JP2001026180A - Optical recording medium and recording / reproducing method using the same - Google Patents

Abstract

(57) [Problem] To provide an optical information recording medium having sufficiently high write sensitivity, sufficient modulation degree, sufficiently low jitter, and more stable reproduction. SOLUTION: The light-transmitting resin molded substrate 1 and the substrate 1
Recording film 2 containing a dye formed thereon, and recording film 2
In the write-once optical disc comprising the light reflection layer 3 formed on the recording medium, the recording film 2 has a maximum absorption wavelength between 400 nm and 800 nm between 400 nm and 620 nm, and three or more dyes having different maximum absorption wavelengths. Consists of a mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a writable optical recording medium, and more particularly to an optical recording medium having a recording film made of an organic dye on a transparent substrate, a light reflection layer formed on the recording film, and an optical recording medium. It relates to the recording / reproducing method used.

[0002]

2. Description of the Related Art A write-once optical disc which can be directly reproduced by a general DVD player has been actively developed to meet market needs, and various proposals have been made. This is due to the increased number of users and general-purpose devices that are trying to utilize enormous data such as high-density image information and high-quality audio frequently used in HDTV and multimedia, as a result of processing or stocking enormous data, This is because a large-capacity recording medium has become indispensable.

[0003] Conventional write-once optical disks include CD-ROMs.
A disc with a diameter of 120 mm such as R and a recording capacity of 64
Optical disks of 0 MB are known (for example, Electronic Ceramics, November 1987, 49-52).
Page).

Conventionally, it has been known to use, for example, a cyanine-based or phthalocyanine-based organic dye in a recording film of a so-called writable optical recording medium such as a CD-R.
And, as a writing method of such an optical recording medium,
The laser beam is focused on a very small area of the recording film, converted into heat energy, and the properties of the recording film are changed (pit formation).

A writing laser beam used for such a type of optical recording medium is irradiated from the transparent substrate side to form optically readable pits in the recording film. The read laser beam for reproducing recorded data has a weaker output than that for writing, and the contrast between the pit-formed portion and the non-pitted portion is read as an electric signal.

[0006]

However, a write-once DVD medium is a disc having the same diameter of 120 mm while having a recording capacity about six times that of a CD-R. This is because the write-once type DVD medium has a track pitch of 0.7 μm to 0.8 μm, which is less than half the track pitch of 1.6 μm of a CD-R.

Further, as the laser wavelength is shortened, heat generated at the time of reproduction increases, and there is a problem that signal deterioration or data destruction is likely to occur.

As described above, since the information density on the substrate is dramatically increased, if the recording principle or method of the conventional write-once optical disc is applied as it is, satisfactory recording characteristics (particularly, jitter characteristics) are obtained. ) Was difficult to improve.

An object of the present invention is to improve such a problem, reduce the heat generated at the time of reproduction, and increase the heat generated at the time of recording, thereby realizing stable high-density recording. Another object of the present invention is to provide an optical recording medium capable of performing stable recording irrespective of variations in laser wavelength during recording, and a recording / reproducing method using the same.

[0010]

In order to achieve the above object, a first aspect of the present invention is to provide a recording film containing an organic dye on a transparent substrate, wherein the recording film has a wavelength of 400 nm to 800 nm. When the spectral absorption spectrum was measured under the condition where the film was formed on a flat transparent substrate, it was measured at a wavelength of 500 nm to 62 nm.
A first organic dye (D1) having a maximum absorption wavelength (λ _max 1) in a range of 0 nm, and the first organic dye (D1)
Maximum absorption wavelength (lambda _max 1) Maximum absorption wavelength greater than the (lambda _max 2) and second organic dye (D2) having a maximum absorption wavelength (lambda _max 1) of the first organic dye (D1) A mixture with a third organic dye (D3) having a smaller maximum absorption wavelength (λ _max 3) than the first organic dye (D1), the second organic dye (D2) and the third organic dye (D2). The mixing weight ratio of the organic dye (D3) is (D1) ≧ (D2), (D
1)> (D3).

According to a second aspect of the present invention, there is provided a recording film containing an organic dye on a transparent substrate, the recording film having a flat spectral absorption spectrum in a wavelength range of 400 nm to 800 nm. A first organic dye (D) having a maximum absorption wavelength (λ _max 1) in the range of 500 nm to 620 nm when measured under the condition in which a film is formed on a transparent substrate.
1) a second organic dye (D2) having a maximum absorption wavelength (λ _max 2) greater than the maximum absorption wavelength (λ _max 1) of the first organic dye (D1); Third organic dye (D3) having a maximum absorption wavelength (λ _max 3) smaller than the maximum absorption wavelength (λ _max 1) of the dye (D1)
And a mixture of the first organic dye (D1) and the second organic dye (D1).
Using an optical recording medium in which the mixing weight ratio of the organic dye (D2) and the third organic dye (D3) is (D1) ≧ (D2), (D1)> (D3), It is characterized in that information is recorded and the information is reproduced with long-wavelength light.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a sectional structure of a write-once optical disc according to the present invention. In the write-once optical disc A of the present invention, a recording film 2 is formed on a disc-shaped transparent substrate 1, and a light reflection layer 3 and a protective layer 4 are sequentially laminated thereon.

As shown in FIG. 1, a tracking pre-groove G is formed concentrically or spirally on one surface of the transparent substrate 1. This pre-groove G
In consideration of cost performance and mass productivity, it is preferable to use an integrally formed injection-molded resin substrate for the transparent substrate 1 having the above. For example, polycarbonate resin (PC), polymethyl methacrylate resin (PMM
It is formed from a transparent resin material such as A). In addition, not limited to injection-molded resin substrates, 2P (photo-polymer)
A substrate formed by the r) method may be used. The thickness of such a substrate 1 is about 0.6 mm.

A recording film 2 is formed on such a substrate 1, and this recording film 2 contains an organic dye as a recording composition. Examples of the organic dye include a cyanine dye, an azo dye, a quinone dye, an indico dye, and the like, and a cyanine dye represented by the following general formula [formula 1] and a general formula [formula 2] shown below The azo dyes shown are preferred.

[0015]

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R1 and R6 in the formula each have 1 carbon atom
Represents an alkyl group of 1 to 16, preferably 1 to 4. X ⁻ represents a counter ion (anion), for example, ClO ₄ ⁻ , I ⁻ , Br ⁻ , PF ₆ ⁻ , BF ₄ ⁻
Are preferred. φ and ψ may each independently be a benzene ring or a naphthalene ring or a benzene ring or a naphthalene ring having a substituent. Preferably, one of φ and ψ is a benzene ring, and the other is a naphthalene ring.

[0017]

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In the formula, X is a divalent group which forms a heterocyclic ring selected from the group consisting of thiazoline, benzothiazoline, pyridine, quinoline and pyrimidine together with the nitrogen atom and carbon atom to which each is bonded. Y represents a divalent group which, together with the two carbon atoms to which each is attached, forms an aromatic ring selected from the group consisting of benzene and naphthalene; and Z represents a hydroxyl group or a carboxyl group. Represents A complex of the monoazo compound represented by the following [Formula 2] and a divalent metal is exemplified.
As the divalent metal, Ni, Cu, Co and the like are preferable.

Such a dye can supply heat necessary for recording even when using low-energy recording light, enables high-density recording with minute recording points, and reproduces the intensity of reproduction light with respect to minute recording points. Does not cause signal degradation or data destruction due to heat.

Further, by using a recording film in which three or more kinds of dyes having different maximum absorption wavelengths are mixed, stable recording / reproducing characteristics can be obtained without being affected by variations in laser wavelength during recording / reproducing. By mixing three or more types of dyes having different absorption wavelengths, the amount of light absorption near the recording / reproducing wavelength can be adjusted very accurately.

The recording film 2 containing the organic dye is formed, for example, by a spin coating method or the like. The recording film 2 to be formed is formed so as to leave the inner peripheral edge on the substrate 1. The thickness of the recording film 2 to be formed is about 0.02 to 0.2 μm. The solvent used for coating includes, for example, ethyl cellosolve, methyl cellosolve, methanol, tetrafluoropropanol, diacetone alcohol and the like.

Further, it is preferable that the recording film 2 contains a quencher in order to prevent light deterioration of the dye.

On the recording film 2, a light reflecting layer 3 is laminated. The light reflection layer 3 is made of a metal such as Au, Ag, Cu, or Al, and is formed by vacuum deposition, sputtering, ion plating, or the like. The thickness of the light reflection layer 3 is 0.0
It is about 5 to 0.2 μm. This is because if the thickness of the light reflecting layer 3 is less than 0.05 μm, the reflectance is reduced, and if it exceeds 0.2 μm, the mechanical properties of the substrate deteriorate.

On the light reflecting layer 3, a protective layer 4 is laminated for protecting the recording film 2 and the light reflecting layer 3 or for the purpose of improving recording characteristics. The protective layer 4 is formed by spin-coating an ultraviolet curable resin to form a film, and then irradiating with ultraviolet light for a certain time to cure the coating. As another method, an epoxy resin, an acrylic resin, a silicone resin, a urethane resin, or the like can be used as a material of the protective layer 4. The thickness of the protective layer 4 is about 0.1 to 100 μm, preferably 4 to 10 μm.

The present invention relates to a transparent substrate 1 formed of a light-transmitting resin.
A write-once optical disc having a dye-containing recording film 2 provided on the substrate 1 and a light reflection layer 3 provided on the recording film 2, wherein It is used in a recording / reproducing method in which reproduction is performed using long-wavelength light of about 650 nm and recording is performed using short-wavelength light of about 630 nm using laser light of various wavelengths. It is characterized in that an organic dye film having a small light absorption at the reproduction wavelength is provided.

Specifically, a mixture of three or more kinds of organic dyes having different absorption wavelengths is used for the organic dye film. The maximum absorption wavelength at 400 nm to 800 nm is between 500 nm and 620 nm. The recording light and the reproduction light have wavelengths in the range of 630 nm to 660 nm using a mixture of three or more kinds of dyes having different absorption wavelengths.

If it is attempted to accurately adjust the amount of light absorption near the recording / reproducing wavelength with a mixture of two dyes having different maximum absorption wavelengths, the margin of the composition ratio of the two dyes becomes narrower. It is difficult to obtain stable recording / reproducing characteristics due to the influence of the variation in the laser wavelength during reproduction.

Therefore, by using a recording film in which three or more kinds of dyes having different maximum absorption wavelengths are mixed, stable recording / reproducing characteristics can be obtained without being affected by variations in laser wavelength during recording / reproducing. Further, by setting the laser wavelength at the time of recording / reproducing to be in the range of 630 nm to 660 nm,
It becomes possible to accompany reproduction compatibility with a VD player.

The above three types of dyes are from 400 nm to 80
500 n when the spectral absorption spectrum in the wavelength range of 0 nm is measured under the condition that the film is formed on a flat transparent substrate.
Maximum absorption wavelength (λ _max 1) within the range of m to 620 nm
The first organic dye (D1), a second organic dye (D having a maximum absorption wavelength (lambda _max 2) greater than the maximum absorption wavelength (lambda _max 1) of the first organic dye (D1) having a
And 2), consisting of a third organic dye (D3) having a first organic maximum absorption wavelength (lambda _max 1) less the maximum absorption wavelength than the dye _{(D1) (λ max 3)} . The relationship between the maximum absorption wavelengths of these dyes is summarized as follows.

Λ _max 3 (D3) <λ _max 1 (D1) <λ
_max 2 (D2) and the first organic dye (D1) and the second organic dye (D
The mixed weight ratio of 2) and the third organic dye (D3) is (D
1) ≧ (D2), (D1)> (D3), and the first organic dye (D1) is a main component.

When the relationship of the mixing ratio is broken, (D1)
In the case of (D2), the amount of light absorption near the recording / reproducing wavelength becomes too large, so that the reflectivity decreases, a sufficient servo signal cannot be obtained, and it is difficult to obtain stable recording / reproducing characteristics. . In the case of (D1) <(D3), the amount of light absorbed in the vicinity of the recording / reproducing wavelength is too small, so that the heat generated at the time of recording is small, and sufficient recording pit formation is not performed. And other problems arise.

In the present invention, a large absorptance at a recording wavelength,
By providing an organic dye film with a small absorptance at the reproduction wavelength, this film becomes a light absorbing layer, that is, a heat source at the time of recording, so that even if low-energy recording light is used, it supplies heat necessary for recording. And high-density recording with minute recording points becomes possible.

On the other hand, since almost no light is absorbed at the time of reproduction, even if the reproduction light intensity for a minute recording point is increased,
It does not cause signal degradation or data destruction due to heat. In addition, since the wavelength dependence of the reflectance near the recording / reproducing wavelength is suppressed to a small value, stable recording / reproducing characteristics can be obtained without being affected by variations in the laser wavelength during recording / reproducing.

Embodiment 1 Hereinafter, a specific embodiment will be described. The following cyanine dyes C1, C2, and C3 were used as the dyes contained in the light absorbing layer.

The first cyanine dye C1 is represented by the above formula
In the formula, φ is a benzene ring, ψ is a naphthalene ring, R ₁ ,
R ₂ is a butyl group and X ⁻ is a perchlorate ion. FIG. 2 shows the spectral absorption spectrum of the second dye C2. The maximum absorption wavelength (λ _max 1) is 595 nm.

The second cyanine dye C2 is represented by the formula
In the formula, φ and ψ are naphthalene rings, R ₁ and R ₂ are butyl groups, and X ⁻ is a perchlorate ion. This first dye C1
Is shown in FIG. Maximum absorption wavelength (λ
_max 2) is 613 nm.

The third cyanine dye C3 is represented by the formula
In the formula, φ and ψ are benzene rings, R ₁ and R ₂ are butyl groups, and X ⁻ is a perchlorate ion. FIG. 4 shows the spectral absorption spectrum of the third dye C3. Maximum absorption wavelength (λ _max
3) is 575 nm. Therefore, λ _max 3 (C3) <λ
_max 1 (C1) <satisfy the relationship of λ _max 2 (C2).

The mixing ratio C1 / C2 / C3 of the cyanine dyes C1, C2 and C3 was set to 80/10/10, and 2% by weight was dissolved in ethylcellosolve as a solvent.
It was applied to a thickness of 0.18 μm on a polycarbonate substrate having a thickness of 20 mm and a thickness of 0.6 mm. Therefore, the mixing weight ratios have a relationship of (C1)> (C2), (C1)> (C3).

The light reflecting layer 3 made of Ag was further laminated on the light absorbing layer to a thickness of 0.15 μm by a sputtering method. Further, an optical disk was prepared by laminating a protective layer of an ultraviolet curable resin.

Example 2 Cyanine dye C of Example 1
Instead of the dyes of 1, C2 and C3, the following general formula [Formula 3]
An optical disk was prepared in the same manner as in Example 1 using the azo dyes A1, A2, and A3 represented by the following formulas.

[0041]

Embedded image

In the first azo dye A1, X is C1 in the above chemical formula 3, and the maximum absorption wavelength (λ _max 1) is 580.
nm. In the second azo dye A2, X is Br in the above chemical formula 3, and the maximum absorption wavelength (λ _max 2) is 590 n.
m. In the third azo dye A3, X is CF ₃ in the above chemical formula ₃ , and the maximum absorption wavelength (λ _max 3) is 570 n.
m.

Therefore, also in this recording film, λ _max 3 (A
_{3) <λ max 1 (A1} ) < satisfies a relationship λ _max 2 (A2), the mixing weight ratio A1 / A2 / A3 is 80/10
/ 10, the relationship is (A1)> (A2), (A1)> (A3).

Embodiment 3 C1, C2, C3 in Embodiment 1
In the same manner as in Example 1 except that a cyanine dye of C4 shown below was further added to the cyanine dye of No. 1 to change the mixing weight ratio of C1, C2, C3, and C4 to 45/10/30/15. To make an optical disc.

The fourth cyanine dye C4 is represented by the above formula
Is a benzene ring, ψ is a naphthalene ring, R ₁ , R
₂ is a butyl group and X ^- is a phosphorus hexafluoride ion. The maximum absorption wavelength of the fourth dye C4 is 592 nm.

In the case of this embodiment, the maximum absorption wavelength (595 nm) of the cyanine dye C1 and the maximum absorption wavelength (592 nm) of the cyanine dye C4 are close to each other. These two organic dyes are both composed of cyanine dyes and have different types of anions. The mixture weight ratio of the first organic dye (D1), the second organic dye (D2), and the third organic dye (D3) is (45 + 15) / 10/3.
0, which satisfies the relationship of (D1) ≧ (D2), (D1)> (D3).

Embodiment 4 A1, A2, A3 in Embodiment 2
Further, in the above azo dye, X is NO
_{2. The} term and fourth azo dyes A4 addition, A1, A2,
An optical disc was prepared in the same manner as in Example 2, except that the mixing weight ratio of A3 and A4 was changed to 35/15/35/15.

The maximum absorption wavelength of the fourth azo dye A4 is 612 nm, which is close to the maximum absorption wavelength (590 nm) of the second azo dye A2, and these two dyes are defined in the present invention. This corresponds to the second organic dye (D2).
Then, the first organic dye (D1) and the second organic dye (D
The mixing weight ratio of 2) and the third organic dye (D3) is 35 /
(15 + 15) / 30, and (D1) ≧ (D2),
The relationship of (D1)> (D3) is satisfied.

Comparative Example 1 Cyanine dye C in Example 1
An optical disc was prepared in the same manner as in Example 1 except that the compositions of 1, C2, and C3 were changed to 90/10/0. That is, in this comparative example, the cyanine dye C3 was not used, and the recording film was composed of two types of cyanine dyes C1 and C2.

Comparative Example 2 A1, A2, A3
An optical disc was prepared in the same manner as in Example 2 except that the composition of was changed to 75/25/0. That is, in this comparative example, the azo dye A3 was not used, and the azo dyes A1 and A
2, the recording film is constituted.

Each of the optical disks created under the above conditions
The reflectance was measured at wavelengths of 30 nm and 650 nm, and the results are shown in the following table.

[0052] As is clear from this table, those of Comparative Examples 1 and 2 have a large wavelength dependence of the reflectance (especially at a wavelength of 650 nm), so that stable recording / reproducing characteristics cannot be obtained. On the other hand, according to Examples 1 to 4 of the present invention, the wavelength dependence of the reflectance is small, so that stable recording / reproducing characteristics can be obtained.

In each of the above embodiments, the cyanine dyes or the azo dyes are mixed, but a recording film may be formed by mixing different types of dyes such as a cyanine dye and an azo dye.

[0054]

According to the present invention, the heat generated at the time of reproduction can be reduced and the heat generated at the time of recording can be increased, so that the recording sensitivity is reduced to such an extent that the signal is not deteriorated by the reproduction light. In addition, sufficiently stable recording can be performed, and stable high-density recording and reproduction can be achieved. Also,
By using a recording film in which three or more types of dyes are mixed, it is possible to obtain a constant reflectance without being affected by a variation in laser wavelength during recording and reproduction. Therefore, an optical recording medium and a recording / reproducing method capable of obtaining stable recording / reproducing characteristics are realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram for explaining a structure of a write-once optical disc in an embodiment of the present invention.

FIG. 2 shows a first dye film [C1] in an embodiment of the present invention.
FIG. 3 is a diagram showing a spectral absorption spectrum of the present invention.

FIG. 3 shows a second dye film [C2] in an embodiment of the present invention.
FIG. 3 is a diagram showing a spectral absorption spectrum of the present invention.

FIG. 4 shows a third dye film [C3] in an embodiment of the present invention.
FIG. 3 is a diagram showing a spectral absorption spectrum of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording film 3 Light reflection layer 4 Protective layer A Write-once optical disk

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G11B 7/24 522 G11B 7/24 522A (72) Inventor Yuichi Sakurai 1-1-1 Ushitora Ushitora, Ibaraki City, Osaka Prefecture No. 88 Hitachi Maxell F-term (reference) 2H111 EA12 FB42 FB43 4H056 CA01 CC08 CE03 DD03 FA06 5D029 JA04 JC01 5D090 AA01 BB03 CC06 DD02 EE01 KK07

Claims (6)

[Claims] A recording film containing an organic dye is provided on a transparent substrate, and the recording film measures a spectral absorption spectrum in a wavelength range of 400 nm to 800 nm under a condition in which the film is formed on a flat transparent substrate. From 500nm to 620nm
And a first organic dye (D1) having a maximum absorption wavelength (λ _max 1) within the range of the maximum absorption wavelength (λ _max ) larger than the maximum absorption wavelength (λ _max 1) of the first organic dye (D1).
_max 2), a second organic dye (D2) having
Has a maximum absorption wavelength (lambda _max 1) a mixture of a third organic dye (D3) having a smaller maximum absorption wavelength (lambda _max 3) than the organic dye (D1), said first organic dye ( D
1), the second organic dye (D2) and the third organic dye (D
(D1) ≧ (D2), (D1)
> (D3). 2. The optical recording medium according to claim 1, wherein the first organic dye (D1) is composed of two or more different types of organic dyes. 3. The method according to claim 2, wherein the two or more different organic dyes serving as the first organic dyes (D1) are both composed of cyanine dyes and have different types of anions. An optical recording medium characterized by the following. 4. The method according to claim 1, wherein the first organic dye (D1), the second organic dye (D2), and the third organic dye (D3) are each composed of a cyanine dye. Optical recording medium. 5. The method according to claim 1, wherein the first organic dye (D1), the second organic dye (D2), and the third organic dye (D3) are both azo dyes. Optical recording medium. 6. A transparent film having a recording film containing an organic dye on a transparent substrate, and the recording film measures a spectral absorption spectrum in a wavelength range of 400 nm to 800 nm under a condition that the film is formed on a flat transparent substrate. From 500nm to 620nm
And a first organic dye (D1) having a maximum absorption wavelength (λ _max 1) within the range of the maximum absorption wavelength (λ _max ) larger than the maximum absorption wavelength (λ _max 1) of the first organic dye (D1).
_max 2), a second organic dye (D2) having
Has a maximum absorption wavelength (lambda _max 1) a mixture of a third organic dye (D3) having a smaller maximum absorption wavelength (lambda _max 3) than the organic dye (D1), said first organic dye ( D
1), the second organic dye (D2) and the third organic dye (D
(D1) ≧ (D2), (D1)
> A recording / reproducing method, wherein information is recorded with short-wavelength light and information is reproduced with long-wavelength light using an optical recording medium having a relationship of (D3).