JPH0628716A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To provide the optical information recording medium which satisfies the requirements specified in CD standard, has reliability and is low in production cost by using Al for the material of a reflection layer and providing antireflection layers on the surface of a substrate opposite recording layer. CONSTITUTION:The recording layer 12 consisting of org. dyestuff, the reflection layer 13 and a protective layer 14 are successively laminated on the substrate 11. Al is used as the material of the reflection layer 13 and at least one layer of the antireflection films 5 are provided on the surface of the substrate 11 on the side opposite the recording layer 12 in order to make up the decrease in the reflectivity of the mirror surface by the Al. The film thicknesses of the respective layers of the antireflection films are set at lambda/4n thickness when a refractive index is designated as (n) and a reproducing wavelength as lambda. The optical information recording medium which meets the requirement specified in CD standard and is low in cost is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium having a recording layer made of an organic dye.

[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 recorded signal can be reproduced by a commercially available CD player because it satisfies the conventional CD standard. As one of the methods for realizing such a medium, JP-A-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 Laid-Open No. 13265/1990
By appropriately selecting the complex refractive index and the film thickness of the light absorbing layer as described in Japanese Patent No. 6, the signal after recording is CD
Now that the standard is satisfied, a write-once CD can be realized.

[0003]

In these prior arts, it is common to use an Au film as a reflective layer in order to satisfy the CD standard, and in particular to set the mirror surface reflectance to 70% or more. FIG. 1 shows a conventional optical information recording medium (CD-
R) An example is shown. This medium comprises a recording layer 12 made of an organic dye, a reflective layer 13 made of Au, and a protective layer 1 on a substrate 11.
4 is provided. However, since Au is expensive, the final media price is expensive. Moreover, since the thermal conductivity of Au is very high, most of the writing energy of the laser at the time of additional recording diffuses through Au, which has the drawback of deteriorating the recording sensitivity.

An object of the present invention is to provide an optical information recording medium which satisfies the CD standard, is reliable, and has a low manufacturing cost.

[0005]

In order to achieve the above object, according to the present invention, a recording layer is provided on a substrate directly or via another layer, and the recording layer is provided directly or via another layer. An optical information recording medium in which a reflective layer is provided, and a protective layer is optionally provided on the reflective layer, the recording layer is made of an organic dye, the reflective layer is made of Al, and An optical information recording medium characterized in that at least one antireflection film is provided on the opposite surface, and when the refractive index of each layer is n and the reproduction wavelength is λ, the film thickness of each layer is λ / 4n. Will be provided.

The optical information recording medium of the present invention will be described in detail below. FIG. 2 is a cross-sectional view of a constitutional example of an optical information recording medium according to the present invention, in which a recording layer 2 made of an organic dye is formed on a substrate 1.
The reflective layer 3 and the protective layer 4 are sequentially stacked and the substrate 1
The antireflection film 5 is provided on the surface opposite to the recording layer 2. In the present invention, a low cost Al is used as the material of the reflective layer 3 in place of Au to reduce the manufacturing cost. However, when Al is used as the reflective layer 3, the CD may be changed depending on the optical constant and film thickness of the organic dye used in the recording layer 2.
It may happen that the standard condition of the mirror surface reflectance of 70% or more is not satisfied. Further, generally, the reflected light on the incident surface of the convergent light reflected from the pickup of the optical disk drive hardly returns to the pickup, which reduces the reflectance of the disk. Therefore, in the present invention, this problem is solved by providing the antireflection film 5 on the surface of the substrate 1 opposite to the recording layer 2.

The antireflection film 5 may be of a single-layer type or a multi-layer type, but a single-layer type or a double-layer type is advantageous for manufacturing reasons. Regardless of whether the antireflection film 5 is a single layer type or a multilayer type, the thickness of each layer is set to be λ / 4n, where n is the refractive index of each layer and λ is the reproduction wavelength. The prevention effect is increased. For example, in the case of a single layer, the substrate reflectance R is R when the refractive index of the substrate 1 is n _{0.
^{= (N 0 -n 2) 2}} / (n 0 + n 2) is ^2, and R = 0 when n = √n _0. When the substrate material is polycarbonate, since n ₀ = 1.58, it is preferable to use a material having n = 1.26 as the antireflection film material. Materials satisfying this are MgF ₂ (n≈1.38), C
There are aF ₂ (n≈1.25) and organosiloxane (n≈1.3). When these are used, the substrate reflectances are about 0.9%, 0.006% and 0.1%, respectively. Become.
The former two are formed by vapor deposition or sputtering. The latter is formed by a spinner.

When the antireflection film 5 has two layers, the substrate reflectance R is R = (n ₂₎ , where n _{1 is} the refractive index of the first layer and n ₂ is the refractive index of the second layer from the laser light incident side. ^2- n ₀ n ₁ ² ) ² / (n
₂ ² + n ₀ n ₁ ² ) ² and when n ₀ = (n ₂ / n ₁ ) ² R =
Since the value is 0, it is preferable to use a material having a refractive index near n ₁ and a material having a refractive index near n ₂ satisfying the relationship of n ₂ / n ₁ = √1.58. When Al ₂ O ₃ (n ₁ ≈1.63) is used for the first layer, SiO (n ₂ ≈2.0), ZnO ₂ (n ₂
≈2.1) or Ta ₂ O ₅ (n ₂ ≈2.16) are preferred. When these are used, the substrate reflectance is about 0.00 each.
It becomes 3%, 0.19%, and 0.5%. SiO _{2 for} the first layer
When (n ₁ ≈1.46) is used, MgO (n ₂ ≈1.7) and Y ₂ O ₃ (n ₂ ≈1.8) are used as the second layer material.
2) is preferred. When these are used, the substrate reflectances are about 0.6% and 0.007%, respectively. MgF _{2 on} the first layer
When (n ₁ ≈1.38) is used, MgO (n ₂ ≈1.7), Al ₂ O ₃ (n ₂ ≈1.6) are used as the second layer material.
3) or CeF ₃ (n ₂ ≈1.6) is preferable. When these are used, the substrate reflectances are about 0.04% and 0.4, respectively.
% And 0.65%. The substrate reflectance is a calculated value. The film made of each of the above materials is formed by vapor deposition or sputtering.

The substrate material usable in the present invention can be arbitrarily selected from conventional substrate materials for optical recording media. For example,
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, fixability of a dye material, and film forming property.

The dye materials usable in the present invention include cyanine dyes, phthalocyanine dyes, azurenium dyes, squarylium dyes, polymethine dyes, pyrylium dyes, thiopyrylium dyes, indoaniline dyes, naphthoquinone dyes, anthraquinone dyes, triallylmethane dyes, Examples thereof include, but are not limited to, aminium dyes, diimonium dyes, metal complex dyes, and the like, and mixtures thereof.

[0011]

EXAMPLES Next, examples of the present invention will be described.

EXAMPLE 1 φ120 mm polycarbonate substrate φ46-80 m
Information pits modulated by EFM are formed in the range of m,
Using a substrate having guide grooves formed in φ80 to φ116 mm, a medium was manufactured with the following prescription and constitution. First, R on the surface opposite to the surface where the guide groove and the information pit of the substrate are located.
An antireflection layer of MgF ₂ was provided by F sputtering to a thickness of about 1400Å. Next, put 2,2,3,3-tetrafluoropropanol on the surface of the substrate where the guide groove and the information pit are located.
1.8% by weight of a cyanine dye (Japan photosensitive dye NK2929) was dissolved in a solution containing 5% by weight of methoxyethanol to prepare a coating solution, and a light absorbing layer was formed by spinner on the entire surface on the outer peripheral side of φ38 mm of the surface. It was set to a thickness of 1200Å. Further, an Al reflection layer having a thickness of about 1000 Å was formed thereon by a sputtering method, and a protective layer made of an ultraviolet curable resin was further formed thereon to a thickness of about 3 μm to obtain an optical disk according to the present invention. The reflectance of the mirror surface of this optical disc and the reflectance of the space portion of the 11T signal in the information pit portion are λ.
= 780 nm, NA = 0.45, and the CD standard was satisfied.

Example 2 φ120 mm polycarbonate substrate φ46-80 m
Information pits modulated by EFM are formed in the range of m,
Using a substrate having guide grooves formed in φ80 to φ116 mm, a medium was manufactured with the following prescription and constitution. First, R on the surface opposite to the surface where the guide groove and the information pit of the substrate are located.
The ZrO ₂ film is provided to a thickness of about 930Å by the F sputtering method,
Next, the Al ₂ O ₃ film is also deposited by the RF sputtering method at about 1200 Å
The anti-reflective film was formed with the thickness of 1. Next, a cyanine dye (Nippon Photosensitive Dye NK2929) was added to a solution prepared by adding 5% by weight of 2-methoxyethanol to 2,2,3,3-tetrafluoropropanol on the surface of the substrate having the guide groove and the information pit.
Of 1.8% by weight to form a coating solution, and the surface has a diameter of 38 mm.
A spinner is used to cover the entire surface on the outer peripheral side with a light absorption layer of about 12
It was set to a thickness of 00Å. Further, an Al reflection layer having a thickness of about 1000 Å was formed thereon by a sputtering method, and a protective layer made of an ultraviolet curable resin was further formed thereon to a thickness of about 3 μm to obtain an optical disk according to the present invention. The reflectance of the mirror surface of this optical disc and the reflectance of the space portion of the 11T signal in the information pit portion were 76% using a pickup with λ = 780 nm and NA = 0.45, which satisfied the CD standard.

[0014]

According to the invention of claim 1, the reflective film is formed of Al.
Despite the use of the above, since an antireflection film is provided on the reproduction light incident surface, a mirror reflectance of 70% or more can be obtained, and an optical information recording medium satisfying the CD standard and having a low manufacturing cost is provided. it can. According to the second aspect of the present invention, Al is used for the reflection film, and a single layer M is used as the antireflection film.
Since the gF ₂ film or the CaF ₂ film is used, a mirror reflectance of about 75% can be obtained, and an optical information recording medium satisfying the CD standard and having a low manufacturing cost can be provided. According to the invention of claim 3, since the reflective film is made of Al and the single-layer organosiloxane film is used as the anti-reflective film, the anti-reflective film can also serve as a hard coat layer and can be applied by a spinner. Because it is possible to reduce the manufacturing cost, C
An optical information recording medium satisfying the D standard can be provided. According to the invention of claim 4, since Al is used for the reflection film, a two-layer film is used as the antireflection film, and the first layer and the second layer are a combination of specific materials, the antireflection film is a hard coat. Since it has a function as a layer and can be formed by the sputtering method, the film thickness control accuracy is good, the reflectance control accuracy is good, the anti-reflection film function is sufficient, and the CD standard is satisfied and the reliability is high. It is possible to provide a high-quality optical information recording medium.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer configuration example of a conventional optical information recording medium.

FIG. 2 is a cross-sectional view showing an example of the layer structure of the optical information recording medium of the present invention.

[Explanation of symbols]

 1 substrate 2 recording layer 3 reflective layer 4 protective layer 5 antireflection film

Claims (4)

[Claims] 1. A recording layer is provided on a substrate directly or via another layer, and a reflective layer is provided on the recording layer directly or via another layer, and a protective layer is provided on the reflective layer if necessary. In the optical information recording medium, the recording layer is made of an organic dye, the reflective layer is made of Al, and at least one antireflection film is provided on the surface of the substrate opposite to the recording layer, and the refractive index of each layer is Is n and the reproduction wavelength is λ, the thickness of each layer is λ / 4n. 2. MgF ₂ or C as the antireflection film
The optical information recording medium according to claim 1, wherein a single layer film made of aF ₂ is provided. 3. The optical information recording medium according to claim 1, wherein a single layer film made of organopolysiloxane is provided as the antireflection film. 4. The following (A) to (11) as the antireflection film:
The optical information recording medium according to claim 1, further comprising a two-layer film made of any combination of (C). When the first layer and the second layer are formed from the reproduction light incident side, (A) the first layer is Al ₂ O ₃ and the second layer is SiO, ZrO ₂
Alternatively, Ta ₂ O ₅ (B) first layer is SiO ₂ , second layer is Y ₂ O ₃ or MgO (C) first layer is MgF ₂ , and second layer is MgO, Al ₂ O ₃
Or CeF ₃