KR20090030858A - Recording method of optical recording medium - Google Patents

Abstract

A recording method of an optical recording medium is provided to secure reproduction stability by performing post-curing for removing a mark formed in the reproduction layer. A recording method of an optical recording medium comprises a step of forming a mark on a recording layer and a step of performing post-curing for removing a mark formed on a reproduction layer(130) while forming the mark by irradiating laser beam with the power of 2.5~3.5mW on the reproduction layer. The recording layer includes a first recording layer(120a) including at least one of silicon(Si), germanium(Ge), tin(Sn), and carbon(C) as main component and a second recording layer(120b) having silver(Ag) as main component.

Description

Recording method of optical recording medium {RECORDING METHOD OF OPTICAL RECORDING MEDIUM}

The present invention relates to a recording method of an optical recording medium, and more particularly, to an optical recording medium capable of recording a mark or pit below a diffraction limit by including a reproducing layer for displaying a super resolution phenomenon. It relates to a recording method.

Currently developed optical discs include a digital versatile disc (DVD) using a red laser and a blue-ray disc (BD) using a blue laser. A DVD has a storage capacity of 4.7 GB and a BD has a storage capacity of 25 GB. Have

However, in order to store the signal flow of high-density digital video as information, an information storage medium capable of recording at a data transfer speed of more than 20GB and a data rate of 25Mbps or more is required. In addition, it is predicted that there will be a need for a technology capable of recording information of more than 100GB and later of terabyte capacity.

Various forms of multifunctional information storage technology have been developed in various multimedia environments. Among them, optical recording technology is the most popular among various information storage methods because of its detachable and large capacity information storage, random access and reliability of data essential in a multimedia environment, and low cost.

Increasing the capacity of the optical recording medium is possible by reducing the size of the marks or pits recorded on the medium. This requires reducing the incident laser beam size. Since the size of the laser beam is proportional to the laser wavelength and inversely proportional to the objective numerical aperture (NA), the capacity of the optical recording medium has been increased by reducing the wavelength or increasing the numerical aperture. Therefore, recording media capable of recording and reproducing using a short wavelength laser have been studied as high density storage media. However, the densification due to the use of short wavelength lasers (blue lasers (405 nm)) and high numerical apertures (NA = 0.85) has reached the theoretical limit and new technologies are needed to achieve higher storage capacities.

Therefore, research and development of optical discs using super-resolution phenomenon are newly progressed as an optical memory that is compatible with existing CD and DVD players and can store high-density information several hundred times higher than the initial CD storage capacity of 650MB. . The optical disc technology using super resolution is expected to increase the storage density by dramatically reducing the recording mark size while using the existing laser optical pickup system.

However, such super-resolution optical discs use high laser power to open the aperture of the reproduction layer during reproduction, which causes problems such as degradation of the reproduction layer, increased noise of the lens, and increased disc reproduction noise. In addition, recording marks are formed not only in the recording layer but also in the reproduction layer during recording of the super-resolution optical disc, which can affect the reproduction noise and reproduction stability.

Accordingly, an object of the present invention is to solve the above problems, and an object of the present invention is to provide a recording method of an optical recording medium capable of preventing degradation of a reproduction layer, reducing reproduction noise during reproduction, and ensuring reproduction stability. There is.

In order to achieve the above object, in the optical recording medium recording method according to the present invention, the optical recording medium recording method is a data recording method of an optical recording medium having a reproducing layer using a super-resolution phenomenon, the mark on the recording layer And post-curing for removing the marks formed in the regeneration layer in the step of forming the mark and forming the mark.

The post curing may be performed by irradiating the reproduction layer with a laser beam having a power of 2.5 mW to 3.5 mW.

The recording layer may include a first recording layer mainly composed of at least one of silicon (Si), germanium (Ge), tin (Sn), and carbon (C), and a second recording layer mainly composed of silver (Ag). have.

The second recording layer may contain at least one element of Ti, Sb, Te, Cu, Mg, Bi, Ge, Si, Sn and Co as an additive.

The second recording layer may contain up to 50 atomic percent of additives.

The first recording layer may contain at least one element of Cu, Zn, B, Bi, Mg, Mn, Fe, Ga, Zr and Te as an additive.

The first recording layer may contain 1 atomic% to 50 atomic% of the additive.

The recording method of the optical recording medium according to the present invention has the effect of preventing deterioration of the reproduction layer, removing recording marks formed during recording, reducing reproduction noise, and ensuring reproduction stability.

The terminology used in the present invention was selected as a general term that is widely used at present, but in some cases, the term is arbitrarily selected by the applicant, and in this case, the meaning of the term is described in detail in the description of the present invention. The present invention should be understood as meanings other than terms.

Hereinafter, the optical recording recording medium means any medium in which data is recorded or can be recorded using light, and specifically, an optical disk may be mentioned. In addition, below any meaning is meant to include a case where there is another part in the middle as well as the case immediately above the other part. In each embodiment, descriptions of overlapping components and the same reference numerals may be omitted.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

1 is a schematic cross-sectional view showing an example of an optical recording medium applicable to an optical recording medium recording method according to an embodiment of the present invention. The optical recording medium according to this embodiment is a write once (WORM) optical recording medium including a recording layer. As shown in FIG. 1, an optical recording medium according to an embodiment of the present invention includes a substrate 100, a reflective layer 110, a recording layer 120, a reproduction layer 130, and a light transmitting layer 140. . In addition, the optical recording medium according to the present embodiment further includes first to third dielectric layers 150, 160, and 170 for protecting the recording layer 120 and the reproduction layer 130.

The substrate 100 is formed in a disk shape of about 0.6 to 1.1 mm in order to secure the thickness of the optical recording medium. Grooves and lands are formed spirally on the surface of the substrate 100 to guide the laser at the center of the substrate and vice versa. The substrate 100 may be formed of various materials, such as glass, ceramic, and resin. In particular, the substrate 100 is light, has excellent injection property, and has a low carbon birefringence (Birefringence) upon laser incidence, thereby increasing the Carrier-to Noise Ratio (CNR). , PC). The substrate 100 is preferably manufactured using an injection molding method using a stamper. However, the substrate 100 can also be manufactured using other methods such as photopolymer method.

The reflective layer 110 reflects the laser beam incident from the light transmitting layer 140 and emits the light to the light transmitting layer 140 once again. The reflective layer 110 may be made of a material such as magnesium, aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, germanium, silver, platinum, or the like. It is preferable to use the metal material of aluminum, gold, silver, copper, or these alloys as having high reflectivity among these. By providing the reflective layer 110 in the optical recording medium, the reflectivity can be ensured to obtain a high reproduction signal (C / N ratio) after optical recording.

In addition to the above optical effects, the reflective layer 110 also absorbs heat generated from the recording layer 120. Therefore, since the shape of the mark generated in the recording layer 120 is maintained without being spread, the signal quality can be improved.

When the thickness of the reflective layer 110 is less than 5 nm, the above effects by the reflective layer 110 cannot be sufficiently obtained. In addition, when the thickness of the reflective layer 110 exceeds 300 nm, not only the surface property of the reflective layer 110 is lowered but also the deposition time is long and productivity is lowered. Therefore, the reflective layer 110 may have a thickness of 5 to 300 nm, and in particular, preferably has a thickness of 20 to 200 nm.

The recording layer 120 is a layer on which an irreversible recording mark is formed, and can record and reproduce due to a difference in reflectance between the mark formed by an appropriate recording power and the unirradiated portion.

Meanwhile, as shown, the recording layer 120 includes two layers of the first recording layer 120a and the second recording layer 120b. The laser irradiated portion having a predetermined power in the recording layer 120 formed of two layers forms a mark by partially or totally mixing two elements of each layer, and the mark and the laser irradiated portion thus formed The recording and reproducing is performed by the difference in reflectance between and.

The first recording layer 120a has one of Si, Ge, Sn, and C as its main component. In addition, the first recording layer 120a further contains at least one element of Cu, Zn, B, Bi, Mg, Mn, Fe, Ga, Zr, and Te as an additive to secure recording characteristics and reduce disk noise. It may include. In this case, the additives are not necessarily included, and may be contained in an amount of 50 atomic% or less with respect to the entire composition of the first recording layer 120a.

The second recording layer 120b has Ag as its main component. In addition, the second recording layer 120b may include, as an additive, a material having a relatively low heat transfer coefficient. Such additives can lower the recording power and easily control the shape of the mark to improve recording characteristics. In this case, at least one element of Ti, Sb, Te, Cu, Mg, Bi, Ge, Si, Sn, and Co may be used as an additive. In addition, such an additive may be contained in an amount of 1 atomic% or more and 50 atomic% or less with respect to the entire composition of the second recording layer 120b.

On the other hand, the thickness of the recording layer 120 is not particularly limited, but in order to sufficiently suppress the noise level of the reproduction signal, ensure sufficient recording sensitivity, and sufficiently increase the reflectance change before and after recording, each layer has a thickness of 1 to 30 nm. It is desirable to have a thickness.

Meanwhile, although the recording layer 120 is illustrated as being disposed between the substrate 100 and the reproduction layer 130 in FIG. 1, the present invention is not limited thereto. That is, the recording layer 120 may be disposed between the reproduction layer 130 and the light transmitting layer 140, unlike in FIG.

The regeneration layer 130 may be made of a material that enables super resolution. Non-linear optical materials, or thermochromic materials or phase change materials whose optical properties change depending on the temperature distribution may be used as the material that enables the super resolution phenomenon. In particular, the regeneration layer 130 may be formed of a GeSbTe series phase change material.

The thickness of the reproduction layer 130 is not particularly limited, but is preferably 3 to 200 nm in order to sufficiently generate an optical change rate while sufficiently generating a super resolution phenomenon.

The light transmitting layer 140 constitutes an incident surface of the laser beam, and is a layer that becomes an optical path of the laser beam at the same time. The light transmission layer 140 may have a thickness of 100um to 0.6mm. The light transmissive layer 140 may be made of a material having a sufficiently high light transmittance in the wavelength region of the laser beam. Acrylic or epoxy-based ultraviolet curable resin can be used as such a material. As the material of the light transmissive layer 140, a light transmissive sheet made of a light transmissive resin and various adhesives or adhesives may be used.

Meanwhile, the optical recording medium according to the present embodiment may further include first and second dielectric layers 150 and 160 protecting the reproduction layer 130. The first and second dielectric layers 150 and 160 physically and chemically protect the reproduction layer 130 interposed therebetween, and effectively prevent deterioration of recording information.

The first to third dielectric layers 150, 160, and 170 are not particularly limited as long as they are transparent dielectrics in the wavelength region of the laser beam used. For example, the dielectric layers 150, 160, and 170 may be formed of an oxide, an emulsion, a nitride, or a material having a combination thereof as a main component.

The dielectric layers 150, 160, 170 may be formed of Al ₂ O ₃ , AlN, ZnO, ZnS, GeN, GeCrN, CeO 2, SiO, It is preferable to use oxides such as SiO 2, Si 3 N 4, SiC, La ₂ O ₃ , TaO, TiO ₂ , silicon, cerium, titanium, zinc, tantalum, oxides, nitrides, and the like, or mixtures thereof.

In particular, it is more preferable to use a mixture of ZnS and SiO ₂ . In this case, the molar ratio of ZnS and SiO ₂ may be set to about 80:20. Meanwhile, the first dielectric layer 150, the second dielectric layer 160, and the third dielectric layer 170 may be made of the same material or may be made of different materials.

In addition, when the thickness of the dielectric layers 150, 160 and 170 is less than 3 nm, the above-described effects may be difficult to be obtained. If the thickness exceeds 200 nm, the deposition time may be long and productivity may be lowered. Cracks may occur depending on the stress of the 160 and 170. Therefore, the dielectric layers 150, 160 and 170 preferably have a thickness of 3 to 200 nm. However, the present invention is not limited thereto.

Meanwhile, the reflective layer 110, the reproduction layer 130, the recording layer 120, and the dielectric layers 150, 160, and 170 may be formed using a sputtering method or a vacuum deposition method. In particular, it is preferable to use sputtering method among these.

On the other hand, the optical recording medium according to the present embodiment may have a disk shape having an outer diameter of about 120 mm and a thickness of about 1.2 mm. Further, in the optical recording medium according to the present embodiment, a laser beam having a wavelength of 230 to 450 nm, preferably about 405 nm is irradiated to the recording layer 120 from the light incident surface which is the surface of the light transmitting layer 140. Is a write-once optical recording medium capable of recording and reproducing data.

In the reproduction of data on an optical recording medium, an objective lens having a numerical aperture of 0.7 or more, preferably about 0.85, can be used. As a result, the size of the beam spot of the laser beam on the recording layer is about 0.4 um.

Hereinafter, a data recording method of an optical recording medium according to an embodiment of the present invention will be described in detail.

The data recording method according to the embodiment of the present invention uses an optical recording medium having a reproduction layer using super resolution phenomenon. At this time, an optical recording medium having the above-described configuration can be used. However, the present invention is not limited to the above-described optical recording medium, and the data recording method described below can be applied to all optical recording media having a super-resolution playback layer.

2 is a schematic diagram showing the appearance of a recording layer during reproduction after data recording. First, a mark 210 is formed by irradiating a recording layer with a laser beam having a predetermined recording power. In particular, in the case where the recording layer includes two layers as described above, the mark 210 is formed while the two elements of each layer are partially or wholly mixed in the portion where the laser having a constant power is irradiated. In this case, the mark 210 formed on the recording layer may have a size less than or equal to the diffraction limit.

As shown in the drawing, a super resolution region 220 in which a temperature distribution change or an optical characteristic change occurs in a portion of the reproduction beam 200 irradiated to the reproduction layer is generated.

3 is a schematic diagram showing the appearance of the playback layer during playback after recording. As described above, in the embodiment of the present invention, the reproduction layer of the super-resolution optical recording medium may be made of a GeSbTe series phase change material. As shown in FIG. 3, since the phase change material is used as a recording layer in another optical recording medium, recording marks 230 are formed not only in the recording layer but also in the reproduction layer during recording, thereby affecting reproduction noise and reproduction stability. Can give

As shown in Fig. 3, the area where the beam passes through the reproduction layer during recording and reproduction can be divided into three areas. First, the first area through which the aperture 240 passes, and second, the second area where the opening 240 does not pass among the areas where the mark 230 is formed during recording, and third, the opening without the mark 230 being formed. Although 240 is not passed, the third region is passed by the reproduction beam 200.

The mark 230 formed in the reproduction layer at the time of recording has a great influence on the RF signal because it is read simultaneously with the mark of the recording layer at the time of reproduction. In addition, melting and cooling occur repeatedly at the boundary between the first region and the second region, the first region and the third region, and the boundary region may act as a starting point of deterioration due to the difference in sensitivity between crystalline and amorphous tropical regions. have.

Therefore, if post-curing is performed to erase the mark 230 formed on the reproduction layer and the image is uniform, the degree of deterioration is reduced by reducing the degree of freedom of phase change of the reproduction layer during reproduction. Only the marks recorded on the recording layer are reproduced, so that the reproduction quality is excellent.

On the other hand, in this case, when the laser power is less than 2.5 mW during post cure, the mark of the reproduction layer is not completely erased, so that the reproduction stability is not good. In addition, when the laser power exceeds 3.5 mW during post curing, recrystallization occurs in the regenerated layer so that a uniform phase is not formed. In addition, regeneration stability worsens again.

Therefore, post curing can be performed by irradiating the reproduction layer with a laser beam having a power of 2.5 mW to 3.5 mW. However, since the proper power of the laser during the post curing may vary depending on the material and structure of the optical disk, the present invention is not limited thereto.

Hereinafter, the present invention will be described in more detail through experimental examples. The following experimental examples are for illustrating the present invention, and the present invention is not limited thereto.

Experimental Example

After the optical recording medium having the structure shown in Fig. 1 was produced and the mark was recorded, the reproduction beam was irradiated. At this time, Si was used as the first recording layer, and a material containing Ag as the main component and GeSbTe was used as the second recording layer. At this time, the thickness of the first recording layer was laminated by 7 nm, the second recording layer was sputtered at the same time, and the thickness was laminated by 5 nm. As a regeneration layer, 7 nm of GeSbTe series phase change materials were stacked.

After 75nm and 50nm marks (2T-2T) were recorded continuously, postcure was performed according to the power using a dynamic tester. The power of the laser during post cure was 0mW, 2mW, 2.5mW, 3.0mW, 3.5mW, 4.0mW. The measurement was carried out under the condition that the laser wavelength of regeneration light was 405 nm, NA was 0.85, and linear velocity was 2.5 m / sec.

Comparative example

As a comparative example, an optical recording medium having the same structure as the above experimental example was produced, the marks were recorded under the same conditions, and the reproduction beam was irradiated. However, unlike the experimental example, postcure was not performed.

4 and 5 are graphs of reproduction spectrum analysis of the optical recording medium according to the comparative example and the experimental example, respectively. It can be seen from FIG. 4 and FIG. 5 that the noise level of Experimental Example is lower than that of Comparative Example.

6 shows the regeneration stability with power during post curing. When the power during post curing was less than 2.5 mW, the mark of the reproduction layer was completely erased, but the power was insufficient and the reproduction stability was not good. In addition, in 2.5mW <Pp≤3.5mW, a section in which CNR reduction did not occur according to the number of regenerations appeared. When the post curing power exceeds 3.5mW, it can be seen that the regeneration of the regenerated layer does not form a uniform phase, and thus the regeneration stability worsens again.

7A and 7B show RF and EQ images before and after post cure at 75 nm marks, respectively. FIGS. 8A and 8B show RF and EQ images before and after post cure at 50 nm marks, respectively. Indicates. In this case, postcure was performed at a power of 3.0 mW. The jitter is 12% in FIG. 7A and 9% in FIG. 7B. In addition, in FIG. 8B, the jitter is 15%. Since the marks recorded on the reproduction layer are erased and the images are uniform after the post curing, it is understood that the RF signal is clear, the jitter characteristics are improved, and the reproduction stability is also improved.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings, and the present invention is also provided. Naturally, it belongs to the range of.

1 is a schematic cross-sectional view of an optical recording medium according to an embodiment of the present invention.

2 is a schematic diagram showing the appearance of a recording layer after recording.

3 is a schematic diagram showing a state of a reproduction layer after recording.

4 is a spectrum analysis graph during reproduction of an optical recording medium according to a comparative example of the present invention.

5 is a graph of spectrum analysis during reproduction of an optical recording medium according to an experimental example of the present invention.

7 is a graph showing the reproduction stability according to the post curing power.

7A and 7B are graphs showing RF and EQ characteristics before and after post cure, after forming a mark of 75 nm, respectively.

8A and 8B are graphs showing RF and EQ characteristics before and after post cure after forming a mark of 50 nm, respectively.

Claims (7)

A data recording method of an optical recording medium having a reproduction layer using super resolution phenomenon, Forming a mark on the recording layer; And Performing post curing to remove the mark formed in the reclaimed layer in the forming of the mark. Method of recording an optical recording medium comprising a. According to claim 1, And the post curing step is performed by irradiating the reproduction layer with a laser beam having a power of 2.5 mW to 3.5 mW. According to claim 1, The recording layer includes a first recording layer composed mainly of at least one of silicon (Si), germanium (Ge), tin (Sn), and carbon (C) and a second recording layer composed mainly of silver (Ag). Recording method of optical recording medium. The method of claim 3, wherein And the second recording layer contains at least one element of Ti, Sb, Te, Cu, Mg, Bi, Ge, Si, Sn, and Co as an additive. According to claim 1, And the second recording layer contains the additive in an amount of 50 atomic% or less. According to claim 1, And the first recording layer contains at least one element of Cu, Zn, B, Bi, Mg, Mn, Fe, Ga, Zr, and Te as an additive. According to claim 1, And the first recording layer contains from 1 atomic% to 50 atomic% of the additive.

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