JP2016036025A - ORGANIC ELECTROLUMINESCENT DEVICE AND π CONJUGATED COMPOUND - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL device which is superior in electric power efficiency and initial drive voltage, and exhibits blue-color light emission with good chromaticity.SOLUTION: An organic EL device of the present invention comprises: a positive electrode; a negative electrode; and an organic layer including at least one light-emitting layer between the positive and negative electrodes. The at least one layer of the organic layer includes a π conjugated compound having, in a molecule, an electron-withdrawing part and an electron-donating part. In the π conjugated compound, the nearest interatomic distance of the electron-withdrawing part and the electron-donating part is 10 nm or less; the absolute value (ΔE) of an energy difference of the minimum excited singlet level and the minimum excited triplet level of the π conjugated compound is 0.5 eV or less.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an organic electroluminescence device and a π-conjugated compound. More specifically, the present invention relates to an organic electroluminescent device that excels in power efficiency and initial driving voltage and exhibits blue light emission with good chromaticity, and a π-conjugated compound.

  Organic electroluminescence (EL) elements that have already been commercialized as electronic displays and flat illumination can be classified according to the light emission mechanism. Fluorescence method using light emission from singlet excitons and light emission from triplet excitons. There are two types of phosphorescence methods that use.

  From the viewpoint of light emission efficiency, the phosphorescence method is the most excellent, and it is desired that phosphorescence emission is used for all light in lighting applications and mobile display applications that require low power consumption. However, the phosphorescence method has a problem that it is difficult to apply blue light emission, particularly pure blue or deep blue (deep blue) for which a short light emission wavelength is required, and the cause is a required band gap.

The triplet excitation energy in the same molecule is always lower than the corresponding singlet excitation energy. That is, in order to obtain blue by phosphorescence emission, it is necessary to widen the original band gap (corresponding to singlet excitation energy). However, in order to obtain such a wide band gap with an organic material, it is usually necessary to reduce or cut the conjugated system, which causes a decrease in the stability of the organic material itself. .
In addition, since a phosphorescent compound (also referred to as a dopant) causes aggregation and crystallization when present at a high concentration, it is necessary to disperse the phosphorescent compound with a host compound in order to maintain an appropriate emission wavelength. There is. In that case, the host compound requires a higher triplet excitation energy, which is also a big obstacle from the viewpoint of the stability of the organic substance.

That is, in order to achieve pure blue to deep blue phosphorescence emission at a practical level, both the dopant and the host compound are molecularly designed with a sufficiently high triplet energy. However, it is not easy to design both at the same time.
However, it can be said that the development of a phosphorescent organic EL element toward the future is almost synonymous with the development of a blue phosphorescent material, that is, a blue phosphorescent dopant and a blue phosphorescent host compound.

  However, in addition to the above technical problems, the phosphorescent light emitting method has a resource problem that iridium and platinum, which are rare metals, must be used. For example, mass production like general lighting is required. It is a big problem in the area where

It was developed to solve the problems of both the conventional fluorescent organic EL element and the phosphorescent organic EL element (that is, the former is a problem of low luminous efficiency and the latter is disadvantageous for blue light emission). This is a delayed fluorescence method.
The delayed fluorescence method includes a triplet-triplet anionization (TTA, triplet-triplet fusion: TTF) method in which one singlet exciton molecule is formed by collision of two triplet excitons. Two types of thermal excitation-type (Thermal Activated Delayed Fluorescence (TADF)) using thermal inverse intersystem crossing from triplet excitons to singlet excitons have been found.
However, in the TTA method, half of the triplet excitons in principle do not contribute to light emission and are thermally deactivated, so that the fundamental light emission efficiency is not improved. When it is converted to about 10% in terms of quantum efficiency and about 40% to 50% in terms of internal quantum efficiency, it cannot be a technology for future low power consumption.
On the other hand, in the TADF method in which the phenomenon has been discovered in recent years, if the singlet excitation energy and the triplet excitation energy are close to each other and the fluorescence quantum yield can be further increased to 100%, in principle, as in the phosphorescence method, Since all excitons generated by electric field excitation can be converted into light, it can be a low power consumption technology similar to phosphorescence.
However, the TADF method also has a weak point.

In order to cause the TADF phenomenon, it is necessary to cause reverse intersystem crossing at room temperature or the temperature of the light emitting layer in the light emitting element. For this purpose, the energy difference between the lowest excited singlet level and the lowest excited triplet level ( hereinafter referred to as ΔE _st.) it is essential extremely small. In order to create such a state with an organic compound, it is desirable not to mix HOMO and LUMO in the molecule, and to localize them as far as possible and completely separate them.
For example, as shown in FIG. 1, in 2CzPN, HOMO is distributed in carbazolyl groups at the 1st and 2nd positions on the benzene ring, and LUMO is distributed in cyano groups at the 4th and 5th positions (FIG. 1 (a ) reference.) it is, and the HOMO and LUMO are isolated, Delta] E _st becomes less 0.1 eV (see FIG. 1 (b).), TADF phenomenon occurs.
On the other hand, as shown in FIG. 2, 2CzXy in which the cyano group at the 4th and 5th positions is replaced with a methyl group cannot clearly separate such HOMO and LUMO (see FIG. 2 (a)). ), ΔE _st cannot be reduced (see FIG. 2B), and the TADF phenomenon does not occur.
All of the reported examples in which the TADF phenomenon has been confirmed as an organic EL device to date uses a compound containing a strong electron-withdrawing group such as a cyano group, a sulfonyl group, or a triazinyl group as a light emitting material (for example, (See Patent Document 1).
Such an organic compound always has a deep HOMO level (−5.5 eV or less).

In organic EL elements, triphenylamine derivatives are often used as the hole transport layer material from the viewpoint of durability and hole transport properties. The triphenylamine derivative has a HOMO level of about −4.5 to −5.5 eV, although it depends on the choice of substituents. Therefore, when the HOMO level of the light emitting material in the light emitting layer becomes deeper, It becomes impossible to inject holes into the light emitting material.
Even when holes are injected through the host compound, the HOMO level of the host compound needs to be equal to or deeper than that of the light emitting material, and in any case, holes are injected into the light emitting layer. In order to emit light, a high voltage that overcomes the band gap is required. No matter how high the light emission quantum efficiency is, if the drive voltage is high, it is difficult to increase the power efficiency represented by [lm / W], and low power consumption cannot be realized.

  This phenomenon becomes more prominent as the required band gap becomes larger: green rather than red, blue than green, and deep blue rather than blue. In other words, even in delayed fluorescence, not only the technical difficulty of luminescent materials but also the lack of choice of host compounds to be combined is a big problem. Is a blue light emitting material.

Next, as another point of view, the problem of localization of HOMO and LUMO will be described.
FIG. 3A schematically shows the electronic state of 2CzPN, which is a TADF compound. As shown in FIG. 3A, the electronic state of 2CzPN depends on Ir (ppy) ₃ which is a typical phosphorescent compound shown in FIGS. 3B and 3C and DBF which is a host compound. Unlike -Cz, its charge distribution is extremely localized.
That is, the fact that HOMO and LUMO are localized can be considered as the same electronic state as the CT complex dye.
A typical example of the CT complex dye is an azomethine dye used as an image dye for color photography. Since such a dye (compound) has an extremely localized charge distribution, it is strongly adsorbed electrostatically by utilizing a slight charge bias of the substance (eg, solvent or host) that becomes the medium. Therefore, it is known that interactions are formed at various positions in various directions, the energy distribution in the excited state is broadened, and the absorption spectrum and emission spectrum are widened.
Since the TADF compound also creates the same situation with the host compound, as shown in FIG. 4 (in the figure, the strength of adsorption is expressed in terms of positional proximity), it is strong and various. Interaction is formed, and the emission spectrum is broadened.

This phenomenon becomes a fatal problem in selecting a host compound, particularly in a blue light emitting device. That is, the difference between the fluorescence maximum wavelength (λmax) that characterizes the emission color and the rising wavelength on the short wavelength side of the emission spectrum that determines the energy (S ₁ ) of the lowest excitation singlet level becomes large. In order to obtain TADF light emission efficiently, a high (S ₁ ) is required, that is, a high S ₁ compound (high T ₁ compound in the same meaning) as a phosphorescent blue host compound is required.
So far, a light blue phosphorescent host compound can be used, so this is not a big problem, but in order to obtain blue light emission and further deep blue light emission by the TADF method, a host compound having a larger band gap is required. Then, the stability of the compound becomes a problem.

FIG. 5 is a schematic diagram showing the interaction between the phosphorescent compound and the host compound for the purpose of comparison.
As shown in FIG. 5, although the iridium complex is loose and HOMO and LUMO are biased, the HOMO portion is present in the iridium metal in the center of the complex, so it does not contribute to the electrostatic interaction. Since LUMO distributed in the ligand is also delocalized in the ligand, the electron density is not so high, and as a result, there is no strong electrostatic interaction with the host compound, resulting in a broad emission spectrum. It will not happen.
Therefore, even in the TADF method, it is necessary to design a molecule of the TADF light emitting material so that the host compound can coexist with such a weak interaction.

I will also think from a different perspective.
TADF light emission is not always composed of a single substance. From the viewpoint of separating HOMO and LUMO far away as described above, the exciplex emission formed from a pair of a donor substance and an acceptor substance is substantially localized because HOMO and LOMO are localized in different molecules. ΔE _st can be minimized. For example, as shown in FIGS. 6A and 6B, a co-deposited film of a triphenylamine compound m-MTDATA as a donor material and an oxadiazole compound t-Bu-PBD as an acceptor material In an organic EL element using a light emitting layer, a TADF phenomenon has been observed (see Non-Patent Document 1). However, as shown in FIG. 6 (c), the exciplex emission is principally because the band gap in effect is an energy difference between the HOMO level of the donor material and the LUMO level of the acceptor material. It is difficult to obtain high band gap light emission. That is, there is a problem that it is difficult to apply to blue light emission, and it can be said that it is almost difficult to apply this technique to blue light emission TADF.

As described above, it is necessary to reduce ΔE _st in order to express TADF. However, if HOMO-LUMO is completely separated in order to reduce ΔE _st , electronic transition does not occur, and as a result, TADF No longer develops. That is, if HOMO and LUMO coexist and the overlap is too large, TADF is not expressed, and if the overlap is too small, the strength of what TADF is expressed is reduced.
For this reason, in conventional compounds, TADF was expressed by slightly overlapping HOMO and LUMO. However, it is not easy to design a molecule exhibiting TADF emission having practical intensity and efficiency, and there is room for improvement. there were.

  By the way, it is known that when a light emitting layer composed of a host compound and a light emitting compound contains a compound exhibiting a TADF phenomenon as a third component (assist dopant) in the light emitting layer, it is effective for high luminous efficiency expression ( For example, refer nonpatent literature 2.). By generating 25% singlet excitons and 75% triplet excitons on the assist dopant by electric field excitation, the triplet excitons are singlet with reverse intersystem crossing (RISC). Term excitons can be generated. The energy of the singlet exciton is transferred to the luminescent compound, and the luminescent compound can emit light by the transferred energy. Therefore, theoretically, it becomes possible to cause the luminescent compound to emit light using 100% exciton energy, and high luminous efficiency is exhibited.

International Publication No. 2013/154064

Applied Physics, Vol.82, No.6, 2013 H. Nakanitani et al. , Nature Communication, 2014, 5, 4016-4022.

  The present invention has been made in view of the above-described problems and situations, and the problem to be solved is an organic electroluminescent element that exhibits blue light emission with excellent power efficiency and initial driving voltage, and good chromaticity, and a π-conjugated compound. Is to provide.

In order to solve the above-mentioned problems, the present inventor contains a π-conjugated compound having an electron-withdrawing part and an electron-donating part in the molecule in at least one layer of the organic layer in the process of examining the cause of the problem. And the energy between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound is such that the distance between the nearest atoms of the electron-withdrawing portion and the electron-donating portion in the π-conjugated compound is 10 nm or less. It was found that when the absolute value of the difference (ΔE _st ) is 0.5 eV or less, it is possible to provide an organic electroluminescence device that exhibits blue light emission with excellent power efficiency and initial driving voltage and good chromaticity, and has led to the present invention. It was.

  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 organic layer contains a π-conjugated compound having an electron withdrawing portion and an electron donating portion in the molecule,
The nearest atomic distance between the electron withdrawing portion and the electron donating portion in the π-conjugated compound is 10 nm or less, and the lowest excited singlet level and the lowest excited triplet level of the π conjugated compound are An organic electroluminescence device characterized in that the absolute value (ΔE _st ) of the energy difference is 0.5 eV or less.

  2. 2. The organic electroluminescence device according to claim 1, wherein the closest interatomic distance between the electron withdrawing portion and the electron donating portion in the π-conjugated compound is 1 nm or less.

  3. The π-conjugated compound has a bond part between the electron withdrawing part and the electron donating part, and the bond part has a part where the π-conjugated system is discontinuous at least at one place. The organic electroluminescent element according to item 1 or 2, characterized in that:

  4). 4. The organic electroluminescence device according to item 3, wherein the π-conjugated compound is a compound having a structure represented by the following general formula (A).

(In General Formula (A), X _{1 to} X ₃ and Y _{1 to} Y ₃ each independently represent a substituted or unsubstituted carbon atom or a nitrogen atom.)

  5. 4. The organic electroluminescence device according to item 3, wherein the π-conjugated compound is a compound having a structure represented by the following general formula (B).

(In general formula (B), R _{1 to} R ₃ each independently represents a hydrogen atom, a methyl group or a phenyl group, but at least two of R _{1 to} R ₃ represent a phenyl group.)

  6). 4. The organic electroluminescence element according to item 3, wherein the coupling portion has an adamantane structure.

  7). 4. The organic electroluminescence element according to item 3, wherein the coupling portion has a borazine structure.

  8). 4. The organic electroluminescence device according to item 3, wherein the bonding part has a dibenzophosphole oxide structure.

  9. 4. The organic electroluminescence device according to item 3, wherein the coupling portion has a triptycene structure.

  10. 4. The organic electroluminescence device according to item 3, wherein the coupling portion has a penthipcene structure.

  11. 4. The organic electroluminescence device according to item 3, wherein the coupling portion has a cyclophane structure.

  12 The organic electro according to any one of items 1 to 11, wherein the electron withdrawing part and the electron donating part in the π-conjugated compound are connected by at least two atoms. Luminescence element.

  13. Any one of Items 1 to 12, wherein the light-emitting layer contains the π-conjugated compound and at least one of a fluorescent compound and a phosphorescent compound. The organic electroluminescence device according to one item.

  14 Item 1 to Item 12, wherein the light emitting layer contains the π-conjugated compound, at least one of a fluorescent compound and a phosphorescent compound, and a host compound. The organic electroluminescent element as described in any one of the above.

15. A π-conjugated compound having an electron withdrawing portion and an electron donating portion in the molecule,
The nearest atomic distance between the electron withdrawing portion and the electron donating portion in the π-conjugated compound is 10 nm or less, and the lowest excited singlet level and the lowest excited triplet level of the π conjugated compound are An absolute value (ΔE _st ) of the energy difference of π is conjugated to a π-conjugated compound, which is 0.5 eV or less.

  By the above means of the present invention, it is possible to provide an organic electroluminescence device that exhibits blue light emission with excellent power efficiency and initial driving voltage and good chromaticity.

  The expression mechanism / action mechanism of the effect of the present invention is not clear, but is presumed as follows.

Although it is to express the TADF phenomenon must Delta] E _st is small is as previously described, TADF expression probability if the following values 0.5eV that increases are known. By the nearest interatomic distance between the electron-withdrawing unit and an electron donor unit in the π-conjugated compound 10nm or less, the LUMO to the electron-withdrawing unit, a Delta] E _st to separate localize HOMO the electron donor unit 0 0.5 eV or less, and the TADF phenomenon can be expressed.

  In general, when the TADF phenomenon occurs, the electron transition is performed between the HOMO localized in the electron donating portion and the LUMO localized in the electron attracting portion via a covalently bonded molecular chain. In the present invention, the space between the HOMO localized in the electron donating portion and the LUMO localized in the electron attracting portion is close to each other. Electron transitions are generated by directly hopping from the localized HOMO to the LUMO localized in the electron withdrawing portion. Since the π-conjugated compound of the present invention requires a shorter electron transition distance than a conventional TADF compound, a strong electron withdrawing portion is not necessarily required, and as a result, the problem of “deep HOMO” occurs. It can be solved (that is, the HOMO level does not become as deep as -5.5 eV).

  In addition, if there is no strong electron withdrawing part, the localized state of the charge will also be gentle, so the bias of charge generated with the surrounding medium (mainly the host compound or solvent) will also be gentle, It is considered that the interaction is smaller than that of the conventional TADF light emitting material, and “broadening of the emission spectrum” can be suppressed.

Schematic diagram showing energy tire grams of 2CzPN Schematic showing energy tiregram of 2CzXy Schematic diagram showing the electronic states of conventional TADF compounds, phosphorescent compounds and host compounds Schematic diagram showing the interaction between a conventional TADF compound and a host compound Schematic diagram showing the interaction between the phosphorescent compound and the host compound Schematic diagram showing the flow of electrons in exciplex light emission The schematic diagram which shows the positional relationship of the conjugation plane of the electron donor part and electron withdrawing part of the π-conjugated compound of the present invention Schematic diagram showing the interaction between the π-conjugated compound of the present invention and the host compound Schematic diagram showing energy tire grams of the π-conjugated compound of the present invention 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

The organic EL device of the present invention has an organic layer including at least one light emitting layer between an anode and a cathode, and at least one layer of the organic layer has an electron withdrawing portion and an electron donating portion in the molecule. a π-conjugated compound is contained, the distance between the nearest atoms of the electron-withdrawing portion and the electron-donating portion in the π-conjugated compound is 10 nm or less, and the lowest excited singlet level and the lowest excited triplet of the π-conjugated compound The absolute value (ΔE _st ) of the energy difference from the term level is 0.5 eV or less. This feature is a technical feature common to the inventions according to claims 1 to 15.

The embodiments of the present invention, from the viewpoint of reducing the Delta] E _st, it is preferable nearest interatomic distance between the electron-withdrawing unit and an electron donor unit in the π-conjugated compound is 1nm or less. This is because, by separating the distance between the centers of HOMO and LUMO to achieve HOMO-LUMO separation, the closest interatomic distance can be made 1 nm or less so that a more spatially close state can be obtained. is there.

Further, the π-conjugated compound has a bonding portion between the electron withdrawing portion and the electron donating portion, and the bonding portion has a portion where the π-conjugated system is discontinuous at least at one place. preferable. Thereby, even if the electron withdrawing part is weak, the distinction between the electron withdrawing part and the electron donating part becomes clear. Further, the HOMO and LUMO is easily completely separated because the separation between the HOMO and LUMO become clear, as a result, it is possible to reduce the Delta] E _st to the limit.

Further, from the viewpoint of reducing ΔE _st , the π-conjugated compound is preferably a compound having a structure represented by the general formula (A) or the general formula (B).

Further, from the viewpoint of easily taking a structure in which the distance between the electron donating part and the electron withdrawing part is close, the bonding part has an adamantane structure, a dibenzophosphole oxide structure, a triptycene structure, a pentypcene structure, or a cyclophane structure. It is preferable.
Moreover, it is preferable that the combined substance has a borazine structure from the viewpoints of improving luminous properties and easily synthesizing a molecule in which an electron donating part and an electron withdrawing part are introduced into a heterocyclic side chain.

  In addition, from the viewpoint of easily taking a structure in which the distance between the electron donating part and the electron withdrawing part is close, the electron withdrawing part and the electron donating part in the π-conjugated compound are connected by at least two atoms. preferable.

  Further, from the viewpoint of improving the light emission efficiency of the organic EL element, the light emitting layer preferably contains a π-conjugated compound and at least one of a fluorescent light emitting compound and a phosphorescent light emitting compound.

  From the viewpoint of improving the light emission efficiency of the organic EL device, the light emitting layer contains a π-conjugated compound, at least one of a fluorescent light emitting compound and a phosphorescent light emitting compound, and a host compound. Is preferred.

In the present invention, a π-conjugated compound having an electron-withdrawing portion and an electron-donating portion in the molecule, and the closest interatomic distance between the electron-withdrawing portion and the electron-donating portion in the π-conjugated compound is 10 nm or less. In addition, a π-conjugated compound having an absolute value (ΔE _st ) of an energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound of 0.5 eV or less is provided.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" showing a numerical range is used by the meaning containing the numerical value described before and behind that as a lower limit and an upper limit.
Before going into the present discussion, the light emitting method and light emitting material of the organic EL element related to the technical idea of the present invention will be described.

≪Light emission method of organic EL element≫
There are two types of emission methods for organic EL elements: phosphorescence emission, which emits light when returning from the triplet excited state to the ground state, and fluorescence emission, which emits light when returning from the singlet excited state to the ground state. There is a street.
When excited by an electric field as in an organic EL element, triplet excitons are generated with a probability of 75% and singlet excitons are generated with a probability of 25%. Therefore, phosphorescence emission emits light more than fluorescence emission. It is an excellent method for realizing high efficiency and low power consumption.
On the other hand, in fluorescence emission, one singlet exciton is generated from two triplet excitons by causing a high density of 75% triplet excitons that normally only become heat due to non-radiation deactivation. Thus, a method using a TTA mechanism for improving luminous efficiency has been found.

  Furthermore, in recent years, the discovery of Adachi et al. Has reduced the energy gap between the singlet excited state and the triplet excited state. Reverse intersystem crossing from the singlet excited state to the singlet excited state, and as a result, a phenomenon that enables nearly 100% fluorescence emission (also referred to as thermally excited delayed fluorescence or thermally excited delayed fluorescence: “TADF”) Fluorescent materials that make this possible have been found (see, for example, “Development of Phosphorescent Organic EL Technology for Lighting”, Applied Physics Vol. 80, No. 4, 2011, etc.).

≪Phosphorescent compound≫
As described above, phosphorescence is theoretically 3 times more advantageous than fluorescence in terms of light emission efficiency, but energy deactivation (= phosphorescence) from triplet excited state to singlet ground state is forbidden. Similarly, since the intersystem crossing from the singlet excited state to the triplet excited state is also a forbidden transition, the rate constant is usually small. That is, since the transition is difficult to occur, the exciton lifetime is increased from millisecond to second order, and it is difficult to obtain desired light emission.
However, when a complex using a heavy metal such as iridium or platinum emits light, the rate constant of the forbidden transition is increased by 3 digits or more due to the heavy atom effect of the central metal. % Phosphorescence quantum yield can be obtained.
However, in order to obtain such ideal light emission, it is necessary to use a rare metal called a white metal such as iridium, palladium, or platinum, which is a rare metal. The price of the metal itself is a major industrial issue.

≪Fluorescent compound≫
A general fluorescent compound is not necessarily a heavy metal complex such as a phosphorescent compound, and is a so-called organic compound composed of a combination of common elements such as carbon, oxygen, nitrogen, and hydrogen. The compounds can be applied, and other non-metallic elements such as phosphorus, sulfur and silicon can be used, and complexes of typical metals such as aluminum and zinc can be used.
However, since only 25% of excitons can be applied to light emission as described above with conventional fluorescent compounds, high efficiency light emission such as phosphorescence emission cannot be expected.

≪Delayed fluorescent compound≫
<Excited triplet-triplet annihilation (TTA) delayed fluorescent compound>
In order to solve the problems of fluorescent compounds, a light emission method using delayed fluorescence has appeared. The TTA method that originates from collisions between triplet excitons can be described by the following general formula. That is, there is a merit that a part of triplet excitons, in which the energy of excitons has been converted only to heat by non-radiation deactivation, can cross back to singlet excitons that can contribute to light emission, Even in an actual organic EL element, an external extraction quantum efficiency that is about twice that of a conventional fluorescent light emitting element can be obtained.

General formula: T ^* + T ^* → S ^* + S
(In the formula, T ^* represents a triplet exciton, S ^* represents a singlet exciton, and S represents a ground state molecule.)

  However, as can be seen from the above equation, since only one singlet exciton that can be used for light emission is generated from two triplet excitons, it is theoretically impossible to obtain 100% internal quantum efficiency by this method.

<Thermal activated delayed fluorescence (TADF) compound>
The TADF method, which is another highly efficient fluorescent emission, is a method that can solve the problems of TTA.
Fluorescent compounds have the advantage that they can be designed indefinitely as described above. In other words, among the compounds that are molecularly designed, there are compounds in which the energy level difference (ΔE _st ) between the triplet excited state and the singlet excited state is extremely close.
Such compounds, even though in the molecule does not have a heavy atom, reverse intersystem crossing from a triplet excited state which can not occur in normal order Delta] E _st is small to the singlet excited state occurs. Furthermore, since the rate constant of deactivation from singlet excited state to ground state (= fluorescence emission) is extremely large, triplet excitons themselves are thermally deactivated to ground state (non-radiative deactivation). It is more kinetically advantageous to return to the ground state while emitting fluorescence via the singlet excited state. Therefore, TADF can ideally emit 100% fluorescence (Patent Document 1, Non-Patent Document 1, and H Nakanotani et al., Scientific Reports 3, Article number: 2127 doi: 10.1038 / srep02127). , H Uotyama et al., Nature 2012, 492, 234-238, Organic Electronics Volume 14, Issue 11, November 2013, Pages 2721-2726).

<Molecular design concept for ΔE _st >
A molecular design for reducing the ΔE _st will be described.
In order to reduce ΔE _st , in principle, it is most effective to reduce the spatial overlap between the highest occupied orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in the molecule. Is.
Generally, it is known that HOMO is distributed in the electron donating part and LUMO is distributed in the electron withdrawing part in the electron orbit of the molecule. By introducing an electron donating and electron withdrawing skeleton into the molecule, HOMO and LUMO are distributed. It is possible to keep away from the position where and exist.

For example, in the above-mentioned document “Development of phosphorescent organic EL technology for illumination”, an electron-withdrawing skeleton such as a cyano group, a sulfonyl group, or a triazine and an electron-donating skeleton such as a carbazole or a diphenylamino group are used. By introducing, LUMO and HOMO are localized.
It is also effective to reduce the change in molecular structure between the ground state and triplet excited state of the compound. As a method for reducing the structural change, for example, making the compound rigid is effective. Rigidity described here means that there are few sites that can move freely in the molecule, for example, by suppressing free rotation in the bond between rings in the molecule or by introducing a condensed ring with a large π conjugate plane. Means. In particular, it is possible to reduce the structural change in the excited state by making the portion involved in light emission rigid.

<General problems with TADF compounds>
TADF compounds have various problems in terms of their light emission mechanism and molecular structure. The following describes some of the problems generally associated with TADF compounds.

In the TADF compound, it is necessary to separate the sites where HOMO and LUMO exist as much as possible in order to reduce ΔE _st . For this reason, the electronic state of the molecule is a donor / acceptor type in which the HOMO and LUMO sites are separated. It becomes a state close to intramolecular CT (intramolecular charge transfer state).
When a plurality of such molecules are present, stabilization is achieved by bringing the donor part (electron donating part) of one molecule and the acceptor part (electron attracting part) of the other molecule close to each other. Such a stabilization state is not limited to the formation between two molecules, but can also be formed between a plurality of molecules such as three or five molecules, resulting in various stabilization with a wide distribution. A state will exist, and the shape of the absorption spectrum and emission spectrum will be broad. In addition, even when a multimolecular assembly exceeding two molecules is not formed, various existence states can be taken depending on the direction and angle of interaction between the two molecules. The shape of the emission spectrum becomes broad.

The broad emission spectrum creates two major problems.
One problem is that the color purity of the emitted color is lowered. This is not a big problem when applied to lighting applications, but when used for electronic displays, the color gamut is small and the color reproducibility of pure colors is low. It becomes difficult.

Another problem is that the rising wavelength (referred to as “fluorescence 0-0 band”) on the short wavelength side of the emission spectrum is shortened, that is, the S _{1 is} increased (the lowest excitation singlet energy is increased). It is to end.
Naturally, when the wavelength of the fluorescent 0-0 band is shortened, the phosphorescent 0-0 band derived from T ₁ having lower energy than S ₁ is also shortened (higher T ₁ ). Therefore, the compound used in the host compound in order not to cause reverse energy transfer from the dopant, arises the need to ₁ reduction and high T ₁ of high S. This is a very big problem.
A host compound consisting essentially of an organic compound takes a plurality of active and unstable chemical species such as a cation radical state, an anion radical state, and an excited state in an organic EL device. By expanding the π-conjugated system, it can exist relatively stably.

However, in order to achieve high S ₁ and high T ₁ , it is necessary to reduce or cut off the π-conjugated system in the molecule, which makes it difficult to achieve both stability and as a result. The life of the light emitting element is shortened.
In addition, in a TADF compound that does not contain a heavy metal, a transition that is deactivated from a triplet excited state to a ground state is a forbidden transition, and therefore the existence time (exciton lifetime) in the triplet excited state is from several hundred microseconds to millisecond. It is very long with second order. Therefore, even if the T ₁ energy of the host compound is higher than that of the fluorescent compound, the reverse energy from the triplet excited state of the fluorescent compound to the host compound is determined from the length of the existence time. The probability of causing movement increases. As a result, the reverse reverse energy transfer from the triplet excited state to the singlet excited state of the originally intended TADF compound does not occur sufficiently, and unfavorable reverse energy transfer to the host compound becomes the mainstream, resulting in sufficient luminous efficiency. Inconvenience that cannot be obtained.

In order to solve the above problems, it is necessary to sharpen the emission spectrum shape of the TADF compound and reduce the difference between the emission maximum wavelength and the rising wavelength of the emission spectrum. This can be basically achieved by reducing the change in the molecular structure of the singlet excited state and the triplet excited state.
In order to suppress reverse energy transfer to the host compound, it is effective to shorten the existence time (exciton lifetime) of the triplet excited state of the TADF compound. To achieve this, it is necessary to take measures such as reducing the molecular structure change between the ground state and the triplet excited state and introducing suitable substituents and elements to undo the forbidden transition. It is possible to solve the point.

The π-conjugated compound of the present invention can be applied as a fluorescent compound or an assist dopant as described later. However, as described above, the fluorescent compound and triplet excited state in which the structural change of the excited state is suppressed. A fluorescent compound having a short existence time is included as a design concept.
Hereinafter, various measurement methods relating to the π-conjugated compound of the present invention will be described.

<Electron density distribution>
Π conjugated compound of the present invention, from the viewpoint of reducing the Delta] E _st, it is preferable that the HOMO and LUMO are substantially separated in the molecule. These HOMO and LUMO of the distribution, and the Delta] E _st can be determined from the electron density distribution when the structure optimization obtained by semi-empirical molecular orbital calculations.
For calculating the values of HOMO, LUMO and ΔE _st of the π-conjugated compound of the present invention, Gaussian 09 (Revision C.01, MJ Frisch, GW Trucks, HB Schlegel, manufactured by Gaussian, USA) was used. , GE Scuseria, MA Robb, JR Cheeseman, G. Scalmani, V. Barone, B. Mennucci, GA A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida. .Nak Jima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, JA Montgomery, Jr., JE Peralta, F. Ogliaro, M. Bearpark, J. J. Heid, E. Brothers. , K. N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Ragavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, Cossi, N. Rega, JM Millam, M. Klene, JE Knox, JB Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann , OY zyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, GA A. Voth, P. Salvador, J .; J. Dannenberg, S. Dapprich, AD Daniels, O. Farkas, J. B. Forsman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian, Inc., Wallingford CT. .) Software, and using the density functional method (B3LYP / 6-31G (d)) as a calculation method. There is no particular limitation on the software and the calculation method, and any of them can be similarly obtained.

Further, “HOMO and LUMO are substantially separated” means that the HOMO orbital distribution calculated by the above molecular calculation and the central part of the LUMO orbital distribution are separated, more preferably the HOMO orbital distribution and the LUMO orbital. This means that the distributions of do not overlap.
As for the separation state of HOMO and LUMO, the time-dependent density functional method (Time-Dependent DFT) is further obtained from the structure optimization calculation using B3LYP as the above-mentioned functional and 6-31G (d) as the basis function. To calculate the energy of S ₁ and T ₁ (E (S ₁ ) and E (T ₁ ), respectively) and calculate ΔE _st = E (S ₁ ) −E (T ₁ ). It is also possible. As the calculated ΔE _st is smaller, HOMO and LUMO are more separated. In the present invention, ΔE _st calculated using the same calculation method as described above is 0.5 eV or less, more preferably 0.2 eV or less, and further preferably 0.1 eV or less.

<Minimum excitation singlet energy S ₁ >
The lowest excited singlet energy S ₁ of the π-conjugated compound of the present invention is defined in the present invention as calculated in the same manner as 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. Considering that the Stokes shift of the π-conjugated compound of the present invention is relatively small 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 room temperature (25 ° C.). The peak value of the maximum emission wavelength in the solution state of the π-conjugated compound in 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.

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

≪Component layer of organic EL element≫
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 /) light emitting layer / (hole blocking layer /) electron transport layer / electron injection layer / cathode

Among the above, the configuration (7) is preferably used, but is not limited thereto.
The light emitting layer according to the present invention is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting auxiliary layer may be provided between the light emitting layers.

If necessary, a hole blocking layer (also referred to as a hole blocking layer) or an electron injection layer (also referred to as a cathode buffer layer) may be provided between the light emitting layer and the cathode. An electron blocking layer (also referred to as an electron barrier layer) or a hole injection layer (also referred to as an anode buffer layer) may be provided therebetween.
The 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. The hole transport layer may be composed of a plurality of layers.
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. Further, the electron transport layer may be composed of a plurality of layers.
In the above typical element configuration, a layer excluding the anode and the cathode is also referred to as an “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.
Examples of typical element configurations of the tandem structure include the following configurations.

  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 may all be the same or different. Two light emitting units may be the same, and the remaining one may be different.
The 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, A known material structure can be used as long as it is also called an intermediate 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 C60, conductive organic substances such as oligothiophene Examples include layers, conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, metal-free porphyrins, etc. However, the present invention is not limited to these.
Examples of a preferable configuration in the light emitting unit include those in which the anode and the cathode are excluded from the configurations (1) to (7) described in the above representative element configurations. It is not limited to.

  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, US 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-34966681, JP-A-3848564, JP-A-4421169, JP 2010-192719, JP 009-076929, JP 2008-078414 A, JP 2007-059848 A, JP 2003-272860 A, JP 2003-045676 A, 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 which comprises the organic EL element of this invention is demonstrated.

≪Luminescent layer≫
The light emitting layer according to 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 a layer of the light emitting layer. Even within, 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 preferable to adjust in the range of 2 nm to 5 μm, more preferably in the range of 2 to 500 nm, and still more preferably in the range of 5 to 200 nm.
The thickness of each light emitting layer used in the present invention is preferably adjusted within the range of 2 nm to 1 μm, more preferably adjusted within the range of 2 to 200 nm, and further preferably 3 to 150 nm. Adjusted within range.
The light emitting layer according to the present invention contains a light emitting dopant (a light emitting compound, a light emitting dopant compound, a dopant compound, also simply referred to as a dopant) and a host compound (a matrix material, a light emitting host compound, also simply referred to as a host). It is preferable.

(1) Luminescent dopant As a luminescent dopant, the conventionally well-known fluorescence emission property used when the (pi) conjugated compound of this invention and the (pi) conjugated compound of this invention function as an assist dopant (light emission auxiliary material) mentioned later. A compound (also referred to as a fluorescent dopant, a fluorescent dopant, or a fluorescent compound) or a phosphorescent compound (also referred to as a phosphorescent dopant, a phosphorescent dopant, or a phosphorescent compound) may be used (details). Will be described later.) In the present invention, the π-conjugated compound of the present invention is contained as a light emitting dopant or an assist dopant in at least one light emitting layer.
In this invention, it is preferable that a light emitting layer contains the light emission dopant within the range of 5-40 mass%, and it is more preferable to contain within the range of 10-30 mass%.
The concentration of the light-emitting dopant in the light-emitting layer can be arbitrarily determined based on the specific light-emitting dopant used and the requirements of the device, and is contained at a uniform concentration in the thickness direction of the light-emitting layer. Or may have an arbitrary concentration distribution.
In addition, a plurality of luminescent dopants may be used in combination, and a combination of luminescent dopants having different structures, a π-conjugated compound of the present invention, or a combination of a fluorescent compound and a phosphorescent compound. It may be used. Thereby, arbitrary luminescent colors can be obtained.

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. 3.16 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 the luminance meter CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.
In the present invention, it is also preferable that the light emitting layer of one layer or a plurality of layers contains a plurality of light emitting dopants having different emission colors and emits white light.
There are no particular limitations on the combination of light-emitting dopants that exhibit white, but examples include blue and orange, and a combination of blue, green, and red.
The white color in the organic EL device of the present invention means that the chromaticity in the CIE 1931 color system at 1000 cd / m ² is x = 0.39 ± 0.09 when the 2 ° viewing angle front luminance is measured by the method described above. Y = 0.38 ± 0.08.

(1.1) π-conjugated compound The π-conjugated compound of the present invention has an electron withdrawing portion and an electron donating portion in the molecule, and the closest atom between the electron withdrawing portion and the electron donating portion in the π conjugated compound. And the absolute value (ΔE _st ) of the energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound is 0.5 eV or less. To do.

As shown in FIGS. 7A and 7B, the π-conjugated compound of the present invention is a conjugated system from the normal direction of the conjugate plane APlane with respect to the conjugate plane APlane of the electron withdrawing portion constituted by the conjugate system. When the conjugate plane DPlane of the electron donating unit composed of is projected, the projected image of the conjugate plane DPlane and the conjugate plane APlane have an overlap D, and the electron donating unit and the electron withdrawing unit are close to each other A compound. The overlap D between the projected image of the conjugate plane DPlane and the conjugate plane APlane may be a part. When there are a plurality of electron donating parts or electron withdrawing parts in the molecule, any combination of the electron donating part and the electron withdrawing part may satisfy the above requirements.
“The state in which the electron donating part and the electron attracting part are close to each other” means that the Forster energy transfer occurs at an intermolecular distance of 10 nm or less. The distance between contact atoms is 10 nm or less.
In the present invention, the closest interatomic distance between the electron donating part and the electron withdrawing part is as described above, with the part where HOMO is localized as the electron donating part and the part where LUMO is localized as the electron attracting part. In the same manner as above, the density functional method (B3LYP / 6-31G (d)) is used as a calculation method using Gaussian 09 software manufactured by Gaussian in the United States. Here, when HOMO and LUMO have a spatial extension to nearby atoms or atomic groups (including part of the atomic group), the HOMO and LUMO are respectively converted into an electron donor and an electron attracting part. Calculate the nearest interatomic distance as part.

  Here, the electron donating part and the electron attracting part are the values of HOMO (D) and LUMO (D) of the electron donating part and HOMO (A) and LUMO (A) of the electron attracting part as shown in the following relational expression. Satisfaction.

  HOMO (D)> HOMO (A), LUMO (D)> LUMO (A)

It is to express the TADF phenomenon must Delta] E _st is small has been described above, if the following values 0.5 eV, is known to TADF expression probability is high. By taking the above structure, the LUMO to the electron-withdrawing unit, the HOMO to the electron donor unit to separate localized can be a Delta] E _st below 0.5 eV, it is possible to express the TADF phenomenon.
Usually, the electronic transition when the TADF phenomenon occurs is performed through a covalently bonded molecular chain between HOMO localized in the electron donating portion and LUMO localized in the electron withdrawing portion.
However, when the electron donating part and the electron attracting part are close to each other on the projection plane as described above, the distance between the electron donating part and the electron attracting part, that is, the space between the HOMO and the LUMO is close to each other. Therefore, there is a feature that electron transition occurs by hopping directly from the HOMO of the electron donating part to the LUMO of the electron attracting part without passing through the molecular chain between the electron donating part and the electron attracting part. Thereby, compared with the conventional TADF compound, the electron transition distance is shorter, so that a strong electron withdrawing portion is not necessarily required. As a result, the problem that “HOMO becomes deeper” can be solved (it does not become deeper to −5.5 eV).

  The nearest interatomic distance between the electron withdrawing portion and the electron donating portion in the π-conjugated compound is preferably 1 nm or less.

Further, the π-conjugated compound of the present invention has a bonding part between the electron withdrawing part and the electron donating part, and the bonding part has a part where the π-conjugated system is discontinuous at least at one place. Preferably it is.
By eliminating the conjugated double bond somewhere in the molecular bond connecting the electron donating part and the electron withdrawing part, the electron withdrawing part can be distinguished from the electron donating part even if the electron withdrawing part is weak. It becomes clear and HOMO and LUMO can be separated and localized, and the conventional TADF compound does not necessarily require a strong electron withdrawing portion that is necessary to separate and localize HOMO and LUMO. When there is no strong electron withdrawing part, the localized state of the charge will be gentle, so the bias of charge generated with the surrounding medium (mainly the host compound or solvent) will also be gentle, The interaction is smaller than that of a conventional TADF light-emitting material, and “broadening of the emission spectrum” can be suppressed (see FIG. 8).

Further, when the waste conjugated double bond between the electron donor unit and an electron withdrawing portion, since the separation of the HOMO and LUMO become clear, the HOMO and LUMO is easily completely separated, as a result, a Delta] E _st to the extreme Can be small. Even if HOMO and LUMO are completely separated, since the electron donating part where HOMO is localized and the electron attracting part where LUMO is localized are close to each other, an electron transition may occur between them, and TADF emission Can be obtained.
That is, since ΔE _st is as small as possible, TADF light emission can be realized efficiently.

  The π-conjugated compound as described above is preferably a compound having a structure represented by the following general formula (A) or general formula (B).

In General Formula (A), X _{1 to} X ₃ and Y _{1 to} Y ₃ each independently represent a substituted or unsubstituted carbon atom or a nitrogen atom.

When X _{1 to} X ₃ and Y _{1 to} Y ₃ are carbon atoms, the substituent that the carbon atom may have is not particularly limited as long as the effects of the present invention are not impaired. Or branched alkyl group, alkenyl group, alkynyl group, aromatic hydrocarbon ring group, aromatic heterocyclic group, non-aromatic hydrocarbon ring group, non-aromatic heterocyclic group, alkoxy group, cycloalkoxy group, aryloxy group, Alkylthio group, cycloalkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, acyl group, acyloxy group, amide group, carbamoyl group, ureido group, sulfinyl group, alkylsulfonyl group, arylsulfonyl group or heteroaryl Sulfonyl group, amino group, halogen atom, fluorinated hydrocarbon group, cyano group, nitro Group, hydroxy group, thiol group, silyl group, deuterium atom and the like.

In general formula (B), R _{1 to} R ₃ each independently represents a hydrogen atom, a methyl group or a phenyl group, and at least two of R _{1 to} R ₃ represent a phenyl group.

Moreover, as a structure of the coupling | bond part of (pi) conjugated compound of this invention, it is preferable that they are an adamantane structure, a borazine structure, a dibenzophosphole oxide structure, a triptycene structure, a pentypcene structure, and a cyclophane structure.
Moreover, it is preferable that the electron withdrawing part and the electron donating part in the π-conjugated compound are connected by at least two atoms.

  As long as the π-conjugated compound of the present invention has an overlap in the projection plane between the electron withdrawing portion and the electron donating portion, the bonding structure connecting the two is not limited. For example, it has an aromatic ring, a helical structure, or a cyclic structure in the side chain instead of a bonding part connecting the electron donating part and the electron withdrawing part, and due to their steric hindrance, May have an overlap. A compound having an adamantane structure is also effective.

  Moreover, the electron donating part and the electron withdrawing part do not need to be one each in the molecule, it is sufficient that each has at least one, and a plurality of each may be provided. The π-conjugated compound may be a low molecule or a high molecule.

  Examples of the π-conjugated compounds FD1 to FD4, FD6 to FD10, and FD13 to FD61 that are preferably used in the present invention will be given below, but the present invention is not limited thereto.

  Examples of the π-conjugated compound include International Publication No. 2012/118164, A.I. Iida et al. , Chemical Communications, 2009, 3002-3004, Qisheng Zhang et al. , Journal of the American Chemical Society 2012, 134, 14706-14709, Atsushi Wakamiya et al. , Journal of the American Chemical Society 2005, 127, 14859-14866, Y. et al. Nakamura et al. , Synthesis, 2004, 2743, H. et al. Shimizu et al. Bull. Chem. Soc. Jpn. , 82.86 (2009), S .; Oi et al. , Tetrahedron, 64, (2008) 6051-6059.

(1.2) Assist dopant The organic EL device of the present invention has a π-conjugated system in which the absolute value of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.5 eV or less in the light emitting layer. It is preferable from the viewpoint of high luminous efficiency that the compound and the fluorescent compound and / or phosphorescent compound are contained. The light emitting layer preferably further contains a host compound. The π-conjugated compound, the luminescent compound, and the host compound of the present invention are not limited in the number of components in the light-emitting layer, but preferably each π-conjugated compound and luminescent compound are contained one by one. More preferably, each π-conjugated compound, luminescent compound, and host compound is contained.

A host compound is contained in a light emitting layer containing a π-conjugated compound and a light emitting compound whose absolute value of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level of the present invention is 0.5 eV or less. In this case, the π-conjugated compound of the present invention acts as an assist dopant, and when no host compound is contained, the π-conjugated compound of the present invention acts as a host compound. The characteristics of the mechanism that exerts the effect are the same in any case, and triplet excitons generated on the π-conjugated compound of the present invention are converted into singlet excitons by reverse intersystem crossing (RISC). In the point. Thereby, all the exciton energies generated theoretically on the π-conjugated compound of the present invention can be transferred to the luminescent compound, and high luminous efficiency can be expressed.
As an example, FIG. 9 shows a schematic diagram in the case where the π-conjugated compound of the present invention acts as an assist dopant (see FIG. 9A) and a host compound (see FIG. 9B), respectively. However, the process of generating triplet excitons generated on the π-conjugated compound of the present invention is not limited to electric field excitation, and includes energy transfer and electron transfer from the light emitting layer or from the peripheral layer interface. Further, in FIG. 9, a fluorescent material is used as a light-emitting material, but the present invention is not limited to this, and a phosphorescent compound may be used, or a fluorescent compound and a phosphorescent compound may be used. Both may be used.

When a π-conjugated compound having an absolute value of the difference between the lowest excited singlet energy level of the present invention and the lowest excited triplet energy level of 0.5 eV or less is used as an assist dopant, the π-conjugated compound of the present invention On the other hand, a host compound having a mass ratio of 100% or more is present, and the fluorescent compound and / or phosphorescent compound is contained within a range of 0.1 to 50% by mass with respect to the π-conjugated compound. The light emitting layer is preferred. Energy level of the S ₁ and T ₁ of the π conjugated compound of the present invention is lower than the energy level of the S ₁ and T ₁ of the host compound, the energy level of the S ₁ and T ₁ of the light-emitting compound Higher than the position is preferred.

When a π-conjugated compound in which the absolute value of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level of the present invention is 0.5 eV or less is used as a host compound, a fluorescent compound and / or phosphorus The light-emitting compound is preferably a light-emitting layer that is contained within a mass ratio of 0.1 to 50% with respect to the π-conjugated compound of the present invention. The energy level between S ₁ and T ₁ of the π-conjugated compound of the present invention is preferably higher than the energy level between S ₁ and T ₁ of the luminescent compound.

  When a π-conjugated compound having an absolute value of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level of the present invention of 0.5 eV or less is used as an assist dopant or host compound, the π conjugate of the present invention It is preferable that the emission spectrum of the compound and the absorption spectrum of the luminescent compound overlap.

(1.2.1) Phosphorescent Compound The phosphorescent compound that can be used in combination with the π-conjugated compound of the present invention will be described.
A phosphorescent compound is a compound in which light emission from an excited triplet is observed. Specifically, it is a compound that emits phosphorescence at room temperature (25 ° C.), and the phosphorescence quantum yield is 25 ° C. Although defined as 0.01 or more compounds, the preferred phosphorescence quantum yield is 0.1 or more.
The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescent compound used in the present invention has the above phosphorescence quantum yield (0.01 or more) in any solvent. It only has to be achieved.

The phosphorescent compound can be appropriately selected from known compounds used for the light emitting layer of the organic EL device. Specific examples of known phosphorescent compounds that can be used in the present invention include compounds described in the following documents.
Nature 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17, 1059 (2005), 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. US Patent Application Publication No. 2009/0108737, US Patent Application Publication No. 2009/0039776, US Patent No. 6921915, US Patent No. 6,687,266, US Patent Application Publication No. 2007/0190359. Specification, US Patent Application Publication No. 2006/0008670, US Patent Application Publication No. 2009/0165846, US Patent Application Publication No. 2008/0015355, US Patent No. 7250226, US Patent No. No. 7396598 , U.S. Patent Application Publication No. 2006/0263635, U.S. Patent Application Publication No. 2003/0138657, U.S. Patent Application Publication No. 2003/0152802, U.S. Patent No. 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. 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. Description, US Pat. No. 7,534,505, US Pat. No. 7,445,855, US Patent Application Publication No. 2007/0190359, US Patent Application Publication No. 2008/0297033, US Pat. No. 7,338,722 , US special Published Patent Application No. 2002/0134984, U.S. Pat. No. 7,279,704, U.S. Patent Application Publication No. 2006/098120, U.S. Patent Application Publication No. 2006/103874, International Publication No. 2005/076380, International Publication No. 2010/032663, 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 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, USA No. 2012/212126, JP 2012-069737, JP 2012-195554, JP 2009-114086, JP 2003-81988, JP 2002-302671. Japanese Patent Laid-Open No. 2002-363552.
Among these, preferable phosphorescent compounds include organometallic complexes having Ir as a central metal. More preferably, a complex containing at least one coordination mode of a metal-carbon bond, a metal-nitrogen bond, a metal-oxygen bond, or a metal-sulfur bond is preferable.

(1.2.2) Fluorescent compound The fluorescent compound that can be used in combination with the π-conjugated compound of the present invention will be described.
The π-conjugated compound can be used in combination of fluorescent compound of the present invention is not particularly limited, for example, Delta] E _st is can be suitably used 0.5eV greater fluorescent compound, other anthracene derivatives, Pyrene derivatives, chrysene derivatives, fluoranthene derivatives, perylene derivatives, fluorene derivatives, arylacetylene derivatives, styrylarylene derivatives, styrylamine derivatives, arylamine derivatives, boron complexes, coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, Squarium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes, polythiophene dyes, rare earth complex phosphors, and fluorescence typified by laser dyes KoOsamuritsu are mentioned higher compounds.

(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, and its own light emission is not substantially observed in the organic EL device.
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.
The host compound that is preferably used in the present invention will be described below.

Although there is no restriction | limiting in particular as a host compound used with the (pi) conjugated compound in this invention, From the viewpoint of reverse energy transfer, what has excitation energy larger than the excitation singlet energy of the (pi) conjugated compound of this invention is preferable, Furthermore, Those having an excited triplet energy larger than that of the π-conjugated compound of the present invention are more preferred.
The host compound is responsible for carrier transport and exciton generation in the light emitting layer. Therefore, it can exist stably in all active species states such as a cation radical state, an anion radical state, and an excited state, and does not cause chemical changes such as decomposition or addition reaction. It is preferable not to move at the angstrom level.

State also, the light emitting dopant especially in combination to indicate TADF emission, since long dwell time of the triplet excited state of the TADF compound, the T ₁ energy of the host compound itself is high, which further host compound with each other in association in prevention of generation of a low T ₁ state, that the TADF compound and the host compound does not form a exciplex, such that the host compound does not form a electro-mer by the electric field, the host compound is a molecular structure such as not to lower T ₁ of Appropriate design is required.
In order to satisfy these requirements, the host compound itself must have high electron hopping mobility, high hole hopping movement, and small structural change when it is in a triplet excited state. It is. Representative examples of host compounds that satisfy these requirements include high π-energy conjugated skeletons with high T ₁ energy, such as carbazole skeleton, azacarbazole skeleton, dibenzofuran skeleton, dibenzothiophene skeleton, or azadibenzofuran skeleton. What has as a partial structure is mentioned preferably. In particular, when the light-emitting layer contains a carbazole derivative, it is possible to promote appropriate carrier hopping and dispersion of the light-emitting material in the light-emitting layer, and the effect of improving the light-emitting performance of the device and the stability of the thin film can be obtained. Therefore, it is preferable.

Further, representative examples include compounds in which these rings have a biaryl and / or multiaryl structure. As used herein, “aryl” includes not only an aromatic hydrocarbon ring but also an aromatic heterocyclic ring.
More preferably, it is a compound in which a carbazole skeleton and a 14π-electron aromatic heterocyclic compound having a molecular structure different from that of the carbazole skeleton are directly bonded, and further a 14π-electron aromatic heterocyclic compound is incorporated in the molecule. A carbazole derivative having at least one is preferred. In particular, the carbazole derivative is preferably a compound having two or more conjugated structures having 14π electrons or more in order to further enhance the effects of the present invention.

Moreover, as a host compound used for this invention, the compound which has a structure represented with the following general formula (I) is also preferable. This is because a compound having a structure represented by the following general formula (I) has a condensed ring structure, so that a π electron cloud spreads, the carrier transportability is high, and the glass transition temperature (Tg) is high. It is. Furthermore, in general, condensed aromatic rings tend to have a small triplet energy (T ₁ ), but a compound having a structure represented by the general formula (I) has a high T ₁ and has a short emission wavelength ( That is, it can be suitably used for a light emitting material having large T ₁ and S ₁ .

In the general formula (I), X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R ₁₀₃ . y _{1 to} y ₈ each represents CR ₁₀₄ or a nitrogen atom. R _{101 to} R ₁₀₄ each represent a hydrogen atom or a substituent, and these may be bonded to each other to form a ring. Ar ₁₀₁ and Ar ₁₀₂ each represent an aromatic ring and may be the same or different. n101 and n102 is each an integer of 0 to _4, when _{R 101} is a hydrogen atom, n101 represents an integer of 1-4.

R _{101 to} R ₁₀₄ in the general formula (I) represent a hydrogen atom or a substituent, and the substituent here refers to what may be contained within a range not inhibiting the function of the host compound used in the present invention; For example, in the case where a substituent is introduced in the synthesis scheme, a compound that exhibits the effect of the present invention is included in the present invention.

Examples of the substituent represented by each of R _{101 to} R ₁₀₄ include a linear or branched alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group). Group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring group (aromatic Also called carbocyclic group, aryl group, etc. For example, benzene ring, biphenyl, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysene ring, naphthacene ring, triphenylene ring, o-terphenyl ring, m- Terphenyl ring, p-terphenyl ring, acenaphthene ring, coronene ring, indene ring, fluorene ring A group derived from a fluoranthrene ring, a naphthacene ring, a pentacene ring, a perylene ring, a pentaphen ring, a picene ring, a pyrene ring, a pyrantolen ring, an anthraanthrene ring, tetralin, etc.), an aromatic heterocyclic group (for example, a furan ring) , Dibenzofuran ring, thiophene ring, dibenzothiophene ring, oxazole ring, pyrrole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, benzimidazole ring, oxadiazole ring, triazole ring, imidazole ring, pyrazole ring, Thiazole ring, indole ring, indazole ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, cinnoline ring, quinoline ring, isoquinoline ring, phthalazine ring, naphthyridine ring, carbazole ring, Borin ring, diazacarbazole ring (group derived from a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is further substituted with a nitrogen atom, etc. In addition, combining the carboline ring and the diazacarbazole ring Sometimes referred to as “azacarbazole ring”), non-aromatic hydrocarbon ring group (eg, cyclopentyl group, cyclohexyl group, etc.), non-aromatic heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl) Group), alkoxy group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (for example, cyclopentyloxy group, cyclohexyloxy group) Etc.), aryloxy group (for example, phenoxy group, naphthyloxy group) Etc.), alkylthio groups (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio groups (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio groups ( For example, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, Phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group) 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) Group, propylcarbonyl 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) Ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), Mido 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 Rubonyl 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-pyridylamino group) Ureido 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) , Dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (eg, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (eg, amino group, ethylamino group, dimethylamino group, Butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom), fluoride Hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, thiol group, silyl group (eg, trimethylsilyl group, triisopropylsilyl group) Group, trifeni Silyl group, a phenyl diethyl silyl group and the like), or the like deuterium atom.
These substituents may be further substituted with the above substituents. In addition, a plurality of these substituents may be bonded to each other to form a ring.

The _y 1 ~y ₈ in the general formula _(I), preferably at least three of the y 1 ~y _4, or at least three of the _y 5 ~y ₈ is represented by _{CR 102,} more preferably y _{1 to} y ₈ are all CR ₁₀₂ . Such a skeleton is excellent in hole transport property or electron transport property, and can efficiently recombine and emit holes / electrons injected from the anode / cathode in the light emitting layer.
Among them, a compound in which X ₁₀₁ is NR ₁₀₁ , an oxygen atom, or a sulfur atom in general formula (I) is preferable as a structure having a shallow LUMO energy level and excellent electron transport properties. More preferably, the condensed ring formed with X ₁₀₁ and y _{1 to} y ₈ is a carbazole ring, an azacarbazole ring, a dibenzofuran ring or an azadibenzofuran ring.

Furthermore, considering that it is preferable to make the host compound rigid, when X ₁₀₁ is NR ₁₀₁ , R ₁₀₁ is an aromatic hydrocarbon ring which is a π-conjugated skeleton among the substituents mentioned above. It is preferably a group or an aromatic heterocyclic group. Further, these R ₁₀₁ may be further substituted with a substituent represented by the aforementioned R _{101 to} R ₁₀₄ .

In the general formula (I), examples of the aromatic ring represented by Ar ₁₀₁ and Ar ₁₀₂ include an aromatic hydrocarbon ring and an aromatic heterocyclic ring. The aromatic ring may be a single ring or a condensed ring, and may be unsubstituted or may have a substituent similar to the substituents represented by R _{101 to} R ₁₀₄ described above.
In the general formula (I), examples of the aromatic hydrocarbon ring represented by Ar ₁₀₁ and Ar ₁₀₂ include the aromatic hydrocarbon rings exemplified as the substituents represented by the aforementioned R _{101 to} R _104. Examples include the same ring as the group.
In the general formula (I), examples of the aromatic heterocyclic ring represented by Ar ₁₀₁ and Ar ₁₀₂ include the aromatic heterocyclic groups exemplified as the substituents represented by R _{101 to} R ₁₀₄ described above. Similar rings are mentioned.

In view of the purpose that the host compound represented by the general formula (I) has a large T ₁ , the aromatic ring itself represented by Ar ₁₀₁ and Ar ₁₀₂ preferably has a high T ₁ , and the benzene ring (Including polyphenylene skeletons (biphenyl, terphenyl, quarterphenyl, etc.) with multiple benzene rings), fluorene ring, triphenylene ring, carbazole ring, azacarbazole ring, dibenzofuran ring, azadibenzofuran ring, dibenzothiophene ring, dibenzothiophene ring A pyridine ring, a pyrazine ring, an indoloindole ring, an indole ring, a benzofuran ring, a benzothiophene ring, an imidazole ring or a triazine ring is preferable. More preferred are a benzene ring, a carbazole ring, an azacarbazole ring and a dibenzofuran ring.
When Ar ₁₀₁ and Ar ₁₀₂ are a carbazole ring or an azacarbazole ring, it is more preferable that they are bonded at the N-position (or 9-position) or the 3-position.
When Ar ₁₀₁ and Ar ₁₀₂ are dibenzofuran rings, they are more preferably bonded at the 2-position or 4-position.

In addition to the above purpose, when considering the use of an organic EL element mounted in a vehicle, the environment temperature in the vehicle is assumed to be high, so the Tg of the host compound is high. Is also preferable. Therefore, for the purpose of increasing the Tg of the host compound having the structure represented by the general formula (I), the aromatic rings represented by Ar ₁₀₁ and Ar ₁₀₂ are each preferably a condensed ring having 3 or more rings. It is an aspect.

Specific examples of the aromatic hydrocarbon condensed ring in which three or more rings are condensed include naphthacene ring, anthracene ring, tetracene ring, pentacene ring, hexacene ring, phenanthrene ring, pyrene ring, benzopyrene ring, benzoazulene ring, chrysene ring , Benzochrysene ring, acenaphthene ring, acenaphthylene ring, triphenylene ring, coronene ring, benzocoronene ring, hexabenzocoronene ring, fluorene ring, benzofluorene ring, fluoranthene ring, perylene ring, naphthoperylene ring, pentabenzoperylene ring, benzoperylene ring, pentaphen A ring, a picene ring, a pyranthrene ring, a coronene ring, a naphtho- coronene ring, an ovalen ring, an anthraanthrene ring, and the like. In addition, these rings may further have the above substituent.
Specific examples of the aromatic heterocycle condensed with three or more rings include an acridine ring, a benzoquinoline ring, a carbazole ring, a carboline ring, a phenazine ring, a phenanthridine ring, a phenanthroline ring, a carboline ring, a cyclazine ring, Kindin ring, tepenidine ring, quinindrin ring, triphenodithiazine ring, triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, diazacarbazole ring (any one of the carbon atoms constituting the carboline ring is a nitrogen atom Phenanthroline ring, dibenzofuran ring, dibenzothiophene ring, naphthofuran ring, naphthothiophene ring, benzodifuran ring, benzodithiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring , Emissions tiger thiophene ring, anthradithiophene ring, thianthrene ring, phenoxathiin ring, such as thio fan train ring (naphthothiophene ring). In addition, these rings may further have a substituent.

In general formula (I), n101 and n102 are each preferably an integer of 0 to 2, and more preferably n101 + n102 is an integer of 1 to 3. _Furthermore, since _{the R 101} is the n101 and n102 when the hydrogen atom is 0 at the same time, the molecular weight of the host compound having a structure represented by the general formula (I) is small, low Tg can only _{achieve, R 101} is hydrogen In the case of an atom, n101 represents an integer of 1 to 4.

  The host compound having a structure represented by the general formula (I) is preferably a compound having a structure represented by the following general formula (II). This is because such a compound tends to have particularly excellent carrier transportability.

In the general formula _{(II), X 101, Ar} 101, Ar 102 and n102 are synonymous with _{X 101, Ar 101,} Ar ₁₀₂ and n102 in formula (I).

n102 is preferably an integer of 0 to 2, more preferably 0 or 1.
In the general formula (II), the condensed ring formed containing X ₁₀₁ may further have a substituent other than Ar ₁₀₁ and Ar ₁₀₂ as long as the function of the host compound used in the present invention is not impaired. .

  The host compound having a structure represented by the general formula (II) is preferably a compound having a structure represented by the following general formula (III-1), (III-2) or (III-3). .

Formula (III-1) ~ (III -3) _in, X _{101, Ar 102} and n102 are synonymous with _{X 101, Ar 102} and n102 in formula (II). Further, in the general formula _{(III-2), R 104} has the same meaning as _{R 104} in the general formula (I).

In the general formulas (III-1) to (III-3), the condensed ring, carbazole ring and benzene ring formed containing X ₁₀₁ are further substituted within the range not inhibiting the function of the host compound used in the present invention. You may have.

  Below, as a host compound used for this invention, the compound which has a structure represented by general formula (I), (II), and (III-1)-(III-3), and another structure Examples are shown, but the invention is not limited to these.

The preferred host compound used in the present invention may be a low molecular compound having a molecular weight that can be purified by sublimation or a polymer having a repeating unit.
In the case of a low molecular weight compound, sublimation purification is possible, so that there is an advantage that purification is easy and a high-purity material is easily obtained. The molecular weight is not particularly limited as long as sublimation purification is possible, but the preferred molecular weight is 3000 or less, more preferably 2000 or less.
In the case of a polymer or oligomer having a repeating unit, there is an advantage that it is easy to form a film by a wet process, and since a polymer generally has a high Tg, it is preferable from the viewpoint of heat resistance.
The polymer used as the host compound used in the present invention is not particularly limited as long as the desired device performance can be achieved, but preferably the general formula (I), (II) or (III-1) to (III- What has the structure represented by 3) in a principal chain or a side chain is preferable. Although there is no restriction | limiting in particular as molecular weight, Molecular weight 5000 or more is preferable, or a thing with a repeating unit number of 10 or more is preferable.

In addition, the host compound has a hole transporting ability or an electron transporting ability, prevents the emission of light from being long-wavelength, and is stable with respect to heat generated when the organic EL element is driven at a high temperature or during the element driving. From the viewpoint of operation, it is preferable to have a high glass transition temperature (Tg). Tg is preferably 90 ° C. or higher, more preferably 120 ° C. or higher.
Here, the glass transition point (Tg) is a value obtained by a method based on JIS K 7121-2012 using DSC (Differential Scanning Calorimetry).

≪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.
Although there is no restriction | limiting in particular about the total layer thickness of an electron carrying layer, Usually, it exists in the range of 2 nm-5 micrometers, More preferably, it exists in the range of 2-500 nm, More preferably, it exists in the range of 5-200 nm.
Also, in the organic EL element, when 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 cause. 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, when the layer thickness of the electron transport layer is increased, the voltage is likely to rise. Therefore, particularly when the layer thickness is thick, the electron mobility of the electron transport layer is 1 × 10 ⁻⁵ cm ² / V · s or more. Preferably there is.
The material used for the electron transport layer (hereinafter, also referred to as an electron transport material) may have any of an electron injection property, a transport property, and a hole barrier property. Any one 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.) That.

In addition, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, for example, tris (8-quinolinol) aluminum (Alq ₃ ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7 -Dibromo-8-quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and metal complexes thereof A metal complex in which the central metal is replaced with In, Mg, Cu, Ca, Sn, Ga, or Pb can also be used as an electron transporting material.
In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transport material. Further, a distyrylpyrazine derivative used as a material for the light-emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si and n-type-SiC as well as a hole injection layer and a hole transport 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 according to 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. Japanese Patent Publication No. 2011-086935, International Publication No. 2010/150593, International Publication No. 2010/047707, European Patent No. 2311826, Japanese Unexamined Patent Publication No. 2010-251675, Japanese Unexamined Patent Publication No. 2009-209133, Japanese Unexamined Patent Publication No. 2009. -1241 No. 4, JP 2008-277810 A, JP 2006-156445 A, JP 2005-340122 A, JP 2003-45662 A, JP 2003-31367 A, JP 2003-282270 A. Gazette, International Publication No. 2012/115034, and the like.

More preferable electron transport materials in the present invention include aromatic heterocyclic compounds containing at least one nitrogen atom. For example, pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, azadibenzofurans. 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 the function of an electron transport layer in a broad sense, and is preferably made of a material having a function of transporting electrons and a small ability to transport holes. By blocking the holes, the probability of recombination of electrons and holes can be improved.
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.
The thickness of the hole blocking layer is preferably in the range of 3 to 100 nm, and 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≫
An electron injection layer (also referred to as a “cathode buffer layer”) is a layer provided between a cathode and a light-emitting layer in order to reduce driving voltage or improve light emission luminance. It is described in detail in the second chapter, Chapter 2, “Electrode Materials” (pages 123 to 166) of “Front Line (published 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 although it depends on the material. Moreover, the nonuniform layer (film | membrane) in which a constituent material exists intermittently may be sufficient.

The details of the electron injection layer are 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.
Although there is no restriction | limiting in particular about the total layer thickness of a positive hole transport layer, Usually, it exists in the range of 5 nm-5 micrometers, More preferably, it exists in the range of 2-500 nm, More preferably, it exists in the range of 5-200 nm. .

The material used for the hole transporting layer (hereinafter also referred to as a hole transporting material) may have any of a hole injecting property, a transporting property, and an electron barrier property. 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, polymer 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 the triarylamine derivative include benzidine type represented by α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), starburst type represented by MTDATA, Examples include compounds having fluorene or anthracene in the triarylamine-linked core.
In addition, hexaazatriphenylene derivatives such as those described in JP-A-2003-519432 and JP-A-2006-135145 can also be used as a hole transport material.
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, 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 a 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. MoI. Lumin. 72-74,985 (1997), Appl. Phys. Lett. 78, 673 (2001), Appl. Phys. Lett. 90, 183503 (2007), 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 Japanese Patent Application Publication No. 2007/0278938, US Patent Application Publication No. 2008/0106190, US Patent Application Publication No. 2008/0018221, International Publication No. 2012/115034, and Japanese Translation of PCT International Publication No. 2003-519432. , JP2006-2006 35145 JP is US Patent Application No. 2013/585981 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 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.
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”) is a layer provided between the anode and the light-emitting layer in order to lower the drive voltage and improve the light emission luminance. It is described in detail in Chapter 2 “Electrode Materials” (pages 123 to 166) in the second volume of “The Frontline (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 also described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069, etc. Examples of the material used for the hole injection layer include: And materials used for the hole transport layer described above.
Among them, phthalocyanine derivatives represented by copper phthalocyanine, hexaazatriphenylene derivatives as described in JP-T-2003-519432, JP-A-2006-135145, etc., metal oxides represented by vanadium oxide, amorphous Conductive polymers such as carbon, polyaniline (emeraldine) and polythiophene, orthometalated complexes represented by tris (2-phenylpyridine) iridium complex, and triarylamine derivatives are preferred.
The materials used for the hole injection layer described above may be used alone or in combination of two or more.

≪Additives≫
The organic layer according to the present invention described above may further contain other additives.
Examples of the additive include halogen elements and halogenated compounds such as bromine, iodine and chlorine, alkali metals and alkaline earth metals such as Pd, Ca and Na, transition metal compounds, complexes and salts.
Although the content of the additive can be arbitrarily determined, it is preferably 1000 ppm or less, more preferably 500 ppm or less, and still more preferably 50 ppm or less, based on 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 of 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 conventionally known methods such as a vacuum deposition method and a wet method (also referred to as a wet process) can be used.
Examples of the wet method include spin coating, casting, ink jet, printing, die coating, blade coating, roll coating, spray coating, curtain coating, and LB (Langmuir-Blodgett). 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 element 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 and xylene. Aromatic hydrocarbons such as mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used.
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 formation 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 vacuum degree of 1 × 10 ⁻⁶ to 1 × 10 ⁻² Pa, and a vapor deposition rate It is desirable to select appropriately within a range of 0.01 to 50 nm / second, a substrate temperature of −50 to 300 ° C., and a layer (film) thickness of 0.1 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 one evacuation, but it may be taken out halfway and subjected to different film forming 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 an electrode substance include a conductive transparent material such as a metal such as Au, CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, 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 depositing these electrode materials by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by photolithography, or when the pattern accuracy is not so high (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered.
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 is greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less.
The film thickness of the anode depends on the material, but 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 low 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 the cathode is preferably several hundred Ω / □ or less. The film thickness is usually selected within 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.
Moreover, after producing the above metal with a film thickness of 1 to 20 nm on the cathode, a transparent or translucent cathode can be produced by producing a conductive transparent material mentioned in the description of the anode on the cathode. By applying the above, an element in which both the anode and the cathode are transmissive can be manufactured.

≪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 polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned.

An inorganic film, an organic film, or a hybrid film of both may be formed on the surface of the resin film, and the water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. , Relative humidity (90 ± 2)% RH) is preferably 0.01 g / (m ² · 24 h) or less gas barrier film, and further measured by a method according to JIS K 7126-1987. It is a high gas barrier film having an oxygen 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 preferred.

As a material for forming the gas 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. Furthermore, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of organic materials. 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 gas barrier film is not particularly limited. For example, the vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma weight A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, and 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.

≪Sealing≫
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of bonding a sealing member, an electrode, and a support substrate with an adhesive. As a sealing member, it should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and it may be concave plate shape or flat plate shape. Moreover, transparency and electrical insulation are not particularly limited.
Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the organic EL element can be thinned. Furthermore, the polymer film has an oxygen permeability measured by a method according to JIS K 7126-1987 of 1 × 10 ⁻³ ml / (m ² · 24 h · atm) or less, a method according to JIS K 7129-1992. It is preferable that the water vapor permeability (25 ± 0.5 ° C., relative humidity 90 ± 2%) measured in (1) is 1 × 10 ⁻³ g / (m ² · 24 h) or less.
For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used.

Specific examples of the adhesive include photocuring and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. be able to. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.
In addition, since an organic EL element may deteriorate by heat processing, what can be adhesive-hardened from room temperature (25 degreeC) to 80 degreeC is preferable. Further, a desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print it like screen printing.

In addition, it is also preferable that the electrode and the organic layer are coated on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and an inorganic or organic layer is formed in contact with the support substrate to form a sealing film. . In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can.
Furthermore, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. There are no particular limitations on the method of forming these films. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

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

≪Protective film, protective plate≫
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided outside the sealing film or sealing film on the side facing the support substrate with the organic layer interposed therebetween. In particular, when sealing is performed with a sealing film, the mechanical strength is not necessarily high, and thus it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, etc. used for sealing can be used. It is preferable to use it.

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

  As a technique for improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the transparent substrate and the air interface (for example, US Pat. No. 4,774,435), A method for improving efficiency by providing light condensing property (for example, JP-A-63-314795), a method for forming a reflective surface on a side surface of an element (for example, JP-A-1-220394), a substrate, etc. A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light emitter (for example, Japanese Patent Application Laid-Open No. Sho 62-172691); A diffraction grating is formed in a method of introducing a flat layer having a low refractive index (for example, Japanese Patent Application Laid-Open No. 2001-202827), or between the substrate, the transparent electrode layer, and the light emitting layer (including between the substrate and the outside). Method No. 11-283751 Publication), and the like.

In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, A method of forming a diffraction grating between any one of the transparent electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used.
In the present invention, by combining these means, it is possible to obtain an element having higher luminance or durability.

If a medium with a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the light extracted from the transparent electrode has a lower efficiency of extraction to the outside as the refractive index of the medium is lower. Get higher.
Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally in the range of about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less, preferably 1.35 or less. More preferred.
The thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave exuded by evanescent enters the substrate.

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

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

≪Condenser sheet≫
The organic EL element of the present invention can be processed in a specific direction, for example, by providing a structure on the microlens array on the light extraction side of the support substrate (substrate) or combining it with a so-called condensing sheet. For example, the brightness | luminance in a specific direction can be raised by condensing in a front direction with respect to an element light emission surface.
As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are arranged two-dimensionally on the light extraction side of the substrate. One side is preferably within a range of 10 to 100 μm. If it is smaller than this, the effect of diffraction is generated and colored, and if it is too large, the thickness becomes thick, which is not preferable.
As the condensing sheet, for example, a sheet that is put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, the base material may be formed by forming a △ -shaped stripe having a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex angle is rounded and the pitch is changed randomly. Other shapes may be used.
Moreover, in order to control the light emission angle from an organic EL element, you may use a light-diffusion plate and a film together with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

≪Usage≫
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 Examples include, but are not limited to, a light source of a sensor. In particular, the light source can be effectively used for a backlight of a liquid crystal display device and a light source for illumination.
In the organic EL element of the present invention, patterning may be performed by a metal mask, an 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, and a conventionally known method is used in the fabrication of the element. be able to.

<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 an evaporation method, a cast method, a spin coating method, an ink jet method, a printing method, 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 provided 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 to the one aspect | mode of manufacture of the organic EL element of said 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 an automobile. In particular, it may be used as a display device for reproducing still images or 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.

  Light-emitting devices include household lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, optical storage media light sources, electrophotographic copying machine light sources, optical communication processor light sources, optical sensor light sources, etc. However, the present invention is not limited to these.

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. 10 is a schematic diagram illustrating an example of a display device including 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 via the display unit A and 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. Each pixel sequentially emits light in accordance with the image data signal, performs image scanning, and displays image information on the display unit A.

FIG. 11 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. 11 shows a case where the light emitted from the pixel 3 is extracted in the direction of the white arrow (downward).

The scanning lines 5 and the plurality of data lines 6 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 orthogonal positions (for details, see FIG. Not shown).
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. 12 is a schematic diagram illustrating 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. 12, 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 of the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10, 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. 13 is a schematic diagram of a display device using a passive matrix method. In FIG. 13, 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, a display device with improved luminous efficiency was obtained.

<Lighting device>
The organic EL element of the present invention can also be used for a lighting device.
The organic EL element of the present invention may be used as an organic EL element having a resonator structure. Examples of the purpose of use of the organic EL element having such a resonator structure include a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processing machine, and a light source of an optical sensor. It is not limited. Moreover, you may use for the said use by making a laser oscillation.
Further, the organic EL element of the present invention may be used as a kind of lamp for illumination or exposure light source, a projection device for projecting an image, or a type for directly viewing a still image or a moving image. It may be used as a display device (display).
The driving method when used as a display device for reproducing a moving image may be either a passive matrix method or an active matrix method. Alternatively, it is possible to produce a full-color display device by using two or more organic EL elements of the present invention having different emission colors.

  In addition, the π-conjugated compound of 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 organic EL device forming method 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.

<One aspect of lighting device>
One mode of a lighting device including the organic EL element of the present invention will be described.
The non-light emitting surface of the organic EL device of the present invention is covered with a glass case, a 300 μm thick glass substrate is used as a sealing substrate, and an epoxy photocurable adhesive (LUX The 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 illuminated as shown in FIGS. A device can be formed.
FIG. 14 shows a schematic diagram of a lighting device, and the organic EL element of the present invention (the organic EL element 101 in the lighting device) is covered with a glass cover 102 (note that the sealing operation with the glass cover is performed by lighting. This was performed 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. 15 shows a cross-sectional view of the lighting device, in which reference numeral 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.
By using the organic EL element of the present invention, a lighting device with improved luminous efficiency can be obtained.

EXAMPLES 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 "%" is used in an Example, unless there is particular notice, "mass%"
Represents. Moreover, the volume% of the compound in each Example was calculated | required from specific gravity by measuring and calculating the thickness of the film | membrane produced by the quartz oscillator microbalance method.

[Example 1]
Exemplified compounds FD1 to FD4, FD6 to FD10 and FD13 to FD61 of the present invention, and TADF compound 2CzPN (Comparative Compound 1) and 4CzIPN (Comparative Compound 2) as the following comparative compounds, B3LYP as functional and 6 as basis function HOMO energy levels (eV), ΔE _st (eV) and nearest interatomic distance (nm) were calculated by molecular orbital calculation using −31G (d).
The results are shown in Table 1.

Example Compound FD1～FD4, the value of Delta] E _st calculated by molecular orbital calculations FD6~FD10 and FD13~FD61 of the present invention are all at 0.5eV or less, was of sufficient level to express the TADF phenomenon. Moreover, the values of the HOMO energy levels of the TADF compounds 2CzPN and 4CzIPN calculated by the same method are −5.90 eV, −5.70 eV and deep HOMO, respectively, and the exemplary compounds FD1 to FD4 and FD6 to FD10 of the present invention. It was confirmed that the HOMO energy level values of FD13 to FD61 were shallower than those of conventional TADF compounds. The measured HOMO values of 2CzPN and 4CzIPN are −6.00 eV and −5.80 eV, respectively, and there is no deviation from the above calculated value. Therefore, the calculated HOMO value was used as a comparison (about the measured HOMO value of 2CzPN). (Organic Electronics Volume 14, Issue 11, November 2013, Pages 2721-2726, 4CzIPN HOMO values are shown in H Nakanotani et al., Scientific Reports 0.13, 27: 1). .

[Example 2]
In the exemplary compounds FD1 to FD4, FD6 to FD10, and FD13 to FD61 of the present invention, the difference between the rising edge on the short wavelength side of the emission spectrum and the maximum absorption wavelength is smaller than that of the conventional TADF compound, and the spectrum width is narrowed. A trend was confirmed.

[Example 3]
<< Production of organic EL elements >>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached 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. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection transport layer was formed.

  Next, in the combinations shown in Table 2, the host compound and the dopant were co-deposited at a deposition rate of 0.1 nm / second so as to be 90% and 10% by volume, respectively, to form a light emitting layer having a layer thickness of 35 nm. .

Thereafter, BAlq was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 10 nm. Further thereon, Alq ₃ (electron transport material) 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 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 organic EL elements 100 to 106.

<< Evaluation of organic EL elements >>
The following evaluation was performed about each produced organic EL element.

(Evaluation of power efficiency)
About each produced organic EL element, it was made to light-emit on the constant current conditions of ^2.5 mA / cm < ² > at room temperature (about 25 degreeC), and the light-emission brightness | luminance immediately after the light emission start was spectral radiance meter CS-2000 (Konica Minolta company). Power efficiency (lm / W) was calculated.
Next, the relative light emission luminance was calculated with the power efficiency of the organic EL element 101 of the comparative example as 100, and this was used as a measure of the power efficiency. The larger the value, the better the power efficiency.
The evaluation results are shown in Table 2.

(Measurement of initial drive voltage)
About each produced organic EL element, the emission luminance of each sample was measured at room temperature (about 25 degreeC) using the spectral radiance meter CS-2000 (made by Konica Minolta), and the initial stage in emission luminance 1000cd / m < ² >. The driving voltage was determined.
Next, a relative initial drive voltage with the initial drive voltage of the organic EL element 101 of the comparative example as 100 was obtained, and this was used as a measure of the initial drive voltage. The smaller the value, the better the initial drive voltage.
The measurement results are shown in Table 2.

(result)
It has been confirmed that the organic EL elements 103 to 106 of the present invention have increased power efficiency, reduced initial drive voltage, and improved performance as compared with the organic EL elements 100 to 102 of the comparative example. .

[Example 4]
<< Production of organic EL elements >>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached 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. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection transport layer was formed.

  Next, in the combinations shown in Table 3, the host compound and the dopant were co-deposited at a deposition rate of 0.1 nm / second so as to be 90% and 10% by volume, respectively, to form a light emitting layer having a layer thickness of 30 nm. .

Thereafter, BAlq was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 10 nm. Further thereon, Alq ₃ (electron transport material) 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 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 organic EL elements 110 to 112.

<< Evaluation of organic EL elements >>
About each produced organic EL element, it carried out similarly to Example 3, and evaluated the power efficiency and the initial stage drive voltage. The power efficiency and initial drive voltage of each organic EL element are shown as relative values with the power efficiency and initial drive voltage of the organic EL element 110 as 100.
The evaluation results are shown in Table 3.

(result)
It has been confirmed that the organic EL elements 111 and 112 of the present invention have increased power efficiency, reduced initial drive voltage, and improved performance as compared to the organic EL element 110 of the comparative example.

[Example 5]
<< Production of organic EL elements >>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached 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. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection transport layer was formed.

  Next, in the combinations shown in Table 4, the host compound and the dopant were co-deposited at a deposition rate of 0.1 nm / second so as to be 90% and 10% by volume, respectively, to form a light emitting layer having a layer thickness of 35 nm. .

Thereafter, PPT was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 10 nm. Further thereon, Alq ₃ (electron transport material) 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 device 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 electrode lead-out wirings were installed to prepare organic EL devices 120 to 122.

<< Evaluation of organic EL elements >>
About each produced organic EL element, it carried out similarly to Example 3, and evaluated the power efficiency and the initial stage drive voltage. The power efficiency and initial drive voltage of each organic EL element are shown as relative values with the power efficiency and initial drive voltage of the organic EL element 120 being 100.
The evaluation results are shown in Table 4.

(result)
It was confirmed that the organic EL elements 121 and 122 of the present invention have increased power efficiency, reduced initial drive voltage, and improved performance as compared with the organic EL element 120 of the comparative example.

[Example 6]
<< Production of organic EL elements >>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached 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. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection transport layer was formed.

  Next, in the combinations shown in Table 5, the host compound and the dopant were co-deposited at a deposition rate of 0.1 nm / second so as to be 90% and 10% by volume, respectively, to form a light emitting layer having a layer thickness of 35 nm. .

Thereafter, DPEPO was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 10 nm. Further thereon, Alq ₃ (electron transport material) 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 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 organic EL elements 130 to 136.

<< Evaluation of organic EL elements >>
About each produced organic EL element, it carried out similarly to Example 3, and evaluated the power efficiency and the initial stage drive voltage. The power efficiency and initial drive voltage of each organic EL element are shown as relative values with the power efficiency and initial drive voltage of the organic EL element 130 as 100.
The evaluation results are shown in Table 5.

(result)
It was confirmed that the organic EL elements 131 to 136 of the present invention have improved power efficiency, reduced initial drive voltage, and improved performance as compared with the organic EL element 130 of the comparative example.

[Example 7]
<< Production of organic EL elements >>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached 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. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection transport layer was formed.

  Subsequently, a host compound, a dopant, and an assist dopant (combined compound) were co-deposited at a deposition rate of 0.1 nm / second so as to have the ratio shown in Table 6, thereby forming a light-emitting layer having a layer thickness of 30 nm.

  Thereafter, TPBi was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer / 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 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 organic EL elements 200 to 206.

<< Evaluation of organic EL elements >>
The following evaluation was performed about the produced organic EL element.

(Evaluation of external quantum yield (emission brightness))
About each produced organic EL element, it was made to light-emit on the constant current conditions of ^2.5 mA / cm < ² > at room temperature (about 25 degreeC), and the light-emission brightness | luminance immediately after the light emission start was spectral radiance meter CS-2000 (Konica Minolta company). ).
Subsequently, the relative light emission luminance which set the light emission luminance of the organic EL element 200 of the comparative example as 100 was obtained, and this was used as a measure of the light emission efficiency (external quantum yield). It represents that it is excellent in luminous efficiency, so that a numerical value is large.
The evaluation results are shown in Table 6.

(Evaluation of half-life (continuous drive stability))
For each organic EL element manufactured, while continuously driven at an initial luminance 3000 cd / ^{m 2,} the luminance was measured by using a spectral radiance meter CS-2000, the measured luminance was determined time by half (LT50).
Subsequently, the relative value which set LT50 of the organic EL element 200 of the comparative example to 100 was calculated | required, and this was made into the scale of continuous drive stability. The larger the value, the better the continuous driving stability (long life).
The evaluation results are shown in Table 6.

(result)
It has confirmed that the organic EL elements 203-206 of this invention were excellent in the external quantum yield and the half life compared with the organic EL elements 200-202 of the comparative example.
This is considered to be an effect that the π-conjugated compound of the present invention assists the emission of other fluorescent compounds. That is, when the π-conjugated compound of the present invention having a higher energy level than the light-emitting substance is excited in the light-emitting element, the π-conjugated compound of the present invention itself emits light when the light-emitting substance efficiently receives the energy. It is thought that the external quantum efficiency comparable to that of can be obtained.

[Example 8]
<< Production of organic EL elements >>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached Was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.

  On this transparent substrate, using a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water, 3000 rpm, A thin film was formed by spin coating under a condition of 30 seconds, and then dried at 200 ° C. for 1 hour to provide a first hole injection transport layer having a layer thickness of 20 nm.

The transparent substrate provided up to the first hole injecting and transporting layer 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. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the first hole injecting and transporting layer at a deposition rate of 0.1 nm / second. A second hole injecting and transporting layer having a thickness of 30 nm was formed.

  Next, a host compound, a dopant, and an assist dopant (combined compound) were co-evaporated at a deposition rate of 0.1 nm / second so as to have the ratio shown in Table 7, thereby forming a light-emitting layer having a layer thickness of 20 nm.

  Thereafter, BAlq was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 10 nm. Further, TPBi was deposited thereon 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 organic EL elements 210 to 213.

<< Evaluation of organic EL elements >>
About each produced organic EL element, it carried out similarly to Example 7, and evaluated the external quantum yield (light emission luminance) and the half life (continuous drive stability). In addition, the external quantum yield and half life of each organic EL element are shown as relative values with the external quantum yield and half life of the organic EL element 210 being 100.
Table 7 shows the evaluation results.

(result)
It was confirmed that the organic EL elements 212 and 213 of the present invention were excellent in external quantum yield and half-life compared to the organic EL elements 210 and 211 of the comparative example.

[Example 9]
<< Production of organic EL elements >>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached Was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.

  On this transparent substrate, using a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water, 3000 rpm, A thin film was formed by spin coating under a condition of 30 seconds, and then dried at 200 ° C. for 1 hour to provide a first hole injection transport layer having a layer thickness of 20 nm.

The transparent substrate provided up to the first hole injecting and transporting layer 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. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the first hole injecting and transporting layer at a deposition rate of 0.1 nm / second. A second hole injecting and transporting layer having a thickness of 30 nm was formed.

  Next, a host compound, a dopant, and an assist dopant (combined compound) were co-evaporated at a deposition rate of 0.1 nm / second so as to have the ratio shown in Table 8, thereby forming a light-emitting layer having a layer thickness of 20 nm.

  Thereafter, PPT was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 10 nm. Further, TPBi was deposited thereon 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 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 organic EL elements 220 to 223.

<< Evaluation of organic EL elements >>
About each produced organic EL element, it carried out similarly to Example 7, and evaluated the external quantum yield (light emission luminance) and the half life (continuous drive stability). In addition, the external quantum yield and half life of each organic EL element are shown as relative values with the external quantum yield and half life of the organic EL element 220 as 100.
The evaluation results are shown in Table 8.

(result)
It was confirmed that the organic EL elements 222 and 223 of the present invention were excellent in external quantum yield and half-life compared to the organic EL elements 220 and 221 of the comparative example.

[Example 10]
<< Production of organic EL elements >>
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached Was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.

  On this transparent substrate, using a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water, 3000 rpm, A thin film was formed by spin coating under a condition of 30 seconds, and then dried at 200 ° C. for 1 hour to provide a first hole injection transport layer having a layer thickness of 20 nm.

The transparent substrate provided up to the first hole injecting and transporting layer 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. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the first hole injecting and transporting layer at a deposition rate of 0.1 nm / second. A second hole injecting and transporting layer having a thickness of 30 nm was formed.

  Next, a host compound, a dopant, and an assist dopant (combined compound) were co-deposited at a deposition rate of 0.1 nm / second so as to have the ratio shown in Table 9, thereby forming a light emitting layer having a layer thickness of 20 nm.

  Thereafter, DPEPO was deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer having a layer thickness of 10 nm. Further, TPBi was deposited thereon 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 organic EL elements 230 to 236.

<< Evaluation of organic EL elements >>
About each produced organic EL element, it carried out similarly to Example 7, and evaluated the external quantum yield (light emission luminance) and the half life (continuous drive stability). In addition, the external quantum yield and half life of each organic EL element are shown as relative values with the external quantum yield and half life of the organic EL element 230 as 100.
Table 9 shows the evaluation results.

(result)
It was confirmed that the organic EL elements 232 to 236 of the present invention were excellent in external quantum yield and half-life compared to the organic EL elements 230 and 231 of the comparative example.

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 trapping agent A Display part B Control part C Wiring part D Overlap APlane, DPlane Conjugate plane

Claims (15)

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 organic layer contains a π-conjugated compound having an electron withdrawing portion and an electron donating portion in the molecule,
The nearest atomic distance between the electron withdrawing portion and the electron donating portion in the π-conjugated compound is 10 nm or less, and the lowest excited singlet level and the lowest excited triplet level of the π conjugated compound are An organic electroluminescence device characterized in that the absolute value (ΔE _st ) of the energy difference is 0.5 eV or less.   2. The organic electroluminescence device according to claim 1, wherein the closest interatomic distance between the electron withdrawing portion and the electron donating portion in the π-conjugated compound is 1 nm or less.   The π-conjugated compound has a bond part between the electron withdrawing part and the electron donating part, and the bond part has a part where the π-conjugated system is discontinuous at least at one place. The organic electroluminescent element according to claim 1 or 2, wherein The organic electroluminescence device according to claim 3, wherein the π-conjugated compound is a compound having a structure represented by the following general formula (A).

(In General Formula (A), X _{1 to} X ₃ and Y _{1 to} Y ₃ each independently represent a substituted or unsubstituted carbon atom or a nitrogen atom.) The organic electroluminescence device according to claim 3, wherein the π-conjugated compound is a compound having a structure represented by the following general formula (B).

(In general formula (B), R _{1 to} R ₃ each independently represents a hydrogen atom, a methyl group or a phenyl group, but at least two of R _{1 to} R ₃ represent a phenyl group.)   The organic electroluminescence device according to claim 3, wherein the coupling portion has an adamantane structure.   The organic electroluminescence device according to claim 3, wherein the coupling portion has a borazine structure.   The organic electroluminescence device according to claim 3, wherein the bonding portion has a dibenzophosphole oxide structure.   The organic electroluminescence device according to claim 3, wherein the coupling portion has a triptycene structure.   The organic electroluminescence device according to claim 3, wherein the coupling portion has a penthipcene structure.   The organic electroluminescence device according to claim 3, wherein the coupling portion has a cyclophane structure.   The organic electro according to any one of claims 1 to 11, wherein the electron withdrawing portion and the electron donating portion in the π-conjugated compound are connected by at least two atoms. Luminescence element.   The light emitting layer contains the π-conjugated compound, and at least one of a fluorescent compound and a phosphorescent compound, according to any one of claims 1 to 12. The organic electroluminescence device according to one item.   13. The light emitting layer contains the π-conjugated compound, at least one of a fluorescent compound and a phosphorescent compound, and a host compound. The organic electroluminescent element as described in any one of the above. A π-conjugated compound having an electron withdrawing portion and an electron donating portion in the molecule,
The nearest atomic distance between the electron withdrawing portion and the electron donating portion in the π-conjugated compound is 10 nm or less, and the lowest excited singlet level and the lowest excited triplet level of the π conjugated compound are An absolute value (ΔE _st ) of the energy difference of π is conjugated to a π-conjugated compound, which is 0.5 eV or less.

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