JP2008130102A - Multiphoton absorption functional material, optical recording medium using the same, optical control element, and optical modeling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance multiphoton absorption efficiency of a multiphoton absorption organic material by three-dimensionally utilizing a localized plasmon enhanced field generated by metal fine particles and to provide a functional device utilizing the same and having excellent sensitivity characteristics. <P>SOLUTION: A multiphoton absorption functional material is a bulk body wherein fine particles of metal generating an enhanced surface plasmon field on a metal surface or the fine particles at least partly coated with the metal are dispersed in a multiphoton absorption material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multiphoton absorption functional material, an optical recording medium to which the multiphoton absorption functional material is applied, an optical limiting element, and an optical modeling system.

When a two-photon absorption reaction, which is one of the multiphoton absorption processes, is used, the reaction is caused by absorption proportional to the square of the excitation light intensity, which is a characteristic of the two-photon absorption reaction. It is known that reactions can only occur at light spots.
In other words, it is possible to cause a reaction only at an arbitrary desired position inside the substance, and furthermore, it is possible to cause a photoreaction only at a portion where the light intensity is high at the center of the focused spot. Expectations for processing records exceeding the limits are increasing.

However, the absorption cross section of the multiphoton absorption reaction represented by the two-photon absorption reaction is extremely small, and it is indispensable to carry out excitation with an expensive and large-sized pulsed laser light source such as a femtosecond laser. It is said that.
Because of these problems, the high-sensitivity that can induce the reaction with a semiconductor laser, for example, does not require the large-sized pulse laser in order to promote the application utilizing the excellent characteristics of the multiphoton absorption reaction. Development of new multiphoton absorbing materials is essential.

On the other hand, as a sensitization method for a one-photon absorption process based on an optical principle, a method for optical evaluation and measurement of a very small amount of substance using a surface plasmon enhancement field excited on a metal surface is known.
For example, when a surface plasmon microscope is applied, an ultrathin film disposed on a metal thin film formed on a high refractive index medium (the surface plasmon enhancement field is generated only in a limited region of about 100 nm or less from the surface. Has been proposed (for example, see Patent Document 1 below).

Conventionally, a technical proposal has been made on a measurement method using a surface plasmon enhancement field excited by metal fine particles.
This technique is similar to the technique disclosed in Patent Document 1 below, and the observation measurement area is limited to an area of 100 nm or less around the metal fine particle, and high-sensitivity observation is performed by observing the sample adsorbed on the particle surface. Is what you do.
Further, as a technique for selecting a wavelength to be applied to observation, a technique for tuning a resonance wavelength by a spherical core cell structure is known (for example, see Patent Document 2 below).
Furthermore, a high-sensitivity observation method including a multiphoton process is disclosed by using aggregated nanoparticles arranged in a microcavity (see, for example, Patent Document 3 below).

On the other hand, in recent years, research has been conducted on a technique using gold nanorods as means for generating a surface plasmon enhancement field instead of the metal fine particles as described above.
The gold nanorod has a characteristic that the resonance wavelength can be changed by changing the aspect ratio, and is a material capable of covering from about 540 nm to the near infrared (about 1100 nm).
As an example of the manufacturing method of this gold nanorod, the method of producing by the electrochemical reaction in the solution containing surfactant is disclosed (for example, refer the following patent document 4).

JP 2004-156911 A JP 2001-513198 A JP 2004-530867 A JP 2005-68447 A

  However, in the technique disclosed in Patent Document 1, regarding the enhancement effect on the thin film, the sample is limited to an extremely thin film on the metal thin film, and the region where the surface plasmon enhancement effect can be used is the metal thin film. Therefore, there is a problem that it is difficult to apply to an application such as three-dimensional processing.

In addition, the technique disclosed in Patent Document 2 uses a surface plasmon enhancement field generated around the particles, such as metal fine particles, but compared with the technique disclosed in Patent Document 1, The degree of freedom on the shape of the enhancement field generation is increasing.
However, this technique enables highly sensitive reaction and detection by distributing particles that generate a surface plasmon enhancement field on the object surface by interaction with the object surface. Has the problem of being constrained.

  Further, in the technique disclosed in Patent Document 3, aggregated nanoparticles, which are means for generating a surface plasmon enhancement field, are arranged in a microspace called a microcavity, and the enhancement field is still limited. have.

  Further, regarding the technique disclosed in Patent Document 4, the surface plasmon enhancement field generating means capable of tuning the wavelength has improved the degree of freedom in selecting the excitation wavelength, but the arrangement of the excitation source and the reactant is not limited. Have issues about.

  Accordingly, in the present invention, in view of the above-mentioned problems of the prior art, a bulk material is used as a sensitizing means for a multiphoton absorption reaction using a surface plasmon enhancement field, and a multiphoton absorption functional material having a wide application range is provided. It was decided.

  In the invention of claim 1, the metal fine particles that generate the surface plasmon enhancement field generated on the metal surface or the fine particles at least partially coated with the metal are dispersed in the multiphoton absorption material. Provided is a multiphoton absorption functional material made of a characteristic bulk type material.

  According to the second aspect of the present invention, there is provided the multiphoton absorption functional material according to the first aspect, wherein the multiphoton absorption functional material is formed as at least one film.

  The invention of claim 3 is characterized in that the multiphoton absorption functional material formed as a film of two or more layers is separated by an intermediate layer having no multiphoton absorption ability. A photon absorption functional material is provided.

  The multiphoton absorption functional material according to claim 2 or 3, wherein the multiphoton absorption functional material formed as a film having two or more layers has substantially the same multiphoton absorption sensitivity in each layer. I will provide a.

  In the invention of claim 5, the metal fine particles that generate a surface plasmon enhancement field of each layer of the multiphoton absorption functional material formed as a film of two or more layers, or fine particles at least partially coated with the metal The multiphoton absorption functional material according to claim 2 or 3, wherein the concentration is set separately by the layer.

  The invention according to claim 6 is characterized in that the metal fine particles that generate the surface plasmon enhancement field or the fine particles at least partially coated with the metal are gold nanorods. A multiphoton absorption functional material according to one item is provided.

  The invention according to claim 7 is characterized in that the metal fine particles that generate the surface plasmon enhancement field, or the fine particles at least partially coated with the metal are aggregate nanoparticles. The multiphoton absorption functional material according to any one of the items is provided.

  According to an eighth aspect of the present invention, there is provided a three-dimensional recording / reproducing operation in the depth direction with respect to incident light perpendicular to the layer plane, using the multiphoton absorption functional material according to any one of the first to seventh aspects. A recording medium is provided.

  According to a ninth aspect of the present invention, there is provided an optical limiting element comprising the multiphoton absorption functional material according to any one of the first to seventh aspects.

  In invention of Claim 10, the optical modeling system characterized by using the multiphoton absorption functional material of any one of Claims 1 thru | or 7 is provided.

  According to the present invention, the metal fine particles that generate the surface plasmon enhancement field or the fine particles that are at least partially coated with the metal are dispersed in the multiphoton absorption material, so that the light that is stronger than the irradiation light intensity is irradiated. As a result, a significant multiphoton photoexcitation sensitization effect can be obtained in the entire material without changing the irradiation light intensity.

  Moreover, the loss due to scattering of excitation light was reduced and avoided by using metal fine particles or the like that generate the surface plasmon enhancement field as ultrafine particles of nanometer order.

According to the second and third aspects of the present invention, the reaction site can be specified in the two-dimensional plane by forming the film.
In particular, when this is a multi-layer structure, it becomes easy to design the amount of absorption by fine particles that generate a surface plasmon enhancement field together with the accuracy of a three-dimensional periodic structure or a recording part of three-dimensional recording, and efficient sensitization is achieved. It has become possible.

  According to the inventions of claims 4 and 5, in the multi-layered material, a desired function can be expressed at a desired location inside the substance by setting the two-photon absorption sensitivity of each layer substantially equal. Thus, a functional material having both the advantages of photon absorption reaction and high sensitivity was obtained.

According to the invention of claim 6, by applying the gold nanorod, fine particles having a diameter of 20 nm or less having a uniform aspect ratio can be obtained with good reproducibility, and has both a wide wavelength selectivity and high enhancement, and Efficient sensitization with low scattering loss is possible.
By changing the aspect ratio, it is possible to easily cover the visible light region to the near-infrared region, thereby enabling more efficient sensitization according to the absorption wavelength of a wide range of multiphoton dyes.

  According to the invention of claim 7, by adopting aggregate nanoparticles as the fine particles for generating the surface plasmon enhancement field, further promoting the reaction of the further enhancement field of plasmon generated in the gap between the nanoparticles constituting the aggregate. Therefore, a functional material with higher sensitivity was obtained.

  Further, according to the inventions of claims 8 to 10, a highly sensitive multiphoton absorption reaction process enables a reaction without using an expensive high-power pulse laser, and makes use of the features of multiphoton absorption. A three-dimensional recording medium capable of multiple recording (Claim 8), a light limiting element (Claim 9) that limits the amount of transmitted light by increasing the amount of absorption as the irradiation intensity increases, Cost reduction (claim 10) of the three-dimensional structure can be realized.

In the present invention, a metal particle that generates a surface plasmon enhancement field generated on a metal surface, or a particle that is at least partially coated with the metal is dispersed in a multiphoton absorbing material, and has a high sensitivity. A multiphoton absorption functional material is provided.
In addition, it may be dispersed in a solvent, in a solid form dispersed in a resin, etc., or in a state dispersed in an uncured resin, or dispersed in a highly viscous resin by gel or partial curing. In this state, it is possible to select the mode according to the application.
Hereinafter, the multiphoton absorption functional material of the present invention will be specifically described.

First, the application of the two-photon absorption material will be described.
In recent years, networks such as the Internet and high-definition TVs are rapidly spreading.
Considering HDTV (High Definition Television), there is an increasing demand for a large-capacity recording medium for easily and inexpensively recording image information of 50 GB or more, preferably 100 GB or more for consumer use.
Further, in business applications such as computer backup applications and broadcast backup applications, there is a demand for optical recording media capable of recording large-capacity information of about 1 TB or more at high speed and at low cost.
Conventionally known two-dimensional optical recording media such as DVD ± R are about 25 GB at most even if the recording / reproducing wavelength is shortened, and there is a concern that it will not be able to sufficiently meet the demand for future large capacity. ing.

Under the present situation as described above, a three-dimensional optical recording medium has attracted attention as a high-density, high-capacity recording medium.
A three-dimensional optical recording medium has a structure in which dozens or hundreds of recording layers are laminated in a three-dimensional (film thickness) direction.
Further, the recording layer may be a thick film so that recording and reproduction can be performed multiple times in the light incident direction.
As described above, the three-dimensional optical recording medium can achieve ultra-high density and ultra-high capacity recording that is tens to hundreds of times that of the conventional two-dimensional recording medium.

  The three-dimensional optical recording medium as described above can access and write at an arbitrary place in the three-dimensional (film thickness) direction. As a means for that, a method using a two-photon absorption material and a holography (interference) ) Is considered.

  First, a three-dimensional optical recording medium using a two-photon absorption material as the first means is capable of bit recording over tens to hundreds of times based on the physical principle, and can be used for high density recording. It is excellent.

  Regarding a three-dimensional optical recording medium using a two-photon absorption material, a method of reading with fluorescence using a fluorescent substance for recording / reproduction (Levic, Eugene, Polis et al., JP-T-2001-524245, Pavel, Eugen et al. Table 2000-512061), a method of reading by absorption or fluorescence using a photochromic compound (Korotif, Nikolai Eye et al., Special Table 2001-522119, Arsenoff, Vladimir et al., Special Table 2001-508221) and the like. Proposed.

However, conventionally, no specific two-photon absorption material has been presented or only an abstract presentation regarding this three-dimensional optical recording medium, and two examples of two-photon absorption compounds are also available. The photon absorption efficiency was extremely small, and there were many problems in practical use.
Furthermore, since the photochromic compounds used in these conventional techniques are reversible materials, they have practical problems in nondestructive reading, long-term storage stability, reproduction S / N ratio, and the like. However, it cannot be said that this is a practical method as an optical recording medium.
In particular, from the viewpoint of non-destructive readout and long-term storage stability of recording, it is preferable to reproduce by changing the reflectance (refractive index or absorption) or emission intensity using an irreversible material, which has such a function. No proposal has been made for a technique that specifically discloses a two-photon absorbing material.

  JP-A-6-28672 and JP-A-6-118306 disclose a recording apparatus, a reproducing apparatus, a reading method, and the like that perform three-dimensional recording by refractive index modulation. A technique regarding a method using a photon-absorbing three-dimensional optical recording material is not disclosed.

As described above, the reaction is caused by using the excitation energy obtained by non-resonant two-photon absorption, and as a result, the emission intensity when light is irradiated at the laser focus (recording) part and the non-focus (non-recording) part cannot be rewritten. If it can be modulated by this method, it is possible to cause emission intensity modulation at an extremely high spatial resolution at an arbitrary place in the three-dimensional space, and it can be applied to a three-dimensional optical recording medium that is considered to be the ultimate high-density recording medium. Become.
Furthermore, since non-destructive readout is possible and the material is an irreversible material, it can be expected to have good storage stability and is practical.

However, conventionally used two-photon absorption compounds have a disadvantage that they require a very high output laser as a light source and take a long recording time because of their low two-photon absorption ability.
In particular, for use in a three-dimensional optical recording medium, a two-photon absorption three-dimensional optical recording material capable of performing recording by two-photon absorption with high sensitivity to achieve a fast transfer rate. Construction is essential. For that purpose, the difference between the two-photon absorption compound that can absorb two-photons with high efficiency and generate an excited state, and the two-photon absorption optical recording material using a two-photon absorption compound excited state in some way. Although a material containing a recording component that can efficiently form a thin film is effective, such a material has hardly been disclosed so far, and it has been desired to construct such a material.

  In the present invention, a multiphoton absorption material, specifically, a multiphoton absorption functional material containing a two-photon absorption material is provided, and this is applied to an optical recording medium, and this two-photon absorption is utilized. Two-photon absorption optical recording / reproduction, characterized in that after recording, the recording material is irradiated with light to detect the difference in emission intensity, or the change in reflectance due to the change in refractive index is detected. A method and a two-photon absorption optical recording (material) medium capable of such recording and reproduction are provided.

  The optical recording medium using the multi- (2) photon absorption functional material of the present invention uses a multi- (2) photon absorption functional material as a predetermined substrate (base material) using a spin coater, roll coater, bar coater or the like. A basic structure can be formed by directly coating the film on top or by casting as a film.

  The multiphoton absorption functional material is composed of a multiphoton absorption material made of a multiphoton absorption dye and the like, and a dispersion of fine particles of a metal that generates a surface plasmon enhancement field, or fine particles coated at least partly with the metal. To do.

The substrate (base material) may be any natural or synthetic support, preferably a flexible or rigid film, sheet, or plate.
Specific examples of the material include polyethylene terephthalate, resin-primed polyethylene terephthalate, polyethylene terephthalate subjected to flame or electrostatic discharge treatment, cellulose acetate, polycarbonate, polymethyl methacrylate, polyester, polyvinyl alcohol, and glass.
Further, predetermined tracking guide grooves and address information may be formed in advance according to the final target recording medium.

In the case of the coating method, the solvent used is removed by evaporation at the time of drying.
The solvent may be removed by evaporation either by a heating method or a reduced pressure method.

Furthermore, a predetermined protective layer (intermediate layer) for oxygen blocking and interlayer crosstalk prevention may be formed on the multi- (2) photon-absorbing optical recording material formed by a coating method or a casting method as described above. Good.
Protective layer (intermediate layer) is made of a plastic film such as polyolefin such as polypropylene and polyethylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyethylene terephthalate, or cellophane film, or an electrostatic adhesion and extrusion machine. It can be formed by laminating by using a layer or the like, or by applying a solution of the polymer. Moreover, it can also form by bonding a glass plate.
Moreover, in order to improve the airtightness between layers, an adhesive or a liquid substance may be present.

  Furthermore, a predetermined tracking guide groove or address information may be added to the protective layer (intermediate layer) in advance according to the final target recording medium.

Recording and / or reproduction is performed focusing on an arbitrary layer of the recording medium using the multi-photon absorption functional material having the above-described three-dimensional multilayer structure.
Further, even when the layers are not separated by a protective layer (intermediate layer), it is possible to perform three-dimensional recording in the depth direction from the characteristics of the multi- (2) photon absorption functional material.

Next, a preferred embodiment of a three-dimensional multilayer optical memory will be described as a specific example of a three-dimensional recording medium using the multiphoton absorption functional material of the present invention.
The present invention is not limited in any way by the following embodiment, and any other structure may be used as long as it can perform three-dimensional recording (recording in a plane and a film thickness direction).

A schematic configuration diagram of a recording / reproducing system of a three-dimensional multilayer optical memory is shown in FIG. 1A, and a schematic cross-sectional view of a three-dimensional recording medium is shown in FIG.
In the three-dimensional recording medium 10 shown in FIGS. 1A and 1B, a flat support (substrate 1), a recording layer 11 using a multi- (2) photon absorbing compound, and an intermediate for preventing crosstalk. It is assumed that 50 layers of protective layers (protective layers) 12 are alternately stacked, and each layer is formed by spin coating.

The recording layer 11 preferably has a thickness of 0.01 to 0.5 μm, and the intermediate layer 12 preferably has a thickness of 0.1 to 5 μm.
According to the above-described structure, terabyte-class ultrahigh density optical recording can be realized with a disk size similar to that of conventionally known CDs and DVDs.

Further, according to the data reproduction method (transmission / or reflection type), a substrate 2 (protective layer) similar to the substrate 1 or a reflection layer made of a high reflectance material is formed on the opposite side of the recording layer 11 interposed. It shall be.
When the recording bit 3 is formed, a single beam (laser light L in the figure) is used, and ultrashort pulse light of femtosecond order is used.
At the time of reproduction, light having a wavelength different from that of the beam used for data recording or light having the same wavelength with low output may be used.
Recording and playback can be performed in either bit units or page units, and parallel recording / playback using a surface light source, a two-dimensional detector, or the like is effective in increasing the transfer rate.
Note that a three-dimensional multilayer optical memory similarly formed according to the present invention may have a card shape, a plate shape, a tape shape, a drum shape, or the like.

Next, as a specific application example of the multi- (2) photon absorption functional material of the present invention, application to a light limiting element will be described.
In optical communication and optical information processing, optical control such as modulation and switching is required to carry signals such as information with light. For this type of light control, an electro-light control method using an electric signal has been conventionally employed. However, the electro-optical control method has limitations such as a band limitation due to a CR time constant as in an electric circuit, a processing speed being limited due to a response speed of the element itself and a speed mismatch between an electric signal and an optical signal. In order to make full use of the broadband and high speed, which are the advantages of light, light-light control technology for controlling an optical signal with an optical signal becomes very important. In order to meet this requirement, the two-photon absorption functional material of the present invention is processed to produce an optical element. This utilizes optical changes such as transmittance, refractive index, and absorption coefficient caused by light irradiation, and modulates the intensity and frequency of light without using electronic circuit technology. It is applied to optical switches in exchanges, optical computers, optical interconnections, etc.
The optical limiting element of the present invention that utilizes the change in optical characteristics due to two-photon absorption provides an optically limiting element that is formed from a normal semiconductor material and an element that has a much higher response speed than those based on one-photon excitation. be able to. Further, because of the high sensitivity, it is possible to provide an optical limiting element excellent in signal characteristics with a high S / N ratio.

Conventionally, a light limiting element has been disclosed in the past. Specifically, focusing is performed by irradiating a photorefractive index material whose refractive index is changed by light irradiation with light having a wavelength whose refractive index changes. And related to an optical waveguide forming a refractive index profile.
FIG. 2 shows an example of an optical limiting element 20 that optically switches signal light having a wavelength that can be excited by one photon by exciting the two-photon absorption functional material of the present invention with control light having a wavelength that can be excited by two photons. The schematic of is shown.
In this example, the light limiting element 20 has a configuration in which the protective layer 21 sandwiches the two-photon absorption material 22 containing the metal fine particles or gold nanorods described in the present invention, but the present invention is limited to this configuration. It is not a thing.

In the operation of the light limiting element, the signal light 24 is optically switched by multi-photon excitation of the light limiting element 20 by the control light 23.
Since the control light 23 uses a two-photon process and the signal light 24 uses a one-photon process, the wavelengths are different. Therefore, it is possible to separate the control light 23 and the signal light 24 using a color filter 25. The separated signal light 24 is detected by a detector 26. With such a configuration, it is possible to achieve both high-speed response and S / N ratio of the light-light control technology.

Next, an application to a two-photon photofabrication material using a two-photon absorption material as a multiphoton absorption functional material will be described.
FIG. 3 shows a schematic diagram of an apparatus applied to a two-photon stereolithography method using a two-photon absorption material.
In this example, light from a near-infrared pulse laser light source 31 is photocured using a lens 37 through a shutter 33 that controls the amount of transmitted light temporally, an ND filter 34, and further through a mirror scanner 35. A two-photon micro-stereolithography method is performed in which the resin 39 is focused in the resin 39, scanned with a laser spot, and two-photon absorption is induced to cure the resin only in the vicinity of the focal point to form an arbitrary three-dimensional structure.

In this example, pulsed laser light is condensed by a lens 37, and a region with high photon density is formed in the vicinity of the condensing point. At this time, since the total number of photons passing through each cross section of the beam is constant, when the beam is scanned two-dimensionally within the focal plane, the total light intensity in each cross section is constant.
However, since the probability of occurrence of two-photon absorption is proportional to the square of the light intensity, a region where the generation of two-photon absorption is high is formed only near the condensing point where the light intensity is high.
In this way, by condensing the pulsed laser light with the lens 37 and inducing two-photon absorption, it is possible to limit the light absorption near the condensing point and harden the resin in a pinpoint manner.
The condensing point can be freely moved in the photocurable resin liquid 39 by controlling the Z stage 36 and the galvanometer mirror by the computer 38, so that the target three-dimensional workpiece in the photocurable resin liquid 39 can be obtained. It can be freely formed.

The two-photon stereolithography described above has the following characteristics.
(A) Processing resolution exceeding the diffraction limit: Processing resolution exceeding the diffraction limit of light can be realized by the non-linearity of the two-photon absorption with respect to the light intensity.
(B) Ultra-high-speed modeling: When two-photon absorption is used, the photocurable resin does not cure in principle in a region other than the focal point. For this reason, the light intensity to be irradiated can be increased, and the beam scanning speed can be increased. For this reason, modeling speed can be improved about 10 times.
(C) Three-dimensional processing: The photocurable resin is transparent to near-infrared light that induces two-photon absorption. Therefore, even when the focused light is condensed deeply into the resin, internal curing is possible. In the conventional SIH, when the beam is condensed deeply, the light intensity at the condensing point is reduced by light absorption, and the internal curing becomes difficult. In the present invention, these problems can be solved reliably. .
(D) High yield: In the conventional method, there is a problem that the modeled object is damaged or deformed due to the viscosity or surface tension of the resin, but in this method, the problem is solved because modeling is performed inside the resin.
(E) Application to mass production: By using ultra-high speed modeling, it is possible to manufacture a large number of parts or movable mechanisms continuously in a short time.

The photocurable resin liquid 39 for two-photon stereolithography is a substance that undergoes a two-photon polymerization reaction when irradiated with light and changes from a liquid to a solid.
The main components are a resin component composed of an oligomer and a reactive diluent and a photopolymerization initiator (including a photosensitizer if necessary).
An oligomer is a polymer having a degree of polymerization of about 2 to 20, and has a large number of reactive groups at its ends.
Furthermore, a reactive diluent is added to adjust viscosity, curability and the like.
When irradiated with laser light, the polymerization initiator or photosensitizing material absorbs two photons, and reactive species are generated directly from the polymerization initiator or through the photosensitizing material, and react with the reactive groups of the oligomer and reactive diluent. Then, the polymerization is started.
Thereafter, a chain polymerization reaction is caused between them to form a three-dimensional cross-link, and the solid resin is changed to a solid resin having a three-dimensional network structure in a short time.

Photocurable resins are used in the fields of photocurable inks, photoadhesives, layered three-dimensional modeling, and the like, and resins having various characteristics have been developed.
In particular, in layered three-dimensional modeling, (1) good reactivity, (2) small shrinkage during curing, (3) excellent mechanical properties after curing, etc. are important. is there.
These characteristics are equally important in this method, and therefore resins developed for layered three-dimensional modeling that have two-photon absorption characteristics can be used as the two-photon photo-molding photocurable resin of this method. Can be used.
Specific examples include acrylate-based and epoxy-based photocurable resins, and urethane acrylate-based photocurable resins are particularly preferable.

Conventionally, regarding optical modeling, a technical disclosure has been made in JP-A-2005-134873.
In this method, pulsed laser light is subjected to interference exposure on the surface of the photosensitive polymer film without using a mask.
It is important that the pulse laser light is light in a wavelength region that causes the photosensitive polymer film to exhibit a photosensitive function.
Therefore, the wavelength region of the pulsed laser light can be appropriately selected according to the type of the photosensitive polymer or the type of group or part that exhibits the photosensitive function in the photosensitive polymer.
In particular, even if the wavelength of the pulsed laser light emitted from the light source is not in a wavelength region that causes the photosensitive polymer film to exhibit a photosensitive function, by utilizing a multiphoton absorption process upon irradiation with the pulsed laser light, The photosensitive polymer film can exhibit a photosensitive function.
Specifically, when the pulsed laser light emitted from the light source is condensed and irradiated with the condensed pulsed laser light, multiphoton absorption (for example, two-photon absorption, three-photon absorption, four-photon absorption) Even if the wavelength of the pulsed laser light emitted from the light source is not in the wavelength region where the photosensitive polymer film exhibits the photosensitive function, the photosensitive polymer film In effect, the pulsed laser beam in the wavelength region that causes the photosensitive polymer film to exhibit a photosensitive function is irradiated.
As described above, the pulsed laser beam for the interference exposure may be substantially a pulsed laser beam in a wavelength region that causes the photosensitive polymer film to exhibit the photosensitive function, and the wavelength is appropriately selected depending on the irradiation conditions. can do.
For example, the two-photon absorbing material according to the present invention is used as a photosensitizing material, dispersed in an ultraviolet curable resin, etc., to form a photosensitive material solid, and only the focal spot is cured using the two-photon absorption ability of the photosensitive material solid. It is possible to obtain an ultra-precise three-dimensional structure using

The two-photon absorption functional material according to the present invention can also be used as a two-photon absorption polymerization initiator or a two-photon absorption photosensitizing material.
Compared to conventional two-photon absorption functional materials (two-photon absorption polymerization initiators or two-photon absorption photosensitizers), the two-photon absorption sensitivity is high, so high-speed modeling is possible, and a compact and inexpensive laser as an excitation light source Since a light source can be used, it is possible to develop practical applications that can be mass-produced.

Next, the adjustment of the absorption sensitivity of the multi- (2) photon absorption functional material of the present invention will be described.
The multi- (2) photon absorption functional material of the present invention is a mixed material of fine particles that generate a surface plasmon enhancement field and a multi-photon absorption material.
For this reason, the approximate sensitivity of an effective multiphoton absorption reaction is considered to be proportional to the amount of light consumed in the multiphoton absorption reaction excited by the excitation light. It is given by the product of the sensitivity of fine particles that generate a plasmon enhancement field.
Therefore, in order to increase the sensitivity of the multiphoton absorption reaction from the viewpoint of the sensitivity condition of the multiphoton absorbing material, it is necessary to increase the multiphoton absorption sensitivity of the multiphoton absorbing material alone or to increase the dispersion concentration of the multiphoton absorbing material. Conceivable.
In addition, from the viewpoint of increasing the sensitivity of the fine particles that generate the surface plasmon enhancement field, select particles that can obtain a larger plasmon enhancement field enhancement effect by changing the shape of the fine particles, or the fine particles that generate the surface plasmon enhancement field. The dispersion concentration will be increased.

However, since the fine particles that generate the surface plasmon enhancement field generate the surface plasmon enhancement field by absorbing one photon, the depth of the fine particles is not reduced in order not to reduce the sensitivity of the deep part (not to reduce the transmittance of the excitation light). The concentration distribution design in the direction is important.
Therefore, in order to make the sensitivity in the depth direction uniform, the distribution of each parameter in the depth direction is considered in consideration of the balance of the amount of transmitted excitation light for each depth and the parameter that determines the effective sensitivity described above. Need to be determined. In the case of a multilayer structure, the parameters can be changed for each layer.
Note that “sensitivity equalization” means that the sensitivities are configured to be substantially equal. Specifically, it is sufficient that the light irradiation power can be uniformed by about ± 10%. It is preferable that the sensitivity is uniformized (same) within ± 5%.

Next, the fine particles generated in the surface plasmon enhancement field will be described.
The surface plasmon is a localized plasmon generated near the fine particle.
Localized plasmons generated in the vicinity of fine particles are characterized by the fact that coupling with excitation light (propagating light) occurs easily (no special optical arrangement is required) and a phenomenon observed in fine particles smaller than the wavelength. The effect of scattering by the fine particles is relatively small, and scattering loss can be avoided.
The plasmon absorption by the fine particles is very strong, and the coloration by absorption to the extent that it can be used as a coloring material can be obtained by dispersing a very small amount of particles. For example, gold fine particles dispersed in glass have long been known as colored glass for glass crafts having red transparency. That is, it is possible to balance the one-photon absorption of the surface plasmon-enhanced field-generated particles dispersed in the bulk body, the enhancement of the absorbed light energy, and the loss due to scattering, and can excite multiphoton absorption in the deep part of the bulk body. .

The excitation light that has been absorbed by one photon in the fine particles generating the surface plasmon enhancement field becomes plasmon oscillation of free electrons, and forms a localized plasmon enhancement field having a distribution inherent to the mode of plasmon oscillation.
In the case of metal fine particles, spherical fine particles are generally given as the most easily obtainable shape.
In the case of gold spherical fine particles, it shows the strongest absorption for light of about 520 nm.
In rod-shaped gold fine particles (called gold nanorods) for which synthetic methods that can be obtained with good reproducibility have been developed, the ratio of thickness to length increases (becomes elongated), and resonance in the longitudinal direction follows. It was confirmed that strong absorption appearing on the longer wavelength side caused by this occurred, and that a plasmon enhancement field with an extremely high intensity was obtained compared to spherical gold fine particles. By using this gold nanorod as a source of the localized plasmon enhancement field, higher sensitization of multiphoton absorption was obtained.

Fine particles that generate a surface plasmon enhancement field generate an independent localized plasmon enhancement field in the excitation light, but when the particles are close to each other, not only the enhancement field is overlapped but also the gap between the particles is further increased. A large localized plasmon enhancement field is generated.
As one of the structures that generate such a large enhancement field, (1) the surface of the fine particles is coated (partially) with a metal that generates a surface plasmon enhancement field, or (2) the fine particles of the metal are adsorbed. Particles with structure are raised. “Metal fine particles that generate a surface plasmon enhancement field generated on a metal surface, or fine particles that are at least partially coated with the metal” described in claim 1 of the present invention in a broad sense means (1) and It shall include both (2).
In addition, there is a method using an aggregate formed of metal fine particles that generate a surface plasmon enhancement field.
In the present invention, the effect of loss due to scattering is relatively small in a small-scale aggregation, such as a substantially dimer in which two particles are combined, a large enhancement effect is obtained, and the sensitization of multiphoton absorption in the bulk body It was found to show an effect.
Such small-scale aggregates can be reproduced by optimizing the balance between the viscosity of the raw material solution and the cohesive force.

  Next, although a specific sample is produced and this invention is demonstrated, this invention is not limited to the following examples.

[Example 1]
To 300 ml of toluene, 10 g of silver nitrate and 37.1 g of oleylamine (85%) were added and stirred for 1 hour. Next, 15.6 g of ascorbic acid was added and stirred for 3 hours. 300 ml of acetone was added thereto, the supernatant was removed by decantation, and the solvent contained in the precipitate was distilled off to obtain spherical silver fine particles having a particle diameter of 10 to 30 nm.
1 mg of the obtained spherical silver fine particles were redispersed in 10 ml of toluene, and 7 mg of a two-photon fluorescent dye represented by the following formula (1) was added and stirred.

  After dissolution of the dye, 1 g of acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon) was added and stirred and melted. This solution was poured into a glass substrate, and the solvent was volatilized and solidified to obtain a spherical silver fine particle / two-photon fluorescent dye-dispersed acrylic resin bulk material having a thickness of 50 μm.

[Example 2]
1 mg of the spherical silver fine particles obtained in Example 1 was redispersed in 10 ml of toluene and mixed with 0.2 g of a toluene solution of 1% by weight polyethyleneimine (manufactured by Nippon Shokubai, average molecular weight 300). Aggregation was confirmed by the change in color of the dispersion.
Further, 7 mg of the two-photon fluorescent dye represented by the above formula (1) was added and stirred, and after dissolving the dye, 1 g of acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon) was added and stirred and melted. This solution was poured into a glass substrate in a frame, and the solvent was volatilized and solidified to obtain an aggregated spherical silver fine particle / two-photon fluorescent dye-dispersed acrylic resin bulk material having a thickness of 50 μm.

Example 3
To 30 ml of water was added 0.37 g of chloroauric acid, and then 2.187 g of tetraoctylammonium bromide and 80 ml of toluene were added and stirred for 2 hours.
Further, 0.2 g of 1-dodecanethiol was added and stirred for 1 hour.
Next, a solution obtained by dissolving 0.378 g of NaBH ₄ in 20 ml of water was added dropwise and stirred for 2 hours.
The reaction product was washed several times with water using a separatory funnel, and then the organic layer solvent was distilled off to obtain spherical gold fine particles having a particle size of 20 to 50 nm.
3 mg of the obtained spherical gold fine particles were redispersed in 10 ml of toluene, and 7 mg of the two-photon fluorescent dye represented by the above formula (1) was added and stirred. After dissolution of the dye, 1 g of acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon) was added and stirred and melted. The solution was poured into a glass substrate, and the solvent was volatilized and solidified to obtain a spherical gold fine particle / two-photon fluorescent dye-dispersed acrylic resin bulk having a thickness of 50 μm.

Example 4
3 mg of spherical gold fine particles obtained in Example 3 above were redispersed in 10 ml of toluene, mixed with 0.2 g of a toluene solution of 1% by weight polyethyleneimine (manufactured by Nippon Shokubai, average molecular weight 300), and stirred. Small-scale aggregation of spherical gold fine particles was confirmed by the change in color of the dispersion.
Further, 7 mg of the two-photon fluorescent dye represented by the above formula (1) was added and stirred. After the dye was dissolved, 1 g of acrylic resin Dianal BR-75 (Mitsubishi Rayon) was added and stirred and melted. This solution was poured into a glass substrate in a frame, and the solvent was volatilized and solidified to obtain an aggregated spherical gold fine particle / two-photon fluorescent dye-dispersed acrylic resin bulk material having a thickness of 50 μm.

Example 5
70 ml of 0.18 mol / l cetyltrimethylammonium bromide aqueous solution, 0.36 ml of cyclohexane, 1 ml of acetone, and 1.3 ml of 0.1 mol / l silver nitrate aqueous solution are mixed and stirred. After adding 0.3 ml of 0.24 mol / l chloroauric acid aqueous solution to this, 0.3 ml of 0.1 mol / l ascorbic acid aqueous solution was added, and it was confirmed that the color of the chloroauric acid solution disappeared. Thereafter, this liquid was transferred to a petri dish and irradiated with ultraviolet light having a wavelength of 254 nm for 20 minutes using a low-pressure mercury lamp, whereby a gold nanorod dispersion liquid having an absorption wavelength of about 830 nm was obtained. The gold nanorod component was precipitated from this dispersion using a centrifuge. The supernatant liquid was removed, and the process of adding water and centrifuging was repeated a plurality of times to remove excess dispersant cetyltrimethylammonium bromide. 1 g of this gold nanorod dispersion was mixed with 0.4 g of an acetone solution of 1 wt% polyethyleneimine (manufactured by Wako Pure Chemical Industries, average molecular weight 1800). To this, 2 g of a DMF solution of 5% by weight acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon) is mixed. Furthermore, 0.7 mg of the two-photon fluorescent dye represented by the above formula (1) was added and stirred. This was concentrated to several ml by reducing the pressure. The solution was cast on a glass substrate and poured, and the solvent was volatilized and solidified to obtain a 50 μm thick gold nanorod / two-photon fluorescent dye-dispersed acrylic resin bulk.

Example 6
1 g of the gold nanorod dispersion obtained in Example 5 was mixed with 0.4 g of an acetone solution of 1% by weight polyethyleneimine (manufactured by Wako Pure Chemical Industries, average molecular weight 1800). This was mixed with 10 g of a DMF solution of 10% by weight acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon). Further, 200 mg of photochromic dye (Tokyo Kasei B1536) was added and stirred. This was concentrated to about 10 ml by reducing the pressure. The solution was made into a frame on a glass substrate, poured into a plurality of times, and the solvent was volatilized and solidified repeatedly to obtain a gold nanorod-photochromic dye-dispersed acrylic resin bulk body having a thickness of 500 μm.

Example 7
1 g of the gold nanorod dispersion obtained in Example 5 was mixed with 0.4 g of an acetone solution of 1 wt% polyethyleneimine (manufactured by Wako Pure Chemical Industries, Ltd., average molecular weight 1800). This was mixed with 1 g of a DMF solution of 1% by weight acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon). Furthermore, 2 mg of photochromic dye (Tokyo Kasei B1536) was added and stirred. The solution was concentrated to several ml by reducing the pressure. A film of this mixed solution was formed on a glass substrate by spin coating so that the film thickness was 0.5 μm. The absorption rate of one photon at the excitation light wavelength of this film was about 11.4%. A 5 wt% PVA aqueous solution was spin-coated on this so as to have a film thickness of 5 μm. Thereafter, a part of the mixed solution is taken, and the mixed solution of the dye and the binder resin is mixed so that the dye concentration in the binder resin at the thickness of 0.5 μm is the same and the one-photon absorption is as shown below. Spin coat film (film thickness 1 μm), the above mixed solution and a spin coat film of PVA aqueous solution (film thickness 5 μm) are alternately spin coated, and five gold nanorods / photochromic dye dispersed acrylic resin layers and PVA layers are alternated. A layered structure was formed by laminating layers and separation layers alternately containing fine particles that generate localized plasmon enhancement fields with modulated concentrations and dyes that absorb two-photons.

<One-photon absorption rate of each layer>
First layer (outermost surface): 5.0%
Second layer: 5.8%
3rd layer: 7.0%
4th layer: 8.7%
5th layer (bottom layer): 11.4%

[Comparative Example 1]
7 mg of the two-photon fluorescent dye represented by the above formula (1) was added to 10 ml of toluene and stirred.
After dissolution of the dye, 1 g of acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon) was added and stirred and melted. This solution was poured into a glass substrate with a frame, and the solvent was volatilized and solidified to obtain a two-photon fluorescent dye-dispersed acrylic resin bulk body having a thickness of 50 μm.

[Comparative Example 2]
200 mg of photochromic dye (Tokyo Kasei B1536) was added to 10 g of DMF solution of 10% by weight acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon) and stirred. The solution was made into a frame on a glass substrate and poured in multiple times, and the solvent was repeatedly volatilized and solidified to obtain a photochromic dye-dispersed acrylic resin bulk body having a thickness of 500 μm.

[Comparative Example 3]
The gold nanorod / photochromic dye mixed solution used for the fifth layer (outermost surface) in Example 7 was spin-coated on a glass substrate so as to have a film thickness of 0.5 μm to form a film.
On top of this, 5 wt% PVA aqueous solution is spin-coated so as to have a film thickness of 5 μm, and the mixed solution and PVA aqueous solution are alternately spin-coated, and five layers of gold nanorods / photochromic dye dispersed acrylic resin layer and PVA layer Are stacked alternately, and a layered structure in which a layer containing fine particles that generate a localized plasmon enhancement field having a uniform concentration and a dye that absorbs two-photons and a separation layer are alternately stacked is produced.

<First evaluation: measurement of two-photon fluorescence intensity and enhancement>
It is not easy to directly measure the two-photon absorption amount of a sample because absorption and scattering of excitation light by fine particles that generate a plasmon enhancement field are present.
In this evaluation, by using a two-photon absorption dye (fluorescent dye with two-photon absorption ability) as the dye, the intensity of two-photon absorption is increased by comparing the amount of fluorescence emitted by two-photon absorption with a comparative example. Was defined and measured.
A measurement system for two-photon fluorescence is shown in FIG.
As the excitation light, an infrared femtosecond laser, MaiTai (repetition frequency 80 MHz, pulse width 100 fs) manufactured by Spectra Physics was used.
In order to adjust the output, a 1 / 2λ plate and an attenuator made of a Glan laser prism are passed through, and the average output is adjusted to 200 mW. And collected by a coupling lens having a focal length of 40 mm to be approximately parallel light.
After the excitation light is removed by the dichroic mirror, the light is roughly condensed on the detection photodiode by a plano-convex lens having a focal length of 100 mm.
An infrared cut glass filter is installed in front of the photodiode.

<Evaluation results>
For each of the above-described samples of [Examples 1 to 5] and [Comparative Example 1], fluorescence of two-photon excitation at the focal position of the excitation light source was measured.
The two-photon fluorescence light amounts of the sample samples of Examples 1 to 5 and Comparative Example 1 are compared, and the relative intensity comparison results are shown below.
In the following, description of [Comparative Example 1] as a reference for relative comparison was omitted.

<Two-photon fluorescence relative intensity comparison result (relative light quantity)>
Example 1: 2.2
Example 2: 2.6
Example 3: 2.5
Example 4: 3.2
Example 5: 7.1

As is clear from the above evaluation results, the present invention consists of a bulk type material having a structure in which metal fine particles generating a surface plasmon enhancement field generated on the metal surface of the present invention and a two-photon absorption material (two-photon absorption fluorescent dye) are dispersed. By using a multiphoton absorption functional material, it was confirmed that two-photon fluorescence can be greatly enhanced as compared with a bulk material in which only a two-photon absorption fluorescent dye is dispersed, which is a conventional comparative example.
Furthermore, it was confirmed that a further enhancing effect can be obtained by dispersing the aggregates in the bulk.

<Second Evaluation: Evaluation of Bulk Sample and Laminated Sample>
Evaluation of the bulk type sample and the laminated type sample will be described.
Evaluation of bulk type samples and stacked type samples is performed by performing three-dimensional recording / reproduction using the reaction occurring only near the focal point of the excitation light, which is a characteristic of the two-photon absorption reaction, and evaluating the threshold power of the recording. I went there.
The recording power threshold value is evaluated by controlling the shutter 311 of the recording light source and changing the exposure time to write a plurality of bits.
After recording, the recording surface was observed with a confocal microscope, and the photochromic effect of diarylethene as a recording material was evaluated by the presence or absence of a change in reflectance.

<Evaluation results>
A sensitivity comparison was made between the gold nanorod dispersion of [Example 6] and the conventional dye-dispersed bulk type multiphoton absorption functional material of [Comparative Example 2].
A relative comparison was made between thresholds of recording power when recording writing was performed at positions where the depth from the surface was about 50 μm and 450 μm.
The reference for comparison was the writing threshold value at a position where the depth from the surface of [Comparative Example 2] was about 50 μm.

<Relative evaluation result of recording power threshold>
(50 μm from the surface)
Example 6: 0.53
Comparative Example 2: 1.00
(450 μm from the surface)
Example 6: 0.68
Comparative Example 2: 1.02

From the above evaluation results, in the sample of Example 6 which is a multiphoton absorption functional material of the present invention, the threshold power is lower than that of Comparative Example 2 at any position at a depth of 50 μm and 450 μm from the surface. It was confirmed that the sensitivity was higher.
Furthermore, it has been demonstrated that the influence of absorption scattering by one photon can be avoided.

<Third evaluation>
Sensitivity comparison evaluation was performed between the gold nanorod dispersion having the concentration modulation in [Example 7] and the dye-dispersed bulk type multiphoton absorption functional material in which the gold nanorods were dispersed in the uniform concentration in [Comparative Example 3]. It was.
Evaluation was performed by relatively comparing the threshold values of the recording power when writing was performed on the outermost dye-containing layer and the fifth deepest dye-containing layer.

<Relative evaluation result of recording power threshold>
(First layer (outermost surface))
Example 7: 0.99
Comparative Example 3: 1.00
(5th layer (lowermost layer))
Example 7: 1.05
Comparative Example 3: 1.51

  From the above evaluation results, in Comparative Example 3, the lower recording layer requires a relatively large recording power, that is, the sensitivity is significantly reduced. In Example 7, one photon is absorbed for each layer. Since the amount is controlled, a decrease in sensitivity is effectively suppressed, and a large difference in sensitivity is not observed between the uppermost layer and the lowermost layer. That is, it became clear that the sensitivity unevenness for each layer can be suppressed by changing the concentration of the fine particles.

  In addition, each said Example is a specific example of embodiment of this invention, Other well-known material structures can also be added suitably, and this does not deviate from the summary of this invention at all.

(A) A system schematic diagram of recording / reproducing of a three-dimensional multilayer optical memory is shown. (B) A schematic sectional view of a three-dimensional recording medium is shown. The schematic of an example of the optical limiting element of this invention is shown. The schematic of the apparatus applied to the two-photon stereolithography method is shown. The measurement system of two-photon fluorescence is shown.

Explanation of symbols

1 substrate 2 substrate (reflection layer)
DESCRIPTION OF SYMBOLS 3 Recording bit 4 Recording laser light source 5 Reproduction laser light source 6 Pinhole 7 Detector 10 Three-dimensional recording medium 11 Recording layer 12 Intermediate layer 20 Optical limiting element 21 Protection layer 22 Two-photon absorption material 23 Control light 24 Signal light 25 Color Filter 26 Detector 30 Stereolithography 31 Laser light source 33 Shutter 34 ND filter 35 Mirror scanner 36 Z stage 37 Lens 38 Computer 39 Photocurable resin liquid

Claims (10)

  It is made of a bulk material characterized in that metal fine particles that generate a surface plasmon enhancement field generated on a metal surface, or fine particles that are at least partially coated with the metal are dispersed in a multiphoton absorbing material. Multiphoton absorption functional material.   The multiphoton absorption functional material according to claim 1, wherein the multiphoton absorption functional material is formed as a film of at least one layer.   The multiphoton absorption functional material according to claim 2, wherein the multiphoton absorption functional material formed as a film having two or more layers is separated by an intermediate layer having no multiphoton absorption ability.   The multiphoton absorption functional material according to claim 2 or 3, wherein the multiphoton absorption functional material formed as a film of two or more layers has substantially the same multiphoton absorption sensitivity in each layer.   The concentration of the fine particles of the metal that generate the surface plasmon enhancement field of each layer of the multiphoton absorption functional material formed as a film of two or more layers, or the fine particles that are at least partially coated with the metal, for each layer The multiphoton absorption functional material according to claim 2, wherein the multiphoton absorption functional material is set separately.   6. The multiphoton absorption according to claim 1, wherein the metal fine particles that generate a surface plasmon enhancement field, or the fine particles at least partially coated with the metal are gold nanorods. Functional material.   The multiparticulate according to any one of claims 1 to 5, wherein the metal fine particles that generate a surface plasmon enhancement field, or the fine particles at least partially coated with the metal are aggregate nanoparticles. Photon absorption functional material.   A three-dimensional recording medium using the multiphoton absorption functional material according to any one of claims 1 to 7 and capable of recording / reproducing in a depth direction with respect to incident light perpendicular to a layer plane.   An optical limiting element using the multiphoton absorption functional material according to any one of claims 1 to 7. An optical modeling system using the multiphoton absorption functional material according to any one of claims 1 to 7.

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