JP7159932B2 - organic electroluminescence element - Google Patents

Description

TECHNICAL FIELD The present invention relates to an organic electroluminescence element, and more particularly, to an organic electroluminescence element that has a low driving voltage and suppresses a voltage rise even when driven over time.

Organic electroluminescence elements (hereinafter also referred to as “organic EL elements”) can be driven at a low voltage and are suitably used for image display devices and lighting devices. An organic EL element has a structure in which a plurality of layers such as an electron transport layer, a light emitting layer, and a hole transport layer are laminated between a cathode and an anode.
Conventionally, an alkali metal compound such as LiF is used as a material for an electron injection layer of an organic EL device. In recent years, attempts have been made to use metal oxides that are stable in the atmosphere.

However, although the metal oxide has high conductivity, the work function is determined by the material, and there is a problem that the selection range of the material is narrow and, in particular, the electron injection barrier from the cathode is high. As a solution to this problem, it is known that the electron injection property can be improved by doping a polymer such as polyethyleneimine or a material such as an aromatic compound having a dimethylamino group (for example, Non-Patent Document 1 and See Patent Document 1.)

However, it is known that when a metal oxide is doped with an organic substance, not only polyethyleneimine, but also a voltage increase of the device often occurs due to deterioration of the interface with the cathode.
For this reason, there is a problem that the drive voltage increases when the device is driven over time, which affects the life of the organic EL device.

JP 2018-093080 A

ACS Appl. Mater. Interface. 2018, 10.17318-17326

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is to provide an organic electroluminescence element that has a low driving voltage and that suppresses a voltage rise even when driven over time.

In order to solve the above problems, the present inventors investigated the causes of the above problems, and found that the electron injection barrier from the cathode was improved by doping a metal oxide with a light-absorbing compound having a specific LUMO energy level. can be reduced, and the driving voltage can be greatly reduced, leading to the present invention.
That is, the above problems related to the present invention are solved by the following means.

1. An organic electroluminescence device comprising, on a substrate, a pair of a cathode and an anode, and an organic functional layer including a light-emitting layer and an electron-transporting layer adjacent to the cathode,
The electron transport layer contains a compound having a triphenylamine skeleton represented by the following formula (II) and a metal oxide,
The LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the following formula (II) is higher than the energy level (E _CB ) of the conduction band bottom of the metal oxide,
The energy difference ΔE (E _DL ) between the LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the following formula (II) and the energy level (E _CB ) at the bottom of the conduction band of the metal oxide -E _CB ) is 0.3 eV or more,
An organic electroluminescence device, wherein an emission wavelength range of a light-emitting compound in the light-emitting layer and an absorption wavelength range of a compound having a triphenylamine skeleton represented by the following formula (II) overlap.

(Wherein, Ar ₂ , Ar ₃ and Ar ₄ each independently represent a substituted or unsubstituted benzene ring. X is an acidic group or an electron-withdrawing group , a substituent having them, or an electron-withdrawing ring represents a substituent having a structure, with the proviso that Ar ₂ , Ar ₃ or Ar ₄ excludes those having a dimethylamino group, n represents an integer of 1 to 4. When n is plural, each X may be the same or different).

2. An organic electroluminescence device comprising, on a substrate, a pair of a cathode and an anode, and an organic functional layer including a light-emitting layer and an electron-transporting layer adjacent to the cathode,
The electron-transporting layer comprises the following A-1, A-2, A-6, A-7, A-8, A-13, A-14, A-16, A-17, A-18 and A-20 , containing a compound A having a structure represented by A-32 and A-35 and a metal oxide,
The LUMO energy level (E _DL ) of the compound A is higher than the energy level (E _CB ) of the conduction band bottom of the metal oxide,
The energy difference ΔE (E _DL −E _CB ) between the LUMO energy level (E _DL ) of the compound A and the energy level (E _CB ) of the conduction band bottom of the metal oxide is 0.3 eV or more,
An organic electroluminescence device, wherein an emission wavelength range of a light-emitting compound and an absorption wavelength range of said compound A in said light-emitting layer overlap with each other.

3. 3. The organic electroluminescence device according to claim 1 or 2, wherein the electron transport layer contains zinc oxide as the metal oxide.

4. 4. The organic electroluminescence device according to any one of items 1 to 3, wherein the metal oxide is nanoparticles.

According to the above means of the present invention, it is possible to provide an organic electroluminescence device that has a low driving voltage and that suppresses voltage rise even when driven over time.

Although the expression mechanism or action mechanism of the effects of the present invention has not been clarified, it is speculated as follows.

In the present invention, part of the light emitted from the light-emitting layer of the organic EL device is absorbed and regenerated by a compound (also referred to as a light-absorbing compound) having a triphenylamine skeleton represented by the formula ( II ) doped into a metal oxide. It is presumed that the carrier density on the metal oxide can be increased by exciting and converting the generated carriers onto the metal oxide, and the device can be driven by reducing the electron injection barrier from the cathode. .
Therefore, the deterioration occurring at the interface between the electron injection layer or the transport layer adjacent to the cathode and the cathode can be greatly reduced, so that the driving voltage can be lowered, and the increase in the driving voltage can be reduced even after long-term driving. presumed to be possible.

Description will be made with reference to the drawings. FIG. 1 is a conceptual diagram showing the energy level relationship of materials included in an organic EL element. The organic EL element shown in FIG. 1 is an example composed of an anode (ITO)/hole transport layer/light emitting layer/electron transport layer/cathode (Al).
The energy level is defined as a negative value on the lower side than the vacuum level of 0 eV, which is the highest energy level. That is, for example, when the energy levels are −(minus) 3 eV and −4 eV, −3 eV is the higher energy level.

The hole-transporting layer contains a hole-transporting material, and the light-emitting layer contains a light-emitting compound. The electron-transporting layer according to the present invention is in contact with the cathode and contains zinc oxide (metal oxide) doped with a compound (light-absorbing compound) having a triphenylamine skeleton represented by formula ( II ). there is

In the present invention, part of the light emitted from the light-emitting compound in the light-emitting layer of the organic EL element is
A compound (also referred to as a light-absorbing compound) having a triphenylamine skeleton represented by formula (I I ) doped into a metal oxide is absorbed and re-excited. The generated excited electrons, that is, the electrons transitioned from the HOMO to the LUMO of the light-absorbing compound move onto the metal oxide, so that the carrier density on the metal oxide can be increased.

That is, the light-absorbing compound absorbs part of the light emitted in the light-emitting layer, so that the electrons of the light-absorbing compound HOMO energy level (E _DH ) transition to the light-absorbing compound LUMO energy level (E _DL ), In addition, electrons in the light absorbing compound LUMO energy level (E _DL ) move to the conduction band bottom energy level (E _CB ) of the metal oxide, thereby increasing the carrier density on the metal oxide.

At this time, electron transfer occurs efficiently from the high energy side to the low energy side, so that the LUMO energy level (E _DL ) of the light absorbing compound is higher than the energy level (E _CB ) at the bottom of the conduction band of the metal oxide, The energy difference ΔE (E _DL −E _CB ) between the LUMO energy level (E _DL ) of the light absorbing compound and the energy level (E _CB ) of the conduction band bottom of the metal oxide is 0.3 eV or more, It is preferable for electrons to efficiently move from the LUMO energy level (E _DL ) of the light absorbing compound to the energy level (E _CB ) at the bottom of the conduction band of the metal oxide. It is more preferably 0.5 eV or more, and more preferably has an energy difference ΔE of 0.7 eV or more.

In the present invention, it is necessary that the emission wavelength region of the light-emitting compound in the light-emitting layer and the absorption wavelength region of the compound having a triphenylamine skeleton represented by formula (I I ) overlap. Using this overlap, part of the light emitted by the light-emitting compound is absorbed by the compound (light-absorbing compound) having a triphenylamine skeleton represented by formula (I I ).

Specifically, the emission spectrum of the light-emitting compound and the absorption spectrum of the light-absorbing compound must overlap. As for the relationship between the peak wavelengths of the emission spectrum and the absorption spectrum, the absorption peak wavelength may be shorter or longer than the emission peak wavelength.
In order for the emission spectrum of the light-emitting compound and the absorption spectrum of the light-absorbing compound to overlap, the difference between the emission spectrum peak wavelength λem of the light-emitting compound and the absorption spectrum peak wavelength λa of the light-absorbing compound is in the range of ±0 to 200 nm. is preferred, and a range of ±0 to 100 nm is more preferred.
The emission spectrum of the light-emitting compound is measured using, for example, a spectroradiometer CS-1000 (manufactured by Konica Minolta), and the absorption spectrum of the light-absorbing compound is measured using, for example, a spectrophotometer U-manufactured by Hitachi High-Tech. 3300 can be used.

Also, the light absorbing compound and the metal oxide must be in contact with each other. In the present invention, the metal oxide doped with a compound (light-absorbing compound) having a triphenylamine skeleton represented by formula (I I ) means only the case where the metal oxide contains a light-absorbing compound. It also includes a mode in which it is adsorbed on the surface of the metal oxide particles. It suffices if electron transfer is possible between the light absorbing compound and the metal oxide.

In order to perform electron transfer more efficiently between the light-absorbing compound and the metal oxide, the strong interaction between the two includes electrostatic interaction, van der Waals force, hydrogen bonding, or It is preferred that chemical bonding or the like occurs. For this purpose, the light-absorbing compound preferably has an acidic group, an electron-withdrawing group, or an electron-withdrawing ring structure, and more preferably has a carboxy group, a sulfo group, or a phosphonic acid group as the acidic group.

Conceptual diagram showing the relationship between the energy levels of the materials contained in the organic EL element Cross-sectional view showing an example of an organic EL element Schematic diagram when forming an electronic device by ejecting it from an inkjet head Schematic diagram showing an example of a method of applying an electronic device using an inkjet printing method Schematic perspective view and bottom view showing an example of the structure of an inkjet head applicable to the inkjet printing method

The organic electroluminescence device of the present invention is an organic electroluminescence device comprising, on a substrate, a pair of a cathode and an anode, and an organic functional layer having a light-emitting layer and an electron-transporting layer adjacent to the cathode,
The electron transport layer contains a compound having a triphenylamine skeleton represented by the formula (II) and a metal oxide,
The LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the formula (II) is higher than the energy level (E _CB ) of the conduction band bottom of the metal oxide,
The energy difference ΔE (E _DL ) between the LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the formula (II) and the energy level (E _CB ) at the bottom of the conduction band of the metal oxide -E _CB ) is 0.3 eV or more,
The emission wavelength range of the light-emitting compound in the light-emitting layer and the absorption wavelength range of the compound having a triphenylamine skeleton represented by formula (II) overlap. This feature is a technical feature common to or corresponding to each of the following embodiments (forms).

In the present invention, the compound having a triphenylamine skeleton represented by the formula (II) efficiently separates charges when the light-absorbing compound absorbs light . The triphenylamine skeleton is a strong donor skeleton, and when it has a structure bonded to an electron-withdrawing skeleton, the HOMO charge distribution of this compound is localized at the donor skeleton site, and the LUMO charge distribution is localized at the electron-withdrawing skeleton. Localized to the site. As a result, the electrons excited by the LUMO of the compound are suppressed from deactivating the HOMO, and electron transfer to the conduction band of the metal oxide is likely to occur.
Further, instead of the compound having a triphenylamine skeleton, the A-1, A-2, A-6, A-7, A-8, A-13, A-14, A-16, A-17 , A-18, A-20, A-32 and A-35, electron transfer to the conduction band of the metal oxide is likely to occur in the same manner as described above.

Further, the electron-transporting layer contains zinc oxide as the metal oxide at a conduction band energy level at which electron transfer from the light-absorbing compound is likely to occur, and the electron mobility is high. preferred from
It is preferable that the metal oxide is a nanoparticle because the surface area is large and the light-absorbing compound is easily adsorbed stably.

DETAILED DESCRIPTION OF THE INVENTION The present invention, its constituent elements, and embodiments and modes for carrying out the present invention will be described in detail below. In the present application, "-" is used to mean that the numerical values before and after it are included as the lower limit and the upper limit.

《Organic electroluminescence device》
The organic electroluminescence device of the present invention is an organic electroluminescence device comprising, on a substrate, a pair of a cathode and an anode, and an organic functional layer having a light-emitting layer and an electron-transporting layer adjacent to the cathode,
The electron transport layer contains a compound having a triphenylamine skeleton represented by the following formula (II) and a metal oxide,
The LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the formula (II) is higher than the energy level (E _CB ) of the conduction band bottom of the metal oxide,
The energy difference ΔE (E _DL ) between the LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the formula (II) and the energy level (E _CB ) at the bottom of the conduction band of the metal oxide -E _CB ) is 0.3 eV or more,
The emission wavelength range of the light-emitting compound in the light-emitting layer and the absorption wavelength range of the compound having a triphenylamine skeleton represented by formula (II) overlap.
Further, instead of the compound having a triphenylamine skeleton, the A-1, A-2, A-6, A-7, A-8, A-13, A-14, A-16, A-17 , A-18, A-20, A-32 and A-35 (hereinafter simply referred to as “compound A”) may also be used.

In addition, in the present invention, the HOMO and LUMO energy levels of the light-absorbing compound used are determined by the following method.
In the present invention, the HOMO energy level (E _DH ) is defined as a negative value of the measured ionization potential (positive value). The ionization potential can be measured with an atmospheric photoelectron spectrometer (for example, AC-1, AC-2, and AC-3 (manufactured by Riken Keiki Co., Ltd.)) or an ultraviolet photoelectron spectrometer (UPS). In this example, AC-3 was used for measurement. When measuring with AC-3, an organic thin film having a thickness of 50 to 100 nm is formed on a powder sample on an aluminum plate or on washed ITO.
The LUMO energy level (E _DL ) is defined as follows.
_{EDL = EDH +} Eg

Here, Eg is the excitation energy corresponding to the energy gap between the HOMO and LUMO of the light-absorbing compound, and the energy of the absorption edge wavelength on the long wavelength side at 5% intensity of the absorption peak of the absorption spectrum of the light-absorbing compound (eV unit conversion value).
The absorption spectrum of the light-absorbing compound can be measured, for example, using a spectrophotometer U-3300 manufactured by Hitachi High-Tech. In this example, light-absorbing compounds were measured as ethanol solutions at concentrations of 10 ⁻⁶ to 10 ⁻⁴ mol/L.

In addition, as a method for estimating the energy level (E _CB ) at the bottom of the conduction band of a metal oxide, the energy level of the valence band obtained by ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and There is a method of estimating from the typical bandgap energy.
In the present invention, it was obtained from the energy level of the valence band and the optical bandgap energy determined by ultraviolet photoelectron spectroscopy.

《Metal oxide》
As described above, the metal oxide that can be used in the present invention is not particularly limited as long as it satisfies the following two requirements.
(1) The LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by formula (II) is higher than the energy level (E _CB ) of the metal oxide at the bottom of the conduction band.
(2) The _energy difference _ΔE ( E _DL −E _CB ) is 0.3 eV or more.
Further, the compound A may be used instead of the compound having a triphenylamine skeleton.

As such metal oxides, oxides of alumina, zirconia, titania, silica, magnesia, or niobium are preferable from the viewpoint of chemical stability and physical stability. Specifically, titanium oxide, zirconium oxide, silicon oxide, aluminum oxide, zinc oxide, magnesium oxide, niobium oxide, hafnium oxide, yttrium oxide, cerium oxide, or hydrates of these metal oxides, and titanium Examples include barium oxide, barium zirconate, potassium niobate, sodium niobate, calcium titanate, strontium tantalate, bismuth titanate, sodium bismuth titanate, or a solid solution containing at least one of these in its composition.

Among them, solid solutions such as zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), zinc oxide (ZnO) or AZO (Al-doped ZnO) are preferred. From the viewpoint of the energy level at the bottom of the conduction band of the metal oxide and the electron mobility, zinc oxide or AZO obtained by doping zinc oxide with Al is more preferable. Zinc oxide is more preferred.

In the present invention, the metal oxide is preferably nanoparticles. “Nanoparticles” refer to spherical particles with a particle diameter of 1 nm or more and 500 nm or less, fibrous particles with a cross-sectional diameter of 1 nm or more and 500 nm or less, or plate-like particles with a thickness of 1 nm or more and 500 nm or less.

<<Compound Having Triphenylamine Skeleton Represented by Formula (II)>>
In the present invention, the electron transport layer adjacent to the cathode contains a compound having a triphenylamine skeleton represented by the following formula (II) and a metal oxide.
In addition, the LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the following formula (II) is higher than the energy level (E _CB ) at the bottom of the conduction band of the metal oxide, and the following formula Energy difference ΔE (E _DL -E) between the LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by (II) and the energy level (E _CB ) of the conduction band bottom of the metal oxide _CB ) is 0.3 eV or more, and there is an overlap between the emission wavelength region of the light-emitting compound in the light-emitting layer and the absorption wavelength region of the compound having a triphenylamine skeleton represented by formula (II).

Further , the compound A may be used instead of the compound having a triphenylamine skeleton represented by the following formula (II).

(Wherein, Ar ₂ , Ar ₃ and Ar ₄ each independently represent a substituted or unsubstituted benzene ring. X is an acidic group or an electron-withdrawing group , a substituent having them, or an electron-withdrawing ring represents a substituent having a structure, provided that Ar ₂ , Ar ₃ or Ar ₄ does not have a dimethylamino group, n represents an integer of 1 to 4. When n is plural, each X may be the same or different).

Ar ₂ , Ar ₃ or Ar ₄ represents a substituted or unsubstituted benzene ring.
Further, the compound A may be used instead of the compound having a triphenylamine skeleton.

Examples of substituents include alkyl groups (e.g., methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), Cycloalkyl group (e.g., cyclopentyl group, cyclohexyl group, etc.), alkenyl group (e.g., vinyl group, allyl group, etc.), alkynyl group (e.g., ethynyl group, propargyl group, etc.), aromatic hydrocarbon group (e.g., phenyl group, etc.) , p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group ( For example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (e.g., 1,2,4-triazol-1-yl group, 1,2,3- triazol-1-yl group, etc.), pyrazolotriazolyl group, oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, carbolinyl group, diazacarbazolyl group (one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced with a nitrogen atom), quinoxalinyl group , pyridazinyl group, triazinyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group (e.g., pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (e.g., methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (e.g., cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (e.g., phenoxy group, naphthyloxy group, etc.), alkylthio group (e.g., methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (e.g., cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (e.g., phenylthio group) , naphthylthio group, etc.), alkoxycarbonyl group (e.g., methyloxy dicarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (e.g., phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (e.g., aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2 -pyridylaminosulfonyl group, etc.), acyl groups (e.g., acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthyl carbonyl group, pyridylcarbonyl group, etc.), acyloxy group (e.g., acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (e.g., methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group group, naphthylcarbonylamino group, etc.), carbamoyl group (e.g., aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2- ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (e.g., methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octyl ureido group, dodecylureido group, phenylureido group naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (e.g., methylsulfinyl group, ethylsulphide Nyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (e.g., methylsulfonyl group, ethylsulfonyl group) , butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (e.g., phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (For example, amino group, ethylamino group, dimethylamino group, diphenylamino group, diisopropylamino group, ditertbutyl group, cyclohexylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atoms (e.g., fluorine atom, chlorine atom, bromine atom, etc.), fluorohydrocarbon groups (e.g., fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluoroethyl group, fluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (eg, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), phosphono group and the like. Preferred are alkyl groups, aromatic hydrocarbon groups, amino groups, hydroxy groups and silyl groups.
In addition, these substituents may be further substituted with the above substituents.

Examples of the acidic group contained in the substituent X include a carboxy group, a sulfo group (--SO ₃ H), a sulfino group, a sulfinyl group, a phosphonic acid group [--PO(OH) ₂ ], a phosphoryl group, a phosphinyl group, a phosphono group, thiol group, hydroxy group, phosphonyl group, and sulfonyl group; and salts thereof (metal salts, organic cation salts), and the like. Among these, the acidic group is preferably a carboxy group, a sulfo group, a phosphonic acid group or a hydroxy group, more preferably a carboxy group, a sulfo group or a phosphonic acid group.
Examples of the acidic ring structure contained in the substituent X include ring structures derived from barbituric acid, thiobarbituric acid, squaric acid, croconic acid, uric acid, uracil, and thymine.

The electron-withdrawing group represented by X or the substituent having an electron-withdrawing ring structure includes, as the electron-withdrawing group, a cyano group, a nitro group, a fluoro group, a chloro group, a bromo group, an iodo group and a perfluoroalkyl group (eg, trifluoromethyl group), alkylsulfonyl group, arylsulfonyl group, perfluoroalkylsulfonyl group, perfluoroarylsulfonyl group, and the like. Among these, a cyano group, a nitro group, a fluoro group and a chloro group are preferred, and a cyano group and a nitro group are more preferred. Examples of electron-withdrawing ring structures include rhodanine ring, zirhodanine ring, imidazolone ring, pyrazolone ring, pyrazoline ring, hydantoin ring, thiohydantoin ring, quinone ring, pyran ring, pyrazine ring, pyrimidine ring, imidazole ring, indole ring, benzothiazole ring, benzimidazole ring, benzoxazole ring, thiadiazole ring and the like. Among them, rhodanine ring, zirhodanine ring, imidazolone ring, pyrazolone ring, pyrazoline ring, quinone ring and thiadiazole ring are preferable, and rhodanine ring, zirhodanine ring, imidazolone ring and pyrazoline ring are more preferable.
Further, in the substituent X, the acidic group, the electron-withdrawing group , or the substituent having an electron-withdrawing ring structure is an oxygen atom (O), a sulfur atom (S), a selenium atom (Se), or a tellurium atom. You may bond through atoms, such as (Te). Alternatively, the substituent X may carry a charge, in particular a positive charge, where Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , H ₂ PO ₄ ⁻ , etc. may have a counterion of

These Xs facilitate charge separation between the electrons that have absorbed light and transitioned to LUMO in the light-absorbing compound and the HOMO holes, and can effectively inject the LUMO electrons into the metal oxide.
X is particularly preferably a rhodanine ring, zirhodanine ring, imidazolone ring, thiohydantoin ring, pyrazolone ring, cyanoacrylic acid or cyanovinylphosphonic acid each having a carboxy group or a phosphonic acid.
These Xs strongly interact with metal oxides and are stably adsorbed or bonded to metal oxides.
In addition, the compound having a triphenylamine skeleton represented by formula ( II ) may have a plurality of Xs, and when it has a plurality of Xs, the Xs may be the same or different good. If it has a plurality of X, it can be adsorbed on the metal oxide at multiple points and stabilized more.

The compound having a triphenylamine skeleton represented by formula (I I ) or compound A functions by absorbing part of the light emitted from the light-emitting layer of the organic EL device. At this time, if the amount of light absorption is extremely large, the amount of emitted light emitted to the outside of the device is reduced, resulting in deterioration of the device performance. Therefore, the absorbance of an electron-transporting layer composed of a metal oxide that provides an appropriate amount of light absorption and a compound having a triphenylamine skeleton represented by formula ( II ) or compound A is at the peak wavelength derived from the light-absorbing compound. , preferably 0.01 to 1.00, more preferably 0.02 to 0.50, still more preferably 0.02 to 0.30.

In order to obtain such absorbance of the electron transport layer, the amount of the light absorbing compound in the electron transport layer is preferably in the range of 1 to 10000 mol/m ³ , although it depends on the thickness of the electron transport layer. , more preferably 10 to 5000 mol/m ³ , more preferably 50 to 2000 mol/m ³ .
The ratio of the metal oxide in the electron transport layer is preferably 0.01 to 1000 parts by mass, more preferably 0.1 to 500 parts by mass, of the light absorbing compound with respect to 100 parts by mass of the metal oxide. More preferably, it is within the range of 0.5 to 100 parts by mass.
The absorbance of the electron-transporting layer can be measured by measuring the absorption spectrum of the electron-transporting layer formed on the transparent glass, for example, using a spectrophotometer U-3300 manufactured by Hitachi High-Tech.

Specific examples of the compounds having a triphenylamine skeleton represented by formula (I I ) and the compound A include the following compounds.

These compounds can be synthesized by known synthetic methods.

[Element configuration of organic EL element]
Typical element configurations of the organic EL element include the following configurations, but are not limited to these.
(1) Anode/light-emitting layer/electron-transporting layer/cathode (2) Anode/hole-transporting layer/light-emitting layer/electron-transporting layer/cathode (3) Anode/hole-transporting layer/light-emitting layer/electron-transporting layer/electron injection Layer/Cathode (4) Anode/Hole Injection Layer/Hole Transport Layer/Emitting Layer/Electron Transport Layer/Cathode (5) Anode/Hole Injection Layer/Hole Transport Layer/(Electron Blocking Layer/) Emitting Layer/ (Hole blocking layer/) electron transport layer/electron injection layer/cathode

Although the configuration (5) is preferably used among the above, it is not limited to this.
In the configuration of (5), the hole injection layer / hole transport layer / (electron blocking layer /) up to the light emitting layer is the organic functional layer group 1, and the (hole blocking layer /) electron transport layer / electron injection layer It may be called organic functional layer group 2 .

The light-emitting layer used in the present invention is composed of a single layer or multiple layers, and when there are multiple light-emitting layers, a non-light-emitting intermediate layer may be provided between each light-emitting layer.
If necessary, a hole-blocking layer (also referred to as a hole-blocking layer) or an electron-injecting layer (also referred to as a cathode buffer layer) may be provided between the light-emitting layer and the cathode. An electron blocking layer (also referred to as an electron blocking layer) or a hole injection layer (also referred to as an anode buffer layer) may be provided between them.

The electron transport layer used in the present invention is a layer having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. Moreover, you may comprise by multiple layers.

The hole transport layer used in the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. Moreover, you may comprise by multiple layers.

FIG. 2 is a cross-sectional view showing an example of a typical organic EL element.
The organic EL element 100 comprises a substrate 101, an anode 102, a hole injection layer 103, a hole transport layer 104, a light emitting layer 105, a hole blocking layer 106, an electron transport layer 107, an electron injection layer 108 and a cathode 109 in this order. I have.
In the above typical device structure, the layer other than the anode and cathode is called "functional layer 110".

(tandem structure)
Further, the organic EL element may be a so-called tandem structure element in which a plurality of light emitting units each including at least one light emitting layer are laminated.

As a representative element configuration of the tandem structure, for example, the following configuration can be given.
anode/first light-emitting unit/intermediate layer/second light-emitting unit/intermediate layer/third light-emitting unit/cathode Here, even if the first light-emitting unit, the second light-emitting unit and the third light-emitting unit are all the same, can be different. Also, two light emitting units may be the same and the remaining one may be different.

A plurality of light-emitting units may be directly laminated or may be laminated via an intermediate layer. Also called an insulating layer, a known material structure can be used as long as the layer has a function of supplying electrons to the adjacent layer on the anode side and holes to the adjacent layer on the cathode side.

Examples of materials used for the intermediate layer include ITO (indium tin oxide), IZO (indium/zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiO _x , VO _x , CuI, InN, GaN, and CuAlO. ₂ , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ , Al and other conductive inorganic compound layers, Au/Bi ₂ O ₃ and other two-layer films, SnO ₂ /Ag/SnO ₂ , ZnO/Ag /ZnO, Bi ₂ O ₃ /Au/Bi ₂ O ₃ , TiO ₂ /TiN/TiO ₂ , TiO ₂ /ZrN/TiO ₂ , fullerenes such as C60, conductive organic substances such as _{oligothiophene} Layers, conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, metal-free porphyrins, and the like, but the present invention is not limited thereto.

Preferred structures in the light-emitting unit include, for example, structures (1) to (5) exemplified in the representative element structures above, except for the anode and the cathode. Not limited.

Specific examples of tandem-type organic EL devices include, for example, US Pat. No. 6,337,492, US Pat. No. 7,420,203, US Pat. Specification, US Patent No. 6337492, WO 2005/009087, JP 2006-228712, JP 2006-24791, JP 2006-49393, JP 2006-49394 , JP 2006-49396, JP 2011-96679, JP 2005-340187, Patent No. 4711424, Patent No. 3496681, Patent No. 3884564, Patent No. 4213169, Patent JP 2010-192719, JP 2009-076929, JP 2008-078414, JP 2007-059848, JP 2003-272860, JP 2003-045676, International Publication No. Although the device configuration, constituent materials, and the like described in 2005/094130 and the like can be mentioned, the present invention is not limited thereto.
Furthermore, each layer constituting the organic EL element will be described.

〔substrate〕
The substrate applicable to the organic EL element is not particularly limited, and examples thereof include glass, plastic, and the like.

The substrates used in the present invention may be light transmissive or non-light transmissive. Substrates applicable to the present invention are not particularly limited, and examples thereof include resin substrates, thin-film metal foils, thin-plate flexible glass, and the like.

Examples of resin substrates applicable to the present invention include polyesters such as polyethylene terephthalate (abbreviation: PET) and polyethylene naphthalate (abbreviation: PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, and cellulose triacetate (abbreviation: TAC). , cellulose acetate butyrate, cellulose acetate propionate (abbreviation: CAP), cellulose acetate phthalate, cellulose esters such as cellulose nitrate and their derivatives, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, Polycarbonate (abbreviation: PC), norbornene resin, polymethylpentene, polyetherketone, polyimide, polyethersulfone (abbreviation: PES), polyphenylene sulfide, polysulfones, polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon , polymethyl methacrylate, acrylic and polyarylates, and cycloolefin resins such as Arton (registered trademark) (manufactured by JSR) and APEL (registered trademark) (manufactured by Mitsui Chemicals).

Among these resin substrates, films such as polyethylene terephthalate (abbreviation: PET), polybutylene terephthalate, polyethylene naphthalate (abbreviation: PEN), and polycarbonate (abbreviation: PC) are flexible in terms of cost and availability. is preferably used as a resin substrate of

The thickness of the resin substrate is preferably in the range of 3 to 200 μm, more preferably in the range of 10 to 150 μm, and most preferably in the range of 20 to 120 μm. be.

Further, the thin glass plate applicable as the substrate used in the present invention is a glass plate thin enough to be curved. The thickness of the thin plate glass can be appropriately set within a range in which the thin plate glass exhibits flexibility.

Examples of thin glass include soda lime glass, barium-strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. The thickness of the thin plate glass is, for example, in the range of 5-300 μm, preferably in the range of 20-150 μm.

In addition, as a material for forming the thin film metal foil, for example, one or more metals selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium and tantalum, or Examples include those made of alloys. The thickness of the thin-film metal foil can be appropriately set within a range in which the thin-film metal foil exhibits flexibility, and is, for example, within the range of 10 to 100 μm, preferably within the range of 20 to 60 μm.

[First electrode: anode]
Examples of the anode constituting the organic EL element include metals such as Ag and Au or alloys containing metals as main components, CuI, or indium-tin composite oxides (ITO), and metal oxides such as SnO ₂ and ZnO. However, it is preferably a metal or an alloy containing metal as a main component, more preferably silver or an alloy containing silver as a main component.

When the transparent anode is composed mainly of silver, the purity of silver is preferably 99% or more. Moreover, palladium (Pd), copper (Cu), gold (Au), and the like may be added to ensure the stability of silver.

The transparent anode is a layer composed mainly of silver. Specifically, it may be formed of silver alone or composed of an alloy containing silver (Ag). Examples of such alloys include silver-magnesium (Ag-Mg), silver-copper (Ag-Cu), silver-palladium (Ag-Pd), silver-palladium-copper (Ag-Pd-Cu), silver - Indium (Ag-In) etc. are mentioned.

Among the constituent materials constituting the anode, the anode constituting the organic EL device used in the present invention is preferably a transparent anode composed mainly of silver and having a thickness in the range of 2 to 20 nm. Preferably, but more preferably the thickness is in the range of 4 to 12 nm. If the thickness is 20 nm or less, the absorption component and the reflection component of the transparent anode are kept low, and high light transmittance is maintained, which is preferable.

In the present invention, the layer composed mainly of silver means that the silver content in the transparent anode is 60% by mass or more, preferably 80% by mass or more, More preferably, the silver content is 90% by mass or more, and particularly preferably 98% by mass or more. Moreover, the term "transparent" as used in the transparent anode according to the present invention means that the light transmittance at a wavelength of 550 nm is 50% or more.

The transparent anode may have a structure in which a layer containing silver as a main component is divided into a plurality of layers and laminated as necessary.

Further, in the present invention, when the anode is a transparent anode composed mainly of silver, from the viewpoint of improving the uniformity of the silver film of the transparent anode to be formed, a base layer may be provided below it. preferable. Although the underlayer is not particularly limited, it is preferably a layer containing an organic compound having a nitrogen atom or a sulfur atom, and a preferred embodiment is a method of forming a transparent anode on the underlayer.

[Light emitting layer]
The light-emitting layer constituting the organic EL element can use a phosphorescent compound or a fluorescent compound (both collectively referred to as a light-emitting compound) as a light-emitting material. A configuration in which a phosphorescent compound is contained as is preferable.

The light-emitting layer is a layer that emits light by recombination of electrons injected from the electrode or the electron-transporting layer and holes injected from the hole-transporting layer. or the interface between the light-emitting layer and an adjacent layer.

There are no particular restrictions on the configuration of such a light-emitting layer as long as the light-emitting material contained satisfies the light-emitting requirements. Moreover, there may be a plurality of layers having the same emission spectrum or emission maximum wavelength. In this case, it is preferable to have a non-light-emitting intermediate layer between each light-emitting layer.

The total thickness of the light-emitting layer is preferably in the range of 1 to 100 nm, and more preferably in the range of 1 to 30 nm because a lower driving voltage can be obtained. Note that the total thickness of the light-emitting layers is the thickness including the intermediate layers when non-light-emitting intermediate layers are present between the light-emitting layers.

The light-emitting layer as described above is formed by applying a light-emitting material or a host compound to be described later, for example, by a known method such as a vacuum deposition method, a spin coating method, a casting method, an LB method (Langmuir Blodgett method), an inkjet method, or the like. can be formed by

A plurality of light-emitting materials may be mixed in the light-emitting layer, or a phosphorescent light-emitting material and a fluorescent light-emitting material (also referred to as a fluorescent dopant or a fluorescent compound) may be mixed in the same light-emitting layer. As for the configuration of the light-emitting layer, it is preferable to contain a host compound (also referred to as a light-emitting host or the like) and a light-emitting material (also referred to as a light-emitting dopant) and emit light from the light-emitting material.

(host compound)
The host compound contained in the light-emitting layer is preferably a compound having a phosphorescence quantum yield of less than 0.1 at room temperature (25° C.). Furthermore, it is preferable that the phosphorescence quantum yield is less than 0.01. In addition, among the compounds contained in the light-emitting layer, the volume ratio in the layer is preferably 50% or more.

As the host compound, a known host compound may be used alone, or multiple types of host compounds may be used. By using a plurality of types of host compounds, it is possible to adjust the movement of electric charges, and the efficiency of the organic electroluminescence device can be improved. In addition, by using a plurality of types of luminescent materials, which will be described later, it is possible to mix different luminescence, thereby obtaining an arbitrary luminescent color.

The host compound used in the light-emitting layer may be a conventionally known low-molecular-weight compound or a high-molecular-weight compound having repeating units. ) can be used.

Examples of host compounds applicable to the present invention include, for example, 2002-352957, 2002-231453, 2002-234888, 2002-260861, 2002-305083, US Patent Application Publication No. 2005/0112407, US Patent Application Publication WO 2009/0030202, WO 2001/039234, WO 2008/056746, WO 2005/089025, WO 2007/063754, WO 2005/030900, WO Compounds described in No. 2009/086028, International Publication No. 2012/023947, JP-A-2007-254297, European Patent No. 2034538 and the like can be mentioned.

(Luminous material)
Examples of light-emitting materials that can be used in the present invention include phosphorescent compounds (also referred to as phosphorescent compounds, phosphorescent light-emitting materials, or phosphorescent light-emitting dopants) and fluorescent light-emitting compounds (also referred to as fluorescent compounds or fluorescent light-emitting materials). ), and it is particularly preferable to use a phosphorescent compound from the viewpoint of obtaining high luminous efficiency.

<Phosphorescent compound>
The phosphorescent compound is a compound in which emission from excited triplet is observed, specifically a compound that emits phosphorescence at room temperature (25 ° C.), and has a phosphorescence quantum yield of 0 at 25 ° C. Preferred phosphorescence quantum yields are 0.1 or greater, although defined as compounds of 0.01 or greater.

The phosphorescence quantum yield can be measured by the method described in Experimental Chemistry Course 7, 4th Edition, Spectroscopy II, page 398 (1992 edition, Maruzen). Phosphorescence quantum yield in a solution can be measured using various solvents, but when the phosphorescent compound is used in the present invention, the phosphorescence quantum yield is 0.01 or more in any solvent. should be achieved.

The phosphorescent compound can be appropriately selected from known compounds used in the light-emitting layer of a general organic EL device, but preferably contains a metal of groups 8 to 10 in the periodic table of the elements. more preferably an iridium compound, an osmium compound, a platinum compound (platinum complex compound) or a rare earth complex, most preferably an iridium compound.

In the present invention, at least one light-emitting layer may contain two or more phosphorescent compounds, and the concentration ratio of the phosphorescent compounds in the light-emitting layer varies in the thickness direction of the light-emitting layer. It may be in the form of

Specific examples of known phosphorescent compounds that can be used in the present invention include compounds described in the following documents.

Nature 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17, 1059 (2005), WO 2009/100991, WO 2008/101842, WO 2003/040257, U.S. Patent Application Publication No. 2006/835469, U.S. Patent Application Publication No. 2006/ 0202194, US Patent Application Publication No. 2007/0087321, US Patent Application Publication No. 2005/0244673, and the like.

Also, Inorg. Chem. 40, 1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chem. Int. Ed. 2006, 45, 7800, Appl. Phys. Lett. 86, 153505 (2005), Chem. Lett. 34, 592 (2005), Chem. Commun. 2906 (2005), Inorg. Chem. 42, 1248 (2003), WO2009/050290, WO2009/000673, US7332232, US2009/0039776, US6687266, United States US2006/0008670, US2008/0015355, US7396598, US2003/0138657, US7090928 and the like.

Also, Angew. Chem. lnt. Ed. 47, 1 (2008), Chem. Mater. 18, 5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics 23, 3745 (2004), Appl. Phys. Lett. 74, 1361 (1999), WO 2006/056418, WO 2005/123873, WO 2006/082742, US 2005/0260441, US 7534505 , US Patent Application Publication No. 2007/0190359, US Patent No. 7338722, US Patent No. 7279704, US Patent Application Publication No. 2006/103874, etc. .

Furthermore, WO 2005/076380, WO 2008/140115, WO 2011/134013, WO 2010/086089, WO 2012/020327, WO 2011/051404 , International Publication No. 2011/073149, JP-A-2009-114086, JP-A-2003-81988, JP-A-2002-363552, and the like.

In the present invention, preferred phosphorescent compounds include organometallic complexes having Ir as a central metal. More preferably, the complex contains at least one coordination mode of metal-carbon bond, metal-nitrogen bond, metal-oxygen bond, and metal-sulfur bond.

The above-described phosphorescent compound (also referred to as a phosphorescent metal complex) is described in, for example, Organic Letter, vol. 16, pp. 2579-2581 (2001); Inorganic Chemistry, Vol. 30, No. 8, pp. 1685-1687 (1991); Am. Chem. Soc. , 123, 4304 (2001), Inorganic Chemistry, 40, 7, 1704-1711 (2001), Inorganic Chemistry, 41, 12, 3055-3066 (2002) , New Journal of Chemistry. , Vol. 26, pp. 1171 (2002), European Journal of Organic Chemistry, Vol. 4, pp. 695-709 (2004), and the methods disclosed in the references described in these documents. can be synthesized by applying

<Fluorescent compound>
Fluorescent compounds include coumarin-based dyes, pyran-based dyes, cyanine-based dyes, croconium-based dyes, squarium-based dyes, oxobenzanthracene-based dyes, fluorescein-based dyes, rhodamine-based dyes, pyrylium-based dyes, perylene-based dyes, and stilbene-based dyes. dyes, polythiophene dyes, rare earth complex phosphors, and the like.

[Organic functional layer group]
Next, each layer constituting the organic functional layer unit will be described in order of the charge injection layer, the hole transport layer, the electron transport layer and the blocking layer.

[Charge injection layer]
A charge injection layer is a layer provided between an electrode and a light-emitting layer in order to reduce driving voltage and improve light-emitting luminance. The details are described in Chapter 2 "Electrode Materials" (pages 123 to 166) of Vol.

The charge injection layer is generally present between the anode and the light emitting layer or the hole transport layer in the case of the hole injection layer, and between the cathode and the light emitting layer or the electron transport layer in the case of the electron injection layer. be able to. Moreover, when used in an intermediate electrode, at least one of the adjacent electron injection layer and hole injection layer should satisfy the requirements of the present invention.

The hole injection layer is a layer that is arranged adjacent to the anode in order to lower the driving voltage and improve the luminance of the emitted light. Publishing Co., Ltd.)”, Volume 2, Chapter 2 “Electrode Materials” (pp. 123-166).

The details of the hole injection layer are also described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069, etc. Materials used for the hole injection layer include, for example, , porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives, Indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, polyvinylcarbazole, polymeric materials or oligomers with aromatic amines introduced into the main chain or side chain, polysilane, conductivity Polymers or oligomers (for example, PEDOT (polyethylenedioxythiophene): PSS (polystyrene sulfonic acid), aniline copolymers, polyaniline, polythiophene, etc.) and the like can be mentioned.

Triarylamine derivatives include benzidine type represented by α-NPD (4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) and MTDATA (4,4′,4″ -tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine), compounds having fluorene or anthracene in the core portion linked to triarylamine, and the like.

Further, hexaazatriphenylene derivatives as described in JP-T-2003-519432, JP-A-2006-135145, etc. can also be used as the hole-transporting material.

The electron injection layer is a layer provided between the cathode and the light-emitting layer in order to lower the driving voltage and improve the light-emitting luminance. Published by TS Co., Ltd.)”, Volume 2, Chapter 2 “Electrode Materials” (pp. 123-166).

Details of the electron injection layer are also described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, etc. Specific examples of materials preferably used for the electron injection layer include , metals typified by strontium and aluminum, alkali metal compounds typified by lithium fluoride, sodium fluoride, potassium fluoride, etc., alkali metal halide layers typified by magnesium fluoride, calcium fluoride, etc., fluoride Alkaline earth metal compound layers such as magnesium, metal oxides such as molybdenum oxide and aluminum oxide, and metal complexes such as lithium 8-hydroxyquinolate (Liq) can be used. Moreover, when the transparent electrode in the present invention is a cathode, an organic material such as a metal complex is particularly preferably used. The electron injection layer is desirably a very thin film, and its layer thickness is preferably in the range of 1 nm to 10 μm, depending on the constituent materials.

[Hole transport layer]
The hole-transporting layer is made of a hole-transporting material having a function of transporting holes, and in a broad sense, the hole-injecting layer and the electron-blocking layer also have the function of a hole-transporting layer. The hole transport layer can be provided as a single layer or multiple layers.

The hole transport material has either hole injection or transport or electron blocking properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples include stilbene derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers and thiophene oligomers.

As the hole transport material, those mentioned above can be used, and porphyrin compounds, aromatic tertiary amine compounds and styrylamine compounds can be used, and aromatic tertiary amine compounds can be used in particular. preferable.

Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N,N,N',N'-tetraphenyl-4,4'-diaminophenyl, N,N'-diphenyl-N,N'- Bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine (abbreviation: TPD), 2,2-bis(4-di-p-tolylaminophenyl)propane, 1,1 -bis(4-di-p-tolylaminophenyl)cyclohexane, N,N,N',N'-tetra-p-tolyl-4,4'-diaminobiphenyl, 1,1-bis(4-di-p -tolylaminophenyl)-4-phenylcyclohexane, bis(4-dimethylamino-2-methylphenyl)phenylmethane, bis(4-di-p-tolylaminophenyl)phenylmethane, N,N'-diphenyl-N, N'-di(4-methoxyphenyl)-4,4'-diaminobiphenyl, N,N,N',N'-tetraphenyl-4,4'-diaminodiphenyl ether, 4,4'-bis(diphenylamino) quadriphenyl, N,N,N-tri(p-tolyl)amine, 4-(di-p-tolylamino)-4'-[4-(di-p-tolylamino)styryl]stilbene, 4-N,N -diphenylamino-(2-diphenylvinyl)benzene, 3-methoxy-4'-N,N-diphenylaminostilbenzene and N-phenylcarbazole.

The hole-transporting layer is formed by applying the above-mentioned hole-transporting material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an inkjet method, and an LB method (Langmuir Blodgett method). can be formed by thinning. The layer thickness of the hole-transporting layer is not particularly limited, but is usually in the range of about 5 nm to 5 μm, preferably 5 to 200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

Further, the p-property can be increased by doping the material of the hole transport layer with impurities. Examples thereof include JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175 and J. Am. Appl. Phys. , 95, 5773 (2004).

Thus, it is preferable to increase the p-property of the hole-transporting layer, since a device with lower power consumption can be produced.

[Electron transport layer]
The electron transport layer is composed of a material having a function of transporting electrons, and broadly includes an electron injection layer and a hole blocking layer. The electron transport layer can be provided as a single layer structure or a multi-layer laminated structure.
In the present invention, as described above, the electron-transporting layer adjacent to the cathode contains the compound having a triphenylamine skeleton represented by formula ( II ) and a metal oxide.
Further, instead of the compound having a triphenylamine skeleton, the A-1, A-2, A-6, A-7, A-8, A-13, A-14, A-16, A-17 , A-18, A-20, A-32 and A-35 may be used.

The method for forming the electron transport layer containing the compound having a triphenylamine skeleton represented by formula (I I ) and the metal oxide is not particularly limited, but there are, for example, the following embodiments.
(a) applying a solution containing a compound having a triphenylamine skeleton represented by the formula (I I ) and a metal salt, and heat-treating the solution to thermally decompose the metal salt to produce a metal oxide; An electron-transporting layer containing the compound having a triphenylamine skeleton represented by formula (I I ) and a metal oxide is formed.
(b) applying a solution containing metal oxide nanoparticles and a compound having a triphenylamine skeleton represented by the above formula (I I ) to form a triphenylamine skeleton represented by the above formula (I I ); forming an electron-transporting layer containing a compound having a metal oxide and a metal oxide;
(c) Applying metal oxide nanoparticles to form a metal oxide film. Thereafter, the metal oxide film is coated with a solution containing a compound having a triphenylamine skeleton represented by the formula (I I ), and the metal oxide nanoparticles are coated with the compound represented by the formula (I I ). A compound having a triphenylamine skeleton is adsorbed to form an electron transport layer containing the compound having a triphenylamine skeleton represented by formula (I I ) and a metal oxide.

In the electron-transporting layer having a laminated structure, an electron-transporting material (also serving as a hole-blocking material) contained in a layer composed of a material having a function of transporting electrons other than the electron-transporting layer constituting the layer portion adjacent to the light-emitting layer Any compound can be selected and used from conventionally known compounds. Examples thereof include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethanes, anthrone derivatives and oxadiazole derivatives. Furthermore, among the above oxadiazole derivatives, a thiadiazole derivative in which an oxygen atom in the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring, which is known as an electron-withdrawing group, can also be used as materials for the electron-transporting layer. can. Furthermore, polymer materials in which these materials are introduced into the polymer chain or polymer materials in which these materials are used as the main chain of the polymer can also be used.

Also, metal complexes of 8-quinolinol derivatives such as tris(8-quinolinol)aluminum (abbreviation: Alq ₃ ), tris(5,7-dichloro-8-quinolinol)aluminum, tris(5,7-dibromo-8- quinolinol)aluminum, tris(2-methyl-8-quinolinol)aluminum, tris(5-methyl-8-quinolinol)aluminum, bis(8-quinolinol)zinc (abbreviation: Znq), etc. and the central metal of these metal complexes Metal complexes substituted for In, Mg, Cu, Ca, Sn, Ga or Pb can also be used as materials for the electron transport layer.

The electron-transporting layer can be formed by thinning the above material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an inkjet method, or an LB method. The layer thickness of the electron-transporting layer is not particularly limited, but is usually in the range of about 2 nm to 5 μm, preferably 5 to 200 nm. The electron-transporting layer may be a single structure composed of one or more of the above materials.

[Blocking layer]
The blocking layer includes a hole blocking layer and an electron blocking layer, which are layers provided as necessary in addition to the constituent layers of the organic functional layer unit 3 described above. For example, JP-A-11-204258, JP-A-11-204359, and page 237 of "Organic EL element and its industrial front (published by NTS on November 30, 1998)". A hole blocking (hole blocking) layer, etc. can be mentioned.

A hole-blocking layer has the function of an electron-transporting layer in a broad sense. The hole-blocking layer is made of a hole-blocking material that has a function of transporting electrons but has an extremely low ability to transport holes, and transports electrons while blocking holes, thereby causing recombination of electrons and holes. You can improve your odds. Moreover, the configuration of the electron transport layer can be used as a hole blocking layer as needed. The hole-blocking layer is preferably provided adjacent to the light-emitting layer.

On the other hand, the electron blocking layer has the function of a hole transport layer in a broad sense. The electron-blocking layer is made of a material that has the function of transporting holes but has a significantly low ability to transport electrons. By blocking electrons while transporting holes, the probability of recombination between electrons and holes is improved. can be made Moreover, the structure of a hole transport layer can be used as an electron blocking layer as needed. The layer thickness of the hole blocking layer applied to the present invention is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.

[Second electrode: cathode]
The cathode is an electrode film that functions to supply electrons to the organic functional layer group and the light-emitting layer, and metals, alloys, organic or inorganic conductive compounds, or mixtures thereof are used. Specifically gold, aluminum, silver, magnesium, lithium, magnesium/copper mixtures, magnesium/silver mixtures, magnesium/aluminum mixtures, magnesium/indium mixtures, indium, lithium/aluminum mixtures, rare earth metals, ITO, ZnO, TiO oxide semiconductors such as ₂ and _SnO2 .

The cathode can be produced by forming a thin film from these conductive materials or their dispersions by a method such as spin coating, casting, inkjet, vapor deposition, or printing. Moreover, the sheet resistance of the second electrode is several hundred Ω/sq. The following is preferable, and the thickness is usually selected in the range of 5 nm to 5 μm, preferably 5 to 200 nm.

In the case where the organic EL element is of a double-sided light emission type in which the emitted light L is extracted also from the cathode side, a cathode having good light transmittance may be selected.

[Sealing member]
As a sealing means used for sealing the organic EL element, for example, a method of adhering a flexible sealing member, a cathode and a transparent substrate with a sealing adhesive can be mentioned.
The sealing member may be arranged so as to cover the display area of the organic EL element, and may be in the form of a concave plate or a flat plate. Moreover, transparency and electric insulation are not particularly limited.

Specifically, flexible thin film glass plates, polymer plates, films, metal films (metal foils) and the like can be mentioned. Examples of glass plates include soda-lime glass, barium-strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Further, examples of the polymer plate include polycarbonate, acryl, polyethylene terephthalate, polyether sulfide, polysulfone, and the like. Metal films include one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium and tantalum.

In the present invention, a polymer film and a metal film can be preferably used as the sealing member from the viewpoint that the organic EL element can be made thinner. Furthermore, the polymer film has a water vapor transmission rate of 1 × 10 ^-3 g/m ² · at a temperature of 25 ± 0.5 ° C and a relative humidity of 90 ± 2% RH measured by a method in accordance with JIS K 7129-1992. It is preferably 24 hours or less, and furthermore, the oxygen permeability measured by a method based on JIS K 7126-1987 is 1 × 10 ^-3 mL/m ² · 24h · atom (1 atom is 1.01325 × 10 ⁵ Pa) or less, and the water vapor permeability at a temperature of 25±0.5° C. and a relative humidity of 90±2% RH is preferably 1×10 ⁻³ g/m ² ·24 h or less.

In the gap between the sealing member and the display area (light-emitting area) of the organic EL element, an inert gas such as nitrogen or argon or an inert liquid such as fluorocarbon or silicone oil is injected in the gas phase or the liquid phase. You can also Also, the gap between the sealing member and the display area of the organic EL element can be evacuated, or the gap can be filled with a hygroscopic compound.

In addition, in a state in which the light-emitting functional layer unit in the organic EL element is completely covered and the terminal portions of the anode (3) as the first electrode and the cathode (6) as the second electrode in the organic EL element are exposed, the transparent A sealing film can also be provided on the substrate.

Such a sealing film is composed of an inorganic material or an organic material, and in particular, a material having a function of suppressing penetration of moisture, oxygen, or the like, such as an inorganic material such as silicon oxide, silicon dioxide, or silicon nitride. Used. Furthermore, in order to improve the fragility of the sealing film, a laminated structure may be formed by using a film made of an organic material together with the film made of these inorganic materials.

The method for forming these sealing films is not particularly limited. A pressure plasma polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

The sealing material as described above exposes the terminal portions of the anode (3), which is the first electrode, and the cathode (6), which is the second electrode, in the organic EL element, and is provided in a state of covering at least the light-emitting functional layer. It is

<<Method for producing organic electroluminescence element>>
As a method for manufacturing an organic EL element, an anode, an organic functional layer group 1, a light-emitting layer, an organic functional layer group 2, and a cathode are laminated on a transparent substrate to form a laminate.

First, a transparent substrate is prepared, and a thin film of a desired electrode material, such as an anode material, is deposited on the transparent substrate to a thickness of 1 μm or less, preferably in the range of 10 to 200 nm. or by a method such as sputtering to form an anode. At the same time, a connection electrode portion to be connected to an external power supply is formed at the anode end.

Next, a hole injection layer and a hole transport layer constituting the organic functional layer group 1, a light emitting layer, an electron transport layer constituting the organic functional layer group 2, and the like are sequentially laminated thereon.

These layers can be formed by spin coating method, casting method, ink jet method, vapor deposition method, printing method and the like. A method, spin coating method or ink jet method is particularly preferred. Furthermore, different formation methods may be applied for each layer. When vapor deposition is employed to form each of these layers, the vapor deposition conditions vary depending on the type of compound used, etc. Generally, the boat heating temperature is 50 to 450° C. and the degree of vacuum is 1×10 ⁻⁶ to 1×10 ⁻² Pa. , a deposition rate of 0.01 to 50 nm/sec, a substrate temperature of -50 to 300° C., and a layer thickness of 0.1 to 5 μm.

After the organic functional layer group 2 is formed as described above, a cathode is formed thereon by an appropriate formation method such as spin coating, casting, inkjet, vapor deposition, or printing. At this time, the cathode is patterned in such a manner that a terminal portion is pulled out from above the organic functional layer group to the peripheral edge of the transparent substrate while maintaining an insulating state from the anode by the organic functional layer group.

After forming the cathode, the transparent substrate, anode, organic functional layer group, light-emitting layer and cathode are sealed with a sealing material. That is, a sealing material covering at least the organic functional layer group is provided on the transparent substrate while the terminal portions of the anode and cathode are exposed.

Among them, forming by a wet coating method such as an inkjet printing method is a preferred embodiment from the viewpoint of productivity and workability.

[Inkjet printing method]
An example of the formation method by the inkjet printing method will be described below with reference to the drawings.

FIG. 3 is a schematic diagram showing an example of a method for forming an electronic device using an inkjet printing method, which is an example of a wet coating method.

FIG. 4 shows an example of a method of ejecting ink containing the composition for electronic devices of the present invention onto a substrate 1 using a wet coating apparatus using an inkjet head 30 .

As shown in FIG. 3, as an example, while the substrate 1 is continuously conveyed, ink containing an electronic device forming material is sequentially ejected as ink droplets by an inkjet head 30, for example, an electronic device that is an electronic device. forming a transport layer;

The inkjet head 30 that can be applied to the manufacturing method of the organic EL device of the present invention is not particularly limited. It may be a shear mode type (piezo type) head that ejects the ink liquid by pressure change, or it has a heating element. A thermal type head that ejects ink liquid may be used.

The ink jet head 30 is connected to a supply mechanism for ejecting ink liquid and the like. The ink liquid is supplied from the tank 38A. In this example, the liquid surface of the tank is kept constant so that the ink liquid pressure in the inkjet head 30 is always kept constant. As a method for this, the ink liquid is overflowed from the tank 38A and returned to the tank 38B by gravity flow. The supply of the ink liquid from the tank 38B to the tank 38A is performed by the pump 31, and is controlled so that the liquid level of the tank 38A is stably kept constant according to the ejection conditions.

It should be noted that the ink liquid is returned from the pump 31 to the tank 38A after passing through the filter 32. FIG. In this manner, before the ink liquid is supplied to the inkjet head 30, it is preferable to pass through a filter medium having an absolute filtration accuracy or a quasi-absolute filtration accuracy of 0.05 to 50 μm at least once.

In addition, the ink liquid from the tank 36 and the cleaning solvent from the tank 37 can be forcibly supplied to the inkjet head 30 by the pump 39 in order to carry out cleaning work and liquid filling work of the inkjet head 30 . Such tank pumps may be divided into a plurality for the ink jet head 30, branched pipes may be used, or a combination thereof may be used. In FIG. 4, a pipe branch 33 is used. Further, in order to sufficiently remove the air in the ink jet head 30, the ink liquid is forcibly fed from the tank 36 to the ink jet 30 by the pump 39, and the ink liquid is extracted from the air vent pipe described below and discharged to the waste liquid tank 34. sometimes send.

FIG. 5 is a schematic external view showing an example of the structure of an inkjet head applicable to the inkjet printing method.

5A is a schematic perspective view showing an inkjet head 100 applicable to the present invention, and FIG. 5B is a bottom view of the inkjet head 100. FIG.

The inkjet head 100 applicable to the present invention is mounted on an inkjet printer (not shown), and includes a head chip for ejecting ink from nozzles, a wiring board on which the head chip is arranged, and the wiring board. and a drive circuit board connected via a flexible board, a manifold for introducing ink into the channel of the head chip through a filter, a housing 56 housing the manifold inside, and a bottom opening of this housing 56. A cap receiving plate 57 attached to block, first and second joints 81a and 81b attached to the first and second ink ports of the manifold, and a third joint 81a and 81b attached to the third ink port of the manifold. A joint 82 and a cover member 59 attached to the housing 56 are provided. Mounting holes 68 are formed for mounting the housing 56 on the printer body side.

The cap receiving plate 57 shown in (b) of FIG. 5 is formed in a substantially rectangular plate shape elongated in the left-right direction corresponding to the shape of the cap receiving plate mounting portion 62. In order to expose the nozzle plate 61 in which a plurality of nozzles are arranged, an elongated nozzle opening 71 is provided in the left-right direction. Further, for the specific structure inside the inkjet head shown in FIG. 5a, for example, FIG.

FIG. 5 shows a representative example of an inkjet head, but in addition to this, for example, Japanese Unexamined Patent Application Publication No. 2
012-140017, JP 2013-010227, JP 2014-058171, JP 2014-097644, JP 2015-142979, JP 2015-142980, JP 2016- 002675, JP-A-2016-002682, JP-A-2016-107401, JP-A-2017-109476, JP-A-2017-177626, and the like are selected appropriately. can be applied

(Ink preparation)
In the method of manufacturing an electronic device of the present invention, in addition to the method of using each of the constituent materials as they are as the ink for electronic devices, the constituent materials are dissolved in an ink solvent or the like in order to obtain an ink suitable for the inkjet printing method. Ink for electronic devices can be prepared by using the ink, and various functional additives can be included.

(ink solvent)
When preparing the ink for electronic devices according to the present invention (hereinafter also simply referred to as ink), various known organic solvents can be used in addition to the components A, B and C according to the present invention.

Examples of organic solvents applicable to the ink according to the present invention include polyhydric alcohol ethers (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol Monobutyl Ether, Propylene Glycol Monomethyl Ether, Propylene Glycol Monobutyl Ether, Ethylene Glycol Monomethyl Ether Acetate, Triethylene Glycol Monomethyl Ether, Triethylene Glycol Monoethyl Ether, Triethylene Glycol Monobutyl Ether, Ethylene Glycol Monophenyl Ether, Propylene Glycol Monophenyl Ether etc.), amines (e.g., ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine , pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (e.g., formamide, N,N-dimethylformamide, N,N-dimethylacetamide, etc.), heterocycles (e.g., 2-pyrrolidone, N-methyl-2 -pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (eg, dimethylsulfoxide, etc.), sulfones (eg, sulfolane, etc.), urea, acetonitrile, acetone, etc. mentioned.

(other additives)
In the ink for electronic devices of the present invention, known inks are used in accordance with the purpose of improving ejection stability, print head compatibility, storage stability, image storage stability, and other various performances within a range that does not impair the intended effect of the present invention. Various additives such as solvents, viscosity modifiers, surface tension modifiers, resistivity modifiers, film-forming agents, dispersants, surfactants, UV absorbers, antioxidants, anti-fading agents, anti-baking agents, A rust inhibitor or the like can be appropriately selected and used.

Organic EL elements can be used as electronic devices such as display devices, displays, and various light-emitting devices. Examples of light-emitting devices include lighting devices (home lighting, vehicle interior lighting), backlights for clocks and liquid crystals, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copiers, light sources for optical communication processors, and light sources. Examples include, but are not limited to, light sources for sensors, and can be effectively used particularly as backlights for liquid crystal display devices and light sources for illumination.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these. In the examples, "parts" or "%" are used, but "mass parts" or "mass%" are indicated unless otherwise specified.

[Preparation of metal oxide ink]
(ZnO ink)
2.0 g (10.9 mmol) of zinc acetate (Zn(Ac) ₂ ) and 360 µL of ion-exchanged water were added to 100 mL of methanol, stirred, and heated to 60°C. To this, a solution of 1.17 g (20.9 mmol) of potassium hydroxide (KOH) dissolved in 55 ml of methanol was added dropwise over 10 to 15 minutes. After stirring at 60° C. for 3 hours, the solvent was replaced with TFPO (1H,1H,3H-tetrafluoropropanol), filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter, and the particle size was 6 to 7 nm. A ZnO nanoink (C-1) was obtained.

(AZO ink)
2.0 g (10.9 mmol) of zinc acetate (Zn(Ac) ₂ ), 0.077 g (0.36 mmol) of aluminum nitrate (Al(NO ₃ ) ₃ ), and 360 μL of deionized water are added to 100 mL of methanol and stirred, Heat to 60°C. To this, a solution of 1.17 g (20.9 mmol) of potassium hydroxide (KOH) dissolved in 55 mL of methanol was added dropwise over 10 to 15 minutes. After stirring at 60 ° C. for 3 hours, the solvent was replaced with TFPO (1H, 1H, 3H-tetrafluoropropanol), filtered through a 0.45 μm PTFE filter, and aluminum-doped ZnO (AZO) with a particle size of 6 to 7 nm. Nanoink (C-2) was obtained.

₍ ZrO2 ink)
6.5 g (20.2 mmol) of zirconium oxychloride octahydrate (ZrOCl _{2.8H 2 O} ) was dissolved in 250 g of ion-exchanged water, and 1.1 g (8.2 mmol) of malic acid was added thereto. After adding 30 g of a 10% by mass KOH aqueous solution, hydrothermal treatment (autoclave 200° C. for 2 hours) was performed. After that, the solvent was replaced with TFPO (1H,1H,3H-tetrafluoropropanol) and filtered through a 0.45 μm PTFE filter to obtain ZrO ₂ nanoink (C-3) with a particle size of 10 to 13 nm.

( _TiO2 ink)
After dissolving 9 g of ammonium carbonate (93.7 mmol) in ion-exchanged water kept at 15° C. to obtain 100 mL of aqueous solution, 6.1 g (32.3 mmol) of titanium tetrachloride solution was gradually added dropwise while stirring. . Stirring was continued at 15° C. for 1 hour to obtain a titanium oxide precipitate. This precipitate was separated by filtration, washed, and ion-exchanged water was added to obtain 90 ml of titanium oxide sol. This titanium oxide sol was subjected to hydrothermal treatment (autoclave at 230° C. for 12 hours). After that, the solvent was replaced with TFPO (1H,1H,3H-tetrafluoropropanol) and filtered through a 0.45 μm PTFE filter to obtain TiO ₂ nano ink (C-4) with a particle size of 15 to 20 nm.

[Example 1]
<<Preparation of organic EL element 1>>
(Formation of anode)
On a glass substrate of 50 mm long, 50 mm wide and 0.7 mm thick, ITO (indium tin oxide) was deposited to a thickness of 120 nm and patterned to form an anode made of an ITO transparent electrode. After that, ultrasonic cleaning was performed with isopropyl alcohol, drying was performed with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.

(Formation of hole injection layer)
A solution obtained by diluting poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (abbreviated as PEDOT/PSS, manufactured by Bayer, Baytron P Al 4083) to 70% with pure water was applied on the ITO anode at 3000 rpm for 30 seconds. and dried at 200° C. for 1 hour to form a hole injection layer having a thickness of 30 nm.

(Formation of hole transport layer)
This substrate was transferred to a nitrogen atmosphere using nitrogen gas (grade G1), and a coating solution for forming a hole transport layer having the following composition was used to form a film by spin coating at 1500 rpm for 30 seconds. for 30 minutes to form a hole transport layer with a thickness of 30 nm.
<Coating solution for forming hole transport layer>
Hole transport material B1 (weight average molecular weight Mw = 80000) 15 parts by mass Chlorobenzene 3000 parts by mass

(Formation of light-emitting layer)
Next, a coating solution for forming a light-emitting layer having the following composition was applied by spin coating at 1500 rpm for 30 seconds to form a film, which was held at 120° C. for 30 minutes to form a light-emitting layer having a thickness of 40 nm after drying.

<Coating solution for forming light-emitting layer>
Host compound B2 10 parts by mass Luminescent compound B3 1 part by mass Propylene acetate 2200 parts by mass

(Formation of electron transport layer)
Subsequently, a film of ZnO ink (C-1) was formed by a spin coating method so as to have a thickness of 40 nm after drying. Furthermore, a 1H,1H,3H-tetrafluoropropanol (TFPO) solution (0.02% by mass) of exemplary compound (A-6) was applied by spin coating at 1000 rpm for 30 seconds, and then held at 120 ° C. for 30 minutes. to form an electron transport layer. The absorbance at the peak wavelength of the absorption spectrum of the electron transport layer was 0.08.

(cathode and sealing)
Next, after forming a cathode by evaporating aluminum with a thickness of 100 nm, the non-light-emitting surface of the light-emitting element is covered with a glass case, and the glass case covers the light-emitting element, which is in contact with the glass substrate (supporting base) on which the light-emitting element is formed. A sealant made of an epoxy-based photocurable adhesive (Luxtrack LC0629B manufactured by Toagosei Co., Ltd.) was provided on the periphery of the . Then, this sealing material was superimposed on the cathode side of the light emitting element and brought into close contact with the glass substrate. After that, UV light was irradiated from the glass case side to harden the sealing material to seal the light emitting element, and the organic EL element 1 was produced. The sealing operation with the glass case was performed in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas with a purity of 99.999% or higher) without exposing the light emitting element to the atmosphere.

<<Production of organic EL elements 2 to 6>>
In the formation of the electron transport layer in the preparation of the organic EL element 1, the exemplary compound (A-6) was changed to the compound shown in the table, and the other procedures were the same as in the preparation of the organic EL element 1. Organic EL Devices 2 to 6 were produced.

<<Preparation of organic EL elements 7 to 10>>
In the formation of the electron transport layer in the production of the organic EL device 1, the ZnO ink (C-1) and the exemplary compound (A-6) were changed to the metal oxide-containing ink and exemplary compound shown in the table, respectively. Organic EL elements 7 to 10 were produced in the same manner as the organic EL element 1 except for the procedure.

<<Production of organic EL element 11>>
In the formation of the light-emitting layer in the preparation of the organic EL device 1, the light-emitting compound B3 was changed to the light-emitting compound B4, and in the formation of the electron transport layer, the compound (A-6) was changed from the exemplary compound shown in the table. , and other procedures were the same as those of the organic EL element 1 to prepare the organic EL element 11 for comparison.

<<Production of Organic EL Element 12>>
In the formation of the electron transport layer in the production of the organic EL device 1, the ZnO ink (C-1) and the exemplary compound (A-6) were changed to the metal oxide-containing ink and exemplary compound shown in the table, respectively. Other procedures were the same as those of the organic EL element 1 to produce the organic EL element 12 .

[LUMO energy level]
The LUMO energy level E _DL of the light-absorbing compound was obtained by measuring the HOMO energy level (E _DH ) as follows and adding Eg shown in the table to the obtained E _DH (E _DL =E _DH + Eg).
The HOMO energy level (E _DH ) of the light absorbing compound was defined as the negative value of the ionization potential measurement (positive value). The ionization potential was measured with an atmospheric photoelectron spectrometer (AC-3 (manufactured by Riken Keiki Co., Ltd.)).
The LUMO energy level (E _DL ) of a light absorbing compound was defined as follows.
_{EDL = EDH +} Eg

Here, Eg represents the excitation energy corresponding to the energy gap between the HOMO and LUMO of the light-absorbing compound, and the energy of the long-wavelength side absorption edge wavelength (eV unit converted value).
The absorption spectrum of the light-absorbing compound was measured using a spectrophotometer U-3300 manufactured by Hitachi High-Tech. Light absorbing compounds were measured as ethanol solutions at concentrations of 10 ⁻⁶ to 10 ⁻⁴ mol/L.

[Overlap of emission spectrum and absorption spectrum]
The portion overlapping the emission wavelength region of the light-emitting compound in the light-emitting layer and the absorption wavelength region of the compound (light-absorbing compound) having a triphenylamine skeleton represented by the formula (I I ) or the compound A is the light emission described above. When the difference between the emission spectrum peak wavelength λem of the light-emitting compound and the absorption spectrum peak wavelength λa of the light-absorbing compound is 200 nm or less, the emission spectrum and the absorption spectrum of the light-absorbing compound are measured. It was determined that the absorption spectra overlapped.

"evaluation"
<Drive voltage>
At room temperature (25° C.), lighting is performed under a constant luminance condition of 1000 cd/m ² , and voltage is applied to the organic EL element and current is measured using Keithley's "2400 type source meter". Using CS-2000 (manufactured by Konica Minolta Sensing Co., Ltd.), the emission luminance of each sample was measured, and the driving voltage at the emission luminance of 1000 cd/m ² was obtained.

In addition, in Table I, the driving voltage of each organic EL element is shown as a relative value, with the initial driving voltage of the organic EL element 1 being 1.00.

<Evaluation of durability>
A current of 400 μA was applied to each of the organic EL devices 1 to 12 at 25° C. for 50 hours. After that, lighting was performed at room temperature (25° C.) under a constant luminance condition of 1000 cd/m ² , and voltage was applied to the organic EL element and current was measured using a “2400 type source meter” manufactured by Keithley. Using a luminance meter CS-2000 (manufactured by Konica Minolta Sensing Co., Ltd.), the emission luminance of each sample was measured, and the driving voltage at the emission luminance of 1000 cd/m ² was determined. Table I shows the driving voltage of each organic EL element after the endurance test as a relative value, with the initial driving voltage of the organic EL element 1 being 1.00.
A smaller value indicates higher stability.

From Table I, it can be seen that the organic EL device of the present invention has a lower drive voltage than the comparative organic electroluminescence device, and the voltage rise is suppressed even when driven over time. Comparative Example 1 emitted red light, but the compound having a triphenylamine skeleton (light-absorbing compound) represented by the formula (I I ) did not have a long-wave end up to the red region. There was no overlap in the absorption spectra of the compound (light-absorbing compound) having a triphenylamine skeleton represented by II ). In Comparative Example 2, ΔE was less than 0.3 eV. Therefore, a large increase in the driving voltage was observed at the initial stage and during driving over time.

REFERENCE SIGNS LIST 100 organic EL element 101 base material 102 anode 103 hole injection layer 104 hole transport layer 105 light emitting layer 106 hole blocking layer 107 electron transport layer 108 electron injection layer 109 cathode 110 functional layer 1 base material 2 single film for evaluation 30, 100 inkjet head 31 pump 32 filter 33 pipe branch 34 waste liquid tank 35 control unit 36 tank 37 tank 38A tank 38B tank 39 pump 30b piezoelectric substrate 30c top plate 30d nozzle plate 30e ink liquid supply pipe 30f pipe 56 housing 57 cap receiving plate 59 Cover member 61 Nozzle plate 62 Cap receiving plate mounting portion 68 Mounting hole 71 Nozzle opening 81a First joint 81b Second joint 82 Third joint

Claims (4)

An organic electroluminescence device comprising, on a substrate, a pair of a cathode and an anode, and an organic functional layer including a light-emitting layer and an electron-transporting layer adjacent to the cathode,
The electron transport layer contains a compound having a triphenylamine skeleton represented by the following formula (II) and a metal oxide,
The LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the following formula (II) is higher than the energy level (E _CB ) of the conduction band bottom of the metal oxide,
The energy difference ΔE (E _DL ) between the LUMO energy level (E _DL ) of the compound having a triphenylamine skeleton represented by the following formula (II) and the energy level (E _CB ) at the bottom of the conduction band of the metal oxide -E _CB ) is 0.3 eV or more,
An organic electroluminescence device, wherein an emission wavelength range of a light-emitting compound in the light-emitting layer and an absorption wavelength range of a compound having a triphenylamine skeleton represented by the following formula (II) overlap.

(Wherein, Ar ₂ , Ar ₃ and Ar ₄ each independently represent a substituted or unsubstituted benzene ring. X is an acidic group or an electron-withdrawing group, a substituent having them, or an electron-withdrawing ring represents a substituent having a structure, provided that Ar ₂ , Ar ₃ or Ar ₄ does not have a dimethylamino group, n represents an integer of 1 to 4. When n is plural, each X may be the same or different). An organic electroluminescence device comprising, on a substrate, a pair of a cathode and an anode, and an organic functional layer including a light-emitting layer and an electron-transporting layer adjacent to the cathode,
The electron-transporting layer comprises the following A-1, A-2, A-6, A-7, A-8, A-13, A-14, A-16, A-17, A-18 and A-20 , containing a compound A having a structure represented by A-32 and A-35 and a metal oxide,
The LUMO energy level (E _DL ) of the compound A is higher than the energy level (E _CB ) of the conduction band bottom of the metal oxide,
The energy difference ΔE (E _DL −E _CB ) between the LUMO energy level (E _DL ) of the compound A and the energy level (E _CB ) of the conduction band bottom of the metal oxide is 0.3 eV or more,
An organic electroluminescence device, wherein an emission wavelength range of a light-emitting compound and an absorption wavelength range of said compound A in said light-emitting layer overlap with each other.

3. The organic electroluminescence device according to claim 1, wherein the electron transport layer contains zinc oxide as the metal oxide. 4. The organic electroluminescence device according to claim 1, wherein said metal oxide is nanoparticles.

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