JPH05325252A - Optical recording medium and its production - Google Patents

Abstract

PURPOSE:To provide DRAW type CD which has a high modulation degree and high recording density and with which good track error signals are obtainable. CONSTITUTION:A light absorption layer 2 is provided directly or via other layer on a substrate 1 on the front surface of which information pits and/or guide grooves are previously formed. A light reflection layer is provided directly or via other layer thereon and further, a protective layer is provided thereon. The light absorption layer is so formed that the real number part (n) and virtual number part (k) of the double refractive indices thereof as well as the film thickness (d) of the light absorption layer satisfy relations 6<n.d/lambda<=1.2, k<=0.3. The information pits and/or guide grooves 3 are so formed that the film thickness of the light absorption layer 2 in the bottoms of the pits or grooves and the film thickness of the light absorption layer 2 in the land parts 4 thereof are approximately equal to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a recording layer composed of a dye coating layer and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, the development of a write-once CD (compact disc) has become active. This is a conventional CD
Unlike the above, the user can record information, and the signal after recording satisfies the standard of the conventional CD and can be reproduced by a commercially available CD player. As one of methods for realizing such a medium, Japanese Patent Laid-Open No. 2-426
In Japanese Patent Laid-Open No. 52-52, it is proposed that a dye is spin-coated on a substrate to provide a light absorbing layer, and a metal reflecting layer is provided behind it. Further, Japanese Patent Application Laid-Open No. 2-126525
By appropriately selecting the complex refractive index and the film thickness of the light absorption layer as described in Japanese Patent Publication No. 6, the signal after recording becomes CD
Now that the standard is satisfied, a write-once CD can be realized.

[0003]

However, although the conventional write-once type CD can obtain a signal satisfying the CD standard, it is still inferior in characteristics such as modulation degree to the conventional read-only CD. Also, a medium having higher recording sensitivity is desired.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made various studies on the write-once CD (Japanese Patent Laid-Open No. 2-42652) having the above-mentioned structure, and as a result, have been disclosed in Japanese Laid-Open Patent No. 2-132656. It was found that a write-once CD having a higher degree of modulation and a higher recording sensitivity than before can be obtained by using a light absorbing layer having a structure different from that of the recording medium, and the present invention has been completed. It was

That is, according to the present invention, a light absorbing layer is provided directly or through another layer on a substrate having information pits and / or guide grooves formed on the surface in advance, and the light absorbing layer is provided directly or otherwise. In the optical recording medium in which the light reflection layer is provided via the layer of, and the protection layer is further provided thereon, the real part n and the imaginary part k of the complex refractive index of the light absorption layer and the film thickness d of the light absorption layer are 0.6 <n · d / λ ≦ 1.2 (where λ is the wavelength of the reproduction light) and k ≦ 0.3, and the light absorption at the bottom of the information pit and / or the guide groove is satisfied. There is provided an optical recording medium, wherein the light absorption layer is formed so that the layer thickness and the light absorption layer thickness of the land portion are substantially the same.

Further, according to the present invention, there is provided an optical recording medium having the above-mentioned constitution, wherein the light absorbing layer contains a dye represented by the following general formula 1.

[Chemical 1]

Further, according to the present invention, there is provided an optical recording medium having the above-mentioned structure, wherein the guide groove depth is 1000 Å or less.

The present invention will be described in detail below. First, a conventional write-once type CD to be compared with the present invention will be described. The conventional write-once type CD has a high reflectance due to the light reflection interference effect of the front and back interfaces of the light absorption layer. The relationship between the thickness of the light absorption layer and the reflectance in this case is as shown in FIG. In the conventional write-once type CD, the value of the range (0.05 ≦ n · d / λ ≦ 0.6) in FIG. 1A is set as the thickness of the light absorption layer capable of obtaining high reflectance. Here, n is the real part of the complex refractive index of the light absorption layer, d is the thickness of the light absorption layer, and λ is the wavelength of the reproduction light. This is for the following reasons. The reflectance satisfying the CD standard can be obtained even in the thickness of the light absorption layer other than the range of (a) in FIG. 1, but the thickness of the light absorption layer is thinner than the range of (a) (n). When d / λ <0.05), the light absorption layer is too thin and thus the recording sensitivity is poor, and the signal change when the light absorption layer is changed by recording is small (the degree of modulation is small).
On the other hand, the range of (c) where the light absorption layer is thick (0.6 <n · d /
At λ), the recording sensitivity is good and the degree of modulation is large. this is,
A part of the heat generated by the light absorption escapes from the light absorption layer to the reflection layer. At this time, the larger the thickness of the light absorption layer, the less heat escapes to the reflection layer, which improves the recording sensitivity. However, in the range of (c), since the light absorption layer is too thick, it is difficult to form a film by coating such as spin coating. Further, when the film is formed by coating, since the light absorption layer is formed in a shape filling the information pit and / or the guide groove as shown in FIG. 2, the track error signal is too small, the polarity is reversed, etc. There is a problem that a proper track error signal cannot be obtained.

Therefore, according to the present invention, the light absorption layer film thickness (0.6 <n · d / λ ≦ 1.2) in the range of FIG. 1C and the imaginary part of the complex refractive index of the optical recording layer are used. By forming the light absorbing layer such that k is 0.3 or less and the thickness of the light absorbing layer at the bottom of the information pit and / or the guide groove and the thickness of the light absorbing layer at the land are substantially the same, To realize a write-once CD that is excellent in recording sensitivity and modulation and can obtain a good track error signal.

In the present invention, a fluorinated alcohol represented by the following general formula 2 and the following general formula are directly or through another layer on a substrate having information pits and / or guide grooves formed on the surface thereof. The solution at the bottom of the information pit and / or the guide groove is formed by spin-coating a solution prepared by dissolving a light absorbing layer material containing a dye as a main component in a solvent containing a mixture with the compound represented by Chemical formula 3 as a main component. The light absorption layer is formed so that the absorption layer film thickness and the land portion light absorption layer film thickness are substantially the same, and the light reflection layer is formed on the light absorption layer directly or through another layer. The optical recording medium as described above is manufactured by a method comprising forming a protective layer on the optical recording medium. As a result, it is possible to manufacture a medium in which the thickness of the light absorbing layer at the bottom of the information pit and / or the guide groove is substantially the same as the thickness of the light absorbing layer at the land, and in which a uniform light absorbing layer is formed.

[Chemical 2]

[Chemical 3]

[Substrate Material Usable] The substrate material usable in the present invention can be arbitrarily selected from the conventional substrate materials for optical recording media. Examples thereof include resin materials such as polycarbonate (PC), polymethylmethacrylate (PMMA), polyvinyl chloride, amorphous polyolefin, epoxy and polyester, and glass. A particularly preferable material is a polycarbonate resin which is excellent in mass productivity by injection molding and has good wettability of a coating solution, fixing property of a dye material, and film forming property.

The depth of the guide groove provided on the substrate is 1000Å
The following are preferred. This is because the reflectance of the write-once portion (guide groove portion) decreases with the depth of the guide groove, and when it exceeds 1000 Å, it becomes difficult to obtain a high reflectance of the CD standard.

[Light Absorbing Layer Material Usable] As the light absorbing layer material usable in the present invention, cyanine dye, phthalocyanine dye, azurenium dye, squarylium dye, polymethine dye, pyrylium dye, thiopyrylium dye, indoaniline dye, Examples thereof include, but are not limited to, naphthoquinone dyes, anthraquinone dyes, triallylmethane dyes, aminium dyes, diimonium dyes, metal complex dyes, and the like, and mixtures thereof. Particularly preferable materials include cyanine dyes represented by the following general formula 1.

[Chemical 1] When the material containing the cyanine dye represented by the above general formula 1 is used as the light absorbing layer material, the thickness of the light absorbing layer at the bottom of the information pit and / or the guide groove and the thickness of the light absorbing layer at the land are substantially the same. The effect of forming the recording layer so that

The complex refractive index and the film thickness of the light absorption layer are 0.6.
<N · d / λ ≦ 1.2 and k ≦ 0.03 is satisfied. n · d / λ is particularly preferably near the second reflection peak in FIG. 1 where the highest reflectance is obtained. n · d / λ is 0.6
If it becomes smaller, the recording sensitivity becomes worse and the modulation degree becomes smaller. On the other hand, when n · d / λ is larger than 1.2, it becomes difficult to obtain a high reflectance of 70% or more. Even when the imaginary part k of the complex refractive index of the light absorption layer is larger than 0.03, it becomes difficult to obtain high reflectance. Even if the thickness of the light absorption layer at the bottom of the information pit and / or the guide groove and the thickness of the light absorption layer at the land are different, the difference is at most about 300Å (λ / 10m)
Try to stay within.

[Solvent] The ratio of the compound (general formula 3) to the fluorinated alcohol (general formula 2) in the coating mixed solvent used for preparing the optical recording medium of the present invention is 2 to 30.
wt% is preferred. If the ratio of the compound (Formula 3) is out of this range, the dye is likely to crystallize.

[Reflective Layer] The reflective layer is preferably formed using gold, silver, aluminum or an alloy thereof.

[0017]

EXAMPLES The present invention will now be described in more detail by way of examples.

Example A disk substrate having a guide groove having a width of about 0.3 μm and a depth of about 400 Å on the surface of a polycarbonate disk having a diameter of 120 mm was prepared. On the other hand, a cyanine dye (n≈2.6, k≈0.05) represented by the following general formula 4 is added to a solvent prepared by adding 8 wt% of 2-methoxyethanol to 2,2,3,3-tetrafluoropropanol. 4 wt% was dissolved to obtain a coating liquid.

[Chemical 4] A light absorption layer was provided on the above substrate by spin coating using this coating solution. The film thickness of the light absorption layer was about 2700Å at both the land and the bottom of the groove. N ・ d / λ
= 0.9. Next, deposit about 100 gold on the light absorption layer.
An optical recording medium was prepared by providing a reflective layer having a thickness of 0Å and further providing a protective layer made of an ultraviolet curable resin on the reflective layer to a thickness of about 5 μm, and used as a medium of an example of the present invention.

This medium has a wavelength of 782 nm and NA 0.
With the semiconductor laser light of No. 5, the CD format signal was recorded and reproduced under the condition of the linear velocity of 1.3 m / s, and the reflectance (I
g), modulation degree (I ₁₁ / Itop), optimum recording power (P
₀ ) was measured. The results are shown in Table 1.

[0020]

[Table 1]

Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1 except that only 2,2,3,3-tetrafluoropropanol was used as the solvent for the coating liquid, and the medium was used as Comparative Example 1. ..
The thickness of the light absorption layer of this medium is about 2500
Å, the bottom of the groove was about 2900Å. Also, n · d / λ ≈
It was 0.9. When this medium was measured in the same manner as the medium of the above example, the results are shown in Table 1.

Comparative Example 2 In the above example, the amount of cyanine dye dissolved was 1.8.
An optical recording medium was prepared in the same manner as the medium of Comparative Example 2 except that the coating liquid was changed to wt%. The thickness of the light absorption layer of this media is about 1 for both the land and the bottom of the groove.
It was 300Å. Also, n · d / λ≈0.43. When this medium was measured in the same manner as in the above example, the results are shown in Table 1.

As is clear from Table 1, the media of the examples of the present invention have a higher degree of modulation than the media of Comparative Examples 1 and 2.
High recording sensitivity and a good track error signal can be obtained. In Table 1, the track error signal of the medium of Comparative Example 1 was 1/3 or less of that of the other media, and tracking was impossible.

[0024]

As described above in detail, according to the present invention, it is possible to provide a write-once type CD which has a higher degree of modulation and a higher recording sensitivity than the conventional one and can obtain a good track error signal. I can.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a film thickness of a light absorption layer and reflectance, transmittance, and absorptance.

2A is a diagram showing a state of a light absorbing layer of a conventional optical recording medium, and FIG. 2B is a diagram showing a state of a light absorbing layer of the optical recording medium of the present invention.

[Explanation of symbols]

 1 substrate 2 light absorption layer 3 guide groove 4 land portion

Claims (4)

[Claims] 1. A light absorbing layer is provided directly or via another layer on a substrate having information pits and / or guide grooves formed on its surface, and a light absorbing layer is provided thereon directly or via another layer. In an optical recording medium having a reflective layer and a protective layer provided thereon, the real part n and the imaginary part k of the complex refractive index of the light absorption layer and the light absorption layer film thickness d are 0.6 <n.
D / λ ≦ 1.2 (where λ is the wavelength of the reproduction light), k ≦
The light absorbing layer is formed such that the relationship of 0.3 is satisfied and the thickness of the light absorbing layer at the bottom of the information pit and / or the guide groove and the thickness of the light absorbing layer at the land are substantially the same. An optical recording medium characterized by being provided. 2. The optical recording medium according to claim 1, wherein the light absorbing layer contains a dye represented by the following general formula 1. [Chemical 1] 3. The optical recording medium according to claim 1, wherein the guide groove depth is 1000 Å or less. 4. A fluorinated alcohol represented by the following general formula 2 and a general formula 3 below on a substrate having information pits and / or guide grooves formed on the surface thereof directly or through another layer. The light absorbing layer film at the bottom of the information pit and / or the guide groove is formed by spin-coating a solution prepared by dissolving a light absorbing layer material containing a dye as a main component in a solvent containing a mixture with a compound represented by The light absorbing layer is formed so that the thickness and the thickness of the light absorbing layer in the land portion are substantially the same, and the light reflecting layer is formed on the light absorbing layer directly or through another layer, and the protective layer is further formed on the light reflecting layer. 4. The method for manufacturing an optical recording medium according to claim 1, which comprises forming a film. [Chemical 2] [Chemical 3]