JPH074973B2 - Optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is directed to bis [1,2-bis (2,4) which exhibits absorption in the near infrared region.
-Dichlorophenyl) -1,2-ethenedithiolate (2
-)-S, S ']-Nickel as an optical absorber and an optical recording medium such as an optical disk.

(Prior Art and Problems Thereof) In recent years, various materials containing a dye having absorption in the near infrared region have been attracting attention as recording materials using a laser beam.

In particular, materials used for a so-called heat mode DRAW recording medium for recording information by forming minute pits in the recording layer or forming minute alteration points with a laser beam are being actively developed. This material (1) has a large absorption in the near infrared region, (2) is chemically stable,
Further, (3) it is necessary that the thin film be easily formed.

Many materials have already been proposed as this type of material, for example, dianine (polymethine), azo, anthraquinone, indanthrene, triarylmethane, naphthoquinone, phthalocyanine, porphyrin, Dithiolate complex systems, croconic methine systems, squarylium systems, indoaniline systems, etc. are mainly studied. However, there is still nothing that completely satisfies the above-mentioned conditions required for the DRAW recording medium.

Among the above recording materials, the 1,2-ethenedithiolato metal complex compound is preferable because it has excellent stability over time, but the absorption wavelength is slightly longer and the solubility is small, so that it is uniformly formed. It had the drawback that it could not be filmed.

Regarding the synthesis method and physical properties of the 1,2-ethenedithiolato metal complex compound, for example, GN Schrauzer, VP Mayweg,
J. Amer. Chem. Soc., 87.1483-1489 (1965), Masaji Kajiya et al., The Chemical Society of Japan, 1985, 433-437.
Further, JP-A-56-92095 describes the use of a 1,2-ethenedithiolatoplatinum complex compound (described as a platinum bis (dithio alpha diketone) complex compound) as a recording layer component of an optical recording medium. It is described that this recording layer can be formed by a vacuum vapor deposition method and has ablative property to a pulse beam of a wavelength of about 800 nm from an AlGaAs injection type laser. However, it has been concluded that the Ni complex compound is unsuitable for use in the recording layer, because the film becomes cloudy, and even if a transparent film is formed, the absorption is small in the vicinity of the oscillation wavelength of the laser light source.

In JP-A-57-195341, a 1,2-ethenedithiolato metal complex compound (described as an aliphatic dithiol metal complex) is originally absorbed by irradiation with recording rays such as ultraviolet rays, electron beams, and X-rays. It is described that the light absorption ability in the wavelength region is reduced or disappears, the pattern of the photomask can be transferred, and the change in the transmittance at a specific wavelength can be detected to be used for recording and reproduction. Furthermore, JP-A-58-16
In 888, it is used as a light absorber that decomposes in the presence of nitrocellulose and loses its absorption ability, and has bis [1,2-bis (4-methoxyphenyl) -1,2- In the case of ethenedithiolato (2-)-S, S ']-nickel, it is dissolved in ethyl cellosolve acetate together with nitrocellulose and methacrylic acid resin and coated on a polyethylene terephthalate film, and the GaAs laser (oscillation wavelength) is applied to this recording film. (905 nm), a clear trajectory was obtained, showing the potential as a writing medium for heat-mode DRAW.

Now, the light source used to record and reproduce information by laser light is a semiconductor laser (wavelength ~ 800 nm), He
-Ne laser (wavelength 633nm) Ar ion laser (wavelength 488)
nm) etc., but in particular, semiconductor lasers are small and lightweight, and in addition to being manufactured at low cost, especially AlGaAs
The system semiconductor laser (wavelength: 830 nm) is practically superior to other available laser light sources, and a recording material corresponding to this oscillation wavelength is required.

Further, the optical recording material is required to have resistance to deterioration by reproduction. That is, the optical recording material is required to have a light absorbing ability to form information pits by forming holes in the recording material layer at the time of recording, and at the same time, the pits are read by reproducing light having a lower output than that at the time of recording. At this time, it is required that the recording layer of the unrecorded portion is not deteriorated by the reproduction light.

On the other hand, it is advantageous that the substrate material used for the optical recording medium is made of synthetic resin which is easy to mold, and polymethylmethacrylate (PMMA), polycarbonate, epoxy, polyvinyl chloride, polymethylpentene, porsulfone, polyether. Although imides and the like have been proposed, polymethylmethacrylate resin that can produce a large-diameter (for example, 300 mmφ diameter and excellent birefringence with excellent optical characteristics) disk-shaped substrate by injection molding is a guide groove for laser beams. As a concentric or spiral so-called pre-groove can be simultaneously molded and transferred, it is particularly preferable as an optical disk substrate material.

Further, the method of forming the recording layer on the substrate is roughly classified into a dry process of depositing the recording material in a vacuum system and a wet process of attaching or coating the recording material on the substrate by means such as a spin coater or dipping. , The former needs to cause sublimation or evaporation by heating under high vacuum, so the compound provided for this must first be thermally stable, and if a thermal decomposition point exists, However, it is indispensable to operate at a heating temperature lower than that, and it is more costly than the wet process. That is, the latter is economically advantageous. However, in the coating method, the compound to be used should be dissolved in a suitable solvent to coat the surface of the substrate material according to the purpose and form a continuous thin layer with uniform optical properties after evaporation of the solvent. Is required. That is, it is necessary that not only the solvent has solubility but also the solvent used does not cause a change in surface condition such as dissolution, swelling or permeation with respect to the substrate material. When the substrate material is glass, there is no limitation on such a solvent to be used. Therefore, the selection of the light absorbing agent used as the recording medium basically depends on the magnitude of absorption in the near infrared region and the chemical stability. Although it can be performed relatively freely in consideration of properties and the like, this point becomes particularly important when plastic is used as the substrate material.

As described above, in the case of forming an optical information recording medium by forming a recording layer on a plastic substrate by a coating method, at least three requirements are required: (1) Absorption maximum near a wavelength of 830 nm, (2) It is necessary to satisfy the requirements that it is chemically stable, that is, there is no deterioration by regeneration, and that (3) the solubility is high and the solvent does not adversely affect the substrate material.

The 1,2-ethenedithiolato metal complex compound is chemically relatively stable due to its molecular structure, but the above (1),
None of them satisfied all the requirements of (2) and (3).

That is, the previously known (JP-A-58-16888) bis [1,2-bis (4-methoxyphenyl) -1,2-ethenedithiolato (2-)-S, S ']-nickel (previously Out)
Since its absorption maximum is 920 nm and the absorption around 830 nm is small, it cannot be used as a recording material for the recording system using the above-mentioned practically available semiconductor laser.

Also, GN Schrauzer, VP Mayweg, J. Amer.che
m.Soc., 87, 1483-1489 (1965), bis [1,2-diphenyl-1,2-ethenedithiolato (2-)-S, S ']-nickel and bis [1,2-bis ( 4-chlorophenyl)
-1,2-Ethenedithiolato (2-)-S, S ']-nickel (GNSchrauzer, VP Mayweg, supra) is 866 nm
And the absorption maximum at 865 nm, and there is sufficient absorption near 830 nm, but bis [1,2
-Bis (4-chlorophenyl) -1,2-ethenedithiolato (2-)-S, S ']-nickel, alcohols, ketones, esters, ethers or aliphatic halogenated hydrocarbons such as dichloroethane and dichloromethane To
The solubility was 0.1% by weight or less, and the highest solubility was 0.23% by weight in toluene, and the obtained recording medium shows no recording property even when a film was formed by a coating method.

As described above, the present inventors have a recording property for a laser beam having a wavelength of about 830 nm, a plastic substrate,
In particular, we searched for 1,2-ethenedithiolatonickel complex compounds for a near-infrared light absorber that can be formed into a film by a coating method on a substrate made of polymethylmethacrylate resin and found that bis [1,2
The present invention was completed by finding -bis (2,4-dichlorophenyl) -1,2-ethenedithiolato (2-)-S, S ']-nickel.

(Object of the invention) Therefore, an object of the present invention is to use a laser beam obtained from an AlGaAs semiconductor laser having a wavelength of about 830 nm for recording and reproduction, and to apply it to a substrate material made of methacrylic acid resin, which is easily available, by a coating method. An object of the present invention is to provide an optical recording medium that can be directly formed into a film and can be manufactured and has no reproduction deterioration.

(Structure of the Invention) The present invention provides an optical information recording medium comprising a support and a recording layer formed on the support, wherein the recording layer is a bis [1,2-bis] compound represented by the following formula (I). (2,4-dichlorophenyl) -1,2-ethenedithiolato (2-) S, S ']-nickel: It is characterized by including.

The above optical information recording medium can be used as a DRAW or WORM type memory, for example, an optical disk, an optical card, an optical tape, an optical drum, or the like, but can also be used as a pattern recording material or the like.

The support may be in any shape such as a disk, card, tape sheet, etc., and its material may be plastic, metal, glass, ceramics or any other material. In particular, the present invention is preferably applied to a DRAW type optical disc, particularly a DRAW type optical disc using a plastic substrate having a pre-groove.

As the plastic, any material such as acrylic resin, polycarbonate resin, or epoxy resin is used, but it is preferable to use a transparent plastic substrate used for the back surface recording method (so-called Philips method).

The compound represented by the above formula (I) may be directly applied to a substrate, that is, a support by dissolving a solution in a solvent, or may be used together with a binder. Examples of the binder include any known polymer materials such as ionomer resins and cellulose derivatives. Other stabilizers, lubricants,
Additives such as antistatic agents, surfactants and plasticizers can be added as necessary.

Further, as described below, since the compound (I) of the present invention has an excellent ability to prevent photodegradation, it can be used as a photodegradation inhibitor, that is, a stabilizer for the above-mentioned known optical recording materials and organic dyes. .

The thickness of the recording layer is generally 100 Å to 5 μm, preferably 200 Å to 1 μm, depending on whether or not a binder is used, and 200 Å to 5,000 Å when no binder is used.
Is preferred.

The recording layer of the present invention can also be used as a laminated film by combining another recording layer and / or a protective layer and an underlayer.

As the solvent, alcohols such as methanol, ketones such as acetone, amides such as dimethylformamide,
Ethers such as ethylene glycol monomethyl ether, esters such as methyl acetate, halogenated hydrocarbons such as chloroform, and aromatics such as benzene can be used alone or in combination. The application or application of the solution can be performed by any means such as spin coating, dip coating, roller coating and the like.

The compound (I) of the present invention is preferably used in a wet type as described above, but in some cases, vapor deposition, CV
It can also be used in a dry process such as D.

Hereinafter, the present invention will be described with reference to the synthesis method of Compound (I) and Examples.

(Synthesis of Compound (I)) The above compound (I): bis [1,2-bis (2,4-dichlorophenyl) -1,2-ethenedithiolato (2-)-S, S ']-
Nickel is the method of GN Schrauzer, VP Mayweg, etc. (supra)
Synthesized by

That is, the corresponding benzoin compound was obtained from 2,4-dichlorobenzaldehyde according to a conventional method, reacted with phosphorus pentasulfide (P ₄ S ₁₀ ) in dioxane under reflux, cooled, and then cooled with nickel chloride (6 water). An aqueous solution of Japanese quinolide) was added and the mixture was heated on a steam bath to obtain the desired compound as a black-green powder. The analytical sample was recrystallized from toluene to obtain black needle crystals.

The analysis results of this standard were as follows.

Near infrared absorption spectrum λmax 790nm (in toluene) ε21,000 Infrared absorption spectrum (KBr method) 1390,1363,1155,1141,110
5,1054 cm ^-1 .

Elemental analysis Calculated value C: 41.06% H: 1.48% Measured value C: 40.78% H: 1.35% Melting point 250-260 ℃ (decomposition) Mass spectrometry m / e817 (30%), 815 (40%), 378 (100%) ) ¹³ C Nuclear magnetic resonance absorption spectrum (CDCl ₃ ) 127.0,129.8,
131.5,132.8,136.0,137.1,179.4ppm This bis [1,2-bis (2,4-dichlorophenyl) -1,2
-Ethenedithiolato (2-)-S, S'-nickel is ethanol, hexane, methyl cellosolve, perkrene,
Although it is slightly soluble in solvents such as toluene, P-xylene, t
-Butylbenzene showed a high solubility and was 6% by weight or more at room temperature. Figure 1 shows the near-infrared absorption spectrum (wavelength range 700-900 nm) of the toluene solution. The absorption maximum is at 790 nm, and the absorbance at 830 nm shows 67% of the maximum value. FIG. 2 is a spectrum of a toluene solution of the above compound coated on an acrylic substrate and air-dried, showing that the shift of the absorption maximum is slight.

(Example) 148 mg of bis [1,2-bis (2,4-dichlorophenyl) -1,2-ethenedithiolato (2-)-S, S '] nickel obtained above was added to t-butylbenzene 10 The solution was stirred and dissolved in gram, and was passed through a Teflon filter (bore size 0.2 micron) to obtain a coating solution. An optical recording medium was obtained by applying this by spin coating on an acrylic substrate onto which 2.5-micron pitch grooves were transferred by injection molding and air-drying. It was confirmed by a microscope that the gravel of the coated substrate was hardly dissolved.

A semiconductor laser beam having a wavelength of 830 nm was condensed on this recording medium and irradiated from the substrate side. Irradiation surface power for signal recording 7.
It was performed by irradiating pulsed light with a pulse width of 1 μsec at a linear velocity of 3.3 m / sec at 5 mW.

A continuous light with an irradiation surface power of 0.8 mW was applied to this recording section to reproduce the signal, and a C / N ratio of 40 dB was obtained. Furthermore, the regeneration operation was continued for 1 hour continuously, but there was no change in the C / N ratio.

(Comparative Example) Conventionally known bis [1,2-bis (4-chlorophenyl)-
1,2-Ethenedithiolato (2-)-S, S ']-Nickel 25
To 0 milligram, 100 grams of toluene was added, and stirring was continued overnight at room temperature to prepare a saturated solution. This solution was passed through a Teflon filter (pore size: 0.2 micron), and the dissolution residue was dried to give 20 mg.

To the solution was added 10 g of toluene, and the mixture was stirred for a short time and then over-operated again. Then, 27 g of carbon tetrachloride that had been similarly overtreated was mixed to obtain a coating solution. In the same manner as in the example, a recording medium was obtained by coating by a spin coating method and a signal was recorded, but it was impossible to reproduce the signal because a clear pit could not be formed and the signal train could not be followed.

As is clear from the above results, the recording layer according to the present invention satisfies all the above-mentioned requirements (1), (2) and (3) as a recording material. That is, since the absorption wavelength peak is extremely close to the wavelength of 830 nm of the semiconductor laser as shown in FIG. 2, the requirement (1) is almost satisfied. Also,
The pregroove of the substrate is hardly affected by an organic solvent such as toluene, and no deterioration due to reproduction is observed. Therefore, the requirement (2) 3) is satisfied. The reason for this is not clear, but the following may be considered.

That is, one of the remarkable properties of the 1,2-ethenedithiolatonickel complex is the quenching ability of singlet oxygen, which has long been known. Generally, a series of screws (1,2
The structure of (diaryl-1,2-ethenedithiolato) nickel complexes is closely related to the quenching ability of singlet oxygen and its stability to singlet oxygen, increasing the electron donating ability of the substituents on the aryl ring. As the quencher ability increases, the stability deteriorates. The screw of the present invention [1,2
-Bis (2,4-dichlorophenyl) -1,2-ethenedithiolato (2-)-S, S ']-nickel has good stability due to the electron withdrawing property of the substituent, but the quenching ability is particularly high. Although not expected to be excellent, the stability of the complex towards singlet oxygen increases dramatically with increasing concentration, and thus it has an improved solubility in toluene like the compounds of the invention. The 2,2-ethenedithiolato nickel complex can be contained in the recording layer at a high concentration. Therefore, it is considered that the photodegradation characteristics are improved. That is, bis [1,2-bis (2,4-dichlorophenyl) -1,2-ethenedithiolato (2-)-S, S ']-nickel is an organic compound that has optical absorption in the wavelength range of a semiconductor laser. It has a qualification as a stabilizer for dyes.

[Brief description of drawings]

FIG. 1 is a near infrared absorption spectrum of a toluene solution of the compound (1) of the present invention. FIG. 2 is a near-infrared absorption spectrum of the above solution coated on an acrylic substrate and air-dried.

Claims (4)

[Claims] 1. An optical information recording medium comprising a support and a recording layer formed on the support, wherein the recording layer is represented by bis [1,2-bis (2,2 4-dichlorophenyl) -1,2-ethenedithiolato (2-)-S, S ']-
nickel: An optical information recording medium comprising: 2. The recording layer comprises the bis [1,2-bis (2,4-
Dichlorophenyl) -1,2-ethenedithiolate (2-)
The optical information recording medium according to claim 1, which is formed by coating or adhering a solution containing -S, S ']-nickel on the support. 3. The optical information recording medium according to claim 1, wherein the support is a plastic molded product. 4. The optical information recording medium according to claim 3, wherein the support is an acrylic resin injection-molded disc with or without pregrooves.