JP2021024873A - Light emitting material, ink composition and electroluminescence device - Google Patents

Abstract

To provide a light emitting material containing semiconductor nanoparticles having excellent dispersion stability, and an ink composition, and an electroluminescence device having reduced drive voltage and having excellent luminous efficiency and durability.SOLUTION: The present invention relates to a light emitting material containing semiconductor nanoparticles having organic ligands on the particle surfaces. The organic ligands in the light emitting material include a first ligand having an aromatic skeleton, and a second ligand having no aromatic skeleton.SELECTED DRAWING: None

Description

The present invention relates to light emitting materials, ink compositions and electroluminescent devices containing semiconductor nanoparticles.

Electroluminescent devices (EL, Electroluminescence) are attracting attention as surface-emitting devices that are lightweight, thin, consume less power, and have an excellent degree of freedom in shape. Such an electroluminescent element has many excellent features such as high-intensity light emission, high-speed response, wide viewing angle, thinness and light weight, and high resolution, and its application to flat panel displays and lighting is being studied. The use of quantum dots is attracting attention as one of the electroluminescent devices.

Quantum dots are small nanoscale semiconductor particles that exhibit intermediate behavior between atomic or molecular behavior and macroscopic solid (bulk form) behavior. Nanoscale materials (semiconductor nanoparticles) in which charge carriers and excitons are confined in all three-dimensional directions are called quantum dots, and the effective bandgap increases as the size decreases. That is, as the size of the quantum dot becomes smaller, its absorption and emission shift to the shorter wavelength side, in other words, from the red direction to the blue direction. Further, by controlling the composition and size of the quantum dots in combination, a wide spectrum from the infrared region to the ultraviolet region can be obtained, and by further controlling the size distribution, the half-value width is narrow and the color purity is narrow. Excellent spectrum can be obtained. Therefore, in recent years, a quantum dot type organic EL device using quantum dots made of semiconductor nanocrystals as a light emitting material has been proposed by taking advantage of these characteristics.

Semiconductor nanocrystals are generally protected by organic ligands. Most of the organic ligands have a structure having an adsorbing group at the end of a long-chain alkyl group. Organic ligands enhance the chemical stability of the surface of semiconductor nanocrystals and improve their durability. In addition, the organic ligand enhances the dispersibility in an organic solvent or water, and improves the dispersion stability of quantum dots composed of semiconductor nanocrystals in the composition.
Further, in recent years, ligand designs have been made for the purpose of improving the electrical characteristics of quantum dots such as charge injection. For example, Patent Documents 1 to 3 describe hole-transporting ligands and electron-transporting ligands. It has been shown that the characteristics of the electroluminescent element can be improved by surface-treating the quantum dots in combination.

Special Table 2005-502176 Japanese Unexamined Patent Publication No. 2008-214363 International Publication No. 2011/074492

However, all of the quantum dots of Patent Documents 1 to 3 are surface-treated only with a hole-transporting ligand and an electron-transporting ligand having an aromatic skeleton, and have a problem of low dispersion stability. Further, there are problems that the quantum dots are easily aggregated due to the decrease in dispersion stability, the luminous efficiency is decreased due to the aggregates, the drive voltage is increased, or the durability at the time of continuous lighting of the element is deteriorated.

That is, an object of the present invention is to provide a light emitting material and an ink composition containing semiconductor nanoparticles having excellent dispersion stability, and an electroluminescent element having a reduced driving voltage and excellent light emitting efficiency and durability.

The luminescent material according to the present invention is a luminescent material containing semiconductor nanoparticles having an organic ligand on the particle surface.
The organic ligand in the luminescent material comprises a first ligand having an aromatic skeleton and a second ligand having no aromatic skeleton.

In one embodiment of the light emitting material, the second ligand has an aliphatic hydrocarbon group having 1 to 18 carbon atoms.

In one embodiment of the luminescent material, the first ligand comprises one or more selected from a hole-transporting ligand and an electron-transporting ligand.

In one embodiment of the light emitting material, the HOMO energy level of the hole transporting ligand is −6.1 eV or more and −5.1 eV or less.

In one embodiment of the light emitting material, the LUMO energy level of the electron transporting ligand is -4.0 eV or more and -3.0 eV or less.

The ink composition according to the present invention contains the light emitting material according to the present invention and a solvent.

An anode, a light emitting layer, and a cathode are provided on the substrate.
The light emitting layer contains the light emitting material according to the present invention.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a light emitting material and an ink composition containing semiconductor nanoparticles having excellent dispersion stability, and an electroluminescent element having a reduced driving voltage and excellent light emitting efficiency and durability.

<Luminescent material>
The luminescent material of the present invention is a luminescent material containing semiconductor nanoparticles having an organic ligand on the particle surface, and the organic ligand in the luminescent material is a first ligand having an aromatic skeleton (hereinafter, simply "first". (Sometimes referred to as a "ligand") and a second ligand having no aromatic skeleton (hereinafter, may be simply referred to as a "second ligand").
By using the first ligand and the second ligand in combination, the luminescent material of the present invention has excellent dispersion stability and excellent hole and electron injection properties. As a result, it has a low driving voltage and excellent luminous efficiency and durability as compared with a light emitting material having only a ligand having an aromatic skeleton.

The light emitting material of the present invention usually contains a plurality of semiconductor nanoparticles. The luminescent material of the present invention may contain a first ligand and a second ligand in the luminescent material, for example, semiconductor nanoparticles having only the first ligand on the particle surface, or particle surface. May contain semiconductor nanoparticles having only a second ligand.
More specifically, the light emitting material of the present invention may be either (1) or (2) below.
(1) A luminescent material containing semiconductor nanoparticles having only a first ligand having an aromatic skeleton on the particle surface and semiconductor nanoparticles having only a second ligand having no aromatic skeleton on the particle surface.
(2) A luminescent material containing semiconductor nanoparticles having a first ligand having an aromatic skeleton on the particle surface and a second ligand having no aromatic skeleton.

<Semiconductor nanoparticles>
As the material of the semiconductor nanoparticles, a single element of Group IV of the periodic table such as carbon (C) (atypical carbon, graphite, graphene, carbon nanotubes, etc.), silicon (Si), germanium (Ge), tin (Sn), etc. A single element of Group V of the periodic table such as phosphorus (P) (black phosphorus); a single element of Group VI of the periodic table such as selenium (Se) and tellurium (Te); tin oxide (IV), boron nitride (BN) ), Boron phosphide (BP), Boron arsenide (BAs), Aluminum nitride (AlN), Aluminum phosphide (AlP), Aluminum arsenide (AlAs), Aluminum antimonized (AlSb), Gallium nitride (GaN), Gallium phosphide Group III elements of the Periodic Table such as (GaP), gallium arsenide (GaAs), gallium antimonized (GaSb), indium nitride (InN), indium phosphate (InP), indium arsenide (InAs), and indium antimonized (InSb). Compounds of Group V elements of the Periodic Table; Aluminum (Al ₂ S ₃ ), Aluminum _{Serene (Al 2} Se ₃ ), Gallium Sulfide (Ga ₂ S ₃ ), Gallium Selenium (Ga Se _{, Ga 2 Se 3} ) Gallium tellalide (GaTe, Ga ₂ Te ₃ ), indium oxide (In ₂ O ₃ ), indium sulfide (In ₂ S ₃ , In S), indium selenium (In ₂ Se ₃ ), indium tellurate (In ₂ Te ₃₎ ) And other compounds of Group III elements of the Periodic Table and Group VI of the Periodic Table; zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenium (ZnSe), zinc tellurate (ZnTe), cadmium oxide (CdO) ), Cadmium sulfide (CdS), Cadmium selenium (CdSe), Cadmium telluride (CdTe), mercury sulfide (HgS), mercury selenium (HgSe), mercury (HgTe) periodic table, etc. the compounds of the periodic table VI elements; copper (I) oxide compound of _(Cu 2 O) of the periodic table I group element and periodic table group VI elements such as; copper chloride (I) (CuCl), bromide Compounds of Group I elements of the Periodic Table and Group VII elements of the Periodic Table such as copper (I) (CuBr), copper (I) (CuI), silver chloride (AgCl), silver bromide (AgBr), etc. These two or more types may be used in combination if necessary. These semiconductors may contain elements other than the constituent elements. For example, taking Group III-V as an example, an alloy system such as InGaP or InGaN may be used. Further, semiconductor nanoparticles doped with a rare earth element or a transition metal element can be used in the above materials, and examples thereof include ZnS: Mn, ZnS: Tb, ZnS: Ce, and LaPO ₄ : Ce.

Among these, silicon (Si), germanium (Ge), gallium nitride (GaN), gallium sulfide (GaP), gallium sulfide (GaAs), indium nitride (InN), indium sulfide (InP), indium sulfide (InAs), Gallium selenium (GaSe, Ga ₂ Se ₃ ), indium sulfide (In ₂ S ₃ , InS), zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenium (ZnSe), zinc telluride (ZnTe), oxidation Alloy systems such as cadmium (CdO), cadmium sulfide (CdS), cadmium selenium (CdSe), cadmium telluride (CdTe), InGaP, and InGaN are preferably used, and indium phosphate (InP) and cadmium selenium (InP) are particularly preferable. CdSe), zinc sulfide (ZnS), and zinc selenium (ZnSe) are particularly preferably used. In particular, it is preferable to use InP as the core and ZnS and / or ZnSe as the shell.

Further, as the material of the semiconductor nanoparticles, perovskite crystals can also be preferably used. The perovskite crystal has a composition represented by the following formula (I) and has a three-dimensional crystal structure.
Formula (I): AQX ₃
[In formula (I), A is a monovalent cation of at least one amine compound selected from the group consisting of _{methylammonium (CH 3} NH ₂ ) and formamidinium (NH _{2 CHNH), or rubidium (} It is a monovalent cation of an alkali metal element which is at least one selected from the group consisting of Rb), cesium (Ce) and franciu (Fr), and Q is from the group consisting of lead (Pb) and tin (Sn). It is a divalent cation of at least one metal element selected, and X is a monovalent shade of at least one halogen element selected from the group consisting of iodine (I), bromine (Br) and chlorine (Cl). It is an ion. ]

As the semiconductor nanoparticles, core-shell type semiconductor nanoparticles having a core-shell structure are preferable. The core-shell type semiconductor nanoparticles have a structure having a core and a shell in which the core is coated with a material different from the material forming the core. By selecting a semiconductor with a large bunt gap for the shell, excitons (electron-hole pairs) generated by photoexcitation are confined in the core. As a result, the probability of non-radiative transition on the particle surface is reduced, and the quantum yield of emission and the stability of fluorescence characteristics are improved. Further, the shell may have a plurality of layers. Further, the boundary between the core and the shell, and one shell and the other shell may be clear or may be a gradient structure in which the core and the shell are gradually joined with a concentration gradient. Further, the shell may cover only a part of the core or the whole core.

The average particle size of the semiconductor nanoparticles including the core and the shell is usually 0.5 nm to 100 nm, preferably 1 to 50 nm, and more preferably 1 to 15 nm.

Here, the average particle size refers to a value obtained by observing semiconductor nanoparticles with a transmission electron microscope, randomly measuring 30 sizes, and adopting the average value. At this time, the semiconductor nanoparticles are accompanied by an organic ligand described later. On the other hand, by using a scanning transmission electron microscope accompanied by energy dispersive X-ray analysis, semiconductor nanoparticles excluding the organic ligand are identified and the particle size is measured. The identification of the semiconductor nanoparticles utilizes the fact that the semiconductor nanoparticles are imaged darker than the organic ligand due to the difference in electron density in the transmission electron microscope image. The shape of the semiconductor nanoparticles is not limited to a spherical shape, and may be a rod shape, a disk shape, or any other shape.

<Organic ligand>
The organic ligand covers at least a part of the surface of the semiconductor nanoparticles and is used for surface treatment of the semiconductor nanoparticles. The luminescent material of the present invention contains, as an organic ligand, a first ligand having an aromatic skeleton and a second ligand having no aromatic skeleton.

[First ligand having an aromatic skeleton]
The first ligand having an aromatic skeleton has an adsorption site to semiconductor nanoparticles and an aromatic skeleton site. Since the aromatic skeleton has a π electron that is easier to move than a σ electron in a conjugated form, it is easy to transfer carriers such as holes and electrons. Therefore, the first ligand having an aromatic skeleton has carrier transportability. Examples of the carrier transportability include hole transportability and electron transportability. The first ligand may be a hole-transporting ligand having hole-transporting property, an electron-transporting ligand having electron-transporting property, or a ligand having both hole-transporting property and electron-transporting property. There may be. Hereinafter, the ligand having both hole-transporting property and electron-transporting property shall be included in both the hole-transporting ligand and the electron-transporting ligand. Whether the carrier transportability is hole transportability or electron transportability is determined by the skeleton and ionization potential.
The hole-transporting ligand and the electron-transporting ligand will be described below.

[Hole-transporting ligand]
The hole-transporting ligand has an adsorption site on the surface of semiconductor nanoparticles and a hole-transporting site having a hole-transporting function. The adsorption site and the hole transporting site do not have to be completely separated. For example, a part of the hole transporting site may be an adsorption site.

Examples of the adsorption site include a carboxyl group (-COOH), an amino group (-NH ₂ ), a phosphino group (-PH ₂ ), a sulfanyl group (-SH), and the like as monovalent groups. Examples of the divalent group include a carbonyl group (> (C = O)), and examples of the trivalent group include a phosphoroso group (> (P = O) −). Further, a 2,2'-bipyridine skeleton, an 8-quinolinol skeleton, or the like can also be used as an adsorption site.

Examples of the hole-transporting moiety include a moiety having a structure composed of a known hole-transporting compound used as an organic electroluminescent element material and a derivative thereof, and are not particularly limited, but for example, a tertiary aromatic amine and thiophene. Oligomers, thiophene polymers, pyrrole oligomers, pyrrol polymers, phenylene vinylene oligomers, phenylene vinylene polymers, vinyl carbazole oligomers, vinyl carbazole polymers, fluorene oligomers, fluorene polymers, phenylene ethine oligomers, phenylene ethine polymers, phenylene oligomers, phenylene polymers, acetylene oligomers, Examples thereof include acetylene polymers, phthalocyanines, phthalocyanine derivatives, porphyrins, and porphyrin derivatives. In addition, the compounds shown below and their derivatives can also be used as hole transporting sites.

Further, as a preferable structure of the hole transporting ligand, a compound represented by the following general formula (1), general formula (2) or general formula (3) can be mentioned.

[In the general formula (1), X ¹ is a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, or an acyl group which may have a substituent. ,
R ^{1 to} R ⁸ are independently hydrogen atoms, an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxy group which may have a substituent, and a substituent. Aryloxy group which may have a substituent, an acyl group which may have a substituent, an amino group which may have a substituent, a (poly) organosiloxane group which may have a substituent, a carboxyl group or It is a sulfanyl group and
Of X ¹ and R ^{1 to} R ⁸ , at least one is a group having a carboxyl group or a group having a sulfanil group. ]

[In the general formula (2), R ^{11 to} R ²⁵ each independently have a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, and a substituent. May have an alkoxy group, an aryloxy group which may have a substituent, an acyl group which may have a substituent, a (poly) organosiloxane group which may have a substituent, a nitro group, and a substituent. It is an amino group, a carboxyl group or a sulfanyl group which may have ^{, and at least one of R 11 to} R ²⁵ is a group having a carboxyl group or a group having a sulfanyl group. ]

[In the general formula (3), X ² has a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent (excluding a phenyl group), or a substituent. It is an acyl group that may be
R ^{26 to} R ³⁵ are independently hydrogen atoms, an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxy group which may have a substituent, and a substituent. Aryloxy group which may have a substituent, (poly) organosiloxane group which may have a substituent, an amino group which may have a substituent, an acyl group which may have a substituent, a carboxyl group or It is a sulfanyl group and
Of X ² and R ^{26 to} R ³⁵ , at least one is a group having a carboxyl group or a group having a sulfanil group. ]
The substituents in the general formulas (1) to (3) will be described below.

The alkyl group is a linear, branched or cyclic alkyl group, and some hydrogen atoms may be shed to form a double bond or a triple bond. From the viewpoint that the content of semiconductor nanoparticles in the composition can be increased, the molecular weight of the treatment agent is preferably small, and the alkyl group preferably has 1 to 30 carbon atoms.
Examples of the alkyl group include a linear alkyl group such as a methyl group, an ethyl group, a hexyl group, a dodecyl group and an eicosyl group; a branched alkyl group such as a 2-ethylhexyl group; and a cyclic group such as a cyclohexyl group and a 3-cyclohexylpropyl group. Alkyl group; alkenyl group such as ethenyl group and dodecenyl group; alkynyl group such as 1-propynyl group and propargyl group can be mentioned.

An aryl group is a residue in which one hydrogen atom is formally removed from an aromatic ring, and more preferably, a residue in which one hydrogen atom is formally removed from an aromatic ring having 6 to 30 carbon atoms.
Examples of aromatic rings include benzene ring, naphthalene ring, pyrene ring, pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, quinoline ring, furan ring, pyrrol ring, thiophene ring, imidazole ring, pyrazole ring, oxazole ring, and thiazole ring. , Indol ring, benzimidazole ring, benzofuran ring, purine ring, aclydin ring, phenothiazine ring, biphenyl group, terphenyl group and the like.

The alkoxy group is a functional group to which an alkyl group is bonded via an ether bond, and the alkyl group is synonymous with the alkyl group in the above general formulas (1) to (3).

The aryloxy group is a functional group to which an aryl group is bonded via an ether bond, and the aryl group is synonymous with the aryl group in the above-mentioned general formulas ((1) to (3)).

The acyl group is a functional group to which an alkyl group or an aryl group is bonded via a carbonyl group, and the alkyl group and the aryl group are synonymous with the alkyl group and the aryl group in the above general formulas (1) to (3). Is.

The (poly) organosiloxane group is a residue obtained by formally removing one hydrogen atom from the siloxane compound, and the silicon of the siloxane compound may be substituted with an alkyl group. The alkyl group which may be substituted is synonymous with the alkyl group in the above general formulas (1) to (3). Examples of siloxane compounds include pentamethyldisiloxane, heptaethyltrisiloxane, undecamethyltetrasiloxane, trimethylsiloxydimethylsilanol, 1,1,3,3, tetramethyl-1,3-dihydroxydisiloxane or 1 , 1,3,3,5,5-hexamethyl-1,5-dihydroxy-trisiloxane and the like.
From the viewpoint that the content of semiconductor nanoparticles in the composition can be increased, the molecular weight of the ligand is preferably small, and the number of repeated siloxane bonds is preferably 4 or less.

The amino group which may have a substituent includes an amino group and a substituted amino group, and examples of the substituent of the substituted amino group include an alkyl group, an aryl group and an acyl group. The alkyl group, aryl group and acyl group are synonymous with the alkyl group, aryl group or acyl group in the above general formulas (1) to (3).

The alkyl group, aryl group, alkoxy group, amino group, aryloxy group and acyl group in the general formulas (1) to (3) may have a substituent.
Examples of the substituent which may be possessed include a halogeno group, a cyano group, a hydroxy group, a nitro group, an alkoxy group, an alkyl group, an aralkyl group, an aryl group, an aryloxy group, a silyloxy group, a heterocyclic oxy group and an acyloxy group. , Carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy, amino group (including anilino group), acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkyl And arylsulfonylamino group, sulfanyl group, alkylthio group, arylthio group, heterocyclic thio group, alkyl and arylsulfinyl group, alkyl and arylsulfonyl group, acyl group, aryloxycarbonyl group, alkoxycarbonyl group, carbamoyl group, imide group, Examples thereof include a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, a silyl group, a group containing a siloxane bond, and the like.
Further, the substituents that may be possessed in the present invention include the above-mentioned monovalent substituent and, if necessary, an alkylene group, an alkenylene group, an arylene group, a heteroarylene group, an ether bond, an ester bond, a sulfide bond and a carbonyl group. It may be a monovalent group in which a group, an imino group, or a divalent linking group combining them is combined.

A group having a carboxyl group or a sulfanyl group is an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, or a (poly) organo, which has a carboxyl group or a sulfanyl group as a substituent in addition to a carboxyl group and a sulfanyl group. Contains a siloxane group or an acyl group. Here, in addition to the carboxyl group and the sulfanyl group, the alkyl group, the aryl group, the alkoxy group, the aryloxy group, the (poly) organosiloxane group, the acyl group or the nitro group having a carboxyl group or a sulfanyl group as a substituent are described above. It is synonymous with the group in the general formulas (1) to (3) of.

Examples of an alkyl group having a carboxyl group or an aryl group having a carboxyl group include, for example, a 2-carbosixyl ethyl group, a 2,2-dicarboxyethyl group, a 2-carbosixyl ethenyl group, and a 2-cyano-. Examples thereof include 2-carbosixyl ethenyl group, 2-trifluoromethyl-2-carbosixyl ethenyl group, 2-fluoro-2-carbosixyl ethenyl group and the like.

Examples of the alkyl group having a sulfanyl group, the aryl group having a sulfanyl group, or the acyl group having a sulfanyl group include [(3-sulfanylpropanoyl) oxy] ethyl group and [(2-sulfanylacetyl) oxy] ethyl group. , 4- (Sulfanylmethyl) phenyl group, [(3-sulfanylpropanoyl) oxy] propyl group, 3-sulfanyl [(3-sulfanylpropanoyl) oxy] ethyl group, or {[(2-sulfanylethoxy) propanoyl] Oxy} ethyl group and the like can be mentioned.

Specific examples of the ligands represented by the general formulas (1) to (3) are shown below, but the present invention is not limited thereto. In the following structural formula, when cis-type and trans-type geometric isomers are present, either cis-type or trans-type may be used, and a mixture of cis-type and trans-type isomers may be used. The same applies to the thin-anti geometric isomerism.

[Electron-transporting ligand]
The electron-transporting ligand has an adsorption site on the surface of semiconductor nanoparticles and an electron-transporting site having an electron-transporting function. The adsorption site and the electron transporting site do not have to be completely separated. For example, a part of the electron transporting site may be an adsorption site. Examples of the adsorption site include those described in the section on hole-transporting ligands.

Examples of the electron-transporting moiety include a moiety having a structure composed of a known electron-transporting compound used as an organic electric field light emitting element material and a derivative thereof, and are not particularly limited, but for example, oxadiazole, oxadiazole derivative, and oxazole. , Oxazole derivative, isoxazole, isooxazole derivative, thiazole, thiazole derivative, isothiazole, isothiazole derivative, thiaxazole, thiazazole derivative, 1,2,3-triazole, 1,2,3-triazole derivative, 1,3,5 -Triazine, 1,3,5-triazine derivative, quinoxaline, quinoxalin derivative, pyrrole oligomer, pyrrol polymer, phenylene vinylene oligomer, phenylene vinylene polymer, vinyl carbazole oligomer, vinyl carbazole polymer, fluorene oligomer, fluorene polymer, phenylene ethine oligomer, phenylene Examples thereof include ethine polymers, phenylene oligomers, phenylene polymers, thiophene oligomers, thiophene polymers, acetylene polymers, and acetylene oligomer derivatives. In addition, the compounds shown below and their derivatives can also be used as electron transport sites.

The hole-transporting site and the electron-transporting site described above contain the same structure, because they can be both an electron-transporting site and a hole-transporting site.
Whether the ligand behaves as hole-transporting or electron-transporting depends on the relative HOMO-LUMO relationship between the hole-transporting ligand and the electron-transporting ligand, and relative to other compounds used in electroluminescent devices. HOMO and LUMO are determined by a specific HOMO-LUMO relationship, and even if the structure is specific, HOMO and LUMO are changed by the presence of an electron-withdrawing or electron-donating substituent. For the above reasons, some structures can be both hole-transporting and electron-transporting sites and are therefore described in both.

The hole-transporting ligand and the electron-transporting ligand may have the above-mentioned hole-transporting site and adsorption site, or the electron-transporting site and adsorption site directly bonded to each other, or may have a linking group such as an alkylene group. It may be connected via. Examples of the alkylene group in this case include a branched or linear alkylene group, and a linear alkylene group is preferable. The alkylene group preferably has about 1 to 5 carbon atoms, and specific examples thereof include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, and an n-pentylene group.

Specific examples of the hole-transporting ligand and the electron-transporting ligand are shown below, but the present invention is not limited thereto.

Among the above-mentioned carrier transporting ligands, HOMO and LUMO are important from the viewpoint of carrier injectability and carrier transportability. HOMO electrons are the most reactive and involved in reactivity. When receiving an electron, LUMO is involved in the reaction. That is, HOMO is a molecular orbital that emits electrons, LUMO is a molecular orbital that accepts electrons, and in an electroluminescent device, HOMO plays a role of transferring holes, and LUMO plays a role of transferring electrons.
In the luminescent material of the present invention, the HOMO energy level of the hole transporting ligand is preferably -6, 5 eV or more and -4.6 eV or less, and more preferably -6.1 eV or more and -5.1 eV or less. preferable. The LUMO energy level of the electron-transporting ligand is preferably −4.5 eV or more and −2.5 eV or less, and more preferably −4.0 eV or more and −3.0 eV or less.
The HOMO energy level of the hole-transporting ligand is preferably 0.2 eV or more higher than the HOMO energy level of the electron-transporting ligand, and more preferably 0.5 eV or more. The LUMO energy level of the hole-transporting ligand is preferably 0.2 eV or more higher than the LUMO energy level of the electron-transporting ligand, and more preferably 0.5 eV or more.

When the HOMO and / or LUMO of the hole-transporting ligand and the electron-transporting ligand satisfy the above conditions, the transport of electrons and holes in the electroluminescent device and the injection of electrons and holes into the semiconductor nanoparticles are performed. It is preferable because it can be made excellent and a high-performance electroluminescent element can be obtained.

[Second ligand without aromatic skeleton]
The second ligand, which does not have an aromatic skeleton, has an adsorption site for semiconductor nanoparticles and a non-aromatic skeleton site.
Examples of the adsorption site include a carboxyl group (-COOH), an amino group (-NH ₂ ), a phosphino group (-PH ₂ ), a sulfanyl group (-SH), and the like as monovalent groups. Examples of the divalent group include a carbonyl group (> (C = O)), and examples of the trivalent group include a phosphoroso group (> (P = O) −), which is more preferable. , At least one selected from the group consisting of a carboxyl group and a sulfanyl group.

More preferably as a second ligand, R ⁱ COOH, R ⁱ NH ₂ , R ⁱ ₂ NH, R ⁱ SH, R ⁱ H ₂ PO, R ⁱ ₂ HPO, R ⁱ ₃ PO, R ⁱ H ₂ P, R ⁱ ₂ ^HP, it is at least one selected from ^{_{R i 3 P, R i PO}} (OH) 2, and the group consisting of ^R _i 2 POOH.
Here, ^Ri is a substituted or unsubstituted aliphatic hydrocarbon group, a substituted or unsubstituted aliphatic heterocyclic group, or a substituted or unsubstituted alkoxy group. In one molecule, the case where a plurality of R ^i, they may be the same or different.

Examples of the aliphatic hydrocarbon group substituted or unsubstituted in the R ^i, include aliphatic hydrocarbon group having 1 to 18 carbon atoms, for example, an alkyl group, an alkenyl group, an alkynyl group or a cycloalkyl group.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a hexyl group, a heptyl group and an octyl group. Examples thereof include alkyl groups having 1 to 18 carbon atoms such as a decyl group, a dodecyl group, a pentadecyl group or an octadecyl group.

Examples of the alkenyl group include a vinyl group, a 1-propenyl group, a 2-propenyl group, an isopropenyl group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, a 1-octenyl group, a 1-decenyl group or 1 -An alkenyl group having 2 to 18 carbon atoms such as an octadecenyl group can be mentioned.

Examples of the alkynyl group include an ethynyl group, a 1-propynyl group, a 2-propynyl group, a 1-butynyl group, a 2-butynyl group, a 3-butynyl group, a 1-octynyl group, a 1-decynyl group or a 1-octadecynyl group. Examples of the alkynyl group having 2 to 18 carbon atoms.

Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclooctadecyl group, a 1-adamantyl group or a 2-adamantyl group having 3 to 18 carbon atoms. Cycloalkyl groups can be mentioned.

The aliphatic heterocyclic group substituted or unsubstituted in the R ^i, for example, 2-Pirazorino group, piperidino group, aliphatic heterocyclic group of 3 to 18 carbon atoms such as a morpholino group or a 2-morpholinyl group.

Examples of the alkoxy group substituted or unsubstituted in the R ^i, for example, a methoxy group, an ethoxy group, a propoxy group, n- butoxy group, sec- butoxy group, tert- butoxy group, pentyloxy group, hexyloxy group, 2-ethylhexyl Examples thereof include an oxy group, a stearyloxy group and a trifluoromethoxy group.

Examples of the substituent R ⁱ may have each independently represent a substituted or unsubstituted aliphatic hydrocarbon group, a substituted or unsubstituted aliphatic heterocyclic group, a substituted or unsubstituted alkoxy group, or Halogen atom can be mentioned. A substituted or unsubstituted aliphatic hydrocarbon group, the substituted or unsubstituted aliphatic heterocyclic group and a substituted or unsubstituted alkoxy group include those described as substituents of R ^i, as the halogen atom, Examples thereof include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Specific examples of the second ligand having no aromatic skeleton of the present invention will be described below, but these are not limited to the present invention.
As the second ligand, for example, methanethiol, ethanethiol, propanethiol, butanethiol, pentanethiol, hexanethiol, octanethiol, dodecanethiol, hexadecanethiol, octadecanethiol; methaneamine, ethaneamine, propaneamine, butylamine, pentylamine. , Hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, dimethylamine, diethylamine, dipropylamine; methaneic acid, ethaneic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, hepanoic acid, octanoic acid, Dodecanoic acid, hexadecanoic acid, octadecanoic acid, oleic acid; substituted or unsubstituted methylphosphin (eg, trimethylphosphine, etc.), substituted or unsubstituted ethylphosphin (eg, triethylphosphine, etc.), substituted or unsubstituted propylphosphin, Phosphines such as substituted or unsubstituted butylphosphines, substituted or unsubstituted pentylphosphins, substituted or unsubstituted octylphosphins (eg, trioctylphosphine (TOP)); substituted or unsubstituted methylphosphin oxides (eg, trimethylphosphine). Oxide, methyldihexylphosphine oxide, etc.), substituted or unsubstituted ethylphosphinoxide (eg, triethylphosphinoxide, etc.), substituted or unsubstituted propylphosphinoxide, substituted or unsubstituted butylphosphinoxide, substituted or unsubstituted. Examples include phosphin oxides such as octylphosphine (eg, trioctylphosphine oxide (TOPO); phosphonic acid) and the like.

The non-aromatic skeleton site of the second ligand having no aromatic skeleton preferably contains an aliphatic site from the viewpoint of exhibiting dispersibility, and more preferably a fat having 1 to 18 carbon atoms as the aliphatic site. It is a group hydrocarbon group.

The ratio of the first ligand to the organic ligand in the present luminescent material is preferably 5:95 to 95: 5 in terms of mass ratio from the viewpoint of achieving both dispersion stability and luminous efficiency. More preferably, 10:90 to 90:10.

<Ink composition>
The ink composition of the present invention may contain the light emitting material and the solvent according to the present invention, and may further contain other components if necessary. In the ink composition of the present invention, since the organic ligand in the luminous material contains a first ligand having an aromatic skeleton and a second ligand having no aromatic skeleton, the semiconductor nanoparticles have excellent dispersion stability. It has both properties and luminous efficiency. Hereinafter, each component contained in the ink composition will be described, but since the light emitting material is as described above, the description here will be omitted.

[solvent]
In the present ink composition, the solvent can be appropriately selected from the solvents capable of dispersing the semiconductor nanoparticles according to the use of the ink composition and the like. Specific examples of the solvent include aromatic hydrocarbons such as toluene, o-xylene, m-xylene, p-xylene, methicylene, cyclohexylbenzene and tetraline; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene and trichlorobenzene. Hydrogen; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetol, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole, etc. Aromatic ethers; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, n-butyl benzoate; ketones having an alicyclic such as cyclohexanone and cyclooctanone; methylethylketone, dibutyl Aliphatic ketones such as ketones; alcohols having an alicyclic such as methyl ethyl ketone, cyclohexanol, cyclooctanol; aliphatic alcohols such as butanol and hexanol; ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate ( Aliphatic ethers such as PGMEA); aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate, n-butyl lactate; n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, Aliphatic hydrocarbons such as 2,3-dimethylbutane, n-heptane, n-decane, 2,2,4-trimethylpentane, cyclohexane, methylcyclohexane, mineral spirit; etc., and may be used alone. It may be mixed and used.

The content ratio of the light emitting material in the ink composition may be appropriately adjusted according to the application of the ink composition and the like. The ratio of the light emitting material to the total amount of the ink composition is preferably 0.001% by mass or more and 50% by mass or less, and more preferably 0.01% by mass or more and 10% by mass or less. When the proportion of the luminescent material is not more than the above upper limit value, the dispersion stability of the luminescent material is excellent.

The ink composition of the present invention may contain other components as long as the object of the present invention is not impaired. Examples of other components include other luminescent materials described later, various additives, and the like. Examples of the additive include an antifoaming agent, a leveling agent, a thickener and the like.
The proportion of the other luminescent material in the total luminescent material including the luminescent material of the present invention and the other luminescent material is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less.

<Electroluminescent element>
The electroluminescent device of the present invention includes an anode, a light emitting layer, and a cathode on a substrate, and the light emitting layer includes the light emitting material according to the present invention. The electroluminescent device of the present invention is excellent in luminous efficiency because the light emitting layer contains the light emitting material according to the present invention.
The electroluminescent device of the present invention has at least a substrate, an anode, a light emitting layer, and a cathode, and may further have another layer if necessary. Further, the light emitting layer may be a single layer or a plurality of layers, and when there are two or more light emitting layers, at least one layer may contain the light emitting material according to the present invention.

That is, examples of the electroluminescent device of the present invention include a single-layer electroluminescent device including an anode, a light emitting layer, and a cathode, and a multi-layer electroluminescent device including another layer. As other layers constituting the multi-layer electroluminescent element, in addition to the light emitting layer, it is easy to inject holes and electrons into the light emitting layer, and the recombination of holes and electrons in the light emitting layer is facilitated. Examples thereof include a hole injection layer, a hole transport layer, a hole blocking layer, an electron injection layer, and the like, which are intended to be used by the user. Further, as another layer, it exists adjacent to the light emitting layer between the light emitting layer and the anode, and has a role of separating the light emitting layer and the anode, or the light emitting layer from the hole injection layer or the hole transport layer. Examples include the interlayer layer, which is a layer.

Typical layer configurations of the multi-layer electric field light emitting element include (1) anode / hole injection layer / light emitting layer / cathode, (2) anode / hole injection layer / hole transport layer / light emitting layer / cathode, and ( 3) anode / hole injection layer / light emitting layer / electron injection layer / cathode, (4) anode / hole injection layer / hole transport layer / light emitting layer / electron injection layer / cathode, (5) anode / hole injection Layer / light emitting layer / hole blocking layer / electron injection layer / cathode, (6) anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron injection layer / cathode, (7) anode / Light emitting layer / hole blocking layer / electron injection layer / cathode, (8) anode / light emitting layer / electron injection layer / cathode (9) anode / hole injection layer / hole transport layer / interlayer layer / light emitting layer / cathode , (10) Electron / hole injection layer / interlayer layer / light emitting layer / electron injection layer / cathode, (11) anode / hole injection layer / hole transport layer / interlayer layer / light emitting layer / electron injection layer / Examples include a cathode.

In addition, each of the above-mentioned layers may be formed by a layer structure of two or more layers, or several layers may be repeatedly laminated. As such an example, in recent years, for the purpose of improving the light extraction efficiency, an element configuration called "multi-photon emission" in which a part of the above-mentioned multi-layer electroluminescent layers is multi-layered has been proposed. This is, for example, in an electroluminescent element composed of a glass substrate / anode / hole transport layer / electron transporting light emitting layer / electron injection layer / charge generating layer / light emitting layer / cathode, of the charge generating layer / light emitting layer. Examples thereof include units in which a plurality of layers are laminated.

[Hole injection layer]
As the hole injection layer, a hole injection material that exhibits an excellent hole injection effect on the light emitting layer and can form a hole injection layer having excellent adhesion to the anode interface and thin film formation is used. Further, when such a material is laminated in multiple layers and a material having a high hole injection effect and a material having a high hole transport effect are laminated in multiple layers, the materials used for each are called a hole injection material and a hole transport material. Sometimes. These hole injection materials and hole transport materials need to have high hole mobility and low ionization energy of usually 5.5 eV or less. As such a hole injection layer, a material that transports holes to the light emitting layer with a lower electric field strength is preferable, and further ^{, when an electric field with a hole mobility of, for example, 10 4} to 10 ⁶ V / cm is applied, at least ^{It is preferably 10-6} cm ² / V · sec. The hole injection material and the hole transport material are not particularly limited as long as they have the above-mentioned preferable properties, and are conventionally used as a hole charge transport material in an optical transmission material or an organic EL element. Any known material used for the hole injection layer can be selected and used.

Examples of such hole injection materials and hole transport materials include triazole derivatives (see US Pat. No. 3,112,197) and oxadiazole derivatives (see US Pat. No. 3,189,447). ), Imidazole derivative (see Japanese Patent Publication No. 37-16906, etc.), polyarylalkane derivative (US Pat. No. 3,615,402, No. 3,820,989, No. 3,542,544). No. 45-555, 51-10983, 51-93224, 55-17105, 56-4148, 55-108667, JP-A. 55-156953, 56-36656, etc.), pyrazoline derivatives and pyrazolone derivatives (US Pat. Nos. 3,180,729, 4,278,746, JP-A-55- 88064, 55-88065, 49-105537, 55-51086, 56-80051, 56-88141, 57-45545, 54-112637. No. 55-74546, etc.), phenylenediamine derivative (US Pat. No. 3,615,404, JP-A No. 51-10105, No. 46-3712, No. 47-25336). , JP-A-54-53435, JP-A-54-11536, JP-A-54-119925, etc.), arylamine derivatives (US Pat. No. 3,567,450, US Pat. No. 3,180,703). No. 3, 240,597, No. 3,658,520, No. 4,232,103, No. 4,175,961, No. 4,175,961 4,012,376, Japanese Patent Publication No. 49-35702, Japanese Patent Application Laid-Open No. 39-27577, JP-A-55-144250, Japanese Patent Application Laid-Open No. 56-119132, Japanese Patent Publication No. 56-22437, Western German Patent No. Disclosure in US Pat. Nos. 1,110,518, etc.), amino-substituted chalcone derivatives (see US Pat. No. 3,526,501, etc.), oxazole derivatives (see US Pat. No. 3,257,203, etc.) ), Styrylanthracene derivative (see JP-A-56-46234, etc.), Fluorenone derivative (see JP-A-54-110837, etc.), Hydrazone derivative (US Pat. No. 3,717,462, etc.) Kaisho 54-59143, Gazette 55-520 See No. 63, No. 55-52064, No. 55-46760, No. 55-85495, No. 57-11350, No. 57-148549, No. 2-311591, etc.). Stilbene derivatives (Japanese Patent Laid-Open No. 61-210363, No. 61-228451, No. 61-14642, No. 61-72255, No. 62-47646, No. 62-36674, No. 62 -10652, 62-30255, 60-93455, 60-94462, 60-174749, 60-175052, etc.), Stilabene derivatives (US Patent No. 4) , 950, 950), polysilane-based (Japanese Patent Laid-Open No. 2-204996), aniline-based copolymer (Japanese Patent Laid-Open No. 2-282263), and conductivity disclosed in JP-A 1-2113999. Examples thereof include high molecular weight oligomers (particularly thiophene oligomers).

Further, as a hole injection material and a hole transport material, a porphyrin compound (Japanese Patent Laid-Open No. 63-29569665), an aromatic tertiary amine compound and a styrylamine compound (US Pat. No. 4,127,412). JP-A-53-27033, No. 54-58445, No. 54-149634, No. 54-64299, No. 55-79450, No. 55-144250, No. 56-119132. , No. 61-295558, No. 61-98353, No. 63-295695, etc.) can also be used. For example, 4,4'-bis (N- (1-naphthyl) -N-phenylamino) biphenyl having two fused aromatic rings in the molecule described in US Pat. No. 5,061,569 and the like. Or, 4,4', 4 "-tris (N- (3-methylphenyl) -N-phenyl" in which three triphenylamine units described in JP-A-4-308688 are linked in a starburst type. Amino) triphenylamine and the like can be mentioned. Further, phthalocyanine derivatives such as copper phthalocyanine and hydrogen phthalocyanine can be mentioned as the hole injection material. Further, aromatic dimethyridene compounds, p-type Si, p-type SiC and the like can be mentioned. Inorganic compounds can also be used as hole injection materials and hole transport materials.

Further, as materials that can be used for the hole injection layer, molybdenum oxide (MnO _x ), vanadium oxide (VO _x ), ruthenium oxide (RuO _x ), copper oxide (CuO _x ), tungsten oxide (WO _x ), iridium oxide Inorganic oxides such as (IrO _x ) and their dopes are also mentioned.

Specific examples of the aromatic tertiary amine compound include, for example, N, N'-diphenyl-N, N'-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine, N, N, N', N'-(4-methylphenyl) -1,1'-phenyl-4,4'-diamine, N, N, N', N'-(4-methylphenyl) -1,1' -Biphenyl-4,4'-diamine, N, N'-diphenyl-N, N'-dinaphthyl-1,1'-biphenyl-4,4'-diamine, N, N'-(methylphenyl) -N, N'-(4-n-butylphenyl) -phenanthrene-9,10-diamine, N, N-bis (4-di-4-tolylaminophenyl) -4-phenyl-cyclohexane, N, N'-bis ( 4'-diphenylamino-4-biphenylyl) -N, N'-diphenylbenzidine, N, N'-bis (4'-diphenylamino-4-phenyl) -N, N'-diphenylbenzidine, N, N'- Bis (4'-diphenylamino-4-phenyl) -N, N'-di (1-naphthyl) benzidine, N, N'-bis (4'-phenyl (1-naphthyl) amino-4-phenyl) -N , N'-diphenylbenzidine, N, N'-bis (4'-phenyl (1-naphthyl) amino-4-phenyl) -N, N'-di (1-naphthyl) benzidine, etc., which are positive It can be used for both pore injection materials and hole transport materials.

Tables 1 and 2 show particularly preferable examples of the hole injection material.

To form the hole injection layer, the above-mentioned compound is thinned by a known method such as a vacuum deposition method, a spin coating method, a casting method, or a Langmuir-Bloget method (LB method). The film thickness of the hole injection layer is not particularly limited, but is usually 5 nm to 5 μm.

Examples of the material used for the interlayer layer include polyvinylcarbazole and its derivatives, polyarylene derivatives having aromatic amines in the side chain or main chain, arylamine derivatives, and polymers containing aromatic amines such as triphenyldiamine derivatives. Further, as a method of forming an interlayer layer, when a high molecular weight material is used, a method of forming a film from a solution is exemplified.

For the deposition of the interlayer layer from the solution, known wet film forming methods such as spin coating method, casting method, micro gravure coating method, gravure coating method, bar coating method, roll coating method, wire bar coating method, etc. A coating method such as a dip coating method, a spray coating method, a screen printing method, a flexographic printing method, an offset printing method, an inkjet printing method, a capillary coating method, or a nozzle coating method can be used.

The optimum value of the thickness of the interlayer layer differs depending on the material used, and it may be selected so that the driving voltage and the luminous efficiency are appropriate values. Usually, it is 1 nm to 1 μm, preferably 2 to 500 nm. More preferably, it is 5 to 200 nm.

[Electron injection layer]
As the electron injection layer, an electron injection material that exhibits an excellent electron injection effect on the light emitting layer and can form an electron injection layer having excellent adhesion to the cathode interface and thin film formation is used. Examples of such electron-injected materials include metal complex compounds, nitrogen-containing five-membered ring derivatives, fluorenone derivatives, anthracinodimethane derivatives, diphenoquinone derivatives, thiopyrandioxide derivatives, perylenetetracarboxylic acid derivatives, fleolenilidenemethane. Examples thereof include derivatives, anthron derivatives, silol derivatives, triarylphosphine oxide derivatives, polyquinolin and its derivatives, polyquinoxalin and its derivatives, polyfluorene and its derivatives, calcium acetylacetonate, sodium acetate and the like. Inorganic / organic composite materials in which a metal such as cesium is doped with vasophenanthroline (Proceedings of the Society of Polymer Science, Vol. 50, No. 4, p. 660, published in 2001) and the 50th Joint Lecture on Applied Physics. Proceedings of the lecture, No. BCP, TPP, T5MPyTZ, etc. described on page 3, 1402, published in 2003 are also mentioned as examples of electron injection materials, but can form a thin film necessary for device fabrication, inject electrons from a cathode, and transport electrons. As long as it is a material, it is not particularly limited to these.

Among the electron-injected materials, preferred ones include a metal complex compound, a nitrogen-containing five-membered ring derivative, a siror derivative, and a triarylphosphine oxide derivative. As a preferable metal complex compound, a metal complex of 8-hydroxyquinoline or a derivative thereof is suitable. Specific examples of the metal complex of 8-hydroxyquinolin or a derivative thereof include tris (8-hydroxyquinolinate) aluminum, tris (2-methyl-8-hydroxyquinolinate) aluminum, and tris (4-methyl-8-). Hydroxyquinolinate) aluminum, tris (5-methyl-8-hydroxyquinolinate) aluminum, tris (5-phenyl-8-hydroxyquinolinate) aluminum, bis (8-hydroxyquinolinate) (1-naphtholate) ) Aluminum, bis (8-hydroxyquinolinate) (2-naphtholate) Aluminum, bis (8-hydroxyquinolinate) (phenolate) aluminum, bis (8-hydroxyquinolinate) (4-cyano-1-naphtholate) ) Aluminum, bis (4-methyl-8-hydroxyquinolinate) (1-naphtholate) aluminum, bis (5-methyl-8-hydroxyquinolinate) (2-naphtholate) aluminum, bis (5-phenyl-8) -Hydroxyquinolinate) (phenolate) aluminum, bis (5-cyano-8-hydroxyquinolinate) (4-cyano-1-naphtholate) aluminum, bis (8-hydroxyquinolinate) chloroaluminum, bis (8) -Aluminum complex compounds such as hydroxyquinolinate (o-cresolate) aluminum, tris (8-hydroxyquinolinate) gallium, tris (2-methyl-8-hydroxyquinolinate) gallium, tris (4-methyl- 8-Hydroxyquinolinate) gallium, tris (5-methyl-8-hydroxyquinolinate) gallium, tris (2-methyl-5-phenyl-8-hydroxyquinolinate) gallium, bis (2-methyl-8) -Hydroxyquinolinate) (1-naphtholate) gallium, bis (2-methyl-8-hydroxyquinolinate) (2-naphtholate) gallium, bis (2-methyl-8-hydroxyquinolinate) (phenolate) gallium , Bis (2-methyl-8-hydroxyquinolinate) (4-cyano-1-naphtholate) gallium, bis (2,4-dimethyl-8-hydroxyquinolinate) (1-naphtholate) gallium, bis (2) , 5-Dimethyl-8-hydroxyquinolinate) (2-naphtholate) gallium, bis (2-methyl-5-phenyl-8-hydroxyquinolinate) (phenolate) gallium, bis (2-methyl-5-si) Anno-8-hydroxyquinolinate) (4-cyano-1-naphtholate) gallium, bis (2-methyl-8-hydroxyquinolinate) chlorogallium, bis (2-methyl-8-hydroxyquinolinate) ( In addition to gallium complex compounds such as o-cresolate) gallium, 8-hydroxyquinolinate lithium, bis (8-hydroxyquinolinate) copper, bis (8-hydroxyquinolinate) manganese, bis (10-hydroxybenzo [h] ] Kinolinate) Metal complex compounds such as berylium, bis (8-hydroxyquinolinate) zinc, and bis (10-hydroxybenzo [h] quinolinate) zinc can be mentioned.

Further, preferred examples of the nitrogen-containing five-membered ring derivative include an oxadiazole derivative, a thiazole derivative, an oxadiazole derivative, a thiadiazole derivative and a triazole derivative, and specifically, 2,5-bis (1-phenyl) -1, 3,4-Oxadiazole, 2,5-bis (1-phenyl) -1,3,4-thiazole, 2,5-bis (1-phenyl) -1,3,4-oxadiazole, 2- (4) '-Tert-butylphenyl) -5- (4 "-biphenyl) 1,3,4-oxadiazole, 2,5-bis (1-naphthyl) -1,3,4-oxadiazole, 1,4 -Bis [2- (5-phenyloxadiazolyl)] benzene, 1,4-bis [2- (5-phenyloxadiazolyl) -4-tert-butylbenzene], 2- (4'-tert-butyl Phenyl) -5- (4 "-biphenyl) -1,3,4-thiadiazole, 2,5-bis (1-naphthyl) -1,3,4-thiadiazole, 1,4-bis [2- (5- (5-) Phenylthiadiazolyl)] Benzene, 2- (4'-tert-butylphenyl) -5- (4 "-biphenyl) -1,3,4-triazole, 2,5-bis (1-naphthyl) -1, Examples thereof include 3,4-triazole and 1,4-bis [2- (5-phenyltriazolyl)] benzene.

Further, examples of the material that can be used for the electron injection layer include _{inorganic oxides such as zinc oxide (ZnO x} ) and titanium oxide (TiO _x ), and their doped bodies.

Specific examples of particularly preferable oxadiazole derivatives, triazole derivatives and siror derivatives are shown in Tables 3 to 5. In addition, Ph in the table represents a phenyl group.

(Oxadiazole derivative)

(Triazole derivative)

(Siror derivative)

Further, as the hole blocking layer, a hole blocking material that can prevent holes that have passed through the light emitting layer from reaching the electron injection layer and can form a layer having excellent thin film forming property is used. Examples of such hole blocking materials include aluminum complex compounds such as bis (8-hydroxyquinolinate) (4-phenylphenolate) aluminum and bis (2-methyl-8-hydroxyquinolinate) ( Examples thereof include gallium complex compounds such as 4-phenylphenolate) gallium and nitrogen-containing condensed aromatic compounds such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP).

[Light emitting layer]
As the light emitting layer of the electroluminescent element, one having the following functions is preferable.
Injection function: A function that can inject holes from the anode or hole injection layer when an electric field is applied, and can inject electrons from the cathode or electron injection layer. Transport function; electric charge (electrons and holes) injected Light emitting function; a function that provides a field for recombination of electrons and holes and connects them to light emission. However, there is a difference between the ease of hole injection and the ease of electron injection. Also, the transport capacity represented by the mobility of holes and electrons may be large or small.

At least one light emitting layer constituting the electroluminescent element of the present invention contains the light emitting material of the present invention. The light emitting layer containing the light emitting material of the present invention is preferably formed from the ink composition of the present invention. Further, the light emitting layer may contain a known light emitting material in addition to the light emitting material of the present invention.
As known light emitting materials that may be added to the ink composition of the present invention, fluorescent whitening agents such as benzothiazole, benzimidazole, and benzoxazole, metal chelated oxinoid compounds, and styrylbenzene compounds can be used. .. Specific examples of these compounds include compounds disclosed in Japanese Patent Application Laid-Open No. 59-194393. Yet other useful compounds are listed in Chemistry of Synthetic Soybeans (1971), pp. 628-637 and 640.

As the metal chelated oxinoid compound, for example, a compound disclosed in JP-A-63-295695 can be used. Typical examples thereof include 8-hydroxyquinoline-based metal complexes such as tris (8-quinolinol) aluminum and dilithium epintridione as suitable compounds.

Further, as the styrylbenzene-based compound, for example, those disclosed in European Patent No. 0319881 and European Patent No. 0373582 can be used. The distyrylpyrazine derivative disclosed in JP-A-2-252793 can also be used as a material for the light emitting layer. In addition, the polyphenyl compound disclosed in European Patent No. 0387715 can also be used as a material for the light emitting layer.

Further, in addition to the above-mentioned fluorescent whitening agents, metal chelated oxynoid compounds, styrylbenzene compounds and the like, for example, 12-phthaloperinone (J. Appl. Phys., Vol. 27, L713 (1988)), 1,4- Diphenyl-1,3-butadiene, 1,1,4,4-tetraphenyl-1,3-butadiene (Apl. Phys. Lett., Vol. 56, L799 (1990)), naphthalimide derivative (Japanese Patent Laid-Open No. 2-305886), perylene derivative (Japanese Patent Laid-Open No. 2-189890), oxadiazole derivative (Japanese Patent Laid-Open No. 2-261791, or disclosed by Hamada et al. At the 38th Joint Lecture on Applied Physics. Oxaziazole derivative), aldazine derivative (Japanese Patent Laid-Open No. 2-220393), pyrazirin derivative (Japanese Patent Laid-Open No. 2-22304), cyclopentadiene derivative (Japanese Patent Laid-Open No. 2-289675), pyrolopyrrole derivative (Japanese Patent Laid-Open No. 2) -296891 (Ab.), Styrylamine derivative (Appl. Phys. Lett., Vol. 56, L799 (1990), coumarin compounds (Japanese Unexamined Patent Publication No. 2-191649), International Patent Publication WO90 / 13148 and Appl. Phys. Higher compounds such as those described in Lett., Vol58,18, P1982 (1991), 9,9', 10,10'-tetraphenyl-2,2'-biantracene, PPV (polyparaphenylene vinylene). ) Derivatives, polyfluorene derivatives, copolymers thereof and the like, for example, those having the structures of the following general formulas (4) to (6).

[In the general formula ^{(4), R x1} and ^{R X2} are each independently represent a monovalent aliphatic hydrocarbon group, n1 represents an integer of 3 to 100. ]

[In the general formula ^{(5), R x3} and ^{R X4} are each independently represent a monovalent aliphatic hydrocarbon group, the n2 and n3 each independently represents an integer of 3 to 100. ]

[In the general formula ^{(6), R X5} and ^{R X6} each independently represent a monovalent aliphatic hydrocarbon group, n4 and n5 are each independently an integer of 3 to 100. Ph represents a phenyl group. ]

In addition, the general formula (Rs-Q) _2- Al-O-L3 [in the formula, L3 is a hydrocarbon having 6 to 24 carbon atoms including a phenyl moiety, which is described in JP-A-5-258862, etc. O-L3 is a phenolate ligand, Q indicates a substituted 8-quinolinolate ligand, and Rs sterically indicates that the substituted 8-quinolinolate ligand is bonded to an aluminum atom in excess of two. Also included are compounds represented by [showing 8-quinolinolate ring substituents selected to interfere]. Specific examples thereof include bis (2-methyl-8-quinolinolate) (para-phenylphenolate) aluminum (III) and bis (2-methyl-8-quinolinolate) (1-naphtholate) aluminum (III). ..

The light emitting layer for obtaining white light emission is not particularly limited, but the following can be used. An energy level of each layer of an organic EL laminated structure is defined, and light is emitted by using tunnel injection (European Patent No. 0390551). Similarly, an element using tunnel injection in which a white light emitting element is described as an example (Japanese Patent Laid-Open No. 3-230584). A light emitting layer having a two-layer structure is described (Japanese Patent Laid-Open No. 2-220390 and JP-A-2-216790). A light emitting layer is divided into a plurality of layers and each is composed of materials having different emission wavelengths (Japanese Patent Laid-Open No. 4-51491). A structure in which a blue illuminant (fluorescence peak 380 to 480 nm) and a green illuminant (480 to 580 nm) are laminated and further contained a red phosphor (Japanese Patent Laid-Open No. 6-207170). A structure in which the blue light emitting layer contains a blue fluorescent dye, the green light emitting layer has a region containing a red fluorescent dye, and further contains a green phosphor (Japanese Unexamined Patent Publication No. 7-142169).

[anode]
As the material used for the anode of the electroluminescent element, a material having a large work function (4 eV or more), an alloy, an electrically conductive compound, or a mixture thereof as an electrode material is preferably used. Specific examples of such an electrode material include metals such as Au and conductive materials such as _{CuI, ITO, SnO 2, and ZnO.} In order to form this anode, these electrode materials can be formed into a thin film by a method such as a vapor deposition method or a sputtering method. When the light emitted from the light emitting layer is taken out from the anode, it is desirable that the anode has a characteristic that the transmittance of the anode with respect to the light emitted is larger than 10%. Further, the sheet resistance of the anode is preferably several hundred Ω / □ or less. Further, the film thickness of the anode is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm, although it depends on the material.

[cathode]
As the material used for the cathode of the electroluminescent element, a metal having a small work function (4 eV or less), an alloy, an electrically conductive compound, or a mixture thereof is used as an electrode material. Specific examples of such electrode materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium / silver alloys, aluminum / aluminum oxide, aluminum / lithium alloys, indium, rare earth metals and the like. This cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. Here, when the light emitted from the light emitting layer is taken out from the cathode, the transmittance of the cathode with respect to the light emitted is preferably larger than 10%. The sheet resistance of the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually 10 nm to 1 μm, preferably 50 to 200 nm.

Regarding the method for producing the electroluminescent device, the anode, the light emitting layer, the hole injection layer if necessary, and the electron injection layer if necessary may be formed by the above materials and methods, and finally the cathode may be formed. .. It is also possible to manufacture electroluminescent devices from the cathode to the anode in the reverse order of the above.

The electroluminescent device is made on a translucent substrate. The translucent base material is a substrate that supports an electroluminescent element, and its translucency is preferably such that the light transmittance in the visible region of 400 to 700 nm is 50% or more, preferably 90% or more. It is preferable to use a smoother base material.

These base materials are not particularly limited as long as they have mechanical and thermal strength and are transparent, and may be a flexible film or sheet-like base material. As the base material, for example, a glass plate, a synthetic resin plate, or the like is preferably used. Examples of the glass plate include plates formed of soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, quartz and the like. Examples of the synthetic resin plate include plates such as polycarbonate resin, acrylic resin, polyethylene terephthalate resin, polyether sulfide resin, and polysulfon resin.

As a method for forming each layer of the electroluminescent device, either a dry film forming method such as vacuum deposition, electron beam irradiation, sputtering, plasma, or ion plating, or a wet film forming method such as spin coating, dipping, or flow coating. Method can be applied. In addition, the special table 2002-534782 and S.A. T. Lee, et al. , Proceedings of SID'02, p. The LITI (Laser Induced Thermal Imaging) method described in 784 (2002), printing (offset printing, flexographic printing, gravure printing, screen printing), inkjet and the like can also be applied. However, the light emitting layer is limited to the film formation by the wet film formation method.

The organic layer is particularly preferably a molecular deposition film. Here, the molecular deposition film is a thin film deposited and formed from a material compound in a vapor phase state, or a film solidified and formed from a material compound in a solution state or a liquid phase state, and is usually this molecular deposition film. Can be classified by the difference in aggregated structure and higher-order structure from the thin film (molecular cumulative film) formed by the LB method, and the functional difference caused by the difference. Further, as disclosed in Japanese Patent Application Laid-Open No. 57-57181, a binder such as a resin and a material compound are dissolved in a solvent to form a solution, which is then thinned by a spin coating method or the like. , An organic layer can be formed. The film thickness of each layer is not particularly limited, but if the film thickness is too thick, a large applied voltage is required to obtain a constant light output, resulting in poor efficiency. Conversely, if the film thickness is too thin, pinholes, etc. Is generated, and it becomes difficult to obtain sufficient emission brightness even when an electric field is applied. Therefore, the film thickness of each layer is preferably in the range of 1 nm to 1 μm, but more preferably in the range of 10 nm to 0.2 μm.

Further, in order to improve the stability of the electroluminescent element with respect to temperature, humidity, atmosphere and the like, a protective layer may be provided on the surface of the element, or the entire element may be coated or sealed with a resin or the like. In particular, when coating or sealing the entire device, a photocurable resin that is cured by light is preferably used.

The current applied to the electroluminescent element is usually direct current, but pulse current or alternating current may be used. The current value and voltage value are not particularly limited as long as the element is not destroyed, but it is desirable to efficiently emit light with as little electric energy as possible in consideration of the power consumption and life of the element.

The electroluminescent element can be driven not only by the passive matrix method but also by the active matrix method. Further, as a method of extracting light from the organic EL element of the present invention, it can be applied not only to a method of bottom emission which extracts light from the anode side but also to a method of top emission which extracts light from the cathode side. These methods and techniques are described in Junji Kido, "All about Organic EL", Nihon Jitsugyo Publishing Co., Ltd. (published in 2003).

The main methods of the full colorization method of the electroluminescent element include a three-color painting method, a color conversion method, and a color filter method. Examples of the three-color painting method include a vapor deposition method using a shadow mask, an inkjet method, and a printing method. In addition, the special table 2002-534782 and S.A. T. Lee, et al. , Proceedings of SID'02, p. The laser thermal transfer method described in 784 (2002) (also referred to as Laser Induced Thermo Imaging, LITI method) can also be used. The color conversion method is a method of converting from blue to green and red having a longer wavelength than blue through a color conversion (CCM) layer in which a fluorescent dye is dispersed by using a light emitting layer that emits blue light. The color filter method is a method of extracting light of three primary colors through a color filter for liquid crystal using an organic EL element that emits white light. In addition to these three primary colors, a part of white light is extracted as it is and used for light emission. As a result, the light emission efficiency of the entire element can be increased.

Further, the electroluminescent element may adopt a microcavity structure. This is because the organic EL element has a structure in which a light emitting layer is sandwiched between an anode and a cathode, and the emitted light causes multiple interference between the anode and the cathode, but the reflectance and transmission of the anode and the cathode are transmitted. It is a technology that positively utilizes the multiple interference effect and controls the emission wavelength extracted from the element by appropriately selecting the optical characteristics such as the rate and the thickness of the organic layer sandwiched between them. .. This also makes it possible to improve the emission chromaticity. Regarding the mechanism of this multiple interference effect, J. AM-LCD Digest of Technical Papers by Yamada et al., OD-2, p. 77-80 (2002).

As described above, the electroluminescent device using the light emitting material of the present invention can obtain light emission for a long time with a low driving voltage. Therefore, this organic EL element can be used as a flat panel display such as a wall-mounted television, various flat light emitters, a light source such as a copier or a printer, a light source such as a liquid crystal display or an instrument, a display board, an indicator light, or the like. Can be applied.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples do not limit the scope of rights of the present invention. Unless otherwise specified, "parts" and "%" in Examples and Comparative Examples represent "parts by mass" and "% by mass".

<Measurement of HOMO level and LUMO level of ligand>
The HOMO energy level and LUMO energy level of the hole-transporting ligand and the electron-transporting ligand were measured by the following evaluation methods.

(HOMO energy level)
The HOMO level was measured using a photoelectron yield spectroscope PYS-202 (manufactured by Sumitomo Heavy Industries Mechatronics). First, a conductive carbon double-sided tape (nonwoven fabric base material: manufactured by Nissin EM) was attached on a glass substrate with ITO (indium tin oxide), and a ligand powder to be evaluated was attached thereto to form a sample. .. Next, the surface of the ITO was grounded, and the evaluation target on the carbon double-sided tape was irradiated with probe light to measure the HOMO level. Measuring range: 4.0 to 7.0 (eV), measurement interval: 0.1 (eV), measured and atmosphere: in vacuum ⁽¹⁰ -2 (Pa) base).

(LUMO energy level)
The LUMO level was calculated from the HOMO value and the bandgap value measured by the above method by estimating the bandgap from the absorption edge of the absorption spectrum. The absorption spectrum was measured using a quartz cell having an optical path length of 1 cm after adjusting the ligand to be evaluated to ^{a concentration of 10-5 (mol / L) using toluene.}

<Manufacturing of quantum dot dispersion>
(Quantum dot dispersion: QD-1)
1.35 parts of indium acetate, 1.30 parts of zinc octanate, 4.65 parts of stearic acid, and 92.7 parts of 1-octadecene were placed in a flask and heated to 100 ° C. Then, it was distilled off under reduced pressure at that temperature. The inside of the flask was filled with argon gas and heated to 300 ° C. Separately, 23 parts of a hexane solution containing 1.16 parts of tris (trimethylsilyl) phosphine prepared in a waterless glove box was injected, reacted at 280 ° C. for 9 minutes, and then rapidly cooled to obtain a solution.
15 parts of the obtained solution, 46 parts of 1-octadecene and 11.5 parts of oleylamine were placed in a flask and stirred for 15 minutes, and then 4.3 parts of zinc dibenzyldithiocarbamate was added. The inside of the reaction flask was replaced with argon, the temperature was raised to 170 ° C. in 45 minutes, and the temperature was kept at 170 ° C. for 2 hours. After cooling, acetone was added, and the mixture was separated by centrifugal sedimentation to obtain a sedimentation paste.
The precipitated paste was dispersed in toluene, 3.7 parts of dodecanethiol was added as a treatment agent, the mixture was stirred at room temperature for 24 hours, concentrated under reduced pressure, acetone was added, and the paste was separated by centrifugal sedimentation to obtain a precipitated paste. Again, the precipitated paste was dispersed in toluene to prepare a solid content concentration of 10%, and the quantum dot dispersion liquid QD-1 containing quantum dots, which are semiconductor nanoparticles surface-treated with the second ligand, dodecanethiol. Got The core of the semiconductor nanoparticles is InP and the shell is ZnS.

(Quantum dot dispersion: QD-2)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, the hole transporting ligand compound (a) is dissolved in toluene to prepare a 1.0% by mass ligand solution, and the ligand solution is 5 times as much as the quantum dot dispersion QD-1 on a mass basis. The amount was added and the mixture was stirred for 12 hours. Semiconductor nanoparticles prepared by the reprecipitation method using hexane and ethanol, adjusted to a solid content concentration of 10% by mass using toluene, and surface-treated with a hole-transporting ligand, which is the first ligand. A quantum dot dispersion QD-2 containing the quantum dots was obtained.

(Quantum dot dispersion: QD-3)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, the electron transporting ligand compound (b) is dissolved in toluene to prepare a 1.0% by mass ligand solution, and the amount of the ligand solution is 5 times as much as the quantum dot dispersion QD-1 on a mass basis. Was added, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration was adjusted to 10% by mass using toluene, and the semiconductor nanoparticles were surface-treated with the electron-transporting ligand, which is the first ligand. A quantum dot dispersion QD-3 containing a certain quantum dot was obtained.

(Quantum dot dispersion: QD-4)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, as a ligand, a ligand solution of 1.0% by mass was prepared by dissolving in toluene so that the mass ratio of the compound (a) and the compound (b) was 1: 1 and the ligand solution was dispersed by quantum dots. To the liquid QD-1, 5 times the amount was added on a mass basis, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration is adjusted to 10% by mass using toluene, and the surface is prepared with the first ligands, the hole-transporting ligand and the electron-transporting ligand. A quantum dot dispersion QD-4 containing quantum dots, which are treated semiconductor nanoparticles, was obtained.

(Quantum dot dispersion: QD-5)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, the hole transporting ligand compound (c) is dissolved in toluene to prepare a 1.0% by mass ligand solution, and the ligand solution is 5 times as much as the quantum dot dispersion QD-1 on a mass basis. The amount was added and the mixture was stirred for 12 hours. Semiconductor nanoparticles prepared by the reprecipitation method using hexane and ethanol, adjusted to a solid content concentration of 10% by mass using toluene, and surface-treated with a hole-transporting ligand, which is the first ligand. A quantum dot dispersion QD-5 containing the quantum dots was obtained.

(Quantum dot dispersion: QD-6)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, the electron-transporting ligand compound (d): Bphen is dissolved in toluene to prepare a 1.0 mass% ligand solution, and the ligand solution is 5 by mass with respect to the quantum dot dispersion QD-1. A double amount was added and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration was adjusted to 10% by mass using toluene, and the semiconductor nanoparticles were surface-treated with the electron-transporting ligand, which is the first ligand. A quantum dot dispersion QD-6 containing a certain quantum dot was obtained.

(Quantum dot dispersion: QD-7)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, as a ligand, a ligand solution of 1.0% by mass was prepared by dissolving in toluene so that the mass ratio of the compound (c) and the compound (d) was 1: 1 and the ligand solution was dispersed by quantum dots. To the liquid QD-1, 5 times the amount was added on a mass basis, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration is adjusted to 10% by mass using toluene, and the surface is prepared with the first ligands, the hole-transporting ligand and the electron-transporting ligand. A quantum dot dispersion QD-7 containing quantum dots, which are processed semiconductor nanoparticles, was obtained.

(Quantum dot dispersion: QD-8)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, as a ligand, a ligand solution of 1.0% by mass was prepared by dissolving in toluene so that the mass ratio of dodecanethiol and the compound (a) was 1: 1 and the ligand solution was used as a quantum dot dispersion QD. A volume of 5 times was added to -1 on a mass basis, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration was adjusted to 10% by mass using toluene, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms was used. A quantum dot dispersion QD-8 containing a hole-transporting ligand as a first ligand and quantum dots as semiconductor nanoparticles surface-treated with is obtained.

(Quantum dot dispersion: QD-9)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, as a ligand, a ligand solution of 1.0% by mass was prepared by dissolving in toluene so that the mass ratio of dodecanethiol and the compound (b) was 1: 1 and the ligand solution was used as a quantum dot dispersion QD. A volume of 5 times was added to -1 on a mass basis, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration was adjusted to 10% by mass using toluene, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms was used. A quantum dot dispersion QD-9 containing an electron-transporting ligand as a first ligand and quantum dots as semiconductor nanoparticles surface-treated with is obtained.

(Quantum dot dispersion: QD-10)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, as a ligand, a ligand solution of 1.0% by mass was prepared by dissolving in toluene so that the mass ratio of dodecanethiol and the compound (c) was 1: 1 and the ligand solution was used as a quantum dot dispersion QD. A volume of 5 times was added to -1 on a mass basis, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration was adjusted to 10% by mass using toluene, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms was used. A quantum dot dispersion QD-10 containing a hole-transporting ligand as a first ligand and quantum dots as semiconductor nanoparticles surface-treated with is obtained.

(Quantum dot dispersion: QD-11)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, as a ligand, a ligand solution of 1.0% by mass was prepared by dissolving in toluene so that the mass ratio of dodecanethiol and the compound (d) was 1: 1 and the ligand solution was used as a quantum dot dispersion QD. A volume of 5 times was added to -1 on a mass basis, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration was adjusted to 10% by mass using toluene, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms was used. A quantum dot dispersion QD-11 containing an electron-transporting ligand as the first ligand and quantum dots as semiconductor nanoparticles surface-treated with the above was obtained.

(Quantum dot dispersion: QD-12)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, as a ligand, a 1.0% by mass ligand solution was prepared by dissolving in toluene so that the mass ratio of dodecanethiol, the compound (a) and the compound (b) was 2: 1: 1. The ligand solution was added in an amount of 5 times the mass of the quantum dot dispersion QD-1 on a mass basis, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration was adjusted to 10% by mass using toluene, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms was used. A quantum dot dispersion QD-12 containing quantum dots, which are semiconductor nanoparticles surface-treated with a hole-transporting ligand and an electron-transporting ligand, which are the first ligands, was obtained.

(Quantum dot dispersion: QD-13)
The quantum dot dispersion QD-1 was diluted with toluene to a solid content concentration of 0.5% by mass. Next, as a ligand, a 1.0 mass% ligand solution was prepared by dissolving in toluene so that the mass ratio of dodecanethiol, the compound (c) and the compound (d) was 2: 1: 1. The ligand solution was added in an amount of 5 times the mass of the quantum dot dispersion QD-1 on a mass basis, and the mixture was stirred for 12 hours. After purification by the reprecipitation method using hexane and ethanol, the solid content concentration was adjusted to 10% by mass using toluene, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms was used. A quantum dot dispersion QD-13 containing quantum dots, which are semiconductor nanoparticles surface-treated with a hole-transporting ligand and an electron-transporting ligand, which are the first ligands, was obtained.

Table 6 shows the measured values of the HOMO energy level and the LUMO energy level of the hole transporting ligand and the electron transporting ligand.

(Quantum dot dispersion: QD-14 to QD-17)
Quantum dot dispersions QD-14 to 17 were obtained in the same manner as the quantum dot dispersions QD-2, except that the compounds (e) to (h) shown in Table 7 were used instead of the compound (a). ..

(Quantum dot dispersion: QD-18-21)
Quantum dot dispersions QD-18 to 21) are obtained in the same manner as the quantum dot dispersions QD-8, except that the compounds (e) to (h) shown in Table 7 are used instead of the compound (a). It was.

(Quantum dot dispersion: QD-22-25)
Quantum dot dispersion liquid QD-22-25) was obtained in the same manner as the quantum dot dispersion liquid QD-13, except that the compounds (e) to (h) shown in Table 7 were used instead of the compound (c). It was.

Table 7 shows the measured values of the HOMO energy level and the LUMO energy level of the compound which is the hole transporting ligand used above.

<Manufacturing of ink composition containing luminescent material>
[Example 1]
(Ink Composition 1)
The quantum dot dispersion QD-1 and the quantum dot dispersion QD-2 are mixed at a mass ratio of 1: 1 to form semiconductor nanoparticles, a hole-transporting ligand, and an aliphatic hydrocarbon group having 1 to 18 carbon atoms. An ink composition 1 containing a light emitting material containing a second ligand having and toluene was obtained.

[Example 2]
(Ink Composition 2)
The semiconductor nanoparticles and the hole-transporting ligand were used in the same manner as in Example 1 except that the quantum dot dispersion QD-1 and the quantum dot dispersion QD-2 were mixed and used at a mass ratio of 1: 9. An ink composition 2 containing a light emitting material containing a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms and toluene was obtained.

[Example 3]
(Ink Composition 3)
The semiconductor nanoparticles and the hole-transporting ligand were used in the same manner as in Example 1 except that the quantum dot dispersion QD-1 and the quantum dot dispersion QD-2 were mixed and used at a mass ratio of 9: 1. An ink composition 3 containing a light emitting material containing a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms and toluene was obtained.

[Example 4]
(Ink Composition 4)
The quantum dot dispersion QD-1 and the quantum dot dispersion QD-3 are mixed at a mass ratio of 1: 1 to have semiconductor nanoparticles, an electron transporting ligand, and an aliphatic hydrocarbon group having 1 to 18 carbon atoms. An ink composition 4 containing a luminescent material containing a second ligand and toluene was obtained.

[Example 5]
(Ink Composition 5)
Semiconductor nanoparticles, electron-transporting ligand, and carbon were used in the same manner as in Example 4, except that the quantum dot dispersion QD-1 and the quantum dot dispersion QD-3 were mixed and used at a mass ratio of 1: 9. An ink composition 5 containing a luminescent material containing a second ligand having an aliphatic hydrocarbon group of numbers 1 to 18 and toluene was obtained.

[Example 6]
(Ink Composition 6)
Semiconductor nanoparticles, electron-transporting ligand, and carbon were used in the same manner as in Example 4, except that the quantum dot dispersion QD-1 and the quantum dot dispersion QD-3 were mixed and used at a mass ratio of 9: 1. An ink composition 6 containing a luminescent material containing a second ligand having an aliphatic hydrocarbon group of numbers 1 to 18 and toluene was obtained.

[Example 7]
(Ink Composition 7)
The quantum dot dispersion QD-1 and the quantum dot dispersion QD-5 are mixed at a mass ratio of 1: 1 to form semiconductor nanoparticles, a hole-transporting ligand, and an aliphatic hydrocarbon group having 1 to 18 carbon atoms. An ink composition 7 containing a light emitting material containing a second ligand having and toluene was obtained.

[Example 8]
(Ink Composition 8)
The quantum dot dispersion QD-1 and the quantum dot dispersion QD-6 are mixed at a mass ratio of 1: 1 to have semiconductor nanoparticles, an electron transporting ligand, and an aliphatic hydrocarbon group having 1 to 18 carbon atoms. An ink composition 8 containing a luminescent material containing a second ligand and toluene was obtained.

[Example 9]
(Ink Composition 9)
Quantum dot dispersion QD-1 and quantum dot dispersion QD-4 are mixed at a mass ratio of 1: 1 to form semiconductor nanoparticles, hole-transporting ligands, electron-transporting ligands, and fats having 1 to 18 carbon atoms. An ink composition 9 containing a light emitting material containing a second ligand having a group hydrocarbon group and toluene was obtained.

[Example 10]
(Ink Composition 10)
Quantum dot dispersion QD-1 and quantum dot dispersion QD-7 are mixed at a mass ratio of 1: 1 to form semiconductor nanoparticles, hole-transporting ligands, electron-transporting ligands, and fats having 1 to 18 carbon atoms. An ink composition 10 containing a light emitting material containing a second ligand having a group hydrocarbon group and toluene was obtained.

[Example 11]
(Ink Composition 11)
Quantum dot dispersion QD-1, quantum dot dispersion QD-2, and quantum dot dispersion QD-3 are mixed at a mass ratio of 2: 1: 1 to transport semiconductor nanoparticles, hole-transporting ligands, and electrons. An ink composition 11 containing a light emitting material containing a sex ligand and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms and toluene was obtained.

[Example 12]
(Ink Composition 12)
Quantum dot dispersion QD-1, quantum dot dispersion QD-5, and quantum dot dispersion QD-6 are mixed at a mass ratio of 2: 1: 1 to transport semiconductor nanoparticles, hole-transporting ligands, and electrons. An ink composition 12 containing a light emitting material containing a sex ligand and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms and toluene was obtained.

[Example 13]
(Ink Composition 13)
Using the quantum dot dispersion QD-8 as it is, an ink composition containing a light emitting material containing semiconductor nanoparticles, a hole transporting ligand, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and toluene. It was set to object 13.

[Example 14]
(Ink Composition 14)
Using the quantum dot dispersion QD-9 as it is, an ink composition containing a light emitting material containing semiconductor nanoparticles, an electron transporting ligand, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and toluene. It was set to 14.

[Example 15]
(Ink Composition 15)
Using the quantum dot dispersion QD-10 as it is, an ink composition containing a luminescent material containing semiconductor nanoparticles, a hole transporting ligand, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and toluene. The thing was 15.

[Example 16]
(Ink Composition 16)
An ink composition containing a luminescent material containing semiconductor nanoparticles, an electron-transporting ligand, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and toluene, using the quantum dot dispersion liquid QD-11 as it is. It was set to 16.

[Example 17]
(Ink Composition 17)
A luminescent material containing semiconductor nanoparticles, a hole-transporting ligand, an electron-transporting ligand, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, using the quantum dot dispersion liquid QD-12 as it is. The ink composition 17 containing toluene was used.

[Example 18]
(Ink Composition 18)
A luminescent material containing semiconductor nanoparticles, a hole-transporting ligand, an electron-transporting ligand, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, using the quantum dot dispersion liquid QD-13 as it is. The ink composition 18 containing toluene was used.

[Examples 19 to 22]
(Ink Compositions 19-22)
Ink compositions 19 to 22 were obtained in the same manner as in Example 1 except that the dispersion liquids QD-14 to 17 were used instead of the dispersion liquid QD-2.

[Examples 23 to 26]
(Ink Composition Examples 23 to 26)
Ink compositions 23 to 26 were obtained in the same manner as in Example 12 except that the dispersion liquids QD-14 to 17 were used instead of the dispersion liquid QD-5.

[Examples 27 to 30]
Using the quantum dot dispersion QD-18-21 as it is, it contains a luminescent material containing semiconductor nanoparticles, a hole-transporting ligand, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and toluene. The ink composition was 27 to 30.

[Examples 31 to 34]
Light emission containing semiconductor nanoparticles, a hole-transporting ligand, an electron-transporting ligand, and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, using the quantum dot dispersion liquid QD-22 to 25 as it is. Ink compositions containing the material and toluene were 31-34.

[Comparative Example 1]
(Ink Composition 35)
Using the quantum dot dispersion QD-1 as it is, it contains semiconductor nanoparticles and a second ligand having an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and emits light without a first ligand having an aromatic skeleton. The ink composition 35 containing the material and toluene was used.

[Comparative Example 2]
(Ink Composition 36)
The quantum dot dispersion QD-7 was used as it was to prepare an ink composition 36 containing a light emitting material containing semiconductor nanoparticles, a hole transporting ligand, and an electron transporting ligand, and toluene.

<Evaluation of ink composition containing luminescent material>
The following evaluation was performed on the obtained ink composition. The results are shown in Table 8.

[Dispersion stability evaluation]
The ink composition was prepared by Marum Co., Ltd. screw tube No. After sealing to 2 and allowing it to stand in a cool and dark place for one week, visual confirmation was performed and evaluation was performed according to the following criteria.
⊚: No turbidity or agglutination is confirmed (good)
◯: There is slight turbidity, but no aggregates are confirmed (usable)
Δ: Aggregates are confirmed (cannot be used)
X: Aggregation and precipitation are confirmed (defective)

[Evaluation of electroluminescent device performance]
Unless otherwise specified, vapor deposition (vacuum vapor deposition) was performed in ^{a vacuum of 10-6} Torr under conditions where temperature control such as heating and cooling of the substrate was not performed. The light emitting characteristics of the element were measured using an electroluminescent element having a light emitting element area of 2 mm × 2 mm.
First, PEDOT / PSS (poly (3,4-ethylenedioxy) -2.5-thiophene / polystyrene sulfonic acid, CLEVIOUS (registered trademark) PVP CH8000 manufactured by Heraeus) was placed on a cleaned glass plate with an ITO electrode. It was coated by a spin coating method and dried at 110 ° C. for 20 minutes to obtain a hole injection layer having a film thickness of 60 nm.
Next, Poly [N, N'-bis (4-butylphenyl) -N, N'-bisphenylbenzidine] (abbreviation: Poly-TPD) was dissolved in monochlorobenzene at a concentration of 0.5% by mass and placed on the hole injection layer. Was coated by a spin coating method and dried at 110 ° C. for 20 minutes to form a hole transport layer having a film thickness of 15 nm.
Next, the ink compositions obtained in Examples and Comparative Examples were diluted 35-fold, coated on the hole transport layer by a spin coating method, held at 80 ° C. for 5 minutes, dried, and dried at 20 nm. A light emitting layer was formed.
Next, 2,2', 2 "-(1,3,5-Benzinetriyl) -tris (1-phenyl-1-H-benzimidazole) (abbreviation: TPBi) is vacuum-deposited on the light emitting layer to form 60 nm electrons. A transport layer was formed. Further, lithium fluoride (LiF) was vacuum-deposited to form a 1 nm electron injection layer, and finally aluminum (Al) was vapor-deposited to 200 nm to form an electrode to obtain an electroluminescent element. ..
Under the conditions of the drive voltage (V) and external quantum efficiency (%) when the obtained electroluminescent element is driven at a current density of 10 (mA / cm ^{2 ), and the initial brightness of 1000 (cd / m 2} ). The relative brightness (= (brightness after 100 hours) / (initial brightness)) after continuous driving for 100 hours was measured. It is evaluated that the higher the relative brightness, the better the durability.
The electroluminescent device using the ink composition of Example 1 had a peak wavelength of 615 nm and a full width at half maximum of 30 nm.

As shown in Table 8, the light emitting material of Comparative Example 1 was excellent in dispersibility, but had a high driving voltage and was inferior in luminous efficiency and durability. The light emitting material of Comparative Example 2 has a low driving voltage and is excellent in luminous efficiency, but has low dispersibility and is inferior in durability as compared with Comparative Example 1. The light emitting materials of Examples 1 to 34 in which the first ligand having an aromatic skeleton and the second ligand having no aromatic skeleton were used in combination improved the dispersibility of the semiconductor nanoparticles and aggregated the quantum dots. As a result of the suppression, it was shown that the drive voltage was further reduced and the quantum efficiency and durability were significantly improved.

Claims (7)

A luminescent material containing semiconductor nanoparticles having an organic ligand on the particle surface.
A luminescent material, wherein the organic ligand in the luminescent material comprises a first ligand having an aromatic skeleton and a second ligand having no aromatic skeleton. The luminescent material according to claim 1, wherein the second ligand has an aliphatic hydrocarbon group having 1 to 18 carbon atoms. The luminescent material according to claim 1 or 2, wherein the first ligand contains one or more selected from a hole-transporting ligand and an electron-transporting ligand. The luminescent material according to claim 3, wherein the HOMO energy level of the hole transporting ligand is −6.1 eV or more and −5.1 eV or less. The luminescent material according to claim 3 or 4, wherein the LUMO energy level of the electron-transporting ligand is -4.0 eV or more and -3.0 eV or less. An ink composition containing the light emitting material according to any one of claims 1 to 5 and a solvent. An anode, a light emitting layer, and a cathode are provided on the substrate.
An electroluminescent device in which the light emitting layer contains the light emitting material according to any one of claims 1 to 5.