JPH11167748A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium which has reflectivity satisfying CD standards, is excellent in an adhesion property between a reflection layer and a recording layer, durability and weatherability and has high reliability. SOLUTION: Org. dyestuffs of a cyanine system are applied by spin coating on a polycarbonate substrate 1 to form a recording layer 2 of a film thickness 700 (5) and a dielectric layer (intermediate layer) 3 consisting of SiO2 is formed thereon by sputtering to a film thickness 1200 Å. Further, a silver film is formed as a lower reflectmon layer 4a on thus dielectric layer 3 to a film thickness 500 Å and a gold film is formed as an upper reflection layer 4b thereon to a film thickness 500 Å, respectively and thereafter, a protective layer 5 is disposed thereon, by which the CD is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a recording layer on a substrate,
The present invention relates to an optical information recording medium in which an intermediate layer, a reflective layer, and a protective layer (protective film) are formed in this order.

[0002]

2. Description of the Related Art Optical information recording media, such as CDs (Compact Discs), have become widespread throughout the world. In recent years, write-once CDs (CD-Recordable) have been actively developed, and have been spreading rapidly. With this write-once CD, data (information) that the user likes can be written using a commercially available writer.
It can be played back with a D player.

In order to enable recorded data to be reproduced by all CD players, a CD (hereinafter, referred to as a CD) is required.
Media) may satisfy the CD standard. In order to make the CD conform to the CD standard, the write-once CD needs to have a high reflectance. In addition, durability to enable long-term storage,
It is important to have excellent weather resistance and maintain the reliability of information.

As an optical information recording medium conforming to the CD standard,
There is known a structure in which a recording layer (dye layer), a reflective layer, and a protective layer are formed in this order on a transparent substrate, and the reflective layer is directly adhered to the recording layer. In this optical information recording medium, a reflective layer of gold (Au) is used because the reflectivity of an aluminum reflective layer used in a normal CD is insufficient. Gold has high reflectivity and excellent corrosion resistance. However, since it is expensive, use of a high-reflectivity metal other than gold and inexpensive, such as copper or a copper alloy, has been considered.

However, when copper or a copper alloy is used for the reflective layer, a reaction with a constituent material of the reflective layer causes deterioration of a dye and a decrease in output of a recording signal, so that sufficient reliability cannot be obtained. In particular, copper has a problem in that it is liable to undergo a chemical reaction with a cyanine dye preferably used for the recording layer, and the dye in the recording layer is liable to be deteriorated under high temperature and high humidity.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to improve the adhesiveness between the reflective layer and the recording layer, the durability and the weather resistance so that the reflectivity satisfies the CD standard. An object of the present invention is to provide an optical information recording medium having excellent and high reliability.

[0007]

According to the optical information recording medium of the present invention, a recording layer mainly composed of an organic dye material is formed on a substrate, and a reflective layer and a protective layer are formed thereon in this order. In the optical information recording medium, the reflective layer is made of silver, and an intermediate layer made of an inorganic dielectric material is provided between the reflective layer and the recording layer.

An optical information recording medium according to claim 2, wherein a recording layer mainly composed of an organic dye material is formed on a substrate, and a reflective layer and a protective layer are formed thereon in that order. Wherein the reflective layer comprises a silver reflective layer on the recording layer side and a gold reflective layer on the protective layer side, and an intermediate layer made of an inorganic dielectric material is provided between the silver reflective layer and the recording layer. It is characterized by having.

According to a third aspect of the present invention, in the optical information recording medium according to the first or second aspect, the intermediate layer is made of Al ₂ O ₃ , SiNx.
(X is 1 or more and 2 or less), SiOx (X is 1 or more and 2 or less), Si ₂ O ₃ , CaF ₂ , MgF ₂ , BiF ₃ , C
It is made of one or more inorganic dielectric materials arbitrarily selected from the group consisting of eF ₃ , LaF ₃ and LiF.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The optical information recording medium of the present invention will be specifically described below. The CD shown in FIG. 1 has a recording layer 2 composed mainly of an organic dye material, an intermediate layer 3 composed of an inorganic dielectric material, a reflective layer 4 composed of a thin film of silver (Ag), and a protective layer 5 on a substrate 1. In this order.

The CD shown in FIG. 2 has a recording layer 2 mainly composed of an organic dye material, an intermediate layer 3 composed of an inorganic dielectric material, a lower reflective layer 4a composed of a thin silver film, a gold ( A
The upper reflective layer 4b and the protective layer 5 are formed in this order. In this CD, a reflection layer 4 is formed by a lower reflection layer 4a and an upper reflection layer 4b.

By the way, in the conventional optical information recording medium, as a material of the reflection layer, gold having high reflectance and excellent corrosion resistance has been used.

However, as shown in FIG. 3, at the CD reproduction wavelength (780 nm), silver has a higher reflectance than gold. FIG. 3 shows a gold film having a thickness of 1000 on a plastic plate.
A silver film was formed on a plastic plate with a film thickness of 10
10 is a graph showing the results of examining the relationship between the wavelength of irradiation light and the reflectance for a sample formed at 00 °. Also, although the corrosion resistance of silver is not as good as gold, it is far superior to copper and the like, and is less expensive than gold. Therefore, as shown in FIG. 1, by providing the reflection layer 4 made of silver, an optical information recording medium having excellent durability and weather resistance can be provided at a relatively low price.

Further, in the optical information recording medium of FIG. 1, since an intermediate layer made of a dielectric material is formed, by setting the thickness of the intermediate layer to an appropriate value, the reflectivity of the medium can be made extremely high. can do. Furthermore, the interposition of the intermediate layer improves the adhesion (indirect adhesion) between the recording layer and the reflective layer, thereby preventing a decrease in media reliability due to separation between the recording layer and the reflective layer. In addition, the silver in the reflective layer can be protected from water, oxygen, corrosive gas and the like entering from the substrate side, and the durability and weather resistance of the media are improved.

On the other hand, in the optical information recording medium shown in FIG. 2, the reflective layer 4 is formed by an upper reflective layer 4b made of gold on the protective layer 5 side and a lower reflective layer 4a made of silver on the recording layer 2 side. I have. For this reason, even if the lower reflective layer 4a has a defect,
This can be protected by the upper reflective layer 4b, and the upper reflective layer 4b has almost the same reflectance as the lower reflective layer 4a. Therefore, the reflective layer 4 has no problem in durability and reflectance.

FIG. 4 is a graph qualitatively showing the relationship between the thickness of the recording layer before data recording and the reflectance and absorptance of the medium. This graph shows the film thickness of the recording layer 2 when the film thickness of the dielectric layer (intermediate layer) 3 is fixed to a certain value, and the reflectance and absorptance of the medium in the optical information recording medium of FIG. This is the result of examining the relationship. In the case of media, the sum of the reflectance and the absorptance is 100%,
The light transmittance is zero. From this graph, it can be seen that there is a recording layer thickness at which the reflectance has a maximum value. It has also been confirmed that, when the thickness of the dielectric layer is changed, the thickness of the recording layer at which the reflectance takes the maximum value changes accordingly.

FIG. 5 is a graph qualitatively showing the relationship between the thickness of the dielectric layer before data recording and the reflectance and absorptance of the medium. This graph shows the film thickness of the dielectric layer (intermediate layer) 3 when the film thickness of the recording layer 2 is fixed to a certain value, and the reflectance and absorptance of the medium in the optical information recording medium of FIG. This is the result of examining the relationship. From this graph, it can be seen that there is a dielectric layer film thickness at which the reflectance has a maximum value. It has been confirmed that, when the film thickness of the recording layer is changed, the film thickness of the dielectric layer at which the reflectance takes the maximum value changes accordingly.

As described above, since the reflectance changes depending on the thickness of the recording layer and the thickness of the dielectric layer, the reflectance can be maximized by setting these to appropriate values.
In addition, in the formation of the recording layer, usually, a method of performing dye coating by spin coating is adopted.However, by setting the dielectric layer film thickness to an appropriate value, while keeping the reflectance of the medium at the maximum value, The coating thickness of the dye can be increased. By increasing the coating film thickness, the dye coating becomes easier.

[0019]

Next, an embodiment of the present invention will be described. Example 1 A cyanine-based organic dye was applied on a polycarbonate substrate by spin coating to a thickness of 700 °.
On this recording layer, SiO ₂ was formed as a dielectric layer (intermediate layer) to a thickness of 1200 ° by sputtering. Further, on this dielectric layer, a silver film having a thickness of 500 was formed as a lower reflective layer.
Then, a gold film was formed to a thickness of 500 ° as an upper reflective layer, and then a protective layer was provided to form a CD [Disc (1)].

Comparative Example 1 Only a gold film was formed as a reflective layer directly on a recording layer to a thickness of 500 Å.
A CD was prepared in the same manner as in Example 1 except that the disk was formed (without a dielectric layer) [Disk (2)].

Comparative Example 2 A silver film alone was formed directly on a recording layer as a reflective layer to a thickness of 500 Å.
A CD was prepared in the same manner as in Example 1 except that the disk was formed (without a dielectric layer) [Disk (3)].

For the discs (1) to (3), writing is performed with an actual machine writer (RS1060C × 2 light).
An Rtop measurement and a storage test (C1 error measurement) were performed. In the Rtop measurement, the reflectance of the medium after data recording when the signal amplitude reaches the maximum value is measured in accordance with the CD standard. The C1 error measurement is carried out at the initial stage (media before storage) and after recording data for 400 hours at a temperature of 80 ° C. and a humidity of 85%.
It is a measure of the accuracy of the reproduction. [Table 1]
Shown in

[0023]

[Table 1]

From Table 1, it can be seen that the reflectance, durability, and weather resistance of the CD of Example 1 are improved as compared with the CDs of Comparative Examples 1 and 2.

[0025]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) Claim 1 In this optical information recording medium, since the reflection layer is formed of a silver film, the CD has a higher reflectance than that of a conventional optical information recording medium provided with a reflection layer of a gold film. Further, it is possible to provide a CD excellent in durability and weather resistance as compared with a conventional CD using a reflection layer of copper or a copper alloy. Further, since silver is cheaper than gold, the CD of the present invention can be provided at a lower cost than that provided with a gold reflective film.

Further, in the CD of the present invention, since an intermediate layer made of an inorganic dielectric material is provided between the reflective layer and the recording layer, by setting the thickness of the intermediate layer to an appropriate value. , The reflectivity of the CD can be maximized.

Furthermore, the interposition of the intermediate layer improves the adhesion (indirect adhesion) between the recording layer and the reflection layer, and thus lowers the reliability of the CD due to separation between the recording layer and the reflection layer. Is prevented, and silver in the reflective layer can be protected from water, oxygen, corrosive gas and the like entering from the substrate side, and the durability and weather resistance of the CD are improved.

(2) Claim 2 In this optical information recording medium, the reflection layer is composed of the silver reflection layer on the recording layer side and the gold reflection layer on the protective layer side. The resulting CD has a higher reflectivity than the provided optical information recording medium. Further, a CD excellent in durability and weather resistance can be provided relatively inexpensively as compared with a conventional CD using a reflection layer of copper or a copper alloy.

Further, since an intermediate layer made of an inorganic dielectric material is provided between the silver reflective layer and the recording layer, even if the lower reflective layer (silver film) has a defect, the upper reflective layer can be used. Since this can be protected, water entering from the protective layer side,
Silver in the reflective layer can be protected from oxygen, corrosive gas, and the like, and the durability and weather resistance of the CD are improved. Further, in the CD of the present invention, the reflectance of the CD can be maximized by setting the thickness of the intermediate layer made of the inorganic dielectric material to an appropriate value.

Further, the interposition of the intermediate layer improves the adhesion between the recording layer and the reflective layer, thereby preventing a decrease in the reliability of the CD due to separation between the recording layer and the reflective layer.

(3) Claim 3 In this optical information recording medium, since a predetermined material is used as the inorganic dielectric material, a CD having the above characteristics without adversely affecting the organic dye in the recording layer is provided. can do.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an optical information recording medium of the present invention.

FIG. 2 is a sectional view showing another example of the optical information recording medium of the present invention.

FIG. 3 is a graph showing a comparison between the reflectance of gold and the reflectance of silver.

FIG. 4 is a graph showing the relationship between the thickness of a recording layer and the reflectance and absorptance of a CD (before data recording) when the thickness of a dielectric layer is constant.

FIG. 5 is a graph showing the relationship between the thickness of a dielectric layer and the reflectivity and absorptance of a CD (before data recording) when the thickness of a recording layer is constant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording layer (dye layer) 3 Intermediate layer (dielectric layer) 4 Reflective layer 4a Lower reflective layer 4b Upper reflective layer 5 Protective layer

Claims (3)

[Claims] 1. An optical information recording medium comprising: a recording layer mainly composed of an organic dye material formed on a substrate; and a reflective layer and a protective layer formed thereon in this order. An optical information recording medium, wherein an intermediate layer made of an inorganic dielectric material is provided between the reflection layer and the recording layer. 2. An optical information recording medium comprising a recording layer mainly composed of an organic dye material formed on a substrate, and a reflective layer and a protective layer formed thereon in this order. Optical information recording, comprising an intermediate layer made of an inorganic dielectric material between the silver reflective layer and the recording layer. Medium. 3. The method according to claim 1, wherein the intermediate layer is made of Al.
₂ O ₃ , SiNx (X is 1 or more and 2 or less), SiOx
(X is 1 or more and 2 or less), Si ₂ O ₃ , CaF ₂ , Mg
_{F 2, BiF 3, CeF 3} , LaF 3 and an optical information recording medium, characterized in that from the group consisting of LiF it is made of one or more inorganic dielectric material selected arbitrarily.