JP5342890B2 - Organic electroluminescence device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescence element emitting narrow-band light high in color purity, and having long life. <P>SOLUTION: This organic electroluminescence element includes: a positive electrode; a first luminescent layer comprising at least a first host material and a first dopant; a second luminescent layer comprising at least a second host material and a second dopant; and a negative electrode in the order: and is characterized in that the energy gap E<SB>gh</SB>1 of the first host material, the energy gap E<SB>gd</SB>1 of the first dopant, the energy gap E<SB>gh</SB>2 of the second host material, and the energy gap E<SB>gd</SB>2 of the second dopant satisfy the following inequalities: E<SB>gh</SB>1&gt;E<SB>gd</SB>1, E<SB>gh</SB>2&gt;E<SB>gd</SB>2 and E<SB>gd</SB>1&gt;E<SB>gd</SB>2&gt;2.7 eV. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an organic electroluminescence device, and more particularly to an organic electroluminescence device having a light emitting layer having a two-layer structure.

An electroluminescent element utilizing electroluminescence (hereinafter, electroluminescence is abbreviated as “EL”) has high visibility due to self-emission and is a completely solid element, and thus has features such as excellent impact resistance. Since it has, utilization as a light emitting element in various display apparatuses attracts attention.
This EL element includes an inorganic EL element using an inorganic compound as a light emitting material and an organic EL element using an organic compound, and among these, the organic EL element can reduce the applied voltage significantly. In addition, since full colorization is easy, power consumption is small, and surface emission is possible, it has been developed as a next-generation light-emitting element.

The configuration of the organic EL element is basically the configuration of the anode / light emitting layer / cathode as shown in FIG.
The organic EL element 10 has a light emitting layer 14 sandwiched between a pair of electrodes composed of an anode 12 and a cathode 13. The light emitting layer 14 is usually a laminate of a plurality of layers. In the element 10, when an electric field is applied between both electrodes 12 and 13, electrons are injected from the cathode 13 side and holes are injected from the anode 12 side. Then, electrons and holes recombine in the light emitting layer 14 to generate an excited state, and energy is released as light when the excited state returns to the ground state.
FIG. 4 shows an energy diagram of the organic EL element of FIG. In FIG. 4, a valence electron level EV0 (HOMO) and a conduction level EC0 (LUMO), which are energy levels of the light emitting layer 14, are shown. Holes enter from the anode 12 side, electrons enter from the cathode 13 side, and these holes and electrons combine in the light emitting layer 14 to emit light.

Based on the above-mentioned configuration, which is appropriately provided with a hole injection / transport layer and an electron injection layer, for example, anode / hole injection / transport layer / light emitting layer / cathode, anode / hole injection / transport layer A structure of / light emitting layer / electron injection layer / cathode is known.
Here, the light emitting layer has the following functions.
(i) Injection function; function that can inject holes from the anode or hole injection layer when an electric field is applied, and can inject electrons from the cathode or electron injection layer
(ii) Transport function: Function to move injected charges (electrons and holes) by the force of electric field
(iii) Luminescent function: A function that provides a field for recombination of electrons and holes and connects it to light emission

  The hole injection / transport layer has a function of injecting holes from the anode and transporting them to the organic light-emitting layer, and may be prepared separately from the hole injection layer / hole transport layer. . The electron injection layer has a function of injecting electrons from the cathode and transporting them to the organic light emitting layer.

A technique for adding a small amount of a fluorescent molecule (dopant) in order to make the light emission in the light emitting layer stronger is known.
FIG. 5 shows an energy diagram of an organic EL device to which a dopant is added. In this figure, ECh is the host conduction level, EVh is the host valence level, ECd is the dopant conduction level, and EVd is the dopant valence level. Egh represents the host energy gap (difference between ECh and EVh), and Egd represents the dopant energy gap (difference between ECd and EVd).
The dopant efficiently receives the energy of the excited host and increases the light emission efficiency.

As a method for multi-coloring the light emission of the organic EL element, there are roughly the following three methods.
(1) A method of extracting white light emitted from an organic EL element by separating it into three colors using three kinds of color filters of red, green and blue
(2) A method of converting blue light emitted from a blue EL element into multiple colors by converting the color of blue light by a fluorescent layer provided on the light extraction side of the light emitting layer.
(3) Methods for Multicoloring Blue, Red, and Green Light-Emitting Layers on the Same Substrate In these methods, high-brightness and long-life organic EL elements are required. For example, in the methods (1) and (2), an organic EL element that emits blue-green or white broadband (broad spectrum) light emission, an organic material having a half-life of tens of thousands of hours or more for an initial luminance of several hundred nits. EL elements are eagerly desired.

In response to such a demand, various element configurations have been studied.
As one of the methods, a method of obtaining white or broadband light emission by multilayering an organic light emitting layer has been proposed as follows.
(a) The organic light emitting layer has a two-layer structure, the first light emitting layer on the anode side is a blue light emitting layer made of an aluminum complex compound, and the second light emitting layer on the cathode side is an aluminum complex compound containing a red fluorescent substance. A method of extracting white light as a red light emitting layer made of (for example, see Patent Document 1).
(b) The organic light-emitting layer has a two-layer structure, the first light-emitting layer on the anode side is a blue light-emitting layer made of a distyrylarylene compound, and the second light-emitting layer on the cathode side is red on an aluminum complex compound that emits green light. A method of extracting white light as a light emitting layer to which a fluorescent material is added (for example, see Patent Document 2).
(c) A light emitting layer composed of a mixed layer of an electron transporting compound composed of an aluminum complex and a hole transporting compound composed of a diamine compound contains coumarin and rubrene as dopants, and has a green component and an orange component. Method for obtaining light emission (for example, see Patent Document 3)
(d) A method of forming two light emitting layers by doping a host material made of a distyrylarylene compound with two or more kinds of fluorescent substances having different color systems (see, for example, Patent Document 4).

These prior arts are methods for obtaining broadband light emission or white light by emitting a plurality of types of dopants equally, and light emitted from the organic EL element is a mixture of various wavelengths.
However, an organic EL element having a multilayer structure having a long lifetime with narrow band (narrow spectrum) emission with high color purity is not known.

EP 0 644 549 US Pat. No. 5,503,910 International Publication No. 98/08360 Pamphlet JP-A-12-68057

  In view of the above problems, an object of the present invention is to provide an organic EL element that emits narrow band light with high color purity and has a long lifetime.

  In order to solve this problem, the present inventor, in an organic EL device having at least two light emitting layers, suppresses light emission of the second light emitting layer or when the two light emitting layers satisfy a certain relationship. The inventors have found that the color purity and / or the life of the device can be improved, and have completed the present invention.

According to the first aspect of the present invention, an anode, a first light-emitting layer composed of at least a first host material and a first dopant, a second light-emitting layer composed of at least a second host material and a second dopant, and a cathode In this order, the energy gap E _gh 1 of the first host material, the energy gap E _gd 1 of the first dopant, the energy gap E _gh 2 of the second host material, and the energy gap E _gd 2 of the second dopant are The emission intensity I1 of the emission maximum wavelength of the emission spectrum derived from the first emission layer and the emission intensity I2 of the emission maximum wavelength of the emission spectrum derived from the second emission layer satisfy the following expressions. An organic electroluminescent device is provided.
E _gh 1> E _gd 1
E _gh 2> E _gd 2
E _gd 1> E _gd 2
I1> 3.5 × I2

According to the second aspect of the present invention, an anode, a first light-emitting layer composed of at least a first host material and a first dopant, a second light-emitting layer composed of at least a second host material and a second dopant, and a cathode In this order, the energy gap E _gh 1 of the first host material, the energy gap E _gd 1 of the first dopant, the energy gap E _gh 2 of the second host material, and the energy gap E _gd 2 of the second dopant are An organic electroluminescent device characterized by satisfying the formula is provided.
E _gh 1> E _gd 1
E _gh 2> E _gd 2
E _gd 1> E _gd 2> 2.7 eV

  According to the present invention, it is possible to provide an organic EL element that emits narrow band light with high color purity and has a long lifetime.

It is a schematic sectional drawing of the organic EL element of this invention. It is an energy diagram of the organic EL element of this invention. It is a schematic sectional drawing of a common organic EL element. It is an energy diagram of an organic EL element. It is an energy diagram of the organic EL element to which the dopant was added.

Hereinafter, the present invention will be described in detail.
The first organic EL device of the present invention includes an anode, a first light emitting layer composed of at least a first host material and a first dopant, a second light emitting layer composed of at least a second host material and a second dopant, and a cathode. In this order, the energy gap E _gh 1 of the first host material, the energy gap E _gd 1 of the first dopant, the energy gap E _gh 2 of the second host material, and the energy gap E _gd 2 of the second dopant are The emission intensity I1 of the emission maximum wavelength of the emission spectrum derived from the first emission layer and the emission intensity I2 of the emission maximum wavelength of the emission spectrum derived from the second emission layer satisfy the following expression.
E _gh 1> E _gd 1
E _gh 2> E _gd 2
E _gd 1> E _gd 2
I1> 3.5 × I2

FIG. 1 is a schematic cross-sectional view of the organic EL device of the present invention.
The organic EL element 1 has at least an anode 2, a first light emitting layer 3, a second light emitting layer 4, and a cathode 5, which are stacked in this order.
FIG. 2 is an energy diagram of the organic EL element 1.
In this energy diagram, energy levels of the anode 2, the first light emitting layer 3, the second light emitting layer 4 and the cathode 5 are shown. The energy gap E _gh 1 of the first host material, the energy gap E _gd 1 of the first dopant, the energy gap E _gh 2 of the second host material, and the energy gap E _gd 2 of the second dopant are shown.
Here, the energy gap corresponds to the energy difference between the valence level and the conduction level of the organic EL material, and is usually obtained from the absorption edge in the light absorption spectrum of the material.

As shown in FIG. 2, in the present invention, the first dopant and the second dopant are doped in different light emitting layers 3 and 4, respectively, and the light emitting layer has a two-layer structure, thereby including a dopant having a large energy gap. One light emitting layer 3 is mainly configured to emit light.
Usually, when two kinds of dopants are contained in one light emitting layer, energy transfer is likely to occur because the distance between the dopants is short, and the two kinds of dopants each emit light or have a smaller energy gap. Usually, only the dopant emits light. It is extremely difficult to emit only a dopant having a large energy gap.

However, if only the light emitting layer has a two-layer structure, the first light emitting layer 3 and the second light emitting layer 4 both emit light, as can be seen from the prior art example, so that narrow band light emission with high color purity cannot be obtained. .
One of the causes is the problem of the position where the recombination of holes and electrons occurs. The concentration of holes injected into the light emitting layer decreases as they proceed to the cathode 5 due to recombination with electrons, but some of them are considered to have reached the vicinity of the cathode 5. For this reason, a recombination region also exists in the vicinity of the cathode 5 side, and the first light emitting layer 3 (the light emitting layer on the anode 2 side) and the second light emitting layer 4 (the light emitting layer on the cathode 5 side) both emit light. It has become.

  Therefore, in the present invention, as a method for suppressing light emission of the light emitting layer containing a dopant having a small energy gap, which is a cause of lowering the color purity, the first light emitting layer 3 is provided on the anode 2 side having a high recombination probability, The second light emitting layer 4 is provided on the cathode 5 side having a low recombination probability. Thereby, the 1st light emitting layer 3 can mainly be light-emitted, and the light emission of the 2nd light emitting layer 4 can be made small enough.

Furthermore, in the present invention, an electron injection layer is provided between the second light-emitting layer 4 and the cathode 5, and electrons in the electric field region having an electric field strength (E) of 1 × 10 ⁵ to 10 ⁶ V / cm. The mobility is preferably 10 ⁻⁴ cm ² / (V · sec) or more.
By providing the electron injection layer having such electron mobility, the light emitting region can be set in the first light emitting layer 3 more stably. Accordingly, since the first light emitting layer 3 can emit light more selectively, narrow band light emission with better color purity can be obtained and the lifetime can be significantly extended.

As a method for measuring electron mobility, there is a Time of flight method (a method of calculating from the travel time of charges in an organic film), a method of calculating from a voltage characteristic of a space-limited current, etc. [Electronic Process in See Organic Crystals (M. Pope, CE Schwenberg), Organic Molecular Solids (W. Jones)].
In this specification, it is calculated by the Time of flight method. Specifically, the time characteristic (transient characteristic time) of the transient current generated by light irradiation was measured for the ITO / organic layer (electron injection layer, etc.) / Al structure, and the electron mobility was calculated by the following equation. Calculated.
Electron mobility = (organic layer thickness) ² / (transient characteristic time / electric field strength)

  In general, a material with a large energy gap has fewer materials with a long half-life compared to a material with a small energy gap, and it is difficult to select a material. By adopting this configuration, the second light-emitting layer contributes almost to light emission. Nevertheless, the lifetime of the organic EL element can be extended.

In this organic EL element 1, the energy gap (E _gh 1) of the first host material is larger than the energy gap E _gd 1 of the first dopant. That is, the relationship of E _gh 1> E _gd 1 is satisfied.
The energy gap E _gd 1 of the first dopant is preferably larger than 2.7 eV. In general, many dopants having a large energy gap have a shorter half-life of the organic EL device than small dopants. Therefore, it is difficult to extend the lifetime of a pure blue organic EL element used in full color. However, the present invention can obtain pure blue emission with an extremely long lifetime by adopting the above-described configuration.

The second light emitting layer contains at least a second host material and a second dopant.
The energy gap E _gh 2 of the second host material is larger than the energy gap E _gd 2 of the second dopant. That is, the relationship of E _gh 2> E _gd 2 is satisfied.

The energy gap E _gd 1 of the first dopant is larger than the energy gap E _gd 2 of the second dopant, that is, the relationship of E _gd 1> E _gd 2 is satisfied.
The energy gap E _gd 2 of the second dopant is preferably larger than 2.7 eV, that is, the relationship of E _gd 2> 2.7 eV is satisfied. Thereby, the organic EL element of blue light emission with high color purity for full colors can be produced.

In this organic EL element, the emission intensity I1 of the emission maximum wavelength of the emission spectrum of light originating from the first emission layer and the emission intensity I2 of the emission maximum wavelength of the emission spectrum of light originating from the second emission layer are I1> Satisfies the relationship of 3.5 × I2. By satisfying this relationship, narrow band light emission with good color purity can be obtained. Preferably I1> 5 × I2, more preferably I1> 10 × I2. Particularly preferably, the emission intensity I2 from the second light emitting layer is zero.
Thus, even when the light emission of the second light emitting layer hardly contributes to the light emission of the entire organic EL element, the life of the organic EL element can be extended.
In general, the smaller the energy gap, the longer the material, and the easier it is to select the material. Accordingly, it has been relatively easy to find a long-life element configuration for EL elements for broadband light emission and white light emission.
However, for narrow band light emission, particularly blue light emission, it is difficult to select a material system having a long lifetime, and there have been few reports on pure blue light emitting materials particularly suitable for full-color applications. The present invention is a technique for extending the lifetime of a known pure blue light emitting material. That is, this is a technique for prolonging the lifetime of an EL element by using a material known to have a long lifetime and using it adjacent to the light emitting layer and limiting light emission therefrom as much as possible.

The second organic EL device of the present invention includes an anode, a first light emitting layer composed of at least a first host material and a first dopant, a second light emitting layer composed of at least a second host material and a second dopant, and a cathode. In this order, the energy gap E _gh 1 of the first host material, the energy gap E _gd 1 of the first dopant, the energy gap E _gh 2 of the second host material, and the energy gap E _gd 2 of the second dopant are Satisfy the formula.
E _gh 1> E _gd 1
E _gh 2> E _gd 2
E _gd 1> E _gd 2> 2.7 eV
That is, the basic configuration is the same as that of the organic EL element described above.

This organic EL element satisfies the relationship of E _gd 1> E _gd 2> 2.7 eV. In order to satisfy this relationship, unlike the organic EL element described above, even if both the first light emitting layer and the second light emitting layer emit light, both emit blue light, and thus it is possible to obtain blue light emission with high color purity. is there.
In addition, by adopting such an element configuration, the lifetime of the organic EL element can be extended as in the first invention.

［式中、Ａｒ^１は核炭素数６〜５０の芳香族環であり、Ｘは置換基である。
ｍは１〜５の整数、ｎは０〜６の整数である。ｍ≧２の時、Ａｒ^１はそれぞれ同じでも異なっていても良い。ｎ≧２の時、Ｘはそれぞれ同じでも異なっていても良い。］ As the host material used for the first light-emitting layer and the second light-emitting layer, known materials can be used as long-lived light-emitting materials, but the material represented by the general formula [1] is used as the host material of the light-emitting material. It is preferable to use as.

[In the formula, Ar ¹ is an aromatic ring having 6 to 50 nuclear carbon atoms, and X is a substituent.
m is an integer of 1 to 5, and n is an integer of 0 to 6. When m ≧ 2, Ar ¹ may be the same or different. When n ≧ 2, X may be the same or different. ]

Specific examples of Ar ¹ include phenyl ring, naphthyl ring, anthracene ring, biphenylene ring, azulene ring, acenaphthylene ring, fluorene ring, phenanthrene ring, fluoranthene ring, acephenanthrylene ring, triphenylene ring, pyrene ring, chrysene ring, A naphthacene ring, a picene ring, a perylene ring, a pentaphen ring, a pentacene ring, a tetraphenylene ring, a hexaphen ring, a hexacene ring, a rubicene ring, a coronene ring, a trinaphthylene ring, and the like can be given.
Preferred examples include phenyl ring, naphthyl ring, anthracene ring, acenaphthylene ring, fluorene ring, phenanthrene ring, fluoranthene ring, triphenylene ring, pyrene ring, chrysene ring, perylene ring, trinaphthylene ring and the like.
More preferable examples include a phenyl ring, a naphthyl ring, an anthracene ring, a fluorene ring, a phenanthrene ring, a fluoranthene ring, a pyrene ring, a chrysene ring, and a perylene ring.

  Specific examples of X include a substituted or unsubstituted aromatic group having 6 to 50 nuclear carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 5 to 50 nuclear atoms, a substituted or unsubstituted carbon number. An alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 50 carbon atoms, a substituted or unsubstituted aralkyl group having 1 to 50 carbon atoms, and a substituted or unsubstituted aryloxy group having 5 to 50 nucleus atoms. Substituted or unsubstituted arylthio groups having 5 to 50 nucleus atoms, substituted or unsubstituted carboxyl groups having 1 to 50 carbon atoms, substituted or unsubstituted styryl groups, halogen groups, cyano groups, nitro groups, hydroxyl groups, etc. It is.

  Examples of the substituted or unsubstituted aromatic group having 6 to 50 nuclear carbon atoms include phenyl group, 1-naphthyl group, 2-naphthyl group, 1-anthryl group, 2-anthryl group, 9-anthryl group, 1- Phenanthryl group, 2-phenanthryl group, 3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group, 1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group, 1-pyrenyl group, 2-pyrenyl group, 4- Pyrenyl group, 2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group, p-terphenyl-4-yl group, p-terphenyl-3-yl group, p-terphenyl-2-yl group M-terphenyl-4-yl group, m-terphenyl-3-yl group, m-terphenyl-2-yl group, o-tolyl group, m-tolyl group, p-tolyl group, p t-butylphenyl group, p- (2-phenylpropyl) phenyl group, 3-methyl-2-naphthyl group, 4-methyl-1-naphthyl group, 4-methyl-1-anthryl group, 4′-methylbiphenylyl Group, 4 "-t-butyl-p-terphenyl-4-yl group, 2-fluorenyl group, 9,9-dimethyl-2-fluorenyl group, 3-fluoranthenyl group and the like.

  Preferably, phenyl group, 1-naphthyl group, 2-naphthyl group, 9-phenanthryl group, 1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group, 1-pyrenyl group, 2-pyrenyl group, 4-pyrenyl group 2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group, o-tolyl group, m-tolyl group, p-tolyl group, pt-butylphenyl group, 2-fluorenyl group, 9,9 -A dimethyl- 2-fluorenyl group, 3-fluoranthenyl group, etc. are mentioned.

  Examples of the substituted or unsubstituted aromatic heterocyclic group having 5 to 50 nuclear atoms include 1-pyrrolyl group, 2-pyrrolyl group, 3-pyrrolyl group, pyrazinyl group, 2-pyridinyl group, 3-pyridinyl group, 4-pyridinyl group, 1-indolyl group, 2-indolyl group, 3-indolyl group, 4-indolyl group, 5-indolyl group, 6-indolyl group, 7-indolyl group, 1-isoindolyl group, 2-isoindolyl group, 3-isoindolyl group, 4-isoindolyl group, 5-isoindolyl group, 6-isoindolyl group, 7-isoindolyl group, 2-furyl group, 3-furyl group, 2-benzofuranyl group, 3-benzofuranyl group, 4-benzofuranyl group, 5-benzofuranyl group, 6-benzofuranyl group, 7-benzofuranyl group, 1-isobenzofuranyl group, 3-isobenzofuran group Group, 4-isobenzofuranyl group, 5-isobenzofuranyl group, 6-isobenzofuranyl group, 7-isobenzofuranyl group, quinolyl group, 3-quinolyl group, 4-quinolyl group, 5- Quinolyl group, 6-quinolyl group, 7-quinolyl group, 8-quinolyl group, 1-isoquinolyl group, 3-isoquinolyl group, 4-isoquinolyl group, 5-isoquinolyl group, 6-isoquinolyl group, 7-isoquinolyl group, 8- Isoquinolyl group, 2-quinoxalinyl group, 5-quinoxalinyl group, 6-quinoxalinyl group, 1-carbazolyl group, 2-carbazolyl group, 3-carbazolyl group, 4-carbazolyl group, 9-carbazolyl group, 1-phenanthridinyl group 2-phenanthridinyl group, 3-phenanthridinyl group, 4-phenanthridinyl group, 6-phenanthridinyl group, 7-phena Thridinyl group, 8-phenanthridinyl group, 9-phenanthridinyl group, 10-phenanthridinyl group, 1-acridinyl group, 2-acridinyl group, 3-acridinyl group, 4-acridinyl group, 9-acridinyl group Group, 1,7-phenanthrolin-2-yl group, 1,7-phenanthrolin-3-yl group, 1,7-phenanthrolin-4-yl group, 1,7-phenanthrolin-5 -Yl group, 1,7-phenanthrolin-6-yl group, 1,7-phenanthrolin-8-yl group, 1,7-phenanthrolin-9-yl group, 1,7-phenanthroline -10-yl group, 1,8-phenanthrolin-2-yl group, 1,8-phenanthrolin-3-yl group, 1,8-phenanthrolin-4-yl group, 1,8-phen group Nansulolin-5-yl group, 1,8-phena Nsulolin-6-yl group, 1,8-phenanthrolin-7-yl group, 1,8-phenanthrolin-9-yl group, 1,8-phenanthrolin-10-yl group, 1,9- Phenanthrolin-2-yl group, 1,9-phenanthrolin-3-yl group, 1,9-phenanthrolin-4-yl group, 1,9-phenanthrolin-5-yl group, 1, 9-phenanthroline-6-yl group, 1,9-phenanthrolin-7-yl group, 1,9-phenanthrolin-8-yl group, 1,9-phenanthrolin-10-yl group, 1,10-phenanthrolin-2-yl group, 1,10-phenanthrolin-3-yl group, 1,10-phenanthrolin-4-yl group, 1,10-phenanthrolin-5-yl Group, 2,9-phenanthrolin-1-yl group, 2,9-phenanthroli -3-yl group, 2,9-phenanthrolin-4-yl group, 2,9-phenanthrolin-5-yl group, 2,9-phenanthrolin-6-yl group, 2,9-phen group Nansulolin-7-yl group, 2,9-phenanthrolin-8-yl group, 2,9-phenanthrolin-10-yl group, 2,8-phenanthrolin-1-yl group, 2,8 -Phenanthrolin-3-yl group, 2,8-phenanthrolin-4-yl group, 2,8-phenanthrolin-5-yl group, 2,8-phenanthrolin-6-yl group, 2 , 8-phenanthroline-7-yl group, 2,8-phenanthrolin-9-yl group, 2,8-phenanthrolin-10-yl group, 2,7-phenanthrolin-1-yl group 2,7-phenanthrolin-3-yl group, 2,7-phenanthrolin-4-yl group, , 7-phenanthroline-5-yl group, 2,7-phenanthrolin-6-yl group, 2,7-phenanthrolin-8-yl group, 2,7-phenanthrolin-9-yl group 2,7-phenanthrolin-10-yl group, 1-phenazinyl group, 2-phenazinyl group, 1-phenothiazinyl group, 2-phenothiazinyl group, 3-phenothiazinyl group, 4-phenothiazinyl group, 10- Phenothiazinyl group, 1-phenoxazinyl group, 2-phenoxazinyl group, 3-phenoxazinyl group, 4-phenoxazinyl group, 10-phenoxazinyl group, 2-oxazolyl group, 4-oxazolyl group, 5-oxazolyl group, 2-oxadiazolyl group, 5 -Oxadiazolyl group, 3-furazanyl group, 2-thienyl group, 3-thienyl group, 2-methylpyrrol-1-yl group, 2 -Methylpyrrol-3-yl group, 2-methylpyrrol-4-yl group, 2-methylpyrrol-5-yl group, 3-methylpyrrol-1-yl group, 3-methylpyrrol-2-yl group, 3 -Methylpyrrol-4-yl group, 3-methylpyrrol-5-yl group, 2-t-butylpyrrol-4-yl group, 3- (2-phenylpropyl) pyrrol-1-yl group, 2-methyl- 1-indolyl group, 4-methyl-1-indolyl group, 2-methyl-3-indolyl group, 4-methyl-3-indolyl group, 2-t-butyl 1-indolyl group, 4-t-butyl 1-indolyl group Group, 2-t-butyl 3-indolyl group, 4-t-butyl 3-indolyl group and the like.

  Examples of the substituted or unsubstituted alkyl group having 1 to 50 carbon atoms 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 group, n-octyl group, hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 2-hydroxyisobutyl group, 1,2-dihydroxyethyl group, 1, 3-dihydroxyisopropyl group, 2,3-dihydroxy-t-butyl group, 1,2,3-trihydroxypropyl group, chloromethyl group, 1-chloroethyl group, 2-chloroethyl group, 2-chloroisobutyl group, 1, 2-dichloroethyl group, 1,3-dichloroisopropyl group, 2,3-dichloro-t-butyl group, 1,2,3-trichloropropyl group Bromomethyl group, 1-bromoethyl group, 2-bromoethyl group, 2-bromoisobutyl group, 1,2-dibromoethyl group, 1,3-dibromoisopropyl group, 2,3-dibromo-t-butyl group, 1,2, 3-tribromopropyl group, iodomethyl group, 1-iodoethyl group, 2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group, 1,3-diiodoisopropyl group, 2,3-diiodo-t- Butyl group, 1,2,3-triiodopropyl group, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group, 2-aminoisobutyl group, 1,2-diaminoethyl group, 1,3-diaminoisopropyl Group, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group, cyanomethyl group, 1-cyanoethyl group, 2-cyanoethyl 2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropyl group, 2,3-dicyano-t-butyl group, 1,2,3-tricyanopropyl group, nitromethyl group, 1- Nitroethyl group, 2-nitroethyl group, 2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropyl group, 2,3-dinitro-t-butyl group, 1,2,3-trinitropropyl Group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, 4-methylcyclohexyl group, 1-adamantyl group, 2-adamantyl group, 1-norbornyl group, 2-norbornyl group and the like.

  The substituted or unsubstituted alkoxy group having 1 to 50 carbon atoms is a group represented by -OY, and examples of Y include methyl, ethyl, propyl, isopropyl, n-butyl, and s-butyl. Group, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 2-hydroxyisobutyl Group, 1,2-dihydroxyethyl group, 1,3-dihydroxyisopropyl group, 2,3-dihydroxy-t-butyl group, 1,2,3-trihydroxypropyl group, chloromethyl group, 1-chloroethyl group, 2 -Chloroethyl group, 2-chloroisobutyl group, 1,2-dichloroethyl group, 1,3-dichloroisopropyl group, 2,3-dichloro-t-butyl group, , 2,3-trichloropropyl group, bromomethyl group, 1-bromoethyl group, 2-bromoethyl group, 2-bromoisobutyl group, 1,2-dibromoethyl group, 1,3-dibromoisopropyl group, 2,3-dibromo- t-butyl group, 1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group, 2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group, 1,3-diiodoisopropyl group 2,3-diiodo-t-butyl group, 1,2,3-triiodopropyl group, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group, 2-aminoisobutyl group, 1,2-diamino Ethyl group, 1,3-diaminoisopropyl group, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group, cyanomethyl group, 1- Anoethyl group, 2-cyanoethyl group, 2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropyl group, 2,3-dicyano-t-butyl group, 1,2,3-tricyanopropyl Group, nitromethyl group, 1-nitroethyl group, 2-nitroethyl group, 2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropyl group, 2,3-dinitro-t-butyl group, 1, Examples include 2,3-trinitropropyl group.

  Examples of the substituted or unsubstituted aralkyl group having 1 to 50 carbon atoms include benzyl group, 1-phenylethyl group, 2-phenylethyl group, 1-phenylisopropyl group, 2-phenylisopropyl group, and phenyl-t-butyl. Group, α-naphthylmethyl group, 1-α-naphthylethyl group, 2-α-naphthylethyl group, 1-α-naphthylisopropyl group, 2-α-naphthylisopropyl group, β-naphthylmethyl group, 1-β- Naphthylethyl group, 2-β-naphthylethyl group, 1-β-naphthylisopropyl group, 2-β-naphthylisopropyl group, 1-pyrrolylmethyl group, 2- (1-pyrrolyl) ethyl group, p-methylbenzyl group, m -Methylbenzyl group, o-methylbenzyl group, p-chlorobenzyl group, m-chlorobenzyl group, o-chlorobenzyl group, p-bromoben Group, m-bromobenzyl group, o-bromobenzyl group, p-iodobenzyl group, m-iodobenzyl group, o-iodobenzyl group, p-hydroxybenzyl group, m-hydroxybenzyl group, o-hydroxybenzyl group P-aminobenzyl group, m-aminobenzyl group, o-aminobenzyl group, p-nitrobenzyl group, m-nitrobenzyl group, o-nitrobenzyl group, p-cyanobenzyl group, m-cyanobenzyl group, o -Cyanobenzyl group, 1-hydroxy-2-phenylisopropyl group, 1-chloro-2-phenylisopropyl group and the like.

  A substituted or unsubstituted aryloxy group having 5 to 50 nuclear atoms is represented as —OY ′, and examples of Y ′ include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-anthryl group, and a 2-anthryl group. Group, 9-anthryl group, 1-phenanthryl group, 2-phenanthryl group, 3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group, 1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group, 1-pyrenyl Group, 2-pyrenyl group, 4-pyrenyl group, 2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group, p-terphenyl-4-yl group, p-terphenyl-3-yl group, p-terphenyl-2-yl group, m-terphenyl-4-yl group, m-terphenyl-3-yl group, m-terphenyl-2-yl group, o-tolyl group, -Tolyl group, p-tolyl group, pt-butylphenyl group, p- (2-phenylpropyl) phenyl group, 3-methyl-2-naphthyl group, 4-methyl-1-naphthyl group, 4-methyl- 1-anthryl group, 4′-methylbiphenylyl group, 4 ″ -t-butyl-p-terphenyl-4-yl group, 2-pyrrolyl group, 3-pyrrolyl group, pyrazinyl group, 2-pyridinyl group, 3- Pyridinyl group, 4-pyridinyl group, 2-indolyl group, 3-indolyl group, 4-indolyl group, 5-indolyl group, 6-indolyl group, 7-indolyl group, 1-isoindolyl group, 3-isoindolyl group, 4- Isoindolyl group, 5-isoindolyl group, 6-isoindolyl group, 7-isoindolyl group, 2-furyl group, 3-furyl group, 2-benzofuranyl group, 3-benzofuranyl group 4-benzofuranyl group, 5-benzofuranyl group, 6-benzofuranyl group, 7-benzofuranyl group, 1-isobenzofuranyl group, 3-isobenzofuranyl group, 4-isobenzofuranyl group, 5-isobenzofuranyl group Nyl group, 6-isobenzofuranyl group, 7-isobenzofuranyl group, 2-quinolyl group, 3-quinolyl group, 4-quinolyl group, 5-quinolyl group, 6-quinolyl group, 7-quinolyl group, 8 -Quinolyl group, 1-isoquinolyl group, 3-isoquinolyl group, 4-isoquinolyl group, 5-isoquinolyl group, 6-isoquinolyl group, 7-isoquinolyl group, 8-isoquinolyl group, 2-quinoxalinyl group, 5-quinoxalinyl group, 6 -Quinoxalinyl group, 1-carbazolyl group, 2-carbazolyl group, 3-carbazolyl group, 4-carbazolyl group, 1-phenanthridinyl Group, 2-phenanthridinyl group, 3-phenanthridinyl group, 4-phenanthridinyl group, 6-phenanthridinyl group, 7-phenanthridinyl group, 8-phenanthridinyl group, 9-phenanthridinyl group, 10-phenanthridinyl group, 1-acridinyl group, 2-acridinyl group, 3-acridinyl group, 4-acridinyl group, 9-acridinyl group, 1,7-phenanthroline-2 -Yl group, 1,7-phenanthrolin-3-yl group, 1,7-phenanthrolin-4-yl group, 1,7-phenanthrolin-5-yl group, 1,7-phenanthroline -6-yl group, 1,7-phenanthrolin-8-yl group, 1,7-phenanthrolin-9-yl group, 1,7-phenanthrolin-10-yl group, 1,8-phen group Nansulolin-2-yl group, 1,8- Phenanthrolin-3-yl group, 1,8-phenanthrolin-4-yl group, 1,8-phenanthrolin-5-yl group, 1,8-phenanthrolin-6-yl group, 1,8- Phenanthrolin-7-yl group, 1,8-phenanthroline-9-yl group, 1,8-phenanthrolin-10-yl group, 1,9-phenanthrolin-2-yl group, 1, 9-phenanthrolin-3-yl group, 1,9-phenanthrolin-4-yl group, 1,9-phenanthrolin-5-yl group, 1,9-phenanthrolin-6-yl group, 1,9-phenanthrolin-7-yl group, 1,9-phenanthrolin-8-yl group, 1,9-phenanthrolin-10-yl group, 1,10-phenanthrolin-2-yl Group, 1,10-phenanthrolin-3-yl group, 1,10-phenanth Rin-4-yl group, 1,10-phenanthrolin-5-yl group, 2,9-phenanthrolin-1-yl group, 2,9-phenanthrolin-3-yl group, 2,9- Phenanthrolin-4-yl group, 2,9-phenanthrolin-5-yl group, 2,9-phenanthrolin-6-yl group, 2,9-phenanthrolin-7-yl group, 2, 9-phenanthroline-8-yl group, 2,9-phenanthrolin-10-yl group, 2,8-phenanthrolin-1-yl group, 2,8-phenanthrolin-3-yl group, 2,8-phenanthrolin-4-yl group, 2,8-phenanthrolin-5-yl group, 2,8-phenanthrolin-6-yl group, 2,8-phenanthrolin-7-yl Group, 2,8-phenanthrolin-9-yl group, 2,8-phenanthrolin-10-yl Group, 2,7-phenanthrolin-1-yl group, 2,7-phenanthrolin-3-yl group, 2,7-phenanthrolin-4-yl group, 2,7-phenanthrolin-5 -Yl group, 2,7-phenanthroline-6-yl group, 2,7-phenanthrolin-8-yl group, 2,7-phenanthrolin-9-yl group, 2,7-phenanthroline -10-yl group, 1-phenazinyl group, 2-phenazinyl group, 1-phenothiazinyl group, 2-phenothiazinyl group, 3-phenothiazinyl group, 4-phenothiazinyl group, 1-phenoxazinyl group, 2-phenoxazinyl group, 3-phenoxazinyl group, 4-phenoxazinyl group, 2-oxazolyl group, 4-oxazolyl group, 5-oxazolyl group, 2-oxadiazolyl group, 5-oxadiazolyl group, 3-flazanyl group 2-thienyl group, 3-thienyl group, 2-methylpyrrol-1-yl group, 2-methylpyrrol-3-yl group, 2-methylpyrrol-4-yl group, 2-methylpyrrol-5-yl group, 3-methylpyrrol-1-yl group, 3-methylpyrrol-2-yl group, 3-methylpyrrol-4-yl group, 3-methylpyrrol-5-yl group, 2-t-butylpyrrol-4-yl Group, 3- (2-phenylpropyl) pyrrol-1-yl group, 2-methyl-1-indolyl group, 4-methyl-1-indolyl group, 2-methyl-3-indolyl group, 4-methyl-3- Indolyl group, 2-t-butyl 1-indolyl group, 4-t-butyl 1-indolyl group, 2-t-butyl 3-indolyl group, 4-t-butyl 3-indolyl group and the like can be mentioned.

  A substituted or unsubstituted arylthio group having 5 to 50 nucleus atoms is represented by —SY ″, and examples of Y ″ include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-anthryl group, and a 2-anthryl group. 9-anthryl group, 1-phenanthryl group, 2-phenanthryl group, 3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group, 1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group, 1-pyrenyl group 2-pyrenyl group, 4-pyrenyl group, 2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group, p-terphenyl-4-yl group, p-terphenyl-3-yl group, p -Terphenyl-2-yl group, m-terphenyl-4-yl group, m-terphenyl-3-yl group, m-terphenyl-2-yl group, o-tolyl group, m Tolyl group, p-tolyl group, pt-butylphenyl group, p- (2-phenylpropyl) phenyl group, 3-methyl-2-naphthyl group, 4-methyl-1-naphthyl group, 4-methyl-1 -Anthryl group, 4'-methylbiphenylyl group, 4 "-t-butyl-p-terphenyl-4-yl group, 2-pyrrolyl group, 3-pyrrolyl group, pyrazinyl group, 2-pyridinyl group, 3-pyridinyl Group, 4-pyridinyl group, 2-indolyl group, 3-indolyl group, 4-indolyl group, 5-indolyl group, 6-indolyl group, 7-indolyl group, 1-isoindolyl group, 3-isoindolyl group, 4-isoindolyl group Group, 5-isoindolyl group, 6-isoindolyl group, 7-isoindolyl group, 2-furyl group, 3-furyl group, 2-benzofuranyl group, 3-benzofuranyl group 4-benzofuranyl group, 5-benzofuranyl group, 6-benzofuranyl group, 7-benzofuranyl group, 1-isobenzofuranyl group, 3-isobenzofuranyl group, 4-isobenzofuranyl group, 5-isobenzofuranyl group Group, 6-isobenzofuranyl group, 7-isobenzofuranyl group, 2-quinolyl group, 3-quinolyl group, 4-quinolyl group, 5-quinolyl group, 6-quinolyl group, 7-quinolyl group, 8- Quinolyl group, 1-isoquinolyl group, 3-isoquinolyl group, 4-isoquinolyl group, 5-isoquinolyl group, 6-isoquinolyl group, 7-isoquinolyl group, 8-isoquinolyl group, 2-quinoxalinyl group, 5-quinoxalinyl group, 6- Quinoxalinyl group, 1-carbazolyl group, 2-carbazolyl group, 3-carbazolyl group, 4-carbazolyl group, 1-phenanthridinyl group 2-phenanthridinyl group, 3-phenanthridinyl group, 4-phenanthridinyl group, 6-phenanthridinyl group, 7-phenanthridinyl group, 8-phenanthridinyl group, 9 -Phenanthridinyl group, 10-phenanthridinyl group, 1-acridinyl group, 2-acridinyl group, 3-acridinyl group, 4-acridinyl group, 9-acridinyl group, 1,7-phenanthroline-2- Yl group, 1,7-phenanthrolin-3-yl group, 1,7-phenanthrolin-4-yl group, 1,7-phenanthrolin-5-yl group, 1,7-phenanthrolin- 6-yl group, 1,7-phenanthroline-8-yl group, 1,7-phenanthrolin-9-yl group, 1,7-phenanthrolin-10-yl group, 1,8-phenance Lorin-2-yl group, 1,8-Fu Nansulolin-3-yl group, 1,8-phenanthrolin-4-yl group, 1,8-phenanthrolin-5-yl group, 1,8-phenanthrolin-6-yl group, 1,8- Phenanthrolin-7-yl group, 1,8-phenanthroline-9-yl group, 1,8-phenanthrolin-10-yl group, 1,9-phenanthrolin-2-yl group, 1, 9-phenanthrolin-3-yl group, 1,9-phenanthrolin-4-yl group, 1,9-phenanthrolin-5-yl group, 1,9-phenanthrolin-6-yl group, 1,9-phenanthrolin-7-yl group, 1,9-phenanthrolin-8-yl group, 1,9-phenanthrolin-10-yl group, 1,10-phenanthrolin-2-yl Group, 1,10-phenanthrolin-3-yl group, 1,10-phenanthro N-4-yl group, 1,10-phenanthrolin-5-yl group, 2,9-phenanthrolin-1-yl group, 2,9-phenanthrolin-3-yl group, 2,9- Phenanthrolin-4-yl group, 2,9-phenanthrolin-5-yl group, 2,9-phenanthrolin-6-yl group, 2,9-phenanthrolin-7-yl group, 2, 9-phenanthroline-8-yl group, 2,9-phenanthrolin-10-yl group, 2,8-phenanthrolin-1-yl group, 2,8-phenanthrolin-3-yl group, 2,8-phenanthrolin-4-yl group, 2,8-phenanthrolin-5-yl group, 2,8-phenanthrolin-6-yl group, 2,8-phenanthrolin-7-yl Group, 2,8-phenanthrolin-9-yl group, 2,8-phenanthrolin-10-yl group 2,7-phenanthrolin-1-yl group, 2,7-phenanthrolin-3-yl group, 2,7-phenanthrolin-4-yl group, 2,7-phenanthrolin-5- Yl group, 2,7-phenanthrolin-6-yl group, 2,7-phenanthrolin-8-yl group, 2,7-phenanthrolin-9-yl group, 2,7-phenanthrolin- 10-yl group, 1-phenazinyl group, 2-phenazinyl group, 1-phenothiazinyl group, 2-phenothiazinyl group, 3-phenothiazinyl group, 4-phenothiazinyl group, 1-phenoxazinyl group, 2-phenoxazinyl group, 3 -Phenoxazinyl group, 4-phenoxazinyl group, 2-oxazolyl group, 4-oxazolyl group, 5-oxazolyl group, 2-oxadiazolyl group, 5-oxadiazolyl group, 3-flazanyl group, -Thienyl group, 3-thienyl group, 2-methylpyrrol-1-yl group, 2-methylpyrrol-3-yl group, 2-methylpyrrol-4-yl group, 2-methylpyrrol-5-yl group, 3 -Methylpyrrol-1-yl group, 3-methylpyrrol-2-yl group, 3-methylpyrrol-4-yl group, 3-methylpyrrol-5-yl group, 2-t-butylpyrrol-4-yl group 3- (2-phenylpropyl) pyrrol-1-yl group, 2-methyl-1-indolyl group, 4-methyl-1-indolyl group, 2-methyl-3-indolyl group, 4-methyl-3-indolyl group Group, 2-t-butyl 1-indolyl group, 4-t-butyl 1-indolyl group, 2-t-butyl 3-indolyl group, 4-t-butyl 3-indolyl group and the like.

  A substituted or unsubstituted carboxyl group having 1 to 50 carbon atoms is represented as —COOZ, and examples of Z 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 group, n-octyl group, hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 2-hydroxyisobutyl group, 1,2 -Dihydroxyethyl group, 1,3-dihydroxyisopropyl group, 2,3-dihydroxy-t-butyl group, 1,2,3-trihydroxypropyl group, chloromethyl group, 1-chloroethyl group, 2-chloroethyl group, 2 -Chloroisobutyl group, 1,2-dichloroethyl group, 1,3-dichloroisopropyl group, 2,3-dichloro-t-butyl group, 1,2 3-trichloropropyl group, bromomethyl group, 1-bromoethyl group, 2-bromoethyl group, 2-bromoisobutyl group, 1,2-dibromoethyl group, 1,3-dibromoisopropyl group, 2,3-dibromo-t-butyl Group, 1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group, 2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group, 1,3-diiodoisopropyl group, 2, 3-diiodo-t-butyl group, 1,2,3-triiodopropyl group, aminomethyl group, 1-aminoethyl group, 2-aminoethyl group, 2-aminoisobutyl group, 1,2-diaminoethyl group, 1,3-diaminoisopropyl group, 2,3-diamino-t-butyl group, 1,2,3-triaminopropyl group, cyanomethyl group, 1-cyano Tyl group, 2-cyanoethyl group, 2-cyanoisobutyl group, 1,2-dicyanoethyl group, 1,3-dicyanoisopropyl group, 2,3-dicyano-t-butyl group, 1,2,3-tricyanopropyl Group, nitromethyl group, 1-nitroethyl group, 2-nitroethyl group, 2-nitroisobutyl group, 1,2-dinitroethyl group, 1,3-dinitroisopropyl group, 2,3-dinitro-t-butyl group, 1, Examples include 2,3-trinitropropyl group.

Examples of the substituted or unsubstituted styryl group include 2-phenyl-1-vinyl group, 2,2-diphenyl-1-vinyl group, 1,2,2-triphenyl-1-vinyl group, and the like.
Examples of the halogen group include fluorine, chlorine, bromine and iodine.

m is preferably 1 to 2, and n is preferably 0 to 4.
Specific examples of the compound of the general formula [1] are shown below.

  In the organic EL element of the present invention, the first host material and the second host material may be the same in order to simplify the vapor deposition.

  As the dopant used for the first light-emitting layer and the second light-emitting layer, known materials can be used as long-lived light-emitting materials, but the material represented by the general formula [2] is used as the dopant material of the light-emitting material. It is preferable to use it.

［式中、Ａｒ^２〜Ａｒ^４は置換又は無置換の核炭素数６〜５０の芳香族基、置換又は無置換のスチリル基である。ｐは１〜４の整数である。ｐ≧２の時、Ａｒ^３、Ａｒ^４はそれぞれ同じでも異なっていても良い。］

[Wherein Ar ^{2 to} Ar ⁴ are a substituted or unsubstituted aromatic group having 6 to 50 nuclear carbon atoms, or a substituted or unsubstituted styryl group. p is an integer of 1 to 4. When p ≧ 2, Ar ³ and Ar ⁴ may be the same or different. ]

  Examples of the substituted or unsubstituted aromatic group having 6 to 50 nuclear carbon atoms include phenyl group, 1-naphthyl group, 2-naphthyl group, 1-anthryl group, 2-anthryl group, 9-anthryl group, 1- Phenanthryl group, 2-phenanthryl group, 3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group, 1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group, 1-pyrenyl group, 2-pyrenyl group, 4- Pyrenyl group, 2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group, p-terphenyl-4-yl group, p-terphenyl-3-yl group, p-terphenyl-2-yl group M-terphenyl-4-yl group, m-terphenyl-3-yl group, m-terphenyl-2-yl group, o-tolyl group, m-tolyl group, p-tolyl group, p t-butylphenyl group, p- (2-phenylpropyl) phenyl group, 3-methyl-2-naphthyl group, 4-methyl-1-naphthyl group, 4-methyl-1-anthryl group, 4′-methylbiphenylyl Group, 4 "-t-butyl-p-terphenyl-4-yl group, 2-fluorenyl group, 9,9-dimethyl-2-fluorenyl group, 3-fluoranthenyl group and the like.

  Preferably, phenyl group, 1-naphthyl group, 2-naphthyl group, 9-phenanthryl group, 1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group, 1-pyrenyl group, 2-pyrenyl group, 4-pyrenyl group 2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group, o-tolyl group, m-tolyl group, p-tolyl group, pt-butylphenyl group, 2-fluorenyl group, 9,9 -A dimethyl- 2-fluorenyl group, 3-fluoranthenyl group, etc. are mentioned.

Examples of the substituted or unsubstituted styryl group include 2-phenyl-1-vinyl group, 2,2-diphenyl-1-vinyl group, 1,2,2-triphenyl-1-vinyl group, and the like.
Specific examples of the compound of the general formula [2] and examples of compounds suitable as other dopants are shown below. In the formulae, Me represents a methyl group, and Et represents an ethyl group.

The ratio of the first dopant to the first host material is preferably 0.1 to 10 mol%, particularly 1 to 10 mol%. If it is less than 0.1 mol%, sufficient light emission cannot be obtained, and if it exceeds 10 mol%, concentration quenching may occur and the light emission efficiency may be reduced.
Moreover, it is preferable that the ratio of the said 2nd dopant with respect to a 2nd host material is 0.1-10 mol%, especially 0.1-5 mol%.
The film thickness of the first light emitting layer is preferably 10 nm or more, particularly preferably 10 nm to 40 nm. If it is less than 10 nm, holes having a sufficient concentration reach the second light emitting layer, the second light emitting layer emits light more than necessary, and the color purity may be deteriorated. Therefore, the first light emitting layer can be thicker than the second light emitting layer.
The film thickness of the second light emitting layer is adjusted according to the first light emitting layer, but is preferably 10 nm to 40 nm, and particularly preferably 10 nm to 30 nm.

As a method for forming the light emitting layer, for example, a known method such as an evaporation method, a spin coating method, or an LB method can be applied. The light emitting layer is particularly preferably a molecular deposited film.
Here, the molecular deposition film is a thin film formed by deposition from a material compound in a gas phase state or a film formed by solidification from a material compound in a solution state or a liquid phase state. Can be classified from a thin film (accumulated film) formed by the LB method according to a difference in an agglomerated structure and a higher-order structure and a functional difference resulting therefrom.
Further, as disclosed in JP-A-57-51781, a binder such as a resin and a material compound are dissolved in a solvent to form a solution, and then this is thinned by a spin coating method or the like. In addition, a light emitting layer can be formed.

The configuration of the organic EL device of the present invention and the components other than the light emitting layer will be described below.
Unless the effects of the present invention are impaired, another organic layer or an inorganic layer is interposed between the first light emitting layer and the second light emitting layer, between the anode and the first light emitting layer, or between the second light emitting layer and the cathode. Can be made.
Examples of the structure of the organic EL device of the present invention include: i) Anode / first light emitting layer / second light emitting layer / cathode
ii) Anode / hole injection layer / first light emitting layer / second light emitting layer / cathode
iii) Anode / first light emitting layer / second light emitting layer / electron injection layer / cathode
iv) Anode / hole injection layer / first emission layer / second emission layer / electron injection layer / cathode
iv) Anode / organic semiconductor layer / first light emitting layer / second light emitting layer / cathode
vi) Anode / organic semiconductor layer / electron barrier layer / first light emitting layer / second light emitting layer / cathode
vii) Anode / organic semiconductor layer / first light emitting layer / second light emitting layer / adhesion improving layer / cathode
viii) Anode / hole injection layer / hole transport layer / first light emitting layer / second light emitting layer
/ Electron injection layer / Cathode
ix) Anode / insulating layer / first light emitting layer / second light emitting layer / insulating layer / cathode
x) Anode / inorganic semiconductor layer / insulating layer / first light emitting layer / second light emitting layer / insulating layer
/cathode
xi) Anode / organic semiconductor layer / insulating layer / first light emitting layer / second light emitting layer / insulating layer
/cathode
xii) Anode / insulating layer / hole injection layer / hole transport layer / first light emitting layer / second light emitting layer
/ Insulating layer / Cathode
xiii) Anode / insulating layer / hole injection layer / hole transport layer / first light emitting layer / second light emitting layer
The structure may be / electron injection layer / cathode.
Of these, the structure of viii) is preferably used.

(1) Translucent substrate The organic EL element of this invention is produced on a translucent board | substrate. The translucent substrate referred to here is a substrate that supports the organic EL element, and is preferably a smooth substrate having a light transmittance in the visible region of 400 to 700 nm of 50% or more.
Specifically, a glass plate, a polymer plate, etc. are mentioned. 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 sulfide, and polysulfone.

(2) Anode The anode of the organic thin film EL element plays a role of injecting holes into the hole transport layer or the light emitting layer, and it is effective to have a work function of 4.5 eV or more. Specific examples of the anode material used in the present invention include indium tin oxide alloy (ITO), tin oxide (NESA), gold, silver, platinum, copper, and the like. The cathode is preferably a material having a low work function for the purpose of injecting electrons into the electron transport layer or the light emitting layer.
The anode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering.
Thus, when light emission from the light emitting layer is taken out from the anode, it is preferable that the transmittance of the anode for light emission is greater than 10%. The sheet resistance of the anode is preferably several hundred Ω / □ or less. Although the film thickness of the anode depends on the material, it is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm.

(3) Hole injection and transport layer The hole injection and transport layer is a layer that assists hole injection into the light emitting layer and transports it to the light emitting region, and has a high hole mobility and usually has an ionization energy of 5.5 eV. The following is small. Such a hole injection and transport layer is preferably a material that transports holes to the light emitting layer with a lower electric field strength, and the mobility of holes is, for example, when an electric field of 10 ⁴ to 10 ⁶ V / cm is applied. , At least 10 ⁻⁴ cm ² / V · sec is preferable.
The material for forming the hole injecting and transporting layer is not particularly limited as long as it has the above-mentioned preferable properties, and conventionally used as a charge transporting material for holes in an optical transmission material or organic EL. Any of known materials used for the hole injection layer of the device can be selected and used.

  Specific examples include, for example, triazole derivatives (see US Pat. No. 3,112,197), oxadiazole derivatives (see US Pat. No. 3,189,447, etc.), imidazole derivatives (Japanese Patent Publication No. 37-16096). Polyarylalkane derivatives (US Pat. Nos. 3,615,402, 3,820,989, 3,542,544, JP-B-45-555). 51-10983, JP-A-51-93224, 55-17105, 56-4148, 55-108667, 55-156953, 56-36656 Patent Publication etc.), pyrazoline derivatives and pyrazolone derivatives (US Pat. Nos. 3,180,729 and 4,278,746) JP-A-55-88064, JP-A-55-88065, JP-A-49-105537, JP-A-55-51086, JP-A-56-80051, JP-A-56-88141, JP-A-57-45545. , 54-1112637, 55-74546, etc.), phenylenediamine derivatives (US Pat. No. 3,615,404, JP-B 51-10105, 46-3712, 47-25336, JP-A 54-53435, 54-110536, 54-1119925, etc.), arylamine derivatives (US Pat. No. 3,567,450, ibid) 3,180,703, 3,240,597, 3,658,520, 4,232,10 No. 4,175,961, No. 4,012,376, JP-B-49-35702, JP-A-39-27577, JP-A-55-144250, 56-119132, 56-22437, West German Patent 1,110,518, etc.), amino-substituted chalcone derivatives (see US Pat. No. 3,526,501, etc.), oxazole Derivatives (disclosed in US Pat. No. 3,257,203, etc.), styryl anthracene derivatives (see JP-A-56-46234, etc.), fluorenone derivatives (see JP-A-54-110837, etc.) Hydrazone derivatives (US Pat. No. 3,717,462, JP-A-54-59143, 55-52063, 55-52064) Gazette, 55-46760, 55-85495, 57-11350, 57-148749, JP-A-2-311591, etc.), stilbene derivatives (JP-A-6210363) Publication No. 61-228451 Publication No. 61-14642 Publication No. 61-72255 Publication No. 62-47646 Publication No. 62-36684 Publication No. 62-10652 Publication No. 62-30255 No. 60-93455, No. 60-94462, No. 60-174749, No. 60-175052), silazane derivatives (US Pat. No. 4,950,950), Polysilane (JP-A-2-204996), aniline copolymer (JP-A-2-282263), JP-A-1- Conductive polymer oligomers disclosed in 11399 JP can (particularly thiophene oligomer).

  Although the above-mentioned materials can be used as the material for the hole injection layer, porphyrin compounds (disclosed in JP-A-63-295965), aromatic tertiary amine compounds and styrylamine compounds (US) Patent No. 4,127,412, JP-A-53-27033, 54-58445, 54-149634, 54-64299, 55-79450, 55 No. 144450, No. 56-119132, No. 61-295558, No. 61-98353, No. 63-295695, etc.), in particular, an aromatic tertiary amine compound is preferably used.

In addition, for example, 4,4′-bis (N- (1-naphthyl) -N-phenylamino having two condensed aromatic rings described in US Pat. No. 5,061,569 in the molecule. ) Biphenyl (hereinafter abbreviated as NPD), and 4,4 ′, 4 ″ -tris (N—) in which three triphenylamine units described in JP-A-4-308688 are linked in a starburst type. (3-methylphenyl) -N-phenylamino) triphenylamine (hereinafter abbreviated as MTDATA) and the like.
In addition to the above-described aromatic dimethylidin compounds shown as the material for the light emitting layer, inorganic compounds such as p-type Si and p-type SiC can also be used as the material for the hole injection layer.

The hole injection and transport layer can be formed by thinning the above-described compound by a known method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method. The thickness of the hole injection or transport layer is not particularly limited, but is usually 5 nm to 5 μm. As long as this hole injection and transport layer contains the compound of the present invention in the hole transport zone, it may be composed of one or more of the above materials, or the hole injection, A layer in which a hole injection / transport layer made of a compound different from the transport layer is laminated may be used.
Further, the organic semiconductor layer is a layer that assists hole injection or electron injection into the light emitting layer, and preferably has a conductivity of 10 ⁻¹⁰ S / cm or more. As a material for such an organic semiconductor layer, a conductive oligomer such as a thiophene-containing oligomer, an arylamine oligomer disclosed in JP-A-8-193191, a conductive dendrimer such as an arylamine dendrimer, or the like is used. Can do.

(4) Electron injection layer The electron injection layer is a layer that assists the injection of electrons into the light emitting layer, and has a high electron mobility, and the adhesion improving layer has particularly good adhesion to the cathode among the electron injection layers. It is a layer made of material.

As a material used for the electron injection layer, 8-hydroxyquinoline and metal complexes of derivatives thereof, or nitrogen-containing heterocyclic derivatives are preferable.
Specific examples of the metal complex of 8-hydroxyquinoline or a derivative thereof include metal chelate oxinoid compounds containing a chelate of oxine (generally 8-quinolinol or 8-hydroxyquinoline).
For example, Alq described in the section of the light emitting material can be used as the electron injection layer.
On the other hand, examples of nitrogen-containing heterocyclic derivatives include oxadiazole derivatives.
Examples of the oxadiazole derivatives include electron transfer compounds represented by the following general formulas [3] to [5].

［式中Ａｒ^５，Ａｒ^６，Ａｒ^７，Ａｒ^９，Ａｒ^１０，Ａｒ^１３はそれぞれ置換又は無置換のアリール基を示し、それぞれ互いに同一であっても異なっていてもよい。また、Ａｒ^８，Ａｒ^１１，Ａｒ^１２は置換又は無置換のアリーレン基を示し、それぞれ同一であっても異なっていてもよい。］

[Wherein Ar ⁵ , Ar ⁶ , Ar ⁷ , Ar ⁹ , Ar ¹⁰ , Ar ¹³ represent a substituted or unsubstituted aryl group, and may be the same or different from each other. Ar ⁸ , Ar ¹¹ , and Ar ¹² represent a substituted or unsubstituted arylene group, and may be the same or different. ]

Here, examples of the aryl group include a phenyl group, a biphenyl group, an anthranyl group, a perylenyl group, and a pyrenyl group. Examples of the arylene group include a phenylene group, a naphthylene group, a biphenylene group, an anthranylene group, a peryleneylene group, and a pyrenylene group. Moreover, as a substituent, a C1-C10 alkyl group, a C1-C10 alkoxy group, a cyano group, etc. are mentioned. This electron transfer compound is preferably a thin film-forming compound.
Specific examples of the electron transfer compound include the following.

(式中、ＨＡｒは、置換基を有していても良い炭素数３〜４０の含窒素複素環であり、Ｌ^１は、単結合、置換基を有していてもよい炭素数６〜６０のアリーレン基、置換基を有していてもよい炭素数３〜６０のヘテロアリーレン基又は置換基を有していてもよいフルオレニレン基であり、Ａｒ^１４は、置換基を有していてもよい炭素数６〜６０の２価の芳香族炭化水素基であり、Ａｒ^１５は、置換基を有していてもよい炭素数６〜６０のアリール基又は、置換基を有していてもよい炭素数３〜６０のヘテロアリール基である。) Moreover, as another nitrogen-containing heterocyclic derivative organic compound, a compound represented by the general formula [6] can be mentioned.

(In the formula, HAr is a nitrogen-containing heterocyclic ring having 3 to 40 carbon atoms that may have a substituent, and L ¹ has 6 to 60 carbon atoms that may have a single bond or a substituent. An arylene group, a C3-C60 heteroarylene group which may have a substituent, or a fluorenylene group which may have a substituent, Ar ¹⁴ may have a substituent. a divalent aromatic hydrocarbon group having 6 to 60 carbon atoms, Ar ¹⁵ is an aryl group which may having 6 to 60 carbon atoms which may have a substituent or may have a substituent carbon (It is a heteroaryl group of several 3 to 60.)

The compound of the above formula [6] can be synthesized by the method described in Japanese Patent Application No. 2003-004139.
In the nitrogen-containing heterocyclic derivative organic compound of the general formula [6], an imidazopyrazine derivative and an imidazole derivative are preferable.

(式中、Ａ^１〜Ａ^３は、窒素原子又は炭素原子であり、Ｒは、置換基を有していてもよい炭素数６〜６０のアリール基、置換基を有していてもよい炭素数３〜６０のヘテロアリール基、炭素数１〜２０のアルキル基、炭素数１〜２０のハロアルキル基、炭素数１〜２０のアルコキシ基であり、ｑは０から５の整数であり、ｑが２以上の整数であるとき、複数のＲは互いに同一又は異なっていてもよい。また、隣接する複数のＲ基同士で互いに結合して、置換又は未置換の炭素環式脂肪族環、あるいは、置換又は未置換の炭素環式芳香族環を形成していてもよい。Ａｒ^１６は、置換基を有していてもよい炭素数６〜６０のアリール基、置換基を有していてもよい炭素数３〜６０のヘテロアリール基であり、Ａｒ^１７は、水素原子、炭素数１〜２０のアルキル基、炭素数１〜２０のハロアルキル基、炭素数１〜２０のアルコキシ基、置換基を有していてもよい炭素数６〜６０のアリール基、置換基を有していてもよい炭素数３〜６０のヘテロアリール基であり、（ただし、Ａｒ^１６、Ａｒ^１７のいずれか一方は置換基を有していてもよい炭素数１０〜６０の縮合環基、置換基を有していてもよい炭素数３〜６０のヘテロ縮合環基である）。Ｌ^２、Ｌ^３は、それぞれ単結合、置換基を有していてもよい炭素数６〜６０の縮合環、置換基を有していてもよい炭素数３〜６０のヘテロ縮合環又は置換基を有していてもよいフルオレニレン基である。) Examples of the imidazopyrazine derivative include a compound represented by the general formula [7].

(In the formula, A ^{1 to} A ³ are a nitrogen atom or a carbon atom, and R is an aryl group having 6 to 60 carbon atoms which may have a substituent, or an optionally substituted carbon. A heteroaryl group having 3 to 60 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, and an alkoxy group having 1 to 20 carbon atoms, q is an integer of 0 to 5, and q is When it is an integer of 2 or more, the plurality of R may be the same or different from each other, and bonded to each other by a plurality of adjacent R groups to form a substituted or unsubstituted carbocyclic aliphatic ring, or A substituted or unsubstituted carbocyclic aromatic ring may be formed, and Ar ¹⁶ may have an optionally substituted aryl group having 6 to 60 carbon atoms or a substituent. heteroaryl group having 3 to 60 carbon atoms, ^{Ar 17} is a hydrogen atom, 1 to carbon atoms An alkyl group having 0, a haloalkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 60 carbon atoms which may have a substituent, and a substituent group. A heteroaryl group having 3 to 60 carbon atoms, wherein any one of Ar ¹⁶ and Ar ¹⁷ has a condensed ring group having 10 to 60 carbon atoms and a substituent which may have a substituent. L ² and L ³ each have a single bond or a C 6-60 condensed ring or substituent which may have a substituent. A C3-C60 hetero-condensed ring which may be substituted or a fluorenylene group which may have a substituent.

  The compound of the above formula [7] can be synthesized by the method described in Japanese Patent Application No. 2003-005184.

(式中、Ｒ^１は、水素原子、置換基を有していてもよい炭素数６〜６０のアリール基、置換基を有していてもよいピリジル基、置換基を有していてもよいキノリル基、置換基を有していてもよい炭素数１〜２０のアルキル基又は置換基を有していてもよい炭素数１〜２０のアルコキシ基で、ｒは０〜４の整数であり、
Ｒ^２は、置換基を有していてもよい炭素数６〜６０のアリール基、置換基を有していてもよいピリジル基、置換基を有していてもよいキノリル基、置換基を有していてもよい炭素数１〜２０のアルキル基又は置換基を有していてもよい炭素数１〜２０のアルコキシ基であり、Ｒ^３は、水素原子、置換基を有していてもよい炭素数６〜６０のアリール基、置換基を有していてもよいピリジル基、置換基を有していてもよいキノリル基、置換基を有していてもよい炭素数１〜２０のアルキル基又は置換基を有していてもよい炭素数１〜２０のアルコキシ基であり、
Ｌ^４は、置換基を有していてもよい炭素数６〜６０のアリーレン基、置換基を有していてもよいピリジニレン基、置換基を有していてもよいキノリニレン基、置換基を有していてもよいフルオレニレン基であり、Ａｒ^１８は、置換基を有していてもよい炭素数６〜６０のアリーレン基、置換基を有していてもよいピリジニレン基、置換基を有していてもよいキノリニレン基であり、Ａｒ^１９は、置換基を有していてもよい炭素数６〜６０のアリール基、置換基を有していてもよいピリジル基、置換基を有していてもよいキノリル基、置換基を有していてもよい炭素数１〜２０のアルキル基又は置換基を有していてもよい炭素数１〜２０のアルコキシ基である。) Examples of the imidazole derivative include compounds represented by general formula [8] or [9].

(In the formula, R ¹ may have a hydrogen atom, an aryl group having 6 to 60 carbon atoms which may have a substituent, a pyridyl group which may have a substituent, or a substituent. A quinolyl group, an optionally substituted alkyl group having 1 to 20 carbon atoms or an optionally substituted alkoxy group having 1 to 20 carbon atoms, r is an integer of 0 to 4;
R ² has an aryl group having 6 to 60 carbon atoms which may have a substituent, a pyridyl group which may have a substituent, a quinolyl group which may have a substituent, and a substituent. An optionally substituted alkyl group having 1 to 20 carbon atoms or an optionally substituted alkoxy group having 1 to 20 carbon atoms, and R ³ may have a hydrogen atom or a substituent. An aryl group having 6 to 60 carbon atoms, a pyridyl group which may have a substituent, a quinolyl group which may have a substituent, and an alkyl group having 1 to 20 carbon atoms which may have a substituent Or it is a C1-C20 alkoxy group which may have a substituent,
L ⁴ has an arylene group having 6 to 60 carbon atoms which may have a substituent, a pyridinylene group which may have a substituent, a quinolinylene group which may have a substituent, and a substituent. Ar ¹⁸ has an optionally substituted arylene group having 6 to 60 carbon atoms, an optionally substituted pyridinylene group, and a substituent. Ar ¹⁹ may be an aryl group having 6 to 60 carbon atoms which may have a substituent, a pyridyl group which may have a substituent, or a substituent. It is a good quinolyl group, an optionally substituted alkyl group having 1 to 20 carbon atoms, or an optionally substituted alkoxy group having 1 to 20 carbon atoms. )

The compound of the said Formula [8] is compoundable by the method as described in Japanese Patent Application No. 2003-67847.
Specific examples of the nitrogen-containing heterocyclic derivative organic compound are shown below.

In the present invention, the electron injection layer preferably has an electron mobility of 10 ⁻⁴ cm ² / (V · sec) or more in a region where the electric field strength (E) is 10 ⁴ to 10 ⁶ V / cm. By using an organic compound having such electron mobility for the electron injection layer, the driving voltage of the organic EL element can be lowered.
Furthermore, since the light emitting region can be shifted to the first light emitting layer on the anode side, light emission of the second light emitting layer can be suppressed, so that narrow band light emission with better color purity can be obtained, and high efficiency and long life can be obtained. can do.

For this reason, it is particularly preferable to use a compound having a particularly high electron mobility, such as the above-mentioned nitrogen-containing heterocyclic derivative organic compound, particularly an imidazopyrazine derivative and / or an imidazole derivative, for the electron injection layer.
Note that the above-described compounds may take the form of lamination, mixing, etc. to form the electron injection layer as necessary.

  In a preferred embodiment of the present invention, there is an element containing a reducing dopant in an electron transporting region or an interface region between a cathode and an organic layer. Here, the reducing dopant is defined as a substance capable of reducing the electron transporting compound. Accordingly, various materials can be used as long as they have a certain reducibility, such as alkali metals, alkaline earth metals, rare earth metals, alkali metal oxides, alkali metal halides, alkaline earth metals. At least selected from the group consisting of oxides, halides of alkaline earth metals, oxides of rare earth metals or halides of rare earth metals, organic complexes of alkali metals, organic complexes of alkaline earth metals, organic complexes of rare earth metals One substance can be preferably used.

  More specifically, preferable reducing dopants include Na (work function: 2.36 eV), K (work function: 2.28 eV), Rb (work function: 2.16 eV) and Cs (work function: 1 .95 eV), at least one alkali metal selected from the group consisting of Ca (work function: 2.9 eV), Sr (work function: 2.0 to 2.5 eV), and Ba (work function: 2.52 eV). Particularly preferred are those having a work function of 2.9 eV or less, including at least one alkaline earth metal selected from the group consisting of: Among these, a more preferable reducing dopant is at least one alkali metal selected from the group consisting of K, Rb, and Cs, more preferably Rb or Cs, and most preferably Cs. .

  These alkali metals have particularly high reducing ability, and the addition of a relatively small amount to the electron injection region can improve the light emission luminance and extend the life of the organic EL element. Further, as a reducing dopant having a work function of 2.9 eV or less, a combination of these two or more alkali metals is also preferable. Particularly, a combination containing Cs, such as Cs and Na, Cs and K, Cs and Rb, or Cs. And a combination of Na and K. By including Cs in combination, the reducing ability can be efficiently exhibited, and by adding to the electron injection region, the emission luminance and the life of the organic EL element can be improved.

In the present invention, an electron injection layer composed of an insulator or a semiconductor may be further provided between the cathode and the organic layer. At this time, current leakage can be effectively prevented and the electron injection property can be improved. As such an insulator, it is preferable to use at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides and alkaline earth metal halides. If the electron injection layer is composed of these alkali metal chalcogenides or the like, it is preferable in that the electron injection property can be further improved. Specifically, preferable alkali metal chalcogenides include, for example, Li ₂ O, LiO, Na ₂ S, Na ₂ Se, and NaO, and preferable alkaline earth metal chalcogenides include, for example, CaO, BaO, SrO, and BeO. , BaS, and CaSe. Further, preferable alkali metal halides include, for example, LiF, NaF, KF, LiCl, KCl, and NaCl. Examples of preferable alkaline earth metal halides include fluorides such as CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ and BeF ₂ , and halides other than fluorides.

  Further, an electron transport layer may be provided. As a semiconductor constituting the electron transport layer, Ba, Ca, Sr, Yb, Al, Ga, In, Li, Na, Cd, Mg, Si, Ta, Sb, and an oxide containing at least one element of Zn, nitriding One kind or a combination of two or more kinds of substances or oxynitrides. Moreover, it is preferable that the inorganic compound which comprises an electron carrying layer is a microcrystal or an amorphous insulating thin film. If the electron transport layer is composed of these insulating thin films, a more uniform thin film is formed, and pixel defects such as dark spots can be reduced. Examples of such inorganic compounds include the alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides described above.

(5) Cathode As the cathode, a material having a small work function (4 eV or less) metal, an alloy, an electrically conductive compound, and a mixture thereof is used. Specific examples of such an electrode material include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / silver alloy, aluminum / aluminum oxide, aluminum / lithium alloy, indium, rare earth metal, and the like.
This cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering.
Here, when light emitted from the light-emitting layer is extracted 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.

(6) Insulating layer Since an organic EL element applies an electric field to an ultra-thin film, pixel defects are likely to occur due to leakage or short circuit. In order to prevent this, it is preferable to insert an insulating thin film layer between the pair of electrodes.
Examples of materials used for the insulating layer include aluminum oxide, lithium fluoride, lithium oxide, cesium fluoride, cesium oxide, magnesium oxide, magnesium fluoride, calcium oxide, calcium fluoride, aluminum nitride, titanium oxide, silicon oxide, and oxide. Examples include germanium, silicon nitride, boron nitride, molybdenum oxide, ruthenium oxide, and vanadium oxide.
A mixture or laminate of these may be used.

As described above, by forming the anode, the light emitting layer, the hole injection layer as necessary, and the electron injection layer as necessary by the exemplified materials and methods, and further forming the cathode, an organic EL device can be produced. . Moreover, an organic EL element can also be produced from the cathode to the anode in the reverse order.
Hereinafter, an example of manufacturing an organic EL element having a structure in which an anode / a hole injection layer / a light emitting layer / an electron injection layer / a cathode are sequentially provided on a translucent substrate will be described.

First, a thin film made of an anode material is formed on a suitable light-transmitting substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 to 200 nm.
Next, a hole injection layer is provided on the anode. As described above, the hole injection layer can be formed by a vacuum deposition method, a spin coating method, a casting method, an LB method, or the like, but a uniform film can be easily obtained and pinholes are hardly generated. From the point of view, it is preferable to form by vacuum deposition. When forming a hole injection layer by vacuum deposition, the deposition conditions vary depending on the compound used (the material of the hole injection layer), the crystal structure of the target hole injection layer, the recombination structure, etc. It is preferable to select appropriately within the range of a source temperature of 50 to 450 ° C., a degree of vacuum of 10 ⁻⁷ to 10 ⁻³ torr, a deposition rate of 0.01 to 50 nm / second, a substrate temperature of −50 to 300 ° C., and a film thickness of 5 nm to 5 μm. .

  Next, the formation of the light emitting layer in which the light emitting layer is provided on the hole injection layer is also performed by thinning the organic light emitting material using a desired organic light emitting material by a method such as vacuum deposition, sputtering, spin coating, or casting. However, it is preferably formed by a vacuum deposition method from the viewpoint that a homogeneous film is easily obtained and pinholes are hardly generated. When the light emitting layer is formed by the vacuum vapor deposition method, the vapor deposition condition varies depending on the compound used, but it can be generally selected from the same condition range as that of the hole injection layer.

Next, an electron injection layer is provided on the light emitting layer. As with the hole injection layer and the light emitting layer, it is preferable to form by a vacuum evaporation method because it is necessary to obtain a homogeneous film. Deposition conditions can be selected from the same condition range as the hole injection layer and the light emitting layer.
Finally, an organic EL element can be obtained by laminating a cathode.
The cathode is made of metal, and vapor deposition or sputtering can be used. However, vacuum deposition is preferred to protect the underlying organic layer from damage during film formation.
It is preferable that the organic EL device described so far is manufactured from the anode to the cathode consistently by a single vacuum.

  The formation method of each layer of the organic EL element of the present invention is not particularly limited. Conventionally known methods such as vacuum deposition and spin coating can be used. In addition, the organic thin film layer is known by a coating method such as a vacuum deposition method, a molecular beam deposition method (MBE method) or a solution dipping method dissolved in a solvent, a spin coating method, a casting method, a bar coating method, a roll coating method, etc. Can be formed by a method.

The film thickness of each organic layer of the organic EL device of the present invention is not particularly limited. Generally, if the film thickness is too thin, defects such as pinholes are likely to occur. Conversely, if it is too thick, a high applied voltage is required and the efficiency is deteriorated. Therefore, the range of several nm to 1 μm is usually preferable.
When a direct current voltage is applied to the organic EL element, light emission can be observed by applying a voltage of 5 to 40 V with the anode set to + and the cathode set to a negative polarity. In addition, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when alternating voltage is applied, uniform light emission is observed only when the anode has a positive polarity and the cathode has a negative polarity. The waveform of the alternating current to be applied may be arbitrary.

  The organic EL device of the present invention emits narrow band light with good color purity, and is particularly excellent as a device that emits blue light. In addition, the service life has been improved.

Examples of the present invention will be described in detail below, but the present invention is not limited to these examples.
In addition, the property of the compound used in each Example and the produced element were evaluated by the following method.
(1) Energy gap: measured from the absorption edge of the absorption spectrum in benzene. Specifically, the absorption spectrum is measured using a commercially available visible ultraviolet spectrophotometer, and the absorption spectrum is calculated from the wavelength at which the absorption spectrum starts to rise.
(2) Luminance: Measured with a spectral radiance meter (CS-1000, manufactured by Minolta).
(3) Luminescence intensity of emission maximum wavelength: A single-layer film of the first light-emitting layer and the second light-emitting layer is respectively prepared under the same conditions as the EL element to be manufactured, and each single-layer film is formed using a commercially available fluorescence measuring device. Measure the fluorescence spectrum. From the obtained fluorescence spectrum of the first light emitting layer, the fluorescence intensity Ia of the first light emitting layer is measured at the light emission maximum wavelength a of the first light emitting layer. Similarly, the fluorescence intensity Ib of the second light-emitting layer is measured from the obtained fluorescence spectrum of the second light-emitting layer at the light emission maximum wavelength b of the second light-emitting layer.
When the light emission maximum wavelengths of the first light emitting layer and the second light emitting layer are sufficiently separated, the light emission intensities Ia and Ib at the wavelengths a and b in the light emission spectrum of the EL element can be approximated to I1 and I2, respectively.
When the emission maximum wavelengths of the first emission layer and the second emission layer are close to each other, the emission spectrum of the entire EL element is the sum of the emission spectrum from the first emission layer and the emission spectrum from the second emission layer. I can assume.
Accordingly, the fluorescence intensities I1a and I1b of the wavelengths a and b are measured in the obtained fluorescence spectrum of the first light emitting layer. Similarly, the fluorescence intensities I2a and I2b at wavelengths a and b are measured in the fluorescence spectrum of the second light emitting layer. The following equations hold for I1 and I2.
Ia = I1 * I1a + I2 * I2a
Ib = I1 * I1b + I2 * I2b
The ratio of I1 and I2 is obtained from the above formula.
(4) Luminous efficiency: It was calculated from the current density value measured using a multimeter and the luminance (100 nit).
(5) C.I. I. E chromaticity coordinates: obtained by measuring in the same manner as in (2).
(6) Half life: Measurement was performed on an element sealed under an initial luminance of 1000 nit and a constant current condition. (room temperature)
(7) Electron mobility: It was calculated by the Time of flight method. Specifically, for the structure of ITO / organic layer (electron injection layer, etc., layer thickness of 1 to 2 μm) / Al, the time characteristic (transient characteristic time) of the transient current generated by light irradiation was measured, and the following The electron mobility was calculated from the equation.
Electron mobility = (organic layer thickness) ² / (transient characteristic time / electric field strength)

The compounds used in the examples are shown below.

Example 1
A glass substrate with an ITO transparent electrode having a thickness of 25 mm × 75 mm × 1.1 mm (manufactured by Geomatic Co., Ltd.) was subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes and then UV ozone cleaning for 30 minutes.
A glass substrate with a transparent electrode line after washing is mounted on a substrate holder of a vacuum deposition apparatus, and N, N ′ having a film thickness of 60 nm is first covered so that the transparent electrode is covered on the surface on which the transparent electrode line is formed. -Bis (N, N'-diphenyl-4-aminophenyl) -N, N-diphenyl-4,4'-diamino-1,1'-biphenyl film (hereinafter abbreviated as "TPD232 film") is formed. did. This TPD232 film functions as a hole injection layer.
Subsequent to the formation of the TPD232 film, a 20 nm thick N, N, N ′, N′-tetra (4-biphenyl) -diaminobiphenylene layer, hereinafter referred to as a “TBDB layer”, was formed on the TPD232 film. This film functions as a hole transport layer.
Further, H1 was used as the host material for the first light emitting layer, D1 was used as the first dopant, and the D1: H1 ratio was 1.0: 20 (weight ratio) to form a 20 nm thick layer. (First dopant about 5.4 mol%). This layer functions as the first light emitting layer.
Further, H1 as the host material of the second light emitting layer, D2 as the second dopant, were vapor-deposited so that the ratio of D2: H1 was 1.0: 20 (weight ratio) to form a layer having a thickness of 20 nm. (Second dopant about 5.7 mol%). This layer functions as a second light emitting layer.
An Alq film having a thickness of 10 nm was formed on this film. This functions as an electron injection layer.
The electron mobility of Alq is 5 × 10 ⁻⁶ cm ² / (V · sec) (E = 5 × 10 ⁵ V / cm).
Thereafter, Li (Li source: manufactured by Saesgetter Co.), which is a reducing dopant, and Alq were vapor-deposited, and an Alq: Li film (film thickness: 10 nm) was formed as an electron injection layer (cathode). Metal Al was vapor-deposited on the Alq: Li film to form a metal cathode, thereby forming an organic EL light emitting device.

Example 2
The film thickness of the first light emitting layer is 10 nm, the ratio of D1: H1 is 0.3: 10 (weight ratio), the film thickness of the second light emitting layer is 30 nm, and the ratio of D2: H1 is 1.4: 30 (weight). The organic EL device was produced in exactly the same manner as in Example 1 except for the ratio (first dopant: about 3.3 mol%, second dopant: about 5.3 mol%).

Example 3
The film thickness of the first light emitting layer is 20 nm, the ratio of D1: H1 is 0.5: 20 (weight ratio), the film thickness of the second light emitting layer is 20 nm, and the ratio of D2: H1 is 1.0: 20 (weight). The organic EL device was fabricated in the same manner as in Example 1 except that the ratio was (the first dopant was about 2.8 mol%, the second dopant was about 5.7 mol%).

Reference example 1
The film thickness of the first light emitting layer is 20 nm, D2 is used instead of D1, the ratio of D2: H1 is 1.0: 20 (weight ratio), the film thickness of the second light emitting layer is 20 nm, and D3 is substituted for D2. And an organic EL device was produced in the same manner as in Example 1 except that the ratio of D3: H1 was 1.0: 20 (weight ratio) (first dopant about 5.7 mol%, second dopant). About 4.8 mol%).

Reference example 2
An organic EL device was produced in the same manner as in Reference Example 1 except that ETM-020 was used instead of Alq for forming the electron injection layer.
The electron mobility of ETM-020 is 4 × 10 ⁻⁴ cm ² / (V · sec) (E = 5 × 10 ⁵ V / cm).

Comparative Example 1
Except for the film thickness of the first light emitting layer being 20 nm, the ratio of D1: H1 being 1.0: 20 (weight ratio), the film thickness of the second light emitting layer being 20 nm, and not using D2, which is exactly the same as in Example 1. Similarly, an organic EL element was produced (first dopant about 5.4 mol%, second dopant 0 mol%).

Comparative Example 2
The film thickness of the first light emitting layer was 20 nm, D2 was used instead of D1, the ratio of D2: H1 was 1.0: 20 (weight ratio), the film thickness of the second light emitting layer was 20 nm, and D2 was not used. Except for the above, an organic EL element was produced in exactly the same manner as in Example 1 (first dopant about 5.7 mol%, second dopant 0 mol%).

Comparative Example 3
The thickness of the first light emitting layer is 20 nm, D2 is used instead of D1, the ratio of D2: H1 is 1.0: 20 (weight ratio), the thickness of the second light emitting layer is 20 nm, and the ratio of D1: H1 The organic EL device was produced in the same manner as in Example 1 except that the ratio was 1.0: 20 (weight ratio) (first dopant about 5.7 mol%, second dopant about 5.4 mol%).

Comparative Example 4
The film thickness of the first light emitting layer was 20 nm, D3 was used instead of D1, the ratio of D3: H1 was 1.0: 20 (weight ratio), the film thickness of the second light emitting layer was 20 nm, and D2 was not used. Except for the above, an organic EL device was produced exactly as in Example 1 (about 4.8 mol% of the first dopant and 0 mol% of the second dopant).

Comparative Example 5
The thickness of the first light emitting layer is 20 nm, D3 is used instead of D1, the ratio of D3: H1 is 1.0: 20 (weight ratio), and the ratio of D2: H1 is 1.0: 20 (weight ratio). Except that, an organic EL device was produced in the same manner as in Example 1 (about 4.8 mol% of the first dopant and about 5.7 mol% of the second dopant).

Comparative Example 6
An organic EL device was produced in the same manner as in Reference Example 2, except that the second light emitting layer had the same configuration as the first light emitting layer.

  About the organic EL element produced in Examples 1-3, Reference Examples 1-2, and Comparative Examples 1-6, the structure of the light emitting layer of each organic EL element, light emission of the maximum emission wavelength of the light emission spectrum derived from the first light emitting layer The ratio (I1 / I2) of the intensity (I1) and the emission intensity (I2) at the emission maximum wavelength of the emission spectrum derived from the second emission layer, the initial emission efficiency, C.I. I. E chromaticity coordinates and half-life were measured. Table 1 shows the results.

As can be seen from Table 1, the organic EL device using only the dopant having a large energy gap had good color purity but low luminous efficiency and short half-life. Conversely, an organic EL device using only a dopant having a small energy gap has high luminous efficiency and long half-life, but has poor color purity and is not suitable for full-color applications.
However, the organic EL device of the present invention has improved lifetime and luminous efficiency compared with the case where only a dopant having a large energy gap is used, and the color purity is almost the same, so that it is very suitable for full color applications. Became clear.
Furthermore, in Reference Example 2 and Comparative Example 6, by using ETM-020 having a high electron mobility for the electron injection layer, only the first light emitting layer could emit light (I2 = 0). In this case, when the energy gap between the first dopant and the second dopant satisfies the requirements of the present invention, the half-life can be remarkably improved, and it has been confirmed that the effect of the present invention is enormous.

  According to the present invention, it is possible to provide an organic EL element that emits narrow band light with high color purity and has a long lifetime.

_{DESCRIPTION OF SYMBOLS} 1 Organic EL element 2 Anode 3 First light emitting layer 4 Second light emitting layer 5 Cathode E _gh 1 Energy gap of first host material E _gd 1 Energy gap of first dopant E _gh 2 Energy gap of second host material E _gd 2 Energy gap of the second dopant

Claims (9)

The anode,
A first light emitting layer comprising at least a first host material and a first dopant;
A second light emitting layer comprising at least a second host material and a second dopant;
A cathode,
In this order,
The first host material and the second host material are the same;
The energy gap E _gh 1 of the first host material, the energy gap E _gd 1 of the first dopant, the energy gap E _gh 2 of the second host material, and the energy gap E _gd 2 of the second dopant satisfy the following formula: An organic electroluminescence device characterized by that.
E _gh 1> E _gd 1
E _gh 2> E _gd 2
E _gd 1> E _gd 2> 2.7 eV   2. The organic electroluminescence device according to claim 1, wherein in the first light emitting layer, a ratio of the first dopant to the first host material is 0.1 to 10 mol%.   3. The organic electroluminescence device according to claim 1, wherein in the second light emitting layer, a ratio of the second dopant to the second host material is 0.1 to 10 mol%. It said first and second host materials is organic electroluminescent device according to claim 1 which is a compound represented by the following general formula [1].

[In the formula, Ar ¹ is an aromatic ring having 6 to 50 nuclear carbon atoms, and X is a substituent.
m is an integer of 1 to 5, and n is an integer of 0 to 6. When m ≧ 2, Ar may be the same or different. When n ≧ 2, X may be the same or different. ] At least one of said 1st or 2nd dopant material is a compound represented by following General formula [2], The organic electroluminescent element as described in any one of Claims 1-4 characterized by the above-mentioned.

[Wherein, Ar ^{2 to} Ar ⁴ are a substituted or unsubstituted aromatic group having 6 to 50 nuclear carbon atoms, a substituted or unsubstituted styryl group, and p is an integer of 1 to 4. When p ≧ 2, Ar ³ and Ar ⁴ may be the same or different. ] The film thickness of said 1st light emitting layer is 10 nm or more, The organic electroluminescent element as described in any one of Claims 1-5 characterized by the above-mentioned. 2. An electron injection layer is provided between the second light emitting layer and the cathode, and the electron mobility of the electron injection layer is 10 ⁻⁴ cm ² / (V · sec) or more. the organic electroluminescent device according to any one of 1-6. The organic electroluminescence device according to claim 7 , wherein the electron injection layer contains an organic compound made of a nitrogen-containing heterocyclic derivative. The organic electroluminescent device according to claim 8 , wherein the organic compound comprising the nitrogen-containing heterocyclic derivative is an imidazopyrazine derivative and / or an imidazole derivative.

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