JP2006269052A - Optical recording medium, optical recording method, and optical recording apparatus - Google Patents

Abstract

An optical recording method, an optical recording apparatus, and an optical recording medium capable of realizing a more reliable and high-speed and high-density optical recording without writing failure.
A pulse train having at least a recording power Pw and a bottom power Pb is used for an optical recording medium having information relating to an optical recording linear velocity and capable of recording with a minimum recording mark length of 0.7 μm or less. When a mark having a predetermined length is recorded, a plurality of optical recording pulse trains having different numbers of pulses are prepared in advance in the optical recording device, and a desired pulse train is selected from the optical recording pulse method. And an optical recording apparatus and an optical recording medium for carrying out this method.
[Selection] Figure 7

Description

  The present invention relates to an optical recording method and optical recording that can be used for high-speed recording such as DVD-R, DVD-RW, DVD + R, DVD + RW, DVD-RAM, and Blu-ray, which can record information by irradiating a laser beam. The present invention relates to an apparatus and an optical recording medium. In particular, the present invention relates to a high-density optical recording method, an optical recording apparatus, and an optical recording medium having a large capacity equivalent to or greater than that of a DVD-ROM. Furthermore, the present invention relates to an ultra-high capacity optical recording method, an optical recording apparatus, and an optical recording medium having two or more multilayer recording layers.

In general, the basic layer structure of an optical recording medium is divided into a once recording type and a rewritable type. The once recording type optical recording medium has a layer structure of substrate / dye recording layer / light reflecting layer. On the other hand, in the rewritable optical recording medium, it is substrate / lower protective layer / optical recording layer / upper protective layer / light reflecting layer. Further, if necessary, intermediate layers are formed between the lower protective layer and the optical recording layer, between the optical recording layer and the upper protective layer, and between the upper protective layer and the light reflecting layer.
In these optical recording media, development of optical recording methods and optical recording media for further higher recording density and higher linear velocity is expected in order to record more information faster. . In particular, as a high-speed recording technique, it is known that recording is performed with n-1 light emission pulses in order to record an nT recording mark. Further, as a high-speed recording technique for CD-RW of 24 times speed or higher, a technique for recording a 2T mark with one pulse has been developed. In this technique, 3T is recorded by 1 pulse, 4T and 5T are 2 pulses, 6T and 7T are 3 pulses, 8T and 9T are 4 pulses, and 10T and 11T are 5 pulses. However, with the uniform light emission pulse pattern rule for nT mark length recording, it was difficult to form a good recording mark, that is, a good shape mark with reduced jitter at high speed and high density. .
In the conventional optical recording technology, the number of light emission pulses is not changed for various optical recording media,
This has been dealt with by adjusting (1) emission pulse width and (2) emission power.
With this method, it was possible to cope with CD system and DVD 2.4-times recording. However, in recording at a recording density equivalent to that of DVD and a DVD speed of 4 × or higher, it is stable with respect to various optical recording media, that is, it absorbs variations in optical recording media and optical recording devices and has good reproducibility. It was difficult to form a recording mark.

  It is an object of the present invention to provide an optical recording method, an optical recording apparatus, and an optical recording medium that can realize more reliable and high-speed and high-density optical recording without writing loss.

The above problems are solved by the following inventions 1) to 9) (hereinafter referred to as the present inventions 1 to 9).
1) Predetermined by using a pulse train having at least recording power Pw and bottom power Pb for an optical recording medium having information relating to the optical recording linear velocity and capable of recording with a minimum recording mark length of 0.7 μm or less. An optical recording method comprising: preparing a plurality of optical recording pulse trains having different numbers of pulses in an optical recording device in advance and recording a desired pulse train from the plurality of optical recording pulse trains.
2) For an optical recording medium having information on the optical recording linear velocity and capable of recording with a minimum recording mark length of 0.7 μm or less, using a pulse train having at least recording power Pw and bottom power Pb, When recording a mark having a length represented by nT in which the time length of the recording mark is n times the basic clock period T (n is a natural number), a plurality of optical recording pulse trains having different pulse numbers are prepared in advance. An optical recording method characterized in that a desired pulse train is selected from them.
3) The number of pulses of a plurality of optical recording pulse trains having different numbers of pulses is any of n, n-1, n / 2, (n-1) / 2, and (n + 1) / 2 with respect to the mark length of nT. 2) The optical recording method according to 2).
4) The optical recording method according to any one of 1) to 3), wherein, among a plurality of optical recording pulse trains having different numbers of pulses, a pulse train having a smaller number of pulses has a higher corresponding recording linear velocity.
5) The optical recording method according to any one of 1) to 4), wherein among a plurality of optical recording pulse trains having different numbers of pulses, a pulse train having a smaller number of pulses has a smaller corresponding recording power Pw.
6) An optical recording apparatus comprising a function capable of executing the optical recording method according to any one of 1) to 5).
7) In an optical recording medium having information relating to the optical recording linear velocity and capable of recording with a minimum recording mark length of 0.7 μm or less, a pulse train having at least the recording power Pw and the bottom power Pb is used. An optical recording medium characterized in that a mark having a length can be recorded, and at that time, a desired pulse train can be selected and used from a plurality of optical recording pulse trains having different numbers of pulses.
8) The number of pulses of a plurality of optical recording pulse trains having different number of pulses is any of n, n-1, n / 2, (n-1) / 2, and (n + 1) / 2 with respect to the mark length of nT. The optical recording medium according to 7), which is designed to be
9) The optical recording medium according to 7) or 8), which has information relating to the number of pulses of a plurality of optical recording pulse trains having different numbers of pulses.

Hereinafter, the present invention will be described in detail.
The optical recording medium that is the subject of the present invention is a medium capable of high-density recording with a minimum recording mark length of 0.7 μm or less. Such an optical recording medium can be produced in the same manner as a known DVD medium. For example, in DVD + RW, a dielectric layer, an optical recording layer, and a reflective layer are formed by sputtering on a 0.6 mm thick polycarbonate substrate having a track pitch of 0.74 μm, and the other thickness of 0.6 mm. It is obtained by pasting together polycarbonate substrates. HD-RW is obtained in the same manner as DVD + RW using a polycarbonate substrate having a thickness of 0.6 mm and a track pitch of 0.4 μm. In BD-RE, a reflective layer, a dielectric layer, and a recording layer are formed by sputtering on a 1.1 mm-thick polycarbonate substrate having a track pitch of 0.32 μm, and the thickness is further increased on the recording or reproducing light incident side. It is obtained by forming a 0.1 mm cover layer by spin coating.
There is no particular lower limit for the minimum recording mark length, and it varies depending on the wavelength of the laser beam used. However, when a 405 nm light source is used, the limit is about 0.15 μm.

  In the following description, DVD + RW 8 × recording will be described in detail, but the present invention can be applied to other high-speed and high-density optical recording media. In 8-times speed recording of DVD + RW, in the conventional recording method in which the recording pulse increases by one pulse as the mark length increases by 1T (1T method), the ratio of the pulse rise and fall times to the pulse emission time increases. An accurate mark length cannot be formed. Further, in the 1T method, the power required for recording increases, and the sensitivity of the optical recording medium needs to be improved. Therefore, a recording method (2T method, see FIG. 1) is proposed in which the recording pulse increases by one pulse as the mark length increases by 2T. However, the 2T method is advantageous for high-speed recording on an optical recording medium, but is inferior to the 1T method from the viewpoint of recording reliability. In particular, it is difficult to adapt to an unknown optical recording medium whose recording characteristics are not well understood.

Therefore, the present invention aims to realize more reliable and high-speed and high-density optical recording without writing failure. That is, the feature of the present invention is that a plurality of light emission pulse patterns (pulse strategy, optical recording) can be applied to various unknown optical recording media and a predetermined mark length can be recorded at a higher speed. The pulse train) is prepared in advance in the optical recording apparatus. The difference in the light emission pulse pattern at that time is the difference in the number of pulses of the optical recording pulse train.
For example, a plurality of pulse trains as shown in FIGS. 1 to 3 are prepared. Specific examples of the pulse train are described in US Pat. Nos. 5,761,179, 5,732,062, 6,628,595, 6,663,109, 6,459,666, 6,674,547, 6,757,232 and the like. The selection criterion is to select a pulse train that can be recorded stably on the optical recording medium to be recorded and that recording errors and reproduction errors are reduced. It is also possible to test-write with a plurality of prepared pulse trains, reproduce and evaluate the signal quality, and select a pulse train with a small error. Further, as a selection criterion item, not only reproduction error but also reflectance, modulation degree, jitter, and the like can be adopted.

As an example, it is effective to prepare the following two types of light emission patterns for recording a 7T mark length. One is a recording pattern of a pulse strategy by the 1T method as shown in FIG. In this pattern, the accuracy of the recording mark length is improved, but the speeding up is somewhat sacrificed. The other is a light emission pulse pattern (pulse strategy) composed of (n + 1) / 2 pulses for the recording mark length nT as shown in FIG. In this pattern, the speed is increased and the accuracy of the recording mark length is ensured. In this way, preparing a plurality of optical recording pulse trains having different numbers of emission pulses for an unknown optical recording medium in advance is effective in improving the reliability of the optical recording system, and more compatible reliability. The system can be high. .
When preparing a plurality of optical recording pulse trains having different numbers of pulses in advance, the smaller the number of pulses, the larger the effective power can be even with the same recording power, thereby improving the recording sensitivity. As a result, it is advantageous for high-speed recording that tends to cause insufficient recording sensitivity. Therefore, it is preferable to set it as the structure like this 4-5.

After reproducing the ID of the optical recording medium and recognizing the recording characteristics of the optical recording medium, it is effective to select a desired pulse train from a plurality of optical recording pulse trains prepared in advance by the optical recording device. is there. It is also effective to perform a test recording of a plurality of optical recording pulse trains prepared in advance and select from the results. An example of these methods is shown in FIG. 7 as a flow diagram.
First, the optical recording medium is set in the optical recording apparatus, and the ID or recording strategy information of the optical recording medium is reproduced. Next, it is determined whether or not it is possible to cope with a recording strategy prepared in advance in the optical recording apparatus. If it is determined that the correspondence is possible, an optimum recording strategy is selected. On the other hand, if it is not possible to determine whether or not it is possible to perform correspondence, a trial writing is performed with a recording strategy having a different number of pulses, and the trial recording is reproduced and evaluated to select an optimum recording strategy.
In addition, generally, the manufacturer, the manufacturing model, and the like are recorded in the ID of the optical recording medium as pit information, wobble information, optical recording information, and the like.
On the other hand, when the optical recording apparatus has prepared several optical recording methods with different numbers of light emission pulses, the optical recording medium is compatible with optical recording methods with different numbers of light emission pulses, which improves the reliability of optical recording. It becomes effective in improving. Furthermore, as shown in FIG. 4, the fact that the optical recording medium has information on the light emission pattern can provide a large amount of information to the optical recording apparatus, which is effective in improving the reliability of optical recording. Is. Various types of information formats such as information pits, recording marks, and wobble modulation can be used.

As an optical recording medium that can cope with optical recording methods having different numbers of light emission pulses, it is effective to use a microcrystalline Ag reflection film as a reflection layer. In order to cope with high-speed and high-density recording, Ag or an Ag alloy having a high thermal conductivity is effective in order to prevent heat generated by incident light of optical recording from escaping in the surface direction of the optical recording medium. Further, in order to generate heat and cool uniformly in the surface, it is effective to make Ag particles smaller so that Ag crystal grain boundaries do not affect. As a method for reducing the particle size of Ag, it is important to form a film in the presence of foreign matter so as to prevent Ag aggregation.
Specifically, in the process of forming the light reflecting film, the incidence can be reduced by controlling the incidence of Ag atoms or clusters on the film surface and the incidence of other atoms, molecules, ions or clusters. More specifically, it is effective to increase the flow rate of the coexisting gas (Ar, N ₂ , O _2, etc.) in the sputter film formation to increase the frequency of the coexisting gas incident on the film surface. It is also effective to increase the frequency of incidence of the coexisting gas on the film surface by decreasing the exhaust speed and increasing the film forming pressure. Further, as a method of reducing the incidence frequency of Ag on the film surface, it is effective to lower the film forming sputtering power in order to reduce the film forming speed. Furthermore, it is also effective to lower the substrate temperature when forming the Ag-based light reflecting film. During actual film formation, the size of Ag particles can be controlled by adjusting these conditions.

For effective Ag particle miniaturization, Mg, Al, Si, Ca, Ti, Cr, Cu, Zn, Y, Ce, Nd, Gd, Tb, Dy, Nb, Mo, Pd, In, Sn, Ta It is also effective to form a film in the presence of foreign matters such as W, P, and Pt. When Ag particles grow, a portion constituting the grain boundary contains a large amount of these additives. Therefore, the presence of these additives makes it possible to refine the Ag particles.
The selection and addition amount of these metal types are also affected by the sputtering conditions of the Ag-based light reflection film. If many additives are added, the Ag particles can be easily refined, but the high reflectivity and high thermal conductivity, which are physical properties expected of Ag, are impaired. When the amount of additives is reduced, the physical properties expected of Ag are ensured, but strict management is required for the film forming conditions.
The kind of additive depends on the film forming conditions of the Ag-based light reflecting film. If Cu, Pd, and Pt, which are easily alloyed with Ag, can be miniaturized while maintaining the physical properties of Ag. However, since it is easy to form an alloy with Ag, it is important to manage the film forming conditions to reduce the particle size. On the other hand, Mg, Al, Si, Ca, Ti, Cr, Zn, Nb, Mo, In, Sn, Ta, W, and the like greatly impair the physical properties of Ag when added in large amounts. It is easy to adsorb and works effectively in forming grain boundaries, suppresses coarsening of Ag crystal particles, and is effective in making Ag crystal particles finer. Further, additives such as Y, Ce, Nd, Gd, Tb, Dy, Zr, Hf, In, and Sn have an atomic radius larger than the atomic radius of Ag, which makes it possible to suppress the crystal growth of Ag particles. The crystal grain size can be reduced.

From the results of the study by the present inventors, the level at which the influence of the grain boundary noise of the Ag-based light reflection film on the recording / reproducing signal can be ignored is 1/3 or less the minimum recording mark. As a result of considering this point, it was found that 1/3 of the minimum recording mark in the experiment by the present inventors corresponds to the channel bit of the mark to be recorded. The channel bit is a minimum unit corresponding to information “0” and “1” in optical recording, and corresponds to 0.133 μm in the DVD-ROM. That is, in DVD-R, DVD-RW, DVD + R, and DVD + RW, it is effective that the average crystal grain length Lag of the light reflecting layer in the recording track direction is 1 bit length Lbi (= 0.133 μm) or less of the mark. It is.
The size of the crystal grains of the Ag-based light reflection layer is preferably less than or equal to the channel bit length, and preferably 2/3 or less of the channel bit length in consideration of variations in crystal grain size. In addition, when the guide groove existing in the optical recording medium is meandering, it is also important that the particle diameter is sufficiently smaller than the meandering (wobble) period.

The optical recording apparatus needs to accurately read the meander of the guide groove of the optical recording medium. However, when the optical recording apparatus reads the grain boundary of Ag particles as noise, the correct address of the optical recording medium cannot be read. In particular, optical recording media having guide grooves with pits such as DVD-R and DVD-RW are more difficult to read.
In the relationship between the crystal grain size of the Ag-based light reflecting film and the wobble of the guide groove, it is desirable that the Ag-based crystal grain size is 1/10 or less of one meander cycle. This is because even if 1/10 portion of noise is included in one meander, the meander information can be complemented. More desirably, the Ag-based crystal grain size is 1/20 or less of one meander cycle. This is because even if noise enters a 1/20 portion in one meander, the noise can be ignored for the meander information. In the case where pits are involved, the Ag crystal grain size is preferably 1/10 or less, more preferably 1/20 or less of the pit interval.

From the experiment results of the present inventor, it is known that the moisture adsorbed on the substrate surface has a considerable influence on the adhesion between the Ag-based light reflecting layer and the layer on which the Ag-based light reflecting layer is formed. It has also been found that an improvement in the passivation ability of the intermediate layer on which the layer is formed leads to an improvement in the adhesion between the Ag-based light reflecting film and the intermediate layer.
The present inventor, as an intermediate layer that ensures the adhesion with the Ag-based light reflection layer and simultaneously satisfies the passivation ability to prevent the reaction between Ag and ZnS · SiO ₂ described later,
(1) A substance capable of forming an interstitial compound in which the packing of atoms is dense in order to ensure the passivation ability. (2) A substance capable of ensuring the wettability of the Ag-based light reflection layer and the intermediate layer in order to ensure adhesion. It was considered effective to contain.
Therefore, from a target composed of Ti, Zr, Nb, Ta carbide targets capable of forming interstitial compounds to ensure passivation ability, and targets composed of those metal oxides to ensure wettability with Ag-based light reflection layers. The formed intermediate layer was examined.
The layer structure of the optical recording medium studied was information substrate with guide groove / lower protective layer / interface layer / optical recording layer / upper protective layer / intermediate layer / light reflecting layer / ultraviolet curable resin / adhesive layer / cover substrate.

An information substrate with a guide groove was prepared by injection molding a polycarbonate substrate having a thickness of 0.25 μm, a groove depth of 27 nm, and a guide groove having a wobble groove period of 4.26 μm and a thickness of 0.6 mm.
The lower protective layer, the interface layer, the optical recording layer, the upper protective layer, the intermediate layer, and the light reflecting layer were sequentially laminated by a sputtering method. The lower protective layer, the interface layer, and the upper protective layer were produced by RF sputtering, and the optical recording layer and the light reflecting layer were produced by DC sputtering.
The lower protective layer to a thickness of 55nm is _{(ZnS) 80 (SiO 2)} 20 ( mol%), SiO ₂ having a thickness of 4nm is the interface layer, the thickness of 11nm on the optical recording layer _Ge 8 _Ga 6 _Sb 68 Sn ₁₈ , (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%) having a thickness of 11 nm was used for the upper protective layer, and pure silver having a thickness of 140 nm was used for the light reflecting layer.
The intermediate layer had a thickness of 6 nm and was produced by DC or RF sputtering of a sintered target made of carbide and oxide. As the carbide, SiC, TiC, ZrC, NbC, and TaC were examined. As the oxide, SiO ₂ , TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , and Ta ₂ O ₅ were examined.
Next, an ultraviolet curable resin (SD318, manufactured by Dainippon Ink and Chemicals, Inc.) having a room temperature viscosity of 120 cps and a glass transition temperature after curing of 149 ° C. is spin-coated on the light reflecting layer to form a resin protective layer. A single disc of a changeable optical recording medium was prepared. The exposure amount was 80% of the required amount.
Subsequently, the laminated substrate made of polycarbonate is laminated with an ultraviolet curable adhesive (Nippon Kayaku Co., Ltd., DVD003) having a room temperature viscosity of 450 cps and a glass transition temperature after curing of 75 ° C., and a phase change optical recording medium. (Optical disk) was obtained. The exposure amount was 80% of the required amount.
Subsequently, using an initialization device manufactured by Hitachi Computer Equipment Co., Ltd. having a large aperture LD (beam diameter: 75 μm × 1 μm), the linear velocity is 70% of the maximum recording linear velocity of the optical disk, the power is 1600 mW, and the feed is 45 μm / r. The entire optical recording layer was crystallized from the periphery to the periphery at a constant linear velocity.

The manufacturing fluctuation durability of the optical disk was evaluated for the following (1) to (3).
(1) DC sputtering possibility (2) Air leak durability during intermediate layer deposition (3) Initialization durability The respective durability evaluation process conditions were the following (1) to (3).
(1) Whether or not film formation by DC sputtering is possible (2) Error after optical recording of optically recorded signal on optical disk with intermediate layer produced by 1E-4mbar air leak at 80 ° C 85% RH (PI error increase rate 50% increase) NG)
(3) Defect rate of optical disk initialized after accelerated deterioration at 80 ° C. and 85% RH for 24 hours (NG at 1E-4 or higher)
The recording characteristics of optical discs are as follows: (1) Groove reflectivity (%) at the recording power that minimizes jitter after recording
(2) Sensitivity (recording power, mW)
It was.

FIG. 5 shows an example of a DVD phase change optical recording medium of the present invention. On a meandering information grooved information substrate, a lower protective layer, a phase change optical recording layer, an upper protective layer, an Ag based reflective layer, A resin layer and / or an adhesive layer and a cover substrate are formed in this order. In order to improve performance, a first interface layer, a second interface layer, and an intermediate layer are formed as necessary. Further, a printed layer may be provided on the cover substrate. Alternatively, the same phase change optical recording medium may be provided in the reverse order on the cover substrate side to form a two-layer type.
FIG. 6 shows an example of the DVD-based double-layer dye-type optical recording medium of the present invention. A dye-type optical recording layer (L0), an Ag-based reflective layer, and a resin layer are formed on a meandering information substrate with guide grooves. The other meandering information substrate with a guide groove has a layer structure in which an Ag-based reflective layer and a dye-type optical recording layer (L1) are formed and bonded as an opposite layer. A printed layer may be provided on the cover substrate.
However, it goes without saying that the present invention is not limited to these layer configurations and is applied to various optical recording media.

The material of the substrate is usually glass, ceramics, or resin, and the resin substrate is preferable in terms of moldability and cost. Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, etc. Polycarbonate resins and acrylic resins that are excellent in terms of moldability, optical characteristics, and cost are preferred.
However, when the optical recording medium of the present invention is applied to DVD + R, it is desirable to give the following specific conditions. That is, the width of the guide groove formed on the substrate is 0.10 to 0.40 μm, preferably 0.15 to 0.35 μm, and the depth of the guide groove is 120 to 200 nm, preferably 140 to 180 nm. It is that you are. One period of the meandering period of the guide groove is 4.3 μm. The thickness of the substrate is preferably 0.55 to 0.65 mm, and the thickness of the disk after bonding is preferably 1.1 to 1.3 mm. These substrate grooves improve reproduction compatibility with a DVD-ROM drive.
In addition, when the optical recording medium of the present invention is applied to DVD + RW, it is desirable that the following specific conditions are given. That is, the width of the guide groove formed on the substrate is 0.10 to 0.40 μm, preferably 0.15 to 0.35 μm, and the depth of the guide groove is 15 to 45 nm, preferably 20 to 40 nm. It is that you are. One period of the meandering period of the guide groove is 4.3 μm. The thickness of the substrate is preferably 0.55 to 0.65 mm, and the thickness of the disk after bonding is preferably 1.1 to 1.3 mm. These substrate grooves improve reproduction compatibility with a DVD-ROM drive.

Examples of the material for the lower or upper protective layer of the phase change optical recording medium include oxides such as SiO, SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, and ZrO ₂ ; Si ₃ N ₄ , AlN, TiN, BN, ZrN and other nitrides; ZnS, TaS ₄ and other sulfides; SiC, TaC, B ₄ C, WC, TiC, ZrC and other carbides; Diamond-like carbon; or a mixture thereof Is mentioned. Among these, materials containing ZnS and SiO ₂ such as (ZnS) ₈₅ (SiO ₂ ) ₁₅ , (ZnS) ₈₀ (SiO ₂ ) ₂₀ , (ZnS) ₇₅ (SiO ₂ ) ₂₅ (both mol%) are preferable, Optical constant, thermal expansion coefficient, and elastic modulus are optimized for the lower protective layer located between the phase change optical recording layer and the substrate with thermal damage due to thermal expansion change and high temperature / room temperature change (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%) is desirable.
Since the film thickness of the lower protective layer greatly affects the reflectivity, the degree of modulation, and the recording sensitivity, it is desirable to set the film thickness so that the disk reflectivity becomes a minimum value with respect to the film thickness of the lower protective layer. In this film thickness region, the recording sensitivity is good, recording is possible with a power with less heat damage, and the overwriting performance is improved. In order to obtain good signal characteristics at the DVD recording / reproducing wavelength, when (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%) is used for the lower protective layer, the thickness is preferably 45 to 65 nm. If the thickness is less than 45 nm, thermal damage to the substrate increases and the groove shape is deformed. On the other hand, if it is thicker than 65 nm, the disk reflectivity increases and the sensitivity decreases.

Further, as the sulfur-free upper protective layer of the phase change optical recording medium, it is effective to suppress the occurrence of cracks, such as zinc oxide, indium oxide, tin oxide, niobium oxide, silicon nitride, aluminum nitride, ZnS, etc. A material having a sputtering rate suitable for manufacturing an optical recording medium is desirable. In the present invention, these suitable materials are used as the main component, and the main component referred to here means exceeding 50 mol%.
As materials used in the present invention, oxidation of Si, Al, Ti, Zn, Zr, Mo, Ta, Nb, and W capable of forming a network with oxygen having a high degree of freedom of divalent bond rotation in terms of film flexibility. The addition of products is preferred. However, even in these upper protective layer materials, when the film thickness is increased, cracks are likely to occur due to internal stress of the film itself and thermal stress between the optical recording layer and the Ag or Ag alloy reflecting layer.
Further, by increasing the number of upper protective layers, the interface of the upper protective layers is formed, and the heat conduction is hindered to form a heat storage structure, whereby the sensitivity of optical recording can be improved. Therefore, the thickness of the upper protective layer is preferably 4 to 24 nm. If the thickness is less than 4 nm, heat storage as a function of the upper protective layer cannot be sufficiently performed, and recording with an existing semiconductor laser becomes difficult. On the other hand, if the thickness exceeds 24 nm, cracks are generated as described above. A more desirable thickness of the upper protective layer is 8 to 20 nm.

In the phase change type optical recording medium, the lower protective layer / optical recording layer / upper protective layer / light reflecting layer are produced by continuous film formation by sputtering. In this case, the film formation time of the lower protective layer or the light reflection layer having a larger film thickness than that of the other layers requires the longest film formation time. Therefore, in order to efficiently produce the upper protective layer without loss, the upper protective layer is formed in a predetermined film with a film formation time that is equal to or shorter than the film formation time of the lower protective layer or the light reflecting layer. Film forming conditions that can form a thickness are desired. When ZnS · SiO ₂ is used for the lower protective layer, Ag or Ag alloy is used for the reflective layer, and the target sputtering time is 7 seconds or less, the film forming speed of the upper protective layer is at least 1 nm / s or more, preferably 3 nm / s or more. is necessary.
On the other hand, when trying to form a 4 to 24 nm thin film as much as possible, if the film forming speed is too high, the rate at which the rise time of plasma generation in sputtering film formation closes increases and the film thickness variation from disk to disk increases. As a disc characteristic, the sensitivity varies greatly. In order to reduce the film thickness variation of the upper protective layer for each disk, the critical film forming speed is 10 nm / s or less, preferably 8 nm / s or less.

Further, in order to ensure the initialization conditions in the manufacturing process of the phase change type optical recording medium, particularly the power margin, Ag-O is provided at the interface between the upper protective layer and the light reflecting layer mainly composed of Ag or Ag alloy. The formation of a bond was effective, and the Ag—O bond was confirmed by an analytical method such as XPS. Even when AlN or Si ₃ N ₄ was used for the upper protective layer, formation of an Ag—O bond was confirmed because oxygen was supplied from the degassed substrate or afterimage gas. However, the amount of Ag—O bonds is relatively small as compared with the case where an oxide is used for the upper protective layer, and the power margin during initialization tends to be small.

The phase change optical recording layer material is preferably a phase change material containing 60 to 90 atomic percent of Sb. Specific examples include InSb, GaSb, GeSb, GeSbSn, GaGeSb, GeSbTe, GaGeSbSn, AgInSbTe, GeInSbTe, and GeGaSbTe containing 60 to 90 atomic percent of Sb. From the relationship between the Sb composition ratio and the time required to record the minimum recording mark that enables DVD compatibility or CD compatibility when a DVD + RW medium is manufactured using these phase change materials, the Sb content of the recording layer is 60 atomic% or more. We know that the recording time can be shortened. That is, the melting time of the optical recording layer at the time of recording / erasing can be shortened, and the thermal damage of the optical recording layer and the upper protective layer can be reduced. Further, when the Sb amount is 60 atomic% or more, since the melt initial crystallization of the optical recording medium can be performed at high speed, thermal damage is reduced. Furthermore, when the Sb content is 70 atomic% or more, the initialization linear velocity can be 10 m / s or more, and thermal damage can be further reduced. However, if Sb exceeds 90 atomic%, even if various elements are added, the high temperature and high humidity reliability of the mark is inferior.
The thickness of the phase change optical recording layer is desirably 8 to 14 nm. If it is thinner than 8 nm, the crystallization of the recording mark at a high temperature and high humidity of 80 ° C. and 85% RH is accelerated, and the lifetime becomes a problem. On the other hand, if the thickness exceeds 14 nm, heat generation becomes large at the time of optical recording erasure, thermal damage to the upper protective layer becomes remarkable, and cracks in the upper protective layer are induced.

Plasma CVD, plasma treatment, ion plating, optical CVD, etc. can be used as a method for producing the lower protective layer, optical recording layer, upper protective layer, and light reflecting layer made of Ag or an Ag alloy of the phase change optical recording medium. However, sputtering widely used in the production of optical recording media is effective. The typical production conditions are a pressure of 10 ⁻² to 10 ⁻⁴ mbar, a sputtering power of 0.1 to 5.0 kW / 200 mmφ, and a film forming speed of 0.1 to 50 nm / s.
As the dye recording layer, conventionally known cyanine dyes, azo dyes, phthalocyanine dyes, squarylium dyes, and the like are used. In the case of a metal complex, it is effective to contain an element selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W as in the present invention as a matching with an Ag-based optical recording medium. It is effective.

As the resin protective layer, an ultraviolet curable resin produced by a spin coating method is suitable. A thickness of 3 to 15 μm is appropriate. If the thickness is less than 3 μm, an increase in error may be observed when a printed layer is provided on the overcoat layer. On the other hand, if it is thicker than 15 μm, the internal stress increases, which greatly affects the mechanical properties of the disk.
When providing a hard coat layer, an ultraviolet curable resin produced by a spin coat method is generally used. The thickness is suitably 2 to 6 μm. If it is thinner than 2 μm, sufficient scratch resistance cannot be obtained. If it is thicker than 6 μm, the internal stress increases, which greatly affects the mechanical properties of the disk. The hardness needs to be not less than the pencil hardness H that does not cause a large scratch even when rubbed with a cloth. It is also effective to mix a conductive material as necessary to prevent electrification by preventing electrification.
The printed layer is used for the purpose of ensuring scratch resistance, label printing such as a brand name, and forming an ink receiving layer for an inkjet printer, and it is preferable to form an ultraviolet curable resin by a screen printing method. The thickness is suitably 3 to 50 μm. If the thickness is less than 3 μm, unevenness occurs when forming the layer, and if the thickness is more than 50 μm, the internal stress increases, which greatly affects the mechanical properties of the disk.

  For the adhesive layer, an adhesive such as an ultraviolet curable resin, a hot melt adhesive, or a silicone resin can be used. These materials are applied on the overcoat layer or the printing layer by a method such as spin coating, roll coating, or screen printing according to the material, and subjected to treatment such as ultraviolet irradiation, heating, and pressurization, so that the opposite surface is coated. Affix with the disc. The disk on the opposite surface may be the same single plate disk or a transparent substrate alone, and the adhesive layer material may or may not be applied to the bonding surface of the opposite disk. Moreover, as an adhesive layer, an adhesive sheet can also be used. The thickness of the adhesive layer is not particularly limited, but it is 5 to 100 μm, preferably 7 to 80 μm, considering the effects of material applicability, curability, and disk mechanical properties. The range of the adhesive surface is not particularly limited, but when applied to a rewritable disc capable of DVD and / or CD compatibility, in order to ensure high-speed recording, it is necessary to ensure the adhesive strength. It is desirable that the position of the peripheral end is φ15 to 40 mm, preferably φ15 to 30 mm.

  According to the present invention, it is possible to provide an optical recording method, an optical recording apparatus, and an optical recording medium capable of realizing a more reliable and high-speed and high-density optical recording without writing loss.

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

Example 1
A 0.6 mm thick polycarbonate substrate having a guide groove with a groove width of 0.25 μm, a groove depth of 27 nm, and a wobble groove period of 4.26 μm is injection-molded and left at room temperature for 10 minutes. The interface layer, the phase change optical recording layer, the upper protective layer, the intermediate layer, and the light reflecting layer were sequentially laminated by the sputtering method. On the inner periphery of the substrate, as a recommended recording strategy, the number of pulses (n-1) / 2 and n / 2 are recorded by the wobble phase modulation method for nT mark length recording.
The lower protective layer is 55 nm thick (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%), the interface layer is 4 nm thick SiO ₂ , and the phase change optical recording layer is 11 nm thick Ge ₈ Ga _6. Sb ₆₈ Sn ₁₈ , (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%) having a thickness of 8 nm for the upper protective layer, Ti ₄₄ C ₂₆ O _{30 having} a thickness of 6 nm for the intermediate layer, and a thickness for the light reflecting layer A light reflecting layer of 140 nm Cu-0.5 wt% -purity 99.5 wt% Ag was used.
As a result, polycarbonate substrate / (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%): 55 nm / SiO ₂ : 4 nm / Ge ₈ Ga ₆ Sb ₆₈ Sn ₁₈ : 11 nm / (ZnS) ₈₀ (SiO ₂ ) ₂₀ (mol%) ): 8 nm / Ti ₄₄ C ₂₆ O ₃₀ : 4 nm / Cu—0.5 wt% —Purity 99.5 wt% Ag: 140 nm layer structure was formed.
At this time, the Ag—Cu reflective layer was produced by sputtering with Ar of 5% nitrogen, and the increase in Ag particle size was suppressed as much as possible.
Next, an ultraviolet curable resin (SD318, manufactured by Dainippon Ink and Chemicals, Inc.) having a room temperature viscosity of 120 cps and a glass transition temperature after curing of 149 ° C. is spin-coated on the light reflecting layer to form a resin protective layer. A single disc of a changeable optical recording medium was prepared.
Subsequently, the laminated substrate made of polycarbonate is laminated with an ultraviolet curable adhesive (Nippon Kayaku Co., Ltd., DVD003) having a room temperature viscosity of 450 cps and a glass transition temperature after curing of 75 ° C., and a phase change optical recording medium. And left at 80 ° C. and 85% RH for 24 hours.
Subsequently, using an initialization device manufactured by Hitachi Computer Equipment Co., Ltd. having a large aperture LD (beam diameter 75 μm × 1 μm), linear velocity 20 m / s, power 1600 mW, feed 45 μm / r, from the inner periphery to the outer periphery, The entire optical recording layer was crystallized at a constant linear velocity.
On the other hand, the optical recording apparatus of the present invention prepared in advance two types of optical recording pulse trains, a pulse train composed of (n-1) / 2 pulses and a pulse train composed of (n-1) pulses. This optical recording apparatus was adjusted to recognize the optical recording medium as unknown.
When the optical recording medium was set in the optical recording apparatus and the operation was confirmed with a recording power Pw of 20 mW and a bias power Pb of 0.1 mW, it was recognized as an unknown optical recording medium and the recording linear velocity was set to 14 m / s. It was lowered, and a more stable recording operation was performed with the number of pulses of (n−1), and recording without error could be executed. The minimum recording mark length was 0.4 μm.

Example 2
Information that the same optical recording medium and optical recording apparatus as in Example 1 are used, and that the pulse train suitable for recording is a pulse train composed of (n−1) / 2 and n / 2 pulses on the optical recording medium. Was held.
When the optical recording medium was set in the optical recording apparatus and the operation was confirmed with a recording power Pw of 35 mW and a bias power Pb of 0.1 mW, it was recognized as a known optical recording medium and the recording linear velocity was set to 28 m / s. , (N-1) / 2 pulses, more stable recording operation was performed, and high-speed recording without errors could be performed. The minimum recording mark length was 0.4 μm.

The figure which shows the pulse strategy of 2T method. (A) EFM signal, (b) optical recording pulse train, (c) recording mark. The figure which shows the pulse strategy of 1T method. (A) EFM signal, (b) optical recording pulse train, (c) recording mark. The figure which shows the pulse strategy comprised by the number of pulses of (n + 1) / 2 with respect to recording mark length nT. (A) EFM signal, (b) optical recording pulse train, (c) recording mark. The figure which shows the relationship between a high recording medium and an optical recording device. The figure which shows an example of the DVD type | system | group phase change type optical recording medium of this invention. The figure which shows an example of the DVD type | system | group double layer dye type | mold optical recording medium of this invention. The flowchart which shows an example of the optical recording method of this invention.

Explanation of symbols

T Basic clock period Pw Recording power Pe Erase power Pb Bottom power

Claims (9)

  A predetermined length using a pulse train having at least recording power Pw and bottom power Pb with respect to an optical recording medium having information on the optical recording linear velocity and capable of recording with a minimum recording mark length of 0.7 μm or less. An optical recording method comprising: preparing a plurality of optical recording pulse trains having different numbers of pulses in an optical recording device in advance and recording a desired pulse train from the plurality of optical recording pulse trains.   For an optical recording medium having information relating to the optical recording linear velocity and capable of recording with a minimum recording mark length of 0.7 μm or less, a recording mark is recorded using a pulse train having at least recording power Pw and bottom power Pb. When recording a mark having a length represented by nT in which the time length is n times the basic clock period T (n is a natural number), a plurality of optical recording pulse trains having different numbers of pulses are prepared in advance. An optical recording method, wherein a desired pulse train is selected therefrom.   The number of pulses of a plurality of optical recording pulse trains having different pulse numbers is n, n−1, n / 2, (n−1) / 2, or (n + 1) / 2 with respect to the mark length of nT, respectively. The optical recording method according to claim 2, wherein:   4. The optical recording method according to claim 1, wherein, among a plurality of optical recording pulse trains having different numbers of pulses, a pulse train having a smaller number of pulses has a higher corresponding recording linear velocity.   5. The optical recording method according to claim 1, wherein among a plurality of optical recording pulse trains having different numbers of pulses, a pulse train having a smaller number of pulses has a smaller corresponding recording power Pw.   An optical recording apparatus comprising a function capable of executing the optical recording method according to claim 1.   In an optical recording medium having information relating to the optical recording linear velocity and capable of recording with a minimum recording mark length of 0.7 μm or less, using a pulse train having at least recording power Pw and bottom power Pb, a predetermined length An optical recording medium is designed so that a desired pulse train can be selected and used from among a plurality of optical recording pulse trains having different numbers of pulses.   The number of pulses of a plurality of optical recording pulse trains having different pulse numbers is n, n−1, n / 2, (n−1) / 2, or (n + 1) / 2 with respect to the mark length of nT, respectively. 8. The optical recording medium according to claim 7, wherein the optical recording medium is designed to be in a certain manner. The optical recording medium according to claim 7 or 8, comprising information on the number of pulses of a plurality of optical recording pulse trains having different numbers of pulses.