JP2010049741A - Nano structure and optical recording medium using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new nano structure formed in an arbitrary organic polymer in which metal microparticle dispersed structure of a nanometer size is highly ordered, and an optical recording medium which uses the nano structure as a recording layer. <P>SOLUTION: The nano structure has a microphase separation structure formed by a block copolymer in which immiscible polymer chains are bonded. The polymer chains which forms one separation phase of the microphase separation structure has a detachable substituent. The nano structure includes two or more types of metal microparticles in a hole formed by detachment of the substituent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nanostructure (nanometer-sized structure) and an optical recording medium using the nanostructure.

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, metal-organic composite materials using metal ultrafine particles (metal nanoclusters) as functional materials have been researched and developed. However, research and development of composite materials in which ultrafine metal particles are introduced into an arbitrary polymer while controlling the ordered structure has not yet been put into practical use.
On the other hand, in the optical memory field, recordable CD-R, DVD-R, and DVD + R corresponding to the CD standard and DVD standard, which are optical recording media having a reflective layer on a substrate, have been commercialized. In the future, in such an optical recording medium, further recording capacity and downsizing are desired, and further improvement in recording density is required.

Patent Documents 1 and 2 are known literatures that are considered to be related to the present invention and that use a microphase-separated structure (or similar technique) for an optical recording medium. Patent Document 3 discloses that a microphase separation structure is used for a magnetic recording medium. Further, there is Patent Document 4 in which metal fine particles are used as a recording material. Furthermore, there are patent documents 5 to 16 as documents related to the prior application of the present applicant. Among them, Patent Document 6 describes that the surface of one phase of the microphase separation structure is crosslinked, and Patent Document 9 contains one phase of microphase separation and contains fine metal particles in the pores. Is described.
In addition, Patent Document 17 discloses a pattern forming method of a microphase separation structure.

JP 2005-209330 A Japanese Patent No. 3229048 JP 2001-151834 A JP 2000-1049 A JP 2003-89269 A JP 2003-94825 A JP 2004-306404 A JP 2004-347978 A JP 2005-112934 A JP 2005-288809 A JP 2006-172584 A JP 2006-241278 A JP 2006-241282 A JP 2006-312253 A JP 2007-15221 A JP 2007-242188 A Japanese Patent No. 3940546

  The present invention provides a novel nanostructure in which a nanometer-sized metal fine particle dispersion structure is constructed in a highly ordered arbitrary organic polymer, and a pickup lens that cannot be realized by a conventional optical disk. It is an object of the present invention to provide an optical recording medium capable of recording / reproducing at a recording density exceeding the diffraction limit. Another object of the present invention is to provide an optical recording medium capable of recording at multiple wavelengths by using a plurality of metal fine particles.

  As a result of various studies, the present inventors have obtained the above-mentioned nanostructure by utilizing the microphase separation phenomenon of the block copolymer and incorporating two or more kinds of metal fine particles in one phase. . Furthermore, by using the nanostructure as an optical recording medium, an optical recording medium capable of recording / reproducing at multiple wavelengths with a recording density exceeding the diffraction limit of the laser pickup has been obtained. The present invention has been made based on such findings.

According to this invention, the said subject is solved by following (1)-(9).
(1) It has a microphase separation structure formed by a block copolymer in which polymer chains that are incompatible with each other are bonded, and the polymer chain forming one separated phase of the microphase separation structure can be removed. A nanostructure having a substituent and containing two or more kinds of fine metal particles in a pore formed by elimination of the substituent.
(2) The nanostructure according to (1), wherein the microphase separation structure is spherical, columnar, or each shape or a structure similar to each shape.
(3) An optical recording medium using the nanostructure according to (1) or (2) as a recording layer.
(4) The optical recording medium according to (3), wherein the recording layer is provided on a substrate.
(5) The optical recording medium as described in (3) or (4) above, wherein the plasmon absorption wavelength of the metal fine particles is in the vicinity of the wavelength of the recording / reproducing laser.
(6) The optical recording medium as described in (5) above, wherein the plasmon absorption wavelength is different for each metal fine particle.
(7) The optical recording medium as described in any one of (3) to (6) above, wherein the metal fine particles are fine particles selected from gold, silver, platinum and alloys thereof.
(8) In an optical recording medium for recording / reproducing with a light spot, the diameter of the cross-section of the spherical, columnar or similar structure of the microphase separation structure is smaller than the spot of the recording / reproducing light. The optical recording medium according to any one of (3) to (7) above.
(9) In the case of forming the nanostructure on a substrate, the nanostructure is provided on a substrate in which a groove is formed. Any one of (3) to (8) above Optical recording media.

  According to the present invention, by using nanometer-sized fine metal particles, electronic properties, conductive properties, optical properties that can be controlled and introduced into any polymer in an ordered structure can be combined. As a functional composite material that exhibits new functions such as nanostructures, and by applying this nanostructure as an optical recording medium, recording beyond the diffraction limit of a pickup lens that cannot be realized with conventional optical discs An optical recording medium capable of recording / reproducing at a density could be provided. Further, by using metal fine particles having a plurality of different absorption wavelengths, an optical recording medium that can be recorded by a plurality of recording systems can be provided. Furthermore, by applying the above-mentioned nanostructure to an optical recording medium, and making the optical recording medium into a dot array in which the area of the recording body itself is smaller than the diffraction limit of irradiation light, an ultrahigh density that could not be achieved in the past An optical recording medium could be provided.

Hereinafter, the present invention will be described in more detail.
The nanostructure of the present invention has a microphase-separated structure formed by a block copolymer in which polymer chains that are incompatible with each other are bonded, and a polymer chain that forms one separated phase of the microphase-separated structure Has a detachable substituent, and two or more kinds of metal fine particles are contained in the pores formed by the elimination of the substituent. That is, the nanostructure has a microphase separation structure formed by a block copolymer in which polymer chains that are incompatible with each other are bonded, and forms one separated phase of the microphase separation structure. At first, a detachable substituent is bonded to the polymer chain, and after forming a thin film, the substituent is eliminated to form a void, and two or more kinds of metal fine particles are contained in the void. Consists of structure. In addition, it is preferable that a substituent is a thing remove | eliminated by an acid catalyst.

A feature of this nanostructure is that a plurality of metal fine particles are nanometer-sized and highly ordered and contained in the pores of the polymer matrix. The micro phase separation phenomenon of the block copolymer is used as a driving force in the formation of the ordered nanometer size structure. As used herein, ordering means that the distances (periods) and sizes of the holes are uniform.
According to the method of the present invention, the initial film formation can be performed from a solution of a block copolymer. Therefore, the film can be formed using a simple method such as a spin coating method, a casting method, or a blade coating method. Further, removal of a part of the separated phase thereafter may be performed only by heating. As a result, when forming a nanostructured material with ordered vacancies, it is not necessary to use complicated and costly techniques such as multi-step reaction, solvent immersion, and etching.

  As the microphase separation structure, a spherical structure, a columnar structure, or a similar structure can be used. FIG. 1 shows a schematic diagram of a typical microphase separation structure of one separated phase containing metal fine particles in the present invention. When the structure is used, the pore portion has a spherical shape, a columnar shape, or a structure similar to each shape, and an ordered structure can be obtained. When a diblock copolymer having two components as a block copolymer is used, four types of structures, spherical (a), columnar (b), lamellar, and co-continuous, can be made. When a block copolymer having three or more types of components is used, the types of structures expand almost infinitely (a structure in which three types of components are regularly arranged (c), a structure having two types of spherical portions (d )etc). In addition, in order to control the structure, other polymers (including block copolymers and the like) and low molecules may be mixed.

  In this way, vacancies are formed in one of the separated phases, nanometer-sized metal fine particles are introduced into the vacancies, and the structure is electronically and electrically conductive by highly controlling the structure in three dimensions. In addition, nanostructures that exhibit new functions such as optical properties can be produced. In the case where the nanostructure is applied to an optical recording medium, it is preferable that the metal fine particles have a function of changing the optical characteristics by light or heat.

  In the nanostructure of the present invention, the leaving group bonded to the polymer chain forming one of the separated phases of the microphase-separated structure is preferably vaporized after being removed, and the boiling point thereof is Tg of the block copolymer (glass (Transition point) or less is preferable. In the present invention, after the microphase separation structure is formed, it is necessary to further heat in order to advance the acid-catalyzed reaction. In this case, in order not to destroy the microphase separation structure, the Tg of the block copolymer ( This is because heating for a short time is preferable. Furthermore, when the desorbed substituent is vaporized, vacancies are formed in the microcopolymerized block copolymer, and metal fine particles can be efficiently embedded in the vacancies.

  Preferable examples of the detachable substituent include groups represented by the following [Chemical Formula 1] and [Chemical Formula 2].

The block copolymer in the present invention can be synthesized by combining polymers that are incompatible with each other. It may be a combination of two or more polymers.
Examples of the method for synthesizing the block copolymer used in the present invention include styrene, isoprene, α-methylstyrene, chloromethylstyrene, 2 vinylpyridine, aminostyrene, 4-vinylpyridine, methacrylates, ε-caprolactone, butadiene, Incompatible with each other obtained by using various monomers such as vinyl methyl ether, 1,3-cyclohexanediene, ethylene oxide, vinylphenol protected by a substituent removable by an acid catalyst, acrylic acid, and methacrylic acid. Living polymerization method (anionic polymerization, living radical polymerization) that polymerizes from the end of the polymer chain, or living polymerization (anionic polymerization) that is synthesized from the center of the chain, or a synthetic method that bonds the end of the terminal functional polymer (anionic polymerization, Such as living radical polymerization) It can be synthesized by the method.
For example, by a living radical polymerization method, a block copolymer of polystyrene having a substituent that is eliminated by an acid catalyst and polymethyl methacrylate, or polystyrene and polymethacrylic acid having a substituent that is eliminated by an acid catalyst. A block copolymer can be synthesized.

The acid catalyst preferably used in the present invention is one that can remove a substituent bonded to a desired polymer chain, does not inhibit pore formation, and does not destroy the microphase separation structure. It can be used without any particular restrictions. As such an acid catalyst, an acid compound or a compound that generates an acid compound by photoirradiation or heating (a photoacid generator or a thermal acid generator) can be used.
As the acid compound, for example, a known compound such as p-toluenesulfonic acid can be used. Moreover, as a compound which generate | occur | produces an acid compound, all can use well-known compounds, such as sulfonium compounds, such as a triphenylsulfonium triflate, iodonium compounds, such as a diphenyl iodonium triflate, and a nitrobenzyl ester compound, for example.
The acid catalyst is appropriately selected according to the object to be applied, the manufacturing process of the nanostructure applied to the target, and the like.

  The nanometer-sized metal fine particles (metal nanoclusters) used in the nanostructure of the present invention are usually obtained by dissolving and heating a metal compound and its reducing agent in an organic solvent. As the metal fine particles of the present invention, those protected by a dispersion stabilizer can also be used. In order to obtain metal fine particles protected by a dispersion stabilizer, for example, the metal compound and its reducing agent are dissolved in an organic solvent, and after adding the dispersion stabilizer, heat treatment (heating) is performed. The organic solvent is not particularly limited as long as it dissolves the metal compound and does not inhibit the reduction, and any organic solvent can be used. Moreover, as a reducing agent of a metal compound, what is generally used, such as an alkali metal borohydride salt, a hydrazine compound, a citric acid and its salt, a succinic acid and its salt, amines, can be used, for example.

  As the dispersion stabilizer, a polymer compound containing nitrogen in the main chain that is adsorbed on the metal fine particles at a multipoint is preferable. Moreover, in order to disperse | distribute uniformly in a solvent, it is preferable to have a substituent which becomes affinity with a solvent high in a side chain.

  For the nanostructure of the present invention, gold, silver, platinum, copper, tin, rhodium, iridium, etc. can be used. From the viewpoint of storage stability and optical properties, dispersion stabilization of gold, silver, platinum and their alloys is possible. Particularly preferred are metal fine particles protected with an agent.

The diameter of the metal fine particles is 5 nm to 500 nm, preferably 10 nm to 200 nm. The shape of the fine particles can be various, such as a spherical shape or a rod shape. Moreover, what shows the absorption derived from a plasmon is preferable.
In the present invention, two or more kinds of metal fine particles are used. By using a plurality of metal fine particles having different absorption wavelengths, it is possible to perform recording with a plurality of recording lights, that is, a plurality of systems.

Next, an optical recording medium in which the nanostructure is applied as a recording material (recording layer) will be described.
A conventional optical recording medium includes a recording layer composed of a continuous recording material (a layer in which the recording material exists). The recording layer is irradiated with a laser beam, and some change corresponding to the shape of the laser beam ( (Physical and chemical changes accompanying optical changes) are formed on the recording material and recorded. Therefore, since the size of the minimum recording pit depends on the laser beam diameter determined by the oscillation wavelength of the optical system and the NA of the lens, in the conventional recording / reproducing system, the increase in density is basically the laser oscillation wavelength or lens. Has been influenced by the practical technology of NA.
Also, because 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 and change of the outermost circumference of the pits formed The amount 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.

On the other hand, the optical recording medium of the present invention is an optical recording medium having a new structure that overcomes the problems of the conventional optical recording medium. That is, in the optical recording medium to which the nanostructure of the present invention is applied, the nanometer-sized recording layer dots formed by the metal fine particles are highly ordered through the matrix in the continuous layer and are discontinuously present. Structure. The size of the recording layer dots is 10 to 500 nm and is formed uniformly.
Therefore, by using such a nanometer-sized recording layer dot formed in advance, the minimum recording pit size is determined only by the recording layer dot to be formed without being determined by the laser oscillation wavelength or lens NA. Therefore, a recording medium having an arbitrary recording density can be designed. In addition, since the outermost edge of the recording pit is also determined by the structure of this nanostructure, high quality signal characteristics with no pit variation can be achieved by recording the entire recording layer dot. Can be obtained.

  Next, the configuration of the optical recording medium of the present invention and the necessary physical properties thereof will be described below.

<Recording medium configuration>
The optical recording medium of the present invention is provided with a recording layer composed of the nanostructure on a substrate, but if necessary, as a constituent layer, an undercoat layer, a metal reflective layer, a protective layer, a substrate surface hard coat layer, etc. The form of the constituent layer is selected according to the purpose and required characteristics. The optical recording medium of the present invention will be described with reference to the drawings.
The optical recording medium of the present invention has a configuration such as the example shown in the schematic cross-sectional views of FIGS. 2 (a) to 2 (d) and FIGS. 3 (a) to 3 (e). That is, in the case of FIGS. 2A to 2D, an example is shown in which a metal reflective layer is not provided on the substrate. 3A to 3E show examples in which a metal reflective layer is provided.
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 are provided on a substrate) and a CD-R structure (recording on a substrate). Providing a layer, a reflective layer, and a protective layer), or a DVD structure in which a CD-R structure is bonded. The above configuration is an example for describing the embodiment, and other configurations may be used.
Hereinafter, each constituent layer of the optical recording medium will be described.

<substrate>
The substrate used for the optical recording medium of the present invention must be transparent to the laser used only when recording / reproducing is performed from the substrate side, and when recording / reproducing is performed from the recording layer side (opposite side of the substrate). The substrate need not be transparent.
As the substrate material, for example, plastic such as polyester, acrylic resin, polyamide, polycarbonate resin, polyolefin resin, phenol resin, epoxy resin, polyimide, glass, ceramic, or metal 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.

<Recording layer>
The recording layer is capable of causing some kind of change (change in optical characteristics or change in shape) by irradiation with laser light, recording information by the change, and optically reproducing the recording layer. The polymer chain that forms one separated phase of the microphase-separated structure is removable, with a microphase-separated structure formed by a block copolymer in which polymer chains that are incompatible with each other are bonded. And a plurality of fine metal particles are contained in the vacancies formed by the elimination of the substituent.
Here, as the metal ultrafine particles, it is more preferable to use metal ultrafine particles exhibiting plasmon absorption. When the metal ultrafine particles are irradiated with light, free electrons in the metal are polarized by the photoelectric field, and electric charges are generated on the surface of the metal ultrafine particles to cause nonlinear polarization. Thus, specific absorption based on a coloring mechanism called plasmon absorption caused by electron plasma vibration is exhibited (the absorption characteristics depend on the type, particle size, shape, etc. of the metal). By using such metal ultrafine particles, for example, the light absorption wavelength of the optical recording medium can be controlled, and effective recording and reproduction can be achieved. For this reason, it is preferable to control the wavelength of each metal fine particle so that plasmon absorption is exhibited in the vicinity of the recording / reproducing laser wavelength.
In addition, in the optical recording medium of the present invention in which recording / reproduction is performed with a light spot, the diameter of the cross-section of the spherical, columnar or similar structure of the microphase separation structure is set smaller than that of the recording / reproducing light spot By doing so, reliable recording and reproduction can be performed.

<Underlayer>
The undercoat layer consists of (1) improved adhesion, (2) a barrier such as water or gas, (3) improved storage stability of the recording layer, (4) improved reflectance, and (5) a substrate from a solvent. And (6) formation of guide grooves, guide pits, and preformats.
For the purpose of (1), polymer materials such as ionomer resins, polyamide resins, vinyl resins, natural resins, natural polymers, silicones, various polymer compounds such as liquid rubber, and silane coupling agents Can be used. For the purpose of (2) or (3), there are inorganic compounds other than the above polymer materials, for example, SiO, MgF, SiO ₂ , TiO, ZnO, TiN, SiN, etc., and further metals or semimetals, Zn, Cu, Ni, Cr, Ge, Se, Au, Ag, Al, or the like can be used. For the purpose of (4), metals such as Al, Au, and Ag, and organic thin films having metallic luster such as methine dyes and xanthene dyes can be used. For the purpose of (5) or (6), 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.

<Metal reflective layer>
The metal reflective layer is provided when necessary according to the required reflectance.
As the reflective layer material, a metal or semimetal that is highly corrosive and is not easily corroded is used. Examples of such materials include Au, Ag, Cr, Ni, Al, Fe, Sn, and the like. It is done. Among these materials, Au, Ag, and Al are most preferable from the viewpoint of reflectance and productivity. These metals and metalloids may be used alone or as two kinds of alloys.
Examples of the method for forming the reflective layer include, but are not limited to, vapor deposition and sputtering.
The thickness of the reflective layer is preferably from 50 to 5000 mm, more preferably from 100 to 3000 mm.

<Protective layer, hard coat layer on substrate surface>
The protective layer and the hard coat layer on the substrate surface are (1) protecting the recording layer (reflection / absorption layer) from scratches, dust, dirt, etc. (2) improving the storage stability of the recording layer (reflection / absorption layer), (3 ) It is provided for the purpose of improving the reflectance. For these purposes, the materials shown in the undercoat layer can be used.
In addition, SiO, SiO ₂ or the like 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 butadiene as the organic material. Thermosoftening and heat melting resins such as resins, chloroprene rubber, waxes, alkyd resins, drying oils and rosins 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, the undercoat layer, the protective layer, and the substrate surface hard coat layer have the same stabilizers, dispersants, flame retardants, lubricants, antistatic agents, surfactants, plasticizers, etc. as in the recording layer. Can be contained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

Examples 1 and 2
It is composed of poly (p-tert-butoxycarbonyloxystyrene) (PBOCST) and polymethyl methacrylate (PMMA), and the volume fractions of PBOCST are 16 vol% (Example 1) and 33 vol% (Example 2), respectively. A block copolymer having a molecular weight of about 50,000 was synthesized by the living radical method.
These copolymers were dissolved in cyclohexanone to form a cast film on mica. Furthermore, when this cast film was heat-treated at 140 ° C. for 8 hours, the phase separation structure was measured by SAXS (small angle X-ray scattering) measurement and TEM (transmission electron microscope) observation, each having a spherical structure of several tens of nm or less (implemented). Example 1) and a columnar structure (Example 2) were confirmed.
Next, the cast film thus prepared was dipped in a 1 wt% isopropyl alcohol solution of p-toluenesulfonic acid, then pulled up, and heat-treated at 90 ° C. for 5 minutes. When the cast film was observed with an AFM (atomic force microscope), it was confirmed that the original PBOCST had a hole. This hole was generated by the removal of the p-tert-butoxycarbonyl group of PBOCST and the change to poly-p-hydroxystyrene (PHS).
Further, an ethanol solution containing gold fine particles having a maximum absorption wavelength of 600 nm and silver fine particles having a wavelength of 420 nm was dropped onto these films and dried. By TEM observation of the surface layer of these structures, it was confirmed that the metal fine particles were segregated in the PHS portion.

Example 3
A block copolymer composed of polystyrene (PSt) and poly tert-butyl methacrylate (PtBMA) and having a PtBMA volume fraction of 28 vol% and a number average molecular weight of about 70,000 was synthesized by the living radical method.
This copolymer and triphenylsulfonium triflate were dissolved in cyclohexanone at a weight ratio of 100: 3 to form a cast film on mica. Furthermore, when this cast film was heat-treated at 140 ° C. for 10 hours, the phase separation structure of this cast film was confirmed to be a columnar structure of several tens of nm or less by SAXS measurement and TEM observation.
Next, the cast film was irradiated with light, then heated at 100 ° C. for 3 minutes, and AFM observation was performed. As a result, it was confirmed that the original PtBMA portion had a hole. This hole is caused by the removal of the tert-butyl group of PtBMA and the change to polymethacrylic acid (PMAA).
Further, this film was dipped in an ethanol solution containing gold fine particles each having a maximum absorption wavelength of 600 nm and silver fine particles having 420 nm, and was dried. By TEM observation of the surface layer of this structure, it was confirmed that the metal fine particles were segregated into a columnar structure (PMAA portion).

Example 4
In Example 3, a structure was formed in the same manner as in Example 3 except that gold fine particles (nanorods) having a maximum absorption wavelength of 780 nm were used instead of silver fine particles. By TEM observation of the surface layer of this structure, it was confirmed that the metal fine particles were segregated into a columnar structure (PMAA portion).

[Comparative Example 1]
In Example 3, when p-toluenesulfonic acid was used instead of triphenylsulfonium triflate, columnar structures were confirmed, but no pores were confirmed.

From the results of Examples 1 to 4, a thin film in which a nanometer-sized spherical and columnar metal fine particle dispersed structure was constructed in an organic polymer could be produced. New electronic properties, conductive properties, and optical properties are expected from the functions of the metal fine particles and the highly ordered structure.
On the other hand, in Comparative Example 1, no pores were confirmed, but this was because the leaving groups also came off together when heating to build a microphase separation structure, and for this reason, PST and PMAA from the beginning. This is probably because block copolymerization has occurred (the gap is filled).

Example 5
The cyclohexanone solution of the block copolymer synthesized in Example 3 was spin-coated on a 1 mm thick, 5 cm square quartz substrate. However, the spin coating stopped rotating when the solvent spread evenly. Thereafter, it was dried and further subjected to a heat treatment at 130 ° C. for 5 hours. After confirming that the phase separation structure of the organic thin film thus obtained was a lamella structure by TEM observation, a 1 wt% methanol solution of p-toluenesulfonic acid was added dropwise and heated at 100 ° C. for 3 minutes. Further, as in Example 3, it was immersed in a mixed solution of gold fine particles and silver fine particles, and the gold fine particles and the silver fine particles were embedded in a lamellar structure made of PMAA to obtain an optical recording medium.
On this optical recording medium, a semiconductor laser having an oscillation wavelength of 650 nm and a beam diameter of 1 μm was scanned 1.0 cm ² at 1.5 μm intervals in the horizontal direction. Further, a semiconductor laser having an oscillation wavelength of 405 nm was scanned in the same manner so as to partially overlap. The irradiated part and the unirradiated part were observed with a TEM, an optical microscope, and the reflectance and transmittance were measured by a microspectroscopic method. The evaluation results of observation and measurement are shown in Table 1.

[Comparative Example 2]
An optical recording medium was formed and recorded in the same manner as in Example 5 except that it was not immersed in a mixed solution of gold fine particles and silver fine particles. The observation and measurement evaluation results are shown in Table 1.

It was also revealed that the cast film of Example 5 was recordable with a laser. From the evaluation results of Comparative Example 2, it is clear that recording was performed on the metal fine particles embedded in PMMA.
In this experiment, since a large beam diameter (1 μm) was recorded with a light source having a large beam diameter (several tens of nanometers), a large number of metal fine particle dots were recorded at one time. It is clear that the metal fine particle dots can be individually recorded by recording.
Since the recording signal can be reproduced as a change in transmittance and a change in reflectance, in the reproduction method using this phenomenon, it is most preferable to control the plasmon absorption wavelength of the metal fine particles in the vicinity of the oscillation wavelength of the recording / reproducing laser. preferable.

It is a schematic diagram which shows a micro phase-separation structure, (a) is a spherical structure, (b) is a columnar structure, (c) is an example when it consists of three types of components, (d) consists of three types of components Another example of the case. (A)-(d) is a figure which shows the layer structure (no metal reflection layer) of the optical recording medium of this invention. (A)-(d) is a figure which shows the layer structure (with a metal reflective layer) of the optical recording medium of this invention.

Explanation of symbols

1 Substrate 2 Recording layer 3 Undercoat layer 4 Protective layer 5 Substrate surface hard coat layer 6 Metal reflective layer

Claims (9)

  It has a micro phase separation structure formed by a block copolymer in which polymer chains that are incompatible with each other are bonded, and the polymer chain forming one separated phase of the micro phase separation structure has a detachable substituent. And a nanostructure comprising two or more kinds of metal fine particles in a pore formed by elimination of the substituent. 2. The nanostructure according to claim 1, wherein the microphase separation structure is spherical, columnar, or each shape or a structure similar to each shape.   An optical recording medium using the nanostructure according to claim 1 as a recording layer.   The optical recording medium according to claim 3, wherein the recording layer is provided on a substrate.   5. The optical recording medium according to claim 3, wherein a plasmon absorption wavelength of the metal fine particle is in the vicinity of a wavelength of a recording / reproducing laser.   The optical recording medium according to claim 5, wherein the plasmon absorption wavelength is different for each metal fine particle.   7. The optical recording medium according to claim 3, wherein the metal fine particles are fine particles selected from gold, silver, platinum or an alloy thereof.   The optical recording medium for recording and reproducing with a light spot is characterized in that the microphase-separated structure has a spherical, columnar shape or a cross-sectional diameter similar to each of the shapes smaller than the spot of the recording / reproducing light. The optical recording medium according to 3 to 7.   8. The optical recording medium according to claim 3, wherein when the nanostructure is formed on a substrate, the nanostructure is provided on a groove formed on the substrate.

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