JPH05128592A - Optical information recording medium and recording / reproducing apparatus using the same - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a high-density optical information recording medium. An optical information recording medium comprising a substrate 1 on which a light absorbing layer 2 and a recording layer 3 are laminated, wherein the light absorbing layer 1 transmits a laser beam that is a recording or reproducing beam. An optical information recording medium made of a material that emits light within a half-value width of a light intensity distribution before light is incident.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium for recording and reproducing information by laser light, and more particularly to an optical information recording medium capable of high density recording by laser light and an optical information recording using the same. Reproduction device

[0002]

2. Description of the Related Art In recent years, a method for reducing the spot diameter by shortening the wavelength of a light source or improving the numerical aperture of a lens has been studied for high density recording on an optical disk. Furthermore, a magneto-optical disk [NIKKEI ELECTRONICS 1 capable of reproducing a signal having a recording pitch narrower than the spot diameter of the light source
991.3.4 (No. 521)], (Japanese Patent Application No. 1-22
9396).

[0003]

In order to shorten the wavelength of the light source, it is necessary to develop a semiconductor laser capable of oscillating a laser beam having a short wavelength. In addition, SHG (Second Harmonic)
It is conceivable to reduce the wavelength to 1/2 by using a (Generation) element, but in the present situation, the one that is practically used has not been found yet.

Further, in order to improve the numerical aperture of a lens, it is necessary to develop a new lens and an optical system accompanying it.

Furthermore, a magneto-optical disk capable of reproducing a signal having a recording pitch narrower than the spot diameter of the light source has been proposed. This disc is composed of a reproducing layer having a small coercive force and a recording layer having a large coercive force, and the temperature is increased in the Curie temperature region for recording, and the recording pit diameter can be made smaller than the spot diameter. In reproduction, an initial magnetic field is applied before reproduction so that all the magnetic signals in the reproduction layer near the detection signal are erased by reversing the magnetization in the same direction. By irradiating the reproduction layer from which recording has been erased with a laser, the information signal transferred from the recording layer to only the high temperature portion of the reproduction layer is detected, thereby achieving high density.

However, the above-mentioned conventional technique for increasing the density requires a new device, and the technique for reducing the recording pitch diameter is applicable only to the magneto-optical disk.

A dye whose absorption coefficient changes depending on the intensity of light, such as 1,3-diethyl-4,2-quinolinoxacarbocyanine iodide (1,3-diethyl-).
4,2-quinolyoxacarbocyanineiodide), 3,3'-
Diethyl oxadicarbocyanine iodide (3,
It is known to use 3'-diethyloxadicarbocyanine iodide) or the like. However, there is a problem that the dye has poor light stability and is difficult to use as a solid film.

As described above, the appearance of an optical information recording medium capable of performing high-density recording with only a substrate structure without using a special device on all read-only type, write-once type, rewritable type optical disks has been developed. Is desired.

An object of the present invention is to provide a light absorbing layer without changing the wavelength of a light source or the numerical aperture of a lens,
An object of the present invention is to provide an optical information recording medium capable of higher density recording than ever before.

Another object of the present invention is to provide a method for producing the above optical information recording medium capable of high density recording.

Another object of the present invention is to provide a recording / reproducing apparatus using the above optical information recording medium.

[0012]

According to the present invention, as a result of various investigations for solving the above-mentioned problems of the high density recording medium, it can be formed as a solid film, and the absorption coefficient depends on the intensity of light. It was made based on the finding that it is possible to obtain an optical information recording medium capable of recording and reproducing with a spot smaller than the conventional laser beam collecting diameter by finding a dye that changes and forming it on a substrate. , Its gist is as follows.

(1) An optical information recording medium in which a light absorbing layer and a recording layer are laminated on a substrate, wherein the light absorbing layer has an absorption coefficient which changes depending on the intensity of light, An optical information recording medium comprising a material capable of forming a recording bit with a diameter equal to or less than a diffraction limit.

(2) An optical information recording medium in which a light absorbing layer and a recording layer are laminated on a substrate, wherein the light absorbing layer transmits the laser light which is the recording or reproducing light. An optical information recording medium made of a material capable of producing light within the half width of the light intensity distribution before incidence.

The light absorbing layer has the general formulas [1] and [2].

[0016]

[Chemical 3]

[0017]

[Chemical 4]

[In the above formula, M ₁ is a Group IV metal atom selected from Si, Ge and Sn, M is a transition atom, Z ₁ , Z ₂ and Z
₃ and Z ₄ are an unsubstituted or pyridine ring having one or more monovalent substituents X, a benzene ring, a naphthalene ring skeleton, X
Is an alkyl group having 1 to 20 carbon atoms, an alkenyl group, an alkylthio group, an aromatic hydrocarbon group, an acyl group, a tri-substituted silyl group, Y ₁ and Y ₂ are -Ar, -OAr, -OSi (OAr).
₃ , -OR, -OSi (R) ₃ , -OSi (OR) ₃ , -OC
(C ₆ H ₅ ) ₃ (wherein Ar is a phenyl group, a substituted phenyl group, a benzyl group, a substituted benzyl group, and R is a carbon number of 1 to 20).
Linear or branched alkyl group) and may be different from each other. ] At least two kinds of derivatives of azaphthalocyanine, phthalocyanine and naphthalocyanine represented by In addition, the above general formula [1]
The compounding ratio of [2] is preferably [1] / [2] of 1 or more by weight.

As the recording layer, an aromatic or unsaturated aliphatic diamine type metal complex, an aromatic or unsaturated aliphatic dithiol type metal complex, a phthalocyanine type complex, a naphthalocyanine type complex, a squalium type dye, a naphthoquinone type complex, an anthraquinone. Examples of organic materials include dyes and polymethine dyes.

When an organic material is used for the recording layer, a protective layer may be provided in order to prevent deterioration of the light absorbing layer due to a solvent or deformation of the light absorbing layer due to absorbed light. In this case, the protective layer material may be an organic or inorganic material.

As the recording layer, Te-Se alloy, Te-C thin film, Pb-Te-Se system, CS ₂ -Te.
Thin film, Sb ₂ Se ₃ / Bi ₂ Te ₃ thin film, oxide, sulfide system (for example, TeO ₂ , GeO ₂ , Sb ₂ O ₃ , MoO ₃ ),
Rare earth metals such as Gd, Tb, Dy and Fe, Co, Ni
InS, an amorphous magnetic film combining transition metals of
Inorganic materials such as bTe alloys and GeSbTe alloys can be used.

When an inorganic material is used as a recording medium,
An adhesion layer may be provided in order to improve the adhesion between the light absorption layer and the recording layer. A water-soluble polymer is used as the adhesion layer.

Examples of the substrate include vinyl chloride resin, acrylic resin, polyolefin resin, polycarbonate resin polyvinyl acetal resin, unsaturated polyester resin,
Thermoplastic and thermosetting resins such as vinyl ester resin, polystyrene resin, polyether sulfone resin, polyether ether ketone resin, epoxy resin, allyl resin polyimide, polyamide resin, or inorganic polymers such as silicone resin and phosphazene resin. Alternatively, glass, SiO ₂ , Si ₃ N ₄ , metal, or the like can be used. These can be formed into an arbitrary shape such as a film shape or a sheet shape according to the purpose. Further, the substrate surface may be a flat surface, a mirror surface, or an engraved guide groove pattern (pre-groove).

If the substrate is transparent, it is desirable that the substrate has a light transmittance of 85% or more at the time of writing and reading signals and has a small optical anisotropy.

In the present invention, the method of forming the light absorbing layer and the recording layer with an organic material can be formed by ordinary spin coating, spray coating or dip coating. For the light absorption layer, a solution of the derivative represented by the general formula [1] or [2] in an amount of 0.1 to 5% by weight is used and the amount is 1000 to 5000 rp.
Preferred is the method of spin coating with m and then evaporating the solvent.

As the solvent, in addition to aromatic solvents and halogen solvents, ketone solvents, ether solvents, saturated hydrocarbon solvents or mixed solvents thereof are used. Particularly, a mixed system of carbon tetrachloride, methylcyclohexane and toluene is preferable.

A binder may also be used. As the binder, a high molecular polymer such as imide, amide, styrene, acrylic, silicone, epoxy and phenol is used.

The thickness of the light absorption layer formed on the substrate is 0.1.
It may be about 1000 nm. However, it is desirable that the film thickness is such that energy does not excessively attenuate due to the light passing through the light absorption layer. The film thickness is preferably 1 to 50 nm. Also,
The light absorption layer has a transmittance of 50 to 80%, preferably 65.
~ 75%.

Further, the recording layer formed on the light absorbing layer may have a film thickness in the range of 20 to 500 nm. However, in an optical information recording medium containing a compound whose absorption wavelength of the recording layer is slightly deviated from the laser wavelength, the interference effect of reflectance due to the film thickness is large. Therefore, it is preferable to use the film thickness region where the reflectance is large. Preferably, the first interference film thickness region having a high reflectance and a low absorptance is 30 to 80 nm.

In the optical information recording medium of the present invention thus produced, the irradiated portion is melted, sublimated or phase-changes by irradiation with a laser beam, and pits are formed by spin inversion in the magnetic film to record information. .. The laser power is preferably 2 to 20 mW on the recording layer. Further, at the time of reproduction, a low level that does not damage the recording layer is preferable, and a laser power that does not affect the pit shape even when reproduced at least 10 ⁵ times is desirable. Such laser power is 0.5 on the recording layer.
~ 1.5 mW is preferred.

The laser light is selected from laser light of N ₂ , He-Ne, Ar, dye, semiconductor, etc. according to the absorption wavelength of the recording layer. Further, the compound of the light absorption layer can be selected according to the wavelength of the laser light used.

In the present invention, by using the derivative represented by the above general formulas [1] and [2], the light absorption layer which has been conventionally used in a solution state can be formed as a solid film. The optical information recording medium of the present invention can be used in compact discs, video discs, optical recording cards, photoconductors for laser beam printers, and the like.

[0033]

According to the present invention, recording and reproducing can be performed with a recording bit smaller than the spot diameter of the light source, when the laser light passes through the light absorption layer, only the central portion of the laser light, which has many photons, reaches the recording layer. This is because recording and reproduction are performed only with the light of that portion. For example, the spot diameter of the laser light transmitted through the light absorption layer can be about 0.6 μm (wavelength 830 nm, lens numerical aperture 0.52), which is about 3 times that of the conventional optical information recording medium using an optical system. Double linear density recording is possible.

[0034]

【Example】

[Example 1] Bis (tributylsiloxy) silicon-tetra (trimethylsilyl) naphthalocyanine and copper tetra-butylnaphthalocyanine were dissolved in carbon tetrachloride at a weight ratio of 1: 0.4 to prepare a 0.3 wt% solution. It was created. This solution was applied on a polycarbonate substrate (thickness: 1.2 mm) 1 having a diameter of 5.25 inches by spin coating and dried in a constant temperature bath at 90 ° C. for 1 hour to form a light absorption layer 2. The light transmittance of this light absorption layer 2 is 72 at a wavelength of 830 nm.
%Met.

As shown in FIG. 2, the disk 11 is provided with a laser beam from the semiconductor laser 4, a collimator lens 5, a shaping prism 6, a 1/4 wavelength plate 9 and an objective lens 10.
The disk 11 provided with the light absorption layer 2 was irradiated with the light through the above, and the reflected light was measured by the detector 8 through the polarization beam splitter 7 to measure the light intensity distribution. Wavelength 83
The light intensity distribution was measured by an optical pickup checker LE-100 / 200 manufactured by Ono Sokki Co., Ltd. at 0 nm and a lens numerical aperture: 0.52.

The laser light intensity had a Gaussian distribution and the spot diameter was 0.6 μm. This value is smaller than the spot diameter value (1.6 μm) given by the following formula (1). It was confirmed that the spot diameter was reduced by passing through the light absorption layer.

[0037]

[Equation 1]

[Comparative Example 1] The intensity distribution of the laser beam was measured in the same manner as in Example 1 except that only a polycarbonate substrate having a diameter of 5.25 inches was used. The intensity of the laser light has a Gaussian distribution, but the spot diameter is 1.6 μm,
It was a value expected by the diffraction limit of the above formula (1).

[Example 2] As in Example 1, bis (trihexylsiloxy) silicon-tetra (trimethylsilyl) phthalocyanine and copper-tetrabutylphthalocyanine were mixed on a polycarbonate substrate 1 in a weight ratio of 1: 0.4.
Example 1 was a 0.3 wt% solution in carbon tetrachloride at
A disk 11 was prepared by applying the same method as the above in the spin coating method. The light transmittance of this light absorption layer is 68 at a wavelength of 670 nm.
%Met.

Semiconductor laser wavelength of this disk 11:
The intensity distribution at 670 nm and lens numerical aperture: 0.55 was measured. The laser light intensity was Gaussian distributed and the spot diameter was 0.4 μm. This value is smaller than the value (1.2 μm) of the spot diameter given by the above formula (1), and it was confirmed that the spot diameter becomes smaller by passing through the light absorption layer.

[Comparative Example 2] The intensity distribution of the laser beam was measured in the same manner as in Example 2 except that only a polycarbonate substrate having a diameter of 5.25 inches was used. The intensity of the laser light has a Gaussian distribution, but the spot diameter was 1.2 μm, which was a value expected at the diffraction limit.

Example 3 As in Example 1, bis (trihexylsiloxy) silicon-tetra (trimethylsilyl) naphthalocyanine and copper-tetrabutylnaphthalocyanine were mixed on a polycarbonate substrate 1 in a weight ratio of 1 :.
A 0.3% by weight solution of 0.4% dissolved in carbon tetrachloride was applied by spin coating to prepare a disk. The light transmittance of this light absorption layer was 72% at a wavelength of 830 nm.

As the information recording layer 3 on this disc 11,
A TeSe alloy layer having a film thickness of 40 nm is formed by the sputtering method,
It was used as an optical information recording medium. Using the same optical system as in Example 1 using the optical information recording medium, the recording frequency dependency of C / N (signal / noise) was measured at a linear velocity of 8 m / s, a writing laser power of 9 mW, and a reproducing light of 1 mW. The result is shown in FIG.

Comparative Example 3 An optical information recording medium without the light absorbing layer of Example 3 was prepared, and the recording frequency dependence of C / N was measured using the same optical system as in Example 3. The result is shown in FIG.

It can be seen that when the recording pit length obtained from the linear velocity and the recording frequency is 0.8 μm or less, the C / N decreases.

Example 4 As in Example 1, bis (trihexylsiloxy) silicon-tetra (trimethylsilyl) naphthalocyanine and copper-tetrabutylnaphthalocyanine were mixed on a polycarbonate substrate 1 in a weight ratio of 1:
A disk 11 was prepared by applying a 0.3% by weight solution of 0.4% dissolved in carbon tetrachloride by spin coating. The light transmittance of this light absorption layer was 72% at a wavelength of 830 nm.

A 2% by weight polyvinyl alcohol aqueous solution was applied thereon by a spin coating method to form a uniform layer of polyvinyl alcohol having a thickness of about 1400 Å. NK for this
Information recording layer 3 by spin coating using a solution of 2014 (manufactured by Nihon Sensitive Dye) in 1,2-dichloroethane
Was deposited.

Using this disc 11 and the same optical system as in Example 1, the recording frequency dependence of C / N was measured at a linear velocity of 8 m / s, a writing laser power of 9 mW, and a reproducing light of 1 mW. The result is shown in FIG.

[Comparative Example 4] An optical information recording medium without the light absorbing layer 2 of Example 4 was prepared, and the recording frequency dependency of C / N was measured using an optical system as in Example 4. The result is shown in FIG. When the pit length is 0.8 μm or less, C / N
You can see that is going down.

Example 5 As in Example 1, bis (trihexylsiloxy) silicon-tetra (trimethylsilyl) phthalocyanine and copper-tetrabutylphthalocyanine were mixed on a polycarbonate substrate 1 in a weight ratio of 1: 0.4.
Then, a 0.3% by weight solution dissolved in carbon tetrachloride was applied by a spin coating method to prepare a disk 22. The light transmittance of this light absorption layer was 72% at a wavelength of 830 nm.

On top of that, SiN, TbFeCo alloy, Si
The information recording layer 3 was formed by sequentially stacking N and Al by a sputtering method.

Using this disc 22, the optical system shown in FIG. 5 was used to measure the recording frequency dependence of C / N at a linear velocity of 8 m / s, a writing laser power of 9 mW, and a reproducing light of 1 mW. The result is shown in FIG.

In FIG. 5, the laser light from the semiconductor laser 12 is applied to the collimator lens 13 and the molding prism 1.
4, through the polarizing beam splitter 15 and the objective lens 16, irradiate the disk 22 provided with the light absorption layer 2,
The reflected light is detected by the detector 17 through the polarization beam splitter 15 and the critical angle prism 18, and the focus,
Take tracking. Also, the polarization beam splitter 1
5, the magneto-optical signal was detected by the detector 21 via the polarizer 19, the condenser lens 20.

[Comparative Example 5] An optical information recording medium without the light absorbing layer of Example 5 was prepared, and the recording frequency dependence of C / N was measured using an optical system as in Example 5. The result is shown in FIG. It can be seen that when the pit length is 0.8 μm or less, the C / N decreases.

An example of a schematic structure of a recording / reproducing apparatus using the optical information recording medium (optical disk) of the present invention is shown in FIG.

An optical head equipped with a laser oscillator, an optical disk for recording and reproducing information by a laser from the optical head, a motor for rotating the recording medium, and a drive circuit for controlling the operation of the optical head and the motor. ,
Recording / reproduction can be performed by an optical information recording / reproducing apparatus including at least a processor for giving a command to the drive circuit and an input means for inputting information to the processor and an output means for outputting information.

[0057]

The present invention provides a high density optical information recording medium capable of writing and erasing (recording, reproducing) with a spot diameter smaller than the diffraction limit of laser light by providing a light absorbing layer on the optical information recording medium. Obtainable. Further, the light absorption layer has excellent light stability.

[Brief description of drawings]

FIG. 1 is a substrate configuration diagram of an optical information recording medium of the present invention.

FIG. 2 is a schematic configuration diagram of an optical system using a semiconductor laser having a wavelength of 830 nm.

FIG. 3 C of an optical information recording medium having an inorganic information recording layer
7 is a graph showing the recording frequency dependence of / N.

FIG. 4 C of an optical information recording medium having an organic information recording layer
7 is a graph showing the recording frequency dependence of / N.

FIG. 5 is a schematic configuration diagram of an optical system using a semiconductor laser having a wavelength of 670 nm.

FIG. 6 is a graph showing the recording frequency dependence of C / N of a magneto-optical recording medium.

FIG. 7 is a block diagram showing a schematic configuration of a recording / reproducing apparatus for recording / reproducing information on / from the optical information recording medium of the present invention.

[Explanation of symbols]

1 ... Substrate, 2 ... Light absorbing layer, 3 ... Information recording layer, 4, 12 ...
Semiconductor laser, 5, 13 ... Collimator lens, 6,
14, 18 ... Prism, 7, 15 ... Polarizing beam splitter, 8, 17 ... Detector, 9 ... Quarter wave plate, 1
0,16 ... Objective lens, 11, 22 ... Disk, 19 ...
Polarizer, 20 ... Condensing lens, 21 ... Detector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Ohara 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hiritsu Manufacturing Co., Ltd.

Claims (9)

[Claims] 1. An optical information recording medium comprising a substrate and a light absorbing layer and a recording layer laminated on the substrate, wherein the light absorbing layer has an absorption coefficient which varies depending on the intensity of light, thereby diffracting incident light. An optical information recording medium comprising a material capable of forming a recording bit with a diameter equal to or smaller than a limit. 2. An optical information recording medium in which a light absorbing layer and a recording layer are laminated on a substrate, wherein the light absorbing layer transmits a laser beam which is a recording or reproducing light. An optical information recording medium, characterized in that it is made of a material capable of making the light within the half width of the light intensity distribution before incidence. 3. The light-absorbing layer has the general formulas [1] and [2]: [Chemical 2] [In the above formula, M ₁ is IV selected from Si, Ge, and Sn.
Group metal atom, M is a transition atom, Z ₁ , Z ₂ , Z ₃ and Z ₄ are unsubstituted or have a pyridine ring having one or more monovalent substituents X, a benzene ring, a naphthalene ring skeleton, and X is a carbon number. 1 to
20 alkyl groups, alkenyl groups, alkylthio groups, aromatic hydrocarbon groups, acyl groups, tri-substituted silyl groups, Y ₁ ,
Y ₂ is -Ar, -OAr, -OSi (OAr) ₃ , -OR,
_{-OSi (R) 3, -OSi (} OR) 3, -OC (C 6 H 5)
₃ (wherein Ar is a phenyl group, a substituted phenyl group, a benzyl group, a substituted benzyl group, and R is a linear or branched alkyl group having 1 to 20 carbon atoms) and may be different from each other. ] The optical information recording medium according to claim 1 or 2, containing at least two kinds of derivatives of azaphthalocyanine, phthalocyanine and naphthalocyanine represented by the following formula. 4. The light absorbing layer comprises the compound represented by the general formula [1],
The azaphthalocyanine represented by [2], phthalocyanine, and at least two derivatives of naphthalocyanine are contained, and the compounding ratio [1] / [2] is 1 or more. Optical information recording medium. 5. The optical information recording medium according to claim 1, wherein the recording layer is made of an organic material or an inorganic material. 6. A method for producing an optical information recording medium, comprising forming a light absorbing layer on a substrate and forming a recording layer on the light absorbing layer,
The light absorption layer is prepared by dissolving at least two kinds of azaphthalocyanine, phthalocyanine and naphthalocyanine derivatives represented by the general formulas [1] and [2] in a solvent to prepare a 0.1-5 wt% solution. A method for manufacturing an optical information recording medium, which comprises coating the substrate and evaporating the solvent. 7. An optical head equipped with a laser oscillator,
An information recording medium that records and reproduces information by a laser from the optical head, a rotating unit that rotates the recording medium, a drive circuit that controls the operation of the optical head and the rotating unit, and a command to the drive circuit. In an optical information recording / reproducing apparatus including at least a processor for giving information and an information input / output unit for inputting / outputting information to / from the processor, the information recording medium has a light absorption layer and a recording layer laminated on a substrate, Optical information recording / reproducing, characterized in that the light absorption layer is made of a material that can transmit a laser beam, which is a recording or reproducing beam, into light within a half-value width of a light intensity distribution before the laser beam is incident. apparatus. 8. The laser power of the laser oscillator is 2 when recording on the recording layer film surface of the information recording medium.
The optical information recording / reproducing apparatus according to claim 7, further comprising a laser oscillator having a power of -20 mW and a reproducing power of 0.5-1.5 mW. 9. The oscillation wavelength of the laser oscillator is 64.
9. The optical information recording / reproducing apparatus according to claim 7, wherein the optical information recording / reproducing apparatus has a thickness of 0 to 720 nm or 780 to 830 nm.