JPH0628717A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To provide the optical information recording medium which is low in cost and high in recording sensitivity and satisfies the requirements specified for CDs. CONSTITUTION:A recording layer 2 consisting of org. dyestuff, a reflection layer 3 and a protective layer 4 are successively laminated on the substrate 1. Al-Ti or Al-Ta is used as the material of the reflection layer 3. An antireflection film 5 is provided on the surface of the substrate 1 opposite from the recording layer 2 in order to prevent the decrease in reflectivity by addition of Ti or Ta.

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 film.

[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, so that it can be reproduced by a commercially available CD player. As one of the methods for realizing such a medium, JP-A-2-
In Japanese Patent No. 42652, 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. Furthermore, Japanese Patent Laid-Open No. 2-13
As described in Japanese Patent No. 2656, by appropriately selecting the complex refractive index and the film thickness of the light absorption layer, the signal after recording can satisfy the CD standard, and the write-once type CD (CD-R) can be obtained.
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 14 on a substrate 11.
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 is low in price, has high recording sensitivity, and satisfies the CD standard.

[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. In the optical information recording medium, a reflective layer is provided on the reflective layer, 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 an Al-Ti alloy, and the substrate is There is provided an optical information recording medium characterized in that an antireflection film is provided on the surface opposite to the recording layer.

According to the present invention, a recording layer is provided on the substrate directly or via another layer, a reflective layer is provided on the recording layer directly or via another layer, and the recording layer is provided on the reflective layer. In an optical information recording medium in which a protective layer is provided if necessary, the recording layer is made of an organic dye, the reflecting layer is made of an Al-Ta alloy, and an antireflection film is provided on a surface of the substrate opposite to the recording layer. An optical information recording medium is provided which is characterized by being 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, as the material of the reflective layer 3, low-priced Al is used instead of Au, and
Has the same thermal conductivity as Au, so Ti or Ta
Is added to Al in a proportion of 0.5 to 10 atm% to reduce thermal conductivity and improve recording sensitivity.
FIG. 3 shows the relationship between the amount of added element and thermal conductivity. From FIG. 3, it can be seen that the thermal conductivity becomes 1/10 and the recording sensitivity is improved by adding 5 atm% of Ti or Ta to Al. Addition amount of Ti or Ta is 0.5 atm%
If it is less than the above range, the thermal conductivity is large, and the prevention of deterioration of the recording sensitivity becomes insufficient. Further, the addition amount of Ti or Ta is 10 at
The reflectance decrease up to m% is at most several%, but the addition amount is 1
If it exceeds 0 atm%, the reflectance is greatly reduced. The reflectance due to the additive elements (Ti, Ta) does not decrease so much and is at most several percent, but the reflectance on the mirror surface of the medium does not satisfy 70% or more of the CD standard depending on the extinction coefficient of the pigment material. Therefore, in the present invention, in order to satisfy the standard, the antireflection film 5 is formed on the laser light incident surface of the substrate 1.
Is provided. The antireflection film 5 has a refractive index of air of 1, a refractive index of the substrate 1 of n ₁ , a refractive index of the antireflection film 5 of n ₂ , a film thickness of the antireflection film 5 of d, and a reproduction wavelength of λ. 1 <n ₂ <n ₁ and d = λ / 4n ₂ are provided. Since the antireflection film 5 is provided on the surface of the substrate, it is desirable that the antireflection film 5 also serves as a hard coat layer. Therefore, materials such as MgF ₂ , CaF ₂ , and organosiloxane are preferably used.

The substrate material that can be used 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 light absorbing layer material usable in the present invention includes cyanine dye, phthalocyanine dye, azurenium dye, squarylium dye, polymethine dye, pyrylium dye, thiopyrylium dye, indoaniline dye, naphthoquinone dye, anthraquinone dye, triallylmethane. Examples thereof include dyes, aminium dyes, diimonium dyes, metal complex dyes, and the like, and mixtures thereof, but are not limited thereto.

[0010]

EXAMPLES Examples of the present invention will be described below.

Example 1 φ46 to φ80 of a polycarbonate substrate of φ120 mm
Using a substrate in which EFM-modulated information pits were formed in the range of mm and guide grooves were formed in the range of φ80 to φ116 mm, a medium was manufactured with the following prescription and configuration. First, using a spinner on the surface opposite to the surface having the guide groove or the information pit of the substrate, as a base layer of the antireflection film, PH
91 (manufactured by Toshiba Silicone Co., Ltd.), and then Tosgard (manufactured by Toshiba Silicone Co., Ltd.) together with the above-mentioned underlayer is about
The thickness was set to 500Å (refractive index of Tosgard = 1.
3). Next, on the surface with the guide groove and the information pit, 2, 2,
1.8% by weight of a cyanine dye represented by the following formula 1 was dissolved in a solvent prepared by adding 5% by weight of 2-methoxyethanol to 3,3-tetrafluoropropanol to obtain a coating liquid.

[Chemical 1]

Using this coating solution, the above substrate of φ38 m
A light absorption layer of about 1000 liters was provided on the entire surface on the outer peripheral side from m by spin coating. On top of that, Ti 5a
Using an Al target containing tm%, a reflective film having a thickness of about 1000 Å was formed by a sputtering method, and a protective layer made of an ultraviolet curable resin was further provided thereon with a thickness of about 3 μm to obtain an optical disk according to the present invention.

Next, with respect to this optical disk, a linear velocity of 1.4
Recording was performed at m / s using a pickup with λ = 780 nm and NA = 0.5. As a result, Au is reflected on the reflective film (10
In comparison with a conventional type optical disc which is used for a thickness of 00 Å) and has no antireflection film, an improvement in sensitivity (recording power of -4% in asymmetry according to the Orange Book standard) of 0.8 mW was observed. The mirror surface reflectance was 73%, which satisfied the CD standard.

Example 2 The same substrate as in Example 1 was used, the same antireflection film and recording layer were provided, and an Al target containing 2% Ta was used to form a reflective film on the same film by sputtering. About 10
The optical disc according to the present invention was provided with a thickness of 00Å and a protective layer similar to that of Example 1. When recording was performed on this optical disc under the same conditions as in Example 1, the sensitivity was improved by 0.6 mW as compared with the conventional type optical disc. The mirror surface reflectance was 76%, which satisfied the CD standard.

[0015]

According to the present invention, the manufacturing cost can be reduced by using Al as a constituent material of the reflective layer instead of expensive Au. Also, Al or Ti or Ta
With the addition of, the thermal conductivity can be lowered and the recording sensitivity can be increased. Further, by providing the antireflection film on the surface of the substrate, it is possible to compensate for the decrease in reflectance due to the use of the Al-Ti or Al-Ta reflective film and satisfy the CD standard.

[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.

FIG. 3 is a diagram showing a change in thermal conductivity when Ti or Ta is added to Al.

[Explanation of symbols]

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

Claims (2)

[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 an Al—Ti alloy, and an antireflection film is provided on the surface of the substrate opposite to the recording layer. Optical recording medium. 2. 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 as necessary. In the optical information recording medium, the recording layer is made of an organic dye, the reflective layer is made of an Al-Ta alloy, and an antireflection film is provided on the surface of the substrate opposite to the recording layer. Optical recording medium.