KR100747577B1 - High definition optical media - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super resolution optical recording medium, and in particular, to record and reproduce a mark below a diffraction limit. The present invention includes a substrate, and is located on the substrate. A recording layer made of a metal selected from among Ti, Zr, V, Cr, Fe, Co, Ni, Pd, Sb, Ta, Al, In, Cu, Sn, Te, Zn, and Bi, and shows a super resolution phenomenon An information recording layer comprising a reproduction layer made of a material, a first dielectric layer positioned between the recording layer and the reproduction layer, and a light transmitting layer positioned on the information recording layer, wherein the super resolution reproduction layer is included. It is possible to reproduce recording pits below the diffraction limit on the optical recording medium thus obtained, to sufficiently suppress the noise of the reproduction signal after recording, to ensure sufficient recording sensitivity, and to sufficiently increase the reflectance change before and after recording.

Medium, super resolution, recording layer, mark, sensitivity.

Description

Super resolution optical recording medium {High definition optical media}

1 is a schematic cross-sectional view showing an example of a conventional optical recording medium.

Fig. 2 is a schematic cross sectional view showing the first embodiment of the super-resolution optical recording medium of the present invention.

3 is a schematic cross-sectional view showing the second embodiment of the super-resolution optical recording medium of the present invention;

4 is a schematic cross-sectional view showing a third embodiment of a super-resolution optical recording medium of the present invention;

5 is a graph showing the CNR ratio to the recording power of the super-resolution optical recording medium of the present invention.

6 is a graph showing the CNR ratio to the reproduction optical power of the super-resolution optical recording medium of the present invention.

<Brief description of the main parts of the drawing>

10: substrate 20: reflective layer

30: information recording layer 31: recording layer

32: reproduction layer 33: the first dielectric layer

40: light transmitting layer 50: second dielectric layer

60: third dielectric layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super resolution optical recording medium. In particular, a recording layer made of a germanium (Ge) / metal film and a reproducing layer made of a material causing a super resolution phenomenon can be recorded and reproduced under a diffraction limit. To a super resolution optical recording medium.

The storage capacity of optical disks currently being developed and used is about DVD level (4.7GB) using a red laser and BD (Blue-lay Disk) level (25GB) using a blue laser recently entered the market.

However, in order to store the current high-density digital video signal flow as information, an information storage medium capable of recording at a data transfer rate of more than 20GB and a data rate of 25Mbps or more is required.

In addition, after 2005, it will require a technology capable of recording information of over 100GB / CD-size, and after 2010, Terabyte (TB) / CD-size.

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 data storage, random access and reliability of data essential in a multimedia environment, and low cost.

Such increase in capacity (density) of the optical recording medium is possible by reducing the size of the recording pit.

Since the size of the recording pit is proportional to the laser wavelength and inversely proportional to the numerical aperture (NA) of the objective lens (d ∝ λ / NA, where d is the laser beam size, λ is the wavelength and NA is the numerical aperture of the lens), To this end, the wavelength of the incident laser has been reduced or the numerical aperture of the objective lens has been increased.

Therefore, the recording medium which is recorded and reproduced using the short wavelength laser is the first step toward the high density storage medium.

However, the densification due to the use of short wavelength lasers (blue lasers (405 nm)) and high numerical apertures (NA = 0.85) has almost reached the theoretical limit, and new storage is needed to achieve higher storage capacities.

Therefore, research and development of optical discs using super-resolution is progressing as an optical memory that is compatible with existing CD and DVD players and can store high density information hundreds of times higher than the initial CD storage capacity of 650MB. .

The optical disk technology using the super resolution is a technology that can significantly increase the storage density by dramatically reducing the recording mark size while using a conventional laser optical pickup system.

Write once read many (WORM) super-resolution optical discs, which have been reported in the past, record nanobubble-type marks (e.g., platinum: Pt) and oxygen or nitrogen in the form of bubbles in the recording layer. Bubbles produced by separating nanoparticles at a specific temperature or more in a conjugate such as the above were used as marks.

It is also known to reproduce small marks by forming apertures of a small size below the diffraction limit using a material having nonlinear optical properties or thermal behavior.

FIG. 1 shows a general structure of a recording super resolution optical disc using PtO _x as the recording layer 4 and GeSbTe as the reproduction layer 5.

That is, the structure is a structure in which the reflective layer 2 is positioned on the substrate 1, and the recording layer 4 and the reproduction layer 5 are covered with the dielectric layer 3, and the light transmitting layer 6 is positioned on the upper side thereof. do.

A lot of researches have been made to use a super-resolution WORM disc using a bubble mark formed on a recording layer at a specific temperature or more by irradiating a laser to the optical disc manufactured as described above. This is a major obstacle to improving jitter.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is possible to reproduce recording pits below the diffraction limit in an optical recording medium including a super-resolution reproduction layer, to sufficiently suppress the noise of the reproduction signal after recording, It is an object of the present invention to provide a super resolution optical recording medium capable of securing sufficient recording sensitivity and sufficiently increasing the reflectance change before and after recording.

In order to achieve the object of the present invention as described above, the present invention is located on the substrate and the substrate, including Ge, Ag, Au, W, Mn, Pt, Ti, Zr, V, Cr, Fe, A recording layer made of a metal selected from Co, Ni, Pd, Sb, Ta, Al, In, Cu, Sn, Te, Zn and Bi, a reproduction layer made of a material exhibiting super-resolution phenomenon, and the recording layer This is achieved by including an information recording layer including a first dielectric layer located between the reproduction layers and a light transmitting layer located on the information recording layer.

Preferably, a second dielectric layer and a third dielectric layer are positioned above and below the information recording layer, and a reflective layer reflecting an incident recording beam is formed between the substrate and the information recording layer.

Ge, Ag, Au, W, Mn, Pt, Ti, Zr, V, Cr, Fe, Co, Ni, Pd, Sb, Ta, Al, In, Cu, Sn, Te, Zn and Bi of the recording layer The metal to be selected may form an alloy, or Ge and the metal may be separately stacked adjacent to each other, or Ge and the metal may be sequentially stacked alternately.

The regenerated layer may use any one of a nonlinear optical material, a thermochronic material, and a phase change material whose optical properties change depending on a temperature distribution.

The first dielectric layer is at least one of Al ₂ O ₃ , AlN, ZnO, ZnS, GeN, GeCrN, CeO ₂ , SiO, SiO ₂ , Si ₃ N ₄ , SiC, La ₂ O ₃ , TaO and TiO ₂ . Is formed.

With respect to the substrate, the positions of the reproduction layer and the recording layer can be different from each other. That is, the reproduction layer may be located above, or the recording layer may be located above.

In some cases, two or more reproduction layers may be provided so that the reproduction layers are positioned above and below the recording layer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in Figs. 2 and 3, the super-resolution optical recording medium of the present invention causes a reflection layer 20, a recording layer 31 made of germanium (Ge) and a metal, and a super resolution phenomenon on the substrate 10. And an information recording layer 30 composed of a reproduction layer 32, a first dielectric layer 33 positioned between the recording layer 31 and the reproduction layer 32, and a light transmitting layer 40.

A second dielectric layer 50 and a third dielectric layer 60 are formed between the reflective layer 20 and the information recording layer 30, and between the information recording layer 30 and the light transmitting layer 40, respectively.

The positions of the recording layer 31 and the reproduction layer 32 may be different from each other as shown in FIGS. 2 and 3.

The recording layer 31 used in the present invention may be formed of two or more layers by using a structure in which germanium (Ge) and a metal layer are sequentially stacked, and in the form of one layer by simultaneously stacking germanium and a metal. It can also be used.

Metals used in this case include Ag, Au, W, Mn, Pt, Ti, Zr, V, Cr, Fe, Co, Ni, Pd, Sb, Ta, Al, In, Cu, Sn, Te, Zn and Bi Can be selected from.

As described above, the super resolution optical recording medium according to the present invention is a material capable of super resolution in addition to the recording layer 31, that is, a non-linear optical material or a thermochromic material or a phase change material whose optical properties change depending on the temperature distribution. Is used as a regeneration layer 32 to enable regeneration.

2 and 3 generally use a disc shaped optical recording medium having an outer diameter of about 120 mm and a thickness of about 1.2 mm.

In the optical recording medium according to the present embodiment, the recording layer 31 is irradiated with a laser beam having a wavelength of 380 to 450 nm, preferably about 405 nm, from the light incident surface that is the surface of the light transmitting layer 40. Record and play back data.

Typically, such an optical recording medium may be an optical recording medium capable of recording once.

In recording and reproducing the data on the optical recording medium, an objective lens having a numerical aperture of 0.7 or more, preferably about 0.85, is used. As a result, the beam spot of the laser beam on the recording layer 31 is about 0.4 mu m. do.

The substrate 10 uses a disk-shaped substrate 10 of about 0.6 to 1.1 mm in order to secure the thickness of the optical recording medium, and grooves and lands for guiding the laser from the center to the outer periphery and vice versa are spirally formed on the surface thereof. Is formed.

The substrate 10 may be made of glass, ceramics, resins, or the like, but may be light, have good injection properties, and exhibit low signal-to-noise ratio (CNR: Carrier-to Noise) by using a characteristic of low birefringence at laser incidence. Polycarbonate (PC) is used to increase the ratio.

The substrate 10 is preferably manufactured by injection molding using a stamper, but other methods such as a photopolymer method may be used.

The reflective layer 20 reflects the laser beam incident from the light transmitting layer 40 and emits the light to the light transmitting layer 40 once again.

As the material of the reflective layer 20, magnesium, aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, germanium, silver, platinum, or the like may be used.

It is preferable to use metal materials, such as aluminum, gold, silver, copper, or these alloys, as having high reflectivity among these.

Although it is not essential to provide the reflective layer 20 in the present invention, securing the reflectivity facilitates obtaining a high reproduction signal (C / N ratio) due to multiple interference effects after optical recording.

It is preferable to set it as 5-300 nm as thickness of the said reflection layer 20, and it is preferable to set to 20-200 nm in some cases. When the thickness of the reflective layer 20 is less than 5 nm, the effect of the reflective layer 20 cannot be sufficiently obtained, whereas when the thickness of the reflective layer 20 is 300 nm or more, the surface property of the reflective layer 20 is lowered and the film formation time is long. This is because productivity is lowered.

On the other hand, the dielectric layers 33, 50, and 60 serve to physically and chemically protect the recording layer 31 and the reproduction layer 32 provided therebetween, and effectively prevent deterioration of recording information.

The material constituting the dielectric layers 33, 50, 60 is not particularly limited as long as it is a transparent dielectric in the wavelength region of the laser beam used. For example, an oxide, an emulsion, a nitride, or a combination thereof may be used as a main component.

From the viewpoint of the thermal deformation prevention and the protection characteristics of the recording layer 31, such as the normal substrate 10, Al ₂ O ₃ , AlN, ZnO, ZnS, GeN, GeCrN, CeO ₂ , SiO, SiO ₂ It is preferable to use oxides such as aluminum, silicon, cerium, titanium, zinc, tantalum, such as Si ₃ N ₄ , SiC, La ₂ O ₃ , TaO ₂ and TiO ₂ , emulsions, nitrides, and the like or mixtures thereof.

In particular, it is more preferable to use a mixture of ZnS and SiO _{2 in} the above materials, and in this case, the molar ratio of ZnS and SiO ₂ is preferably set at about 80:20.

The dielectric layers 33, 50, and 60 may be made of the same material or different materials. The thickness of the dielectric layers 33, 50, and 60 is not particularly limited, but is preferably set to 3 to 200 nm.

This may be difficult to obtain the above effects when the layer thickness is less than 3nm, and if the layer thickness is more than 200nm, there is a fear that the film forming time is long and productivity is lowered, and at the same time, depending on the stress of the dielectric layers 33, 50, and 60, This is because there is a risk of cracking.

The recording layer 31 is a layer on which an irreversible recording mark is formed, and as described above, is made of germanium (Ge) and a metal.

This means that the germanium (Ge) and the metal are partially or wholly mixed in the portion irradiated with a laser having a constant power to form a recording mark, and recording and reproduction can be performed by the difference in reflectance from the portion not irradiated.

The recording layer 31 may be formed of two or more layers by using a structure in which germanium (Ge) and a metal layer are sequentially stacked, and may be used in the form of one layer by simultaneously stacking germanium (Ge) and a metal. It may be.

Metals used in this case include Ag, Au, W, Mn, Pt, Ti, Zr, V, Cr, Fe, Co, Ni, Pd, Sb, Ta, Al, In, Cu, Sn, Te, Zn and Bi Among these, Ag, Au, W, Ti, Cr, Co, Al, Cu may be more suitable.

The thickness of each layer is not particularly limited, but is preferably 1 to 30 nm in order to sufficiently suppress the noise level of the reproduction signal, to ensure sufficient recording sensitivity, and to sufficiently increase the reflectance change before and after recording.

The regeneration layer 32 is made of a material that enables super resolution, and the material used is a nonlinear optical material or a thermochromic material or a phase change material whose optical properties change depending on the temperature distribution.

The reproduction layer 32 may be above or below the recording layer 31 when viewed in the order of being stacked on the substrate 10 as described above, and as shown in FIG. It may be configured on both sides of the layer 31.

As described above, when the recording layer 31 is configured on both sides, the dielectric layer 33 is added as much as the reproduction layer 32 is added.

Although the thickness of the said regeneration layer 32 is not specifically limited, It is preferable that it is 3-200 nm in order to fully generate an optical change rate, fully generating a super resolution phenomenon.

In addition, as a method of forming the reflective layer 20, the dielectric layers 33, 50, 60, the recording layer 31 and the reproduction layer 32, a phase growth method using a chemical species containing such a member element, for example, A sputtering method or a vacuum vapor deposition method can be used, and it is preferable to use a sputtering method among these.

The light transmitting layer 40 forms an incident surface of the laser beam and becomes a light path of the laser beam, and the thickness thereof is about 100 μm to 0.6 mm.

The material of the light transmitting layer 40 is not particularly limited as long as the material has a sufficiently high light transmittance in the wavelength range of the laser beam to be used, but acrylic or epoxy ultraviolet curable resin is preferably used.

Alternatively, a light-transmissive sheet made of a light-transmissive resin and various adhesives or pressure-sensitive adhesives may be used.

5 is a graph showing the CNR ratio of the reproduction signal to the recording power in the optical recording medium produced in the above embodiment.

As the recording layer used in this embodiment, germanium (Ge) and silver (Ag) alloys were used, and a GeSbTe series phase change material was used as the regeneration layer.

At this time, recording was recorded with a single pit of 75 nm, and the measurement was performed under conditions of a laser wavelength of 405 nm, a NA of 0.85, a linear velocity of 2.5 m / sec, and a power of regenerating light of 1.5 mW.

Although the reproduction limit of the optical system is 119 nm, the signal-to-noise ratio of about 40 dB is shown by using a structure representing the super resolution phenomenon.

6 is a graph showing the CNR ratio with respect to the power of the reproduction light in the optical system as described above. Records were likewise recorded with a single pit of 75 nm.

The above embodiment is an example for explaining the technical idea of the present invention in detail, and the present invention is not limited to the above embodiment, various modifications are possible, and various embodiments of the technical idea are all protected by the present invention. It belongs to the scope.

As described above, the present invention can reproduce recording pits below the diffraction limit on an optical recording medium including a super-resolution playback layer, sufficiently suppresses noise of a reproduction signal after recording, ensures sufficient recording sensitivity, and records There is an effect that the change of reflectance before and after can be sufficiently large.

Claims (17)

A substrate; Located on the substrate, including Ge, Ag, Au, W, Mn, Pt, Ti, Zr, V, Cr, Fe, Co, Ni, Pd, Sb, Ta, Al, In, Cu, Sn, Te And a recording layer comprising at least one metal selected from Zn and Bi, a reproducing layer containing a material exhibiting super resolution phenomenon, and an information recording layer including a first dielectric layer positioned between the recording layer and the reproducing layer; ; And a light transmitting layer on the information recording layer. The super resolution optical recording medium according to claim 1, further comprising a second dielectric layer and a third dielectric layer formed above and below the information recording layer. 2. The super resolution optical recording medium according to claim 1, wherein a reflective layer is formed between the substrate and the information recording layer to reflect an incident recording beam. The super resolution optical recording medium according to claim 1, wherein Ge and the metal of the recording layer are formed of an alloy. 2. The super resolution optical recording medium according to claim 1, wherein the recording layer is stacked adjacent to Ge and the metal. The super resolution optical recording medium according to claim 1, wherein the recording layer is formed by alternately stacking Ge and the metal. 2. The super resolution optical recording medium according to claim 1, wherein the recording layer has a thickness of 1 to 30 nm. The super-resolution optical recording medium according to claim 1, wherein the reproduction layer uses any one of a nonlinear optical material, a thermochronic material whose optical properties change depending on a temperature distribution, and a phase change material. The super resolution optical recording medium according to claim 1, wherein the reproduction layer is GeSbTe. The method of claim 1, wherein the first dielectric layer is Al ₂ O ₃ , AlN, ZnO, ZnS, GeN, GeCrN, CeO ₂ , SiO, SiO ₂ , Si ₃ N ₄ , SiC, La ₂ O ₃ , TaO and TiO ₂ A super-resolution optical recording medium, characterized in that formed by at least one of. The super resolution optical recording medium according to claim 1, wherein the first dielectric layer is made of a mixture of ZnS and SiO ₂ . 12. The super resolution optical recording medium according to claim 11, wherein the molar ratio of ZnS and SiO ₂ is 80:20. A substrate; A recording layer comprising Ge and a recording layer comprising at least one metal selected from Ag, Au, W, Ti, Cr, Co, Al and Cu, a reproduction layer made of a material exhibiting super resolution phenomenon; An information recording layer including a first dielectric layer positioned between the recording layer and the reproduction layer; A second dielectric layer and a third dielectric layer formed above and below the information recording layer, respectively; And a light transmitting layer on the information recording layer. The method of claim 13, wherein at least one of the first dielectric layer, the second dielectric layer, and the third dielectric layer is Al ₂ O ₃ , AlN, ZnO, ZnS, GeN, GeCrN, CeO ₂ , SiO, SiO ₂ , Si ₃ N _4. , SiC, La ₂ O ₃ , TaO and TiO ₂ At least one super-resolution optical recording medium, characterized in that formed from. A substrate; A second dielectric layer on the substrate; A recording layer on the second dielectric layer, the recording layer including Ge and at least one metal selected from Ag, Au, W, Ti, Cr, Co, Al, and Cu; A first dielectric layer on the recording layer; A regeneration layer on the first dielectric layer, the regeneration layer comprising a material exhibiting super resolution phenomenon; A third dielectric layer positioned on the reproduction layer; And a light transmitting layer on the third dielectric layer. A substrate; A second dielectric layer on the substrate; A regeneration layer on the second dielectric layer, the regeneration layer comprising a material exhibiting super resolution phenomenon; A first dielectric layer on the reproduction layer; A recording layer on the first dielectric layer, the recording layer including Ge and at least one metal selected from Ag, Au, W, Ti, Cr, Co, Al, and Cu; A third dielectric layer on the recording layer; And a light transmitting layer on the third dielectric layer. A substrate; A second dielectric layer on the substrate; A first regeneration layer on the second dielectric layer, the first regeneration layer comprising a material exhibiting super resolution phenomenon; A first dielectric layer on the reproduction layer; A recording layer on the first dielectric layer, the recording layer including Ge and at least one metal selected from Ag, Au, W, Ti, Cr, Co, Al, and Cu; A third dielectric layer on the recording layer; A second regeneration layer on the second dielectric layer, the second regeneration layer made of a material exhibiting super resolution phenomenon; A fourth dielectric layer positioned on the second reproduction layer; And a light transmitting layer on the fourth dielectric layer.

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