JPH0562080B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is based on the above formula () which exhibits absorption in the near-infrared region.
The present invention relates to an optical recording medium such as an optical disk containing an acetylene derivative represented by the following as a light absorbing agent.

(Prior Art and its Problems) In recent years, various materials containing dyes that absorb in the near-infrared region have attracted attention as recording materials that use laser beams.

In particular, so-called heat mode DRAW that records information by making minute pits in the recording layer or forming minute alteration points using a laser beam.
Materials for use in recording media are being actively developed, but these materials (1) have high absorption in the near-infrared region, (2) are chemically stable, and (3) are suitable for thin films. It is necessary that it be easy to form.

Many materials of this kind have already been proposed, such as cyanine-based (polymethine-based),
Azo series, anthraquinone series, indanthrene series,
Mainly studied are triarylmethane series, naphthoquinone series, phthalocyanine series, porphyrin series, dithiolate complex series, croconic metine series, squalium series, indoaniline series, etc. However, there is still no one that completely satisfies the above conditions required for a DRAW recording medium. for example,
Among the above recording materials, triarylmethane-based (or triphenylmethane-based) materials are
It is known that it can be used for optical recording because it is easy to manufacture, inexpensive, has a large molecular extinction coefficient, dissolves in various solvents, and can form a thin film by coating. The disadvantage was that the wavelength was on the shorter side.

Now, the light sources used to record and reproduce information with laser light are semiconductor laser (wavelength ~800nm), He-Ne laser (wavelength 633nm), Ar
There are ion lasers (wavelength: 488 nm), etc., but semiconductor lasers in particular are small and lightweight, and can be produced at low cost.In particular, AlGaAs semiconductor lasers (wavelength: 830 nm) are practically inferior to other available lasers. There is a need for a recording material that is superior to light sources and compatible with this oscillation wavelength.

Furthermore, optical recording materials are required to have read deterioration resistance. In other words, the optical recording material is required to have enough light absorption ability to form information pits by drilling holes in the layer of the recording material during recording, and at the same time, it is required to have sufficient light absorption ability to form information pits by drilling holes in the layer of the recording material. When reading the pits, it is required that the unrecorded portion of the recording layer is not deteriorated by the reproducing light.

On the other hand, it is advantageous for the substrate material used for optical recording media to be made from synthetic resins that are easy to mold, such as polymethyl methacrylate (PMMA), polycarbonate, epoxy, polyvinyl chloride, polymethylpentene, porsulfone, etc. Polyetherimide, etc. have been proposed, but polycarbonate resin, which can be injection molded to produce a disk-shaped substrate with excellent mechanical and optical properties and low birefringence, is suitable for forming concentric or circular guide grooves for laser beams. It is particularly preferred as an optical disk substrate material because a spiral so-called pregroove can be molded and transferred at the same time.

Furthermore, methods for forming the recording layer on the substrate can be roughly divided into a dry process in which the recording material is deposited in a vacuum system and a wet process in which the recording material is attached or coated onto the substrate using a spin coater, dipping, or other means. However, since the former requires sublimation or evaporation by heating under high vacuum, the compound used for this process must first be thermally stable, and if a thermal decomposition point exists. In addition, it is essential to operate at a heating temperature lower than that, and it is more disadvantageous than the wet process in terms of cost. In other words, the latter is economically advantageous. However, in the coating method, the compound used is dissolved in a suitable solvent, coated on the surface of the substrate material according to the purpose, and after the solvent evaporates, forms a continuous thin layer with uniform optical properties. is required. In other words, it not only has solubility in solvents, but also dissolves and dissolves the substrate material in the solvent used.
It is necessary that changes in surface conditions such as swelling or penetration do not occur. When the substrate material is glass, there are no such restrictions on the solvent used, so the choice of light absorption to be used as a recording medium basically depends on the magnitude of absorption in the near-infrared region and chemical stability. This can be done relatively freely taking into account the following, but this point is particularly important when plastic is used as the substrate material.

As described above, when producing an optical information recording medium by forming a recording layer on a plastic substrate by a coating method, there are at least three requirements: (1) It must have an absorption maximum near a wavelength of 830 nm; (2) It must be chemically stable, that is, there is little deterioration due to reproduction, and (3) It must have high solubility and the solvent must not have an adverse effect on the substrate material.

(Object of the invention) Therefore, the object of the present invention is to
A laser beam obtained from an AlGaAs semiconductor laser can be used for recording and reproduction, and it can be manufactured by directly forming a film on an easily available polycarbonate resin substrate material by a coating method. The objective is to provide an optical recording medium that does not deteriorate.

(Structure of the Invention) The present invention provides an optical information recording medium including a substrate and a recording layer formed on the substrate, wherein the recording layer is an acetylene derivative represented by the following formula (): (In the formula, Y represents O and S, X is ClO ₄ ,
BF ₄ , PF ₆ , Cl, F or Br).

The above optical information recording media are DRAW or
It can be used as a WORM type memory, such as an optical disk, an optical card, an optical tape, an optical drum, etc., but it can also be used as a pattern recording material, etc.

The support can be in any shape such as a disk, card, or tape sheet, and its material can be plastic, metal, glass, ceramics, or any other material. In particular, the present invention
It is preferable to apply the present invention to a DRAW type optical disk, particularly a DRAW type optical disk using a plastic substrate having a pre-group.

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

The compound represented by the above formula () may be dissolved in a solvent and applied directly onto the substrate, ie, the support, or may be used together with a binder. Examples of the binder include any known polymeric materials, such as ionomer resins and cellulose derivatives. In addition, stabilizers, lubricants, antistatic agents,
Additives such as surfactants and plasticizers can be added as necessary.

The thickness of the recording layer depends on whether or not a binder is used, but generally it is 100 Å to 5 μm, preferably 200 Å.
to 1 μm, and preferably in the range of 200 Å to 5000 Å when no binder is used.

Note that the recording layer of the present invention can also be used as a laminated film in combination with other recording layers and/or protective layers and underlayers.

The above-mentioned solvents include 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, benzene, etc. Aromatics can be used alone or in combination. Application or attachment of the above solution can be carried out by any means such as spin coating, dip coating, roller coating, etc.

The above-mentioned compound () of the present invention is preferably used in a wet type as described above, but in some cases it can also be used in a dry process such as vapor deposition or CVD.

The present invention will be explained below using a method for synthesizing compound () and examples.

(Synthesis of compound ()) The compound of the above formula () is Shuzo AKIYAMA
etc. (CHEMISTRY LETTERS, pp.311-314,
It was synthesized in a similar manner to the method of (see 1981).

That is, an equivalent amount of 60% perchloric acid aqueous solution is added to a benzene solution of an alkynyl alcohol precursor (melting point ~ 175 ° C decomposition) obtained from the reaction of 4-dimethylaminophenyl acetylene and xanthone,
By stirring at room temperature, crude crystals of the compound () are obtained. This was separated and washed according to a conventional method, and the dried specimen was further recrystallized from dichloromethane to obtain a compound of formula () with a melting point of 164°C.
Obtained as needle-like crystals (decomposition). Absorption spectrum λmax 737nm (in cyclomethane), ε76000.

(Synthesis of compound ()) The compound of the above formula () is Shuzo AKIYAMA
etc. (CHEMISTRY LETTERS, pp.311-314,
It was synthesized in a similar manner to the method of (see 1981). That is, by adding an equivalent amount of 60% perchloric acid aqueous solution to a benzene solution of an alkynyl alcohol precursor (melting point ~ 135 ° C decomposition) obtained from the reaction of 4-dimethylaminophenyl acetylene and thioxanthone, and stirring at room temperature. , crude crystals of the compound () are formed.

This was separated and washed according to a conventional method, dried, and further recrystallized from dichloromethane.
The compound was obtained as needle crystals with a melting point of 195°C (decomposed). Absorption spectrum λmax 775nm (in dichloromethane), ε83500.

Example 1 100 milligrams of the compound represented by the above formula () was dissolved in a mixture of 5 grams of 2,2,2-trifluoroethanol and 5 grams of 2,2,3,3-tetrafluoro-1-propanol, The coating solution was filtered through a Teflon filter (pore size 0.2 microns). This coating solution is applied using a spin coating method (rotation speed
600 rpm) and air-dried to obtain an optical recording medium. The absorbance of this recording medium at a wavelength of 830 nm was 0.197, and the reflectance measured from the substrate side at the same wavelength was 16%.

A semiconductor laser beam with a wavelength of 830 nm was focused on this recording medium and irradiated from the substrate side. Signal recording was performed by irradiating pulsed light with a pulse width of 1 μsec at an irradiation surface power of 10.0 mW and a linear velocity of 4.24 m/sec.

When this recording section was irradiated with continuous light with an irradiation surface power of 0.8 mW and the signal was reproduced, a C/N ratio of 43 dB was obtained. Further, this regeneration operation was continued for one hour, but there was no change in the C/N ratio at all.

Also, when recording signals on this recording medium, if the irradiation surface power of the laser beam is 2.0 mW or less,
The reproduced signal showed a C/N ratio of 1 dB or less, and no recording occurred.

Example 2 177 milligrams of the compound represented by the above formula () was dissolved in 10 grams of 2,2,3,3,4,4,5,5-octafluoro-1-pentanol,
The coating solution was filtered through a Teflon filter (pore size 0.2 microns).

This coating solution was applied by spin coating (rotation speed: 900 rpm) onto a polycarbonate substrate onto which grooves with a pitch of 1.6 microns were transferred by injection molding, and air-dried to obtain an optical recording medium. The absorbance of this recording medium at a wavelength of 830 nm was 0.318, and the reflectance measured from the substrate side at the same wavelength was 17%.

A semiconductor laser beam having a wavelength of 380 nm was focused on this recording medium and irradiated from the substrate side. Signal recording was performed by irradiating pulsed light with a pulse width of 1 μsec at an irradiation surface power of 9.0 mW and a linear velocity of 4.24 m/sec.

When this recording section was irradiated with continuous light with an irradiation surface power of 0.8 mW and the signal was reproduced, a C/N ratio of 49 dB was obtained. Furthermore, this regeneration operation was continued for one hour, but there was no change in the C/N ratio at all.

Also, when recording signals on this recording medium, if the laser beam irradiation surface power is 1.7mW or less,
The reproduced signal showed a C/N ratio of 1 dB or less, and no recording occurred.

Example 3 79 milligrams of the compound represented by the above formula () and 79 milligrams of the compound represented by the above formula () were combined into 2,2,3,3,4,4,5,5-octafluoro-1-pene. It was dissolved in 10 grams of ethanol and filtered through a Teflon filter (pore size 0.2 microns) to prepare a coating solution. by injection molding
This coating solution was applied by spin coating (rotation speed: 800 revolutions/min) onto a polycarbonate substrate onto which grooves with a pitch of 1.6 microns had been transferred, and air-dried to obtain an optical recording medium. Wavelength of this recording medium
The absorbance at 830 nm was 0.248, and the reflectance measured from the substrate side at the same wavelength was 18%.

A semiconductor laser beam with a wavelength of 830 nm was focused on this recording medium and irradiated from the substrate side. Signal recording was performed by irradiating pulsed light with a pulse width of 1 μsec at an irradiation surface power of 6.0 mW and a linear velocity of 4.24 m/sec.

When this recording section was irradiated with continuous light with an irradiation surface power of 0.8 mW and the signal was reproduced, a C/N ratio of 49 dB was obtained. Furthermore, this regeneration operation was continued for one hour, but there was no change in the C/N ratio at all.

Also, when recording signals on this recording medium, if the laser beam irradiation surface power is 1.6 mW or less,
The reproduced signal showed a C/N ratio of 1 dB or less, and no recording occurred.

Claims (1)

[Claims] 1. An optical information recording medium composed of a substrate and a recording layer formed on the substrate, wherein the recording layer has the following general formula (): (Here, Y is O or S, X is ClO ₄ ,
1. An optical information recording medium comprising an acetylene derivative represented by BF ₄ , PF ₆ , Cl, F or Br). 2. The optical information recording medium according to claim 1, wherein the substrate is made of polycarbonate resin.