JP6634838B2 - Electronic device material, organic electroluminescence element, display device, and lighting device - Google Patents

Description

  The present invention relates to an electronic device material, an organic electroluminescence element using the electronic device material, and a display device and a lighting device including the organic electroluminescence element.

  2. Description of the Related Art An organic EL device (organic electroluminescent device) using electroluminescence (EL) of an organic material is a technology that has already been put to practical use as a light emitting system that enables planar light emission. The organic EL element is applied not only to an electronic display but also recently to lighting equipment, and its development is expected.

  When an electric field is applied to the organic EL element, holes and electrons are injected from the anode and the cathode, respectively, and recombine in the light emitting layer to generate excitons. At this time, singlet excitons and triplet excitons are generated at a ratio of 25%: 75%. For this reason, it is known that phosphorescence using triplet excitons theoretically has higher internal quantum efficiency than fluorescence. However, in order to actually obtain high quantum efficiency in the phosphorescence emission method, it is necessary to use a complex containing a rare metal such as iridium or platinum as the central metal. For this reason, there is a concern that the reserves of rare metals and the price of the metals themselves will become major industrial problems in the future.

  On the other hand, various developments have been made in the fluorescent light emitting type in order to improve the luminous efficiency. For example, attention is paid to a phenomenon (Triplet-Triplet Annihilation: TTA or Triplet-Triplet Fusion: TTF) in which a singlet exciton is generated by collision of two triplet excitons. A technique for increasing the efficiency has been proposed (for example, see Patent Document 1). According to this technique, the luminous efficiency of the fluorescent material is improved to two to three times that of the conventional fluorescent material. However, since the theoretical singlet exciton generation efficiency in TTA is only about 40%, there is still a problem of higher luminous efficiency than phosphorescent light emission.

  More recently, the phenomenon that reverse intersystem crossing (RISC) from triplet excitons to singlet excitons occurs, so-called thermally activated delayed fluorescence (TADF) It has been reported that a fluorescent light-emitting material utilizing the above-mentioned method and the possibility of using this light-emitting material in an organic EL device (for example, see Patent Document 2, Non-Patent Document 1, and Non-Patent Document 2). The use of the delayed fluorescence by the TADF mechanism makes it possible to theoretically achieve 100% internal quantum efficiency equivalent to that of phosphorescence even in fluorescence emission by electric field excitation.

In order for the TADF phenomenon to occur, at room temperature or the temperature of the light-emitting layer in the light-emitting element, it is necessary to generate reverse intersystem crossings from 75% of triplet excitons to singlet excitons generated by electric field excitation. Furthermore, unless the singlet exciton generated by the inverse intersystem crossing emits fluorescence similarly to the 25% singlet exciton generated by the direct excitation, the internal quantum efficiency of 100% cannot be obtained. In order for this intersystem crossing to occur, the absolute value of the difference between the lowest excited singlet energy level (S ₁ ) and the lowest excited triplet energy level (T ₁ ) (hereinafter referred to as ΔEst) must be extremely small. Is required.

  On the other hand, it is known that adding a material having TADF properties as a third component (assist dopant material) to a light-emitting layer containing a host material and a light-emitting material is effective in achieving high luminous efficiency (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 produce singlet excitons with inverse intersystem crossing (RISC) . The energy of the generated singlet exciton moves to the light-emitting compound by fluorescence resonance energy transfer (FRET), and the light-emitting compound emits light by the transferred energy. Therefore, the light emitting compound can emit light using the exciton energy of 100% in theory, and the light emission efficiency can be increased.

  Here, it is known that in order to minimize ΔEst in an organic compound, it is preferable to localize the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) without mixing them. ing.

  Conventionally, a technique for introducing a strong electron-donating group (donor unit) or an electron-withdrawing group (acceptor unit) into a molecule has been known to clearly separate HOMO and LUMO. However, when a strong electron-donating group or an electron-withdrawing group is introduced, an excited state of strong intramolecular charge transfer (CT) is formed, so that the absorption spectrum or emission spectrum of the compound becomes longer (broader). It becomes a factor. This makes it difficult to control the emission wavelength of the organic EL element. Further, in a π-conjugated compound having a strong electron-withdrawing group, the HOMO level also decreases as the LUMO level decreases. For this reason, when a π-conjugated compound having a strong electron-withdrawing group is applied to a light-emitting material or the like, the HOMO level or the LUMO level of the light-emitting material is low, so that selection of a host material is difficult and carrier balance during EL driving is reduced. There is a problem of collapse.

  In an organic EL device, the use of a π-conjugated boron compound as a material exhibiting TADF properties (TADF compound) has been studied. The π-conjugated boron compound does not have a strong electron-withdrawing property such as a cyano group or a sulfonyl group, but can function as a mild acceptor unit, and has excellent electron-transporting properties and high luminescence. This is because it can be expected to be used for a light emitting layer in an organic EL device.

  However, π-conjugated boron compounds have a problem in low stability. Boron, which is a Group 13 element, is an electron-deficient element having an empty p-orbital, and thus is easily attacked by nucleophiles. Therefore, compounds containing boron are generally unstable.

  In order to improve the thermodynamic stability of a π-conjugated boron compound, a technique of introducing a sterically bulky substituent such as an alkyl group or an aryl group around boron is known. In recent years, it has been reported that a new π-conjugated boron compound, which has a structure cyclized around boron, that is, a structure in which boron is the central atom and forms a ring together with carbon atoms and hetero atoms, and its use as an organic EL device material has been reported. (For example, see Patent Literature 3, Patent Literature 4, Non-Patent Literature 4).

  Patent Literature 3 discloses a π-conjugated compound using a hetero atom (mainly an oxygen atom) as a bridging atom. Although this compound is said to be thermodynamically stable and excellent in charge transferability, the synthesis examples show only compounds having a nitrogen atom at the central atom, so a specific π-conjugated boron compound is shown. Not. That is, there is no description about a thermodynamically stable π-conjugated boron compound. In the examples, only use for a hole transport layer is described, and application to a light emitting layer is not described.

  Patent Literature 4 discloses a π-conjugated compound in which a central atom is mainly boron and a bridging atom is mainly an oxygen atom and NR (R is a substituent). In particular, it has been shown that a π-conjugated compound can be used as a host for a phosphorescent dopant or a TADF dopant by utilizing a wide HOMO-LUMO band gap and a high triplet energy. Non-Patent Document 4 shows that the π-conjugated compound described in Patent Document 4 described above is excellent as a host material of Ir (ppy) 3 which is a general phosphorescent dopant. Further, Non-Patent Document 4 suggests that the molecular structure and molecular design can be expected as a TADF compound because ΔEst of a π-conjugated compound is small. However, the π-conjugated boron compound described in Patent Document 4 has insufficient thermodynamic stability.

WO 2010/134350 JP 2013-116975 A JP 2013-053253 A WO 2015/102118

H. See Uoyama, et al. , Nature, 2012, 492, 234-238. Q. Zhang et al. , Nature, Photonics, 2014, 8, 326-332. H. Nakananotani, et al. , Nature Communication, 2014, 5, 4016-4022. T. Hatakeyama, et al. Angew. Chem. 2015, 127, 1-6.

As described above, the thermodynamic stability of the π-conjugated boron compound cannot be sufficiently increased even by using the methods described in each of the patent documents and the non-patent documents. For this reason, there is a demand for an electronic device material that has a small ΔEst, can be an excellent TADF compound, and has high thermodynamic stability.
Further, there is a need for an organic electroluminescent element having high luminous efficiency using the electronic device material, and a display device and a lighting device using the organic electroluminescent element.

  In order to solve the above-described problems, in the present invention, an electronic device material having high thermodynamic stability, and an organic electroluminescent element and a display device capable of improving luminous efficiency by including the electronic device material To provide lighting devices.

  The electronic device material of the present invention has a structure represented by the following general formula (1), and the absolute value ΔEst of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.90 eV or less. It is.

However, in the general formula (1), X ₁ and X ₂ each independently represent NR ₁₀ , an oxygen atom or a sulfur atom. R ₁₀ represents a hydrogen atom, a chain alkyl group, a cyclic alkyl group, an aromatic hydrocarbon ring group or an aromatic heterocyclic group. Y ₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group. R _{1 to} R ₉ each independently represent a hydrogen atom or a substituent.

  The organic electroluminescence element of the present invention includes a light emitting layer containing the above electronic device material. Further, a display device of the present invention includes the above-mentioned organic electroluminescence element. The lighting device of the present invention has the above-mentioned organic electroluminescence element.

  According to the present invention, it is possible to provide an electronic device material having high thermodynamic stability, and an organic EL element, a display device, and a lighting device capable of improving luminous efficiency by including the electronic device material as the electronic device material. .

FIG. 2 is a diagram illustrating a schematic configuration of an organic EL element. FIG. 2 is a schematic diagram illustrating an example of a display device including an organic EL element. It is a schematic diagram of a display device using an active matrix system. It is the schematic which showed the circuit of the pixel. It is a schematic diagram of a display device based on a passive matrix system. It is a schematic diagram of a lighting device. It is a schematic diagram of a lighting device.

Hereinafter, examples of embodiments for carrying out the present invention will be described, but the present invention is not limited to the following examples.
The description will be made in the following order.
1. 1. Electronic device materials 2. Organic electroluminescence element Lighting device, display device

<1. Electronic device materials>
The structure of the electronic device material is represented by the following general formula (1). An electronic device material represented by the following general formula (1) is a π-conjugated boron compound having high thermodynamic stability and useful as a material applied to a light emitting layer of an organic EL element.

In the general formula (1), X ₁ and X ₂ each independently represent NR ₁₀ , an oxygen atom or a sulfur atom. R ₁₀ represents a hydrogen atom, a chain alkyl group, a cyclic alkyl group, an aromatic hydrocarbon ring group or an aromatic heterocyclic group. Y ₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group. R _{1 to} R ₉ each independently represent a hydrogen atom or a substituent.

The substituents represented by R _{1 to} R ₉ are not particularly limited. Examples thereof include an alkyl group, an alkoxy group, an amino group, an aromatic hydrocarbon ring group, and an aromatic heterocyclic group. Note that these substituents include the case where a part of the structure has another substituent.

The alkyl group represented by R _{1 to} R ₉ may have any of a linear, branched, and cyclic structure. Examples of the alkyl group include a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms. Specifically, methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, n-pentyl, neopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl group, n-heptyl group, n-octyl group, 2-hexyloctyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group , N-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group and n-icosyl group. Preferably, a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclohexyl group, a 2-ethylhexyl group, and a 2-hexyloctyl group are exemplified. Examples of the substituents of these alkyl groups include a halogen atom, an aromatic hydrocarbon ring group described below, an aromatic heterocyclic group described below, and an amino group described below.

The alkoxy groups represented by R _{1 to} R ₉ may have any of a linear, branched, or cyclic structure. Examples of the alkoxy group include a linear, branched, or cyclic alkoxy group having 1 to 20 carbon atoms. Specifically, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, t-butoxy group, n-pentyloxy group, neopentyloxy group, n-hexyloxy group, Cyclohexyloxy group, n-heptyloxy group, n-octyloxy group, 2-ethylhexyloxy group, nonyloxy group, decyloxy group, 3,7-dimethyloctyloxy group, n-undecyloxy group, n-dodecyloxy group, n-tridecyloxy group, n-tetradecyloxy group, 2-n-hexyl-n-octyloxy group, n-pentadecyloxy group, n-hexadecyloxy group, n-heptadecyloxy group, n-octadecyl Examples thereof include an oxy group, an n-nonadecyloxy group, and an n-icosyloxy group. Among these, a methoxy group, an ethoxy group, an isopropoxy group, a t-butoxy group, a cyclohexyloxy group, a 2-ethylhexyloxy group, and a 2-hexyloctyloxy group are preferred. Examples of the substituents of these alkoxy groups include a halogen atom, an aromatic hydrocarbon ring group described below, an aromatic heterocyclic group described below, and an amino group described below.

Examples of the aromatic hydrocarbon ring group represented by R _{1 to} R ₉ include a benzene ring, an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a chrysene ring, Naphthacene ring, pyrene ring, pentalene ring, aceanthrylene ring, heptalene ring, triphenylene ring, as-indacene ring, chrysene ring, s-indacene ring, preiaden ring, phenalene ring, fluoranthene ring, perylene ring, acephenanthrylene Ring, biphenyl ring, terphenyl ring, tetraphenyl ring and the like. Examples of the substituents of these aromatic hydrocarbon ring groups include a halogen atom, the above-mentioned alkyl group, the above-mentioned alkoxy group, the later-described aromatic heterocyclic group, and the later-described amino group.

Examples of the aromatic heterocyclic group represented by R _{1 to} R ₉ include a carbazole ring, an indoloindole ring, a 9,10-dihydroacridine ring, a phenoxazine ring, a phenothiazine ring, a dibenzothiophene ring, and a benzofurylindole ring Benzothienoindole ring, indolocarbazole ring, benzofurylcarbazole ring, benzothienocarbazole ring, benzothienobenzothiophene ring, benzocarbazole ring, dibenzocarbazole ring, dibenzofuran ring, benzofurylbenzofuran ring, dibenzosilole ring, etc. . Examples of the substituents of these aromatic heterocyclic groups include a halogen atom, the above-mentioned alkyl group, the above-mentioned alkoxy group, the above-mentioned aromatic hydrocarbon ring group, and the below-mentioned amino group.

Examples of the substituent of the amino group represented by R _{1 to} R ₉ include a halogen atom, the above-mentioned alkyl group, the above-mentioned aromatic hydrocarbon ring group, and the above-mentioned aromatic heterocyclic group. .

The electronic device material preferably contains an electron donating group in at least one of R _{1 to} R ₉ . By bonding an electron-donating substituent to a boron compound having an electron-donating property and having an excellent electron-transport property, it is possible to stabilize a charge separation state in a wide π-conjugated plane.

In the above structures exemplified as R _{1 to} R ₉ , examples of the electron donating group include a carbazole ring, an indoloindole ring, a 9,10-dihydroacridine ring, a phenoxazine ring, a phenothiazine ring, a dibenzothiophene ring, and a benzofurylindole ring. An aromatic heterocyclic group such as a benzothienoindole ring, an indolocarbazole ring, a benzofurylcarbazole ring, a benzothienocarbazole ring, a benzothienobenzothiophene ring, a benzocarbazole ring, a dibenzocarbazole ring, a benzofurylbenzofuran ring, and an electron. The aromatic hydrocarbon ring group substituted with a donating group is exemplified. Examples of the electron donating group include the above-described alkyl group, alkoxy group, amino group, and the like.

  As the electron donating group, arylamine is preferable. By bonding a carbon atom and a nitrogen atom, charge separation based on the difference in electronegativity between the two atoms easily occurs, and the arylamine easily acts as an electron donating group. The number of electron donating groups is preferably 1 to 3. As the number of electron donating groups increases, the donor property of the electronic device material increases. However, from the viewpoint of difficulty in synthesis and decrease in solubility, 1 to 3 is preferable.

In the general formula (1), X ₁ and X ₂ each independently represent NR ₁₀ , an oxygen atom or a sulfur atom. When X ₁ and X ₂ are oxygen atoms or sulfur atoms, the acceptability of the electronic device material is improved. Further, an oxygen atom because the strong acceptor properties than the sulfur atom, of X _1, X _2, it is preferable that at least one is an oxygen atom, more preferably X _1, X ₂ are all oxygen atoms.

In the above structure represented by NR ₁₀ , R ₁₀ represents a hydrogen atom, a chain alkyl group, a cyclic alkyl group, an aromatic hydrocarbon ring group, or an aromatic heterocyclic group. Examples of the chain alkyl group and the cyclic alkyl group represented by R ₁₀ include a chain or cyclic alkyl group from the alkyl groups represented by R _{1 to} R ₉ described above. Examples of the aromatic hydrocarbon ring group and the aromatic heterocyclic group include the same aromatic hydrocarbon ring groups and aromatic heterocyclic groups represented by R _{1 to} R ₉ described above.

In the general formula (1), Y ₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group. Examples of the aromatic hydrocarbon ring group and the aromatic heterocyclic group represented by Y ₁ include the same aromatic hydrocarbon ring groups and aromatic heterocyclic groups represented by R _{1 to} R ₉ described above. Can be

  Preferred specific examples of the electronic device material represented by the general formula (1) are described below. The following compounds mentioned here may further have a substituent, and may be structural isomers or the like thereof.

(1. Exemplary compound)

(2. N position is not electron withdrawing, ΔEst is 0.45 or more)

(3. N position is not electron withdrawing, ΔEst is less than 0.45)

(4. N position is electron withdrawing, ΔEst is 0.45 or more)

(5. N position is electron withdrawing, ΔEst is less than 0.45)

(6. Donor for substituent)

(7. Acceptor for substituent)

(8. X ₁ and X ₂ are N, O)

(9. X ₁ and X ₂ are N, N)

  The electronic device material represented by the general formula (1) is a novel “planar π-conjugated boron compound” having a structure in which three sides are completely cyclized around boron and has at least one N as a bridging atom. . This π-conjugated boron compound can be used as a fluorescent light-emitting material (TADF light-emitting material; emitter) using the above-mentioned thermally activated delayed fluorescence (TADF). Further, it can be used as a host compound (TADF host material; assist dopant) of the light emitting layer.

  It is known that a boron atom in a π-conjugated boron compound almost always becomes LUMO due to its electron acceptor property. However, a π-conjugated boron compound has a weaker electron accepting property than a cyano group, a sulfonyl group, and the like, which are generally well known as electron-withdrawing substituents, and thus has a “mild acceptor unit”. Can be expressed as

This mild acceptor unit will be described.
When trying to realize a TADF compound using this unit, as another substituent in the molecule of the π-conjugated boron compound, a donor unit such as arylamine or carbazole, or a neutral substitution such as a phenyl group may be used. When a group is present, the boron atom in the π-conjugated boron compound naturally functions as an acceptor unit. On the other hand, as other substituents in the molecule, when there is no donor unit or neutral substituent, and there is a stronger acceptor unit such as a cyano group or a sulfonyl group, the π-conjugated boron compound Boron atoms serve as donor units.
That is, while a mild acceptor unit has an acceptor property that can clearly realize HOMO-LUMO charge separation, it also has a donor unit when it coexists with a stronger acceptor property than itself. Become.

[Use as TADF luminescent material (emitter)]
The electronic device material represented by the general formula (1) is excellent in an electron transport property and a light emission property which are properties derived from boron. Furthermore, by introducing an appropriate substituent into the substituent Y ₁ of NY ₁ , ΔEst is reduced, and an excellent TADF compound is obtained.

For example, when an electron-withdrawing substituent is introduced into Y _{1 of the} electronic device material represented by the general formula (1), the π-conjugated boron moiety becomes a donor unit. This becomes clear from the molecular calculations of the electronic device materials. The reason that the π-conjugated boron moiety serves as the donor unit is that the electron withdrawing property of the electronic device material is weaker than a cyano group, a sulfonyl group, a triazinyl group, or the like, and N has a lower electronegativity than O. It is possible.

  In addition, since the electronic device material contains an electron-donating group, it is possible to stabilize the state of charge separation over a wide π-conjugated plane, and it can be used as an acceptor unit for a delayed fluorescent material (TADF luminescent material). it can. Further, since the electronic device material has a π-conjugated system wider than conventionally known carbazole and acridan, HOMO is delocalized in a wide range and has high stability. Therefore, the electronic device material is a TADF compound having excellent light emitting characteristics.

[Use as TADF host material (assist dopant)]
Aryl boron compounds conventionally known as assist dopants have excellent electron transport properties. An arylamine compound conventionally known as an assist dopant has excellent hole transportability. On the other hand, since the electronic device material is bipolar having B and N, it satisfies the requirements of the host. Further, since the electronic device material has a wide HOMO-LUMO band gap and a high triplet energy, it can be used as a TADF host material (assist dopant). By utilizing the above electronic device material as a host material (assist dopant), the lowest excited singlet energy level S ₁ in the host is passed to the deep blue fluorescent dopant, so that high-efficiency deep blue light emission while emitting fluorescence is achieved. realizable. Therefore, it is possible to realize a display with high color purity and a white OLED with high color temperature.

[Thermodynamic stability]
In general, boron, which is a Group 13 element, is an electron-deficient element having an empty p-orbital, and thus is susceptible to attack by nucleophiles and is unstable. On the other hand, in the electronic device material represented by the general formula (1), three sides around boron are completely cyclized by incorporating boron into the carbon skeleton. For this reason, the structure is such that boron does not accept the attack of impurities, and the structure is such that boron hardly comes off the molecule. Furthermore, by including a sulfur atom, an oxygen atom, and a nitrogen atom as X ₁ and X ₂ as bridging atoms, the S, O, and N lawn pairs flow into the free orbit of B, thereby forming a B-S, B- A coordination bond acts between O and BN to form a strong ring structure.

  Further, the electronic device material has a structure having at least one N as a bridging atom. In general, N has a stronger coordination property than S or O, so that the flow of electrons from N to B becomes larger, and it is considered that the bridging atom becomes stronger than a ring composed of only S or O.

  As described above, the electronic device material represented by the general formula (1) can enhance the thermal stability at high temperatures without impairing the electron acceptability of boron. Therefore, the electronic device material represented by the general formula (1) has improved thermodynamic stability as compared with the compounds described in Patent Document 4 and Non-Patent Document 4 described above, and is higher than the conventional TADF compound. Has thermodynamic stability.

[Molecular design concept regarding ΔEst]
The molecular design for reducing ΔEst in the electronic device material represented by the general formula (1) will be described. In order to reduce ΔEst, it is most effective to reduce the spatial overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in principle. It is.

  In general, it is known that, in the electron orbit of a molecule, HOMO is distributed to an electron donating site and LUMO is distributed to an electron withdrawing site. Therefore, by introducing an electron-donating skeleton and an electron-withdrawing skeleton into the molecule, the position where HOMO and LUMO exist can be kept away.

  For example, in “Organic Optoelectronics at the Practical Stage”, Applied Physics Vol. 82, No. 6, 2013, electron-withdrawing skeletons such as cyano groups and triazines, and electron donations such as carbazole and diphenylamino groups By introducing a sex skeleton, LUMO and HOMO are respectively localized.

  In order to reduce ΔEst, it is also effective to reduce the change in molecular structure between the ground state and the triplet excited state of the compound. As a method for reducing the structural change, for example, it is effective to make the compound rigid. Rigidity described here means that there are few free-moving sites in a molecule, such as suppressing free rotation in the bond between rings in a molecule or introducing a condensed ring having a large π-conjugated plane. means. In particular, by making the site involved in light emission rigid, it is possible to reduce the structural change in the excited state.

[Electron density distribution]
In the electronic device material represented by the general formula (1), HOMO and LUMO are preferably substantially separated in the molecule from the viewpoint of reducing ΔEst. The distribution states of HOMO and LUMO can be obtained from the electron density distribution obtained when the structure is optimized, which is obtained by molecular orbital calculation.

  The structure optimization and the calculation of the electron density distribution of the electronic device material by molecular orbital calculation can be performed by molecular orbital calculation software using B3LYP as a functional and 6-31G (d) as a basis function. There is no particular limitation on the software, and any software can be used for the same calculation. In the molecular orbital calculation of the electronic device material of this example, Gaussian 09 (Revision C.01, M.J.Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian Corporation of the United States is used as software for molecular orbital calculation.

In addition, “the HOMO and the LUMO are substantially separated” means that the central parts of the HOMO orbital distribution and the LUMO orbital distribution calculated by the above molecular calculation are far apart, and more preferably the distribution of the HOMO orbital and the LUMO orbital. Mean that the distributions do not substantially overlap. The separation state between HOMO and LUMO is determined by the above-described structure optimization calculation using B3LYP as a functional and 6-31G (d) as a basis function, and further by a time-dependent density functional method (Time-Dependent DFT). Excited state calculation is performed to determine the energy levels of S ₁ and T ₁ (E (S ₁ ) and E (T ₁ ), respectively), and calculated as ΔEst = | E (S ₁ ) −E (T ₁ ) | It is also possible. The smaller the calculated ΔEst, the more the HOMO and the LUMO are separated.

  When the above electronic device material is applied to the light emitting layer of the organic EL element, ΔEst of the electronic device material calculated using the above calculation method is 0.90 eV or less. As a result of the experiment, when ΔEst of the electronic device material exceeds 0.90 eV, TADF properties are not exhibited. Further, ΔEst of the electronic device material is preferably 0.45 eV or less, more preferably 0.30 eV or less, and particularly preferably 0.10 eV or less.

[Lowest excited singlet energy level S ₁ ]
Lowest excited singlet energy level S ₁ of the electronic device material represented by the general formula (1) can be calculated by a conventionally known method. That is, a compound to be measured is vapor-deposited on a quartz substrate to prepare a sample, and an absorption spectrum (vertical axis: absorbance, horizontal axis: wavelength) of the sample is measured at normal temperature (300 K). Then, a tangent is drawn 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 and the horizontal axis.

However, when the aggregation property of the molecules of the electronic device material itself is relatively high, an error due to aggregation may occur in the measurement of the thin film. Considering that the Stokes shift of the π-conjugated compound is relatively small and the structural change between the excited state and the ground state is small, the lowest excited singlet energy level S ₁ is determined at room temperature (25 ° C.). The peak value of the maximum emission wavelength in the solution state is used as an approximate value. Here, as a solvent to be used, a solvent which does not affect the aggregation state of the electronic device material, that is, a solvent which has little influence of the solvent effect, for example, a non-polar solvent such as cyclohexane or toluene is used.

[Lowest excited triplet energy level T ₁ ]
For the lowest excited triplet energy level T ₁ of the electronic device material represented by the general formula (1) is calculated by photoluminescence (PL) properties of the solution or a thin film. For example, as a calculation method for a thin film, a fluorescent component and a phosphorescent component are separated by measuring a transient PL characteristic using a streak camera after a dispersion of a diluted π-conjugated compound is formed into a thin film. The lowest excited triplet energy level T ₁ can be obtained from the lowest excited singlet energy level S ₁ by setting the absolute value of this energy difference to ΔEst.

  In the measurement and evaluation, the absolute PL quantum yield was measured using an absolute PL quantum yield measuring device C9920-02 (manufactured by Hamamatsu Photonics). The luminescence lifetime was measured using a streak camera C4334 (manufactured by Hamamatsu Photonics) while exciting the sample with laser light.

[Energy levels of HOMO and LUMO]
The energy levels of HOMO and LUMO of the electronic device material represented by the general formula (1) are calculated by a structural optimization calculation using B3LYP as a functional and 6-31G (d) as a basis function.

  The LUMO energy level of the electronic device material represented by the general formula (1) is -1.8 eV or more, preferably -1.7 to -0.6 eV, more preferably -1.5 to -1. 1 eV. The fact that the energy level of LUMO is -1.8 eV or more means that the electronic device material represented by the general formula (1) does not have a strong electron-withdrawing group, that is, the energy level of HOMO does not become excessively low. Indicates that The HOMO energy level of the electronic device material represented by the general formula (1) is -5.5 eV or more, preferably -5.3 to -4.0 eV, and more preferably -5.0 to -5.0. It is 4.5 eV.

  In a conventional π-conjugated compound having a strong electron-withdrawing group, the HOMO level also decreases as the LUMO level decreases. When such a compound is used as a light-emitting material, the HOMO level and the LUMO level of the light-emitting material are low, so that it is difficult to select a host material, and there is a problem that a carrier balance during EL driving is lost. On the other hand, in the electronic device material represented by the general formula (1), since the LUMO level is relatively high, the HOMO level does not become excessively low, and excitons are easily generated on the electronic device material.

<2. Organic electroluminescence device>
[Application of electronic device materials to organic EL devices]
The structure of an organic EL element to which the electronic device material represented by the general formula (1) can be applied will be described.
In the organic EL element, the electronic device material represented by the above general formula (1) applicable to the organic EL element has an absolute value of ΔEst of 0.90 eV or less, and easily exhibits TADF properties. Therefore, the electronic device material represented by the general formula (1) can be used for various applications as an electronic device material of the delayed fluorescent substance. For example, in an organic EL device, an electronic device material represented by the general formula (1) can be used as a fluorescent compound.

  Further, since the electronic device material represented by the general formula (1) has bipolar properties and can cope with various energy levels, it can be used as a fluorescent compound, a host compound, and an assist dopant in an organic EL device. In addition, it can be used as a compound suitable for hole transport and electron transport. Therefore, the electronic device material represented by the general formula (1) is not limited to use as an electronic device material in a light emitting layer of an organic EL element, but includes a hole injection layer, a hole transport layer, an electron blocking layer, It can be used as an electronic device material in a hole blocking layer, an electron transport layer, an electron injection layer, an intermediate layer, and the like.

  For example, when the electronic device material represented by the general formula (1) is used as a host compound of an organic EL device, it is highly likely that the light emitting layer contains at least one of a fluorescent compound and a phosphorescent compound. It is preferable from the viewpoint of light emission. When the electronic device material represented by the general formula (1) is used as an assist dopant, the light emitting layer may contain at least one of a fluorescent compound and a phosphorescent compound and a host compound. It is preferable from the viewpoint of high light emission.

  The external quantum efficiency at room temperature (25 ° C.) of light emission of the organic EL element is preferably 1% or more, more preferably 5% or more. Here, [external quantum efficiency (%) = number of photons emitted to the outside of the organic EL element / number of electrons flowing to the organic EL element × 100].

[Configuration of Organic EL Element]
FIG. 1 shows a schematic configuration diagram (cross-sectional view) of the organic EL element. The organic EL element 10 shown in FIG. 1 is provided on a support substrate 14 and, in order from the support substrate 14 side, a first electrode (transparent electrode) 11, an organic layer 13 formed using an organic material, and the like. Two electrodes (counter electrodes) 12 are stacked in this order. At the end of the first electrode 11, a take-out portion 16 for the first electrode 11 is provided. The first electrode 11 and an external power supply (not shown) are electrically connected via the extraction unit 16. At the end of the second electrode 12, a take-out portion 17 for the second electrode 12 is provided. The second electrode 12 and an external power supply (not shown) are electrically connected through a take-out unit 17. The organic EL element 10 is configured to extract generated light at least from the support substrate 14 side.

  The organic EL element 10 has an auxiliary electrode 15 provided in contact with the first electrode 11 for the purpose of reducing the resistance of the first electrode 11. Examples of the auxiliary electrode 15 include a grid electrode connected to the extraction portion 16 of the first electrode 11. Further, the organic EL element 10 is sealed on a support substrate 14 with a sealing member 18 described below for the purpose of preventing the organic layer 13 made of an organic material or the like from being deteriorated. The sealing member 18 is fixed to the support substrate 14 via an adhesive 19. However, the terminal portions of the first electrode 11 (extracting portion 16) and the second electrode 12 (extracting portion 17) are exposed from the sealing member 18 while being insulated from each other by the organic layer 13 on the support substrate 14. It is provided in the state where it was set.

  Further, the layer structure of the organic EL element 10 is not limited, and may be a general layer structure. Here, the first electrode 11 functions as an anode (that is, an anode), and the second electrode 12 functions as a cathode (that is, a cathode). In this case, for example, the organic layer 13 has a configuration in which a hole injection layer 13a / a hole transport layer 13b / a light emitting layer 13c / an electron transport layer 13d / an electron injection layer 13e are sequentially stacked from the first electrode 11 side serving as an anode. As an example, among them, it is essential to have at least the light emitting layer 13c configured using an organic material. The hole injection layer 13a and the hole transport layer 13b may be provided as a hole transport injection layer. The electron transport layer 13d and the electron injection layer 13e may be provided as an electron transport injection layer. Further, these organic layers 13 may have a layer containing a material other than the organic material. For example, the electron injection layer 13e may be made of an inorganic material.

[Organic layer]
The organic EL element has a configuration having at least an organic layer between an anode and a cathode, and at least one of the organic layers is a light-emitting layer containing the above-mentioned electronic device material. The organic layer is a layer mainly composed of an organic material. The organic EL element can be suitably used for a lighting device and a display device. Typical element configurations of the organic EL device include the following configurations, but are 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 / emission layer / electron transport layer / electron injection layer / cathode (6) anode / hole injection layer / hole transport layer / emission 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

  In the above configuration, the organic EL element has an organic layer including a light-emitting layer except for an anode and a cathode. The space between the anode and the cathode may be entirely composed of an organic layer, or a layer other than the organic layer may be provided between the anode and the cathode. Among the above configurations, the configuration (7) is preferably used. Further, the organic layer is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the respective light emitting layers.

  If necessary, a hole blocking layer (also called a hole blocking layer) or an electron injection layer (also called a cathode buffer layer) may be provided between the light emitting layer and the cathode. Further, an electron blocking layer (also called an electron barrier layer) or a hole injection layer (also called an anode buffer layer) may be provided between the light emitting layer and the anode.

  The electron transport layer is a layer having a function of transporting electrons. In a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The hole transport layer is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The electron transporting layer and the hole transporting layer may be composed of a plurality of layers.

(Tandem structure)
Further, the organic layer of the organic EL element may have a so-called tandem structure in which a plurality of light emitting units each including at least one light emitting layer are stacked. As a typical element configuration of a tandem structure, for example, the following configuration 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 may be all the same or different. Further, two light emitting units may be the same, and the other one may be different. The plurality of light emitting units may be stacked directly or may be stacked via an intermediate layer. When a plurality of light emitting units are stacked via an intermediate layer, the configuration of the organic layer may or may not include the intermediate layer. The intermediate layer is generally called an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, and an intermediate insulating layer.Electrons are provided in an adjacent layer on the anode side, and holes are provided in an adjacent layer on the cathode side. As long as the layer has a function of supplying, a known material configuration can be used.

As a material used for the intermediate layer, for example, ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiOx, VOx, CuI, InN, GaN, CuAlO ₂ , Conductive inorganic compound layers such as 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 / Ag / ZnO , Bi ₂ O ₃ / Au / Bi ₂ O ₃ , TiO ₂ / TiN / TiO ₂ , TiO ₂ / ZrN / TiO _2, etc., fullerenes such as C ₆₀ , conductive organic layers such as oligothiophene, etc. Examples include conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, and metal-free porphyrins. It is not limited to these.
Preferred configurations in the light-emitting unit include, for example, those obtained by removing the anode and the cathode from the configurations of (1) to (7) described in the above representative element configurations, but are not limited thereto.

  Specific examples of the tandem type organic EL device include, for example, US Pat. No. 6,337,492, US Pat. No. 7,420,203, US Pat. No. 7,473,923, US Pat. No. 6,872,472, US Pat. No. 6,107,734, US Pat. Publication No. 2005/009087, JP-A-2006-228712, JP-A-2006-24791, JP-A-2006-49393, JP-A-2006-49394, JP-A-2006-49396, and JP-A-2011 JP-A-96679, JP-A-2005-340187, JP-A-47111424, JP-A-3496681, JP-A-38884564, JP-A-421213, JP-A-2010-192719, JP-A-2009-076929, Open 2008-0784 4, Japanese Patent Application Laid-Open No. 2007-059848, Japanese Patent Application Laid-Open No. 2003-272860, Japanese Patent Application Laid-Open No. 2003-045676, and the element configuration and constituent materials described in International Publication No. 2005/094130. It is not limited to these.

[Light-emitting layer]
The light-emitting layer that constitutes the organic EL element 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 a light-emitting portion is a light-emitting layer. Or the interface between the light emitting layer and the adjacent layer.

  There is no particular limitation on the total thickness of the light emitting layer, but the uniformity of the formed film, the prevention of applying an unnecessary high voltage at the time of light emission, and the improvement of the stability of the emission color with respect to the driving current are improved. From the viewpoint, it is preferably adjusted to a range of 2 nm to 5 μm, more preferably to a range of 2 to 500 nm, and still more preferably to a range of 5 to 200 nm. The thickness of each light emitting layer is preferably adjusted to a range of 2 nm to 1 μm, more preferably to a range of 2 to 200 nm, and still more preferably to a range of 3 to 150 nm.

  The light emitting layer may be a single layer or may be composed of a plurality of layers. When the electronic device material represented by the above general formula (1) is used for the light emitting layer, it may be used alone, or may be used as a mixture with a host material, a fluorescent light emitting material, a phosphorescent light emitting material, and the like described later. . It is preferable that at least one of the light-emitting layers contains an electronic device material as a light-emitting dopant (light-emitting compound, light-emitting dopant, simply dopant) or a host compound (matrix material, light-emitting host compound, host material).

  For example, at least one of the light-emitting layers preferably contains the electronic device material represented by the general formula (1) and a host compound. In this case, the electronic device material acts as a luminescent compound.

  Further, it is preferable that at least one of the light emitting layers contains the conjugated boron compound represented by the general formula (1) and at least one of a fluorescent compound and a phosphorescent compound. When the light emitting layer contains an electronic device material represented by the general formula (1) and a luminescent compound and does not contain a host compound, the electronic device material represented by the general formula (1) is used as a host compound. Works.

  Further, it is preferable that at least one of the light emitting layers contains the electronic device material represented by the general formula (1), at least one of a fluorescent compound and a phosphorescent compound, and a host compound. In these cases, the electronic device material acts as an assist dopant.

In each of the above-described configurations, the mechanism in which each action is expressed is the same. These mechanisms appear because the triplet exciton generated on the electronic device material represented by the general formula (1) is converted to a singlet exciton by inverse intersystem crossing (RISC). Therefore, when the light emitting layer contains the two components of the electronic device material represented by the general formula (1) and the light emitting compound, the energy levels of S ₁ and T ₁ of the electronic device material are determined by the light emitting compound Is preferably higher than the energy levels of S ₁ and T ₁ . Similarly, when the light emitting layer contains three components of the electronic device material represented by the general formula (1), the light emitting compound, and the host compound, the energy levels of S ₁ and T ₁ of the electronic device material It is lower than the energy level of the S ₁ and T ₁ of the host compound, higher than the energy level of the S ₁ and T ₁ of the luminescent compound.

  In this mechanism, all exciton energies generated on the electronic device material represented by the general formula (1) can be theoretically subjected to fluorescence resonance energy transfer (FRET) to the light emitting compound. Therefore, high luminous efficiency can be achieved.

When the electronic device material represented by the general formula (1) is used as an assist dopant, the light emitting layer contains a host compound in a mass ratio of 100% or more based on the electronic device material, and the light emitting compound contains the host compound in the electronic device material. It is preferable to contain 0.1 to 50% by mass ratio.
When the electronic device material represented by the general formula (1) is used as a host compound, the light-emitting layer preferably contains the light-emitting compound in a mass ratio of 0.1 to 50% based on the electronic device material.

  When the electronic device material represented by the general formula (1) is used as an assistant dopant or a host compound, it is preferable that the emission spectrum of the electronic device material represented by the general formula (1) and the absorption spectrum of the light-emitting compound overlap.

(1.1 Light-emitting compound (light-emitting dopant))
As the luminescent compound, a fluorescent dopant (fluorescent compound, fluorescent dopant) and a phosphorescent dopant (phosphorescent compound, phosphorescent dopant) are preferably used. It is preferable that the light emitting layer in the organic EL element contains the electronic device material represented by the above general formula (1) in a range of 0.1 to 50% by mass as a fluorescent compound or an assist dopant, particularly, It is preferable to contain it in the range of 1 to 30 mass%.

  The light emitting layer contains a light emitting compound in the range of 0.1 to 50% by mass, and particularly preferably in the range of 1 to 30% by mass. The concentration of the light-emitting compound in the light-emitting layer can be arbitrarily determined based on the specific light-emitting compound to be used and the requirements of the device. It may be contained and may have an arbitrary concentration distribution. Further, a plurality of kinds of light-emitting compounds may be used in combination, or a combination of fluorescent compounds having different structures or a combination of a fluorescent compound and a phosphorescent compound may be used. Thereby, an arbitrary luminescent color can be obtained.

  An electronic device material represented by the general formula (1) in which the absolute value (ΔEst) of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.90 eV or less, a luminescent compound, and a host compound In the case where is contained in the light emitting layer, the electronic device material represented by the general formula (1) acts as an assist dopant. When the light emitting layer contains only the electronic device material represented by the general formula (1), the electronic device material represented by the general formula (1) acts as a host compound and a light emitting compound.

  The color emitted by the organic EL element and the luminescent compound is shown in FIG. 3.16 on page 108 of the “New Edition of Color Science Handbook” (edited by The Japan Society of Color Science, The University of Tokyo Press, 1985), and the spectral radiance meter CS-2000 ( It is determined by the color when the result measured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.

In the organic EL device, it is preferable that one or a plurality of light-emitting layers contain a plurality of light-emitting compounds having different emission colors, and emit white light by synthesizing light of each color. There is no particular limitation on the combination of the light-emitting compounds that emit white light, and examples thereof include a combination of blue and orange or a combination of blue, green, and red. The white color in the organic EL element means that the chromaticity in the CIE1931 color system at 1000 cd / m ² is x = 0.39 ± 0.09, y = 0.38 ± 0.08.

(1.2 Fluorescent compound)
As the fluorescent compound (fluorescent dopant), an electronic device material represented by the general formula (1) may be used, or a known fluorescent dopant or a delayed fluorescent dopant used in a light emitting layer of an organic EL element may be appropriately used. You may select and use.

  Specific examples of known fluorescent dopants include, for example, anthracene derivatives, pyrene derivatives, chrysene derivatives, fluoranthene derivatives, perylene derivatives, fluorene derivatives, arylacetylene derivatives, styrylarylene derivatives, styrylamine derivatives, arylamine derivatives, boron complexes, coumarins Derivatives, pyran derivatives, cyanine derivatives, croconium derivatives, squarium derivatives, oxobenzanthracene derivatives, fluorescein derivatives, rhodamine derivatives, pyrylium derivatives, perylene derivatives, polythiophene derivatives, rare earth complex compounds, and the like. In recent years, light-emitting compounds utilizing delayed fluorescence have also been developed, and these may be used. Specific examples of the luminescent compound using delayed fluorescence include, for example, compounds described in International Publication No. 2011/156793, JP-A-2011-213643, JP-A-2010-93181, and JP-A-5366106. But not limited to these.

(1.3 Phosphorescent compound)
A phosphorescent compound is a compound in which light emission from an excited triplet is observed. Specifically, it is a compound that emits phosphorescence at room temperature (25 ° C.), and is defined as a compound having a phosphorescence quantum yield of 0.01 or more at 25 ° C. Preferably, the phosphorescence quantum yield is 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopy II, 4th Edition, Experimental Chemistry Lecture 7, pp. 398 (1992 edition, Maruzen). The phosphorescence quantum yield in a solution can be measured using various solvents, and it is sufficient that the phosphorescence quantum yield (0.01 or more) can be achieved in an arbitrary solvent.

The phosphorescent dopant can be appropriately selected and used from known ones used for the light emitting layer of the organic EL device. Specific examples of known phosphorescent dopants 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), WO 2009/100991, WO 2008/101842, WO 2003/040257, U.S. Patent Application Publication No. 2006/835469, U.S. Patent Application Publication 2006/2006. No. 0202194, U.S. Patent Application Publication No. 2007/0087321, U.S. Patent Application Publication No. 2005/02444673, 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), WO 2009/050290, WO 2002/015645, WO 2009/000673, US Patent Application Publication No. 2002/0034656, US Patent No. 7,332,232, US Patent Application Publication No. 2009/0108737, U.S. Patent Application Publication No. 2009/0039776, U.S. Patent No. 6,921,915, U.S. Patent No. 6,687,266, U.S. Patent Application Publication No. 2007/0190359, U.S. Patent Application Publication No. 2006/0008670, U.S. Patent Application Publication No. 2009/0165846, U.S. Patent Application Publication No. 2008/0015355, U.S. Patent No. 72050226, U.S. Patent No. 7396598, U.S. Patent Application Publication No. 2006 0263635 Pat, U.S. Patent Application Publication No. 2003/0138657, U.S. Patent Application Publication No. 2003/0152802, U.S. Patent No. 7090928, Angew. Chem. lnt. Ed. 47, 1 (2008), Chem. Mater. 18, 5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics 23, 3745 (2004), Appl. Phys. Lett. 74,1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/009024, International Publication No. 2006/056418, International Publication No. 2005/0193373, International Publication No. 2005/123873, International Publication No. 2005/123873, WO 2007/004380, WO 2006/082742, U.S. Patent Application Publication No. 2006/0251923, U.S. Patent Application Publication No. 2005/0260441, U.S. Patent No. 7393599. U.S. Patent No. 7,534,505, U.S. Patent No. 7,445,855, U.S. Patent Application Publication No. 2007/0190359, U.S. Patent Application Publication No. 2008/0297033, U.S. Patent No. 7,338,722, U.S. Patent Application Publication No. 2002/2002. 0 No. 34984, U.S. Pat. No. 7,279,704, U.S. Patent Application Publication No. 2006/098120, U.S. Patent Application Publication No. 2006/103874, International Publication No. 2005/076380, International Publication No. 2010/032663. WO 2008140115, WO 2007/052431, WO 2011/134013, WO 2011/157339, WO 2010/086089, WO 2009/113646, WO 2009/113646. 2012/020327, International Publication No. 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149, U.S. Patent Application Publication No. 2012/228584, U.S. Patent Application Publication No. 2012/2121. No. 6, JP-A-2012-069737, JP-A-2011-181303, JP-A-2009-1114086, JP-A-2003-81988, JP-A-2002-302671, JP-A-2002-363552 And the like.
Preferred phosphorescent dopants include organometallic complexes having Ir as a central metal. Further, a complex containing at least one coordination mode of a metal-carbon bond, a metal-nitrogen bond, a metal-oxygen bond, and a metal-sulfur bond is preferable.

(2 Host compound)
The host compound is a compound mainly responsible for charge injection and transport in the light emitting layer, and substantially no light emission of itself is observed in the organic EL device. The host compound preferably has a mass ratio of 20% or more in the layer 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 transfer of electric charge, and to increase the efficiency of the organic electroluminescence device.

  As the host compound, the electronic device material represented by the general formula (1) can be used. Further, a known host compound other than the electronic device material may be used, or the electronic device material represented by the general formula (1) and the known host compound may be used in combination. From the viewpoint of reverse energy transfer, it is preferable to use a host compound having an excitation energy higher than the lowest singlet energy of the light-emitting compound. Further, it is preferable to use a host compound having the lowest excited triplet energy larger than the excited triplet energy of the light-emitting compound.

  The host compound is responsible for transporting carriers and generating excitons in the light emitting layer. Therefore, it is preferable that the active species can be stably present in all of the active species in the cation radical state, the anion radical state, and the excited state, and does not cause a chemical change such as decomposition or addition reaction. Furthermore, it is preferable that the host molecules in the light emitting layer do not move at the angstrom level during the passage of time.

Further, luminescent compounds especially in combination is to indicate TADF emission host compound is required appropriate design of the molecular structure so as not to lower T ₁ reduction. For example, since long dwell time of the triplet excited state of the TADF compound, the higher the T ₁ energy level of the host compound itself is required. Further, the host compound with each other not to create a low T ₁ state in a state in association, 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 is required.

In order to satisfy the conditions required for such a host compound, the host compound itself must have a high electron hopping mobility, a high hole hopping mobility, and a structure in a triplet excited state. The change must be small. Examples of the host compound satisfying such requirements include a carbazole skeleton, an azacarbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an azadibenzofuran skeleton having a high T ₁ energy level.

  In addition, the host compound has a hole-transporting ability or an electron-transporting ability, prevents a long wavelength of light emission, and operates at a high glass transition temperature for stable driving of the organic EL element against high-temperature driving and heat generation during driving. (Tg) is preferred. The Tg of the host compound is preferably 90 ° C. or higher, and more preferably the Tg of the host compound is 120 ° C. or higher. The glass transition point (Tg) is a value determined by a method based on JIS K 7121-2012 using DSC (Differential Scanning Calorimetry).

It is preferable to use an electronic device material represented by the general formula (1) as the host compound. The electronic device material represented by the general formula (1) has a high T ₁ and is preferably used for a light-emitting material having a short emission wavelength (that is, a high energy level of T ₁ and S ₁ ). Can be.

When a known host compound is used for the organic EL device, specific examples thereof include compounds described in the following documents, but are not limited thereto.
JP-A-2001-257076, JP-A-2002-308855, JP-A-2001-313179, JP-A-2002-319493, JP-A-2001-357977, JP-A-2002-334786, JP-A-2002-8860, JP-A-2002-334787, JP-A-2002-15871, JP-A-2002-334788, JP-A-2002-43056, JP-A-2002-334789, JP-A-2002 No. 75645, JP-A-2002-338579, JP-A-2002-105445, JP-A-2002-343568, JP-A-2002-141173, JP-A-2002-352957, JP-A-2002-203683 Gazette, JP-A-2002-363227 JP-A-2002-231453, JP-A-2003-3165, JP-A-2002-234888, JP-A-2003-27048, JP-A-2002-255934, JP-A-2002-260861, JP-A-2002-280183, JP-A-2002-299060, JP-A-2002-302516, JP-A-2002-305083, JP-A-2002-305084, JP-A-2002-308837, U.S. Patent Publication No. 20030175553, U.S. Patent Publication No. 20060280965, U.S. Patent Publication No. 20050112407, U.S. Patent Publication No. 20090017330, U.S. Patent Publication No. 20090030202, U.S. Patent Publication No. 20050238919, International Publication No. 200910 International Publication No. 9234, International Publication No. 2009021262, International Publication No. 2008056746, International Publication No. 2004093207, International Publication No. 2005089025, International Publication No. 2007067796, International Publication No. 2007067754, International Publication No. 2004107822, International Publication No. 2005030900 WO2006114966, WO200986028, WO2009003898, WO201220947, JP2008-074939, JP2007-254297, EP20345538, WO2011055933, WO2012105933, No. 2012035853 and the like.
Specific examples of the compound include compounds represented by H-1 to H230 described in paragraphs [0255] to [0293] of JP-A-2015-38941, and the following chemical formulas H-231 to H-234. But not limited thereto.

[Electron transport layer]
The electron transporting layer may be 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 transporting layer is not particularly limited, but is usually in the range of 2 nm to 5 μm, more preferably 2 to 500 nm, and still more preferably 5 to 200 nm.

Further, in the organic EL element, when light generated in the light emitting layer is extracted from the electrode, light directly extracted from the light emitting layer and light extracted after being reflected by the electrode for extracting light and the electrode located on the opposite electrode interfere with each other. It is known to cause. In the case where light is reflected by the cathode, the interference effect can be efficiently used by appropriately adjusting the total thickness of the electron transporting layer between several nm and several μm. On the other hand, if 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 have any of an electron injecting or transporting property and a hole blocking property, and may be any of conventionally known compounds. Can be selected and used. For example, nitrogen-containing aromatic heterocyclic group derivatives (carbazole derivatives, azacarbazole derivatives (in which 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, benzothiazole derivatives, etc.), dibenzofuran derivatives , Dibenzothiophene derivatives, silole derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, triphenylene derivatives, etc.) and the like. It is.

Further, metal complexes having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, for example, tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7- Dibromo-8-quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, A metal complex in which the central metal is replaced with In, Mg, Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material.
In addition, metal-free or metal phthalocyanine, or those whose terminals are substituted with an alkyl group, a sulfonic acid group, or the like can be preferably used as the electron transporting material. Further, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as the electron transporting material, and an inorganic semiconductor such as n-type Si or n-type SiC like the hole injection layer and the hole transport layer. Can also be used as an electron transport material. In addition, a material in which these materials are introduced into a polymer chain, or a polymer material in which these materials are a main chain of a polymer can be used.

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

Specific examples of known electron transport materials used for organic EL devices include, but are not limited to, compounds described in the following documents.
U.S. Patent No. 6,528,187, U.S. Patent No. 7,230,107, U.S. Patent Application Publication No. 2005/0025993, U.S. Patent Application Publication No. 2004/0036077, U.S. Patent Application Publication No. 2009/0115316, U.S. Patent Published Application No. 2009/0101870, U.S. Patent Application Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132905, Appl. Phys. Lett. 75, 4 (1999), Appl. Phys. Lett. 79, 449 (2001), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 79,156 (2001), U.S. Patent No. 7,964,293, U.S. Patent Application Publication No. 2009/030202, WO 2004/080975, WO 2004/063159, WO 2005/085387, International WO 2006/067931, WO 2007/086552, WO 2008/114690, WO 2009/069442, WO 2009/066779, WO 2009/054253, WO 2011/0886935, WO 2010/150593, WO 2010/047707, EP23111826, JP2010-251675A, JP2009-209133A, JP2009-124114A, JP 2 08-277810, JP-A-2006-156445, JP-A-2005-340122, JP-A-2003-45662, JP-A-2003-31367, JP-A-2003-282270, International Publication 2012 / 115034 and the like.

Preferred known electron transporting materials include aromatic heterocyclic compounds containing at least one nitrogen atom and compounds containing a phosphorus atom. Examples include a pyridine derivative, a pyrimidine derivative, a pyrazine derivative, a triazine derivative, a dibenzofuran derivative, a dibenzothiophene derivative, an azadibenzofuran derivative, an azadibenzothiophene derivative, a carbazole derivative, an azacarbazole derivative, a benzimidazole derivative, and an arylphosphine oxide derivative.
The electron transport material may be used alone, or two or more kinds may be used in combination.

[Hole blocking layer]
The hole blocking layer is a layer having a function of an electron transporting layer in a broad sense, and is preferably made of a material having a function of transporting electrons and having a small ability to transport holes. , The probability of recombination of electrons and holes can be improved.

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

[Electron injection layer]
The electron injection layer (also referred to as a “cathode buffer layer”) is a layer provided between the cathode and the light emitting layer for lowering driving voltage and improving light emission luminance. For details of the electron injection layer, refer to “Organic EL Devices and the Forefront of Industrialization (NTS, November 30, 1998),” Vol. 2, Chapter 2, “Electrode Materials” (pages 123 to 166). Has been described.

  In the organic EL device, the electron injection layer can be provided as necessary, and can be provided 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 its thickness is preferably in the range of 0.1 to 5 nm depending on the material. It may be a non-uniform layer (film) in which the constituent material is intermittent.

The details of the electron injection layer are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586 and the like. Specific examples of materials preferably used for the electron injection layer include metals such as strontium and aluminum, alkali metal compounds such as lithium fluoride, sodium fluoride, and potassium fluoride, magnesium fluoride, and fluorides. Examples thereof include an alkaline earth metal compound represented by calcium, a metal oxide represented by aluminum oxide, a metal complex represented by lithium 8-hydroxyquinolinate (Liq), and the like. Further, the above-described electron transport material can be used.
The materials used for the electron injection layer may be used alone or in combination of two or more.

[Hole transport layer]
The hole transport layer may be 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 is not particularly limited, but is usually in the range of 5 nm to 5 μm, more preferably 2 to 500 nm, and still more preferably 5 to 200 nm.

  The material used for the hole transporting layer (hereinafter, referred to as a hole transporting material) may have any of a hole injecting or transporting property and an electron barrier property. Any one can be selected from 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, polyvinylcarbazole, polymer materials or oligomers having aromatic amines introduced into the main chain or side chain, polysilane, conductive Functional polymers or oligomers (eg, PEDOT / PSS, aniline-based copolymer, polyaniline, polythiophene, etc.).

Examples of the triarylamine derivative include a benzidine type represented by α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), a star burst type represented by MTDATA, Examples include compounds having fluorene or anthracene in the triarylamine-linked core.
Further, hexaazatriphenylene derivatives described in JP-T-2003-519432, JP-A-2006-135145, and the like can also be used as the hole transport material.
Further, a highly p-type hole transporting layer doped with impurities can be used. For example, JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, and J.P. Appl. Phys. , 95, 5773 (2004).

  Also, JP-A-11-251067, J.P. Huang et. al. It is also possible to use so-called p-type hole transporting materials and inorganic compounds such as p-type-Si and p-type-SiC described in a well-known document (Applied Physics Letters 80 (2002), p. 139). Further, an orthometalated organometallic complex having Ir or Pt as a central metal, such as Ir (ppy) 3, is also preferably used.

  As the hole transporting material, a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organic metal complex, and a polymer material or an oligomer in which an aromatic amine is introduced into a main chain or a side chain are preferable. Used.

Specific examples of known preferable hole transporting materials used for the organic EL device include, but are not limited to, compounds described in the following documents in addition to the above-mentioned documents.
For example, Appl. Phys. Lett. 69, 2160 (1996); 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); 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. 2006/02420279, U.S. Patent Application Publication No. 2008 / No. 0220265, U.S. Pat. No. 5,061,569, WO2007 / 002683, WO2009 / 018809, EP6509555, U.S. Patent Application Publication No. 2008/0124572, U.S. Patent Application Publication No. 2007/0278938. Specification, U.S. Patent Application Publication No. 2008/0106190, U.S. Patent Application Publication No. 2008/0018221, International Publication No. 2012/115034, JP-T-2003-519432, JP-A-2006-135145 , It includes country Patent Application No. 13/585981 Patent like.
The hole transport material may be used alone, or two or more kinds may be used in combination.

[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 a layer made of a material having a function of transporting holes and having a small ability to transport electrons. By blocking electrons while transporting holes, the probability of recombination between electrons and holes can be improved.

  The electron blocking layer provided in the organic EL element is preferably provided adjacent to the light emitting layer on the anode side. The thickness of the electron blocking layer is preferably in the range of 3 to 100 nm, and more preferably in the range of 5 to 30 nm. As the material used for the electron blocking layer, the above-described material used for the hole transporting layer is preferably used, and the above-described host compound is also preferably used for the electron blocking layer.

[Hole injection layer]
The hole injection layer (also referred to as an “anode buffer layer”) is a layer provided between an anode and a light emitting layer for lowering driving voltage and improving light emission luminance. For details of the hole injection layer, refer to Chapter 2, Chapter 2, "Electrode Materials" (pages 123 to 166) of "Organic EL Devices and Their Forefront of Industrialization (published by NTT Corporation on November 30, 1998)". It is described in. The hole injection layer is provided as needed, and is provided between the anode and the light emitting layer or between the anode and the hole transport layer.

The details of the hole injection layer are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-28869, and the like. Examples of the material used for the hole injection layer include the materials used for the above-described hole transport layer. In particular, phthalocyanine derivatives represented by copper phthalocyanine are described in JP-T-2003-519432, JP-A-2006-135145, and the like. Hexazatriphenylene derivatives, metal oxides such as vanadium oxide, amorphous carbon, conductive polymers such as polyaniline (emeraldine) and polythiophene, and orthometalated complexes such as tris (2-phenylpyridine) iridium complex And triarylamine derivatives.
The materials used for the above-described hole injection layer may be used alone or in combination of two or more.

[Additive]
The organic layer may further contain other additives in addition to the above-mentioned materials constituting each layer. Examples of the additives include halogen elements such as bromine, iodine and chlorine, halogenated compounds, alkali metal and alkaline earth metals such as Pd, Ca, and Na, and transition metal compounds, complexes, and salts. The content of the additive is not particularly limited, and is 1000 ppm or less, preferably 500 ppm or less, more preferably 50 ppm or less, based on the total mass% of the contained layer. However, it is not within this range depending on the purpose of improving the transportability of electrons and holes, the purpose of making the energy transfer of excitons advantageous, and the like.

[Method of forming organic layer]
A method for forming an organic layer (a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, an intermediate layer, and the like) of the organic EL element will be described. The method for forming the organic layer is not particularly limited, and a conventionally known method such as a vacuum deposition method or a wet method (wet process) can be used. In forming the organic layer, a different film formation method may be applied to each layer.

When an evaporation method is used to form the organic layer, conditions vary depending on the type of compound used and the like, but generally, the boat heating temperature is 50 to 450 ° C., the degree of vacuum is 10 ⁻⁶ to 10 ⁻² Pa, and the evaporation rate is 0. 0.01 to 50 nm / sec, the substrate temperature is −50 to 300 ° C., and the thickness of the layer (film) is 0.1 nm to 5 μm, preferably 5 to 200 nm. In the formation of the organic layer by the vapor deposition method, it is preferable that the hole injection layer to the cathode are produced consistently by one evacuation. However, the film may be taken out and subjected to a different film formation method. In that case, it is preferable to perform the operation in a dry inert gas atmosphere.

  As a wet method, a spin coating method, a casting method, an inkjet method, a printing method, a die coating method, a blade coating method, a roll coating method, a spray coating method, a curtain coating method, an LB method (Langmuir-Blodgett method), or the like is used. Can be. From the viewpoint of easily obtaining a uniform thin film and high productivity, it is preferable to use a method having high suitability for a roll-to-roll method such as a die coating method, a roll coating method, an ink jet method, and a spray coating method.

  In the wet method, as a liquid medium for dissolving or dispersing the material constituting the organic layer, for example, methyl ethyl ketone, ketones such as cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, Aromatic hydrocarbons such as xylene, mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used. In addition, as a dispersion method, ultrasonic waves, high shear force dispersion, media dispersion, and the like can be used.

  In the production of the organic layer, patterning may be performed by a metal mask, an inkjet printing method, or the like at the time of forming each layer as needed. When patterning, only the light emitting layer may be patterned, another layer may be patterned together with the light emitting layer, or the entire organic layer may be patterned.

[anode]
As the anode in the organic EL device, metals, alloys, electrically conductive compounds, and mixtures thereof having a large work function (4 eV or more, preferably 4.5 eV or more) are preferably used. When light emission of the organic EL element is taken out from the anode side, it is desirable that the light transmittance of the anode be greater than 10%. The sheet resistance of the anode is several hundred Ω / sq. The following is preferred. The thickness of the anode depends on the material, but is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm.

Examples of the material forming the anode include metals such as Au and Ag, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, a material such as IDIXO (In ₂ O ₃ —ZnO) that can form an amorphous and transparent conductive film may be used. Further, an organic material such as an organic conductive compound can be used. s

  In the formation of the anode, a thin film is formed using any of the above materials by an arbitrary method such as an evaporation method or a sputtering method, and a pattern is formed into a desired shape by a photolithography method or the like. Alternatively, when the pattern accuracy is not so required (about 100 μm or more), a pattern may be formed through a mask having a desired shape when the above material is formed by an evaporation method or a sputtering method. In the case of using a coatable substance such as an organic conductive compound, a wet film forming method such as a printing method and a coating method can be used.

[cathode]
For the cathode, a metal having a small work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof are used. Specifically, 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 ) mixture, indium, Lithium / aluminum mixtures, aluminum, rare earth metals and the like. Among them, a mixture of an electron-injecting metal and a second metal that is a stable metal having a large work function value, such as a magnesium / silver mixture, from the viewpoint of durability against electron injection and oxidation. Preferred are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like.

  In forming the cathode, a thin film is formed using the above-described material by an arbitrary method such as an evaporation method or a sputtering method. The sheet resistance as a cathode is several hundred Ω / sq. The following is preferred, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In addition, after the above-mentioned metal mentioned as a material for the cathode is formed in a thickness of 1 to 20 nm, a conductive transparent material described as a material for the anode is formed, thereby forming a cathode having a laminated structure, and is transparent or translucent. Can be manufactured. Thereby, for example, an organic EL element in which both the anode and the cathode have light transmittance can be manufactured.

[Support substrate]
There is no particular limitation on the type of glass, plastic, or the like as a support substrate (hereinafter, also referred to as a substrate or a base material) applicable to the organic EL element. When light is not extracted from the support substrate side, the support substrate may be opaque. Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films and opaque resin substrates, and ceramic substrates. When light is extracted from the support substrate side, the support substrate is preferably transparent. Preferred examples of the transparent support substrate include glass, quartz, and a transparent resin film. A particularly preferred supporting substrate is a resin film capable of giving flexibility to the organic EL element.

  Examples of the resin film include polyester such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, and cellulose acetate propionate ( CAP), cellulose esters such as cellulose acetate phthalate and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyetherketone, polyimide , Polyether sulfone (PES), polyphenylene sulfide, polysulfones, Riether imide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acryl, polyarylates, and cycloolefins such as ARTON (trade name, manufactured by JSR) and Apel (trade name, manufactured by Mitsui Chemicals) Base resin.

On the surface of the resin film, a gas barrier layer composed of an inorganic or organic film or a hybrid film of both may be formed. In this case, the resin film having the gas barrier layer has a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) of 0. 0 measured by a method according to JIS K 7129-1992. it is preferably not more than 01g ^/ m 2 · 24h. Furthermore, the oxygen permeability measured by a method according to JIS K 7126-1987 is 1 × 10 ⁻³ ml / m ² · 24 h · atm or less, and the water vapor permeability is 1 × 10 ⁻⁵ g / m ² · It is preferably 24 hours or less.

  As a material for forming the gas barrier layer, any material may be used as long as it has a function of suppressing intrusion of elements such as moisture and oxygen which cause deterioration of the organic EL element, and for example, silicon oxide, silicon dioxide, silicon nitride and the like can be used. Further, in order to improve the brittleness of the gas barrier layer, it is more preferable to have a laminated structure of a layer made of an inorganic material and a layer made of an organic material. The order of laminating the inorganic layer and the organic layer is not particularly limited, but it is preferable that both are alternately laminated plural times.

  There is no particular limitation on the method for forming the gas barrier layer, and examples thereof include a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, an ion plating method, a plasma polymerization method, and an atmospheric pressure plasma polymerization method. , A plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used. For the formation of the gas barrier layer, it is particularly preferable to use the atmospheric pressure plasma polymerization method described in JP-A-2004-68143.

[Sealing]
As a method of sealing the organic EL element, for example, a method of adhering a sealing member to a supporting substrate so as to sandwich the organic EL element can be used. The sealing member only needs to be disposed so as to cover a portion of the organic EL element excluding the extraction electrode and the like, and may have a concave plate shape or a flat plate shape. In addition, transparency and electrical insulation are not particularly limited.

  Examples of the sealing member include a glass plate, a polymer plate, a polymer film, a metal plate, and a metal 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 and the polymer film include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate and metal film include 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.

From the viewpoint that the organic EL element can be made thinner, it is preferable to use a polymer film or a metal film as the sealing member. Further, the polymer film has an oxygen permeability of 1 × 10 ⁻³ ml / m ² · 24 h or less measured by a method according to JIS K 7126-1987, and a water vapor measured by a method according to JIS K 7129-1992. permeability (25 ± 0.5 ℃, relative humidity of 90 ± 2%) is preferably not less than ^{1 × 10 -3 g / m 2} · 24h.

  As the adhesive for bonding the sealing member, for example, an acrylic acid-based oligomer, a photocurable and thermosetting adhesive having a reactive vinyl group of a methacrylic acid-based oligomer, a moisture-curable type such as 2-cyanoacrylate, etc. Adhesives. Further, a heat and chemical curing type (two-liquid mixing) of an epoxy type or the like can be used. In addition, hot melt type polyamide, polyester, and polyolefin can be used. In addition, a cation-curable ultraviolet-curable epoxy resin adhesive can be used.

  Note that since an organic EL element may be deteriorated by heat treatment, it is preferable to use an adhesive that can be adhesively cured at room temperature to 80 ° C. or lower. Further, a desiccant may be dispersed in the adhesive. A commercially available dispenser may be used for applying the adhesive to the sealing portion, or printing may be performed like screen printing.

  Further, the sealing member preferably has a laminated structure of an inorganic layer and a layer made of an organic material. The method for forming these films is not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, an ion plating method, a plasma polymerization method, and an atmospheric pressure plasma pressure method. A legal method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

  It is preferable to inject an inert gas such as nitrogen or argon, or an inert liquid such as fluorocarbon or silicon oil into the gap between the sealing member and the support substrate. It is also possible to make a vacuum. Further, a hygroscopic compound can be sealed in the gap. Examples of the hygroscopic compound include metal oxides (eg, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide, etc.) and sulfates (eg, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate) Etc.), metal halides (eg, calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), perchloric acids (eg, perchloric acid) Barium, magnesium perchlorate, etc.). Among sulfates, metal halides and perchloric acids, anhydrous salts are preferably used.

[Protective film, protective plate]
In order to increase the mechanical strength of the organic EL element, a protective film or a protective plate may be provided outside the sealing member. In particular, when the organic EL element is sealed with a sealing film, it is preferable to provide a protective film or a protective plate in order to increase mechanical strength. As a material that can be used as the protective film and the protective plate, a glass plate, a polymer plate, a polymer film, a metal plate, a metal film, or the like can be used as in the above-described sealing member. It is preferable to use a polymer film as a protective film because it is lightweight and can be made thin.

[Light extraction enhancement technology]
Since the organic EL element emits light inside a layer having a refractive index higher than that of air (with a refractive index in the range of about 1.6 to 2.1), about 15% to about 20% of light generated in the light emitting layer is emitted. It is generally said that you can only take it out. This is because light incident on an interface (for example, an interface between a transparent substrate and air) at an angle θ equal to or larger than the critical angle causes total reflection and cannot be extracted outside the element. In addition, light is totally reflected at each interface between the transparent electrode, the organic layer, the transparent substrate, and the like, and light is guided in each layer and escapes in the lateral direction of the element.

  As a method and a configuration for improving the light extraction efficiency of the organic EL element, for example, a method of forming irregularities on the surface of a transparent substrate to prevent total reflection at an interface between the transparent substrate and air (for example, US Pat. No. 4,774,435) ), A method of improving efficiency by imparting light condensing properties to a substrate (for example, JP-A-63-31479), and a method of forming a reflective surface on a side surface of an element (for example, JP-A-1-220394). Japanese Patent Application Laid-Open No. 62-172691), a method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between a substrate and a luminous body, A method of introducing a flat layer having a lower refractive index than that of a substrate (for example, Japanese Patent Application Laid-Open No. 2001-202827) and a method of forming a diffraction grating between layers constituting an element (including between a substrate and the outside world) 11- JP), etc. 83751 can be mentioned.

  An organic EL element can be used in combination with the above-described method and configuration for improving light extraction efficiency. In particular, it is preferable to apply a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light-emitting body, or a method of forming a diffraction grating between each layer (including between the substrate and the outside world).

[Light collecting sheet]
The organic EL element can be provided with, for example, a microlens array-like structure or a so-called light-collecting sheet on the light-extracting side of a supporting substrate (substrate) to condense light in a specific direction, thereby increasing luminance in a specific direction. As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably in the range of 10 to 100 μm. If it is smaller than this, the effect of diffraction occurs and coloring occurs, and if it is too large, the thickness increases, which is not preferable. As the condensing sheet, for example, a sheet practically used in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. The shape of the prism sheet may be, for example, a substrate in which a triangular stripe having a vertex angle of 90 degrees and a pitch of 50 μm is formed, or a shape in which the vertex angle is rounded and the pitch is randomly changed. The shape may be a bent shape or another shape. Further, a light diffusing plate / film may be used in combination with the light-condensing sheet in order to control the light emission angle from the organic EL element. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

<3. Lighting device, display device>
The above-described organic EL element can be used as an electronic device, for example, a display device, a display, and various light emitting devices. Light emitting devices include, for example, lighting devices (home lighting, car interior lighting), clocks and backlights for LCDs, signboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copiers, light sources for optical communication processors, and light sources. Light sources for sensors and the like can be mentioned. In particular, it can be effectively used for a backlight of a liquid crystal display device and a light source for illumination.

[Display device]
The organic EL element can be applied to a single-color display device and a multi-color display device. In the following description, a multicolor display device will be described as an example of a display device.

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

  In the case of forming a multicolor display device, when forming a light emitting layer of an organic EL element, a shadow mask is arranged and a film is formed on one surface by an evaporation method, a casting method, a spin coating method, an inkjet method, a printing method, or the like. Form. Thus, in the organic EL element, a light emitting layer having an arbitrary light emitting pattern can be formed for each light emitting layer of a different light emitting color. By combining the patterned light emitting layers, a display device capable of multicolor display can be formed.

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

  Light emitting sources include home lighting, interior lighting, backlights for clocks and liquid crystals, advertising signs, traffic lights, light sources for optical storage media, light sources for electrophotographic copiers, light sources for optical communication processors, light sources for optical sensors, etc. Is mentioned.

(Configuration of display device)
Hereinafter, an example of a display device having an organic EL element will be described with reference to the drawings. FIG. 2 is a schematic diagram illustrating a configuration of a display device including an organic EL element. The display device 20 shown in FIG. 2 can display image information by light emission of the organic EL element, and is applied to a display such as a mobile phone, for example.

  The display device 20 includes a display unit 21 having a plurality of pixels, a control unit 22 that performs image scanning of the display unit 21 based on image information, and a wiring unit 23 that electrically connects the display unit 21 and the control unit 22. Having. The control unit 22 is electrically connected to the display unit 21 via the wiring unit 23. The control unit 22 sends a scanning signal and an image data signal based on image information from the outside to each pixel. Each pixel sequentially emits light for each scanning line in accordance with an image data signal by performing image scanning by a scanning signal. Thereby, the image information is displayed on the display device 20.

  Next, a schematic diagram of a display portion of a display device using an active matrix system is shown in FIG. The display unit 31 illustrated in FIG. 3 includes a wiring unit including a plurality of scanning lines 33 and data lines 34, a plurality of pixels 32, and the like on a substrate 35. FIG. 3 shows a case where the light emitted from the pixel 32 is extracted in the direction of the white arrow (downward).

  The scanning lines 33 and the plurality of data lines 34 of the wiring portion are each made of a conductive material. The scanning lines 33 and the data lines 34 are orthogonal to each other in a grid pattern, and the pixels 32 are connected at positions where the scanning lines 33 and the data lines 34 are orthogonal to each other. When a scanning signal is applied from the scanning line 33, the pixel 32 receives an image data signal from the data line 34 and emits light according to the received image data.

  Next, a light emitting process of the pixel will be described. FIG. 4 is a schematic diagram showing a pixel circuit. The pixel includes an organic EL element 40, a switching transistor 41, a driving transistor 42, a capacitor 43, and the like. In FIG. 4, an image data signal is applied to the drain of the switching transistor 41 via the data line 34 from the control unit. Then, when a scanning signal is applied from the control unit to the gate of the switching transistor 41 via the scanning line 33, the driving of the switching transistor 41 is turned on, and the image data signal applied to the drain is applied to the capacitor 43 and the driving transistor 42. It is transmitted to the gate.

  By transmitting the image data signal, the capacitor 43 is charged according to the potential of the image data signal, and the drive of the drive transistor 42 is turned on. The drive transistor 42 has a drain connected to the power supply line 44, a source connected to the electrode of the organic EL element 40, and from the power supply line 44 to the organic EL element 40 according 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 33 by the sequential scanning of the control unit, the driving of the switching transistor 41 is turned off. However, even when the driving of the switching transistor 41 is turned off, the capacitor 43 holds the potential of the charged image data signal, so that the driving of the driving transistor 42 is kept on and the next scanning signal is applied. Light emission of the organic EL element 40 continues until this. When the next scanning signal is applied by the sequential scanning, the driving transistor 42 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 40 emits light.

  Here, the light emission of the organic EL element 40 may be a light emission of a plurality of gradations by a multi-valued image data signal having a plurality of gradation potentials, or a predetermined light emission amount on / off by a binary image data signal. Good. Further, the holding of the potential of the capacitor 43 may be continued until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.

  The drive of the display device is not limited to the active matrix method described above, and may be a passive matrix light emission drive in which the organic EL element emits light in accordance with the data signal only when the scanning signal is scanned. FIG. 5 is a schematic view of a display portion of a display device using a passive matrix system. In the display unit 51 shown in FIG. 5, a plurality of scanning lines 55 and a plurality of image data lines 56 are provided in a lattice shape so as to face each other with a pixel 53 therebetween. When the scanning signal of the scanning line 55 is applied by the sequential scanning, the pixels 53 connected to the applied scanning line 55 emit light according to the image data signal. In the passive matrix method, there is no active element in the pixel 53, and the manufacturing cost can be reduced.

[Lighting device]
The organic EL element can be used for a lighting device. The organic EL element may be used as an organic EL element having a resonator structure. The intended use of the organic EL device having such a resonator structure is, for example, a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processor, a light source of an optical sensor, and the like. Not limited. Further, it may be used for the above purpose by causing laser oscillation. Further, the organic EL element may be used as a kind of lamp for illumination or as an exposure light source, or may be used as a projection device of a type for projecting an image.

  Further, the electronic device material represented by the general formula (1) can be applied to a lighting device including an organic EL element which emits substantially white light. For example, when a plurality of light-emitting materials are used, white light can be obtained by simultaneously emitting a plurality of light-emitting colors and mixing the colors. As a combination of a plurality of emission colors, those containing three emission maximum wavelengths of the three primary colors of red, green and blue may be used, or two using the relationship of complementary colors such as blue and yellow, blue green and orange, etc. It may contain a maximum emission wavelength.

  One mode of a lighting device including an organic EL element is described. 6 and 7 are schematic diagrams of the lighting device. FIG. 6 shows a schematic diagram of the lighting device 60, and FIG. 7 shows a cross-sectional view of the lighting device 60.

  As shown in FIG. 6, the organic EL element 61 in the lighting device 60 is covered with a glass substrate 68 and a glass cover 62. The sealing work of the organic EL element 61 by the glass substrate 68 and the glass cover 62 is performed by using a glove box (purity of 99.999% or higher) under a nitrogen atmosphere without bringing the organic EL element 61 in the lighting device 60 into contact with the atmosphere. Under an atmosphere of pure nitrogen gas).

  As shown in FIG. 7, in the lighting device 60, a support substrate 65 with a transparent electrode, an organic layer 64, and a cathode 65 are stacked on a glass substrate 68 to provide an organic EL element 61. Further, a water catching agent 67 is arranged in the glass cover 62, and a gap between the glass substrate 68 and the glass cover 62 is filled with an inert gas such as nitrogen.

  The lighting device 60 shown in FIGS. 6 and 7 can be manufactured as follows. First, the non-light-emitting surface of the organic EL element 61 on the glass substrate 68 is covered with a glass cover 62. At this time, an epoxy-based photocurable adhesive (Lux Track LC0629B manufactured by Toagosei Co., Ltd.) is disposed as a sealing material at a contact portion between the glass substrate 68 and the glass cover 62. Then, the glass substrate 68 and the glass cover 62 are brought into close contact with each other, and UV light is irradiated from the glass substrate 68 side to cure the sealing material. Thus, the organic EL element 61 is sealed with the glass substrate 68 and the glass cover 62, and the lighting device 60 can be manufactured.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto. In the following examples, ΔEst, HOMO, and LUMO of the compound were determined by the following methods.

(Calculation of ΔEst, HOMO and LUMO energy levels)
The energy levels of HOMO and LUMO were calculated from the structure optimization calculation using B3LYP as a functional and 6-31G (d) as a basis function. Gaussian 09 (Revision C.01, MJFrisch, et al, Gaussian, Inc., 2010.), a molecular orbital calculation software manufactured by Gaussian, USA, was used for the structure optimization calculation.
Further, using the optimized structure, an excited state calculation is performed by a time-dependent density functional method (Time-Dependent DFT) using B3LYP as a functional and 6-31G (d) as a basis function, and each compound is excited. The energy levels E (S ₁ ) and E (T ₁ ) were obtained, and ΔEst was calculated from [ΔEst = | E (S ₁ ) −E (T ₁ ) |].

[Example 1]
(Preparation of organic EL element 1-1)
On a 50 mm × 50 mm × 0.7 mm (thickness) glass substrate, ITO (indium tin oxide) was deposited to a thickness of 150 nm and then patterned to form an ITO transparent electrode as an anode. The transparent substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and then subjected to UV ozone cleaning for 5 minutes. The obtained transparent substrate was fixed to a substrate holder of a commercially available vacuum evaporation apparatus.

  Each of the evaporation crucibles in the vacuum evaporation apparatus was filled with the constituent material of each layer in an amount optimal for the device fabrication. The crucible for vapor deposition used was made of a molybdenum or tungsten resistance heating material.

After reducing the pressure in the vacuum deposition apparatus to a degree of vacuum of 1 × 10 ⁻⁴ Pa, a current was passed through a deposition crucible containing HAT-CN (1,4,5,8,9,12-hexaazatriphenylenehexacarbonitrile). Then, HAT-CN was deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / sec to form a hole injection transport layer having a thickness of 10 nm.

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

  MCP (1,3-bis (N-carbazolyl) benzene) as a host compound and Comparative Compound 1 as a luminescent compound were deposited at a deposition rate of 0.1 nm / sec so as to be 95% and 5% by volume, respectively. Co-evaporation was performed to form a light emitting layer having a thickness of 30 nm. Note that Comparative Compound 1 has the following structure.

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

  Further, after depositing lithium fluoride to a thickness of 0.5 nm, aluminum was further deposited to a thickness of 100 nm to form a cathode.

  In an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more, the non-light-emitting surface side of the obtained device was covered with a can-shaped glass cover, and an electrode lead-out wiring was provided to produce an organic EL device 1-1. .

(Preparation of organic EL elements 1-2 to 1-16)
Organic EL devices 1-2 to 1-16 were produced in the same manner as in the organic EL device 1-1, except that the luminescent compound was changed as shown in Table 1. In addition, the comparative compound 2 has the following structure.

(Evaluation 1: Measurement of relative luminous efficiency)
The produced organic EL device emitted light at room temperature (about 25 ° C.) and a constant current of ^2.5 mA / cm ² . Then, the light emission luminance of the organic EL element immediately after the start of light emission was measured using a spectral radiance meter CS-2000 (manufactured by Konica Minolta), and the obtained light emission luminance was applied to the following equation to obtain the luminance of each organic EL element. The light emission luminance was obtained as a relative light emission luminance with respect to the light emission luminance of the organic EL element 1-1. The larger the numerical value obtained, the better the result.
Relative luminous efficiency (%) = (Emission luminance of each organic EL element / Emission luminance of organic EL element 1-1) × 100

(Evaluation 2: Measurement of change in relative emission luminance due to high-temperature storage)
The prepared organic EL device was allowed to emit light at a temperature of 80 ° C. and a constant current of ^2.5 mA / cm ² , and the emission luminance immediately after the start of emission and the emission luminance 120 hours after the start were measured using a spectral radiance meter CS-2000. (Manufactured by Konica Minolta). From the obtained light emission luminance immediately after the start of light emission and after 120 hours, a change in light emission luminance was determined.
The amount of change in light emission luminance obtained above was applied to the following equation to determine the relative value of the amount of change in light emission luminance of each organic EL element to the amount of change in light emission luminance of organic EL element 2-1.
Relative luminance change (%) due to high temperature storage = (luminance change of each organic EL element / luminous luminance change of organic EL element 1-1) × 100

  Table 1 shows the luminescent compounds of each of the prepared organic EL devices 1-1 to 16, ΔEst of the luminescent compounds, and the evaluation results.

As is clear from Table 1, the organic EL elements 1-3 to 1-16 using the electronic device material represented by the above general formula (1) as a luminescent compound all have a relative luminous efficiency of 118 or more. In addition, a change in relative light emission luminance due to high-temperature storage is suppressed to 55 or less. On the other hand, the organic EL device 1-1 using the comparative compound 1 in which a part around boron is not cyclized as the light emitting compound, or X ₁ and X ₂ of the general formula (1) are carbon atoms. The organic EL element 1-2 using the comparative compound 2 which is an atom as a light-emitting compound has lower luminous efficiency than the organic EL elements 1-3 to 1-16 and has a large decrease in luminance during high-temperature storage. Therefore, by using the electronic device material represented by the general formula (1) as a light emitting compound, an organic EL element having high luminous efficiency and little change in relative luminous luminance due to high temperature storage can be configured.

[Example 2]
(Production of Organic EL Element 2-1)
On a glass substrate of 50 mm × 50 mm × 0.7 mm (thickness), ITO (indium tin oxide) was formed in a thickness of 150 nm and patterned. Further, the transparent substrate provided with the ITO transparent electrode was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. Thereafter, this transparent substrate was fixed to a substrate holder of a commercially available vacuum evaporation apparatus.

  In each of the resistance heating boats for vapor deposition in the vacuum vapor deposition apparatus, the constituent material of each layer was filled in an amount optimal for producing each element. The resistance heating boat was made of molybdenum or tungsten.

After reducing the pressure to a degree of vacuum of 1 × 10 ⁻⁴ Pa, the resistance heating boat containing HAT-CN was energized and heated, and was deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / sec. A hole injection layer was formed.

  Next, α-NPD was deposited at a deposition rate of 0.1 nm / sec to form a hole transport layer having a thickness of 30 nm.

  Next, the resistance heating boat containing Comparative Compound 3 and the Firpic, which is a comparative host compound, is heated by energization, and is co-evaporated on the hole transport layer at an evaporation rate of 0.1 nm / sec and 0.010 nm / sec, respectively. Thus, a light emitting layer having a thickness of 40 nm was formed.

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

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

(Production of Organic EL Devices 2-2, 2-3, 2-5 to 2-9, 2-11, 2-12, 2-14, 2-15)
The organic EL elements 2-2, 2-3, 2-5 to 2-9, and 2-11 were manufactured in the same manner as the organic EL element 2-1 except that the host compound was changed from the comparative compound 1 as shown in Table 2. , 2-12, 2-14, and 2-15. In addition, the comparative compound 4 has the following structure.

(Preparation of Organic EL Devices 2-4, 2-10, 2-13, 2-16)
The organic EL elements 2-4, 2-10, 2-13, and 2--2 were changed in the same manner as the organic EL element 2-1 except that the host compound was changed as shown in Table 2 and the Firpic was changed to Dopant-1. 16 were produced.

  The same evaluation as in Example 1 described above was performed on each of the manufactured organic EL elements 2-1 to 2-16. Table 2 shows the host compound, the dopant material, the ΔEst of the host compound, and the results of the above-mentioned evaluations for the organic EL devices 2-1 to 2-16.

As is clear from Table 2, the organic EL elements 2-3 to 2-16 using the electronic device material represented by the general formula (1) as a host compound all have a relative luminous efficiency of 131 or more, In addition, a change in relative light emission luminance due to high-temperature storage is suppressed to 58 or less. On the other hand, the organic EL device 2-1 and the organic EL device 2-2 using the comparative compound 3 or the comparative compound 4 in which X ₁ and X ₂ of the general formula (1) are carbon atoms as the host compound are the organic EL devices. The luminous efficiency is lower than that of the devices 2-3 to 2-16, and the decrease in luminance during high-temperature storage is large. Therefore, by using the electronic device material represented by the above general formula (1) as a host compound, an organic EL element having high luminous efficiency and little change in relative luminous luminance due to high-temperature storage can be configured.

[Example 3]
(Preparation of Organic EL Element 3-1)
After patterning a substrate (NA45 manufactured by AvanStrate) having a film of ITO (indium tin oxide) formed on a 100 mm × 100 mm × 1.1 mm glass substrate as an anode, the substrate with an ITO transparent electrode was washed with isopropyl alcohol. Ultrasonic cleaning, drying with dry nitrogen gas, and UV ozone cleaning were performed for 5 minutes.

  Next, a solution prepared by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water was used on the ITO transparent electrode. Under a condition of 3000 rpm and 30 seconds, a thin film was formed by a spin coating method. Thereafter, the resultant was dried at 200 ° C. for 1 hour to provide a hole injection layer having a thickness of 20 nm. The above substrate on which the hole injection layer is formed is fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus, and each crucible for vapor deposition in the vacuum vapor deposition apparatus is filled with a constituent material of each layer with an optimal amount for producing each element. did. The crucible for vapor deposition used was made of a molybdenum or tungsten resistance heating material.

After reducing the pressure to a degree of vacuum of 1 × 10 ⁻⁴ Pa, α-NPD was deposited on the hole injection layer at a deposition rate of 0.1 nm / sec to form a hole transport layer having a thickness of 40 nm. The following HOST-1 and 1,2,5,8,11-tetra-t-butylperylene as a luminescent compound were deposited at a deposition rate of 0.1 nm / sec so that the volume percentages were 96% and 4%, respectively. Co-evaporation was performed to form a light-emitting layer having a thickness of 35 nm.
Thereafter, TPBi (1,3,5-tris (N-phenylbenzimidazol-2-yl)) was deposited at a deposition rate of 0.1 nm / sec to form an electron transport layer having a thickness of 30 nm.
Further, after forming sodium fluoride with a film thickness of 1 nm, aluminum was evaporated to 100 nm to form a cathode.
The non-light-emitting surface side of the device was covered with a can-shaped glass cover in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was provided to produce an organic EL device 3-1.

(Preparation of organic EL element 3-2)
The above-mentioned HOST-1 was used as a host compound, 2,5,8,11-tetra-t-butylperylene as a luminescent compound, and Comparative Compound 4 as a third component (assist dopant material). %, And 15% by volume, and the organic EL element 3-2 was produced in the same manner as the production of the organic EL element 3-1 except that the light emitting layer was formed.

(Preparation of organic EL elements 3-3 to 3-16)
Organic EL devices 3-3 to 3-16 were produced in the same manner as in the organic EL device 3-2 except that the third component (assist dopant material) was changed as shown in Table 3.

  The same evaluation as in Example 1 described above was performed on each of the manufactured organic EL elements 3-1 to 3-16. Table 3 shows the assist dopant material, the ΔEst of the assist dopant material, and the above-described evaluation results of the manufactured organic EL elements 3-1 to 3-16.

As is clear from Table 3, the organic EL elements 3-4 to 3-16 using the electronic device material represented by the general formula (1) as an assist dopant material all have a relative luminous efficiency of 130 or more. In addition, the change in relative emission luminance due to high-temperature storage is suppressed to 64 or less. On the other hand, an organic EL element 3-1 using no assist dopant material, an organic EL element 3-2 using a comparative compound 2 in which a part around boron is not cyclized as an assist dopant material, The organic EL element 3-3 using the comparative compound 4 in which X ₁ and X ₂ of the general formula (1) are carbon atoms as the dopant material has lower luminous efficiency than the organic EL elements 3-4 to 3-16, The decrease in luminance during high-temperature storage is large. Therefore, by using the electronic device material represented by the above general formula (1) as an assist dopant material, an organic EL element having high luminous efficiency and little change in relative luminous luminance due to high-temperature storage can be configured.

  It should be noted that the present invention is not limited to the configuration described in the above embodiment, and various modifications and changes can be made without departing from the configuration of the present invention.

  10, 40, 61 organic EL element, 11 first electrode, 12 second electrode, 13, 64 organic layer, 13a hole injection layer, 13b hole transport layer, 13c light emitting layer, 13d electron transport layer, 13e electron injection layer , 14 support substrate, 15 auxiliary electrode, 16, 17 take-out unit, 18 sealing member, 19 adhesive, 20 display device, 21, 31, 51 display unit, 22 control unit, 23 wiring unit, 32, 53 pixel, 33 , 55 scanning lines, 34 data lines, 35 substrates, 41 switching transistors, 42 driving transistors, 43 capacitors, 44 power lines, 50 pitches, 56 image data lines, 60 lighting devices, 62 glass covers, 65 cathodes, 65 with transparent electrodes Support substrate, 67 water collecting agent, 68 glass substrate

Claims (9)

Having a structure represented by the following general formula (1),
An electronic device material, wherein the absolute value ΔEst of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.90 eV or less.

[In the general formula (1), X ₁ and X ₂ each independently represent NR ₁₀ , an oxygen atom or a sulfur atom. R ₁₀ represents a hydrogen atom, a chain alkyl group, a cyclic alkyl group, an aromatic hydrocarbon ring group or an aromatic heterocyclic group. Y ₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group. R _{1 to} R ₉ each independently represent a hydrogen atom or a substituent. ] _2. The electronic device material according to claim 1, wherein in the general formula (1), X ₁ and X ₂ are oxygen atoms. 3. In the general formula (1), X ₁ is NR ₁₁ and X ₂ is an oxygen atom (provided that R ₁₁ is a hydrogen atom, a chain alkyl group, a cyclic alkyl group, an aromatic hydrocarbon ring group, or an aromatic hydrocarbon group). The electronic device material according to claim 1, wherein the material represents a heterocyclic group. In the general formula (1), X ₁ is NR ₁₂ and X ₂ is NR ₁₃ (provided that R ₁₂ and R ₁₃ are a hydrogen atom, a chain alkyl group, a cyclic alkyl group, an aromatic hydrocarbon ring The electronic device material according to claim 1, which represents a group or an aromatic heterocyclic group). An anode, a cathode, and an organic electroluminescence device having an organic layer sandwiched between the anode and the cathode,
The organic layer includes a light-emitting layer containing an electronic device material represented by the following general formula (1).
Organic electroluminescent element.

[In the general formula (1), X ₁ and X ₂ each independently represent NR ₁₀ , an oxygen atom or a sulfur atom. R ₁₀ represents a hydrogen atom, a chain alkyl group, a cyclic alkyl group, an aromatic hydrocarbon ring group or an aromatic heterocyclic group. Y ₁ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group. R _{1 to} R ₉ each independently represent a hydrogen atom or a substituent. ]   The organic material according to claim 5, wherein an absolute value ΔEst of a difference between a lowest excited singlet energy level and a lowest excited triplet energy level of the electronic device material represented by the general formula (1) is 0.45 eV or less. Electroluminescent element. The aromatic hydrocarbon ring group or the aromatic heterocyclic group represented by Y ₁ in the general formula (1) is an electron-withdrawing group, and is characterized by the above-mentioned. Organic electroluminescent element.   A display device comprising the organic electroluminescence device according to claim 1.   A lighting device comprising the organic electroluminescence element according to claim 1.

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