JP5417684B2 - Mixture, optical recording medium using the same, photoelectric conversion element, light limiting element, and optical modeling system - Google Patents

Description

  The present invention relates to a sensitization technique of a multiphoton absorption organic material using a localized plasmon enhancement field generated in metal fine particles, and a functional device using the same.

First, the multiphoton absorption organic material will be described.
Conventionally, various proposals have been made on techniques using multiphoton transitions. This multiphoton transition is a transition in which atoms or molecules simultaneously absorb or emit two or more photons, and is representative. Transitions include multiphoton absorption that absorbs many photons simultaneously, multiphoton emission that emits many photons simultaneously, Raman effect that absorbs one photon and emits another one at the same time.
Generally, it is a transition due to higher-order perturbation that occurs even when there is no energy level that absorbs or emits one photon at that frequency, and it is observed at a high photon density such as laser light. And the selection rules are different.
In particular, the two-photon absorption phenomenon involving two photons is related to the third-order nonlinear optical effect, and various studies have been conducted in the past.

On the other hand, an organic material is known to generate a transition state (excited state) that is allowed by the selection rule of one-photon absorption by absorbing one photon that is usually equal to the transition energy (excitation energy). .
However, when light with a high photon density, such as laser light, is irradiated, two photons equal to half the energy of the excitation energy are simultaneously absorbed and a transition may occur.

The phenomenon of simultaneously absorbing these two photons is
(1) Since absorption occurs in proportion to the square of the incident light intensity, a transition occurs only near the focal point where the photon density is high.
(2) Since it can be excited by a photon having half the energy of absorbing one photon, incident light reaches the deep part of the material without attenuation of light due to one-photon absorption.
In recent years, various application technologies that take advantage of the above characteristics have been studied along with the technological progress of high-power lasers. ing.

For example, in an optical recording medium that uses three-dimensional high resolution as described above and records and reproduces light that is formed on a plane and is incident in a direction perpendicular to the plane, the three-dimensional layer is formed by laminating them. Studies on optical recording media have been conducted (see, for example, Patent Documents 1 to 6 below).
These are considered to be capable of super-resolution recording because data can be recorded by causing spectral change, refractive index change or polarization change due to two-photon absorption only in the vicinity of the focal point where photon density is high.

In addition, development related to photo-induced charge separation type devices consisting of pairs of multiphoton absorbing organic materials and electron acceptors and photoelectric conversion devices using electrodes modified with only multiphoton absorbing organic materials has been actively conducted. It has been broken. This utilizes a reaction in which electrons move from a photoexcited molecule to an electron acceptor. When such a pair is immobilized on the electrode surface as the nucleus of the photoelectric conversion function, in the presence of a sacrificial reagent or an electron carrier. It is known that it has a photoelectric conversion function.
In recent years, various studies on next-generation dye-sensitized organic solar cells using multiphoton absorbing organic materials have been reported (for example, see Non-Patent Documents 1 and 2 below).

In addition, the generation of such a photocurrent is regarded as extremely important for applications such as sensors and light limitation (for example, see Patent Documents 7 and 8 below).
Furthermore, technical proposals have also been made for application to stereolithography (see, for example, Patent Document 9 below).

Next, localized plasmon enhancement will be described.
A plasmon is a particle in which free electrons in a metal are collectively oscillating, but in a fine metal particle (a nanometer-order metal fine particle, hereinafter sometimes referred to as a metal nanoparticle), the plasmon is localized on the surface. It is called a localized (surface) plasmon.
In metal nanoparticles, photoelectric fields in the visible to near-infrared wavelength region and plasmons are efficiently coupled and light absorption occurs, and light is converted into localized plasmons and an electric field that is significantly enhanced locally is generated. To do. That is, the light energy is converted into localized plasmons, so that the light energy is stored on the surface of the metal nanoparticle, and therefore light control in a region smaller than the diffraction limit of light becomes possible. Moreover, since this phenomenon is a phenomenon observed in fine particles smaller than the wavelength of the incident photoelectric field, there is an advantage that it is hardly affected by light scattering.

  Since the plasmon electric field generated as described above can excite the organic material existing on the surface in the same manner as light, in recent photochemical technology, the interaction between metal nanoparticles and light has been reduced. It has been attracting attention.

For example, a technical proposal as an example in which the plasmon enhancement technique is applied in the one-photon transition process has been made (see, for example, Patent Document 10 below).
In this method, surface plasmons generated on a metal surface are used to evaluate the optical properties of trace substances, but it is generally known that the enhancement field due to surface plasmons is limited to a region of about 100 nm or less from the surface. The measurement sample is fixed as a very thin film on a metal thin film formed on a high refractive index medium.

In addition, proposals have been made regarding applied technology using localized plasmons generated in metal fine particles (see, for example, Patent Document 11 below).
This is a technique for observing a sample adsorbed on the surface of a fine particle with high sensitivity, and utilizes metal nanoparticles fixed in a microcavity. Similarly, it is known that the enhanced field of localized plasmons is limited to a region of 100 nm or less around the metal fine particles.

Conventionally, various studies using gold nanorods as means for generating a localized plasmon enhancement field have been conducted.
Gold nanorods are rod-shaped gold nanoparticles, and by controlling the aspect ratio (major axis / minor axis value), any specific wavelength from the visible region to the near infrared region can be absorbed. It is a very specific material.
This can be produced by an electrochemical reaction in a solution containing a surfactant (see, for example, Patent Document 12 below).

JP-T-2001-524245 Special table 2000-512061 gazette Special table 2001-522119 gazette Special table 2001-508221 gazette JP-A-6-28672 JP-A-6-118306 JP 2001-210857 A JP-A-8-320422 JP 2005-134873 A JP 2004-156911 A Japanese translation of PCT publication No. 2004-530867 JP 2005-68447 A M. Lahav, T. Gabriel, A.N. Shipway, I. Willner, J. Am. Chem. Soc., 121, 258 (1999) (Three-dimensional gold nanostructure electrode) Y.Kuwahara, T.Akiyama, S.Yamada, Thin Solid Films, 393, 273 (2001) (Dye-sensitized organic solar cell)

  As electronics devices have been integrated and miniaturized with the advent of all-solid-state devices such as the transition from vacuum tubes to transistors, the same steps have been taken in plasmonic devices, as they have become the foundation of today's information society. In other words, it is considered that all solidification is essential, and it is considered that improvement in safety and reliability of the element, lightness, thinness, and the like can be achieved by total solidification.

If liquid is used, homogeneity can be expected from its fluidity, but there is a disadvantage that there is an influence of light disturbance and refraction due to thermal distortion, and thus the necessity of using a circulatory system, etc. arises. .
On the other hand, when forming a solid material, compared to a liquid in which metal fine particles are present in a relatively discrete manner, the density per unit volume is higher and the metal fine particles are more likely to aggregate. The concept of agents is very important.

When a mixed solid of metal fine particles and a multiphoton absorbing organic material is formed using a dispersant, it is preferable to use a dispersant having a high affinity for both the metal fine particles and the multiphoton absorbing organic material.
However, on the other hand, if the metal fine particles are covered with a thick dispersant, the effect of the enhancement field due to plasmons decreases exponentially according to the distance from the surface of the metal fine particles, so that an effective enhancement effect cannot be obtained. There is also a problem. Therefore, it is important to control the distance between the multiphoton-absorbing organic material and the metal fine particles (close to each other).

  In addition, regarding the excitation of multiphoton absorption organic materials using localized plasmon enhancement fields, even if efficient enhancement excitation is performed with plasmons, energy transfer from the excited state of the molecule to the metal microparticles occurs quickly and the excited state is quenched. Since a defect occurs, there is also a problem that some spacer must be provided between the metal fine particles and the excited molecules to ensure insulation.

  Furthermore, there has been an increasing demand for providing a functional device with more excellent sensitivity characteristics by proposing a highly efficient multiphoton absorption organic material and applying it.

Patent Documents 1 to 6 propose a three-dimensional optical recording medium that takes advantage of the excellent characteristics of two-photon absorption.
As recording / reproducing means for each medium, those using fluorescence by a fluorescent material, those using a photochromic reaction of a photochromic compound, those using refractive index modulation, etc. have been proposed. A specific example of the absorbing material is not clearly described, and even if the currently reported two-photon absorbing material is used, the absorption efficiency is still low, so a high-output light source is required. Furthermore, in a system that uses the photochromic reaction as its recording / reproducing principle, problems remain in nondestructive reading, long-term storage stability of recording, and SN at the time of reproduction, which cannot be said to be a practical device. there were.

In Non-Patent Documents 1 and 2 and Patent Documents 7 and 8, various photoelectric conversion devices utilizing the excellent characteristics of the multiphoton absorption have been proposed.
In particular, dye-sensitized organic solar cells using localized plasmon enhancement technology have the advantages of high efficiency and low cost compared to conventional silicon solar cells. It is very promising.

In solar cells, in order to extract a large amount of current, it is important to effectively use a light source having a wide wavelength distribution called sunlight.
However, long-wavelength light does not have the energy to excite the photosensitizer used in solar cells, so it does not lead to a direct increase in current, so the energy conversion efficiency of solar cells is theoretically It is said that there is a limit.

On the other hand, it has been confirmed that the use of a multiphoton absorbing material for the photosensitizer can excite molecules even with light having a long wavelength with a small energy, thereby increasing the energy conversion efficiency of the solar cell. Can do.
However, even in such a case, since the multiphoton absorption efficiency of the conventional multiphoton absorbing material is extremely low, it has been extremely difficult to obtain practically satisfactory characteristics.

Furthermore, in the conventionally known dye-sensitized organic solar cell, since an electrolytic solution containing an organic solvent that is easily volatilized in the electrolyte is used, problems remain in terms of leakage and long-term stability.
In the above-mentioned Patent Document 9, although an application technique relating to photomolding utilizing the excellent characteristics of the multiphoton absorption has been proposed, the multiphoton absorption efficiency of the conventional multiphoton absorbing organic material is still extremely low, so The above satisfactory characteristics could not be obtained.

One way to improve multiphoton absorption efficiency is to increase the concentration of molecules.
However, since there is an upper limit on solubility, significant improvement in properties cannot be expected.
If the concentration of a specific material is increased, there is a possibility of adversely affecting other components other than the multiphoton absorbing material, so that it is not an effective method from a practical aspect. That is, for example, in three-dimensional optical recording, there is a decrease in fluorescence intensity due to concentration quenching, and in optical modeling, inhibition of polymer curing characteristics.

If the multiphoton absorption efficiency cannot be increased due to the nature of the material, there is a method of increasing the incident light intensity.
However, as a result, a higher-power laser device is required, which is difficult to put into practical use and may deteriorate the material itself.

In the future, there is an increasing demand for a technology that uses the localized plasmon enhancement field generated in the metal fine particles in a three-dimensional manner.
In Patent Document 10, in order to obtain an enhancement effect using surface plasmons, the sample needs to be an extremely thin film on a metal thin film, and the enhancement effect depends on the shape of the film and the arrangement of the optical system. Therefore, application to three-dimensional stereolithography is difficult.

  Moreover, in the said patent document 11, since the metal nanoparticle which generate | occur | produces a localized plasmon enhancement field is being fixed in the closed microspace called a microcavity, a three-dimensional and uniform enhancement effect is acquired. It has the problem that it is difficult.

  Therefore, in the present invention, a technique for utilizing the localized plasmon enhancement field generated in the metal fine particles with high efficiency in three dimensions is proposed, and the multiphoton absorption efficiency of the multiphoton absorbing organic material is dramatically improved. I decided to let them.

The present invention has the technical features described in (1) to ( 9 ) below.
(1): containing at least a multiphoton absorption organic material, fine metal particles that generate a localized plasmon enhancement field, and a dispersing agent,
The dispersant has a function of suppressing electron transfer between the multiphoton absorbing organic material and the fine metal particles that generate the localized plasmon enhancement field ,
The mixture , wherein the dispersant is a silane coupling agent .
(2): the entire surface of the fine metal particles to generate the localized plasmon enhancing field, or a part of the surface, the mixture according to (1), characterized in that it is coated with the dispersant.
( 3 ): The mixture as described in (1) or (2) above, which is solid at normal temperature.
( 4 ): The mixture according to any one of (1) to ( 3 ), wherein the metal fine particles that generate the localized plasmon enhancement field are nanorods.
( 5 ): An optical recording medium that is formed on a plane and performs recording and reproduction by light incident in a direction perpendicular to the plane,
An optical recording medium, wherein the mixture according to any one of (1) to ( 4 ) is used as at least a part of its constituent elements.
( 6 ): A three-dimensional optical recording medium, characterized in that the optical recording medium according to ( 5 ) is laminated.
( 7 ): A photoelectric conversion element, wherein the mixture according to any one of (1) to ( 4 ) is used as at least a part of the constituent elements.
( 8 ): An optical limiting element, wherein the mixture according to any one of (1) to ( 4 ) is used as at least a part of the constituent elements.
( 9 ): An optical modeling system, wherein the mixture according to any one of (1) to ( 4 ) above is used as at least a part of the constituent elements.

The mixture of the present invention contains at least a multiphoton-absorbing organic material, metal fine particles that generate a localized plasmon-enhancing field, and a dispersant. Can be used efficiently three-dimensionally, and the multiphoton absorption efficiency of the multiphoton absorbing organic material can be dramatically improved.
Moreover, the functional element and functional device which are excellent in a sensitivity characteristic were provided by utilizing the mixture of this invention for various uses.

  In the present invention, a mixture containing at least a multiphoton absorbing organic material, metal fine particles that generate a localized plasmon enhancement field, and a dispersant, an optical recording medium using the mixture, a three-dimensional optical recording medium, a photoelectric conversion element, An optical limiting element and an optical modeling system are provided.

First, the said mixture is demonstrated.
The multiphoton absorption organic material constituting the mixture of the present invention is preferably a π-conjugated molecule.
In general, the main cause of the nonlinearity of molecules is that the charge transfer in the molecule is dominant. This is because conjugated molecules with a long effective conjugate length cause a large nonlinear effect, that is, multiphoton transition. It means easy.
In the molecular structure, π-conjugated molecules correspond to this, and specific examples include benzene derivatives, styryl derivatives, stilbene derivatives, porphyrin compounds, conjugated ketone derivatives, and conjugated polymers such as polyacetylene and polydiacetylene. .

Examples of metal fine particles that generate a localized plasmon enhancement field include nanometer-order metal fine particles, predetermined fine particles that are at least partially coated with the metal fine particles, and metal that has at least a part of the surface coated with a predetermined material. Examples thereof include fine particles.
If these are spherical particles, the production can be facilitated.

  The above-mentioned fine particles are coupled with light alone with high efficiency to generate plasmon vibration due to free electrons, and form a plasmon enhancement field having a distribution inherent in the mode of plasmon vibration. In addition, it has been confirmed that a very large plasmon enhancement field is generated between the fine particles, which is not simply an addition, and the form of a two-body or a small-scale aggregate formed by linking two particles is the present invention. It is particularly suitable as a form of fine particles constituting the mixture.

The dispersant constituting the mixture of the present invention has a function of suppressing electron transfer between the multiphoton absorbing organic material and the metal fine particles generating the localized plasmon enhancement field.
As described above, when a multiphoton absorption organic material is excited using a localized plasmon enhancement field, energy transfer occurs from the excited state of the molecule to the metal microparticles even if the enhanced excitation is efficiently performed by the plasmon, and the excited state is In order to quench the light, it is necessary to provide some spacer between the fine particles and the excited molecules to ensure insulation.
From this point of view, it can be considered as a proposal to coat the surface of the metal fine particles with an oxide film (or an inorganic film such as a nitride film) and to provide an insulating film as the spacer. Since it is necessary to introduce a dispersant, there is a possibility that reproducibility may be reduced by a few factors depending on the conditions, and it is difficult to obtain optimum reaction conditions.
On the other hand, if the dispersant originally has an insulating function, stable multiphoton absorption characteristics can be obtained. Examples of the dispersant having such a function include silane compounds and organic thiol compounds. And organic amine compounds.

It is preferable that the entire surface of the metal fine particles generating the localized plasmon enhancement field or at least a part of the surface thereof is coated with the dispersant.
When the entire surface of the metal fine particle is coated with the dispersant, energy transfer from the excited molecule to the metal fine particle is suppressed, and an efficient plasmon enhancing effect can be obtained.
In addition, for the metal fine particles coated on a part of the surface, the present invention provides a highly efficient multiphoton absorption organic material, which is intended to be applied to a functional device such as a photoelectric conversion element. In this case, since the possibility that the metal functions not only as a plasmon medium but also as an electrode is considered, it is necessary to isolate the excited molecules from the metal fine particles and to secure the electron conductivity to the metal fine particles. Therefore, it is desirable to optimize the distance between the excited molecule and the fine particles, and the coating ratio of the dispersing agent, considering the effect of enhancing the plasmon while suppressing the energy transfer to the metal and effectively causing the electron conduction.

The dispersant is preferably a silane coupling agent.
The silane coupling agent has a high affinity for the metal fine particles, and can exhibit an excellent effect as a spacer function. The material used as the silane coupling agent is represented by the following formula (1).

In the formula, X represents a reactive group chemically bonded to the metal fine particles, and examples thereof include a vinyl group, an epoxy group, an amino group, a methacryl group, and a mercapto group.
Examples of Z include a methoxy group and an ethoxy group.
Y is usually a hydrophobic atom or atomic group such as long-chain alkyl.
In Z, it becomes a silanol by a hydrolysis reaction and partially forms an oligomer state, so that it is a dispersant that can easily realize the surface coating of the metal fine particles.

By the way, the localized plasmon electric field decreases exponentially as the distance from the surface of the metal fine particle increases. Therefore, in order to obtain an efficient plasmon enhancement effect, it is necessary to bring the multiphoton absorption organic material close to the metal fine particles.
The method of bringing the multiphoton absorbing organic material close to the metal fine particles includes changing the concentration of the dispersant to reduce the coverage of the surface of the metal fine particles (in this case, the number of layers of the dispersant that overlaps multiple layers). And a method of controlling the molecular length of the dispersant.
In order to maintain the distance at which the electric field enhancement effect by the localized plasmons can be obtained with certainty, it is preferable to use a dispersant having a distance from the surface of the metal fine particles to the multiphoton absorbing organic material of about 20 nm. An enhancement effect is obtained.
However, on the other hand, if the metal microparticles and the multiphoton absorption organic material are too close to each other, a decrease in insulation due to energy tunnel leakage (and hence a decrease in multiphoton absorption efficiency) is caused. In the case where Y is composed of linear alkyl, the carbon number is preferably 10 or more and 30 or less.

The form of the mixture of the present invention shall be solid.
In addition, as a solid form, all formed from a mixture of at least the multiphoton absorbing organic material, the fine particles generating the plasmon enhancement field, and the dispersant in a thin film, thick film, granule, powder, or bulk And a mixture obtained by solidifying the mixture in addition to an acrylic resin such as polymethyl methacrylate or a matrix material such as polycarbonate, polyester, or polyvinyl alcohol.
In particular, the thin film is suitable for high performance of the device, that is, high integration, miniaturization, and weight reduction, and further, the shape effect (for example, electrical property, thermal property, quantum effect, superconducting property, magnetic property) by thinning the device. Furthermore, it is possible to obtain new effects in terms of physical properties and functions and has a wide range of application to devices, which is extremely suitable.

The fine particles that generate the localized plasmon enhancement field are preferably nanorods.
Here, the nanorod means a rod-like nanoparticle, and gold or silver is particularly known as a metal from which a strong resonance due to a localized plasmon is obtained in the visible range.
The advantage of nanorods is the ability to excite localized surface plasmons with a single nanoparticle, and the difference in particle size is related to the resonance wavelength, so the aspect ratio (major axis / minor axis value) is controlled. Thus, it is possible to select absorption at an arbitrary specific wavelength from the visible region to the near infrared region.

The above-mentioned mixture of the present invention can be used for various functional devices.
For example, it is also useful as a polymerization initiator or a photosensitizer (or a part thereof) in an optical recording material in a three-dimensional optical recording medium, a photoelectric conversion material in a photoelectric conversion system, and a photocuring material of an optical modeling curing resin. .
Hereinafter, although various specific application forms are demonstrated, utilization of the mixture of this invention is not limited to the following examples.

(3D optical recording)
In view of the expansion of networks such as the Internet and Intranet, the widespread use of high-definition TV with 1920 x 1080 (vertical x horizontal) dot image information, and HDTV (High Definition Television) broadcasts, etc. The consumer demands a recording medium of 50 GB or more, preferably 100 GB or more.
Further, as a backup application for computers and broadcast videos, a recording medium capable of recording large-capacity information of about 1 TB or more at high speed and at low cost is required.
A three-dimensional optical recording medium attracting attention as the ultimate high-density, high-capacity recording medium is a recording medium capable of recording / reproducing in the vertical and horizontal directions with respect to incident light, and has several tens of dimensions in the three-dimensional (film thickness) direction. By recording hundreds of recording layers, or by making the recording layer thick, recording and reproduction can be performed multiple times with respect to the light incident direction. It is a recording medium that has the possibility of ultra-high density and ultra-high capacity recording that is dozens or hundreds of times higher than that of a two-dimensional optical recording medium.

FIG. 1 is a schematic cross-sectional view (a) of a three-dimensional optical recording medium using the solid-form mixture (multiphoton absorption organic material) of the present invention as an optical recording material, and a schematic configuration of an example recording apparatus (b). The figure is shown.
A three-dimensional optical recording medium 10 in FIG. 1A includes a support (substrate 11a) having a recording layer 13a made of a multiphoton absorbing organic material according to the present invention and an intermediate layer 14a (protective layer) for preventing crosstalk. It has a configuration in which 50 layers are alternately stacked.
The film thickness of the recording layer 13a is preferably 0.01 to 0.5 μm, and the film thickness of the intermediate layer 14a is preferably 0.1 to 5 μm.
According to the three-dimensional optical recording medium 10, a large capacity of terabytes can be realized with the same size as a CD or DVD. Depending on the data reproduction method (transmission / or reflection type), a substrate 12a similar to the substrate 11a or a predetermined reflection layer made of a highly reflective material may be provided.

When performing three-dimensional recording of information, the light 15a from the light source 11b is focused on a desired location in the recording layer 13a. In addition to the bit-unit and depth-unit recording methods, a parallel recording method using a surface light source is preferable because it achieves a high transfer rate.
It is also possible to realize a high transfer rate by producing a bulk three-dimensional optical recording medium (not shown) having no intermediate layer and recording page data in a lump like the hologram recording method. .

  Examples of the material for the substrates 11a and 12a 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. These may be provided with a guide groove for tracking and address information in advance according to the target optical recording medium.

  The recording layer 13a can be formed by directly applying the mixture (multiphoton absorbing organic material) of the present invention onto a substrate using a spin coater, roll coater, bar coater, blade coater, dipping method or the like.

  For the intermediate layer 14a, a polyolefin film such as polypropylene and polyethylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyethylene terephthalate, a plastic film such as a cellophane film, or a plate can be applied. The recording layer 13a is laminated by a method such as bonding using a machine.

(Photoelectric conversion)
In FIG. 2, the schematic block diagram of an example of the dye-sensitized organic solar cell 30 which utilized the mixture (multiphoton absorption organic material) of the solid form of this invention as an electrode is shown.
FIG. 2 shows the arrangement of a mixture (multiphoton absorption organic material) 23 according to the present invention and metal fine particles 24 carrying a dispersant on a transparent conductive film (electrode) 21 that can transmit light, and the counter electrode side thereof. 2 represents a dye-sensitized dye solar cell in which a solid electrolyte 22 is laminated.

For the solid electrolyte 22, an inorganic compound having a hole transport function, an organic low molecule, an organic polymer compound, or the like can be applied. The former is an oxide having oxygen vacancies in a crystal (stabilized zirconia, CeO _2, etc.). However, the latter is exemplified by an ion conductive polymer (polyethylene oxide or the like). Examples of the transparent conductive film include tin oxide, ITO, and zinc oxide.

  Such a dye-sensitized organic solar cell 30 has an electrode area that is three-dimensionally expanded as compared to conventionally known ones, and can effectively use light having a long wavelength with small energy. It has the advantage that it is excellent in energy extraction efficiency (energy conversion efficiency). In addition to simple production, long-term stability can be ensured by solidifying the device.

(Light limiting device)
FIG. 3 is a schematic diagram showing an outline of an example of the light limiting device 40 using the mixture of the present invention, that is, the solid-state multiphoton absorbing organic material as a light limiting material.
In optical communication and optical information processing, optical control such as modulation and switching is required to carry signals such as information with light.
In general, for this type of light control, an electro-light control method using an electric signal is employed.
However, in the electro-optical control method, in addition to the response speed of the element itself, there are restrictions on the processing speed due to the band limitation due to the CR time constant as in the electric circuit and the unbalance of the speed between the electric signal and the optical signal. In order to make full use of the broadband property and high speed, which are the advantages of light, light-light control technology for controlling an optical signal by an optical signal is very important.
FIG. 3 shows an example of a light limiting device that uses a solid-form mixture (multiphoton absorbing organic material) according to the present invention as a light limiting element. By exciting the light limiting element 33 with a control light 31, multiphoton excitation is performed. The signal light 32 is optically switched.
Such a light limiting device 40 uses optical changes such as transmittance, refractive index and absorption coefficient caused by light irradiation to modulate its intensity and frequency, without using electronic circuit technology. It can be applied to optical switches in optical communication, optical exchange, optical computer, optical interconnection, etc. In addition, the response speed is far superior to that of a normal semiconductor element, and because of the high sensitivity, the signal-to-noise ratio is high and the signal characteristics are excellent.

(Optical modeling equipment)
FIG. 4 is a schematic diagram showing an outline of an example of an optical modeling apparatus 50 that uses the mixture (multiphoton absorption organic material) of the present invention as a polymerization initiator or a photosensitizer (or part thereof) of a photocuring material. is there.
When the light from the light source 41 is condensed on the photocurable material 44 containing the mixture (multiphoton absorption organic material) of the present invention via the movable mirror 42 and the condensing lens 43, the photon density is only in the vicinity of the condensing point. A high region is formed, and the photocuring material 44 is cured. By controlling the movable mirror 42 and the movable stage 45, an arbitrary three-dimensional structure can be formed.

Here, the photocuring material is a material that undergoes a multiphoton polymerization reaction when irradiated with light and changes from a liquid to a solid.
The main components are a resin component comprising an oligomer and a reactive diluent, and a photopolymerization initiator.
Further, as other components, a photosensitizer may be further contained.
An oligomer is a polymer having a degree of polymerization of about 2 to 20, has a large number of reactive groups at its terminal, and is usually added with a reactive diluent for adjusting viscosity and curability.
When light is irradiated, the polymerization initiator (or photosensitizer) absorbs multiphotons, and reactive species are generated directly from the polymerization initiator (or via the photosensitizer) to initiate polymerization. Thereafter, a three-dimensional cross-linking is formed through a chain polymerization reaction, and the resin is changed to a solid resin having a three-dimensional network structure in a short time.

  By using the mixture (multiphoton absorbing organic material) of the present invention as a polymerization initiator or photosensitizer (or part thereof) of a photocuring material, the reactivity is good and the production stability is excellent, and It was confirmed that ultra-precise three-dimensional modeling exceeding the diffraction limit is possible.

  As described above, by using the mixture of the present invention (solid-state multiphoton absorption organic material), it becomes possible to efficiently use the localized plasmon enhancement field generated in the metal fine particles in three dimensions. Thus, functional materials and functional devices at a practical level that do not require expensive and high-output light sources can be provided.

Hereinafter, a specific sample of the mixture (multiphoton absorption organic material) of the present invention was prepared, and the two-photon fluorescence intensity and the enhancement were measured and evaluated. Examples 1 to 3 are Reference Examples 1 to 3 not included in the present invention.
[Example 1]
0.37 g of chloroauric acid was added to 30 ml of water, a mixed solution consisting of 2.187 g of tetraoctylammonium bromide and 80 ml of toluene was added, and the mixture was stirred for 2 hours. Next, 0.25 g of octadecanethiol 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 to be reacted. 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 spherical gold fine particles were redispersed in 10 ml of toluene, and further 7 mg of a two-photon absorption organic material represented by the following formula (2) was added and stirred.

  After stirring, 1 g of acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon) was added and further stirred and melted. This solution is cast on a glass substrate (casting), the solvent is volatilized and solidified, and a 50 μm thick acrylic resin bulk body composed of spherical gold fine particles, a two-photon absorbing organic material and a dispersant (octadecanethiol) is formed. Produced.

[Example 2]
3 mg of spherical gold fine particles obtained in Example 1 were redispersed in 10 ml of toluene, and 7 mg of a two-photon absorption organic material represented by the above formula (2) was further added and stirred. After stirring, this solution was applied onto a glass substrate by spin coating to produce a thin film having a thickness of 200 nm composed of spherical gold fine particles, a two-photon absorbing organic material, and a dispersant (octadecanethiol).

Example 3
0.37 g of chloroauric acid was added to 30 ml of water, a mixed solution consisting of 2.187 g of tetraoctylammonium bromide and 80 ml of toluene was added, and the mixture was stirred for 2 hours. Subsequently, 0.025 g of octadecanethiol was added and stirred for 1 hour.
Next, a solution in which 0.378 g of NaBH4 was dissolved in 20 ml of water was dropped, and the mixture was stirred for 2 hours to be reacted.
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 spherical gold fine particles were redispersed in 10 ml of toluene, and 7 mg of a two-photon absorption organic material represented by the above formula (2) was further added and stirred. After stirring, this solution is applied onto a glass substrate by spin coating, and a thin film having a thickness of 200 nm is formed of a spherical gold fine particle, a two-photon absorbing organic material, and a dispersant (octadecanethiol) covering a part of the surface of the spherical gold fine particle. Was made.

Example 4
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 were 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 to confirm that the color of the chloroauric acid aqueous solution disappeared. The solution was transferred to a petri dish and irradiated with ultraviolet light having a wavelength of 254 nm for 20 minutes with a low-pressure mercury lamp to obtain a gold nanorod dispersion having an absorption peak near 830 nm. The gold nanorod component was precipitated from the obtained dispersion using a centrifuge, and the supernatant was removed. Then, water is added again, and the gold nanorod component is precipitated again using a centrifuge, and this process is repeated a plurality of times to remove the excess cetyltrimethylammonium bromide (dispersant) adsorbed on the gold nanorod. Removed.
By adding 0.1 ml of a 1% toluene solution of 3-aminopropylethyldiethoxysilane to the gold nanorod dispersion thus prepared and stirring, and further adding 10 ml of toluene and stirring, the gold nanorods are added to the toluene layer. Was dispersed. Thereafter, the solution was decanted to obtain a toluene solution of gold nanorods coated with 3-aminopropylethyldiethoxysilane.
To 1 ml of this solution, 7 mg of a two-photon absorption organic material represented by the above formula (2) was further added and stirred. After stirring, this solution was applied onto a glass substrate by spin coating, and a thin film having a thickness of 200 nm comprising gold nanorods, a two-photon absorbing organic material, and a dispersant (Si coupling agent: 3-aminopropylethyldiethoxysilane). Was made.

Example 5
To the gold nanorod dispersion prepared in Example 4, 0.1 ml of a 1% toluene solution of 3-mercaptopropyltriethoxysilane was added and stirred, and further, 10 ml of toluene was added and stirred to form gold nanorods in the toluene layer. Dispersed. Thereafter, the solution was decanted to obtain a toluene solution of gold nanorods coated with 3-mercaptopropyltriethoxysilane.
To 1 ml of this solution, 7 mg of a two-photon absorption organic material represented by the above formula (2) was further added and stirred. After stirring, this solution was applied onto a glass substrate by spin coating, and a thin film having a thickness of 200 nm composed of gold nanorods, a two-photon absorbing organic material, and a dispersant (Si coupling agent: 3-mercaptopropyltriethoxysilane) was formed. Produced.

Example 6
0.1 g of chloroauric acid tetrahydrate was dissolved in 950 ml of ultrapure and heated to boiling. While stirring this solution, 1% aqueous sodium citrate solution was added, heated to reflux, and allowed to cool to room temperature to obtain a spherical gold fine particle solution. To 100 ml of the resulting spherical gold fine particle solution, 0.1 ml of a 1% acetone solution of 3-mercaptopropyltrimethoxysilane was added and stirred, and then 7 mg of the two-photon absorbing organic material represented by the above formula (2) was further added to 1 ml of this solution. Added and stirred. After stirring, this solution was applied onto a glass substrate by spin coating, and a thin film having a thickness of 200 nm comprising spherical gold fine particles, a two-photon absorbing organic material, and a dispersant (Si coupling agent: 3-mercaptopropyltrimethoxysilane). Was made.

Example 7
0.1 g of chloroauric acid tetrahydrate was dissolved in 950 ml of ultrapure and heated to boiling. While stirring this solution, 1% aqueous sodium citrate solution was added, heated to reflux, and allowed to cool to room temperature to obtain a spherical gold fine particle solution. 1 ml of a 1% acetone solution of 3-mercaptopropyltriethoxysilane is added to 100 ml of the resulting spherical gold fine particle solution and stirred. Then, 7 mg of the two-photon absorption organic material represented by the above formula (2) is further added to 1 ml of this solution and stirred. did. After stirring, this solution was applied onto a glass substrate by spin coating, and a thin film having a thickness of 200 nm composed of spherical gold fine particles, a two-photon absorbing organic material, and a dispersant (Si coupling agent: 3-mercaptopropyltriethoxysilane). Was made.

[Comparative Example 1]
7 mg of a two-photon absorption organic material represented by the above formula (2) was added to 10 ml of toluene and stirred. After stirring, 1 g of acrylic resin Dianal BR-75 (manufactured by Mitsubishi Rayon) was added and stirred and melted. The solution was cast on a glass substrate by casting (casting), and the solvent was volatilized and solidified to produce an acrylic resin bulk body having a thickness of 50 μm.

[Comparative Example 2]
7 mg of a two-photon absorption organic material represented by the above formula (2) was added to 10 ml of toluene, and the mixture was stirred and applied on a glass substrate by spin coating to produce a thin film having a thickness of 200 nm.

(Measurement of two-photon fluorescence intensity and enhancement)
In general, the measurement of the two-photon absorption efficiency is not easy to directly measure because of the influence of absorption and scattering of incident light by the metal fine particles.
From this point of view, in the sample two-photon absorption organic materials prepared in each of the above-described Examples and Comparative Examples, a material having fluorescence characteristics is particularly exemplified, and the amount of fluorescence generated as a result of the two-photon absorption is determined by two-photon absorption. We decided to evaluate it as an alternative characteristic of efficiency.

FIG. 5 shows a schematic diagram of a measurement system for the amount of fluorescent light.
As the excitation light source for two-photon absorption, MaiTai (infrared femtosecond laser, repetition frequency 80 MHz, pulse width 100 fs) manufactured by Spectra Physics was used. In order to adjust the output, an attenuator composed of a 1 / 2λ plate and a Glan laser prism was provided to adjust the average output to 200 mW. After adjusting the output, the excitation light was converted into circularly polarized light through a ¼λ plate, and then condensed in a sample installed with a plano-convex lens having a focal length of 100 mm.
Fluorescence generated at the focal position of the excitation light is condensed by a coupling lens with a focal length of 40 mm to be approximately parallel light, separated from the excitation light by a dichroic mirror, and passed through an infrared cut glass filter, and is then flattened with a focal length of 100 mm. The light was roughly condensed with a convex lens and then detected with a photodiode.

(Evaluation results)
The two-photon fluorescence light amount of Examples 1 to 7 was evaluated as a relative value with Comparative Examples 1 and 2. The relative values of Example 1 with Comparative Example 1 are shown in Table 1, and the relative values of Examples 2 to 7 with Comparative Example 2 are shown in Table 2.

  As shown in the evaluation results of Tables 1 and 2, according to the present invention, the multiphoton absorption efficiency of the multiphoton absorbing organic material is dramatically improved by utilizing the localized plasmon enhancement field generated in the metal fine particles. I was able to.

  In addition, each said Example is an example of embodiment of this invention, It is also possible to take another well-known material structure, and does not change the summary of this invention at all.

(A) A schematic sectional view of a three-dimensional recording medium is shown. (B) The schematic block diagram of a recording device is shown. The schematic block diagram of an example of a dye-sensitized organic solar cell is shown. The schematic block diagram of an example of an optical limiting device is shown. The schematic block diagram of an example of an optical shaping apparatus is shown. The schematic of the measurement system of a fluorescence light quantity is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Three-dimensional optical recording medium 11a Substrate 11b Light source 12a Substrate 12b Light source 13a Recording layer 14a Intermediate layer 15a Light 21 Transparent conductive film 22 Solid electrolyte 23 Multiphoton absorption organic material 24 Metal fine particle 30 Dye-sensitized organic solar cell 31 Control light 32 Signal light 33 Light limiting element 34 Color filter 35 Detector 40 Light limiting device 41 Light source 42 Movable mirror 43 Condensing lens 44 Photocurable material 45 Movable stage 50 Stereolithography device

Claims (9)

Containing at least a multiphoton absorbing organic material, fine metal particles that generate a localized plasmon enhancement field, and a dispersant,
The dispersant has a function of suppressing electron transfer between the multiphoton absorbing organic material and the fine metal particles that generate the localized plasmon enhancement field ,
The mixture , wherein the dispersant is a silane coupling agent . A mixture according to claim 1, wherein the entire surface of the fine metal particles to generate local plasmon enhanced field, or a part of the surface, characterized in that it is coated with the dispersant. The mixture according to claim 1 or 2 , which is solid at normal temperature. The mixture according to any one of claims 1 to 3 , wherein the metal fine particles that generate the localized plasmon enhancement field are nanorods. An optical recording medium that is formed on a plane and performs recording and reproduction by light incident in a direction perpendicular to the plane,
An optical recording medium using the mixture according to any one of claims 1 to 4 as at least a part of its constituent elements. 6. A three-dimensional optical recording medium having a structure in which the optical recording medium according to claim 5 is laminated. The photoelectric conversion element characterized by using the mixture as described in any one of Claims 1 thru | or 4 as at least one part of a component. As at least a part of the components, optical limiting element characterized by mixture is used according to any one of claims 1 to 4. The stereolithography system, wherein the mixture according to any one of claims 1 to 4 is used as at least a part of the constituent elements.

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