JP2005161831A - Write once optical recording medium and method for regenerating its recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a write once optical recording medium in which a multiple value recording can be performed at a short wavelength of at most a blue laser wavelength region, and a method for regenerating its recording. <P>SOLUTION: (1) The write once optical recording medium is characterized by having a thin film (hereinafter described as an RMO film) comprising at least R, M and O elements (wherein R is at least one element selected from Y, Bi, In and elements of lanthanum series; M is at least one element selected from Al, Cr, Mn, Sc, In, Ru, Rb, Co, Fe, Cu, Ni, Zn, Li, Si, Ge, Zr, Ti, Hf, Sn, Pb, Mo, V and Nb; O is oxygen) and an organic material thin film. (2) The method for regenerating its recording of the write once optical recording medium described in (1) is characterized by forming a recording part by an optical absorption function at a recording regeneration wavelength of the RMO film only or the RMO film and the organic material thin film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a write once read many (WORM) optical recording medium, and more particularly to a write once optical recording medium capable of high density recording even in a blue laser wavelength region.

1. Write-once type optical recording media capable of recording / reproducing below the wavelength of the blue laser The development of blue lasers capable of ultra-high-density recording is progressing rapidly, and the development of write-once type optical recording media corresponding to it has been carried out. Yes.
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.
Therefore, it is necessary to select an organic material used for the recording layer of the write-once type optical recording medium compatible with blue laser, which has an appropriate optical property 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 long wavelength side skirt of the large absorption band of the organic material is a wavelength region having an appropriate absorption coefficient and a large refractive index (see FIG. 1. Recording conventional organic materials) In a recordable optical recording medium having a layer, a recording / reproducing wavelength is set in a hatched portion in the figure).

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.
Further, in the conventional write-once type optical recording medium, recording is performed by the deformation of the substrate as well as the change in refractive index due to the decomposition and alteration of the organic material. For example, FIG. 3 [Parts recorded on a commercially available DVD-R As shown in FIG. 1, the substrate surface is deformed to the reflective layer side, and the degree of modulation is generated by the deformation. As shown in FIG. 2, the substrate surface is observed with an AFM (Atomic Force Microscope).

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, there is no description about recording conditions and recording density, and there is only a description that good recording pits can be formed. is there.
In Patent Document 9, although there is a description of recording in the examples, the recording wavelength is 430 nm, there is no description regarding recording conditions and recording density, and there is only a description that a good modulation degree is obtained.
In Patent Documents 10 to 19, there is a recording example with a recording wavelength of 430 nm and NA of 0.65 in Examples, but the low recording density condition (the 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 about the recording density, and the recording density is a low recording density condition of recording a 14T-EFM signal.

The organic materials disclosed in the above patent documents have optical constants required for a recording layer of a conventional write-once optical recording medium in the vicinity of 405 nm, which is the center of the oscillation wavelength of a blue semiconductor laser currently in practical use. It is not a material having the same optical constant. In addition, since there is no example in which recording conditions are clarified in the vicinity of 405 nm and recording is performed at a higher recording density than DVD, it is unclear whether high-density recording such as 15 to 25 GB can actually be performed. Furthermore, many of the examples in the above-mentioned known art are experiments in a conventional disk configuration (substrate / organic material layer / reflection layer), and the dyes used therein are required to have the same optical characteristics and functions as in the past. .
A conventional write-once optical recording medium using an organic material has a large refractive index and a relatively small absorption coefficient (about 0.05 to 0.10) with respect to the recording / reproducing wavelength from the viewpoint of securing the degree of modulation and the reflectance. You can only use organic materials that you have.

Therefore, in a write-once type optical recording medium using a conventional organic material, the main absorption band of the organic material exists in the vicinity of the recording / reproducing wavelength, so that the wavelength dependence of the optical constant of the organic material is large as shown in FIG. (Optical constants vary greatly depending on the wavelength), recording characteristics such as recording sensitivity, modulation factor, jitter, error rate, and reflectivity for recording / reproducing wavelength fluctuations due to individual differences in lasers and environmental temperature changes There was a problem that etc. changed greatly.
Furthermore, since the organic material does not have sufficient absorption capability for recording light, it is impossible to reduce the film thickness of the organic material, and thus it is necessary to use a substrate having a deep groove. (Organic materials are usually formed by spin coating, so they are thickened by burying them in deep grooves). Therefore, it becomes very difficult to form a substrate having a deep groove, which is a factor of deteriorating the quality as an optical recording medium.
In addition, since the film thickness of the organic material cannot be reduced, there is a problem that the recording power margin and the like are narrowed (the problem that various margins of the recording / reproducing characteristics are narrow).

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 recording by changing the depth of the groove portion by changing the film thickness of the recording layer 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.
The above disclosed technology is not basically 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. Furthermore, in the above-described technique, since the dye in the recording layer needs to have a light absorption function, the main absorption band of the dye must exist in the vicinity of the recording / reproducing wavelength, which greatly restricts the selection of the dye.
In the above-described techniques, the main subject of the recording principle is mostly due to deformation. If this deformation becomes the main component of the recording principle, there is a problem that even if a good jitter and modulation degree are obtained, the interference between recording marks increases, and the margin of various recording / reproducing characteristics becomes narrow.

As for the write-once type optical recording medium considered to be a diffusion system, for example, TDK announced a medium having a structure of substrate / ZnSSiO ₂ / Si / Cu / ZnSSiO ₂ / Ag at CEATEC JAPAN 2003. This medium was reported to have characteristics of a modulation degree of 65%, a jitter of 6%, and a reflectivity of 14%. Interdiffusion occurred and deterioration of characteristics was observed. This is one drawback of the two-layer diffusion mixing type. In addition, this medium requires many processes and costs, such as requiring _two upper and lower layers of ZnSSiO ₂ that is a dielectric film in order to obtain the degree of modulation.
In addition, in the prior application (Japanese Patent Application No. 2002-223720), the present applicant disclosed a two-layer diffusion mixed medium of In and GeTe. In this prior application, the C / N of a single pattern of 3T was evaluated. However, it has not been studied whether or not an important random pattern can be recorded in binary recording.
As described above, the above prior art is not sufficient for realizing a write-once type optical recording medium in the blue laser wavelength region, and is not a layer configuration or recording method effective in the blue laser wavelength region.

2. Write-once type optical recording medium capable of multi-value recording In recent years, multi-value recording technology has been developed for the purpose of increasing the recording capacity. Recently, even home users have been handling audio data and image / video data with a large capacity. On the other hand, the capacity of hard disks has been increasing, and the recording capacity of CD and DVD optical recording media has become insufficient. Yes.
Under such circumstances, as a recording method for increasing the capacity of a conventional optical recording medium, “Multi Level Technology” has been proposed by a US venture company, Calimetrics, Inc. In short, this multi-value recording technique improves the recording linear density.
In conventional CD and DVD optical recording media, recording is performed by changing the position and length of the end of each recording mark according to the data string to be recorded, and the length of the recording mark is determined during reproduction (slice method). ). The current slice method will be briefly described.

As shown in FIG. 4, first, a recording mark row (c) is formed on an optical recording medium using a recording waveform (b) corresponding to recording data (a) which is information to be recorded.
When information is reproduced by irradiating the recording mark row (c) recorded on the recording medium with reproduction light, a reproduction signal waveform as shown in FIG.
Since this reproduced signal waveform is not a rectangular wave like the recording waveform shown in (b) but becomes a dull waveform, the reproduced signal waveform is shaped by an equalizer (specifically, a high frequency component of the reproduced signal). Is amplified).
Next, an intersection between the equalized waveform (e) and the threshold is detected, and binary data is output as “1” if an intersection is detected in the window, and “0” if no intersection is detected (f). .
The binary data (f) obtained for the intersection detection is subjected to NRZ conversion to obtain decoded data as shown in (g).

On the other hand, in multi-level recording, information is expressed by multi-leveling of the reflectance of a mark to be recorded in a fixed-length area called a basic cell. That is, in a conventional CD or DVD optical recording medium, one bit is expressed by the presence or absence of a recording mark, but in multi-value recording, recording is performed by changing the size of the recording mark to, for example, eight types. Reading is performed as reflectivity having different levels (see FIG. 5). Therefore, since information for 3 bits can be expressed by one recording mark, the recording density can be increased.
In this multi-value recording, the beam spot diameter of the laser beam during reproduction is usually larger than the basic cell length. As a result, a signal for 3 bits can be expressed by one recording mark, so that the recording linear density can be increased and the recording capacity can be increased without reducing the track pitch.

The write-once type optical recording medium capable of multi-value recording is described in Patent Documents 35 to 41 and the like. Further, Patent Document 35 has a concept of performing multilevel recording on an optical recording medium having a recording layer made of an organic dye, and a concept of performing multilevel recording in the depth direction of the recording layer on the optical recording medium. It is shown. However, this document assumes a write-once type optical recording medium capable of multi-value recording corresponding to the red laser wavelength, and the layer configuration and organic dye are different from conventional CD and DVD type write-once optical recording media. Absent.
Patent Document 36 discloses an invention that defines the glass transition point of a substrate and the thermal conductivity of reflectance in an optical recording medium having a recording layer made of an organic dye capable of multilevel recording.
Patent Document 37 describes an invention that defines the thermal decomposition characteristics of an organic dye in an optical recording medium having a recording layer made of an organic dye capable of multilevel recording.
Patent Documents 38 to 39 describe an invention in which a relationship between wavelength, NA, and groove width is defined in an optical recording medium having a recording layer made of phthalocyanine or cyanine dye capable of multilevel recording.
Patent Document 40 describes an invention that defines the relationship between the recording layer thickness on the groove and the groove depth in an optical recording medium having a recording layer made of an organic dye capable of multi-value recording.
Patent Document 41 describes an invention in which an optical recording medium having a recording layer made of an organic dye capable of multilevel recording has a reflectance of 40 to 80% when not recorded.

By the way, in multi-level recording, in order to realize higher-density recording than in conventional binary recording, roughly speaking, the basic cell length must be made as small as the shortest mark length in conventional binary recording. That is, the shortest mark in multilevel recording is much smaller (shorter) than the shortest mark in binary recording.
That is, if multi-level recording with sufficiently high density can be performed with the conventional recording material, layer structure, etc., this means that the shortest mark can be shortened even with the conventional recording material, layer structure, etc. Therefore, even in binary recording, the shortest mark length can be shortened to increase the density (in actual binary recording, the recording density cannot be increased beyond the current level unless a special recording / reproducing method or the like is used. ).
Therefore, in order to realize a write-once type optical recording medium capable of multi-level recording with a sufficiently higher density than binary recording, it cannot be realized with conventional recording materials, layer configurations, etc. Different recording materials and layer structures should be newly required.

However, in the above known technique, although the film thickness of the recording layer and the reflective layer material are finely adjusted, multi-value recording is performed with almost the same conventional recording material, layer configuration, etc. Compared to conventional recording marks, it does not mean that smaller recording marks can be formed (recording / reproduction is much less reliable than conventional recording marks). The recording / reproducing method is merely applied to a write-once optical recording medium.
Further, in the above known technique, a recording mark is formed mainly by deformation (see FIG. 3 described above). This deformation is particularly problematic when the length between the recording marks is sufficiently long (when the recording linear density is low), or when the length of the cell in which the multilevel level is recorded is not continuous beyond the beam diameter of the reproduction light. However, if the recording linear density is high, or if the length of the cell in which the multilevel level is recorded is longer than the beam diameter of the reproduction light, the deformation interferes and the interference is linear. (Not far from linear).

The fact that the interference is linear means that the deformed shape after the interference is expressed, for example, by substantially adding the deformation amount of a certain cell and the deformation amount of the next adjacent cell, as shown in FIG. [FIG. 6A is a plan view showing a state in which recording marks mainly composed of deformation are formed in three consecutive cells, and FIG. 6B is a sectional view showing the deformation amount of each recording mark when there is no interference. (C) is a diagram showing how the deformation is added].
FIG. 7 shows a case where a recording mark mainly composed of deformation is formed in three consecutive cells, and when the series of recorded cells has a length equal to or smaller than the reproduction beam diameter, the interference of the deformation of the three cells. The change of the reproduction signal due to the difference is schematically shown. If the deformation interference is linear, the deformation state is as shown in FIG. 7B. If the deformation interference is not linear, the deformation state is shown in FIGS. 7C and 7D. .
However, since the interfering deformation is not longer than the reproduction beam diameter, the difference in deformation state cannot be detected, and the deformation states are different as shown in (b), (c), (d). However, a reproduction signal almost as shown in (e) can be obtained.
Accordingly, if the reflection level is detected at the sampling times T ₁ , T ₂ , and T ₃ shown in (e), correct data can be restored.

On the other hand, FIG. 8 shows a case where seven recording marks mainly composed of deformation are formed in succession, in which recorded cells are continuous, and the series length is larger than the reproduction beam diameter. In this case, the relationship between the difference in deformation interference and the reproduction signal is schematically shown.
In this case, the deformation interference is less linear than in the case of FIG. 7, and for example, the deformation states as shown in FIGS. 8B, 8C, and 8D are shown (actually more complicated). Become). Since this interfering deformation is longer than the reproduction beam diameter, the difference in deformation state can be clearly detected. According to the deformation states of (b), (c), and (d), for example, Playback signals such as (e), (f), and (g) are obtained.
Therefore, when the reflection level is detected at the sampling times T _{1 to} T ₇ shown in (e), (f), and (g), different data is restored due to the difference in interference, and correct data is no longer restored. I can't.
As described above, when the deformation becomes the main subject of recording, the interference between the recording marks is completely different depending on the recording pattern (it is impossible to predict what kind of reproduction signal is obtained), so that the recording / reproduction characteristics are deteriorated.

3. Recording and playback method using the PRML method As a high-density technology different from the multi-value recording technology, instead of the current slice method, the PRML (Partial Response and Maximum Lifecycle, Partial Response and Maximum Likelihood) method Application to optical recording media is being studied.
When the recording linear density is increased in order to increase the density, the reproduction signal becomes a dull waveform. (As described in FIG. 4, the reproduction signal waveform (d) is a rectangle like the recording waveform (b). It means no waves.] The reproduction signal is amplified by a high frequency component by an equalizer and converted into an equalized waveform. However, when the density is increased and the waveform becomes blunt, it is necessary to amplify the high frequency component. When this high frequency component is amplified, the equalizer amplifies even the signal degradation component, which causes a problem that the SNR of the reproduction signal is greatly reduced. The technique called PRML is a reproduction signal processing method for suppressing a decrease in SNR of a reproduction signal due to the increase in density.

Hereinafter, the PRML system will be briefly described.
9 (a) to 9 (d) are the same as FIGS. 4 (a) to 4 (d), and recording data (a), recording waveform (b), and recording mark string, which are information to be recorded, respectively. (C) Reproduction signal waveform (d).
9D is equalized based on the PR (1, 1) characteristic, the PR (1, 2, 1) characteristic, and the PR (1, 2, 2, 1) characteristic by an equalizer. The equalized waveforms when performed are shown in FIGS. 9 (e) to (g), respectively. Here, the PR (1, 1) characteristic indicates a characteristic in which an impulse response appears at a ratio of 1: 1 at two consecutive identification points, and the PR (1, 2, 1) characteristic indicates an impulse. The response shows a characteristic that appears at a ratio of 1: 2: 1 at three consecutive discrimination points, and the PR (1, 2, 2, 1) characteristic means that the impulse response is at four consecutive discrimination points. Each characteristic appears at a ratio of 1: 2: 2: 1. As shown in FIGS. 9E to 9G, it can be understood that the equalization waveform becomes dull as the PR characteristic becomes more complicated.
In the PRML system, it is possible to suppress amplification of the reproduction signal deterioration component by the equalizer by performing waveform equalization with PR characteristics close to those of the reproduction waveform.

In the reproduction signal processing of the PRML method, a Viterbi decoder, which is a representative maximum likelihood decoder, is generally used for decoding an equalized waveform signal. For example, when the reproduced waveform is equalized to the PR (1, 2, 1) characteristic by the equalizer, the Viterbi decoder equalizes from all the sequences that satisfy the PR (1, 2, 1) characteristic. A sequence having the smallest error from the waveform sample sequence is selected, and binary data (decoded data) corresponding to the selected sequence is output.
As described above, by using the PRML technology, a high density can be realized even if an optical system equivalent to the conventional one is used. However, even when the PRML technology is used, interference between recording marks ( When the intersymbol interference becomes large and the interference becomes non-linear (unpredictable inter-record mark interference occurs), highly reliable recording / reproduction is no longer possible. In other words, the PRML method can be applied on the premise that interference between predictable recording marks occurs, and if the actual interference between recording marks is different from the prediction, the effect of using the PRML method is lost.
Therefore, in order to suppress the interference between the recording marks to a predictable level, it is necessary to suppress the deformation of the recording marks.

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 2001-184647 A JP 2002-25114 A Japanese Patent Laid-Open No. 2002-83445 JP 2002-334438 A JP 2002-352428 A JP 2002-352429 A JP 2002-367182 A

If a write-once type optical recording medium capable of multi-value recording at a short wavelength below the blue laser wavelength range can be realized, a recording mark having higher quality than conventional binary recording can be formed as described in detail above. Therefore, it is possible to simultaneously realize a write-once type optical recording medium that can perform conventional binary recording at a short wavelength below the blue laser wavelength region, and a write-once type optical recording medium that is made dense by applying the PRML method. Therefore, a problem in realizing a write-once type optical recording medium corresponding to the blue laser wavelength range or less is a problem to realize a write-once type optical recording medium capable of multi-value recording at a short wavelength below the blue laser wavelength range. You can think of it.
In order to realize a write-once type optical recording medium capable of multi-value recording at a short wavelength below the blue laser wavelength range, the following (1) to (3) are problems.
(1) A small recording mark can be formed.
(2) There is little interference between recording marks.
(3) The stability of the recording mark is high.

By the way, in the conventional write-once type optical recording medium, as described in detail in the above-mentioned [Prior Art], recording is often performed mainly with deformation.
In the case of binary recording, since the shortest mark has a sufficient size with respect to the reproduction beam diameter (approximately about ½ of the reproduction beam diameter), the amplitude obtained from the shortest mark is also large. That is, the deformation amount of the shortest mark portion is large.
On the other hand, in multilevel recording, since the shortest mark does not have a sufficient size with respect to the reproduction beam diameter, the amplitude obtained from the shortest mark is less than a fraction of the amplitude obtained from the shortest mark in binary recording. Become. That is, it means that the deformation amount of the shortest mark portion is very small.
By the way, in the conventional CD-type and DVD-type write-once optical recording media, since the organic dye having the light absorption function is provided in direct contact with the substrate, the substrate is greatly deformed (the complex refractive index due to the decomposition of the organic dye). Although there is a contribution such as change, the degree of modulation is likely to occur mainly due to substrate deformation). If the amount of deformation of the substrate increases, the deformation exceeds the elastic deformation region, so that the deformation is fixed. However, the deformation that is the deformation amount in the elastic deformation region may be relaxed by heat from the outside. . Even if the deformation exceeds the elastic deformation region, the deformation shape may change greatly due to heat at the time of forming the adjacent recording mark or deformation of the adjacent recording mark.
This state will be described with reference to FIGS.
FIG. 10 shows a state of a recording mark of a write-once type optical recording medium having a conventional structure, that is, a substrate / dye layer / Ag reflective layer / protective layer configuration.
A shows the waveform of the reproduction signal, B shows an image obtained by detaching the protective layer, Ag reflection layer, and dye layer and observing the substrate surface by AFM, and C is obtained from the AFM image of the substrate measured by B It is the figure which displayed the deformation amount of the board | substrate cross section. From this figure, it can be seen that the recording portion has undergone a very large deformation, and the deformation shape of the substrate shows a concave shape near the central portion of the recording mark. Further, as described with reference to FIGS. 6 to 8, it is clear that the deformation interference (deformation interference in the recording mark) is not linear.

FIG. 11 shows the state of a recording mark when this conventional write-once type optical recording medium is irradiated with weak DC light of about 1/5 of the recording power after performing the same recording as in FIG.
In FIG. 11, similarly to FIG. 10, A shows the waveform of the reproduction signal, B shows the image obtained by observing the substrate surface by AFM after removing the protective layer, Ag reflection layer, and dye layer, and C is It is the figure which displayed the deformation amount of the board | substrate cross section obtained from the AFM image of the board | substrate measured by B. FIG. From this figure, it can be seen that the deformation state of the substrate changes by irradiating weak DC light, and the waveform of the reproduction signal also changes accordingly. This is presumably because the distortion in the deformed portion of the substrate was alleviated by the irradiation of weak DC light.
In addition, since the deformation shape of the substrate of the recording mark portion changes due to weak DC light irradiation, the dye layer on the recording mark portion should still have a sufficient light absorption function. It can be seen that in the type optical recording medium, the modulation is generated mainly by deformation.

In this way, when recording is performed mainly with deformation,
(1) Deformation interference in the recording mark is increased, and the reproduction signal waveform changes depending on the deformation state, that is, the recording mark length. (2) Interference between recording marks is increased, and the deformation state is different. The playback signal waveform varies depending on the recording pattern (depending on the type of recording mark between the front and back or adjacent tracks). (3) Deformation is mitigated by playback, recording on adjacent tracks, leaving under high temperature environment, or leaving over time. Because the problem that the playback signal waveform changes,
(B) Jitter or error rate deteriorates (b) Recording power margin such as jitter or error rate becomes narrow (c) Asymmetry is improper in the recording state where optimum jitter or minimum error rate is obtained (Asymmetry deviates greatly from zero)
(D) A small recording mark cannot be formed stably. (E) There is a problem that interference between recording marks cannot be predicted.
These problems are naturally problems in the conventional binary recording, but the write-once type optical recording medium having a higher recording linear density than the conventional binary recording, that is, the write-once type using the multi-level recording or the PRML method. This becomes more remarkable in the case of an optical recording medium.

Furthermore, as described in [Prior Art], the write-once type optical recording medium using a conventional organic material as a recording layer has the following problems (a) to (d).
(B) The selection range of organic materials is very narrow (b) The wavelength dependence is very large (c) Good recording / reproduction characteristics cannot be realized unless the groove depth of the substrate is increased (d) So-called land portions ( Therefore, the present invention solves the above-mentioned problems and problems, has the following characteristics (1) to (7), and has a large modulation with a recording mark with a small deformation amount. It is an object of the present invention to realize an optical recording medium and a recording / reproducing method thereof.
(1) A high-density recordable write-once optical recording medium and a recording / reproducing method thereof capable of easily performing binary recording / reproduction even in a blue laser wavelength region (500 nm or less), particularly in a wavelength region near 405 nm.
(2) A high-density recordable write-once optical recording medium and a recording / reproducing method thereof capable of easily performing multi-value recording / reproduction even in a blue laser wavelength region (500 nm or less), particularly in a wavelength region near 405 nm.
(3) Write-once type optical recording medium capable of high-density recording suitable for recording / reproducing in a signal processing system using the PRML system, and recording / reproducing thereof, even in a blue laser wavelength region (500 nm or less), particularly in the wavelength region near 405 nm Method.
(4) A write-once optical recording medium having a wide margin such as jitter and error rate with respect to fluctuations in recording power and a recording / reproducing method thereof.
(5) A write-once optical recording medium in which recording characteristics such as recording sensitivity, modulation degree, jitter, and error rate, and reflectivity, etc. change little with respect to fluctuations in recording / reproducing wavelength, and a recording / reproducing method thereof.
(6) A write-once optical recording medium and a recording / reproducing method thereof that can be easily recorded / reproduced even on a shallow groove substrate having good transferability
(7) A write-once optical recording medium capable of recording on a land portion and a recording / reproducing method thereof.

The above problems are solved by the following inventions 1) to 37).
1) At least each element of R and O (where R represents one or more elements selected from Y, Bi, In, Mo, V, and lanthanum series elements, and O represents oxygen). A write-once type optical recording medium comprising: a first thin film; and a second thin film that suppresses deformation and destruction of the first thin film and accepts a change in state of the first thin film.
2) The first thin film contains the element M, where M is Al, Cr, Mn, Sc, In, Ru, Rh, Co, Fe, Cu, Ni, Zn, Li, Si, Ge, Zr, Ti 1) The write-once type optical recording medium according to 1), which is at least one selected from Hf, Sn, Pb, Mo, V, and Nb.
3) The recordable optical recording medium according to 1) or 2), further comprising an organic material thin film.
4) The write once optical recording medium according to 3), wherein the first thin film has a structure sandwiched between the second thin film and the organic material thin film.
5) The write-once type optical recording medium as described in 4), wherein at least a second thin film, a first thin film, an organic material thin film, and a reflective layer are sequentially laminated on a substrate.
6) The write-once type optical recording medium according to 4), wherein at least an organic material thin film, a first thin film, a second thin film, and a reflective layer are sequentially laminated on a substrate.
7) The recordable optical recording medium according to 1) or 2), wherein at least a first thin film, a second thin film, and a reflective layer are sequentially laminated on a substrate.
8) The write-once type optical recording medium according to 4), wherein at least a reflective layer, a second thin film, a first thin film, an organic material thin film, and a cover layer are sequentially laminated on a substrate.
9) The write-once type optical recording medium according to 4), wherein at least a reflective layer, an organic material thin film, a first thin film, a second thin film, and a cover layer are sequentially laminated on a substrate.
10) The write-once type optical recording medium according to 1) or 2), wherein at least a reflective layer, a second thin film, a first thin film, and a cover layer are sequentially laminated on a substrate.
11) The second thin film, ZnS, or write-once optical recording medium according to any one of features 1) to 10) that the ZnS-SiO ₂ as a main component.
12) The first thin film is represented by a composition of RxMyO (x and y are atomic ratios), and x / (x + y) ≧ 0.3. Write-once optical recording medium.
13) The write-once type optical recording medium according to any one of 1) to 11), wherein the first thin film contains R (element R) and RO (oxide of element R).
14) The write-once type optical recording medium according to any one of 2) to 11), wherein the first thin film contains R (element R) and MO (oxide of element M).
15) The write-once optical recording medium according to any one of 2) to 11), wherein the first thin film contains RO (oxide of element R) and MO (oxide of element M).
16) The first thin film contains R (element R), RO (element R oxide), and MO (element M oxide), according to any one of 2) to 11) Write-once optical recording medium.
17) The write once optical recording medium according to any one of 1) to 11), wherein the first thin film contains bismuth oxide.
18) The write once optical recording medium according to any one of 1) to 11), wherein the first thin film contains bismuth and bismuth oxide.
19) The first thin film is Bia4BbOd (where 4B is at least one element selected from Group 4B, a, b, d are composition ratios, 10 ≦ a ≦ 40, 3 ≦ b ≦ 20, 50) The write-once type optical recording medium according to any one of 2) to 11), which has a composition of ≦ d ≦ 70).
20) The first thin film is Bia4BbXcOd (where 4B is at least one element selected from Group 4B, X is Al, Cr, Mn, In, Co, Fe, Cu, Ni, Zn, Ti) And at least one element selected from Sn, a, b, c, d are composition ratios, 10 ≦ a ≦ 40, 3 ≦ b ≦ 20, 3 ≦ c ≦ 20, 50 ≦ d ≦ 70) The write-once type optical recording medium according to any one of 2) to 11), which has the following composition:
21) The write-once type according to any one of 1) to 20), wherein a recording mark for generating three or more different reproduction signal levels can be formed, and the type of the recording mark can be determined based on the reproduction signal level. Optical recording medium.
22) The write-once type optical recording medium according to any one of 1) to 21), which is recordable and reproducible by a signal processing system using a PRML system.
23) The write-once optical recording medium according to any one of 1) to 22), wherein the main absorption band of the organic material thin film is located on the long wavelength side with respect to the recording / reproducing wavelength.
24) The write-once type optical recording medium according to 23), wherein the value of the imaginary part of the complex refractive index at the recording / reproducing wavelength of the organic material thin film is smaller than that of the first thin film.
25) The write-once optical recording medium as described in 23) or 24), wherein the organic material thin film has an absorption band that does not belong to the main absorption band in the vicinity of the recording / reproducing wavelength.
26) The write-once optical recording medium according to any one of 1) to 25), wherein a recording mark can be formed by at least one recording principle of the following a) to b) by the light absorption function of the first thin film. .
A) Deform the first thin film and / or the second thin film b) Change the complex refractive index of the first thin film and / or the second thin film c) The first thin film and / or the second thin film Changing the composition d) Melting the first thin film e) Diffusing the constituent elements in the first thin film to the second thin film or organic material thin film f) Changing the crystal state and crystal structure of the first thin film G) Oxidation / reduction of the constituent elements in the first thin film h) Change the composition distribution in the first thin film i) Change the volume of the organic material thin film n) Change the complex refractive index of the organic material thin film (2) Forming a cavity in the organic material thin film 27) It is possible to form a recording mark that generates three or more different reproduction signal levels in the area direction and the film thickness direction of the first thin film and / or the organic material thin film. 26) Write-once type optical recording medium
28) The write-once type optical recording according to 26), wherein recording marks for generating three or more different reproduction signal levels can be formed in the area direction and film thickness direction of the first thin film and / or the second thin film. Medium.
29) The write-once type optical recording medium according to any one of 1) to 28), wherein recording and reproduction are possible with light of 500 nm or less.
30) The recording / reproducing method for a write-once optical recording medium according to any one of 1) to 29), wherein the recording portion is formed by a light absorption function at a recording / reproducing wavelength of the first thin film.
31) The recording / reproducing method for a write-once optical recording medium according to any one of 1) to 29), wherein the recording portion is formed by a light absorption function at a recording / reproducing wavelength of the first thin film and the organic material thin film.
32) The recording / reproducing method according to 30) or 31), wherein a recording mark for generating three or more different reproduction signal levels is formed, and the type of the recording mark is determined based on the reproduction signal level.
33) The recording / reproducing method according to any one of 30) to 32), wherein recording / reproducing is performed in a signal processing system using a PRML system.
34) The recording / reproducing method according to any one of 30) to 33), wherein a recording mark is formed on the basis of at least one of the following recording principles (a) to (l) by the light absorption function of the first thin film.
A) Deform the first thin film and / or the second thin film b) Change the complex refractive index of the first thin film and / or the second thin film c) The first thin film and / or the second thin film Changing the composition d) Melting the first thin film e) Diffusing the constituent elements in the first thin film to the second thin film or organic material thin film f) Changing the crystal state and crystal structure of the first thin film G) Oxidation / reduction of the constituent elements in the first thin film h) Change the composition distribution in the first thin film i) Change the volume of the organic material thin film n) Change the complex refractive index of the organic material thin film Lu) Form a cavity in the organic material thin film 35) Form a recording mark that generates three or more different reproduction signal levels in the area direction and film thickness direction of the first thin film and / or the organic material thin film. 30) to 34) characterized in that Recording and reproducing method.
36) Any one of 30) to 34), wherein recording marks for generating three or more different reproduction signal levels are formed in the area direction and film thickness direction of the first thin film and / or the second thin film. The recording / reproducing method according to claim 1.
37) The recording / reproducing method according to any one of 30) to 36), wherein recording / reproducing is performed at a wavelength of 500 nm or less.

Hereinafter, the present invention will be described in detail.
In order to solve the above-mentioned problems, the present inventors have made at least each of R and O elements (provided that R is Y, Bi, In, Mo, V, and lanthanum series) on a substrate as a related invention of the present invention. One or more elements selected from the elements are represented, and O represents oxygen (hereinafter referred to as RO film, which corresponds to the first thin film of the present invention), an organic material thin film, and further a reflective layer. A laminated write-once optical recording medium and a recording / reproducing method thereof have been invented.
Some examples of the configuration of the related invention are very effective for solving the above-described problems. For example, in a write-once optical recording medium composed of a substrate / RO film / organic material thin film / reflection layer, an RO film or It has been found that if the thickness of the organic material thin film is not optimized, the deformation of the RO membrane increases, and in some cases, the RO membrane may be destroyed. For example, in the case of a write-once type optical recording medium having this layer structure, good recording / reproducing characteristics can be obtained in the vicinity of the optimum recording power. However, if the recording power is increased beyond the optimum recording power, the deformation of the RO film increases. (Destruction may occur in some cases), and the recording power margin of jitter and error rate may be narrowed (specifically, as the recording power is increased, the modulation degree increases rapidly and discontinuously).

The phenomenon in which the contribution of deformation increases is not only the case where the recording power increases, but the same effect can be seen even when the recording mark length increases (the longer the recording mark length, the greater the contribution of deformation). For this reason, there is a possibility that the asymmetry deteriorates (minus) in the recording state where the optimum jitter and error rate can be obtained.
One of the reasons for the large deformation of the RO membrane is one of the recording modes on the RO membrane, which is accompanied by relatively large changes such as deformation and melting. This is because it cannot be suppressed. That is, the previous layer configuration example has a layer configuration in which there is a high possibility that a recording form with a relatively large change such as deformation or melting in the RO film will occur freely. In addition, since the substrate is in direct contact with the RO membrane, a large amount of heat is also transmitted to the substrate. Therefore, the substrate causes expansion deformation, and this deformation causes the RO membrane to be deformed more greatly, and in some cases, causes destruction.
Therefore, in the present invention, in addition to the first thin film corresponding to the RO film, the deformation and destruction of the first thin film are suppressed, and the first thin film is melted, changed in composition, diffused, changed in crystalline state, oxidized / reduced. The second thin film is provided as a layer that accepts a state change such as the above.
When the second thin film is in contact with the first thin film, the deformation and destruction of the first thin film are suppressed, and the first thin film is melted, changed in composition, diffused, changed in crystalline state, oxidized / reduced, etc. The function of accepting the state change can be used effectively, but other layers may be interposed between the first thin film and the second thin film (the function of the second thin film is not lost). ).

The following points (a) to (e) are points for realizing generation of a large degree of modulation with a recording mark having a small deformation amount, which is an object of the present invention.
(A) A layer having a light absorption function undergoes state changes such as melting, composition change (including decomposition, alteration, etc.), diffusion, crystal state change, oxidation / reduction, and the light absorption function layer itself is not greatly deformed. (B) A layer that suppresses deformation / destruction is provided in the vicinity of the layer having the light absorption function, and the layer having the light absorption function is not greatly deformed. (C) The layer having the light absorption function is melted and composed. Change (including decomposition, alteration, etc.), diffusion, crystalline state change, state change such as oxidation / reduction, etc., do not transmit much heat to adjacent deformable layers such as substrates (in a layer with light absorption function) The generated heat is consumed by the layer having a light absorption function, which makes it possible to reduce the deformation of the substrate and the like.)
(D) having a layer that causes a large change in optical constant in order to generate a sufficient degree of modulation even if the amount of deformation is reduced, and (e) in order to generate a sufficient degree of modulation even if the amount of deformation is reduced, Taking advantage of the recording principle that obscure the layer interface with the adjacent layer, taking into account these points, the deformation and destruction of the first thin film and the first thin film are suppressed, By combining with a second thin film that accepts state changes such as composition change, diffusion, crystal state change, oxidation / reduction, etc., the contribution of deformation in the recording mark can be made much smaller than before, and recording can be performed. Since it is possible to prevent a drastic increase in the contribution of deformation due to an increase in power, the problems and problems described in [Problems to be Solved by the Invention] can be solved.

By the way, in the conventional write-once type optical recording medium, the absorption coefficient at the recording / reproducing wavelength is lowered by the decomposition and alteration of the organic material, and the degree of modulation is generated by utilizing the large refractive index change.
In contrast, the write-once type optical recording medium of the present invention has conventionally functioned as a heat generation layer with a light absorption function and a recording layer with a change in refractive index (real part of complex refractive index) caused by decomposition and alteration. The feature is that the function of the main heat generating layer is separated from the organic material thin film, the first thin film having a light absorption function is provided separately from the organic material thin film, and the second thin film is further provided.
In the present invention, a recording mark is formed based on the following recording principles (a) to (l).
A) Deform the first thin film and / or the second thin film b) Change the complex refractive index of the first thin film and / or the second thin film c) The first thin film and / or the second thin film Changing the composition d) Melting the first thin film e) Diffusing the constituent elements in the first thin film to the second thin film or organic material thin film f) Changing the crystal state and crystal structure of the first thin film G) Oxidation / reduction of the constituent elements in the first thin film h) Change the composition distribution in the first thin film i) Change the volume of the organic material thin film n) Change the complex refractive index of the organic material thin film Le) Make a cavity in the organic material thin film

In particular, in the present invention, it is preferable to form a recording mark mainly using various state changes of the first thin film and / or the second thin film [that is, the above a) to h)]. Of these, b) to h) are preferred. For example, since the composition change, melting, change in crystal state, oxidation / reduction, or diffusion of constituent elements to adjacent layers (state change in the present invention) can be used, the complex refractive index of the first thin film Can be greatly changed, and the layer interface with the adjacent layer can be obscured. For example, since the multiple reflection effect can be made ineffective, a large degree of modulation can be obtained even with a small deformation. it can.
That is, by using these recording principles, it is possible to achieve recording that does not mainly use deformation recording.

1. Function of first thin film In the present invention, the first thin film bears the main light absorption function.
This first thin film is a material exhibiting normal dispersion (since it is not a material having a large absorption band in a certain wavelength range like an organic material, the wavelength dependency of the complex refractive index is small). Significantly eliminates the conventional problem of significant changes in recording characteristics such as recording sensitivity, modulation factor, jitter, and error rate, and reflectivity in response to fluctuations in recording and playback wavelengths due to differences and changes in environmental temperature. be able to.
In the conventional write-once type optical recording medium, since the organic material thin film functions as both the recording layer and the light absorption layer, the organic material has a large refractive index n and a relatively small absorption coefficient k with respect to the recording / reproducing wavelength. Therefore, in order to reach the temperature at which the organic material is decomposed, a relatively thick film thickness is required (and the groove depth of the substrate is very deep with respect to the phase change type optical recording medium). )
However, in the optical recording medium of the present invention, the organic material thin film does not need to have a main light absorption function or recording function, and therefore the organic material thin film can be made thinner than the conventional one.
In addition, since the organic material thin film can be made thinner, it is possible to use a substrate having a shallow groove depth with excellent transferability (moldability), and the signal quality of the optical recording medium is greatly improved. In addition, the substrate can be manufactured (molded) easily and at a lower cost than in the past.
Further, due to the recording principle described above, it is difficult to be affected by the groove shape of the substrate during reproduction, and the tolerance for variations in the substrate shape is increased, so that the substrate can be manufactured easily and inexpensively as compared with the conventional case.
In addition, since the organic material thin film can be thinned, the recording power margin and the like can be increased.

The first thin film has a recording function as well as a light absorption function.
Specifically, the first thin film itself undergoes the following state change by the light absorption function of the first thin film.
B) Deformation (however, the amount of deformation is smaller than conventional)
B) Changes in complex refractive index c) Changes in composition d) Melting e) Diffusion of constituent elements into adjacent layers f) Changes in crystal state and crystal structure g) Oxidation / reduction of constituent elements h) Changes in composition distribution in thin film For example, in order to have a light absorption function with respect to a recording / reproducing wavelength of 500 nm or less and also to have a recording function, an element having a light absorption function with respect to a recording / reproducing wavelength of 500 nm or less is selected for R or M It is preferable.
Further, in order to diffuse a constituent element to a large complex refractive index change, composition change, crystal state change, melting, or adjacent layer, in the first thin film, in the state of R element alone or oxide, It is preferable to select an element having a relatively low melting point.
From the above viewpoint, as R of the first thin film, one or more elements selected from Y, Bi, In, Mo, V, and lanthanum series elements are used. O represents oxygen. Among them, bismuth oxide (composed of Bi and O) in which R is Bi, and a mixture of bismuth and bismuth oxide are preferable examples for performing multilevel recording. Furthermore, the first thin film includes Al, Cr, Mn, Sc, In, Ru, Rh, Co, Fe, Cu, Ni, Zn, Li, Si, Ge, Zr, Ti, Hf, Sn, Pb, Mo, It is preferable to contain at least one element M selected from V and Nb.

The advantages of using a material composed of R and O or R, M and O are as follows.
(1) The hardness of the film can be increased by using an oxide (deformation of the first thin film itself or deformation of adjacent layers such as a substrate can be suppressed).
(2) Storage stability can be improved by using an oxide. (3) Recording sensitivity is improved by including an element having a high light absorptance with respect to light of a wavelength region of 500 nm or less such as Bi. (4) By including a low-melting-point element such as Bi or an element that easily causes diffusion, a recording mark that generates a large degree of modulation can be formed despite large deformation ( 5) A good thin film can be formed by vapor deposition such as sputtering.

In the first thin film represented by RxMyO (where x and y are atomic ratios), by setting x / (x + y) ≧ 0.3, deformation of the first thin film itself or deformation of adjacent layers such as a substrate can be performed. It is possible to suppress the interference between the recording marks.
In order to further improve the recording / reproduction characteristics, it is preferable to select Bi as R.
Further, by adopting the first thin film represented by Bia4BbOd or Bia4BbXcOd, it is possible to improve recording / reproduction characteristics, storage stability, and the like. Examples of the group 4B element include C, Si, Ge, Sn, and Pb. Among these, Si and Ge are particularly preferable. X is at least one element selected from Al, Cr, Mn, In, Co, Fe, Cu, Ni, Zn, Ti, and Sn.
In the case of Bia4BbXcOd, the ability of the additive element M further increases the ability to cause a large complex refractive index change, composition change, melting, or diffusion of constituent elements in the adjacent layer.

By the way, the first thin film of the present invention is not limited to a film made only of a complete oxide of R element, but may contain an R element and an oxide of R element simultaneously (abbreviated as R + RO). ).
Further, when the RO film contains the element M, (1) R-M-O ternary compound, (2) R + MO (mixture of oxides of element R and element M), (3) RO + MO (element A mixture of an oxide of R and an oxide of element M), (4) R + RO + MO (a mixture of an oxide of element R, an oxide of element R, and an oxide of element M), or a combination of (1) to (4) An element and a compound may be contained at the same time. In other words, the first thin film referred to in the present invention is a general term including the mixture as described above.
For example, the element R (non-oxide state) can be oxidized by recording, and the complex refractive index of the first thin film can be greatly changed accordingly. If this recording principle of oxidation is used, non-deformed recording can be realized and recording with small intersymbol interference can be performed.

However, in the first thin film, when the element R and / or the element M are present in a large amount in a non-oxide state, the storage stability of the first thin film may be lowered. Therefore, the element R and / or the element M The content of the simple substance is preferably smaller than the oxide amount of element R and / or element M. This ratio is preferably adjusted as appropriate in consideration of the recording sensitivity, jitter, storage stability, and the like.
On the other hand, for the elements R and M in the oxide state, the recording principle of reduction can be used, and the same effect as in the case of oxidation can be obtained.
In the present invention, the main component of the light absorption function and the recording function is the element R or an oxide thereof, and the element R group listed in the present invention has a unique effect.
In particular, when the first thin film is represented by a composition of RxMyO (x and y are atomic ratios), x / (x + y) ≧ 0.3 can improve recording / reproduction characteristics. However, it is also effective to use the first thin film outside the range of x / (x + y) ≧ 0.3 for fine adjustment of recording / reproduction characteristics and storage stability. In the present invention, x / (x + y) ≧ 0. It is not limited to the range of .3.
The thickness of the first thin film is desirably 20 to 500 mm.

2. Function of the second thin film The second thin film suppresses deformation and destruction of the first thin film, and accepts state changes such as melting, composition change, diffusion, crystal state change, oxidation / reduction, etc. of the first thin film. In general, since the first thin film has a relatively large absorption with respect to the recording / reproducing wavelength, it is formed thin from the viewpoint of reflectivity and the like (however, depending on the absorption coefficient of the first thin film) Is not this limit). Therefore, when the first thin film is provided directly on the substrate, the first thin film is a thin film having a high hardness, but it is greatly deformed or sometimes destroyed by the expansion of the substrate.
Therefore, in the present invention, deformation and destruction of the first thin film are suppressed by the second thin film. For example, in order to suppress the deformation / destruction of the first thin film due to the deformation of the substrate by the second thin film, the order between the substrate and the first thin film is as follows: substrate / second thin film / first thin film. It is effective to insert the second thin film into the substrate, but the effect can be sufficiently exhibited even in the order of the substrate / first thin film / second thin film. This is presumably because the effect of the second thin film is likely to occur because the thickness of the first thin film is relatively thin.

The second thin film has a recording function in addition to suppressing deformation and destruction of the first thin film. That is, in the write-once type optical recording medium of the present invention, as described above,
A) Deform the first thin film and / or the second thin film b) Change the complex refractive index of the first thin film and / or the second thin film c) The first thin film and / or the second thin film Change the composition d) Melt the first thin film e) Diffuse the constituent elements in the first thin film to the second thin film or organic material thin film f) Change the crystal state and crystal structure of the first thin film G) Oxidation / reduction of constituent elements in the first thin film. H) Recording is performed by changing the composition distribution in the first thin film. For example, the first thin film and the second thin film are adjacent to each other. In the case of the structure, the second thin film has a function of receiving a change in state of the first thin film and obfuscating the interface with the first thin film.

This obscuration of the interface widely refers to an interface state different from that at the time of non-recording. For example, mixing occurs at the interface between the first thin film and the second thin film, or constituent elements of each layer diffuse. In this case, the gradient of the complex refractive index occurs near the interface between the first thin film and the second thin film (in the unrecorded state, the complex refractive index becomes discontinuous at the layer interface, The gradual change of the complex refractive index in the vicinity is called inclination).
In this way, the second thin film accepts the melting, composition change, diffusion, crystal state change, oxidation / reduction, etc. of the first thin film, and the layer interface between the first thin film and the second thin film is unclear. For example, the multiple reflection effect can be greatly changed, and as a result, a large degree of modulation can be obtained.
In addition, an important function of the second thin film is a function of adjusting thermal conductivity. By adjusting the thermal conductivity of the second thin film, minute recording marks with little variation can be formed efficiently.
Further, the second thin film has a function of controlling the reflectance, the tracking signal, and the recording sensitivity, and these characteristics can be appropriately adjusted by selecting a material and setting the film thickness.

As the second thin film, a material which does not cause decomposition, sublimation, cavitation, etc. by the heat of the first thin film is usually preferable. For example, Al ₂ O ₃ , MgO, BeO, ZrO ₂ , UO ₂ , ThO _2, etc. oxides of simple _{oxide-based; SiO 2, 2MgO · SiO 2} , MgO · SiO 2, CaO · SiO 3, ZrO 2 · SiO 2, 3Al 2 O 3 · 2SiO 2, 2MgO · 2Al 2 O 3 · 5SiO 2 Silicate-based oxides such as Li ₂ O.Al ₂ O ₃ .4SiO ₂ ; Al ₂ TiO ₅ , MgAl ₂ O ₄ , Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , BaTiO ₃ , LiNbO ₃ , PZT [Pb (Zr, Ti) O ₃ ], PLZT [(Pb, La) (Zr, Ti) O ₃ ], double oxide oxides such as ferrite; or Si ₃ N ₄ , Si _{6-Z Al Z O Z N} 8-Z, AlN, BN, non-oxide of the nitride such as _{TiN; SiC, B 4 C,} TiC, non-oxide carbide system such as _WC; LaB 6, TiB ₂ Boron-based non-oxides such as ZrB ₂ ; Sulfide-based non-oxides such as CdS and MoS ₂ ; Silicide-based non-oxides such as MoSi ₂ ; Carbon-based non-oxides such as amorphous carbon, graphite and diamond Non-oxides can be used. Furthermore, an organic substance can be used as the second thin film.

For example, it is preferable to use SiO ₂ , ZnS, or ZnS · SiO ₂ as a main component (main component) from the viewpoint of transparency to recording / reproducing light and productivity. In order to obtain a sufficient heat insulating effect, it is also preferable to use ZrO ₂ as a main component (main component). Furthermore, it consists of an oxide made of ZnS, ZrO ₂ , Y ₂ O ₃ , SiO ₂ , or made of ZrO ₂ , TiO ₂ , SiO ₂ and X, and X is Y ₂ O ₃ , CeO, Al ₂ O ₃ , MgO, CaO. An oxide that is at least one selected from NbO and rare earth oxides is also preferable.
In addition, the second thin film has a function of accepting state changes such as melting, composition change, diffusion, crystal state change, oxidation / reduction, etc. of the first thin film. In some cases, the thermal conductivity and hardness of the second thin film are also important. In terms of the thermal conductivity and hardness, it is preferable that ZnS is mainly used as the second thin film (in the case of using ZnS · SiO ₂ , it is preferable to increase the ratio of ZnS). When the second thin film mainly composed of ZnS is adjacent to the reflective layer mainly composed of Ag, a sulfidation resistant layer for preventing sulfidation of Ag can be provided.
The second thin film is preferably transparent to the recording / reproducing wavelength in order to increase the reflectance, but it is also possible to provide a light absorption function to the recording / reproducing wavelength to adjust the recording sensitivity. It is.
The thickness of the second thin film is preferably 20 to 2000 mm. In general, the second thin film is preferably thicker than the first thin film.

3. Functions of the organic material thin film The functions of the organic material thin film include (a) a heat insulation function (for example, a structure in which the organic material thin film is sandwiched between the reflective layer and the first thin film), (b) a modulation generation function, (c It can be roughly divided into a function for compensating the reproduction signal waveform, a function for controlling the reflectivity and the tracking signal, and a function for controlling the recording sensitivity.
In the case of a write once optical recording medium having a reflective layer, if the first thin film and the reflective layer are adjacent to each other, the energy absorbed by the first thin film is not efficiently converted into heat, and recording is performed with an appropriate recording power. The case where it becomes impossible occurs. In this case, when an organic material thin film is introduced between the first thin film and the reflective layer, a sufficient heat insulating effect can be obtained even with a very thin organic material thin film.
By the way, an organic material thin film is often formed by spin coating. When an organic material thin film is formed by this spin coating method, the film thickness of the organic material thin film in the groove portion is thicker than that in the land portion. It becomes a structure (thus, crosstalk can be suppressed). Therefore, in the case of groove recording, it is possible to improve the recording / reproducing characteristics by using an organic material thin film as the heat insulating layer.

In addition, the organic material thin film exhibits the following phenomenon, and (b) exhibits a function of generating a modulation degree.
・ Recording changes the volume of the organic material thin film ・ Recording changes the complex refractive index of the organic material thin film ・ Recording forms a cavity in the organic material thin film ・ Accepts changes in the state of the first thin film due to recording・ Receiving deformation of the reflective layer Note that the “change in state of the first thin film” referred to here is deformation, change in complex refractive index, change in composition, melting, diffusion of constituent elements to adjacent layers (mixing) , Crystal state / crystal structure change, oxidation / reduction, composition distribution change, etc.

The function of compensating the reproduction signal waveform in (c) is that the reproduction signal waveform may be disturbed only with the first thin film [the recording polarity is unlikely to be a single polarity of High to Low (High to Low). ] By providing an organic material thin film as an adjacent layer, the reproduction signal waveform can be made into a desired waveform (generally, the recording polarity is made High to Low).
Since the organic material thin film can control the complex refractive index and the film thickness within a very wide range, it is clear that the organic material thin film has a control function such as the reflectance and tracking signal of (d).
In addition, regarding the function of (e), the present invention provides the first thin film with a main light absorption function, but by controlling the complex refractive index (particularly, the imaginary part of the complex refractive index) of the organic material thin film, Since the material thin film can be supplementarily used as the light absorption layer, the recording sensitivity can be controlled.

In the present invention, in order to greatly expand the range of selection of the organic material and to reduce the complex refractive index change in the vicinity of the recording / reproducing wavelength while being a write-once type optical recording medium using an organic material thin film (wavelength It is preferable that the organic material thin film has a main absorption band located on the long wavelength side with respect to the recording / reproducing wavelength (see FIG. 12, the hatched portion indicates the recording / reproducing wavelength).
When an organic material thin film is used supplementarily as a light absorbing layer, the value of the imaginary part of the complex refractive index at the recording / reproducing wavelength of the organic material thin film may be smaller than the value of the imaginary part of the complex refractive index of the first thin film. preferable. This is because increasing the value of the imaginary part of the complex refractive index at the recording / reproducing wavelength of the organic material thin film more than necessary leads to worsening the wavelength dependency.
When an organic material thin film is used as a light absorption layer as an auxiliary layer, the organic material thin film has a main absorption band located on the long wavelength side with respect to the recording / reproducing wavelength and has a main absorption band near the recording / reproducing wavelength. It is preferable to have an absorption band that does not belong.

In addition, as shown in FIG. 13, the “main absorption band” in the present invention refers to an absorption band having the largest absorption in the visible range, and generally refers to a transition of HOMO-LUMO. Refers to the absorption band based on. The “absorption band not belonging to the main absorption band and located on the shorter wavelength side than the main absorption band” as used in the present invention is an absorption band based on a transition different from the main absorption band as shown in FIG. (It is not an absorption band mainly composed of a HOMO-LUMO transition).
Thus, even when an organic material thin film is supplementarily provided with a light absorption function, the wavelength dependence is reduced because an organic material thin film having an absorption band that does not belong to the main absorption band in the vicinity of the recording / reproducing wavelength is used. It becomes possible to do.
The above description is a case where one organic material has a main absorption band and an absorption band that does not belong to the main absorption band. In the present invention, two or more organic materials are mixed and as shown in FIG. An organic material thin film in which an absorption spectrum is formed can also be used. In this case, the wavelength dependency can be greatly improved as compared with the conventional case.

In the present invention, a recording principle that does not mainly involve deformation is used, but this does not exclude deformation, and the aim is to reduce the deformation amount in order to suppress the interference between recording marks to a predictable level. Therefore, in the write-once type optical recording medium of the present invention, for example, deformation of the first thin film, the second thin film, and the reflective layer can be used.
The organic material thin film can control the ease of deformation of the adjacent layer by controlling the film thickness. That is, when using deformation recording, the recording sensitivity can be adjusted by the film thickness of the organic material layer.
As described above, the organic material thin film can control the recording sensitivity by changing the complex refractive index and the film thickness.

  In the present invention, since the main of the recording function and the light absorption function is the first thin film, the main recording function and the main light absorption function can be excluded from the organic material thin film. As a result, it is basically unnecessary to use the change in the real part of the complex refractive index at the recording / reproducing wavelength of the organic material thin film (of course, the real part of the complex refractive index may be changed by recording). Since the thin film does not need to have a light absorption function with respect to the recording / reproducing wavelength, it has a remarkable effect that a strict restriction as in the related art relating to the optical constant of the organic material becomes unnecessary. Therefore, even when recording / reproduction is performed in the blue laser wavelength region, as an organic material, a material that has a large absorption band in the red laser wavelength region and does not have a large absorption band in the blue laser wavelength region, for example, CD-R And a dye for DVD-R can be used.

Conventionally, in order to control the wavelength, it has been necessary to use a complicated substituent or a dye having a high synthesis difficulty as a recording layer. However, the organic material thin film of the present invention does not require such a complicated wavelength control. Therefore, it is possible to select an organic material with a low cost.
Furthermore, since the organic material thin film in the present invention can use an organic material such as a dye having a large absorption band sufficiently away from the recording / reproducing wavelength (the refractive index shows anomalous dispersion near the large absorption band). The refractive index varies greatly depending on the wavelength, but in the wavelength region sufficiently away from the large absorption band, the refractive index shows normal dispersion, and the refractive index shows a gradual change with respect to the wavelength.) In addition, recording characteristics such as recording sensitivity, modulation degree, jitter, and error rate, and reflectivity greatly change with respect to fluctuations in recording / reproducing wavelength due to changes in environmental temperature, etc. Can do.

In the normal mode of the present invention, the relationship between the main absorption band of the organic material thin film and the recording / reproducing wavelength is set so that “the main absorption band of the organic material exists on the long wavelength side with respect to the recording / reproducing wavelength”. However, the present invention is not limited to this, and the relationship between the main absorption band of the organic material and the recording / reproducing wavelength can be arbitrarily set.
However, since a separate light absorption layer (first thin film) is present in the practice of the present invention, it is preferable to keep the main absorption band of the organic material thin film away from the recording / reproducing wavelength in order to increase the reflectance. In this case, the main absorption band of the organic material thin film may exist on the long wavelength side with respect to the recording / reproducing wavelength, or conversely, may exist on the short wavelength side.
As can be seen from the above description, the present invention can be applied to a wide range of recording / reproducing wavelengths from the red region to the blue region, and even below the blue region, and according to the recording / reproducing wavelength used, A desired optical recording medium can be obtained by appropriately selecting a material satisfying the above conditions from known organic materials (particularly dyes) as described later.

As the organic material used for the organic material thin film, a so-called pigment is preferable.
In the present invention, it is preferable to sufficiently keep the main absorption band of the organic material and the recording / reproducing wavelength sufficiently in order to ensure the reflectance. For example, when the recording / reproducing wavelength is in the red region, the recording / reproducing wavelength may be on the short wavelength side or the long wavelength side with respect to the main absorption band of the organic material. On the other hand, when the recording / reproducing wavelength is below the blue region, setting the recording / reproducing wavelength to the longer wavelength side with respect to the main absorption band of the organic material requires a smaller molecular skeleton of the organic material (conjugated system). This is not preferable because it may lead to degradation of decomposition and explosive properties, and it may become difficult to form a thin film due to a decrease in solubility and an improvement in crystallinity.
Therefore, in order to ensure sufficient thermal decomposition characteristics and to form a high-quality thin film, when the recording / reproducing wavelength is below the blue laser wavelength region, the main absorption band exists on the longer wavelength side than the recording / reproducing wavelength. It is preferable to select such an organic material.

The dyes that satisfy the above requirements include polymethine, naphthalocyanine, phthalocyanine, squarylium, croconium, pyrylium, naphthoquinone, anthraquinone (indanthrene), xanthene, triphenylmethane, and azulene. , Tetrahydrocholine-based, phenanthrene-based, triphenothiazine-based, azo-based and formazan-based dyes, and metal complex compounds thereof.
The dye layer can be formed by ordinary means such as vapor deposition, sputtering, CVD, and solvent coating. In the case of using the coating method, the above-described dye or the like can be dissolved in an organic solvent, and the coating can be performed by a conventional coating method such as spraying, roller coating, dipping, or spin coating.
As the organic solvent to be used, alcohols such as methanol, ethanol and isopropanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylacetamide and N, N-dimethylformamide; sulfoxide such as dimethyl sulfoxide Ethers such as tetrahydrofuran, dioxane, diethyl ether and ethylene glycol monomethyl ether; esters such as methyl acetate and ethyl acetate; aliphatic halogenated carbons such as chloroform, methylene chloride, dichloroethane, carbon tetrachloride and trichloroethane; Aromatics such as benzene, xylene, monochlorobenzene and dichlorobenzene; cellosolves such as methoxyethanol and ethoxyethanol; hexane, pentane, Cyclohexane, and hydrocarbons such as methylcyclohexane.
The film thickness of the dye layer is 100 to 10 μm, preferably 100 to 2000 mm.

In the present invention, recording marks that generate three or more different reproduction signal levels can be formed in the area direction and film thickness direction of the first thin film and / or the organic material thin film.
Usually, in order to generate three or more different reproduction signal levels, the recording mark area ratio (area ratio in the planar direction of the optical recording medium) is set to the virtual basic cell as shown in FIG. It is common to change. However, in the present invention, in addition to the area ratio, three or more different reproduction signal levels can be generated by changing the size of the recording mark formation region in the cross-sectional direction of the optical recording medium.
In the present invention, “to form a recording mark that generates three or more different reproduction signal levels in the film thickness direction” means to change the size of the recording mark forming area in the cross-sectional direction of the optical recording medium. This means that three or more different reproduction signal levels are generated based on the difference in the size of the recording mark formation region in the cross-sectional direction.
In the present invention, it is preferable to record with a gradation in the cross-sectional direction of the optical recording medium, but it is of course possible to record with a gradation in the plane direction.
In the present invention, as described above, the composition change of the first thin film and / or the second thin film, the melting of the first thin film, the diffusion of the constituent elements in the first thin film, the crystal state of the first thin film. Forming the recording part by changing the crystal structure, oxidizing / reducing the constituent elements in the first thin film, changing the composition distribution in the first thin film, changing the volume of the organic material thin film, forming the cavity of the organic material thin film, etc. Therefore, it is possible to produce a “super-resolution effect” caused by dispersion of nanoparticles or formation of a cavity. Therefore, the write-once type optical recording medium of the present invention is suitable for high density recording and multilevel recording.

The write once optical recording medium of the present invention has a structure having at least the first thin film and the second thin film on a substrate, or at least the first thin film, the second thin film, and an organic material thin film on the substrate. The other components are described below.
As a material of the substrate, there is a special restriction as long as it has excellent thermal and mechanical properties and has excellent light transmission characteristics when recording / reproducing is performed from the substrate side (through the substrate). Absent.
Specific examples include polycarbonate, polymethyl methacrylate, amorphous polyolefin, cellulose acetate, polyethylene terephthalate and the like, and polycarbonate and amorphous polyolefin are preferred.
The thickness of the substrate varies depending on the application and is not particularly limited.

As a material of the reflective layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal such as Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, alone or in an alloy is used. Can be used. Among them, Au, Al, Ag, and alloys thereof have high reflectivity and are suitable as a material for the reflective layer.
Further, the above metal may be the main component and other elements may be included. Examples of other elements include Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Mention may be made of metals and metalloids such as Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi.
Among these, those containing Ag and an alloy thereof as a main component are particularly preferable from the viewpoint 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.
Examples of the method for forming the reflective layer include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition.
A preferable film thickness of the reflective layer is 50 to 300 nm.

Also, a known inorganic or organic overcoat layer, undercoat layer, or adhesive layer is provided on the substrate or under the reflective layer in order to improve reflectivity, improve recording characteristics, improve adhesion, etc. You can also.
The material of the protective layer formed on the reflective layer and the interference layer is not particularly limited as long as it protects the reflective layer and the interference layer from external force. Examples of the organic material include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and a UV curable resin. Examples of the inorganic material include SiO ₂ , SiN ₄ , MgF ₂ , SnO _{2 and the} like.
Thermoplastic resins and thermosetting resins can be formed by applying a coating solution dissolved in a suitable solvent and drying. The UV curable resin can be formed by applying a coating solution as it is or dissolved in an appropriate solvent and irradiating with UV light to cure. As the UV curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used.
These materials may be used alone or in combination, and may be used as a multilayer film as well as a single layer.

As a method for forming the protective layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, or the like is used as in the recording layer. Among these, a spin coating method is preferable.
The thickness of the protective layer is generally in the range of 0.1 to 100 μm, but is preferably 3 to 30 μm in the present invention.
Further, the substrate may be further bonded to the reflective layer or the interference layer surface, or two optical recording media may be bonded to each other with the reflective layer or the interference layer surface facing each other.
An ultraviolet curable resin layer, an inorganic thin film, or the like may be formed on the mirror surface side of the substrate in order to protect the surface and prevent the adhesion of dust.

The cover layer is necessary when using a lens with a high NA in order to increase the density. For example, 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, the thickness of the substrate is reduced to minimize the influence of aberration on the tilt angle.
Therefore, for example, a recording layer is formed by forming irregularities on a substrate, a reflective layer is provided on the recording layer, and a light-transmitting cover layer, which is a thin film that transmits light, is provided on the recording layer. An optical recording medium (so-called ROM type) that reproduces information on the recording layer by irradiating light, or a reflective layer provided on the substrate, a recording layer provided thereon, and a light-transmitting cover thereon There has been proposed an optical recording medium in which a layer is provided and information on the recording layer is reproduced by irradiating the reproducing 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 cover layer is generally formed of a polycarbonate sheet or an ultraviolet curable resin. Further, the cover layer referred to in the present invention may include a layer for adhering the cover layer.
The laser beam used in the write-once type optical recording medium of the present invention is preferably as the wavelength is shorter for high-density recording, but a laser beam with a wavelength of 350 to 530 nm is particularly preferable. Is mentioned.

According to the present invention, the following write-once type optical recording medium and the recording / reproducing method thereof can be realized as in the following (1) to (7).
(1) A high-density recordable write-once optical recording medium and a recording / reproducing method thereof capable of easily performing binary recording / reproduction even in a blue laser wavelength region (500 nm or less), particularly in a wavelength region near 405 nm.
(2) A high-density recordable write-once optical recording medium and a recording / reproducing method thereof capable of easily performing multi-value recording / reproduction even in a blue laser wavelength region (500 nm or less), particularly in a wavelength region near 405 nm.
(3) Write-once type optical recording medium capable of high-density recording suitable for recording / reproducing in a signal processing system using the PRML system, and recording / reproducing thereof, even in a blue laser wavelength region (500 nm or less), particularly in the wavelength region near 405 nm Method.
(4) A write-once optical recording medium having a wide margin such as jitter and error rate with respect to fluctuations in recording power and a recording / reproducing method thereof.
(5) A write-once optical recording medium in which recording characteristics such as recording sensitivity, modulation degree, jitter, and error rate, and reflectivity, etc. change little with respect to fluctuations in recording / reproducing wavelength, and a recording / reproducing method thereof.
(6) A write-once optical recording medium and a recording / reproducing method thereof that can be easily recorded / reproduced even with a shallow groove substrate having good transferability.
(7) A write-once optical recording medium capable of recording on a land portion and a recording / reproducing method thereof.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited by these Examples.

Example 1
On a polycarbonate substrate having a guide groove (groove depth 50 nm) (substrate thickness 0.6 mm), a ZnS—SiO ₂ thin film (second thin film, ZnS: SiO ₂ = 85: 15) having a film thickness of 65 nm is formed by sputtering. ) And a 15 nm thick BiFeO thin film (first thin film, target composition: Bi ₃ Fe ₅ O ₁₂ ) were sequentially laminated.
Next, on the BiFeO thin film, an organic material thin film (average film thickness of about 30 nm) made of a dye represented by the following [Chemical Formula 1] is formed by a spin coating method, and an Ag reflection layer having a film thickness of 150 nm is formed thereon by a sputtering method. A write-once optical recording medium of the present invention was prepared by providing a protective layer made of an ultraviolet curable resin and having a thickness of about 5 μm.
The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
Conventional binary recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
<Recording conditions>
Modulation method: 8-16 modulation Recording linear density: 1T = 0.0917 (μm)
Shortest mark length 3T = 0.275 (μm)
・ Recording linear velocity: 6.0 (m / s)
Waveform equalization: normal equalizer As a result, as shown in FIG. 15, a good jitter value of 8.0% was obtained at a recording power of 7.0 mW, and a good binary recording characteristic could be realized. .
Further, even when the recording power exceeds the optimum recording power, the reproduction signal level (RF Level) of the recording mark portion does not change greatly, and has a high modulation degree and a wide recording power margin. The medium could be realized.
Further, the protective layer made of an ultraviolet curable resin and the Ag reflection layer of the write-once optical recording medium on which this recording was performed were peeled off, and the organic material thin film was washed away with ethanol, and the deformation state of the BiFeO thin film surface was examined by AFM.
As a result, it was confirmed that the deformation amount was 20 nm at the maximum.

Comparative Example 1
A write-once optical recording medium was prepared in the same manner as in Example 1 except that the ZnS-SiO ₂ thin film (second thin film) was not provided and that the BiFeO thin film (first thin film) was 5 nm thick. As a result of performing the same recording / reproduction evaluation as in Example 1, the result as shown in FIG. 14 was obtained.
With this write-once optical recording medium, a very good jitter value of 10.0% was obtained in the vicinity of 5.8 mW, and good binary recording characteristics could be realized.
However, when the recording power exceeds the optimum recording power, the reproduction signal level (RF Level) of the recording mark portion changes greatly.
Comparative diagrams of the experimental results of Example 1 and Comparative Example 1 are shown as FIGS.
FIG. 16 is a diagram comparing the jitters of the two, and FIG. 17 is a diagram comparing the changes in the reproduction signal levels of the space part and the recording mark part of both.
As is clear from FIG. 17, it was confirmed that the write-once type optical recording medium of the present invention can realize recording with a high degree of modulation and no sudden increase in the degree of modulation.
Further, as is apparent from FIG. 16, it was confirmed that the jitter value and the recording power margin of the jitter can be greatly improved as a result of reducing the rapid increase in the modulation degree.

Example 2
A write-once optical recording medium of the present invention was prepared in the same manner as in Example 1 except that the film thickness of ZnS—SiO ₂ was 50 nm and the film thickness of BiFeO was 10 nm, and the recording power is shown in Table 1. The same recording experiment was conducted except that the point was changed to the one. As a result, as shown in Table 1, good binary recording characteristics could be realized.

Example 3
Except for using BiFeCuO instead of BiFeO and changing the film thickness to 12 nm, the write-once optical recording medium of the present invention was prepared in the same manner as in Example 1, and the recording power was changed to that shown in Table 1. Conducted a similar recording experiment. As a result, as shown in Table 1, good binary recording characteristics could be realized.

Example 4
Except that BiFeAlO was used instead of BiFeO and the film thickness was changed to 10 nm, the write-once type optical recording medium of the present invention was prepared in the same manner as in Example 1, and the recording power was changed to that shown in Table 1. Conducted a similar recording experiment. As a result, as shown in Table 1, good binary recording characteristics could be realized.

Example 5
Except that BiAlO was used instead of BiFeO and the film thickness was 7 nm, the write-once type optical recording medium of the present invention was prepared in the same manner as in Example 1, and the recording power was changed to that shown in Table 1. Conducted a similar recording experiment. As a result, as shown in Table 1, good binary recording characteristics could be realized.

Example 6
A write-once optical recording medium of the present invention was prepared in the same manner as in Example 1 except that BiDyFeO was used instead of BiFeO and the film thickness was changed to 17 nm, and the same recording experiment was performed. As a result, as shown in Table 1, good binary recording characteristics could be realized.

Example 7
Except for using InFeO instead of BiFeO and changing the film thickness to 8 nm, the write-once type optical recording medium of the present invention was prepared in the same manner as in Example 1 and the recording power was changed to that shown in Table 1. Conducted a similar recording experiment. As a result, as shown in Table 1, good binary recording characteristics could be realized.

Example 8
The write-once light of the present invention is the same as in Example 1, except that the dye represented by [Chemical 2] is used instead of the dye represented by [Chemical 1] and the film thickness of the first thin film is 12 nm. A similar recording experiment was performed except that a recording medium was prepared and the recording power was changed to that shown in Table 1. As a result, as shown in Table 1, good binary recording characteristics could be realized. The organic material of [Chemical Formula 2] is a material that can be used for conventional DVD-R and DVD + R, but has a broad absorption band with a small absorption coefficient in the blue laser region as shown in FIG. (However, the main absorption band exists on the longer wavelength side than the recording / reproducing wavelength).
Therefore, in this embodiment, recording can be performed with the light absorption function of both the BiFeO film and the organic material thin film of [Chemical Formula 2], and the optimum recording power can actually be reduced by about 1.0 mW.

Example 9
A write-once optical recording medium of the present invention was prepared in the same manner as in Example 1 except that AlN was used instead of ZnS-SiO ₂ and the thickness of the first thin film was 10 nm. A similar recording experiment was conducted except that the points were changed to those shown in. As a result, as shown in Table 1, good binary recording characteristics could be realized.

Example 10
A write-once optical recording medium of the present invention was prepared in the same manner as in Example 1 except that Si ₃ N ₄ was used instead of ZnS—SiO ₂ and the thickness of the first thin film was 10 nm. A similar recording experiment was conducted except that the above was changed to that shown in Table 1. As a result, as shown in Table 1, good binary recording characteristics could be realized.

Example 11
On a polycarbonate substrate having a guide groove (groove depth 50 nm) (substrate thickness 0.6 mm), a BiFeO thin film (first thin film) having a film thickness of 15 nm and a ZnS-SiO ₂ thin film having a film thickness 100 nm are formed by sputtering. The second thin film) was sequentially laminated.
Next, a 150 nm-thick Ag reflecting layer and a protective layer having a thickness of about 5 μm made of an ultraviolet curable resin were provided on the ZnS—SiO ₂ thin film by sputtering to produce a write-once type optical recording medium of the present invention.
Conventional binary recording was performed on the optical recording medium under the same conditions as in Example 1.
As a result, as shown in Table 1, good binary recording characteristics could be realized.
Further, even when the recording power exceeds the optimum recording power, the reproduction signal level (RF Level) of the recording mark portion does not change greatly, and has a high modulation degree and a wide recording power margin. The medium could be realized.

Example 12
The write-once type optical recording medium of the present invention was prepared in the same manner as in Example 1 except that BiO was used instead of BiFeO and the film thickness was 12 nm, and the recording power was changed to that shown in Table 1. A similar recording experiment was conducted except for the above. As a result, as shown in Table 1, good binary recording characteristics could be realized.
Further, the write-once type optical recording medium of this example had a high reflectance of about 25 (%) when unrecorded, and a high degree of modulation of about 70 (%).
Furthermore, in the storage stability test at 80 ° C and 85% RH for 100 hours, both archival jitter and shelf jitter were confirmed to have very good storage stability with an increase in jitter of 0.7% or less. did.

Example 13
Except for using BiO instead of BiFeO, a write-once optical recording medium of the present invention was prepared in the same manner as in Example 11, and the same recording experiment was performed except that the recording power was changed to that shown in Table 1. Went. As a result, as shown in Table 1, good binary recording characteristics could be realized.
Furthermore, the write-once type optical recording medium of this example had a high reflectance of about 25 to 30 (%) when unrecorded, and the degree of modulation was as high as about 70 (%).

Example 14
On a polycarbonate substrate having a guide groove (groove depth 50 nm) (substrate thickness 0.6 mm), a ZnS—SiO ₂ thin film (second thin film, ZnS: SiO ₂ = 70: 30) having a film thickness of 50 nm using a sputtering method. ) And a target having a composition of BixFeyO (x and y are atomic ratios), BiFeO thin films (first thin films) having a thickness of 10 to 15 nm and different x and y were sequentially laminated.
Next, on each BiFeO thin film, an organic material thin film (average film thickness of about 40 nm) made of the dye represented by the above [Chemical Formula 1] is formed by a spin coating method. A write-once optical recording medium of the present invention was prepared by providing an AgPdCu reflective layer and a protective layer made of an ultraviolet curable resin and having a thickness of about 5 μm.
Conventional binary recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
<Recording conditions>
Modulation method: (1) 8-16 modulation and (2) 1-7 modulation Recording linear density: (1) 8-16 modulation
1T = 0.0917 (μm)
Shortest mark length 3T = 0.275 (μm)
(2) 1-7 modulation
1T = 0.026 (μm)
Shortest mark length 2T = 0.205 (μm)
・ Recording linear velocity: 6.0 (m / s)
Waveform equalization: normal equalizer FIG. 48 shows the relationship between x / (x + y) and jitter (σ / Tw), and FIG. 49 shows the results of examining the relationship between x / (x + y), modulation factor (modulated amplitude), and reflectance. is there. However, the degree of modulation in FIG. 49 is a value when 1-7 modulation is used. 48 and 49, the horizontal axis x / (x + y) indicates that 0 is FeO is 100%, and 1 is BiO is 100%.
From the above results, when the first thin film is represented by the composition of RxMyO (x and y are atomic ratios), good jitter characteristics can be realized in the range of x / (x + y) ≧ 0.3, Moreover, it was confirmed that a high degree of modulation and a high reflectance could be realized, and the effectiveness of the present invention was proved.

Comparative Example 2
On a polycarbonate substrate having a guide groove (groove depth 50 nm) (substrate thickness 0.6 mm), an organic material thin film (average film thickness of about 80 nm) made of FOM-559 (phthalocyanine manufactured by Wako Pure Chemical Industries, Ltd.) is formed by spin coating. Further, a write-once optical recording medium was prepared by providing a 150 nm-thick Ag reflection layer and a protective layer having a thickness of about 5 μm made of an ultraviolet curable resin by sputtering. Example applied to the blue region).
Note that FOM-559 (phthalocyanine manufactured by Wako Pure Chemical Industries, Ltd.) has a relatively small complex refractive index imaginary part (absorption) in the vicinity of 405 nm, which is the recording / reproducing wavelength, like the organic material used in the conventional write-once optical recording medium. Coefficient) and a relatively large complex refractive index real part.
Conventional binary recording was performed on the optical recording medium under the same conditions as in Example 1.
As a result, as shown in Table 1, the jitter value was 10.1% at a recording power of 11.0 mW.
Further, the protective layer made of the ultraviolet curable resin and the Ag reflection layer of the write-once type optical recording medium on which this recording was performed were peeled off, and the organic material thin film was washed away with ethanol, and the deformation state of the substrate surface was examined by AFM.
As a result, the deformation amount exceeded 100 nm at the maximum, and it was confirmed that deformation more than the substrate groove depth occurred.
Further, as shown in FIG. 18, the deformation state of the recording mark recorded earlier in time (N in FIG. 18) by the deformation of the recording mark recorded in the adjacent track (M in FIG. 18). It was confirmed that the shape changed greatly due to interference.
Therefore, it became clear that it was disadvantageous for further densification.

Example 15
On a polycarbonate substrate having a guide groove (groove depth 50 nm) (substrate thickness 0.6 mm), using a sputtering method, a 12 nm thick BiaSibOd thin film (first thin film), a 65 nm thick ZnSSiO ₂ thin film ( _second thin film) The write-once type optical recording medium of the present invention was prepared by sequentially providing an Ag reflective layer having a thickness of 100 nm and a protective layer having a thickness of about 5 μm made of an ultraviolet curable resin by sputtering.
Conventional binary recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
<Recording conditions>
Modulation method: 8-16 modulation Recording linear density: 1T = 0.0917 (μm)
・ Recording linear velocity: 6.0 (m / s)
-Waveform equalization: Normal equalizer In this example, when the composition ratio of the BiaSibOd thin film was changed variously, jitter of approximately 12% or less was obtained, but in particular, 10≤a≤40, 3≤b≤20, In the range of 50 ≦ d ≦ 70, a medium having a jitter of 10% or less was obtained. The recording power at that time was about 8.5 mW, and good binary recording characteristics could be realized.
In addition, as a result of investigating jitter degradation under an environment of 80 ° C. and relative humidity 85% and investigating jitter degradation, archival jitter was 0.8% or less and shelf jitter was 0.4% or less. It was.

Example 16
Except for using BiaGebOd instead of BiaSibOd, the write-once type optical recording medium of the present invention was prepared in the same manner as in Example 15 and the same recording experiment was conducted. As a result, a medium having a jitter of 10% or less was obtained particularly in the range of 10 ≦ a ≦ 40, 3 ≦ b ≦ 20, and 50 ≦ d ≦ 70. The recording power at that time was around 8.4 mW, and good binary recording characteristics could be realized.
In addition, as a result of investigating jitter degradation under an environment of 80 ° C. and relative humidity 85% and investigating jitter degradation, archival jitter was 0.7% or less and shelf jitter was 0.4% or less. It was.

Example 17
A write-once optical recording medium of the present invention was prepared in the same manner as in Example 15 except that a BiaSibFecOd thin film was used instead of BiaSibOd, and a similar recording experiment was performed. As a result, a medium having a jitter of 9.5% or less was obtained in the range of 10 ≦ a ≦ 40, 3 ≦ b ≦ 20, 3 ≦ c ≦ 20, and 50 ≦ d ≦ 70. The recording power at that time was around 8.8 mW, and good binary recording characteristics could be realized.
In addition, as a result of investigating jitter deterioration under the environment of 80 ° C. and relative humidity 85% and investigating jitter deterioration, archival jitter is 0.8% or less and shelf jitter is 0.2% or less. It was.

Example 18
The same composition as in Example 17 except that the composition ratio of BiaSibFecOd was Bi ₃ SiFe ₄ O ₁₂ and Al, Cr, Mn, In, Co, Cu, Ni, Zn, and Ti were used instead of Fe, respectively. The write-once type optical recording medium of the invention was prepared and the same recording experiment was conducted. As a result, a medium having a jitter of 10% or less was obtained no matter which element was used instead of Fe. The recording power at that time was about 8.2 mW, and good binary recording characteristics could be realized.
In addition, as a result of investigating jitter degradation under a 100-hour storage test in an environment of 80 ° C. and relative humidity 85%, archival jitter is 1.0% or less and shelf jitter is 0.3% or less. It was.

Comparative Example 3
A write-once optical recording medium was prepared in the same manner as in Example 15 except that Bi ₁ Fe ₉ O ₁₂ was used instead of BiaSibOd, and the same recording experiment was performed. As a result, a medium having a jitter of 12.0% or less was obtained particularly in the range of 10 ≦ a ≦ 40, 3 ≦ b ≦ 20, and 50 ≦ d ≦ 70.
However, as a result of investigating jitter degradation under a 100-hour storage test in an environment of 80 ° C. and relative humidity 85%, archival jitter was 4.8% and shelf jitter was 0.9%. .

Example 19
On a polycarbonate substrate having a guide groove (groove depth of 50 nm) (substrate thickness: 0.6 mm), a ZnS—SiO ₂ thin film having a thickness of 65 nm ( _second thin film referred to in the present invention: ZnS: SiO ₂ ) by sputtering. = 90:10).
On this second thin film, using a Bi target and a FeO target (composition Fe ₂ O ₃ ) (binary sputtering), a BiFeO thin film (first thin film referred to in the present invention) having a thickness of 10 nm is formed as Bi and The film was formed by changing the sputtering power of FeO.
Subsequently, an organic material thin film (average film thickness of about 30 nm) made of the dye represented by the above [Chemical Formula 1] is formed on the first thin film by a spin coating method, and further a film thickness of 150 nm is formed thereon by a sputtering method. A write-once optical recording medium of the present invention was prepared by providing an AgNdCu reflective layer and a protective layer made of an ultraviolet curable resin and having a thickness of about 5 μm.
The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. (conventional binary recording) ).
<Recording conditions>
Modulation method: 8-16 modulation, 3T signal repetitive recording Recording linear density: Shortest mark length (3T) = 0.275 (μm)
-Recording linear velocity: 6.0 (m / s)
-Waveform equalization: Normal equalizer As a result, as shown in FIG. 50, it was confirmed that the jitter was significantly improved as the sputtering power of the Bi target was increased with respect to the sputtering power of the FeO target.
The legend in FIG. 50 indicates the sputtering power applied to the Bi and FeO targets.
The film obtained by this binary sputtering can be represented by the composition of BixFeyO, but this BiFeO film is considered to be a mixture of Bi and FeO or a mixture of Bi, BiO and FeO.
Therefore, from the results of this example, it was proved that a mixture of Bi and FeO or a mixture of Bi, BiO, and FeO is important for realizing high-density recording.

As described above, Examples 1 to 13 and Comparative Example 2 show examples in which recording is performed at a medium recording density by conventional binary recording. The contents are summarized in Table 1 below.

Examples 20 to 28 below show examples of high density recording by conventional binary recording.
Example 20
Conventional binary recording was performed on the write-once type optical recording medium prepared in Example 1 under the following conditions in order to investigate the possibility of further high-density recording.
<Recording conditions>
Modulation method: 1-7 modulation Recording density: Shortest mark length 2T = 0.273 (μm), 0.261
(Μm), 0.250 (μm), 0.240 (μm),
0.231 (μm), 0.222 (μm), 0.214
(Μm), 0.205 (μm)
Recording linear velocity: 6.0 (m / s)
Waveform equalization: Normal equalizer FIG. 19 shows the recording power dependence of jitter (σ / Tw) when recording one track alone, and FIG. 20 shows the recording power dependence of jitter (σ / Tw) during continuous track recording. (In each figure, the legend indicates the length of the shortest mark length 2T).
From any of the results, it can be seen that the write-once type optical recording medium of the present invention exhibits excellent recording / reproducing characteristics even at a very high recording density.
In the recordable optical recording medium of Comparative Example 2, recording at 2T = 0.205 (μm) could not be performed (jitter measurement is impossible). However, in the recordable optical recording medium of the present invention, 2T = 0.205. Even under the recording condition of (μm) (recording of only one track), a very good value of jitter (σ / Tw) of 13.3 (%) is obtained with a recording power of about 7.4 (mw). (When the recording density was low, as shown in Table 1, the difference between the write-once type optical recording medium of the present invention and the conventional write-once type optical recording medium was not so noticeable. However, when recording at high density, the difference between the two becomes obvious.)

Example 21
In order to verify the effectiveness of the write-once optical recording medium of the present invention, the short mark forming ability of the write-once optical recording medium created in Example 1 and the write-once optical recording medium created in Comparative Example 2 was compared. .
The recording conditions were as follows, and recording was performed in a single cycle (2T) in order to eliminate the influence of the recording strategy.
<Recording conditions>
Modulation method: 1-7 modulation (however, recording of 2T single mark)
Recording density: shortest mark length 2T = 0.273 (μm), 0.261
(Μm), 0.250 (μm), 0.240 (μm),
0.231 (μm), 0.222 (μm), 0.214
(Μm), 0.205 (μm)
Recording linear velocity: 6.0 (m / s)
Waveform equalization: Normal equalizer As a result of obtaining the minimum jitter value (σ / Tw) by changing the recording power at each recording linear velocity, the result shown in FIG. 21 was obtained with respect to the mark length (2T).
As is apparent from FIG. 21, it was confirmed that the write-once type optical recording medium of the present invention has a short mark forming ability superior to that of the conventional write-once type optical recording medium.

Example 22
In order to verify the effectiveness of another write-once type optical recording medium of the present invention, the short mark forming ability of the write-once type optical recording medium produced in Example 11 and the write-once type optical recording medium produced in Comparative Example 2 was compared. went.
The recording conditions were as follows, and recording was performed in a single cycle (2T) in order to eliminate the influence of the recording strategy.
<Recording conditions>
Modulation method: 1-7 modulation (however, recording of 2T single mark)
Recording density: shortest mark length 2T = 0.273 (μm), 0.261
(Μm), 0.250 (μm), 0.240 (μm),
0.231 (μm), 0.222 (μm), 0.214
(Μm), 0.205 (μm)
Recording linear velocity: 6.0 (m / s)
Waveform equalization: Normal equalizer As a result of obtaining the minimum jitter value (σ / Tw) by changing the recording power at each recording linear velocity, the result as shown in FIG. 22 was obtained for the mark length (2T).
As is apparent from FIG. 22, it was confirmed that the write-once type optical recording medium of the present invention has a short mark forming ability superior to that of the conventional write-once type optical recording medium.

Example 23
On a polycarbonate substrate having a guide groove (groove depth 50 nm) (substrate thickness 0.6 mm), a ZnS—SiO ₂ thin film ( _second thin film as referred to in the present invention) having a thickness of 65 nm using a sputtering method, and a film thickness 10 nm. BiO thin films (first thin film referred to in the present invention) are sequentially provided, and an organic material thin film (average film thickness of about 30 nm) made of the dye represented by the above [Chemical Formula 1] is formed thereon by spin coating, A write-once optical recording medium of the present invention was prepared by providing an Ag reflection layer having a thickness of 150 nm and a protective layer having a thickness of about 5 μm made of an ultraviolet curable resin on the surface by sputtering.
The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. (conventional binary recording) ).
<Recording conditions>
Modulation method: 1-7 modulation Recording linear density: Shortest mark length (2T) = 0.231 (μm)
-Recording linear velocity: 6.0 (m / s)
-Waveform equalization: Normal equalizer As a result, as shown in FIG. 23, in the continuous recording section (the legend “σ / Tw 3Track” in the figure. On the other hand, “σ / Tw 1Track” records only one track, Track indicates recording in an unrecorded state), a good jitter value of 9.5% is obtained at a recording power of 6.2 mW, and a good binary value having a modulation degree of 60% or more (Modulated Amplitude) Recording characteristics could be realized. It can also be seen that there is no significant difference in jitter between 1-track recording and continuous recording, and that recording with small crosstalk can be realized.

Example 24
A recordable optical recording medium similar to that in Example 23 was manufactured, and a recording experiment similar to that in Example 23 was performed, except that the shortest mark length (2T) was set to 0.222 (μm).
As a result, as shown in FIG. 24, the continuous recording section (refer to the legend “σ / Tw 3Track” in the figure. Note that “σ / Tw 1Track” records only one track, and both adjacent tracks are unrecorded. A good jitter value of 9.5% is obtained at a recording power of 6.8 mW and a good binary recording characteristic having a modulation degree of 60% or more is realized. I was able to. It can also be seen that there is no significant difference in jitter between 1-track recording and continuous recording, and that recording with small crosstalk can be realized.

Example 25
A recordable optical recording medium similar to that in Example 23 was manufactured, and a recording experiment similar to that in Example 23 was performed, except that the shortest mark length (2T) was 0.214 (μm).
As a result, as shown in FIG. 25, the continuous recording section (refer to the legend “σ / Tw 3Track” in the figure. Note that “σ / Tw 1Track” records only one track, and both adjacent tracks are unrecorded. (1) shows a good jitter value of 11.4% at a recording power of 6.6 mW, and realizes a good binary recording characteristic having a modulation degree of 60% or more. I was able to. It can also be seen that there is no significant difference in jitter between 1-track recording and continuous recording, and that recording with small crosstalk can be realized.

Example 26
A recordable optical recording medium similar to that in Example 23 was manufactured, and a recording experiment similar to that in Example 23 was performed, except that the shortest mark length (2T) was set to 0.205 (μm).
As a result, as shown in FIG. 26, the continuous recording portion (refer to the legend “σ / Tw 3Track” in the figure. Note that “σ / Tw 1Track” records only one track, and both adjacent tracks are unrecorded. In this case, a good jitter value of 13.0% is obtained at a recording power of 6.6 mW, and a good binary recording characteristic having a modulation degree of 60% or more is realized. I was able to. It can also be seen that there is no significant difference in jitter between 1-track recording and continuous recording, and that recording with small crosstalk can be realized.
In the write-once type optical recording medium of Comparative Example 2, recording at 2T = 0.205 (μm) could not be performed (jitter measurement is impossible), but in the write-once type optical recording medium of the present invention, 2T = 0.205. Even under the recording condition of (μm) (recording of only one track), a very good value of jitter (σ / Tw) 11.8 (%) is obtained with a recording power of about 6.6 (mw). (When the recording density was low, as shown in Table 1, the difference between the write-once type optical recording medium of the present invention and the conventional write-once type optical recording medium was not so noticeable. However, when recording at high density, the difference between the two becomes obvious.)

Example 27
A write-once optical recording medium of the present invention was prepared in the same manner as in Example 23 except that the dye represented by [Chemical Formula 2] was used instead of the dye represented by [Chemical Formula 1], and the same recording was performed. The experiment was conducted. The organic material of [Chemical Formula 2] is a material that can be used for conventional DVD-R and DVD + R, but has a broad absorption band with a small absorption coefficient in the blue laser region as shown in FIG. (However, the main absorption band exists on the longer wavelength side than the recording / reproducing wavelength).
Therefore, in this embodiment, recording can be performed with the light absorption function of both the BiO film (first thin film) and the organic material thin film of [Chemical Formula 2], and the optimum recording power is actually reduced by about 0.8 mW. I was able to.

Example 28
On a polycarbonate substrate having a guide groove (groove depth of 50 nm) (substrate thickness: 0.6 mm), a ZnS—SiO ₂ thin film having a thickness of 50 nm ( _second thin film referred to in the present invention, ZnS: SiO ₂ ) by sputtering. = 80: 20), a BiFeO thin film having a thickness of 15 nm (the first thin film referred to in the present invention, the target composition is Bi ₆ Fe ₅ O _z , and the oxygen amount is not identifiable) are sequentially provided, ] An organic material thin film (average film thickness of about 30 nm) made of a dye represented by the following formula is formed by a spin coating method, and further a film thickness of about 150 nm made of an Ag reflection layer having a film thickness of 150 nm and an ultraviolet curable resin is formed thereon by a sputtering method. A write-once optical recording medium of the present invention was prepared by providing a protective layer of 5 μm.
The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. (conventional binary recording) ).
<Recording conditions>
Modulation method: 1-7 modulation Recording linear density: Shortest mark length (2T) = 0.205 (μm)
-Recording linear velocity: 6.0 (m / s)
-Waveform equalization: Limit equalizer As a result, as shown in FIG. 51, in the continuous recording section, a very good jitter value of 8.6% is obtained at a recording power of around 7.5 mW, and 70% or more. Good binary recording characteristics with a modulation factor could be realized (reproduction power was 0.5 mW).
Note that the legend “σ / Tw” in the figure indicates the jitter value, and “Modulated amplitude” indicates the modulation degree.
The eye pattern at that time is shown in FIG. 52, and it was confirmed that very good recording was performed.

Examples 29 to 35 and Comparative Examples 4 to 5 below show examples in which multi-value recording is performed.
Example 29
For the write-once optical recording medium created in Example 1, eight values were used under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. Multi-valued recording was performed.
<Recording conditions>
Recording linear density: Basic cell length = 0.47 (μm)
Recording linear velocity: 3.5 (m / s)
・ Recording pattern: Isolated mark and continuous mark (with two empty basic cells
Then, four consecutive recording marks with the same multi-value level
One isolated mark was recorded for 7 different multilevel levels)
As a result, as shown in FIG. 27, it has been found that the modulation degree (dynamic range) is large (modulation degree is 60%), and even in the continuous recording portion, it is possible to realize recording in which the fluctuation of the multilevel recording level is very small.
In the above experiment, multi-value recording was performed on the groove (groove), but recording was also possible on the groove (land).

Comparative Example 4
For the write-once type optical recording medium of Comparative Example 2, an optical disc evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. was used. Value recording was performed.
<Recording conditions>
Recording linear density: Basic cell length = 0.47 (μm)
Recording linear velocity: 3.5 (m / s)
Recording pattern: isolated mark and continuous mark (same as Example 29)
As a result, as shown in FIG. 28, so-called “modulation whisker” occurs in the continuous recording portion, and the fluctuation of the multi-level recording level becomes very large (the playback level must be the same in the continuous recording portion). It was confirmed that it was not suitable for multi-value recording. Further, it was confirmed that when the recording power was reduced, the modulation factor was not whisked, but at this time, the modulation factor (dynamic range) was very small (modulation factor was 20%) and the SNR was reduced. did.
Further, the protective layer made of the ultraviolet curable resin and the Ag reflection layer of the write-once type optical recording medium on which this recording was performed were peeled off, and the organic material thin film was washed away with ethanol, and the deformation state of the substrate surface was examined by AFM.
As a result, as shown in FIG. 29, interference between non-linear recording marks is generated in the continuous recording portion having a large area ratio of the recording mark to the basic cell [(d) to (f)]. It was confirmed that the “modulation whiskers” were based on a significant deterioration of the deformed shape due to deformation interference.
Further, as shown in FIG. 30, as a result of examining the relationship between the deformation amount of the substrate and the whisker amount of the modulation degree (difference in reproduction level between the head and the rear end of the continuous recording mark portion), the deformation amount exceeds about 50 nm. As a result, it was found that the level uniformity of the continuous recording portion was disturbed, making it unsuitable for multi-value recording.
That is, it became clear that the write-once type optical recording medium corresponding to multilevel recording cannot be realized unless the deformation amount is reduced (however, the write-once type optical recording medium of Comparative Example 4 is sufficient unless the deformation amount is increased). The degree of modulation does not occur).
Furthermore, in the above experiment, multi-value recording was performed in the groove portion (groove portion), but no recording was possible in the groove portion (land).

Example 30
In Example 29, the basic cell was further reduced (assumed capacity 25 GB), and 8-level multi-value recording was performed under the following conditions.
<Recording conditions>
Recording linear density: Basic cell length = 0.24 (μm)
Recording linear velocity: 5.0 (m / s)
Recording pattern: staircase waveform (see FIG. 31. Level 0 is recorded in 5 basic cells and level x is recorded in the following 32 basic cells, and x is changed from level 0 to level 7)
As a result, as shown in FIG. 31, it has been found that the modulation degree (dynamic range) is large (modulation degree is 60% or more), and even in the continuous recording portion, it is possible to realize recording in which the fluctuation of the multilevel recording level is very small. .
In addition, the protective layer made of the ultraviolet curable resin and the Ag reflection layer of the write-once optical recording medium on which this recording was performed were peeled off, and the organic material thin film was washed away with ethanol to show the deformation state of the BiFeO surface by SEM (scanning electron microscope). We investigated by.
As a result, as shown in FIG. 32, it was confirmed that the recording mark was formed with almost no deformation (an obvious deformation was not recognized in the SEM photograph. However, in order to clarify the state of the recording mark. The cell length was recorded as 0.26 μm).
Further, from the TEM image observation of the surface and cross section of the recording portion, the write-once type optical recording medium capable of multi-value recording of the present invention has a BiFeO thin film (first thin film), ZnS-SiO ₂ (second thin film), and organic It was confirmed that multi-value recording was also performed in the film thickness direction along with multi-value recording in the area direction of the material thin film.

Example 31
In Example 29, eight-value multi-value recording was performed under the following conditions with a basic cell length of 0.24 (μm).
<Recording conditions>
Recording linear velocity: 3.0 (m / s)
・ Recording pattern: Multi-level 0-1-0-3-0-5-0-7-0
Repeated recording (see Fig. 5)
Further, the protective layer made of an ultraviolet curable resin and the Ag reflection layer of the write-once type optical recording medium on which this recording was performed were peeled off, and the organic material thin film was washed away with ethanol to show the deformation state of the BiFeO surface by SEM (scanning electron microscope). We investigated by.
FIG. 33 shows an SEM image when the basic cell length is 0.24 (μm), and FIG. 34 shows a reproduction signal when the basic cell length is 0.24 (μm).
From this result, it was found that the recording part was formed on the BiFeO surface without significant deformation, and it was possible to obtain a reproduction signal in which each multi-value level could be clearly separated.

Comparative Example 5
In Comparative Example 4, 8-level multi-value recording was performed under the following conditions with the basic cell lengths of 0.32 (μm) and 0.24 (μm).
<Recording conditions>
Recording linear velocity: 4.0 (m / s) when the basic cell length is 0.32 (μm)
3.0 (m / s) when 0.24 (μm)
・ Recording pattern: Multi-level 0-1-0-3-0-5-0-7-0
Repeated recording (see Fig. 5)
In addition, the protective layer made of the ultraviolet curable resin and the Ag reflection layer of the write-once optical recording medium on which this recording was performed were peeled off, and the organic material thin film was washed away with ethanol to show the deformation state of the substrate surface by SEM (scanning electron microscope). We investigated by.
35 is an SEM image when the basic cell length is 0.32 (μm), FIG. 36 is a reproduction signal when the basic cell length is 0.32 (μm), and FIG. 37 is when the basic cell length is 0.24 (μm). FIG. 38 shows a reproduction signal when the basic cell length is 0.24 (μm).
From this result, in the conventional write-once type optical recording medium, the recording part is formed with a large deformation, and when the basic cell length is shortened, the interference between marks increases (see FIG. 37. The mark of level 7 is heated). As shown in FIG. 38, it is understood that each multi-value level becomes a reproduction signal that cannot be clearly separated (compared with FIG. 34).

Example 32
For the write-once type optical recording medium produced in Example 23, 8-level multi-value recording was performed under the following conditions with a basic cell length of 0.24 (μm).
<Recording conditions>
Recording linear velocity: 3.0 (m / s)
・ Recording pattern: Multi-level 0-1-0-3-0-5-0-7-0
Repeated recording (see Fig. 5)
In addition, the protective layer made of an ultraviolet curable resin and the Ag reflection layer of the write-once optical recording medium on which this recording was performed were peeled off, and the organic material thin film was washed away with ethanol to change the deformation state of the BiO surface with an SEM (scanning electron microscope). It was investigated by. 39 shows an SEM image when the basic cell length is 0.24 (μm), and FIG. 40 shows a reproduction signal when the basic cell length is 0.24 (μm).
From this result, a recording part is formed on the BiO surface without a large deformation (a slightly deformed region is observed, but the deformed region is very small with respect to the basic cell length), and each multi-value level It was found that a reproduced signal that was clearly separated could be obtained. In the above experiment, multi-value recording was performed on the groove (groove), but recording was also possible on the groove (land).

Example 33
On a polycarbonate substrate having a guide groove (groove depth of 50 nm) (substrate thickness: 0.6 mm), a ZnS—SiO ₂ thin film having a thickness of 50 nm ( _second thin film referred to in the present invention, ZnS: SiO ₂ ) by sputtering. = 85: 15), a 20 nm thick BiO thin film (the first thin film referred to in the present invention, the target composition is Bi ₂ O ₃ ), and an organic material comprising the dye represented by the above [Chemical Formula 1] A material thin film (average film thickness of about 25 nm) is formed by a spin coating method, and further, an Ag reflection layer having a film thickness of 150 nm and a protective layer made of an ultraviolet curable resin are provided by sputtering. The write-once type optical recording medium of the invention was prepared.
The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
Recording was performed on the above optical recording medium under the following conditions using an optical disk evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd. (conventional binary recording) ).
<Recording conditions>
Recording linear density: Basic cell length = 0.24 to 0.32 (μm)
Recording linear velocity: 5.0 (m / s)
Recording pattern: Random pattern The details of recording / reproduction used the conditions and methods described in the following documents (1) to (3).
(1) A. Shimizu et al. : “Data Detection using Pattern Recognition for Multi-level Optical Recording”, ISOM 2001 Technical Digest, Taipei, Taiwan, (October 2001), p. 300-301.
(2) K. Sakagami et al. : "A New Data Modulation Method for Multi-level Optical Recording", ISO / ODS 2002 Postdeline Papers, Waikoloa, Hawaii, (July 2002), p. 54-56.
(3) Y. Kadokawa et al. "Multi-level Optical Recording Using a Blue Laser", ODS 2003 Technical Digest, Vancouver, BC Canada, (May 2003), pp. 294-296.
In addition, SDR (sigma to dynamic range) was used for evaluation of multi-level recording. SDR is a value obtained by the following equation (1).
In equation (1), σk is the standard deviation of each multilevel, DR is the dynamic range (the difference between the central value of the multilevel having the maximum reflection level and the central value of the multilevel having the minimum reflection level), n Is the number of multilevel levels.
Also, as described in the above document, in order to realize recording with a BER (bit error rate) of 10 ⁻⁵ or less, the SDR must be 3.2% or less. Based on this premise, SDR was measured by changing the basic cell length.
The recording capacity corresponding to each basic cell length is shown in FIG. “Required value” in the figure indicates the level of the required SDR value. That is, it must be lower than this required value. As can be seen from the figure, the SDR is 3.2% or less in the continuous recording portion when the basic cell length is larger (longer) than about 0.24 μm, which is multivalued compared to the recording medium of the present invention. By applying the recording, it became clear that even a system using a substrate thickness of 0.6 mm and an objective lens NA of 0.65 can realize a super large capacity of a recording capacity of 23 GB or more (single layer).
Thus, as far as the inventors know, there is no example in which a super large capacity of a recording capacity of 23 GB or more is realized by a system using a substrate thickness of 0.6 mm and an objective lens NA of 0.65.
Furthermore, in the case of a system using a substrate thickness of 0.1 mm and an objective lens NA of 0.85, an ultra-high capacity of 30 GB or more (single layer) is realized by applying multi-value recording to the recording medium of the present invention. It became clear that we could do it.
This example shows an example of experimental results, and the recording capacity of the write-once type optical recording medium of the present invention is not limited to 23 GB.

Example 34
In Example 30 (that is, with respect to the write-once type optical recording medium of Example 1), except that the first thin film was made of MoO ₃ , the same write-once type optical recording medium was prepared and the same recording pattern was recorded. did. As a result, a recording waveform almost similar to that in Example 30 could be obtained.

Example 35
In Example 30 (that is, with respect to the write-once type optical recording medium of Example 1), the same write-once type optical recording medium was prepared and the same recording pattern was used except that the first thin film was V ₂ O _5. Was recorded. As a result, a recording waveform almost similar to that in Example 30 could be obtained.

Example 36
Recording / reproduction was performed on the write-once type optical recording medium prepared in Example 1 using the PR (1, 2, 1) system at a recording linear density at which the shortest mark length was 0.205 μm.
As a result of decoding by the PRML method, it was confirmed that the BER (bit error rate) was 10 ⁻⁵ units and very good recording and reproduction could be performed.

Example 37
Recording / reproduction was performed on the write-once type optical recording medium prepared in Example 23 using the PR (1, 2, 1) method at a recording linear density where the shortest mark length was 0.205 μm.
As a result of decoding by the PRML method, it was confirmed that the BER (bit error rate) was 10 ⁻⁵ units and very good recording and reproduction could be performed.

Comparative Example 6
Recording / reproduction was performed on the write-once type optical recording medium prepared in Comparative Example 2 using the PR (1, 2, 1) method at a recording linear density where the shortest mark length was 0.205 μm.
As a result, in jitter evaluation in normal binary recording, the jitter value exceeds 20%, and as a result of decoding by the PRML method, the BER (bit error rate) is 10 ⁻³ units, and the PRML method is applied at this recording linear density. However, it was confirmed that recording and playback could not be performed.

Example 38
The absorptance Q of the write-once type optical recording medium prepared in Example 1 was measured. Specifically, the reflectance R and transmittance T of the optical recording medium were measured, and the value 1-RT was defined as the absorption factor Q (X in FIG. 41).
For comparison, as in the write-once type optical recording medium of Example 1, the absorption factor Q of a commercially available CD-R using a phthalocyanine compound, which is a material that can be recorded and reproduced even in the blue laser wavelength region (see FIG. 41) and the absorption factor Q (Y in FIG. 41) of the write-once type optical recording medium prepared in Comparative Example 2 were also measured (the track pitch of the substrate with the commercially available CD-R using the phthalocyanine compound as it was. Due to the relationship between the thickness of the substrate and the thickness of the substrate, it cannot be recorded / reproduced by an evaluation device compatible with blue lasers. However, when a commercially available CD-R is destroyed, the phthalocyanine compound is washed away with a solvent and applied again to a substrate compatible with blue lasers. It can be recorded and played back with a corresponding evaluation device).
As a result, it was confirmed that the write-once type optical recording medium of the present invention has a very small variation in the absorptance Q in the wavelength region of 500 nm or less, particularly in the vicinity of 400 nm.
Therefore, the write-once optical recording medium of the present invention is a write-once optical recording medium with little change in recording characteristics such as recording sensitivity, modulation degree, jitter, error rate, and reflectance, etc., with respect to fluctuations in the recording / reproducing wavelength. It was confirmed that it could be realized.

Example 39
Similarly to Example 38, the absorptivity Q of the write-once optical recording medium prepared in Example 23 was measured. Specifically, the reflectance R and transmittance T of the optical recording medium were measured, and the value 1-RT was defined as the absorption factor Q (W in FIG. 42). 42, Y and Z are the same as in Example 38.
As a result, it was confirmed that the write-once type optical recording medium of the present invention has a very small variation in the absorptance Q in the wavelength region of 500 nm or less, particularly in the vicinity of 400 nm.
Therefore, according to the present invention, it is confirmed that a write-once type optical recording medium can be realized in which recording characteristics such as recording sensitivity, modulation degree, jitter, and error rate, and changes in reflectance and the like are small with respect to fluctuations in recording and reproducing wavelengths. did it.

Example 40
An experiment was conducted to confirm on what principle the recording marks formed on the write-once type optical recording media prepared in Example 1 and Comparative Example 1 were formed, and whether there was a difference between the two.
The recording part of the write-once type optical recording medium prepared in Example 1 and Comparative Example 1 was cut with FIB (focused ion beam processing apparatus), and this part was observed with a TEM (transmission electron microscope).
As a result, in Comparative Example 1, the BiFeO thin film was greatly deformed and destroyed in the recording mark portion of the portion where the modulation degree increased rapidly (the portion recorded with a recording power higher than the minimum jitter) as shown in FIG. It was confirmed that the large deformation and destruction led to deterioration of jitter and recording power margin.
On the other hand, as shown in FIG. 43, it was confirmed that the recording mark portion of Example 1 shows no significant deformation or destruction in the BiFeO thin film.
Obviously, the interface between the BiFeO thin film (first thin film) and the ZnS-SiO ₂ thin film (second thin film) is obscured, and the organic material thin film may have a cavity. Yes, the validity of the recording principle of the present invention was confirmed.
From the above results, it was confirmed that the recording principle of the present invention is not mainly composed of deformation.

Example 41
Based on what principle the recording portion having the basic cell length of 0.24 (μm) in Example 31 was formed was observed by FIB and TEM as in Example 40.
As a result, as shown in FIG. 45, the decomposition and deterioration of the organic material thin film (dye layer), and volume expansion, small deformation of the BiFeO layer and ZnS-SiO ₂ layer, BiFeO layer and ZnS-SiO ₂ layer obscuring the interface It was confirmed that the recording mark was formed by crystallization (melting, mixing, and diffusion of the materials of both layers).
Furthermore, in the analysis by electron beam diffraction, crystallization occurred in the recording portion, and it was confirmed that crystal grains were formed, and the validity of the recording principle of the present invention was confirmed.

Example 42
On a polycarbonate substrate having a guide groove (groove depth of 50 nm) (substrate thickness 0.6 mm), a BiO thin film (first thin film; target composition is Bi ₂ O ₃ ) and a film having a film thickness of about 10 nm by sputtering. A ZnS—SiO ₂ thin film (second thin film) having a thickness of about 100 nm was sequentially laminated.
Then, a write-once optical recording medium of the present invention was prepared by providing an Ag reflective layer having a thickness of about 150 nm and a protective layer made of an ultraviolet curable resin on the ZnS-SiO ₂ thin film by sputtering.
This write-once optical recording medium was subjected to single period recording with a mark length of about 0.89 (μm), and observed by FIB and TEM in the same manner as in Example 40.
As a result, as shown in FIG. 47 (FIG. 46 is a TEM image of an unrecorded part), the BiO layer and the ZnS—SiO ₂ layer are slightly deformed, and the interface between the BiO layer and the ZnS—SiO ₂ layer is obscured (both layers) It was confirmed that the recording mark was formed by melting, mixing, and diffusion of the material.
Furthermore, in the analysis by electron beam diffraction, crystallization occurred in the recording portion, and it was confirmed that crystal grains were formed, and the validity of the recording principle of the present invention was confirmed.

The figure which shows the relationship between the base of the large absorption band wavelength side of an organic material, and the recording / reproducing wavelength in the write-once type optical recording medium which used the conventional organic material as the recording layer. FIG. 6 is a diagram for explaining that a wavelength-dependent optical constant of an organic material has a large problem in a write-once type optical recording medium using a conventional organic material. The figure which observed the mode of the deformation | transformation of the board | substrate surface in the conventional write-once type | mold optical recording medium, and observed with AFM. The figure for demonstrating the mode of the data decoding by the conventional slice system. (A): Recording data which is information to be recorded. (B) Recording waveform corresponding to (a). (C): a recording mark row formed on the optical recording medium. (D) Reproduction signal waveform of the recording mark row of (c). (E): An equivalent waveform obtained by shaping the reproduced signal waveform of (d) with an equalizer. (F): Value data obtained by detecting the intersection of the equalized waveform (e) and the threshold value. (G): decoded data obtained by subjecting the binary data (f) to NRZ conversion. The conceptual diagram of the recording mark in multi-value recording. The figure for demonstrating the meaning that the interference of a deformation | transformation is linear. (A): Plan view showing a state in which recording marks mainly composed of deformation are formed in three consecutive cells. (B): A cross-sectional view showing the deformation amount of each recording mark when there is no deformation interference. (C); The figure which shows a mode that the deformation | transformation of (b) was added. When recording marks mainly composed of deformation are formed in three consecutive cells, and the series of recorded cells has a length equal to or smaller than the reproduction beam diameter, reproduction is performed due to the difference in deformation of the three cells. The figure which showed the change of the signal. (O): A diagram showing a reproduction beam diameter. (A): Plan view showing a state in which recording marks mainly composed of deformation are formed in three consecutive cells. (B); The figure which shows the state where deformation | transformation was added. (C); The figure which shows a deformation | transformation state when the interference of a deformation | transformation is not linear. (D); The figure which shows the deformation | transformation state in the case where deformation | transformation interference is not linear. The figure which shows the reproduction signal obtained in the case of (e); (b) (c) (d). In the case where seven recording marks mainly composed of deformation are formed continuously, when recorded cells are continuous and the series of lengths becomes larger than the reproduction beam diameter, deformation interference occurs. The figure which showed the relationship between a difference and a reproduction signal. (O): A diagram showing a reproduction beam diameter. (A): Plan view showing a state in which recording marks mainly composed of deformation are formed in seven continuous cells. (B); The figure which shows the state to which the deformation | transformation was added. (C); The figure which shows a deformation | transformation state when the interference of a deformation | transformation is not linear. (D); The figure which shows the deformation | transformation state in the case where deformation | transformation interference is not linear. The figure which shows the reproduction signal obtained in the case of (e); (b). The figure which shows the reproduction | regeneration signal obtained in the case of (f); (c). (G); The figure which shows the reproduction signal obtained in the case of (d). The figure for demonstrating the mode of the data decoding by a PRML system. (A): Recording data which is information to be recorded. (B) Recording waveform corresponding to (a). (C): a recording mark row formed on the optical recording medium. (D) Reproduction signal waveform of the recording mark row of (c). (E): An equalized waveform when the reproduced signal waveform of (d) is equalized by an equalizer based on the PR (1, 1) characteristic. (F): an equalized waveform when the reproduced signal waveform of (d) is equalized by an equalizer based on the PR (1, 2, 1) characteristics. (G): an equalized waveform when the reproduced signal waveform of (d) is equalized by an equalizer based on the PR (1, 2, 2, 1) characteristics. The figure which shows the relationship between the board | substrate deformation | transformation shape of the recording mark in a conventional write-once type optical recording medium, and a reproduction signal. The figure which shows the relationship between a substrate deformation | transformation shape at the time of irradiating weak DC light, after recording on the conventional write-once type optical recording medium, and a reproduced signal. The figure which shows the relationship between the main absorption band of the organic material in the write-once type optical recording medium of this invention, and a recording / reproducing wavelength. The figure for demonstrating the "main absorption band" said by this invention. The figure which shows the result of having performed binary recording on the write-once type optical recording medium of the comparative example 1. FIG. FIG. 3 is a diagram illustrating a result of performing binary recording on the write-once type optical recording medium of Example 1; The figure which compared the jitter of the write once optical recording medium of Example 1 and Comparative Example 1. FIG. The figure which compared the reproduction | regeneration signal level of the space part of a write-once type optical recording medium of Example 1 and the comparative example 1, and a recording mark part. The figure which observed the deformation | transformation state of the substrate surface of the write-once type optical recording medium of the comparative example 2 by AFM. The figure which shows the result of having measured the recording power dependence of the jitter ((sigma) / Tw) at the time of changing the shortest mark length (2T) and recording one track on the write-once type optical recording medium of Example 20. FIG. The figure which shows the result of having measured the recording power dependence of the jitter ((sigma) / Tw) at the time of changing to the shortest mark length (2T) and recording continuously on the write-once type optical recording medium of Example 20. FIG. The figure which shows the result of having evaluated the high density recording adaptability of the write-once type optical recording media of Example 1 and Comparative Example 2. The figure which shows the result of having evaluated the high-density recording adaptability of the write-once type optical recording medium of Example 11 and Comparative Example 2. FIG. The recording power dependence of jitter (σ / Tw) and modulation degree (Modulated Amplitude) was evaluated at a recording density of 2T = 0.231 (μm) for the write-once optical recording medium of Example 23. Figure. The recording power dependence of jitter (σ / Tw) and modulation degree (Modulated Amplitude) was evaluated at a recording density of 2T = 0.222 (μm) for the write-once optical recording medium of Example 23. Figure. The recording power dependence of jitter (σ / Tw) and modulation degree (Modulated Amplitude) at the recording density of 2T = 0.214 (μm) for the recordable optical recording medium of Example 23 is shown. Figure. The recording power dependence of jitter (σ / Tw) and modulation degree (Modulated Amplitude) at the recording density of 2T = 0.205 (μm) with respect to the recordable optical recording medium of Example 23 is shown. Figure. FIG. 6 is a diagram illustrating a result of performing 8-level multi-value recording on the write-once type optical recording medium of Example 1; The figure which shows the result of having performed 8-level multi-value recording on the write-once type optical recording medium of the comparative example 4. FIG. The figure which observed the deformation | transformation state of the substrate surface of the write-once type optical recording medium of the comparative example 4 by AFM. (A) Diagram showing deformation of substrate surface (B) LL sectional view of (A) FIG. 10 is a diagram showing the relationship between the deformation height of the substrate surface of the write-once type optical recording medium of Comparative Example 4 and the amount of whiskers. The figure which shows the result of having performed the multi-value recording of 8 values in Example 30. FIG. The figure which investigated the deformation | transformation state of the BiFeO surface of the write-once type optical recording medium of Example 30 by SEM. The figure which investigated the deformation | transformation state of the BiFeO surface of the write-once type optical recording medium of Example 31 by SEM. The figure which shows the reproduction signal obtained from the write-once type optical recording medium of Example 31. The figure which investigated the deformation | transformation state of the BiFeO surface of the write-once type optical recording medium of the comparative example 5 with SEM (basic cell length = 0.32 micrometer). The figure which shows the reproduction | regeneration signal obtained from the write-once type optical recording medium of the comparative example 5 (basic cell length = 0.32 micrometer). The figure which examined the deformation | transformation state of the BiFeO surface of the write-once type optical recording medium of the comparative example 5 with SEM (basic cell length = 0.24 micrometer). The figure which shows the reproduction | regeneration signal obtained from the write-once type optical recording medium of the comparative example 5 (basic cell length = 0.24 micrometer). The figure which investigated the deformation | transformation state of the BiO surface of the write-once type optical recording medium of Example 32 by SEM. FIG. 40 shows a reproduction signal obtained from the write-once type optical recording medium of Example 32. The figure which shows the measurement result of the absorptivity Q of the write-once type optical recording medium of Example 1, the write-once type optical recording medium of the comparative example 2, and commercially available CD-R. The figure which shows the measurement result of the absorption factor Q of the write-once type optical recording medium of Example 23, the write-once type optical recording medium of the comparative example 2, and commercially available CD-R. The figure which cut | disconnected the recording part of the write-once type optical recording medium of Example 1 by FIB (radial direction), and observed this part by TEM. The figure which cut | disconnected the recording part of the write-once type optical recording medium of the comparative example 1 by FIB (radial direction), and observed this part by TEM. The figure which cut | disconnected the recording part of the write-once type optical recording medium of Example 31 by FIB (guide groove direction), and observed this part by TEM. The figure which cut | disconnected the non-recording part of the write-once type optical recording medium of Example 42 by FIB (radial direction), and observed this part by TEM. The figure which cut | disconnected the recording part of the write-once type optical recording medium of Example 42 by FIB (radial direction), and observed this part by TEM. The figure which shows the relationship between x / (x + y) and jitter ((sigma) / Tw) at the time of performing the conventional binary recording with respect to the write-once type optical recording medium of Example 14. FIG. The figure which shows the relationship between x / (x + y), a modulation degree (Modulated amplitude), and a reflectance at the time of performing the conventional binary recording with respect to the write-once type optical recording medium of Example 14. FIG. FIG. 25 is a diagram showing a relationship between recording power and jitter when conventional binary recording is performed on the write-once type optical recording medium of Example 19; FIG. 29 is a diagram showing a relationship between recording power and jitter when conventional binary recording is performed on the write-once type optical recording medium of Example 28. FIG. 28 shows eye patterns when conventional binary recording is performed on the write-once type optical recording medium of Example 28. The figure which shows SDR in each basic cell length at the time of performing multi-value recording with respect to the write-once type optical recording medium of Example 33.

Explanation of symbols

n Real part of complex index of refraction k Imaginary part of complex index of refraction δn Change of real part of complex index of refraction due to fluctuations in recording and reproduction wavelength δk Change of imaginary part of complex index of refraction due to fluctuations in recording and reproduction wavelength δλ Width of recording and reproduction wavelength (variation )
T _{1 to} T ₇ Sampling time A Reproduced signal waveform B Image obtained by removing the protective layer, Ag reflection layer, and dye layer and observing the substrate surface with AFM CB Amount of deformation of the substrate cross section was displayed from the AFM image of the substrate measured with CB Fig. M Recording mark recorded on adjacent track NM Recording mark recorded earlier in time than M a Continuous recording section of multi-level 2 (see Fig. 5) b Continuous recording of multi-level 3 (see Fig. 5) Part c Continuous recording part of multi-level 4 (see FIG. 5) d Continuous recording part of multi-level 5 (see FIG. 5) e Continuous recording part of multi-level 6 (see FIG. 5) f Multi-level 7 (FIG. 5) X) Absorption rate of write-once optical recording medium of Example 1 W Absorption rate of write-once optical recording medium of Example 23 Y Absorption rate of write-once optical recording medium of Comparative Example Z Commercially available CD -R absorption

Claims (37)

  At least each element of R and O (where R represents one or more elements selected from Y, Bi, In, Mo, V, and lanthanum series elements, and O represents oxygen) is the minimum constituent element. A write-once optical recording medium comprising: a first thin film; and a second thin film that suppresses deformation and destruction of the first thin film and accepts a change in state of the first thin film.   The first thin film contains the element M, and M is Al, Cr, Mn, Sc, In, Ru, Rh, Co, Fe, Cu, Ni, Zn, Li, Si, Ge, Zr, Ti, and Hf. The write-once type optical recording medium according to claim 1, wherein the write-once type optical recording medium is at least one selected from the group consisting of Sn, Pb, Mo, V, and Nb.   3. The write once optical recording medium according to claim 1, further comprising an organic material thin film.   4. The write once optical recording medium according to claim 3, wherein the first thin film has a structure sandwiched between the second thin film and the organic material thin film.   The write-once type optical recording medium according to claim 4, wherein at least a second thin film, a first thin film, an organic material thin film, and a reflective layer are sequentially laminated on the substrate.   The write-once type optical recording medium according to claim 4, wherein at least an organic material thin film, a first thin film, a second thin film, and a reflective layer are sequentially laminated on the substrate.   The write-once type optical recording medium according to claim 1 or 2, wherein at least a first thin film, a second thin film, and a reflective layer are sequentially laminated on the substrate.   The write-once type optical recording medium according to claim 4, wherein at least a reflective layer, a second thin film, a first thin film, an organic material thin film, and a cover layer are sequentially laminated on the substrate.   5. The write-once type optical recording medium according to claim 4, wherein at least a reflective layer, an organic material thin film, a first thin film, a second thin film, and a cover layer are sequentially laminated on the substrate.   3. The write-once optical recording medium according to claim 1, wherein at least a reflective layer, a second thin film, a first thin film, and a cover layer are sequentially laminated on the substrate. The write-once type optical recording medium according to claim 1, wherein the second thin film contains ZnS or ZnS—SiO ₂ as a main component.   The write-once type according to any one of claims 2 to 11, wherein the first thin film is represented by a composition of RxMyO (x and y are atomic ratios) and x / (x + y) ≥0.3. Optical recording medium.   The write-once type optical recording medium according to claim 1, wherein the first thin film contains R (element R) and RO (oxide of element R).   The write-once type optical recording medium according to any one of claims 2 to 11, wherein the first thin film contains R (element R) and MO (oxide of element M).   The write-once type optical recording medium according to any one of claims 2 to 11, wherein the first thin film contains RO (oxide of element R) and MO (oxide of element M).   The write-once type according to any one of claims 2 to 11, wherein the first thin film contains R (element R), RO (oxide of element R), and MO (oxide of element M). Optical recording medium.   The write-once type optical recording medium according to claim 1, wherein the first thin film contains bismuth oxide.   The write once optical recording medium according to any one of claims 1 to 11, wherein the first thin film contains bismuth and bismuth oxide.   The first thin film is Bia4BbOd (where 4B is at least one element selected from the group 4B, a, b, d are composition ratios, 10 ≦ a ≦ 40, 3 ≦ b ≦ 20, 50 ≦ d) The write-once type optical recording medium according to claim 2, which has a composition of ≦ 70).   The first thin film is Bia4BbXcOd (where 4B is at least one element selected from Group 4B, X is Al, Cr, Mn, In, Co, Fe, Cu, Ni, Zn, Ti, and At least one element selected from Sn, a, b, c, d is a composition having a composition ratio of 10 ≦ a ≦ 40, 3 ≦ b ≦ 20, 3 ≦ c ≦ 20, 50 ≦ d ≦ 70) The write-once type optical recording medium according to claim 2, wherein   The write-once type optical recording according to any one of claims 1 to 20, wherein a recording mark for generating three or more different reproduction signal levels can be formed, and a type of the recording mark can be determined based on the reproduction signal level. Medium.   The write-once type optical recording medium according to any one of claims 1 to 21, wherein recording and reproduction are possible in a signal processing system based on a PRML system.   The write-once type optical recording medium according to any one of claims 1 to 22, wherein the main absorption band of the organic material thin film is located on the long wavelength side with respect to the recording / reproducing wavelength.   The write-once type optical recording medium according to claim 23, wherein the value of the imaginary part of the complex refractive index at the recording / reproducing wavelength of the organic material thin film is smaller than that of the first thin film.   25. The write-once type optical recording medium according to claim 23 or 24, wherein the organic material thin film has an absorption band that does not belong to the main absorption band in the vicinity of the recording / reproducing wavelength. The write-once type optical recording medium according to any one of claims 1 to 25, wherein a recording mark can be formed by at least one of the following recording principles (a) to (l) by the light absorption function of the first thin film.
A) Deform the first thin film and / or the second thin film b) Change the complex refractive index of the first thin film and / or the second thin film c) The first thin film and / or the second thin film Changing the composition d) Melting the first thin film e) Diffusing the constituent elements in the first thin film to the second thin film or organic material thin film f) Changing the crystal state and crystal structure of the first thin film G) Oxidation / reduction of the constituent elements in the first thin film h) Change the composition distribution in the first thin film i) Change the volume of the organic material thin film n) Change the complex refractive index of the organic material thin film Le) Make a cavity in the organic material thin film   27. The write-once type optical recording medium according to claim 26, wherein recording marks for generating three or more different reproduction signal levels can be formed in the area direction and the film thickness direction of the first thin film and / or the organic material thin film.   27. The write-once type optical recording medium according to claim 26, wherein recording marks for generating three or more different reproduction signal levels can be formed in the area direction and the film thickness direction of the first thin film and / or the second thin film. .   29. The write-once type optical recording medium according to any one of claims 1 to 28, wherein recording and reproduction are possible with light of 500 nm or less.   30. The recording / reproducing method for a write-once optical recording medium according to claim 1, wherein the recording portion is formed by a light absorption function at a recording / reproducing wavelength of the first thin film.   30. The recording / reproducing method for a write-once optical recording medium according to claim 1, wherein the recording portion is formed by a light absorption function at a recording / reproducing wavelength of the first thin film and the organic material thin film.   32. The recording / reproducing method according to claim 30, wherein a recording mark for generating three or more different reproduction signal levels is formed, and the type of the recording mark is determined based on the reproduction signal level.   33. The recording / reproducing method according to claim 30, wherein recording / reproducing is performed by a signal processing system based on a PRML system. 34. The recording / reproducing method according to claim 30, wherein a recording mark is formed by at least one of the following recording principles (a) to (l) by the light absorption function of the first thin film.
A) Deform the first thin film and / or the second thin film b) Change the complex refractive index of the first thin film and / or the second thin film c) The first thin film and / or the second thin film Changing the composition d) Melting the first thin film e) Diffusing the constituent elements in the first thin film to the second thin film or organic material thin film f) Changing the crystal state and crystal structure of the first thin film G) Oxidation / reduction of the constituent elements in the first thin film h) Change the composition distribution in the first thin film i) Change the volume of the organic material thin film n) Change the complex refractive index of the organic material thin film Le) Make a cavity in the organic material thin film   35. The recording mark for generating three or more different reproduction signal levels is formed in the area direction and film thickness direction of the first thin film and / or the organic material thin film. Recording and playback method.   35. The recording mark for generating three or more different reproduction signal levels is formed in the area direction and the film thickness direction of the first thin film and / or the second thin film. The recording / reproducing method described.   The recording / reproducing method according to any one of claims 30 to 36, wherein recording / reproducing is performed at a wavelength of 500 nm or less.