JP4075006B2 - Optical information recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical information recording medium, and more particularly to an optical information recording medium that enables high-density optical recording using laser light having a shorter wavelength than conventional ones.
[0002]
[Prior art]
There is a demand for performing optical information recording with a higher density than conventional optical information recording media.
In order to achieve high-density optical information recording, that is, a large capacity and a high transfer rate, it is effective to reduce the spot size of laser light for recording and improve the recording linear velocity.
In order to reduce the spot size of the laser beam, specifically, the wavelength λ is set to a shorter wavelength side than the conventionally used red light side, and the laser beam is focused on the optical information recording medium. Numerical aperture of the objective lens A. There are ways to increase the size.
[0003]
In particular, the method of shortening the wavelength λ of the laser beam and the numerical aperture N.I. A. By using both of these methods and the method of increasing the spot size, the spot size can be further reduced as compared with the case where each method is applied alone.
For example, as a light source, blue-violet laser light having a wavelength near λ = 400 nm is used and a numerical aperture of N.P. A. It is theoretically possible to achieve higher density recording by using an objective lens in which = 0.85. That is, in order to increase the recording density, it is necessary to increase the value of (NA / λ).
For example, in order to obtain an optical information recording medium having a recording capacity of 8 GB, at least the numerical aperture of the objective lens is N.P. A. Is known to be 0.7 or more, and the wavelength λ of the laser light needs to be 680 nm or less.
[0004]
FIG. 7 is a schematic cross-sectional view showing an example of an optical information recording medium that has been proposed in order to realize high density information recording. The optical information recording medium 1 includes a support substrate 2, a light reflection layer, and the like. 3, an optical recording layer 4, and a light transmission layer 5 are sequentially stacked.
[0005]
The support substrate 2 is made of, for example, glass, polycarbonate resin, polyolefin resin or the like excellent in impact resistance, and has a thickness of, for example, about 1.2 mm.
[0006]
The light reflecting layer 3 is formed by depositing gold, silver, copper, aluminum, or an alloy or other metal containing these, which can totally reflect the laser light, by means of vapor deposition, sputtering, or the like. The thickness is, for example, about 50 to 100 nm.
The light reflecting layer 3 is not necessarily required if a predetermined level of reflectance can be obtained in the layer boundary with the support substrate 2 due to the characteristics of the optical recording layer 4 itself.
[0007]
The optical recording layer 4 is a layer capable of recording optical information by absorbing laser light. That is, the optical recording layer 4 is a layer made of a light-absorbing substance (light-absorbing substance) and is a layer that generates heat, melts, sublimates, deforms, or modifies when irradiated with laser light. This optical recording layer 4 is formed by uniformly coating the surface of the light reflecting layer 3 with, for example, a cyanine dye dissolved in a solvent by means such as spin coating.
Although any optical recording material can be adopted as the material used for constituting the optical recording layer 4, a light-absorbing organic dye is desirable. The thickness of the optical recording layer 4 is, for example, about 50 to 100 nm.
[0008]
The light transmission layer 5 protects the optical recording layer 4 from the outside, and irradiates laser light 7 from the surface (main surface) side through the objective lens 6 to perform optical recording and reproduction on the optical recording layer 4. This is a transparent base material that has the same impact resistance as that of the substrate 2 and is coated with, for example, an ultraviolet curable resin by a spin coating method and cured by irradiating it with ultraviolet rays. Form.
The thickness of the light transmission layer 5 is, for example, about 100 μm.
In particular, when the optical information recording medium 1 corresponding to the current red laser to blue laser is considered as the recording light, the thickness of the light transmission layer 5 is preferably 10 to 177 μm.
[0009]
The substrate 2 and the light reflecting layer 3 are in contact with each other through the first layer boundary 8.
The light reflecting layer 3 and the optical recording layer 4 are in contact with each other by the second layer boundary 9.
The optical recording layer 4 and the light transmission layer 5 are in contact with each other by the third layer boundary 10.
[0010]
In the optical information recording medium 1 having such a configuration, in order to perform optical information recording with higher density than before, the laser light 7 having a shorter wavelength and the larger numerical aperture N.D. A. When the objective lens 6 is used, the converging distance becomes shorter. Therefore, when the laser beam 7 is irradiated from the support substrate 2 side having a relatively large thickness, the optical recording layer 4 is recorded and reproduced. Since it is difficult to focus the laser spot necessary for the optical recording layer 4, the laser beam 7 is directly applied to the optical recording layer 4 from the side of the light transmitting layer 5 having a smaller thickness.
[0011]
Thus, when the optical recording layer 1 is an organic dye film when the optical information recording medium 1 is produced, the optical recording layer 4 is formed in order to stack the light transmission layer 5 thereon. It is necessary to spin coat an ultraviolet curable resin, which is a material of the light transmission layer 5, but when a liquid ultraviolet curable resin is directly laminated on the organic dye optical recording layer 4, it is in a liquid state before the curing is completed. As a result of the optical recording layer 4 being dissolved in the ultraviolet curable resin, there is a problem that the optical recording layer 4 cannot be properly formed, and an adverse effect on optical recording is considered.
[0012]
8 is a cross-sectional view showing a spin coating process for forming the light transmission layer 5 in the optical information recording medium 1, and FIG. 9 is a cross-sectional view after the spin coating is completed. The tracking pregroove 11 and its left and right lands 12 are formed in a spiral shape in the circumferential direction.
The light reflecting layer 3 and the optical recording layer 4 are also uneven according to the shape of the pregroove 11 and the land 12, and the pits 13 can be formed on the optical recording layer 4 in the pregroove 11 or the land 12.
[0013]
As shown in FIG. 8, since the liquid ultraviolet curable resin 5A is applied to the formed optical recording layer 4, the liquid ultraviolet curable resin 5A and the optical recording layer 4 are in direct contact with each other.
Therefore, the optical recording layer 4 dissolves in the third layer boundary 10 between the optical recording layer 4 and the light transmission layer 5 and comes out of the dropping portion of the liquid ultraviolet curable resin 5A, or by its rotation in the spin coating method. Along with the liquid UV curable resin 5A shaken off in the outer peripheral direction, a phenomenon occurs in which the dissolved material (organic dye) of the optical recording layer 4 flows out in the outer peripheral direction, and as shown in FIG. When the liquid ultraviolet curable resin 5 </ b> A is cured, an indefinite third layer boundary 10 </ b> A is formed between the optical recording layer 4 and the light transmission layer 5.
That is, there is a problem that the optical recording layer 4 and the light transmission layer 5 are not properly formed, and the recording and reproduction of the pits 13 by the laser light 7 are adversely affected.
[0014]
[Problems to be solved by the invention]
The present invention has been considered in view of the above problems, and is an optical information recording medium having a structure in which recording light or reproduction light is irradiated from the light transmitting layer side, and the optical recording layer is dissolved by the material of the light transmitting layer. It is an object of the present invention to provide an optical information recording medium capable of suppressing the above problem.
[0015]
Another object of the present invention is to provide an optical information recording medium with high reliability by appropriately forming an optical recording layer and a light transmission layer.
[0016]
The present invention also provides an optical information recording medium capable of preventing the optical recording layer from being dissolved and obstructing the formation of the optical recording layer when the light transmission layer is formed by spin coating using an ultraviolet curable resin. This is the issue.
[0017]
[Means for Solving the Problems]
That is, the present invention has focused on selecting a material for a light transmission layer that is less soluble in the optical recording layer, specifically, employing an ultraviolet curable urethane acrylate as the ultraviolet curable resin for the light transmission layer. And a support substrate, an optical recording layer formed on the support substrate, and a light transmission layer formed on the optical recording layer, and irradiating laser light from a main surface on the light transmission layer side. Thus, an optical information recording medium for reproducing or recording information on the optical recording layer, wherein the light transmission layer is composed of an ultraviolet curable urethane acrylate. .
[0018]
The optical recording layer can be composed of an organic dye.
[0019]
The optical recording layer can be composed of a cyanine dye or an azo dye.
[0020]
The light transmission layer can be formed by spin coating.
[0021]
A light reflection layer can be formed between the support substrate and the optical recording layer.
[0022]
In the optical information recording medium according to the present invention, since UV curable urethane acrylate is employed as the UV curable resin of the light transmitting layer, the light recording layer is prevented from being dissolved or eluted by the light transmitting layer. The layer can be appropriately formed.
Therefore, the optical recording layer and the light transmission layer can be formed as designed, and recording and reproduction by laser light irradiation from the light transmission layer side is performed with good reliability, and high-density optical information recording is realized. Can do.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Next, an optical information recording medium 20 according to an embodiment of the present invention will be described with reference to FIGS. However, the same parts as those in FIGS. 7 to 9 are denoted by the same reference numerals, and detailed description thereof will be omitted.
FIG. 1 is a cross-sectional view showing a spin coating process for forming the light transmission layer 5 of the optical information recording medium 20, and FIG. 2 is a cross-sectional view of the optical information recording medium 20 in a state where the spin coating is finished.
As shown in FIG. 2, the optical information recording medium 20 includes a support substrate 2, a light reflecting layer 3, an optical recording layer 4, and a light transmitting layer 5, similarly to the optical information recording medium 1 (FIG. 7) described above. The pregroove 11 and the land 12 are formed on the support substrate 2.
However, an ultraviolet curable urethane acrylate is employed as the liquid ultraviolet curable resin 5A for forming the light transmissive layer 5, and the light transmissive layer 5 is laminated on the optical recording layer 4 by spin coating.
The optical recording layer 4 is preferably a cyanine dye, an azo dye or other organic dye.
[0024]
Further, by making the radii of the support substrate 2 and the light transmission layer 5 larger than the radii forming the light reflection layer 3 and the optical recording layer 4, the support substrate 2 and the light transmission layer 5 are in direct contact with each other at the outer peripheral portion. Thus, the adhesion between the support substrate 2 and the light transmission layer 5 can be enhanced.
[0025]
By using the optical information recording medium 20 having such a configuration, as shown in FIG. 1, even when the liquid ultraviolet curable resin 5A is applied to the optical recording layer 4 and spin-coated, the organic dye in the optical recording layer 4 is in the liquid ultraviolet. It does not dissolve in the cured resin 5A.
Furthermore, if the liquid ultraviolet curable resin 5A is cured by irradiating with ultraviolet rays, the third layer boundary 10 between the optical recording layer 4 and the light transmission layer 5 is clearly formed as shown in FIG. Thus, recording and reproduction with the laser beam 7 can be performed correctly.
[0026]
【Example】
Next, examples of the optical information recording medium according to the present invention will be described.
Example 1
A polycarbonate support substrate 2 having a thickness of 1.1 mm on which the continuous spiral pregroove 11 was formed was molded by an injection molding method. Gold (Au) was sputtered on the support substrate 2 to form a light reflecting layer 3 having a thickness of 100 nm.
On this light reflecting layer 3, as a recording dye, a recording layer coating solution of an organic dye (cyanine dye) having the structure shown in FIG. 3 is spin-coated at a rotation speed of 2000 rpm to form an optical recording layer 4 having a thickness of 50 nm. did.
[0027]
On this optical recording layer 4, as a liquid ultraviolet curable resin 5A, an ultraviolet curable urethane acrylate having the structure shown in FIG. 4 is spin-coated at a rotational speed of 2000 rpm, and cured by irradiating with ultraviolet rays to have a thickness of 100 μm. The light transmission layer 5 was formed to produce an optical information recording medium 20.
There was no omission due to dissolution of the optical recording layer 4 (cyanine dye) at the site where the ultraviolet curable urethane acrylate was disposed, and no discoloration or omission due to dissolution of the optical recording layer 4 was observed at the end of spin coating.
[0028]
With respect to the optical information recording medium 20 thus obtained, writing of the pits 13 was performed as follows.
First, the shortest pit 13 was measured using an optical disk evaluation apparatus (DDU-1000) manufactured by Pulstec Industrial Co., Ltd. equipped with a blue harmonic conversion laser head having a wavelength of 405 nm (numerical aperture NA = 0.85). Was recorded with a laser power of 10 mV. After recording, the signal was reproduced using the same evaluation apparatus with a laser output of 0.5 mV, and the reflectance, error rate, and jitter were measured. As a result, all showed good values.
[0029]
(Example 2)
Instead of the recording dye in Example 1, a recording layer coating solution with an organic dye (azo dye) having the structure shown in FIG. 5 was spin-coated at a rotational speed of 2000 rpm to form an optical recording layer 4. An optical information recording medium 20 was prepared in the same manner as described above.
No dropout due to dissolution of the optical recording layer 4 (azo dye) was observed at the arrangement site of the ultraviolet curable urethane acrylate, and no discoloration or loss due to dissolution of the optical recording layer 4 was observed at the end of spin coating.
As in Example 1, the reflectance, error rate, and jitter were measured and all showed good values.
[0030]
(Example 3)
Instead of the liquid UV curable resin 5A in Example 1, the UV curable urethane acrylate having the structure shown in FIG. 6 was spin-coated at a rotation speed of 2000 rpm to form a light transmission layer 5 having a thickness of 100 nm. An optical information recording medium 20 was produced in the same manner as in Example 1.
There was no omission due to dissolution of the optical recording layer 4 (cyanine dye) at the site where the ultraviolet curable urethane acrylate was disposed, and no discoloration or omission due to dissolution of the optical recording layer 4 was observed at the end of spin coating.
As in Example 1, the reflectance, error rate, and jitter were measured and all showed good values.
[0031]
Example 4
Instead of the liquid ultraviolet curable resin 5A in Example 2, the ultraviolet curable urethane acrylate having the structure shown in FIG. 6 was spin-coated at a rotational speed of 2000 rpm to form a light transmitting layer 5 having a thickness of 100 nm. An optical information recording medium 20 was produced in the same manner as in Example 1.
No dropout due to dissolution of the optical recording layer 4 (azo dye) was observed at the arrangement site of the ultraviolet curable urethane acrylate, and no discoloration or loss due to dissolution of the optical recording layer 4 was observed at the end of spin coating.
As in Example 1, the reflectance, error rate, and jitter were measured and all showed good values.
[0032]
(Comparative example)
In place of the liquid ultraviolet curable resin 5A in Example 1, an ultraviolet curable acrylate resin (SD661, manufactured by Dainippon Ink & Chemicals, Inc.) was spin-coated at a rotational speed of 2000 rpm, and optical recording was performed on the resin arrangement site. Omission due to dissolution of layer 4 (cyanine dye) was observed, and discoloration due to dissolution of the optical recording layer 4 was observed on the entire surface at the end of spin coating.
[0033]
【The invention's effect】
As described above, according to the present invention, since the ultraviolet curable urethane acrylate is adopted as the ultraviolet curable resin for forming the light transmissive layer, the light transmission of the optical recording layer composed of an organic dye such as a cyanine dye or an azo dye is used. Dissolution by the layer was avoided, and an optical information recording medium having good characteristics could be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a spin coating process for forming a light transmission layer 5 in an optical information recording medium 20 according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the optical information recording medium 20 in a state where spin coating has been completed.
3 is a structural formula of an organic dye (cyanine dye) used as a recording dye in Example 1. FIG.
4 is a structural formula of an ultraviolet curable urethane acrylate used as an ultraviolet curable resin in Example 1. FIG.
5 is a structural formula of an organic dye (azo dye) used as a recording dye in Example 2. FIG.
6 is a structural formula of an ultraviolet curable urethane acrylate used as an ultraviolet curable resin in Example 3. FIG.
FIG. 7 is a schematic cross-sectional view showing an example of an optical information recording medium 1 that has been proposed in order to realize high density information recording.
8 is a cross-sectional view showing a spin coating process for forming a light transmission layer 5 in the optical information recording medium 1. FIG.
FIG. 9 is a sectional view showing a state where spin coating is completed.
[Explanation of symbols]
1 Optical information recording medium (Fig. 7)
2 Support substrate 3 Light reflection layer 4 Optical recording layer 5 Light transmission layer 5A Liquid ultraviolet curable resin (head 1, FIG. 8) for forming the light transmission layer 5
6 Objective lens 7 Laser light (recording light, reproduction light)
8 First layer boundary 9 between the substrate 2 and the light reflecting layer 3 Second layer boundary 10 between the light reflecting layer 3 and the optical recording layer 4 Between the optical recording layer 4 and the light transmitting layer 5 Third layer boundary 10A An indefinite third layer boundary between the optical recording layer 4 and the light transmission layer 5 (FIG. 9)
11 Pregroove 12 Land 13 Pit 20 Optical Information Recording Medium (Embodiment, FIG. 2)

Claims (4)

A support substrate;
An optical recording layer formed on the support substrate;
A light transmission layer formed on the optical recording layer,
An optical information recording medium for reproducing or recording information on the optical recording layer by irradiating laser light from the main surface on the light transmitting layer side,
The light transmission layer is composed of an ultraviolet curable urethane acrylate ,
The optical information recording medium , wherein the optical recording layer is composed of an organic dye .     2. The optical information recording medium according to claim 1, wherein the optical recording layer is composed of a cyanine dye or an azo dye.     2. The optical information recording medium according to claim 1, wherein the light transmission layer can be formed by a spin coating method.     The optical information recording medium according to claim 1, wherein a light reflection layer is formed between the support substrate and the optical recording layer.

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