JP2685054B2 - Naphthoquinone methide compounds - Google Patents

Description

TECHNICAL FIELD The present invention relates to a naphthoquinone methide compound useful for an optical recording medium.

(Prior Art) Optical recording using a laser has been particularly promoted in recent years because it enables high-density information recording and storage and reproduction.

An optical disc, which is an example of optical recording, is one in which a thin recording layer provided on a circular substrate is irradiated with laser light focused to about 1 μm to perform high density information recording. The recording is performed by causing the recording layer at that location to undergo thermal deformation such as decomposition, evaporation, and dissolution by absorbing the irradiated laser light energy. Reproduction of recorded information is performed by reading a difference in reflectance between a portion where deformation has occurred and a portion where no deformation has occurred due to laser light.

Therefore, as an optical recording medium, it is necessary to efficiently absorb the energy of laser light, so that it has a large absorption for the laser light of a specific wavelength used for recording, and it is used for reproduction in order to accurately reproduce information. It is necessary that the reflectance with respect to the laser light of the specified wavelength is high.

Various types of optical recording media are known as this type of optical recording medium.

For example, Japanese Unexamined Patent Publication (Kokai) No. 55-97033 discloses a structure in which a single layer of a phthalocyanine dye is provided on a substrate. However, phthalocyanine dyes have low sensitivity,
In addition, it has a problem that it has a high decomposition point and is difficult to vapor-deposit, and further has a problem that its solubility in an organic solvent is extremely low and it cannot be used for coating by application.

Further, JP-A-58-83344 discloses a phenalene dye, and JP-A-58-224793 discloses a naphthoquinone dye in a recording layer. However, while such a dye has the advantage of being easy to deposit, it has a problem of low reflectance. When the reflectance is low, the difference in reflectance between the portion recorded with the laser beam and the unrecorded portion is small, and sufficient contrast cannot be obtained, which makes it difficult to reproduce the recorded information. Further, organic dyes generally have a problem of poor storage stability.

(Problems to be Solved by the Invention) The present invention has a high solubility in an organic solvent, enables coating by coating, and has a large molecular extinction coefficient, and thus has excellent recording sensitivity, good contrast, and excellent storage stability. It is an object of the present invention to provide a naphthoquinone methide compound useful for optical recording.

(Means for Solving the Problems) The present invention provides a novel naphthoquinone methyl group represented by the following general formula [I] suitable as a dye for an optical recording medium for recording and reproducing by causing a state change by a laser beam. The gist is a compound of the type d.

General formula [I] (Wherein, R ^1, R ² represents a lower alkyl group.) In the formula [I], the lower alkyl group represented by R ¹ and R ^2, a methyl group, an ethyl group, a propyl group, a butyl group Examples thereof include alkyl groups such as a pentyl group and a hexyl group, and these alkyl groups may be linear or branched.

The naphthoquinone methide compound represented by the general formula [I] has absorption in the wavelength band of 600 to 700 nm.

The general synthesis of the naphthoquinone methide compound represented by the general formula [I] of the present invention can be carried out, for example, by the structural formula [II] The compound represented by is dissolved in an alkaline aqueous solution,
Next, the following general formula [III] (In the formula, R ¹ and R ² are the same as those defined above.) And can be obtained by heating and refluxing.

The naphthoquinone methide-based compound of the present invention is used as a dye for an optical recording medium, and the optical recording medium is basically composed of a substrate and a recording layer containing the naphthoquinone methide-based compound, and further if necessary. An undercoat layer is provided on the substrate, and a protective layer is provided on the recording layer.

The substrate used here may be either transparent or opaque to the laser light used. Examples of the material of the substrate material include general recording material supports such as glass, plastic, paper, plate-shaped or foil-shaped metal, and plastic is preferable from various points. As plastics, acrylic resin, methacrylic resin, vinyl acetate resin, vinyl chloride resin, nitrocellulose, polyethylene resin, polypropylene resin, polycarbonate resin,
Examples thereof include polyimide resin, epoxy resin, polysulfone resin and the like.

When the naphthoquinone methide compound of the present invention is used as an information recording layer in an optical recording medium, the film thickness is 100Å ~
It is 5 μm, preferably 1000Å to 3 μm. As a film forming method, a film can be formed by a generally used thin film forming method such as a vacuum evaporation method, a sputtering method, a doctor blade method, a casting method, a spinner method, and an immersion method. Further, a binder can be used if necessary. Known binders such as PVA, PVP, nitrocellulose, cellulose acetate, polyvinyl butyral, and polycarbonate are used, and the amount of the resin with respect to the naphthoquinone methide-based compound is preferably 10 wt% or more.
When forming a film by the spinner method, the rotation speed is 500 to 5000 rpm
However, after spin coating, a treatment such as heating or exposure to a solvent vapor may be performed if necessary. Also,
In order to improve the stability and light resistance of the recording material, a transition metal chelate compound (for example, acetylacetonato chelate, bisphenyldithiol, a singlet oxygen quencher,
Salicylaldehyde oxime, bisdithio-α-diketone, etc.) may be contained. Further, other dyes can be used in combination as needed. The other dye may be a different type of the same type of compound, or may be a different type of dye such as a triarylmethane type dye, an azo dye, a cyanine type dye, and a squarylium type dye.

Doctor blade method, casting method, spinner method, dipping method, in particular, as a coating solvent when forming a recording layer by a coating method such as spinner method, tetrachloroethane, bromoform, dibromoethane, ethyl cellosolve, xylene, chlorobenzene, cyclohexanone Boiling point of 120
Those having a temperature of up to 160 ° C are preferably used.

The recording layer of the optical recording medium may be provided on both sides of the substrate, or may be provided only on one side.

Recording on the recording medium obtained as described above is performed by irradiating a recording layer provided on both sides or one side of the substrate with a laser beam focused to about 1 μm, preferably a semiconductor laser beam. Thermal deformation of the recording layer, such as decomposition, evaporation, and melting, occurs due to absorption of laser energy in the portion irradiated with the laser light.

Reproduction of recorded information is performed by reading the difference in reflectance between a portion where thermal deformation has occurred and a portion where thermal deformation has not occurred using a laser beam.

The laser light used for the optical recording medium is N ₂ , He-C.
Examples thereof include d, Ar, He-Ne, ruby, semiconductor, and dye laser, and the semiconductor laser is particularly preferable from the viewpoints of lightness, easy handling, compactness, and the like.

(Examples) Hereinafter, the present invention will be specifically described with reference to examples, but the examples do not limit the present invention.

Example 1 (a) Production Example The following structural formula 1-naphthyl-malononitrile 384 mg (2m mo
l) and NaOH 360mg (9mmol) in 40ml water. 2-amino-5-dimethylaniline thiosulfate
992 mg (4 mmol) was slowly added as a powder, then stirred for 10 minutes, then heated under reflux for 10 minutes, cooled and extracted with chloroform. Then, it was separated and purified by silica gel column chromatography using chloroform as a mobile phase, washed with cyclohexane, and then recrystallized with pyridine to obtain dark brown fine needle-like crystals of a naphthoquinone methide compound represented by the following structural formula. Obtained. The yield was 4.2%.

This compound had a λmax (CHCl ₃ ) of 652 nm and a molecular extinction coefficient ε of 5 × 10 ⁴ .

(B) Example of recording medium Naphthoquinone methide compound prepared in (a) above.
1 g was dissolved in 10 g of tetrachloroethane and filtered through a 0.22 μm filter to obtain a solution. 1 ml of this solution was dropped onto a polymethylmethacrylate (PMMA) resin substrate (diameter: 52 mm) and applied by a spinner method at a rotation speed of 800 rpm. After the application, it was dried at 60 ° C. for 10 minutes. The film thickness was about 700Å.

(C) Optical recording method The coating film obtained in (b) above was coated with He having a central wavelength of 633 nm.
-When irradiated with a Ne laser beam at an output of 4 mW, very sharply outlined bits were formed.

When the coating film was irradiated with a semiconductor laser beam having a central wavelength of 650 nm at an output of 6 mW, a bit with a very clear contour was formed.

This coating film was stable for more than 20 days in an accelerated test under high temperature and high humidity of 60 ° C and 80% RH.

Example 2 The following structural formula 1-naphthyl-malononitrile 384 mg (4m mo
l) and NaOH 360mg (9mmol) dissolved in 40ml water. 2-amino-5-diethylaniline thiosulfate
1104 mg (4 mmol) was added slowly as a powder, then 912 mg (4 mmol) ammonium persulfate in 40 ml water was added dropwise and stirred for 10 minutes. Then, extracted with chloroform, further separated and purified by silica gel column chromatography using chloroform as a mobile phase, washed with cyclohexane, and then recrystallized with benzene, and the naphthoquinone methide compound represented by the following structural formula Fine brown plate crystals were obtained. The yield was 11%.

This compound had a λmax (CHCl ₃ ) of 659 nm and a molecular extinction coefficient ε of 6.13 × 10 ⁴ .

When a recording medium was manufactured under the same conditions as in Example 1 and irradiated with He—Ne laser light and semiconductor laser light by the same optical recording method, a bit with an extremely clear outline was formed in each case. Also, the accelerated stability test of the coating film under high temperature and high humidity showed similar stability.

Example 3 By the method according to Example 1, the naphthoquinone methide compounds shown in the following table were synthesized.

(Effects of the Invention) The novel naphthoquinone methide-based compound of the present invention has high solubility in organic solvents, can be coated by coating, and has high reflectance, good contrast, and storage stability. Since it has excellent properties, it is extremely useful as a dye for optical recording media.

Claims (1)

(57) [Claims] 1. A compound of the general formula [I] (In the formula, R ¹ and R ² represent a lower alkyl group.) A naphthoquinone methide compound.