JP6701649B2 - Organic electroluminescence element, display device, lighting device, π-conjugated compound, and light-emitting thin film - Google Patents

Description

  The present invention relates to an organic electroluminescence device, a display device, a lighting device, a π-conjugated compound and a light-emitting thin film, and particularly, an organic electroluminescence device having excellent luminous efficiency, a π-conjugated compound used for the organic electroluminescence device, The present invention relates to a light-emitting thin film containing the π-conjugated compound, a display device provided with the organic electroluminescent element, and a lighting device.

  An organic EL element (also referred to as an “organic electroluminescent element”) that uses electroluminescence (hereinafter, abbreviated as “EL”) of an organic material has already been put into practical use as a new light emitting system capable of planar light emission. It is a technology that is being used. Organic EL devices have been applied not only to electronic displays but also to lighting devices in recent years, and their development is expected.

There are two types of organic EL emission methods: "phosphorescence emission" that emits light when returning from the triplet excited state to the ground state, and "fluorescence emission" that emits light when returning from the singlet excited state to the ground state. There is.
When an electric field is applied to the organic EL element, holes and electrons are injected from the anode and cathode, respectively, and recombine in the light emitting layer to generate excitons. At this time, since singlet excitons and triplet excitons are generated at a ratio of 25%:75%, phosphorescence emission using triplet excitons has a theoretically higher internal quantum than fluorescence emission. It is known that efficiency can be obtained. However, in order to actually obtain high quantum efficiency in the phosphorescence emission method, it is necessary to use a complex using a rare metal such as iridium or platinum as the central metal, and in the future, the reserves of rare metals and the metal itself There is concern that price will become a big issue in the industry.

On the other hand, various developments have been made in order to improve the luminous efficiency even in the fluorescent light emitting type, and a new movement has recently been made.
For example, in Patent Document 1, a phenomenon in which singlet excitons are generated by collision of two triplet excitons (hereinafter, referred to as Triplet-Triple Annihilation: hereinafter, abbreviated as "TTA" as appropriate. In addition, Triplet-Triplet Fusion: (Also referred to as "TTF"), a technique for efficiently causing TTA to improve the efficiency of the fluorescent element is disclosed. With this technology, the power efficiency of the fluorescent light emitting material (hereinafter, also referred to as fluorescent light emitting material and fluorescent material) has been improved to 2 to 3 times that of the conventional fluorescent light emitting material. Since the production efficiency is only about 40%, it still has a problem of higher emission efficiency than phosphorescence emission.
Furthermore, in recent years, Adachi et al. have used a thermally-activated delayed fluorescence (also referred to as “thermally-excited delayed fluorescence”: Thermally Activated Delayed Fluorescence: hereinafter, abbreviated as “TADF”) mechanism as a fluorescent light-emitting material. , And the possibility of use in organic EL devices has been reported (see, for example, Non-Patent Documents 1 to 7 and Patent Document 2).

  As shown in FIG. 1, the TADF mechanism is a compound having a small difference (ΔEst) between the singlet excitation energy level and the triplet excitation energy level (ΔEst(TADF) in FIG. Is smaller than ΔEst(F).), a light emission mechanism utilizing a phenomenon in which an inverse intersystem crossing from a triplet exciton to a singlet exciton occurs. That is, due to the small ΔEst, triplet excitons generated at a probability of 75% by electric field excitation cannot originally contribute to light emission, but transition to a singlet excited state due to thermal energy when driving an organic EL element, Radiation deactivation (also referred to as “radiation transition” or “radiation deactivation”) from that state to the ground state causes fluorescence emission. It is believed that the use of the delayed fluorescence due to this TADF mechanism enables theoretically 100% internal quantum efficiency even in fluorescence emission.

  Furthermore, it is known that when a compound exhibiting TADF property is included as a third component (assisting dopant) in the light emitting layer composed of a host compound and a light emitting compound as a third component (assist dopant), it is effective in achieving high light emission efficiency (for example, , Non-Patent Document 8.). By generating 25% singlet excitons and 75% triplet excitons on the assisting dopant by electric field excitation, the triplet excitons generate singlet excitons with inverse intersystem crossing (RISC). be able to. The energy of singlet excitons is transferred to the light emitting compound, and the light emitting compound can emit light. Therefore, theoretically 100% of the exciton energy can be used to cause the light-emitting compound to emit light, and high light emission efficiency is exhibited.

  In order to reduce ΔEst in an organic compound, it is desirable to localize the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in the molecule without mixing them. For this purpose, a method using a strong electron-donating group or electron-withdrawing group is known. Non-Patent Document 3 and Patent Document 4 describe that the following compound 1 having a carbazolyl group as an electron-donating group and a triazinyl group as an electron-withdrawing group emits delayed fluorescence.

  Further, Non-Patent Document 9 describes the relationship between the twist of the donor plane of diallylaminoanthracene and the electronic state and luminescence of the compound. Although this document describes that a compound having an electron-donating group having low planarity such as dibenzoazepine spreads a π-conjugated system, it has an electron-withdrawing dibenzoazepine structure and an electron-withdrawing group. There is no mention of a structure having

International Publication No. 2010/134350 JP, 2013-116975, A JP, 2013-041106, A International Publication No. 2014/133121

"Development of phosphorescent organic EL technology for lighting" Applied Physics Volume 80, No. 4, 2011 H. Uoyama, et al. , Nature, 2012, 492, 234-238. S. Y. Lee et al. , Applied Physics Letters, 2012, 101, 093306-093309. Q. Zhang et al. J. Am. Chem. Soc. , 2012, 134, 14706-14709 T. Nakagawa et al. Chem. Commun. , 2012, 48, 9580-9582 A. Endo et al. , Adv. Mater. , 2009, 21, 4802-4806 Organic EL Debate 10th Annual Meeting Proceedings p11-12,2010 H. Nakanotani, et al. , Nature Communication, 2014, 5, 4016-4022. J. Phys. Chem. A. , 2015, 119, 4898-4906

  The compound 1 described in Patent Document 4 described above is a compound that exhibits TADF property, but since HOMO and LUMO are localized without being mixed, the compound 1 has low light emitting property. Non-Patent Document 9 discloses a compound exhibiting a light emitting property, but does not describe a compound exhibiting TADF property. Therefore, a method of exhibiting TADF property while maintaining high light emission property is desired.

  The present invention has been made in view of the above problems and circumstances, and a problem to be solved is to use a π-conjugated compound that exhibits TADF properties while maintaining high light emission properties, and to obtain fluorescence quantum yield and light emission efficiency. Another object of the present invention is to provide an excellent organic electroluminescence device. Another object of the present invention is to provide a display device and a lighting device provided with the organic electroluminescence element, a π-conjugated compound used for the organic electroluminescence element, and a light-emitting thin film containing the π-conjugated compound.

The present inventor includes a π-conjugated compound represented by the following general formula (1), which uses an electron-donating group having low planarity, in at least one of the light-emitting layers in the organic electroluminescence device to obtain high fluorescence. The inventors have found that an organic electroluminescence device having a quantum yield and excellent emission efficiency can be obtained, and the present invention has been completed.
That is, the above-mentioned subject concerning the present invention is solved by the following means.

The first aspect of the present invention relates to an organic electroluminescence device.
[1] An organic electroluminescence device comprising an anode, a cathode, and at least one organic layer sandwiched between the anode and the cathode,
At least one of the organic layers has a structure represented by the following general formula (1), and the absolute value ΔEst of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.50 eV. An organic electroluminescence device comprising the following π-conjugated compound.
(In the general formula (1),
EDG is represented by the following general formula (1A):
(In the general formula (1A),
X and Y each independently represent CR ₂ , SiR ₂ , or an oxygen atom,
R represents a hydrogen atom or a substituent,
R ¹ and R ² each independently represent a substituent,
n4 and n5 are each independently an integer of 1 to 3),
Is a structure represented by
L represents a single bond or a substituted or unsubstituted arylene group,
EWG is a fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, an optionally substituted carbonyl group, an optionally substituted sulfonyl group, an optionally substituted phosphine oxide group, and an optionally substituted Represents an electron withdrawing group selected from the group consisting of an electron withdrawing heterocyclic ring,
n1, n2 and n3 are each independently an integer of 1 to 3. )
[2] The organic electroluminescence device according to [1], wherein in the π-conjugated compound, EDG has a structure represented by the general formula (2A).
(In the general formula (2A),
R ¹ and R ² each independently represent a substituent,
n4 and n5 are each independently an integer of 1 to 3. )
[3] In the above general formulas (1A) and (2A), at least one of R ¹ and R ² is an electron-donating substituent, the organic compound according to [1] or [2]. Electroluminescent device.
[4] The electron-donating substituent is one selected from the group consisting of a substituted or unsubstituted phenyl group, a carbazolyl group, a diphenylamino group, and a tert-butyl group, [3 ] The organic electroluminescent element of description.
[5] The organic layer includes a light emitting layer,
The organic electroluminescent element according to any one of [1] to [4], wherein the light emitting layer contains a π-conjugated compound represented by the general formula (1).
[6] In [5], the light emitting layer contains a π-conjugated compound represented by the general formula (1) and at least one of a fluorescent material and a phosphorescent material. The organic electroluminescence device described.
[7] The light emitting layer contains a π-conjugated compound represented by the general formula (1), at least one of a fluorescent material and a phosphorescent material, and a host compound. The organic electroluminescence device according to [5].

A second aspect of the present invention relates to a display device and a lighting device using the organic electroluminescence element of the present invention.
[8] A display device comprising the organic electroluminescent element according to any one of [1] to [7].
[9] A lighting device comprising the organic electroluminescence device according to any one of [1] to [7].
[10] A display device comprising a lighting device according to [9] and a liquid crystal element as display means.

The third aspect of the present invention relates to a π-conjugated compound and a light emitting thin film containing the same.
[11] It has a structure represented by the following general formula (1), and an absolute value ΔEst of a difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.50 eV or less. Characterized is a π-conjugated compound.
(In the general formula (1),
EDG is represented by the following general formula (1A):
(In the general formula (1A),
X and Y each independently represent CR ₂ , SiR ₂ , or an oxygen atom,
R represents a hydrogen atom or a substituent,
R ¹ and R ² each independently represent a substituent,
n4 and n5 are each independently an integer of 1 to 3),
Is a structure represented by
L represents a single bond or a substituted or unsubstituted arylene group,
EWG is a fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, an optionally substituted carbonyl group, an optionally substituted sulfonyl group, an optionally substituted phosphine oxide group, and an optionally substituted Represents an electron-withdrawing group selected from the group consisting of an electron-withdrawing heterocycle,
n1, n2, and n3 are each independently an integer of 1 to 3. )
[12] A luminescent thin film containing the π-conjugated compound of [11].

  According to the present invention, it is possible to provide an organic electroluminescence device using a π-conjugated compound and having improved fluorescence quantum yield and emission efficiency. Further, it is possible to provide a display device and a lighting device provided with the organic electroluminescence element, a π-conjugated compound used in the organic electroluminescence element, and a light-emitting thin film containing the π-conjugated compound.

Schematic diagram showing the energy diagrams of ordinary fluorescent compounds and TADF compounds A diagram showing the structure of a compound having a highly planar electron-donating group and its electronic state A diagram showing the structure of a compound having an electron-donating group having low planarity and its electronic state Schematic diagram showing an example of the case where the π-conjugated compound according to the present invention acts as an assist dopant and a host compound, respectively. Schematic diagram showing another example of the case where the π-conjugated compound according to the present invention acts as an assist dopant and a host compound, respectively. Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram of active matrix display device Schematic diagram showing the pixel circuit Schematic diagram of a passive matrix display device Illumination device schematic Sectional view of lighting equipment

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and after that as a lower limit and an upper limit.

  In the present invention, attention was paid to the high light-emitting property in the structure using an electron-donating group having low planarity, and further diligent studies were conducted to express the TADF property. As a result, dibenzoazepine, which is an electron-donating group, was obtained. It has a structure represented by the following general formula (1) having a structure and an electron-withdrawing group, and the absolute value ΔEst of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0. It was found that the π-conjugated compound having a voltage of 0.50 eV or less improves the light emission efficiency of the organic electroluminescence device.

(In the general formula (1),
EDG is represented by the following general formula (1A):
(In the general formula (1A),
X and Y each independently represent CR ₂ , SiR ₂ , or an oxygen atom,
R represents a hydrogen atom or a substituent,
R ¹ and R ² each independently represent a substituent,
n4 and n5 are each independently an integer of 1 to 3),
Is a structure represented by
L represents a single bond or a substituted or unsubstituted arylene group,
EWG is a fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, an optionally substituted carbonyl group, an optionally substituted sulfonyl group, an optionally substituted phosphine oxide group, and an optionally substituted Represents an electron withdrawing group selected from the group consisting of an electron withdrawing heterocyclic ring,
n1, n2 and n3 are each independently an integer of 1 to 3. )

  The present invention is an organic electroluminescence device having an anode, a cathode, and at least one organic layer sandwiched between the anode and the cathode, wherein at least one of the organic layers is the above-mentioned general formula (1). A π-conjugated compound having a structure represented by and having ΔEst which is the absolute value of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.50 eV or less. It is a featured organic electroluminescence element. Next, the light emitting method and the light emitting material of the organic EL, which are related to the technical idea of the present invention, will be described.

<Organic EL emission method>
There are two types of organic EL emission methods: "phosphorescence emission" that emits light when returning from the triplet excited state to the ground state, and "fluorescence emission" that emits light when returning from the singlet excited state to the ground state. is there.
When excited by an electric field such as an organic EL, triplet excitons are generated with a probability of 75% and singlet excitons are generated with a probability of 25%. Therefore, phosphorescence emission is more efficient than fluorescence emission. It is an excellent method for realizing low power consumption.
On the other hand, even in fluorescence emission, triplet excitons, which normally generate heat with a probability of 75% and are only heat due to non-radiative deactivation, are caused to exist at high density. A method using a TTA (triplet-triplet annealing, or abbreviated as "triple-triplet fusion (TTF)") mechanism for generating one singlet exciton from two triplet excitons to improve light emission efficiency. Found

  Further, in recent years, by the discovery of Adachi et al., by making the energy gap between the singlet excited state and the triplet excited state small, triple energy with low energy level due to Joule heat during light emission and/or environmental temperature where the light emitting element is placed. Phenomenon that causes inverse intersystem crossing from a singlet excited state to a singlet excited state, resulting in nearly 100% fluorescence emission (also called thermally excited delayed fluorescence or thermally excited delayed fluorescence: "TADF") And a fluorescent substance that enables this have been found (see, for example, Non-Patent Document 1).

<Phosphorescent compound>
As described above, phosphorescence is theoretically three times more advantageous in terms of luminous efficiency than fluorescence, but energy deactivation (=phosphorescence) from the triplet excited state to the singlet ground state is forbidden. Since it is a transition, and similarly, intersystem crossing from a singlet excited state to a triplet excited state is also a forbidden transition, its rate constant is usually small. That is, since transition is less likely to occur, the exciton lifetime is extended from millisecond to second order, and it is difficult to obtain desired light emission.
However, in the case where a complex using a heavy metal such as iridium or platinum emits light, the heavy atom effect of the central metal increases the rate constant of the forbidden transition by three orders of magnitude or more, and depending on the selection of the ligand, 100 It is also possible to obtain a phosphorescence quantum yield of %.
However, in order to obtain such ideal light emission, it is necessary to use a precious metal called a so-called white metal such as iridium, palladium, or platinum, which is a rare metal, and when it is used in a large amount, its reserves or The price of metal itself becomes a big problem in industry.

<Fluorescent compound>
A general fluorescent compound does not need to be a heavy metal complex such as a phosphorescent compound, and is a so-called organic compound composed of a combination of general elements such as carbon, oxygen, nitrogen and hydrogen. Can be applied, and other non-metal elements such as phosphorus, sulfur, and silicon can be used, and the complex of typical metals such as aluminum and zinc can be utilized.
However, in the conventional fluorescent compound, only 25% of excitons can be applied to light emission as described above, and thus highly efficient light emission such as phosphorescence cannot be expected.

<Delayed fluorescent compound>
[Excited triplet-triplet annihilation (TTA) delayed fluorescent compound]
A light emitting method using delayed fluorescence was introduced to solve the problems of the fluorescent compound. The TTA method, which originates from the collision of triplet excitons, can be described by the following general formula. That is, conventionally, the energy of excitons has a merit that a part of triplet excitons, which has been converted into only heat by non-radiative deactivation, can cross the singlet excitons that can contribute to light emission. In the actual organic EL device, the external extraction quantum efficiency about twice that of the conventional fluorescent light emitting device can be obtained.
General formula: T ^* +T ^* →S ^* +S
(In the formula, T ^* represents triplet excitons, S ^* represents singlet excitons, and S represents a ground state molecule.)
However, as can be seen from the above equation, since only one singlet exciton that can be used for light emission is generated from two triplet excitons, it is theoretically impossible to obtain 100% internal quantum efficiency by this method.

[Thermal activated delayed fluorescence (TADF) compound]
Another highly efficient fluorescent emission, the TADF method, is a method that can solve the problems of TTA.
Fluorescent compounds have the advantage that they can be designed infinitely as described above. That is, among the molecularly designed compounds, there is a compound in which the absolute value of the energy level difference between the triplet excited state and the singlet excited state (hereinafter referred to as ΔEst) is extremely close (FIG. 1).
Although such a compound does not have a heavy atom in the molecule, an inverse intersystem crossing from a triplet excited state to a singlet excited state, which normally cannot occur because ΔEst is small, occurs. Furthermore, since the rate constant of deactivation (=fluorescence emission) from the singlet excited state to the ground state is extremely large, the triplet exciton itself is thermally deactivated to the ground state (non-radiative deactivation). It is kinetically more advantageous than returning to the ground state while emitting fluorescence via the singlet excited state. Therefore, TADF ideally enables 100% fluorescence emission.

<Molecular design concept regarding ΔEst>
A molecular design for reducing ΔEst will be described.
In order to reduce ΔEst, it is most effective in principle to reduce the spatial overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in the molecule. Is.
It is generally known that in the electron orbit of a molecule, HOMO is distributed in the electron-donating site and LUMO is distributed in the electron-withdrawing site. It is possible to move away the position where and LUMO exist.

For example, in Non-Patent Document 1 described above, by introducing an electron-withdrawing skeleton such as a cyano group, a sulfonyl group, or triazine, and an electron-donating skeleton such as carbazole or diphenylamino group, LUMO and HOMO can be obtained. Are localized respectively.
It is also effective to reduce the change in molecular structure between the ground state and the triplet excited state of the compound. As a method for reducing the structural change, for example, making the compound rigid is effective. The rigidity described here means that there are few sites that can move freely in the molecule, such as suppressing free rotation in the bond between rings in the molecule and introducing a condensed ring with a large π-conjugated surface. means. In particular, it is possible to reduce the structural change in the excited state by making the region involved in light emission rigid.

  Hereinafter, various measuring methods for the π-conjugated compound according to the present invention will be described.

[Electron density distribution]
The π-conjugated compound according to the present invention preferably has a small overlap between HOMO and LUMO in the molecule, from the viewpoint of reducing ΔEst. The distribution states of these HOMO and LUMO can be obtained from the electron density distribution upon structure optimization obtained by semi-empirical molecular orbital calculation.
The structure optimization and the calculation of the electron density distribution of the π-conjugated compound in the present invention by the semi-empirical molecular orbital calculation are carried out by using a molecular orbital calculation using B3LYP as a functional and 6-31G(d) as a basis function as a calculation method. The calculation can be performed using any software, and there is no particular limitation on the software, and the same can be obtained using any software.

  In the present invention, as software for molecular orbital calculation, Gaussian09 (Revision C.01, MJ Frisch, GW Trucks, H. B. Schlegel, GE Scuseria, M.; A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B, Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, HP P. Hratchian, AF. Izmaylov, J. Blino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Kitao, H. Nakai, T. Vraven, JA Montgomery, Jr., JE Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Res. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazeyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, AD Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian, Inc., Wallingford CT, 2010.) were used.

Regarding the separated state of HOMO and LUMO, from the structure optimization calculation using B3LYP as the above-mentioned functional and 6-31G(d) as the basis function, further by the time-dependent density functional method (Time-Dependent DFT). Performing an excited state calculation to obtain the energies of S ₁ and T ₁ (E(S ₁ ), E(T ₁ ), respectively) and calculate as ΔEst=|E(S ₁ )−E(T ₁ )| Is also possible. The smaller the calculated ΔEst, the smaller the overlap between HOMO and LUMO. In the present invention, ΔEst calculated using the same calculation method as described above is preferably 0.5 eV or less, more preferably 0.2 eV or less, and further preferably 0.1 eV or less.
When ΔEst is 0.5 eV or less, the π-conjugated compound in the present invention exhibits a heat-activated delayed fluorescence.

[Fluorescence quantum yield]
The fluorescence quantum yield is represented by the ratio of the number of photons absorbed and the number of photons emitted. If all the excited molecules return to the ground state by fluorescence, the fluorescence quantum yield will be 1, but will not actually be 1 due to non-radiative deactivation.
Non-radiative deactivation is a transition that returns to the ground state without emitting fluorescence, and in addition to relaxation to the triplet state due to intersystem crossing, the energy of the electronic state is converted into vibrational energy and finally becomes thermal energy. Internal conversion and energy transfer that transfers energy to other molecules.
Letting Kf and Knr be the rate constants of fluorescence transition and non-radiative transition of the molecule in the excited state, the quantum yield Φ is
Φ=Kf/(Kf+Knr)
It is represented by.

<<Organic EL element constituent layers>>
Typical element configurations of the organic EL element of the present invention include, but are not limited to, the following configurations.
(1) Anode/light emitting layer//cathode (2) Anode/light emitting layer/electron transport layer/cathode (3) Anode/hole transport layer/light emitting layer/cathode (4) Anode/hole transport layer/light emitting layer/ Electron transport layer/cathode (5) Anode/hole transport layer/light emitting layer/electron transport layer/electron injection layer/cathode (6) Anode/hole injection layer/hole transport layer/light emitting layer/electron transport layer/cathode (7) Anode/hole injection layer/hole transport layer/(electron blocking layer/) light emitting layer/(hole blocking layer/) electron transport layer/electron injection layer/cathode It is preferably used, but not limited thereto.
The light emitting layer used in the present invention is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the respective light emitting layers.

If necessary, a hole blocking layer (also referred to as a hole blocking layer) or an electron injection layer (also referred to as a cathode buffer layer) may be provided between the light emitting layer and the cathode. An electron blocking layer (also referred to as an electron barrier layer) or a hole injection layer (also referred to as an anode buffer layer) may be provided therebetween.
The electron transport layer used in the present invention is a layer having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. Also, it may be composed of a plurality of layers.
The hole transport layer used in the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. Also, it may be composed of a plurality of layers.
In the above-mentioned typical element structure, the layer excluding the anode and the cathode is also referred to as "organic layer".

(Tandem structure)
The organic EL element of the present invention may be an element having a so-called tandem structure in which a plurality of light emitting units including at least one light emitting layer are laminated.
Examples of typical tandem structure element configurations include the following configurations.
Anode/first light emitting unit/intermediate layer/second light emitting unit/intermediate layer/third light emitting unit/cathode Here, even if the first light emitting unit, the second light emitting unit and the third light emitting unit are all the same, It may be different. Further, the two light emitting units may be the same and the other one may be different.
The plurality of light emitting units may be directly laminated or may be laminated with an intermediate layer interposed therebetween. A known material structure can be used as long as it is also called an insulating layer and has a function of supplying electrons to the adjacent layer on the anode side and supplying holes to the adjacent layer on the cathode side.

Examples of the material used for the intermediate layer include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiO _x , VO _x , CuI, InN, GaN, and the like. A conductive inorganic compound layer such as CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ , and Al, a two-layer film such as Au/Bi ₂ O ₃ , SnO ₂ /Ag/SnO ₂ , ZnO/ Multilayer films of Ag/ZnO, Bi ₂ O ₃ /Au/Bi ₂ O ₃ , TiO ₂ /TiN/TiO ₂ , TiO ₂ /ZrN/TiO _2, etc., and fullerene such as C ₆₀ , and electroconductivity of oligothiophene etc. Examples include organic material layers, metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, metal-free porphyrins, and other conductive organic compound layers, but the present invention is not limited thereto.
Examples of preferable configurations in the light emitting unit include those obtained by removing the anode and the cathode from the configurations of (1) to (7) mentioned in the above typical element configurations. Not limited.

  Specific examples of the tandem organic EL device include, for example, US Pat. No. 6,337,492, US Pat. No. 7,420,203, US Pat. No. 7,473,923, US Pat. No. 6,872,472, US Pat. No. 6,107,734, US Pat. Publication No. 2005/009087, JP 2006-228712 A, JP 2006-24791 A, JP 2006-49393 A, JP 2006-49394 A, JP 2006-49396 A, JP 2011 A. -96679, Japanese Patent Laid-Open No. 2005-340187, Japanese Patent No. 4711424, Japanese Patent No. 34096681, Japanese Patent No. 3884564, Japanese Patent No. 4213169, Japanese Patent No. 2010-192719, Japanese Patent Laid-Open No. 2009-076929. No. JP-A-2008-078414, JP-A-2007-059848, JP-A-2003-272860, JP-A-2003-045676, and International Publication No. 2005/094130. Examples of the material include, but are not limited to, the present invention.

Hereinafter, each layer constituting the organic EL device of the present invention will be described.
<Light emitting layer>
The light-emitting layer used in the present invention is a layer that provides a field where electrons and holes injected from an electrode or an adjacent layer are recombined and emit light via excitons. It may be in the layer or at the interface between the light emitting layer and the adjacent layer. The structure of the light emitting layer used in the present invention is not particularly limited as long as it satisfies the requirements specified in the present invention.

The total thickness of the light emitting layer is not particularly limited, but the uniformity of the formed film and the application of an unnecessary high voltage during light emission are prevented, and the stability of the emission color with respect to the drive current is improved. From the viewpoint, it is preferably adjusted to the range of 2 nm to 5 μm, more preferably adjusted to the range of 2 to 500 nm, and further preferably adjusted to the range of 5 to 200 nm.
The layer thickness of each light emitting layer used in the present invention is preferably adjusted within the range of 2 nm to 1 μm, more preferably within the range of 2 to 200 nm, and further preferably within the range of 3 to 150 nm. Adjusted within range.

  The light-emitting layer used in the present invention contains a light-emitting dopant (a light-emitting compound, a light-emitting dopant compound, a dopant compound, or simply a dopant), and further a host compound (a matrix material, a light-emitting host compound, or simply a host). .) is preferably contained.

(1) Luminescent Dopant As the luminescent dopant, a fluorescent luminescent dopant (also referred to as a fluorescent luminescent compound, a fluorescent dopant, or a fluorescent compound), a delayed fluorescent dopant, a phosphorescent luminescent dopant (phosphorescent luminescent compound, phosphorescent) A dopant or a phosphorescent compound) is preferably used.
In the present invention, at least one light emitting layer has a structure represented by the above general formula (1) and contains a π-conjugated compound having ΔEst of 0.5 eV or less as a light emitting dopant or an assist dopant. It is characterized by
In the present invention, the light emitting layer preferably contains the π-conjugated compound in the range of 5 to 40% by mass, and particularly preferably in the range of 10 to 30% by mass.
The concentration of the π-conjugated compound in the light emitting layer can be arbitrarily determined based on the specific π-conjugated compound used and the requirements of the device, and is uniform in the thickness direction of the light emitting layer. It may be contained at any concentration, and may have any concentration distribution.
Further, the π-conjugated compound according to the present invention may be used in combination of two or more kinds, and may be a combination of π-conjugated compounds having different structures, or a combination of the π-conjugated compound and a phosphorescent compound. You may use. As a result, any luminescent color can be obtained.

The luminescent color of the organic EL device of the present invention or the compound used in the present invention is shown in FIG. It is determined by the color when the result measured by the luminance meter CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.
In the present invention, it is also preferable that one or a plurality of light emitting layers contain a plurality of light emitting dopants having different light emitting colors and emit white light.

The combination of light emitting dopants exhibiting white is not particularly limited, but examples thereof include combinations of blue and orange, combinations of blue, green and red, and the like.
White in the organic EL device of the present invention means that the chromaticity in the CIE1931 color system at 1000 cd/m ² is x=0.39±0.09 when the 2° viewing angle front luminance is measured by the above method. , Y=0.38±0.08.

(1.1) π-Conjugated Compound The π-conjugated compound according to the present invention is characterized by having a structure represented by the following general formula (1) and having a ΔEst of 0.5 eV or less.

(In the general formula (1),
EDG is represented by the following general formula (1A):
(In the general formula (1A),
X and Y each independently represent CR ₂ , SiR ₂ , or an oxygen atom,
R represents a hydrogen atom or a substituent,
R ¹ and R ² each independently represent a substituent,
n4 and n5 are each independently an integer of 1 to 3),
Is a structure represented by
L represents a single bond or a substituted or unsubstituted arylene group,
EWG is a fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, an optionally substituted carbonyl group, an optionally substituted sulfonyl group, an optionally substituted phosphine oxide group, and an optionally substituted Represents an electron withdrawing group selected from the group consisting of an electron withdrawing heterocyclic ring,
n1, n2 and n3 are each independently an integer of 1 to 3. )

  The π-conjugated compound represented by the general formula (1) has an electron donating group EDG represented by the general formula (1A) and an electron withdrawing group EWG. Such a structure can exhibit TADF property while maintaining high light emission. Although the mechanism of action or mechanism of action of the present invention has not been clarified, it is presumed as follows.

  FIG. 2A shows a compound having an electron donating group, dihydroacridine, and anthracene. In this compound, the dihedral angle θ formed by the π planes of the two benzene rings of dihydroacridine is 0°, and the planarity is very high. It has been clarified by the software for molecular orbital calculation that the electron orbit of the HOMO of the electron-donating group having high planarity is localized on the electron-donating group. This is because the two benzene rings of the electron-donating group are in the same plane, and thus they easily interact with each other. In this compound, since dihydroacridine and anthracene are largely twisted, and the conjugated system is divided between the electron-donating group and the anthracene site, ΔEst becomes small. However, the spread of the conjugated system is small, so that the light emitting property is low.

  FIG. 2B shows a compound having diphenylamine, which is an electron-donating group, and anthracene. In this compound, the dihedral angle θ formed by the π planes of the two benzene rings of diphenylamine is about 44°, and the flatness is low. The HOMO of the electron-donating group having low planarity is distributed on the electron-donating group and the anthracene. This is because the two benzene rings of the electron-donating group are twisted, so that the interaction between the benzene rings is reduced and the orbit of anthracene interacts to compensate for the decrease. As described above, the compound in which the π-conjugated system is widely distributed in the electron-donating group and the anthracene site has high light emitting property. However, since the orbits of HOMO and LUMO overlap each other, ΔEst becomes large.

  Unlike the conventional compounds shown in FIGS. 2A and 2B, the structure of the general formula (1) has an electron donating group EDG represented by the general formula (1A) and an electron withdrawing group EWG. Therefore, the electron donating group EDG represented by the general formula (1A) has a dibenzoazepine structure having low planarity. In this structure, the two benzene rings are twisted, and the dihedral angle θ formed by the π plane containing one benzene ring and the π plane containing the other benzene ring exceeds 0° and is less than 40°. There is. Since the HOMO of the electron-donating group having low planarity is widely distributed on the dibenzoazepine structure which is the electron-donating group and the structure bonded thereto, the compound has high light emitting property. Further, in the compound of the general formula (1), the steric repulsion between the dibenzoazepine structure, which is the electron donating group EDG, and the electron withdrawing group EWG is large, and the conjugated system is composed of the electron donating group and the electron withdrawing group. Since they are divided, ΔEst becomes small and TADF property is exhibited.

L in the general formula (1) represents a single bond or a substituted or unsubstituted arylene group. The arylene group which L can take may be a monocyclic arylene group or a condensed ring arylene group. For example, a ring structure selected from the following ring structure group X is preferable.
Ring structure group X:
Benzene ring, indene ring, naphthalene ring, azulene ring, fluorene ring, phenanthrene ring, anthracene ring, acenaphthylene ring, biphenylene ring, chrysene ring, naphthacene ring, pyrene ring, pentalene ring, aceanthrylene ring, heptalen ring, triphenylene ring, as-indacene ring, chrysene ring, s-indacene ring, pleiaden ring, phenalene ring, fluoranthene ring, perylene ring, acephenanthrylene ring, biphenyl ring, terphenyl ring, tetraphenyl ring, carbazole ring, indoloindole ring , 9,10-dihydroacridine ring, phenoxazine ring, phenothiazine ring, dibenzothiophene ring, benzofurylindole ring, benzothienoindole ring, indolocarbazole ring, benzofurylcarbazole ring, benzothienocarbazole ring, benzothienobenzothiophene ring , Benzocarbazole ring, dibenzocarbazole ring, dibenzofuran ring, benzofurylbenzofuran ring, dibenzosilole ring.

  Among the ring structures selected from the above ring structure group, more preferred are a benzene ring, a naphthalene ring, a fluorene ring, a phenanthrene ring, a biphenylene ring, a pyrene ring, a triphenylene ring, a chrysene ring, a fluoranthene ring, a perylene ring and a biphenyl ring. , Terphenyl ring, carbazole ring, indoloindole ring, 9,10-dihydroacridine ring, phenoxazine ring, phenothiazine ring, benzofurylindole ring, benzothienoindole ring, indolocarbazole ring, benzothienobenzothiophene ring, dibenzo Examples thereof include a carbazole ring, a dibenzofuran ring, and a benzofurylbenzofuran ring. These structures are preferable because they improve the stability of the compound.

  In the formula (1), n2 representing the number of L is an integer of 1 to 3.

  EWG in the general formula (1) is an electron-withdrawing group, and specifically, a fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, an optionally substituted carbonyl group, or an optionally substituted carbonyl group. It is one selected from the group consisting of a good sulfonyl group, an optionally substituted phosphine oxide group, and an optionally substituted electron withdrawing heterocycle. Particularly, the electron withdrawing group is preferably a fluorine atom, a cyano group, or an optionally substituted electron withdrawing heterocyclic ring from the viewpoint of improving the stability of the compound.

  The "optionally substituted carbonyl group", the "optionally substituted sulfonyl group", and the "optionally substituted phosphine oxide group" include a deuterium atom, a fluorine atom, a cyano group, and a fluorine atom. An alkyl group optionally substituted with, an aryl ring substituted with an alkyl group, an aryl ring optionally substituted with an electron-withdrawing group, an electron-donating heterocycle optionally substituted, substituted with A good electron-withdrawing heterocycle can be mentioned.

Examples of the “electron-withdrawing heterocycle” of the “optionally substituted electron-withdrawing heterocycle” include heterocycles having 3 to 24 carbon atoms, and specific examples thereof include a pyridine ring, Pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, isoquinoline ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, phenanthridine ring, phenanthroline ring, dibenzofuran ring, dibenzothiophenedioxide ring, Examples thereof include a dibenzosilole ring, a dibenzoborol ring and a dibenzophosphole oxide ring.
Examples of the substituent of the “optionally substituted electron-withdrawing heterocycle” include a fluorine atom, a cyano group, an optionally substituted alkyl group, and an optionally substituted aryl ring.

  In the formula (1), n3 representing the number of EWGs is an integer of 1 to 3.

The EDG in the general formula (1) has a structure represented by the following general formula (1A).
(In the general formula (1A),
X and Y each independently represent CR ₂ , SiR ₂ , or an oxygen atom,
R represents a hydrogen atom or a substituent,
R ¹ and R ² each independently represent a substituent,
n4 and n5 are each independently an integer of 1 to 3. )

  In the formula (1), n1 representing the number of EDGs is an integer of 1 to 3.

The substituent used as R ¹ and R ² in the general formula (1A) is not particularly limited, and may be an electron-withdrawing substituent or an electron-donating substituent. Examples of such a substituent include an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group). Etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aromatic hydrocarbon group (aromatic) Also called aromatic hydrocarbon ring group, aromatic carbocyclic group, aryl group, etc., for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group. Group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group [eg, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (For example, 1,2,4-triazol-1-yl group, 1,2,3-triazol-1-yl group, etc.), oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, flazanyl Group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, carborinyl group, diazacarbazolyl group (carbon atom constituting the carboline ring of the carborinyl group One of which is replaced by a nitrogen atom), quinoxalinyl group, pyridazinyl group, triazinyl group, quinazolinyl group, phthalazinyl group, etc.], heterocyclic group (for example, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), Alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryl Oxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group) Group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group) Etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxy) Carbonyl group), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenyl Aminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc., acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group) , Dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc., acyloxy group (eg, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyl) Oxy group etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group) Group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc., carbamoyl group (eg, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylamino) Carbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc., ureido group (for example, methylureido group, ethylureido group) , Pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl Group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group ( For example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (eg, phenylsulfonyl group, naphthylsulfonyl group, 2 -Pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, diphenylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group) Group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, etc.), fluorohydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl) Group), a cyano group, a nitro group, a hydroxy group, a mercapto group, a silyl group (for example, a trimethylsilyl group, a triisopropylsilyl group, a triphenylsilyl group, a phenyldiethylsilyl group, etc.), and a phosphono group.

In the structure of the general formula (1A), since dibenzoazepine is an electron-donating site, it is preferable that at least one of the substituents R ¹ and R ² bonded to the site be an electron-donating group. . Specifically, it is preferably one selected from the group consisting of an electron-donating alkyl group, a cycloalkyl group, an aromatic hydrocarbon group, an aromatic heterocyclic group, an amino group, and a silyl group. More preferably, it is one selected from the group consisting of a group, a carbazolyl group, a diphenylamino group, and a tert-butyl group.

  Moreover, these substituents may be further substituted by the above-mentioned substituents. Further, a plurality of these substituents may be bonded to each other to form a ring.

X and Y in the general formula (1A) each independently represent CR ₂ , SiR ₂ , or an oxygen atom. R in CR ₂ and SiR ₂ is a hydrogen atom or a substituent. Specific examples of the substituent include an alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group). Etc.), a cycloalkyl group (for example, a cyclopentyl group, a cyclohexyl group, etc.), an aromatic hydrocarbon group (for example, an aromatic hydrocarbon ring group, an aromatic carbocyclic group, an aryl group, etc.), for example, a phenyl group, p- Chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc., aromatic heterocyclic group (for example, pyridyl) Group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1,2,4-triazol-1-yl group, 1,2,3-triazole-1 -Yl group, etc.), heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyl group) Oxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), amino group (eg, amino group, ethylamino group, dimethylamino group, diphenylamino group, butylamino group, cyclopentyl group) Amino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (for example, fluorine atom, chlorine atom, bromine atom, etc.), fluorohydrocarbon group (for example, , Fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (eg, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl) Group, a phenyldiethylsilyl group, etc.), a phosphono group, etc. Preferred are an electron-donating alkyl group, a cycloalkyl group, an aromatic hydrocarbon group, an aromatic heterocyclic group, an amino group and a silyl group. Be done.

  In the π-conjugated compound represented by the general formula (1), the electron donating group EDG preferably has a structure represented by the following general formula (2A) from the viewpoint of improving the stability of the compound.

(In the general formula (2A),
R ¹ and R ² each independently represent a substituent,
n4 and n5 are each independently an integer of 1 to 3. )

^{R 1} and ^{R 2} in the general formula (2A), similar to ^{R 1} and ^{R 2} in general formula (1A), each independently represent a substituent, at least one of ^{R 1} and ^{R 2} is an electron-donating It is preferably a substituent. Specific examples of the substituent that can be used as R ¹ and R ² in the general formula (2A) are the same as those exemplified as R ¹ and R ² in the general formula (1A).

In formulas (1A) and (2A), n4 and n5 representing the numbers of R ¹ and R ² are each independently an integer of 1 to 3.

  Preferred specific examples of the π-conjugated compound represented by the general formula (1) are shown below, but these compounds may further have a substituent and may be structural isomers of these, The present invention is not limited to these.

<Method for synthesizing π-conjugated compound of the present invention>
The π-conjugated compound can be synthesized by a known method. The synthesis method will be described by taking the compound D-1 as an example.

  Dibenzazepine (intermediate 1) (5.00 g, 25.6 mmol), 1,4-dibromobenzene (intermediate 2) (7.25 g, 30.7 mmol), palladium acetate (575 mg, 2.56 mmol), xantphos (2.96 g, 5.12 mmol) and cesium carbonate (16.7 g, 51.2 mmol) are dissolved in 100 mL of xylene and heated to 140° C. for 16 hours under nitrogen atmosphere. After cooling to room temperature, the reaction solution was diluted with ethyl acetate and passed through Celite. After the solution was distilled off with an evaporator, the residue was purified by silica gel column chromatography (ethyl acetate 20%, heptane 80%) to obtain Intermediate 3 as a white solid (7.44 g, yield 83%).

  Intermediate 3 (7.44 g, 21.2 mmol), bis(pinacolato)diboron (5.92 g, 30.7 mmol) and potassium acetate (4.16 g, 42.4 mmol) were dissolved in 200 mL of dimethyl sulfoxide, and nitrogen atmosphere was added. Heating to 80° C. for 4 hours. After cooling to room temperature, 200 mL of ethyl acetate and 200 mL of water are added to the reaction solution to separate it. The obtained organic layer is distilled off with an evaporator and recrystallized from a mixed solvent of ethyl acetate and heptane to obtain Intermediate 4 as a white solid (5.49 g, yield 65%).

  Intermediate 4 (2.00 g, 5.03 mmol), 2-chloro-4,6-diphenyl-1,3,5-triazine (Intermediate 5) (1.35 g, 5.04 mmol), palladium acetate ( 113 mg, 0.50 mmol), 2-dicyclohexylphosphino-2,6-dimethoxybiphenyl (410 mg, 1.00 mmol) and potassium phosphate (2.14 g, 10.1 mmol) in toluene (80 mL) water (10 mL) 1, Dissolve in a mixed solution of 4-dioxane (10 mL) and heat to 100° C. for 16 hours under nitrogen atmosphere. After cooling to room temperature, the reaction solution was diluted with ethyl acetate and passed through Celite. After distilling off this solution with an evaporator, the residue is purified by silica gel column chromatography (ethyl acetate 20%, heptane 80%) to obtain D-1 as a white solid (2.02 g, yield 80%).

(1.2) Phosphorescent Luminescent Dopant The phosphorescent luminescent dopant used in the present invention will be described.
The phosphorescent dopant used in the present invention is a compound in which light emission from an excited triplet is observed, specifically, a compound which emits phosphorescence at room temperature (25° C.), and has a phosphorescence quantum yield. Is defined as a compound of 0.01 or more at 25° C., but a preferable phosphorescence quantum yield is 0.1 or more.
The above-mentioned phosphorescence quantum yield can be measured by the method described on page 398 of Spectroscopy II of Fourth Edition Experimental Chemistry Course 7 (1992 version, Maruzen). The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescence dopant used in the present invention achieves the above phosphorescence quantum yield (0.01 or more) in any solvent. Just do it.

The phosphorescent dopant can be appropriately selected and used from known ones used for the light emitting layer of the organic EL device. Specific examples of known phosphorescent dopants that can be used in the present invention include compounds described in the following documents.
Nature 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17, 1059 (2005), International Publication No. 2009/100991, International Publication No. 2008/101842, International Publication No. 2003/040257, US Patent Application Publication No. 2006/835469, US Patent Application Publication No. 2006/ 0202194, US Patent Application Publication No. 2007/0087321, US Patent Application Publication No. 2005/0244673, Inorg. Chem. 40, 1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chem. lnt. Ed. 2006, 45, 7800, Appl. Phys. Lett. 86,153505 (2005), Chem. Lett. 34, 592 (2005), Chem. Commun. 2906 (2005), Inorg. Chem. 42, 1248 (2003), International Publication No. 2009/050290, International Publication No. 2002/015645, International Publication No. 2009/000673, US Patent Application Publication No. 2002/0034656, US Patent No. 7332232. U.S. Patent Application Publication No. 2009/0108737, U.S. Patent Application Publication No. 2009/00397776, U.S. Patent No. 6,921,915, U.S. Patent No. 6,687,266, U.S. Patent Application Publication No. 2007/0190359. Description, U.S. Patent Application Publication No. 2006/0008670, U.S. Patent Application Publication No. 2009/0165846, U.S. Patent Application Publication No. 2008/0015355, U.S. Patent No. 7,250,226, U.S. Patent No. 7396598, U.S. Patent Application Publication No. 2006/0263635, U.S. Patent Application Publication No. 2003/0138657, U.S. Patent Application Publication No. 2003/0152802, U.S. Patent No. 7,090,928, Angew. ． Chem. lnt. Ed. 47, 1 (2008), Chem. Mater. 18, 5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics 23, 3745 (2004), Appl. Phys. Lett. 74, 1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/009024, International Publication No. 2006/056418, International Publication No. 2005/019373, International Publication No. 2005/123873, International Publication No. 2007/004380, International Publication No. 2006/082742, US Patent Application Publication No. 2006/0251923, US Patent Application Publication No. 2005/0260441, US Patent No. 7393599, US Patent No. 7534505. Description, U.S. Pat.No. 7,445,855, U.S. Patent Application Publication No. 2007/0190359, U.S. Patent Application Publication No. 2008/0297033, U.S. Patent No. 7,338,722, U.S. Patent Application Publication No. 2002/ No. 0134984, U.S. Pat. No. 7,279,704, U.S. Patent Application Publication No. 2006/098120, U.S. Patent Application Publication No. 2006/103874, International Publication No. 2005/076380, International Publication No. 2010/ 0326663, International Publication No. 2008140115, International Publication No. 2007/052431, International Publication No. 2011/134013, International Publication No. 2011/157339, International Publication No. 2010/086089, International Publication No. 2009/113646, International Publication No. 2012/020327, International Publication No. 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149, US Patent Application Publication No. 2012/228583, US Patent Application Publication No. 2012/ No. 212126, JP2012-069737A, JP2012-195554A, JP2009-114086A, JP2003-81988A, JP2002-302671A, JP2002-363552. Issue publications and the like.

  Among them, preferable phosphorescent dopants include organic metal complexes having Ir as a central metal. More preferably, a complex containing at least one coordination mode of a metal-carbon bond, a metal-nitrogen bond, a metal-oxygen bond and a metal-sulfur bond is preferable.

(1.3) Fluorescent compound that can be used in combination with π-conjugated compound A fluorescent compound (also called a fluorescent dopant) that can be used in combination with the π-conjugated compound according to the present invention will be described.
The fluorescent light-emitting compound that can be used in combination with the π-conjugated compound according to the present invention is not particularly limited, and for example, a fluorescent light-emitting compound having ΔEst larger than 0.5 eV can also be preferably used, and other anthracene derivatives, Pyrene derivative, chrysene derivative, fluoranthene derivative, perylene derivative, fluorene derivative, arylacetylene derivative, styrylarylene derivative, styrylamine derivative, arylamine derivative, boron complex, coumarin dye, pyran dye, cyanine dye, croconium dye, Squarium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes, polythiophene dyes, rare earth complex dyes, etc. A compound having a high quantum yield may be mentioned.

(2) Host compound The host compound used in the present invention is a compound mainly responsible for injecting and transporting charges in the light emitting layer, and emission of light itself is not substantially observed in the organic EL device.
Among the compounds contained in the light emitting layer, the host compound preferably has a mass ratio of 20% or more in the layer.
The host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the transfer of charges and improve the efficiency of the organic EL device.
The host compound preferably used in the present invention is described below.

The host compound used with the π-conjugated compound in the present invention is not particularly limited, but from the viewpoint of reverse energy transfer, those having an excitation energy larger than the excitation singlet energy of the π-conjugated compound according to the present invention are preferable. Further, those having an excited triplet energy larger than that of the π-conjugated compound according to the present invention are more preferable.
The host compound is responsible for transporting carriers and generating excitons in the light emitting layer. Therefore, cation radical state, anion radical state, and can exist stably in the state of all active species of the excited state, does not cause chemical changes such as decomposition and addition reactions, further, the host molecule in the layer over time with electricity It is preferable not to move at the Angstrom level.

Further, particularly when the luminescent dopant used in combination exhibits TADF emission, since the existence time of the triplet excited state of the TADF compound is long, the T ₁ energy of the host compound itself is high, and further the state in which the host compounds are associated with each other. in prevention of generation of a low T ₁ state, that the TADF compound and the host compound does not form a exciplex, such that the host compound does not form a electro-mer by the electric field, the host compound is a molecular structure such as not to lower T ₁ of Appropriate design is required.
In order to meet these requirements, the host compound itself must have high electron hopping mobility, high hole hopping mobility, and a small structural change in the triplet excited state. Is. As a typical example of a host compound satisfying such requirements, a carbazole skeleton, an azacarbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an azadibenzofuran skeleton, which has a high T ₁ energy and an extended π-conjugated skeleton of a 14π electron system, is used. Those having a partial structure are preferred. In particular, when the light emitting layer contains a carbazole derivative, proper carrier hopping in the light emitting layer and dispersion of the light emitting material can be promoted, and an effect of improving the light emitting performance of the device and the stability of the thin film can be obtained. Therefore, it is preferable.

Furthermore, typical examples include compounds in which these rings have a biaryl and/or multiaryl structure. The term "aryl" used herein includes not only an aromatic hydrocarbon ring but also an aromatic heterocycle.
More preferably, it is a compound in which a carbazole skeleton and a 14π-electron aromatic heterocyclic compound having a molecular structure different from that of the carbazole skeleton are directly bonded, and a 14π-electron aromatic heterocyclic compound is further incorporated into the molecule. Carbazole derivatives having three or more are preferred. Particularly, it is preferable that the carbazole derivative is a compound having two or more conjugated structure portions having 14π electrons or more in order to further enhance the effects of the present invention.

The preferred host compound used in the present invention may be a low molecular weight compound having a molecular weight such that sublimation purification is possible, or a polymer having a repeating unit.
In the case of a low molecular weight compound, since sublimation purification is possible, there is an advantage that purification is easy and a high-purity material is easily obtained. The molecular weight is not particularly limited as long as sublimation purification is possible, but the preferable molecular weight is 3,000 or less, more preferably 2,000 or less.
A polymer or oligomer having a repeating unit is advantageous in that it can be easily formed into a film by a wet process, and in general, the polymer has a high Tg and is preferable in terms of heat resistance.

In addition, the host compound has a hole transporting ability or an electron transporting ability, prevents the emission of light having a long wavelength, and is stable against heat generation during driving of the organic EL device at high temperature or during device driving. From the viewpoint of operation, it is preferable to have a high glass transition temperature (Tg). The Tg is preferably 90°C or higher, more preferably 120°C or higher.
Here, the glass transition point (Tg) is a value determined by a method according to JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

When a known host compound is used in the organic EL device of the present invention, specific examples thereof include compounds described in the following documents, but the present invention is not limited thereto.
JP-A-2001-257076, JP-A-2002-308855, JP-A-2001-313179, JP-A-2002-319491, JP-A-2001-357977, JP-A-2002-334786, and JP-A-2002-8860, No. 2002-334787, No. 2002-15871, No. 2002-334788, No. 2002-43056, No. 2002-334789, No. 2002-75645, No. 2002-338579, No. No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453, No. 2003. No. 3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-260861, No. 2002-280183, No. 2002-299060, No. 2002. No. 302516, No. 2002-305083, No. 2002-305084, No. 2002-308837, U.S. Patent Application Publication No. 2003/01775553, U.S. Patent Application Publication No. 2006/0280965, U.S.A. Patent Application Publication No. 2005/0112407, US Patent Application Publication No. 2009/0017330, US Patent Application Publication No. 2009/0030202, US Patent Application Publication No. 2005/0238919, International Publication No. 2001/039234, International Publication No. 2009/021126, International Publication No. 2008/056746, International Publication No. 2004/093207, International Publication No. 2005/089025, International Publication No. 2007/063796, International Publication No. 2007/ 063754, International Publication No. 2004/107822, International Publication No. 2005/030900, International Publication No. 2006/114966, International Publication No. 2009/086028, International Publication No. 2009/003898, International Publication No. 2012/023947. Japanese Patent Application Laid-Open No. 2008-074939, Japanese Patent Application Laid-Open No. 2007-254297, European Patent No. 2034538, International Publication No. 2011/055933, International Publication No. 2012/035853 and the like.
Specific examples of the host compound used in the present invention include compounds represented by H-1 to H231 described in paragraphs [0255] to [0293] of JP-A-2015-38941 and the following H- Examples of the host compound that can be used in the present invention are not limited to these.

(3) Action of π-conjugated compound In the light-emitting layer according to the present invention, the π-conjugated compound according to the present invention, which has the structure represented by the general formula (1) and ΔEst is 0.5 eV or less, It is preferable to contain a fluorescent and/or phosphorescent compound from the viewpoint of exhibiting high luminous efficiency.
The light emitting layer may or may not contain a host compound, but preferably contains it.
The π-conjugated compound, the light-emitting compound, and the host compound according to the present invention are not limited in the number of components in the light-emitting layer. It is preferable that there is no compound, or that one type is contained, and it is further preferable that one type of each of the π-conjugated compound, the light emitting compound, and the host compound be contained.

  When the host compound is contained in the light emitting layer including the π-conjugated compound having the ΔEst of 0.5 eV or less according to the present invention and the luminescent compound, the π-conjugated compound according to the present invention acts as an assist dopant. However, when the host compound is not contained, the π-conjugated compound according to the present invention acts as a host compound.

  The mechanism for producing the effect is the same in any case, and the point of converting triplet excitons generated on the π-conjugated compound according to the present invention into singlet excitons by reverse intersystem crossing (RISC). It is in. As a result, theoretically all excitonic energies generated on the π-conjugated compound according to the present invention can be energy-transferred to the luminescent compound, and high luminous efficiency can be realized.

As an example, FIGS. 3A and 3B show schematic diagrams in the case where the π-conjugated compound according to the present invention acts as an assist dopant and a host compound, respectively.
However, the generation process of triplet excitons generated on the π-conjugated compound according to the present invention is not limited to electric field excitation, and includes energy transfer and electron transfer in the light emitting layer or from the peripheral layer interface. Further, in FIGS. 3A and 3B, a fluorescent light emitting compound is used as the light emitting material, but the light emitting material is not limited to this, and a phosphorescent light emitting compound may be used, or a fluorescent light emitting compound and a phosphorescent light emitting compound may be used. Both of the sex compounds may be used.

When a π-conjugated compound having a ΔEst of 0.5 eV or less according to the present invention is used as an assist dopant, 100% or more by mass of the π-conjugated compound is present in the host compound, resulting in fluorescence and/or phosphorescence emission. It is preferable that the light-emitting layer contain the functional compound in a mass ratio of 0.1% to 50% with respect to the π-conjugated compound.
Energy levels of S ₁ and T ₁ of the π-conjugated compounds according to the present invention is lower than the energy level of the S ₁ and T ₁ of the host compound, than the energy level of the S ₁ and T ₁ of the light-emitting compound Higher is also preferable.

When a π-conjugated compound having ΔEst of 0.5 eV or less according to the present invention is used as a host compound, the fluorescent and/or phosphorescent compound has a mass ratio of 0.1% to 50 with respect to the π-conjugated compound. % Of the light emitting layer is preferable.
The energy levels of S ₁ and T ₁ of the π-conjugated compound according to the present invention are preferably higher than the energy levels of S ₁ and T ₁ of the light emitting compound.

  When a π-conjugated compound having ΔEst of 0.5 eV or less according to the present invention is used as an assist dopant or a host compound, it is preferable that the emission spectrum of the π-conjugated compound and the absorption spectrum of the luminescent compound overlap.

<Electron transport layer>
In the present invention, the electron transport layer is made of a material having a function of transporting electrons, and may have a function of transmitting the electrons injected from the cathode to the light emitting layer.
The total thickness of the electron transport layer according to the present invention is not particularly limited, but is usually in the range of 2 nm to 5 μm, more preferably 2 to 500 nm, further preferably 5 to 200 nm.

  Further, in the organic EL element, when the light generated in the light emitting layer is extracted from the electrode, the light directly extracted from the light emitting layer interferes with the light extracted after being reflected by the electrode located opposite the electrode for extracting the light. It is known to wake up. When the light is reflected by the cathode, it is possible to efficiently use this interference effect by appropriately adjusting the total layer thickness of the electron transport layer within the range of several nm to several μm.

On the other hand, when the layer thickness of the electron transport layer is increased, the voltage tends to increase. Therefore, especially when the layer thickness is large, the electron mobility of the electron transport layer is preferably 10 ⁻⁵ cm ² /Vs or more. ..
The material used for the electron-transporting layer (hereinafter referred to as electron-transporting material) may have any of an electron injecting property, a transporting property, and a hole blocking property, and may be selected from conventionally known compounds. Those selected can be used.

  For example, nitrogen-containing aromatic heterocyclic derivatives (carbazole derivatives, azacarbazole derivatives (one or more of the carbon atoms constituting the carbazole ring are substituted with nitrogen atoms), pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, pyridazine derivatives, Triazine derivative, quinoline derivative, quinoxaline derivative, phenanthroline derivative, azatriphenylene derivative, oxazole derivative, thiazole derivative, oxadiazole derivative, thiadiazole derivative, triazole derivative, benzimidazole derivative, benzoxazole derivative, benzthiazole derivative, etc.), dibenzofuran derivative, Examples thereof include dibenzothiophene derivatives, silole derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, triphenylene derivatives, etc.).

  Further, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, for example, tris(8-quinolinol)aluminum (Alq), tris(5,7-dichloro-8-quinolinol)aluminum, tris(5,7- Dibromo-8-quinolinol)aluminum, tris(2-methyl-8-quinolinol)aluminum, tris(5-methyl-8-quinolinol)aluminum, bis(8-quinolinol)zinc (Znq), and the like, and their metal complexes. A metal complex in which the central metal is replaced with In, Mg, Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material.

In addition, metal-free or metal phthalocyanine, or those whose terminal is substituted with an alkyl group, a sulfonic acid group, or the like can be preferably used as the electron transport material. Further, the distyrylpyrazine derivatives exemplified as the material for the light emitting layer can also be used as the electron transport material, and like the hole injection layer and the hole transport layer, an inorganic semiconductor such as n-type-Si or n-type-SiC. Can also be used as an electron transport material.
Further, a polymer material obtained by introducing these materials into a polymer chain or using these materials as a polymer main chain can also be used.

  In the electron transport layer according to the present invention, the electron transport layer may be doped with a dopant as a guest material to form an electron transport layer having a high n property (electron rich). Examples of the doping material include n-type dopants such as metal compounds such as metal complexes and metal halides. Specific examples of the electron transport layer having such a structure include, for example, JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175 and J. Appl. Phys. , 95, 5773 (2004) and the like.

Specific examples of known preferable electron transporting materials used in the organic EL device of the present invention include compounds described in the following documents, but the present invention is not limited thereto.
U.S. Patent No. 6,528,187, U.S. Patent No. 7,230,107, U.S. Patent Application Publication No. 2005/0025993, U.S. Patent Application Publication No. 2004/0036077, U.S. Patent Application Publication No. 2009/0115316. , U.S. Patent Application Publication No. 2009/0101870, U.S. Patent Application Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132085, Appl. Phys. Lett. 75, 4 (1999), Appl. Phys. Lett. 79, 449 (2001), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 79, 156 (2001), U.S. Patent No. 7,964,293, U.S. Patent Application Publication No. 2009/030202, International Publication No. 2004/080975, International Publication No. 2004/063159, International Publication No. 2005/085387. , International Publication No. 2006/067931, International Publication No. 2007/086552, International Publication No. 2008/114690, International Publication No. 2009/06942, International Publication No. 2009/066779, International Publication No. 2009/054253, International Publication No. 2011/086935, International Publication No. 2010/150593, International Publication No. 2010/047707, European Patent No. 2311826, JP 2010-251675 A, JP 2009-209133 A, JP 2009 A. -124114, JP2008-277810, JP2006-156445, JP2005-340122, JP2003-45662, JP2003-31367, and JP2003-282270. Japanese Patent Publication No. 2012/115034 and the like.

More preferable electron transport materials in the present invention include aromatic heterocyclic compounds containing at least one nitrogen atom, for example, pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, azadibenzofuran derivatives. , An azadibenzothiophene derivative, a carbazole derivative, an azacarbazole derivative, and a benzimidazole derivative.
The electron transport materials may be used alone or in combination of two or more.

<Hole blocking layer>
The hole blocking layer is a layer having a function of an electron transporting layer in a broad sense, and is preferably made of a material having a function of transporting an electron and a small ability to transport a hole. By blocking the above, the recombination probability of electrons and holes can be improved.
Further, the structure of the electron transport layer described above can be used as the hole blocking layer according to the present invention, if necessary.

The hole blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the cathode side of the light emitting layer.
The layer thickness of the hole blocking layer according to the present invention is preferably in the range of 3 to 100 nm, more preferably 5 to 30 nm.
As the material used for the hole blocking layer, the material used for the electron transporting layer described above is preferably used, and the material used as the host compound described above is also preferably used for the hole blocking layer.

<Electron injection layer>
The electron injection layer (also referred to as “cathode buffer layer”) according to the present invention is a layer provided between the cathode and the light emitting layer in order to reduce the driving voltage and improve the light emission brightness. It is described in detail in Chapter 2, "Electrode Materials" (Pages 123 to 166), Volume 2, "Forefront of Industrialization" (published on Nov. 30, 1998, NTS Co., Ltd.).
In the present invention, the electron injection layer may be provided as necessary and may be present between the cathode and the light emitting layer or between the cathode and the electron transport layer as described above.
The electron injection layer is preferably a very thin film, and the layer thickness is preferably in the range of 0.1 to 5 nm, although it depends on the material. Further, it may be a non-uniform layer (film) in which the constituent material is present intermittently.

Details of the electron injection layer are also described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like, and specific examples of materials preferably used for the electron injection layer are as follows. , Metals such as strontium and aluminum, alkali metal compounds such as lithium fluoride, sodium fluoride and potassium fluoride, alkaline earth metal compounds such as magnesium fluoride and calcium fluoride, oxidation Examples thereof include metal oxides typified by aluminum, metal complexes typified by lithium 8-hydroxyquinolinate (Liq), and the like. It is also possible to use the above-mentioned electron transport material.
The materials used for the electron injection layer may be used alone or in combination of two or more.

<Hole transport layer>
In the present invention, the hole transport layer is made of a material having a function of transporting holes, and may have a function of transmitting the holes injected from the anode to the light emitting layer.
The total layer thickness of the hole transport layer according to the present invention is not particularly limited, but is usually in the range of 0.5 nm to 5 μm, more preferably 2 to 500 nm, further preferably 5 to 200 nm.

  The material used for the hole-transporting layer (hereinafter referred to as the hole-transporting material) may have any of the hole-injecting or transporting property and the electron-blocking property. Any of these can be selected and used.

  For example, porphyrin derivative, phthalocyanine derivative, oxazole derivative, oxadiazole derivative, triazole derivative, imidazole derivative, pyrazoline derivative, pyrazolone derivative, phenylenediamine derivative, hydrazone derivative, stilbene derivative, polyarylalkane derivative, triarylamine derivative, carbazole derivative. , Indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, and polyvinylcarbazole, polymer materials or oligomers containing aromatic amines introduced into the main chain or side chains, polysilane, conductive Polymers or oligomers (for example, PEDOT/PSS, aniline-based copolymers, polyaniline, polythiophene, etc.) and the like can be mentioned.

Examples of the triarylamine derivative include benzidine type compounds represented by α-NPD (4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) and starburst type compounds represented by MTDATA. Examples thereof include compounds having fluorene or anthracene in the triarylamine-linked core portion.
Further, a hexaazatriphenylene derivative as described in JP-A-2003-159432 and JP-A-2006-135145 can be similarly used as the hole transport material.
Further, a hole transport layer having a high p property doped with impurities can be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, and JP-A-2001-102175, and J. Appl. Phys. , 95, 5773 (2004) and the like.

Further, JP-A No. 11-251067, J. Huang et. al. It is also possible to use a so-called p-type hole transporting material or an inorganic compound such as p-type-Si or p-type-SiC as described in the literature (Applied Physics Letters 80 (2002), p.139). Furthermore, an orthometallated organometallic complex having Ir or Pt as a central metal, which is represented by Ir(ppy) ₃ , is also preferably used.

  As the hole-transporting material, the above-mentioned ones can be used, but a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organometallic complex, and an aromatic amine are introduced into the main chain or side chains. The polymer materials or oligomers mentioned above are preferably used.

Specific examples of known preferable hole transport materials used in the organic EL device of the present invention include the compounds described in the following documents in addition to the above-mentioned documents, but the present invention is not limited thereto. Not done.
For example, Appl. Phys. Lett. 69, 2160 (1996), J. Lumin. 72-74, 985 (1997), Appl. Phys. Lett. 78, 673 (2001), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 51, 913 (1987), Synth. Met. 87, 171 (1997), Synth. Met. 91, 209 (1997), Synth. Met. 111, 421 (2000), SID Symposium Digest, 37, 923 (2006), J. Am. Mater. Chem. 3, 319 (1993), Adv. Mater. 6, 677 (1994), Chem. Mater. 15, 3148 (2003), US Patent Application Publication No. 2003/0162053, US Patent Application Publication No. 2002/0158242, US Patent Application Publication No. 2006/0240279, and US Patent Application Publication No. 2008/. No. 0220265, U.S. Pat. Patent Application Publication No. 2007/0278938, U.S. Patent Application Publication No. 2008/0106190, U.S. Patent Application Publication No. 2008/0018221, International Publication No. 2012/115034, and Japanese Patent Publication No. 2003-515432. JP-A 2006-135145, U.S. Patent Application No. 13/585981, and the like.
The hole transport material may be used alone or in combination of two or more kinds.

<Electron blocking layer>
The electron blocking layer is a layer having a function of a hole transporting layer in a broad sense, and is preferably made of a material having a function of transporting holes and a small ability of transporting electrons, while transporting holes. By blocking electrons, the recombination probability of electrons and holes can be improved.
Further, the structure of the hole transport layer described above can be used as the electron blocking layer according to the present invention, if necessary.

The electron blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the anode side of the light emitting layer.
The layer thickness of the electron blocking layer according to the present invention is preferably in the range of 3 to 100 nm, more preferably 5 to 30 nm.
As the material used for the electron blocking layer, the materials used for the hole transport layer described above are preferably used, and the host compound described above is also preferably used for the electron blocking layer.

<Hole injection layer>
The hole injection layer (also referred to as “anode buffer layer”) according to the present invention is a layer provided between the anode and the light emitting layer for lowering the driving voltage and improving the light emission brightness. It is described in detail in Chapter 2, “Electrode Materials” (Pages 123 to 166), Volume 2, “Forefront of Industrialization” (published on Nov. 30, 1998, NTS Co., Ltd.).
In the present invention, the hole injection layer may be provided as necessary and may be present between the anode and the light emitting layer or between the anode and the hole transport layer as described above.
The hole injection layer is described in detail in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like, and examples of materials used for the hole injection layer include: Examples include the materials used for the hole transport layer described above.
Among them, a phthalocyanine derivative typified by copper phthalocyanine, a hexaazatriphenylene derivative as described in JP 2003-515432 A, JP 2006-135145 A, a metal oxide typified by vanadium oxide, or an amorphous carbon. Conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometallated complexes represented by tris(2-phenylpyridine)iridium complex, triarylamine derivatives and the like are preferable.
The above-mentioned materials used for the hole injection layer may be used alone or in combination of two or more.

"Additive"
The organic layer in the present invention described above may further contain other additives.
Examples of the additives include halogen elements such as bromine, iodine and chlorine and halogenated compounds, alkali metals and alkaline earth metals such as Pd, Ca and Na, compounds and complexes of transition metals, salts and the like.
The content of the additive can be arbitrarily determined, but it is preferably 1000 ppm or less, more preferably 500 ppm or less, and further preferably 50 ppm or less based on the total mass% of the layer to be contained. ..
However, it is not within this range depending on the purpose of improving the transportability of electrons and holes and the purpose of making energy transfer of excitons advantageous.

<Method of forming organic layer>
A method for forming the organic layer (hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) according to the present invention will be described.
The method for forming the organic layer according to the present invention is not particularly limited, and a conventionally known method such as a vacuum deposition method or a wet method (also referred to as a wet process) can be used.
As the wet method, there are spin coating method, casting method, ink jet method, printing method, die coating method, blade coating method, roll coating method, spray coating method, curtain coating method, LB method (Langmuir-Blodgett method) and the like. From the viewpoint of easy production of a uniform thin film and high productivity, a roll-to-roll method having high suitability such as a die coating method, a roll coating method, an ink jet method, and a spray coating method is preferable.

As a liquid medium for dissolving or dispersing the organic EL material used in the present invention, for example, methyl ethyl ketone, ketones such as cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, Aromatic hydrocarbons such as mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used.
As the dispersion method, it is possible to disperse by a dispersion method such as ultrasonic wave, high shearing force dispersion or media dispersion.

Further, a different film forming method may be applied for each layer. When a vapor deposition method is adopted for film formation, the vapor deposition conditions vary depending on the type of compound used and the like, but generally, the boat heating temperature is 50 to 450° C., the vacuum degree is 10 ⁻⁶ to 10 ⁻² Pa, the vapor deposition rate is 0.01 to 50 nm/sec, substrate temperature −50 to 300° C., layer (film) thickness 0.1 nm to 5 μm, preferably 5 to 200 nm are appropriately selected.
In forming the organic layer according to the present invention, it is preferable to consistently form from the hole injection layer to the cathode by vacuuming once, but it is also possible to take out in the middle and apply a different film forming method. In that case, it is preferable to carry out the work in a dry inert gas atmosphere.

"anode"
As the anode in the organic EL element, a material having a high work function (4 eV or more, preferably 4.5 eV or more), an alloy, an electrically conductive compound, or a mixture thereof as an electrode substance is preferably used. Specific examples of such an electrode substance include a conductive transparent material such as a metal such as Au, CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, a material such as IDIXO (In ₂ O ₃ —ZnO) that can form an amorphous transparent conductive film may be used.

  The anode may be formed into a thin film by a method such as vapor deposition or sputtering of these electrode substances, and a pattern of a desired shape may be formed by a photolithography method, or when pattern accuracy is not required so much (about 100 μm or more). Alternatively, a pattern may be formed through a mask having a desired shape during vapor deposition or sputtering of the electrode material.

Alternatively, when a coatable substance such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can be used. When the emitted light is taken out from this anode, it is desirable that the transmittance is higher than 10%, and the sheet resistance as the anode is preferably several hundred Ω/□ or less.
Although the 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.

"cathode"
As the cathode, a metal having a low work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, or a mixture thereof is used as an electrode material. Specific examples of such an electrode material include sodium, sodium-potassium alloy, magnesium, lithium, magnesium/copper mixture, magnesium/silver mixture, magnesium/aluminum mixture, magnesium/indium mixture, aluminum/aluminum oxide (Al ₂ O 3 ). ₃ ) Mixtures, indium, lithium/aluminum mixtures, aluminum, rare earth metals and the like. Among these, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than that of the electron injecting metal, for example, a magnesium/silver mixture, from the viewpoint of electron injecting property and durability against oxidation and the like. A magnesium/aluminum mixture, a magnesium/indium mixture, an aluminum/aluminum oxide (Al ₂ O ₃ ) mixture, a lithium/aluminum mixture, aluminum and the like are suitable.

The cathode can be produced by forming a thin film of these electrode substances by a method such as vapor deposition or sputtering. The sheet resistance of the cathode is preferably several hundred Ω/□ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.
Since the emitted light is transmitted, if either the anode or the cathode of the organic EL element is transparent or semi-transparent, the emission brightness is improved, which is convenient.
In addition, a transparent or semitransparent cathode can be produced by producing the above-mentioned metal in a thickness of 1 to 20 nm on the cathode and then producing the conductive transparent material mentioned in the description of the anode thereon. By applying, it is possible to fabricate a device in which both the anode and the cathode are transparent.

[Supporting substrate]
The supporting substrate (hereinafter, also referred to as a substrate, a substrate, a substrate, a support, etc.) that can be used in the organic EL device of the present invention is not particularly limited in the kind of glass, plastic, etc., and is transparent. Or it may be opaque. When extracting light from the supporting substrate side, the supporting substrate is preferably transparent. Examples of transparent support substrates that are preferably used include glass, quartz, and transparent resin films. A particularly preferable support substrate is a resin film that can give flexibility to the organic EL element.

  Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate ( CAP), cellulose acetate phthalate, cellulose esters such as cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), Polyphenylene sulfide, Polysulfones, Polyetherimide, Polyetherketone imide, Polyamide, Fluorine resin, Nylon, Polymethylmethacrylate, Acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Apel (Trade name, manufactured by Mitsui Chemicals, Inc.) and the like. Further, when the emitted light is transmitted through the sealing member, materials other than transparent resin can be selected, for example, metal such as copper, copper alloy, aluminum, aluminum alloy, gold, nickel, titanium, stainless steel, tin, etc. Is mentioned. One of these may be used alone, or two or more of them may be mixed or multilayered.

  Although the thickness of the element substrate is not particularly limited, it is preferably 50 μm to 500 μm in consideration of moldability, handleability and the like. The thickness of the element substrate can be measured using a micrometer.

On the surface of the resin film, an inorganic film, an organic film, or a hybrid film of both of them may be formed, and the water vapor permeability (25±0.5° C.) measured by a method according to JIS K 7129-1992. , Relative humidity (90±2)% RH) is preferably a barrier film having a relative humidity of 0.01 g/m ² ·24 h or less, and further, oxygen permeability measured by a method according to JIS K 7126-1987. Is preferably 1×10 ⁻³ mol/m ² ·s·Pa or less and a water vapor permeability of 1×10 ⁻⁵ g/m ² ·24 h or less, which is a high barrier film.

  As a material for forming the barrier film, any material may be used as long as it has a function of suppressing entry of moisture or oxygen, which causes deterioration of the element, but, for example, silicon oxide, silicon dioxide, silicon nitride or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and a layer made of an organic material. The order of laminating the inorganic layer and the organic layer is not particularly limited, but it is preferable to alternately laminate the both layers a plurality of times.

  The method for forming the barrier film is not particularly limited, and examples thereof include vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma polymerization method. The plasma CVD method, the laser CVD method, the thermal CVD method, the coating method and the like can be used, but the method by the atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films and opaque resin substrates, and ceramic substrates.
The external extraction quantum efficiency of light emission of the organic EL device of the present invention at room temperature (25° C.) is preferably 1% or more, and more preferably 5% or more.
Here, the external extraction quantum efficiency (%)=the number of photons emitted outside the organic EL element/the number of electrons flown into the organic EL element×100.
Further, a hue improving filter such as a color filter or the like may be used together, or a color conversion filter that converts the emission color from the organic EL element into multiple colors by using a phosphor may be used together.

[Sealing]
As a sealing means used for sealing the organic EL element of the present invention, for example, a method of adhering a sealing member, an electrode, and a supporting substrate with an adhesive can be mentioned. The sealing member only needs to be arranged so as to cover the display region of the organic EL element, and may have a concave plate shape or a flat plate shape. Moreover, the transparency and the electrical insulation are not particularly limited.

  Specific examples thereof include glass plates, polymer plates/films, metal plates/films, and the like. 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, polysulfone and the like. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium and tantalum.

In the present invention, a polymer film or a metal film can be preferably used because the organic EL device can be made thin. Furthermore, the polymer film has an oxygen permeability of 1×10 ⁻³ mol/m ² ·s·Pa or less measured by a method according to JIS K 7126-1987, and a method according to JIS K 7129-1992. Moreover, it is preferable that the water vapor permeability (25±0.5° C., relative humidity 90±2%) is 1×10 ⁻³ g/m ² ·24 h or less.
Sandblasting, chemical etching or the like is used to process the sealing member into a concave shape.

Specific examples of the adhesive include photocurable and thermosetting adhesives having a reactive vinyl group of acrylic acid-based oligomer and methacrylic acid-based oligomer, and moisture-curable adhesives such as 2-cyanoacrylic acid ester. be able to. In addition, epoxy and other heat and chemical curing types (mixing of two liquids) can be used. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Further, a cation-curing type UV-curing type epoxy resin adhesive can be mentioned.
Since the organic EL element may be deteriorated by heat treatment, it is preferable that the adhesive can be cured from room temperature to 80°C. A desiccant may be dispersed in the adhesive. The adhesive may be applied to the sealing portion using a commercially available dispenser or may be printed by screen printing.

Further, it is also preferable that the electrode and the organic layer are covered on the outer side of the electrode on the side opposite to the supporting substrate with the organic layer sandwiched therebetween, and an inorganic or organic material layer is formed in contact with the supporting substrate to form a sealing film. . In this case, the material for forming the film may be any material that has a function of suppressing the intrusion of water or oxygen, which causes deterioration of the element, such as silicon oxide, silicon dioxide, and silicon nitride. it can.
Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of an organic material. The method for forming these films is not particularly limited, and examples thereof include vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, and atmospheric pressure plasma heavy. A legal method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

In the gap between the sealing member and the display region of the organic EL element, an inert gas such as nitrogen or argon or an inert liquid such as fluorocarbon or silicon oil may be injected in the vapor phase and the liquid phase. preferable. A vacuum can also be used. Also, a hygroscopic compound can be enclosed inside.
Examples of the hygroscopic compound include metal oxides (eg, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide), sulfates (eg, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg, calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), perchloric acids (eg, perchloric acid) Barium, magnesium perchlorate, etc.) and the like, and anhydrous salts are preferably used for sulfates, metal halides and perchloric acids.

[Protective film, protective plate]
A protective film or a protective plate may be provided outside the encapsulating film or the encapsulating film on the side facing the support substrate with the organic layer sandwiched therebetween in order to enhance the mechanical strength of the device. In particular, when the sealing is performed by the sealing film, its mechanical strength is not necessarily high, so that it is preferable to provide such a protective film or protective plate. As the material that can be used for this, the same glass plate, polymer plate/film, metal plate/film, etc. as those used for the above-mentioned encapsulation can be used, but the polymer film is lightweight and thin. Is preferably used.

[Light extraction improvement technology]
The organic EL element emits light inside a layer having a refractive index higher than air (refractive index within a range of about 1.6 to 2.1), and emits 15% to 20% of the light generated in the light emitting layer. It is generally said that it can only be taken out. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ equal to or greater than the critical angle causes total reflection and cannot be extracted to the outside of the device. This is because the light undergoes total internal reflection between them, and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the lateral direction of the element.

  As a method for improving the efficiency of extracting light, for example, a method of forming irregularities on the surface of a transparent substrate to prevent total internal reflection at the interface between the transparent substrate and the air (for example, US Pat. No. 4,774,435), is used. A method of improving efficiency by providing light condensing property (for example, Japanese Patent Laid-Open No. 63-314795), a method of forming a reflecting surface on a side surface of an element (for example, Japanese Patent Laid-Open No. 1-220394), substrate And a light-emitting body by introducing a flat layer having an intermediate refractive index to form an antireflection film (for example, Japanese Patent Application Laid-Open No. 62-172691), a low refractive index between the substrate and the light-emitting body than the substrate. (For example, Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any of the substrate, the transparent electrode layer, and the light emitting layer (including the substrate and the outside) ( JP-A No. 11-283751) and the like.

In the present invention, these methods can be used in combination with the organic EL device of the present invention. A method of forming a diffraction grating between any of the electrode layers and the light emitting layer (including between the substrate and the outside) can be preferably used.
In the present invention, by combining these means, it is possible to obtain an element which is further excellent in high brightness or durability.

When a medium with a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness that is longer than the wavelength of light, the light emitted from the transparent electrode has a higher extraction efficiency to the outside as the refractive index of the medium is lower. Become.
Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and fluoropolymer. Since the refractive index of the transparent substrate is generally within the range of about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Further, it is preferably 1.35 or less.
Moreover, it is desirable that the thickness of the low-refractive-index medium be at least twice the wavelength in the medium. This is because when the thickness of the low-refractive-index medium becomes about the wavelength of light and the electromagnetic wave exuded by evanescent enters into the substrate, the effect of the low-refractive-index layer diminishes.

  The method of introducing a diffraction grating into the interface that causes total internal reflection or into any one of the media is characterized by a high effect of improving the light extraction efficiency. This method uses the property that the diffraction grating can change the direction of light to a specific direction different from refraction by means of so-called Bragg diffraction such as first-order diffraction and second-order diffraction. The light that cannot go out due to total reflection between layers is diffracted by introducing a diffraction grating into any of the layers or into the medium (in the transparent substrate or transparent electrode). , Trying to get the light out.

The diffraction grating to be introduced preferably has a two-dimensional periodic refractive index. This is because the light emitted from the light emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating that has a periodic refractive index distribution only in a certain direction, only the light traveling in a specific direction is diffracted. Therefore, the light extraction efficiency does not increase so much.
However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and the light extraction efficiency is improved.
The position where the diffraction grating is introduced may be in any layer or in the medium (in the transparent substrate or in the transparent electrode), but is preferably near the organic light emitting layer where light is generated. At this time, the period of the diffraction grating is preferably in the range of about 1/2 to 3 times the wavelength of the light in the medium. The array of diffraction gratings is preferably a two-dimensional array such as a square lattice shape, a triangular lattice shape, or a honeycomb lattice shape.

[Condensing sheet]
The organic EL device of the present invention is processed in such a manner that a structure on a microlens array is provided on the light extraction side of a supporting substrate (substrate) or is combined with a so-called light condensing sheet so that the organic EL device has a specific direction, for example, a device. By condensing light in the front direction with respect to the light emitting surface, it is possible to increase the brightness in a specific direction.
As an example of the microlens array, square pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably in the range of 10 to 100 μm. If it is smaller than this, the effect of diffraction occurs and it is colored, and if it is too large, the thickness becomes thick, which is not preferable.
As the light-condensing sheet, it is possible to use, for example, one that has been put to practical use in an LED backlight of a liquid crystal display device. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, a Δ-shaped stripe having a vertical angle of 90° and a pitch of 50 μm may be formed on the base material, or the vertical angle may be rounded or the pitch may be changed randomly. It may have a different shape or another shape.
Further, a light diffusing plate/film may be used together with the light collecting sheet in order to control the light emission angle from the organic EL element. For example, a diffusion film (light up) manufactured by Kimoto Co., Ltd. can be used.

[Use]
The organic EL element of the present invention can be used as an electronic device such as a display device, a display, and various light emitting devices.
Examples of light-emitting devices include lighting devices (home lighting, interior lighting), clocks and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, and light sources. Examples thereof include a light source of a sensor, but are not limited thereto. In particular, it can be effectively used as a backlight of a liquid crystal display device and a light source for illumination.
In the organic EL element of the present invention, patterning may be performed by a metal mask, an inkjet printing method, or the like at the time of film formation, if necessary. When patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire element layer may be patterned. In the fabrication of the element, a conventionally known method may be used. You can

<Display device>
A display device including the organic EL element of the present invention may be monochromatic or polychromatic. Here, a multicolor display device will be described.

In the case of a multicolor display device, a shadow mask is provided only when the light emitting layer is formed, and the film can be formed on one surface by a vapor deposition method, a casting method, a spin coating method, an inkjet method, a printing method, or the like.
When patterning only the light emitting layer, the method is not limited, but vapor deposition method, ink jet method, spin coating method and printing method are preferable.

  The configuration of the organic EL element included in the display device is selected from the above-described configuration examples of the organic EL element as needed.

  The method for manufacturing the organic EL element is as shown in the above-described one aspect of manufacturing the organic EL element of the present invention.

  When a direct current voltage is applied to the thus obtained multicolor display device, light emission can be observed by applying a voltage of about 2 to 40 V with the anode having a positive polarity and the cathode having a negative polarity. Further, even if a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the − state. The waveform of the alternating current applied may be arbitrary.

  The multicolor display device can be used as a display device, a display, or various light emitting light sources. In a display device or display, full-color display can be performed by using three types of organic EL elements that emit blue, red, and green light.

Examples of the display device or display include a television, a personal computer, a mobile device, an AV device, a teletext display, and an information display in a car. In particular, it may be used as a display device for reproducing a still image or a moving image, and a driving system for use as a display device for reproducing a moving image may be either a simple matrix (passive matrix) system or an active matrix system.

  Light-emitting devices include home lighting, interior lighting, backlights for watches and liquid crystals, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. However, the present invention is not limited thereto.

Hereinafter, an example of a display device having the organic EL element of the present invention will be described with reference to the drawings.
FIG. 4 is a schematic diagram showing an example of a display device including an organic EL element. It is a schematic diagram of a display such as a mobile phone, which displays image information by light emission of an organic EL element.

The display 1 has a display section A having a plurality of pixels, a control section B that performs image scanning of the display section A based on image information, a wiring section C that electrically connects the display section A and the control section B, and the like.
The control unit B is electrically connected to the display unit A via the wiring unit C, sends a scanning signal and an image data signal to each of a plurality of pixels based on image information from the outside, and the pixels for each scanning line by the scanning signal. Emits light sequentially according to the image data signal to perform image scanning and display image information on the display unit A.

FIG. 5 is a schematic view of a display device of the active matrix system.
The display section A has a wiring section C including a plurality of scanning lines 5 and data lines 6 and a plurality of pixels 3 and the like on a substrate. The main members of the display unit A will be described below.
FIG. 5 shows a case where the light emitted from the pixel 3 is extracted in the direction of the white arrow (downward).

The scanning lines 5 and the plurality of data lines 6 of the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a grid pattern and are connected to the pixels 3 at the orthogonal positions (details are shown in the drawings). Not).
When the scan signal is applied from the scan line 5, the pixel 3 receives the image data signal from the data line 6 and emits light according to the received image data.
Full color display is possible by appropriately arranging pixels in the red region, pixels in the green region, and pixels in the blue region in parallel on the same substrate.

Next, the light emitting process of the pixel will be described. FIG. 6 is a schematic diagram showing a pixel circuit.
The pixel includes an organic EL element 10, a switching transistor 11, a drive transistor 12, a capacitor 13 and the like. Full-color display can be performed by using red, green, and blue light-emitting organic EL elements as the organic EL elements 10 in a plurality of pixels and arranging them in parallel on the same substrate.

  In FIG. 6, an image data signal is applied from the control unit B to the drain of the switching transistor 11 via the data line 6. Then, when a scanning signal is applied to the gate of the switching transistor 11 from the control unit B via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is transferred to the capacitor 13 and the driving transistor 12. Is transmitted to the gate.

  By transmitting the image data signal, the capacitor 13 is charged according to the potential of the image data signal, and the driving of the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10. The drive transistor 12 is connected from the power supply line 7 to the organic EL element 10 according to the potential of the image data signal applied to the gate. Electric current is supplied.

When the scanning signal is transferred to the next scanning line 5 by the sequential scanning of the control unit B, the driving of the switching transistor 11 is turned off. However, since the capacitor 13 holds the potential of the charged image data signal even if the switching transistor 11 is turned off, the driving transistor 12 is kept on and the next scanning signal is applied. The organic EL element 10 continues to emit light. When a scanning signal is applied next by sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.
That is, the light emission of the organic EL element 10 is such that the switching transistor 11 and the drive transistor 12 which are active elements are provided for the organic EL element 10 of each of the plurality of pixels, and the organic EL element 10 of each of the plurality of pixels 3 emits light. It is carried out. Such a light emitting method is called an active matrix method.

Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations according to a multivalued image data signal having a plurality of gradation potentials, or may be ON or OFF of a predetermined light emission amount according to a binary image data signal. Good. Further, the potential of the capacitor 13 may be held continuously until the next scan signal is applied, or may be discharged immediately before the next scan signal is applied.
The present invention is not limited to the above-mentioned active matrix system, but may be a passive matrix system light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

FIG. 7 is a schematic diagram of a display device of a passive matrix system. In FIG. 7, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice pattern so as to face each other with the pixel 3 interposed therebetween.
When the scanning signal of the scanning line 5 is applied by sequential scanning, the pixels 3 connected to the applied scanning line 5 emit light according to the image data signal.
In the passive matrix method, the pixel 3 has no active element, and the manufacturing cost can be reduced.
By using the organic EL element of the present invention, a display device having improved luminous efficiency was obtained.

<Lighting device>
The organic EL element of the present invention can also be used in a lighting device.
The organic EL element of the present invention may be used as an organic EL element having a resonator structure. Examples of the purpose of using the organic EL element having such a resonator structure include a light source for an optical storage medium, a light source for an electrophotographic copying machine, a light source for an optical communication processor, a light source for an optical sensor, and the like. Not limited. Moreover, you may use for the said application by making a laser oscillation.

  Further, the organic EL element of the present invention may be used as a kind of lamp for illumination or as an exposure light source, or may be a projection device of a type that projects an image, or a type that directly visually recognizes a still image or a moving image. It may be used as a display device (display).

When used as a display device for reproducing moving images, either a passive matrix system or an active matrix system may be used as a driving system. Alternatively, a full-color display device can be manufactured by using two or more kinds of the organic EL elements of the present invention having different emission colors.

  Further, the fluorescent compound used in the present invention can be applied to an organic EL element that emits substantially white light as a lighting device. For example, when a plurality of light emitting materials are used, white light emission can be obtained by simultaneously emitting a plurality of light emitting colors and mixing the colors. As a combination of a plurality of emission colors, one containing three emission maximum wavelengths of three primary colors of red, green and blue may be used, or two combinations of complementary colors such as blue and yellow, blue green and orange may be used. It may contain a maximum emission wavelength.

In addition, in the method for forming an organic EL device of the present invention, a mask is provided only when the light emitting layer, the hole transporting layer, the electron transporting layer, or the like is formed, and it is only necessary to simply arrange the masks such that they are separately coated. Since the other layers are common, patterning such as a mask is unnecessary, and for example, an electrode film can be formed on one surface by a vapor deposition method, a cast method, a spin coating method, an inkjet method, a printing method, or the like, and the productivity is improved.
According to this method, unlike a white organic EL device in which light emitting elements of a plurality of colors are arranged in parallel in an array, the element itself emits white light.

[One Embodiment of Lighting Device of the Present Invention]
An aspect of the lighting device of the present invention, which is equipped with the organic EL element of the present invention, will be described.
The non-emission surface of the organic EL device of the present invention is covered with a glass case, a glass substrate having a thickness of 300 μm is used as a sealing substrate, and an epoxy photocurable adhesive (Lux manufactured by Toagosei Co., Ltd. is used as a sealing material around the periphery. Track LC0629B) is applied, and this is stacked on the cathode and brought into close contact with the transparent support substrate, and UV light is irradiated from the glass substrate side to cure and seal the illumination, as shown in FIGS. 8 and 9. A device can be formed.

  FIG. 8 shows a schematic view of a lighting device. The organic EL element of the present invention (organic EL element 101 in the lighting device) is covered with a glass cover 102 (note that the sealing work with the glass cover is performed by lighting). The organic EL element 101 in the apparatus was placed in a glove box (under an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) under a nitrogen atmosphere without contacting the atmosphere.

FIG. 9 shows a cross-sectional view of the lighting device, in which 105 is a cathode, 106 is an organic layer, and 107 is a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and is provided with a water catching agent 109.
By using the organic EL element of the present invention, a lighting device having improved luminous efficiency was obtained.

<Light emitting thin film>
The π-conjugated compound according to the present invention can also be used in a light emitting thin film, a display device and a lighting device.
Here, the luminescent thin film of the present invention will be described.

The luminescent thin film of the present invention can be produced in the same manner as the method for forming the organic layer.
The method for forming the luminescent thin film of the present invention is not particularly limited, and a conventionally known method such as a vacuum vapor deposition method or a wet method (also referred to as a wet process) can be used.
As the wet method, there are spin coating method, casting method, ink jet method, printing method, die coating method, blade coating method, roll coating method, spray coating method, curtain coating method, LB method (Langmuir-Blodgett method) and the like. From the viewpoint of easy production of a uniform thin film and high productivity, a roll-to-roll method having high suitability such as a die coating method, a roll coating method, an ink jet method, and a spray coating method is preferable.

  Examples of the liquid medium for dissolving or dispersing the π-conjugated compound used in the present invention include, for example, ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene and xylene. , Aromatic hydrocarbons such as mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used.

As the dispersion method, it is possible to disperse by a dispersion method such as ultrasonic wave, high shearing force dispersion or media dispersion.
Further, a different film forming method may be applied for each layer. When the vapor deposition method is adopted for film formation, the vapor deposition conditions vary depending on the type of compound used and the like, but generally, the boat heating temperature is in the range of 50 to 450° C., and the vacuum degree is in the range of 10 ⁻⁶ to 10 ⁻² Pa. Among them, the vapor deposition rate is 0.01 to 50 nm/sec, the substrate temperature is −50 to 300° C., the layer thickness is 0.1 nm to 5 μm, and preferably 5 to 200 nm. desirable.
When the spin coating method is used for film formation, it is preferable to perform the spin coater in a dry inert gas atmosphere within a range of 100 to 1000 rpm and within a range of 10 to 120 seconds.

Further, the light-emitting thin film of the present invention can be used for a display device and a lighting device.
As a result, a display device and a lighting device with improved luminous efficiency can be obtained.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, "parts" or "%" is used, but unless otherwise specified, "parts by mass" or "mass%" is shown.
Further, the volume% of the compound in each example was determined from the specific gravity by measuring the layer thickness to be prepared by the crystal oscillator microbalance method and calculating the mass.

  The compounds used in this example are those having the following chemical structural formulas.

[Example 1]
<Synthesis method of π-conjugated compound>
(Synthesis of Compound D-1)

  Dibenzazepine (intermediate 1) (5.00 g, 25.6 mmol), 1,4-dibromobenzene (intermediate 2) (7.25 g, 30.7 mmol), palladium acetate (575 mg, 2.56 mmol), xantphos (2.96 g, 5.12 mmol) and cesium carbonate (16.7 g, 51.2 mmol) were dissolved in 100 mL of xylene and heated to 140° C. for 16 hours in a nitrogen atmosphere. After cooling to room temperature, the reaction solution was diluted with ethyl acetate and passed through Celite. After the solution was distilled off with an evaporator, the residue was purified by silica gel column chromatography (ethyl acetate 20%, heptane 80%) to obtain Intermediate 3 as a white solid (7.44 g, yield 83%).

  Intermediate 3 (7.44 g, 21.2 mmol), bis(pinacolato)diboron (5.92 g, 30.7 mmol) and potassium acetate (4.16 g, 42.4 mmol) were dissolved in 200 mL of dimethyl sulfoxide, and nitrogen atmosphere was added. It was heated to 80° C. for 4 hours. After cooling to room temperature, 200 mL of ethyl acetate and 200 mL of water were added to the reaction solution to separate it. The obtained organic layer was evaporated with an evaporator and recrystallized from a mixed solvent of ethyl acetate and heptane to obtain Intermediate 4 as a white solid (5.49 g, yield 65%).

  Intermediate 4 (2.00 g, 5.03 mmol), 2-chloro-4,6-diphenyl-1,3,5-triazine (Intermediate 5) (1.35 g, 5.04 mmol), palladium acetate ( 113 mg, 0.50 mmol), 2-dicyclohexylphosphino-2,6-dimethoxybiphenyl (410 mg, 1.00 mmol) and potassium phosphate (2.14 g, 10.1 mmol) in toluene (80 mL) water (10 mL) 1, It was dissolved in a mixed solution of 4-dioxane (10 mL) and heated to 100° C. for 16 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction solution was diluted with ethyl acetate and passed through Celite. After distilling off this solution with an evaporator, the residue was purified by silica gel column chromatography (ethyl acetate 20%, heptane 80%) to obtain D-1 as a white solid (2.02 g, yield 80%).

(Synthesis of other compounds)
Compounds D-2, D-3, D-4, D-7, D-10, D-12, D-14, D-16, D-26, D-27, D-30 in the same manner as described above. , D-32 and D-33 were synthesized.

≪ΔEst≫
ΔEst of the synthesized π-conjugated compound and the comparative compound was calculated using Gaussian09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian in the United States. From the structure optimization calculation using B3LYP as the function and 6-31G(d) as the basis function, the excited state calculation by the time-dependent density functional method (Time-Dependent DFT) is further performed to calculate S ₁ and T ₁ energy (respectively _{E (S 1), E (} T 1)) of seeking _{ΔEst = | E (S 1)} -E (T 1) | were derived. The results obtained are shown in Table 1.

As is clear from Table 1, each of the π-conjugated compounds having an electron-withdrawing group having a low planarity and an electron-withdrawing group had ΔEst of less than 0.50 eV. Further, although ΔEst of Comparative Compound 1 having an electron-withdrawing group and an electron-withdrawing group is 0.50 eV or less, ΔEst of Comparative Compound 2 and Comparative Compound 3 having no electron-withdrawing group is: Both were very expensive.
Further, when comparing compounds D-4 and D-7 having the same structure other than EDG, the EDG represented by the general formula (2A) is better than the compound D-7 having the EDG represented by the general formula (1A). The compound D-4 had a lower ΔEst.

[Example 2]
(Production of Organic EL Element 2-1)
An ITO (indium tin oxide) film having a thickness of 150 nm was formed on a glass substrate having a size of 50 mm×50 mm×a thickness of 0.7 mm, followed by patterning to form an ITO transparent electrode as an anode. The transparent substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol and dried with dry nitrogen gas, and then UV ozone cleaning was performed for 5 minutes. The obtained transparent substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition device.

  Each of the resistance heating boats for vapor deposition in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an optimum amount for device production. The resistance heating boat was made of molybdenum or tungsten.

After decompressing the inside of the vacuum vapor deposition apparatus to a vacuum degree of 1×10 ⁻⁴ Pa, the resistance heating boat containing HI-1 was energized and heated, and vapor deposition was performed on the ITO transparent electrode at a vapor deposition rate of 0.1 nm/sec. A hole injection layer having a thickness of 15 nm was formed.

  Then, α-NPD (4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) is vapor-deposited at a vapor deposition rate of 0.1 nm/sec to form a hole-transporting layer having a thickness of 30 nm. did.

  Next, a resistance heating boat containing Comparative Compound 1 as a host compound and GD-1 as a light emitting compound is energized and heated to generate holes at vapor deposition rates of 0.1 nm/sec and 0.010 nm/sec, respectively. Co-evaporation was performed on the transport layer to form a light emitting layer having a thickness of 40 nm.

  Next, HB-1 was vapor-deposited at a vapor deposition rate of 0.1 nm/sec to form a 5 nm-thick first electron transport layer.

  Furthermore, ET-1 was vapor-deposited thereon at a vapor deposition rate of 0.1 nm/sec to form a second electron transport layer having a thickness of 45 nm.

  After that, lithium fluoride was vapor-deposited to a thickness of 0.5 nm, and then 100 nm of aluminum was vapor-deposited to form a cathode, to fabricate an organic EL element 2-1.

(Production of Organic EL Elements 2-2 to 2-16)
Except that the host compound was changed as shown in Table 2, a light emitting layer was formed in the same manner as in the organic EL device 2-1, and organic EL devices 2-2 to 2-16 were produced.

The obtained organic EL device was caused to emit light under a constant current condition of ^2.5 mA/cm ² at room temperature (about 25° C.). Then, the emission brightness of the organic EL element immediately after the start of emission was measured using a spectral radiance meter CS-2000 (manufactured by Konica Minolta).
The obtained light emission luminance was applied to the following formula to obtain the relative light emission luminance with respect to the light emission luminance of the organic EL element 2-1 and defined as the light emission efficiency.
Relative emission brightness=(emission brightness of each organic EL element/emission brightness of organic EL element 2-1)×100
The obtained results are shown in Table 2.

  From the results shown in Table 2, in the organic EL device using the π-conjugated compound according to the present invention as a host compound, Comparative Compound 1 having an electron-donating group having high planarity and an electron-withdrawing group was used. It was confirmed that the luminous efficiency was superior to that of the organic EL device using as a host compound. In addition, the compound does not have an electron-withdrawing group, and the electron-donating group has Comparative Compound 2 having a highly planar structure and the electron-donating group having low planarity, but has an electron-withdrawing group. Regarding Comparative Compound 3 which does not have any of them, the luminous efficiency of the organic EL device using them as the host compound was very low.

[Example 3]
(Production of Organic EL Element 3-1)
ITO (indium tin oxide) having a thickness of 150 nm was formed as an anode on a glass substrate having a size of 50 mm×50 mm and a thickness of 0.7 mm and patterned. After that, the transparent substrate with the ITO transparent electrode is ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes, and then the transparent substrate is placed on a substrate holder of a commercially available vacuum deposition apparatus. Fixed
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an optimum amount for producing each element. The vapor deposition crucible was made of a resistance heating material made of molybdenum or tungsten.

After reducing the degree of vacuum to 1×10 ⁻⁴ Pa, the crucible for vapor deposition containing α-NPD was energized and heated, and vapor-deposited on the ITO transparent electrode at a vapor deposition rate of 0.1 nm/sec. A hole injecting and transporting layer was formed.
Next, mCP as a host compound and Comparative Compound 1 as a dopant were co-evaporated at a vapor deposition rate of 0.1 nm/sec so that the volume percentage was 90% and 10%, respectively, to form a light emitting layer having a layer thickness of 35 nm.

After that, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) was deposited as an electron transport material at a deposition rate of 0.1 nm/sec to form an electron transport layer having a layer thickness of 30 nm.
Furthermore, after forming lithium fluoride with a film thickness of 0.5 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-light-emission surface side of the above device was covered with a can glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and electrode lead-out wiring was installed to fabricate an organic EL device 3-1.

(Production of Organic EL Elements 3-2 to 3-16)
Organic EL elements 3-2 to 3-16 were produced in the same manner as in the organic EL element 3-1, except that the dopant was changed as shown in Table 3.

(Evaluation)
The following evaluations were performed on the organic EL devices 3-1 to 3-16.

(Evaluation of external quantum yield (luminance))
Each of the organic EL devices produced above was allowed to emit light at room temperature (about 25° C.) under a constant current condition of ^2.5 mA/cm ² , and the emission brightness immediately after the start of emission was measured by a spectral radiance meter CS-2000 (Konica Minolta). (Manufactured by the company).
Next, relative light emission luminance was calculated with the light emission luminance of the organic EL element 3-1 of the comparative example being 100, and this was used as a measure of light emission efficiency (external quantum yield). The larger the value, the better the luminous efficiency. The results obtained are shown in Table 3.

(result)
From the results shown in Table 3, in the organic EL device using the π-conjugated compound according to the present invention as a dopant, Comparative Compound 1 having an electron-donating group having high planarity and an electron-withdrawing group was used. It was confirmed that the external quantum yield was superior to that of the organic EL device used as the dopant. In addition, the compound does not have an electron-withdrawing group, and the electron-donating group has Comparative Compound 2 having a highly planar structure and the electron-donating group having low planarity, but has an electron-withdrawing group. Regarding the non-Comparative Compound 3, the external quantum yield of the organic EL device using them as a dopant was very low.

[Example 4]
(Production of Organic EL Element 4-1)
After patterning a substrate (NA45 manufactured by NH Techno Glass Co., Ltd.) in which ITO (Indium Tin Oxide) was formed to a thickness of 100 nm on a glass substrate of 100 mm×100 mm×1.1 mm as an anode, this ITO transparent electrode was provided as a transparent support. The substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaned for 5 minutes.

  On this transparent support substrate, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT/PSS, manufactured by Bayer, Baytron P Al 4083) was diluted to 70% with pure water to obtain 3000 rpm, After forming a thin film by a spin coating method under the condition of 30 seconds, it was dried at 200° C. for 1 hour to provide a hole injection layer having a layer thickness of 20 nm. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition device, and each of the vapor deposition crucibles in the vacuum vapor deposition device was filled with the constituent material of each layer in an optimum amount for device production. The vapor deposition crucible was made of a resistance heating material made of molybdenum or tungsten.

After reducing the vacuum degree to 1×10 ⁻⁴ Pa, α-NPD was vapor-deposited on the hole injection layer at a vapor deposition rate of 0.1 nm/sec to form a hole transport layer having a layer thickness of 40 nm. MCP as the host compound (B) and TBPe as the dopant (A) were co-deposited at a deposition rate of 0.1 nm/sec so as to be 94% and 6% by volume, respectively, to form a light emitting layer having a layer thickness of 30 nm. ..
Then, TPBi (1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene) was vapor-deposited at a vapor deposition rate of 0.1 nm/sec to form an electron transport layer having a layer thickness of 30 nm.
Further, after forming sodium fluoride with a film thickness of 1 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-emission surface side of the above device was covered with a can glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and electrode lead-out wiring was installed to fabricate an organic EL device 4-1.

(Production of Organic EL Element 4-2)
Same as the organic EL device 4-1, except that mCP was used as the host compound (B), Comparative Compound 3 was used as the assist dopant (C), and the light emitting layer was formed so that the respective ratios were 85% and 15% by volume, respectively. Then, the organic EL element 4-2 was produced.

(Production of Organic EL Element 4-3)
The host compound (B) was mCP, the dopant (A) was TBPe, and the assist dopant (C) was comparative compound 4, and the light emitting layer was formed so that the respective ratios were 79%, 6%, and 15% by volume, respectively. An organic EL element 4-3 was produced in the same manner as the organic EL element 4-1 except for the above.

(Production of Organic EL Elements 4-4 to 4-7)
The organic EL device 4 was manufactured in the same manner as the organic EL device 4-3 except that the host compound (B), the dopant (A), and the assist dopant (C) in the light emitting layer and the ratio thereof were changed as shown in Table 4. -4 to 4-7 were prepared.

(Evaluation)
The following evaluations were performed on the organic EL devices 4-1 to 4-7.

(Measurement of luminous efficiency)
The luminous efficiency of each sample when the organic EL device was driven was evaluated by performing the following measurement.
With respect to each sample, at room temperature (about 25° C.), the emission brightness of each sample was measured using a spectral radiance meter CS-2000 (manufactured by Konica Minolta Co., Ltd.), and the initial emission efficiency at an emission brightness of 3000 cd/m ² was measured. I asked.
The evaluation value of the luminous efficiency was calculated by the following formula.
Luminous efficiency (relative value)=(luminous efficiency of each element at a luminous luminance of 3000 cd/m ² /luminous efficiency of the organic EL element 4-1 at a luminous luminance of 3000 cd/m ² )×100
The results obtained are shown in Table 4. Note that Table 4 shows that the larger the relative value of the luminous efficiency, the lower the power consumption of driving the element.

(Voltage during driving)
The driving voltage of each sample when driving the organic EL element was evaluated by performing the following measurement.
-Measurement of initial drive voltage For each sample, the emission brightness of each sample was measured at room temperature (about 25°C) using a spectral radiance meter CS-2000 (manufactured by Konica Minolta Co., Ltd.), and the emission brightness was 1000 cd/m. The initial drive voltage in ² was determined.

(Voltage increase during driving)
The voltage value of the driving voltage, (initial driving voltage of the light emitting luminance 1000 cd / ^{m 2} initial drive voltage / organic EL element 4-1 in the light emitting luminance 1000 cd / ^{m 2} for each device) × 100 voltage value = calculated by the following formula
The results obtained are shown in Table 4. Note that Table 4 shows that the smaller the relative value of the voltage is, the better the conductivity of the element is, and the element is driven at a lower voltage.

(result)
From the results shown in Table 4, the organic EL elements 4-4 to 4-7 in which the π-conjugated compound according to the present invention is used as the assist dopant are different from the organic EL element 4-1 in which the π-conjugated compound is not used. It is clear that the luminous efficiency is high. This is considered to be the effect that the π-conjugated compound according to the present invention assists the emission of other fluorescent compounds. That is, when the π-conjugated compound according to the present invention, which has a higher energy level than the luminescent substance, is excited in the light-emitting device, the luminescent substance efficiently receives the energy of the π-conjugated compound itself. It is considered that luminous efficiency comparable to that of emitting light can be obtained. Further, the organic EL element 4-3 having the electron-donating group having low planarity but also the comparative compound 3 having no electron-withdrawing group is the organic EL element 4 not using the light emitting compound (TBPe). Although the luminous efficiency was higher than that of -2, the luminous efficiency was lower than that of the organic EL element 4-1 which did not use the π-conjugated compound together.

  According to the present invention, it is possible to provide an organic electroluminescence device having a high fluorescence quantum yield and excellent emission efficiency. Further, it is possible to provide a π-conjugated compound used for the organic electroluminescence element, a light emitting thin film containing the π-conjugated compound, a display device and a lighting device provided with the organic electroluminescence element.

1 Display 3 Pixel 5 Scanning Line 6 Data Line 7 Power Supply Line 10 Organic EL Element 11 Switching Transistor 12 Driving Transistor 13 Capacitor 101 Organic EL Element in Lighting Device 102 Glass Cover 105 Cathode 106 Organic Layer 107 Glass Substrate with Transparent Electrode 108 Nitrogen Gas 109 Water catching agent A Display section B Control section C Wiring section

Claims (11)

An anode, a cathode, an organic electroluminescent element having at least one organic layer sandwiched between the anode and the cathode,
At least one of the organic layers has a structure represented by the following general formula (1), and the absolute value ΔEst of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.50 eV. An organic electroluminescence device comprising the following π-conjugated compound.
(In the general formula (1),
EDG is represented by the following general formula (1A):
(In the general formula (1A),
X and Y each independently represent CR ₂ , SiR ₂ , or an oxygen atom,
R represents a hydrogen atom or a substituent,
R ¹ and R ² each independently represent an electron-donating substituent other than a carbazole group and a phenylcarbazole group ,
n4 and n5 are each independently an integer of 1 to 3),
Is a structure represented by
L represents a single bond or a substituted or unsubstituted arylene group,
EWG is a fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, an optionally substituted carbonyl group, an optionally substituted sulfonyl group, an optionally substituted phosphine oxide group, and an optionally substituted Represents an electron-withdrawing group selected from the group consisting of an electron-withdrawing heterocycle,
n1, n2, and n3 are each independently an integer of 1 to 3. ) The organic electroluminescence device according to claim 1, wherein in the π-conjugated compound, EDG has a structure represented by the general formula (2A).
(In the general formula (2A),
R ¹ and R ² each independently represent an electron-donating substituent other than a carbazole group and a phenylcarbazole group ,
n4 and n5 are each independently an integer of 1 to 3. ) The electron donating substituent is a substituted or unsubstituted phenyl group, and wherein the carbazolyl group is one selected from the group consisting of diphenylamino group, and tert- butyl group, claim 1 or 2 The organic electroluminescence device described in 1. The organic layer includes a light emitting layer,
The said electroluminescent layer contains the (pi) conjugated system compound represented by the said General formula (1), The organic electroluminescent element as described in any one of Claims 1-3 characterized by the above-mentioned. The organic layer according to claim 4 , wherein the light emitting layer contains a π-conjugated compound represented by the general formula (1) and at least one of a fluorescent material and a phosphorescent material. Electroluminescent device. The light emitting layer is characterized by containing a π-conjugated compound represented by the general formula (1), at least one of the fluorescent material and phosphorescent material, a host compound, according to claim 4 The organic electroluminescent device according to item 1. A display device comprising the organic electroluminescence element according to claim 1 . An illuminating device comprising the organic electroluminescence element according to claim 1 . A display device comprising a lighting device according to claim 8 and a liquid crystal element as a display means. It has a structure represented by the following general formula (1), and has an absolute value ΔEst of a difference between the lowest excited singlet energy level and the lowest excited triplet energy level of 0.50 eV or less. , Π-conjugated compound.
(In the general formula (1),
EDG is represented by the following general formula (1A):
(In the general formula (1A),
X and Y each independently represent CR ₂ , SiR ₂ , or an oxygen atom,
R represents a hydrogen atom or a substituent,
R ¹ and R ² each independently represent an electron-donating substituent other than a carbazole group and a phenylcarbazole group ,
n4 and n5 are each independently an integer of 1 to 3),
Is a structure represented by
L represents a single bond or a substituted or unsubstituted arylene group,
EWG is a fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, an optionally substituted carbonyl group, an optionally substituted sulfonyl group, an optionally substituted phosphine oxide group, and an optionally substituted Represents an electron-withdrawing group selected from the group consisting of an electron-withdrawing heterocycle,
n1, n2, and n3 are each independently an integer of 1 to 3. ) A luminescent thin film comprising the π-conjugated compound according to claim 10 .