JPH0441672B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an optical recording medium on which information can be recorded and reproduced using laser light, and more particularly to an optical recording medium using an organic dye. (Prior art and its problems) Conventionally, as this type of optical recording medium, Te alloy,
Te oxide and organic dyes are used. Organic dyes generally have excellent properties in that highly sensitive and non-polluting media can be produced at low cost, and various media have been developed so far. They can be roughly divided into single dye types and compatible types in which the dye is dissolved in a polymer resin using a solvent. A compatible medium is, for example, as disclosed in JP-A-55-161690, in which polyvinyl acetate, which is a polymeric resin, is mixed with polyester yellow as a pigment using a solvent, and formed on a substrate by a spin coating method. be done. Generally, for compatible media, the media formation method is limited to solvent coating. Therefore, when using resin for the substrate, there is a restriction that a solvent must be selected that does not dissolve the resin. On the other hand, a dye-only medium formed by vapor deposition is a practically desirable medium because it does not impose restrictions on the selection of a substrate. However, vapor-deposited dye films generally exhibit deterioration in surface properties due to association (aggregation). This deterioration determines the lifespan of the medium, so in the case of a dye-only medium, it is important to use a dye material with low association, but no medium with a sufficient lifespan has been developed so far. (Objective of the Invention) An object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide an optical recording medium made of an organic dye that has excellent long-term storage stability. (Structure of the Invention) The present invention provides an optical recording medium in which a recording layer is provided on one or both sides of a substrate, and information is recorded and read by a laser beam.
Metal complex of amino-8-(substituted anilino)-2,3-dicyano-1,4-naphthoquinone dye or 5,8-(substituted anilino)-2,3-dicyano-
It is characterized by forming an organic thin film whose main component is a metal complex of 1,4-naphthoquinone dye. Further, the method for manufacturing an optical recording medium according to the present invention is characterized in that the metal complex of the naphthoquinone dye is formed on the substrate by a vapor deposition method. (Detailed Description of Configuration) The present invention solves the problems of the prior art by adopting the above-described configuration. 5-amino-8-(substituted anilino)-2,3-dicyano-1,4-naphthoquinone dye or 5,8
-(substituted anilino)-2,3-dicyano-1,4-
By selecting an alkyl group, an alkoxyl group, an allyl group, an amino group, or a substituted amino group as a substituent for the substituted anilino of the naphthoquinone dye, the film formability by vapor deposition and the associativity of the vapor deposited film can be improved by unsubstituted anilino (

[Formula]) is better. By forming these dyes into metal complexes, the associativity is further reduced. The number of carbon atoms in the alkyl group and alkoxyl group of the substituent is more preferably 1 to 4. These metal complexes of naphthoquinone dyes show an absorption maximum in the near-infrared region, and when a semiconductor laser is used as a recording/reproducing laser, the oscillation wavelength matches well with the semiconductor laser, and it is expected that a highly sensitive medium can be formed. A synthesis example of the naphthoquinone dye metal complex is shown below. First, known 2,3-dichloro-1,4-naphthoquinone was nitrated with nitric acid and sulfuric acid to produce 5-nitro-
2,3-dichloro1,4-naphthoquinone is obtained.
Next, cyanation is performed with sodium cyanide to obtain 5-nitro-2,3-dicyano-1,4-dihydroxynaphthalene. Subsequently, after reduction treatment with stannous chloride and hydrochloric acid, oxidation treatment is performed with ferric chloride to obtain 5-amino-2,3-dicyano-1,4-naphthoquinone [1]. [1] Thoroughly crush 1 g, disperse in 400 ml of ethanol, and reflux. A solution of 1.23 g (2 molar ratio) of p-ethoxyaniline in ethanol (10 ml) was added dropwise to this, and the mixture was stirred for 10 minutes under reducing conditions.
After the reaction is heated, the solution is cooled on ice, the resulting precipitate is filtered, and after drying, it is recrystallized from chloroform.
380 mg (yield 24%) of purified product (mp 254-256°C) is obtained. The identification results for this purified product are: (1) λmax 760nm (in acetonitrile) (2) Mass spectrometry (M/e) 358, 330, 329 (3) Direct elemental analysis Calculated values C: 67.03% N: 15.64% H:
3.94% Experimental value C: 67.09% N: 15.85% H:
3.85%, which is 5-amino-8-(P-ethoxyanilino)-2,3-dicyano-1,4-
It was confirmed to be naphthoquinone. Next, dissolve 200 mg of [] in 300 ml of acetonitrile, add a solution of 72 mg of cobalt chloride (1 molar ratio) dissolved in 50 ml of acetonitrile,
Reflux at the boiling point of acetonitrile for 3 hours. After that, it was distilled under reduced pressure, and the residue was washed with acetonitrile to wash away [ ], further washed with water, and then dried to obtain 5-amino-8-(p-ethoxyanilino)-2,3-dicyano-1,4- 130 mg of purified cobalt complex of naphthoquinone dye was obtained. When this purified product was analyzed by silica gel thin layer chromatography using acetonitrile as a developing agent, no complex was developed. Note that the Rf value of [] is 0.9. Metal complexes of other naphthoquinone dyes can also be synthesized in the same manner as in the above synthesis example. The naphthoquinone dye metal complex thin film can be formed on a substrate by a conventional resistance heating vapor deposition method.
Although various substrate materials can be used, glass, aluminum alloy, and synthetic resin are generally preferred. Synthetic resins include polymethyl methacrylate (PMMA), polycarbonate, epoxy,
Examples include polyetherimide, polysulfone, and polyvinyl chloride. The substrate shape can be a disk shape, a tape shape, or a sheet shape. When a thin film of a naphthoquinone dye metal complex formed on a substrate is irradiated with semiconductor laser light focused by a lens, the thin film in the irradiated area is removed and holes are formed. Although the mechanism of this pore formation is not clear, it is thought to be due to melting and aggregation accompanied by vapor deposition (sublimation).
The size of the hole formed depends on the focused diameter of the laser beam, laser power, and irradiation time, but is approximately 0.2~
The thickness is preferably 3 μm. The laser energy required to form such a hole is small, and therefore the hole can be formed in a short time. Specifically, when AlGaAs semiconductor laser light with a wavelength of 830 nm is focused to a beam diameter of 1.4 μm, holes can be formed on the thin film surface with a power of 2 to 13 mW and an irradiation time of 50 to 300 nsec. . Naturally, holes can be formed under conditions that exceed the upper limits of the above power or irradiation time, but the above conditions are desirable usage conditions. Recording information is 2.
This is done by associating advance information with the presence or absence of holes. Information is recorded by rotating a regular plate-shaped medium at a constant speed and forming holes in accordance with the recorded information. In addition,
In the above cases, the thickness of the thin film is 0.01 to 0.5 μm,
It is preferably 0.02 to 0.2 μm. Reading out the information (holes) recorded in this way is as follows:
This is done by detecting changes in the amount of light reflected or transmitted from the medium. Generally, a method of detecting reflected light is adopted. This is because the optical system for reflected light detection is simpler. That is, this is because one optical system can project and collect light. For reading, laser light is continuously irradiated. The light intensity at that time is set to a weak energy that does not cause any shape change to the medium, and is 1/5 to 1/10 of the light intensity during normal recording.
It is. There are two directions of incidence of light during recording and reproduction: toward the medium surface and toward the substrate surface. Both orientations can be used with single layer media such as the present example. When the light is incident on the substrate surface side, recording and reproduction are possible without being affected by dust attached to the medium surface, which is a more desirable form. Note that if the substrate thickness is 1 mm or more, the beam diameter on that surface is sufficiently large to prevent dust adhering to the surface of the substrate opposite to the surface on which the medium is formed, as well as defects such as scratches on that surface. Does not adversely affect recording or playback. Information is recorded as a series of holes. The rows of holes generally form a number of concentric or spiral tracks. When reproducing, the light beam needs to accurately track the hole array of a specific track. One way to achieve this is to increase the precision of the rotating mechanism by using air bearings or the like. However, in this case, the rotation system becomes complicated and expensive, so it is not practical. More desirable is a method in which light guide grooves are provided on the substrate. When light enters a groove about the diameter of a beam, it is diffracted. As the beam center shifts from the groove, the spatial distribution of the diffraction intensity changes, and a servo system can be configured to detect this and direct the beam to the center of the groove. Usually, the width of the groove is set in the range of 0.4 to 1.2 μm, and the depth is set in the range of 1/8 to 1/4 of the recording/reproducing wavelength used. The recording layer is therefore formed on the grooved substrate surface. Embodiments of the present invention will be described in detail below with reference to the drawings. (Example 1) Figure 1 shows a thin film of a cobalt complex of 5-amino-8-(p-methoxyanilino)-2,3-dicyano-1,4-naphthoquinone dye actually produced on a substrate by vapor deposition. This shows the absorption spectrum.
From this, it was confirmed that there was an absorption maximum near 800 nm, which is the oscillation wavelength of an AlGaAs semiconductor laser, and that this thin film was suitable as an optical recording medium using a semiconductor laser. The complex refractive index of the deposited film was 2.2-i0.7 at a wavelength of 830 nm. Next, a cobalt complex of 5-amino-8-(p-methoxyanilino)-2,3-dicyano-1,4-naphthoquinone dye was resistance heated on a disc-shaped PMMA substrate with a thickness of 1.2 mm and a diameter of 120 mm. The film thickness is
A pink film of 620 Å was obtained. The resistance heating boat material was Mo, and the degree of vacuum during vapor deposition was 1.5×10 ^-5 Torr or less. The substrate was left to stand at room temperature, and almost no rise in substrate temperature due to vapor deposition was observed. The boat temperature was fixed at approximately 220°C for deposition. The deposition rate is approximately 0.5 Å/sec. FIG. 2 shows the media thus formed. A dye film 20 is formed on a PMMA substrate 10. Wavelength from the direction of arrow 30 to this medium
Semiconductor laser light of 830 nm was focused and irradiated with an optical system (not shown). Furthermore, the NA of the objective lens is
It is 0.55. The power of the laser beam on the medium surface
10mW, recording frequency 2.5MHz, linear velocity 12m/
When recording is performed under conditions of sec, approximately
A pit 40 with a diameter of 0.8 μm was formed. Such recording was similarly possible even when light was incident on the medium from the front side, that is, from the direction of arrow 50. When the recorded pit is played back with 0.7mW continuous light,
A C/N ratio of 54 dB was obtained. Note that the bandwidth is
It is 30KHz. The long-term stability of the recording film was evaluated by the following method. The deposited film was observed with an optical microscope at 2000x magnification, and the presence or absence of agglomerated particles on the film surface was used as a criterion for deterioration.The lifespan at room temperature (25°C) was determined by performing an accelerated test, and the lifespan was determined to be over 25 years. Obtained. This value is the value of 5-amino-8-(p-methoxyanilino)-2,3-dicyano-1,4-naphthoquinone dye (several years to
10 years). Furthermore, the life of 5-amino-8-(unsubstituted anilino)-2,3-dicyano-1,4-naphthoquinone dye evaluated in the same manner was within several tens of days. (Example 2) In the same manner as in Example 1, 5-amino-8-(p
-methoxyanilino)-2,3-dicyano-1,
Cobalt complex of 4-naphthoquinone dye with a film thickness of 720 mm
The film was formed using Å. Leave the board naturally at room temperature, and the degree of vacuum is 2.
×10 ^-5 Torr or less, the boat temperature was 235°C, and the deposition rate was 1 Å/sec. The complex refractive index at a wavelength of 830 nm was 2.3−i0.7. When recorded and reproduced in the same manner as in Example 1,
A CN ratio of 54dB was obtained. When the long-term stability of the recording film was evaluated in the same manner, it was found that forming a metal complex resulted in a long life almost equivalent to that of Example 1. In addition, the boat temperature in Examples 1 and 2 was 30℃~
Temperatures up to 50℃ higher are possible. (Effects of the Invention) As is clear from the above examples, the present invention provides an optical recording medium with excellent long-term stability and good characteristics, and a method for producing the same.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the absorption spectrum of a cobalt complex vapor-deposited film of 5-amino-8-(p-methoxyanilino)-2,3-dicyano-1,4-naphthoquinone dye, and FIG. 2 is an optical diagram according to the present invention. 1 is a schematic diagram of a recording medium, and in the figure, 10 is a substrate, 20 is an organic thin film, 30 and 50 are light incident directions, and 40 is a hole.

Claims (1)

[Claims] 1. In an optical recording medium in which a recording layer is provided on one or both sides of a substrate and information is recorded and read by a laser beam, the recording layer is 5-amino-
8-(substituted anilino)-2,3-dicyano-1,4
-Metal complex of naphthoquinone dye or 5,8-
An optical recording medium comprising an organic thin film containing a metal complex of (substituted anilino)-2,3-dicyano-1,4-naphthoquinone dye as a main component.