Quantum dot light-emitting element, quantum dot display device, quantum dot illumination, and method for manufacturing a quantum dot light-emitting element.

Abstract

To provide a quantum dot light-emitting element having a light-emitting layer containing quantum dots, low drive voltage, and a long drive life.SOLUTION: A quantum dot light-emitting element has an anode, a cathode, a light-emitting layer, and a hole-injection layer. The light-emitting layer is provided between the anode and the cathode. The hole-injection layer is provided between the anode and the light-emitting layer. The light-emitting layer contains quantum dots. The hole-injection layer contains a cross-linked compound of an electron-accepting compound having a cross-linked group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a quantum dot light-emitting element, a quantum dot display device, quantum dot illumination, and a method for manufacturing a quantum dot light-emitting element. [Background technology]

[0002] As a thin-film type electroluminescent device, organic electroluminescent devices using organic thin films are being developed. Organic electroluminescent devices (OLEDs) typically have a hole injection layer, a hole transport layer, an organic light-emitting layer, and an electron transport layer between the anode and cathode. Materials suitable for each of these layers are being developed, and development is progressing on the emission colors, including red, green, and blue.

[0003] In recent years, attempts have been made to cover a wider color gamut by using "quantum dots," which are inorganic light-emitting materials, in the light-emitting layer to produce sharper emission spectra for red, green, and blue light sources. Electroluminescent devices using quantum dots are also called quantum dot light-emitting devices (QLEDs).

[0004] Furthermore, quantum dot light-emitting devices are typically formed by a wet deposition method (coating method). The wet deposition method has advantages such as easy large-area deposition and the ability to easily form layers containing multiple materials with various functions by using a coating solution that is a mixture of multiple materials with various functions. For these reasons, research and development of quantum dot light-emitting devices using the coating method has been progressing.

[0005] For example, Patent Documents 1 to 3 and Non-Patent Document 1 describe a quantum dot light-emitting device having a hole injection layer containing polystyrene sulfonic acid and a light-emitting layer containing quantum dots. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-107867 [Patent Document 2] Japanese Patent Publication No. 2020-161476 [Patent Document 3] Japanese Patent Publication No. 2020-173937 [Non-patent literature]

[0007] [Non-Patent Document 1] Nature, 2014, Vol. 515, pp. 96-99 [Overview of the project] [Problems that the invention aims to solve]

[0008] Generally, quantum dots have many highly reactive surface atoms and therefore readily react with various reactive groups. For this reason, the technologies disclosed in Patent Documents 1-3 and Non-Patent Document 1 have not adequately reduced the driving voltage of quantum dot light-emitting devices and have failed to improve the driving life. In the technologies disclosed in Patent Documents 1-3, a hole injection layer containing strongly acidic polystyrene sulfonic acid is used, and it is thought that this is because moisture and sulfonic acid groups incorporated during the formation of the hole injection layer react with the quantum dots or promote reactions between the quantum dots and oxygen, etc.

[0009] This invention has been made in view of the above-mentioned conventional circumstances, and aims to solve the problem of providing a quantum dot light-emitting element having a light-emitting layer containing quantum dots, a low driving voltage, and a long driving life. [Means for solving the problem]

[0010] As a result of diligent research, the inventors of the present invention have found that the above problems can be solved by using a hole injection layer containing a crosslinked product of an electron-accepting compound having a crosslinking group, and have completed the present invention.

[0011] In other words, the gist of this invention is as follows: <1> ~ <7> That is correct. <1> A quantum dot light-emitting device having an anode, a cathode, a light-emitting layer, and a hole injection layer, The light-emitting layer is provided between the anode and the cathode, The hole injection layer is provided between the anode and the light-emitting layer, The light-emitting layer contains quantum dots, The hole injection layer contains a crosslinked product of an electron-accepting compound having a crosslinking group, in a quantum dot light-emitting device. <2> The aforementioned crosslinking group is represented by any of the following formulas (X1) to (X18): <1> Quantum dot light-emitting device as described above.

[0012] [ka]

[0013] (In formulas (X1) to (X4), the benzene ring and the naphthalene ring may have substituents. The substituents may also be bonded to each other to form a ring.) In formula (X5), R 1 represents an alkyl group which may have substituents. In formula (X6), R 2 represents an alkyl group which may have substituents. In formula (X10), R 3 (This represents an alkyl group which may have substituents.) <3> The aforementioned crosslinking group is represented by any of the above formulas (X1) to (X3), <2> Quantum dot light-emitting device as described above. <4> <1> ~ <3> A quantum dot display device or quantum dot illumination comprising a quantum dot light-emitting element as described in any one of the following. <5> A method for manufacturing a quantum dot light-emitting device having an anode, a hole injection layer, a light-emitting layer, and a cathode on a substrate in this order, A step of forming the hole injection layer by a wet film deposition method using a hole injection layer formation composition, and The process includes a step of forming the light-emitting layer by a wet film deposition method using a light-emitting layer forming composition, The hole injection layer forming composition comprises an electron-accepting compound having a crosslinking group and an organic solvent. The aforementioned light-emitting layer forming composition comprises quantum dots and an organic solvent. A method for manufacturing quantum dot light-emitting devices. <6> The aforementioned crosslinking group is represented by any of the following formulas (X1) to (X18): <5> A method for manufacturing quantum dot light-emitting devices as described above.

[0014] [ka]

[0015] (In formulas (X1) to (X4), the benzene ring and the naphthalene ring may have substituents. The substituents may also be bonded to each other to form a ring.) In formula (X5), R 1 represents an alkyl group which may have substituents. In formula (X6), R 2 represents an alkyl group which may have substituents. In formula (X10), R 3 (This represents an alkyl group which may have substituents.) <7> The aforementioned crosslinking group is represented by any of the above formulas (X1) to (X3), <6> A method for manufacturing quantum dot light-emitting devices as described above. [Effects of the Invention]

[0016] The quantum dot light-emitting element of the present invention exhibits excellent device characteristics, particularly a low drive voltage and a long operating life. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of the structure of the quantum dot light-emitting element of the present invention. [Modes for carrying out the invention]

[0018] The following describes in detail embodiments of a quantum dot light-emitting element, a quantum dot display device equipped with the quantum dot light-emitting element, and a quantum dot illumination device equipped with the quantum dot light-emitting element, which are embodiments of one of the present inventions. The following description is a first embodiment, which is an example (representative example) of the present invention, but the present invention is not limited to these contents unless it exceeds the gist of the invention.

[0019] <Quantum dot light-emitting element> The quantum dot light-emitting device of the present invention is a quantum dot light-emitting device having an anode, a cathode, a light-emitting layer, and a hole injection layer, wherein the light-emitting layer is provided between the anode and the cathode, the hole injection layer is provided between the anode and the light-emitting layer, the light-emitting layer contains quantum dots, and the hole injection layer contains a crosslinked product of an electron-accepting compound having a crosslinking group.

[0020] The reason why the quantum dot light-emitting element of the present invention has a low driving voltage and a long operating life is not clear, but the following is presumed to be the reason.

[0021] Because quantum dots have many highly reactive surface atoms, they readily react with a variety of reactive groups.

[0022] Generally, a method is used in hole injection layers that utilizes electron-accepting compounds to promote hole injection from the metallic anode and reduce the drive voltage. However, in conventional techniques, when the layer above the hole injection layer is formed by a wet deposition method, the electron-accepting compound of the hole injection layer diffuses to the light-emitting layer. It is thought that the electron-accepting compound reacts with the surface atoms of the quantum dots during device operation, or that the electron-accepting compound promotes the reaction between the surface atoms of the quantum dots, the quantum dots, and oxygen, etc., which leads to an increase in the drive voltage and a reduction in the drive life.

[0023] On the other hand, by incorporating a crosslinking group into the electron-accepting compound, if the crosslinking reaction is promoted during the formation of the hole injection layer, thereby immobilizing the electron-accepting compound on the hole injection layer, it is thought that the electron-accepting compound will not diffuse when the layer above the hole injection layer is formed by a wet deposition method. Therefore, it is presumed that using an electron-accepting compound with a crosslinking group can suppress degradation reactions during operation.

[0024] As described above, we have found that the above problems can be solved by using quantum dots as the light-emitting layer, forming a hole injection layer using an electron-accepting compound having a crosslinking group, and using a hole injection layer containing a crosslinked product of the electron-accepting compound having a crosslinking group, and have thus completed the present invention.

[0025] [Quantum dots] The light-emitting layer contains quantum dots as the light-emitting material. Quantum dots are light-emitting semiconductor nanoparticles, typically with a diameter in the range of 1 to 20 nm.

[0026] Quantum dots are preferably composed of group II-VI compounds, group III-V compounds, group IV-VI compounds, group IV elements, group IV compounds, and combinations thereof.

[0027] Examples of group II-VI compounds include CdSe, CdTe, CdS, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, AgInS, CuInS, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HeSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HeZnSe, HeZnTe, MgZnSe, MgZnS, HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe.

[0028] Group III-V compounds include GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InNP, InNAs. , InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb.

[0029] Examples of group IV-VI compounds include SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe.

[0030] Examples of Group IV elements and Group IV compounds include Si, Ge, SiC, and SiGe. ru.

[0031] A quantum dot may have a homogeneous single structure, or a core / shell dual structure. It may also have a triple or quadruple or higher structure, such as core / shell / shell. The materials constituting the core and shell are different compounds. In this case, it is preferable that the energy band gap of the shell compound is greater than the energy band gap of the core compound. Specifically, structures such as ZnTeSe / ZnSe / ZnS, CdSe / ZnS, and InP / ZnS are preferred.

[0032] [Composition for forming a light-emitting layer] The light-emitting layer can be formed by either vacuum deposition or wet deposition, but wet deposition is preferred. In the wet deposition method, the light-emitting layer is formed by applying and drying a light-emitting layer-forming composition containing an organic solvent. The composition for forming the light-emitting layer contains quantum dots and an organic solvent.

[0033] (Organic solvents) The organic solvent contained in the light-emitting layer forming composition is a volatile liquid component used to form a layer containing quantum dots by wet film deposition.

[0034] The organic solvent is not particularly limited as long as it is an organic solvent that dissolves the quantum dots, which are the solute, well.

[0035] Preferred organic solvents include, for example, alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, mesitylene, phenylcyclohexane, tetralin, and methylnaphthalene; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, and trichlorobenzene; and aromatics such as 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenethole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole, and diphenyl ether. Alicyclic ethers; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; alicyclic ketones such as cyclohexanone, cyclooctanone, and fencone; alicyclic alcohols such as cyclohexanol and cyclooctanol; aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; aliphatic alcohols such as butanol and hexanol; aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); and so on.

[0036] Among these, alkanes, aromatic hydrocarbons, and aromatic esters are preferred from the viewpoint of viscosity and boiling point.

[0037] These organic solvents may be used individually, or two or more may be used in any combination and ratio.

[0038] The boiling point of the organic solvent used is usually 80°C or higher, preferably 100°C or higher, more preferably 120°C or higher, and usually 350°C or lower, preferably 330°C or lower, more preferably 300°C or lower. If the boiling point of the organic solvent falls below this range, the film formation stability may decrease during wet film formation due to solvent evaporation from the light-emitting layer forming composition. If the boiling point of the organic solvent exceeds this range, the film formation stability may decrease during wet film formation due to solvent residue after film formation.

[0039] (Content) The quantum dot content in the light-emitting layer forming composition is typically 0.001% by mass or more, preferably 0.01% by mass or more, typically 30.0% by mass or less, and preferably 20.0% by mass or less. By setting the content within this range, holes and electrons can be efficiently injected from adjacent layers (e.g., hole transport layers and hole blocking layers) to the light-emitting layer, thereby reducing the driving voltage. Note that the light-emitting layer forming composition may contain only one type of quantum dot, or two or more types in combination.

[0040] The organic solvent content in the light-emitting layer-forming composition is usually 10% by mass or more, preferably 50% by mass or more, particularly preferably 80% by mass or more, and usually 99.95% by mass or less, preferably 99.9% by mass or less, particularly preferably 99.8% by mass or less. If the organic solvent content is above the lower limit, it has a moderate viscosity and the coatability is improved, and if it is below the upper limit, a uniform film is easily obtained and the film-forming properties are good.

[0041] (Other ingredients) The light-emitting layer-forming composition may, if necessary, contain other compounds in addition to the above-mentioned compounds. Preferred other compounds include phenols such as dibutylhydroxytoluene and dibutylphenol, which are known antioxidants, and known charge-transporting compounds.

[0042] (Film forming method) The preferred method for forming the light-emitting layer is a wet film deposition method. A wet film deposition method is a method in which a composition is applied to form a liquid film, which is then dried to remove the organic solvent and form a light-emitting layer. As for the application method, for example, a wet film deposition method such as spin coating, dip coating, die coating, bar coating, blade coating, roll coating, spray coating, capillary coating, inkjet, nozzle printing, screen printing, gravure printing, or flexographic printing is employed, and the coated film is dried to form the film. Among these application methods, spin coating, spray coating, inkjet, and nozzle printing are preferred. When manufacturing a quantum dot display device equipped with a quantum dot light-emitting element, the inkjet method or nozzle printing method is preferred, and the inkjet method is particularly preferred.

[0043] The drying method is not particularly limited, but natural drying, vacuum drying, heat drying, or vacuum drying with heating can be used as appropriate. Heat drying may be performed after natural drying or vacuum drying to further remove residual organic solvents.

[0044] Vacuum drying is preferably performed by reducing the pressure to below the vapor pressure of the organic solvent contained in the luminescent layer forming composition.

[0045] When heating, the heating method is not particularly limited, but heating by hot plate, heating in an oven, infrared heating, etc. can be used. The heating temperature is usually 80°C or higher, preferably 100°C or higher, more preferably 110°C or higher, and preferably 200°C or lower, and even more preferably 150°C or lower.

[0046] The heating time is usually 1 minute or more, preferably 2 minutes or more, usually 60 minutes or less, preferably 30 minutes or less, and more preferably 20 minutes or less.

[0047] [Hole injection layer] The hole injection layer requires the function of transporting holes, and therefore contains a hole transport material.

[0048] To improve hole injection from the anode to the hole injection layer and to improve hole transport within the hole injection layer, it is preferable that the hole transport material contained in the hole injection layer includes a cation radical moiety. To cationize the hole transport material, an electron-accepting compound is used when forming the hole injection layer. As the parent skeleton of the electron-accepting compound, an ionic compound consisting of a tetraarylborate ion, which is an anion with an ionic charge of 1 (described later), and a countercation is preferred because it has high stability.

[0049] The cation radicalization of hole transport materials is carried out as follows. When a compound having a triarylamine structure is used as the hole transport material, for example, if a tetraarylborate with diaryliodonium as the countercation is used as the electron-accepting compound, the countercation may change from diaryliodonium to triarylaminium during hole implantation layer formation, as shown in the following formula.

[0050] [ka]

[0051] (For example, Ar, Ar 1 ~Ar 4 Each of these is independently a monovalent group consisting of multiple structures selected from optionally substituted aromatic hydrocarbon groups, optionally substituted aromatic heterocyclic groups, or optionally substituted aromatic hydrocarbon ring groups and optionally substituted aromatic heterocyclic groups.

[0052] Since the triarylaminium produced in the above reaction has a semi-occupied orbital (SOMO) capable of accepting electrons, tetraarylborates with triarylaminium as the countercation are electron-accepting compounds.

[0053] In this invention, a compound consisting of a cation and an anion, the tetraarylborate ion, of this hole transport material is referred to as a charge-transporting ionic compound. Further details will be described later.

[0054] [Electron-accepting compound having a crosslinking group] (Crosslinking group) The hole injection layer of the quantum dot light-emitting device of the present invention contains a crosslinked product of an electron-accepting compound having a crosslinking group. The crosslinking group refers to a group that reacts with another group located in the vicinity of the crosslinking group upon irradiation with heat and / or active energy rays to form a new chemical bond. In this case, the other group to react may be the same group as the crosslinking group or a different group.

[0055] As the crosslinking group, a crosslinking group represented by any of the following formulas (X1) to (X18) is preferable.

[0056]

Chemical formula

[0057] (In formulas (X1) to (X4), the benzene ring and naphthalene ring may have substituents. Further, the substituents may be bonded to each other to form a ring. In formula (X5), R 1 represents an alkyl group that may have a substituent. In formula (X6), R 2 represents an alkyl group that may have a substituent. In formula (X10), R 3 represents an alkyl group that may have a substituent.)

[0058] R 1 ~R 3 The alkyl group represented by is a straight-chain, branched or cyclic structure, has 1 or more carbon atoms, preferably 24 or less, more preferably 12 or less, and still more preferably 8 or less.

[0059] The benzene ring and naphthalene ring of formulas (X1) to (X4), and the R 1 ~R 3 The substituents that may be possessed by are preferably an alkyl group, an aromatic hydrocarbon group, an alkyloxy group, and an aralkyl group.

[0060] The alkyl group as a substituent has a linear, branched, or cyclic structure, and the number of carbon atoms is preferably 24 or less, more preferably 12 or less, even more preferably 8 or less, and preferably 1 or more.

[0061] The number of carbon atoms in the aromatic hydrocarbon group as a substituent is preferably 24 or less, more preferably 18 or less, even more preferably 12 or less, and preferably 6 or more. The aromatic hydrocarbon group may further have the alkyl group as a substituent.

[0062] The number of carbon atoms in the alkyloxy group as a substituent is preferably 24 or less, more preferably 12 or less, even more preferably 8 or less, and preferably 1 or more.

[0063] The number of carbon atoms in the aralkyl group as a substituent is preferably 30 or less, more preferably 24 or less, even more preferably 14 or less, and preferably 7 or more. The alkylene group contained in the aralkyl group is preferably linear or branched. The aryl group contained in the aralkyl group may further have the alkyl group as a substituent.

[0064] As the bridging group, a bridging group represented by any of formulas (X1) to (X3) is preferred because the bridging reaction proceeds solely by heat, it has low polarity, and has little effect on charge transport.

[0065] The bridging group represented by formula (X1) undergoes ring-opening of the cyclobutene ring upon heat, as shown in the following formula, and the opened rings bond with each other to form a bridging structure.

[0066] [ka]

[0067] The bridging group represented by formula (X2) undergoes ring-opening of the cyclobutene ring upon heat, as shown in the following formula, and the opened rings bond with each other to form a bridging structure.

[0068] [ka]

[0069] The bridging group represented by formula (X3) undergoes ring-opening of the cyclobutene ring upon heat, as shown in the following formula, and the opened rings bond with each other to form a bridging structure.

[0070] [ka]

[0071] A bridging group represented by any of the formulas (X1) to (X3) undergoes ring-opening of the cyclobutene ring upon heat. If a double bond is present nearby, the opened ring reacts with the double bond to form a bridging structure. Below is an example of how a bridging group represented by formula (X1) and a bridging group represented by formula (X4) with a double bond site form a bridging structure.

[0072] [ka]

[0073] In addition to the bridging group represented by formula (X4), other double bond-containing groups that can react with the bridging group represented by formulas (X1) to (X3) include the bridging group represented by formulas (X5), (X6), (X12), (X15), (X16), (X17), and (X18).

[0074] When these double bond-containing groups are used as crosslinking groups in electron-accepting compounds, it is preferable to include a crosslinking group represented by any of formulas (X1) to (X3) in other components that form a hole injection layer, such as hole-transporting compounds, as this increases the likelihood of forming a crosslinked structure.

[0075] As the crosslinking group, a crosslinking group represented by any of the radical polymerizable formulas (X4) to (X6) is preferred because it has low polarity and does not easily hinder charge transport.

[0076] As a crosslinking group, the crosslinking group represented by formula (X7) is preferred in terms of enhancing electron-accepting ability. When the crosslinking group represented by formula (X7) is used, the following crosslinking reaction proceeds.

[0077] [ka]

[0078] A crosslinking group represented by either formula (X8) or formula (X9) is preferred due to its high reactivity. When a crosslinking group represented by formula (X8) or formula (X9) is used, the following crosslinking reaction proceeds.

[0079] [ka]

[0080] As the crosslinking group, a crosslinking group represented by any of the cationic polymerizable formulas (X10) to (X12) is preferred due to its high reactivity.

[0081] (Electron-accepting compound crosslinking) As described later, the hole injection layer of the quantum dot light-emitting device of the present invention is preferably obtained by wet deposition of a hole injection layer forming composition. The hole injection layer forming composition is preferably a composition obtained by dissolving or dispersing a first ionic compound having a tetraarylborate ion structure (described later) and a hole transport material (described later) in an organic solvent. Furthermore, the hole transport layer of the quantum dot light-emitting device of the present invention preferably contains a charge-transporting ionic compound in which the tetraarylborate ion structure (described later in the present invention) is an anion and the cation of the hole transport material is a counter-cation.

[0082] Therefore, a crosslinked product of an electron-accepting compound having a crosslinking group includes the following cases: • Compounds formed by cross-linking electron-accepting compounds. A compound in which an electron-accepting compound and a hole-transporting material are cross-linked. • A compound formed by crosslinking an electron-accepting compound with the tetraarylborate ion in the present invention. • A compound in which tetraarylborate ions are crosslinked together in the present invention. • A compound in which a tetraarylborate ion and a hole transport material are crosslinked according to the present invention.

[0083] Here, “tetraarylborate ion in the present invention” includes cases where it exists as an electron-accepting compound which is an ionic compound consisting of a tetraarylborate ion and a countercation as described later, and cases where it exists as a charge-transporting ionic compound which is consisting of a tetraarylborate ion and a cation of a hole-transporting material as described later.

[0084] The two crosslinking groups that undergo the crosslinking reaction may be the same group or different groups, as long as they are capable of crosslinking.

[0085] [Tetraarylborate ion] As the parent skeleton of the electron-accepting compound described above, an ionic compound consisting of a tetraarylborate ion, which is an anion with an ionic value of 1, and a countercation, is preferred because it has high stability, in which the boron atom is substituted with four optionally substituted aromatic hydrocarbon rings or optionally substituted aromatic heterocycles.

[0086] The tetraarylborate ion is more preferably characterized by having a fluorine atom or a fluorine-substituted alkyl group as a substituent on the aryl group, as shown in formula (2) below, in order to further improve stability.

[0087] [ka]

[0088] (In formula (2), Ar 1 Ar 2 Ar 3 and Ar 4Each of these independently represents a monovalent group consisting of multiple structures selected from optionally substituted aromatic hydrocarbon ring groups, optionally substituted aromatic heterocyclic groups, or optionally substituted aromatic hydrocarbon ring groups and optionally substituted aromatic heterocyclic groups. Ar 1 Ar 2 Ar 3 and Ar 4 At least one of them has a fluorine atom or a fluorine-substituted alkyl group as a substituent, Ar 1 Ar 2 Ar 3 and Ar 4 At least one of them has the aforementioned crosslinking group as a substituent.

[0089] Ar 1 Ar 2 Ar 3 and Ar 4 The aromatic hydrocarbon rings used in the aromatic hydrocarbon ring group are preferably monocyclic or 2-6 condensed rings. Specifically, examples include benzene rings, naphthalene rings, anthracene rings, phenanthrene rings, perylene rings, tetracene rings, pyrene rings, benzpyrene rings, chrysene rings, triphenylene rings, acenaphthene rings, fluorantene rings, fluorene rings, biphenyl structures, terphenyl structures, or quaterphenyl structures.

[0090] Ar 1 Ar 2 Ar 3 and Ar 4The aromatic heterocyclic rings used in the aromatic heterocyclic group are preferably monocyclic rings or 2-6 fused rings. Specifically, examples include furan rings, benzofuran rings, thiophene rings, benzothiophene rings, pyrrole rings, pyrazole rings, imidazole rings, oxadiazole rings, indole rings, carbazole rings, pyrroloimidazole rings, pyrrolopyrrole rings, pyrrolopyrrole rings, thienopyrrole rings, thienopyrrole rings, phlopyrrole rings, phlofuran rings, thienofuran rings, benzoisoxazole rings, benzoisothiazole rings, benzimidazole rings, pyridine rings, pyrazine rings, pyridazine rings, pyrimidine rings, triazine rings, quinoline rings, isoquinoline rings, sinnoline rings, quinoxaline rings, phenanthidine rings, perimidine rings, quinazoline rings, quinazolinone rings, or azulene rings.

[0091] Among these, monovalent groups or biphenyl groups derived from a benzene ring, naphthalene ring, fluorene ring, pyridine ring, or carbazole ring are more preferred due to their excellent stability and heat resistance. Particularly preferred are monovalent groups derived from a benzene ring, i.e., phenyl groups or biphenyl groups.

[0092] The number of monocyclic or 2- to 6-fused aromatic hydrocarbon ring groups and monocyclic or 2- to 6-fused aromatic heterocyclic ring groups included in a monovalent group, which is composed of multiple structures selected from optionally substituted aromatic hydrocarbon ring groups and optionally substituted aromatic heterocyclic ring groups, is 2 or more, preferably 8 or less, more preferably 4 or less, and even more preferably 3 or less.

[0093] Ar 1 Ar 2 Ar 3 and Ar 4 Examples of substituents that may be present include the groups listed in the substituent group W described later.

[0094] Ar 1 Ar 2 Ar 3 and Ar 4As substituents, fluorine atoms or fluorine-substituted alkyl groups are preferred because they increase the stability of the anion and improve the effect of stabilizing the cation. Furthermore, fluorine atoms or fluorine-substituted alkyl groups are Ar 1 Ar 2 Ar 3 and Ar 4 It is preferable that two or more of these are substituted, more preferably three or more are substituted, and most preferably four are substituted.

[0095] Ar 1 Ar 2 Ar 3 and Ar 4 As the fluorine-substituted alkyl group as the substituent, a linear or branched alkyl group having 1 to 12 carbon atoms with a fluorine atom substituted is preferred, a perfluoroalkyl group is more preferred, a linear or branched perfluoroalkyl group having 1 to 5 carbon atoms is even more preferred, a linear or branched perfluoroalkyl group having 1 to 3 carbon atoms is particularly preferred, and a perfluoromethyl group is most preferred. This is because it stabilizes the hole injection layer containing a crosslinked product of an electron-accepting compound having a crosslinking group, and the coating film laminated on top thereof.

[0096] The tetraarylborate ion contained in the quantum dot light-emitting element of the present invention further increases the stability of the anion and further improves the effect of stabilizing the cation, as in the Ar in formula (2) above. 1 Ar 2 Ar 3 and Ar 4 Preferably, at least one of the groups is represented by the following formula (3), and Ar 1 Ar 2 Ar 3 and Ar 4 It is more preferable that at least two of these are groups that are independently represented by the following formula (3), and Ar 1 Ar 2 Ar 3 and Ar 4 It is even more preferable that at least three of these are groups that are independently represented by the following formula (3), Ar 1 Ar2 Ar 3 and Ar 4 It is most preferable that all of them are groups that are independently represented by the following formula (3).

[0097] [ka]

[0098] (In formula (3), R 4 Each of these is independently an optionally substituted aromatic hydrocarbon ring group, an optionally substituted aromatic heterocyclic group, or a fluorine-substituted alkyl group. F4 indicates that four fluorine atoms are substituted. F (5-m) Each of these independently represents that 5-m fluorine atoms are substituted. k represents an integer from 0 to 5, independently of each other. (Each 'm' represents an integer from 0 to 5, independently.)

[0099] k is preferably 1 or greater, and more preferably 2 or greater, as this further improves the stability of the anion. k is preferably 0 or 1, and more preferably 0, as this facilitates even dispersion.

[0100] m is preferably 0 in terms of superior durability, preferably 1 or more in terms of the ability to introduce various functions into the tetraarylborate ion, and even more preferably 1 or 2 in terms of compatibility with durability. It is preferable that k+m≧1, as this improves the stability and durability of the anion.

[0101] R 4 The preferred structure and optional substituents of the aromatic hydrocarbon ring group or aromatic heterocyclic group are Ar 1 Ar 2 Ar 3 and Ar 4 It is similar to the structure and any substituents it may have.

[0102] R 4Examples of substituents include the groups listed in substituent group W below.

[0103] In equation (3), the stability of the anion is further increased, and the effect of stabilizing the cation is further improved, with at least one R 4 Preferably, the group is a fluorine-substituted alkyl group, preferably a perfluoroalkyl group, and more preferably a trifluoromethyl group.

[0104] In equation (3), at least one R 4 It is preferable that the crosslinking group is present in order to achieve both crosslinking and electron-accepting properties. 4 Preferably, the crosslinking group is the aforementioned crosslinking group, or one or more of the crosslinking groups are bonded to an aromatic hydrocarbon group.

[0105] R 4 However, when the crosslinking group has a structure in which one or more aromatic hydrocarbon groups are bonded, the aromatic hydrocarbon group is preferably a group that includes a benzene ring, a naphthalene ring, or a structure in which two or more selected from a benzene ring and a naphthalene ring are linked, and the number of links is preferably four or less. In this case, a more preferable R 4 The group is a group having a structure in which the crosslinking group is bonded to a benzene ring monocycle or a naphthalene ring monocycle, more preferably a group having a structure in which the crosslinking group is bonded to a benzene ring, and particularly preferably a group having a structure in which one or two crosslinking groups are bonded.

[0106] (Substituent group W) The substituent group W consists of a hydrogen atom, a halogen atom, a cyano group, an aromatic ring group consisting of 1 to 5 aromatic rings, a hydrocarbon ring group, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkoxy group, an alkylthio group, an arylthio group, an alkylketone group, or an arylketone group.

[0107] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms, with fluorine atoms being preferred due to the stability of the compound. It is particularly preferable for the compound to be substituted with four or more fluorine atoms for stability reasons.

[0108] Aromatic ring groups consisting of 1 to 5 aromatic rings include phenyl group, biphenyl group, terphenyl group, quaterphenyl group, naphthyl group, phenantrenyl group, triphenylene group, naphthylphenyl group, etc., with phenyl group, naphthyl group, biphenyl group, terphenyl group, or quaterphenyl group being preferred due to the stability of the compound.

[0109] Examples of hydrocarbon ring groups include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups.

[0110] The alkyl group typically has 1 or more carbon atoms, preferably 4 or more, typically 24 or less, preferably 12 or less, more preferably 8 or less, and more preferably 6 or less. Specifically, examples include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, tert-butyl group, n-hexyl group, cyclohexyl group, octyl group, 2-ethylhexyl group, dodecyl group, and the like.

[0111] Alkenyl groups typically have 2 or more carbon atoms, usually 24 or fewer, and preferably 12 or fewer. Specifically, examples include vinyl groups, propenyl groups, and butenyl groups.

[0112] Alkynyl groups typically have 2 or more carbon atoms, usually 24 or fewer, and preferably 12 or fewer. Specifically, examples include acetyl groups, propynyl groups, and butynyl groups.

[0113] Examples of aralkyl groups include the benzyl group, phenylethyl group, and phenylhexyl group.

[0114] The alkoxy group typically has 1 or more carbon atoms, 24 or fewer carbon atoms, preferably 12 or fewer carbon atoms, and more preferably 6 or fewer carbon atoms. Specific examples include methoxy groups, ethoxy groups, butyloxy groups, hexyloxy groups, octyloxy groups, and the like.

[0115] The aryloxy group typically has 4 or more carbon atoms, preferably 5 or more, more preferably 6 or more, usually 36 or fewer, preferably 24 or fewer, and more preferably 12 or fewer. Specific examples include the phenoxy group and the naphthyloxy group.

[0116] Alkylthio groups typically have one or more carbon atoms, usually 24 or fewer, and preferably 12 or fewer. Specific examples include methylthio groups, ethylthio groups, butylthio groups, and hexylthio groups.

[0117] The arylthio group typically has 4 or more carbon atoms, preferably 5 or more, usually 36 or fewer, and preferably 24 or fewer. Specific examples include the phenylthio group and the naphthylthio group.

[0118] Alkyl ketone groups typically have 1 or more carbon atoms, 24 or fewer carbon atoms, preferably 12 or fewer carbon atoms, and more preferably 6 or fewer carbon atoms. Specific examples include acetyl groups, ethyl carbonyl groups, butyl carbonyl groups, and octyl carbonyl groups.

[0119] The aryl ketone group typically has 5 or more carbon atoms, preferably 7 or more, usually 25 or fewer, and preferably 13 or fewer. Specific examples include the benzoyl group and the naphthylcarbonyl group.

[0120] Furthermore, adjacent substituents may bond to each other to form a ring. Examples of ring formations include cyclobutene rings and cyclopentene rings.

[0121] Furthermore, these substituents may be further substituted with substituents, and examples of such substituents include halogen atoms, alkyl groups, or aryl groups.

[0122] Among these substituents, halogen atoms or aryl groups are preferred in terms of compound stability. Halogen atoms are most preferred.

[0123] [Specific examples of tetraarylborate ions] The following are specific examples of tetraarylborate ions that can be used in the quantum dot light-emitting device of the present invention, but are not limited to these.

[0124] [ka]

[0125] [ka]

[0126] [ka]

[0127] [Ionic compounds containing tetraarylborate ions] The tetraarylborate ion is also preferably used as an electron-accepting ion compound containing the tetraarylborate ion. The electron-accepting ion compound containing the tetraarylborate ion is referred to as the first ion compound. The first ion compound consists of the tetraarylborate ion, which is an anion, and a countercation. The first ion compound is used as an electron-accepting compound.

[0128] Preferred countercations include iodonium cations, sulfonium cations, carbocations, oxonium cations, ammonium cations, phosphonium cations, cycloheptyltrienyl cations, or ferrocenium cations having a transition metal; iodonium cations, sulfonium cations, carbocations, and ammonium cations are more preferred, and iodonium cations are particularly preferred.

[0129] The iodonium cation is preferably the structure represented by the general formula (6) described below, and a more preferred structure is also the same.

[0130] Specifically, preferred iodonium cations include diphenyliodonium cation, bis(4-tert-butylphenyl)iodonium cation, 4-tert-butoxyphenylphenyliodonium cation, 4-methoxyphenylphenyliodonium cation, and 4-isopropylphenyl-4-methylphenyliodonium cation.

[0131] Specifically, preferred sulfonium cations include triphenylsulfonium cation, 4-hydroxyphenyldiphenylsulfonium cation, 4-cyclohexylphenyldiphenylsulfonium cation, 4-methanesulfonylphenyldiphenylsulfonium cation, (4-tert-butoxyphenyl)diphenylsulfonium cation, bis(4-tert-butoxyphenyl)phenylsulfonium cation, and 4-cyclohexylsulfonylphenyldiphenylsulfonium cation.

[0132] Specifically, preferred carbocations include trisubstituted carbocations such as triphenylcarbocation, tri(methylphenyl)carbocation, and tri(dimethylphenyl)carbocation.

[0133] Specifically, preferred ammonium cations include trialkylammonium cations such as trimethylammonium cation, triethylammonium cation, tripropylammonium cation, tributylammonium cation, and tri(n-butyl)ammonium cation; N,N-dialkylanilinium cations such as N,N-diethylanilinium cation and N,N-2,4,6-pentamethylanilinium cation; and dialkylammonium cations such as di(isopropyl)ammonium cation and dicyclohexylammonium cation.

[0134] Specifically, preferred phosphonium cations include tetraarylphosphonium cations such as tetraphenylphosphonium cation, tetrakis(methylphenyl)phosphonium cation, and tetrakis(dimethylphenyl)phosphonium cation; and tetraalkylphosphonium cations such as tetrabutylphosphonium cation and tetrapropylphosphonium cation.

[0135] Among these, iodonium cations, carbocations, and sulfonium cations are preferred in terms of the film stability of the compound, with iodonium cations being more preferred.

[0136] The iodonium cation serving as the countercation for the first ionic compound is preferably structured as shown in formula (6) below.

[0137] [ka]

[0138] In formula (6), Ar 5 Ar 6 Each of these is independently an aromatic hydrocarbon group which may have substituents, or an aromatic heterocyclic group which may have substituents. 5 Ar 6 Aromatic hydrocarbon ring groups or aromatic heterocyclic groups as Ar 1 Ar 2 Ar 3 and Ar4 It can be selected from the same structure as in the case, and the preferred structure is also Ar 1 , Ar 2 , Ar 3 and Ar 4 It can be selected from the same structure as in the case.

[0139] Also, the counter cation represented by the formula (6) is preferably represented by the following formula (7).

[0140] [Chemical formula]

[0141] In the formula (7), Ar 7 and Ar 8 are the same as the substituents that Ar 5 and Ar 6 in the aforementioned formula (6) may have.

[0142] The molecular weight of the first ionic compound used in the present invention is usually 900 or more, preferably 1000 or more, more preferably 1200 or more, and usually 10000 or less, preferably 5000 or less, more preferably 3000 or less. If the molecular weight is too small, delocalization of positive and negative charges may be insufficient, resulting in a possible decrease in electron accepting ability. If the molecular weight is too large, it may hinder charge transport.

[0143] [Specific examples] Hereinafter, specific examples of ionic compounds with iodonium cations as the first ionic compound in the present invention are given, but the present invention is not limited thereto.

[0144] [Chemical formula]

[0145] [Chemical formula]

[0146] [ka]

[0147] [Hole transport materials] The hole implantation layer preferably contains a hole transport material. As the hole transport material, compounds having an ionization potential of 4.5 eV to 5.5 eV are preferred in terms of hole transport ability. Examples include aromatic amine compounds, phthalocyanine derivatives, porphyrin derivatives, and oligothiophene derivatives. Among these, aromatic amine compounds are preferred in terms of amorphous nature, solubility in solvents, and visible light transmittance.

[0148] Among aromatic amine compounds, aromatic tertiary amine compounds are particularly preferred in this invention. In this invention, an aromatic tertiary amine compound refers to a compound having an aromatic tertiary amine structure, and also includes compounds having a group derived from an aromatic tertiary amine.

[0149] The type of aromatic tertiary amine compound is not particularly limited, but aromatic tertiary amine polymer compounds, which are polymer compounds, are preferred. The weight-average molecular weight of the polymer compound is preferably 5000 or more, more preferably 7000 or more, particularly preferably 10000 or more, preferably 1,000,000 or less, more preferably 200,000 or less, and particularly preferably 100,000 or less, from the viewpoint of surface smoothing effect. Among aromatic tertiary amine polymer compounds, polymer compounds having a triphenylamine structure in the main chain are even more preferred from the viewpoint of hole transportability.

[0150] [Aromatic tertiary amine polymer compounds] A preferred example of an aromatic tertiary amine polymer compound is a polymer compound having repeating units represented by the following formula (11).

[0151] [ka]

[0152] In the above formula (11), j10 、k 10 、l 10 、m 10 、n 10 、p 10 each independently represents an integer of 0 or more. However, l 10 + m 10 ≧ 1.

[0153] In the above formula (11), Ar 11 、Ar 12 、Ar 14 each independently represents a divalent aromatic ring group which may have a substituent. Ar 13 represents a divalent aromatic ring group which may have a substituent or a divalent group represented by the following formula (12), and Q 11 、Q 12 each independently represents an oxygen atom, a sulfur atom, or a hydrocarbon chain having 6 or less carbon atoms which may have a substituent, and S 1 ~ S 4 are each independently represented by a group represented by the following formula (13).

[0154] Ar 11 、Ar 12 、Ar 14 The aromatic ring groups of Ar 11 、Ar 12 、Ar 14 preferably have 60 or less carbon atoms.

[0155] As the aromatic hydrocarbon group, it preferably has 6 to 30 carbon atoms. Specifically, a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzopyrene ring, a chrysene ring, a triphenylene ring, an acenaphthene ring, a fluoranthene ring, or a fluorene ring, etc., a monocyclic 6-membered ring or a divalent group of a 2-5 condensed ring is exemplified.

[0156] The aromatic heterocyclic group is preferably one with 3 to 30 carbon atoms, and specifically, examples include divalent groups such as furan rings, benzofuran rings, thiophene rings, benzothiophene rings, pyrrole rings, pyrazole rings, imidazole rings, oxadiazole rings, indole rings, carbazole rings, pyrroloimidazole rings, pyrrolopyrrole rings, thienopyrrole rings, thienopyrrole rings, phlopyrrole rings, phlofuran rings, thienofuran rings, benzoisoxazole rings, benzoisothiazole rings, benzimidazole rings, pyridine rings, pyrazine rings, pyridazine rings, pyrimidine rings, triazine rings, quinoline rings, isoquinoline rings, sinnoline rings, quinoxaline rings, phenanthidine rings, benzimidazole rings, perimidine rings, quinazoline rings, quinazolinone rings, or azulene rings.

[0157] In particular, divalent groups or biphenyl groups derived from benzene rings, naphthalene rings, fluorene rings, pyridine rings, or carbazole rings are preferred due to their excellent charge transport properties, durability, and heat resistance.

[0158] These aromatic ring groups may have substituents, and the substituents that may be present can be selected from the substituent group W.

[0159] Ar 13 If it is an aromatic ring group, Ar 11 Ar 12 Ar 14 This is the same as in the previous case. Ar 13 Furthermore, a divalent group represented by the following formula (12) is preferred.

[0160] [ka]

[0161] In the above equation (12), R 11 R represents an alkyl group, an aromatic ring group, or a trivalent group consisting of an alkyl group having 40 or fewer carbon atoms and an aromatic ring group, and these may have substituents. 12represents an alkyl group, an aromatic ring group, or a divalent group consisting of an alkyl group with 40 or fewer carbon atoms and an aromatic ring group, which may have substituents. 31 represents a monovalent aromatic ring group or a monovalent bridging group, and these groups may have substituents. An asterisk (*) indicates a bond with the nitrogen atom in formula (11).

[0162] R 11 Specific examples of aromatic ring groups include phenyl rings, naphthalene rings, carbazole rings, dibenzofuran rings, dibenzothiophene rings, and trivalent groups derived from linked rings with 30 or fewer carbon atoms.

[0163] R 11 Specific examples of alkyl groups include trivalent groups derived from methane, ethane, propane, isopropane, butane, isobutane, and pentane.

[0164] R 12 Specific examples of aromatic ring groups include phenyl rings, naphthalene rings, carbazole rings, dibenzofuran rings, dibenzothiophene rings, and divalent groups derived from linked rings with 30 or fewer carbon atoms.

[0165] R 12 Specific examples of alkyl groups include divalent groups derived from methane, ethane, propane, isopropane, butane, isobutane, and pentane.

[0166] Ar 31 Specific examples of aromatic ring groups include monovalent groups derived from phenyl rings, naphthalene rings, carbazole rings, dibenzofuran rings, dibenzothiophene rings, and linked rings with 30 or fewer carbon atoms formed by the linkage of these rings.

[0167] Ar 31 The crosslinking group is not particularly limited, but preferred examples include groups derived from a benzocyclobutene ring, naphthocyclobutene ring, or oxetane ring, vinyl groups, and acrylic groups. Due to the stability of the compound, groups derived from a benzocyclobutene ring or naphthocyclobutene ring are more preferred.

[0168] S 1 ~S 4 Each is independently a group represented by the following formula (13).

[0169]

Chemical formula

[0170] In the above formula (13), q and r each independently represent an integer from 0 to 6. q and r are each independently preferably from 0 to 4, and more preferably 0 or 1.

[0171] Ar 21 and Ar 23 each independently represent a divalent aromatic ring group, and these groups may have substituents. Ar 22 represents a monovalent aromatic ring group which may have a substituent, and R 13 represents an alkyl group, an aromatic ring group or a divalent group composed of an alkyl group and an aromatic ring group, and these may have substituents. Ar 32 represents a monovalent aromatic ring group or a monovalent crosslinking group, and these groups may have substituents. The asterisk (*) indicates the bond to the nitrogen atom of the general formula (11).

[0172] Ar 21 and Ar 23 Examples of the aromatic ring groups of are the same as those in the case of Ar 11 and Ar 12 and Ar 14 is the same.

[0173] Ar 22 and Ar 32 The aromatic ring groups of represent a monovalent aromatic hydrocarbon group which may have a substituent, a monovalent aromatic heterocyclic group which may have a substituent, or a monovalent group in which at least two groups selected from a monovalent aromatic hydrocarbon group and a monovalent aromatic heterocyclic group are linked. Ar 22 and Ar 32 The aromatic ring groups preferably have 60 or fewer carbon atoms.

[0174] As the aromatic hydrocarbon group, it is preferably a group having 6 to 30 carbon atoms. Specifically, it includes monovalent groups of a 6-membered single ring or a 2- to 5-condensed ring such as a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzopyrene ring, a chrysene ring, a triphenylene ring, an acenaphthene ring, a fluoranthene ring, or a fluorene ring.

[0175] As the aromatic heterocyclic group, it is preferably a group having 3 to 30 carbon atoms. Specifically, it includes monovalent groups such as a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, a carbazole ring, a pyrroloimidazole ring, a pyrrolopyrazole ring, a pyrrolopyrrole ring, a thienopyrrole ring, a thienothiophene ring, a furopyrrole ring, a furofuran ring, a thienofuran ring, a benzoisoxazole ring, a benzoisothiazole ring, a benzimidazole ring, a pyridine ring, a pyrazine ring, a pyridazine ring, a pyrimidine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a cinnoline ring, a quinoxaline ring, a phenanthridine ring, a benzimidazole ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, or an azulene ring.

[0176] Among them, a monovalent group or a biphenyl group derived from a benzene ring, a naphthalene ring, a fluorene ring, a pyridine ring or a carbazole ring is preferable because of excellent charge transport properties, durability and heat resistance.

[0177] These aromatic ring groups may have substituents, and the possible substituents can be selected from the above-mentioned substituent group W.

[0178] R 13 Examples of the alkyl group or aromatic ring group of are the same as those of R 12 and the same.

[0179] Ar 32 The crosslinking group of is not particularly limited, but is the same as the examples of the crosslinking group of Ar 31 and the preferred examples are also the same.

[0180] The above Ar 11 ~Ar 14 , R 11 , R 12 Ar 21 ~Ar 23 Ar 31 ~Ar 32 Q 11 Q 12 Each of these substituents may have further substituents, as long as it does not contradict the spirit of the present invention. The molecular weight of the substituent is usually 400 or less, and preferably about 250 or less. The type of substituent is not particularly limited, but examples include one or more substituents selected from the substituent group W.

[0181] In particular, among polymer compounds having repeating units represented by formula (11), polymer compounds having repeating units represented by the following formula (14) are preferred because they exhibit very high hole injection and hole transport properties.

[0182] [ka]

[0183] In the above equation (14), R 21 ~R 25 Each of these independently represents an arbitrary substituent. 21 ~R 25 Specific examples of substituents are the same as those listed in substituent group W above.

[0184] Y' represents a divalent aromatic ring group having 30 or fewer carbon atoms, which may have substituents. An example of the aromatic ring group of Y' is the aforementioned Ar 11 Ar 12 and Ar 14 The same applies to the case where substituents may be present.

[0185] s and t each represent an integer between 0 and 5, independent of each other. u, v, and w each independently represent integers between 0 and 4 (inclusive).

[0186] Preferred examples of aromatic tertiary amine polymer compounds include polymer compounds containing repeating units represented by the following formulas (15) and / or (16).

[0187] [ka]

[0188] In equations (15) and (16) above, Ar 45 Ar 47 and Ar 48 Each of these independently represents a potentially substituted monovalent aromatic hydrocarbon group or a potentially substituted monovalent aromatic heterocyclic group. 44 and Ar 46 Each of these independently represents a potentially substituted divalent aromatic hydrocarbon group or a potentially substituted divalent aromatic heterocyclic group. 41 ~R 43 Each of these independently represents a hydrogen atom or any substituent. r is an integer between 0 and 2.

[0189] Ar 45 Ar 47 and Ar 48 Specific examples, preferred examples, examples of optional substituents, and examples of preferred substituents are each independently of Ar 22 and Ar 32 This is the same as in the previous case.

[0190] Ar 44 and Ar 46 Specific examples, preferred examples, examples of optional substituents, and examples of preferred substituents are each independently of Ar 11 and Ar 14 This is the same as in the previous case.

[0191] R 41 ~R 43 Preferably, the substituent is a hydrogen atom or one of the substituents listed in the substituent group W, and most preferably a hydrogen atom, an alkyl group, an alkoxy group, an amino group, an aromatic hydrocarbon group, or an aromatic heterocyclic group.

[0192] r is preferably 0 or 1, more preferably 0.

[0193] Preferred specific examples of the repeating unit represented by formula (15) and / or formula (16) applicable in the present invention are given below, but the present invention is not limited thereto.

[0194]

Chemical formula

[0195] Other aromatic amine compounds applicable as hole transport materials include conventionally known compounds that have been used as hole injection and hole transport layer-forming materials in quantum dot light-emitting devices. For example, aromatic diamine compounds in which tertiary aromatic amine units such as 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane are linked (Japanese Patent Publication No. 59-194393); aromatic amines containing two or more tertiary amines represented by 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl in which two or more condensed aromatic rings are substituted with nitrogen atoms (Japanese Patent Publication No. 5-234681); aromatic triamines of triphenylbenzene having a starburst structure (USA). Japanese Patent No. 4,923,774; Aromatic diamines such as N,N'-diphenyl-N,N'-bis(3-methylphenyl)biphenyl-4,4'-diamine (U.S. Patent No. 4,764,625); α,α,α',α'-tetramethyl-α,α'-bis(4-di-p-tolylaminophenyl)-p-xylene (Japanese Patent Publication No. 3-269084); Triphenylamine derivatives that are sterically asymmetrical as a whole molecule (Japanese Patent Publication No. 4-129271); Aromatic diamino group attached to pyrenyl group Compounds with multiple substitutions (Japanese Patent Publication No. 4-175395); Aromatic diamines in which tertiary aromatic amine units are linked by ethylene groups (Japanese Patent Publication No. 4-264189); Aromatic diamines having a styryl structure (Japanese Patent Publication No. 4-290851); Compounds in which aromatic tertiary amine units are linked by thiophene groups (Japanese Patent Publication No. 4-304466); Starburst type aromatic triamines (Japanese Patent Publication No. 4-308688); Benzylphenyl compounds (Japanese Patent Publication No. 4-364 Japanese Patent Publication No. 153); Tertiary amines linked by fluorene groups (Japanese Patent Publication No. 5-25473); Triamine compounds (Japanese Patent Publication No. 5-239455); Bis-dipyridylaminobiphenyl (Japanese Patent Publication No. 5-320634); N,N,N-triphenylamine derivatives (Japanese Patent Publication No. 6-1972); Aromatic diamines having a phenoxazine structure (Japanese Patent Publication No. 7-138562); Diaminophenylphenanthridine derivatives (Japanese Patent Publication No. 7-252474);Examples include hydrazone compounds (Japanese Patent Publication No. 2-311591), silazane compounds (U.S. Patent No. 4,950,950), silanamine derivatives (Japanese Patent Publication No. 6-49079), phosphatamine derivatives (Japanese Patent Publication No. 6-25659), and quinacridone compounds. These aromatic amine compounds may be used in mixtures of two or more types as needed.

[0196] Furthermore, other specific examples of aromatic amine compounds applicable as hole transport materials include metal complexes of 8-hydroxyquinoline derivatives having diarylamino groups. In these metal complexes, the central metal is selected from alkali metals, alkaline earth metals, Sc, Y, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Al, Ga, In, Si, Ge, Sn, Sm, Eu, and Tb, and the ligand 8-hydroxyquinoline has one or more diarylamino groups as substituents, but may also have arbitrary substituents other than diarylamino groups.

[0197] Furthermore, preferred specific examples of phthalocyanine derivatives or porphyrin derivatives applicable as hole transport materials include porphyrin, 5,10,15,20-tetraphenyl-21H,23H-porphyrin, 5,10,15,20-tetraphenyl-21H,23H-porphyrin cobalt(II), 5,10,15,20-tetraphenyl-21H,23H-porphyrin copper(II), and 5,10,15,20-tetraphenyl-21H,23H-porphyrin zinc(II). Examples include 5,10,15,20-tetraphenyl-21H,23H-porphyrin vanadium(IV) oxide, 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphyrin, 29H,31H-phthalocyanine copper(II), phthalocyanine zinc(II), phthalocyanine titanium, phthalocyanine oxide magnesium, phthalocyanine lead, phthalocyanine copper(II), and 4,4',4'',4'''-tetraaza-29H,31H-phthalocyanine.

[0198] Furthermore, preferred specific examples of oligothiophene derivatives applicable as hole transport materials of the present invention include α-sexithiophene.

[0199] The molecular weight of these hole transport materials is typically in the range of 5000 or less, preferably 3000 or less, more preferably 2000 or less, even more preferably 1700 or less, and particularly preferably 1400 or less, except in the case of polymer compounds having the specific repeating units described above. If the molecular weight of the hole transport material is too high, synthesis and purification become difficult and are undesirable, while if the molecular weight is too low, there is a risk of low heat resistance, which is also undesirable.

[0200] The hole injection layer of the quantum dot light-emitting device of the present invention may contain one of the above-mentioned hole transport materials alone, or it may contain two or more of them. When the hole injection layer contains two or more hole transport materials, the combination is arbitrary, but it is preferable to use one or more aromatic tertiary amine polymer compounds in combination with one or more other hole transport materials. Aromatic amine compounds are preferred as the type of hole transport material used in combination with the polymer compounds mentioned above.

[0201] The content of the hole transport material in the hole injection layer of the quantum dot light-emitting device of the present invention shall be within a range that satisfies the ratio with the electron-accepting compound described above. When two or more charge transport film compositions are used in combination, their total content shall fall within the above range.

[0202] [Charge-transporting ionic compounds] The hole injection layer of the quantum dot light-emitting device of the present invention preferably contains a charge-transporting ionic compound in which the tetraarylborate ion and the cation radical of the hole transport material are ionically bonded.

[0203] The hole injection layer of the quantum dot light-emitting device of the present invention is particularly preferably composed of a charge-transporting ionic compound in which the tetraarylborate ion and the cation radical of the aromatic tertiary amine polymer compound are ionically bonded as a hole transport material.

[0204] This charge-transporting ionic compound can be obtained by one of the following methods. i) The first ionic compound and the hole transport material are dissolved or dispersed in an organic solvent and mixed. ii) The first ionic compound and the hole transport material are dissolved or dispersed in an organic solvent and mixed, and then heated. iii) The composition obtained in i) or ii) above is wet-formed into a film, and the film is heated.

[0205] Since the first ionic compound is an electron-accepting compound, the hole transport material is oxidized by the first ionic compound by one of the above methods, resulting in the formation of a cation radical. As a result, a charge-transporting ionic compound is generated, which is an ionic compound in which the tetraarylborate ion acts as the counter-anion and the cation radical of the hole transport material acts as the counter-cation.

[0206] The hole injection layer of the quantum dot light-emitting device of the present invention preferably comprises a first ionic compound containing the tetraarylborate ion as a counteranion and a hole transport material, and more preferably, from the viewpoint of charge transport properties, comprises a charge transporting ionic compound in which the tetraarylborate ion is used as a counteranion and the cation radical of the hole transport material is used as a countercation.

[0207] [Composition for forming hole injection layers] The hole injection layer of the quantum dot light-emitting element of the present invention is preferably obtained by wet deposition of a hole injection layer forming composition.

[0208] The hole injection layer forming composition is preferably a composition obtained by dissolving or dispersing the first ionic compound having the tetraarylborate ion structure and the hole transport material in an organic solvent.

[0209] From the viewpoint of obtaining a uniform hole-injection layer film, the hole-injection layer forming composition is preferably a solution in which the first ionic compound and the hole transport material are dissolved in an organic solvent.

[0210] Even if the hole implantation layer formation composition obtained by method i) does not contain the charge transporting ion compound, it is sufficient if the charge transporting ion compound is obtained by method ii) or iii), and even if the hole implantation layer formation composition obtained by method ii) does not contain the charge transporting ion compound, it is sufficient if the charge transporting ion compound is obtained by method iii).

[0211] The mixing ratio of the first ionic compound to the hole transport material for obtaining a hole implantation layer forming composition is such that the amount of the first ionic compound is usually 0.1 parts by mass or more, preferably 1 part by mass or more, and usually 100 parts by mass or less, preferably 40 parts by mass or less, per 100 parts by mass of the hole transport material. If the content of the first ionic compound is above the lower limit, sufficient free carriers (cationic radicals of the hole transport material) can be generated, which is preferable as it improves hole transportability, and if it is below the upper limit, sufficient charge transportability can be ensured, which is preferable. When two or more types of the first ionic compound are used in combination, their total content should fall within the above range. The same applies to the hole transport material.

[0212] (Organic solvents) The concentration of the organic solvent in the hole injection layer forming composition is usually 10% by mass or more, preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more, and is usually within the range of 99.999% by mass or less, preferably 99.99% by mass or less, and even more preferably 99.9% by mass or less. When two or more organic solvents are mixed and used, the total concentration of these organic solvents should satisfy this range.

[0213] Examples of preferred organic solvents include ether-based solvents and ester-based solvents.

[0214] Specifically, examples of ether-based solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); and aromatic ethers such as 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenethole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, and 2,4-dimethylanisole. Any one of these may be used alone, or two or more may be used in any combination and ratio.

[0215] Examples of ester solvents include aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate, and n-butyl lactate; and aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate. Any one of these may be used alone, or two or more may be used in any combination and ratio.

[0216] Other usable solvents besides the ether-based and ester-based solvents mentioned above include, for example, aromatic hydrocarbon solvents such as benzene, toluene, and xylene; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; and dimethyl sulfoxide. These may be used individually or in any combination and ratio of two or more. Furthermore, one or more of these solvents may be used in combination with one or more of the ether-based and ester-based solvents mentioned above. In particular, aromatic hydrocarbon solvents such as benzene, toluene, and xylene have a low ability to dissolve electron-accepting compounds and free carriers (cationic radicals), so it is preferable to use them in mixture with ether-based and ester-based solvents.

[0217] Among these organic solvents, solvents having an aromatic hydrocarbon structure are even more preferred.

[0218] (Film forming method) The hole injection layer can be formed by wet deposition using a hole injection layer forming composition. The wet deposition method is the same as the method for wet deposition of a light-emitting layer forming composition, but it is preferable to heat after coating and drying. The heating temperature is preferably 120°C or higher, more preferably 150°C or higher, even more preferably 180°C or higher, preferably 300°C or lower, and even more preferably 260°C or lower.

[0219] The hole-injected layer can be crosslinked by heating the film after coating and drying. The following crosslinking reactions can occur in these combinations: • Crosslinking of hole transport materials • Crosslinking groups of hole transport materials and charge-receiving compound crosslinking groups • Electron-accepting compound crosslinking groups • Crosslinking group of hole transport material and crosslinking group of tetraarylborate ion in the present invention • The crosslinking groups of the tetraarylborate ion in this invention • Electron-accepting compound crosslinking group and the tetraarylborate ion crosslinking group in the present invention

[0220] Furthermore, heating promotes the formation of a charge-transporting ionic compound, which is an ionic compound formed by the tetraarylborate ion, the counter-anion of the first ionic compound, and the cation radical of the hole transport material, which is preferable.

[0221] <Structure of quantum dot light-emitting element> As an example of the structure of the quantum dot light-emitting element of the present invention, Figure 1 shows a schematic diagram (cross-section) of an example of the structure of a quantum dot light-emitting element 8. In Figure 1, 1 represents the substrate, 2 the anode, 3 the hole injection layer, 4 the hole transport layer, 5 the light-emitting layer, 6 the electron transport layer, and 7 the cathode.

[0222] [substrate] The substrate 1 serves as a support for the quantum dot light-emitting element, and is typically made of quartz, glass, metal, metal foil, plastic film, or sheet. Of these, glass plates and transparent synthetic resin plates such as polyester, polymethacrylate, polycarbonate, or polysulfone are preferred. The substrate is preferably made of a material with high gas barrier properties to prevent degradation of the quantum dot light-emitting element by the outside air. Therefore, especially when using a material with low gas barrier properties, such as a synthetic resin substrate, it is preferable to provide a dense silicon oxide film or the like on at least one side of the substrate to improve its gas barrier properties.

[0223] [anode] Anode 2 is responsible for injecting holes into the layer on the light-emitting layer 5 side.

[0224] Anode 2 is typically composed of metals such as aluminum, gold, silver, nickel, palladium, and platinum; metal oxides such as indium and / or tin oxides; metal halides such as copper iodide; carbon black; and conductive polymers such as poly(3-methylthiophene), polypyrrole, and polyaniline.

[0225] The formation of anode 2 is usually carried out by dry methods such as sputtering or vacuum deposition. When forming the anode using metal nanoparticles such as silver, nanoparticles such as copper iodide, carbon black, conductive metal oxide nanoparticles, or conductive polymer fine powder, it can also be formed by dispersing them in a suitable binder resin solution and coating it onto a substrate. In the case of conductive polymers, the anode can also be formed by directly forming a thin film on the substrate by electrolytic polymerization, or by coating the substrate with the conductive polymer (Appl. Phys. Lett., Vol. 60, p. 2711, 1992).

[0226] Anode 2 is usually a single-layer structure, but may be a multilayer structure as appropriate. If anode 2 is a multilayer structure, different conductive materials may be laminated on the first layer of anode.

[0227] The thickness of anode 2 can be determined according to the required transparency and material. When particularly high transparency is required, a thickness that allows for a visible light transmittance of 60% or more is preferable, and a thickness that allows for a visible light transmittance of 80% or more is even more preferable. The thickness of anode 2 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less. On the other hand, if transparency is not required, the thickness of anode 2 can be arbitrarily set according to the required strength, etc., and in this case, anode 2 may be the same thickness as the substrate.

[0228] When depositing other layers on the surface of anode 2, it is preferable to remove impurities from anode 2 and adjust its ionization potential to improve hole injection properties by treating it with ultraviolet / ozone, oxygen plasma, argon plasma, etc., before deposition.

[0229] [Hole injection layer] The hole injection layer in the quantum dot light-emitting device of the present invention is as described above. Although the wet deposition method was described above for the hole injection layer deposition method, a vacuum deposition method may also be used.

[0230] [Formation of hole injection layer by vacuum deposition method] When forming the hole injection layer of the quantum dot light-emitting element of the present invention by vacuum deposition, the first ionic compound can be used as the material containing tetraarylborate ions, and a depositable low-molecular-weight hole transport material can be used as the hole transport material. Preferably, the depositable low-molecular-weight hole transport material has a molecular weight of 1500 or less, more preferably 1000 or less, more preferably 400 or more, and more preferably 600 or more. Preferably, the low-molecular-weight hole transport material is an aromatic amine compound, and more preferably an aromatic tertiary amine compound.

[0231] When forming the hole injection layer 3 by vacuum deposition, typically one or more of the constituent materials for the hole injection layer 3 are placed in a crucible installed inside a vacuum chamber (if more than two materials are used, each is usually placed in a separate crucible), and the inside of the vacuum chamber is vacuumed with a vacuum pump for 10°C. -4 The system is evacuated to approximately Pa. Then, the crucible is heated (if two or more materials are used, each crucible is usually heated separately) to evaporate the materials in the crucible while controlling the evaporation rate (if two or more materials are used, each is usually evaporated independently) to form a hole injection layer on the anode on the substrate placed facing the crucible. Alternatively, if two or more materials are used, a mixture of these materials can be placed in the crucible, heated, and evaporated to form the hole injection layer.

[0232] The vacuum level during deposition is not limited as long as it does not significantly impair the effects of the present invention, but is typically 0.1 × 10⁻⁶. -6 Torr(0.13×10 -4 Pa) or more, 9.0×10 -6 Torr(12.0×10 -4 The pressure is less than or equal to Pa. The deposition rate is not limited as long as it does not significantly impair the effects of the present invention, but is usually 0.1 Å / sec or more and 5.0 Å / sec or less. The deposition temperature during deposition is not limited as long as it does not significantly impair the effects of the present invention, but is preferably 10°C or more and 50°C or less.

[0233] [Hole transport layer] The hole transport layer 4 is a layer responsible for transporting holes from the anode 2 to the light-emitting layer 5. Although the hole transport layer 4 is not an essential layer in the quantum dot light-emitting device of the present invention, it is preferable to form this layer in order to enhance the function of transporting holes from the anode 2 to the light-emitting layer 5. When the hole transport layer 4 is formed, it is usually formed between the anode 2 and the light-emitting layer 5. Also, if the hole injection layer 3 described above is present, it is formed between the hole injection layer 3 and the light-emitting layer 5.

[0234] The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and on the other hand, it is usually 300 nm or less, preferably 100 nm or less.

[0235] The hole transport layer 4 may be formed by vacuum deposition or wet deposition. Wet deposition is preferable because it offers superior film formation properties.

[0236] The hole transport layer 4 typically contains a hole transport compound.

[0237] Examples of hole-transporting compounds include aromatic diamines containing two or more tertiary amines and in which two or more condensed aromatic rings are substituted with nitrogen atoms, such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (Japanese Patent Publication No. 5-234681), and aromatic amine compounds having a starburst structure such as 4,4',4''-tris(1-naphthylphenylamino)triphenylamine (J. Lumin., Vol. 72-74, pp. 98). Preferred materials include aromatic amine compounds consisting of a tetramer of triphenylamine (Chem.Commun., p. 2175, 1996), spiro compounds such as 2,2',7,7'-tetrakis-(diphenylamino)-9,9'-spirobifluorene (Synth.Metals, Vol. 91, p. 209, 1997), and carbazole derivatives such as 4,4'-N,N'-dicarbazolebiphenyl. Furthermore, materials such as polyvinylcarbazole, polyvinyltriphenylamine (Japanese Patent Publication No. 7-53953), and polyarylene ethersulfone containing tetraphenylbenzidine (Polym.Adv.Tech., Vol. 7, p. 33, 1996) may also be included.

[0238] [Formation of hole transport layer by wet deposition method] When forming a hole transport layer using a wet deposition method, the hole transport layer is usually formed using a hole transport layer formation composition instead of a hole injection layer formation composition, in the same manner as when forming the hole injection layer using the wet deposition method described above.

[0239] When forming a hole transport layer by a wet film deposition method, the hole transport layer forming composition typically also contains a solvent. The solvent used in the hole transport layer forming composition can be the same solvent used in the hole injection layer forming composition described above.

[0240] The concentration of the hole-transporting compound in the hole-transporting layer-forming composition can be within the same range as the concentration of the hole-transporting compound in the hole-injection layer-forming composition.

[0241] [Formation of a hole transport layer by vacuum deposition] When forming a hole transport layer by vacuum deposition, it is usually possible to form it using a hole transport layer formation composition instead of a hole injection layer formation composition, in the same manner as when forming the hole injection layer by vacuum deposition described above. The deposition conditions, such as the degree of vacuum, deposition rate, and temperature, can be the same as those for vacuum deposition of the hole injection layer.

[0242] [Luminous layer] The light-emitting layer 5 is a layer that is excited and emits light when an electric field is applied between a pair of electrodes, by the recombination of holes injected from the anode 2 and electrons injected from the cathode 7. The light-emitting layer 5 is formed between the anode 2 and the cathode 7. If there is a hole injection layer above the anode, the light-emitting layer is formed between the hole injection layer and the cathode. If there is a hole transport layer above the anode, the light-emitting layer is formed between the hole transport layer and the cathode.

[0243] As described above, the light-emitting layer of the quantum dot light-emitting device in the present invention preferably contains quantum dots as the light-emitting material.

[0244] The film thickness of the light-emitting layer 5 is arbitrary as long as it does not significantly impair the effects of the present invention. However, a thicker film is preferable in that defects are less likely to occur in the film, while a thinner film is preferable in that it is easier to achieve a low driving voltage. For this reason, the film thickness of the light-emitting layer 5 is preferably 3 nm or more, more preferably 5 nm or more, and usually preferably 200 nm or less, and even more preferably 100 nm or less.

[0245] The light-emitting layer 5 contains at least a material having light-emitting properties (light-emitting material), and preferably contains one or more host materials.

[0246] [Hole Blocking Layer] A hole-blocking layer may be provided between the light-emitting layer 5 and the electron injection layer described later. The hole-blocking layer is a layer laminated on top of the light-emitting layer 5 so as to be in contact with the interface of the light-emitting layer 5 on the cathode 7 side.

[0247] This hole-blocking layer has two roles: preventing holes moving from anode 2 from reaching cathode 7, and efficiently transporting electrons injected from cathode 7 towards the light-emitting layer 5. The required properties for the material constituting the hole-blocking layer include high electron mobility and low hole mobility, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1).

[0248] Examples of hole blocking layer materials that satisfy these conditions include mixed ligand complexes such as bis(2-methyl-8-quinolinolato)(phenolato)aluminum and bis(2-methyl-8-quinolinolato)(triphenylsilanolato)aluminum, metal complexes such as bis(2-methyl-8-quinolato)aluminum-μ-oxo-bis-(2-methyl-8-quinolinolato)aluminum dinuclear metal complexes, styryl compounds such as distyrylbiphenyl derivatives (Japanese Patent Publication No. 11-242996), triazole derivatives such as 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (Japanese Patent Publication No. 7-41759), and phenanthroline derivatives such as basocproine (Japanese Patent Publication No. 10-79297). Furthermore, compounds having at least one pyridine ring substituted at the 2,4, and 6 positions, as described in International Publication No. 2005 / 022962, are also preferred as materials for hole blocking layers.

[0249] There are no restrictions on the method of forming the hole blocking layer. Therefore, it can be formed by wet deposition, vapor deposition, or other methods.

[0250] The thickness of the hole blocking layer is arbitrary as long as it does not significantly impair the effects of the present invention, but is usually 0.3 nm or more, preferably 0.5 nm or more, and is usually 100 nm or less, preferably 50 nm or less.

[0251] [Electron transport layer] The electron transport layer 6 is provided between the light-emitting layer 5 and the cathode 7 with the aim of further improving the current efficiency of the device.

[0252] The electron transport layer 6 is formed from a compound that can efficiently transport electrons injected from the cathode 7 towards the light-emitting layer 5 between electrodes under an applied electric field. The electron transport compound used in the electron transport layer 6 must have high electron injection efficiency from the cathode 7, high electron mobility, and be able to efficiently transport the injected electrons.

[0253] Examples of electron-transporting compounds used in the electron transport layer include, for example, metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Publication No. 59-194393), metal complexes of 10-hydroxybenzo[h]quinoline, oxadiazole derivatives, distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolbenzene (U.S. Patent No. 5645948), quinoxaline compounds (Japanese Patent Publication No. 6-207169), phenanthroline derivatives (Japanese Patent Publication No. 5-331459), 2-tert-butyl-9,10-N,N'-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide, and the like.

[0254] The film thickness of the electron transport layer 6 is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

[0255] The electron transport layer 6 is formed by laminating it onto the hole blocking layer using either a wet deposition method or a vacuum deposition method, as described above. Vacuum deposition is typically used.

[0256] [Electron injection layer] An electron injection layer may be provided to efficiently inject electrons injected from the cathode 7 into the electron transport layer 6 or the light-emitting layer 5.

[0257] To efficiently perform electron injection, the material forming the electron injection layer is preferably a metal with a low work function. Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. The film thickness is usually preferably between 0.1 nm and 5 nm.

[0258] Furthermore, doping organic electron transport materials, such as nitrogen-containing heterocyclic compounds like bathophenanthroline and metal complexes like aluminum complexes of 8-hydroxyquinoline, with alkali metals such as sodium, potassium, cesium, lithium, and rubidium (as described in Japanese Patent Publication No. 10-270171, Japanese Patent Publication No. 2002-100478, Japanese Patent Publication No. 2002-100482, etc.) is also preferable because it improves electron injection and electron transport properties and enables the achievement of excellent film quality.

[0259] The thickness of the electron injection layer is typically 5 nm or more, preferably 10 nm or more, and typically 200 nm or less, preferably 100 nm or less.

[0260] The electron injection layer is formed by laminating it onto the light-emitting layer 5 or the hole-blocking layer or electron transport layer 6 located thereon, using a wet deposition method or a vacuum deposition method. The details for the wet film deposition method are the same as those for the luminescent layer described above.

[0261] In some cases, the hole blocking layer, electron transport layer, and electron injection layer are combined into a single layer by co-doping the electron transport material with a lithium complex.

[0262] [cathode] The cathode 7 plays the role of injecting electrons into the layer on the light-emitting layer 5 side (such as the electron injection layer or light-emitting layer).

[0263] As the material for the cathode 7, the same material used for the anode 2 can be used. However, for efficient electron injection, it is preferable to use a metal with a low work function. For example, metals such as tin, magnesium, indium, calcium, aluminum, and silver, or alloys thereof, can be used. Specific examples include low-work-function alloy electrodes such as magnesium-silver alloys, magnesium-indium alloys, and aluminum-lithium alloys.

[0264] In terms of the stability of quantum dot light-emitting devices, it is preferable to protect the cathode, which is made of a metal with a low work function, by laminating a metal layer with a high work function and stability to the atmosphere on top of the cathode. Examples of metals that can be laminated include aluminum, silver, copper, nickel, chromium, gold, and platinum.

[0265] The film thickness of the cathode is usually the same as that of the anode.

[0266] [Other layers] The quantum dot light-emitting element of the present invention may have any other layer, provided that it does not significantly impair the effects of the present invention. That is, it may have any other layer between the anode and the cathode.

[0267] [Other component configurations] The quantum dot light-emitting device of the present invention can also have a structure reversed from the above description, that is, for example, stacking cathode, electron injection layer, electron transport layer, hole blocking layer, light-emitting layer, hole transport layer, hole injection layer, and anode on a substrate in that order.

[0268] When applying the quantum dot light-emitting element of the present invention to an organic electroluminescent device, it may be used as a single quantum dot light-emitting element, as a configuration in which multiple quantum dot light-emitting elements are arranged in an array, or as a configuration in which the anode and cathode are arranged in an XY matrix.

[0269] <Quantum dot display device> The quantum dot display device (quantum dot light-emitting device display device) of the present invention comprises the quantum dot light-emitting element of the present invention. There are no particular restrictions on the type or structure of the quantum dot display device of the present invention, and it can be assembled according to conventional methods using the quantum dot light-emitting element of the present invention.

[0270] For example, the quantum dot display device of the present invention can be formed by replacing the organic light-emitting layer with a light-emitting layer containing quantum dots, referring to a method such as the one described in "Organic EL Display" (Ohmsha, published August 20, 2004, authored by Shizuka Tokito, Chihaya Adachi, and Hideyuki Murata).

[0271] <Quantum dot lighting> The quantum dot illumination (quantum dot light-emitting element illumination) of the present invention comprises the quantum dot light-emitting element of the present invention. There are no particular restrictions on the type or structure of the quantum dot illumination of the present invention, and it can be assembled according to conventional methods using the quantum dot light-emitting element of the present invention. [Examples]

[0272] [Example 1] Quantum dot light-emitting devices were fabricated using the following method. A deposition model (Geomatec Co., Ltd., sputter-deposited) was prepared by depositing a transparent conductive indium tin oxide (ITO) film to a thickness of 50 nm on a glass substrate. The deposition model was patterned into 2 mm wide stripes using conventional photolithography techniques and hydrochloric acid etching to form an anode. The substrate with the ITO pattern was then cleaned in the following order: ultrasonic cleaning with a surfactant aqueous solution, rinsing with ultrapure water, ultrasonic cleaning with ultrapure water, rinsing with ultrapure water, drying with compressed air, and finally, ultraviolet ozone cleaning.

[0273] As a composition for forming a hole injection layer, a composition was prepared by dissolving 3.0% by mass of a hole-transporting polymer compound having a repeating structure of the following formula (P-1) and 0.6% by mass of an electron-accepting compound (HI-1) in ethyl benzoate.

[0274] [ka]

[0275] This composition was spin-coated onto the substrate in air, dried on a hot plate at 240°C for 30 minutes in air to form a uniform thin film with a thickness of 40 nm, which served as the hole injection layer.

[0276] Next, 100 parts by mass of a charge-transporting polymer compound having the following structural formula (HT-1) was dissolved in 1,3,5-trimethylbenzene to prepare a 2.0% by mass solution.

[0277] This solution was spin-coated onto a substrate coated with the hole injection layer in a nitrogen glove box, and dried on a hot plate in the nitrogen glove box at 230°C for 30 minutes to form a uniform thin film with a thickness of 40 nm, which served as the hole transport layer.

[0278] [ka]

[0279] Subsequently, a 1.5% by mass toluene solution of CdZnSeS nanoparticles was spin-coated onto the substrate coated with the hole transport layer described above, at 3000 revolutions per minute for 30 seconds in a nitrogen glove box, and then dried on a hot plate in the nitrogen glove box at 100°C for 10 minutes to form the light-emitting layer.

[0280] A substrate with the light-emitting layer deposited is placed in a vacuum deposition apparatus, and the inside of the apparatus is 2 × 10 -4 The exhaust was vented until the pressure dropped below Pa.

[0281] Next, the following structural formula (ET-1) and 8-hydroxyquinolinolatritium were co-deposited onto the light-emitting layer in a film thickness ratio of 2:3 using vacuum deposition to form an electron transport layer with a thickness of 45 nm.

[0282] [ka]

[0283] Next, a 2mm wide striped shadow mask was placed in close contact with the substrate so as to be perpendicular to the ITO stripe of the anode, and the aluminum was heated using a molybdenum boat to form an aluminum layer with a thickness of 80nm, thereby forming the cathode. In this way, a quantum dot light-emitting device having an emitting area of ​​2mm x 2mm was obtained.

[0284] [Comparative Example 1] A quantum dot light-emitting element was fabricated in the same manner as in Example 1, except that a composition was prepared by dissolving 3.0% by mass of (P-1) and 0.6% by mass of the following electron-accepting compound (HI-2) in ethyl benzoate as a hole injection layer formation composition.

[0285] [ka]

[0286] [Evaluation of quantum dot light-emitting devices] When the quantum dot light-emitting devices obtained in Example 1 and Comparative Example 1 were activated, red light emission with a peak wavelength of 628 nm and a full width at half maximum of 27 nm was obtained. 2 The external quantum efficiency (%) was measured when the light was emitted using the following method. Additionally, a quantum dot light-emitting element was subjected to 10 mA / cm². 2 The luminance half-life (LT50) was measured when the device was continuously energized at the specified current density. Table 1 shows the external quantum efficiency and relative lifetime of Example 1, with the lifetime of Comparative Example 1 set to 1.

[0287] [Table 1]

[0288] The results in Table 1 show that the quantum dot light-emitting device of the present invention exhibits improved performance. [Explanation of symbols]

[0289] 1 circuit board 2 Anode 3. Hole injection layer 4. Hole transport layer 5. Emitting layer 6 Electron transport layer 7 Cathode 8 Quantum dot light-emitting devices

Claims

1. A quantum dot light-emitting device having an anode, a cathode, a light-emitting layer, and a hole injection layer, The light-emitting layer is provided between the anode and the cathode, The hole injection layer is provided between the anode and the light-emitting layer, The light-emitting layer contains quantum dots, The hole injection layer contains a crosslinked product of an electron-accepting compound having a crosslinking group, However, the light-emitting layer does not contain a charge transport material including a triazine and / or pyrimidine skeleton, in the quantum dot light-emitting device.

2. The quantum dot light-emitting element according to claim 1, wherein the crosslinking group is represented by any of the following formulas (X1) to (X18). 【Chemistry 1】 (In formulas (X1) to (X4), the benzene ring and the naphthalene ring may have substituents. The substituents may also be bonded to each other to form a ring.) In formula (X5), R １ represents an alkyl group which may have substituents. In formula (X6), R ２ represents an alkyl group which may have substituents. In formula (X10), R ３ (This represents an alkyl group which may have substituents.)

3. The quantum dot light-emitting element according to claim 2, wherein the bridging group is represented by any one of the formulas (X1) to (X3).

4. A quantum dot display device or quantum dot illumination comprising a quantum dot light-emitting element according to any one of claims 1 to 3.

5. A method for manufacturing a quantum dot light-emitting device having an anode, a hole injection layer, a light-emitting layer, and a cathode on a substrate in this order, A step of forming the hole injection layer by a wet film deposition method using a hole injection layer formation composition, and The process includes a step of forming the light-emitting layer by a wet film deposition method using a light-emitting layer forming composition, The hole injection layer forming composition comprises an electron-accepting compound having a crosslinking group and an organic solvent. The aforementioned light-emitting layer forming composition comprises quantum dots and an organic solvent. However, the light-emitting layer does not contain a charge transport material including a triazine and / or pyrimidine skeleton. A method for manufacturing quantum dot light-emitting devices.

6. The method for manufacturing a quantum dot light-emitting element according to claim 5, wherein the crosslinking group is represented by any of the following formulas (X1) to (X18). 【Chemistry 2】 (In formulas (X1) to (X4), the benzene ring and the naphthalene ring may have substituents. The substituents may also be bonded to each other to form a ring.) In formula (X5), R １ represents an alkyl group which may have substituents. In formula (X6), R ２ represents an alkyl group which may have substituents. In formula (X10), R ３ (This represents an alkyl group which may have substituents.)

7. The method for manufacturing a quantum dot light-emitting element according to claim 6, wherein the crosslinking group is represented by any one of the formulas (X1) to (X3).

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