WO2014112359A1

WO2014112359A1 - Organic electroluminescent element

Info

Publication number: WO2014112359A1
Application number: PCT/JP2014/000130
Authority: WO
Inventors: 亮平橋本; 圭吉田; 俊裕岩隈
Original assignee: 出光興産株式会社
Priority date: 2013-01-15
Filing date: 2014-01-14
Publication date: 2014-07-24

Abstract

This organic electroluminescent element contains a first light-emitting layer and a second light-emitting layer between a positive electrode and a negative electrode, the first light-emitting layer contains a red phosphorescent light-emitting material and a compound represented by formula (1), and the second light-emitting layer contains a blue phosphorescent light-emitting material and a compound containing a dibenzothiophene skeleton or a compound containing a dibenzofuran skeleton.

Description

Organic electroluminescence device

The present invention relates to an organic electroluminescence element.

Organic electroluminescence (EL) elements include a fluorescent type and a phosphorescent type, and an optimum element design has been studied according to each light emission mechanism. With respect to phosphorescent organic EL elements, it is known from their light emission characteristics that high-performance elements cannot be obtained by simple diversion of fluorescent element technology. The reason is generally considered as follows.
Since phosphorescent light emission is light emission using triplet excitons, the energy gap of the compound used for the light emitting layer needs to be large. This is because the energy gap (hereinafter also referred to as singlet energy) of a compound is usually larger than the triplet energy (which means the energy difference between the lowest excited triplet state and the ground state) of the compound. It is.

In order to efficiently confine the triplet energy of the phosphorescent dopant material in the light emitting layer, a host material having a triplet energy larger than the triplet energy of the phosphorescent dopant material must first be used for the light emitting layer. .

In order to reduce the driving voltage of the organic EL element, it is necessary to use a material excellent in charge injection property or charge transport property. However, in the case of using such a material excellent in charge injection property and charge transport property, instead of reducing the driving voltage, the charge balance in the light emitting layer is deteriorated, which may lead to shortening of the device life. That is, a charge transport material that reduces the driving voltage while maintaining the lifetime of the element is required.

For the reasons described above, material enhancement and element design different from those of fluorescent organic EL elements are required for enhancing the performance of phosphorescent organic EL elements.

Further, as shown in Patent Documents 1 to 3, the development of a layer in contact with the anode side of the light emitting layer and the development of an element have been energetically performed. For example, Patent Document 3 proposes that a compound having an amine skeleton is used for the hole transport layer and the charge balance in the light emitting layer is adjusted to achieve both high efficiency and long life of the device.

WO2007-108459 brochure JP 2010-205815 A WO2012-128298 Brochure

A white organic EL device for illumination or the like includes a green light-emitting layer or a red light-emitting layer / green light-emitting layer, and a red light-emitting layer / blue light-emitting layer through an intermediate electrode, the first light-emitting unit and the second light-emitting unit. In general, stacked tandem light-emitting elements are used.
However, it cannot be said that the lifetime of a conventional organic EL element in which a red light emitting layer / blue light emitting layer are stacked, which is used as one of the light emitting units, is sufficient.

An object of the present invention is to provide a long-life organic EL element in which a red light emitting layer / blue light emitting layer are laminated.

As a result of intensive studies, the present inventors have found that a compound represented by formula (1) having a specific structure and a red phosphorescent material are included in the first light-emitting layer, and a compound or dibenzo containing a dibenzofuran skeleton in the second light-emitting layer. The present invention was completed by finding that an organic EL device containing a compound containing a thiophene skeleton and a blue phosphorescent material has a long lifetime.

According to one aspect of the present invention,
Between the anode and the cathode, including a first light emitting layer and a second light emitting layer,
The first light emitting layer includes a compound represented by the following formula (1) and a red phosphorescent material,
The second light emitting layer is provided with an organic electroluminescence device including a compound containing a dibenzofuran skeleton or a compound containing a dibenzothiophene skeleton and a blue phosphorescent material.

(In the formula (1),
X is a group represented by O, S, or N-Ra.
Y ¹ to Y ¹² are each a group represented by N or C—Ra.
Ar ¹ and Ar ² are each a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms.
Ra is a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, a substituted or unsubstituted carbon atom having 1 to 30 carbon atoms. An alkyl group, a substituted or unsubstituted fluoroalkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, A substituted phosphoryl group, a substituted silyl group, a cyano group, a nitro group, or a carboxy group.
In Formula (1), when there are two or more Ras, the plurality of Ras may be the same or different. )

According to the present invention, a long-life organic EL element in which a red light emitting layer / blue light emitting layer are laminated can be provided.

It is the schematic which shows the layer structure of one Embodiment of the organic EL element of this invention.

The organic EL element of the present invention is
Between the anode and the cathode, including a first light emitting layer and a second light emitting layer,
The first light emitting layer includes a compound represented by the following formula (1) and a red phosphorescent material,
The second light-emitting layer includes a compound containing a dibenzofuran skeleton or a compound containing a dibenzothiophene skeleton and a blue phosphorescent material.

In formula (1),
X is a group represented by O, S, or N-Ra.
Y ¹ to Y ¹² are each a group represented by N or C—Ra.
Ar ¹ and Ar ² are each a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms.
Ra is a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, a substituted or unsubstituted carbon atom having 1 to 30 carbon atoms. An alkyl group, a substituted or unsubstituted fluoroalkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, A substituted phosphoryl group, a substituted silyl group, a cyano group, a nitro group, or a carboxy group.
In Formula (1), when there are two or more Ras, the plurality of Ras may be the same or different.
However, when Ar ¹ and Ar ² are the same group, Y ¹ and Y ¹² , Y ² and Y ¹¹ , Y ³ and Y ¹⁰ , Y ⁴ and Y ⁹ , Y ⁵ and Y ⁸ , and Y ⁶ and Y ^At least one pair of ⁷ is not identical to each other.

In the compound of formula (1), when Ar ¹ and Ar ² are the same substituent, Y ¹ and Y ¹² , Y ² and Y ¹¹ , Y ³ and Y ¹⁰ , Y ⁴ and Y ⁹ , Y ⁵ and Y ⁸ and at least one pair of Y ⁶ and Y ⁷ are not identical to each other. That is, the carbazole moiety including Y ¹ to Y ⁶ and the carbazole moiety including Y ⁷ to Y ¹² are different from each other, and the two carbazole moieties do not have a line-symmetric structure.
In the compound of formula (1), Ar ¹ and Ar ² are preferably different substituents.

When the compound of the formula (1) is an asymmetric structure compound, the crystallinity is reduced, and appropriate charge transport can be maintained by maintaining an amorphous organic film.

The organic EL device of the present invention in which a red light emitting layer / blue light emitting layer is laminated includes a green light emitting layer and a red light emitting layer / blue light emitting layer that are stacked as a first light emitting unit and a second light emitting unit via an intermediate electrode. The tandem white light-emitting organic EL device is useful as either the first or second light-emitting unit.
The organic EL device of the present invention can be used for a flat light emitter such as a flat panel display of a wall-mounted television, a light source such as a copying machine, a printer, a backlight of a liquid crystal display or an instrument, a display board, a marker lamp, an illumination device, and the like.

X is preferably O or S, more preferably O.

Y ₁ to Y ₁₂ are each preferably a group represented by C—Ra from the viewpoint of extending the life. More preferred is —CH (Ra = H).
When two adjacent ones of Y ₁ to Y ₁₂ are C—Ra (may be —CH), the two adjacent Ras may combine to form a ring. In terms of maintaining the spread of the π-conjugated plane, the ring formed by combining two adjacent Ras is preferably an aromatic ring. In this case, the ring-forming atom may be a heteroaromatic ring containing a heteroatom such as N, O, or S.
Y ¹ to Y ¹² are preferably C—Ra, more preferably C—H.

In one embodiment, Ar ¹ and / or Ar ² is represented by -L ¹ -R ¹ . L ¹ represents a substituted or unsubstituted arylene group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroarylene group having 5 to 30 ring atoms, and R ¹ represents a substituted or unsubstituted ring aryl group. It represents an aryl group having 6 to 30 ring carbon atoms or a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms.

The compound represented by the formula (1) is preferably a compound represented by the following formula (1a).

In the formula (1a), X, Ar ¹ , Ar ² , Y ¹ , Y ² , Y ⁵ , Y ⁶ , Y ⁷ , Y ⁸ , Y ¹¹ and Y ¹² are as defined in the formula (1). .

The compound represented by the formula (1) is preferably a compound represented by the following formula (1b).

In the formula (1b), X, Ar ² , Y ¹ , Y ² , Y ⁵ , Y ⁶ , Y ⁷ , Y ⁸ , Y ¹¹ and Y ¹² are as defined in the formula (1).
Ar ¹¹ is a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.

X is preferably O.

Ar ² is preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.

Ar ¹ and Ar ² , or Ar ¹¹ and Ar ² are preferably different groups.

Ra is substituted or unsubstituted

(X ¹⁰ is O, S or C—RaRa, Ra is as defined in the above formula (1), Y ²⁰ is C—H or N). It is preferable.

The triplet energy of the compound of formula (1) is preferably 2.85 eV or more. Although an upper limit is not limited, Usually, it is 3.5 eV or less.
Since the compound of formula (1) has a high hole transport property, the voltage of the device can be reduced.

The hole mobility of the compound of formula (1) is preferably 5 × 10 ⁻⁸ cm ² / Vs or more. High hole mobility is preferable because the voltage is lowered.
The hole mobility (cm ² / Vs) can be measured using impedance spectroscopy.
Specifically, ITO (indium tin oxide) is used as an anode on a substrate, an organic layer containing a measurement target compound is formed thereon, and then Al is stacked as a cathode, thereby producing a hole-only device. A DC voltage carrying an AC voltage of 100 mV is applied, and the complex modulus is measured. When the frequency at which the imaginary part of the modulus is maximum is f _max (Hz),
The response time T (second) is calculated as T = 1/2 / π / f _max ,
This value is used to determine the electric field strength dependence of the hole mobility, and the value extrapolated to the electric field strength of 0.25 MV / cm ² is defined as the hole mobility.

Hereinafter, examples of each group of the above-described formula will be described.
In this specification, the number of ring-forming carbon atoms constitutes the ring itself of a compound having a structure in which atoms are bonded cyclically (for example, a monocyclic compound, a condensed ring compound, a bridged compound, a carbocyclic compound, or a heterocyclic compound). Represents the number of carbon atoms in the atom. When the ring is substituted with a substituent, the carbon contained in the substituent is not included in the number of ring-forming carbons. The “ring-forming carbon number” described below is the same unless otherwise specified. For example, the benzene ring has 6 ring carbon atoms, the naphthalene ring has 10 ring carbon atoms, the pyridinyl group has 5 ring carbon atoms, and the furanyl group has 4 ring carbon atoms. Further, when an alkyl group is substituted as a substituent on the benzene ring or naphthalene ring, the carbon number of the alkyl group is not included in the number of ring-forming carbons. In addition, for example, when a fluorene ring is bonded to the fluorene ring as a substituent (including a spirofluorene ring), the carbon number of the fluorene ring as a substituent is not included in the number of ring-forming carbons.

In this specification, the number of ring-forming atoms means a compound (for example, a monocyclic compound, a condensed ring compound, a bridging compound, a carbocyclic compound, a heterocycle) having a structure in which atoms are bonded in a cyclic manner (for example, a monocyclic ring, a condensed ring, or a ring assembly) Of the ring compound) represents the number of atoms constituting the ring itself. An atom that does not constitute a ring (for example, a hydrogen atom that terminates a bond of an atom that constitutes a ring) or an atom contained in a substituent when the ring is substituted by a substituent is not included in the number of ring-forming atoms. The “number of ring-forming atoms” described below is the same unless otherwise specified. For example, the pyridine ring has 6 ring atoms, the quinazoline ring has 10 ring atoms, and the furan ring has 5 ring atoms. A hydrogen atom bonded to a carbon atom of a pyridine ring or a quinazoline ring or an atom constituting a substituent is not included in the number of ring-forming atoms. Further, when, for example, a fluorene ring is bonded to the fluorene ring as a substituent (including a spirofluorene ring), the number of atoms of the fluorene ring as a substituent is not included in the number of ring-forming atoms.

In the present specification, the “carbon number XX to YY” in the expression “substituted or unsubstituted ZZ group having XX to YY” represents the number of carbon atoms in the case where the ZZ group is unsubstituted. The carbon number of the substituent in the case where it is present is not included. Here, “YY” is larger than “XX”, and “XX” and “YY” each mean an integer of 1 or more.

In this specification, “atom number XX to YY” in the expression “a ZZ group having a substituted or unsubstituted atom number XX to YY” represents the number of atoms when the ZZ group is unsubstituted. In this case, the number of substituent atoms is not included. Here, “YY” is larger than “XX”, and “XX” and “YY” each mean an integer of 1 or more.

In this specification, “unsubstituted” in the case of “substituted or unsubstituted” means that a hydrogen atom is bonded without being substituted with the above substituent.

In this specification, the aromatic hydrocarbon ring includes a monocyclic aromatic hydrocarbon ring group and a condensed aromatic hydrocarbon ring group in which a plurality of hydrocarbon rings are condensed, and the heteroaromatic ring is a monocyclic heterocycle. An aromatic ring group, a hetero-fused aromatic ring group in which a plurality of heteroaromatic rings are condensed, and a hetero-fused aromatic ring group in which an aromatic hydrocarbon ring and a heteroaromatic ring are condensed are included.

In the compound used in the present invention, the hydrogen atom includes isotopes having different numbers of neutrons, that is, light hydrogen (protium), deuterium (triuterium), and tritium.

When each group of Ar ¹ , Ar ² , and Ra has a substituent, the substituent is, for example, a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 ring carbon atoms, or a carbon number An alkoxy group having 1 to 20 carbon atoms, a cycloalkoxy group having 3 to 20 ring carbon atoms, an aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, an aryloxy group having 6 to 18 ring carbon atoms, and the number of ring atoms Examples thereof include a 5- to 18-heteroaromatic ring group, a silyl group, a fluorine atom, a fluoroalkyl group having 1 to 20 carbon atoms, a fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group.

Specific examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group, n- Heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n- And heptadecyl group, n-octadecyl group, neopentyl group, 1-methylpentyl group, 2-methylpentyl group, 1-pentylhexyl group, 1-butylpentyl group, 1-heptyloctyl group, 3-methylpentyl group and the like. Of these, those having 1 to 6 carbon atoms are preferred.

Specific examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a norbornyl group, an adamantyl group, etc. Among them, those having 5 or 6 ring carbon atoms are preferable.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, and a hexyloxy group. Those having 3 or more carbon atoms may be linear, cyclic or branched, Of these, those having 1 to 6 carbon atoms are preferred.

Examples of the cycloalkoxy group include a cyclopentoxy group and a cyclohexyloxy group, and among them, those having 5 or 6 ring carbon atoms are preferable.

Specific examples of the aromatic hydrocarbon ring group (aryl group) include phenyl group, tolyl group, xylyl group, mesityl group, o-biphenyl group, m-biphenyl group, p-biphenyl group, o-terphenyl group, m -Terphenyl group, p-terphenyl group, naphthyl group, phenanthryl group, triphenylene group and the like. Of these, a phenyl group, m-biphenyl group, and m-terphenyl group are preferred. Those having 6 to 18 ring carbon atoms are preferred.

Examples of the arylene group include groups in which the above-described aromatic hydrocarbon ring group (aryl group) is divalent.

Examples of the aralkyl group include the above-described alkyl group substituted by the above-described aromatic hydrocarbon ring group (aryl group).

Specific examples of the aromatic heterocyclic group (heteroaromatic ring group) (heteroaryl group) include pyrrolyl group, pyrazinyl group, pyridinyl group, pyrimidinyl group, pyridazinyl group, triazinyl group, indolyl group, isoindolyl group, furyl group, Benzofuranyl group, isobenzofuranyl group, dibenzofuranyl group, dibenzothiophenyl group, quinolyl group, isoquinolyl group, quinoxalinyl group, carbazolyl group, azacarbazolyl group, phenanthridinyl group, acridinyl group, phenanthrolinyl group, thienyl Group, pyrrolidinyl group, dioxanyl group, piperidinyl group, morpholinyl group, piperazinyl group, carbazolyl group, thiophenyl group, oxazolyl group, oxadiazolyl group, benzoxazolyl group, thiazolyl group, thiadiazolyl group, benzothiazolyl group, Examples include a riazolyl group, an imidazolyl group, a benzimidazolyl group, a pyranyl group, a benzo [c] dibenzofuranyl group, an azadibenzofuranyl group, an azadibenzothiophenyl group, an azacarbazolyl group, and of these, those having 6 to 14 ring atoms Those are preferred.

Examples of the heteroarylene group include groups in which the above-described aromatic heterocyclic group (heteroaryl group) is divalent.

Examples of the fluoroalkyl group include a group in which one or more fluorine atoms are substituted on the above-described alkyl group, and specifically include a trifluoromethyl group, a pentafluoroethyl group, a 2,2,2-trifluoroethyl group. Etc. are preferred.

Examples of the fluoroalkoxy group include groups in which one or more fluorine atoms are substituted on the above-described alkoxy group, and specifically include a trifluoromethoxy group, a pentafluoroethoxy group, a 2,2,2-trifluoroethoxy group. Etc. are preferred.

Examples of the aryloxy group include a group in which the above-described aryl group is substituted on an oxygen atom.
Examples of the arylthio group include a group in which the above aryl group is substituted on a sulfur atom.
Examples of the arylsulfonyl group include a group in which the above aryl group is substituted on the sulfonyl group.
Examples of the heteroaryloxy group include groups in which the above-described heteroaryl group is substituted on an oxygen atom.
Examples of the heteroarylthio group include a group in which the above-described heteroaryl group is substituted on a sulfur atom.
Examples of the heteroarylsulfonyl group include a group in which the above aryl group is substituted on the sulfonyl group.
As an alkylene group, the group which made the alkyl group mentioned above bivalent is mentioned.
Examples of the cycloalkylene group include groups in which the above-described cycloalkyl group is divalent.

Specific examples of the compound represented by the above formula (1) are shown below.

Next, a compound containing a dibenzofuran skeleton and a compound containing a dibenzothiophene skeleton contained in the second light emitting layer (hereinafter sometimes referred to as a compound of the second light emitting layer) will be described.

The triplet energy of the compound of the second light emitting layer is usually 2.85 eV or more, preferably 2.90 eV or more. Although an upper limit is not limited, Usually, it is 3.5 eV or less.
The compound of the second light emitting layer has a dibenzofuran skeleton or a dibenzothiophene skeleton.
If a compound of the second light-emitting layer having a skeleton such as a dibenzofuran ring or a dibenzothiophene ring having electron resistance while maintaining the electron transporting ability is used, the lifetime can be extended.
Hereinafter, the compounds of the second light-emitting layer will be described with specific structural formulas, but each compound includes a dibenzofuran skeleton and / or a dibenzothiophene skeleton as a partial structure.

Preferably, the compound of the second light emitting layer is a compound represented by the following formula (2).

In formula (2),
X ¹ is an oxygen atom or a sulfur atom,
One of X ² and Y ² is an oxygen atom, a sulfur atom or NR, and the other is a single bond, C (R) ₂ , NR, an oxygen atom or a sulfur atom,
Each R is independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted ring forming carbon number; An aromatic hydrocarbon ring group having 6 to 30 or a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 ring atoms;
Z ¹ , Z ² and Z ³ are each independently a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 30 ring carbon atoms or a substituted or unsubstituted aromatic hetero ring having 3 to 30 ring atoms. A ring,
n is an integer of 0 to 5, and when n is 2 or more, the plurality of Z ² may be the same or different from each other, and the plurality of X ² may be the same or different from each other The plurality of Y ² may be the same as or different from each other. Preferably n is an integer of 0 or 1.

When R, Z ¹ , Z ² and Z ³ have a substituent, the substituent R ′ is, for example, a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a cycloalkyl group having 3 to 20 ring carbon atoms. An alkoxy group having 1 to 20 carbon atoms, a cycloalkoxy group having 3 to 20 ring carbon atoms, an aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, an aryloxy group having 6 to 18 ring carbon atoms, a ring A heteroaromatic cyclic group having 5 to 18 atoms, a silyl group, a fluorine atom, a fluoroalkyl group having 1 to 20 carbon atoms, a fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group.

More specifically, the compound of the second light emitting layer is preferably a compound represented by the following formula (2-1).

(In the formula (2-1),
G ₁ to G ₆ are each independently CR ₁ or a nitrogen atom.
G ₁₁ to G ₁₈ are each independently CR ₂ or a nitrogen atom.
R and R ₁ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, a substituted or unsubstituted carbon, An alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, a substituted or unsubstituted aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, a substituted or unsubstituted ring group; Aryloxy group having 6 to 18 ring carbon atoms, substituted or unsubstituted heteroaryloxy group having 5 to 18 ring atoms, substituted or unsubstituted arylthio group having 6 to 18 ring carbon atoms, substituted or unsubstituted A heteroarylthio group having 5 to 18 ring atoms, a substituted or unsubstituted arylsulfonyl group having 6 to 18 ring carbon atoms, and a substituted or unsubstituted ring atom number 5-18 heteroarylsulfonyl group, substituted or unsubstituted heteroaromatic ring group having 5 to 18 ring atoms, substituted or unsubstituted silyl group, fluorine atom, substituted or unsubstituted fluoroalkyl group, substituted or An unsubstituted fluoroalkoxy group or a cyano group.
When a plurality of CR ₁ are present, the plurality of R ₁ may be the same as or different from each other.
However, when one or both of G ₂ and G ₅ are CR ₁ , R ₁ of G ₂ and G ₅ is each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, A substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, substituted or An unsubstituted silyl group, a fluorine atom, a substituted or unsubstituted fluoroalkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted fluoroalkoxy group having 1 to 20 carbon atoms.
R ₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, or a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms. A substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, a substituted or unsubstituted aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, a substituted or unsubstituted ring carbon number 6 to 18 aryloxy groups, substituted or unsubstituted heteroaromatic ring groups having 5 to 18 ring atoms, substituted or unsubstituted silyl groups, fluorine atoms, substituted or unsubstituted fluoroalkyl groups having 1 to 20 carbon atoms A substituted or unsubstituted C 1-20 fluoroalkoxy group or cyano group.
When a plurality of CR ₂ are present, each R ₂ may be the same or different.
When R, R ₁ and R ₂ have a substituent, the substituent R ′ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 ring carbon atoms, or 1 to 20 carbon atoms. Alkoxy groups having 3 to 20 ring carbon atoms, aromatic hydrocarbon ring groups having 6 to 18 ring carbon atoms, aryloxy groups having 6 to 18 ring carbon atoms, and 5 to 18 ring atoms. A heteroaromatic ring group, a silyl group, a fluorine atom, a fluoroalkyl group having 1 to 20 carbon atoms, a fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group.
Xa is an oxygen atom or a sulfur atom. )

The compound of the second light emitting layer is preferably represented by any one of the following formulas (2-2a) to (2-2c), (2-3a) to (2-3c), and (2-4a). Is done.

(In the formulas (2-2a) to (2-2c),
G ₂₁₁ to G ₂₁₄ are each independently CR ₂₁ or a nitrogen atom.
G ₂₂₁ to G ₂₂₈ are each independently CR ₂₂ or a nitrogen atom.
Ga to Gk are each independently CR ₂₃ or a nitrogen atom.
When G ₂₁₄ and Ga are carbon atoms, they may be bonded via an oxygen or sulfur atom.
When _G213 and Gd are carbon atoms, they may be bonded via an oxygen or sulfur atom.
R ₂₁ , R ₂₂ and R ₂₃ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, substituted or unsubstituted Unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, substituted or unsubstituted aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, substituted Or an unsubstituted aryloxy group having 6 to 18 carbon atoms, a substituted or unsubstituted heteroaromatic ring group having 5 to 18 ring atoms, a substituted or unsubstituted silyl group, a fluorine atom, substituted or unsubstituted A fluoroalkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group.
When a plurality of CR ₂₁ are present, the plurality of R ₂₁ may be the same or different from each other.
When a plurality of CR ₂₂ are present, the plurality of R ₂₂ may be the same or different from each other.
When a plurality of CR ₂₃ are present, the plurality of R ₂₃ may be the same or different from each other.
When R ₂₁ , R ₂₂ and R ₂₃ have a substituent, the substituent R ′ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 ring carbon atoms, or 1 to 20 alkoxy groups, cycloalkoxy groups having 3 to 20 ring carbon atoms, aromatic hydrocarbon ring groups having 6 to 18 ring carbon atoms, aryloxy groups having 6 to 18 ring carbon atoms, 5 to 5 ring atoms An 18 heteroaromatic ring group, a silyl group, a fluorine atom, a fluoroalkyl group having 1 to 20 carbon atoms, a fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group.
X ₁ is an oxygen atom or a sulfur atom.
X ₂ is an oxygen atom, a sulfur atom, or C (CH ₃ ) ₂ . )

The compound of the second light emitting layer is preferably represented by any of the following formulas (2-5a) to (2-5f).

(In the formulas (2-5a) to (2-5f),
E ₁ and E ₂ are each independently an oxygen atom, a sulfur atom or NR ₅ ;
However, at least one of E ₁ and E ₂ is an oxygen atom or a sulfur atom,
G ₅₁ to G ₆₀ are each independently CR ₆ or a nitrogen atom.
R ₅ represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted ring carbon atom having 6 to 30 carbon atoms. An aromatic hydrocarbon ring group or a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 ring atoms,
R ₆ represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms. Group, substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 ring carbon atoms, substituted or unsubstituted ring carbon atoms having 6 to 18 carbon atoms An aryloxy group, a substituted or unsubstituted heteroaromatic ring group having 5 to 18 ring atoms, a substituted or unsubstituted silyl group, a fluorine atom, a substituted or unsubstituted fluoroalkyl group having 1 to 20 carbon atoms, A substituted or unsubstituted C1-C20 fluoroalkoxy group or cyano group.
When a plurality of NR ₅ are present, the plurality of R ₅ may be the same or different from each other.
When a plurality of CR ₆ are present, the plurality of R ₆ may be the same or different from each other.
When R ₅ and R ₆ have a substituent, the substituent R ′ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 ring carbon atoms, or an alkoxy having 1 to 20 carbon atoms. Group, a cycloalkoxy group having 3 to 20 ring carbon atoms, an aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, an aryloxy group having 6 to 18 ring carbon atoms, and a hetero ring having 5 to 18 ring atoms. An aromatic ring group, a silyl group, a fluorine atom, a fluoroalkyl group having 1 to 20 carbon atoms, a fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group. )

Further, the compound of the second light emitting layer may be a compound represented by the following formulas (2-4) to (2-9).

In formulas (2-4) to (2-9), X ₁ and X ₂ are each independently an oxygen atom or a sulfur atom,
Each R ₁ independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted ring forming carbon; An aromatic hydrocarbon ring group of 6-30, or a substituted or unsubstituted aromatic heterocyclic group of 3-30 ring-forming atoms,
s, t, and u are each independently an integer of 1-4.

Specific examples of each group and its substituent in the compound of the second light emitting layer include those exemplified for the compound of formula (1).

Specific examples of the compound containing a dibenzofuran skeleton and the compound containing a dibenzothiophene skeleton contained in the second light emitting layer are shown below.

Next, a phosphorescent material (sometimes called a phosphorescent dopant) will be described.

The phosphorescent material is a so-called phosphorescent dopant.
Examples of the phosphorescent dopant include metal complex compounds, preferably a compound having a metal atom selected from Ir, Pt, Os, Au, Cu, Re and Ru and a ligand. The ligand preferably has an ortho metal bond.
The phosphorescent dopant is preferably a compound containing a metal atom selected from Ir, Os and Pt in that the phosphorescent quantum yield is high and the external quantum efficiency of the light-emitting element can be further improved, and an iridium complex, It is more preferable that it is a metal complex such as an osmium complex and a platinum complex, among which an iridium complex and a platinum complex are more preferable, and an orthometalated iridium complex is most preferable. The dopant may be a single type or a mixture of two or more types.
The red phosphorescent material contained in the first light emitting layer is a compound that can emit phosphorescence having an emission wavelength in the range of 550 to 750 nm, preferably in the range of 570 to 730 nm.
Examples of the compound used as the red phosphorescent material include Ir (pic) ₃ , (pic) ₂ Ir (acac), (btp) ₂ Ir (acac), and (pic) ₂ Ir (acac), (Btp) ₂ Ir (acac) and the like are preferable.

The triplet energy Eg ^T of the red phosphorescent material is preferably 2.10 eV or more.

The blue phosphorescent material contained in the second light emitting layer is a compound that can emit phosphorescence having an emission wavelength in the range of 430 to 550 nm, preferably in the range of 430 to 530 nm, more preferably in the range of 430 to 510 nm.
Examples of the compound used as the blue phosphorescent material include FIrpic, FCNIrpic, FIr6, iridium complex of carbene ligand, iridium complex of phenylimidazole ligand, iridium complex of carbene ligand, phenylimidazole, and the like. An iridium complex of a ligand or the like is preferable.

The triplet energy Eg ^T of the blue phosphorescent material is preferably 2.70 eV or more.

The organic EL device of the present invention includes a first light emitting layer containing the compound of the above formula (1) and a red phosphorescent material, and a compound containing a dibenzofuran skeleton or a compound containing a dibenzothiophene skeleton and a blue phosphorescent material. Other configurations are not particularly limited as long as they have an element configuration including a second light-emitting layer that includes.

The first light emitting layer may contain one or more compounds of formula (1). The first light-emitting layer contains one kind of red phosphorescent material (phosphorescent dopant) alone or two or more kinds.
The second light emitting layer may contain one or more compounds containing a dibenzofuran skeleton and / or a compound containing a dibenzothiophene skeleton. A 2nd light emitting layer contains blue phosphorescent light emitting material (phosphorescent dopant) 1 type individually, or contains 2 or more types.

The first light emitting layer and the second light emitting layer are preferably adjacent to each other.
In addition, the organic layer adjacent to the second light emitting layer may contain a compound containing a dibenzofuran skeleton and / or a compound containing a dibenzothiophene skeleton alone or in combination of two or more. This organic layer can function as a hole blocking layer.
Furthermore, when a hole transporting material is added to the first light emitting layer, deterioration of the compound of the formula (1) is suppressed, so that the lifetime of the element can be improved.
The first light-emitting layer is preferably composed of only the compound of formula (1) and the red phosphorescent material, or only the compound of formula (1), the red phosphorescent material and the hole transporting material (including inevitable impurities). .

The addition concentration of the red phosphorescent dopant or hole transporting material in the first light emitting layer is not particularly limited, but is preferably 0.1 to 20% by weight (wt%), more preferably 0.1% each. ˜10 wt% (wt%).

Examples of the hole transporting material include a material for a hole injection / transport layer described later.

The addition concentration of the blue phosphorescent dopant in the second light emitting layer is not particularly limited, but is preferably 0.1 to 40% by weight (wt%), more preferably 0.1 to 30% by weight (wt%). It is.

FIG. 1 is a schematic view showing a layer structure of an embodiment of the organic EL device of the present invention.
The organic EL element 1 includes an anode 20, a hole injection layer 30, a hole transport layer 40, an electron blocking layer 50, a first light emitting layer 60, a second light emitting layer 62, and a hole blocking layer 70 on a substrate 10. The electron transport layer 80, the electron injection layer 90, and the cathode 100 are stacked in this order.
Any of the hole injection layer, the hole transport layer, the electron blocking layer, the hole blocking layer, the electron transport layer, and the electron injection layer may be formed.

In addition to the above-described embodiments, the organic EL element of the present invention can employ various known configurations.

In the organic EL element of the present invention, the configuration other than the layer using the organic EL element material of the present invention described above is not particularly limited, and a known material or the like can be used. Hereinafter, although the layer of the element of Embodiment 1 is demonstrated easily, the material applied to the organic EL element of this invention is not limited to the following.

[substrate]
As the substrate, a glass plate, a polymer plate or the like can be used.
Examples of the glass plate include soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfone, and polysulfone.

[anode]
The anode is made of, for example, a conductive material, and a conductive material having a work function larger than 4 eV is suitable.
Examples of the conductive material include carbon, aluminum, vanadium, iron, cobalt, nickel, tungsten, silver, gold, platinum, palladium, and their alloys, ITO substrate, tin oxide used for NESA substrate, indium oxide, and the like. Examples thereof include metal oxides and organic conductive resins such as polythiophene and polypyrrole.
The anode may be formed with a layer structure of two or more layers if necessary.

[cathode]
The cathode is made of, for example, a conductive material, and a conductive material having a work function smaller than 4 eV is suitable.
Examples of the conductive material include, but are not limited to, magnesium, calcium, tin, lead, titanium, yttrium, lithium, ruthenium, manganese, aluminum, lithium fluoride, and alloys thereof.
Examples of the alloy include magnesium / silver, magnesium / indium, lithium / aluminum, and the like, but are not limited thereto. The ratio of the alloy is controlled by the temperature of the vapor deposition source, the atmosphere, the degree of vacuum, etc., and is selected to an appropriate ratio.
If necessary, the cathode may be formed with a layer structure of two or more layers, and the cathode can be produced by forming a thin film from the conductive material by a method such as vapor deposition or sputtering.

When light emitted from the light emitting layer is taken out from the cathode, the transmittance of the cathode for light emission is preferably greater than 10%.
The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually 10 nm to 1 μm, preferably 50 to 200 nm.

[Light emitting layer]
In the case where a phosphorescent light emitting layer is further formed in addition to the first and second light emitting layers of the organic EL device of the present invention, known materials can be used as the material of the phosphorescent light emitting layer. Specifically, Japanese Patent Application No. 2005-517938 may be referred to.
The organic EL element of the present invention may have a fluorescent light emitting layer. A known material can be used for the fluorescent light emitting layer.

The light emitting layer may be a double host (also referred to as a host / cohost). Specifically, the carrier balance in the light emitting layer may be adjusted by combining an electron transporting host and a hole transporting host in the light emitting layer.
Moreover, it is good also as a double dopant. In the light emitting layer, each dopant emits light by adding two or more dopant materials having a high quantum yield. For example, a yellow light emitting layer may be realized by co-evaporating a host, a red dopant, and a green dopant.
The light emitting layer may be a single layer or a laminated structure. When the light emitting layer is stacked, the recombination region can be concentrated on the light emitting layer interface by accumulating electrons and holes at the light emitting layer interface. This improves the quantum efficiency.

[Hole injection layer and hole transport layer]
The hole injection layer and the hole transport layer (hole injection / transport layer) help to inject holes into the light emitting layer and transport them to the light emitting region, and have high hole mobility and low ionization energy. Is a layer.
As the material for the hole injection / transport layer, a material that transports holes to the light emitting layer with lower electric field strength is preferable. Further, when an electric field is applied with a hole mobility of, for example, 10 ⁴ to 10 ⁶ V / cm, At least 10 ⁻⁴ cm ² / V · sec is preferable.

Specific examples of the material for the hole injection / transport layer include triazole derivatives (see US Pat. No. 3,112,197) and oxadiazole derivatives (see US Pat. No. 3,189,447). ), Imidazole derivatives (see JP-B-37-16096, etc.), polyarylalkane derivatives (US Pat. Nos. 3,615,402, 3,820,989, 3,542,544) Nos. 45-555, 51-10983, 51-93224, 55-17105, 56-4148, 55-108667, 55-156953, 56-36656, etc.), pyrazoline derivatives and pyrazolone derivatives (US Pat. No. 3,180,729, No. 4) Nos. 278,746, 55-88064, 55-88065, 49-105537, 55-51086, 56-80051, 56-88141 57-45545, 54-112737, 55-74546, etc.), phenylenediamine derivatives (US Pat. No. 3,615,404, JP-B 51-10105, 46-3712, 47-25336, 54-119925, etc.), arylamine derivatives (US Pat. Nos. 3,567,450, 3,240,597, No. 3,658,520, No. 4,232,103, No. 4,175,961, No. 4,012,376 Description, JP-B-49-35702, JP-A-39-27577, JP-A-55-144250, JP-A-56-119132, JP-A-56-22437, West German Patent No. 1,110,518 ), Amino-substituted chalcone derivatives (see US Pat. No. 3,526,501, etc.), oxazole derivatives (disclosed in US Pat. No. 3,257,203 etc.), styrylanthracene derivatives (See JP 56-46234 A, etc.), fluorenone derivatives (see JP 54-110837 A, etc.), hydrazone derivatives (US Pat. No. 3,717,462, JP 54-59143 A). Gazette, 55-52063, 55-52064, 55-46760, 57-11350, 57- No. 148749, JP-A-2-311591, etc.), stilbene derivatives (JP-A Nos. 61-210363, 61-228451, 61-14642, 61-72255, etc.) 62-47646, 62-36684, 62-10652, 62-30255, 60-93455, 60-94462, 60-174749, 60 -175052, etc.), silazane derivatives (US Pat. No. 4,950,950), polysilanes (JP-A-2-204996), aniline copolymers (JP-A-2-282263) Etc.
In addition, inorganic compounds such as p-type Si and p-type SiC can also be used as the hole injection material.

As the material for the hole injection / transport layer, a cross-linkable material can be used. Mater. 2008, 20, 413-422, Chem. Mater. Examples include a layer obtained by insolubilizing a cross-linking material such as 2011, 23 (3), 658-681, WO2008108430, WO2009102027, WO2009123269, WO2010016555, WO2010018813 by heat, light or the like.

[Electron injection layer and electron transport layer]
The electron injection layer and the electron transport layer (electron injection / transport layer) are layers that assist the injection of electrons into the light emitting layer and transport them to the light emitting region, and have high electron mobility.
In the organic EL element, since emitted light is reflected by an electrode (for example, a cathode), it is known that light emitted directly from the anode interferes with light emitted via reflection by the electrode. In order to efficiently use this interference effect, the electron injecting / transporting layer is appropriately selected with a film thickness of several nm to several μm. However, particularly when the film thickness is large, in order to avoid a voltage increase, 10 ⁴ to 10 ^6. The electron mobility is preferably at least 10 ⁻⁵ cm ² / Vs or more when an electric field of V / cm is applied.

As the electron transporting material used for the electron injection / transport layer, an aromatic heterocyclic compound containing one or more heteroatoms in the molecule is preferably used, and a nitrogen-containing ring derivative is particularly preferable. The nitrogen-containing ring derivative is preferably an aromatic ring having a nitrogen-containing 6-membered ring or 5-membered ring skeleton, or a condensed aromatic ring compound having a nitrogen-containing 6-membered ring or 5-membered ring skeleton, such as a pyridine ring. , Pyrimidine ring, triazine ring, benzimidazole ring, phenanthroline ring, quinazoline ring and the like.

In addition, an organic layer having semiconductivity may be formed by doping a donor material (n) and acceptor material (p). A typical example of N doping is to dope an electron transport material with a metal such as Li or Cs, and a typical example of P doping is to dope an acceptor material such as F4TCNQ into a hole transport material ( For example, see Japanese Patent No. 3695714).

For the formation of each layer of the organic EL device of the present invention, a known method such as a dry film forming method such as vacuum deposition, sputtering, plasma, or ion plating, or a wet film forming method such as spin coating, dipping, or flow coating is applied. be able to.
The thickness of each layer is not particularly limited, but must be set to an appropriate thickness. If the film thickness is too thick, a large applied voltage is required to obtain a constant light output, resulting in poor efficiency. If the film thickness is too thin, pinholes and the like are generated, and sufficient light emission luminance cannot be obtained even when an electric field is applied. The normal film thickness is suitably in the range of 5 nm to 10 μm, but more preferably in the range of 10 nm to 0.2 μm.

Next, the present invention will be described in further detail using examples. However, the present invention is not limited to the following examples.

1. The material used for manufacture of the organic EL element of an Example and a comparative example is shown below.

2. The measuring method of the characteristic of a compound is as follows.
(1) Triplet energy (E ^T )
The measurement was performed using a commercially available apparatus F-4500 (manufactured by Hitachi). The conversion formula of triplet energy (E ^T ) is as follows.
E ^T (eV) = 1239.85 / λ _ph
In the formula, “λ _ph ” (unit: nm) draws a tangent line to the rising edge of the phosphorescence spectrum on the short wavelength side when the phosphorescence spectrum is represented with the phosphorescence intensity on the vertical axis and the wavelength on the horizontal axis. , The wavelength value of the intersection of the tangent and the horizontal axis.

(2) Ionization potential A thin film of the measurement compound was formed on the ITO substrate by a vacuum deposition method or a coating method, and the measurement was performed using a commercially available atmospheric photoelectron spectrometer AC-3 (manufactured by Riken Keiki Co., Ltd.).

3. The evaluation method of the organic EL element is as follows.

(1) Half life (hours)
A continuous energization test (DC) was performed at an initial luminance of 1000 cd / m ² and the time until the initial luminance was reduced by half was measured.

(2) Voltage (V)
Using a KEITLY 236 SOURCE MEASURE UNIT under a dry nitrogen gas atmosphere at 23 ° C., voltage was applied to the electrically wired element to emit light, and the voltage applied to the wiring resistance other than the element was subtracted to measure the element applied voltage. .
At the same time as the voltage application / measurement, the luminance was also measured using a luminance meter (Spectral Luminance Radiometer CS-1000 manufactured by Minolta Co., Ltd.), and the voltage when the element luminance was 1000 cd / m ² was read from these measurement results.

As shown in Table 2, it can be seen that the organic EL device of the example using the compound of the present invention as the host of the red phosphorescent light emitting layer has an improved half-life compared to the device of Comparative Example 1.

Example 1
A glass substrate with a 130 nm-thick ITO electrode line (manufactured by Geomatic) was ultrasonically cleaned in isopropyl alcohol for 5 minutes, followed by UV ozone cleaning for 30 minutes.
The glass substrate with the ITO electrode line after the cleaning is mounted on the substrate holder of the vacuum deposition apparatus, and the compound (HI1) is first thickened so as to cover the ITO electrode line on the surface on which the ITO electrode line is formed. At 20 nm, the compound (HT1) was then vapor deposited by resistance heating at a thickness of 50 nm, and thin films were sequentially formed. The film formation rate was 1 Å / s. These thin films function as a hole injection layer and a hole transport layer, respectively.

On this hole injection / transport layer, a compound (1) and a compound (RD1) were simultaneously deposited by resistance heating to form a thin film having a thickness of 10 nm. The film formation rates were 1.0 Å / s and 0.064 Å / s, respectively. At this time, the compound (RD1) was deposited so as to have a mass ratio of 6% with respect to the total mass of the compound (1) and the compound (RD1). This thin film functions as a red phosphorescent light emitting layer.
Next, on the electron blocking layer, the compound (H1) and the compound (BD1) were simultaneously deposited by resistance heating to form a thin film having a thickness of 50 nm. At this time, the compound (BD1) was deposited so as to have a mass ratio of 20% with respect to the total mass of the compound (H1) and the compound (BD1). The film formation rates were 1.2 Å / s and 0.3 Å / s, respectively. This thin film functions as a phosphorescent light emitting layer.
Next, a thin film having a thickness of 10 nm was formed on the phosphorescent light emitting layer by resistance heating vapor deposition of the compound (H1). The film formation rate was 1 Å / s. This thin film functions as a hole blocking layer.

On this hole blocking layer, a compound (ET1) was deposited by resistance heating vapor deposition to form a thin film having a thickness of 10 nm. The film formation rate was 1 Å / s. This film functions as an electron injection layer.
LiF having a film thickness of 1.0 nm was deposited on the electron injection layer at a film formation rate of 0.1 Å / s.
Next, metal aluminum was vapor-deposited on the LiF film at a film formation rate of 8.0 Å / s to form a metal cathode having a film thickness of 80 nm, thereby manufacturing an organic EL element.

Example 2 and Comparative Examples 1 and 2
An organic EL device was prepared and evaluated in the same manner as in Example 1 except that the compounds shown in Table 2 were used as the host material for the red phosphorescent light emitting layer instead of the compound (1). The results are shown in Table 3. The “half life (relative%)” is a relative ratio when the half life of the element of Comparative Example 2 is 100%. Table 1 shows the triplet energy and ionization potential of the compounds used, and Table 2 shows the evaluation results of the devices.

As shown in Table 2, it can be seen that the organic EL device of the example using the compound of the present invention as the host material of the red phosphorescent light emitting layer has an improved lifetime as compared with the devices of Comparative Examples 1 and 2. .

Examples 3 and 4 and Comparative Examples 3 and 4
The same procedure as in Example 1 was conducted except that compound (H2) was used as the host for the phosphorescent layer instead of compound (H1), and the compounds listed in Table 3 were used as the host material for the red phosphorescent layer instead of compound (1). Thus, an organic EL element was produced and evaluated. The results are shown in Table 3. The “half life (relative%)” is a relative ratio when the half life of the element of Comparative Example 4 is 100%.

As shown in Table 3, the organic EL device of the example using the compound of the present invention as the host material of the red phosphorescent light emitting layer has an improved lifetime as compared with the devices of Comparative Examples 3 and 4. .

Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will appreciate that these exemplary embodiments and / or embodiments are substantially without departing from the novel teachings and advantages of the present invention. It is easy to make many changes to the embodiment. Accordingly, many of these modifications are within the scope of the present invention.
The entire contents of the documents described in this specification are incorporated herein by reference.

Claims

Between the anode and the cathode, including a first light emitting layer and a second light emitting layer,
The first light emitting layer includes a compound represented by the following formula (1) and a red phosphorescent material,
The second light-emitting layer is an organic electroluminescence device including a compound containing a dibenzofuran skeleton or a compound containing a dibenzothiophene skeleton and a blue phosphorescent material.

(In the formula (1),
X is a group represented by O, S, or N-Ra.
Y 1 to Y 12 are each a group represented by N or C—Ra.
Ar 1 and Ar 2 are each a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms.
Ra is a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, a substituted or unsubstituted carbon atom having 1 to 30 carbon atoms. An alkyl group, a substituted or unsubstituted fluoroalkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, A substituted phosphoryl group, a substituted silyl group, a cyano group, a nitro group, or a carboxy group.
In Formula (1), when there are two or more Ras, the plurality of Ras may be the same or different. )
The organic electroluminescence device according to claim 1, wherein the compound represented by the formula (1) is a compound represented by the following formula (1a).

(In the formula (1a), X, Ar 1 , Ar 2 , Y 1 , Y 2 , Y 5 , Y 6 , Y 7 , Y 8 , Y 11 and Y 12 are as defined in the formula (1). is there.)
The organic electroluminescent device according to claim 2, wherein the compound represented by the formula (1) is a compound represented by the following formula (1b).

(In the formula (1b), X, Ar 2 , Y 1 , Y 2 , Y 5 , Y 6 , Y 7 , Y 8 , Y 11 and Y 12 are as defined in the formula (1).
Ar 11 is a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms. )
The organic electroluminescence device according to any one of claims 1 to 3, wherein X is O.
The organic electroluminescence device according to any one of claims 1 to 4, wherein Ar 2 is a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
6. The organic electroluminescence device according to claim 1 , wherein Ar 1 and Ar 2 , or Ar 11 and Ar 2 are different groups.
Ra is substituted or unsubstituted

(X 10 is O, S or C—RaRa, Ra is as defined in the above formula (1), Y 20 is C—H or N). The organic electroluminescence device according to any one of claims 1 to 6.
The organic electroluminescence device according to any one of claims 1 to 7, wherein an emission wavelength of the red phosphorescent material is in a range of 550 to 750 nm.
The organic electroluminescence device according to any one of claims 1 to 8, wherein an emission wavelength of the blue phosphorescent material is in a range of 440 to 550 nm.
10. The organic electroluminescence device according to claim 1, wherein the compound represented by the formula (1) has a triplet energy of 2.85 eV or more.
The organic electroluminescent device according to claim 10, wherein the triplet energy of the compound represented by the formula (1) is 2.85 eV or more and 3.5 eV or less.
12. The organic electroluminescence device according to claim 1, wherein the hole mobility of the compound represented by the formula (1) is 5 × 10 −8 cm 2 / Vs or more.
The organic electroluminescence device according to any one of claims 1 to 12, wherein the compound containing the dibenzofuran skeleton or the compound containing the dibenzothiophene skeleton is represented by the following formula (2).

(In the formula (I),
X 1 is an oxygen atom or a sulfur atom,
One of X 2 and Y 2 is an oxygen atom, a sulfur atom or NR, and the other is a single bond, C (R) 2 , NR, an oxygen atom or a sulfur atom,
Each R is independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted ring forming carbon number; An aromatic hydrocarbon ring group having 6 to 30 or a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 ring atoms;
Z 1 , Z 2 and Z 3 are each independently a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 30 ring carbon atoms or a substituted or unsubstituted aromatic hetero ring having 3 to 30 ring atoms. A ring,
n is an integer of 0 to 5, and when n is 2 or more, the plurality of Z 2 may be the same or different from each other, and the plurality of X 2 may be the same or different from each other The plurality of Y 2 may be the same as or different from each other.
However, the compound of formula (I) includes a dibenzothiophene skeleton or a dibenzothiophene skeleton as a partial structure. )
The organic electroluminescence device according to claim 13, wherein the compound of the formula (2) is represented by the following formula (2-1).

(In the formula (2-1),
G 1 to G 6 are each independently CR 1 or a nitrogen atom.
G 11 to G 18 are each independently CR 2 or a nitrogen atom.
R and R 1 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, a substituted or unsubstituted carbon, An alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, a substituted or unsubstituted aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, a substituted or unsubstituted ring group; Aryloxy group having 6 to 18 ring carbon atoms, substituted or unsubstituted heteroaryloxy group having 5 to 18 ring atoms, substituted or unsubstituted arylthio group having 6 to 18 ring carbon atoms, substituted or unsubstituted A heteroarylthio group having 5 to 18 ring atoms, a substituted or unsubstituted arylsulfonyl group having 6 to 18 ring carbon atoms, and a substituted or unsubstituted ring atom number 5-18 heteroarylsulfonyl group, substituted or unsubstituted heteroaromatic ring group having 5 to 18 ring atoms, substituted or unsubstituted silyl group, fluorine atom, substituted or unsubstituted fluoroalkyl group, substituted or An unsubstituted fluoroalkoxy group or a cyano group.
When a plurality of CR 1 are present, the plurality of R 1 may be the same as or different from each other.
However, when one or both of G 2 and G 5 are CR 1 , R 1 of G 2 and G 5 is each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, A substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, substituted or An unsubstituted silyl group, a fluorine atom, a substituted or unsubstituted fluoroalkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted fluoroalkoxy group having 1 to 20 carbon atoms.
R 2 represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, or a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms. A substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, a substituted or unsubstituted aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, a substituted or unsubstituted ring carbon number 6 to 18 aryloxy groups, substituted or unsubstituted heteroaromatic ring groups having 5 to 18 ring atoms, substituted or unsubstituted silyl groups, fluorine atoms, substituted or unsubstituted fluoroalkyl groups having 1 to 20 carbon atoms A substituted or unsubstituted C 1-20 fluoroalkoxy group or cyano group.
When a plurality of CR 2 are present, each R 2 may be the same or different.
When R, R 1 and R 2 have a substituent, the substituent R ′ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 ring carbon atoms, or 1 to 20 carbon atoms. Alkoxy groups having 3 to 20 ring carbon atoms, aromatic hydrocarbon ring groups having 6 to 18 ring carbon atoms, aryloxy groups having 6 to 18 ring carbon atoms, and 5 to 18 ring atoms. A heteroaromatic ring group, a silyl group, a fluorine atom, a fluoroalkyl group having 1 to 20 carbon atoms, a fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group.
Xa is an oxygen atom or a sulfur atom. )
The organic electroluminescence device according to claim 13, wherein the compound of the formula (2) is represented by any one of the following formulas (2-2a) to (2-2c).

(In the formulas (2-2a) to (2-2c),
G 211 to G 214 are each independently CR 21 or a nitrogen atom.
G 221 to G 228 are each independently CR 22 or a nitrogen atom.
Ga to Gk are each independently CR 23 or a nitrogen atom.
When G 214 and Ga are carbon atoms, or G 213 and Gd are carbon atoms, they may be bonded via an oxygen or sulfur atom.
When G213 and Gd are carbon atoms, or when G213 and Gd are carbon atoms, they may be bonded via an oxygen or sulfur atom.
R 21 , R 22 and R 23 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, substituted or unsubstituted Unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, substituted or unsubstituted aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, substituted Or an unsubstituted aryloxy group having 6 to 18 carbon atoms, a substituted or unsubstituted heteroaromatic ring group having 5 to 18 ring atoms, a substituted or unsubstituted silyl group, a fluorine atom, substituted or unsubstituted A fluoroalkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group.
When a plurality of CR 21 are present, the plurality of R 21 may be the same or different from each other.
When a plurality of CR 22 are present, the plurality of R 22 may be the same or different from each other.
When a plurality of CR 23 are present, the plurality of R 23 may be the same or different from each other.
When R 21 , R 22 and R 23 have a substituent, the substituent R ′ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 ring carbon atoms, or 1 to 20 alkoxy groups, cycloalkoxy groups having 3 to 20 ring carbon atoms, aromatic hydrocarbon ring groups having 6 to 18 ring carbon atoms, aryloxy groups having 6 to 18 ring carbon atoms, 5 to 5 ring atoms An 18 heteroaromatic ring group, a silyl group, a fluorine atom, a fluoroalkyl group having 1 to 20 carbon atoms, a fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group.
X 1 is an oxygen atom or a sulfur atom.
X 2 is an oxygen atom, a sulfur atom, or C (CH 3 ) 2 . )
The organic electroluminescence device according to claim 13, wherein the compound represented by the formula (2) is represented by any one of the following formulas (2-5a) to (2-5f).

(In the formulas (2-5a) to (2-5f),
E 1 and E 2 are each independently an oxygen atom, a sulfur atom or NR 5 ;
However, at least one of E 1 and E 2 is an oxygen atom or a sulfur atom,
G 51 to G 60 are each independently CR 6 or a nitrogen atom.
R 5 represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted ring carbon atom having 6 to 30 carbon atoms. An aromatic hydrocarbon ring group or a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 ring atoms,
R 6 represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 ring carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms. Group, substituted or unsubstituted cycloalkoxy group having 3 to 20 ring carbon atoms, substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 ring carbon atoms, substituted or unsubstituted ring carbon atoms having 6 to 18 carbon atoms An aryloxy group, a substituted or unsubstituted heteroaromatic ring group having 5 to 18 ring atoms, a substituted or unsubstituted silyl group, a fluorine atom, a substituted or unsubstituted fluoroalkyl group having 1 to 20 carbon atoms, A substituted or unsubstituted C1-C20 fluoroalkoxy group or cyano group.
When a plurality of NR 5 are present, the plurality of R 5 may be the same or different from each other.
When a plurality of CR 6 are present, the plurality of R 6 may be the same or different from each other.
When R 5 and R 6 have a substituent, the substituent R ′ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 ring carbon atoms, or an alkoxy having 1 to 20 carbon atoms. Group, a cycloalkoxy group having 3 to 20 ring carbon atoms, an aromatic hydrocarbon ring group having 6 to 18 ring carbon atoms, an aryloxy group having 6 to 18 ring carbon atoms, and a hetero ring having 5 to 18 ring atoms. An aromatic ring group, a silyl group, a fluorine atom, a fluoroalkyl group having 1 to 20 carbon atoms, a fluoroalkoxy group having 1 to 20 carbon atoms, or a cyano group. )
The organic electroluminescence device according to any one of claims 1 to 16, further comprising an electron blocking layer adjacent to the first light emitting layer.
The organic electroluminescence device according to any one of claims 1 to 17, further comprising a hole blocking layer adjacent to the second light emitting layer.
The organic electroluminescence device according to any one of claims 1 to 18, wherein the first light emitting layer further contains a hole transporting material.
21. The organic electroluminescence device according to claim 1, further comprising one or both of a hole injection layer and a hole transport layer between the anode and the first light emitting layer.
The organic electroluminescent device according to any one of claims 1 to 20, wherein the first or second tandem type light emitting device in which a first light emitting unit and a second light emitting unit are laminated via an intermediate electrode. A white light emitting device used as a light emitting unit.
The white light-emitting element according to claim 21, which is a flat light emitter of a flat panel display, a backlight of a copying machine, a printer or a liquid crystal display, a light source of an instrument, a display board, a marker lamp or a lighting device.