JP2005288809A - Optical recording medium, its manufacturing method, and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-density optical recording medium by which high-contrast recording reproduction small in recording wavelength dependence can be performed with recording density of exceeding the diffraction limit of a pickup lens which can not be realized by a conventional optical disc. <P>SOLUTION: The optical recording medium comprises an organic thin film which are mainly composed of a non-compatible block copolymer each other and including at least one kind of pigments, having an absorbing power in the vicinity of a recording reproduction wavelength, and metal ultrafine particles expressing the plasmon absorption in the vicinity of the recording reproduction wavelength only in one phase of its micro phase separation structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical recording medium, a method for manufacturing the same, and a recording method, and in particular, by irradiating the optical recording medium with a light beam, an optical change such as transmittance and reflectance is caused in the recording material to record information. The present invention relates to an ultra-high density optical recording medium that performs reproduction, a manufacturing method thereof, and a recording method.

  In the optical memory field, recordable CD-Rs and DVD-Rs corresponding to CD standards and DVD standards, which are optical recording media having a reflective layer on a substrate, have been commercialized. In the future, it is desired to further increase the capacity and size of such optical recording media, and further improvement of the recording density is required.

  Elemental technologies for improving the recording capacity in the current system include a recording pit miniaturization technology and an image compression technology represented by MPEG2. In order to reduce the recording / reproducing light wavelength and increase the diffraction limit, the recording pit miniaturization technology has been studied to increase the numerical aperture NA of the optical system, but recording / reproduction exceeding the diffraction limit is not possible. Is possible. Therefore, super-resolution technology capable of recording / reproduction exceeding the diffraction limit and optical memory systems using near-field light have attracted attention as promising means, but they have yet to be put into practical use due to the high technical hurdles. Not in.

  In contrast to the conventional approach from the light source side, we have introduced an organic thin film that combines a nanometer-sized functional material (metal fine particles or organic dye) into a polymer microphase separation structure as an optical recording medium. By applying the recording medium, a recording medium in which the area of the recording body itself is a dot array smaller than the diffraction limit of irradiation light has been proposed.

  Conventionally, a metal cluster complex in which a metal cluster of 10 nm or less is protected by a water-insoluble organic polymer is a complex known as an organic polymer-protected metal cluster. A method obtained by dissolving a reducing agent and heating is known (for example, see Patent Document 1).

  In addition, a metal / organic polymer composite and a porous body, which is a composite or a porous body containing a metal ultrafine particle of 10 nm or less in only one phase in a microphase separation structure of an incompatible block copolymer, A method of forming a phase separation structure by solvent casting or temperature reduction has been proposed (see, for example, Patent Document 2).

  In addition, an ultra-fine phase separation structure of polymer alloy having an ultra-fine phase separation structure of 100 nm or less in two or more incompatible polymer blends is known. Also known is a method for producing a polymer alloy ultrafine phase separation structure by using a supercritical fluid solvent of a high temperature and high pressure fluid solvent to form a superfine phase separation structure by compatibilizing and rapidly reducing the pressure. (For example, see Patent Document 3).

  Furthermore, a polymer microphase separation structure is known which is a three-dimensional (single grain) anisotropic block copolymerized microphase separation structure obtained by contacting an oriented interface having affinity for one polymer chain. As its formation method, a method of heating near the transition temperature is known, in which microphase separation is started from the orientation interface, and the phase separation structure formation region is moved to grow grains with a uniform orientation direction. (For example, see Patent Document 4).

  Also, a composite fine pore having a fine pore in which metal ultrafine particles are supported only in one phase in a microphase separation structure of an incompatible block copolymer or polymer blend: 10 nm to 1 μm Metal ultrafine particles: A metal / organic polymer composite having a thickness of 1 to 10 nm is known. In this composite, fine pores are formed by decomposing or eluting one phase of a microphase separation structure, and ultrafine metal particles are formed with no electric field. A method of carrying by plating or subsequent electroplating is known (for example, see Patent Document 2).

  In addition, in a micro phase separation structure of an incompatible block copolymer, a composite containing metal ultrafine particles of 10 nm or less in the vicinity of the skeleton surface in one phase and the other polymer phase are vacated. Metal / organic polymer composite structures and porous bodies that are composite materials are known, and these composite structures dissolve and heat block copolymer polymer chains, metal compounds, and reducing agents with and without affinity. Reduce and protect the surface of the metal fine particles, form a phase separation structure by solvent casting or lowering the temperature, decompose the porous body, or decompose one phase or add homopolymer, oligomer, low molecule and then microphase separation A method of forming a porous body by elution treatment to form pores is known (for example, see Patent Document 5).

  In addition, a metal / organic polymer composite structure, which is a composite having a micro phase separation structure of an incompatible block copolymer and containing ultrafine metal particles near the center in one phase, is also known. The solution of the metal / organic polymer (Mn1) complex and the matrix polymer (Mn2) forms a phase separation structure by solvent casting or temperature reduction, and the polymer phase not containing metal fine particles is removed by Mn1> Mn2. A method for producing a metal / organic polymer composite structure has also been proposed (see, for example, Patent Document 6).

In addition, a metal containing ultrafine metal particles arranged in a row, which is a composite in which ultrafine particles of metal are contained in a row in one phase in a microphase separation structure of an incompatible block copolymer Organic composite structures are known, and block copolymer polymers and metal ions with and without affinity are dissolved in reducing high-boiling solvents and low-boiling solvents, and low-boiling solvents are removed and phase separation is performed. A method for producing a metal / organic composite structure containing metal ultrafine particles arranged in a line by reducing metal ions while forming a structure and removing a high-boiling solvent has been proposed (for example, Patent Documents) 7).
JP-A-10-251548 JP-A-10-330492 Japanese Patent Laid-Open No. 10-330493 Japanese Patent Laid-Open No. 10-330528 Japanese Patent Application Laid-Open No. 11-60891 JP 2000-72951 A JP 2000-72952 A

  Introducing a nanometer-sized functional material into a polymer to form a composite can yield a functional composite material that exhibits new functions such as electronic properties, conductive properties, optical properties, and magnetic properties. It is an important technology. Conventionally, research and development of metal-organic composite materials using ultrafine metal particles (metal nanoclusters) as functional materials has been underway. However, there is a problem that research and development as an optical recording medium is hardly advanced as far as the inventors know.

  However, in the case where an organic thin film in which nanometer-sized metal fine particles are introduced into a polymer and applied to an optical recording medium is applied to the optical recording medium, the recording contrast depends on the optical constant change and deformation based on the plasmon absorption of the metal fine particles. It was obtained by the accompanying phase difference, and the optical constant based on the plasmon absorption of the metal fine particles was not so large, so it was difficult to obtain a high recording contrast.

  On the other hand, when an organic thin film in which an organic dye is incorporated into a polymer and applied to an optical recording medium is applied to an optical recording medium, the optical constant change is large and a high recording contrast can be obtained, but the refractive index and extinction coefficient with respect to the wavelength can be obtained. There is a problem that the wavelength dependency is large, and there is a problem in that the recording sensitivity is insufficient and the reflectivity is insufficient due to manufacturing variations of semiconductor lasers and a shift to a longer transmission wavelength at high temperatures.

  The present invention has been made in consideration of the above-mentioned circumstances, and has a recording density exceeding the diffraction limit of a pickup lens, which cannot be realized with a conventional optical disk, and has high contrast and small recording wavelength dependency. It is an object of the present invention to provide a high-density optical recording medium that enables recording.

  The present invention also provides an organic thin film in which a nanometer-sized ultrafine metal particle dispersion structure that expresses plasmon absorption in the vicinity of a recording / reproducing wavelength and at least one kind of dye having an absorption ability in the vicinity of the recording / reproducing wavelength is optically converted. By applying to a recording medium, an optical recording medium capable of recording / reproducing with a recording density exceeding the diffraction limit of a pickup lens, which is impossible to achieve with a conventional optical disk, and with high contrast and small recording wavelength dependency is provided. With the goal.

  In order to solve the above-mentioned problems, the invention described in claim 1 is characterized in that at least one kind of dye having a block copolymer incompatible with each other as a main component and having an absorption ability in the vicinity of the recording / reproducing wavelength in one phase thereof. And an optical recording medium comprising an organic thin film containing ultrafine metal particles that exhibit plasmon absorption in the vicinity of the recording / reproducing wavelength.

  The invention according to claim 2 is characterized in that the microphase-separated structure containing at least one kind of dye having an absorption capability near the recording / reproducing wavelength and ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength is spherical. 2. The optical recording medium according to claim 1, comprising an organic thin film having a structure or a columnar structure.

  According to a third aspect of the present invention, the microphase-separated structure containing at least one dye having an absorption ability near the recording / reproducing wavelength and ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength is a spherical structure. 3. An optical recording medium according to claim 1, comprising an organic thin film formed with a film thickness smaller than the diameter of the spherical structure.

  According to a fourth aspect of the present invention, there is provided a columnar structure in which the microphase-separated structure containing at least one kind of dye having an absorption ability near the recording / reproducing wavelength and ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength. The optical recording medium according to claim 1, wherein the optical recording medium is formed of an organic thin film formed perpendicularly to the thin film surface.

  The invention according to claim 5 contains the ultrafine metal particles whose particle size and shape are controlled so as to have a maximum absorption wavelength in the vicinity of the recording / reproducing wavelength, and a dye in the vicinity of the recording / reproducing wavelength. The optical recording medium described in item 1 is characterized.

  The invention according to claim 6 contains at least one of ultrafine metal particles whose particle diameter and shape are controlled so as to have a maximum refractive index in the vicinity of the recording / reproducing wavelength and a dye having a maximum absorption wavelength in the vicinity of the recording / reproducing wavelength. An optical recording medium according to any one of claims 1 to 4 is characterized.

  The invention according to claim 7 is the optical recording medium according to any one of claims 1 to 6, wherein the ultrafine metal particles are gold, silver, platinum and an alloy thereof.

  The invention according to claim 8 is also directed to at least one dye having an absorption ability in the vicinity of the recording / reproducing wavelength compatible with one phase of the microphase separation structure, and a metal that exhibits plasmon absorption in the vicinity of the recording / reproducing wavelength. The optical recording medium manufacturing method according to any one of claims 1 to 6, wherein a preparation liquid prepared by preparing a solution containing ultrafine particles and a block copolymer is applied and annealed.

  The invention according to claim 9 is compatible with one phase of the microstructure after preparing and applying a solution containing a block copolymer and forming a microphase separation structure by annealing. The light according to any one of claims 1 to 6, wherein at least one dye having an absorption ability near a recording / reproducing wavelength is brought into contact with a solution containing ultrafine metal particles that exhibit plasmon absorption near the recording / reproducing wavelength. A recording medium manufacturing method is characterized.

  The invention according to claim 10 is compatible with one phase of the microstructure after preparing and applying a solution containing a block copolymer and forming a microphase separation structure by annealing. 7. The method according to any one of claims 1 to 6, wherein a layer containing at least one dye having an absorption ability near a recording / reproducing wavelength and a layer containing metal ultrafine particles expressing plasmon absorption near the recording / reproducing wavelength is laminated and then heated and diffused. The manufacturing method of the optical recording medium described is characterized.

  The invention according to claim 11 is a microphase separation containing at least one kind of dye having an absorption ability near the recording / reproducing wavelength and ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength by laser light irradiation. 7. A recording / reproducing method using the optical recording medium according to claim 1, wherein recording / reproducing is performed by changing an optical characteristic of one phase of the structure.

  The invention according to claim 12 is a microphase separation containing at least one kind of dye having an absorption capability near the recording / reproducing wavelength and ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength by laser light irradiation. 7. A recording / reproducing method using the optical recording medium according to claim 1, wherein the recording / reproducing is performed by changing a shape of one phase of the structure.

  According to the present invention, at least one kind of dye having an absorption capacity in the vicinity of the recording / reproducing wavelength and in the vicinity of the recording / reproducing wavelength only in one phase of the microphase-separated structure, which is mainly composed of mutually incompatible block copolymers. An optical recording medium comprising an organic thin film containing ultrafine metal particles that exhibit plasmon absorption enables recording and reproduction at a recording density that exceeds the diffraction limit of a pickup lens, which is impossible with conventional optical disks. It becomes possible to provide the basic structure and material configuration of the optical recording medium.

  In addition, an organic thin film having a microphase separation structure having a spherical structure or a columnar structure containing at least one dye having an absorption ability near the recording / reproducing wavelength and a metal ultrafine particle that expresses plasmon absorption near the recording / reproducing wavelength, An organic thin film formed with a film thickness smaller than the diameter of the structure and an organic thin film having a columnar structure formed perpendicular to the thin film surface can provide a preferable application shape.

  Furthermore, it contains at least one metal ultrafine particle whose particle size and shape are controlled so as to have a maximum absorption wavelength near the recording / reproducing wavelength and a dye having a maximum refractive index near the recording / reproducing wavelength, and has a maximum refraction near the recording / reproducing wavelength. It is possible to obtain suitable optical characteristics as an optical recording medium by containing ultrafine metal particles whose particle diameter and shape are controlled so as to have a refractive index and at least one dye having a maximum absorption wavelength near the recording / reproducing wavelength. Become.

  Furthermore, when the metal ultrafine particles are gold, silver, platinum, or an alloy containing at least one of these, it is possible to give better characteristics as an optical recording medium.

  Furthermore, at least one dye having an absorption ability near the recording / reproducing wavelength compatible with only one phase of the microphase-separated structure, ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength, and a block copolymer Are prepared by applying a coating method such as a spin coating method or a dipping method, and then annealing to form a solution containing a block copolymer, and a spin coating method or After applying a coating method such as a dipping method, and then forming a microphase separation structure by annealing, at least one dye having an absorption ability near the recording / reproducing wavelength that is compatible only with one phase of the microstructure , Manufacturing method and block copolymer formed by contacting with a solution containing ultrafine metal particles that express plasmon absorption in the vicinity of a recording / reproducing wavelength Prepare a solution containing it, apply it by a spin coating method or dipping method, etc., and then form a microphase separation structure by annealing, then record and playback wavelength compatible with only one phase of the microstructure Employing one of the production methods in which a layer containing at least one kind of dye having absorption ability in the vicinity and a metal ultrafine particle that expresses plasmon absorption in the vicinity of the recording / reproducing wavelength is laminated and then heated and diffused. Thus, a preferable and most productive manufacturing method of the optical recording medium of the present invention can be appropriately selected and provided.

  Furthermore, when one of the phases of the microphase-separated structure contains at least one kind of dye having an absorption capability near the recording / reproducing wavelength and ultrafine metal particles that exhibit plasmon absorption near the recording / reproducing wavelength by laser irradiation. A preferred recording / reproducing method of the optical recording medium of the present invention is performed by changing the characteristics and recording / reproducing by changing the shape of one phase of the micro phase separation structure (or the structure of one phase). It becomes possible to provide.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As a result of the study, the present inventors made use of the microphase separation phenomenon of the polymer, and at least one of the dyes having an absorption ability near the recording / reproducing wavelength only in one phase and the plasmon absorption near the recording / reproducing wavelength were expressed. By dispersing and containing nanometer-sized metal ultrafine particles, an organic thin film intended for the present invention was obtained. By using the organic thin film as an optical recording medium, an optical recording medium capable of recording / reproducing with a recording density exceeding the diffraction limit (optical limit) of a laser pickup, high contrast, and small recording wavelength dependence I came to get.

  The organic thin film used in the optical recording medium of the present invention is mainly composed of mutually incompatible block copolymers, and at least one kind of dye having an absorption ability near the recording / reproducing wavelength only in one phase of the microphase separation structure. And nanometer-sized ultrafine metal particles that exhibit plasmon absorption near the recording / reproducing wavelength.

  This organic thin film is highly ordered in the polymer matrix with at least one dye having an absorption ability near the recording / reproducing wavelength and nanometer-sized ultrafine metal particles that exhibit plasmon absorption near the recording / reproducing wavelength. It is a structure that exists. The micro phase separation phenomenon of the block copolymer is used as the driving force.

  As the microphase separation structure, a spherical structure 11 as shown in FIG. 1 (a) or a columnar structure 12 as shown in FIG. 1 (b) can be preferably used. The portion 13 containing at least one kind of dye having an absorption ability near the recording / reproducing wavelength and nanometer-sized ultrafine metal particles expressing plasmon absorption near the recording / reproducing wavelength has its optical characteristics by light and / or heat. And a function of changing the phase difference.

Next, the manufacturing method of the organic thin film of this invention is demonstrated.
The present invention has been conceived from the phenomenon that mutually incompatible block copolymers form a microphase-separated structure by solvent casting or temperature change. That is, as shown in FIG. 2, the first manufacturing method of the recording layer 2 of the optical recording medium of the present invention has an absorption capability in the vicinity of the recording / reproducing wavelength that is compatible with only one phase of the microphase separation structure. Coating methods such as spin coating and dipping using a coating solution prepared by mixing a solution containing at least one dye and nanometer-sized ultrafine metal particles that exhibit plasmon absorption near the recording / reproducing wavelength and a block copolymer After the film is thinned, a microphase separation structure is formed by annealing. This formed microphase-separated structure is composed of at least one kind of dye having an absorption capability near the recording / reproducing wavelength only in one phase constituting the structure, and a nanometer-sized metal superstructure that exhibits plasmon absorption near the recording / reproducing wavelength. It is a structure containing fine particles.

  In the second method, a solution containing a block copolymer is prepared, the obtained preparation solution is applied by a spin coating method or a dipping method, and then a micro phase separation structure is formed by annealing treatment. Contact with a solution containing at least one dye having an absorption ability near the recording / reproducing wavelength compatible with only one phase and a metal ultrafine particle that exhibits plasmon absorption near the recording / reproducing wavelength. Only one phase forms a structure containing at least one dye having an absorption ability near the recording / reproducing wavelength and nanometer-sized ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength.

  In the third method, a solution containing a block copolymer is prepared, the obtained preparation solution is applied by a spin coating method or a dipping method, and then a micro phase separation structure is formed by annealing treatment. After laminating a layer containing at least one dye having an absorption ability near the recording / reproducing wavelength compatible with only one phase and a metal ultrafine particle that expresses plasmon absorption near the recording / reproducing wavelength, the layer is heated and diffused, Only one phase of the phase separation structure forms a structure containing at least one kind of dye having an absorption ability near the recording / reproducing wavelength and nanometer-sized ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength.

  In order to promote microphase separation, a homopolymer or other polymer constituting the block copolymer may be added in addition to the block copolymer. Nanometer-sized metal ultrafine particles (metal nanoclusters) are usually obtained by dissolving a metal compound and its reducing agent in an organic solvent (or organic dispersion medium) and heating. In order to improve the stability of ultrafine metal particles (metal nanoclusters), nanometer-sized ultrafine metal particles (metal nanoclusters) protective colloids obtained by coexisting low molecular weight organic compounds and polymers may be used.

Next, an optical recording medium in which this organic thin film is applied as an optical recording material will be described.
The recording layer of the conventional optical recording medium (the layer in which the recording material exists) is a continuous layer, which is irradiated with a laser beam, causing the recording material to undergo some change corresponding to the shape of the laser beam, and this change causes recording. Is done. Therefore, since the size of the minimum recording pit depends on the laser beam diameter determined by the oscillation wavelength and the lens NA, in the conventional recording / reproducing system, the increase in the density is basically the practical use of the laser oscillation wavelength and the lens NA. It has been influenced by the technology of chemical technology. In addition, since the beam shape is a Gaussian distribution and there is almost no material that changes with a clear threshold for heat or light as a recording material, the size of the outermost circumference of the pits to be formed The amount of change is not uniform, and there is always a variation factor in the quality of the reproduced signal, and there is a limit to obtaining high-quality signal characteristics.

  The recording medium of the present invention is an optical recording medium having a new structure that overcomes the problems of the conventional recording medium. That is, the main component is mutually incompatible block copolymer, and at least one dye having an absorption ability near the recording / reproducing wavelength and plasmon absorption near the recording / reproducing wavelength are expressed only in one phase of the microphase separation structure. Optical recording media using organic thin films with a structure containing dispersed nanometer-sized ultrafine metal particles that are highly ordered in a continuous layer, the recording layer dots are discontinuous through the matrix. Exist. In addition, the recording layer dots have a uniform nanometer size (10 to 500 nm). Therefore, the size of the minimum recording pit is not determined by the laser oscillation wavelength or the lens NA, but is determined only by the recording layer dots to be formed, and a recording medium having an arbitrary recording density can be designed. Furthermore, since the outermost peripheral edge of the pit is also determined by this organic thin film structure, it is possible to obtain high-quality signal characteristics free from pit variations by recording the entire recording layer dot to change. It becomes possible.

  In general, the microphase separation structure forms a structure such as a spherical shape, a columnar shape, a lamellar shape, and a co-continuous shape depending on its constituent material and composition, but the structure applicable to the optical recording medium of the present invention is a spherical shape and a columnar shape. This is because, as described above, the structure of the optical recording medium of the present invention requires that the recording layer dots exist discontinuously through the matrix.

  When the microphase separation structure is a spherical structure, the thickness of the recording layer 2 of the optical recording medium is preferably smaller than the diameter of the spherical structure. In this way, ultrafine metal particles (metal nanoclusters) can be formed as a single layer, and a structure in which dots having an optical recording function are uniformly present on the surface of the recording medium through the matrix can be formed. is there. Even if the thickness of the recording layer 2 is larger than the diameter of the ultrafine metal particles (metal nanoclusters), the above structure (dots having an optical recording function uniformly on the surface of the recording medium are present discontinuously through the matrix) If the structure can be controlled, it can be used.

  When the microphase separation structure is a columnar structure, the columnar structure is preferably a structure formed perpendicular to the recording medium surface. By so doing, similarly, it is possible to form a structure in which dots having an optical recording function uniformly exist on the recording medium surface in a discontinuous manner through a matrix.

  Organic dyes generate large electronic polarization by light irradiation, so that a large extinction coefficient and refractive index can be obtained. As recording materials for optical recording media, they exhibit excellent characteristics capable of high sensitivity recording and high contrast reproduction. . However, the spectrum is highly wavelength-dependent, and there is a problem that recording sensitivity is insufficient and reflectance is insufficient due to a variation in the manufacturing of semiconductor lasers and a shift in the transmission wavelength at high temperatures.

  On the other hand, when light is applied to the metal ultrafine particles (metal nanoclusters), free electrons in the metal are polarized by the photoelectric field, and charges are generated on the surface of the metal ultrafine particles (metal nanoclusters), resulting in nonlinear polarization. Therefore, it has specific absorption by a coloring mechanism called plasmon absorption caused by electron plasma oscillation, and the absorption characteristics depend on the type, particle size, and shape of the metal. Usually, the extinction coefficient and refractive index are not so large compared to organic dyes, and it is difficult to obtain a high recording contrast, but the spectrum is not so large in wavelength dependence, and it is difficult to produce semiconductor lasers at high temperatures. The change in characteristics due to the shift of the transmission wavelength to a longer wavelength is small.

  The optical recording medium of the present invention is preferably used with its optical characteristics controlled so as to have a maximum absorption wavelength or maximum refractive index in the vicinity of the oscillation wavelength used. This is because the optical recording medium is used for recording / reproduction by detecting a change in the optical characteristics of the recording layer 2, so that the most contrast is obtained. However, since the maximum absorption wavelength and the maximum refractive index cannot be compatible in a single composition system, it is possible to achieve both high sensitivity and high contrast by using a complementary relationship between the organic dye and metal fine particles used in combination. .

  In other words, a combination of ultrafine metal particles whose particle size and shape are controlled so as to have a maximum absorption wavelength near the recording / reproducing wavelength and a dye having a maximum refractive index near the recording / reproducing wavelength, and a maximum refractive index near the recording / reproducing wavelength. Thus, a combination of ultrafine metal particles having a controlled particle diameter and shape and a dye having a maximum absorption wavelength near the recording / reproducing wavelength is most useful.

  The optical recording medium of the present invention irradiates micro phase-separated recording layer dots with a recording laser beam, records the change caused by the irradiation, detects the change with a reproducing laser beam having a lower power than the recording laser beam, and reproduces it. As the recording / reproducing method of this optical recording medium, recording is performed by changing the optical characteristics (absorbance, reflectance, refractive index, etc.) of the recording layer dots, and reproducing is performed with the intensity of the changes in the optical characteristics, and the shape of the recording layer dots The recording is performed by changing (unevenness, smoothness, etc.) and reproduced by the intensity of the change in the optical optical characteristics due to the scattering or phase difference.

The configuration of the optical recording medium and its necessary physical properties will be described.
The structure of the optical recording medium of the present invention may be a write-once optical disk structure (a so-called air sandwich structure in which two recording layers 2 are provided on a substrate 1) and a CD-R structure (substrate 1). The recording layer 2, the reflective layer, and the protective layer may be formed thereon, or a DVD structure in which a CD-R structure is bonded may be used.

  The substrate 1 to be used must be transparent to the laser beam used only when recording / reproducing is performed at least from the substrate 1 side. When recording / reproducing is performed from the recording layer 2 side, it is not necessary to be transparent. . As the material of the substrate 1, for example, plastic such as polyester, acrylic resin, polyamide, polycarbonate resin, polyolefin resin, phenol resin, epoxy resin, polyimide, glass, ceramic, metal, or the like can be used. Note that a guide groove for tracking, a guide pit, and a preformat such as an address signal may be formed on the surface of the substrate 1.

  The recording layer 2 is caused to undergo some kind of change upon irradiation with laser light, and information can be recorded and optically reproduced by the change. The recording layer 2 is mainly composed of mutually incompatible block copolymers. As a component, only one phase of the microphase separation structure has a structure containing at least one kind of dye having an absorption ability in the vicinity of the recording / reproducing wavelength and optical recording metal fine particles that express plasmon absorption in the vicinity of the recording / reproducing wavelength. Become. The recording is recorded as a change in optical characteristics or a change in shape, and the reproduction is reproduced as an optical change caused by the recording.

  As the optical characteristics of the optical recording recording layer, when reproducing using the change in absorption characteristics with respect to the recording / reproducing laser wavelength, it is preferable to control the recording layer to have a maximum absorption wavelength in the vicinity of the laser wavelength, When reproducing using the refractive index change with respect to the recording / reproducing laser wavelength, it is preferable to control so that the maximum refractive index is in the vicinity of the laser wavelength.

  When the size of the recording pit as in the present optical recording medium is determined from the beginning, recording can be performed with much lower energy than in the conventional method. In the conventional method, a clear pit shape must be formed by recording, and recording cannot be performed unless the reaction rate of the recording material by laser irradiation is high. On the other hand, in the present recording medium in which pits are already formed, the change can be detected even with a small reaction rate (for example, reaction of only the surface).

  The block copolymer is synthesized by combining two or more polymers that are incompatible with each other. The synthesis methods include styrene, isoprene, α-methylstyrene, chloromethylstyrene, 2-vinylpyridine, aminostyrene, 4-vinylpyridine, methacrylates, ε-caprolactone, butadiene, vinyl methyl ether, 1,3-cyclohexanediene. , Living polymerization methods (anionic polymerization, living radical polymerization) that polymerize from the end of the chain using monomers such as ethylene oxide, living polymerization (anionic polymerization) that is synthesized from the center of the chain, and the end of a terminal functional polymer Synthetic methods (anionic polymerization, living radical polymerization) can be employed.

  Examples of recording dyes include polymethine dyes that change their optical constants in a heat mode (thermal decomposition, etc.) by laser irradiation energy, squarylium-based, pyrylium-based, porphyrin-based, porphyrazine-based, azo-based, azomethine-based dyes, etc. , And its metal complex compounds, and fulgides that change their optical constants in photon mode by laser irradiation energy, diarylethenes, azobenzenes, spiropyrans, stilbenes, dihydropyrenes, thioindigos, bipyridines, aziridines, Photochromic materials such as aromatic polycycles, allylidene anilines, xanthenes and the like can be mentioned, and photochromic materials capable of rewriting recording are particularly preferable. The above dyes (or pigments: may be simply referred to as dyes in the present specification) may be used alone or in combination of two or more. Furthermore, it is used in the above dyes together with stabilizers (for example, transition metal complexes), ultraviolet absorbers, dispersants, flame retardants, lubricants, antistatic agents, surfactants, plasticizers, etc., for the purpose of improving characteristics. You can also.

  Nanometer-sized metal ultrafine particles (metal nanoclusters) are usually obtained by dissolving and heating a metal compound and its reducing agent in an organic solvent. In order to improve the stability of ultrafine metal particles (metal nanoclusters), nanometer-sized ultrafine metal particles (metal nanoclusters) protective colloids obtained by coexisting low molecular weight organic compounds and polymers may be used. In the optical recording medium of the present invention, all metal ultrafine particles (metal nanoclusters) such as gold, silver, platinum, copper, tin, rhodium and iridium can be used. However, from the viewpoint of storage stability and optical properties, gold, silver, Platinum and an alloy comprising at least one of these may be used, and alloys are particularly preferred.

  One kind of the above ultrafine metal particles (metal nanocluster) may be used alone, or two or more kinds may be combined. The dot diameter of the optical recording dye is 5 nm to 500 nm, preferably 10 nm to 200 nm.

  When the microphase separation structure is a spherical structure (see FIG. 1A), the thickness of the recording layer 2 of the optical recording medium is preferably smaller than the diameter of the spherical structure. When the structure is a columnar structure (see FIG. 1B), it is preferable that the columnar structure is formed perpendicular to the recording medium surface.

The undercoat layer is 1. Improved adhesion,
2. Improve chemical stabilization by barriers such as water or gas,
3. Improved storage stability of the recording layer,
4). Improved reflectivity,
5). Protection of the substrate from solvents (or dispersants),
6). Used for the purpose of forming guide grooves, guide pits, and preformats.

  Above 1. For the purpose of improving the adhesion, a polymer material can be used. For example, various polymer compounds such as ionomer resin, polyamide resin, vinyl resin, natural resin, natural polymer, silicone, liquid rubber, silane coupling agent, and the like can be used.

In addition, 2. And 3. In addition to the above polymer materials, there are inorganic compounds such as SiO, MgF, SiO ₂ , TiO, ZnO, TiN, SiN, and metals or semimetals for the purpose of improving the chemical stabilization of For example, Zn, Cu, Ni, Cr, Ge, Se, Au, Ag, Al, or the like can be used. 4. For this purpose, metals such as Al, Au and Ag, and organic thin films having a metallic luster such as methine dyes and xanthene dyes can be mentioned. 6. For this purpose, an ultraviolet curable resin, a thermosetting resin, a thermoplastic resin, or the like can be used. The thickness of the undercoat layer is 0.01 to 30 μm, preferably 0.05 to 10 μm.

  The metal reflective layer is used when necessary according to the required reflectance. Examples of the metal reflective layer include a metal, a semi-metal, and the like that are not easily corroded to obtain high reflectivity, and examples of materials include Au, Ag, Cr, Ni, Al, Fe, Sn, etc. Au, Ag, and Al are most preferable from the viewpoint of productivity, and these metals and metalloids may be used alone or as two kinds of alloys. Examples of the film forming method include vapor deposition and sputtering, and the film thickness is 50 to 5000 mm, preferably 100 to 3000 mm.

The protective layer and the substrate surface hard coat layer are
1. Protect the recording layer (reflection absorption layer) from scratches, dust, dirt, etc.
2. Improved storage stability of the recording layer (reflection absorption layer),
3. Used for the purpose of improving reflectivity.

For these purposes, the materials shown in the undercoat layer can be used. Moreover, SiO, SiO ₂ , etc. can be used as the inorganic material, and polymethyl acrylate, polycarbonate, epoxy resin, polystyrene, polyester resin, vinyl resin, cellulose, aliphatic hydrocarbon resin, natural rubber, styrene as the organic material. Thermal softening and heat melting resins such as butadiene resin, chloroprene rubber, wax, alkyd resin, drying oil and rosin can also be used. The most preferable example among the above materials is an ultraviolet curable resin excellent in productivity. The film thickness of the protective layer or the substrate surface hard coat layer is 0.01 to 30 μm, preferably 0.05 to 10 μm.

  In the present invention, as in the case of the recording layer 2, the undercoat layer, the protective layer, and the substrate surface hard coat layer are provided with a stabilizer, a dispersant, a flame retardant, a lubricant, an antistatic agent, a surfactant, a plasticizer. An agent or the like can be contained.

[Example 1]
Living block copolymer consisting of polystyrene (PSt) with a number average molecular weight of ~ 182,000 and poly- (2-vinylpyridine) (P2VP), with a volume fraction of poly- (2-vinylpyridine) of 18 vol% Synthesized by radical method. In 2-butanone, this block copolymer (2.3 × 10 ⁻² mol / l), sodium chloroaurate dihydrate (6.8 × 10 ⁻⁴ mol / l), terephthalaldehyde (1.7 × 10 ⁻³ mol) / l), aluminum acetylacetonate (4.0 × 10 ⁻⁴ mol / l) and triphenylsilanol (1.4 × 10 ⁻² mol / l) were dissolved and heated at 70 ° C. for 10 hours. After cooling, Bis (p-dimethylaminophenyl) phenyl-4-hydroxymethylium iodide (1.1 × 10 ⁻³ mol / l) was dissolved in this solution to form a cast film on the molded substrate and annealed at 140 ° C. for 10 hours.

  The phase separation structure of the cast membrane is confirmed by TEM and AFM measurement to form a spherical structure of ~ 40 nm or less in which ultrafine gold particles and dyes are selectively dispersed in poly- (2-vinylpyridine). did.

  Next, using the above solution, a spinner coating was formed on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was ˜30 nm. The recording material was annealed for a time.

  By TEM and AFM measurement, it was confirmed that a spherical structure in which gold ultrafine particles and a dye were selectively dispersed in poly- (2-vinylpyridine) was formed as a single layer on a PMMA substrate.

[Example 2]
In Example 1, sodium chloroaurate dihydrate was changed to silver acetate, and a coating solution was prepared under the same conditions. Similarly, a spinner was applied on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was ˜30 nm, and a film was formed / annealed to obtain a recording material.

  Similarly, it was confirmed that a spherical structure in which silver ultrafine particles were selectively dispersed in poly- (2-vinylpyridine) was formed as a single layer on a PMMA substrate.

[Example 3]
Living block copolymer consisting of polystyrene (PSt) with a number average molecular weight of ~ 154,000 and poly- (4-vinylpyridine) (P4VP), with a volume fraction of poly- (2-vinylpyridine) of 16 vol% Synthesized by radical method. This block copolymer (2.6 × 10 ⁻² mol / l) and palladium acetonate (6.5 × 10 ⁻⁴ mol / l) are dissolved in a mixed solvent of benzene / n-propyl alcohol (50/50 volume%), Heated at 85 ° C. for 48 hours. After cooling, Bis (4-dimethylaminophenyl) streptomethinecyanine chloride (1.5 × 10 ⁻³ mol / l) was dissolved in this solution to form a cast film on the molded substrate and annealed at 140 ° C. for 10 hours.

  The phase separation structure of the cast membrane is confirmed by TEM and AFM measurement to form a spherical structure of ~ 30 nm or less in which palladium ultrafine particles and dye are selectively dispersed in poly- (4-vinylpyridine). did.

  Next, using the above solution, a spinner coating was formed on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was ˜25 nm. The recording material was annealed for a time.

  By TEM and AFM measurement, it was confirmed that a spherical structure in which palladium ultrafine particles and a pigment were selectively dispersed in poly- (2-vinylpyridine) was formed as a single layer on a PMMA substrate.

[Example 4]
A block copolymer comprising polyethylene glycol (PEG) having a number average molecular weight of ~ 168,000 and polymethyl methacrylate (Poly1) represented by the following chemical formula modified with azobenzene, and having a volume fraction of polyethylene glycol of 29 vol% is a living radical method. Was synthesized.

In 2-butanone, this block copolymer (1.5 × 10 ⁻² mol / l), sodium chloroaurate dihydrate (6.5 × 10 ⁻⁴ mol / l), terephthalaldehyde (1.7 × 10 ⁻³ mol) / l), aluminum acetylacetonate (3.8 × 10 ⁻⁴ mol / l), and triphenylsilanol (1.0 × 10 ⁻² mol / l) were dissolved and heated at 70 ° C. for 10 hours. After cooling, Bis (4-dimethylaminophenyl) streptopolymethinecyanine chloride (1.5 × 10 ⁻³ mol / l) was dissolved in this solution, and the film thickness after drying on a PMMA substrate surface-cured with an acrylic photopolymer was about 60 nm. A film was formed by applying a spinner under such conditions as described above, and similarly annealed at 120 ° C. for 10 hours to obtain a recording material.

  By TEM and AFM measurements, it was confirmed that a columnar structure in which gold ultrafine particles and a pigment were selectively dispersed in polyethylene glycol was formed perpendicularly to the thin film surface on a PMMA substrate.

[Examples 5 and 6]
In Example 4, sodium chloroaurate dihydrate was changed to silver acetate and chloroplatinic acid hexahydrate, and a coating solution was prepared under the same conditions. Similarly, a spinner was applied on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was ˜60 nm, and a film was formed / annealed to obtain a recording material.

  Similarly, it was confirmed that a columnar structure in which silver ultrafine particles or platinum and a pigment were selectively dispersed in polyethylene glycol was formed perpendicular to the thin film surface on a PMMA substrate.

[Comparative Example 1]
In Example 1, it consists of polystyrene (PSt) having a number average molecular weight of -182,000 and poly- (2-vinylpyridine) (P2VP), and the volume fraction of poly- (2-vinylpyridine) is 18 vol%. A coating solution was prepared under the same conditions for only the block copolymer. Similarly, a spinner was applied on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was ˜30 nm, and a film was formed / annealed to obtain a recording material. It was confirmed that the spherical structure was formed as a single layer on the PMMA substrate.

[Comparative Example 2]
In Example 4, it is composed of polyethylene glycol (PEG) having a number average molecular weight of ˜168,000 and polymethyl methacrylate (Poly1) modified with azobenzene, and only the block having a volume fraction of polyethylene oxide of 29 vol% is the same. The coating solution was adjusted under the conditions. Similarly, a spinner was applied on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was ˜60 nm, and a film was formed / annealed to obtain a recording material. It was confirmed that a columnar structure was formed on the PMMA substrate at a right angle to the thin film surface.

[Comparative Example 3]
In Example 1, it consists of polystyrene (PSt) having a number average molecular weight of -182,000 and poly- (2-vinylpyridine) (P2VP), and the volume fraction of poly- (2-vinylpyridine) is 18 vol%. The coating solution consisting of the block copolymer and sodium chloroaurate dihydrate, terephthalaldehyde, aluminum acetylacetonate, and triphenylsilanol were prepared under the same conditions. Similarly, a spinner was applied on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was ˜30 nm, and a film was formed / annealed to obtain a recording material. It was confirmed that the spherical structure was formed as a single layer on the PMMA substrate.

[Comparative Example 4]
In Example 1, it consists of polystyrene (PSt) having a number average molecular weight of -182,000 and poly- (2-vinylpyridine) (P2VP), and the volume fraction of poly- (2-vinylpyridine) is 18 vol%. A coating solution consisting of the block copolymer and Bis (p-dimethylaminophenyl) phenyl-4-hydroxymethylium iodide was prepared under the same conditions. Similarly, a spinner was applied on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was ˜30 nm, and a film was formed / annealed to obtain a recording material. It was confirmed that the spherical structure was formed as a single layer on the PMMA substrate.

On this recording medium, a semiconductor laser having oscillation wavelengths of 654 nm and 667 nm and a beam diameter of 1.0 μm was scanned 1.0 cm ^{2 in the} horizontal direction at intervals of 1.5 μm. The irradiated part and the unirradiated part were observed by TEM and AFM, and the reflectance and transmittance were measured by a microspectroscopic method.

  Under the above recording conditions, since the recording dots are several tens of nm and the recording beam diameter is 1.0 μm, a large number of recording dots are irradiated with a single laser scan. The regeneration evaluation is also a macro observation. Strictly speaking, the recording is performed in units of recording dots and is not reproduced in units of recording dots. However, recording and reproduction on the recording dots can be verified by comparison with the comparative example. Table 1 shows the evaluation results.

  It is clear from the comparison between Example and Comparative Examples 1 and 2 that the recording material of the Example can be recorded by laser, and that the recording was performed on the dye and the ultrafine metal particles present in the spherical or columnar structure. it is obvious.

  According to the comparison between the example and the comparative examples 3 and 4, the recording medium of the example containing the dye and the metal fine particles may have a higher reflectance contrast by recording than the comparative example containing the dye and the metal fine particles, respectively. it is obvious.

  From the comparison of the recording wavelength dependence of the reflectance / change due to the recording of Example 1 and Comparative Examples 3 and 4, the recording material of Example 1 containing the dye and the metal fine particles contains the dye and the metal fine particles independently. It is clear that the reflectance / change dependency on the recording wavelength is smaller than that of the comparative example.

  In this experiment, a large number of ultrafine particle dots were recorded at one time because the recording was performed using a light source with a large beam diameter (1.0 μm) compared to the ultrafine metal particle dot diameter (several tens of nanometers). Obviously, it is possible to individually record the metal ultrafine particle dots by recording with the beam diameter of.

  Since the recording signal can be reproduced as a change in transmittance, it is most preferable to control the maximum absorption wavelength of the recording layer in the vicinity of the oscillation wavelength of the recording / reproducing laser in the reproducing method using this phenomenon.

  Since the recording signal can be reproduced as a change in reflectance, it is most preferable to control the maximum refractive index of the recording layer in the vicinity of the oscillation wavelength of the recording / reproducing laser in the reproducing method using this phenomenon. In the present invention, the main component is a block copolymer that is incompatible with each other, and at least one kind of dye having an absorption capability in the vicinity of the recording / reproducing wavelength in one phase, and a metal that exhibits plasmon absorption in the vicinity of the recording / reproducing wavelength. In the present invention, the meaning of the term “main component” means that the metal ultrafine particles, which are parts having a function of recording, and the dye are present. It is only necessary to be present in one phase of the incompatible block copolymer, and the amount of the incompatible block copolymer is used in a sense including a case where it is not main.

It is a schematic diagram of the thin film of the phase-separation structure containing the metal ultrafine particle of this invention. It is sectional drawing which shows the layer structural example of the optical recording medium of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording layer 3 Reflective layer 11 Spherical structure 12 Columnar structure 13 Organic dye / metal ultrafine particle containing part

Claims (12)

  Containing a block copolymer that is incompatible with each other as a main component, one phase containing at least one dye having an absorption ability near the recording / reproducing wavelength and ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength An optical recording medium comprising an organic thin film.   The microphase-separated structure containing at least one dye having an absorption ability near the recording / reproducing wavelength and ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength is an organic thin film having a spherical structure or a columnar structure. The optical recording medium according to claim 1.   A microphase-separated structure containing at least one kind of dye having an absorption capability near the recording / reproducing wavelength and a metal ultrafine particle that expresses plasmon absorption near the recording / reproducing wavelength forms a spherical structure, which is larger than the diameter of the spherical structure. 3. The optical recording medium according to claim 1, comprising an organic thin film formed with a thin film thickness.   A microphase-separated structure containing at least one dye having an absorption capability near the recording / reproducing wavelength and a metal ultrafine particle that expresses plasmon absorption near the recording / reproducing wavelength forms a columnar structure, and the columnar structure corresponds to the thin film surface. 3. The optical recording medium according to claim 1, comprising an organic thin film formed vertically.   5. The light according to claim 1, comprising ultrafine metal particles whose particle diameter and shape are controlled so as to have a maximum absorption wavelength near the recording / reproducing wavelength, and a dye near the recording / reproducing wavelength. recoding media.   5. The metallic ultrafine particles whose particle diameter and shape are controlled so as to have a maximum refractive index in the vicinity of the recording / reproducing wavelength, and at least one dye having a maximum absorption wavelength in the vicinity of the recording / reproducing wavelength. The optical recording medium according to any one of the above.   The optical recording medium according to claim 1, wherein the ultrafine metal particles are gold, silver, platinum, or an alloy thereof.   Contains at least one kind of dye that is compatible with one phase of the microphase separation structure and has an absorption ability near the recording / reproducing wavelength, ultrafine metal particles that exhibit plasmon absorption near the recording / reproducing wavelength, and a block copolymer The method for producing an optical recording medium according to any one of claims 1 to 6, wherein a preparation liquid prepared by applying the solution is applied and annealed.   After preparing and applying a solution containing a block copolymer and forming a microphase separation structure by annealing, a dye having an absorption ability near the recording / reproducing wavelength compatible with one phase of the microstructure 7. The method for producing an optical recording medium according to claim 1, wherein at least one kind is brought into contact with a solution containing metal ultrafine particles that express plasmon absorption in the vicinity of the recording / reproducing wavelength.   After preparing and applying a solution containing a block copolymer and forming a microphase separation structure by annealing, a dye having an absorption ability near the recording / reproducing wavelength compatible with one phase of the microstructure The optical recording medium according to any one of claims 1 to 6, wherein a layer containing at least one kind and a metal ultrafine particle that expresses plasmon absorption in the vicinity of a recording / reproducing wavelength is laminated and then heated and diffused. Production method.   Irradiation with laser light changes the optical characteristics of one phase of a microphase-separated structure containing at least one dye having an absorption ability near the recording / reproducing wavelength and ultrafine metal particles that exhibit plasmon absorption near the recording / reproducing wavelength. The recording / reproducing method using the optical recording medium according to claim 1, wherein recording / reproducing is performed.   By irradiating with laser light, the shape of one phase of the microphase separation structure containing at least one kind of dye having absorption ability near the recording / reproducing wavelength and ultrafine metal particles that express plasmon absorption near the recording / reproducing wavelength is changed. 7. A recording / reproducing method using the optical recording medium according to claim 1, wherein recording / reproducing is performed.

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