JP2006252712A - Optical information recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which records and reproduces high-density information, which exceeds the resolution limit of light, and increases a recording density by reducing a track pitch, and also to provide its manufacturing method. <P>SOLUTION: (1) The optical information recording medium has laminated composition comprising: a structure body, a first deformation material layer which absorbs light and generates heat to deform; and a second deforming material layer which transmits light and is deformed by heat. In the shape of the section of the recording medium in the vertical direction to recording tracks of unrecorded state, the end part of the structure body is vertical or reversely tapered, and the film thickness of the first deforming material layer decreases at the end part of the structure body. (2) In the shape of the section of the optical information recording medium in the parallel direction to the recording tracks, to which information has been recorded, the film thickness of the first deformation material layer changes according to recording information to make a recording mark center thicker than a recording mark end part, and the second deforming material layer is deformed according to a concave and convex corresponding to the recording information which both are formed on the first deformation material layer, and the first deformation material layer changes from a solid state to a melted state when the information is reproduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical recording medium for recording / reproducing information by light and a manufacturing method thereof. In particular, the present invention relates to a technique for recording information at a narrow track pitch and reproducing high-density recorded information exceeding the resolution limit of light. Here, the light resolution limit refers to the period of the recording mark in the recording track direction represented by λ / 2NA where λ is the wavelength of the light and NA is the numerical aperture of the objective lens.

In the recording type optical recording medium, a margin is provided in the track pitch in order to suppress cross write and cross erase. For example, in the case of an optical pickup in which the wavelength of the laser beam is 405 nm and the numerical aperture NA of the objective lens is 0.85, the track pitch is set to 320 nm or more. The track pitch refers to the period of the recording track in the radial direction of the disc-shaped medium.
Patent Documents 1 to 4 disclose medium structures for the purpose of suppressing cross light and cross erase. That is, Patent Documents 1 and 2 disclose a medium structure in which a recording material is embedded in a groove in order to prevent heat conduction between tracks. Patent Document 3 discloses a medium structure in which a recording material is processed by photolithography in order to prevent heat conduction between tracks. Patent Document 4 discloses a medium structure in which a protrusion is provided at an end of a land in order to prevent heat conduction between tracks.

Also, a medium super-resolution technique is known as a technique for reproducing a recording mark exceeding the optical resolution limit. In this technique, a super-resolution material layer is provided to reproduce a minute mark or minute pit.
A phase change material is often used for the super-resolution material layer. Patent Document 5 discloses a method of regenerating a phase pit that reaches the resolution limit by laminating a phase change material layer on the phase pit, liquidating a part of the phase change material layer in the reproduction laser beam spot. Has been. Patent Document 6 discloses a method of reproducing a recording mark by providing a mask layer made of a Ge—Te alloy, forming a reproduction window with increased light transmittance on the mask layer. Patent Document 7 discloses a method for reproducing a recording mark by providing an optical shutter layer mainly composed of three elements of Ge, Sb, and Te and partially melting the optical shutter layer in the reproduction laser beam spot. Yes. Patent Document 8 discloses a method of reproducing a recording mark by providing a mask layer made of Sb and irradiating a reproduction laser beam from the mask layer side to form an optical opening in the mask layer.
Patent Document 9 discloses a medium structure obtained by processing a conductor material of an optical recording medium into a line shape.
On the other hand, there are many known optical information recording media that perform recording and reproduction by forming a recording mark in a deformation mode as in the present invention. However, as in the present invention, high-density information exceeding the resolution limit of light can be obtained. As far as the present inventors know, there are no documents that devise recording forms or layer structures for the purpose of recording and reproduction.

JP 2000-276770 A Japanese Patent Laid-Open No. 2001-236589 JP 2001-266405 A Japanese Patent Application Laid-Open No. 2004-039106 Japanese Patent No. 3310791 Japanese Patent No. 3602589 JP-A-8-306073 JP 2000-229479 A JP 2003-228880 A

As described above, a medium for reducing the recording track pitch by suppressing cross light and cross erase is known. However, it is difficult to completely prevent cross-write and cross-erase in any medium structure, and the track pitch cannot be greatly reduced. In addition, because of the configuration that requires processing by photolithography, the process cost increases and it is difficult to reduce the cost of the medium.
A medium super-resolution technique is also known as a technique for reproducing a recording mark exceeding the optical resolution limit. However, as can be seen from the well-known literature using expressions such as a mask layer, a playback window, an optical shutter layer, and an optical aperture, the conventional super-resolution playback method uses the inside of the playback laser beam spot. The optical characteristics of the super-resolution material are changed in a part of the image, the effective laser beam spot diameter is reduced, and minute marks or minute pits are reproduced. As a method of changing the optical characteristics of the super-resolution material in a part of the reproduction laser beam spot, a phase-change material is used as the super-resolution material, and the phase-change material in a part of the reproduction laser beam spot is melted and optically changed. A method of forming an opening is used.

FIG. 1 shows an outline of the configuration of a conventional optical information recording medium.
FIG. 1A is a cross-sectional view of the optical information recording medium in a direction perpendicular to the recording track.
Reference numeral 101 denotes a support substrate, 102 denotes a recording material layer, 103 denotes a super-resolution material layer, 104 arrows denote recording tracks, and 105 denotes a track pitch. The surface of the support substrate 101 has gentle irregularities for tracking a laser beam spot. Each layer is laminated in an uneven state. When recording information, the recording layer 102 is heated by laser irradiation. A recording mark is formed in a portion where the temperature is higher than a certain temperature due to heat generation. Since heat spreads in the radial direction, the recording mark also spreads in the radial direction. In order to avoid the overlap (cross-write) of recording marks adjacent in the radial direction, the track pitch 105 is sufficiently widened.

FIG. 1B is a cross-sectional view in the direction parallel to the recording track. It corresponds to the XX cross section of FIG. 1A and shows a super-resolution reproduction state. Reference numeral 101 denotes a support substrate, 102 denotes a recording material layer, 103 denotes a super-resolution material layer, 106 denotes a recording mark, 107 denotes an optical aperture formed in the super-resolution material layer, 108 denotes a laser beam, and 109 arrow denotes a laser beam A spot diameter is indicated, and 110 indicates a moving direction of the laser beam. As shown in the figure, in the conventional super-resolution reproduction method, an optical aperture is formed in a part of the super-resolution material layer within the laser beam spot diameter to reproduce a minute mark. Therefore, the portion other than the optical aperture within the laser beam spot diameter is shielded from light by the super-resolution material layer. The recording layer 102 is located on the back side of the super-resolution material layer 103 when viewed from the laser beam 108.
In this structure, the laser beam spot is shielded by the super-resolution material layer, the amount of light reaching the recording layer 102 is reduced, and the signal intensity is reduced. However, as the recording density increases and the recording mark 106 becomes smaller, the optical aperture 107 must be made smaller accordingly. As a result, a considerable portion of the laser beam spot diameter is shielded from light by the super-resolution material, and the signal intensity is further reduced and cannot be detected.

The present invention has been made to solve such a problem of conventional super-resolution reproduction, and exceeds the resolution limit of light regardless of the method of forming an optical aperture in the super-resolution material layer. An object of the present invention is to provide an optical recording medium capable of recording and reproducing high-density information and increasing the recording density by reducing the track pitch, and a method for manufacturing the same.
In a recording-type optical recording medium, light irradiated during recording is absorbed on the medium surface and converted to heat. A portion where the temperature is raised above a predetermined temperature becomes a recording mark. Therefore, it is necessary to limit the spread of heat in order to suppress cross light. It is an object of the present invention to limit the spread of heat with a simple structure to reliably suppress cross light, and to greatly reduce the track pitch compared to a conventional medium.

The above problems are solved by the following inventions 1) to 8) (hereinafter referred to as the present inventions 1 to 8).
1) At least a structure, a first deformable material layer that absorbs light and generates heat and deforms, and a second deformable material layer that transmits light and deforms by heat, and in a non-recorded state, The cross-sectional shape perpendicular to the recording track is characterized in that the end of the structure is perpendicular or inversely tapered, and the thickness of the first deformable material layer is reduced at the end of the structure. Optical information recording medium.
2) After recording information, the cross-sectional shape in the direction parallel to the recording track is such that the thickness of the first deformable material layer changes according to the recording information, and the center of the recording mark is thicker than the end of the recording mark, The second deformable material layer is deformed according to the unevenness corresponding to the recording information formed in the first deformable material layer, and the first deformable material layer changes from a solid phase state to a molten state at the time of reproducing information. 1) The optical information recording medium according to 1). (Here, the recording mark refers to a deformed portion of the first deformable material layer and the second deformable material layer.)
3) The optical information recording medium according to 1) or 2), wherein the first deformable material layer contains at least antimony (Sb) and tellurium (Te).
4) The optical information according to any one of 1) to 3), wherein the second deformable material layer contains at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2 or less). recoding media.
5) On a support substrate, it has a laminated structure of a heat generating material layer that absorbs light and generates heat and a structure, and the structure has at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2 or less) 1) The optical information recording medium according to any one of 1) to 4).
6) The optical information recording medium according to 5), wherein in the cross-sectional shape perpendicular to the recording track, there are irregularities on the surface of the support substrate, and the structures are present on the concave portions and the convex portions.
7) Any one of 1) to 6), wherein the structure has a linear shape continuous in the recording track direction, and the line width is in a range of 0.7 to 0.95 times the recording track pitch. An optical information recording medium described in 1.
8) A step of irradiating a support substrate, a heat generating material layer, and a medium having at least a laminated structure composed of a thin film containing at least zinc sulfide (ZnS) and silicon oxide (SiOx, where x is 2 or less) with laser light. The light according to 5) or 6), comprising: a step of etching the medium with an aqueous solution containing hydrofluoric acid (HF); and a step of forming a first deformable material layer and a second deformable material layer. A method for manufacturing an information recording medium.

The present inventors have previously filed an application relating to an optical information recording medium capable of recording / reproducing high-density information exceeding the resolution limit of light (Japanese Patent Application No. 2005-44664). The present invention is characterized in that a structure is further added to the prior invention. As a result, it is possible to restrict the spread of heat with a simple configuration and to reliably suppress cross light, and to significantly reduce the track pitch as compared with a conventional medium.
The optical information recording medium of the first aspect of the present invention has a laminated structure of at least a structure, a first deformable material layer that absorbs light and generates heat and deforms, and a second deformable material layer that transmits light and deforms by heat. Have. In the unrecorded state, the cross-sectional shape in the direction perpendicular to the recording track is such that the end of the structure is vertical or inversely tapered, and the thickness of the first deformable material layer is reduced at the end of the structure. It has become. The second deformable material layer is laminated following the structure and the first deformable material layer, and usually has a semicircular shape.
The present invention 2 defines the state after information is recorded in the optical information recording medium of the present invention 1, and the cross-sectional shape in the direction parallel to the recording track is the first in accordance with the recorded information. The thickness of the deformable material layer changes, the center of the recording mark becomes thicker than the end of the record mark, and the second deformable material layer deforms according to the unevenness corresponding to the recording information formed in the first deformable material layer. ing. Here, the recording mark refers to a deformed portion of the first deformable material layer and the second deformable material layer.

The present invention 3 defines a preferable material for the first deformable material layer. That is, a material containing at least antimony (Sb) and tellurium (Te) and having a composition ratio of Sb and Te (Sb / Te ratio) in the range of 1.5 to 4 is used. Tellurium (Te) may be in the state of tellurium oxide (TeOx). As a result, the signal quality of the reproduction signal can be improved.
The present invention 4 defines a preferable material for the second deformable material layer. That is, a material containing at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2 or less) is used. As a result, information can be recorded and reproduced with low light intensity.

In the fifth aspect of the present invention, a heat generating material layer that absorbs light to generate heat and a structure are stacked on a supporting substrate, and at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2) The following): This makes it possible to form a medium with a simple manufacturing process.
In the sixth aspect of the present invention, in addition to the requirements of the fifth aspect of the present invention, in the cross-sectional shape in the direction perpendicular to the recording track, the support substrate surface is uneven, and the structure is provided on the concave portion and the convex portion. As a result, the medium can be formed by a simple manufacturing process, and the tracking of the laser beam spot in recording and reproduction can be stabilized.
In the present invention 7, a structure having a continuous line shape in the recording track direction and having a line width in the range of 0.7 to 0.95 times the recording track pitch is used. Thereby, the strength of the reproduction signal can be increased.
The present invention 8 is the method for producing the optical information recording medium of the present invention 5-6, and by this, the optical information recording medium of the present invention 5-6 can be produced by a simple process.

Next, embodiments of the present invention 1 to 4 will be described.
An example of the optical information recording medium of the present invention is shown in FIG. FIG. 2 is a cross-sectional view perpendicular to the recording track in an unrecorded state. Reference numeral 201 denotes a support substrate, 202 denotes a structure, 203 denotes a first deformable material layer, and 204 denotes a second deformable material layer.
For the support substrate 201, glass, quartz, or the like can be used. Also, substrates for semiconductor manufacturing such as Si and SOI (silicon on insulator), HDD (hard disk) substrates such as Al and opaque glass substrates, and resin substrates such as polycarbonate, acrylic, polyolefin, epoxy, vinyl ester and pet Can be used.
The structure 202 has a feature in its shape. In the cross-sectional shape in the direction perpendicular to the recording track, the end of the structure has a vertical or reverse taper shape. As a material, an organic material such as a thermoplastic resin or a photo-curable resin, or an inorganic material such as ZnS / SiO ₂ can be used, but any material can be used as long as the end of the structure can be formed into a vertical or reverse tapered shape. You may use.
The first deformable material layer 203 uses a material that absorbs light at the wavelength of light for recording information and generates heat, and melts and deforms by generating heat. As a material, a low melting point metal such as Bi, In, Sn, or Sb can be used. Alternatively, an intermetallic compound material containing a low melting point metal such as BiTe, BiIn, GaSb, InP, InSb, InTe, or SbSn can be used.

A material that contains at least antimony (Sb) and tellurium (Te) is preferable as the first deformable material layer. A binary material of SbTe can be used, and elements other than Sb and Te may be included. A ternary material such as GeSbTe or a quaternary material such as AgInSbTe can also be used. More preferred is a material having a composition ratio of Sb and Te (Sb / Te ratio) in the range of 1.5 to 4. SbTe compounds in this range belong to a crystal system called δ phase. The SbTe-based compound having a δ phase composition enters a molten state without causing phase separation or phase transition when the temperature is increased. In the optical information recording medium of the present invention, the reproduction signal is detected by utilizing the change between the solid state and the molten state of the first deformable material layer. If phase separation or phase transition occurs in the process of change between the solid state and the molten state, a plurality of signal levels are generated, the signal quality is lowered, and it is difficult to determine the signal level. On the other hand, a high-quality reproduction signal can be obtained by simply using the material that changes only between the solid phase state and the molten state.
The thickness of the first deformable material layer is reduced at the end of the structure. The structure has a vertical or reverse tapered end. In the first deformable material layer laminated on the structure, the covering performance (step coverage) is lowered in the vertical or reverse tapered portion. Utilizing this reduction in step coverage, the film thickness of the first deformable material layer is reduced at the end of the structure.

  For the second deformable material layer 204, a material having a high light transmittance at the wavelength of light for recording information is used. When the second deformable material layer is a material having high light transmittance, light is absorbed by the first deformable material layer located in the lower layer. As a result, the shape change of the second deformable material layer can be made to reflect the deformation of the first deformable material layer. The second deformable material layer is preferably a material that has a low density and / or softness in a film formation state and becomes dense and / or hardened by heating. By using such a material as the second deformable material layer, it is possible to record that the first deformable material layer is changed in shape by light heating and the shape of the second deformable material layer is changed in accordance with the shape. It becomes. The melting point of the second deformable material layer is preferably higher than the melting point of the first deformable material layer. Furthermore, it is desirable that the difference between the melting points of both layers is large. It is desirable to use a material having a melting point of 1000 ° C. or higher for the second deformable material layer, and use a material having a melting point of about 100 to 700 ° C. for the first deformable material layer. By providing such a melting point difference, mutual diffusion of materials in the recording / reproducing process can be suppressed, and deterioration of signal quality can be prevented.

Examples of the second deformable material include silicon compound materials such as SiO ₂ , SiON, and SiN, sulfide materials such as ZnS, CaS, and BaS, selenide materials such as ZnSe and BaSe, and fluorine compounds such as CaF ₂ and BaF ₂ . Examples thereof include oxide materials such as ZnO.
As a film forming method of these materials, a sputtering method is preferable. In particular, a sputtering method at room temperature is preferable as a film forming method for forming a low-density material.
Further, pigment materials such as cyanine pigments and phthalocyanine pigments, and resin materials such as polycarbonate, acrylic, polyolefin, epoxy, and vinyl ester can also be used. In the case of organic materials, the film is formed by spin coating.

Preferred as the second deformable material is a material containing at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2 or less). ZnS and SiOx may exist in an independent state, or may exist in a state where elements constituting ZnS and SiOx are combined. Further, materials other than ZnS and SiOx may be included. For example, zinc oxide (ZnO) which is a compound of elements constituting ZnS and SiOx, ZnO _x S _1-x in which zinc oxide is sulfided, and zinc nitride (Zn ₃ N ₂ ) which is a compound with an atmospheric gas In addition, a compound of Sb and Zn (ZnSb) included in the light absorbing material may be included.
As a film forming method, a sputtering method is preferable. In particular, a sputtering method at room temperature is preferable as a film forming method for forming a low-density material. For the sputtering target, a mixture material of ZnS and SiO ₂ is used. A material having a ratio of ZnS to SiO ₂ (ZnS / SiO ₂ ) in the range of 1 to 20, that is, a material in the range of ZnS: SiO ₂ = 50: 50 to 95: 5 (mol%) is used.
A material containing ZnS and SiOx has a high transmittance in a wide wavelength range. By containing SiOx, it becomes very soft and low density in the film formation state. It is easily deformed by recording and hardened by heating. Further, since the thermal conductivity is very small, the light intensity required for recording / reproduction can be reduced by using this material as the second deformable material layer. Furthermore, since this material has a low density in the film formation state, the residual stress of the film is small and can be formed even on a large area substrate.

FIG. 3 is a cross-sectional view in the direction along the recording track of the medium after recording the information defined in the second aspect of the present invention.
Reference numeral 301 denotes a structure, 302 denotes a first deformable material layer, and 303 denotes a second deformable material layer. Reference numeral 304 denotes a recording mark cycle, and the figure shows a state in which a recording mark having the shortest cycle is repeatedly recorded. Reference numeral 305 denotes a recording mark center, and 306 denotes an end of the recording mark. Here, the recording mark indicates a deformed portion of the first deformable material layer and the second deformable material layer. 307 is the thickness of the first deformable material layer 302 at the center of the recording mark, 308 is the thickness of the first deformable material layer 302 at the end of the recording mark, 309 is the thickness of the second deformable material layer 303 at the center of the recording mark, 310 Indicates the film thickness of the second deformable material layer 303 at the end of the recording mark. The form of recording is deformation, and the film thickness of the first deformable material layer changes. The film thickness of the first deformable material layer is thick at the center of the recording mark and thin at the end of the recording mark. In the first deformable material layer, the center of the recording mark is deformed into a convex shape, and the end portion of the recording mark is concave. The difference between the film thickness of the first deformable material layer at the center of the recording mark and the film thickness of the first deformable material layer at the end of the record mark is about 5 to 50 nm. The second deformable material layer is deformed in a state following the unevenness formed in the first deformable material layer. In other words, the second deformable material layer is in a state like a shell covering the unevenness formed in the first deformable material layer. The structure may be deformed, but it is preferable that the structure is not deformed. Since the structure does not deform, a convex lens shape can be formed. When the deformed shape becomes a lens shape, light is condensed by the second deformable material layer, and a medium shape suitable for reproducing high-density information can be obtained.

FIG. 4 is a cross-sectional view of the medium after recording information in a direction perpendicular to the recording track. 4 is a cross section of a recording mark center 305 shown in FIG. 3.
Reference numeral 401 denotes a structure, 402 denotes a first deformable material layer, and 403 denotes a second deformable material layer. Reference numeral 404 denotes a track pitch, 405 denotes a recording track, and 406 and 407 denote unrecorded tracks. The difference between the recording mark portion of the recording track and the unrecorded track is the film thickness of the first deformable material layer. In the recording mark portion, the film thickness of the first deformable material layer is large. The second deformable material layer is deformed following the convex first deformable material layer.

The reproduction method will be described with reference to FIGS. When reproducing recorded information, the first deformable material layer is melted and light is irradiated with an intensity that does not deform the second deformable material layer.
FIG. 5A shows a recording state. It is sectional drawing of the direction along a recording track, and has expanded and showed one recording mark. Reference numeral 501 denotes a structure, 502 denotes a first deformable material layer, 503 denotes a second deformable material layer, and 504 denotes an end of a recording mark. The heat conduction in the thin film is greatly influenced by the film thickness. The thermal conductivity changes in proportion to the film thickness. The film thickness of the first deformable material layer is decreased at the end of the recording mark. The first deformable material is a material that absorbs light and generates heat. Since the film thickness is reduced at the end of the recording mark, the heat of the first deformable material layer is not easily conducted to the recording mark adjacent in the recording track direction. That is, heat is likely to be localized for each recording mark.

FIG. 5B shows the playback state. Reference numeral 513 denotes a first deformable material layer in a molten state, 505 denotes a second deformable material layer, 506 denotes a laser beam, and 507 denotes a moving direction of the laser beam. When reproducing recorded information, the first deformable material layer is melted and light is irradiated with an intensity that does not deform the second deformable material layer. The second deformable material layer is deformed at the recording stage, and is in a state of being densified and / or hardened following the deformation of the first deformable material layer. The shape of the second deformable material layer is maintained during the regeneration process. The second deformable material layer is in a state like a shell, and the first deformable material layer melts inside the shell. Following the shell-shaped second deformable material layer, the first deformable material layer melts and solidifies. Therefore, even when melted in the regeneration process, the shape of the first deformable material layer does not collapse and can be repeatedly regenerated.
FIG. 5C is a top view of the state of the recording mark. Reference numeral 508 denotes a laser beam spot diameter, 509 denotes a moving direction of the laser beam, 510 denotes a structure, and 511 and 512 denote recording marks. A recording mark 511 at the center of the laser beam spot is in a molten state. Reference numeral 512 denotes a recording mark located in front, which is in a solid phase state. As shown in FIG. 5A, since the film thickness of the first deformable material layer is reduced at the end portion of the recording mark, heat is likely to be localized for each recording mark. Therefore, even if the recording mark at the center of the laser beam spot is in a molten state, the recording mark adjacent to the front is in a solid state. During reproduction, in the recording mark portion, the first deformable material layer is melted in order for each recording mark.

FIG. 6 shows changes in the reproduction signal level. In the drawings, (a), (c), and (e) are top views of the medium, showing the structure, the first deformable material layer, and the recording marks. In the figure, (b), (d), and (f) show changes in the reproduction signal level corresponding to the top view of the medium.
FIG. 6A shows a state where an unrecorded portion is reproduced with low power, and FIG. 6B shows a reproduction signal level at that time. 601 is a laser beam spot diameter, 602 is a moving direction of the laser beam spot, 603 is a structure, 604 is a first deformation material layer laminated on the structure, 605 is a recording track positioned at the center of the laser beam spot, Reference numeral 606 denotes a track adjacent in the radial direction, and reference numeral 607 denotes a time change of the signal level. The signal level indicates a certain level.
FIG. 6C shows a state where an unrecorded portion is reproduced with high power, and FIG. 6D shows a reproduction signal level at that time. Reference numerals 601 to 606 are the same as those in FIG. The first deformable material layer is melted by increasing the reproduction power. Reference numeral 608 denotes a melted portion of the first deformable material layer. The first deformable material layer reaches a high temperature with a slight delay with respect to the moving direction of the laser beam spot. Therefore, a part of the melted portion is in a state of being applied to the laser beam spot. In addition, by providing the structure, heat is localized on the structure. Therefore, the first deformable material layer on the adjacent track does not become high temperature and does not melt. Reference numeral 609 denotes a time change of the signal level. The signal level becomes a constant level. Since a part of the melted portion of the first deformable material layer is included in the laser beam spot, the signal level is slightly lower than the signal level during low power reproduction.

  FIG. 6E shows a state in which the recorded portion is reproduced with high power, and FIG. 6F shows the reproduction signal level at that time. Reference numerals 601 to 606 are the same as those in FIG. Reference numerals 610, 611, and 612 denote recording marks, 610 denotes a recording mark in a molten state, and 611 and 612 denote recording marks in a solid phase. Heat is easily localized for each recording mark. Therefore, even if the recording mark at the center of the laser beam spot is in a molten state, the recording mark adjacent to the front is in a solid state. In the recording track direction, the melting of the first deformable material layer occurs sequentially for each recording mark. Further, by providing the structure, heat is localized on the structure. Therefore, the recording mark on the adjacent track is not in a high temperature but is in a solid state. Reference numeral 613 denotes a signal level when the laser beam spot is at the center of the recording mark, and 614 denotes a signal level when the laser beam spot is between the recording marks. As shown at 613, the signal level is lowered by melting of the recording mark. As shown at 614, when the laser beam spot moves between the recording marks, the signal level increases because the front recording mark is in the solid phase. This is because the ratio of the melted portion included in the laser beam spot changes. Since the recording mark is melted in order for each recording mark, the ratio of the melted portion included in the laser beam spot varies depending on the relative position of the laser beam spot and the recording mark. As a result, a periodic signal corresponding to the recording mark period that changes between the high signal level 615 and the low signal level 616 can be detected. The recording mark on the adjacent track is not in a high temperature but is in a solid state. Therefore, a signal change due to melting on the adjacent track is not included in the reproduction signal. That is, no crosstalk occurs.

  As described above, in the recording / reproducing method of the information recording medium, heat is localized for each recording mark by irradiating light with an intensity at which the first deformable material layer melts and the second deformable material layer deforms. An easy recording form can be formed. When reproducing recorded information, the first deformable material layer is melted and light is irradiated with an intensity that does not deform the second deformable material layer. As a result, the recording information at the resolution limit can be detected by the signal level change accompanying the melting of the first deformable material layer that occurs sequentially for each recording mark.

Next, an embodiment of the present invention 5 will be described.
FIG. 7 is a cross-sectional view of an example of the optical information recording medium of the fifth aspect, perpendicular to the recording track, before information is recorded. Reference numeral 701 denotes a support substrate, 702 denotes a low thermal conductive material layer, 703 denotes a heat generating material layer, 704 denotes a structure, 705 denotes a first deformable material layer, 706 denotes a second deformable material layer, and 707 denotes a track pitch.
As the support substrate 701, the same material as that of the present invention 1 can be used.
Reference numeral 702 denotes a low thermal conductive material layer. The low thermal conductive material layer is provided to suppress thermal diffusion to the substrate and concentrate heat on the heat generating material layer 703, and to suppress thermal diffusion to the substrate and prevent deformation of the substrate. Materials include silicon compound materials such as SiO ₂ , SiON, and SiN, sulfide materials such as ZnS, CaS, and BaS, selenide materials such as ZnSe and BaSe, fluorine compound materials such as CaF ₂ and BaF ₂ , C, SiC, and the like. Carbide materials such as can be used. A material containing at least zinc sulfide (ZnS) and silicon oxide (SiOx, where x is 2 or less), which is the second deformable material of the present invention 4, can be used.
Reference numeral 703 denotes a heat generating material layer. The heat generating material layer is provided in order to form the structure body 704 with a simple manufacturing process. Any material that absorbs laser light and generates heat may be used. For example, a semiconductor material such as Si or Ge, an intermetallic compound material containing a low melting point metal such as Bi, Ga, In, or Sn, a material such as BiTe, BiIn, GaSb, GaP, InP, InSb, InTe, or SnSb, C, A carbide material such as SiC or a nitride material such as AlN or GaN can be used. Further, a material containing at least antimony (Sb) and tellurium (Te), which is the first deformable material of the third aspect of the present invention, can be used.
Reference numeral 704 denotes a structure. The structure is made of a material containing at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2 or less). ZnS and SiOx may exist in an independent state, or may exist in a state where elements constituting ZnS and SiOx are combined. Further, materials other than ZnS and SiOx may be included. For example, ZnS zinc oxide is a compound according to elements constituting the _{SiOx (ZnO), ZnO X S} 1-X of the state where the zinc oxide is sulfide, zinc nitride is a compound of the ambient gas _(Zn 3 _{N 2),} etc. May be included. Further, a compound of an element constituting the heat generating material layer 703 and Zn, S, Si, or O may be included.
Reference numeral 705 denotes a first deformable material layer. The same material as that of the present invention 1 can be used.
Reference numeral 706 denotes a second deformable material layer. The same material as that of the present invention 1 can be used.

Next, an embodiment of the present invention 6 will be described.
FIG. 8 is a cross-sectional view of an example of the optical information recording medium of the sixth aspect, perpendicular to the recording track, before information is recorded. 801 is a supporting substrate, 802 is a low thermal conductive material layer, 803 is a heat generating material layer, 804 is a structure, 805 is a first deformable material layer, 806 is a second deformable material layer, 807 is a track pitch, and 808 is a surface of the supporting substrate. A convex portion 809 indicates a concave portion on the surface of the support substrate. There are convex portions and concave portions formed by the convex portions on the surface of the support substrate. The structure exists on the convex portion and the concave portion. Reference numeral 810 denotes the height of the convex portion. The height is 10-50 nm. When the height is less than 10 nm, tracking of the laser beam spot with respect to the recording track becomes unstable. When the height is higher than 50 nm, the recording and reproducing conditions at the convex part and the concave part are greatly different, and the cost of the recording / reproducing apparatus increases.

Next, an embodiment of the present invention 7 will be described.
FIG. 9 is a top view of an example of the optical information recording medium of the present invention 7 and shows only the structure and the recording mark. Reference numeral 901 denotes a laser beam spot, 902 a structure, 903 a recording mark, 904 a track pitch, 905 a structure width, 906 a recording mark width, and 907 a space between adjacent structures in the radial direction.
By providing the structure, heat is localized on the structure. Therefore, the recording mark is formed in a state of conforming to the structure, and the width of the recording mark substantially matches the width of the structure. As the width of the recording mark is wider, the ratio of the recording mark included in the laser beam spot increases and the reproduction signal intensity increases. However, when the structure width is widened and the adjacent structures in the radial direction are connected, heat cannot be localized and cross light cannot be suppressed. Therefore, as shown in the present invention 7, the width of the structure is set to 0.7 to 0.95 times the track pitch. If there is a slight space between structures adjacent in the radial direction, heat can be localized on the structure, and a cross-light suppressing effect can be obtained.
The preferred dimensions when the laser beam spot diameter (diameter) is about 400 nm are as follows. The track pitch is 150 to 300 nm. If it is less than 150 nm, the tracking of the recording track of the laser beam spot becomes unstable. If it is larger than 300 nm, the recording density does not increase. The width of the structure is set to a range of 105 to 140 nm when the track pitch is 150 nm, and is set to a range of 210 to 285 nm when the track pitch is 300 nm.

Next, an embodiment of the present invention 8 will be described.
FIG. 10 shows a manufacturing method using the medium configuration shown in FIG. 8 as an example. (A) is a cross-sectional view of a medium structure for forming a structure, (b) is a laser light irradiation step, (c) is an etching step, (d) is a first deformation material layer forming step, and (e) is a first step. 2 shows a film forming process of a deformable material layer.
In FIG. 10A, 1001 is a supporting substrate, 1002 is a low thermal conductive material layer, 1003 is a heat generating material layer, and 1004 contains at least zinc sulfide (ZnS) and silicon oxide (SiOx, where x is 2 or less). A thin film (hereinafter referred to as a heat change layer) is shown. For the supporting substrate 1001, the low thermal conductive material layer 1002, and the heat generating material layer 1003, the same material as that of the first invention can be used.
As a film forming method of the heat change layer, a sputtering method is preferable. In particular, a sputtering method at room temperature is preferable as a film forming method for forming a low-density material. The sputtering target is a material having a ratio of ZnS to SiO ₂ (ZnS / SiO ₂ ) in the range of 1 to 20, that is, a material in the range of ZnS: SiO ₂ = 50: 50 to 95: 5 (mol%). Is preferably used. A material containing ZnS and SiOx is a material having high transmittance in a wide wavelength range. By containing SiOx, it becomes very low density and / or soft in the film formation state. It is a material that is easily deformed by recording and hardened and / or densified by heating. By forming a structure with a material exhibiting such characteristics, the structure can be formed with a simple manufacturing process.

FIG. 10B shows a laser beam irradiation process. Reference numeral 1005 denotes a laser beam. The heat change layer is changed by laser light irradiation. Reference numeral 1006 denotes a changed portion. The form of change includes a change in material density, a change in phase state, dissociation of constituent elements, a reaction with atmospheric gas, and the like. There may be multiple changes. Laser light is irradiated from the heat change layer side to the laminated structure of the support substrate, the low heat conductive material layer, the heat generating material layer, and the heat change layer. In the following description, this irradiation method is referred to as “film surface irradiation”.
By irradiating the film surface, the numerical aperture NA of the objective lens can be increased. By increasing NA, a small laser beam spot can be formed, and a minute region of the heat change layer can be changed, so that a fine structure can be formed. A semiconductor laser can be used as the laser light source. The wavelength of the semiconductor laser is 370 to 780 nm, preferably 370 to 410 nm. For example, a GaN-based semiconductor laser is used. By using a semiconductor laser, an inexpensive apparatus can be obtained, and the process cost can be reduced.

FIG. 10C shows an etching process. Reference numeral 1007 denotes a structure. A part of the heat change layer 1004 is removed to form a structure body 1007. An etching rate difference is generated between a changed portion and a non-changed portion due to laser irradiation. The etching rate of the changed portion decreases, and the changed portion remains as a structure after the etching. In the etching process, at least the heat change layer is etched. Alternatively, both the heat change layer and the heat generating material layer may be etched. In the etching step, an aqueous solution (HF + H ₂ O) containing hydrofluoric acid is used as an etching solution. A preferred solution ratio is in the range of HF: H ₂ O = 1: 50 to 1:20. If the HF concentration is lower than 1:50, the etching rate decreases and the process time becomes longer. If the HF concentration is higher than 1:20, the surface of the medium becomes rough, which causes noise during signal reproduction.
The aqueous solution containing hydrofluoric acid selectively dissolves silicon oxide. By etching, the silicon oxide is dissolved in the portion not irradiated with the laser beam. As the silicon oxide is dissolved, ZnS is released (lifted off). In the changed portion 1006 due to laser light irradiation, the etching resistance to an aqueous solution containing hydrofluoric acid is increased. Therefore, the changed portion remains and a structure can be formed. In addition, anisotropic etching can be performed by etching with an aqueous solution containing hydrofluoric acid. In the etching process, anisotropic etching of the heat change layer proceeds, and a structure having an end portion with a reverse taper shape can be formed.

FIG. 10D shows a film forming process of the first deformable material layer. Reference numeral 1008 denotes a first deformable material layer.
FIG. 10E shows a film forming process of the second deformable material layer. Reference numeral 1009 denotes a first deformable material layer.
The optical information recording medium shown in FIG. 8 is completed by the above manufacturing method.

  According to the present invention, high-density information exceeding the resolution limit of light can be recorded and reproduced, and the recording density is increased by reducing the track pitch, regardless of the method of forming an optical aperture in the super-resolution material layer. An optical recording medium that can be used and a manufacturing method thereof can be provided.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples.
An optical information recording medium having the structure shown in FIG. 8 was produced as follows.
The support substrate 801 is made of polycarbonate, the low thermal conductive material layer 802 is ZnS-SiOx with a thickness of 50 nm, the heat generating material layer 803 is AgInSbTe with a thickness of 20 nm, the structure 804 is ZnS-SiOx with a height of 45 nm, and the first deformation. The material layer 805 was AgInSbTe with a film thickness of 30 nm, and the second deformable material layer 806 was ZnS—SiOx with a film thickness of 60 nm.
All materials were formed by sputtering at room temperature. For the formation of the AgInSbTe film, Ag ₄ In ₇ Sb ₆₁ Te ₂₈ (atomic%) having an Sb / Te ratio of about 2.2 was used as a sputtering target. For the formation of the ZnS—SiOx film, a mixture of ZnS and SiO ₂ (ZnS / SiO ₂ = 4) was used as a sputtering target. Reference numeral 807 denotes a track pitch of 220 nm. Reference numeral 808 denotes a convex portion of the support substrate, 809 denotes a concave portion, and 810 denotes the height of the convex portion, which is 20 nm.
FIG. 11 is a cross-sectional TEM image of the optical information recording medium in an unrecorded state. FIG. 11A is a cross-sectional image over several tracks, and FIG. 11B is an enlarged image of the structure end.
Reference numeral 1101 denotes a supporting substrate, 1102 denotes a low thermal conductivity material layer, 1103 denotes a heat generating material layer, 1104 denotes a structure, 1105 denotes a first deformable material layer, 1106 denotes a second deformable material layer, and 1107 denotes a track pitch. Reference numeral 1108 denotes a structure end.
As shown in the drawing, the film thickness of the first deformable material layer is reduced at the end of the structure.

Next, information was recorded on the optical information recording medium. The recording conditions are as follows.
Using a GaN semiconductor laser with a wavelength of 405 nm, the shortest mark corresponding to a storage capacity equivalent to 50 GB was repeatedly recorded with a numerical aperture NA of 0.85 and a recording linear velocity of 4.5 m / sec. The laser power level was modulated at two levels having a relationship of P1> P2. P1 = 3.5 mW and P2 = 1 mW. The power level is a value on the medium side. The pulse width W = 12 nsec, the pulse period S = 44 nsec, and the pulse duty W / S = 27%.
FIG. 12 is a cross-sectional SEM image in a direction parallel to the recording track after information is recorded. This is the result of processing the vicinity of the center of the recording track with FIB and observing the cross section with SEM.
Reference numeral 1201 denotes a supporting substrate, 1202 denotes a low thermal conductivity material layer, 1203 denotes a heat generating material layer, 1204 denotes a structure, 1205 denotes a first deformable material layer, and 1206 denotes a second deformable material layer. Reference numeral 1207 denotes a recording mark period, which is 230 nm. Reference numeral 1208 denotes a recording mark center, and 1209 denotes a recording mark end. The film thickness of the first deformable material layer is thick at the center of the recording mark and thin at the end of the recording mark. The difference in film thickness between the center and end of the recording mark is 26 nm. The film thickness change of the second deformable material layer is small, and the second deformable material layer is deformed according to the unevenness of the first deformable material layer. Recording in a shell shape in which the irregularities of the first deformable material layer are covered with the second deformable material layer can be performed.

FIG. 13 is an SEM image showing the effect on the cross light. This is a top view of the medium, and processing is performed to make it easy to observe the recording mark by SEM. FIG. 13A shows the result of the conventional medium configuration and the result of the medium configuration without the structure. FIG. 13B shows the result of the medium configuration of this example.
In FIG. 13A, reference numeral 1301 denotes a laser beam spot. The laser beam spot diameter calculated from the wavelength of the laser beam and the NA of the objective lens is 391 nm. 1302 is a recording mark, 1303 is a track pitch, and is 220 nm. Reference numeral 1304 denotes a recording mark width, and 1305 denotes a state of a recording mark adjacent in the radial direction.
In a medium configuration without a conventional structure, when the recording mark width is increased and the track pitch is reduced, the recording marks adjacent in the radial direction are connected (see 1305). That is, cross light occurs. Therefore, the track pitch cannot be reduced.
In FIG. 13B, reference numeral 1306 denotes a laser beam spot. The laser beam spot diameter is the same as in FIG. Reference numeral 1307 denotes a recording mark, and 1308 denotes a track pitch. The track hitch pitch is the same as in FIG. Reference numeral 1309 denotes a structure. It is a portion 805 in FIG. Reference numeral 1310 denotes a recording mark width, and reference numeral 1311 denotes a state of recording marks adjacent in the radial direction.
In the medium configuration provided with the structure of the present invention, the recording mark width does not extend beyond the width of the structure. Therefore, even if the track pitch is reduced, the recording marks adjacent in the radial direction are separated (see 1311). That is, no cross light occurs. Therefore, the track pitch can be reduced. FIG. 13B shows the result with a track pitch of 220 nm. In the structure provided with the structure of the present invention, the recording mark width matches the width of the structure, so the width of the structure is narrowed. By doing so, the track pitch can be further reduced.

The state in which the shortest mark was repeatedly recorded on the optical information recording medium was reproduced. The recording mark period is 150 nm and 200 nm. 150 nm corresponds to a storage capacity of 70 GB, and 200 nm corresponds to a storage capacity of 55 GB. The reproduction conditions are as follows.
A GaN semiconductor laser having a wavelength of 405 nm was used, and the numerical aperture NA of the objective lens was 0.85, the reproducing linear velocity was 4.5 m / sec, and the reproducing power was 1.1 mW. Recording was performed on adjacent tracks at a track pitch of 220 nm, and the CNR (carrier to noise ratio) of the reproduction signal was measured.
As a result, the CNR value of the reproduction signal was 29 dB at a recording mark period of 150 nm and 34 dB at a recording mark period of 200 nm, and the reproduction signal was detected. The laser wavelength λ for reproducing the signal is 405 nm, and the numerical aperture NA of the objective lens is 0.85. The resolution limit λ / 2NA is 238 nm. High-density information with a recording mark period of 150 nm and 200 nm corresponding to a period shorter than the resolution limit of light could be recorded and reproduced.

The figure which shows the outline | summary of the conventional optical information recording medium structure. (A) Cross-sectional view perpendicular to the recording track, (b) Cross-sectional view parallel to the recording track. FIG. 3 is a cross-sectional view of the optical information recording medium of the present invention in an unrecorded state in a direction perpendicular to the recording track. Sectional drawing of the direction along the recording track of the medium after recording information. FIG. 3 is a cross-sectional view in a direction perpendicular to a recording track of a medium after information is recorded. The figure which shows the reproduction | regeneration method. (A) Recording state, (b) Playback state, (c) Recording mark state viewed from above. The figure which shows the change of a reproduction signal level. (A) medium top view, (b) playback signal level, (c) medium top view, (d) playback signal level, (e) medium top view, (f) playback signal level. Sectional drawing of the optical information recording medium of this invention 5 perpendicular | vertical with respect to a recording track before recording information. Sectional drawing of the optical information recording medium of this invention 6 perpendicular | vertical with respect to a recording track before recording information. The figure which shows the structure of the optical information recording medium of this invention 7 (upward view). The figure which shows the manufacturing method of a medium. (A) sectional view of medium structure for forming structure, (b) laser irradiation step, (c) etching step, (d) first deformation material layer formation step, (e) second deformation material layer formation Membrane process. The figure which shows the cross-sectional TEM image of the unrecorded state of the optical information recording medium of an Example. (A) Cross-sectional image of several tracks, (b) Enlarged image. The figure which shows the cross-sectional SEM image of a medium after recording information in a direction parallel to a recording track. The figure which shows the SEM observation result of a crosslight. (A) Conventional configuration without structure, (b) Configuration of the present invention provided with a structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Support substrate 102 Recording material layer 103 Super-resolution material layer 104 Recording track 105 Track pitch 106 Recording mark 107 Optical aperture of super-resolution material layer 108 Laser beam 109 Laser beam spot diameter 110 Laser beam moving direction 201 Support substrate 202 Structure Body 203 First deformable material layer 204 Second deformable material layer 205 Track pitch 301 Structure 302 First deformable material layer 303 Second deformable material layer 304 Recording mark 305 Recording mark center 306 Recording mark end 307 First of recording mark center Film thickness of deformable material layer 308 Film thickness of first deformable material layer at end of recording mark 309 Film thickness of second deformable material layer at center of record mark 310 Film thickness of second deformable material layer at end of record mark 401 Structure 402 First deformable material layer 403 Second deformable material layer 404 Tiger Cpit 405 Recording track 406 Unrecorded track 407 Unrecorded track 501 Structure 502 First deformable material layer 503 Second deformable material layer 504 Recording mark end 505 Second deformable material layer 506 Laser beam 507 Laser beam moving direction 508 Laser beam spot Diameter 509 Laser beam moving direction 510 Structure 511 Melting mark at the center of the laser beam spot 512 Solid state mark 513 adjacent to the front 513 Molten first deformable material layer 601 Laser beam spot 602 Laser beam spot moving direction 603 Structure 604 First 1 Deformation material layer 605 Recording track in the center of the laser beam spot 606 Recording track adjacent in the radial direction 607 Signal level 608 Melting portion of the first deformation material layer 609 Signal level 610 Mark 611 Recording mark in solid phase 612 Recording mark in solid phase 613 Signal level when laser beam spot is in the center of recording mark 614 Signal level when laser beam spot is between recording marks 615 High signal level 616 Low signal level 701 Support substrate 702 Low thermal conductive material layer 703 Heat generating material layer 704 Structure 705 First deformable material layer 706 Second deformable material layer 707 Track pitch 801 Support substrate 802 Low heat conductive material layer 803 Heat generating material layer 804 Structure 805 First 1 deformable material layer 806 2nd deformable material layer 807 track pitch 808 support substrate surface convex portion 809 support substrate surface concave portion 810 height of convex portion 901 laser beam spot 902 structure 903 recording mark 904 track pitch 905 structure width 90 Recording mark width 907 Space between adjacent structures in the radial direction 1001 Support substrate 1002 Low thermal conductive material layer 1003 Heat generation material layer 1004 Thermal change layer 1005 Laser beam 1006 Change portion 1007 Structure 1008 First deformation material layer 1009 First deformation material Material layer 1101 Support substrate 1102 Low thermal conductivity material layer 1103 Heat generating material layer 1104 Structure 1105 First deformable material layer 1106 Second deformable material layer 1107 Track pitch 1108 Structure end 1201 Support substrate 1202 Low thermal conductivity material layer 1203 Heat generating material Layer 1204 Structure 1205 First deformable material layer 1206 Second deformable material layer 1207 Recording mark period 1208 Recording mark center 1209 Recording mark edge 1301 Laser beam spot 1302 Recording mark 1303 Track pitch 304 state of a recording mark adjacent to state 1306 the laser beam spot 1307 recording marks 1308 track pitch 1309 structure 1310 recording mark width 1311 radial direction of the recording mark to be adjacent to the recording mark width 1305 radially

Claims (8)

  A recording track having at least a structure, a first deformable material layer that absorbs light and generates heat and deforms, and a second deformable material layer that transmits light and deforms by heat, and in an unrecorded state The optical information is characterized in that the cross-sectional shape in the vertical direction is such that the end of the structure is vertical or inversely tapered, and the thickness of the first deformable material layer is reduced at the end of the structure. recoding media.   After the information is recorded, the cross-sectional shape in the direction parallel to the recording track is such that the thickness of the first deformable material layer changes according to the recording information and the center of the recording mark becomes thicker than the end of the recording mark. The deformable material layer is deformed according to irregularities corresponding to the recording information formed in the first deformable material layer, and the first deformable material layer changes from a solid phase state to a molten state when reproducing information. The optical information recording medium according to claim 1. (Here, the recording mark refers to a deformed portion of the first deformable material layer and the second deformable material layer.)   The optical information recording medium according to claim 1 or 2, wherein the first deformable material layer contains at least antimony (Sb) and tellurium (Te).   4. The optical information recording medium according to claim 1, wherein the second deformable material layer contains at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2 or less). .   The supporting substrate has a laminated structure of a heat generating material layer that absorbs light and generates heat, and the structure includes at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2 or less). The optical information recording medium according to claim 1, wherein the optical information recording medium is contained.   6. The optical information recording medium according to claim 5, wherein in the cross-sectional shape perpendicular to the recording track, the support substrate surface has irregularities, and the structure exists on the concave portions and the convex portions.   7. The structure according to claim 1, wherein the structure has a continuous line shape in the recording track direction, and the line width is in a range of 0.7 to 0.95 times the recording track pitch. Optical information recording medium. Irradiating a support substrate, a heat generating material layer, a medium having at least a laminated structure composed of a thin film containing at least zinc sulfide (ZnS) and silicon oxide (SiOx; where x is 2 or less) with laser light, 7. The optical information recording according to claim 5, further comprising: etching the medium with an aqueous solution containing hydrofluoric acid (HF); and forming the first deformable material layer and the second deformable material layer. A method for manufacturing a medium.