WO2016017514A1

WO2016017514A1 - Organic electroluminescent element, light-emitting thin film, display device, and lighting device

Info

Publication number: WO2016017514A1
Application number: PCT/JP2015/070917
Authority: WO
Inventors: 周穂谷本; 池水　大; 鈴木　隆嗣; 康生宮田
Original assignee: コニカミノルタ株式会社
Priority date: 2014-07-31
Filing date: 2015-07-23
Publication date: 2016-02-04
Also published as: JPWO2016017514A1

Abstract

The present invention addresses the problem of providing an organic electroluminescent element which has low drive voltage and with which high light emission efficiency can be realized. Further provided are: a light-emitting thin film that contains a conjugated compound according to the present invention; and a display device and lighting device that are provided with the organic electroluminescent element. This organic electroluminescent element is characterized by having, between an anode and cathode, an organic layer group that includes at least one light-emitting layer, wherein at least one layer of said organic layer group contains a π-conjugated compound having a structure represented by general formula (1). [In the formula, A represents an electron-withdrawing group, and D represents an electron-donating group. m and n each independently represent integers of 1 or 2. X represents an aromatic hydrocarbon group selected from a structure represented by a specific structure.]

Description

ORGANIC ELECTROLUMINESCENT ELEMENT, LIGHT-EMITTING THIN FILM, DISPLAY DEVICE AND LIGHTING DEVICE

The present invention relates to an organic electroluminescence element, a light-emitting thin film, and a display device and an illumination device including the organic electroluminescence element. More specifically, the present invention relates to an organic electroluminescence element with improved luminous efficiency.

An organic electroluminescence element (hereinafter, also referred to as “organic EL element” or “organic electroluminescence element”) using organic electroluminescence (Electro Luminescence: hereinafter abbreviated as “EL”) emits planar light. This technology has already been put into practical use as a new light-emitting system that enables this. Organic EL elements are applied not only to electronic displays but also recently as lighting devices, and their development is expected.

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 an electric field is applied to the organic EL element, holes and electrons are injected from the anode and the cathode, respectively, and recombined in the light emitting layer or its interface region to generate excitons. At this time, since singlet excitons and triplet excitons are generated at a ratio of 25%: 75%, phosphorescence emission using triplet excitons is theoretically higher than fluorescence emission. It is known that quantum efficiency can be obtained.

However, in order to actually obtain high quantum efficiency in the phosphorescence emission method, it is necessary to use a complex using a rare metal such as iridium or platinum as a central metal. There is concern that the price will be a major industrial issue.

On the other hand, various developments have been made to improve the light emission efficiency in the fluorescent light emission method, and a new movement has recently been made.

For example, a phenomenon in which singlet excitons are generated by collision of two triplet excitons (hereinafter referred to as “triplet-triplet annihilation: abbreviated as“ TTA ”where appropriate. Also referred to as triplet-triplet fusion:“ TTF ””). Attention has been paid to a technique for efficiently increasing the efficiency of a fluorescent element by efficiently causing TTA (see, for example, Patent Document 1). With this technology, the power efficiency of fluorescent materials (hereinafter also referred to as fluorescent materials) is improved to 2 to 3 times that of conventional fluorescent materials, but the theoretical singlet in TTA. Since the exciton generation efficiency is limited to about 40%, there is still a problem of higher emission efficiency than phosphorescence emission.

In recent years, thermally activated delayed fluorescence (reverse intersystem crossing: hereinafter, abbreviated as “RISC” where appropriate) is a phenomenon that uses a characteristic that causes triplet excitons to singlet excitons. Hereinafter, a fluorescent light-emitting material to which “also referred to as“ thermally-excited delayed fluorescence ”: Thermally Activated Delayed Fluorescence: abbreviated as“ TADF ”as appropriate” and its possibility of use in organic EL devices has been reported ( For example, refer to Patent Document 2, Non-Patent Document 1, and Non-Patent Document 2.) Utilizing delayed fluorescence by this TADF mechanism enables 100% internal quantum efficiency that is theoretically equivalent to phosphorescence emission even in fluorescence emission by electric field excitation.

In order to develop the TADF phenomenon, it is necessary to generate a reverse intersystem crossing from 75% of triplet excitons to singlet excitons generated by electric field excitation at room temperature or the temperature of the light emitting layer in the light emitting element. Furthermore, a singlet exciton generated by crossing between inverses emits fluorescence similarly to a 25% singlet exciton generated by direct excitation, so that an internal quantum efficiency of 100% is theoretically possible. In order for this reverse intersystem crossing to occur, the absolute value (hereinafter referred to as ΔEst) of the difference between the lowest excited singlet energy level (S ₁ ) and the lowest excited triplet energy level (T ₁ ) is extremely small. It is essential.

Further, when a light emitting layer composed of a host compound and a light emitting compound contains a compound exhibiting TADF properties as a third component (hereinafter also referred to as an assist dopant) in the light emitting layer, it is effective for high luminous efficiency. It is known (see, for example, Non-Patent Document 3). By generating 25% singlet excitons and 75% triplet excitons on the assist dopant by electric field excitation, the triplet excitons generate singlet excitons with reverse intersystem crossing (RISC). be able to. The energy of the singlet exciton is transferred to the light emitting compound, and the light emitting compound can emit light. Therefore, theoretically, it becomes possible to cause the luminescent compound to emit light using 100% exciton energy, and high luminous efficiency is exhibited.

As shown in FIG. 1A, the TADF mechanism is a compound in which the difference (ΔEst) between the singlet excitation energy level and the triplet excitation energy level (ΔEst (TADF in FIG. 1A) is smaller than that of an ordinary fluorescent compound material. ) Is smaller than ΔEst (F).) Is a light emission mechanism that utilizes the phenomenon that reverse intersystem crossing from triplet excitons to singlet excitons occurs. That is, since ΔEst is small, triplet excitons generated with a probability of 75% due to electric field excitation cannot contribute to light emission originally, but transition to a singlet excited state by thermal energy at the time of driving an organic EL element, From this state to the ground state, radiation is deactivated (also referred to as “radiation transition” or “radiation deactivation”) to cause fluorescence emission. If delayed fluorescence due to the TADF mechanism is used, it is considered that 100% internal quantum efficiency is theoretically possible even in fluorescence emission.

Although various development studies have been conducted to achieve such high luminous efficiency, the performance obtained is still not sufficient for practical use.

In addition, since aromatic hydrocarbon materials having a carbazole structure, a dibenzothiophene structure, a dibenzofuran structure, and the like have high charge transport properties, it is disclosed that the performance of an organic electroluminescence device is improved by using the material. (For example, refer to Patent Document 3). However, the technical idea focuses on the charge transport property of carbazole, and does not describe any idea that emphasizes the bipolarity (bipolarity) of the compound as disclosed in this specification.

International Publication No. 2010/134350 JP 2013-116975 A JP 2012-107005 A

The present invention has been made in view of the above-described problems and situations, and a problem to be solved is to provide an organic electroluminescence element that can be driven at a low voltage and can realize high luminous efficiency. Another object of the present invention is to provide a light-emitting thin film containing the conjugated compound according to the present invention, a display device and an illumination device provided with the organic electroluminescence element.

As a result of studying the cause of the above problem and the like in order to solve the above problems, the present inventor has an organic layer group including at least one light emitting layer between the anode and the cathode, and at least one layer of the organic layer group. And an organic electroluminescence device containing a π-conjugated compound which is an aromatic hydrocarbon compound having an electron-donating group and an electron-withdrawing group in the same molecule represented by the general formula (1). It was found that an organic electroluminescence element that can be driven at a high speed and that can obtain high luminous efficiency can be realized.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. An organic electroluminescence device having an organic layer group including at least one light emitting layer between an anode and a cathode,
At least one layer of the organic layer group contains a π-conjugated compound having a structure represented by the following general formula (1).

[In the formula, A represents an electron-withdrawing group, and D represents an electron-donating group. m and n are each independently an integer of 1 or 2. X represents an aromatic hydrocarbon group selected from structures represented by the following general formulas (1a) to (1k). ]

[In the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k), R ₁ , R ₂ , Ra, Rb, Rc and Rd each independently represents a hydrogen atom or a substituent. . p, q, r and s each independently represent an integer of 0 to 4. These substituents may be the same or different, and each substituent may be bonded to form a ring. ]
2. When at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron-withdrawing group, The attractive group represents an aromatic heterocyclic group, a sulfonyl group (—SO ₂ R ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. ), A sulfenyl group (—SOR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a cyano group (—CN), halogeno A group, a carbonyl group (—COR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a pentafluorophenyl group (—C ₆ F ₅₎ a trifluoromethyl group _(-CF 3), trifluoromethyl Eniru group _{_{_{(-C 6 H 4 CF 3)}}} , and boryl group ^_(-BR ¹ 2; ^R 1 represents an aromatic heterocyclic group of aromatic hydrocarbon group having 6 to 30 carbon atoms, or 3 to 20 carbon atoms The organic electroluminescent device according to item 1, wherein the organic electroluminescent device is at least one selected from the group consisting of:

3. When at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron donating group, The donating group is an aromatic heterocyclic group having 3 to 20 carbon atoms, an amino group (—NH ₂ ), an arylamino group (—NHR ¹ or —NR ¹ ₂ ; R ¹ is an aromatic carbon group having 6 to 30 carbon atoms; A hydrogen group or an aromatic heterocyclic group having 3 to 20 carbon atoms), an alkoxy group (—OR ¹ ; R ¹ is a linear or cyclic hydrocarbon group having 1 to 10 carbon atoms), and an aryloxy group ( —OR ² ; R ² represents a linear or cyclic hydrocarbon group, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. 2. The organic electroluminescence according to item 1, characterized in that Ssensu element.

4). When at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron-withdrawing group, The attractive group represents an aromatic heterocyclic group, a sulfonyl group (—SO ₂ R ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. ), A sulfenyl group (—SOR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a cyano group (—CN), halogeno A group, a carbonyl group (—COR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a pentafluorophenyl group (—C ₆ F ₅₎ a trifluoromethyl group _(-CF 3), trifluoromethyl Eniru group _{_{_{(-C 6 H 4 CF 3)}}} , and boryl group ^_(-BR ¹ 2; ^R 1 represents an aromatic heterocyclic group of aromatic hydrocarbon group having 6 to 30 carbon atoms, or 3 to 20 carbon atoms And at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the general formulas (1a) to (1k) is an electron donating group. When the electron donating group is an aromatic heterocyclic group having 3 to 20 carbon atoms, an amino group (—NH ₂ ), an arylamino group (—NHR ¹ or —NR ¹ ₂ ; R ¹ has 6 to 30 carbon atoms) An aromatic hydrocarbon group or an aromatic heterocyclic group having 3 to 20 carbon atoms), an alkoxy group (—OR ¹ ; R ¹ is a linear or cyclic hydrocarbon group having 1 to 10 carbon atoms), and aryloxy groups ^(-OR ^{2; R} 2 is a linear or cyclic hydrocarbon group, the carbon Aromatic hydrocarbon group having 6 to 30, or an organic electroluminescence device according to paragraph 1, wherein the at least one selected from the representative.) An aromatic heterocyclic group having 3 to 20 carbon atoms.

5. X in the π-conjugated compound having the structure represented by the general formula (1) is the general formula (1a), (1b), (1d), (1e), (1g), (1h), (1i The organic electroluminescence device according to any one of items 1 to 4, wherein the organic electroluminescence device is an aromatic hydrocarbon group represented by (1) or (1j).

6). X in the π-conjugated compound having the structure represented by the general formula (1) is the general formula (1a), (1b), (1d), (1e), (1g), (1h), (1i ) Or (1j), wherein at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd is an electron-withdrawing group, and at least one is an electron donor 6. The group according to item 5, wherein all of R ₁ , R ₂ , Ra, Rb, Rc and Rd which are non-corresponding to the electron-withdrawing group and the electron-donating group are hydrogen atoms. Organic electroluminescence device.

7. The absolute value (ΔEst) of the energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound having the structure represented by the general formula (1) is 0.5 eV or less. The organic electroluminescent element according to any one of items 1 to 6, wherein:

8. The light emitting layer contains a π-conjugated compound having a structure represented by the general formula (1) and at least one of a fluorescent compound and a phosphorescent compound. The organic electroluminescent element according to any one of items 1 to 7.

9. Any one of Items 1 to 8, wherein the light-emitting layer contains a π-conjugated compound, at least one of a fluorescent compound and a phosphorescent compound, and a host compound. The organic electroluminescence device according to one item.

10. A luminescent thin film comprising a π-conjugated compound having a structure represented by the following general formula (1).

[In the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k), R ₁ , R ₂ , Ra, Rb, Rc and Rd each independently represents a hydrogen atom or a substituent. . p, q, r and s each independently represent an integer of 0 to 4. These substituents may be the same or different, and each substituent may be bonded to form a ring. ]
11. The absolute value (ΔEst) of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level of the π-conjugated compound having the structure represented by the general formula (1) is 0.5 eV or less. The light-emitting thin film according to item 10, wherein

12. A display device comprising the organic electroluminescence element according to any one of items 1 to 9.

13. An organic electroluminescence device according to any one of items 1 to 9 is provided.

The above-described means of the present invention can provide an organic electroluminescence device that achieves high luminous efficiency with a reduced driving voltage. In addition, a light-emitting thin film containing the conjugated compound according to the present invention, and a display device and a lighting device including the organic electroluminescence element can be provided.

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

In the conventional organic EL element, improvement of luminous efficiency has become a big issue. In the organic EL element, the voltage required for light emission varies greatly depending on the physical properties of the charge transfer thin film existing between the electrodes and the configuration of these materials. Since the organic electroluminescence element that can be driven at a low voltage has a small load when energized, it can be expected that the power consumption can be kept low and the life of the element can be improved. In addition, an improvement in luminous efficiency with respect to electric power is expected.

As a material for an organic thin film used for an organic EL element, a material having a characteristic capable of transporting carriers such as electrons and holes is required. In particular, the material used for the light-emitting layer is required to have a property of efficiently transporting both electrons and holes because the charges are recombined. Therefore, the compound preferably has bipolar properties.

The compound having an electron donating group and an electron withdrawing group in the same molecule is bipolar, which is advantageous for charge transfer in the thin film, which is preferable from the viewpoint of lowering the driving voltage. On the other hand, bipolar compounds tend to separate HOMO and LUMO, and the electronic transition between HOMO and LUMO necessary for light emission tends to be forbidden, resulting in low oscillator strength and light emission. There is a tendency to become difficult. In contrast, an aromatic hydrocarbon compound is suitable as a field for generating HOMO-LUMO overlap, and is incorporated into a compound having an electron-donating group and an electron-withdrawing group, so that high luminous efficiency and high charge transport are achieved. It is possible to achieve both performance.

On the other hand, if the π conjugate surface becomes too large, the compounds are likely to aggregate due to π stacking, which causes a decrease in luminous efficiency. Therefore, the aromatic hydrocarbon compound having an electron donating group and an electron withdrawing group preferably has a size of a π-conjugated surface of about 4 rings.

Schematic diagram showing energy diagrams of normal fluorescent compounds and TADF compounds Schematic showing energy diagram in the presence of assist dopant Schematic diagram showing the energy diagram when a π-conjugated compound functions as a host compound Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram showing an example of the structure of a display device using an active matrix method Schematic showing the pixel circuit Schematic diagram showing an example of the structure of a display device using a passive matrix method Schematic showing an example of the configuration of the lighting device Sectional drawing which shows an example of a structure of an illuminating device

The organic electroluminescence device of the present invention is an organic electroluminescence device having an organic layer group including at least one light emitting layer between an anode and a cathode, wherein at least one layer of the organic layer group is represented by the general formula (1). And a π-conjugated compound having a structure having an electron-donating group and an electron-withdrawing group in the same molecule.

This feature is common to or corresponds to the inventions according to claims 1 to 13.

In the present invention, as a more preferred embodiment, at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having a structure represented by the general formulas (1a) to (1k) is preferable. When one is an electron-withdrawing group, the electron-withdrawing group is an aromatic heterocyclic group, a sulfonyl group (—SO ₂ R ¹ ; R ¹ is an aromatic hydrocarbon group having 6 to 30 carbon atoms, or 3 carbon atoms. Represents an aromatic heterocyclic group having ˜20, sulfenyl group (—SOR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. ), A cyano group (—CN), a halogeno group, a carbonyl group (—COR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. ), Pentafluorophenyl group (—C ₆ F ₅ ), trifluoro A romethyl group (—CF ₃ ), a trifluoromethylphenyl group (—C ₆ H ₄ CF ₃ ), and a boryl group (—BR ¹ ₂ ; R ¹ is an aromatic hydrocarbon group having 6 to 30 carbon atoms, or a carbon number; 3 to 20 aromatic heterocyclic groups)), the localization of LUMO on the electron-withdrawing group is promoted, and the bipolar property of the whole compound is improved. By increasing, it is preferable from the viewpoint that the drive voltage can be further lowered and higher luminous efficiency can be obtained.

When at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron donating group, The electron-donating group is an aromatic heterocyclic group having 3 to 20 carbon atoms, an amino group (—NH ₂ ), an arylamino group (—NHR ¹ or —NR ¹ ₂ ; R ¹ is an aromatic group having 6 to 30 carbon atoms. An aromatic hydrocarbon group or an aromatic heterocyclic group having 3 to 20 carbon atoms), an alkoxy group (—OR ¹ ; R ¹ is a linear or cyclic hydrocarbon group having 1 to 10 carbon atoms), and aryloxy At least selected from a group (—OR ² ; R ² represents a linear or cyclic hydrocarbon group, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms). It is one type to localize HOMO on the electron donating group There is promoted by bipolar character of the whole compound increases, further, a driving voltage can be lowered, from the viewpoint of capable of obtaining a higher luminous efficiency.

Further, X in the π-conjugated compound having the structure represented by the general formula (1) is the general formula (1a), (1b), (1d), (1e), (1g), (1h), Since the aromatic hydrocarbon group represented by (1i) or (1j) has a small number of condensed rings or a zigzag conjugated structure, it has a structure in which a large number of rings are condensed in series. This is advantageous in that the excitation energy level is higher than that of the compound having the same. Since the proximity between the energy levels of the excited state and the ground state increases non-radiative deactivation, X in the π-conjugated compound having the structure represented by the general formula (1) is represented by the general formula (1a), ( It is an aromatic hydrocarbon group represented by 1b), (1d), (1e), (1g), (1h), (1i) or (1j) from the viewpoint of obtaining high luminous efficiency. preferable.

The absolute value (ΔEst) of the energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound having the structure represented by the general formula (1) is 0.5 eV or less. In some cases, there is a possibility of emitting thermally activated delayed fluorescence, which is preferable from the viewpoint that power efficiency can be improved by using more excitons during driving than a general fluorescent material.

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

Before going into this discussion, the light emitting method and light emitting material of the organic EL element related to the technical idea related to the present invention will be described.

<< Light emission method of organic EL >>
As organic EL light emission methods, a) “phosphorescence emission” that emits light when returning from the triplet excited state to the ground state, and b) “fluorescence emission that emits light when returning from the singlet excited state to the ground state. There are two ways.

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, 75% triplet excitons, which are normally non-radiatively deactivated, are present at a high density, thereby generating one singlet exciton from two triplet excitons. A method using a TTA mechanism for improving efficiency has been found.

Furthermore, in recent years, the discovery of Adachi et al. Has made the energy level lower due to the Joule heat during light emission and / or the ambient temperature where the light emitting element is placed by reducing the energy gap between the singlet excited state and the triplet excited state. Reverse intersystem crossing from the triplet excited state to the singlet excited state, and as a result, a phenomenon that enables fluorescence emission close to 100% (thermally excited delayed fluorescence or thermally excited delayed fluorescence, “TADF”) and that For example, Non-Patent Document 1 and the like describe a fluorescent substance that enables the above.

[Phosphorescent compound]
As described above, the luminous efficiency of phosphorescence is theoretically 4 times more advantageous than fluorescence, but energy deactivation (= phosphorescence) from triplet excited state to singlet ground state is a forbidden transition. 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 increases 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. And the price of the metal itself is a big problem for the industry.

[Fluorescent compound]
A general fluorescent compound is not necessarily a heavy metal complex like a phosphorescent compound, and is a so-called organic compound composed of a combination of general elements such as carbon, oxygen, nitrogen and hydrogen. In addition, 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, with conventional fluorescent compounds, only 25% of excitons can be applied to light emission as described above, and thus 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 above-mentioned problems of fluorescent compounds, a light emission method using delayed fluorescence has been introduced. The TTA method that originates from collisions between triplet excitons can be described by the following formula (I). That is, there is a merit that a part of triplet excitons, in which the energy of excitons has been converted only to heat due to non-radiation deactivation, can cross back to singlet excitons that can contribute to light emission. Even in an actual organic EL device, it is possible to obtain an external extraction quantum efficiency approximately twice that of a conventional fluorescent light emitting device.

Formula (I)
T ^* + T ^* → S ^* + S
In the above formula (I), 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 formula (I), only two singlet excitons S ^* that can be used for light emission are generated from two triplet excitons T ^*. Obtaining efficiency is impossible in principle.

(Thermal activated delayed fluorescence (TADF) compound)
The TADF method, which is another highly efficient fluorescent emission, is a method that can solve the above-mentioned problems of TTA.

Fluorescent compounds have the advantage of being able to design an infinite number of molecules as described above. That is, among the molecularly designed compounds, there is a compound in which the absolute value (ΔEst) of the energy level difference between the triplet excited state and the singlet excited state is extremely close (see FIG. 1A).

Such a compound has a small ΔEst even though it does not have a heavy atom in the molecule. Therefore, a reverse intersystem crossing from a triplet excited state to a singlet excited state, which cannot normally occur, 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% of fluorescence.

(Molecular design concept for ΔEst)
The molecular design for reducing the ΔEst will be described.

In order to reduce ΔEst, in principle, it is most effective to reduce the spatial overlap between the highest occupied orbital (Highest Occupied Molecular Orbital: HOMO) and the lowest empty orbital (Lowest Unoccupied Molecular Orbital: LUMO) in the molecule. Is.

In general, it is known that HOMO is distributed in electron donating sites and LUMO is distributed in electron withdrawing sites in the electron orbit of the molecule. By introducing an electron donating and electron withdrawing skeleton into the molecule, HOMO is distributed. It is possible to move away the position where LUMO exists.

For example, in Non-Patent Documents 1 to 3 described above, by introducing 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, LUMO and HOMO is localized.

It is also effective to reduce the molecular structure change 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 and introducing a condensed ring with a large π conjugate plane. To do. 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 with general 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 ΔEst. Therefore, the electronic state of the molecule is a donor / acceptor type molecule in which the HOMO site and the LUMO site are separated. It becomes a state close to the inner CT (intramolecular charge transfer state).

In such a molecule, when there are a plurality of molecules, stabilization is achieved by bringing the donor part of one molecule and the acceptor 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 between three molecules, between five molecules, etc. As a result, various stabilization states having a wide distribution Therefore, the shape of the absorption spectrum and emission spectrum is 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 causes the following 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 display applications, the color reproduction range is narrowed and the color reproducibility of pure colors is reduced. It becomes difficult.

Another problem is that the rising wavelength on the short wavelength side of the emission spectrum (hereinafter referred to as “fluorescence zero-zero band”) is shortened, that is, the S _{1 is} increased (the lowest excitation singlet energy is increased). It is to do.

Naturally, when the fluorescence zero-zero band is shortened, the phosphorescence zero-zero 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. Can be solved.

The present invention includes a π-conjugated compound (including a fluorescent compound) that suppresses the structural change of the excited state as described above and a π-conjugated compound having a short triplet excited state as design philosophy. .

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

(Electron density distribution)
In the π-conjugated compound according to the present invention, it is preferable that HOMO and LUMO are substantially separated in the molecule from the viewpoint of reducing ΔEst. The distribution states of these HOMO and LUMO can be obtained from the electron density distribution when the structure is optimized by molecular orbital calculation.

In the present invention, structure optimization and calculation of electron density distribution by molecular orbital calculation of π-conjugated compounds in the present invention are performed using molecular orbital calculation software using B3LYP as a functional and 6-31G (d) as a basis function as a calculation method. There is no particular limitation on the software, and any of them can be similarly calculated.

In the present invention, Gaussian 09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian, USA was used as molecular orbital calculation software.

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, from the above-mentioned structure optimization calculation using B3LYP as the functional and 6-31G (d) as the basis function, the time-dependent density functional method (Time-Dependent DFT) is used. It is also possible to calculate the excited state calculation to obtain S ₁ and T ₁ energies (E (S ₁ ) and E (T ₁ ), respectively) and calculate ΔEst = E (S ₁ ) −E (T ₁ ) It is. As the calculated ΔEst is smaller, HOMO and LUMO are more separated. In the present invention, ΔEst calculated using the same calculation method as described above is preferably 0.5 eV or less, more preferably 0.2 eV or less, and 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 in the present invention is defined in the present invention as calculated in the same manner as in a normal method. That is, a sample to be measured is deposited on a quartz substrate to prepare a sample, and the absorption spectrum (vertical axis: absorbance, horizontal axis: wavelength) of this sample is measured at room temperature (300 K). A tangent line is drawn with respect to the rising edge of the absorption spectrum on the long wavelength side, and is calculated from a predetermined conversion formula based on the wavelength value at the intersection of the tangent line and the horizontal axis.

Here, as the solvent to be used, a solvent that does not affect the aggregation state of the fluorescent compound, that is, a solvent having a small influence of the solvent effect, for example, a nonpolar solvent such as cyclohexane or toluene can be used.

(Minimum excited triplet energy T ₁ )
The lowest excited triplet energy (T ₁ ) of the π-conjugated compound used in the present invention was calculated from the photoluminescence (PL) characteristics of the solution or thin film. For example, as a calculation method in a thin film, after making a dispersion of a dilute π-conjugated compound into a thin film, using a streak camera, the transient PL characteristics are measured to separate the fluorescent component and the phosphorescent component, The lowest excited triplet energy can be obtained from the lowest excited singlet energy with the energy difference as ΔEst.

<< Constituent layers of organic EL elements >>
As typical element structures in the organic EL element of the present invention, the following structures can be exemplified, but the invention is not limited thereto.
(1) Anode / light emitting layer // cathode (2) Anode / light emitting layer / electron transport layer / cathode (3) Anode / hole transport layer / light emitting layer / cathode (4) Anode / hole transport layer / light emitting layer / Electron transport layer / cathode (5) anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (6) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode (7) Anode / hole injection layer / hole transport layer / (electron blocking layer /) light emitting layer / (hole blocking layer /) electron transport layer / electron injection layer / cathode Among the above, the configuration of (7) is Although used preferably, it is not limited to this.

The light emitting layer used in the present invention is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the light emitting layers.

If necessary, a hole blocking layer (also referred to as a hole blocking layer) or an electron injection layer (also referred to as a cathode buffer layer) may be provided between the light emitting layer and the cathode. An electron blocking layer (also referred to as an electron barrier layer) or a hole injection layer (also referred to as an anode buffer layer) may be provided therebetween.

The electron transport layer used in the present invention is a layer having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. Moreover, you may be comprised by multiple layers.

The hole transport layer used in the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. Moreover, you may be comprised by multiple layers.

In the above-described typical element configuration, the constituent layers excluding the anode and the cathode are also referred to as “organic layer group”.

(Tandem structure)
The organic EL element of the present invention may be a so-called tandem element in which a plurality of light emitting units including at least one light emitting layer are stacked.

As typical element configurations of the tandem structure, for example, the following configurations can be given.

Anode / first light emitting unit / intermediate layer / second light emitting unit / intermediate layer / third light emitting unit / cathode Here, the first light emitting unit, the second light emitting unit and the third light emitting unit are all the same, May be different. Two light emitting units may be the same, and the remaining one may be different.

The plurality of light emitting units constituting the tandem structure may be directly stacked or may be stacked via the intermediate layer as described above. The intermediate layer is generally called an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, or an intermediate insulating layer. It has electrons in the adjacent layer on the anode side and holes in the adjacent layer on the cathode side. Any layer having a function of supplying can be formed using a known material.

Examples of materials used for forming the intermediate layer include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiOx, VOx, CuI, InN, GaN, Conductive inorganic compound layers such as CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ and Al, two-layer films such as Au / Bi ₂ O ₃ , SnO ₂ / Ag / SnO ₂ , ZnO / Multi-layer film such as Ag / ZnO, Bi ₂ O ₃ / Au / Bi ₂ O ₃ , TiO ₂ / TiN / TiO ₂ , TiO ₂ / ZrN / TiO ₂ , fullerenes such as C ₆₀ , conductivity such as oligothiophene Examples include organic layers, conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, and metal-free porphyrins. However, the present invention is not limited to these.

Preferred examples of the configuration within the light emitting unit include, for example, the configurations of (1) to (7) exemplified as the typical element configurations described above except that the anode and the cathode are excluded. It is not limited.

Specific examples of the tandem organic EL element include, for example, US Pat. No. 6,337,492, US Pat. No. 7,420,203, US Pat. No. 7,473,923, US Pat. No. 6,872,472, US Pat. No. 6,107,734. Specification, U.S. Pat. No. 6,337,492, International Publication No. 2005/009087, JP-A-2006-228712, JP-A-2006-24791, JP-A-2006-49393, JP-A-2006-49394 JP-A-2006-49396, JP-A-2011-96679, JP-A-2005-340187, JP-A-4711424, JP-A-3496868, JP-A-3848564, JP-A-4421169, No. 2010-192719, Special Elements described in JP2009-076929, JP2008-078414, JP2007-059848, JP2003-272860, JP2003-045676, International Publication No. 2005/094130, etc. Although a structure, a constituent material, etc. are mentioned, this invention is not limited to these.

Hereinafter, details of each constituent layer of the organic EL element of the present invention will be described.

<Light emitting layer>
The light-emitting layer used in the present invention is a layer that provides a field in which electrons and holes injected from an electrode or an adjacent layer are recombined to emit light via excitons, and the light-emitting portion is the light-emitting layer. Even in the layer, it may be the interface between the light emitting layer and the adjacent layer. If the light emitting layer used for this invention satisfy | fills the requirements prescribed | regulated by this invention, there will be no restriction | limiting in particular in the structure.

The total thickness of the light emitting layer is not particularly limited, but it prevents the homogeneity 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. In view of the above, it is preferable to adjust within the range of 2 nm to 5 μm, more preferably within the range of 2 to 500 nm, and even more preferably within the range of 5 to 200 nm.

Further, the thickness of each light emitting layer used in the present invention is preferably adjusted in the range of 2 nm to 1 μm, more preferably adjusted in the range of 2 to 200 nm, and further preferably 3 to 150 nm. Adjusted within range.

The light-emitting layer used in the present invention contains a light-emitting dopant (a light-emitting compound, a light-emitting dopant compound, a dopant compound, also simply referred to as a dopant), and further, the above-described host compound (matrix material, light-emitting host compound, simply host). It is also preferable to contain.

(1) Luminescent dopant As the luminescent dopant, a fluorescent luminescent dopant (also referred to as a fluorescent luminescent compound, a fluorescent dopant, or a fluorescent compound) and a phosphorescent dopant (phosphorescent compound, phosphorescent dopant, phosphorescence). It is also referred to as a functional compound). In the present invention, at least one light emitting layer contains a fluorescent compound described later and a π-conjugated compound functioning as a light emission auxiliary agent (assist dopant).

In the present invention, the light emitting layer preferably contains a fluorescent compound within the range of 5 to 40% by mass, particularly within the range of 10 to 30% by mass.

The concentration of the fluorescent compound in the light emitting layer can be arbitrarily determined based on the fluorescent compound having a specific structure to be used and the requirements of the device, and is uniform in the thickness direction of the light emitting layer. It may be contained in a concentration, or may have a concentration distribution in an arbitrary pattern.

In recent years, luminescent dopants using delayed fluorescence have been developed, and these may be used. Specific examples of the luminescent dopant using delayed fluorescence include, for example, compounds described in International Publication No. 2011/156793, Japanese Patent Application Laid-Open No. 2011-213643, Japanese Patent Application Laid-Open No. 2010-93181, and the like. Is not limited to these.

In addition, the fluorescent compounds used in the present invention may be used in combination of two or more types, and combinations of fluorescent compounds having different structures or combinations of fluorescent compounds and phosphorescent compounds. Also good. Thereby, arbitrary luminescent colors can be obtained.

Furthermore, the π-conjugated compound according to the present invention can be used for assisting light emission of different fluorescent compounds or phosphorescent compounds. In that case, the light emitting layer contains a host having a mass ratio of 100% or more with respect to the π-conjugated compound according to the present invention, and 0.1 to 0.1 mass ratio with respect to the π-conjugated compound according to the present invention. It is preferable that different fluorescent substances or phosphorescent compounds exist within a range of 50%.

When the π-conjugated compound according to the present invention is used for assisting light emission of different fluorescent compounds or phosphorescent compounds, the substance contained in the light-emitting layer includes three or more components including the host compound. It is preferable.

Specifically, in the light-emitting layer, a π-conjugated compound, preferably a π-conjugated compound having an absolute value (ΔEst) of a difference between the lowest excited singlet energy level and the lowest excited triplet energy level of 0.5 eV or less. It is also suitable from a viewpoint of high luminous efficiency expression to contain a system compound and at least 1 sort (s) of a fluorescent compound and a phosphorescent compound. More preferably, the light emitting layer further contains a host compound.

The number of each component contained in the light-emitting layer of the π-conjugated compound, the luminescent compound, and the host compound is not limited, but it is more preferable that at least one of the three components is contained.

The light emitting layer has a difference in absolute value between the lowest excited singlet energy level and the lowest excited triplet energy level (ΔEst) of 0.5 eV or less, the π-conjugated compound according to the present invention, a luminescent compound, When the host compound is contained, the π-conjugated compound according to the present invention acts as an assist dopant. On the other hand, when the light emitting layer contains the π-conjugated compound and the luminescent compound according to the present invention and does not contain the host compound, the π-conjugated compound according to the present invention acts as a host compound.

The mechanism for producing the effect is the same in any case, and triplet excitons generated on the π-conjugated compound according to 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 according to the present invention can be transferred to the luminescent compound, and high luminous efficiency can be realized.

Therefore, when the light emitting layer contains the three components of the π-conjugated compound, the luminescent compound, and the host compound according to the present invention, the energy levels of S ₁ and T ₁ of the π-conjugated compound are S of the host compound. ₁ and T ₁ of the lower than the energy level, it is preferably higher than the energy level of the S ₁ and T ₁ of the light-emitting compound.

Similarly, light emitting layer, the energy level of the S ₁ and T ₁ of the case containing the two components of the light emitting compound and [pi conjugated compound according to the present invention, [pi-conjugated compounds, S ₁ luminescent compound higher than the energy level of T ₁ and is preferable.

FIG. 1B and FIG. 1C are schematic views when the π-conjugated compound of the present invention acts as an assist dopant and a host compound, respectively. 1B and 1C are examples, and the generation process of the triplet exciton generated on the π-conjugated compound according to the present invention is not limited to the electric field excitation, and energy from the light emitting layer or the peripheral layer interface. Movement, electronic movement, etc. are also included.

Further, in FIGS. 1B and 1C, a fluorescent compound is used as a light-emitting material, but the present invention is not limited thereto, and a phosphorescent compound may be used, or a fluorescent compound and a phosphorescent compound are used. Both of these may be used.

When the π-conjugated compound according to the present invention is used as an assist dopant, the light-emitting layer contains 100% or more of the host compound by mass ratio with respect to the π-conjugated compound, and the fluorescent compound or phosphorescent compound is It is preferably contained within a range of 0.1 to 50% by mass ratio with respect to the π-conjugated compound.

When the π-conjugated compound according to the present invention is used as a host compound, the light-emitting layer has a mass ratio of 0.1 to 50% with respect to the π-conjugated compound. It is preferable to contain within.

When the π-conjugated compound according to the present invention is used as an assist dopant or a host compound, the emission spectrum of the π-conjugated compound according to the present invention and the absorption spectrum of the luminescent compound preferably overlap.

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 a luminance meter CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.

In the present invention, it is also one of preferred embodiments that the light emitting layer of one layer or plural layers contains a plurality of light emitting dopants having different light emission colors and exhibits white light emission.

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 In the organic EL device of the present invention, at least one layer of the organic layer group contains a π-conjugated compound having a structure represented by the following general formula (1). Furthermore, the absolute value (ΔEst) of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level of the π-conjugated compound is preferably 0.5 eV or less.

The π-conjugated compound having the structure represented by the general formula (1) according to the present invention converts a triplet exciton generated on the π-conjugated compound into a singlet exciton by reverse intersystem crossing (RISC). In addition, it is a compound that has the function of increasing the luminous efficiency as an assist dopant for improving the luminous efficiency by not deactivating, and the function of improving the luminous efficiency as a fluorescent compound having a TADF property. Useful as a material.

Specifically, the luminous efficiency can be improved by including a π-conjugated compound as an assist dopant or a host compound together with a light-emitting compound in the light-emitting layer of the organic EL element.

Hereinafter, the details of the π-conjugated compound having the structure represented by the general formula (1) will be described.

In the general formula (1), A represents an electron withdrawing group, and D represents an electron donating group. m and n are each independently an integer of 1 or 2.

X represents an aromatic hydrocarbon group selected from structures represented by the following general formulas (1a) to (1k).

In the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k), R ₁ , R ₂ , Ra, Rb, Rc and Rd each independently represent a hydrogen atom or a substituent. p, q, r and s each independently represent an integer of 0 to 4. These substituents may be the same or different, and each substituent may be bonded to form a ring.

When at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron withdrawing group, The electron-withdrawing group is an aromatic heterocyclic group, a sulfonyl group (—SO ₂ R ¹ ; R ¹ is an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. ), A sulfenyl group (—SOR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms or an aromatic heterocyclic group having 3 to 20 carbon atoms), a cyano group (—CN) A halogeno group, a carbonyl group (—COR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a pentafluorophenyl group (—C ₆ F _5), trifluoromethyl group _(-CF 3), trifluoroacetic Butylphenyl group _{_{_{(-C 6 H 4 CF 3)}}} , and boryl group ^_(-BR ¹ 2; ^R 1 represents an aromatic heterocyclic group of aromatic hydrocarbon group having 6 to 30 carbon atoms, or 3 to 20 carbon atoms It is a preferred embodiment that it is at least one kind selected from.

When at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron donating group, The electron-donating group is an aromatic heterocyclic group having 3 to 20 carbon atoms, an amino group (—NH ₂ ), an arylamino group (—NHR ¹ or —NR ¹ ₂ ; R ¹ is an aromatic group having 6 to 30 carbon atoms. An aromatic hydrocarbon group or an aromatic heterocyclic group having 3 to 20 carbon atoms), an alkoxy group (—OR ¹ ; R ¹ is a linear or cyclic hydrocarbon group having 1 to 10 carbon atoms), and aryloxy At least selected from a group (—OR ² ; R ² represents a linear or cyclic hydrocarbon group, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms). One type is a preferred embodiment.

Furthermore, when at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron-withdrawing group The electron-withdrawing group is an aromatic heterocyclic group, a sulfonyl group (—SO ₂ R ¹ ; R ¹ is an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. ), A sulfenyl group (—SOR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a cyano group (—CN ), A halogeno group, a carbonyl group (—COR ¹ ; R ¹ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a pentafluorophenyl group (— C ₆ F _5), trifluoromethyl group _(-CF 3), trifluoperazine Methylphenyl group _{_{_{(-C 6 H 4 CF 3)}}} , and boryl group ^_(-BR ¹ 2; ^R 1 is an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms It is at least one kind selected from. When at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd in the general formulas (1a) to (1k) is an electron donating group, the electron donating group has 3 to 3 carbon atoms. 20 aromatic heterocyclic group, amino group (—NH ₂ ), arylamino group (—NHR ¹ or —NR ¹ ₂ ; R ¹ is an aromatic hydrocarbon group having 6 to 30 carbon atoms, or 3 to 20 carbon atoms Represents an aromatic heterocyclic group), an alkoxy group (—OR ¹ ; R ¹ is a straight or cyclic hydrocarbon group having 1 to 10 carbon atoms), and an aryloxy group (—OR ² ; R ² is a straight chain) Or a cyclic hydrocarbon group, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms). is there.

Further, X in the π-conjugated compound having the structure represented by the general formula (1) is the general formula (1a), (1b), (1d), (1e), (1g), (1h), A preferred embodiment is an aromatic hydrocarbon group represented by (1i) or (1j).

Furthermore, X in the π-conjugated compound having the structure represented by the general formula (1) is the general formula (1a), (1b), (1d), (1e), (1g), (1h) , (1i) or (1j), wherein at least one of R ₁ , R ₂ , Ra, Rb, Rc and Rd is an electron-withdrawing group, and at least 1 One is an electron donating group, and it is a preferred embodiment that all of R ₁ , R ₂ , Ra, Rb, Rc and Rd not corresponding to the electron withdrawing group and the electron donating group are hydrogen atoms.

In the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k), when R ₁ , R ₂ , R _a , R _b , R _c , and R _d represent a substituent, Examples of the substituent include alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc. ), A cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), an alkenyl group (eg, vinyl group, allyl group, etc.), an alkynyl group (eg, ethynyl group, propargyl group, etc.), an aromatic hydrocarbon group (aromatic Also referred to as hydrocarbon ring group, aromatic carbocyclic group, aryl group, etc., for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xyl group Group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group (for example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl) Group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1,2,4-triazol-1-yl group, 1,2,3-triazol-1-yl group, etc.), oxazolyl group, Benzoxazolyl, thiazolyl, isoxazolyl, isothiazolyl, furazanyl, thienyl, quinolyl, benzofuryl, dibenzofuryl, benzothienyl, dibenzothienyl, indolyl, carbazolyl, carbolinyl, diaza Carbazolyl group (Carborini 1), a quinoxalinyl group, a pyridazinyl group, a triazinyl group, a quinazolinyl group, a phthalazinyl group, etc.), a heterocyclic group (for example, a pyrrolidyl group, an imidazolidyl group) Group, morpholyl group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyl) Oxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc. , Cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group) Octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (eg, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group) Butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylamino Sulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, 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), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbo group) Nylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group) Dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2- Pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexyl) Raid group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexyl) Sulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group) , Dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (for example, phenylsulfonyl group, naphthylsulfonyl group, 2- Lysylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, diphenylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group) , 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, etc.), fluorinated hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group) Etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), phosphono group and the like. Preferably, an alkyl group, an aromatic hydrocarbon group, an aromatic heterocyclic group, an alkoxy group, an amino group, and a cyano group are exemplified.

Furthermore, indole ring, indazole ring, benzothiazole ring, benzoxazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, isoindole ring, naphthyridine ring, phthalazine ring, carbazole ring, carboline ring, diaza Such as carbazole ring (in which one of carbon atoms constituting carboline ring is replaced by nitrogen atom), acridine ring, acridan ring, phenanthridine ring, phenanthroline ring, phenazine ring, azadibenzofuran ring, azadibenzothiophene ring, etc. Substituents can also be suitably used. These substituents can also be suitably used as electron withdrawing groups.

Further, these substituents may be further substituted with the above substituents. Further, these substituents may be bonded together to form a ring.

In the present invention, the absolute value (ΔEst) of the energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound having the structure represented by the general formula (1) according to the present invention is , 0.5 eV or less is preferable.

Hereinafter, specific examples of the π-conjugated compound having a structure represented by the general formula (1) preferably used in the present invention are exemplified, but the present invention is not limited thereto.

Examples of the π-conjugated compound having the structure represented by the general formula (1) according to the present invention are described in JP-A No. 2004-103576, US Pat. No. 8,865,543, International Publication No. 2013/133359, and the like. Or a method described in a reference document described in these patent documents.

(1.2) Phosphorescent dopant The phosphorescent dopant used in the present invention will be described.

The phosphorescent dopant used in the present invention is a compound in which light emission from an excited triplet is observed, specifically, a compound that emits phosphorescence at room temperature (25 ° C.), and a phosphorescence quantum yield. Is defined as a compound of 0.01 or more at 25 ° C., but a preferable phosphorescence quantum yield is 0.1 or more.

The phosphorescent quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of the Fourth Edition Experimental Chemistry Course 7. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant used in the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. Just do it.

The phosphorescent dopant can be appropriately selected from known materials used for the light emitting layer of the organic EL element. Specific examples of known phosphorescent dopants that can be used in the present invention include compounds described in the following documents.

Nature 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17, 1059 (2005), International Publication No. 2009/100991, International Publication No. 2008/101842, International Publication No. 2003/040257, US Patent Application Publication No. 2006/835469, US Patent Application Publication No. 2006 /. No. 0202194, U.S. Patent Application Publication No. 2007/0087321, U.S. Patent Application Publication No. 2005/0244673, Inorg. Chem. 40, 1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chem. lnt. Ed. 2006, 45, 7800, Appl. Phys. Lett. 86, 153505 (2005), Chem. Lett. 34, 592 (2005), Chem. Commun. 2906 (2005), Inorg. Chem. 42, 1248 (2003), International Publication No. 2009/050290, International Publication No. 2002/015645, International Publication No. 2009/000673, US Patent Application Publication No. 2002/0034656, and US Pat. No. 7,332,232. 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. US Patent Application Publication No. 2006/0008670, US Patent Application Publication No. 2009/0165846, US Patent Application Publication No. 2008/0015355, US Pat. No. 7,250,226, US Pat. No. 7,396,598 Statement, rice Patent Application Publication No. 2006/0263635, U.S. Patent Application Publication No. 2003/0138657, U.S. Patent Application Publication No. 2003/0152802, U.S. Pat. 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. Specification, 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 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 Public Publication No. 2010/032663, International Publication No. 2008140115, International Publication No. 2007/052431, International Publication No. 2011/134013, International Publication No. 2011/157339, International Publication No. 2010/086089, International Publication No. 2009 / No. 113646, International Publication No. 2012/020327, International Publication No. 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149, US Patent Application Publication No. 2012/228583, US Patent Application JP 2012/212126, JP 2012-069737, JP 2012-195554, JP 2009-114086, JP 2003-81988, JP 2002-302671, No. 2002-363552.

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

(1.3) Fluorescent compound The fluorescent compound that can be used in combination with the π-conjugated compound according to the present invention will be described.

The fluorescent compound that can be used in combination with the π-conjugated compound according to the present invention is not particularly limited. For example, a fluorescent compound having a ΔEst of greater than 0.5 eV can be suitably used. In addition, an anthracene derivative, 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, Squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes, polythiophene dyes, rare earth complex phosphors, and laser dyes A compound with a high fluorescence quantum yield is mentioned.

(2) Host compound The light emitting layer preferably contains a π-conjugated compound according to the present invention, at least one of a fluorescent compound and a phosphorescent compound, and a 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.

The host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient.

Hereinafter, host compounds preferably used in the present invention will be described.

The host compound used with the fluorescent compound used in the present invention is not particularly limited, but has an excitation energy larger than the excitation singlet energy of the fluorescent compound according to the present invention from the viewpoint of reverse energy transfer. Further preferred are those having an excitation triplet energy greater than the excitation triplet energy of the fluorescent compound according to the present invention.

When a known host compound is used for the organic EL device of the present invention, specific examples thereof include compounds described in the following documents, but the present invention is not limited thereto.

For example, Japanese Patent Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860 Gazette, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579 No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453. Gazette, 2003-3165 gazette, 2002-234888 gazette, 2003-27048 gazette, 2002-255934 gazette, 2002-260861 gazette, 2002-280183 gazette, 2002-299060 gazette. No. 2002-302516, No. 2002-305083, No. 2002-305084, No. 2002-308837, No. 2003/0175553, No. 2006/0280965. US Patent Application Publication No. 2005/0112407, US Patent Application Publication No. 2009/0017330, US Patent Application Publication No. 2009/0030202, US Patent Application Publication No. 2005/0238919 , International Publication No. 2001/039234, International Publication No. 2009/021126, International Publication No. 2008/056746, International Publication No. 2004/093207, International Publication No. 2005/089025, International Publication No. 2007/063796, International Publication No. 2007/063754, International Publication No. 2004/107822, International Publication No. 2005/030900, International Publication No. 2006/114966, International Publication No. 2009/086028, International Publication No. 2009/003898, International Publication No. 2012 No. 02/03947, JP 2008-074939 A, JP 2007-254297 A, European Patent No. 2034538, International Publication No. 2011/055933, International Publication No. 2012/035853, and the like.

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 cation radical state, anion radical state, and excited state, and does not cause chemical changes such as decomposition and addition reaction. It is preferable not to move at the angstrom level.

In particular, when the light-emitting dopant used in combination exhibits TADF light emission, since the existence time of the triplet excited state of the TADF compound is long, the T ₁ energy of the host compound itself is high, and the host compounds are associated with each other. in prevention of generation of a low T ₁ state, that the TADF compound and the host compound does not form a exciplex, such that the host compound does not form a electro-mer by the electric field, the host compound is a molecular structure such as not to lower T ₁ of Appropriate design is required.

In order to 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 satisfying such requirements include a carbazole skeleton, an azacarbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an azadibenzofuran skeleton, which have high T ₁ energy and an extended π conjugate of a 14π electron system. Those having a skeleton as a partial structure are preferred. 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 structure or a 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 represented by the following general formula (I) is also preferable. This is because the compound represented by the following general formula (I) has a condensed ring structure, and therefore a π electron cloud spreads, the carrier transportability is high, and the glass transition temperature (Tg) is high. Further, generally, the condensed aromatic ring tends to have a small triplet energy (T ₁ ), but the compound represented by the general formula (I) has a high T ₁ and has a short emission wavelength (that is, T _1). and larger S ₁₎ it can be suitably used also for the light emitting material.

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 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 represents an 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 hydrogen or a substituent, and the substituent referred to 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 synthetic scheme, the compound having the effect of the present invention is defined as being included in the present invention.

Examples of the substituent represented by each of R ₁₀₁ to R ₁₀₄ include linear or branched alkyl groups (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 referred to as 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 Sulfonyl 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 (eg, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.) ), Alkylsulfonyl groups (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group) , Dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (eg, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (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 etc.), 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.

As y ₁ to y ₈ in the general formula (I), preferably at least three of y ₁ to y ₄ or at least three of y ₅ to y ₈ are 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, for the purpose that the host compound preferably has a rigid structure, 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 the substituents represented by R ₁₀₁ to R ₁₀₄ described above.

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 R ₁₀₁ to R ₁₀₄ described above. Examples include the same ring as the group.

In the partial structure represented by the general formula (I), examples of the aromatic heterocycle represented by Ar ₁₀₁ and Ar ₁₀₂ include the substituents represented by R ₁₀₁ to R ₁₀₄ described above. The same ring as an aromatic heterocyclic group is mentioned.

Considering the purpose that the host compound represented by the general formula (I) has a large T ₁ , it is preferable that the aromatic ring itself represented by Ar ₁₀₁ and Ar ₁₀₂ has a high T ₁ , for example, Benzene ring (including polyphenylene skeletons with multiple benzene rings linked (biphenyl, terphenyl, quarterphenyl, etc.)), fluorene ring, triphenylene ring, carbazole ring, azacarbazole ring, dibenzofuran ring, azadibenzofuran ring, dibenzothiophene ring, dibenzo A thiophene ring, pyridine ring, pyrazine ring, indoloindole ring, indole ring, benzofuran ring, benzothiophene ring, imidazole ring or triazine ring is preferred. 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 represented by the general formula (I), each of the aromatic rings represented by Ar ₁₀₁ and Ar ₁₀₂ is preferably a condensed ring having three or more rings. .

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, an acridan ring, a benzoquinoline ring, a carbazole ring, a carboline ring, a phenazine ring, a phenanthridine ring, a phenanthroline ring, a carboline ring, Cyclazine ring, quindrine 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) Phenanthroline ring, dibenzofuran ring, dibenzothiophene ring, naphthofuran ring, naphthothiophene ring, benzodifuran ring, benzodithiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, ant Difuran ring, anthracite 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 represented by the general formula (I) is small, low Tg only be _achieved, if _{R 101} is a hydrogen atom N101 represents an integer of 1 to 4.

As the host compound used in the present invention, the carbazole derivative is preferably a compound having a structure represented by the general formula (II). This is because such a compound tends to have particularly excellent carrier transportability.

In formula _{_{_{(II), X 101, Ar}}} 101, Ar 102, n102 have the same meanings as _{_{_{X 101, Ar 101, Ar 102}}} , n102 in each of the general 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 inhibited. .

Furthermore, the compound represented by the general formula (II) is preferably represented by the following general formula (III-1), (III-2) or (III-3).

In the general formula (III-1) ~ (III -3), X 101, Ar 102, n102 is the same meaning as _X _101, Ar 102, n102 in the general formula (II). In the general formula _{(III-2), R 104} has the same meaning as _{R 104} in 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.

In the following, examples of host compounds that can be used in the present invention include compounds represented by general formulas (I), (II), (III-1) to (III-3), and other compounds composed of other structures. However, it is not limited to these.

The preferred host compound used in the present invention may be a low molecular compound having a molecular weight capable of sublimation purification or a polymer having a repeating unit.

In the case of a low-molecular compound, sublimation purification is possible, so that there is an advantage that purification is easy and it is easy to obtain a high purity material. 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 formulas (I), (II), (III-1) to (III- What has the structure of 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 10 or more repeating units 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 determined by a method based on JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

《Electron transport layer》
The electron transport layer in the present invention 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.

The total thickness of the electron transport layer according to the present invention is not particularly limited, but is usually in the range of 2 nm to 5 μm, more preferably in the range of 2 to 500 nm, and still more preferably in the range of 5 to 200 nm. Is within.

Further, in the organic EL element, when the light generated in the light emitting layer is extracted from the electrode, the light extracted directly from the light emitting layer interferes with the light extracted after being reflected by the electrode from which the light is extracted and the electrode located at the counter electrode. It is known to wake up. When light is reflected by the cathode, this interference effect can be efficiently utilized by appropriately adjusting the total thickness of the electron transport layer between several nanometers and several micrometers.

On the other hand, when the layer thickness of the electron transport layer is increased, the voltage is likely to increase. Therefore, particularly when the layer thickness is large, the electron mobility of the electron transport layer is preferably 10 ⁻⁵ cm ² / Vs or more. .

The material used for the electron transport layer (hereinafter referred to as an electron transport material) may be any of electron injecting or transporting properties and hole blocking properties, and can be selected from conventionally known compounds. Can be selected and used.

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

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

In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. In addition, the distyrylpyrazine derivative exemplified as the material for the light emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer. Can also be used as an electron transporting material.

Also, a polymer material in which these materials are introduced into a polymer chain or these materials as a polymer main chain can 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. JP 2011/086935, WO 2010/150593, WO 2010/047707, EP 2311826, JP 2010-251675, JP 2009-209133, JP 2009-124114, JP-A-2008-277810, JP-A-2006-156445, JP-A-2005-340122, JP-A-2003-45662, JP-A-2003-31367, JP-A-2003-282270, International Publication No. 2012/115034 or 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 a function of an electron transport layer in a broad sense, and preferably made of a material having a function of transporting electrons and a small ability to transport holes, while transporting electrons. By blocking holes, the recombination probability of electrons and holes can be improved.

Moreover, the structure of the electron transport layer described above can be used as a hole blocking layer according to the present invention, if necessary.

In the organic EL device of the present invention, the hole blocking layer is preferably provided adjacent to the cathode side of the light emitting layer.

The layer thickness of the hole blocking layer according to the present invention is preferably in the range of 3 to 100 nm, and more preferably in the range of 5 to 30 nm.

As the material used for the hole blocking layer, the same materials as those used for the electron transport layer are preferably used, and the materials used as the host compound are also preferably used for the hole blocking layer.

《Electron injection layer》
The electron injection layer (hereinafter also referred to as “cathode buffer layer”) according to the present invention is a layer provided between a cathode and a light emitting layer for lowering driving voltage and improving light emission luminance. It is described in detail in the second chapter, Chapter 2, “Electrode Materials” (pages 123 to 166) of “Elements and the Forefront of Industrialization (issued by NTT Corporation on November 30, 1998)”.

In the present invention, the electron injection layer may be provided as necessary and may exist 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 although depending on the material, the layer thickness is preferably in the range of 0.1 to 5 nm. Moreover, the nonuniform layer (film | membrane) in which a constituent material exists intermittently may be sufficient.

Details of the electron injection layer are also described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specific examples of materials preferably used for the electron injection layer are as follows. , Metals typified by strontium and aluminum, alkali metal compounds typified by lithium fluoride, sodium fluoride, potassium fluoride, etc., alkaline earth metal compounds typified by magnesium fluoride, calcium fluoride, etc., oxidation Metal oxides typified by aluminum, metal complexes typified by lithium 8-hydroxyquinolinate (abbreviation: Liq), and the like can be given. Further, the above-described electron transport material can also be used.

Moreover, the materials used for the electron injection layer may be used alone or in combination of two or more.

《Hole transport layer》
In the present invention, the hole transport layer is made of a material having a function of transporting holes and may have a function of transmitting holes injected from the anode to the light emitting layer.

The total thickness of the hole transport layer according to the present invention is not particularly limited, but is usually in the range of 5 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. Within range.

As a material used for the hole transport layer (hereinafter referred to as a hole transport material), any material that has either a hole injection property or a transport property or an electron barrier property may be used. Any one can be selected and used.

For example, porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives , Indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, and polyvinyl carbazole, polymer materials or oligomers with aromatic amines introduced into the main chain or side chain, polysilane, conductive Polymer or oligomer (for example, PEDOT / PSS, aniline copolymer, polyaniline, polythiophene, etc.)

Examples of triarylamine derivatives include benzidine type typified by α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), starburst type typified by MTDATA, Examples include compounds having fluorene or anthracene in the triarylamine-linked core.

In addition, hexaazatriphenylene derivatives such as those described in JP-T-2003-519432 and JP-A-2006-135145 can also be used as a hole transport material.

Further, a hole transport layer having a high p property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

JP-A-11-251067, J. Org. Huang et. al. It is also possible to use so-called p-type hole transport materials and inorganic compounds such as p-type-Si and p-type-SiC, as described in the literature (Applied Physics Letters 80 (2002), p. 139). Further, ortho-metalated organometallic complexes having Ir or Pt as the central metal as typified by Ir (ppy) ₃ are also preferably used.

Although the above-mentioned materials can be used as the hole transport material, a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organometallic complex, or an aromatic amine is introduced into the main chain or side chain. The polymer materials or oligomers used are preferably used.

Specific examples of known preferred hole transport materials used in the organic EL device of the present invention include the compounds described in the following documents in addition to the documents listed above, but the present invention is not limited thereto. Not.

For example, Appl. Phys. Lett. 69, 2160 (1996), J. 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. , JP 2006- 35145 JP is US Patent Application No. 13/585981 Pat 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 above-described configuration of the hole transport layer can be used as an electron blocking layer according to the present invention, if necessary.

The electron blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the anode side of the light emitting layer.

The layer thickness of the electron blocking layer according to the present invention is preferably in the range of 3 to 100 nm, and 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”) according to the present invention is a layer provided between the anode and the light emitting layer for the purpose of lowering the driving voltage and improving the light emission luminance. It is described in detail in Volume 2, Chapter 2, “Electrode Materials” (pages 123 to 166) of “The Forefront of Industrialization (issued by NTT Corporation on November 30, 1998)”.

In the present invention, the hole injection layer may be provided as necessary, and may be present between the anode and the light emitting layer or between the anode and the hole transport layer as described above.

The details of the hole injection layer are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069, etc. Examples of materials used for the hole injection layer include: And the same compounds as those used for the hole transport layer described above.

Among them, phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives, metal oxides typified by vanadium oxide, amorphous carbon as described in JP-T-2003-519432, JP-A-2006-135145, etc. Preferred are conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometalated complexes represented by tris (2-phenylpyridine) iridium complex, and triarylamine derivatives.

The materials used for the hole injection layer described above may be used alone or in combination of two or more.

"Additive"
The organic layer group in the present invention described above may further contain other additives.

Examples of additives 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.

The content of the additive can be arbitrarily determined, but is preferably 1000 ppm or less, more preferably 500 ppm or less, and further preferably 50 ppm or less with respect to the total mass% of the contained layer. .

However, it is not within this range depending on the purpose of improving the transportability of electrons and holes and the purpose of favoring the exciton energy transfer.

<Method for forming organic layer group>
A method for forming the organic layer group (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 formation method of the organic layer group according to the present invention is not particularly limited, and a conventionally known formation method such as a vacuum deposition method or a wet method (also referred to as a wet process) can be used.

Examples of the wet method include spin coating method, casting method, ink jet method, printing method, die coating method, blade coating method, roll coating method, spray coating method, curtain coating method, and LB method (Langmuir-Blodgett method). From the viewpoint of obtaining a homogeneous thin film easily and high productivity, a method with high roll-to-roll method suitability such as a die coating method, a roll coating method, an ink jet method and a spray coating method is preferable.

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

Further, as a dispersion method, the dispersion can be performed by a method such as ultrasonic dispersion, high shearing force dispersion or media dispersion.

Further, different film forming methods may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, etc., but generally the boat heating temperature is in the range of 50 to 450 ° C., and the degree of vacuum is in the range of 10 ⁻⁶ to 10 ⁻² Pa. It is formed by appropriately selecting a deposition rate within a range of 0.01 to 50 nm / second, a substrate temperature within a range of −50 to 300 ° C., and a layer (film) thickness within a range of 0.1 nm to 5 μm, preferably 5 to 200 nm. It is desirable to do.

The formation of the organic layer group according to the present invention is preferably a method of consistently forming from the hole injection layer to the cathode by a single evacuation, but a different film formation method may be applied by taking it out halfway. At that time, the operation is preferably performed in a dry inert gas atmosphere.

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

For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material.

Alternatively, when a material that can be applied, such as an organic conductive compound, is used, a wet film forming method such as a printing method or a coating method can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less.

The film thickness of the anode is usually selected within the range of 10 nm to 1 μm, preferably 10 to 200 nm, although it depends on the applied material.

"cathode"
As the cathode, a material having a work function (4 eV or less) metal (hereinafter 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 from 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, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

In order to transmit the emitted light, it is convenient that either one of the anode or the cathode of the organic EL element is transparent or translucent because the emission luminance is improved.

In addition, a transparent or translucent cathode can be produced by producing a conductive transparent material mentioned in the description of the anode on the cathode after producing the above metal with a thickness of 1 to 20 nm. By applying the above, it is possible to manufacture a device in which both the anode and the cathode are transparent.

《Support substrate》
The support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention is not particularly limited in the type of glass, plastic, etc., and is transparent. Or opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element.

Examples of the resin film include polyesters such as polyethylene terephthalate (abbreviation: PET), polyethylene naphthalate (abbreviation: PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (abbreviation: TAC), cellulose acetate butyrate, Cellulose acetates such as cellulose acetate propionate (abbreviation: CAP), cellulose acetate phthalate, cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, poly Methylpentene, polyetherketone, polyimide, polyethersulfone (abbreviation: PES), polypheny Sulfide, polysulfones, polyether imide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylic or polyarylate, arton (trade name, manufactured by JSR) or appel (trade name, manufactured by Mitsui Chemicals) And the like.

An inorganic or organic film or a hybrid film of both may be formed on the surface of the resin film. 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, and further, oxygen permeability measured by a method according to JIS K 7126-1987. However, it is preferably a high-barrier film having 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.

The material for forming the barrier film may be any material that has a function of suppressing the entry of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, and the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer group, It is preferable to laminate | stack both alternately several times.

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

Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films, opaque resin substrates, ceramic substrates, and the like.

The external extraction quantum efficiency of the organic EL device of the present invention at room temperature (25 ° C.) is preferably 1% or more, and more preferably 5% or more.

Here, the external extraction quantum efficiency (%) is obtained by the following equation.

External extraction quantum efficiency (%) = number of photons emitted to the outside of the organic EL element / number of electrons sent 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 or a metal film can be preferably used from the viewpoint of reducing the thickness of the organic EL element. Further, 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, and measured by a method according to JIS K 7129-1992. The water vapor permeability (25 ± 0.5 ° C., relative humidity 90 ± 2%) is preferably 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 of 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 adhesively cured from room temperature to 80 ° C. is preferable. 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 like screen printing.

It is also preferable to coat the electrode and the organic layer group on the outer side of the electrode facing the support substrate with the organic layer group interposed therebetween, and form an inorganic or organic layer in contact with the support substrate to form a sealing film. Can be. In this case, the material for forming the sealing 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, inorganic films such as silicon oxide, silicon dioxide, silicon nitride, etc. Can be used.

In order to further improve the brittleness of the sealing film, it is preferable to have a laminated structure of these inorganic films and films 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 the sealing film on the side facing the support substrate with the organic layer group interposed therebetween. In particular, when sealing is performed by the 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 the sealing can be used, but the polymer film is light and thin. Is preferably used.

《Light extraction enhancement 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 device, or between the transparent electrode or light emitting layer and the transparent substrate. This is because light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the side surface of the device.

As a method 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 interface between the transparent substrate and the air (see, for example, US Pat. No. 4,774,435), A method for improving the efficiency by giving the substrate a light condensing property (for example, see JP-A-63-314795), a method for forming a reflective surface on the side surface of the element (for example, JP-A-1-220394) (See Japanese Laid-Open Patent Publication No. 62-172691), a method of introducing a flat layer having an intermediate refractive index between the substrate and the light emitter to form an antireflection film (see, for example, Japanese Patent Application Laid-Open No. 62-172691), the substrate and the light emitter. A method of introducing a flat layer having a lower refractive index than the substrate (see, for example, Japanese Patent Application Laid-Open No. 2001-202827), any of the substrate, the transparent electrode layer, and the light emitting layer (including the substrate and the outside world). Times) How to form a grating (e.g., see JP Hei 11-283751.) And the like.

In the present invention, these methods can be used in combination with the organic EL device of the present invention. 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, transparent A method of forming a diffraction grating between any layers of the 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.

When a low refractive index medium 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 higher extraction efficiency to the outside as the refractive index of the medium is lower. Become.

Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and 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. Furthermore, it is preferable that it is 1.35 or less.

Also, 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 that causes total reflection or in any medium has a feature that the effect of improving the light extraction efficiency is high. 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 due to total internal reflection between layers is diffracted by introducing a diffraction grating into any layer or medium (in the transparent substrate or transparent electrode). , Trying to extract light out.

It is desirable that the diffraction grating to be introduced 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, the light extraction efficiency increases by diffracting the light traveling in all directions.

The position where the diffraction grating is introduced may be in any one of the layers or in the medium (in the transparent substrate or the transparent electrode), but is preferably in the vicinity of the light emitting layer where light is generated. At this time, the period of the diffraction grating is preferably in the range of about 1/2 to 3 times the wavelength of 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 is processed to provide, for example, a microlens array-like structure on the light extraction side of the support substrate (substrate), or in combination with a so-called condensing sheet, for example, a specific direction, Condensing light from the front direction with respect to the element light emitting surface can increase luminance in a specific direction.

As an example of the microlens array, a quadrangular pyramid having a side of 30 μm and an apex angle of 90 degrees is 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 becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

As the condensing sheet, it is possible to use, for example, a sheet that has been put to practical use in an LED backlight of a liquid crystal display device. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, 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.

Further, in order to control the light emission angle from the organic EL element, a light diffusion plate / film may be used in combination with the light collecting sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

<Application>
The organic EL element of the present invention can be used as an electronic device such as a display device, a display, and various light emitting devices.

As a light emitting device, for example, a lighting device (for example, household lighting, interior lighting, etc.), a backlight for a clock or a liquid crystal, a billboard advertisement, a traffic light, a light source of an optical storage medium, a light source of an electrophotographic copying machine, an optical communication processor However, the present invention is not limited to this, but it can be effectively used particularly as a backlight of a liquid crystal display device and a light source for illumination.

In the organic EL device of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like during film formation, if necessary. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned. In the fabrication of the element, a conventionally known method is used. Can do.

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

In the case of a multicolor display device, a shadow mask is provided only at the time of forming a light emitting layer, and a film can be formed on one surface by vapor deposition, casting, spin coating, ink jet or printing.

In the case of patterning only the light emitting layer, the method is not limited, but a vapor deposition method, an ink jet method, a spin coating method, and a printing method are preferable.

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

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

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

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

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

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 including the organic EL element of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic view showing an example of a display device composed of organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element.

The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, a wiring unit C that electrically connects the display unit A and the control unit B, and the like. .

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

FIG. 3 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 and a plurality of pixels 3 on the substrate.

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

The scanning line 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a grid pattern and are connected to the pixels 3 at the orthogonal positions (details are illustrated Not)

When the scanning signal is applied from the scanning line 5, the pixel 3 receives the image data signal from the data line 6 and emits light according to the received image data.

A full color display can be achieved 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. 4 is a schematic diagram showing a pixel circuit.

The pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. A full color display can be performed by using red, green, and blue light emitting organic EL elements as the organic EL elements 10 in a plurality of pixels, and juxtaposing them on the same substrate.

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

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

When the scanning signal moves 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 when 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 providing the switching transistor 11 and the driving transistor 12 which are active elements with respect to 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 an organic EL element emits light according to a data signal only when a scanning signal is scanned.

FIG. 5 is a schematic view of a passive matrix display device. In FIG. 5, 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 pixel 3 connected to the applied scanning line 5 emits light according to the image data signal.

In the passive matrix method, there is no active element in the pixel 3, and the manufacturing cost can be reduced.

By using the organic EL element of the present invention, a display device with improved luminous efficiency can be obtained.

[Lighting device]
The organic EL element of the present invention can be applied to 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 drive method when used as a display device for moving image reproduction 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.

Further, the π-conjugated compound used in the present invention can be applied to a lighting device including an organic EL element that emits substantially white light. 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 transporting layer, an electron transporting layer, etc. 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 the lighting device of the present invention)
One aspect of the lighting device of the present invention that includes 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 (for example, Toagosei Co., Ltd.) is used as a sealing material around Manufactured by LUX TRACK LC0629B), which is stacked on the cathode and brought into close contact with the transparent support substrate, irradiated with UV light from the glass substrate side, cured, and sealed, as shown in FIGS. A lighting device as shown can be formed.

FIG. 6 is a schematic view of the lighting device, and the organic EL element of the present invention (organic EL element 101 in the lighting device) is covered with a glass cover 102. In addition, the sealing operation with the glass cover is performed in a glove box in a nitrogen atmosphere without bringing the organic EL element 101 in the lighting device into contact with the atmosphere, specifically in an atmosphere of high purity nitrogen gas with a purity of 99.999% or more. went.

FIG. 7 is a cross-sectional view of the lighting device, 105 is a cathode, 106 is an organic layer group, and 107 is a glass substrate with a transparent electrode (anode). 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, an illumination device having excellent luminous efficiency can be obtained.

[Luminescent thin film]
The light-emitting thin film of the present invention contains a π-conjugated compound having a structure represented by the general formula (1) according to the present invention, and can be produced in the same manner as the method for forming the organic layer group. it can.

The method for forming the light-emitting thin film of the present invention is not particularly limited, and a conventionally known thin film forming method such as a vacuum deposition method or a wet method (also referred to as a wet process) can be used.

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

Further, different film forming methods may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally the boat heating temperature is in the range of 50 to 450 ° C., and the degree of vacuum is in the range of 10 ⁻⁶ to 10 ⁻² Pa. Of these, the deposition rate is within the range of 0.01 to 50 nm / second, the substrate temperature is within the range of −50 to 300 ° C., the layer thickness is within the range of 0.1 to 5 μm, and preferably within the range of 5 to 200 nm. desirable.

Further, when the spin coat method is adopted for film formation, it is preferable to perform the spin coater within a range of 100 to 1000 rpm and within a range of 10 to 120 seconds in a dry inert gas atmosphere.

Further, the luminescent thin film of the present invention can also be used for display devices and lighting devices.

Thereby, a display device and a lighting device with improved luminous efficiency can be obtained.

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

Example 1
<< Production of organic EL element >>
[Production of Organic EL Element 1-1]
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 deposition crucibles in the vacuum deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

The pressure was reduced to 1 × 10 ⁻⁴ Pa as the degree of vacuum, and then the energization crucible containing HAT-CN (1, 4, 5, 8, 9, 12-hexaazatriphenylenehexacarbonitrile) was energized and heated. It vapor-deposited on the ITO transparent electrode with the vapor deposition rate of 0.1 nm / sec, and formed the 10-nm-thick hole injection layer.

Next, α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) was deposited on the hole injection layer at a deposition rate of 0.1 nm / second, and the layer thickness was 40 nm. The hole transport layer was formed. Next, mCBP (3,3-di (9H-carbazol-9-yl) biphenyl) as the host compound and the following comparative compound 1 as the light-emitting compound were deposited at a deposition rate of 0 to 90% and 10% by volume, respectively. Co-evaporated at a rate of 1 nm / second to form a light emitting layer having a layer thickness of 30 nm.

Thereafter, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) was deposited at a deposition rate of 0.1 nm / second to form an electron transport layer having a layer thickness of 30 nm.

Further, after forming lithium fluoride with a film thickness of 0.5 nm, 100 nm of aluminum was vapor-deposited to form a cathode.

The non-light-emitting surface side of the above element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 1-1.

[Production of Organic EL Elements 1-2 to 1-31]
In the production of the organic EL element 1-1, organic EL elements 1-2 to 1-31 were produced in the same manner except that the luminescent compound was changed from the comparative compound 1 to each luminescent compound shown in Table 1. did.

[Measurement of difference (ΔEst) between lowest excited singlet energy and lowest excited triplet energy of luminescent compound]
The difference ΔEst between the lowest excited singlet energy and the lowest excited triplet energy is calculated by the density functional method using the functional B3LYP and the basis function 6-31G (d) by Gaussian09, and the obtained result is Table 1 shows.

<< Measurement of characteristic values of organic EL elements >>
(Measurement of luminous efficiency)
Luminous efficiency at the time of driving each organic EL element was measured according to the method shown below.

Using a spectral radiance meter CS-2000 (manufactured by Konica Minolta Co., Ltd.) at room temperature (about 25 ° C.), the light emission luminance of each organic EL element is measured, and the light emission efficiency at a light emission luminance of 3000 cd / m ² is obtained. The light emission efficiency (relative value) was determined according to the following formula using the light emission efficiency of the element 1-1 as a reference.

Luminous efficiency (relative value) = (Luminous efficiency of sample at a luminance of 3000 cd / m ² / Luminous efficiency of organic EL device 1-1 at a luminance of 3000 cd / m ² ) × 100
Table 1 shows that the larger the relative value of the light emission efficiency is, the lower the power the element is driven.

(Measurement of drive voltage)
The driving voltage at the time of driving each organic EL element was measured by the following measurement.

Using a spectral radiance meter CS-2000 (manufactured by Konica Minolta Co., Ltd.) at room temperature (about 25 ° C.), the light emission luminance of each organic EL element is measured, and the initial drive voltage at the light emission luminance of 1000 cd / m ² is obtained. Based on the drive voltage of the EL element 1-1, the drive voltage (relative value) was obtained according to the following equation.

Driving voltage (relative value) = (initial drive voltage of the light emitting luminance 1000 cd / ^{m 2} initial drive voltage / organic EL element 1-1 in the light emitting luminance 1000 cd / ^{m 2} samples) × 100
Table 1 shows that the smaller the relative value of the voltage value, the better the conductivity of the element, and that the element is driven at a low voltage. Table 1 shows the results obtained as described above.

As is clear from the results shown in Table 1, it is clear that the organic EL device of the present invention produced using the compound specified in the present invention acquires good conductive properties and the driving voltage decreases. Furthermore, since the drive voltage was reduced, the power consumption was reduced and the light emission efficiency was also improved. In particular, the smaller the ΔEst, the more prominently the effect described above.

Example 2
<< Production of organic EL element >>
[Production of Organic EL Element 2-1]
A transparent support substrate (NH45 manufactured by NH Techno Glass Co., Ltd.) in which ITO (indium tin oxide) was formed as a positive electrode on a 100 mm × 100 mm glass substrate having a thickness of 1.1 mm was subjected to patterning treatment. Thereafter, the transparent support substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.

On this transparent support substrate, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (abbreviation: PEDOT / PSS, Bayer, Baytron PAl 4083) to 70% with pure water was used. A thin film was formed by spin coating under the conditions of 3000 rpm and 30 seconds, and then dried at 200 ° C. for 1 hour to form a hole injection layer having a layer thickness of 20 nm. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus, and each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with a constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) was deposited at a deposition rate of 0.1 nm / second. It vapor-deposited on the formed said positive hole injection layer, and the positive hole transport layer whose layer thickness is 40 nm was formed. Next, the host compound H-46, which is an exemplary compound, and the following comparative compound 2 were co-deposited at a deposition rate of 0.1 nm / second under the conditions of 94% and 6% by volume, respectively, and a light emitting layer having a layer thickness of 30 nm Formed.

Thereafter, TPBi (1,3,5-tris (N-phenylbenzimidazol-2-yl) benzene) was deposited at a deposition rate of 0.1 nm / second to form an electron transport layer having a layer thickness of 30 nm.

Further, after forming sodium fluoride with a film thickness of 1 nm, aluminum was deposited with a thickness of 100 nm to form a cathode.

The non-light emitting surface side of the organic EL element is covered with a can-shaped glass case in an atmosphere of high-purity nitrogen gas with a purity of 99.999% or more, and an electrode lead-out wiring is installed to produce an organic EL element 2-1. did.

[Production of Organic EL Element 2-2]
In the production of the organic EL device 2-1, the exemplified compound H-46 is used as the host compound, the comparative compound 2 is used as the light emitting compound, and the comparative compound 1 is used as the combined compound, and the ratios are 75%, 10%, and 15%, respectively. An organic EL device 2-2 was produced in the same manner except that the light emitting layer was formed so as to have a volume%.

[Production of organic EL elements 2-3 to 2-11]
In the production of the organic EL device 2-2, the organic EL devices 2-3 to 2--2 were prepared in the same manner except that the host compound, the light emitting compound, the combination compound and the ratio thereof in the light emitting layer were changed to the combinations shown in Table 2. 11 was produced.

[Measurement of difference (ΔEst) between first excited singlet energy and first excited triplet energy of combined compound (C)]
The difference ΔEst between the first excited singlet energy and the first excited triplet energy is obtained by calculating by density functional method using the functional B3LYP and the basis function 6-31G (d) by Gaussian09. The results are shown in Table 2.

<< Measurement of characteristic values of organic EL elements >>
The organic EL elements 2-1 to 2-11 produced above were measured for luminous efficiency and driving voltage in the same manner as described in Example 1. The reference sample for each measurement was the organic EL element 2-1.

Table 2 shows the results obtained as described above.

As is clear from the results shown in Table 2, the organic EL elements 2-4 to 2-11 of the present invention have higher luminous efficiency than the organic EL elements 2-1 to 2-3 of Comparative Examples. Obviously. This is considered to be the effect that the compound according to the present invention assists the emission of other fluorescent compounds. That is, when the fluorescent compound according to the present invention having a higher energy level than the luminescent material is excited in the light emitting device, the luminescent material efficiently receives the energy, whereby the compound according to the present invention emits light. It is thought that luminous efficiency comparable to that can be obtained.

Example 3
When a toluene solution of Exemplified Compound D15 according to the present invention was prepared and irradiated with light at 280 nm at 300 K while bubbling nitrogen, green light emission was observed. In this exemplary compound D15, components having a long emission lifetime were observed in addition to ns order fluorescence. The time-resolved spectrum was measured with a fluorescence lifetime measuring device Quantaurus-tau manufactured by Hamamatsu Photonics Co., Ltd., and the component having a short emission lifetime was determined to be fluorescence. The long component was judged as delayed fluorescence.

Example 4
<< Production of organic EL element >>
(Preparation of organic EL element 4-1)
An ITO (indium tin oxide) film having a thickness of 150 nm was formed on a 50 mm × 50 mm × 0.7 mm thick glass substrate, followed by patterning to form an ITO transparent electrode as an anode. The transparent substrate provided with the ITO transparent electrode was subjected to ultrasonic cleaning with isopropyl alcohol and dried with dry nitrogen gas, followed by UV ozone cleaning for 5 minutes. The obtained transparent substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.

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

After reducing the vacuum inside the vacuum evaporation system to a vacuum of 1 × 10 ⁻⁴ Pa, energize a resistance heating boat containing HAT-CN (1,4,5,8,9,12-hexaazatriphenylenehexacarbonitrile). And heated and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second to form a 15 nm thick hole injection layer.

Next, α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) was deposited on the hole injection layer formed above at a deposition rate of 0.1 nm / second, A hole transport layer having a thickness of 30 nm was formed.

Next, a resistance heating boat containing comparative compound 4 as a host compound and GD-1 as a luminescent compound is energized and heated, and the hole transport is performed at a deposition rate of 0.1 nm / second and 0.010 nm / second, respectively. A light-emitting layer having a thickness of 40 nm was formed by co-evaporation on the layer.

Next, Exemplary Compound H-42 was deposited at a deposition rate of 0.1 nm / second to form a first electron transport layer having a thickness of 5 nm.

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

Thereafter, sodium fluoride was vapor-deposited so as to have a thickness of 0.5 nm, and then aluminum was vapor-deposited with a thickness of 100 nm to form a cathode, thereby producing an organic EL element 4-1.

(Production of organic EL elements 4-2 to 4-11)
Organic EL devices 4-2 to 4-11 were fabricated in the same manner as the organic EL device 4-1, except that the host compound used for forming the light emitting layer was changed to each compound shown in Table 3.

<< Evaluation of organic EL elements >>
In the same manner as in the method described in Example 1, the driving voltage and the luminous efficiency of the organic EL element 4-1 were measured, and the measured values of the organic EL elements 4-1 of each organic EL element were set to 100. Values were obtained and the results obtained are shown in Table 3.

As is apparent from the results shown in Table 3, the organic EL elements 4-2 to 4-11 have a lower driving voltage and excellent luminous efficiency than the organic EL element 4-1 as a comparative example. I understand.

This proved that the compound according to the present invention is also effective as a host material. That is, it is presumed that the compound according to the present invention is excellent in carrier transportability and can assist in light emission of the dopant.

The organic electroluminescence device of the present invention can achieve a high luminous efficiency with a reduced driving voltage, and can be suitably used for a light-emitting thin film, a display device, and a lighting device containing a conjugated compound according to the present invention.

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 in a lighting device 102 Glass cover 105 Cathode 106 Organic layer group 107 Glass substrate 108 with a transparent electrode 108 Nitrogen Gas 109 Water capturing agent A Display unit B Control unit C Wiring unit

Claims

An organic electroluminescence device having an organic layer group including at least one light emitting layer between an anode and a cathode,
At least one layer of the organic layer group contains a π-conjugated compound having a structure represented by the following general formula (1).

[In the formula, A represents an electron-withdrawing group, and D represents an electron-donating group. m and n are each independently an integer of 1 or 2. X represents an aromatic hydrocarbon group selected from structures represented by the following general formulas (1a) to (1k). ]

[In the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k), R 1 , R 2 , Ra, Rb, Rc and Rd each independently represents a hydrogen atom or a substituent. . p, q, r and s each independently represent an integer of 0 to 4. These substituents may be the same or different, and each substituent may be bonded to form a ring. ]
When at least one of R 1 , R 2 , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron-withdrawing group, The attractive group represents an aromatic heterocyclic group, a sulfonyl group (—SO 2 R 1 ; R 1 represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. ), A sulfenyl group (—SOR 1 ; R 1 represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a cyano group (—CN), halogeno A group, a carbonyl group (—COR 1 ; R 1 represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a pentafluorophenyl group (—C 6 F 5) a trifluoromethyl group (-CF 3), trifluoromethyl Eniru group (-C 6 H 4 CF 3) , and boryl group (-BR 1 2; R 1 represents an aromatic heterocyclic group of aromatic hydrocarbon group having 6 to 30 carbon atoms, or 3 to 20 carbon atoms The organic electroluminescence device according to claim 1, wherein the organic electroluminescence device is at least one selected from the group consisting of.
When at least one of R 1 , R 2 , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron donating group, The donating group is an aromatic heterocyclic group having 3 to 20 carbon atoms, an amino group (—NH 2 ), an arylamino group (—NHR 1 or —NR 1 2 ; R 1 is an aromatic carbon group having 6 to 30 carbon atoms; A hydrogen group or an aromatic heterocyclic group having 3 to 20 carbon atoms), an alkoxy group (—OR 1 ; R 1 is a linear or cyclic hydrocarbon group having 1 to 10 carbon atoms), and an aryloxy group ( —OR 2 ; R 2 represents a linear or cyclic hydrocarbon group, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. The organic electron according to claim 1, wherein Nessensu element.
When at least one of R 1 , R 2 , Ra, Rb, Rc and Rd in the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k) is an electron-withdrawing group, The attractive group represents an aromatic heterocyclic group, a sulfonyl group (—SO 2 R 1 ; R 1 represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms. ), A sulfenyl group (—SOR 1 ; R 1 represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a cyano group (—CN), halogeno A group, a carbonyl group (—COR 1 ; R 1 represents an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 20 carbon atoms), a pentafluorophenyl group (—C 6 F 5) a trifluoromethyl group (-CF 3), trifluoromethyl Eniru group (-C 6 H 4 CF 3) , and boryl group (-BR 1 2; R 1 represents an aromatic heterocyclic group of aromatic hydrocarbon group having 6 to 30 carbon atoms, or 3 to 20 carbon atoms And at least one of R 1 , R 2 , Ra, Rb, Rc and Rd in the general formulas (1a) to (1k) is an electron donating group. When the electron donating group is an aromatic heterocyclic group having 3 to 20 carbon atoms, an amino group (—NH 2 ), an arylamino group (—NHR 1 or —NR 1 2 ; R 1 has 6 to 30 carbon atoms) An aromatic hydrocarbon group or an aromatic heterocyclic group having 3 to 20 carbon atoms), an alkoxy group (—OR 1 ; R 1 is a linear or cyclic hydrocarbon group having 1 to 10 carbon atoms), and aryloxy groups (-OR 2; R 2 is a linear or cyclic hydrocarbon group, the carbon Aromatic hydrocarbon group having 6 to 30, or an organic electroluminescent device according to claim 1, characterized in that at least one selected from the representative.) An aromatic heterocyclic group having 3 to 20 carbon atoms.
X in the π-conjugated compound having the structure represented by the general formula (1) is the general formula (1a), (1b), (1d), (1e), (1g), (1h), (1i The organic electroluminescence device according to any one of claims 1 to 4, wherein the organic electroluminescence device is an aromatic hydrocarbon group represented by (1) or (1j).
X in the π-conjugated compound having the structure represented by the general formula (1) is the general formula (1a), (1b), (1d), (1e), (1g), (1h), (1i ) Or (1j), at least one of R 1 , R 2 , Ra, Rb, Rc and Rd is an electron withdrawing group, and at least one is an electron 6. All of R 1 , R 2 , Ra, Rb, Rc and Rd which are donating groups and do not correspond to the electron withdrawing group and the electron donating group are hydrogen atoms. Organic electroluminescence element.
The absolute value (ΔEst) of the energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound having the structure represented by the general formula (1) is 0.5 eV or less. The organic electroluminescence element according to claim 1, wherein the organic electroluminescence element is characterized in that:
The luminescent layer contains a π-conjugated compound having a structure represented by the general formula (1) and at least one of a fluorescent luminescent compound and a phosphorescent luminescent compound. The organic electroluminescent element according to any one of claims 1 to 7.
9. The light emitting layer according to any one of claims 1 to 8, wherein the light emitting layer contains a π-conjugated compound, at least one of a fluorescent compound and a phosphorescent compound, and a host compound. The organic electroluminescence device according to one item.
A luminescent thin film comprising a π-conjugated compound having a structure represented by the following general formula (1).

[In the formula, A represents an electron-withdrawing group, and D represents an electron-donating group. m and n are each independently an integer of 1 or 2. X represents an aromatic hydrocarbon group selected from structures represented by the following general formulas (1a) to (1k). ]

[In the aromatic hydrocarbon group having the structure represented by the general formulas (1a) to (1k), R 1 , R 2 , Ra, Rb, Rc and Rd each independently represents a hydrogen atom or a substituent. . p, q, r and s each independently represent an integer of 0 to 4. These substituents may be the same or different, and each substituent may be bonded to form a ring. ]
The absolute value (ΔEst) of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level of the π-conjugated compound having the structure represented by the general formula (1) is 0.5 eV or less. The luminescent thin film according to claim 10.
A display device comprising the organic electroluminescence element according to any one of claims 1 to 9.
An illuminating device comprising the organic electroluminescence element according to any one of claims 1 to 9.