JP3495589B2 - Optical recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical recording medium having a dye film as a recording layer, and particularly to a short wavelength (600 to 68).
The present invention relates to an optical recording medium capable of recording and reproducing at 0 nm).

[0002]

2. Description of the Related Art A recording method for an optical recording medium which has been put into practical use at present is a heat mode recording method in which an irradiating laser beam is used as a heat source to cause evaporation and decomposition of a recording layer to form optically detectable concave pits. Is.

However, the recording / reproducing wavelength is around 780 nm, and it is necessary to shorten the recording / reproducing wavelength to support high density recording. The shortening of the recording / reproducing wavelength requires the change of the organic dye contained in the recording layer and the change of the groove shape. Specifically, the track pitch becomes 0.8 μm or less, and the groove width becomes narrower accordingly.

Further, since the laser wavelength is shortened and the numerical aperture (NA) is increased, the focal depth of the laser light becomes shallow. Therefore, such as CD-ROM, CD-R, etc.
A 2 mm thick transparent substrate cannot be used, and a 0.6 mm thick transparent substrate, which is half the thickness, is used.

As an example of proposing a groove shape for high density recording, JP-A-9-81966 and JP-A-9-198 are known.
No. 714 is disclosed, but none of them has achieved good recording / reproducing characteristics as an optical recording medium. Among them, Japanese Patent Laid-Open No. 9-198714 discloses
Although it is disclosed that the inclination of the wall of the groove of the substrate (the angle formed by the horizontal line between the grooves and the tangent line drawn to the wall of the groove) is 70 to 85 degrees, such a groove has preferable characteristics. Was found not to show.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical recording medium having a recording and / or reproducing wavelength of 600 to 680 nm and a track pitch of 0.8 μm or less,
An object of the present invention is to provide an optical recording medium having excellent mechanical precision and excellent recording / reproducing characteristics.

[0007]

The above object can be achieved by the present invention described below. (1) Recording and / or reproduction wavelength is 600 to 680
nm, a recording layer containing an organic dye is formed on a grooved substrate, and the substrate has a groove depth of A in an optical recording medium having a track pitch of 0.8 μm or less.
(Μm), the angle θ between the tangent line of the groove wall and the tangent line of the flat portion of the land at the position of half the groove depth A / 2 is 30 to 55 degrees, and the half depth of the groove is Groove width B at A / 2 position is 0.25 to 0.45μ
An optical recording medium that is a transparent substrate of m 2. (2) The optical recording medium according to (1) above, wherein the recording layer in the land portion has a thickness of 0.15 μm or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The optical recording medium of the present invention has a track pitch of 0.8.
The recording and / or reproducing wavelength is 600 μm or less.
It has a short wavelength of ˜680 nm and is suitable for high density recording.

An example of the structure of such an optical recording medium is shown in FIG. As shown in FIG. 1, an optical recording disk, which is an optical recording medium, is formed by laminating two protective films 14 of two disks having the same structure. The thickness of the adhesive layer 15 is 10 to
It is about 200 μm. The substrate (normally polycarbonate) in this case is a transparent substrate and has a groove for tracking servo. The thickness per board is 0.6 mm
The recording layer 12, the reflection layer 13, and the protective film 14 are sequentially formed on the grooved substrate 11, while the recording layer 12, the reflection layer 1 are similarly formed on the grooved substrate 11.
3. The protective film 14 is formed, and the protective film 14 is bonded as described above. As a bonding method, a hot melt adhesive, a slow-acting UV adhesive, a pressure sensitive adhesive sheet or the like can be used. The groove is omitted in FIG.

Further, FIG. 2 shows a substrate 11 on which a groove is formed, on which a recording layer 12,
A one-sided disc having a reflective layer 13 and a protective film 14 is shown.

Further, FIG. 3 shows an enlarged view of the groove portion and the land portion of the substrate 11.

In such an optical recording medium, the shape of the groove provided on the transparent substrate for tracking / servo, particularly the angle θ of the groove wall, is defined as follows, so that the optical recording medium has excellent mechanical characteristics. An optical recording medium having excellent recording / reproducing characteristics can be obtained.

That is, when the groove depth is A (μm), the shape of the groove of the transparent substrate has an angle θ between the tangent of the groove wall and the tangent of the flat portion of the land at the position A / 2 of 30. The degree ≤ θ ≤ 55 degrees, and the groove width B at the position A / 2 is 0.25 to 0.45 µm.

2 and 3 for the track pitch P, the groove 111, the land 115, the groove depth A, and the groove width B in the above description. Here, the groove width B is a value at the position of A / 2, as described above.

The angle θ of the groove wall at the A / 2 position is the angle between the tangent line of the groove wall and the tangent line of the flat land portion at the A / 2 position, as described with reference to FIG.

The angle θ of the groove wall at the position A / 2 is
Scanning tunneling microscope (STM), atomic force microscope (A
FM).

Although the groove wall exists on both sides of the groove, it is usually the average value of the measured values on both sides. Also,
Normally, the land portion has a flat portion as shown in the figure,
In the present invention, as will be described later, a shape having a flat portion is preferable, but when there is no flat portion, the tangent line at the uppermost portion is used.

The angle θ is 30 ° ≦ θ ≦ 55 °, preferably 35 ° ≦ θ ≦ 50 °, and more preferably 40 ° ≦ θ ≦ 48 °. If the angle θ is smaller than 30 degrees, the flat portion of the land portion becomes too narrow, which deteriorates crosstalk. On the other hand, if the angle θ exceeds 55 degrees, the transparent substrate injection molding is adversely affected, and the balance between the transfer rate from the stamper and the like and the mechanical characteristics is deteriorated. This balance means that when the transfer rate is improved, the mechanical properties are significantly deteriorated, and when the mechanical properties are improved, the transfer rate is lowered. Furthermore, if the angle θ exceeds 55 degrees, the jitter characteristic deteriorates. It is considered that this is because the angle of the groove wall becomes large and the state at the time of film formation by spin coating changes, and the leveling of the recording layer changes.

Further, the optical recording medium of the present invention will be described with reference to FIGS.

The substrate 11 has a disk shape, and recording light and reproducing light (wavelengths of about 600 to 680 nm,
Furthermore, the wavelength of 630 to 680 nm, especially the wavelength of 63
Laser light of about 5 to 680 nm, especially 635 nm to 650
It is preferable to use a resin or glass that is substantially transparent (preferably a transmittance of 88% or more) to (nm).
The size is about 120 mm in diameter and about 0.6 mm in thickness.

The surface of the substrate 11 on which the recording layer 12 is formed is shown in FIG.
As shown in, groove 11 for tracking servo
1 is formed. The groove 111 is preferably a spiral continuous groove, and the depth A is 0.12.
.About.0.2 .mu.m, the width B is 0.25 to 0.45 .mu.m, and the track pitch (groove pitch) P is 0.80 .mu.m or less, specifically 0.65 to 0.80 .mu.m. By configuring the groove in this way,
A good tracking signal can be obtained without lowering the reflection level of the groove. On the other hand, when the groove depth is shallower than 0.12 μm, it becomes difficult to obtain sufficient modulation. Further, if it exceeds 0.2 μm, it is not realistic because it is technically difficult to mold the substrate and the mechanical precision is deteriorated. If the groove width exceeds 0.45 μm, the factor of crosstalk becomes large and the jitter is likely to deteriorate. When the groove width is less than 0.25 μm, it is difficult to obtain a sufficiently large tracking signal, and a slight offset of tracking during recording tends to increase jitter. Moreover, a sufficient degree of modulation cannot be obtained.

As the material of the substrate 11, it is preferable to use a resin, and various thermoplastic resins such as polycarbonate, (meth) acrylic resin, amorphous polyolefin, TPX, polystyrene resin are suitable. And
It can be manufactured using such a resin according to a known method such as injection molding. The groove 111 is the substrate 11
It is preferable to form it at the time of molding. A resin layer having the groove 111 may be formed by the 2P method or the like after the substrate 11 is manufactured. A glass substrate may be used depending on the case.

Further, the recording layer 12 provided on the substrate 11
Contains an organic dye, and is preferably formed by a spin coating method using an organic dye-containing coating liquid. Spin coating may be performed according to normal conditions by adjusting the rotation speed from 500 to 5000 rpm from the inner circumference to the outer circumference.

With respect to the thickness of the recording layer 12 thus formed, the thickness D _{L of the} recording layer formed on the land 115 of the substrate 11 is preferably 0.15 μm or less,
The thickness is more preferably 0.1 μm or less, and particularly preferably 0.03 to 0.1 μm. The thickness D _G of the recording layer formed on the groove portion 111 of the substrate 11 is determined from the groove depth A as D _L + ( ^{2 to} 3.5) A ² .

By thus regulating the thickness of the recording layer, good recording / reproducing characteristics can be obtained. If the thickness is out of the above range, the reflectance is lowered and it becomes difficult to perform good reproduction. In particular, the recording layer 12 of the land portion 115
If the thickness is too thick, the crosstalk factor is increased and the jitter is deteriorated.

The thickness D _G of the recording layer in the groove portion and the thickness D _L of the recording layer in the land portion are average values at 5 points or more in the recording area in the disc.

In the present invention, in-groove recording is performed.

The complex refractive index of the recording layer 12 at the wavelengths of recording light and reproducing light is such that the real part n = 2.0 to 2.8 and the imaginary part k = 0.4 or less.

By restricting n and k as described above, good recording and reproduction can be performed. If k exceeds 0.4, sufficient reflectance cannot be obtained. When n is less than 2.0, the modulation degree of the signal is too small. The upper limit of n is not particularly limited, but is usually about 2.8 for convenience of synthesis of the dye compound.

For the recording layers n and k, a recording layer is formed on a predetermined transparent substrate to a thickness of, for example, about 40 to 100 nm under actual conditions to prepare a measurement sample, and then, It is determined by measuring the reflectance of this measurement sample through the substrate or the reflectance from the recording layer side. In this case, the reflectance is the recording / reproducing light wavelength (635-6
It is measured by specular reflection (about 5 °) using 50 nm).
In addition, the transmittance of the sample is measured. Then, from these measured values, for example, Kyoritsu Zensho "Optics" Kozo Ishiguro P16
8 and 178, n and k may be calculated.

In the present invention, as the organic dye that can be used in the recording layer, cyanine dyes, metal complex dyes, styryl dyes, porphyrin dyes, azo dyes,
Examples include formazan metal complexes and rhodamine dyes.

Specific examples of the coating solvent used in the present invention include alcohols (including keto alcohols and alkoxy alcohols such as ethylene glycol monoalkyl ethers), aliphatic hydrocarbons, ketones, and esters. It may be appropriately selected from a system, an ether system, an aromatic system, an alkyl halide system and the like. The dye content in the coating liquid is usually 0.05 to 10 wt%. Further, the coating liquid may appropriately contain a binder, a dispersant, a stabilizer and the like.

As shown in FIGS. 1 and 2, a reflective layer 13 is provided on the recording layer 12 in direct contact with it. Reflective layer 1
As 3, it is preferable to use a high reflectance metal such as Au, Pt, Cu, Al, Ag or an alloy thereof. Reflective layer 1
The thickness of 3 is preferably 50 nm (500 A) or more, and may be formed by vapor deposition, sputtering or the like. Although the upper limit of the thickness is not particularly limited, it is preferably about 120 nm (1200 A) or less in consideration of cost, production work time and the like. As a result, the reflectance of the reflective layer 13 alone becomes 90% or more, and the reflectance of the unrecorded portion of the medium through the substrate is sufficient.

As shown in FIGS. 1 and 2, a protective film 14 is provided on the reflective layer 13. The protective film 14 is made of various resin materials such as an ultraviolet curable resin, and is usually 0.5
The layer may be formed to a thickness of about 100 μm. Protective film 14
May be layered or sheet-shaped. Protective film 1
4 is spin coating, gravure coating, spray coating,
It may be formed by an ordinary method such as dipping.

In order to perform recording or additional recording on the optical recording disk 1 having such a structure, for example, recording light of 635 nm to 650 nm is radiated in a pulse form through the substrate 11 to change the light reflectance of the irradiation portion. When the recording light is irradiated, the recording layer 12 absorbs the light and generates heat, and at the same time, the substrate 11 is also heated. As a result, in the vicinity of the interface between the substrate 11 and the recording layer 12, the recording layer material such as an organic dye is melted or decomposed, pressure is applied to the interface between the recording layer 12 and the substrate 11, and the bottom surface or side wall of the groove is deformed. There is something to do.

In the present invention, when the recording signal is pulse-divided on the optical recording medium and recording is performed using the pulse train, the length of the leading pulse of the pulse train (divided pulse) is Ttop.
When (T), in relation to the groove depth A (μm), A × Ttop is preferably in the range of 0.15 to 0.25, more preferably 0.18 to 0.22. It is preferable to use an optical recording medium and a recording method satisfying such conditions. By satisfying these conditions, excellent jitter characteristics can be obtained. On the other hand, 0.1
When it is less than 5, deterioration of recording sensitivity and deterioration of jitter are likely to occur. If it exceeds 0.25, the deterioration of jitter is likely to occur.

It is preferable that Ttop is 1.15 to 1.4T.

Although Ttop is shown with T as one unit (one unit), Ttop used for displaying Ttop
Is defined according to the following formula: [Minimum pit length (3T length: unit nm) / 3] / Linear velocity (unit
m / s) = T (unit: ns)

The length of the second and subsequent pulses in the pulse train is 0.6 to 0.7T, and the interval is 0.3 to 0.
It is preferably 4T. The linear velocity during recording and reproduction is CLV 3 to 20 m / s, preferably 3 to 12 m / s.

[0040]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 Diameter 120 mm with grooves as shown in Table 1,
Using a 1.0 wt% 2,2,3,3-tetrafluoropropanol solution containing the following organic dyes on a polycarbonate substrate having a thickness of 0.6 mm, the thickness as shown in Table 1 was obtained by spin coating. The recording layer was formed. next,
An Au reflective layer having a thickness of 100 nm was formed on the recording layer by a sputtering method, and a transparent protective film (film thickness 5 μm) of an ultraviolet curable acrylic resin was further formed. Two discs formed in the same manner were attached to each other with the protective film on the inner side with an adhesive to produce a disc (see FIG. 1). In this way, the samples shown in Table 1 were prepared.

The angle (groove wall angle) θ of the groove wall at the A / 2 position was measured by measuring the profile of the groove shape by STM, and as shown in FIG. 3, the tangent line of the groove wall at the A / 2 position was used. The angle θ formed by the tangent line of the flat portion of the land portion is measured on both sides of the groove, and is represented by the average value thereof.

The groove width B is the width at the position A / 2 (see FIG. 3).

[0043]

[Chemical 1]

[0044]

[Table 1]

For the sample produced in this way,
The mechanical characteristics and recording / reproducing characteristics were evaluated.

The mechanical characteristics are LM1200 (D
(For VD), and the surface vibration amount, the surface vibration acceleration, and the warp angle were evaluated. Although these values depend on the groove shape and the like, the smaller the better.

Further, the recording / reproducing characteristics are as follows:
Record the signal at linear velocity CLV 3.8 m / s using 8 nm,
Next, this disk was evaluated by reproducing it with a 638 nm laser beam having a linear velocity of CLV 3.8 m / s.

At this time, the recording signal is divided into pulses, and the length Ttop of the pulse at the beginning of the pulse train is as shown in Table 1. In any case, the length of the second and subsequent pulses is 0.
7T and the pulse interval was 0.3T. The lens numerical aperture NA was 0.6. Characteristics are reflectance at 638 nm,
Modulation degree (14 TMod.), Jitter (Jite)
r), and the recording sensitivity (P0) at 638 nm was evaluated.

The results are shown in Table 2.

[0050]

[Table 2]

From Table 2, the samples of the present invention have mechanical properties such as surface vibration amount, surface vibration acceleration, and warp angle which are all within the permissible level when viewed in relation to the groove shape, and
It can be seen that the reproduction characteristics are excellent. On the other hand, the comparative sample has poor mechanical properties, especially the jitter properties.

[0052]

According to the present invention, it is possible to obtain an optical recording medium having excellent mechanical precision, a good balance of reflectance and degree of modulation, high recording sensitivity and excellent jitter characteristics. In addition, a good recording method can be achieved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an example of an optical recording disk of the present invention.

FIG. 2 is a partial cross-sectional view for explaining the configuration of the optical recording disk of FIG.

FIG. 3 is an enlarged view of a substrate for explaining an angle θ of a groove wall at a position of A / 2.

[Explanation of symbols]

11 board 12 recording layers 13 Reflective layer 14 Protective film 15 Adhesive layer 111 Groove or groove 115 Land

Claims (2)

(57) [Claims] 1. A recording and / or reproducing wavelength of 600 to
680 nm, a recording layer containing an organic dye is formed on a grooved substrate, and the track pitch is 0.8 μm.
In the following optical recording medium, when the groove depth of the substrate is A (μm),
The angle θ formed by the tangent line of the groove wall and the tangent line of the flat portion of the land at a position where the depth is half the groove A / 2 is 30 to 55.
An optical recording medium which is a transparent substrate having a groove width B of 0.25 to 0.45 μm at a position where the depth is half the groove A / 2. 2. The land recording layer has a thickness of 0.15 μm.
The optical recording medium according to claim 1, wherein: