JP2006172584A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium capable of performing recording and reproduction with high recording density which cannot be realized in a conventional optical recording medium and exceeds a diffraction limit of a pickup lens by applying an organic thin film formed by constructing a micro phase separation structure wherein a recording material of a nanometer size is dispersed in an organic polymer matrix, wherein tracking can be stably performed without providing any guide groove and colorful decorations which is nice to look at can be easily provided on a recording and reproducing surface. <P>SOLUTION: The optical recording medium has the organic thin film, as a recording layer, consisting essentially of a block copolymer having two or more polymer blocks which are not compatible with each other and containing the recording material having an optically recording and reproducing function in only one phase of the micro phase separation structure and a functional optical material having no optically recording and reproducing function in only another phases of the micro phase separation structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical recording medium capable of recording and reproducing at a high recording density exceeding the diffraction limit of a pickup lens.

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, at present, research and development as an optical recording medium is hardly progressed.
In the optical memory field, CD-R and DVD-R, which are optical recording media having a reflective layer on a substrate and capable of recording corresponding to the CD standard and the DVD standard, have been commercialized. In the medium, further increase in capacity and size are desired, and further improvement in recording density is demanded.
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. As technology for miniaturizing recording pits, in order to shorten the wavelength of recording / reproducing light and improve the diffraction limit, an increase in the numerical aperture NA of the optical system is being studied. However, 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 not yet been put into practical use due to the high technical hurdles. .

For example, the following patent documents 1 to 8 are known as prior art optical memories using a super-resolution mask.
That is, Patent Document 1 discloses a metal cluster composite having a particle size of 10 nm or less, which is obtained by dissolving a water-insoluble polymer, a metal compound, and a reducing agent in an organic solvent and heating. An invention related to this is disclosed.
Patent Document 2 discloses a micro phase separation structure of an incompatible block copolymer obtained by forming a phase separation structure by solvent casting or lowering the temperature. ) Is disclosed.
In Patent Document 3, two or more incompatible types obtained by forming a superfine phase separation structure by compatibilizing with a high-temperature and high-pressure fluid solvent (supercritical fluid solvent) and rapidly reducing the pressure. An invention relating to a polymer alloy having an ultrafine phase separation structure of 100 nm or less in a polymer blend is disclosed.
Patent Document 4 is obtained by starting microphase separation starting from an orientation interface, moving the phase separation structure formation region to grow grains having a uniform orientation direction, and then heating near the transition temperature. , An invention relating to a three-dimensional (single grain) anisotropic block copolymer microphase separation structure is disclosed.

In Patent Document 5, a fine pore is formed by decomposing or eluting one phase of a microphase-separated structure, and ultrafine metal particles are obtained by supporting by electroless plating or subsequent electroplating. An invention relating to a composite having fine pores in which ultrafine metal particles are supported in only one phase in a micro phase separation structure of a soluble block copolymer or polymer blend is disclosed. Here, the fine pore diameter is 10 nm to 1 μm, and the metal ultrafine particle diameter is 1 to 10 nm.
Patent Document 6 discloses that a block copolymer polymer chain having affinity and a block copolymer polymer chain having no affinity, a metal compound, and a reducing agent are dissolved, heated and reduced, and the surface of the metal fine particles is coated and protected. A phase separation structure is formed by casting or lowering the temperature, and the pores are obtained by decomposing one phase or by forming a microphase separation by adding homopolymer, oligomer or low molecule, and then elution treatment. A micro phase separation structure of a compatible block copolymer, a composite containing ultrafine metal particles (particle size of 10 nm or less) in the vicinity of the skeleton surface in one phase, and the other polymer phase is vacated. An invention relating to the composite is disclosed.

In Patent Document 7, a phase separation structure is formed by solvent casting or temperature reduction of a solution of a metal / organic polymer (Mn1) complex and a matrix polymer (Mn2) (Mn1> Mn2), and no metal fine particles are contained. An invention relating to a composite in which ultrafine metal particles are contained near the center of one phase in a microphase separation structure of an incompatible block copolymer obtained by removing a polymer phase is disclosed.
In Patent Document 8, a block copolymer polymer chain having affinity and a block copolymer polymer chain and metal ion having no affinity are dissolved in a high boiling solvent and a low boiling solvent having a reducing ability, and the low boiling solvent is removed. A micro phase separation structure of incompatible block copolymer obtained by forming a phase separation structure and reducing metal ions while removing a high boiling point solvent. An invention relating to a composite containing the above is disclosed.

However, in the above prior art, the miniaturization of dots depends on the size of the light spot, and it has been impossible to realize an optical recording medium capable of recording and reproducing at a recording density exceeding the diffraction limit of the pickup lens. .
Therefore, the present inventors are completely different from the conventional approach from the light source side, and an organic material in which nanometer-sized functional materials (metal ultrafine particles or organic dyes) are introduced into a polymer microphase separation structure to be combined. By applying a thin film to an optical recording medium and making the area of each dot of the recording dot array formed on the recording layer itself smaller than the diffraction limit of irradiation light, an ultra A density optical recording medium was proposed (Patent Documents 9 to 11).
Further, in the conventional optical disc, since the recording layer is a continuous layer, a tracking guide groove is provided on the substrate, and tracking is performed using the phase difference. In the invention of the application, the recording material exists only in one phase of the micro phase separation structure, and the other phase of the micro phase separation structure is composed only of the polymer, so that a complex refractive index difference occurs between them, and the guide groove is formed. It has a feature that tracking is possible even if it is not formed. However, in the prior invention, the tracking performance may become unstable because the complex refractive index difference is not so large.
On the other hand, in order to respond to the user's desire to decorate the optical disk in a colorful manner, the conventional optical disk has been decorated by applying various dye materials on the surface opposite to the recording / reproducing surface. However, there are problems that a new coating process is required and that the recording / reproducing surface cannot be decorated with colors other than the colors according to the recording material and the reflective layer material.

JP-A-10-251548 JP-A-10-330492 Japanese Patent Laid-Open No. 10-330493 Japanese Patent Laid-Open No. 10-330494 Japanese Patent Laid-Open No. 10-330528 Japanese Patent Laid-Open No. 11-060891 JP 2000-72951 A JP 2000-72952 A JP 2003-089269 A JP 2003-094825 A Japanese Patent Application Laid-Open No. 2004-326956

  The present invention goes beyond the diffraction limit of a pickup lens, which cannot be realized with conventional optical recording media, by applying an organic thin film in which an organic polymer matrix is constructed with a microphase-separated structure in which nanometer-sized recording materials are dispersed. An optical recording medium that enables recording and reproduction at a high recording density, can be stably tracked without a guide groove, and can be easily decorated with a colorful decoration on the recording and reproduction surface. It is an object to provide an optical recording medium that can be used.

The above problems are solved by the following inventions 1) to 13).
1) A microphase separation containing a recording material having an optical recording / reproducing function only in one phase of the microphase separation structure, the main component of which is a block copolymer having two or more polymer blocks that are incompatible with each other. An optical recording medium having an organic thin film containing a functional optical material having no optical recording / reproducing function only in another phase of the structure as a recording layer.
2) The optical recording medium according to 1), wherein the recording material comprises a dye having an ability to absorb light in the vicinity of the recording / reproducing wavelength.
3) The optical recording medium according to 2), wherein the dye is directly bonded to the block copolymer.
4) The optical recording medium according to 1), wherein the recording material comprises ultrafine metal particles (metal nanoclusters) that exhibit plasmon absorption in the vicinity of the recording / reproducing wavelength.
5) The optical recording medium according to any one of 1) to 4), wherein the phase containing the functional optical material has an antireflection function.
6) The optical recording medium according to 5), wherein an antireflection effect is given to light in the vicinity of the recording / reproducing wavelength.
7) The optical recording medium according to 6), wherein an antireflection effect is provided by using a low refractive index material as the functional optical material.
8) The optical recording medium according to 6), wherein the thickness of the organic thin film is adjusted to provide an antireflection effect by a multiple interference effect.
9) The optical recording medium according to any one of 1) to 4), wherein the phase containing the functional optical material has a coloring function.
10) The optical recording medium according to 9), wherein the functional optical material comprises a coloring material that does not absorb light in the vicinity of the recording / reproducing wavelength.
11) The optical recording medium according to 10), wherein the coloring material is a pigment.
12) The optical recording medium according to 11), wherein the dye is directly bonded to the block copolymer.
13) The optical recording medium according to 10), wherein the coloring material is metal ultrafine particles (metal nanoclusters) that do not exhibit plasmon absorption with respect to light in the vicinity of the recording / reproducing wavelength.

Hereinafter, the present invention will be described in detail.
A feature of the organic thin film of the present invention is that the recording material is nanometer-sized and highly ordered in the polymer matrix. In order to realize such a structure, the microphase separation phenomenon of the block copolymer is used. As the microphase separation structure, a spherical shape or a columnar shape can be used. A recording material having a light absorption capability near the recording / reproducing wavelength (recording / reproducing wavelength range of about ± 50 nm) has the function of changing its optical characteristics and phase difference by light or heat. By doing so, it can be used as an optical recording medium.
Further, it is preferable to maximize the difference in reflectance between the phase containing the recording material having the optical recording / reproducing function and the phase containing the functional optical material not having the optical recording / reproducing function.

The first function of the phase containing the functional optical material is an antireflection function. By providing an antireflection function, it is possible to increase the difference in reflectance from the phase containing the recording material, and it is stable only by the reflectance difference without using the phase difference due to the guide groove of the substrate as in the past. Tracking becomes possible. In order to perform tracking and recording / reproduction with a single laser pickup, it is more preferable to have an antireflection effect near the recording / reproducing wavelength of the laser used. As a method for giving an antireflection effect, a method using a low refractive index material as a functional optical material and a method for adjusting the film thickness of an organic thin film to reduce the reflectivity by a multiple interference effect are preferable. The proportion of the phase containing the recording material in the organic thin film is usually about 10 to 40% by weight, and most of the phase contains the functional optical material, so that it substantially contributes to the multiple interference effect. This is a phase containing a functional optical material. As the low refractive index material, a fluorine compound is particularly preferable as the organic material, SiO ₂ , MgF ₂ , and InP are preferable as the inorganic material, and silsesquioxane (RSiO _1.5 ) is particularly preferable as the organic / inorganic composite material.

The second function of the phase containing the functional optical material is a coloring function. By providing the coloring function, the optical recording medium can be easily decorated with any color, and coloring on the recording / reproducing surface, which has been impossible in the past, can also be performed. From the viewpoint of the tracking stability and the quality of the recording / reproducing signal, the coloring material preferably does not have the ability to absorb light in the vicinity of the recording / reproducing wavelength. As such a coloring material, a pigment or nanometer-sized ultrafine metal particles (metal nanoclusters) exhibiting plasmon absorption can be used. As the dye, the same dye as the recording dye (described later) used for the recording material can be used. However, it is designed so as not to have a light absorption ability near the recording / reproducing wavelength. As a metal nanocluster, the same thing as what is illustrated with the recording material mentioned later can be used.
Further, when a coloring material is used as the functional optical material, an antireflection function can be provided by setting the film thickness of the layer containing the coloring material to a film thickness that satisfies the non-reflection condition. However, since the reflectance of the recording layer does not always become the maximum with the film thickness, in reality, the film thickness is set so that the difference in reflectance between the two becomes the largest.

Next, the manufacturing method of the organic thin film used for this invention is demonstrated.
It has been known before this application that a block copolymer having two or more types of polymer blocks that are incompatible with each other forms a microphase separation structure by solvent casting or temperature change. This is applied to a recording medium.
That is, the first manufacturing method of the recording layer is a nanometer-sized recording material that is compatible with only one phase of the microphase separation structure, and a functionality that is compatible only with the other phase of the microphase separation structure. A solution containing an optical material and the above block copolymer is prepared, and then thinned by a spin coating method, a dipping method, or the like, and then a microphase separation structure is formed by annealing treatment, so that only one phase is recorded. And a structure containing the functional optical material only in the other phase.
In the second production method, a solution containing the block copolymer is prepared and applied by spin coating or dipping, and then a microphase separation structure is formed by annealing treatment. Contacted with a solution containing a recording material compatible only with one phase and a functional optical material compatible only with the other phase, containing the recording material only in one phase and functional only in the other phase A structure containing an optical material is formed.

In the third production method, a solution containing the block copolymer is prepared and 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 a recording material compatible only with the phase and a functional optical material compatible only with the other phase, the layer is heated and diffused to contain the recording material only in one phase and the other. A structure containing the functional optical material is formed only in this phase.
In each of the above production methods, in order to promote microphase separation, a homopolymer or other polymer constituting the block copolymer may be added, but the block copolymer is the main component. It is necessary to. Here, the main component is usually 80% by weight or more. Moreover, when using a pigment | dye as an optical material or a functional optical material, you may make this pigment | dye and a block copolymer react chemically, and you may make it couple | bond together directly.

Next, the optical recording medium of the present invention in which the organic thin film is applied as a recording layer will be described.
A recording layer (a layer in which a recording material exists) of a conventional optical recording medium is usually a continuous and almost homogeneous layer, and a laser beam is irradiated on the recording layer, and any change corresponding to the shape of the laser beam is applied to the recording material. Record by waking up. Therefore, since the size of the minimum recording pit depends on the laser beam diameter determined by the oscillation wavelength and the NA of the lens, in the conventional recording / reproducing system, the increase in the density is basically the laser oscillation wavelength or the lens NA. It has been influenced by practical technology. In addition, since the beam shape is a Gaussian distribution and there is almost no recording material that changes with a clear threshold for heat or light, the size and amount of change in the outermost periphery of the formed pits are uniform. In addition, 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 optical recording medium of the present invention is an optical recording medium having a new structure that overcomes the problems of the prior art. That is, an organic thin film having a structure in which a recording material is contained only in one phase of a microphase separation structure, the main component of which is a block copolymer having two or more types of incompatible polymer blocks. In the continuous layer of the recording layer, highly ordered recording dots exist discontinuously through the matrix, and the recording 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 size of the recording dots to be formed. Therefore, an optical recording medium having an arbitrary recording density can be designed. Become. Furthermore, since the edge of the outermost peripheral edge of the pit is determined by the structure of the organic thin film if the end of the recording dot is an edge, recording is performed so that the entire recording dot is changed. By doing so, it becomes possible to obtain high-quality signal characteristics without pit variations.

In general, the microphase-separated structure forms a spherical shape, a columnar shape, a lamellar shape, a co-continuous shape, or the like depending on its constituent materials and composition. Preferred structures applicable to the optical recording medium of the present invention are a spherical shape and a columnar shape. This is because in the optical recording medium of the present invention, as described above, the recording dots need to exist discontinuously through the matrix.
When the microphase separation structure is a spherical structure, the thickness of the recording layer is preferably thinner than the diameter of the spherical structure. By doing so, a phase-separated spherical structure is formed as a single layer, and a recording dot having an optical recording function with a uniform diameter can be formed uniformly and non-continuously on the recording medium surface through the matrix. .
However, even if the thickness of the recording layer is larger than the diameter of the spherical structure, the above structure (a structure in which recording dots having an optical recording function with a uniform diameter on the recording medium surface exist discontinuously through a matrix) Of course, it can be used if it can be controlled.
When the microphase separation structure is a columnar structure, the columnar structure is preferably a structure formed perpendicular to the organic thin film surface. As a result, as in the case of the spherical structure, it is possible to obtain a structure in which the recording dots having the optical recording function uniformly exist on the recording medium surface through the matrix.

The configuration of the optical recording medium and the necessary physical properties will be described below.
<Configuration of optical recording medium>
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), or a CD-R structure (recording layer on a substrate). , A reflective layer, a protective layer), or a DVD structure in which a CD-R structure is bonded. The basis of the layer structure is a substrate and a recording layer as shown in FIG. 2A, and a reflective layer may be provided as shown in FIGS.
"substrate"
The substrate to be used must be transparent to the laser used only when recording / reproduction is performed from the substrate side, and need not be transparent when recording / reproduction is performed from the recording layer side.
As the substrate material, for example, a polyester resin, an acrylic resin, a polyamide resin, a polycarbonate resin, a polyolefin resin, a phenol resin, an epoxy resin, a polyimide resin such as a polyimide resin, 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.

<Recording layer>
The recording layer of the present invention contains, as a main component, a block copolymer having two or more types of polymer blocks that are incompatible with each other, and contains a recording material having an optical recording / reproducing function only in one phase of the microphase separation structure. And an organic thin film containing a functional optical material having no optical recording / reproducing function only in the other phase of the microphase separation structure.
Then, recording is performed by a change caused by irradiating the recording light to the recording dots, and the change is detected and reproduced by a reproduction laser beam having a power smaller than that of the recording light. As the recording / reproducing method, recording is performed by changing the optical characteristics (absorbance, reflectance, refractive index, etc.) of the recording dots, and the recording dots are reproduced by the intensity of the changes in the optical characteristics, and the shape of the recording dots (irregularity, smoothness). And the like and recorded with changes in the optical characteristics due to scattering and phase difference due to the change in shape.

The optical characteristics of the recording layer are controlled so as to have a maximum light absorption wavelength in the vicinity of the laser wavelength when reproducing using the change in absorption characteristics (absorbance, transmittance) with respect to the recording / reproducing laser wavelength. It is preferable to control the recording / reproducing laser wavelength so as to have a maximum refractive index in the vicinity of the laser wavelength when reproducing using the change in reflectance. Usually, control is performed by selecting a recording material having such characteristics.
When the size of the recording pit is determined from the beginning as in the optical recording medium of the present invention, recording can be performed with significantly 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. However, in this recording medium in which pits have already been formed, The change can be detected even in the 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 method (anionic polymerization, living radical polymerization) polymerized from the chain end using monomers such as ethylene oxide, living polymerization (anionic polymerization) synthesized from the center of the chain, synthetic method to join the end of the terminal functional polymer (Anionic polymerization, living radical polymerization).
In general, the block copolymer used in the present invention is composed of two kinds of polymers, but three or more kinds of polymers may be combined. In this case, the phase containing the functional optical material may be all or a part of the phases except the phase containing the recording material.

Examples of the recording material include a dye having a light absorption ability near the recording / reproducing wavelength (recording dye), a metal ultrafine particle (metal nanocluster) that exhibits plasmon absorption near the recording / reproducing wavelength, and the like. These recording materials are usually dispersed and contained in the block copolymer, but in the case of a dye, they may be directly bonded to the block copolymer by a chemical reaction.
As a recording dye, for example, a polymethine dye that changes its optical constant in a heat mode (thermal decomposition or the like) by laser irradiation energy, squarylium-based, pyrylium-based, porphyrin-based, porphyrazine-based, azo-based, azomethine-based dye, etc. And its metal complex compounds, fulgides, diarylethenes, azobenzenes, spiropyrans, stilbenes, dihydropyrenes, thioindigos, bipyridines, aziridines, aromatics whose optical constants are changed in photon mode by laser irradiation energy Photochromic materials such as polycyclics, allylidene anilines, and xanthenes can be mentioned, and photochromic materials that can rewrite records are particularly preferable. The above dyes may be used alone or in combination of two or more.
Furthermore, for the purpose of improving the characteristics of the recording dye or the block copolymer directly bonded to the recording dye, a stabilizer (for example, a transition metal complex), an ultraviolet absorber, a dispersant, a flame retardant, a lubricant, a charge An inhibitor, a surfactant, a plasticizer, or the like may be added.

Metal nanoclusters are usually obtained by dissolving a metal compound and its reducing agent in an organic solvent and heating. In order to increase the stability of the metal nanocluster, a protective colloid in which an organic low molecular weight compound, a high molecular weight compound, or the like coexists may be used. Various metal nanoclusters such as gold, silver, platinum, copper, tin, rhodium and iridium can be used, but gold, silver, platinum and alloys thereof are particularly preferable from the viewpoint of storage stability and optical properties. The particle size of the metal nanocluster is usually about 1 to 20 nm. These metal nanoclusters may be used alone or in combination of two or more.
The dot diameter of the phase containing the recording material is 5 to 500 nm, preferably 10 to 200 nm.

<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), various polymer compounds such as ionomer resin, polyamide resin, vinyl resin, natural resin, natural polymer, silicone, liquid rubber, and silane coupling agent can be used. .
For the purposes of (2) and (3), besides the above polymer materials, inorganic compounds such as SiO, MgF, SiO ₂ , TiO, ZnO, TiN, SiN, Zn, Cu, Ni, Cr, Ge , Se, Au, Ag, Al, or other metals or metalloids can be used.
For the purpose of (4), an organic thin film having a metallic luster such as a metal such as Al, Au or Ag, or a methine dye or a xanthene dye can be used.
For the purposes (5) and (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.

<Reflective layer>
The reflective layer is used when necessary according to the required reflectance.
Examples of the material for the reflective layer include metals and semi-metals that are difficult to be corroded and have high reflectivity, and specific examples include Au, Ag, Cr, Ni, Al, Fe, and Sn. Au, Ag, and Al are most preferable from the viewpoints of rate and productivity. These metals and metalloids may be used alone or as an alloy of two or more.
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.

《Protective layer, hard coat layer on substrate surface》
The protective layer and the hard coat layer on the substrate surface are (1) protection from scratches, dust and dirt on the recording layer (reflection / absorption layer), (2) improvement in storage stability of the recording layer (reflection / absorption layer), (3 ) Used 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 resin, polycarbonate resin, epoxy resin, polystyrene resin, polyester resin, vinyl resin, cellulose, aliphatic hydrocarbon resin, natural rubber as the organic material. Thermal softening and heat melting resins such as styrene butadiene resin, chloroprene rubber, wax, alkyd resin, drying oil, and rosin can also be used. The most preferable among the above materials is the ultraviolet curable resin excellent in productivity exemplified in the undercoat layer.
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, the undercoat layer, the protective layer, and the substrate surface hard coat layer include a stabilizer, a dispersant, a flame retardant, a lubricant, an antistatic agent, a surfactant, and a plasticizer. Etc. can be contained.

  According to the present invention, by applying an organic thin film in which a microphase-separated structure in which a nanometer-sized recording material is dispersed is built in an organic polymer matrix, the diffraction limit of a pickup lens that cannot be realized with a conventional optical recording medium is achieved. An optical recording medium that enables recording and reproduction at a high recording density that exceeds the above, can be stably tracked without providing a guide groove, and can be easily decorated with a colorful decoration on the recording and reproduction surface. Can be provided.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited by these Examples.

Example 1
Living block copolymer having a number average molecular weight of about 182,000 consisting of polystyrene (PSt) and poly- (2-vinylpyridine) (P2VP) and having a volume fraction of poly- (2-vinylpyridine) of 18 vol% Synthesized by radical method.
On the other hand, 10 mmol of chloroauric acid and 1.0 g of a polymer pigment dispersant (Solsperse 24000: manufactured by Zeneca) were dissolved in 40 ml of acetone / pure (90/10 vol%), and then 5.0 ml of dimethylamino was dissolved. Alcohol was added and heated to prepare ultrafine gold particles.
Next, in 2-butanone, the above block copolymer, the gold ultrafine particle adjustment solution, and bis (p-dimethylaminophenyl) phenyl-4-hydroxymethyl iodide dye were added to 1/1 / 0.01 ( (Weight ratio), and this solution was spin-coated on a PMMA (polymethylmethacrylate) substrate surface-cured with an acrylic photopolymer, and annealed at 120 ° C. for 12 hours.
As a result of TEM (transmission electron microscope) and AFM (atomic force microscope) measurements, the phase separation structure of the film is due to the compatibility of the polymer part forming each block with the above gold ultrafine particles and the dye, It was confirmed that the gold ultrafine particles were selectively dispersed in PSt and the dye was selectively dispersed in P2VP, and the phase containing the dye had a spherical structure.
Since the spectral characteristics of the PSt part in which the gold ultrafine particles are dispersed and the P2VP part in which the dye is dispersed are completely different, the block copolymer / gold ultrafine particle / dye film is contained in the PSt containing the gold ultrafine particles. The recording medium is an ultra-high density optical recording medium interspersed with nanometer-order recording parts made of P2VP containing a dye.
From observation of the unirradiated part (corresponding before recording) and the irradiated part (corresponding after recording) of the laser beam (recording condition 1) with a microscope / microspectroscopy, the unirradiated part is plasmon absorption of gold ultrafine particles and electron transition of the dye A color based on the electronic transition of the pigment and a mixed color of plasmon absorption were observed in the irradiated part.

Example 2
Number consisting of polyethylene glycol (PEG) and polymethyl methacrylate modified with azobenzene (Poly1: 6- [4- (4-ethylphenyl) diazenylphenyloxy] hexylmethyl methacrylate), and the volume fraction of PEG is 29 vol% A block copolymer having an average molecular weight of about 168,000 was synthesized by the living radical method.
Subsequently, 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) are dissolved at 70 ° C. For 10 hours. After cooling, a spinner was applied on a PMMA substrate surface-cured with an acrylic photopolymer under conditions such that the film thickness after drying was about 60 nm, and annealed at 120 ° C. for 12 hours.
By TEM and AFM measurement, it was confirmed that a columnar structure of a phase in which gold ultrafine particles were selectively dispersed in PEG was formed perpendicular to the thin film surface on the PMMA substrate.
That is, the block copolymer / gold ultrafine particle film is an ultrahigh density optical recording medium in which a nanometer-order columnar recording portion made of PEG containing ultrafine gold particles is dispersed in Poly 1 modified with azobenzene. ing.

Example 3
A block copolymer composed of Poly1 modified with PEG and azobenzene as in Example 2 and having a volume fraction of Poly1 of 19 vol% and a number average molecular weight of about 168,000 was synthesized by the living radical method.
Subsequently, this block copolymer (2.6 × 10 ⁻² mol / l), bis (4-dimethylaminophenyl) streptmethine cyanine chloride dye (in a mixed solvent of benzene / n-propyl alcohol (50/50 vol%)) ( 1.5 × 10 ⁻³ mol / l) was dissolved and spinner-coated on a PMMA substrate surface-cured with an acrylic photopolymer, and annealed at 120 ° C. for 12 hours.
As a result of TEM and AFM measurement, as a phase separation structure of the membrane, a spherical structure made of Poly1 is formed in PEG in which the dye is selectively dispersed due to the compatibility between each block of the block copolymer and the dye. I confirmed.
That is, the block copolymer / dye film is an ultra-high density optical recording medium in which spherical recording parts of nanometer order made of Poly 1 are scattered in PEG decorated with a dye.
From the observation of the unirradiated part (corresponding before recording) and the irradiated part (corresponding after recording) of the laser beam (recording condition 2) with a microscope / microspectroscopy, the unirradiated part shows color based on the electron transition of Poly1 and the dye In the irradiation part, a mixed color of the color based on the electron transition of Poly1 and the color in which the pigment was changed was observed.

Example 4
1 / 0.01 (weight ratio) of the block copolymer synthesized in Example 2 and HAS-10 (ethyl silicate hydrolyzate, manufactured by Colcoat Co.) mixed with benzene / n-propyl alcohol (50/50 volume%) A PMMA substrate dissolved in a solvent and surface-cured with an acrylic photopolymer was applied with a spinner to form a film, and annealed at 120 ° C. for 24 hours.
As a phase separation structure of the membrane by TEM and AFM measurement, from the compatibility of each block of the block copolymer and HAS-10, a spherical structure of nanometer order made of Poly1 in PEG containing HAS-10 is obtained. It was confirmed that it was formed.
Due to the film thickness dependence of the reflectivity of each of the polyethylene glycol (PEG) / HAS-10 dispersion film and the Poly1 film, the difference in reflectivity between them at the same film thickness is 9% at the maximum. If the condition is such that the difference in reflectance is 9%, the non-recording portion becomes an optical recording medium having an antireflection function.

Example 5
The block copolymer synthesized in Example 1, bis (p-dimethylaminophenyl) phenyl-4-hydroxymethylium iodide dye, and a mixed solvent of pyridine / chloroform / n-propyl alcohol (30/30/40 vol%) and Hexafluoroacetylacetone was dissolved at 1 / 0.01 / 0.1 (weight ratio), spinner-coated on a PMMA substrate surface-cured with an acrylic photopolymer, and then annealed at 120 ° C. for 12 hours. .
According to the TEM and AFM measurement, the phase separation structure of the membrane was determined by the compatibility of each block of the block copolymer with the dye and the fluorine compound, so that the nano-particle made of P2VP containing the dye in PSt containing the fluorine compound was used. It was confirmed that a spherical structure of meter order was formed.
From the observation of the unirradiated part (corresponding before recording) and the irradiated part (corresponding after recording) of the laser beam (recording condition 2) by a microscope / microspectroscopy, the unirradiated part shows a color based on the electronic transition of the dye, In the irradiated area, the color of the pigment changed.
From the dependence of the reflectance on the thickness of the PSt portion in which the fluorine compound is dispersed and the P2VP portion in which the dye is dispersed, the reflectance difference between them at the same thickness is a maximum of 13%. By setting the film thickness to a condition where the reflectance difference is 13%, the non-recording portion becomes an optical recording medium having an antireflection function.

<< Comparative Example 1 >>
Only the same block copolymer as in Example 1 was dissolved in 2-butanone to prepare a coating solution. Next, a spinner was applied onto the PMMA substrate surface-cured with the same acrylic photopolymer as in Example 1, and the film was annealed at 120 ° C. for 12 hours.
TEM and AFM measurements confirmed that a nanometer-order spherical structure composed of P2VP was formed in PSt as the phase separation structure of the membrane. From observation of the unirradiated part (corresponding before recording) and the irradiated part (corresponding after recording) of the laser beam (recording condition 1) by a microscope / microspectroscopic method, no difference was observed between the unirradiated part and the irradiated part. Colors based on plasmon absorption and pigment electronic transitions were seen.

<< Comparative Example 2 >>
Only the same block copolymer as in Example 4 was used, and a coating solution was prepared using the same solvent as in Example 4. This solution was spin-coated on a PMMA substrate surface-cured with an acrylic photopolymer to form a film, and annealed at 120 ° C. for 24 hours.
By TEM and AFM measurement, it was confirmed that a nanometer-order spherical structure made of Poly 1 was formed in polyethylene glycol (PEG) as the phase separation structure of the membrane.
From the film thickness dependence of the reflectivity of each of the polyethylene glycol (PEG) film and the Poly1 film, the difference in reflectivity between them at the same film thickness was 6% at the maximum.

<< Comparative Example 3 >>
In the same mixed solvent as in Example 5, the block copolymer and bis (p-dimethylaminophenyl) phenyl-4-hydroxymethylium iodide dye used in Example 1 were dissolved at 1 / 0.01 (weight ratio). Then, a spinner was applied onto a PMMA substrate surface-cured with an acrylic photopolymer to form a film, and annealed at 120 ° C. for 12 hours.
As a result of TEM and AFM measurement, as the phase separation structure of the membrane, a spherical structure of nanometer order made of P2VP containing a dye is formed in PSt due to the compatibility between each block of the block copolymer and the dye. Confirmed that.
From the observation of the unirradiated part (corresponding before recording) and the irradiated part (corresponding after recording) of the laser beam (recording condition 2) by a microscope / microspectroscopy, the unirradiated part shows a color based on the electronic transition of the dye, In the irradiated area, the color of the pigment changed.
From the film thickness dependence of the reflectance of each of the PSt part and the P2VP part in which the pigment was dispersed, the reflectance difference between the two at the same film thickness was a maximum of 10%.

<Recording and playback conditions>
A semiconductor laser having an oscillation wavelength of 405 nm, a beam diameter of 0.7 μm (recording condition 1), and an oscillation wavelength of 654 nm and a beam diameter of 1.0 μm (recording condition 2) is placed on each optical recording medium at intervals of 1.5 μm in the horizontal direction. 1.0 cm ² scan. The irradiated part and the non-irradiated part were observed by a microscope / 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 (TEM, AFM, microspectroscopy) 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, but recording and reproduction on the recording dots can be verified by comparison with the comparative example. The comparison results are summarized below.
From the comparison between Examples 1, 3, and 5 and Comparative Examples 1 and 2, it is clear that the optical recording medium of the example can be recorded by a laser, and the dye or dye present in the spherical or columnar structure is directly used. It is clear that recording was made on the bonded block copolymer or ultrafine metal particles.
According to Examples 1, 2, and 3, it is clear that the non-recording material portion can be easily decorated with an arbitrary color, and coloring on the recording / reproducing surface, which has been impossible in the past, is also possible. It is also clear that a dye, a block copolymer directly bonded to the dye, or metal ultrafine particles are effective as the method.
From Examples 3 and 4 and Comparative Example 2, the optical recording medium of the example has a large reflectance difference between the recording material part and the other non-recording material part, and is a method of tracking as it is without providing a guide groove on the substrate. It is clear that more stable tracking is possible. It is also clear that a method using a low refractive index material and a method of adjusting the film thickness and reducing the reflectivity by the multiple interference effect are effective as the method.
In this experiment, since recording was performed with a light source having a large beam diameter (1.0 μm) compared to the recording material part diameter (several tens of nanometers), a large number of recording material parts were recorded at one time. Obviously, if the diameter is recorded, it is possible to individually record the recording material portions.

The figure explaining the organic thin film structure of the optical recording medium of this invention. (A) The figure which shows a spherical structure (sea island structure). (B) The figure which shows columnar structure. The figure which shows the layer structural example of an optical recording medium. (A) An example in which a recording layer is provided on a substrate. (B) An example in which a reflective layer is further provided on the recording layer. (C) An example in which the recording layer and the reflective layer are interchanged.

Explanation of symbols

1 Substrate 2 Recording layer 3 Reflective layer

Claims (13)

  The main component is a block copolymer having two or more kinds of polymer blocks that are incompatible with each other, and contains a recording material having an optical recording / reproducing function only in one phase of the microphase separation structure. An optical recording medium having an organic thin film containing a functional optical material having no optical recording / reproducing function only in another phase as a recording layer.   2. The optical recording medium according to claim 1, wherein the recording material comprises a dye having an ability to absorb light in the vicinity of the recording / reproducing wavelength.   The optical recording medium according to claim 2, wherein the dye is directly bonded to the block copolymer.   2. The optical recording medium according to claim 1, wherein the recording material comprises metal ultrafine particles (metal nanoclusters) that exhibit plasmon absorption near the recording / reproducing wavelength.   The optical recording medium according to claim 1, wherein the phase containing the functional optical material has an antireflection function.   6. The optical recording medium according to claim 5, wherein an antireflection effect is given to light in the vicinity of the recording / reproducing wavelength.   The optical recording medium according to claim 6, wherein an antireflection effect is provided by using a low refractive index material as the functional optical material.   The optical recording medium according to claim 6, wherein the thickness of the organic thin film is adjusted to provide an antireflection effect by a multiple interference effect.   The optical recording medium according to claim 1, wherein the phase containing the functional optical material has a coloring function.   The optical recording medium according to claim 9, wherein the functional optical material is a coloring material that does not absorb light in the vicinity of the recording / reproducing wavelength.   The optical recording medium according to claim 10, wherein the coloring material is a dye.   The optical recording medium according to claim 11, wherein the dye is directly bonded to the block copolymer. The optical recording medium according to claim 10, wherein the coloring material is metal ultrafine particles (metal nanoclusters) that do not exhibit plasmon absorption with respect to light in the vicinity of the recording / reproducing wavelength.

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