WO2017126370A1 - Organic electroluminescence element, display device, and lighting device - Google Patents

Abstract

The present invention addresses the problem of providing: an organic electroluminescence (EL) element having minimal initial degradation, high light-emitting efficiency, and long element service life; and a display device and a lighting device equipped with said organic EL element. This organic EL element has organic layers where at least one light-emitting layer is included between an anode and a cathode, wherein the organic EL element is characterized in that at least one of the light-emitting layers contains a π-conjugated compound and a compound having a prescribed structure as a light-emitting compound, electron transition between HOMO and LUMO occurring in the π-conjugated compound due to through-space interaction in the same molecule, and the π-conjugated compound having a π-conjugated aromatic ring in the area in which the HOMO and/or the LUMO is localized.

Description

Organic electroluminescence element, display device and lighting device

The present invention relates to an organic electroluminescence element, a display device including the organic electroluminescence element, and a lighting device. More specifically, the present invention relates to an organic electroluminescence element that suppresses initial deterioration, has high light emission efficiency, and has a long element lifetime, and a display device and an illumination device including the organic electroluminescence element.

Organic electroluminescence (hereinafter abbreviated as “EL”) is a field-excited luminescence due to carrier (electron and hole) recombination, so it has high luminous efficiency and does not use any harmful substances such as mercury. Since then, it has begun to be used for electronic displays, lighting, illumination, illumination, etc., and its 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 organic compound is excited by electricity (electric field), since the spin direction is random, only 25% of the singlet excited state is generated stochastically, and 75% is a triplet excited state. In order to change from a triplet excited state to a singlet excited state, a forbidden transition accompanied by spin inversion is required. In this case, generally, everything is thermally deactivated (non-radiatively deactivated), and no light is obtained. .

By the way, transition metal complexes of heavy atoms such as platinum and iridium accelerate electronic transition accompanied by spin inversion from triplet to singlet and singlet to triplet, which are forbidden transitions due to heavy atom effect, and coordination Depending on the selection of the element, it has been found that there is a substance that can obtain phosphorescence emission with almost no radiation deactivation, and this makes it possible to realize a highly efficient organic EL element. In fact, as of 2015, red phosphorescence and green phosphorescence are applied to smartphones and televisions. However, blue phosphorescence with a short emission lifetime still uses traditional fluorescence, and electronic displays using blue phosphorescence have not yet been put into practical use.

There are many factors that shorten the emission lifetime of blue phosphorescent devices, but host compounds that transmit energy and carriers to the luminescent dopant become triplet excitons (triplets), which can exist for a long time, It has been found to be a big factor.

One solution is to speed up the forbidden transition accompanied by spin inversion from the triplet excited state (T ₁ ) to the ground state (S ₀ ) by imparting a heavy atom effect to the host compound. In this case, the luminous efficiency in order to maintain a high, it is necessary to move quickly energy to T ₁ of the light emitting dopant from T ₁ of the host compound. That is, it is necessary to use a heavy atom complex having a shorter phosphorescence emission wavelength than the emission dopant.
However, at present, it is very difficult to design a thermally and electrochemically stable molecule that emits light from pure blue to blue-violet, and it is included for the purpose of preventing aggregation of the luminescent dopant (concentration quenching) in the first place. It is rare that the host compound is composed of a heavy atom complex that is the same category substance as the luminescent dopant, and it cannot be a universal technique.

Another solution is to use, as a host compound, a molecule in which the absolute value of the energy level difference between the triplet excited state and the singlet excited state (hereinafter also referred to as ΔEst) is minimized. This is a method of shortening the existence time of a term exciton.
This phenomenon is referred to as a thermally activated delayed fluorescence (hereinafter abbreviated as “TADF”) phenomenon. In the TADF phenomenon, a forbidden transition is originally generated, and a reverse electron transition from a high to a low energy level occurs. That is, even when the triplet excited state is reached, the singlet excited state is immediately brought about, so that the existence time of the triplet exciton of the host compound can be shortened.

In order to reduce ΔEst with an organic compound, the highest occupied orbit (Highest Occupied Molecular Orbital: hereinafter abbreviated as “HOMO”) and the lowest unoccupied molecular orbital (Lowest Unoccupied Molecular Orbital: hereinafter abbreviated as “LUMO”). ) Should not be mixed, and if possible, it should be localized as far as possible and completely separated. For example, in 2CzPN (4,5-bis (carbazol-9-yl) -1,2-dicyanobenzene) in FIG. 1A, HOMO is distributed in the carbazolyl groups at the 1st and 2nd positions on the benzene ring, and the 4th and 5th positions. By distributing LUMO to the cyano group at the position, HOMO and LUMO can be isolated (localized). At this time, ΔEst becomes a very small value of about 0.1 eV or less, and the TADF phenomenon appears. In contrast, 2CzXy (FIG. 1B) in which the cyano group at the 4th and 5th positions of 2CzPN is replaced with a methyl group cannot clearly separate such HOMO and LUMO (mixed). It is not possible to develop the TADF phenomenon.

This TADF phenomenon occurs when HOMO and LUMO exist completely separately in a molecule and form a charge transfer complex (Electron-Donor-Acceptor Complex: EDA complex) in the molecule. Therefore, an electron acceptor (hereinafter also simply referred to as “acceptor”) molecule and an electron donor (hereinafter also simply referred to as “donor”) molecule coexist and charge transfer (CT) transition occurs between the molecules. The same thing happens when you wake up. Actually, a highly efficient delayed fluorescence organic EL device has been realized using an exciplex which is an excited state charge transfer complex formed of two molecules (Non-patent Document 1).

That is, it is possible to substantially shorten the existence time of the triplet exciton of the host compound by using both the donor molecule and the acceptor molecule as the host compound. Whether it is based on this concept is not certain, but there is a known example of extending the lifetime of a green phosphorescent organic EL device with a light-emitting layer configuration in which two host compounds coexist to form an exciplex. (Patent Document 1).

However, Patent Document 1 does not mention any blue phosphorescent element. This is because the formation of an exciplex itself causes an electronic transition between the high (shallow) HOMO level of the donor substance and the low (deep) LUMO level of the acceptor substance. This is considered to be because the energy difference (gap) between the excited state and the ground state of the active substance becomes small (narrow), that is, the emission spectrum of the exciplex has a long wavelength. That is, it is considered that this technical concept cannot be applied to a blue phosphor element having a short emission wavelength and high triplet excited state energy.

As described above, as a problem that must be solved in order to achieve a long lifetime of the blue phosphor element, there is a problem that the host compound becomes a triplet exciton (triplet) and it exists for a long time. is there. Theoretically, it should be possible to shorten the existence time of triplet excitons (triplets) by using a heavy atom complex, a TADF compound, or a bimolecular exciplex compound as a host compound. .
However, the method using a heavy metal complex and an exciplex compound cannot be substantially applied to a blue phosphor element for the reasons described above. On the other hand, the use of the TADF compound as a host compound for blue phosphorescence has no principle contradiction and is considered possible.

The basic guideline for molecular design of TADF compounds is to have a strong acceptor and a strong donor coexist in the molecule. This is similar to the exciplex that was previously determined to be impossible. That is, this TADF compound can also be considered as an “intramolecular exciplex”.
Actually, the sulfone derivative DMAC-DPS (Bis [4- (9,9-dimethyl-9,10-dihydrocrine) phenyl] solone) is known as a TADF compound emitting blue light (Non-patent Document 2). The TADF compound that emits green and red light has been discovered for some time, and its molecular design is difficult to imagine from its temporal background.
Furthermore, for use as a blue phosphorescent host compound, the energy level of the triplet excited state of the TADF compound is significantly higher than the energy level of the triplet excited state of the blue phosphorescent dopant (empirically, it is 0. 0. This is difficult to apply with TADF molecules that emit blue light.

In addition, it should not function as a host compound unless it is a TADF substance that emits light in the near ultraviolet region. However, since TADF molecules have intramolecular exciplex properties, the concept of designing conventional TADF molecules is blue. It is difficult to molecularly design a TADF compound as a phosphorescent host compound.

JP 2012-186461 A

K. Goushi et al. , Applied Physics Letters, 2012, 101, 023306. H. Uoyama et al. , Nature, 2012, 492, 234-238.

The present invention has been made in view of the above-described problems and situations, and the problem to be solved is an organic electroluminescence element in which initial deterioration is suppressed, luminous efficiency is high, and element lifetime is long, and the organic electroluminescence element is It is to provide a display device and a lighting device provided.

As a result of studying the cause of the above-mentioned problems in order to solve the above-mentioned problems, the present inventors have found that the electron transition between HOMO and LUMO is caused by the through-space interaction in the same molecule in the light-emitting layer of the organic electroluminescence element. Occurring and containing a π-conjugated compound having a π-conjugated aromatic ring at a site where at least one of the HOMO or the LUMO is localized as a host compound has high luminous efficiency and device lifetime. The inventors have found that a long organic electroluminescence element can be realized, and have reached the present invention.
That is, the said subject which concerns on this invention is solved by the following means.

1. An organic electroluminescence device having an organic layer including at least one light emitting layer between an anode and a cathode,
At least one layer of the light emitting layer contains a π-conjugated compound and a compound having a structure represented by the following general formula (1),
In the π-conjugated compound, an electronic transition between HOMO and LUMO occurs through through-space interaction in the same molecule, and at least one of the HOMO or the LUMO is localized at a site where π-conjugated aromatic An organic electroluminescence device comprising a ring.

(In the above general formula (1), M represents Ir, Pt, Rh or Os. A ₁ , A ₂ , B ₁ and B ₂ each represent a carbon atom or a nitrogen atom. Ring Z ₁ represents A _1. And A represents a 6-membered aromatic hydrocarbon ring formed with A ₂ or a 5-membered or 6-membered aromatic heterocycle, and ring Z ₂ represents a 5-membered or 6-membered ring formed with B ₁ and B ₂ . represents an aromatic heterocyclic ring. ring Z ₁ and the ring Z ₂ may have a substituent, may form a condensed ring structure with substituent mutually bonded. further, the ring Z ₁ And ring Z ₂ may be such that the substituents of each ligand are bonded to each other so that the ligands are linked to each other, L ′ is a monoanionic bidentate ligand coordinated to M M ′ represents an integer of 0 to 2. n ′ represents an integer of 1 to 3. m ′ + n ′ is 2 or 3. m ′ and n ′ are In the case of 2 or more, the ligands represented by the ring Z ₁ and the ring Z ₂ and L ′ may be the same or different.)

2. 2. The organic electroluminescent device according to item 1, wherein the π-conjugated compound comprises a compound having a structure represented by the following general formula (2).

(In the general formula (2), X _a and X _b each independently represent an oxygen atom, a sulfur atom or NR _c . X ₂₁ to X ₂₆ each independently represent a nitrogen atom or CR _d, and Each of R _c , R _d , and R ₂₁ to R ₂₆ independently represents a hydrogen atom or a substituent, L ₂₁ to L ₂₆ each represents a divalent linking group, p and q Represents an integer of 0 or 1.)

3. 2. The organic electroluminescence device according to item 1, which contains a compound having a structure represented by the following general formula (3) as the π-conjugated compound.

(In the general formula (3), X ₃₁ represents PR _b (═O), SO ₂ or SO. R _b and R ₃₁ to R ₃₈ each independently represents a hydrogen atom or a substituent. The proportion of the LUMO electron density of the tricondensed mother nucleus structure portion containing X ₃₁ is 80% or more, and at least one of R ₃₁ , R ₃₃ , R ₃₆ and R ₃₈ is represented by the following general formula (3 -A).

In the general formula (3-A), Y ₃₁ represents a divalent linking group. Z ₃ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the total ratio of electron density of HOMO is 80% or more. p3 represents an integer of 0 or 1. )

4. 2. The organic electroluminescence device according to item 1, which contains a compound having a structure represented by the following general formula (4) as the π-conjugated compound.

(In the above general formula (4), X ₄₁ to X ₄₅ each independently represents a nitrogen atom or CR _e . R _e represents a hydrogen atom or a substituent. L ₄₁ represents an aromatic hydrocarbon ring group or R ₄₁ represents an aromatic heterocyclic group, and at least one R ₄₁ is represented by the following general formula (4-A).

In the general formula (4-A), Y ₄₁ represents a divalent linking group. Z ₄ represents an aromatic total percentage of the HOMO of the electron density is 80% or more hydrocarbon ring group or an aromatic heterocyclic group. p4 represents an integer of 0 or 1. )

5. 2. The organic electroluminescent device according to item 1, wherein the π-conjugated compound comprises a compound having a structure represented by the following general formula (5).

(In the general formula (5), R ₅₁ to R ₅₆ each independently represents a hydrogen atom or a substituent. One of Z ₅₁ and Z ₅₂ is an aromatic having a HOMO electron density ratio of 80% or more. Represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, and the other represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group having a LUMO electron density ratio of 80% or more.)

6. 2. The organic electroluminescence device according to item 1, which contains a compound having a structure represented by the following general formula (6) as the π-conjugated compound.

(In the general formula (6), X ₆₁ represents O or S. R ₆₁ to R ₆₈ each independently represents a hydrogen atom or a substituent. R ₆₁ and R ₆₈ , or R ₆₄ and R _65. is, .R ₆₁ and R ₆₈ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, each, when each represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, one of R ₆₁ and R ₆₈ Represents an aromatic hydrocarbon ring group or aromatic heterocyclic group having a HOMO electron density ratio of 80% or more, and the other is an aromatic hydrocarbon ring group having a LUMO electron density ratio of 80% or more. Or R ₆₄ and R ₆₅ each represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, and one of R ₆₄ and R ₆₅ has a ratio of the electron density of HOMO. Aromatic hydrocarbons that are 80% or more It represents a cyclic group or an aromatic heterocyclic group and the other represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group the proportion of the electron density of the LUMO is less than 80%.)

7. 2. The organic electroluminescence device according to item 1, which contains a compound having a structure represented by the following general formula (7) as the π-conjugated compound.

(In the general formula (7), R ₇₁ to R ₈₀ each independently represents a hydrogen atom or a substituent. At least two of R ₇₁ , R ₇₂ , R ₇₉ , and R ₈₀ are aromatic hydrocarbons. In addition, one of these aromatic hydrocarbon ring groups or aromatic heterocyclic groups has a HOMO electron density ratio of 80% or more, and these aromatic carbon groups. The other one of the hydrogen ring group or the aromatic heterocyclic group has a LUMO electron density ratio of 80% or more.)

8. 2. The organic electroluminescent device according to item 1, which contains a compound having a structure represented by the following general formula (8) as the π-conjugated compound.

(In the above general formula (8), R ₈₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO or LUMO is 80% or more. R ₈₂ to R ₈₉ are respectively Independently represents a hydrogen atom or a substituent, provided that when R ₈₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO is 80% or more, R ₈₂ or R ₈₉ is the proportion of the electron density of the LUMO represents a aromatic hydrocarbon ring group or aromatic heterocyclic group is 80% or higher. in addition, R ₈₁ is an aromatic hydrocarbon fraction of the electron density of the LUMO is less than 80% In the case of representing a cyclic group or an aromatic heterocyclic group, R ₈₂ or R ₈₉ represents an aromatic hydrocarbon cyclic group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO is 80% or more.)

9. 2. The organic electroluminescence device according to item 1, which contains a compound having a structure represented by the following general formula (9) as the π-conjugated compound.

(In the general formula (9), R ₉₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO is 80% or more. R ₉₂ represents the ratio of the electron density of LUMO. Represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which R is 80% or more, and R ₉₃ to R ₉₆ each represents a hydrogen atom or a substituent.

10. Wherein the ring Z ₂ in the general formula (1), a pyridine ring, an imidazole ring, an isoquinoline ring, an organic according to any one of the first term, which is a triazole ring or a pyrazole ring to paragraph 9 Electroluminescence element.

11. A display device comprising the organic electroluminescence element according to any one of items 1 to 10.

12. An illuminating device comprising the organic electroluminescence element according to any one of items 1 to 10.

By the above means of the present invention, it is possible to provide an organic electroluminescence element that suppresses initial deterioration, has high light emission efficiency, and has a long element lifetime, and a display device and an illumination device including the organic electroluminescence element.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

4CzIPN (2,4,5,6-tetrakis (carbazol-9-yl) -1,3-dicyanobenzene), which is a representative TADF compound, and DMAC-DPS, which is a blue light-emitting TADF compound, as shown below (Bis [4- (9,9-diMethyl-9,10-dihydroacidine) phenyl] solone) and HAP-3MF (2,5,8-tris (4-fluor-3--3-) which is a red light emitting TADF compound. methylphenyl) -1,3,4,6,7,9,9b-heptazaphenalelene) all have a π-conjugated aromatic compound as a skeleton, and a substituent is introduced into the skeleton to thereby form a HOMO site in the molecule. Localizing LUMO sites is a feature of molecular structure Yes, it has become a dogma.

Such a molecule has a donor portion where HOMO is localized and an acceptor portion where LUMO is localized via a π-conjugated site (hereinafter also referred to as “core”) between them. In most cases, at least the donor part has a molecular structure with a twist relative to the core.
The twisted structure is deformed while changing its twist angle when changing from the ground state to the excited state, and returns to the original molecular structure when the ground state is reached, so the emission spectrum becomes broad, the emission maximum wavelength and The wavelength difference between the light emitting ends on the short wave side becomes large.

Since the wavelength of this light emitting end, that is, the energy is S ₁ energy, higher S ₁ energy is required as compared with a light emitting material having the same emission color and a sharp emission spectrum. That is, it is indispensable to have a wider band gap than the emission color, which is a cause of difficulty in molecular design of TADF compounds emitting blue or near ultraviolet light.

Furthermore, since the twisted structure of the molecule fluctuates at the time of intersystem crossing from the singlet excited state to the triplet excited state, and conversely from the triplet excited state to the singlet excited state, it takes time for the displacement, In addition, since the intersystem crossing is repeatedly performed in the forward direction and the reverse direction, the existence time of the triplet exciton becomes longer, and as a result, even if sometime it becomes a singlet excited state, it is the gist of the present invention. It cannot be a completely compatible technique for “reducing the existence time of host triplet excitons”.

Next, let's think from a different perspective.
In order to develop the TADF phenomenon, a strong donor site and a strong acceptor site are required. However, there are not so many substituents (compounds) that can serve as donors, and they are limited to amino group substituents (acridane, diphenylamine, carbazole, indoloindole, etc.), and other suitable substituents have been found so far. Not.
On the other hand, the acceptor site is not so varied, and the substituents include cyano groups having a large σp value, which are representative indicators of electron-withdrawing properties, sulfonyl groups, phosphate groups, pyrimidines, triazines, azatriphenylenes, etc. It is practically limited to aromatic heterocyclic compounds containing a large number of nitrogen atoms. Actually, such a typical TADF compound has such a molecular structure.

In the case of such a molecule, the HOMO level of the molecule becomes low (deep) due to the influence of a strong electron-withdrawing group. In this case, the level difference from the compound constituting the adjacent hole transport layer becomes large, so that it becomes difficult to inject holes into the light emitting layer. In addition, when a molecule having a high (shallow) HOMO level is applied to the luminescent dopant, the difference in the HOMO level between the TADF compound and the dopant becomes too large, so that all the holes that have entered the luminescent layer are all holes. There is a problem in that it is trapped by the dopant existing in the vicinity of the transport interface and recombination in an ideal state cannot be performed.
On the other hand, in the case of a space electron transition type TADF compound that we have found, having a donor part and an acceptor part in the molecule is the same as a conventional TADF compound. However, it is not a charge transfer transition through a π-conjugated core, but the molecular structure at the time of the electronic transition because the donor part and the acceptor part that overlap (or approach) spatially cause an electronic transition spatially. The change is very small, so it is also possible to sharpen the emission spectrum shape. In addition, the intersystem crossing between the singlet excited state and the triplet excited state also contributes to the absence of the structural change, thereby increasing the speed, and as a result, the existence time in the triplet excited state can be shortened. Yes.

In addition, intramolecular space electronic transition is a phenomenon that occurs only in molecules that are designed so that the donor part and the acceptor part overlap in the molecule because of its chemical structure, so it is milder than the exciplex formation that usually occurs between two molecules. It is a major feature that it is expressed even in various donors and acceptors. For example, even in the combination of dibenzofuran, which is very weak as an acceptor, and carbazole, which is never strong as a donor, spatial electron transition occurs due to the steric molecular structure, and very short triplet excitons It is possible to realize the existence time.

It is also known that the TADF compound does not emit light itself and is used as a host of a conventional fluorescent material. It is a technology called TADF assistant dopant, and it is known that the light emission lifetime is extended (reference: H. Nakatani, et al., Nature Communication, 2014, 5, 4016-4022.). However, a sufficient light emission lifetime has not been obtained with blue high-efficiency light emission.
In this technique, the triplet excited state of the TADF molecule also gradually crosses back to the singlet excited state, and the singlet excited state emits light by transferring energy to a fluorescent dopant having lower S1 energy. The broadening of the emission spectrum, which was a weak point of TADF emission, is eliminated because the conventional sharp uses a fluorescent dopant of the emission spectrum, and it is possible to bring out a level comparable to a phosphorescent device with luminous efficiency. This is a very good technology.

However, the existence time in the triplet excited state of the TADF molecule as the host compound is never short as described above. Therefore, it is a fact that a sufficient light emission lifetime improving effect cannot be expected in principle in blue light emission in which the influence appears.

On the other hand, what happens with a so-called phosphorescent device in which a host compound, TADF molecules, and a luminescent dopant are transition metal complexes will be considered.
The triplet excited state generated in the TADF molecule which is the host compound becomes a singlet excited state of the TADF molecule at a certain speed. The singlet excited state may shine as it is, but is returned to the triplet excited state by the external heavy atom effect of the transition metal complex with high probability. The returned triplet excited state and the originally formed triplet excited state cause energy transfer between T ₁ T ₁ to the phosphorescent dopant which is a transition metal complex, and light emission from the phosphorescent dopant is obtained. That is, the TADF molecule as the host compound is more advantageous from the viewpoint of shortening the existence time of the triplet exciton of the host compound than when it is used as the host compound of the phosphorescent dopant. Long life can be expected.
Furthermore, if the TADF molecule was spatial electronic transition type TADF molecules, as previously described, eliminates or mismatch level with phosphorescent dopant, the high T ₁ of TADF molecule itself (i.e., high S ₁ of) is also made possible, said to be almost perfect technical means.
In accordance with such logic, we have confirmed that the emission lifetime has never been increased by using space-electron transition type TADF molecules as phosphorescent dopants as host compounds, and completed the present invention. .

The light-emitting layer of the organic EL of the present invention contains a compound having the structure represented by the general formula (1) as a light-emitting dopant, containing the above-described space electron transition type TADF molecule as a host compound and a π-conjugated compound. contains. In the π-conjugated compound, an electronic transition between HOMO and LUMO occurs by through-space interaction in the same molecule, and at least one of the HOMO or the LUMO is localized at a site where the π-conjugated aromatic compound is localized. It has a ring.
Usually, electronic transition when TADF is expressed is performed by a through-bond passing through a covalently bonded molecular chain between HOMO localized in the donor part and LUMO localized in the acceptor part. On the other hand, the π-conjugated compound according to the present invention is characterized in that the electronic transition when TADF is expressed is performed by through-space interaction. The electron transition in the through-space interaction is made up of an electron group constituting HOMO and an electron group constituting LUMO in a π-conjugated compound, each of which is formed by a group of atoms that are separated from each other in the molecule. In the compound, although the electron group constituting HOMO and the electron group constituting LUMO are each composed of atomic groups present at distant positions in the molecule, there is an electronic transition between the atomic groups. It means that the light emission phenomenon occurs by happening. It is speculated that the electron transition due to this through-space interaction is likely to occur when the HOMO and LUMO distribution states are clearly separated. Specifically, the ratio of the electron density distribution of the HOMO and LUMO is at least 80% or more, respectively. Further, it is presumed that through space interaction is likely to occur when the overlap of electron density distributions of the HOMO and the LUMO is at least less than 20%. Further, it is presumed that through space interaction is likely to occur when HOMO and LUMO are spatially close to each other.

Thus, the organic EL light-emitting layer contains the above-described π-conjugated compound, which is a space electron transition type TADF molecule, as the host compound, thereby shortening the existence time of triplet excitons of the host compound. It is considered that an organic EL having a high luminous efficiency and a long luminous lifetime was obtained. In addition, since the π-conjugated compound according to the present invention is considered to suppress movement in the light emitting layer, the exciton stability is also improved by suppressing aggregation of the π-conjugated compound during device driving. It is considered that the initial deterioration of the light emitting layer was suppressed.

By the way, many technologies and compound groups are already known in the industry and the academic world surrounding organic EL. However, as in the present invention, the space electron transition type TADF compound in which the three-dimensional chemical structure and electronic state of the host molecule are controlled is applied to the phosphorescent dopant so as to match from the above-mentioned multiple viewpoints. However, it is considered that the achievement of the extension of the light emission lifetime is an innovative technology and development in the organic EL industry.
In known academic literatures and patent literatures, such a combination of compounds may be unintentionally listed. However, it is clear that they do not use the technical idea described here, and are considered to be distinguished from the present invention.

Schematic diagram showing energy diagram of TADF compound (2CzPN: HOMO and LUMO are separated) Schematic diagram showing the energy diagram of a normal fluorescent compound (2CzXy: HOMO and LUMO are not separated) Schematic diagram when π-conjugated compound acts as host compound Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram of an active matrix display device Schematic showing the pixel circuit Schematic diagram of a passive matrix display device Schematic of lighting device Cross section of the lighting device HOMO electron density distribution in Example Compound H2-12 LUMO electron density distribution in Example Compound H2-12 HOMO electron density distribution in Example Compound H3-11 LUMO electron density distribution chart of Exemplified Compound H3-11

The organic electroluminescent device of the present invention is an organic electroluminescent device having an organic layer including at least one light emitting layer between an anode and a cathode, wherein at least one layer of the light emitting layer includes a π-conjugated compound, A compound having a structure represented by the general formula (1), wherein the π-conjugated compound has an electronic transition between HOMO and LUMO caused by a through-space interaction in the same molecule, and It has a π-conjugated aromatic ring at a site where at least one of HOMO or LUMO is localized. This feature is common to or corresponds to the invention according to each claim.

As an embodiment of the present invention, a compound having a structure represented by any one of the general formula (2) to the general formula (9) is used as the π-conjugated compound from the viewpoint of the effect of the present invention. It is preferable to contain.

As an embodiment of the present invention, the space electron transition type compound of the present invention is characterized in that the radiation rate in the triplet excited state is high, but the luminescent compound combined with this also has a high radiation rate. It is desirable. From this viewpoint, it is preferable that the ring Z ₂ in the general formula (1) is a pyridine ring, an imidazole ring, an isoquinoline ring, a triazole ring, or a pyrazole ring.
The organic electroluminescence element of the present invention can be preferably applied to a display device and a lighting device.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

[Organic EL device]
The organic EL device of the present invention is an organic electroluminescence device having an organic layer including at least one light emitting layer between an anode and a cathode, wherein at least one of the light emitting layers is a π-conjugated compound, which will be described later. Wherein the π-conjugated compound has an electronic transition between HOMO and LUMO caused by through-space interaction in the same molecule, and It has a π-conjugated aromatic ring at a site where at least one of HOMO or LUMO is localized. HOMO and LUMO of the π-conjugated compound can be obtained by molecular orbital calculation using B3LYP as a functional and 6-31G (d) as a basis function.
Hereinafter, the organic EL element of the present invention will be described in order.

<< Constituent layers of organic EL elements >>
As typical element structures in the organic EL element of the present invention, the following structures can be exemplified, but the invention is not limited thereto.
(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 /) luminescent layer / (hole blocking layer /) electron transport layer / electron injection layer / cathode Among the above, the configuration of (7) is preferable. Although used, it is not limited to this.
The light emitting layer used in the present invention is composed of a single layer or a plurality of layers. When there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the light emitting layers.

If necessary, a hole blocking layer (also referred to as a hole barrier 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. Moreover, you may be comprised by multiple layers.
The hole transport layer used in the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. Moreover, you may be comprised by multiple layers.
In the above-described typical element configuration, 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 a so-called tandem element in which a plurality of light emitting units including at least one light emitting layer are stacked.
As typical element configurations of the tandem structure, for example, the following configurations can be given.
Anode / first light emitting unit / intermediate layer / second light emitting unit / intermediate layer / third light emitting unit / cathode Here, the first light emitting unit, the second light emitting unit and the third light emitting unit are all the same, May be different. Two light emitting units may be the same, and the remaining one may be different.
A plurality of light emitting units may be laminated directly or via an intermediate layer, and the intermediate layer is generally an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, an intermediate layer. 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 anode-side adjacent layer and holes to the cathode-side adjacent layer.

Examples of materials used for the intermediate layer include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiO _x , VO _x , CuI, InN, GaN, Conductive inorganic compound layers such as CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ and Al, two-layer films such as Au / Bi ₂ O ₃ , SnO ₂ / Ag / SnO ₂ , ZnO / Multi-layer film such as Ag / ZnO, Bi ₂ O ₃ / Au / Bi ₂ O ₃ , TiO ₂ / TiN / TiO ₂ , TiO ₂ / ZrN / TiO ₂ , fullerenes such as C ₆₀ , conductivity such as oligothiophene Examples include organic material layers, conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, and metal-free porphyrins. The present invention is not limited thereto.
Preferred examples of the configuration within the light emitting unit include, for example, those obtained by removing the anode and the cathode from the configurations (1) to (7) mentioned in the above representative device configurations. It is not limited.

Specific examples of the tandem organic EL element 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. Specification, U.S. Pat. No. 6,337,492, International Publication No. 2005/009087, JP-A-2006-228712, JP-A-2006-24791, JP-A-2006-49393, JP-A-2006-49394 JP-A-2006-49396, JP-A-2011-96679, JP-A-2005-340187, JP-A-4711424, JP-A-3496868, JP-A-3848564, JP-A-4421169, No. 2010-192719, Special Elements described in JP2009-076929, JP2008-078414, JP2007-059848, JP2003-272860, JP2003-045676, International Publication No. 2005/094130, etc. Although a structure, a constituent material, etc. are mentioned, this invention is not limited to these.

Hereinafter, each layer constituting the organic EL element 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 in which electrons and holes injected from an electrode or an adjacent layer are recombined to emit light via excitons, and the light-emitting portion is the light-emitting layer Even in the layer, it may be the interface between the light emitting layer and the adjacent layer. If the light emitting layer used for this invention satisfy | fills the requirements prescribed | regulated by this invention, there will be no restriction | limiting in particular in the structure.
The total thickness of the light emitting layer is not particularly limited, but it prevents the uniformity of the film to be formed, the application of unnecessary high voltage during light emission, and the improvement of the stability of the emission color against the drive current. From the viewpoint, it is preferably adjusted to a range of 2 nm to 5 μm, more preferably adjusted to a range of 2 to 500 nm, and further preferably adjusted to a range of 5 to 200 nm.
The thickness of each light emitting layer used in the present invention is preferably adjusted to a range of 2 nm to 1 μm, more preferably adjusted to a range of 2 to 200 nm, and further preferably in a range of 3 to 150 nm. Adjusted.

In the light-emitting layer used in the present invention, a light-emitting dopant (a light-emitting compound, a light-emitting dopant compound, a dopant compound, or simply a dopant) and a host compound (a matrix material, a light-emitting host compound, or simply a host) are included. contains.
Moreover, the light emitting layer which concerns on the organic EL element of this invention is a compound in which at least 1 layer of the light emitting layer provided in the organic EL element has a structure represented by General formula (1) mentioned later as a light emitting dopant, and a host. A π-conjugated compound is contained as a compound.

(1) Luminescent dopant As the luminescent dopant, a phosphorescent dopant (also referred to as a phosphorescent dopant or a phosphorescent compound) and a fluorescent dopant (also referred to as a fluorescent dopant or a fluorescent compound) are preferably used. Moreover, in this invention, at least 1 layer of a light emitting layer contains the following phosphorescent dopant.

(1.1) Phosphorescent dopant A phosphorescent dopant is a compound in which light emission from an excited triplet is observed, specifically, a compound that emits phosphorescence at room temperature (25 ° C.), and has a phosphorescent quantum efficiency of The phosphorescence quantum efficiency is preferably 0.1 or more, although it is defined as a compound of 0.01 or more at 25 ° C.
The phosphorescence quantum efficiency can be measured by the method described in Spectra II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum efficiency in a solution can be measured using various solvents, the phosphorescence dopant used in the present invention can be obtained as long as the phosphorescence quantum efficiency (0.01 or more) is achieved in any solvent. Good.

There are two types of light emission of the phosphorescent dopant in principle. One is the recombination of carriers on the host compound to which carriers are transported to generate the excited state of the luminescent host compound, and this energy is used as the phosphorescent dopant. It is an energy transfer type in which light emission from a phosphorescent dopant is obtained by moving to. The other is a carrier trap type in which a phosphorescent dopant becomes a carrier trap, and carrier recombination occurs on the phosphorescent dopant, and light emission from the phosphorescent dopant is obtained. In any case, it is a condition that the excited state energy of the phosphorescent dopant is lower than the excited state energy of the host compound.

The phosphorescent dopant according to the present invention is represented by the following general formula (1) from the viewpoint of easily making the energy of the triplet excited state lower than the energy of the triplet excited state of the host compound according to the present invention. A compound having a structure is preferably used.

In general formula (1), M represents Ir, Pt, Rh, or Os. Of these, M is particularly preferably Ir or Pt.
A ₁ , A ₂ , B ₁ and B ₂ each represent a carbon atom or a nitrogen atom.

Ring Z ₁ represents a 6-membered aromatic hydrocarbon ring formed together with A ₁ and A ₂ or a 5-membered or 6-membered aromatic heterocycle.
Examples of the 6-membered aromatic hydrocarbon ring or 5-membered or 6-membered aromatic heterocycle formed by the ring Z ₁ include a benzene ring, a pyridine ring, a pyrimidine ring, a pyrrole ring, a thiophene ring, a pyrazole ring, and an imidazole. A ring, an oxazole ring, a thiazole ring, etc. are mentioned.
Ring Z ₁ may have a substituent, and the substituents may be bonded to each other to form a condensed ring structure.

Ring Z ₂ represents a 5-membered or 6-membered aromatic heterocycle formed together with B ₁ and B ₂ . Among these, the ring Z ₂ is preferably a 5-membered aromatic heterocyclic ring, and at least one of B ₁ and B ₂ is preferably a nitrogen atom.
The aromatic heterocyclic ring used for the ring Z ₂ is preferably a pyridine ring, an imidazole ring, an isoquinoline ring, a triazole ring or a pyrazole ring from the viewpoint of radiation speed.

Ring Z ₁ and ring Z ₂ may have a substituent, and the substituents may be bonded to each other to form a condensed ring structure. Further, in the ring Z ₁ and the ring Z ₂ , the substituents of the respective ligands may be bonded to each other so that the ligands are connected to each other. The “substituent” here is appropriately selected in terms of molecular design in order to enable fine adjustment of the target performance of the present invention. Examples of the substituent include alkyl groups (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 (for example, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (for example, vinyl group, allyl group, etc.), alkynyl group (for example, ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring group (aromatic Also referred to as 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, phenanthryl group, indenyl group , Pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group (eg For example, a pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl 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, furazanyl group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group, dibenzothienyl group , Indolyl group, carbazolyl group, carbolinyl group, diazacarbazolyl group (in which one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced by a nitrogen atom), quinoxalinyl group, pyridazinyl group, triazinyl group , Quinazolinyl group, phthalazini Group), heterocyclic group (for example, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group) , Dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, propylthio group) Group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (for example, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (for example, phenylthio group, naphthylthio group, etc.), alkoxycarbo Nyl group (for example, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (for example, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.) Sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, Naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentyl) Rubonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, butyl) Carbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (eg, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group) Cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbo Ruamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2 -Ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (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, methylsulfide group) Finyl 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 (for example, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.) ), Amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, Silamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group) Group) and the like. Of these substituents, preferred are an alkyl group and an aryl group.

L ′ represents a monoanionic bidentate ligand coordinated to M.
m ′ represents an integer of 0 to 2. n ′ represents an integer of 1 to 3. m ′ + n ′ is 2 or 3. When m ′ and n ′ are 2 or more, the ligands represented by the ring Z ₁ and the ring Z ₂ and L ′ may be the same or different.

(1.2) Fluorescent compound A known fluorescent compound can be used as the luminescent material used in the present invention. Known fluorescent compounds include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes. Stilbene dyes, polythiophene dyes or rare earth complex phosphors, and compounds having a high fluorescence quantum yield such as laser dyes.

(1.3) Combined use with conventionally known dopants In addition, the light emitting dopant used in the present invention may be used in combination with a plurality of compounds, and combinations of phosphorescent dopants having different structures or phosphorescent dopants. And a fluorescent dopant may be used in combination.
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. No. 0202194, U.S. Patent Application Publication No. 2007/0087321, U.S. 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, and US Pat. No. 7,332,232. United States Patent Application Publication No. 2009/0108737, United States Patent Application Publication No. 2009/0039776, United States Patent No. 6921915, United States Patent No. 6,687,266, United States Patent Application Publication No. 2007/0190359. No., US Patent Application Publication No. 2006/0008670, US Patent Application Publication No. 2009/0165846, US Patent Application Publication No. 2008/0015355, US Pat. No. 7,250,226, US Patent No. 7396598 Writing, 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. 7090928, 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 Pat. No. 7,393,599, US Pat. No. 7,534,505. No. 7, 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. Pat. No. 7,338,722, U.S. Patent Application Publication No. 2002. / 013498 No. 7, U.S. Pat. No. 7,279,704, U.S. Patent Application Publication No. 2006/098120, U.S. Patent Application Publication No. 2006/103874, WO 2005/076380, WO 2010/032663 No., International Publication No. 2008/140115, 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 / 21212 Specification, JP 2012-069737 A, JP 2011-181303 A, JP 2009-114086 A, JP 2003-81988 A, JP 2002-302671 A, JP 2002-363552 A. Such as a gazette.
Among these, a preferable phosphorescent dopant includes an organometallic complex having Ir as a central metal. More preferably, a complex containing at least one coordination mode among a metal-carbon bond, a metal-nitrogen bond, a metal-oxygen bond, and a metal-sulfur bond is preferable.

(1.4) Illustrative examples of phosphorescent dopants Specific examples of phosphorescent dopants that can be used in the present invention are listed below, but the present invention is not limited thereto.

(2) Host Compound The host compound used in the present invention is a compound mainly responsible for charge injection and transport in the light emitting layer. The host compound preferably has a mass ratio in the layer of 20% or more among the compounds contained in the light emitting layer.
A host compound may be used independently or may be used in combination of multiple types. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient.

(2.1) π-conjugated compound At least one of the light-emitting layers according to the present invention contains a compound having a structure represented by the above general formula (1) as a light-emitting dopant, and a π-conjugated compound as a host compound. Containing. As used herein, “π-conjugated compound” means that an electronic transition between HOMO and LUMO occurs through through-space interaction within the same molecule, and at least one of HOMO or LUMO is localized. It is a compound having a π-conjugated aromatic ring at the site to be treated.
Here, the electronic transition in the through-space interaction referred to in this specification means that an electron group constituting HOMO and an electron group constituting LUMO in a π-conjugated compound are present at positions separated from each other in the molecule. In spite of the fact that the electron group constituting the HOMO and the electron group constituting the LUMO in the π-conjugated compound are constituted by atomic groups that are present at distant positions in the molecule. It means that a light emission phenomenon occurs when an electronic transition occurs between the atomic groups.
It is speculated that the electron transition due to this through-space interaction is likely to occur when the HOMO and LUMO distribution states are clearly separated. Specifically, the ratio of the electron density distribution of the HOMO and LUMO is at least 80% or more, respectively. Further, it is presumed that through space interaction is likely to occur when the overlap of electron density distributions of the HOMO and the LUMO is at least less than 20%. Further, it is presumed that through space interaction is likely to occur when HOMO and LUMO are spatially close to each other.

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 in a concentration and may have any concentration distribution.
In addition, the π-conjugated compound according to the present invention may be used in combination of a plurality of types.

FIG. 2 shows a schematic diagram when the π-conjugated compound according to the present invention acts as a host compound. The mechanism for producing the effect is that triplet excitons generated on the π-conjugated compound are converted to singlet excitons by reverse intersystem crossing (RISC). As a result, all the exciton energies generated on the π-conjugated compound are transferred to the luminescent compound by fluorescence resonance energy transfer (Fluorescence).
Resonance Energy Transfer (FRET), which enables high luminous efficiency. Here, the generation process of the triplet exciton generated on the π-conjugated compound is not limited to the electric field excitation, and includes energy transfer and electron transfer from the light emitting layer or from the peripheral layer interface. FIG. 2 shows an example using a phosphorescent compound, but a fluorescent compound can also be used, and both a phosphorescent compound and a fluorescent compound can be used.
The content of the luminescent compound is preferably included in a mass ratio of 0.1% to 50% with respect to the π-conjugated compound. The energy levels of S ₁ and T ₁ of the π-conjugated compound are preferably higher than the energy levels of S ₁ and T ₁ of the luminescent compound.

In addition, it is preferable that the emission spectrum of the π-conjugated compound and the absorption spectrum of the luminescent compound overlap.

HOMO and LUMO of a π-conjugated compound can be obtained by molecular orbital calculation using B3LYP as a functional and 6-31G (d) as a basis function.

Specifically, the π-conjugated compound according to the present invention preferably contains a compound having a structure represented by any one of the following general formulas (2) to (9). Hereinafter, the following general formulas (2) to (9) will be described in order.

(2.1.1) Compound Represented by General Formula (2) The π-conjugated compound according to the present invention preferably contains a compound having a structure represented by the following general formula (2).

In the general formula (2), _{X a} and _{X b} each independently represents an oxygen atom, a sulfur atom or NR _c. X ₂₁ to X ₂₆ each independently represents a nitrogen atom or CR _d , and at least one is a nitrogen atom. R _c , R _d , and R ₂₁ to R ₂₆ each independently represent a hydrogen atom or a substituent. L ₂₁ to L ₂₆ represent a divalent linking group. p and q represent an integer of 0 or 1.
In the case _{where X a} and _{X b} are represented by respective NR _c, they may form a ring _{R c} each other.
In the compound having the structure represented by the general formula (2), the ratio of the electron density of HOMO is 80 in the tricondensed mother nucleus structure portion including Xa and X ₂₁ to X ₂₆ on the near side in the formula. % Or more. Further, in the tricondensed ring mother nucleus structure portion including _Xb on the back side in the formula, the ratio of the LUMO electron density is 80% or more.

In addition, when R _c , R _d , and R ₂₁ to R ₂₆ represent a substituent, the substituent includes an electron between HOMO and LUMO in the compound having the structure represented by the general formula (2). Any material can be used as long as it does not hinder the transition and does not impair the effects of the present invention. Note that the “substituent” here is not directly involved in the structural portion that performs the electronic transition between HOMO and LUMO, and in order to enable fine adjustment of the target performance of the present invention, It is appropriately selected in terms of molecular design. Examples of the substituent include alkyl groups (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 groups (for example, cyclopentyl group, cyclohexyl group, etc.), alkenyl groups (for example, vinyl group, allyl group, etc.), alkynyl groups (for example, ethynyl group, propargyl group, etc.), aromatic hydrocarbon groups (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, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc. An 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-triazol-1-yl group, etc.), oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, Benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, carbolinyl group, diazacarbazolyl group (indicating that one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced by a nitrogen atom), quinoxalinyl group , Pyridazinyl group, triazinyl group, quinazo Nyl group, phthalazinyl 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) Octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group etc.), aryloxy group (eg, phenoxy group, naphthyloxy group etc.), alkylthio group (eg, methylthio group, etc.) Ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.) ), Alkoxycarbonyl groups (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl groups (eg, phenyloxycarbonyl group, naphthyloxycarbonyl) Group), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylamino) Sulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propyl group) Bonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyl group) Oxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, Pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group Group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylamino) Carbonyl 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 (for example, phenylsulfonyl group, naphthylsulfonyl group, 2- Pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, diphenylamino group, butylamino group, cyclopentyl) Mino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogeno group (eg, fluoro group, chloro group, bromo group etc.), fluorinated hydrocarbon group (eg. , Fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group) Group, phenyldiethylsilyl group, etc.), phosphono group and the like. Preferably, an alkyl group, an aromatic hydrocarbon group, an aromatic heterocyclic group, an alkoxy group, an amino group, and a cyano group are exemplified. Moreover, these substituents may be further substituted with the above substituents. Further, these substituents may be bonded together to form a ring.

As the divalent linking group used for L ₂₁ to L ₂₆ , any divalent linking group can be used as long as it can smoothly perform electronic transition between HOMO and LUMO and does not impair the effects of the present invention. Examples of the divalent linking group include a chalcogen atom such as oxygen or sulfur, a dialkylsilyl group, an alkylene group (for example, an ethylene group, a trimethylene group, a tetramethylene group, a propylene group, an ethylethylene group, a pentamethylene group, a hexamethylene group). Methylene group, 2,2,4-trimethylhexamethylene group, heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group, cyclohexylene group (for example, 1,6-cyclohexanediyl group) Etc.), cyclopentylene group (eg, 1,5-cyclopentanediyl group, etc.), alkenylene group (eg, vinylene group, propenylene group, butenylene group, pentenylene group, 1-methylvinylene group, 1-methylpropene group) Nylene group, 2-methylpropenylene group, 1-methyl Pentenylene group, 3-methylpentenylene group, 1-ethylvinylene group, 1-ethylpropenylene group, 1-ethylbutenylene group, 3-ethylbutenylene group, etc.), alkynylene group (for example, ethynylene group, 1-propynylene group, 1 -Butynylene, 1-pentynylene, 1-hexynylene, 2-butynylene, 2-pentynylene, 1-methylethynylene, 3-methyl-1-propynylene, 3-methyl-1-butynylene, etc.), arylene A group (for example, o-phenylene group, p-phenylene group, naphthalenediyl group, anthracenediyl group, naphthacenediyl group, pyrenediyl group, naphthylnaphthalenediyl group, biphenyldiyl group (for example, [1,1′-biphenyl] -4, 4'-diyl, 3,3'-biphenyldiyl, 3,6-bi Enyldiyl group, terphenyldiyl group, quaterphenyldiyl group, kinkphenyldiyl group, sexiphenyldiyl group, septiphenyldiyl group, octylphenyldiyl group, nobiphenyldiyl group, deciphenyldiyl group), A heteroarylene group (for example, a carbazole ring, a carboline ring, a diazacarbazole ring (also referred to as a monoazacarboline ring, which indicates a ring structure in which one of carbon atoms constituting the carboline ring is replaced by a nitrogen atom), a triazole ring, A pyrrole ring, a pyridine ring, a pyrazine ring, a quinoxaline ring, a thiophene ring, an oxadiazole ring, a dibenzofuran ring, a dibenzothiophene ring, a divalent group derived from the group consisting of an indole ring, etc.) A group derived from a fused aromatic heterocyclic ring (where The condensed aromatic heterocyclic ring formed by condensing three or more rings is preferably an aromatic heterocyclic condensed ring containing a hetero atom selected from N, O and S as an element constituting the condensed ring. Specifically, acridine ring, benzoquinoline ring, carbazole ring, phenazine ring, phenanthridine ring, phenanthroline ring, carboline ring, cyclazine ring, quindrine ring, tepenidine ring, quinindrine ring, triphenodithiazine ring , Triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, diazacarbazole ring (representing any one of carbon atoms constituting a carboline ring replaced by a nitrogen atom), phenanthroline ring, dibenzofuran ring, Dibenzothiophene ring, naphthofuran ring, naphthothiophene ring, ben Difuran ring, benzodithiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring, anthrathiophene ring, anthradithiophene ring, thianthrene ring, phenoxathiin ring, thiophanthrene ring (naphthothiophene ring) ) Etc.).

(2.1.2) Compound Represented by General Formula (3) The π-conjugated compound according to the present invention preferably contains a compound having a structure represented by the following general formula (3).

　上記一般式（３）において、Ｘ_３１は、ＰＲ_ｂ（＝Ｏ）、ＳＯ_２又はＳＯを表す。Ｒ_ｂ、Ｒ_３１～Ｒ_３８は、各々独立に水素原子又は置換基を表す。式中のＸ_３１を含む三縮環式母核構造部分が、ＬＵＭＯの電子密度の割合が８０％以上である。Ｒ_３１、Ｒ_３３、Ｒ_３６及びＲ_３８の少なくとも一つは、下記一般式（３－Ａ）で表される。

In the general formula (3), X ₃₁ represents PR _b (═O), SO ₂ or SO. _{R b,} R 31 _~ R ₃₈ each independently represent a hydrogen atom or a substituent. The proportion of the LUMO electron density of the tricondensed mother nucleus structure portion containing X ₃₁ in the formula is 80% or more. At least one of R ₃₁ , R ₃₃ , R ₃₆ and R ₃₈ is represented by the following general formula (3-A).

In the general formula (3-A), Y ₃₁ represents a divalent linking group. Z ₃ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the total ratio of electron density of HOMO is 80% or more. p3 represents an integer of 0 or 1.

In the general formula (3), when R _b and R ₃₁ to R ₃₈ represent a substituent, the substituent includes HOMO and LUMO in the compound having the structure represented by the general formula (3). Any material can be used as long as it does not easily disturb the electron transition between the two and does not impair the effects of the present invention. Note that the “substituent” here is not directly involved in the structural portion that performs the electronic transition between HOMO and LUMO, and in order to enable fine adjustment of the target performance of the present invention, It is appropriately selected in terms of molecular design. As the substituent, for example, the substituent described in the general formula (2) can be used.
The divalent linking group for use in Y _31, proceed smoothly electronic transitions between the HOMO and LUMO, as long as it does not impair the effects of the present invention, it is suitably used. As the divalent linking group, for example, the divalent linking group described in the general formula (2) can be used.

As the aromatic hydrocarbon ring group or aromatic heterocyclic group used for Z ₃ , the electron density ratio of HOMO is 80% or more, and the electronic transition between HOMO and LUMO is caused by through-space interaction in the same molecule. From the viewpoint of making it possible, for example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl 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, furazanyl group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, Benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, cal A borinyl group, a diazacarbazolyl group (in which one of carbon atoms constituting the carboline ring of the carbolinyl group is replaced by a nitrogen atom), a quinoxalinyl group, a pyridazinyl group, a triazinyl group, a quinazolinyl group, a phthalazinyl group, etc. Can be mentioned.

(2.1.3) Compound Represented by General Formula (4) The π-conjugated compound according to the present invention preferably contains a compound having a structure represented by the following general formula (4).

In the general formula _{(4), X 41 ~ X} 45 represents a nitrogen atom or CR _e independently. R _e represents a hydrogen atom or a substituent. L ₄₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group. At least one R ₄₁ is represented by the following general formula (4-A).

In the general formula (4-A), Y ₄₁ represents a divalent linking group. Z ₄ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the total of the electron density ratios of HOMO is 80% or more. p4 represents an integer of 0 or 1.

In the compound having the structure represented by the general formula (4), the ratio of the LUMO electron density is 80% or more in the ring portion containing X ₄₁ to X ₄₅ in the formula.

When R _e represents a substituent, the substituent does not hinder the electronic transition between HOMO and LUMO in the compound having the structure represented by the general formula (4), and does not impair the effects of the present invention. If it is a thing, it is used suitably. Note that the “substituent” here is not directly involved in the structural portion that performs the electronic transition between HOMO and LUMO, and in order to enable fine adjustment of the target performance of the present invention, It is appropriately selected in terms of molecular design. As the substituent, for example, the substituent described in the general formula (2) can be used.

As the aromatic hydrocarbon ring group or aromatic heterocyclic group used for L ₄₁ , the ratio of the electron density of HOMO is 80% or more, and the electronic transition between HOMO and LUMO is due to through-space interaction in the same molecule. From the viewpoint of enabling the occurrence, for example, the aromatic hydrocarbon ring group or the aromatic heterocyclic group described in the general formula (3) can be used.

As the divalent linking group used for Y ₄₁ , any divalent linking group can be used as long as it can smoothly perform electronic transition between HOMO and LUMO and does not impair the effects of the present invention. As the divalent linking group, for example, the divalent linking group described in the general formula (2) can be used.

As the aromatic hydrocarbon ring group or aromatic heterocyclic group used for Z ₄ , the electron density ratio of HOMO is 80% or more, and the electronic transition between HOMO and LUMO is caused by through-space interaction in the same molecule. From the viewpoint of enabling the occurrence, for example, the aromatic hydrocarbon ring group or the aromatic heterocyclic group described in the general formula (3) can be used.

(2.1.4) Compound Represented by General Formula (5) The π-conjugated compound according to the present invention preferably contains a compound having a structure represented by the following general formula (5).

In the general formula (5), R ₅₁ to R ₅₆ each independently represents a hydrogen atom or a substituent. One of Z ₅₁ and Z ₅₂ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group having a HOMO electron density ratio of 80% or more, and the other represents a LUMO electron density ratio of 80% or more. Represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group.

In the case where R ₅₁ to R ₅₆ represent a substituent, the substituent includes a compound having a structure represented by the general formula (5), which hardly hinders electronic transition between HOMO and LUMO, and is effective for the present invention. If it does not spoil, it is used appropriately. Note that the “substituent” here is not directly involved in the structural portion that performs the electronic transition between HOMO and LUMO, and in order to enable fine adjustment of the target performance of the present invention, It is appropriately selected in terms of molecular design. As the substituent, for example, the substituent described in the general formula (2) can be used.

As the aromatic hydrocarbon ring group or aromatic heterocyclic group used for Z ₅₁ and Z ₅₂ , the ratio of the electron density of HOMO or LUMO is 80% or more, and the electronic transition between HOMO and LUMO is within the same molecule. From the viewpoint of enabling the occurrence of through space interaction, for example, the aromatic hydrocarbon ring group or the aromatic heterocyclic group described in the general formula (3) can be used.

(2.1.5) Compound Represented by General Formula (6) The π-conjugated compound according to the present invention preferably contains a compound having a structure represented by the following general formula (6).

In the general formula (6), X ₆₁ represents O or S. R ₆₁ to R ₆₈ each independently represents a hydrogen atom or a substituent. R ₆₁ and R ₆₈ , or R ₆₄ and R ₆₅ each represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group. When R ₆₁ and R ₆₈ each represent an aromatic hydrocarbon ring group or an aromatic heterocyclic group, one of R ₆₁ and R ₆₈ is an aromatic hydrocarbon in which the ratio of the electron density of HOMO is 80% or more. A cyclic group or an aromatic heterocyclic group is represented, and the other represents an aromatic hydrocarbon cyclic group or an aromatic heterocyclic group having a LUMO electron density ratio of 80% or more. When R ₆₄ and R ₆₅ each represent an aromatic hydrocarbon ring group or an aromatic heterocyclic group, one of R ₆₄ and R ₆₅ is an aromatic hydrocarbon in which the ratio of the electron density of HOMO is 80% or more. A cyclic group or an aromatic heterocyclic group is represented, and the other represents an aromatic hydrocarbon cyclic group or an aromatic heterocyclic group having a LUMO electron density ratio of 80% or more.

In the case where R ₆₁ to R ₆₈ represent a substituent, the substituent does not hinder an electron transition between HOMO and LUMO in the compound having the structure represented by the general formula (6). If it does not spoil, it is used appropriately. Note that the “substituent” here is not directly involved in the structural portion that performs the electronic transition between HOMO and LUMO, and in order to enable fine adjustment of the target performance of the present invention, It is appropriately selected in terms of molecular design. As the substituent, for example, the substituent described in the general formula (2) can be used.

The aromatic hydrocarbon ring group or aromatic heterocyclic group in which the ratio of the electron density of HOMO or LUMO used for R ₆₁ , R ₆₈ , R ₆₄ and R ₆₅ is 80% or more includes the electron density of HOMO or LUMO. From the viewpoint of allowing the electronic transition between HOMO and LUMO to be caused by through-space interaction in the same molecule, for example, the aromatic hydrocarbon ring group or aromatic group described in the general formula (3) is 80% or more. Group heterocyclic groups can be used.

(2.1.6) Compound Represented by General Formula (7) The π-conjugated compound according to the present invention preferably contains a compound having a structure represented by the following general formula (7).

In the general formula (7), R ₇₁ to R ₈₀ each independently represents a hydrogen atom or a substituent. At least two of R ₇₁ , R ₇₂ , R ₇₉ and R ₈₀ represent an aromatic hydrocarbon ring group or an aromatic heterocyclic group. Further, one of these aromatic hydrocarbon ring groups or aromatic heterocyclic groups has a HOMO electron density ratio of 80% or more, and among these aromatic hydrocarbon ring groups or aromatic heterocyclic groups, The other is that the LUMO electron density ratio is 80% or more.

In the case where R ₇₁ to R ₈₀ represent a substituent, the substituent includes a compound having a structure represented by the general formula (7), and it is difficult to prevent electronic transition between HOMO and LUMO, and thus the effect of the present invention. If it does not spoil, it is used appropriately. Note that the “substituent” here is not directly involved in the structural portion that performs the electronic transition between HOMO and LUMO, and in order to enable fine adjustment of the target performance of the present invention, It is appropriately selected in terms of molecular design. As the substituent, for example, the substituent described in the general formula (2) can be used.

The aromatic hydrocarbon ring group or aromatic heterocyclic group in which the ratio of the electron density of HOMO or LUMO used for R ₇₁ , R ₇₂ , R ₇₉ , and R ₈₀ is 80% or more includes the electron density of HOMO or LUMO. From the viewpoint of allowing the electronic transition between HOMO and LUMO to be caused by through-space interaction in the same molecule, for example, the aromatic hydrocarbon ring group described in the general formula (3) or Aromatic heterocyclic groups can be used.

(2.1.7) Compound Represented by General Formula (8) The π-conjugated compound according to the present invention preferably contains a compound having a structure represented by the following general formula (8).

In the above general formula (8), R ₈₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO or LUMO is 80% or more. R ₈₂ to R ₈₉ each independently represents a hydrogen atom or a substituent. However, when R ₈₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the HOMO electron density ratio is 80% or more, R ₈₂ or R ₈₉ has an LUMO electron density ratio of 80%. It represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group as described above. When R ₈₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the LUMO electron density ratio is 80% or more, R ₈₂ or R ₈₉ has a HOMO electron density ratio of 80%. It represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group as described above.

When R ₈₂ to R ₈₉ represent a substituent, the substituent includes a compound having a structure represented by the general formula (8), and it is difficult to prevent electronic transition between HOMO and LUMO. If it does not spoil, it is used appropriately. Note that the “substituent” here is not directly involved in the structural portion that performs the electronic transition between HOMO and LUMO, and in order to enable fine adjustment of the target performance of the present invention, It is appropriately selected in terms of molecular design. As the substituent, for example, the substituent described in the general formula (2) can be used.

As the aromatic hydrocarbon ring group or aromatic heterocyclic group in which the ratio of electron density of HOMO or LUMO used for R ₈₁ , R ₈₂ and R ₈₉ is 80% or more, the ratio of electron density of HOMO or LUMO is 80 From the viewpoint of allowing the electronic transition between HOMO and LUMO to occur by through-space interaction in the same molecule, for example, the aromatic hydrocarbon ring group or aromatic heterocycle described in the general formula (3) Groups can be used.

(2.1.8) Compound Represented by General Formula (9) The π-conjugated compound according to the present invention preferably contains a compound having a structure represented by the following general formula (9).

In the general formula (9), R ₉₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO is 80% or more. R ₉₂ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group having a LUMO electron density ratio of 80% or more. R ₉₃ to R _{96 each} represents a hydrogen atom or a substituent.

As the aromatic hydrocarbon ring group or aromatic heterocyclic group in which the ratio of the electron density of HOMO or LUMO used for R ₉₁ and R ₉₂ is 80% or more, the ratio of the electron density of HOMO or LUMO is 80% or more. From the viewpoint of allowing electronic transition between HOMO and LUMO to occur through through-space interaction in the same molecule, for example, the aromatic hydrocarbon ring group or aromatic heterocyclic group described in the general formula (3) is used. be able to.

In the case where R ₉₃ to R ₉₆ represent a substituent, the substituent includes a compound having a structure represented by the general formula (9), which hardly hinders the electronic transition between HOMO and LUMO, and is effective for the present invention. If it does not spoil, it is used appropriately. Note that the “substituent” here is not directly involved in the structural portion that performs the electronic transition between HOMO and LUMO, and in order to enable fine adjustment of the target performance of the present invention, It is appropriately selected in terms of molecular design. As the substituent, for example, the substituent described in the general formula (2) can be used.

The π-conjugated compound having any one of the structures from the general formulas (2) to (9) preferably has a molecular weight of 2000 or less from the viewpoint of film formability. Specific examples of the π-conjugated compound include the following exemplified compounds.

<Synthesis method>
The π-conjugated compound can be synthesized, for example, by referring to a method described in the following document or a reference document described in the document.
(1) S.M. Riedmuller and Boris J Nachtsheim
. , Beilstein J .; Org. Chem. 2013, 9, 1202-1209
(2) Wako Organic Square No. 27 (2009)
(3) N. M.M. Moazzam et al. , Appl. Organomet. Chem. 2012, 26, 7, 330-334
(4) H. Kawai, et al. , Chemical Communication, 2008, 12, 1464-1466.
(5) S.M. Oi, et al. , Tetrahedron, 2008, 64, 26, 6051-6059
(6) S.M. Oi, et al. , Organic Letters, 2008, 10, 9, 1832-1826.
(7) H. Uoyama, et al. , Nature, 2012, 492, 234-238.
(8) Y. Nakamura, et al. Bull. Chem. Soc. Jpn. , 2009, 82, 2743.

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

(Electron density distribution)
In the π-conjugated compound according to the present invention, HOMO and LUMO are substantially separated in the molecule from the viewpoint of reducing the absolute value (ΔEst) of the energy level difference between the triplet excited state and the singlet excited state. Preferably it is.
The distribution states of these HOMO and LUMO can be obtained from the electron density distribution when the structure is optimized by molecular orbital calculation.
In the present invention, structure optimization and calculation of electron density distribution by molecular orbital calculation of π-conjugated compounds in the present invention are performed using molecular orbital calculation software using B3LYP as a functional and 6-31G (d) as a basis function as a calculation method. There is no particular limitation on the software, and any of them can be similarly calculated.
In the present invention, Gaussian 09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian, USA is used as molecular orbital calculation software.

As for the electron density separation state of HOMO and LUMO, the time-dependent density functional method (Time-Dependent DFT) is further calculated from the structure optimization calculation using B3LYP as the above-mentioned functional and 6-31G (d) as the basis function. ) To obtain the energy of S ₁ and T ₁ (E (S ₁ ) and E (T ₁ ), respectively), and calculate as ΔEst = E (S ₁ ) −E (T ₁ ) Is also possible. As the calculated ΔEst is smaller, HOMO and LUMO are more separated. 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 most preferably 0.1 eV or less.

(Minimum excitation singlet energy S ₁ )
The lowest excited singlet energy S ₁ of the π-conjugated compound in the present invention is defined in the present invention as calculated in the same manner as in a normal method. That is, a sample to be measured is deposited on a quartz substrate to prepare a sample, and the absorption spectrum (vertical axis: absorbance, horizontal axis: wavelength) of this sample is measured at room temperature (300 K). A tangent line is drawn with respect to the rising edge of the absorption spectrum on the long wavelength side, and is calculated from a predetermined conversion formula based on the wavelength value at the intersection of the tangent line and the horizontal axis.
However, when the molecules themselves of the π-conjugated compound used in the present invention have a relatively high aggregation property, an error due to aggregation may occur in the measurement of the thin film. In consideration of the fact that the π-conjugated compound in the present invention has a relatively small Stokes shift and that the structural change between the excited state and the ground state is small, the lowest excited singlet energy S ₁ in the present invention is at room temperature (25 ° C.). The peak value of the maximum emission wavelength in the solution state of the π-conjugated compound was used as an approximate value.
Here, as the solvent to be used, a solvent that does not affect the aggregation state of the π-conjugated compound, that is, a solvent having a small influence of the solvent effect, for example, a nonpolar solvent such as cyclohexane or toluene can be used.

(Minimum excited triplet energy T ₁ )
The lowest excited triplet energy (T ₁ ) of the π-conjugated compound in the present invention was calculated from the photoluminescence (PL) characteristics of the solution or thin film. For example, as a calculation method in a thin film, after making a dispersion of a dilute π-conjugated compound into a thin film, using a streak camera, the transient PL characteristics are measured to separate the fluorescent component and the phosphorescent component, The lowest excited triplet energy can be obtained from the lowest excited singlet energy with the energy difference as ΔEst.
In measurement / evaluation, an absolute PL quantum yield measuring apparatus C9920-02 (manufactured by Hamamatsu Photonics) was used for measuring the absolute PL quantum yield. The light emission lifetime is measured using a streak camera C4334 (manufactured by Hamamatsu Photonics) while exciting the sample with laser light.

(How to find the ratio of electron density)
The aromatic hydrocarbon ring group or aromatic heterocyclic group in which the ratio of the electron density of HOMO in this specification is 80% or more means that the total electron density distribution of HOMO calculated by molecular orbital calculation is 100%. Sometimes, the ratio of the electron density of HOMO of the atoms of the aromatic hydrocarbon ring group or aromatic heterocyclic group part is 80% or more. That is, the fact that the ratio of the electron density of HOMO is 80% or more means that the electron density distribution is unevenly present in that portion.
Hereinafter, the calculation method of the ratio of the electron density distribution when the ratio of the electron density of HOMO is 80% or more in the aromatic hydrocarbon ring group or the aromatic heterocyclic group will be described.

First, the stable structure of the ground state of the molecule of interest is calculated using Gaussian 09 with the functional as B3LYP and the basis function as 6-31G (d). The molecular orbitals of HOMO and LUMO are output by using #p and pop = regular as keywords. Then, by analyzing the electron distribution of the HOMO site of the molecular orbit obtained there, the ratio of the electron density of HOMO can be obtained. Specifically, the coefficients of all atoms in the orbit corresponding to HOMO are squared and added to calculate the ratio of carbon atoms and heteroatoms in the portion corresponding to the aromatic hydrocarbon ring group or aromatic heterocyclic group. .
The value of the LUMO electron density ratio can be obtained by the same analysis. Also in this case, the ratio of the LUMO electron density at the site of the aromatic hydrocarbon ring group or aromatic heterocyclic group is 80% or more, which means that the total electron density distribution of LUMO calculated by molecular orbital calculation is 100%. In this case, the ratio of the LUMO electron density of the carbon atom and hetero atom of the aromatic hydrocarbon ring group or aromatic heterocyclic group part is 80% or more.
An example of the result of calculating the ratio of the electron density of the π-conjugated compound according to the present invention will be described in Examples described later (FIGS. 9A, 9B, 10A, and 10B).

(2.2) Combined use with conventionally known host compounds As the host compound, the above-mentioned π-conjugated compounds may be used alone or in combination of two or more. In addition, by using a known host compound in combination, the movement of charges can be adjusted, and the organic EL element can be made highly efficient.

There is no restriction | limiting in particular as a conventionally well-known host compound which can be used in combination, The compound conventionally used with an organic EL element can be used. A low molecular compound or a high molecular compound having a repeating unit may be used, and a compound having a reactive group such as a vinyl group or an epoxy group may be used. Further, the conventionally known host compound has a hole transport ability or an electron transport ability, prevents the emission of light from becoming longer, and further prevents the organic EL element from generating heat during high temperature driving or during element driving. It is preferable to have a high glass transition temperature (Tg) from the viewpoint of stable and stable operation. 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 based on JIS-K-7121 using DSC (Differential Scanning Calorimetry).

Specific examples of conventionally known host compounds that can be used in combination include the compounds described in the following documents, but the present invention is not limited thereto.
For example, Japanese Patent Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860 Gazette, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579 No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453. No. 2003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060. No. 2002-302516, No. 2002-305083, No. 2002-305084, No. 2002-308837, No. 2003/0175553, No. 2006/0280965. US 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 ,Country Public 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. 2012/0038 / No. 023947, Japanese Patent Application Laid-Open No. 2008-074939, Japanese Patent Application Laid-Open No. 2007-254297, and European Patent Application No. 2034538.

《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 electrons injected from the cathode to the light emitting layer.
In the present invention, the total thickness of the electron transport layer is not particularly limited, but is usually in the range of 2 nm to 5 μm, more preferably 2 to 500 nm, and 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 extracted directly from the light emitting layer interferes with the light extracted after being reflected by the electrode from which the light is extracted and the electrode located at the counter electrode. It is known to wake up. When light is reflected by the cathode, this interference effect can be efficiently utilized by appropriately adjusting the total thickness of the electron transport layer between several nanometers and several micrometers.
On the other hand, since the voltage is likely to increase when the thickness of the electron transport layer is increased, the electron mobility of the electron transport layer is 10 ⁻⁵ cm ² / V · s or more, particularly when the layer thickness is large. Is preferred.
The material used for the electron transport layer (hereinafter referred to as an electron transport material) may be any of electron injecting or transporting properties and hole blocking properties, and can be selected from conventionally known compounds. Can be selected and used.

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

In addition, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, such as 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), etc., 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 in which the terminal thereof is substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transport material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transporting material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc., like the hole injection layer and the hole transporting layer. Can also be used as an electron transporting material.
Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

In the electron transport layer used in the present invention, the electron transport layer may be doped with a doping material 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 complexes and metal compounds such as 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, 2001-102175, J. Pat. Appl. Phys. , 95, 5773 (2004) and the like.

Specific examples of known preferable electron transport 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.
US Pat. No. 6,528,187, US Pat. No. 7,230,107, US Patent Application Publication No. 2005/0025993, US Patent Application Publication No. 2004/0036077, US 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. 2008/120855, 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. 7964293, 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. 2007/085652, International Publication No. 2008/114690, International Publication No. 2009/066942, International Publication No. 2009/066779, International Publication No. 2009/054253, International Publication No. JP 2011/086935, WO 2010/150593, WO 2010/047707, EP 2311826, JP 2010-251675, JP 2009-209133, JP 2009-124114 JP 2008-277810 A, JP 2006-156445 A, JP 2005-340122 A, JP 2003-45662 A, JP 2003-31367 A, JP 2003-282270 A, International Publication. No. 2012/115034.

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. , Azadibenzothiophene derivatives, carbazole derivatives, azacarbazole derivatives, benzimidazole derivatives, and the like.
The electron transport material 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 transport layer in a broad sense, and is preferably made of a material having a function of transporting electrons while having a small ability to transport holes, and transporting electrons while transporting holes. The probability of recombination of electrons and holes can be improved by blocking.
Moreover, the structure of the electron carrying layer mentioned above can be used as a hole-blocking layer as needed.
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.
In the present invention, the thickness of the hole blocking layer is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.
As the material used for the hole blocking layer, the material used for the above-described electron transport layer is preferably used, and the material used as the above-described host compound is also preferably used for the hole blocking layer.

《Electron injection layer》
In the present invention, the electron injection layer (also referred to as “cathode buffer layer”) is a layer provided between the cathode and the light emitting layer in order to lower the driving voltage or improve the light emission luminance. It is described in detail in Chapter 2, “Electrode Materials” (pages 123 to 166), Volume 2 of “The Frontline (issued by NTT Corporation on November 30, 1998)”.
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 depending on the material. Moreover, the nonuniform layer (film | membrane) in which a constituent material exists intermittently may be sufficient.

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. Specific examples of materials preferably used for the electron injection layer are as follows. , Metals typified by strontium and aluminum, alkali metal compounds typified by lithium fluoride, sodium fluoride, potassium fluoride, etc., alkaline earth metal compounds typified by magnesium fluoride, calcium fluoride, etc., oxidation Examples thereof include metal oxides typified by aluminum, metal complexes typified by 8-hydroxyquinolinate lithium (Liq), and the like. Further, the above-described electron transport material can also be used.
Moreover, the material used for said electron injection layer may be used independently, and may be used in combination of multiple types.

《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 holes injected from the anode to the light emitting layer.
In the present invention, the total thickness of the hole transport layer is not particularly limited, but is usually in the range of 5 nm to 5 μm, more preferably 2 to 500 nm, and further preferably 5 to 200 nm.
As a material used for the hole transport layer (hereinafter referred to as a hole transport material), any material that has either a hole injection property or a transport property or an electron barrier property may be used. Any one can be selected and used.
For example, porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives , Indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, and polyvinyl carbazole, polymeric materials or oligomers with aromatic amines introduced into the main chain or side chain, polysilane, conductive And polymer (for example, PEDOT / PSS, aniline copolymer, polyaniline, polythiophene, etc.).

Examples of triarylamine derivatives include benzidine type typified by α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), starburst type typified by MTDATA, Examples include compounds having fluorene or anthracene in the triarylamine-linked core.
In addition, hexaazatriphenylene derivatives such as those described in JP-T-2003-519432 and JP-A-2006-135145 can also be used as hole transport materials.
Furthermore, a hole transport layer having a high p property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

JP-A-11-251067, J. Org. Huang et. al. It is also possible to use so-called p-type hole transport materials and inorganic compounds such as p-type-Si and p-type-SiC, as described in the literature (Applied Physics Letters 80 (2002), p. 139). Further, ortho-metalated organometallic complexes having Ir or Pt as the central metal as typified by Ir (ppy) ₃ are also preferably used.
Although the above-mentioned materials can be used as the hole transport material, a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organometallic complex, or an aromatic amine is introduced into the main chain or side chain. The polymer materials or oligomers used are preferably used.

Specific examples of known preferred 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 documents listed above, but the present invention is not limited thereto. Not.
For example, Appl. Phys. Lett. 69, 2160 (1996), J.A. 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), U.S. Patent Application Publication No. 2003/0162053, U.S. Patent Application Publication No. 2002/0158242, U.S. Patent Application Publication No. 2006/0240279, U.S. Patent Application Publication No. 2008/2008. No. 0220265, US Pat. No. 5,061,569, WO 2007/002683, WO 2009/018009, EP 650955, US Patent Application Publication No. 2008/0124572, US Patent Application Publication No. 2007 / No. 02798938, US Patent Application Publication No. 2008/0106190, US Patent Application Publication No. 2008/0018221, International Publication No. 2012/115034, Japanese Translation of PCT International Publication No. 2003-519432, Japanese Patent Application Laid-Open No. 2006-135145. issue Distribution is US Patent Application No. 13/585981 Patent like.
The hole transport material may be used alone or in combination of two or more.

《Electron blocking layer》
The electron blocking layer is a layer having a function of a hole transport layer in a broad sense, and is preferably made of a material having a function of transporting holes and a small ability to transport electrons, while transporting holes. By blocking electrons, the probability of recombination of electrons and holes can be improved.
Moreover, the structure of the positive hole transport layer mentioned above can be used as an electron blocking layer in this invention as needed.
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.
In the present invention, the thickness of the electron blocking layer is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.
As the material used for the electron blocking layer, the material used for the above-described hole transport layer is preferably used, and the above-mentioned host compound is also preferably used for the electron blocking layer.

《Hole injection layer》
The hole injection layer (also referred to as “anode buffer layer”) in the present invention is a layer provided between the anode and the light emitting layer in order to lower the driving voltage and improve the light emission luminance. It is described in detail in Chapter 2 “Electrode Materials” (pages 123 to 166) of the second edition of “The Forefront of Industrialization (issued by NTT Corporation on November 30, 1998)”.
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 details of the hole injection layer are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069, etc. Examples of materials used for the hole injection layer include: Examples thereof include materials used for the hole transport layer described above.
Among them, phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives, metal oxides typified by vanadium oxide, amorphous carbon as described in JP-T-2003-519432 and JP-A-2006-135145, etc. Preferred are conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometalated complexes represented by tris (2-phenylpyridine) iridium complex, and triarylamine derivatives.
The materials used for the hole injection layer described above 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 additive include halogen elements such as bromine, iodine and chlorine, halogenated compounds, alkali metals such as Pd, Ca and Na, alkaline earth metals, transition metal compounds, complexes, and salts.
The content of the additive can be arbitrarily determined, but is preferably 1000 ppm or less, more preferably 500 ppm or less, and further preferably 50 ppm or less with respect to the total mass% of the contained layer. .
However, it is not within this range depending on the purpose of improving the transportability of electrons and holes or the purpose of favoring the exciton energy transfer.

<Method for forming organic layer>
A method for forming an 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.
Examples of the wet method include 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, and LB method (Langmuir-Blodgett method). From the viewpoint of obtaining a homogeneous thin film easily and high productivity, a method with high roll-to-roll method 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 organic EL material used in the present invention include ketones such as methyl ethyl ketone and 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.
Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.
Further, different film forming methods may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a degree of vacuum of 10 ⁻⁶ to 10 ⁻² Pa, and a vapor deposition rate of 0.01 to It is desirable to select appropriately within the range of 50 nm / second, substrate temperature −50 to 300 ° C., layer (film) thickness 0.1 nm to 5 μm, preferably 5 to 200 nm.
The organic layer according to the present invention is preferably formed from the hole injection layer to the cathode consistently by a single evacuation, but it may be taken out halfway and subjected to different film formation methods. In that case, it is preferable to perform the work in a dry inert gas atmosphere.

"anode"
As the anode in the organic EL element, a material having a work function (4 eV or more, preferably 4.5 eV or more) of a metal, an alloy, an electrically conductive compound, or a mixture thereof is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used.
For the anode, a thin film may be formed by vapor deposition or sputtering of these electrode materials, and a pattern of a desired shape may be formed by photolithography, or when pattern accuracy is not required (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material.
Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is several hundred Ω / sq. The following is preferred.
Although the film thickness of the anode depends on the material, it is usually selected within the range of 10 nm to 1 μm, preferably 10 to 200 nm.

"cathode"
As the cathode, a material having a work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials 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 ) Mixtures, indium, lithium / aluminum mixtures, aluminum, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as a cathode is several hundred Ω / sq. The film thickness is usually selected from the range of 10 nm to 5 μm, preferably 50 to 200 nm.
In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the emission luminance is advantageously improved.
In addition, a transparent or translucent cathode can be produced by producing the conductive transparent material mentioned in the description of the anode on the cathode after producing the metal with a thickness of 1 to 20 nm on the cathode. By applying the above, it is possible to manufacture a device in which both the anode and the cathode are transparent.

《Support substrate》
The support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention is not particularly limited in the type of glass, plastic, etc., and is transparent. Or opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving 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 esters such as cellulose acetate phthalate, 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 Cycloolefin resins such as polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylates, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned.

The surface of the resin film may be formed with an inorganic film, an organic film, or a hybrid film of both, and the water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. And a relative humidity (90 ± 2)% RH) of 0.01 g / (m ² · 24 h) or less is preferable, and oxygen measured by a method in accordance with JIS K 7126-1987 A high barrier film having a permeability of 1 × 10 ⁻³ mL / (m ² · 24 h · atm) or less and a water vapor permeability of 1 × 10 ⁻⁵ g / (m ² · 24 h) or less is preferable. .

As a material for forming the barrier film, any material may be used as long as it has a function of suppressing entry of elements that cause deterioration of elements such as moisture and oxygen. 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 organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.
The method for forming the barrier film is not particularly limited. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma polymerization A plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used, but an 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, opaque resin substrates, and ceramic substrates.
The external extraction quantum efficiency at room temperature (25 ° C.) of light emission of the organic EL device of the present invention is preferably 1% or more, and more preferably 5% or more.
Here, external extraction quantum efficiency (%) = number of photons emitted to the outside of the organic EL element / number of electrons flowed to the organic EL element × 100.
In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor may be used in combination.

<Other configuration>
As a sealing means, a protective film, a protective plate, a technique for improving light extraction efficiency and a light collecting sheet that can be used in the present invention, a known technique described in JP 2014-152151 A can be used. .

<Application>
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 backlights for liquid crystals, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, It can use effectively for the use as a backlight of a liquid crystal display device, and an illumination light source especially.
In the organic EL element of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like as needed during film formation. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned. In the fabrication of the element, a conventionally known method is used. Can do.

[Display device]
The display device including the organic EL element of the present invention may be single color or multicolor, but here, the multicolor display device will be described.

In the case of a multicolor display device, a shadow mask is provided only at the time of forming a light emitting layer, and a film can be formed on one surface by vapor deposition, casting, spin coating, ink jet, printing, or the like.
In the case of patterning only the light emitting layer, there is no limitation on the method, but a vapor deposition method, an inkjet method, a spin coating method, and a 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 necessary.

Moreover, the manufacturing method of an organic EL element is as having shown in the one aspect | mode of manufacture of the organic EL element of said this invention.

When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Further, even when 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 alternating current waveform to be applied may be arbitrary.

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

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

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. 3 is a schematic view showing an example of a display device composed of organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element.

The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, a wiring unit C that electrically connects the display unit A and the control unit B, and the like.
The control unit B is electrically connected to the display unit A via the wiring unit C, and sends a scanning signal and an image data signal to each of a plurality of pixels based on image information from the outside. Sequentially emit light according to the image data signal, scan the image, and display the image information on the display unit A.

FIG. 4 is a schematic diagram of a display device using an active matrix method.
The display unit A includes a wiring unit C including a plurality of scanning lines 5 and data lines 6, a plurality of pixels 3 and the like on a substrate. The main members of the display unit A will be described below.
FIG. 4 shows a case where the light emitted from the pixel 3 is extracted in the direction of the white arrow (downward).

The scanning line 5 and the plurality of data lines 6 in 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 illustrated). Not)
When a scanning signal is applied from the scanning line 5, the pixel 3 receives an 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, the green region, and the blue region on the same substrate.

Next, the light emission process of the pixel will be described. FIG. 5 is a schematic diagram showing a pixel circuit.
The pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. A 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 juxtaposing them on the same substrate.

In FIG. 5, an image data signal is applied from the control unit B to the drain of the switching transistor 11 through the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 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 supplied 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 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, and the power supply line 7 connects to the organic EL element 10 according to the potential of the image data signal applied to the gate. Current is supplied.

When the scanning signal is moved 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 charged potential of the image data signal even if the driving of the switching transistor 11 is turned off, the driving of the driving transistor 12 is kept on and the next scanning signal is applied. Until then, the light emission of the organic EL element 10 continues. When the scanning signal is next applied 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 organic EL element 10 emits light by the switching transistor 11 and the drive transistor 12 that are active elements for the organic EL element 10 of each of the plurality of pixels, and the light emission of the organic EL element 10 of each of the plurality of pixels 3. 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 by a multi-value image data signal having a plurality of gradation potentials, or by turning on / off a predetermined light emission amount by a binary image data signal. Good. The potential of the capacitor 13 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.
In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

FIG. 6 is a schematic diagram of a passive matrix display device. In FIG. 6, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice shape 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 system, the pixel 3 has no active element, and the manufacturing cost can be reduced.
By using the organic EL element of the present invention, an initial deterioration of light emission can be suppressed, a display device with high light emission efficiency and a long light emission lifetime can be obtained.

[Lighting device]
The organic EL element of the present invention can also be used for a lighting device.

Further, the light-emitting dopant 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 emission colors and mixing the colors. The combination of a plurality of emission colors may include three emission maximum wavelengths of three primary colors of red, green, and blue, or two of the complementary colors such as blue and yellow, blue green and orange, etc. The thing containing the light emission maximum wavelength may be used.

In addition, the method for forming the organic EL device of the present invention may be simply arranged by providing a mask only when forming a light emitting layer, a hole transport layer, an electron transport layer, or the like, and separately coating with the mask. Since the other layers are common, patterning of a mask or the like 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 ink jet method, a printing method, or the like, and 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 elements themselves emit white light.

The light emission color of the organic EL device of the present invention and the compound used in the present invention is shown in FIG. 7.16 on page 108 of “New Color Science Handbook” (edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with a luminance meter CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.
When the organic EL element of the present invention is a white element, white means that the chromaticity in the CIE1931 color system at 1000 cd / m ² is X when the 2 ° viewing angle front luminance is measured by the above method. = 0.33 ± 0.07 and Y = 0.33 ± 0.1.

The organic EL element of the present invention can be provided in a lighting device using a known technique described in JP 2014-152151 A.
Specifically, the non-light emitting 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 ( Tokusei Co., Ltd. Lux Track LC0629B) is applied, and this is overlaid on the cathode and brought into close contact with the transparent support substrate, irradiated with UV light from the glass substrate side, cured, sealed, and FIGS. 7 and 8 A lighting device as shown in FIG.

FIG. 7 shows a schematic diagram of a lighting device, and the organic EL element (organic EL element 101 in the lighting device) of the present invention is covered with a glass cover 102 (note that the sealing operation with the glass cover is performed by lighting This is carried out in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) without bringing the organic EL element 101 in the apparatus into contact with the air.
FIG. 8 shows a cross-sectional view of the lighting device. In FIG. 8, 105 denotes a cathode, 106 denotes an organic layer, and 107 denotes a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

The structural formulas of the compounds used in Examples and Comparative Examples are shown below.

[Example 1]
<Calculation method of ratio of electron density of π-conjugated compound>
First, the stable structure of the ground state of the target molecule was calculated using Gaussian 09 with the functional as B3LYP and the basis function as 6-31G (d). Next, the molecular orbitals of HOMO and LUMO were output by using #p and pop = regular as keywords. Thus, the total electron density distribution of the HOMO site and LUMO site of the molecular orbital obtained was analyzed.
The ratio of the electron density of HOMO was calculated as the ratio of the electron density distribution of HOMO when the total electron density distribution of HOMO calculated by molecular orbital calculation was 100%. The ratio of LUMO electron density was calculated as the ratio of LUMO electron density distribution when the total electron density distribution of LUMO calculated by molecular orbital calculation was 100%.

<Calculation result of electron density ratio>
The ratio of the electron density was calculated for the π-conjugated compound according to the present invention used in the examples and the compound of the comparative example. In the following, with respect to the π-conjugated compound, the result will be described with one representative example given in each of the general formulas (2) to (9).
As an example of calculating the electron density distribution, FIG. 9A shows the HOMO electron density distribution and FIG. 9B shows the LUMO electron density distribution in the host compound H2-12. Further, FIG. 10A shows the electron density distribution of HOMO and FIG. 10B shows the electron density distribution of LUMO in the host compound H3-11.

(General formula (2): Host compound H2-12)
From the calculation results, it was found that the ratio of the electron density of HOMO in the dibenzofuran group was 91% for the host compound H2-12, which is a compound having the structure represented by the general formula (2) (FIG. 9A). Moreover, it turned out that the ratio of the electron density of LUMO in a diazadibenzofuran group is 93% (FIG. 9B).

(General formula (3): Host compound H3-11)
From the calculation results, it was found that the ratio of the electron density of HOMO in the carbazole group was 85% for the host compound H3-11 which is a compound having the structure represented by the general formula (3) (FIG. 10A). It was also found that the LUMO electron density ratio in the phosphindol group was 91% (FIG. 10B).

(General formula (4): Host compound H4-4)
From the calculation results, it was found that the ratio of the electron density of HOMO in the carbazole group was 88% for the host compound H4-4, which is a compound having the structure represented by the general formula (4). It was also found that the LUMO electron density ratio in the diphenyltriazine group was 93%.

(General formula (5): Host compound H5-9)
From the calculation results, it was found that the ratio of the electron density of HOMO in the carbazole group was 84% for the host compound H5-9, which is a compound having the structure represented by the general formula (5). It was also found that the LUMO electron density ratio in the diphenyltriazine group was 84%.

(General formula (6): Host compound H6-3)
From the calculation results, it was found that the ratio of the electron density of HOMO in the carbazole group was 87% for the host compound H6-3, which is a compound having the structure represented by the general formula (6). It was also found that the LUMO electron density ratio in the dibenzofuran-triazine group was 90%.

(General formula (7): Host compound H7-12)
From the calculation results, it was found that the ratio of the electron density of HOMO in the phenylcarbazole group of the host compound H7-12, which is a compound having the structure represented by the general formula (7), was 98%. Moreover, it turned out that the ratio of the electron density of LUMO in a dicyano substituted benzene group is 81%.

(General formula (8): Host compound H8-26)
From the calculation results, it was found that the ratio of the electron density of HOMO in the carbazole group was 88% for the host compound H8-26, which is a compound having the structure represented by the general formula (8). Moreover, it turned out that the ratio of the electron density of LUMO in a carbazole group is 98%.

(General formula (9): Host compound H9-10)
From the calculation results, it was found that the ratio of the electron density of HOMO in the carbazole group was 89% for the host compound H9-10, which is a compound having the structure represented by the general formula (9). Moreover, it turned out that the ratio of the electron density of LUMO in a dicyano substituted benzene group is 91%.

(result)
When HOMO and LUMO are completely separated by molecular orbital calculation and have a molecular structure that is physically close enough to allow electronic transition, electronic transition between HOMO and LUMO occurs through through-space interaction.
As described above, the π-conjugated compound according to the present invention has a portion having a HOMO electron density ratio of 80% or more and a LUMO electron density ratio of 80% or more in the molecule. It turns out that it is separated into HOMO and LUMO respectively. It was also found that the molecular structure is physically close enough to allow electronic transition.
Therefore, it was found that the π-conjugated compound according to the present invention satisfies the condition in which the electronic transition between HOMO and LUMO occurs due to the through-space interaction in the same molecule.
Moreover, when the same calculation was performed for the π-conjugated compound used in the other examples and the exemplified compounds of the π-conjugated compound described above, the ratio of the electron density of HOMO in the molecule was 80% or more. It was found that there was a part and a part where the ratio of the LUMO electron density was 80% or more, and the molecular structure was physically close enough to allow electronic transition.

On the other hand, when the same calculation was performed for Comparative Compound 1, Comparative Compound 2-1, Comparative Compound 2-2, and Comparative Compound 3 which are the compounds of Comparative Examples, they were different from the π-conjugated compound according to the present invention. The molecular structure was not physically close enough to allow electronic transitions in the molecule. In other words, it was found that the electronic transition between HOMO and LUMO does not satisfy the conditions that occur due to through-space interaction in the same molecule.

[Example 2]
<Preparation of organic EL element 1-1>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm as a positive electrode on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and then attached with this ITO transparent electrode After ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen gas and UV ozone cleaning for 5 minutes, this transparent substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.

Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.
After reducing the vacuum to 1 × 10 ⁻⁴ Pa, energize and heat the evaporation crucible containing HAT-CN (1,4,5,8,9,12-hexaazatriphenylenehexacarbonitrile) to evaporate Vapor deposition was performed on the ITO transparent electrode at a speed of 0.1 nm / second to form a hole injection transport layer having a layer thickness of 10 nm.

Next, α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) was deposited on the hole injection layer at a deposition rate of 0.1 nm / second, and the layer thickness was 40 nm. The hole transport layer was formed. Comparative compound 1 as the host compound and exemplary compound (D-37) as the luminescent dopant were co-evaporated at a deposition rate of 0.1 nm / second so as to be 85% and 15% by volume, respectively. Formed.
Thereafter, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) was deposited at a deposition rate of 0.1 nm / second 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-emitting surface side of the above element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 1-1.

<Preparation of organic EL elements 1-2 to 1-32>
Organic EL devices 1-2 to 1-32 were produced in the same manner as the organic EL device 1-1 except that the host compound was changed as shown in Table 1.

<Preparation of light-emitting layer monolayer film 1-1 for exciton stability evaluation>
A co-deposited film was prepared on a quartz substrate using Comparative Compound 1 as the host compound and the exemplified compound (D-37) as the luminescent dopant (deposition rates of 0.1 nm / second, 0.010 nm / second, and 40 nm, respectively) Covering the non-light emitting surface with a glass case, using a glass substrate having a thickness of 300 μm as a sealing substrate, and applying an epoxy photo-curing adhesive (Lux Track LC0629B manufactured by Toagosei Co., Ltd.) as a sealing material around This was stacked on the cathode and brought into close contact with the transparent support substrate, irradiated with UV light from the glass substrate side, cured and sealed. By these operations, the light emitting layer monolayer film 1-1 was formed.

<Preparation of light-emitting layer monolayer films 1-2 to 1-32 for exciton stability evaluation>
The light emitting layer single layer films 1-2 to 1-32 were formed in the same manner as the light emitting layer single layer film 1-1 except that the host compound was changed from the comparative compound 1 to the compound shown in Table 1.
The light emitting layer single-layer films 1-1 to 1-32 correspond to the organic EL elements 1-1 to 1-32, respectively, and are excited in the light emitting layers 1-1 to 1-32 of the organic EL elements. In order to evaluate the child stability, a single layer film of the light emitting layer is separately formed.

<Evaluation>
Exciton stability, luminous efficiency, and device lifetime were evaluated as follows. The evaluation results are shown in Table 1. In addition, the exciton stability was evaluated by a light emitting layer single layer film for exciton stability evaluation, and the light emission efficiency and element lifetime were evaluated by an organic EL element.

(1. Exciton stability)
A light-emitting layer monolayer film for exciton stability evaluation was irradiated with a UV-LED (5 W / cm ² ) light source for 20 minutes. At this time, the distance between the light source and the sample was 15 mm. A constant current of ^2.5 mA / cm ² was applied to the UV-irradiated sample, the light emission luminance immediately after light emission was measured, and the luminance residual ratio was calculated using the following formula. The initial light emission luminance is the light emission luminance (L0) at the time of evaluating the light emission efficiency.
Exciton stability (%) = (emission luminance after 20 minutes UV) / (initial emission luminance (L0)) × 100
Table 1 shows the light emitting layer corresponding to the organic EL element 1-3 as a relative value with 100. A larger value of the luminance residual ratio indicates better exciton stability. In addition, the high exciton stability indicates that the initial deterioration of the light emitting layer is suppressed.

(2. Luminous efficiency)
The organic EL device is turned on at room temperature (about 23 ° C.) under a constant current condition of ^2.5 mA / cm ² , and the emission luminance [cd / m ² ] immediately after the start of lighting is measured to obtain an external extraction quantum efficiency ( η) (luminescence efficiency) was calculated. Here, the measurement of emission luminance was performed using CS-1000 (manufactured by Konica Minolta), and the external extraction quantum efficiency was expressed as a relative value with the organic EL element 1-3 being 100.

(3. Device life)
Each organic EL element was driven at a constant current of 0.65 mA / cm ² to obtain a time during which the luminance was half of the initial luminance, and this was evaluated as a measure of the element lifetime. The device lifetime was expressed as a relative value with the organic EL device 1-3 being 100.

As described above, it was found that the organic EL elements of the examples have high exciton stability of the light emitting layer, that is, initial deterioration can be suppressed. Furthermore, it turned out that the organic EL element of an Example has high luminous efficiency and long element lifetime.
On the other hand, the organic EL element of the comparative example was inferior about any item. Comparative compound 1 according to organic EL element 1-1 is a general blue-emitting TADF compound, and has a molecular structure capable of localizing HOMO sites and LUMO sites in the molecule. Further, Comparative Compound 2-1 and Comparative Compound 2-2 related to the organic EL element 1-2 are those in which a TADF phenomenon occurs by forming a charge transfer complex between two molecules in the presence of two types of hosts. It is. In addition, the comparative compound 3 according to the organic EL element 1-3 is a host compound that does not cause space electron transition unlike these compounds. Since these comparative compounds 1 to 3 do not satisfy the conditions in which the electronic transition between HOMO and LUMO is caused by through-space interaction in the same molecule, as shown in Example 1, the effects of the present invention are obtained. It is thought that it was not obtained.

[Example 3]
<Preparation of organic EL elements 2-1 to 2-38>
The organic EL device 2-1 was prepared in the same manner as the organic EL device 1-1 except that the host compound was changed to the compound shown in Table 2 and the luminescent dopant was changed from the exemplary compound (D-37) to the exemplary compound (D-63). ˜2-38 was produced. In the exemplified compound (D-63), the ring Z _{2 in the} general formula (1) is an imidazole ring.

<Preparation of light-emitting layer monolayer films 2-1 to 2-38 for exciton stability evaluation>
The light emitting layer single layer was prepared in the same manner as the light emitting layer single layer film 1-1 except that the host compound was changed to the compound shown in Table 2 and the light emitting dopant was changed from the exemplified compound (D-37) to the exemplified compound (D-63). Layer films 2-1 to 2-38 were produced.

<Evaluation>
Exciton stability, luminous efficiency, and device lifetime were evaluated in the same manner as in Example 2. The evaluation results are shown in Table 2. The exciton stability, the light emission efficiency, and the element lifetime are expressed as relative values with the organic EL element 2-3 being 100, respectively.

As described above, it was found that the organic EL elements of the examples have high exciton stability of the light emitting layer, that is, initial deterioration can be suppressed. Furthermore, it turned out that the organic EL element of an Example has high luminous efficiency and long element lifetime. On the other hand, the organic EL element of the comparative example was inferior about any item.

[Example 4]
<Preparation of organic EL elements 3-1 to 3-7>
The organic EL device 3-1 was prepared in the same manner as the organic EL device 1-1 except that the host compound was changed to the compound shown in Table 3 and the light-emitting dopant was changed from the exemplary compound (D-37) to the exemplary compound (D-15). ~ 3-7 were produced. In the exemplified compound (D-15), the ring Z _{2 in the} general formula (1) is a pyridine ring.

<Preparation of single-layer films 3-1 to 3-7 for evaluating exciton stability>
The light emitting layer single layer was obtained in the same manner as the light emitting layer single layer film 1-1 except that the host compound was changed to the compound shown in Table 3 and the light emitting dopant was changed from the exemplified compound (D-37) to the exemplified compound (D-15). Layer films 3-1 to 3-7 were produced.

<Evaluation>
Exciton stability, luminous efficiency, and device lifetime were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3. The exciton stability, the light emission efficiency, and the element lifetime are expressed as relative values with the organic EL element 3-3 as 100, respectively.

As described above, it was found that the organic EL elements of the examples have high exciton stability of the light emitting layer, that is, initial deterioration can be suppressed. Furthermore, it turned out that the organic EL element of an Example has high luminous efficiency and long element lifetime. On the other hand, the organic EL element of the comparative example was inferior about any item.

[Example 5]
<Preparation of organic EL elements 4-1 to 4-7>
The organic EL device 4-1 was prepared in the same manner as the organic EL device 1-1 except that the host compound was changed to the compound shown in Table 4 and the light-emitting dopant was changed from the exemplary compound (D-37) to the exemplary compound (D-2). ~ 4-7 were produced. In the exemplified compound (D-2), the ring Z _{2 in the} general formula (1) is an isoquinoline ring.

<Preparation of light-emitting layer monolayer films 4-1 to 4-7 for exciton stability evaluation>
The light emitting layer single layer film 1-1 was prepared in the same manner as the light emitting layer single layer film 1-1 except that the host compound was changed to the compound shown in Table 4 and the light emitting dopant was changed from the exemplified compound (D-37) to the exemplified compound (D-2). Layer films 4-1 to 4-7 were produced.

<Evaluation>
Exciton stability, luminous efficiency, and device lifetime were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 4. The exciton stability, the light emission efficiency, and the element lifetime were expressed as relative values with 100 as the organic EL element 4-3.

As described above, it was found that the organic EL elements of the examples have high exciton stability of the light emitting layer, that is, initial deterioration can be suppressed. Furthermore, it turned out that the organic EL element of an Example has high luminous efficiency and long element lifetime. On the other hand, the organic EL element of the comparative example was inferior about any item.

[Example 6]
<Preparation of organic EL elements 5-1 to 5-7>
The organic EL device 5-1 was prepared in the same manner as the organic EL device 1-1 except that the host compound was changed to the compound shown in Table 5 and the light-emitting dopant was changed from the exemplary compound (D-37) to the exemplary compound (D-64). ~ 5-7 were made. In the exemplified compound (D-64), the ring Z _{2 in the} general formula (1) is a triazole ring.

<Preparation of single-layer films 5-1 to 5-7 for exciton stability evaluation>
The light emitting layer single layer was obtained in the same manner as the light emitting layer single layer film 1-1 except that the host compound was changed to the compound shown in Table 5 and the light emitting dopant was changed from the exemplified compound (D-37) to the exemplified compound (D-64). Layer films 5-1 to 5-7 were produced.

<Evaluation>
Exciton stability, luminous efficiency, and device lifetime were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 5. The exciton stability, the light emission efficiency, and the element lifetime were expressed as relative values with the organic EL element 5-3 being 100.

As described above, it was found that the organic EL elements of the examples have high exciton stability of the light emitting layer, that is, initial deterioration can be suppressed. Furthermore, it turned out that the organic EL element of an Example has high luminous efficiency and long element lifetime. On the other hand, the organic EL element of the comparative example was inferior about any item.

[Example 7]
<Preparation of organic EL elements 6-1 to 6-7>
The organic EL device 6-1 was prepared in the same manner as the organic EL device 1-1 except that the host compound was changed to the compound shown in Table 6 and the light-emitting dopant was changed from the exemplary compound (D-37) to the exemplary compound (D-50). ~ 6-7 were prepared. In the exemplified compound (D-50), the ring Z _{2 in the} general formula (1) is a pyrazole ring.

<Preparation of light-emitting layer monolayer films 6-1 to 6-7 for exciton stability evaluation>
The light emitting layer single layer was obtained in the same manner as the light emitting layer single layer film 1-1 except that the host compound was changed to the compound shown in Table 6 and the light emitting dopant was changed from the exemplified compound (D-37) to the exemplified compound (D-50). Layer films 6-1 to 6-7 were produced.

<Evaluation>
Exciton stability, luminous efficiency, and device lifetime were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 6. The exciton stability, the light emission efficiency, and the element lifetime are expressed as relative values with the organic EL element 6-3 as 100, respectively.

As described above, it was found that the organic EL elements of the examples have high exciton stability of the light emitting layer, that is, initial deterioration can be suppressed. Furthermore, it turned out that the organic EL element of an Example has high luminous efficiency and long element lifetime. On the other hand, the organic EL element of the comparative example was inferior about any item.

The organic electroluminescence element of the present invention can be suitably used for, for example, a display device and a lighting device because the initial deterioration is suppressed, the luminous efficiency is high, and the element lifetime is long.

DESCRIPTION OF SYMBOLS 1 Display 3 Pixel 5 Scan line 6 Data line 7 Power supply line 10 Organic EL element 11 Switching transistor 12 Drive transistor 13 Capacitor 101 Organic EL element 102 in an illuminating device Glass cover 105 Cathode 106 Organic layer 107 Glass substrate 108 with a transparent electrode Nitrogen gas 109 Water capturing agent A Display part B Control part C Wiring part

Claims (12)

An organic electroluminescence device having an organic layer including at least one light emitting layer between an anode and a cathode,
At least one layer of the light emitting layer contains a π-conjugated compound and a compound having a structure represented by the following general formula (1),
In the π-conjugated compound, an electronic transition between HOMO and LUMO occurs through through-space interaction in the same molecule, and at least one of the HOMO or the LUMO is localized at a site where π-conjugated aromatic An organic electroluminescence device comprising a ring.

(In the above general formula (1), M represents Ir, Pt, Rh or Os. A ₁ , A ₂ , B ₁ and B ₂ each represent a carbon atom or a nitrogen atom. Ring Z ₁ represents A _1. And A represents a 6-membered aromatic hydrocarbon ring formed with A ₂ or a 5-membered or 6-membered aromatic heterocycle, and ring Z ₂ represents a 5-membered or 6-membered ring formed with B ₁ and B ₂ . represents an aromatic heterocyclic ring. ring Z ₁ and the ring Z ₂ may have a substituent, may form a condensed ring structure with substituent mutually bonded. further, the ring Z ₁ And ring Z ₂ may be such that the substituents of each ligand are bonded to each other so that the ligands are linked to each other, L ′ is a monoanionic bidentate ligand coordinated to M M ′ represents an integer of 0 to 2. n ′ represents an integer of 1 to 3. m ′ + n ′ is 2 or 3. m ′ and n ′ are In the case of 2 or more, the ligands represented by the ring Z ₁ and the ring Z ₂ and L ′ may be the same or different.) The organic electroluminescence device according to claim 1, wherein the π-conjugated compound comprises a compound having a structure represented by the following general formula (2).

(In the general formula (2), X _a and X _b each independently represent an oxygen atom, a sulfur atom or NR _c . X ₂₁ to X ₂₆ each independently represent a nitrogen atom or CR _d, and Each of R _c , R _d , and R ₂₁ to R ₂₆ independently represents a hydrogen atom or a substituent, L ₂₁ to L ₂₆ each represents a divalent linking group, p and q Represents an integer of 0 or 1.) The organic electroluminescent device according to claim 1, wherein the π-conjugated compound comprises a compound having a structure represented by the following general formula (3).

(In the general formula (3), X ₃₁ represents PR _b (═O), SO ₂ or SO. R _b and R ₃₁ to R ₃₈ each independently represents a hydrogen atom or a substituent. The proportion of the LUMO electron density of the tricondensed mother nucleus structure portion containing X ₃₁ is 80% or more, and at least one of R ₃₁ , R ₃₃ , R ₃₆ and R ₃₈ is represented by the following general formula (3 -A).

In the general formula (3-A), Y ₃₁ represents a divalent linking group. Z ₃ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the total ratio of electron density of HOMO is 80% or more. p3 represents an integer of 0 or 1. ) The organic electroluminescent device according to claim 1, wherein the π-conjugated compound contains a compound having a structure represented by the following general formula (4).

(In the above general formula (4), X ₄₁ to X ₄₅ each independently represents a nitrogen atom or CR _e . R _e represents a hydrogen atom or a substituent. L ₄₁ represents an aromatic hydrocarbon ring group or R ₄₁ represents an aromatic heterocyclic group, and at least one R ₄₁ is represented by the following general formula (4-A).

In the general formula (4-A), Y ₄₁ represents a divalent linking group. Z ₄ represents an aromatic total percentage of the HOMO of the electron density is 80% or more hydrocarbon ring group or an aromatic heterocyclic group. p4 represents an integer of 0 or 1. ) The organic electroluminescent device according to claim 1, wherein the π-conjugated compound comprises a compound having a structure represented by the following general formula (5).

(In the general formula (5), R ₅₁ to R ₅₆ each independently represents a hydrogen atom or a substituent. One of Z ₅₁ and Z ₅₂ is an aromatic having a HOMO electron density ratio of 80% or more. Represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, and the other represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group having a LUMO electron density ratio of 80% or more.) The organic electroluminescent device according to claim 1, wherein the π-conjugated compound comprises a compound having a structure represented by the following general formula (6).

(In the general formula (6), X ₆₁ represents O or S. R ₆₁ to R ₆₈ each independently represents a hydrogen atom or a substituent. R ₆₁ and R ₆₈ , or R ₆₄ and R _65. is, .R ₆₁ and R ₆₈ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, each, when each represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, one of R ₆₁ and R ₆₈ Represents an aromatic hydrocarbon ring group or aromatic heterocyclic group having a HOMO electron density ratio of 80% or more, and the other is an aromatic hydrocarbon ring group having a LUMO electron density ratio of 80% or more. Or R ₆₄ and R ₆₅ each represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group, and one of R ₆₄ and R ₆₅ has a ratio of the electron density of HOMO. Aromatic hydrocarbons that are 80% or more It represents a cyclic group or an aromatic heterocyclic group and the other represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group the proportion of the electron density of the LUMO is less than 80%.) The organic electroluminescent device according to claim 1, wherein the π-conjugated compound comprises a compound having a structure represented by the following general formula (7).

(In the general formula (7), R ₇₁ to R ₈₀ each independently represents a hydrogen atom or a substituent. At least two of R ₇₁ , R ₇₂ , R ₇₉ , and R ₈₀ are aromatic hydrocarbons. In addition, one of these aromatic hydrocarbon ring groups or aromatic heterocyclic groups has a HOMO electron density ratio of 80% or more, and these aromatic carbon groups. The other one of the hydrogen ring group or the aromatic heterocyclic group has a LUMO electron density ratio of 80% or more.) The organic electroluminescent device according to claim 1, wherein the π-conjugated compound contains a compound having a structure represented by the following general formula (8).

(In the above general formula (8), R ₈₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO or LUMO is 80% or more. R ₈₂ to R ₈₉ are respectively Independently represents a hydrogen atom or a substituent, provided that when R ₈₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO is 80% or more, R ₈₂ or R ₈₉ is the proportion of the electron density of the LUMO represents a aromatic hydrocarbon ring group or aromatic heterocyclic group is 80% or higher. in addition, R ₈₁ is an aromatic hydrocarbon fraction of the electron density of the LUMO is less than 80% In the case of representing a cyclic group or an aromatic heterocyclic group, R ₈₂ or R ₈₉ represents an aromatic hydrocarbon cyclic group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO is 80% or more.) The organic electroluminescent device according to claim 1, wherein the π-conjugated compound comprises a compound having a structure represented by the following general formula (9).

(In the general formula (9), R ₉₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which the ratio of the electron density of HOMO is 80% or more. R ₉₂ represents the ratio of the electron density of LUMO. Represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group in which R is 80% or more, and R ₉₃ to R ₉₆ each represents a hydrogen atom or a substituent. Said ring Z ₂ in the general formula (1) is a pyridine ring, an imidazole ring, an isoquinoline ring, an organic according to any one of claims 1 to 9, characterized in that a triazole ring or a pyrazole ring Electroluminescence element. A display device comprising the organic electroluminescence element according to any one of claims 1 to 10. An illumination device comprising the organic electroluminescence element according to any one of claims 1 to 10.

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