ₆ ⁻ , B
F ₄ ⁻ , I ^{− and the} like are preferred.

In forming the recording layer 2 of a CD-R to which the present invention is applied, first, the dye represented by the above formula (3) is dissolved in, for example, tetrafluoropropanol to form a coating solution (dye concentration: 2.0% by weight). %). Then, the coating liquid is applied to the disk substrate 1 in which the wobbling grooves 5 are formed in advance in the information recording area by using a spinner.
As a result, the recording layer 2 made of an organic dye-based recording material containing the dye shown in Chemical Formula 3 is formed on the disk substrate 1 on which the wobbling grooves 5 are formed.

In the CD-R to which the present invention is applied, the track pitch Tp is set to 1.3 μm or less by using a material containing the dye shown in Chemical formula 3 as a recording material constituting the recording layer 2. The jitter component of the ATIP wobble signal from the wobbling groove 5 is suppressed to a sufficiently low value for practical use even if the absolute time information is stably obtained, and the recording and reproduction of the EFM signal can be performed stably. It has been done.

That is, in a CD-R for recording and reproducing an EFM signal while reproducing the ATIP wobble signal from the wobbling groove 5 and obtaining absolute time information,
When the track pitch Tp is reduced, the amount of signal leakage from the adjacent wobbling groove 5 increases,
The jitter component of the ATIP wobble signal also tends to increase. When the jitter component of the ATIP wobble signal increases, for example, by more than 10% with respect to the clock of the ATIP wobble signal, it becomes difficult to stably recognize the absolute time information.
Recording and reproduction of signals cannot be performed stably.

In a CD-R using an organic dye material as a recording material, the jitter characteristic of the ATIP wobble signal largely depends on the state of the organic dye material to be filled in the wobbling groove 5. are doing. In other words, the jitter characteristic of the ATIP wobble signal largely depends on the viscosity and wettability of the coating liquid applied onto the disk substrate 1 when forming the recording layer 2.

The viscosity, wettability and the like of such a coating solution are determined by the inherent properties of the dye used.
Therefore, if the recording material is formed using a dye having properties suitable for suppressing the jitter component of the ATIP wobble signal to a low value, even if the track pitch Tp is narrowed to 1.3 μm or less, the ATIP wobble signal is reduced. The jitter component of the EFM signal can be suppressed to, for example, 10% or less with respect to the clock of the ATIP wobble signal, and the recording and reproduction of the EFM signal can be performed stably while the absolute time information is obtained stably.

The dye represented by Chemical Formula 3 is a dye having properties suitable for suppressing the jitter component of the ATIP wobble signal to a low value. Therefore, in the CD-R in which the material containing the dye shown in Chemical formula 3 is used as the recording material constituting the recording layer 2, even if the track pitch Tp is narrowed to 1.3 μm or less, the ATIP wobble is reduced. The jitter component of the signal is suppressed to 10% or less of the clock of the ATIP wobble signal, and the recording and reproduction of the EFM signal can be performed stably while the absolute time information is obtained stably.

Therefore, in the CD-R to which the present invention is applied, it is possible to realize a recording capacity of 1.0 GB or more by increasing the recording density.

[0041]

EXAMPLES Specific examples to which the present invention is applied will be described below based on experimental results.

In order to confirm the effects of the present invention, a CD-R (Example 1) using a material containing a dye represented by the following formula 4 as a recording material was actually produced, and an ATIP wobble signal was recorded. Jitter characteristics were evaluated.

[0043]

Embedded image

As a comparative control, a CD-ROM using a material containing a dye represented by the following formula 5 as a recording material:
CD-R (Comparative Example 2) using R (Comparative Example 1) and a material containing a dye shown in Chemical Formula 6 below as a recording material;
CD-R (Comparative Example 3) using a material containing a dye represented by the following formula 7 as a recording material was prepared,
The jitter characteristics of these ATIP wobble signals were also evaluated.

[0045]

Embedded image

[0046]

Embedded image

[0047]

Embedded image

Production of CD-R First, polycarbonate was injection-molded to have a diameter of about 120 mm.
A disk substrate 1 having a thickness of about 1.2 mm and a thickness of about 1.2 mm was produced.
When the disk substrate 1 is injection-molded, the stamper having an uneven pattern corresponding to the wobbling groove 5 is used to form the wobbling groove 5 on the disk substrate 1.
Was formed in a spiral shape. The wobbling groove 5 has an ATIP wobble signal.

Next, the dyes represented by Chemical Formulas 4 to 7 are
Four types of coating liquids were prepared by dissolving each in tetrafluoropropanol so as to have a concentration of 2.0% by weight. Then, these four kinds of coating liquids were respectively applied on separate disk substrates 1 using a spinner to form a recording layer 2.

Next, on each disk substrate 1 on which the recording layer 2 is formed, a silver thin film is formed by sputtering to form a reflective film 3 having a thickness of about 100 nm. Curing resin is applied and cured to a thickness of about 10μm
Example 1, Comparative Examples 1 to 3
4 types of CD-Rs were completed.

Each of these CD-Rs has a track pitch of 1.10 μm and a track pitch of 0.90 μm.
Recording / reproducing is performed at a linear velocity of m / s (linear density is 0.4 μm / bit), so that a recording capacity of 1.3 GB is provided.

Evaluation of Recording / Reproduction Characteristics Each of the CD-Rs manufactured as described above was irradiated with a laser beam for reproduction while rotating so that the linear velocity became 0.90 m / s, and ATIP wobbling was performed. The signal was reproduced. The laser beam for reproduction used had a wavelength of 780 nm, and the numerical aperture NA of the optical system was set to 0.55. The power of the reproducing laser beam was set to 0.7 mW.

Then, the jitter characteristic of the reproduced ATIP wobble signal was evaluated. Regarding the jitter of the absolute time information included in the ATIP wobble signal, generally, A
It is required to be 10% or less with respect to the clock of the TIP wobble signal. Therefore, the evaluation of the jitter characteristics of the ATIP wobble signal was determined based on whether or not the ratio of the jitter component to the clock (frequency: 6.3 kHz) of the ATIP wobble signal was suppressed to 10% or less.
Table 1 shows the results.

[0054]

[Table 1]

From the results shown in Table 1, Comparative Examples 1 to 3 are shown.
In the CD-R, the ratio of the jitter component to the clock of the ATIP wobble signal greatly exceeds 10%,
It has been found that stable reproduction of the ATIP wobble signal cannot be expected.

This is because the dyes represented by Chemical Formulas 5 to 7 used as recording materials for CD-Rs of Comparative Examples 1 to 3 are not suitable for CD-Rs having a narrow track pitch. Probably because there is.

[0057] Particularly, in Comparative Example 1, despite of the same types of Example 1 and the dye, the counter ion ClO ₄ ^- in order to be, the proportion of jitter components is increased.

Incidentally, even when the dyes represented by the above formulas (5) to (7) are used as a recording material, the track pitch is 1.6.
In an existing CD-R set to μm, the ratio of the jitter component to the clock of the ATIP wobble signal is 10%.
It can be suppressed to the following.

On the other hand, in the CD-R of the first embodiment,
The ratio of the jitter component to the clock of the ATIP wobble signal was suppressed to 10% or less, and it was found that good jitter characteristics were obtained. This is equivalent to C in Example 1.
This is because the dye represented by Chemical Formula 4 used as a recording material for DR has properties suitable for suppressing the jitter component of the ATIP wobble signal to a low value.

As described above, in the CD-R of the first embodiment, A
By using a dye having a property suitable for suppressing the jitter component of the TIP wobble signal to a low value as a recording material, the track pitch can be reduced to 1.10 μm, and the recording density can be increased. In addition, it is possible to stably record and reproduce the EFM signal while stably obtaining the absolute time information by making the jitter characteristic of the ATIP wobble signal good.

[0061] Study of the counterion Next, the counter ion in the dye represented by the chemical formula 4 (anion X ₁ ^-) was prepared in the same manner as a CD-R in place of the anion shown in Table 2, the track pitch 1.6μm and The jitter characteristics at 1.1 μm were measured.

Table 2 also shows the results.

[0063]

[Table 2]

In the dye represented by Chemical formula 4, Cl
O ₄ ^- If the counter ions other than, regardless of the type of counter ions, the track pitch 1.6μm and 1.
At any 1 μm, the ratio of the jitter component to the clock of the ATIP wobble signal is suppressed to 10% or less.

[0065]

As described above in detail, according to the optical recording medium of the present invention, even if the track pitch is narrowed to 1.3 μm or less, the jitter component of the wobble signal required for recording and reproducing is reduced. It can be suppressed to a sufficiently low value for practical use. Therefore, with this optical recording medium, information recording and reproduction can be performed stably while realizing high recording density.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a CD-R to which the present invention is applied.

FIG. 2 is a plan view schematically showing a state of an information recording area of the CD-R.

[Explanation of symbols]

1 disk substrate, 2 recording layer, 3 reflective film, 4 protective layer, 5 wobbling groove

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G11B 7/24 561 B41M 5/26 Y (72) Inventor Manabu Sato 6-7 Kita Shinagawa, Shinagawa-ku, Tokyo No. 35 Sony Corporation F term (reference) 2H111 EA03 EA22 FA12 FA14 FB43 GA07 4H056 CA01 CA04 CC02 CC08 CE03 DD03 5D029 JA04 WA02 WB11 5D090 AA01 BB03 CC01 DD01 EE02 FF04 FF11 GG09 JJ11

Claims (5)

[Claims] 1. A wobbling groove is formed along a recording track in an optical recording medium in which a signal is recorded as a change in reflectance of an organic dye-based recording material on the recording track, and the track pitch of the recording track is 1.3 μm or less. And an optical recording medium comprising a compound represented by the following chemical formula 1 as the recording material. Embedded image Here, in the formula, R ₁ and R ₂ are n-C ₄ H ₉ , n-C ₃ H ₇ , n
Alkyl group selected from -C ₅ H _11, X ^- is an anion (provided, ClO ₄ ^- excluding.) Is. 2. The anion X ⁻ is PF ₆ ⁻ , BF ₄ ⁻ ,
I ^- claim, characterized in that one selected from 1
The optical recording medium according to the above. 3. The signal recorded on the recording track is E
The wobble signal is a signal to which FM modulation has been applied.
2. The optical recording medium according to claim 1, wherein the signal is an M-modulated signal containing absolute time information or a signal containing address information. 4. The optical recording medium according to claim 3, wherein a jitter component of time information obtained from said wobble signal is 10% or less. 5. While maintaining CD format, 1.0
2. An information capacity of at least GB.
The optical recording medium according to the above.