JP2003045661A - Light-emitting nanostructure and light-emitting element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting nanostructure and a light-emitting element having a high emission efficiency and improved particularly for the efficiency of taking out light. SOLUTION: The light-emitting nanostructure has a support having a plurality of mutually independent pores with average aperture diameters of 50 nm to 200 nm and a depth of 2000 nm or less and a porous surface on which the apertures of the plurality of pores are positioned; and a light-emitting organic material and a charge-transport material both of which are enveloped in the plurality of pores. The light-emitting element using the nanostructure is also disclosed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a luminescent nanostructure using a luminescent organic material and a luminescent device using the luminescent nanostructure. It belongs to the technical field of a light-emitting nanostructure and a light-emitting element that are applicable to a polychromatic light source and have improved light emission efficiency and directivity.

[0002]

2. Description of the Related Art Since an organic light emitting device can easily obtain a planar light source, it has been studied by a great many research institutes for the purpose of application to a flat display.
Usually, an organic light emitting device is manufactured by coating or vapor depositing a hole transport layer, a light emitting layer and an electron transport layer made of an organic material on a transparent electrode provided on a substrate, and disposing a cathode thereon. When a voltage is applied to the device, holes are injected from the transparent electrode side and electrons are injected from the cathode side, and those carriers are recombined in the light emitting layer to generate an excited state of the organic light emitting material. The light emitting phenomenon of a light emitting element is based on the emission of photons when it is deactivated from its excited state to the ground state. It has been reported that the external quantum efficiency of the organic light-emitting device has been dramatically improved in recent years, and that an ortho-metallated complex-doped device using a triplet, for example, has achieved an efficiency of nearly 20%. There is a theory that most of the quantum efficiency loss of the device is a loss of light extraction efficiency. Therefore, efficient extraction of emitted light from the substrate side has become a very important theme in recent years. .

On the other hand, solid-state microfabrication techniques that support the development of solid-state optoelectronic devices such as light-emitting devices have been steadily progressed by three-dimensional microfabrication techniques that make full use of lithography with light or electron beams. The micro-fabrication of semiconductor DRAM (Dynamic Random Access Memory), which is the leading technology, has achieved high integration at a pace of about 4 times in 3 years according to Moore's law. However, in the future, it will be difficult to secure the performance such as the physical limit of the line width (about 100 nm) in the optical processing technology, and the target thin film and three-dimensional structure that exceed this limit, such as the target electrical characteristics. Currently, there are enormous barriers to technological development in relying solely on optical processing technology for further functional integration. Therefore, in order to add a highly reliable function to an extremely small nano space, it is considered difficult to use the “top-down” method, which aims at the limit as an extension of the conventional optical processing technology. From such a background, a pore forming method utilizing self-assembly in a chemical reaction has been reviewed as an ultrafine processing method for a solid of 100 nm or less.

One of these is H.264. Masuda et al., Sci
Ence, 268, 1466 (1995), and forming a pore-arranged alumina film by an anodic electrolytic oxidation method. For example, in JP-A-6-32675, starting from an anodized alumina film prepared by self-assembly, the uneven structure of pores is once transferred to a polymer such as polymethylmethacrylate, and then transferred onto a transfer body. A method of forming a porous layer of various inorganic metal oxides by a sol-gel reaction or the like is disclosed. Further, Japanese Unexamined Patent Publication No. 6-200378 discloses a porous structure made of metal or the like made by this transfer method, and Japanese Unexamined Patent Publication No. 8-186245 discloses a porous structure mainly composed of silicon. . The pores with a diameter of tens to hundreds of nanometers formed in these porous inorganic structures and their regular arrangement are effective in fixing functions of ultrafine materials using nanospace and in exhibiting functions by geometrical orientation. It is useful, and researches are being conducted to add a new function as an element by filling the guest material in the pores. For example, in Japanese Patent Laid-Open No. 10-284766,
Japanese Patent Laid-Open No. 2000-31462 discloses a method of expressing a magnetoresistive effect by introducing an ultrafine material having magnetism into pores.
A method is disclosed in which a conductive material such as carbon nanotube is put into the pores to produce an electron-emitting device and the electron-emitting device is applied to a light-emitting device such as an LED.

[0005]

However, in these conventional methods, pores are used as a space for accommodating solid crystals or particles having a certain shape, and organic molecules such as organic molecules having an extremely small size of several nm or less are used. No attempt has been made to apply the functional body to the molecular function of an organic light emitting device by confining the functional body in the pores. Further, in improving the light emission characteristics of the organic EL element, no technique has been proposed for using a nanostructure, which is an aggregate of pores having a size of several tens of nm, as a field for light emission.

The present invention has a high luminous efficiency, in particular
It is an object of the present invention to provide a light emitting nanostructure and a light emitting device with improved light extraction efficiency.

[0007]

The objects of the present invention have been achieved by the following matters which specify the present invention and preferred embodiments thereof. (1) The average aperture diameter is 50 nm to 200 nm,
And a support having a plurality of independent pores having a depth of 2000 nm or less and a porous surface in which the openings of the plurality of pores are arranged, and a luminescent organic material included in the plurality of pores. And a charge transporting material. (2) The luminescent nanostructure according to (1), wherein the luminescent organic material is electroluminescent. (3) The luminescent nanostructure according to (1) or (2), wherein the material forming at least a part of the plurality of pores is an insulating material. (4) The luminescent nanostructure according to (3), wherein the insulating material is at least one selected from aluminum oxide, zirconium oxide and silicon carbide. (5) The luminescent nanostructure according to any one of (1) to (4), wherein the charge transporting material is an electron transporting material. (6) A conductive layer disposed at least in contact with the charge-transporting material (1) to (5).
The luminescent nanostructure according to any one of 1. (7) The luminescent nanostructure according to any one of (1) to (6), wherein the luminescent organic material emits phosphorescence. (8) The luminescent nanostructure according to any one of (1) to (7), wherein the luminescent organic material is a metal complex. (9) The luminescent nanostructure according to any one of (1) to (8), wherein the luminescent organic material is a polymer compound or is included in pores together with the polymer compound. . (10) The emission wavelength region of the luminescent organic material included in at least two adjacent pores of the plurality of pores is different from each other, (1) to (9). Luminescent nanostructure. (11) The luminescent organic material forms an organic layer having a thickness of 20 nm to 1900 nm inside the plurality of pores, according to any one of (1) to (10). Luminescent nanostructure. (12) A light emitting device configured by using the light emitting nanostructure according to any one of (1) to (11). (13) The light emitting device according to (12), which is used as a light source for exposure.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. In addition, in this specification, "-" shows the range which includes the numerical value described before and after that as a minimum value and a maximum value, respectively. The luminescent nanostructure of the present invention has an average diameter of 50.
nm-200 nm and a depth of 2000 nm or less and a plurality of pores independent of each other and a support having a porous surface on which openings of the pores are arranged, and included in the pores. And a light emitting organic material and a charge transporting material.

First, the pores of the support of the luminescent nanostructure of the present invention will be described. A plurality of pores having a diameter sufficiently smaller than the wavelength of visible light (which will be referred to as “pores” in the present specification, but there are other expressions such as “small pores”) are formed on the support. ing. The support is a nanostructure formed by assembling these pores in close proximity to each other and regularly arrayed, and is typically a tabular nanostructure. The shape of the openings of the pores may be any of point-symmetrical circles and polygons, line-symmetrical ellipses and polygons, and asymmetrical amorphous shapes, and can be appropriately selected according to the purpose. Generally, they are circular and point-symmetrical polygons (particularly triangles and hexagons). The pores may have a shape and a cross-sectional area that have the same cross-section over the entire length in the depth direction, or may have a cross-sectional shape and a cross-sectional area that change with depth (including continuous change and intermittent change). Good. Examples of the latter are pores with a large cross-sectional area at the surface and a small cross-sectional area at the deep part, and a polygonal cross-sectional area at the surface,
Examples include pores having a circular cross section in the deep part.

The average diameter of the pores means the edge length of the openings of the pores. When the openings are circular, the diameter is measured, and when the openings are elliptical or polygonal, the length between the edges including the diagonal line is calculated. It means the longest straight length. The average diameter of the pores is 50 to 20.
It is 0 nm. When the diameter is less than 50 nm, it becomes difficult to fill the organic light emitting material and the like into the pores. Also, the caliber is 2
If it exceeds 00 nm, the uniformity of the pores tends to be distorted, for example, the shape of the pores and the control of the regular arrangement become incomplete in the self-assembly reaction for forming the pores described later. In this respect, the average aperture is preferably 70 to 150 nm. Further, the depth of the pores is 2000 nm or less. When the depth exceeds 2000 nm, the thickness of the light emitting layer and the charge transport layer inside the pores becomes large, the internal resistance increases, and the light emitting efficiency and the light emitting characteristics are deteriorated. On the other hand, if the depth of the pores is too small, it becomes difficult to fill the luminescent organic material or the like. From such a viewpoint, the depth of the plurality of pores is preferably 100 nm to 1800 nm, and more preferably 200 nm to 1000 nm.

Depth (L) with respect to the diameter (R) of the pores
When the ratio (L / R) is defined as the aspect ratio, the preferable aspect ratio of the pores is 2 to 40, and the more preferable aspect ratio is 5 to 30.

It is preferable that the plurality of pores of the support are independent of each other, that is, they do not have a communication path leading to two or more pores. It is preferable that the support has a porous surface in which openings of the plurality of pores are two-dimensionally arranged regularly. "A two-dimensionally regular array" means that the openings are arranged in a two-dimensional matrix at equal intervals, or
It means a state in which openings or a group of openings of pores are distributed with a regular arrangement on a two-dimensional plane.
The porous surface preferably forms a mesh structure. The two-dimensionally regular array, for example,
An array in which the openings are regularly arranged in a mesh shape so as to occupy the vertices of an equilateral triangle, an array in which the openings are arranged in a regular mesh shape so as to form a checkerboard pattern, and the openings form a honeycomb structure. An array arranged in a mesh pattern is included. Such a network structure of the porous surface can be confirmed by observation with an electron microscope.

It is preferable that the ratio of the area of the openings of the pore group to the area of the porous surface is higher because the optical function can be efficiently expressed. When the ratio of the total projected area of the openings of the pore group to the total projected area of the porous surface (including the opening area of the pores) is defined as the opening ratio, the preferred opening ratio is 30% or more. And more preferably 60%
That is all.

The plane density of the pores on the porous surface (the number of pores per unit area) is usually 4 × 10 ^{8 to} 5
× 10 ¹¹ pieces / cm ² , preferably 2 × 10 ⁹ to 10
¹¹ pieces / cm ² . When the pitch between the openings of the pores on the porous surface is defined by the distance between the centers, the preferred pitch is 100 to 800 nm.

In the present invention, the number 1 which the support has
The arrangement of pores having a size of 0 to several hundreds of nanometers can be partially achieved by physical means only by photolithography and electron beam lithography. However, even with these means, it is difficult to process while controlling the pore pitch over a wide area for mass production. Such an array of pores can be produced by controlling a self-assembly reaction involving diffusion and transport of ions and molecules in a chemical reaction.
As a method for preparing a porous nanostructure having a regular pore array by self-assembly, H. H. et al. Masuda et al., Sc
Ience, 268, 1466 (1995), the anodic electrolytic oxidation synthesis method of the alumina coating is useful, and can be preferably applied to the present invention. In addition, H. Masuda
Et al., Advanced Materials, 12, 4
44 (2000), the porous alumina oxide film can be used as a template material to produce various types of inorganic porous structures other than alumina. It can be preferably applied to the present invention.

For example, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. Hei 6-32675, an uneven surface structure of pores is transferred once to a polymer such as polymethylmethacrylate by using an anodized alumina film prepared by self-assembly. After that, a porous nanostructure made of various materials can be prepared by a method of forming an inorganic metal oxide layer on the transfer body by a sol-gel reaction or the like. Porous nanostructures produced by these methods can also be used as a support in the present invention. Furthermore, JP-A-6-200378
A porous structure made of a metal or the like produced by the transfer method disclosed in Japanese Patent Laid-Open No. 8-186245, or a porous structure mainly composed of silicon formed by the method disclosed in Japanese Patent Laid-Open No. 8-186245 is also a support of the present invention. Can be used as

When the anodic electrolytic oxidation synthesis method of the alumina film is used as a method for producing the support, a plurality of pores have a two-dimensional regularity and a porosity in which they are arranged in a dense (high aperture ratio) array. Alumina is obtained, which is preferable. Usually, the porous alumina produced by the above method is obtained as a porous film laminated on an aluminum substrate. In the present invention, a laminate of an aluminum substrate and porous alumina can be used as a support, or after removing the aluminum substrate with a solvent, only porous alumina can be used as a support. By removing the aluminum substrate, the plurality of pores become through holes each having an opening at the bottom. Furthermore, after collecting only the porous alumina layer from the aluminum substrate, a laminated body obtained by laminating the porous alumina layer on another substrate (for example, a glass substrate or the like) can be used as a support. After laminating porous alumina on another substrate such as a glass substrate, heat treatment may be performed.

Support with Regular Pore Array Used in the Present Invention
Both inorganic and organic materials can be used as body materials.
Can be used. The preferred material is electrically
Alumina as an insulating inorganic material (especially anodized aluminum
), Silica, zirconium oxide, SiC, glass, TE
Freon (registered trademark), etc .; electrically insulating organic materials
And as a polymer resin, polyimide, polysulfonic acid,
Polyester, polyethylene terephthalate, polycarbonate
Bonates, etc .; T as a metal oxide material containing a semiconductor
iO ₂, SrTiO₃, ZnO, SnO₂, InSnO_x,
Nb₂O₃, WO₃, CuO, CoO₂, MnO₂, V₂O_Five
Etc .; metal chalcogenides including compound semiconductors and poly
CdS, CdS, ZnS, Ga as element composite compounds
P, GaAs, InP, FeS₂, PbS, CuIn
S₂, CuInSe₂So-called compound half represented by
Conductor, compound having perovskite structure or composite compound
Etc .; as metal and metalloid materials, gold, platinum, silver, copper,
Chrome, zinc, tin, titanium, tungsten, aluminum
Um, nickel, iron, silicon, germanium, etc .; charcoal
As raw materials, graphite, glassy carbon, die
Almonds and the like;

The support used in the present invention may be composed of a single material or may be composed of a plurality of materials. When the support is composed of a plurality of materials, it is preferable that the material is changed depending on the structure, such as a wall material and a bottom material in the pores or an upper part and a lower part of the pores. The material forming at least part of the inside of the pores of the support (preferably the walls of the pores) is an electrically insulating material (herein, “insulating material”).
In this case, it is used in this sense). Among them, metal chalcogenides (for example, oxides, sulfides, selenides, etc.) are preferable, metal oxides are more preferable, and alumina is most preferable. Further, in a support having a structure in which the bottoms of pores are closed, that is, in a support having a structure in which a porous layer having a plurality of pores and a non-porous layer are laminated, a porous layer and a non-porous It may be different from the material of the layers. As a material for the non-porous layer, a conductive material is preferable, and a particularly preferable material is a conductive metal or carbon material. Further, the non-porous layer may be composed of two or more layers made of different materials.

The support preferably has a flat plate shape. When the support has a flat plate shape, the thickness of the support in the direction perpendicular to the porous surface is preferably 100 nm to 2 mm, more preferably 50 nm.
0 nm to 1 mm, more preferably 1 to 500 μ
m. The pore may be a through hole having an opening at the bottom or a non-through hole having a closed bottom. When the pores are through-holes, the thickness of the support corresponds to the depth of the pores, and when the pores are non-through-holes, the depth of the pores and the non-porous layer disposed thereunder. And the total thickness.

Next, the light emitting organic material and the charge transporting material used in the present invention will be described. The present invention is characterized in that the light emitting organic material and the charge transporting material are included inside the pores of the support.
In the present invention, the light emitting organic compound and the charge transporting material are brought into a state of being physically or electrically in contact with each other inside the pores to improve the efficiency of extracting light from the light emitting organic material. There is.

As used herein, the term "luminescent organic material" means a dry thin film or powder in a solid state at 0 to 150 ° C. as a result of being subjected to electronic excitation such as absorption of electromagnetic waves and electronic redox. Refers to organic compounds (including metal complexes) that emit light in the temperature range of. Here, the term “light emission” is used to mean either or both of fluorescence and phosphorescence. Electroluminescent organic materials that emit light when an electric field is applied are well known, but are also preferably used in the present invention. The luminescent organic material may be a low molecular weight compound or a high molecular weight compound. The luminescent organic compounds may be used alone or in combination of two or more.

As the light emitting organic material, a phosphorescent organic compound and a metal complex are preferable. Some metal complexes exhibit phosphorescence, and such metal complexes are also preferably used. In the present invention, it is very desirable to use an orthometallated complex, particularly from the viewpoint of improving the luminous efficiency. The orthometalated complex is described in, for example, Akio Yamamoto, "Organometallic Chemistry-Basics and Applications-", p. 232, p. 232, Sokabosha (issued in 1982); H. Yersin, "Photochemistry".
and Photophysics of Coordination Compounds "71
~ 77, pp. 135-146, Springer-Verlag (1
(Issued in 987); As the ligand forming the orthometalated complex,
There are various types, which are also described in the above literature. As a preferred ligand, a 2-phenylpyridine derivative,
7,8-benzoquinoline derivative, 2- (2-thienyl)
Pyridine derivatives, 2- (1-naphthyl) pyridine derivatives, 2-phenylquinoline derivatives and the like can be mentioned. These derivatives may have a substituent. Examples of the central metal of the orthometalated complex include Ir, Pd, Pt and the like, but an iridium (Ir) complex is particularly preferable. The orthometalated complex may have other ligands in addition to the ligand necessary for forming the orthometalated complex. The orthometalated complex also includes a compound that emits light from a triplet exciton, which is preferable from the viewpoint of improving luminous efficiency.

In addition, examples of the luminescent organic compound that can be used in the present invention are shown below. However, the luminescent organic compound used in the present invention is not limited to the following, and it is excited to emit fluorescence or Any compound may be used as long as it is a compound capable of emitting phosphorescence. Examples of the light-emitting organic compound include oxinoid compounds, perylene compounds, coumarin compounds, azacoumarin compounds, oxazole compounds, oxadiazole compounds, perinone compounds, pyrrolopyrrole compounds, naphthalene compounds, anthracene compounds, fluorene compounds, fluoranthene compounds, tetracene compounds, pyrene. Compounds, coronene compounds, quinolone compounds, azaquinolone compounds, pyrazoline derivatives, pyrazolone derivatives, rhodamine compounds, chrysene compounds, phenanthrene compounds, cyclopentadiene compounds, stilbene compounds, diphenylquinone compounds, styryl compounds, distyrylbenzene compounds, butadiene compounds, dicyanomethylene Pyran compound, dicyanomethylene thiopyran compound, fluorescein compound, pyrylium compound, Apiririumu compounds, Serena pyrylium compounds,
Telluropyrylium compound, aromatic aldadien compound,
Oligophenylene compounds, xanthene compounds and thioxanthene compounds, cyanine compounds, acridine compounds,
Examples thereof include acridone compounds and quinoline compounds.

Further, it is preferable that the luminescent organic material is a polymer compound itself or is contained in the pores together with the polymer compound because the luminous efficiency can be increased. Examples of the light emitting polymer compound include poly-p-phenylene vinylene (PPV) derivatives such as MEH-PPV;
Examples thereof include π-conjugated polymer compounds such as polyfluorene derivatives and polythiophene derivatives; low molecular weight dyes and polymers in which tetraphenyldiamine or triphenylamine is introduced into the main chain or side chains. The compound filled in the pores together with the luminescent organic compound is not particularly limited, but the luminescent polymer compound exemplified above is preferably used. Further, the light emitting polymer compound and the light emitting low molecular weight compound can be used in combination.

A plurality of light emitting organic materials having different emission wavelength regions may be separately included in the pores. For example, it is possible to use luminescent organic materials whose emission wavelength ranges are blue, green and red, respectively, and to encapsulate these luminescent organic materials in different pores. By dividing the plurality of pores into a group of blue light emitting pores, a group of green light emitting pores and a group of red light emitting pores, by arranging each group regularly, without using a color filter,
A luminescent nanostructure capable of emitting full-color light with high density and high efficiency can be produced.

Next, in the present invention, the charge-transporting material to be included in the pores together with the above-mentioned luminescent organic material will be described. In the present specification, the “charge transporting material” refers to a material capable of propagating and transporting either an electron or a hole, and a material having conductivity with respect to an electron or a hole. An electron transport material defined as a material capable of transporting electrons is included in the concept of a charge transport material (a carbon material and a metal, which are generally called “electron conductive material” and “conductive material”). Materials), and hole transport materials (also commonly referred to as "hole injection materials") defined as materials capable of transporting or releasing holes and injecting holes.

The hole transporting material may be an organic material or an inorganic material, and it is also possible to use a combination of both. Examples of the organic hole transport material include N, N'-diphenyl-N, N'-bis (4-methoxyphenyl)-(1,1'-biphenyl) -4,4 '.
-Diamine (J. Hagen et al., Synthetic Metal 89 (1997)
215-220), 2,2 ', 7,7'-tetrakis (N, N
-Di-p-methoxyphenylamine) 9,9'-spirobifluorene (Nature, Vol. 395, 8 Oct. 1998, p583-585
And WO97 / 10617), an aromatic diamine compound in which a tertiary aromatic amine unit of 1,1-bis {4- (di-p-tolylamino) phenyl} cyclohexane is linked (JP-A-59-194393). , 4,
Aromatic amines containing two or more tertiary amines represented by 4, -bis [(N-1-naphthyl) -N-phenylamino] biphenyl and having two or more fused aromatic rings substituted by nitrogen atoms ( JP-A-5-234681), an aromatic triamine having a starburst structure of a derivative of triphenylbenzene (US Pat. No. 4,923,774 and JP-A-4-308688), N, N'-. Diphenyl-N, N'-bis (3-methylphenyl)-
Aromatic diamines such as (1,1′-biphenyl) -4,4′-diamine (US Pat. No. 4,764,625), α, α, α ′, α′-tetramethyl-α, α '-
Bis (4-di-p-tolylaminophenyl) -p-xylene (JP-A-3-269084), p-phenylenediamine derivative, triphenylamine derivative which is sterically asymmetric as a whole molecule (JP-A-4-12971) JP-A-4-264189, a compound in which a pyrenyl group is substituted with a plurality of aromatic diamino groups (JP-A-4-175395), and an aromatic diamine in which a tertiary aromatic amine unit is linked with an ethylene group (JP-A-4-264189). ), An aromatic diamine having a styryl structure (JP-A-4-290851), and a benzylphenyl compound (JP-A-4-36415).
3), one in which a tertiary amine is linked by a fluorene group (JP-A-5-25473), a triamine compound (JP-A-5-239455), and pisdipyridylaminobiphenyl (JP-A-5-320634). ,
N, N, N-triphenylamine derivative (Japanese Patent Laid-Open No. 6-1
972), an aromatic diamine having a phenoxazine structure (JP-A-7-138562), a diaminophenylphenanthridine derivative (JP-A-7-25247).
Aromatic amines shown in JP-A No. 4) and the like can be preferably used.

Further, α-octylthiophene and α,
ω-dihexyl-α-octylthiophene (Adv. Mate
r. 1997,9, N0.7, p557), hexadodecyldodecithiophene (Angew. Chem. Int. Ed. Engl. 1995, 34, No. 3, p.
303-307), 2,8-dihexyl anthra [2,3-b:
6,7-b '] dithiophene (JACS, Vol120, N0.4, 1998,
p664-672) and other oligothiophene compounds, polypyrrole (K. Murakoshi et al.,; Chem. Lett. 1997, p471), H
andbook of Organic Conductive Molecules and Polyme
rs Vol.1,2,3,4 (NALWA, WILEY Publishing), polyacetylene and its derivatives, poly (p-phenylene) and its derivatives, poly (p-phenylenevinylene) and its derivatives, polythieny Conductive polymers such as renvinylene and its derivatives, polythiophene and its derivatives, polyaniline and its derivatives, and polytoluidine and its derivatives can be preferably used. For hole transport materials, Nature, Vo
Tris (4) to control dopant levels as described in L.395, 8 Oct. 1998, p583-585.
-Bromophenyl) aminium hexachloroantimonate to add a compound containing a cation radical, or to control the potential of the oxide semiconductor surface (compensation of the space charge layer), Li [(CF ₃ S
A salt such as O ₂ ) ₂ N] may be added.

A p-type inorganic compound semiconductor can be used as the inorganic hole transport material. The band gap of the p-type inorganic compound semiconductor is preferably large because it does not prevent dye absorption. The band gap of the p-type inorganic compound semiconductor is preferably 2 eV or more, and more preferably 2.5 eV or more. Further, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than that of the dye adsorption electrode in order to reduce the dye holes. The preferable range of the ionization potential of the p-type inorganic compound semiconductor used as the hole transport material in the present invention is generally 4.5 eV to 5.5 eV, and more preferably 4.7 eV to 5.3 eV. .
The p-type inorganic compound semiconductor preferably used in the present invention is a compound semiconductor containing monovalent copper, and the compound semiconductor containing monovalent copper includes CuI, CuSCN, and CuInS.
e ₂ , Cu (In, Ga) Se ₂ , CuGaSe ₂ , Cu ₂
O, CuS, CuGaS ₂ , CuInS ₂ , CuAlSe
₂ etc. Among these, CuI and CuSC
N is preferred and CuI is most preferred. Besides compounds containing copper, GaP, NiO, CoO, FeO, Bi
P-type inorganic compound semiconductors such as ₂ O ₃ , MoO ₂ and Cr ₂ O ₃ are also preferably used.

The hole mobility of the organic hole transport material is preferably 1.0 × 10 ⁻⁷ cm ² / V · sec to 1.0 ×.
10 ⁴ cm ² / V · sec, more preferably 1.0
× 10 ^-5 cm ² / V · sec to 1.0 × 10 ² cm ² / V
・ Sec, and more preferably 1.0 × 10 ⁻³ cm
² / V · sec to 1.0 × 10 ⁻¹ cm ² / V · sec. When the hole transport material contains the p-type inorganic compound semiconductor, its preferable hole mobility is 1.0.
× 10 ^-4 cm ² / V · sec to 1.0 × 10 ⁴ cm ² / V
・ Sec, and more preferably 1.0 × 10 ⁻³ cm
² / V · sec to 1.0 × 10 ³ cm ² / V · sec. The preferable conductivity of the hole transport material used in the present invention is 1.0 × 10 ⁻⁸ S / cm to 1.0 × 10 ² S / cm, and more preferably 1.0 × 10 ⁻⁶ S / cm. -10S
/ Cm.

The electron transporting material usable in the present invention includes oxadiazole derivatives, triazole derivatives, triazine derivatives, nitro-substituted fluorenone derivatives, thiopyrandioxide derivatives, diphenylquinone derivatives,
Examples thereof include compounds such as a perylene tetracarboxyl derivative, an anthraquinodimethane derivative, a fluorenylidene methane derivative, an anthrone derivative, a perinone derivative, an oxine derivative and a quinoline complex derivative. Also, it is generally said to be an electron conductive material (or conductive material),
Carbon materials and metallic materials can be used as electron transport materials. As the metal material, aluminum, copper,
Metals such as gold, platinum and chromium; conductive metal oxides such as tin oxide, indium tin oxide (ITO) and indium zinc oxide; alkali metals such as Li and K; alkaline earth metals such as Mg and Ca. To be Examples of the carbon material include graphite, carbon black such as acetylene black, fullerene, and carbon nanotube.

The electron mobility of the electron transport material is preferably 1.0 × 10 ⁻¹⁰ cm ² / V · sec to 1.0 × 10.
² cm ² / V · sec, more preferably 1.0 × 1
0 ^-7 cm ² / V ・ sec to 1.0 × 10 ^-1 cm ² / V ・ s
ec, and more preferably 1.0 × 10 ⁻⁵ cm ² /
V · sec to 1.0 × 10 ⁻³ cm ² / V · sec.

In the present invention, it is preferable that the light emitting organic material and the charge transporting material are in physical contact with the conductive material in the pores. The conductive material is not particularly limited, but among them, a metal material or a carbon material having high conductivity is preferable. For example, by forming a conductive layer made of a conductive material on the bottom of the pores and introducing the luminescent organic material or the like onto the conductive layer, the luminescent organic material or the like can be brought into contact with the conductive material. it can. The metal material is preferably aluminum, copper or the like, which has a low resistance, but is preferably selected according to the configuration of the organic light emitting device to be included. For example, when it is desired to inject holes into the light-emitting organic material from the pore material, a material having a large work function is particularly preferable, and gold or platinum can be used. In recent years, it has been reported that even if the work function is relatively large, holes can be sufficiently injected by using, for example, a VI group metal material, and chromium is preferable among the VI group metal materials.
Alternatively, a metal oxide material can be used, and for example, tin oxide, indium tin oxide (ITO), indium zinc oxide, or the like is preferably a material capable of forming a light-transmitting thin film. On the other hand, when it is desired to inject electrons into the light-emitting organic material from the porous material, alkali metals such as Li and K having a low work function; alkaline earth metals such as Mg and Ca; . Further, aluminum which is hard to be oxidized and is stable is also preferable. In order to achieve both stability and electron injection properties, a layer containing two or more materials may be formed at the bottom of the pores.
It is described in detail in JP-A-5595 and JP-A-5-121172. As the carbon material, graphite, carbon black such as acetylene black, fullerene and carbon nanotube are useful.

Further, it is preferable that the conductive layer which is in physical contact with the light emitting organic material acts as a part of the electrode, that is, as a terminal. In addition, it is preferable that the terminals are electrically insulated from each other and configured as independent terminals in terms of an electrical equivalent circuit. For example, the pores are made of an insulating material such as alumina, and a conductive layer made of a conductive material is formed at the bottom of the pores by using electrodeposition or the like. Introduced into the luminescent material makes it possible to obtain a luminescent nanostructure which is electrically insulated from each pore and which can form an independent terminal. Further, the conductive layer may be arranged outside the pores, for example, a structure having pores of through holes is arranged on an electrode (preferably a pattern electrode) made of a conductive material, It is also preferable that the both are in contact with each other by exposing the light-emitting organic material or the like inside to the electrode.

In the present invention, both the luminescent organic material and the charge transporting material are immobilized inside the pores of the support by chemical adsorption or physical adsorption to the material constituting the pores. It may be encapsulated in a state, or may be encapsulated in a state where a part or all of the material forming the inner wall or the bottom of the pore is chemically bound by a covalent bond. Further, the light-emitting organic material and the charge-transporting material are the primary materials (for example, coupling compounds such as organosilane compounds, lipid dimolecules) previously supported in the pores by chemical bonding or chemical or physical adsorption. Membrane, synthetic polymer, etc.) may be used as an intermediary, and the substance may be encapsulated in a state where it is immobilized by chemical bonding or chemical or physical adsorption.

The light emitting organic compound and the charge transporting material must be in physical or electrical contact with each other in the pores of the support. For example, by stacking a layer made of the light emitting organic compound and a layer made of the charge transporting material inside the pores, the layers can be included in the pores in a state of being in contact with each other. In addition, the light emitting organic material and the charge transporting material are mixed in advance, and the mixture is introduced into the pores to form an organic layer containing both materials inside the pores. It can be encapsulated in the pores in a contact state. The thickness of the organic layer containing at least the light-emitting organic material formed inside the pores is preferably 20 nm to 1900 nm, more preferably 30 to 800 nm.

A material serving as an element having a light emitting function of a light emitting organic material and a charge transporting material (hole transporting material and / or electron transporting material (including conductive material)) is inserted into the pores of the support. Then, as a means for fixing, on the porous surface of the support, a solution in which the material is dissolved in any solvent is sequentially applied, and then the solvent is dried and removed so that the material as a solute is introduced into the pores. A method of solidifying; on the porous surface,
A solution in which the material is dissolved is printed, and if desired, the solvent is then dried and removed to solidify the material that is a solute into the pores; a wet printing method; a vacuum film-forming method such as vapor deposition is used. Method; and the like. Application methods include a roller method and a dip method as an application system; an air knife method, a blade method and the like as a metering system; and a method in which application and metering can be performed in the same part, which is disclosed in Japanese Patent Publication No. 58-4589. Wire bar method, US Pat. No. 268129
No. 4, No. 2761419, No. 2761791, and the like; slide hopper method, extrusion method, curtain method and the like; A spin method or a spray method is also preferable as a general-purpose machine. As the wet printing method, it is preferable to use the three major printing methods of letterpress, offset and gravure, intaglio, rubber plate, screen printing and the like.
The vacuum film forming method includes resistance heating vacuum evaporation method, electron beam evaporation method, sputtering method, MOVPE method, MBE method,
The PLD method and the like can be used, but the method is not limited thereto. From these, a preferable method can be selected according to the liquid viscosity and the wet thickness.

When the plurality of pores of the support are divided into two or more compartments and different compartments are filled with different luminescent organic materials, each luminescent organic material is treated as an extremely small amount of solution and the surface of the pores is treated. It can be carried out by spotting and injecting it into the pores. For example, a stamp pin, which is a chip for solution spotting, which is commonly used in DNA microarray fabrication equipment (arrayer) in the field of biodevices, is used. can do. An example of a stamp pin is S.M. D. Rose
Et al, Association for Laborat
ory Automation 3,53 (1998)
Including the Pin & Ring method disclosed in, Applied Physics, 69, p1415 (2000).
As a method other than the pin method, an inkjet type arrayer using a piezo-piezoelectric element may be used. V. Lem
mo et al., Anal. Chem. 69,543 (199
The non-contact pL (picoliter) scale precision dispenser reported in 7) is useful. By using these arrayers, it is possible to form regions having emission wavelengths different from each other in the pores of the support by dividing the regions into divisional regions having a size order of several μm to several tens of μm.

The light emitting device of the present invention is constituted by using the light emitting nanostructure of the present invention, and its form is not particularly limited. As one embodiment of the light emitting device of the present invention, the light emitting nanostructure is provided, and a means for applying a voltage to the light emitting organic material and the charge transporting material included in the pores of the support. A light emitting element is mentioned. The means for supplying the voltage can be constituted by, for example, an electrode arranged in contact with the light emitting organic material and the charge transporting material contained in the pores of the support. It is preferable that the means for applying a voltage is configured to be able to apply a voltage for each individual pore.

FIG. 1 shows a schematic sectional view of an embodiment of an electroluminescence (EL) element according to the present invention. The EL element 10 has a porous thin film 12 having a plurality of pores 14. The porous thin film 12 is preferably made of an insulating material such as alumina. Inside the pores 14, an organic layer 16 containing a polymer compound, an electroluminescent organic material, and a charge transporting material (for example, a hole transporting material) and a conductive layer 18 made of a transparent conductive material are formed. ing. Here, the conductive layer 18 is a layer additionally provided for the purpose of reinforcing the electrical contact between the organic layer 16 and the pattern electrode 20, and may be omitted. In the organic layer 16, the light emitting organic material and the charge transporting material are in contact with each other. A substrate 22 with a pattern electrode 20 is disposed below the porous thin film 12, and one pattern electrode 20 is provided.
Are in contact with the conductive layer 18 inside the plurality of arranged pores 14. The pattern electrode 20 and the substrate 22 are preferably light transmissive. For example, it is preferable to use indium tin oxide or the like for the pattern electrode 20 and a glass plate or the like for the substrate 22. On the other hand, on the surface of the porous thin film 12 opposite to the surface on which the substrate 22 is arranged, the pattern electrodes 24 are arranged in an array orthogonal to the pattern electrodes 20, and one pattern electrode 24 is plural. It is in contact with the organic layer 16 formed inside the arrayed pores 14. Pattern electrode 24
Can be made of, for example, aluminum.
The light emitting element 10 includes a pattern electrode 20 and a pattern electrode 24.
By appropriately combining and
4 is configured to be able to apply a voltage to the organic layer 16 inside.

The pattern electrode 20 and the pattern electrode 24 are combined to form the organic layer 16 inside the pores 14 at desired positions.
When a voltage is applied to the organic layer 16, the patterned electrode 2 is formed on the organic layer 16.
Holes are injected from 0 (anode) and electrons are injected from the pattern electrode 24 (cathode), and are recombined inside the organic layer 16, and the light emitting organic material in the organic layer 16 is in an excited state. From the substrate 22 side, the light emitted when the luminescent organic material returns from the excited state to the ground state can be observed. The light-emitting element of this embodiment has high light extraction efficiency and thus exhibits high light emission efficiency.

The light emitting device of the present invention is preferably used as a light emitting display material such as a high density color light display material and a light illuminating material for interior use. In addition, an information transmission element and an information conversion element for optical communication using the light emitting nanostructure of the present invention as a two-dimensional light emitting array,
The form of the image information calculation element is also preferable. Further, the light emitting device of the present invention can be applied as a light source for exposure used for monochrome and color printing photosensitive materials and the like.

[0044]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The materials, reagents, ratios, operations and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

Example 1 A light emitting device having the same structure as the light emitting device 10 shown in FIG. 1 was produced. However, the conductive layer 18 was not formed. The pattern electrode layer 26 has a two-layer laminated structure. 1. Preparation of Nanoporous Structure Having Plane Pore Arrangement An aluminum base metal substrate having a purity of 99.99% (thickness: 0. 0%) was added to an electrolytic aqueous solution containing 56% by mass of phosphoric acid, 14% by mass of sulfuric acid and 3% by mass of ethylene glycol. 5 mm, effective surface area of electrolysis 2 cm ² ) is immersed as a working electrode and a carbon electrode as a counter electrode,
A constant current of 0.5A is applied to the working electrode as a positive electrode at a temperature of 60 ℃
It was flowed for a minute and electrolytically etched to finish the surface of the aluminum substrate into an optically flat mirror surface.

0.3 m of the obtained mirror-finished aluminum substrate
The aluminum surface was anodized by immersing in an ol / L sulfuric acid aqueous solution and applying a voltage of 25 V at a temperature of 20 ° C. for 20 minutes. As described above, a film of aluminum oxide having a thickness of about 700 nm was formed on the surface of the aluminum substrate. When the surface of the coating was observed with a scanning electron microscope (SEM), the average diameter of the coating was 120 n.
The circular openings of m are arranged in a two-dimensional regularity in a hexagonal close-packed arrangement (arrangement in which the openings occupy the vertices of an equilateral triangle) in a mesh shape at equal intervals of 200 nm between centers. I was able to confirm that. Further, as a result of observing a fracture surface perpendicular to the surface of the network structure, it was found that the depth of the pores having the openings was about 650 nm. Also,
The average pore size of the pores is in the range of 20 nm to 400 nm due to the anodic oxidation treatment of alumina under different electrolysis conditions (temperature, time, electrolytic solution composition) and the etching treatment of the anodic oxide film with dilute phosphoric acid (expansion treatment of the pore size). To produce different aluminum substrates. Further, by prolonging the electrolysis time and growing an alumina thin film, samples with different pore depths were prepared, and the depth of the pores was 50 nm to 3000 n.
Different porous structures were prepared in the range of m.

2. Adjustment of Pore Depth and Preparation of Electrode Substrate Using a Lagmuir-Blodgett thin film manufacturing apparatus, with the aluminum surface of the porous support facing downward,
The aluminum substrate was dissolved in a water bath containing a dilute aqueous solution of phosphoric acid, the aluminum surface was subjected to etching treatment at 15 ° C., and the etching time was controlled to obtain a porous alumina thin film. The etching was stopped by neutralizing the solution in the water bath. On the other hand, a transparent conductive film of indium tin oxide (ITO) (thickness: 0.22 μm, resistance: 10 ohm / cm ² ) was formed on a glass substrate by vacuum sputtering, and the ITO thin film was formed by lithography to have a width of 10 μm and an interval of 10 μm. A patterned electrode was used as the grid pattern. The surface of the glass substrate on which this pattern electrode was formed was 1 cm × 1 cm. This patterned electrode substrate was fixed to a Teflon support, immersed vertically in a water tank, and then slowly pulled up at a low speed to deposit a porous alumina thin film on the water surface on the patterned electrode surface of the substrate. Further, the patterned electrode substrate coated with the porous alumina thin film was placed in an electric furnace at 600 ° C. for 3 days.
Heat treatment was performed for 0 minutes. Thus, the porous alumina thin film was fixed on the pattern electrode.

3. Installation of organic light-emitting device in pores Compound 1 (PVK) 400 m below as a host polymer
g, 120 mg of the following compound 2 (PBD) as a charge transporting material (in this case, an electron transporting material), and 10 mg of the following compound 3 (Ir (ppy) ₃ ) as a light emitting organic material.
Was mixed with 40 g of dichloroethane, and dissolved in a glow box filled with argon gas (dew point was −60 °) by ultrasonic waves until there were no suspended matters (about 24 hours). This solution was loaded into an inkjet ejector in a glow box and ejected onto the porous alumina thin film with a patterned electrode prepared above. The discharge conditions were controlled so that the dry film thickness was 100 nm. After the material was discharged, it was sufficiently dried in the glow box as it was (about 2 hours), and transferred to a vacuum device directly connected. Then, a LiF layer and an Al layer are formed with a thickness of 0.3 nm and 0.4 μm on the surface of the porous alumina layer opposite to the surface in contact with the ITO electrode by using a vacuum evaporation apparatus. did. The LiF layer and the Al layer were formed in a grid pattern orthogonal to the ITO pattern electrodes with a width of 10 μm and an interval of 10 μm.

A light emitting device was manufactured in the same manner except that the substrate shown in Table 1 below was changed.

[0050]

[Chemical 1]

4. Preparation of Comparative Example Not Using Porous Structure As a comparative example, the same procedure was performed except that the porous alumina thin film was not arranged on the ITO patterned substrate,
A device was produced.

5. Evaluation of Light-Emitting Properties of Devices Each of the manufactured light-emitting devices shown in Table 1 below was placed in a glow box in a source meter (Keithley 240
0) was used to apply a voltage, and the current value was measured. In addition, the emission luminance at that time was measured using a micro area measuring luminance meter BM-5A manufactured by Topcon Corporation. Further, the emission spectrum was measured by PMA-11 manufactured by Hamamatsu Photonics, the number of emitted photons from the luminance and the emission spectrum, the number of input electrons from the current value and the area of the light emitting element, and the external quantum efficiency from the ratio. Table 1 below shows that the emission brightness of each light emitting element is 1
The luminous efficiency in the state of 00 cd / m ² is shown.

[0053]

[Table 1]

From the results shown in Table 1, the emission luminance is 100 cd.
In / m ² , the luminous efficiency of the device of the comparative example was 8.2%, while the luminous efficiency of the light emitting device of the present invention was 10% or more.

Example 2 In Example 1, various light emitting organic materials shown in Table 2 below were used in place of the compound 3 as the light emitting organic material to manufacture a light emitting device. The support used was the same as that of the light-emitting element No. 4 in Table 1, and a support having pores with a diameter of 120 nm and a depth of 650 nm was used. The luminous efficiency of each light emitting element was measured in the same manner as in Example 1. The results are shown in Table 2 below.

[0056]

[Table 2]

Substrates were replaced with the same substrates as those for the elements 1, 2, 6 and 7, and various light emitting organic materials shown in Table 2 below were used to produce light emitting elements. Similarly, the luminous efficiency was measured and found to be 80% from the results shown in Table 2.
It was below.

[Example 3] In the structure of the light emitting device manufactured in Example 1, the device was manufactured by changing the kinds and conditions of constituent materials (pore structure, electron transport material) other than the light emitting organic material. did. According to a transfer method disclosed in JP-A-6-32675, etc., starting from an anodized alumina film prepared by self-assembly, the uneven structure of pores is once transferred to a polymer such as polymethylmethacrylate, By a method of forming an inorganic oxide layer on a transfer body by a sol-gel reaction, zirconium oxide (ZrO ₂ ) of an insulator is formed.
In addition, a porous nanostructure made of n-type semiconductor zinc oxide (ZnO) was prepared. Further, aluminum was vapor-deposited on the polymer transfer body produced in the same manner by a vacuum sputtering method to produce a porous nanostructure made of aluminum.

In the same manner as in Example 1, the pores of the various porous nanostructures produced were filled with a material containing a luminescent organic material or the like. However, by changing the amount of the material including the light-emitting organic material and the like, various light emitting devices were produced in which the total dry film thickness of the organic compound layer formed in the pores was in the range of 20 to 1800 nm. Further, as a comparison with the device of the present invention, a device having no charge transporting material (device No. 1) in the constitution without mixing the charge transporting material (electron conductive material in this case) with the light emitting organic material. 22) was also produced. For various elements with different configurations as described above,
The luminous efficiency of the device was measured in the same manner as in Example 1. The results are shown in Table 3 below.

[0060]

[Table 3]

[0061]

According to the present invention, it is possible to provide a light-emitting nanostructure and a light-emitting device which have high light-emission efficiency, and particularly improved light extraction efficiency.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment of a light emitting device according to the present invention.

[Explanation of symbols] 10 EL element 12 Porous thin film 14 pores 16 organic layers 18 Conductive layer 20 pattern electrodes 22 Substrate 24 pattern electrodes

Claims (13)

[Claims] 1. The average aperture diameter is 50 nm to 200 n.
m and a support having a porous surface in which a plurality of pores having a depth of 2000 nm or less and independent of each other and openings of the plurality of pores are arranged; and light emission included in the plurality of pores. Emissive nanostructure having a crystalline organic material and a charge transporting material. 2. The luminescent nanostructure according to claim 1, wherein the luminescent organic material is electroluminescent. 3. The luminescent nanostructure according to claim 1, wherein the material forming at least a part of the plurality of pores is an insulating material. 4. The insulating material is aluminum oxide,
The luminescent nanostructure according to claim 3, which is at least one selected from zirconium oxide and silicon carbide. 5. The luminescent nanostructure according to claim 1, wherein the charge transporting material is an electron transporting material. 6. The luminescent nanostructure according to claim 1, further comprising a conductive layer disposed in contact with at least the charge transporting material. 7. The luminescent nanostructure according to claim 1, wherein the luminescence of the luminescent organic material is phosphorescence. 8. The luminescent nanostructure according to claim 1, wherein the luminescent organic material is a metal complex. 9. The luminescent nanomaterial according to claim 1, wherein the luminescent organic material is a polymer compound or is included in pores together with the polymer compound. Structure. 10. The emission wavelength range of the luminescent organic material included in at least two adjacent pores of the plurality of pores is different from each other. The luminescent nanostructure described. 11. The light emitting organic material forms an organic layer having a thickness of 20 nm to 1900 nm inside the plurality of pores, according to any one of claims 1 to 10. The luminescent nanostructure described. 12. A light emitting device comprising the light emitting nanostructure according to claim 1. Description: 13. The light emitting device according to claim 12, which is used as a light source for exposure.