JPH0765413A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having high durability and safety by forming an Ag or Ag alloy reflecting layer and forming a recording layer containing a cyanine dye of specified compsn. CONSTITUTION:This information recording medium 1 has a light-transmitting recording layer 12 on a substrate 11 and has a reflecting layer 13 on the recording layer 12. The reflecting layer 13 on the recording layer 12 formed on the substrate 11 consists of Ag or Ag alloy. Further, the recording layer 12 contains at least one kind of cyanine dye selected from among cyanine dyes expressed by formula I. In formula I, R1, R2 are alkyl groups of 3-8 carbon number, R3-R6 are alkyl groups of l-8 carbon number or aryl groups of 6-10 carbon number, X<-> is a counter anion except for single halogen ions, (n) is an integer >=2, and A, A' are substd. or unsubstd. benzene rings or condensed benzene ring residues. Since Ag is used for the reflecting layer instead of Au, the production cost is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium such as an optical disk, and more particularly to a writable write-once type information recording medium having a recording layer and a light reflecting layer on a light transmitting substrate.

[0002]

2. Description of the Related Art As an information recording medium such as an optical disk,
A compact disc called a so-called CD
ROM (read only memor) where data is recorded in advance
The y) type medium exists and is widely used in the fields of voice recording and information processing. In a CD, pre-pits corresponding to the data to be reproduced are already formed on a plastic substrate by injection molding, a reflective layer made of metal such as A1 is formed thereon, and a protective layer is further formed thereon. ing. The specifications of the recording and reading signals of this CD have been standardized, and in accordance with this standard, a CD reproducing device is widely used as a compact disc player (CD player).

By the way, in conformity with the standard of the CD specification, the CD
A writable information recording medium that can be used as it is for a player is a so-called CD-R, and has a recording layer formed on a substrate as a light absorbing layer that absorbs light, and a reflective layer formed on the recording layer. have. It is generally well known that, for example, a cyanine dye having halogen as a counter anion is used for a recording layer of a CD-R, and Au having a high reflectance and durability is used as a reflective film.

As a method of writing on such an information recording medium, a laser beam is focused on a very small area of the recording layer, converted into thermal energy, and the properties of the recording layer are changed to perform recording (black pit formation). )It is carried out. A laser beam for writing used in such a type of information recording medium is irradiated from the transparent substrate side to form an optically readable pit in the recording layer. The reading laser beam for reproducing the recorded data has a weaker output than that for writing, and the contrast between the portion where the pit is formed and the portion where the pit is not formed is read as an electric signal.

[0005]

However, when Au is used as the reflective film, the cost becomes high. An object of the present invention is to solve the above problems and provide a writable information recording medium having excellent durability.

[0006]

The information recording medium of the present invention is an information recording medium having a substrate, a recording layer formed on the substrate, and a reflective layer formed on the recording layer. The reflective layer is made of Ag or an Ag alloy, and the recording layer has the following chemical formula 1.

[0007]

[Chemical 2]

(In the formula 1, R ₁ and R ₂ are each an alkyl group having 3 to 8 carbon atoms, and R _{3 to} R ₆ are each 1 to 8 carbon atoms.
Alkyl group or aryl group having 6 to 10 carbon atoms, X ⁻ is a counter anion excluding a single halogen ion, n is an integer of 2 or more, and A and A ′ are a substituted or unsubstituted benzene ring or a condensed benzene ring residue. Group) and at least one cyanine dye selected from the group consisting of cyanine dyes represented by

[0009]

When Ag, which has the same reflectance as Au, is used in the reflective layer instead of Au, the cost is low, but after the accelerated test, the halogen of the counter anion reacts with Ag to deteriorate the sensitivity ( The dye decomposes). However, since the counter anion is other than a single halogen, the dye does not decompose by reacting with Ag. Therefore, according to the present invention, Ag can be used instead of Au for the reflective layer, so that the cost is reduced. Also, the counter anion is changed from halogen to BF.
₄ ^- be changed for the change in absorption properties is not, you do not need the change of the other steps by simply changing the reflective film Ag.

[0010]

Embodiments of the present invention will now be described in more detail with reference to the drawings. FIG. 1 is a schematic partial cross-sectional view of the information recording medium of this embodiment. In this information recording medium 1, a light transmissive recording layer 12 is provided on a substrate 11, and a light reflecting layer 13 is provided on the recording layer 12.
A protective layer 14 is formed on the top surface of layer 3. A pre-groove may be provided on the substrate 11 in advance.

The recording layer 12 formed on the substrate 11 has the following chemical formula 1.

[0012]

[Chemical 3]

At least one cyanine dye selected from the cyanine dyes represented by In the above chemical formula 1, R ₁ and R ₂ each have 3 to 8 carbon atoms.
Represents an alkyl group, more preferably 3 to 5 alkyl groups. When the carbon number exceeds 8, waxing occurs and inconvenience occurs in handling.

X ⁻ represents a counter anion, and specific examples thereof include anions excluding a single halogen such as C1O ₄ ⁻ and BF ₄ ⁻ . Examples of the other anion excluding a single halogen include PF ₆ ⁻ . Specifically, the recording layer 12 has, for example, the following chemical formulas 2 and 3, as the cyanine dye,

[0015]

[Chemical 4]

A mixture of the cyanine dyes of is used. Further, in the recording layer 12, in addition to the above cyanine dye mixture,
For example, the film may be formed by mixing a quencher (photooxidation inhibitor) made of a transition metal chelate compound and an ultraviolet absorber. The recording layer 12 containing the cyanine dye and the photodeterioration preventing agent is applied by a conventional means such as spin coating.

The thickness of the recording layer 12 applied is 30 to 90.
It is 0 nm, preferably 100 to 300 nm. This value is 3
If it is less than 0 nm, the absorption is reduced and the sensitivity in the semiconductor laser wavelength range is lowered, which causes the inconvenience that signals cannot be recorded. If this value exceeds 900 nm, the dye becomes too thick and the absorption increases, resulting in reflectance. Is reduced.

As the solvent used for coating, various known solvents are used, for example, diacetone alcohol,
Examples thereof include ethyl cellosolve, methyl cellosolve, isophorone, methanol, tetrafluoropropanol and the like. The substrate 11 on which the recording layer 12 is coated is usually in the shape of a disk, and the substrate 11 is a so-called integrally formed injection-molded resin substrate from the viewpoint of improving productivity. It is preferably made of a transparent material such as polycarbonate resin (PC) or polymethylmethacrylate resin (PMMA). Particularly, it is preferable to use a polycarbonate resin (PC) having an average molecular weight of 32,000 to 40,000. In addition, the so-called 2P (phot
It may be a substrate formed by an o-polymer) method. The thickness of such a substrate 11 is about 1.0 to 1.5 mm.

Recording layer 12 coated on this substrate 11
The light reflection layer 13 is provided on the top. The light reflection layer 13 is made of inexpensive Ag or Ag alloy instead of Au, and is formed by vacuum vapor deposition, sputtering, ion plating or the like. The thickness of such a light reflecting layer 13 is 0.
It is about 05-2.0 μm. A protective layer 14 is usually provided on the light reflection layer 13 to protect the light absorption layer 12 and the light reflection layer 13. The protective layer 14 is generally formed by spin-coating an ultraviolet curable resin and applying it, and then irradiating it with ultraviolet rays to cure the coating film. Besides, epoxy resin, acrylic resin, silicone resin, urethane resin or the like is used as the material of the protective layer 14. The thickness of such a protective layer 14 is usually about 0.1 to 100 μm.

An intermediate layer for protecting the substrate 11 from the solvent may be provided between the substrate 11 and the light absorption layer 12. Further, an intermediate layer may be provided between the light absorption layer 12 and the light reflection layer 13 in order to improve the efficiency of light absorption. The wavelength of light used for recording and reproducing information in the case of the present invention is approximately 780 to 830 nm.

In the following, concrete examples and comparative examples are prepared,
An acceleration test (60 ° C., 90% RH) was performed for each of the bit error rate (BER) and the recording power (indicating recording sensitivity) required for recording. Example First, chemical formulas 2, 4 and 5 containing a cyanine dye having a counter anion BF ₄ ⁻ shown in the chemical formula 3 above
A recording layer made of a mixture to which the substance shown in (1) was added was formed on an acrylic substrate, and Ag was formed thereon as a reflective film to prepare an optical disc provided with a protective film. (Comparative Example 1) Comparative Example 1 was prepared in the same manner as in Example except that Au was used as a reflective film. (Comparative Example 2) Formula 3 counter anion BF ₄ ^- instead of the cyanine dye having a cyanine dye represented by the following chemical formula 6

[0022]

[Chemical 5]

Comparative Example 1 was prepared in the same manner as in Example 1 except that the recording layer was formed by using as a component. (Comparative Example 3) Comparative Example 3 was prepared in the same manner as Comparative Example 2 except that Au was used as the reflective film.

Table 1 shows the results of the acceleration tests of the above Examples and Comparative Example 1, and Table 2 shows Comparative Examples 2 and 3. From the results shown in Tables 1 and 2, the counter anion I ⁻
In comparison with Comparative Example 2 including the recording layer containing the cyanine dye having Ag and the Ag reflecting layer, this example maintained the same sensitivity and bit error rate as the disc of Comparative Example 1 including the expensive Au reflecting film. It can be seen that it is an optical disc.

[0025] In the above embodiment, BF ₄ as a counter anion ^- has been described Ag as a reflective film, BF ₄ ^-
Instead C10 ₄ of ^- like can also be used, it is also possible to use an Ag alloy instead of Ag.

[0026]

According to the present invention, in a rewritable optical disc having a substrate, a recording layer formed on the substrate, and a reflective layer formed on the recording layer, the reflective layer is made of Ag or Ag alloy. Since the recording layer contains the cyanine dye having the counter anion X ^{− other} than the single halogen ion represented by the chemical formula 1, the recording is excellent in durability and safety while maintaining the initial sensitivity and bit error rate. The medium can be obtained. Therefore, according to the invention, Ag can be used in place of Au in the reflective layer, so that the manufacturing cost is reduced.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of an information recording medium of the present invention.

[Explanation of symbols]

 1 Information Recording Medium 11 Substrate 12 Recording Layer 13 Light Reflection Layer 14 Protective Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Takishita 2680 Nishi Hanawa, Tatomi-cho, Nakakoma-gun, Yamanashi Pioneer Video Co., Ltd. (72) Inventor Kiyohide Ogasawara 2680 Nishi Hanawa, Tatomi Town, Nakakoma District, Yamanashi Prefecture Pioneer Video Co., Ltd.

Claims (1)

[Claims] 1. An information recording medium having a substrate, a recording layer formed on the substrate, and a reflective layer formed on the recording layer, wherein the reflective layer is made of Ag or an Ag alloy. The recording layer has the following chemical formula 1. (In Formula 1, R ₁ and R ₂ are each an alkyl group having 3 to 8 carbon atoms, R _{3 to} R ₆ are each an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms, and X ⁻ is a single group. Counter anion excluding one halogen ion, n is an integer of 2 or more, A
And A ′ represents a substituted or unsubstituted benzene ring or a condensed benzene ring residue), the information recording medium comprising at least one cyanine dye selected from the cyanine dyes.