JP3020219B2 - Optical information recording medium - Google Patents

Description

The present invention relates to an improved optical information recording medium that can be used in the optical recording field.

[Problems to be solved by conventional technology and invention]

Hitherto, as an optical information recording medium, those having a recording layer made of a low-melting-point metal or a low-melting-point metal and a dielectric on a substrate have been proposed, but these have poor storage stability, low resolution, and low recording. It has disadvantages such as low density, difficult manufacturing conditions and high cost. Therefore, it has recently been proposed to use an organic dye thin film instead of a metal thin film as a recording layer. This organic dye thin film has low melting point, low decomposition temperature, and low thermal conductivity, so it has the potential for high sensitivity and high density. In addition, mass production is high because the film can be formed by coating, and low cost is expected. There are advantages such as being able to.

Conventionally, it is known to use a film of a polymethine compound such as a cyanine dye or a merocyanine dye as the organic dye thin film. However, a recording layer composed of such a dye has poor heat and light stability, has a problem in storage stability, and has a drawback that reproduction is easily deteriorated.

Also, a recording material in which a photopolymer layer is formed on a substrate and provided on the photopolymer layer has already been developed, but a recording material having high solubility and excellent stability which can be directly applied to an injection substrate has been developed. Development is not satisfactory.

A polymethine-based organic dye thin film containing an asymmetric dithiolate metal complex has been proposed as a recording material that can be directly applied to an injection substrate (JP-A-1-14971).
Nos. 1-183926 and 2-58575.

However, since the asymmetric dithiolate metal complex has poor stability in solution, it has been difficult to produce a dye thin film having stable quality.

Therefore, the present invention provides an optical information recording medium which is capable of producing a recording film having a stable quality without changing the composition in the coating liquid over time, and has excellent heat and light stability. The purpose is to do.

[Means for solving the problem]

The above object is achieved by including an equilibrium mixture of an asymmetric dithiolate metal complex and a symmetric dithiolate metal complex in at least one of an undercoat layer, a protective layer, and a recording layer in an optical information recording medium. . The term "equilibrium mixture" as used herein refers to a mixture of three types of dithiolate metal complexes represented by the following formula (excluding isomer mixtures).

In the formula, and represent a skeleton residue forming a dithiolate ligand, M represents a transition metal, and X represents a cationic species.

The equilibrium state is symmetrical dithiolate metal complex (I), (I
Although it varies depending on the ratio of I), the type of solvent, etc., here, the asymmetric dithiolate metal complex is usually 40%.
8080 mol%, wherein the symmetrical dithiolate metal complexes (I) and (II) are mixed in a proportion of 5-50 mol%.

Examples of the solvent used for forming the equilibrium state include acetonitrile, acetone, ethyl acetate, 1,2-dichloroethane, and the like. The ratio of the symmetrical dithiolate metal complex to the asymmetrical dithiolate metal complex in the equilibrium mixture preferably applied to the optical information recording medium is desirably 6: 4 to 2: 8 in molar ratio. If the ratio of the asymmetric dithiolate metal complex is smaller than 40% or larger than 80%, the composition stability is deteriorated. Further, the temperature condition for forming the equilibrium state is not particularly limited, but is usually from room temperature to 150 ° C.
Performed in the range of ° C. As the dithiolate ligand, conventionally known ones are used, and specific examples thereof include the following.

(R¹~ R_FourIs hydrogen, chlorine, methyl, tert-butyl
Group, trifluoromethyl group, dimethylamino group, hydride
Roxymethyl groups, which may be the same or different
No. )(R^Five~ R⁶Is a substituted or unsubstituted alkyl group or
Represents an aryl or cyano group. )(R⁷~ R⁹Represents a hydrogen atom, a halogen atom, an alkyl group,
Represents a fluoromethyl group, even if they are the same or different
Good. ) From the above, two different types are combined
It's good to have itAnd the like. Cation species X As for the fourth grade Ann
Cationic species such as monium salts and quaternary phosphonium salts
Examples of the transition metal M include Ni, Pd, and Pt.
You.

The optical information recording medium of the present invention is basically constituted by providing a recording layer composed of an organic dye containing a polymethine compound as a main component on a substrate, and if necessary, between the substrate and the recording layer. A protective layer can be provided on the undercoat layer or on the recording layer. Further, the pair of recording media thus configured may be formed into an air sandwich structure in which the recording layer is inwardly sealed with another substrate through a space, or an adhesive sandwich bonded through a protective layer (lamination). ) It may be structured.

Next, the material constituting the optical information recording medium of the present invention and the required characteristics of each layer will be specifically described.

(1) Substrate The required characteristic of the substrate is that it must be transparent to the laser beam used only when recording and reproducing from
When performing from the recording layer side, it is not necessary to be transparent. As the substrate material, for example, polyester, acrylic resin, polyamide, polycarbonate resin, polyolefin resin, phenol resin, epoxy resin, plastic such as polyimide, glass, ceramic, metal or the like can be used.

Note that a preformat of an address signal or a pregroove of a guide groove may be formed on the surface of the substrate.

(2) Recording Layer The recording layer is capable of causing some optical change by laser light irradiation and recording information by the change, and its main component is an organic dye mainly containing a polymethine compound. In this case, the polymethine compound includes a polymethine dye, a cyanine dye, a merocyanine dye, a croconium dye, a pyrylium dye, a squarylium dye, an azulene dye, and specific examples thereof include, for example, JP-A-58-194595. Some are described in

In the recording layer of the recording medium of the present invention, for improving recording characteristics and stability, if necessary, other dyes, for example,
Phthalocyanine, tetrahydrocholine, dioxazine, triphenothiazine, phenanthrene, cyanine (merocyanine), anthraquinone (indanthrene), xanthene, triphenylmethane, croconium, pyrylium, squarylium, triphenyl amine, and azulene dyes, metals or metal compounds, for example, in, Sn, Te, Bi , Al, Se, TeO 2, SnO, As, may be mixed dispersed Cd, etc., or may be laminated . In addition, the recording layer may contain a polymer material or a low molecular material, a storage stabilizer (metal complex, phenolic compound), a dispersant, a flame retardant, a lubricant, a plasticizer, and the like. The thickness of the recording layer is 100 to 10 μm, preferably 200 to 2 μm. As a method for forming the recording layer, other than vapor deposition, CVD method, sputtering method, solvent coating method, for example, dip coating,
Spray coating, spinner coating, blade coating, roller coating, curtain coating and the like can be used.

(3) Undercoat layer The undercoat layer comprises (a) an improvement in adhesiveness, (b) a barrier against water or gas, (c) an improvement in storage stability of the recording layer, and (d) an improvement in reflectance, and (e). ) Protection of the substrate from solvents,
(F) It is used for the purpose of forming a pre-groove. For the purpose of (a), polymer materials, for example, various polymer materials such as ionomer resins, polyamide resins, vinyl resins, natural resins, natural polymers, silicones, liquid rubbers, and silane coupling agents are used. For the purposes of (b) and (c), inorganic compounds other than the above-mentioned polymer materials, for example, SiO ₂ , MgF ₂ , SiO, TiO ₂ , Zn
Metals or metalloids such as O, TiN, SiN, for example, Zn, Cu, S, N
i, Cr, Ge, Se, Au, Ag, Al and the like can be used. Further, for the purpose of (d), a metal, for example, Al, Ag or the like, or an organic thin film having a metallic luster, for example, methine dye,
A xanthene dye or the like can be used, and for the purposes of (e) and (f), an ultraviolet curable resin, a thermosetting resin, a thermoplastic resin, or the like can be used.

(4) Protective layer The protective layer (a) protects the recording layer from scratches, dust, dirt, etc., (b) improves the storage stability of the recording layer, and (c)
It is used for the purpose of improving the reflectance. For these purposes, the materials shown in the undercoat layer can be used.

In the present invention, the undercoat layer and the protective layer may contain a stabilizer, a dispersant, a flame retardant, a lubricant, an antistatic agent, a surfactant, a plasticizer, and the like, as in the case of the recording layer. .

In the present invention, in order to improve the light resistance of the polymethine compound, an equilibrium mixture of an asymmetric dithiolate metal complex and a symmetric dithiolate metal complex is contained in at least one of a recording layer, an undercoat layer and a protective layer. Let it. The polymethine compound and the above equilibrium mixture are in a weight ratio of 30:70 to 99:
1, preferably in a ratio of 60:40 to 95: 5.

〔Example〕

Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to these examples. In the following, parts and% are based on weight.

(Preparation Example 1) bis (cis-1,2-dicyano-1,2-ethylenedithiolate) nickel / tetra-n-butylammonium 7.38
Part and bis (3,4,6-trichloro-1,2-benzenedithiolate) nickel tetra-n-butylammonium in 100 parts of 1,2-dichloroethane for 5 hours under reflux.
Thereafter, 1,2-dichloroethane was distilled off to obtain the above-mentioned equilibrium mixture (IV). The product was analyzed by high performance liquid chromatography to find that bis (cis-1,2-dicyano-1,2-
Ethylenedithiolate) nickel tetra-n-butylammonium 14.3%, bis (3,4,6-trichloro-1,2-)
Benzene dithiolate) nickel tetra-n-butylammonium 17%, (cis-1,2-dicyano-1,2-ethylenedithiolate) (3,4,6-trichloro-1,2-benzenedithiolate) nickel -It was a mixture of tetra-n-butylammonium 68.7%.

(Preparation Example 2) bis (cis-1,2-dicyano-1,2-ethylenedithiolate) nickel tetra-n-butylammonium 5.89
Part and bis (2,5,6-trichloro-3,4-pyridinedithiolate) nickel tetra-n-butylammonium in 100 parts of 1,2-dichloroethane were heated under reflux for 5 hours, and After distilling off 2-dichloroethane, the above (V)
An equilibrium mixture was obtained. When this product was analyzed by high performance liquid chromatography, bis (cis-1,2-dicyano-1,
2-ethylenedithiolate) nickel tetra-n-butylammonium 21.5%, bis (2,5,6-trichloro-
3,4-pyridinedithiolate) nickel tetra-n-
Butyl ammonium 25.4%, (cis-1,2-dicyano-1,
2-ethylenedithiolate) (2,5,6-trichloro-3,4
-Pyridine dithiolate) nickel tetra-n-butylammonium 53.1% mixture.

Example 1 A substrate having a spiral guide groove having a depth of 2000 mm, a half width of 0.4 μm, and a pitch of 1.6 μm provided by acrylic photopolymer on a polymethyl methacrylate (PMMA) plate (diameter: 130 mm) having a thickness of 1.2 mm. Above, the following dye (VI) and Preparation Example 1
With the equilibrium mixture (IV) obtained in (1) in a weight ratio of 100: 20 to 1,2.
-Immediately after mixing the coating solution dissolved in dichloroethane, spinner coating was performed to form a recording layer having a thickness of 800 mm to obtain a recording medium.

(Example 2) In Example 1, the equilibrium mixture (V) obtained in Preparation Example 2 was used instead of the equilibrium mixture (IV) obtained in Preparation Example 1.
A recording medium was obtained in the same manner except for using.

(Example 3) A recording medium was obtained in the same manner as in Example 1, except that the following dye (VII) was used instead of the above dye (VI).

Example 4 A recording medium was obtained in the same manner as in Example 2, except that the dye (VII) was used instead of the dye (VI).

(Example 5) A polycarbonate substrate was obtained by injection molding using a stamper having the same guide groove shape as the substrate of Example 1. On top of that, the following dye (VIII) and the equilibrium mixture (I
V) is dissolved in methanol / 1,2-dichloroethane (weight ratio 8: 2) in a weight ratio of 100: 15, and a coating solution is prepared and immediately spin-coated to form a recording layer having a thickness of 800 mm. Thus, a recording medium was obtained.

Example 6 A recording medium was obtained in the same manner as in Example 5, except that the equilibrium mixture (V) was used.

(Comparative Example 1) A recording medium was obtained by using the recording layer containing only the dye in Example 1.

(Comparative Example 2) A recording medium was obtained by using the recording layer containing only the dye in Example 3.

(Comparative Example 3) A recording medium was obtained by using the recording layer containing only the dye in Example 5.

(Comparative Example 4) Instead of the equilibrium mixture in Example 5, bis (cis
An attempt was made to prepare a recording medium using (-1,2-dicyano-1,2-ethylenedithiolate) nickel / tetra-n-butylammonium alone, but a precipitate was formed in the coating solution and the preparation was not possible.

(Comparative Example 5) Instead of the equilibrium mixture in Example 5, bis (3,4,
An attempt was made to prepare a recording medium using 6-trichloro-1,2-benzenedithiolate) nickel / tetra-n-butylammonium alone, but a precipitate was formed in the coating solution and the preparation could not be performed.

(Comparative Example 6) Instead of the equilibrium mixture in Example 5, bis (2,5,
An attempt was made to prepare a recording medium using only 6-trichloro-3,4-pyridinedithiolate) nickel / tetra-n-butylammonium, but a precipitate was formed in the coating solution and could not be prepared.

(Comparative Example 7) Instead of the equilibrium mixture in Example 5, (cis-1,2
A recording medium was prepared using -dicyano-1,2-ethylenedithiolate) (3,4,6-trichloro-1,2-benzenedithiolate) nickel-tetra-n-butylammonium alone.

Comparative Example 8 Instead of the equilibrium mixture in Example 5, (cis-1,2
-Dicyano-1,2-ethylenedithiolate) (2,5,6-trichloro-3,4-pyridinedithiolate) nickel / tetra-n-butylammonium alone was used to prepare a recording medium.

On each recording medium obtained as described above, a semiconductor laser light having a wavelength of 790 nm was recorded from the substrate side at a recording frequency of 5 MHz and a linear velocity of 2.1 m.
Write / reproduce information at / sec and analyze the waveform of the reproduced waveform (scanning filter, bandwidth 30KHz)
Was performed, and the reflectance and C / N were measured. Furthermore, the same recording medium is irradiated with 1KW tungsten light for 20 hours at a distance of 30 cm.
And the C / N were measured after performing the accelerated regeneration degradation test by continuous irradiation from. In this case, the reflectance was measured by parallel light from the substrate side. The following measurement results are shown in the following table.

In addition, the composition change of the dithiolate metal complex in the coating solutions prepared in Examples 5 and 6 and the coating solutions prepared in Comparative Examples 7 and 8 was analyzed by high performance liquid chromatography. FIG. 1 shows the time-dependent changes after the preparation of the coating liquid. In the figure, the ordinate indicates the rate of change in purity of the dithiolate metal complex.

As shown in FIG. 1, in Comparative Examples 7 and 8, the composition of the coating liquid changed over time, and a stable recording medium could not be manufactured, whereas in Examples 5 and 6, there was almost no composition change and stable recording was performed. This indicates that the medium can be manufactured.

〔The invention's effect〕

The optical information recording medium of the present invention configured as described above can perform recording and reproduction with long-wavelength light such as a semiconductor laser, and as shown in the results of Table 1, improved thermal stability and light stability. It has a performance equal to or higher than that of the conventional product, has excellent storage stability, and has little reproduction deterioration.

In producing the optical information recording medium of the present invention,
It is possible to apply a recording material directly to the injection substrate, and the stability of the coating liquid is extremely improved as compared with the conventional product as shown in FIG. Can be manufactured.

As described above, it has become possible to provide an optical information recording medium with high reliability and stable quality.

[Brief description of the drawings]

FIG. 1 is a graph showing the change over time in the purity after the coating liquids of Examples and Comparative Examples of the present invention were prepared.

Claims (2)

(57) [Claims] In an optical information recording medium comprising a substrate and a recording layer containing an organic dye containing a polymethine compound as a main component, an equilibrium mixture of an asymmetric dithiolate metal complex and a symmetric dithiolate metal complex (wherein An optical information recording medium characterized in that the optical information recording medium contains 2. The optical information recording medium according to claim 1, further comprising an undercoat layer and / or a protective layer.