JP2005100577A - Recordable optical recording medium, and its recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recordable optical recording medium wherein recording and reproduction can be easily performed even when high density recording and reproduction are performed in a wavelength region of a blue laser wavelength or below, especially a wavelength region of 450 nm or below and even when a shallow groove substrate having satisfactory transfer properties is used and an improvement of recording characteristics such as recording sensitivity, a modulation degree, and jitter and a power margin can be realized. <P>SOLUTION: In the recordable optical recording medium having a recording layer consisting of an organic dye or its metal complex compound directly or via an inorganic layer on a substrate having a guide groove, the maximum height H of deformation of a recording mark part generated when recording is performed and the depth D of the guide groove satisfy the relation of 0.05<H/D<1 and recording and reproduction of a multi-level of a binary level or more can be performed by irradiation with a laser beam whose irradiation power or irradiation time is modulated in a binary level or more and having ≤450 nm wavelength. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a write-once type optical recording medium (WORM) having a recording layer made of an organic dye or a metal complex compound thereof capable of high-density recording even in a blue laser wavelength region.

Development of blue lasers capable of ultra-high density recording is rapidly progressing, and write-once type optical recording media corresponding thereto are being developed.
In conventional write-once optical recording media, recording pits are formed by irradiating a recording layer made of an organic material with laser light and causing a change in refractive index mainly due to decomposition and alteration of the organic material. The optical constant and decomposition behavior of the organic material used are important factors for forming good recording pits.
Accordingly, it is necessary to select an organic material used for the recording layer that is suitable for optical properties and decomposition behavior with respect to the blue laser wavelength. In other words, the recording / reproducing wavelength has a large absorption band in order to increase the reflectivity when unrecorded, and to cause a large change in refractive index due to decomposition of the organic material by laser irradiation (this provides a large degree of modulation). It is selected so as to be located at the bottom of the long wavelength side.
This is because the skirt on the long wavelength side of the large absorption band of the organic material is a wavelength region having an appropriate absorption coefficient and a large refractive index.
However, an organic material having an optical property with respect to a blue laser wavelength that is the same as the conventional value has not yet been found. In order to obtain an organic material having an absorption band in the vicinity of the blue laser wavelength, it is necessary to reduce the molecular skeleton or shorten the conjugated system, but this leads to a decrease in absorption coefficient, that is, a decrease in refractive index. Because.
That is, there are many organic materials having an absorption band near the blue laser wavelength, and the absorption coefficient can be controlled. However, since there is no large refractive index, a large degree of modulation cannot be obtained.

For example, Patent Documents 1 to 5 describe organic materials for blue lasers.
However, these publications only measure the spectra of the solution and the thin film even when looking at the examples, and there is no description regarding recording and reproduction.
In Patent Documents 6 to 8, although there is a description of recording in the examples, the recording wavelength is 488 nm, and there is no description regarding recording conditions and recording density, and only a description that good recording pits can be formed. It is.
Although Patent Document 9 has a description of recording in the examples, the recording wavelength is 430 nm, and there is no description regarding recording conditions and recording density, but only a description that a good degree of modulation has been obtained. .
In Patent Documents 10 to 19, there is an example of recording at a recording wavelength of 430 nm and NA of 0.65 in the examples, but the low recording density condition (recording density equivalent to DVD) is that the shortest pit is 0.4 μm.
In Patent Document 20, the recording / reproducing wavelength is 405 to 408 nm, but there is no specific description regarding the recording density, and a low recording density condition of recording a 14T-EFM signal.

Further, the following technologies are disclosed regarding the layer configuration and recording method different from those of conventional CD and DVD optical recording media.
Patent Document 21 discloses a technique for recording by changing the extinction coefficient (absorption coefficient in the present invention) of a saturable absorbing dye in a layer structure of substrate / saturable absorbing dye-containing layer / reflective layer. .
Patent Document 22 discloses a technique for recording by changing the color or deformation of a metal vapor deposition layer by heat generated by the light absorption layer in a layer configuration of substrate / metal vapor deposition layer / light absorption layer / protective sheet. Has been.
Patent Document 23 discloses a technique for performing recording by changing the film thickness of the recording layer and changing the depth of the groove in the layer configuration of substrate / dielectric layer / recording layer including light absorber / reflective layer. ing.
Patent Document 24 discloses a technique for performing recording by changing the film thickness of the recording layer by 10 to 30% in a layer configuration of substrate / recording layer including light absorber / metal reflective layer.
Patent Document 25 discloses a technique for recording by increasing the groove width of a substrate by 20 to 40% with respect to an unrecorded portion in a layer configuration of substrate / recording layer containing organic dye / metal reflective layer / protective layer. Is disclosed.

Patent Document 26 discloses a technique for recording by forming a bubble by deforming a metal thin film with a layer structure of substrate / intermediate layer / metal thin film.
In Patent Document 27, the recording auxiliary layer is deformed into a concave shape in a layer configuration of substrate / light absorption layer / recording auxiliary layer / light reflecting layer, and the light reflecting layer is deformed into a concave shape along with the deformation of the recording auxiliary layer. Thus, a technique for recording is disclosed.
In Patent Document 28, a recording auxiliary layer having a layer structure of substrate / light absorbing layer / porous recording auxiliary layer / light reflecting layer or substrate / porous recording auxiliary layer / light absorbing layer / light reflecting layer is provided. A technique is disclosed in which recording is performed by deforming into a concave shape and deforming the light reflecting layer into a concave shape along with the deformation of the recording auxiliary layer.
In Patent Document 29, the light absorption layer is deformed into a concave shape in a layer configuration of substrate / porous light absorption layer / light reflection layer, and the light reflection layer is deformed into a concave shape along with the deformation of the light absorption layer. A technique for recording with the above is disclosed.
In Patent Document 30, recording is performed by shifting the absorption spectrum of an organic dye to the short wavelength side in a layer structure of a substrate / recording layer containing an organic dye / recording auxiliary layer, in which the recording auxiliary layer and the organic dye are compatible. Techniques for performing are disclosed.

Patent Document 31 discloses a technique in which recording is performed by forming bumps on a substrate and the composite functional layer in a layer configuration in which a composite functional layer having a function of a reflective layer and a recording layer and a protective layer are sequentially formed on the substrate. Has been. In addition, as a composite functional layer, there exists a prescription | regulation with metals, such as nickel, chromium, titanium, or those alloys.
In Patent Document 32, a metal thin film layer, a deformable buffer layer, a reflective layer, and a protective layer are sequentially formed on a substrate, and the substrate and the metal thin film layer are deformed at the same time. A technique for recording by reducing the thickness is disclosed. In addition, as a metal thin film layer, there exists prescription | regulation with metals, such as nickel, chromium, titanium, or those alloys. In addition, as the buffer layer, there is a description that a resin that is easily deformable and has an appropriate fluidity is used, and a pigment may be contained in order to promote deformation.
In Patent Document 33, a metal thin film layer, a buffer layer, and a reflective layer are sequentially laminated on a substrate, and the substrate and the metal thin film layer are deformed. At the same time, the buffer layer thickness and the optical constant at the deformed portion are set. A technique for recording by changing is disclosed. In addition, as a metal thin film layer, there exists a description that metals, such as nickel, chromium, titanium, or those alloys are preferable. The buffer layer is made of a mixture of a dye and an organic polymer, and a dye having a large absorption band near the recording / reproducing wavelength is used.

In Patent Document 34, a metal recording layer, a buffer layer, and a reflective layer are sequentially laminated on a substrate, and the substrate and the metal recording layer are deformed. At the same time, the buffer layer thickness and the optical constant at the deformed portion are set. A technique for recording by changing is disclosed. In addition, as a metal recording layer, there exists a description that metals, such as nickel, chromium, titanium, or those alloys are preferable. The buffer layer is made of a mixture of a dye and a resin, and a dye having a large absorption band near the recording / reproducing wavelength is used.
However, although there is a description in the literature using these metal thin film layers that a laser having a wavelength of 400 to 850 nm can be used as a light source, what is actually used in the example is a 780 nm for CD-R. The effect is confirmed only in the case of a laser only and a recording density as low as about CD-R. Moreover, the evaluation item is CNR, which is an evaluation with a single pattern of only 3T. As is well known, binary recording has no practical meaning unless jitter evaluation is performed in recording with a random pattern. Therefore, it cannot be said that these documents describe a technique capable of realizing high-density binary recording.

Patent Document 35 discloses an invention for performing multilevel recording using phthalocyanine in a recording layer, but the object of the invention is a medium for CD-R / RW, which is specifically described as an embodiment. Only when the laser wavelength is 785 nm and NA is 0.5. That is, since it is an invention relating to multi-level recording at a very low density and λ / NA is used to define the range of the groove width W, which is an essential requirement, a medium for high density recording can be easily obtained. It is not an invention whose contents can be diverted. In addition, according to the study by the present inventors, a good multilevel signal was not obtained at all in high-density recording using a laser having a wavelength of 450 nm or less as in the present invention.
Patent Document 36 aims to provide a stable protective layer by providing a protective layer mainly composed of TeO in contact with the information recording layer. That is, the invention avoids the use of a protective film that releases the S primitive that diffuses and enters the recording film, such as ZnSSiO ₂ that is normally used. However, this prior art uses TeO as a protective layer, and does not use TeO as a recording auxiliary layer as in the present invention. In this prior art, the recording layer uses a phase change film and is evaluated according to the DVD-RAM standard. Therefore, it is not an invention for a write-once optical recording medium using a blue laser as in the present invention, but is a completely different technique.

  Patent Documents 37 to 38 disclose an invention in which recording is performed by applying a phthalocyanine dye to a blue laser medium, but it has been known for a long time that phthalocyanine has an absorption region near 400 nm. Simply changing the reflectivity is technically meaningless. In addition, in binary level recording, it is important to be able to write a random pattern, but these documents only show evaluation items such as recording by a single pattern and C / N and modulation degree as examples, There is no description or suggestion about the conditions for writing the random pattern. If the single pattern is used, the modulation level will increase as the input energy rises. However, if high energy that is not common sense is input to increase the modulation level, the substrate change should be deformed beyond the groove depth. Even if the degree is increased, if a random pattern cannot be written, there is no meaning as binary level recording.

As described above, the above prior art is not aimed at realizing an optical recording medium in the blue laser wavelength region, and is not a layer configuration or a recording method effective in the blue laser wavelength region.
In particular, in the vicinity of 405 nm, which is the center of the oscillation wavelength of a blue semiconductor laser currently in practical use, an organic compound having an optical constant comparable to the optical constant required for the recording layer of a conventional write-once optical recording medium is present. There is almost no.
In addition, there are no examples in which recording conditions are clarified near 405 nm and recording is performed at a higher recording density than DVD.
Furthermore, many of the examples in the above-mentioned patent documents are experiments with a conventional disk configuration, and although a configuration different from the conventional disk configuration has been proposed, the same optical characteristics as the conventional dyes are used. There is no effective proposal for a layer structure, a recording principle, or a recording method for easily realizing a write-once optical recording medium using an organic compound as a recording layer in the blue laser wavelength region.

Further, in a write-once type optical recording medium using a conventional organic compound for the recording layer, a large refractive index and a relatively small absorption coefficient (0.05 to 0) with respect to the recording / reproducing wavelength from the viewpoint of securing the degree of modulation and reflectance. Only organic compounds having (about .07) can be used.
That is, since the organic compound does not have a large absorption capacity for the recording light, it is impossible to reduce the film thickness of the organic compound, and thus it is necessary to use a substrate having a deep groove ( Since organic compounds are usually formed by spin coating, the organic compound was buried in deep grooves to increase the film thickness).
Therefore, it becomes very difficult to form a substrate having a deep groove, which has been a factor of deteriorating the quality as an optical information recording medium.
Furthermore, in a write once optical recording medium using a conventional organic compound for the recording layer, the main absorption band of the organic compound exists in the vicinity of the recording / reproducing wavelength, so that the wavelength dependence of the optical constant of the organic compound increases (depending on the wavelength). Recording characteristics such as recording sensitivity, modulation factor, jitter, error rate, and reflectivity change greatly with respect to fluctuations in recording / reproducing wavelength due to individual differences of lasers, environmental temperature changes, etc. There was a problem.

JP 2001-181524 A JP 2001-158865 A JP 2000-343824 A JP 2000-343825 A JP 2000-335110 A Japanese Patent Application Laid-Open No. 11-221964 Japanese Patent Laid-Open No. 11-334206 JP 2000-43423 A JP-A-11-58955 JP 2001-39034 A JP 2000-149320 A JP 2000-113504 A JP 2000-108513 A JP 2000-222772 A JP 2000-218940 A JP 2000-222771 A JP 2000-158818 A JP 2000-280621 A JP 2000-280620 A Japanese Patent Laid-Open No. 2001-146074 JP-A-7-304258 JP-A-8-83439 JP-A-8-138245 JP-A-8-297838 JP-A-9-198714 Japanese Patent No. 2506374 Japanese Patent No. 2591939 Japanese Patent No. 2591940 Japanese Patent No. 2591941 Japanese Patent No. 2998925 JP-A-9-265660 Japanese Patent Laid-Open No. 10-134415 Japanese Patent Application Laid-Open No. 11-306591 JP-A-10-124926 JP 2002-334438 A JP 2002-298436 A JP 2002-301870 A JP 2002-324337 A

  The present invention solves the above-mentioned problems, and even when recording / reproduction is performed at a high density at a binary level or higher in a region of a blue laser wavelength or less, particularly in a wavelength region of 450 nm or less, a shallow groove substrate having good transferability is obtained. An object of the present invention is to provide a write-once type optical recording medium that can be easily recorded and reproduced even when used, and that can improve recording characteristics such as recording sensitivity, modulation factor, jitter, and power margin.

（式中、フタロシアニン骨格周辺の１〜１６は炭素原子の位置を表す。フタロシアニン骨格に結合する酸素原子は、１又は４、５又は８、９又は１２、１３又は１６の何れかの炭素原子に結合している。また、Ｒ１はフッ素置換されたアルキル基を表し、Ｒ２はフェニル基、又はアルキル基を有するフェニル基を表し、Ｒ３はアルキル基、フッ素置換されたアルキル基、又は水素原子を表す。ＭはＶＯ又はＴｉＯを表す。）
１１） 照射時間と照射パワーの少なくとも一方が３段階以上に設定されたレーザにより、グルーブに沿った記録再生用レーザの進行方向における任意の単位長さ及びこれと直行する方向の任意の単位幅となる仮想記録セルに３種類以上の大きさの異なる記録マークが形成される事により、光反射率が変調され情報をマルチレベル記録できる事を特徴とする１）〜１０）の何れかに記載の追記型光記録媒体。
１２） 記録マーク部の変形の最大高さＨと案内溝の深さＤとの関係が０．０５＜Ｈ／Ｄ＜１という関係を満足し、ビ−ム径以上の長さを有する記録マ−ク部の前端エッジと後端エッジの変調度差が±２０％以内となる再生信号を発生する記録部を形成できるような記録パワー又は記録ストラテジで２値レベル以上の記録を行うことを特徴とする４）〜１１）の何れかに記載の追記型光記録媒体の記録方法。但し、上記変調度差は、後端エッジの変調度をＴ、前端エッジの変調度をＬとして、下記式で定義されるものである。
変調度差（％）＝（Ｔ−Ｌ）×１００／Ｔ The above problems are solved by the following inventions 1) to 12) (hereinafter referred to as the present invention 1 to 12).
1) A recording layer made of an organic dye or a metal complex compound thereof is provided directly on a substrate having a guide groove or via an inorganic layer. When recording is performed, the maximum height H of deformation of the recording mark portion and guidance are provided. By irradiating a laser beam having a wavelength of 450 nm or less, in which the groove depth D satisfies the relationship of 0.05 <H / D <1, and the irradiation power or irradiation time is modulated to a binary level or more, 2 A write-once type optical recording medium capable of multi-level recording / reproduction of a value level or three or more values.
2) The guide groove has a track pitch of 0.25 to 0.5 μm, a depth of 20 to 150 nm, a groove bottom width of 0.10 to 0.25 μm, and an unrecorded reflectance of 2 to 50%. The write-once type optical recording medium as described in 1) above.
3) A reproduction signal is generated in which a difference in modulation degree between the leading edge and the trailing edge of the recording mark portion having a length equal to or larger than the beam diameter is within ± 20%. 1) or 2) The write-once type optical recording medium as described. However, the modulation degree difference is defined by the following equation, where T is the modulation degree of the trailing edge and L is the modulation degree of the leading edge.
Modulation difference (%) = (TL) × 100 / T
4) The write-once type optical recording medium according to any one of 1) to 3), wherein a recording auxiliary layer made of an inorganic material is provided between the substrate and the recording layer.
5) The write-once type optical recording medium as described in 4), wherein the main component of the recording auxiliary layer is Te or Te oxide.
6) The write-once type optical recording medium as described in 4) or 5), wherein the oxygen content in the material of the recording auxiliary layer is 0 to 60 atomic%.
7) The recordable optical recording medium according to any one of 4) to 6), wherein the recording auxiliary layer has a thickness of 1 to 100 mm.
8) The write-once type optical recording medium as described in any one of 1) to 7) above, wherein the organic dye is mainly composed of tetraazaporphyrin.
9) The write-once type optical recording medium according to 8), wherein the tetraazaporphyrin is phthalocyanine or porphyrazine.
10) The write-once type optical recording medium according to 7), wherein tetraazaporphyrin is a compound represented by the following general formula (a).

(In the formula, 1 to 16 around the phthalocyanine skeleton represent the position of the carbon atom. The oxygen atom bonded to the phthalocyanine skeleton is 1 or 4, 5 or 8, 9 or 12, 13 or 16 carbon atoms. R1 represents a fluorine-substituted alkyl group, R2 represents a phenyl group or a phenyl group having an alkyl group, and R3 represents an alkyl group, a fluorine-substituted alkyl group, or a hydrogen atom. M represents VO or TiO.)
11) An arbitrary unit length in the traveling direction of the recording / reproducing laser along the groove and an arbitrary unit width in a direction perpendicular thereto by a laser in which at least one of irradiation time and irradiation power is set to three or more stages. Any one of 1) to 10), wherein three or more types of recording marks having different sizes are formed in the virtual recording cell, whereby the light reflectance is modulated and information can be recorded in a multi-level manner. Write-once optical recording medium.
12) The relationship between the maximum deformation height H of the recording mark portion and the depth D of the guide groove satisfies the relationship of 0.05 <H / D <1, and has a length greater than the beam diameter. Recording at a binary level or higher is performed with a recording power or a recording strategy capable of forming a recording unit that generates a reproduction signal in which a difference in modulation degree between the front end edge and the rear end edge is within ± 20%. The recording method of a write-once type optical recording medium according to any one of 4) to 11). However, the modulation degree difference is defined by the following equation, where T is the modulation degree of the trailing edge and L is the modulation degree of the leading edge.
Modulation difference (%) = (TL) × 100 / T

Hereinafter, the present invention will be described in detail.
In the case where random recording at a binary level or higher is performed in a medium having a recording layer made of an organic dye or a metal complex compound thereof directly or via an inorganic layer on a substrate having a guide groove, If the maximum height H of the deformation of the recording mark portion and the depth D of the guide groove satisfy the relationship of 0.05 <H / D <1, the crosstalk is reduced, the jitter is reduced, and the power margin It was found that a write-once type optical recording medium having a wide range can be realized. In particular, it has a remarkable effect during continuous writing (overlapping wave), and is effective for high-density recording by binary level recording. When H / D is 1 or more, crosstalk increases and jitter and power margin deteriorate. On the other hand, when H / D is 0.05 or less, a clear signal cannot be obtained and the modulation degree becomes small. A more preferable range is 0.1 <H / D <0.9.

In the present invention, at least one of irradiation time and irradiation power is set to three or more stages, and an arbitrary unit length in the laser traveling direction for recording / reproduction along the groove by the laser and an arbitrary direction in the direction orthogonal thereto The recording density can be drastically improved by forming three or more types of recording marks having different sizes in the virtual recording cell having the unit width of the unit width and modulating the light reflectance to record the information in a multilevel manner. .
Further, a substrate having a guide groove track pitch of 0.25 to 0.5 μm, a depth of 20 to 150 nm, and a groove bottom width of 0.10 to 0.25 μm is used, and an unrecorded reflectance is 2 to 50. If it is made into%, crosstalk, a power margin, and a jitter can be improved further.
Further, if the reproduction signal having a modulation degree difference within ± 20% is generated as in the third aspect of the present invention, the recording / reproduction characteristics can be further improved.
The front end edge and the rear end edge in the definition of the modulation degree difference (%) are front and rear end portions of the recording portion conceptually shown in FIG.

In addition, if a recording auxiliary layer made of an inorganic material is inserted between the substrate and the recording layer, functions such as suppressing deformation of the substrate can further reduce crosstalk, reduce jitter, and realize a medium with a wide power margin. can do. Here, the recording auxiliary layer means a layer that assists the recording principle of the recording layer and improves its recording characteristics, and is not limited to the function of suppressing the deformation of the substrate.
Materials for the recording auxiliary layer include carbide-based non-oxides such as SiC, B ₄ C, TiC, and WC; ceramics typified by carbon-based non-oxides such as amorphous carbon, graphite, and diamond; Te-TeO ₂ , Te—TeO ₂ —Pd, Sb ₂ Se ₃ / Bi ₂ Te ₃ , Ge—Te—Sb—S, Te—TeO ₂ —Ge—Sn, Te—Ge—Sn—Au, Ge—Te—Sn, Sn-Se-Te, Sb-Se-Te, Sb-Se, Ga-Se-Te, Ga-Se-Te-Ge, In-Se, In-Se-Tl-Co, Ge-Sb-Te, In- Phase change recording materials such as Se—Te, Ag—In—Sb—Te, Ag—Zn, Cu—Al—Ni, In—Sb, In—Sb—Se, In—Sb—Te; Ni, Cr, Ti, Pure metals such as Ta; Cu / Al, Ni Alloy such as / Fe; semimetal such as Si; semiconductor such as Ge.

The material and thickness of the recording auxiliary layer are selected so that the absorbance at the wavelength used for recording is 0.5 or less. If the absorbance is higher than 0.5, the light is absorbed and the reflectance is lowered, and good recording cannot be performed. A material having a melting point of 700 ° C. or lower and a thermal conductivity of 1 W / cm · K or lower is preferable.
In particular, Te or Te oxide is suitable, and shows a great effect on the medium characteristics of the present invention. Te-based materials are prone to deterioration due to oxidation and have hindered the production of media using Te. However, the storage characteristics have been dramatically improved by setting the oxygen ratio in the recording auxiliary layer material to 0 to 60 atomic%. improves. The main component of the recording auxiliary layer is Te or Te oxide, and the oxygen ratio in the material of the recording auxiliary layer is 0 to 60 atomic%, or the film thickness of the recording auxiliary layer is 1 to 100%. If one of them is satisfied, the recording sensitivity and power margin are further improved by the synergistic effect of the change in the optical constant of tetraazaporphyrin and the deformation of the recording auxiliary layer. The reason why TeO can further increase the degree of modulation while suppressing deformation is considered to be a phase change of TeO. Here, the main component means that a sufficient amount of Te or Te oxide is used to function as a recording auxiliary layer, but usually only Te or Te oxide is used. Further, if the oxygen ratio exceeds 60%, Te may become unstable. If the film thickness is less than 1 mm, the function as a recording auxiliary layer is not achieved, and if it exceeds 100 mm, the jitter may be deteriorated.

Recording materials include polymethine, naphthalocyanine, phthalocyanine, squarylium, croconium, pyrylium, naphthoquinone, anthraquinone (indanthrene), xanthene, triphenylmethane, azulene, tetrahydrocholine, Examples thereof include phenanthrene-based, triphenothiazine-based dyes, and metal complex compounds.
In the present invention, a dye mainly composed of tetraazaporphyrin (for example, naphthalocyanine, phthalocyanine, porphyrazine, etc.) having a light absorption ability in a short wavelength region and capable of recording due to decomposition and alteration is used. It is preferable. Here, the main component means that a sufficient amount of tetraazaporphyrin is used to function as a recording layer of the present invention to be described later. Usually, unless otherwise specified, tetraazaporphyrin is used. Only the recording layer.

However, when tetraazaporphyrin is used in the recording layer in the layer structure of the substrate / recording layer / reflective layer as in the conventional CD-R and DVD-R, sensitivity and high-speed response compared to the case of using other dyes, It is known that the characteristics such as jitter, modulation degree, and pit deviation are inferior. This is due to the fact that tetraazaporphyrin is difficult to decompose and the refractive index change is small.
Further, tetraazaporphyrin has a great disadvantage that its wavelength dependency is large and its characteristics are unstable.
Furthermore, since tetraazaporphyrin basically has a high decomposition temperature and the threshold for decomposition is not clear, the mode mismatch between deformation and decomposition increases. That is, the difference between the recording area due to deformation and the recording area due to decomposition becomes large. Therefore, the following problems (1) and (2) occur.
(1) Undesirably large substrate deformation, but if the substrate deformation is not large, the degree of modulation does not occur.
(2) Not suitable for high linear velocity recording due to increased thermal interference.

Further, in the conventional layer structure such as substrate / recording layer (dye layer) / reflective layer, the dye layer has both a recording function and a light absorption function. Although it is necessary to use a dye having a small absorption coefficient k, for example, when tetraazaporphyrin is selected as a dye satisfying this condition, a relatively thick film is required to reach its high decomposition temperature (and the phase The groove depth of the substrate is much deeper than that of the change-type optical recording medium). If the dye layer is made thin, recording cannot be performed due to heat dissipation in the reflective layer. However, since the dye layer also functions as a deformation receiving layer, increasing the thickness of the dye layer causes an increase in the amount of deformation of the substrate.
Summarizing the disadvantages of increasing the thickness of the dye layer: (1) Deterioration of jitter, (2) Deterioration of reproduction stability, (3) Increase in deformation, detection of crosstalk and tracking defects, address and wobble signal Impossible, (4) Deterioration of recording power margin, etc. are conceivable.
Furthermore, by using phthalocyanine or porphyrazine as tetraazaporphyrin, the light absorption characteristics of the recording layer can be further improved.

In the present invention, the recording / reproducing wavelength is preferably set to 450 nm or less for the following reason, whereby the recording pit can be reduced and the recording density can be greatly improved.
(1) For example, when the recording / reproducing wavelength is around 400 nm, the main absorption band of the dye is 400 nm.
However, there are many materials with excellent decomposition characteristics because the molecular skeleton of a dye having a main absorption band in the wavelength region exceeding 500 nm is large.
(2) The absorption wavelength of molecules and molecular groups generated by the decomposition of the dye should be approximately 450 nm or less.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Examples of the layer structure of the present invention are shown in FIGS. FIG. 1 is an enlarged cross-sectional view of a main part of an example in which recording / reproduction is performed by entering a laser from the substrate side. This optical recording medium has a layer structure in which a substrate 1, a recording layer 3, a reflective layer 4, and a protective layer 5 having a fine uneven preformat pattern (not shown) on one side are laminated in this order.
In the optical recording medium of FIG. 2, a substrate 1, a recording auxiliary layer 2, a recording layer 3, a reflective layer 4, and a protective layer 5 having a fine uneven preformat pattern (not shown) on one side are laminated in this order. It has a layer structure.

As the substrate 1, for example, a transparent resin material (preferably having a glass transition temperature Tg of 100 to 200 ° C.) such as polycarbonate, polymethyl methacrylate, polymethylpentene, epoxy resin, polyester, and amorphous polyolefin is molded into a desired shape. Well-known, such as those with a desired preformat pattern transferred on one side, or a transparent resin layer with a desired preformat pattern transferred to one side of a transparent ceramic plate such as glass formed in a desired shape Any transparent substrate belonging to can be used.
Further, in the case of a substrate constituting a disk-shaped optical recording medium (optical disk), it is formed in a disk shape having a center hole at the center.
The substrate 1 can be produced by a known method.

The preformat pattern includes at least a beam guide for causing the recording / reproducing laser beam to follow the recording track. For example, the beam guide portion can be constituted by a guide groove formed concentrically or concentrically with the center hole, and pre-pits such as address pits and clock pits can be formed along the guide grooves.
When the prepits are formed on the guide grooves, the guide grooves and the prepits are formed at different depths so that they can be discriminated optically. When the prepits are formed between the adjacent guide grooves, both can be set to the same depth.
In addition, as a beam guide part, it can replace with a guide groove and can also form a wobble pit along a recording track. Alternatively, the prepits may be omitted and only the guide grooves may be formed.

As is well known, tetraazaporphyrin has a large absorption band of Q band at the long wavelength and S band at the short wavelength.
Accordingly, tetraazaporphyrin is suitable as a material for the recording layer of the present invention, and examples thereof include phthalocyanine, naphthalocyanine, and porphyrazine. Among them, phthalocyanine and porphyrazine are particularly preferable.
Specific examples thereof are shown in the following general formulas (1) to (9). General formulas (1) to (3) are naphthalocyanines, general formulas (4) to (6) are phthalocyanines, and general formulas (7) to (9) are porphyrazines.

Hereinafter, the tetraazaporphyrin represented by the general formulas (1) to (9) will be described.
Wherein, M, Ib group as ^{M 1,} IIa Group, IIb group, IIIa group, IVa group, IVb group, Vb group, VIb group, VIIb group, VIII group metals, or oxides thereof, halides, A hydroxide etc. are mentioned, Furthermore, the said metal may have a substituent.
Examples of the metal include Cu, Zn, Mg, Al, Ge, Ti, Sn, Pb, Cr, Mo, Mn, Fe, Co, Ni, In, Pt, and Pd. Examples of the oxide include TiO and VO. There are AlCl, GeCl ₂ , SiCl ₂ , FeCl ₂ , SnCl ₂ , InCl ₂ etc. as the halide, and Al (OH) ₃ , Si (OH) ₂ , Ge (OH) ₂ , Sn as the hydroxide. (OH) ₂ etc.

Further, when the metal has a substituent, the metal includes Al, Ti, Si, Ge, Sn, etc., and the substituent includes an aryloxyl group, an alkoxyl group, a trialkylsiloxyl group, a triarylsiloxyl group, Examples include trialkoxysiloxyl group, triaryloxysiloxyl group, trityloxyl group, and acyloxyl group.
Hereinafter, although the example of a substituent is illustrated more concretely, about an alkyl group and an alkoxy group, a cycloalkyl group and a cycloalkoxy group are included, respectively.
Aryloxyl group: phenoxyl group, tolyloxyl group, anisyloxyl group and the like.
Alkoxyl group: amyloxyl group, hexyloxyl group, octyloxyl group, decyloxyl group, dodecyloxyl group, tetradecyloxyl group, hexadecyloxyl group, octadecyloxyl group, eicosiloxyl group, docosiloxyl group and the like.
Trialkylsiloxyl group: trimethylsiloxyl group, triethylsiloxyl group, tripropylsiloxyl group, tributylsiloxyl group and the like.
Triarylsiloxyl group: triphenylsiloxyl group, trianisylsiloxyl group, tritolylsiloxyl group and the like.
Trialkoxysiloxyl group: trimethoxysiloxyl group, triethoxysiloxyl group, tripropoxysiloxyl group, tributoxysiloxyl group and the like.
Triaryloxysiloxyl group: triphenoxysiloxyl group, trianisyloxysiloxyl group, tolyloxysiloxyl group, and the like.
Acyloxyl group: acetoxyl group, propionyloxyl group, butyryloxyl group, valeryloxyl group, pivaloyloxyl group, hexanoyloxyl group, octanoyloxyl group and the like.

Q is a sulfonamide optionally substituted with an amino group, an alkyl group or an aryl group which may be N-substituted with an alkyl group, aryl group, alkyloxy group, aryloxy group, halogen, alkyl group or aryl group. Groups, nitro groups, alkylthioether groups, arylthioether groups, alkylsulfonyl groups, arylsulfonyl groups, and the like. These may be substituted with a halogen, a hydroxyl group, an alkoxy group or the like.
k, l, m, and n represent 0 or an integer of 1 to 8, k + 1 + m + n ≧ 1, and when there are a plurality of Qs, they may be the same or different, and examples of Z include —S— or —SO _2- .
Y represents an aryloxyl group, an alkoxyl group, a trialkylsiloxyl group, a triarylsiloxyl group, a trialkoxysiloxyl group, a triaryloxysiloxyl group, a trityloxyl group or an acyloxyl group. It may be different.

Examples of alkyl groups where R ^{1 to} R ⁴ are alkyl groups include methyl group, ethyl group, n-propyl group, sec-propyl group, n-butyl group, sec-butyl group, t-butyl group, n-amyl group, t -Amyl group, 2-amyl group, 3-amyl group, hexyl group, heptyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, eicosyl group, docosyl group, cyclopropyl group, cyclobutyl group , Cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, 2-methylcyclopentyl group, 3-methylcyclopentyl group, 4-methylcyclohexyl group, and the like.

Examples of the alkyl group in which R ^{1 to} R ⁴ have a substituent include an alkyl group having an ester group, an alkyl group having an amide group, an alkyl group having a hydroxyl group, an aralkyl group, an alkoxyalkyl group, a haloalkyl group, 1- Dicyclohexylmethyl group, 1,1-dicyclopentylmethyl group, cyclohexylmethyl group, cyclopropylmethyl group, 2-cyclohexylethyl group, 2-cyclopentylethyl group, 2-cyclohexylpropyl group, 3-cyclohexylpropyl group, etc. , — (CR ⁵ R ⁶ ) _y SiR ⁷ R ⁸ R ⁹ (wherein R ^{5 to} R ⁹ represent hydrogen, halogen, alkyl group, alkoxyl group, aryl group or aryloxyl group, and these are the same) However, they may be different, and y represents an integer of 1 to 30). That.
The alkyl group in the above groups may be substituted with halogen or the like.
Examples of the aryl group in R ^{1 to} R ⁴ include a halophenyl group such as a phenyl group, a tolyl group, an anisyl group, and a fluorophenyl group.

  The tetraazaporphyrin may be used in combination with other dyes. Other dyes include polymethine dyes, anthraquinone dyes, dioxidine dyes, triphenodithiazine dyes, phenanthrene dyes, cyanine dyes, dicarbocyanine dyes, merocyanine dyes, pyrylium dyes, xanthene dyes. , Triphenylmethane dye, azulene dye, metal-containing azo dye, azo dye, azo dye, squarylium dye, polyene dye, base styryl dye, formazan chelate dye, croconium dye, indigoid dye, methine System dyes, sulfide dyes, methanedithiolate rate dyes, and the like. In addition, a dye material to which various quenchers such as an aminium dye are added can also be used.

The tetraazaporphyrin layer is formed by spin-coating a solvent solution of a dye selected from the dye group on the recording auxiliary layer formed on the preformat pattern forming surface of the transparent substrate 1. That is, after filling the groove-shaped preformat pattern with the dye, the dye attached to the land portion between the preformat patterns is selectively removed to expose the surface of the transparent substrate 1 and only within the preformat pattern. It is formed by filling a pigment with a dye. As a solvent for the dye, it is necessary to use a solvent having a dielectric constant of less than 80 at 25 ° C. and capable of dissolving the dye by 0.1% by weight or more. If the dissolution capacity is less than 0.1% by weight, the film thickness cannot be ensured. Specific examples include alcohol solvents and cellosolve solvents.
When a cover layer described later is provided, a tetraazaporphyrin layer is provided by spin coating on the reflective layer or protective layer formed on the preformat pattern forming surface of the substrate 1 in the same manner as described above.

Examples of solvents having a low dielectric constant for forming a tetraazaporphyrin layer include esters such as butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; dichloromethane, 1,2-dichloroethane, chloroform Chlorinated hydrocarbons such as: Amides such as dimethylformamide; Hydrocarbons such as cyclohexane; Ethers such as tetrahydrofuran, ethyl ether, dioxane; Alcohols such as ethanol, n-propanol, isopropanol, n-butanol diacetone alcohol; 2,2 Fluorine-based solvents such as 1,3,3-tetrafluoropropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl And the like glycol ethers, such as ether.
The above solvents can be appropriately used alone or in combination of two or more in consideration of the solubility of the dye used. Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution depending on the purpose.

Furthermore, the chelating agent which can take a bidentate coordination is contained, and the fading prevention of a pigment | dye can also be aimed at. Examples of such chelating agents include inorganic acids, dicarboxylic acids, oxycarboxylic acids, dioxy compounds, oxioximes, oxyaldehydes and derivatives thereof, diketones and similar compounds, oxyquinones, trobolones, and N-oxide compounds. Aminocarboxylic acids and similar compounds, hydroxylamines, oxines, aldimines, oxyazo compounds, nitrosonaphthols, triazenes, piurets, formazanes and dithizones, biquarides, glyoximes, diamines and similar compounds , Hydrazine derivatives, thioethers and the like. Furthermore, derivatives having an imino group can also be used.
Examples of the coating method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method.
The film thickness of the tetraazaporphyrin layer is preferably 10 to 200 nm. If the thickness is less than 10 nm, the absorptance decreases, and the conversion from light to heat becomes insufficient. If the thickness is more than 200 nm, the volume is too large, and the shape change and heat transfer are insufficient.
The tetraazaporphyrin layer may be a single layer or a multilayer of two or more layers.

Next, alteration of the tetraazaporphyrin layer will be described.
A dye material containing tetraazaporphyrin as a main component receives heat from an adjacent layer, or the dye itself absorbs light, and part or all of the dye material undergoes thermal state changes such as decomposition, melting, and sublimation. As a result, the dye material is usually altered, the altered part of tetraazaporphyrin is adhered to the reflective layer, and when the tetraazaporphyrin layer is peeled off at the boundary, the altered part is the reflective layer and the unaltered part is the recording auxiliary layer. Preferentially adheres and peels off.
In an embodiment having a reflective layer, the reflective layer / tetraazaporphyrin layer interface is the leader of the reflection. Therefore, it is important in the sense of controlling the reflected light from the part that the pigment material altered to the reflective layer interface is adhered. It is.

Further, it is necessary to determine the recording power, the length and type of the recording pulse while confirming the state and range of alteration. Since the structure of the altered portion of the dye is destroyed, the solubility changes. The change may be in a direction in which it is difficult to dissolve or in a direction in which the dye is decomposed to lower the molecular weight and increase the solubility, that is, in a direction in which it is easily dissolved. If there is a difference between the altered portion and the non-altered portion with respect to the change in solubility, the range of alteration can be confirmed.
According to the study by the present inventors, the change in optical properties accompanying changes in the thermal state such as melting, decomposition, and sublimation of the pigment is caused by the change in optical properties accompanying the melting, decomposition, and sublimation of the pigment. This was suitable because it coincided with the direction of rate reduction.
In the present invention, in particular, the change amount of the apparent optical characteristic in the unrecorded portion after recording is set to be within ± 50% relative to the value of the optical property of the unrecorded portion before recording. In this case, since the reflectance of the unrecorded portion does not change due to recording, track off or the like due to a change in reflectance between the recording area and the non-recording area does not occur.

Moreover, in this invention, the layer (reflection layer) which has a light reflection function can be provided as needed. For the layer having the light reflection function, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal selected from Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Cr, and Pd is used alone. Or an alloy. Among them, Au, Al, and Ag have high reflectivity and are suitable as a material for the reflective layer.
Further, the main component is Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, A material containing a metal and a semimetal such as Te, Pb, Po, Sn, and Bi may be used.
Among these, those containing Ag as a main component are particularly preferable because of low cost and high reflectivity.
It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.
The thickness of the reflective layer is preferably about 50 to 100 nm.
Examples of the method for forming the reflective layer include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.

The protective layer can be formed using an inorganic material such as SiO, SiN, or AlN, or an organic material such as a photocurable resin.
The inorganic protective layer can be formed by a vacuum film forming method, and the organic protective layer is spin-coated with a photocurable resin film (for example, SD1700, SD318, SD301 manufactured by Dainippon Ink & Chemicals, Inc.) on the reflective layer. Then, it can be formed by irradiating resin curing light.
In addition, when a high NA lens is used to increase the density, the protective layer needs to be light transmissive.
Furthermore, when the NA is increased, it is necessary to reduce the thickness of the portion through which the reproduction light is transmitted. This is due to the angle at which the disk surface deviates from the optical axis of the optical pickup as the NA increases (so-called tilt angle, proportional to the square of the product of the reciprocal of the wavelength of the light source and the numerical aperture of the objective lens). This is because the allowable amount of generated aberration is reduced, and this tilt angle is easily affected by the aberration due to the thickness of the substrate.
Therefore, it is necessary to reduce the thickness of the substrate so that the influence of aberration on the tilt angle is as small as possible.

Therefore, for example, an unevenness is formed on a substrate to form a recording layer, a reflective layer is provided on the recording layer, and a light-transmitting protective layer (cover layer) that is a thin film that transmits light is provided on the recording layer. An optical recording medium that reproduces information from the recording layer by irradiating the reproducing light from the layer side, or a reflective layer on the substrate, and a heat receiving layer and a light absorbing layer are formed thereon to form a recording layer. There has been proposed an optical recording medium in which a protective layer (cover layer) having optical transparency is provided thereon, and information on the recording layer is reproduced by irradiating reproduction light from the cover layer side. In this way, the NA of the objective lens can be increased by reducing the thickness of the cover layer. That is, it is possible to further increase the recording density by providing a thin cover layer and recording / reproducing from the cover layer side.
Such a protective layer (cover layer) is generally formed by a method using a polycarbonate sheet or an ultraviolet curable resin, or by fixing a 70 μm thick sheet (cover substrate) with a 30 μm thick adhesive. It is. The total thickness of the protective layer and the adhesive layer when fixing with an adhesive is preferably about 0.1 mm.

In the case of a disk form, a structure in which two substrates are bonded with a reflective layer sandwiched inside may be used, or a so-called single plate structure may be used without bonding two substrates. Furthermore, a structure in which two substrates provided with an adhesive layer and a protective layer are bonded together as necessary may be employed. Each of these two substrates has a recording layer. By irradiating a light beam from one of the substrates, information is recorded on each recording layer, and the light beam irradiation side is irradiated. The substrate, the first light absorbing layer, the second light absorbing layer, and the heat receiving layer are configured to transmit 40% or more of the light beam.
Further, as a disk form, it is possible to provide two or more recording layers on a single substrate. At this time, information may be recorded on each recording layer by irradiating the light beam from the substrate side, or information recording may be performed on each recording layer by irradiating the light beam from the side opposite to the substrate. May be performed.
As described above, when information is recorded on a plurality of recording layers by irradiating a light beam from a certain direction, the recording layer on the light beam incident side and the recording layer on the opposite side have different film thicknesses. You may have.
Further, the material that is the main component of the light beam incident side layer and the material that is the main component of the opposite layer may be the same or different.

Address information and the like of the write-once optical recording medium can be formed in advance on the substrate as a preformat signal. For this purpose, a concave or convex embossed pit method, or a wobble method that modulates the width of the groove or land according to information is possible. As the wobble method, a method of meandering either one or both side surfaces of the inner and outer peripheral sides of the groove portion can be employed.
In the present invention, a medium having two recording / reproducing layers on one side can also be used. The configuration is that a recording layer and a recording auxiliary layer are respectively formed on two substrates, both are bonded with a transparent material, and laser light is incident from one of the substrates, and information is recorded on both recording layers. Is recorded and reproduced. As the bonding material, a material having good flatness such as an ultraviolet curable resin or a double-sided tape is used.
In the present invention, a medium in which two recording / reproducing layers are formed on a single substrate may be used. In this configuration, two recording layers and a recording auxiliary layer are formed on one substrate, laser light is incident from the substrate side or the opposite side of the substrate, and information is recorded and reproduced on both recording layers. Is.
In these cases, if the recording layer and the recording auxiliary layer formed on the substrate on which the recording / reproducing laser beam is incident are the first layer and the opposite layer is the second layer, information is recorded on the second layer. In order to reproduce the information on the second layer, the first layer must transmit at least part of the recording / reproducing laser beam.

  Even if recording / reproduction is performed at a high density at a binary level or higher in a blue laser wavelength region or less, particularly a wavelength region of 450 nm or less, or when a shallow groove substrate with good transferability is used, recording / reproduction can be easily performed. It is possible to provide a write-once optical recording medium that can realize improvement in recording characteristics such as sensitivity, modulation degree, and jitter, and power margin.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

Example 1
On a polycarbonate substrate having a guide groove with a track pitch of 0.43 μm, a groove bottom width of 0.14 μm, and a groove depth of 50 nm, a phthalocyanine dye represented by the following general formula (10) [wherein M is VO, (Q) k, (Q) l, (Q) m, and (Q) n are all the following substituents (11)] were applied by spin coating.
The dielectric constant and mixing ratio of the solvent used are as follows.
Solvent Dielectric constant Mixing ratio (wt%)
Methanol 33.1 (25 ° C.) 23
Ethanol 23.8 (25 ° C.) 55
2-propanol 18.3 (25 ° C.) 22
The absorbance of the dye layer at a wavelength of 405 nm was unified at 0.65.
The talocyanine dye of the general formula (10) was synthesized as follows.
(1) Synthesis of phthalonitrile derivative A reaction flask was charged with 10 g of 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propanol, 16 g of anhydrous potassium carbonate, and 25 ml of N, N-dimethylformamide. While stirring, 4.8 g of 3-nitrophthalonitrile was charged over 40 minutes at 50 to 60 ° C. After stirring at 70 ° C. for 6 hours, the reaction product was poured into 600 ml of water, and the precipitated crystals were collected by filtration and dried to obtain 5.2 g of a solid. This compound had a melting point of 150 to 152 ° C., and a molecular weight peak (370) was confirmed by mass spectrum.
(2) Cyclization reaction The reaction flask was charged with 5.2 g of the phthalonitrile derivative obtained in (1), 5.1 g of DBU, 30 ml of n-pental, and 0.73 g of vanadium trichloride. Stir for hours. The reaction solution was poured into 600 ml of methanol, 80 ml of water was added, and the precipitate was collected by filtration and dried to obtain 2.4 g of a crude product. This crude product was purified by column chromatography (silica gel / toluene: ethyl acetate = 80: 1) to obtain 1.1 g of a purified product. This phthalocyanine compound was dissolved at least 2% in 1,2-dichloroethane at room temperature. In DSC (Differential Scanning Calorimetry) analysis, an exothermic peak was observed at around 300 ° C. (Ti 296 ° C., Tp 311 ° C.), and in differential thermal analysis, weight loss was observed from around 250 ° C.

次いで、フタロシアニン色素層上にＡｇを厚さ１０００Åスパッタして反射層とした。
最後に、反射層上に、大日本インキ化学工業社製のＳＤ１７００を膜厚５μｍで積層して保護層とし、図１に示す層構成の光記録媒体を得た。

Subsequently, Ag was sputtered to a thickness of 1000 mm on the phthalocyanine dye layer to form a reflective layer.
Finally, SD1700 manufactured by Dainippon Ink & Chemicals, Inc. was laminated on the reflective layer with a film thickness of 5 μm to form a protective layer, and an optical recording medium having the layer structure shown in FIG. 1 was obtained.

Multi-level recording was performed on these optical recording media under the following recording conditions using an optical disc evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial.
・ Waveform (strategy) Level 1 2 3 4 5 6 7 8
Signal 0T 2T 4T 5T 6T 7T 8T 10T
・ Solitary wave recording program (corresponding to FIG. 6)
11211311411511611711811
That is, an isolated multilevel signal of each level was recorded across two levels 1 (spaces). (The protruding waveform portion in FIG. 6 corresponds to levels 2 to 8)
-Overlapping and solitary wave recording program (corresponding to Fig. 3)
8888118117777117116666666115155515
11444411411333311311222211211
That is, four consecutive superposed waves and one solitary wave were recorded across two levels 1 (spaces). (The protruding waveform in Fig. 3 corresponds to levels 8 and 2)
・ Recording speed: 6m / s
・ Frequency: 65.4MHz
・ Recording power: 10.0mW
-Reflectance of unrecorded part: 28%
As shown in FIG. 3, the heights of the four consecutive superposed waves and the solitary wave are evenly aligned. The modulation degree was 24%.

Next, the silver reflective film side of the optical recording medium after recording is peeled off at the interface between the silver reflective film and the phthalocyanine dye using a tape, and the phthalocyanine dye on the substrate is washed away with ethanol, and then AFM observation of the substrate surface is performed. Went. The results are shown in FIGS.
Note that although the laser traveling direction in FIG. 3 is left to right, the laser traveling direction of the AFM observation images in FIGS. 4 and 5 is opposite and left to right, so care should be taken. This relationship is the same in the combination of a diagram showing all the waveforms described later and a diagram showing an AFM observation image.
From the AFM images shown in FIGS. 4 and 5, it can be seen that the shape of the largest signal (level 8) and four consecutive writings (overlapping waves) is almost uniform and the waveform is stable.
The optical recording medium corresponding to FIG. 6 on which a solitary wave was recorded was also subjected to AFM observation by performing the same processing as described above. The results are shown in FIG.
FIG. 8 shows data obtained as a result of measuring the deformation level of the mark portion substrate at each level from the AFM cross section of the solitary wave. The results of Example 2 and Comparative Example 1 described later are also shown in the figure. As can be seen from this figure, the maximum deformation height of the mark portion substrate in Example 1 is less than 50 nm at all recording levels, which is an important factor for the uniform signal of the superimposed wave.
Next, FIG. 9 shows the relationship between the modulation degree difference and the substrate deformation height in the multilevel recording of this embodiment. From this figure, it can be seen that, in the overlapped / isolated wave, when the input amount of recording energy increases, the fourth modulation degree difference among the four continuous overlapped waves becomes particularly large. (Details are described in Comparative Example 1)
In this embodiment, superimposed / isolated waves in multi-level are shown, but the modulation degree difference between the leading edge and the trailing edge of a long recording mark portion having a length equal to or larger than the beam diameter in binary level recording (see FIG. 23). The same phenomenon occurs with respect to), and the effect of the present invention is the same for the modulation degree difference in binary level recording.

Next, when the relationship between the magnitude of the modulation degree difference and the substrate deformation height was examined, as shown in FIG. 10, the modulation degree difference suddenly increased with 50 nm as a boundary. Errors in level recording became too large and reading was impossible. This means that continuous recording becomes difficult by setting the substrate deformation height to 50 nm or more (groove depth or more), and reading becomes impossible when the modulation degree difference is 20% or more. That is, by making the substrate deformation height lower than the groove depth of the substrate, a write-once type optical recording medium having high density and high reliability can be obtained without affecting adjacent signals.
FIG. 11 shows power margins of the optical recording media of Example 1, Example 2, and Comparative Example 1 when a random pattern is recorded by binary level recording. The recording conditions are as follows.
<Recording conditions>
Recording linear velocity: 6.0 m / s
・ Recording strategy: Basic strategy
Ttop-Tmp = 1.40-0.75 (T)
・ Recording frequency: 65.4MHz
From this figure, it can be seen that the optical recording medium of the present example has a relatively wide power margin and the jitter value is as good as 7.7%. Example 2 and Comparative Example 1 will be described later.
The range of the deformation height of the substrate at the optimum recording power (jitter lowest value) in FIG. 11 (random recording in binary level recording) is as follows: Example 1: 10 to 45 nm, Example 2: 5 to 35 nm, Comparative Example 1 : 65 to 110 nm.

Example 2
On a polycarbonate substrate having a guide groove with a track pitch of 0.43 μm, a groove bottom width of 0.14 μm, and a groove depth of 50 nm, a recording auxiliary layer having a film thickness of 15 nm was provided by sputtering using a Te target. Film formation was performed in an argon + oxygen mixed gas atmosphere (5 × 10 ⁻³ torr). The mixing ratio of oxygen was 10%.
Next, in the same manner as in Example 1, a recording layer made of phthalocyanine represented by the general formula (10), a reflective layer, and a protective layer were provided to obtain an optical recording medium of this example.
This optical recording medium was recorded and evaluated in the same manner as in Example 1 except that the recording power was changed to 11.7 mW. The reflectance of the unrecorded part was 26%.
FIG. 12 shows the waveform of the superimposed / isolated wave. The modulation degree was 31%, and the modulation degree was further improved by using TeO as a recording auxiliary layer.
Further, AFM observation images of the substrate surface are shown in FIGS.
From the AFM observation image of FIG. 14, it can be seen that the shape of the largest signal (level 8) and four consecutive writings (overlapping waves) is almost uniform and the waveform is stable.
Further, it can be seen that the deformation amount is remarkably small although the degree of modulation is larger than that of the first embodiment. This is the effect of suppressing deformation of the recording auxiliary layer TeO.
FIG. 15 shows the waveform of the solitary wave. FIG. 16 shows an AFM observation image when an isolated wave is recorded. Further, FIG. 17 shows the relationship between the modulation degree difference and the substrate deformation height in the multilevel recording of this embodiment. As can be seen from FIG. 17, the difference in modulation degree suddenly increased at 50 nm. This means that continuous recording becomes difficult by setting the substrate deformation height to 50 nm or more (groove depth or more), and reading becomes impossible when the modulation degree difference is 20% or more. That is, by making the substrate deformation height lower than the groove depth of the substrate, a write-once type optical recording medium having high density and high reliability can be obtained without affecting adjacent signals.
Further, although the degree of modulation is improved in FIG. 12 as compared with FIG. 3, the substrate deformation height at each recording level in Example 2 is much smaller than that in Example 1 as shown in FIG. It can be seen that the recording auxiliary layer works as a deformation suppressing layer. As a result, as shown in FIG. 11, the power margin characteristic in binary level recording is further improved.

Example 3
On a polycarbonate substrate having a guide groove having a track pitch of 0.43 μm, a groove bottom width of 0.14 μm, and a groove depth of 50 nm, a recording auxiliary layer is sputtered under an argon atmosphere (5 × 10 ⁻³ torr) using a Te target. Formed. On the recording auxiliary layer, the phthalocyanine dye of the general formula (10) was applied by spin coating in the same manner as in Example 1. The absorbance of the dye layer at a wavelength of 405 nm was 0.65.
On this phthalocyanine dye layer, Ag was sputtered to a thickness of 1000 mm to form a reflective layer.
Finally, SD1700 manufactured by Dainippon Ink & Chemicals, Inc. was laminated on the reflective layer with a film thickness of 5 μm to form a protective layer, and an optical recording medium having a layer structure shown in FIG. 1 was obtained.

Examples 4-12
An optical recording medium was prepared in the same manner as in Example 2 except that the oxidation degree, film thickness, type of recording layer, etc. of the recording auxiliary layer Te were changed. Shown in
Table 1 shows the oxygen ratio in the material of the recording auxiliary layer measured by fluorescent X-ray.
Further, the reflectance of the unrecorded portion of each optical recording medium was in the range of 24 to 29%.
As can be seen from Table 1, Examples 4 to 12 also showed good results for the degree of modulation, jitter, and power margin.

Examples 13-14
Table 1 shows the results of creating and evaluating an optical recording medium in the same manner as in Example 2 except that the groove depth of the substrate of Example 13 is 20 nm and the groove depth of the substrate of Example 14 is 150 nm. Table 1 shows the oxygen ratio in the material of the recording auxiliary layer measured by fluorescent X-ray.
As can be seen from Table 1, Examples 13 to 14 also showed good results for the modulation factor, jitter, and power margin.

また、上記表１に示した各実施例の光記録媒体に対し、２値レベルのランダムパターン記録を行ったところ、基板変形は全て、０．０５＜Ｈ／Ｄ＜１という要件を満足した。

When binary level random pattern recording was performed on the optical recording media of the examples shown in Table 1, all substrate deformations satisfied the requirement of 0.05 <H / D <1.

Comparative Example 1
The same optical recording medium as in Example 1 was recorded and evaluated in the same manner as in Example 1, except that the multi-pulse width of the multi-level recording strategy was changed to increase the modulation degree.
FIG. 18 shows the waveform of the superimposed / isolated wave. The degree of modulation is 62%.
Although the degree of modulation is higher than that in the first embodiment, the first three of the four superposed waves are observed as small waveforms. This proves that it cannot be used as a multi-level recording medium. AFM observation images in this state are shown in FIGS.
As can be seen from FIG. 20, when the solitary wave portion (left side portion) is observed from the cross section, the central portion is depressed. It has been calculated from simulation that the degree of modulation is increased by this, but in the overlapped wave portion (right side portion), the three marks in the first half are convex in the center. This indicates that when a large signal is recorded adjacently, the mark immediately before that is deformed into a convex shape. It has also been calculated from simulation that the degree of modulation decreases when the mark is convex.
In other words, it was found by AFM observation that the three marks recorded adjacently deformed into a convex shape and the degree of modulation decreased, and only the last four marks had an original concave shape.
FIG. 21 shows the waveform of the solitary wave. FIG. 22 shows an AFM observation image when a solitary wave is recorded. When the substrate deformation height of each multilevel recording mark was measured from this AFM observation image, the maximum deformation amount was a value close to 80 nm as shown in FIG. This is a value that greatly exceeds the groove depth of the substrate of 50 nm. In Example 1, the deformation of the substrate is less than 50 nm at the maximum, and when the recording power is further applied, only the modulation degree of the fourth waveform increases. From these facts, it can be seen that the quality of the recording characteristics is different depending on whether the size of the substrate deformation is smaller than the groove depth of the substrate.
That is, it can be seen that the maximum height of substrate deformation is larger than the groove depth of the substrate, and thus has the above-described drawbacks. It has been found that the multi-level recording characteristics can be remarkably improved by making it smaller than this. The same applies to the board evaluation in binary level recording.
In FIG. 11, it can be seen that the jitter and power margin in the binary level recording of Comparative Example 1 are deteriorated and the power margin is narrower than that of Example 1. This is thought to be due to the large amount of deformation that affects the adjacent grooves and marks.

In the above embodiment, the disk-shaped optical recording medium has been described as an example. However, the present invention is not limited to this, and other forms of write-once type, such as a card shape, a stick shape, and a tape shape. Of course, it can also be applied to optical recording media.
Moreover, in the said Example, although the reflective film was provided in order to obtain highly reflected light, when there is no restriction | limiting of a reflectance, a reflective film can also be abbreviate | omitted. In that case, a protective layer is laminated instead of the reflective layer.
From the above embodiments, the layer structure and recording principle of the write-once optical recording medium of the present invention is the realization of the write-once optical recording medium corresponding to the blue laser wavelength, and further the write-once optical recording medium capable of ensuring a high degree of modulation. It was confirmed that it was very effective.

FIG. 3 is an enlarged cross-sectional view of a main part showing an example of a layer structure of the write-once type optical recording medium of the present invention. The principal part expanded sectional view which shows the other example of the layer structure of the write-once type optical recording medium of this invention. The figure which shows the waveform of the overlap and the solitary wave of Example 1. FIG. The top view which shows AFM observation data when the superposition and solitary wave of a level 8 signal are recorded. XX sectional drawing of FIG. FIG. 6 is a diagram illustrating a waveform of an isolated wave according to the first embodiment. The top view which shows AFM observation data when a solitary wave is recorded. The figure which shows the measurement result of each recording level and a mark part board | substrate deformation | transformation height. FIG. 4 is a diagram illustrating a relationship between a modulation degree difference and a substrate deformation height when multilevel recording is performed on the medium according to the first exemplary embodiment. The figure which shows the relationship between board | substrate deformation | transformation height and a modulation degree difference. The figure which shows the power margin at the time of recording a random pattern by binary level recording. The figure which shows the waveform of the overlap and the solitary wave of Example 2. FIG. The top view which shows AFM observation data when the superposition and solitary wave of a level 8 signal are recorded. XX sectional drawing of FIG. The figure which shows the waveform of the solitary wave of Example 2. FIG. The top view which shows AFM observation data when a solitary wave is recorded. FIG. 10 is a diagram illustrating a relationship between a modulation degree difference and a substrate deformation height when multilevel recording is performed on the medium according to the second embodiment. The figure which shows the waveform of the overlap and the solitary wave of the comparative example 1. FIG. The top view which shows AFM observation data when the superposition and solitary wave of a level 8 signal are recorded. XX sectional drawing of FIG. The figure which shows the waveform of the solitary wave of the comparative example 1. FIG. The top view which shows AFM observation data when a solitary wave is recorded. The figure for demonstrating a front-end edge and a rear-end edge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording auxiliary layer 3 Recording layer 4 Reflective layer 5 Protective layer 6 Cover layer L Modulation degree of front edge T Modulation degree of rear edge

Claims (12)

  A recording layer made of an organic dye or its metal complex compound is directly or via an inorganic layer on a substrate having a guide groove. When recording is performed, the maximum height H of deformation of the recording mark portion and the guide groove Depth D satisfies the relationship of 0.05 <H / D <1, and is irradiated with laser light having a wavelength of 450 nm or less in which irradiation power or irradiation time is modulated to a binary level or higher, thereby providing a binary level. Alternatively, a write-once type optical recording medium capable of multilevel recording / reproduction of three or more values.   The guide groove has a track pitch of 0.25 to 0.5 μm, a depth of 20 to 150 nm, a groove bottom width of 0.10 to 0.25 μm, and an unrecorded reflectance of 2 to 50%. The write-once type optical recording medium according to claim 1, wherein 3. A reproduction signal in which a difference in modulation degree between a front end edge and a rear end edge of a recording mark portion having a length equal to or larger than a beam diameter is within ± 20% is generated. Write-once optical recording medium. However, the modulation degree difference is defined by the following equation, where T is the modulation degree of the trailing edge and L is the modulation degree of the leading edge.
Modulation difference (%) = (TL) × 100 / T   The write-once type optical recording medium according to claim 1, further comprising a recording auxiliary layer made of an inorganic material between the substrate and the recording layer.   The write-once type optical recording medium according to claim 4, wherein the main component of the recording auxiliary layer is Te or Te oxide.   6. The write-once type optical recording medium according to claim 4, wherein the oxygen content in the material of the recording auxiliary layer is 0 to 60 atomic%.   The write-once type optical recording medium according to any one of claims 4 to 6, wherein the recording auxiliary layer has a thickness of 1 to 100 mm.   The write-once type optical recording medium according to any one of claims 1 to 7, wherein the organic dye contains tetraazaporphyrin as a main component.   9. The write-once type optical recording medium according to claim 8, wherein the tetraazaporphyrin is phthalocyanine or porphyrazine. 8. The write once optical recording medium according to claim 7, wherein the tetraazaporphyrin is a compound represented by the following general formula (a).

(In the formula, 1 to 16 around the phthalocyanine skeleton represent the position of the carbon atom. The oxygen atom bonded to the phthalocyanine skeleton is 1 or 4, 5 or 8, 9 or 12, 13 or 16 carbon atoms. R1 represents a fluorine-substituted alkyl group, R2 represents a phenyl group or a phenyl group having an alkyl group, and R3 represents an alkyl group, a fluorine-substituted alkyl group, or a hydrogen atom. M represents VO or TiO.)   A laser in which at least one of the irradiation time and the irradiation power is set to three or more stages has an arbitrary unit length in the advancing direction of the recording / reproducing laser along the groove and an arbitrary unit width in a direction perpendicular to the recording / reproducing laser. The write-once type according to any one of claims 1 to 10, wherein the recording cell is formed with three or more kinds of recording marks having different sizes, whereby the light reflectance is modulated and information can be recorded in a multi-level manner. Optical recording medium. A recording mark having a relationship between the maximum deformation height H of the recording mark portion and the depth D of the guide groove satisfies a relationship of 0.05 <H / D <1, and has a length greater than the beam diameter. Recording at a binary level or higher is performed with a recording power or a recording strategy capable of forming a recording section that generates a reproduction signal in which a difference in modulation degree between the front end edge and the rear end edge is within ± 20%. The recording method of a write-once type optical recording medium according to any one of claims 4 to 11. However, the modulation degree difference is defined by the following equation, where T is the modulation degree of the trailing edge and L is the modulation degree of the leading edge.
Modulation difference (%) = (TL) × 100 / T

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