JP7081898B2 - Organic electroluminescence elements, display devices and lighting devices - Google Patents

Description

The present invention relates to a π-conjugated compound, an organic electroluminescence element material, a light emitting material, a charge transport material, a light emitting thin film, an organic electroluminescence element, a display device and a lighting device.

An organic electroluminescence element (also referred to as an "organic electroluminescent element" or "organic EL element") using an organic material electroluminescence (hereinafter abbreviated as "EL") enables planar light emission. It is a technology that has already been put into practical use as a new electroluminescence system. Organic EL elements have recently been applied not only to electronic displays but also to lighting equipment, and their development is expected.

There are two light emission methods for organic EL elements: "phosphorus light emission" that emits light when returning from the triplet excited state to the ground state, and "fluorescent emission" that emits light when returning from the singlet excited state to the ground state. There is a street.

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

On the other hand, various developments have been made to improve the luminous efficiency of the fluorescent light emitting type, and new movements have emerged in recent years. For example, in Patent Document 1, a phenomenon in which singlet excitons are generated by collision of two triplet excitons (Triplet-Triplet Annihilation: hereinafter, abbreviated as “TTA” as appropriate. Further, Triplet-Triplet Fusion: “TTF”. A technique for efficiently causing TTA to improve the efficiency of the fluorescent element is disclosed. Although the luminous efficiency of the fluorescent light emitting material is improved to 2 to 3 times that of the conventional fluorescent light emitting material by this technology, the theoretical single term exciter generation efficiency in TTA is only about 40%, so that the phosphorescent light emission is still performed. It has a problem of high luminous efficiency.

Further, in recent years, a phenomenon utilizing a phenomenon in which reverse intersystem crossing (Reverse Intersystem Crossing: hereinafter abbreviated as "RISC" as appropriate) occurs from a triplet exciton to a singlet exciton ("heat-activated delayed fluorescence" ("" It is also reported that it can be used for fluorescent light emitting materials using "thermally excited delayed fluorescence": hereinafter abbreviated as "TADF" as appropriate) and for organic EL elements (for example,). (See Patent Document 2, Non-Patent Document 1, and Non-Patent Document 2). When the delayed fluorescence by this TADF mechanism is used, the internal quantum efficiency of 100% is theoretically equivalent to that of phosphorus light emission even in the fluorescence emission by electric field excitation. Is possible.

In order for the TADF phenomenon to occur, it is necessary to have an inverse intersystem crossing from 75% triplet excitons to singlet excitons generated by electric field excitation at room temperature or the temperature of the light emitting layer in the light emitting element. Further, the singlet excitons generated by the intersystem crossing fluoresce in the same manner as the 25% singlet excitons generated by the direct excitation, so that 100% internal quantum efficiency is theoretically possible. In order for this inverse intersystem crossing to occur, it is required that the absolute value ( _ΔEST ) of the difference between the lowest excited singlet energy level (S1) and the lowest triplet excited energy level (T1) is small.

Further, it is known that if a material exhibiting TADF property is included in the light emitting layer as a third component (assist dopant material) in the light emitting layer composed of a host material and a light emitting material, it is effective in exhibiting high luminous efficiency (they are effective in exhibiting high luminous efficiency). See Non-Patent Document 3). By generating 25% singlet excitons and 75% triplet excitons on the assist dopant material by field excitation, the triplet excitons generate singlet excitons with inverse intersystem crossing (RISC). can do. The energy of the singlet excitons is transferred to the light emitting material by fluorescence resonance energy transfer (hereinafter, abbreviated as “FRET” as appropriate), and the light emitting material can emit light by the transferred energy. .. Therefore, it is theoretically possible to make the light emitting material emit light by using 100% exciton energy, and high luminous efficiency is exhibited.

For example, in order to express the TADF phenomenon, it is effective to reduce the _ΔEST of the organic compound; in order to reduce the _ΔEST , the highest occupied molecular orbital (HOMO) and the lowest empty molecular orbital (HOMO) in the molecule ( It is effective to localize (clearly separate) without mixing LUMO).

1 and 2 are schematic diagrams showing energy diagrams of compounds exhibiting the TADF phenomenon (TADF compounds) and general fluorescent light emitting materials. For example, in 2CzPN having the structure shown in FIG. 1, HOMO is localized in the carbazolyl groups at the 1st and 2nd positions on the benzene ring, and LUMO is localized in the cyano groups at the 4th and 5th positions. Therefore, HOMO and LUMO of 2CzPN can be separated, _ΔEST becomes extremely small, and the TADF phenomenon is exhibited. On the other hand, in 2CzXy (FIG. 2) in which the cyano groups at the 4- and 5-positions of 2CzPN are replaced with methyl groups, although the structures are similar, ΔE cannot be clearly separated from HOMO and LUMO as seen in 2CzPN. The _ST cannot be reduced, and the TADF phenomenon cannot be manifested.

As described above, although the TADF phenomenon can be exhibited by a conventional compound such as 2CzPN, it is required to further reduce _ΔEST and further improve the luminous efficiency of the organic EL device.

International Publication No. 2010/134350 Japanese Unexamined Patent Publication No. 2013-116975

H. Uoyama, et al. , Nature, 2012, 492, 234-238 Q. Zhang et al. , Nature, Photonics, 2014,8,326-332 H. Nakanоtani, et al. , Nature Communication, 2014, 5, 4016-4022.

The present invention has been made in view of the above problems and situations, and a solution thereof is to provide, for example, a new π-conjugated compound capable of improving the luminous efficiency of an organic electroluminescence element. Further, the present invention provides an organic electroluminescence element material, a light emitting material, a charge transport material, a light emitting thin film, an organic electroluminescence element, and a display device and a lighting device provided with the organic electroluminescence element using the π-conjugated compound. It is to be.

（一般式（１）中、Ｑ^１～Ｑ^３は、それぞれ－ＣＨ又は窒素原子を表し、Ｌ^１、Ｌ^２及びＭは、それぞれ電子供与性基Ｄ又は電子求引性基Ａを表し、前記Ｌ^１及びＬ^２が前記電子供与性基Ｄであり、且つ前記Ｍが前記電子求引性基Ａであるか、又は前記Ｌ^１及びＬ^２が前記電子求引性基Ａであり、且つ前記Ｍが前記電子供与性基Ｄであり、前記電子供与性基Ｄは、置換されていてもよい１０，１１－ジヒドロジベンゾアゼピン環、置換されていてもよい９，１０－ジヒドロアクリジン環、置換されていてもよい５，１０－ジヒドロフェナジン環、置換されていてもよい５，１０－ジヒドロフェナザシリン環、置換されていてもよいフェノキサジン環、置換されていてもよいフェノチアジン環、置換されていてもよいベンゾフリルインドール環、置換されていてもよいベンゾチエノインドール環、置換されていてもよいベンゾチエノベンゾチオフェン環、置換されていてもよいベンゾカルバゾール環、置換されていてもよいジベンゾカルバゾール環、置換されていてもよいアザカルバゾール環、及び置換されていてもよいジアザカルバゾール環からなる群より選ばれる置換されていてもよい電子供与性の複素環基、又は置換されたアミノ基であり、前記電子求引性基Ａは、フッ素原子、シアノ基、フッ素原子で置換されたアルキル基、置換されたカルボニル基、置換されたスルホニル基、置換されたホスフィンオキサイド基、置換されたボリル基、電子求引性基で置換されていてもよいアリール基、及び置換されていてもよい電子求引性の複素環基からなる群より選ばれる基である）
［２］ 前記Ｌ^１及びＬ^２が前記電子供与性基Ｄであり、且つ前記Ｍが前記電子求引性基Ａである、［１］に記載のπ共役系化合物。
［３］ 前記Ｌ^１及びＬ^２が前記電子求引性基Ａであり、且つ前記Ｍが前記電子供与性基Ｄであり、前記Ｌ^１とＬ^２が同時にシアノ基ではない、［１］に記載のπ共役系化合物。
［４］ 前記Ｑ^１～Ｑ^３は、いずれも－ＣＨである、［１］～［３］のいずれか一項に記載のπ共役系化合物。
［５］ 前記Ｑ^１～Ｑ^３は、いずれも窒素原子である、［１］～［３］のいずれか一項に記載のπ共役系化合物。
［６］ 前記電子供与性基Ｄは、置換されていてもよい９，１０－ジヒドロアクリジン環、置換されていてもよい５，１０－ジヒドロフェナザシリン環、及び置換されていてもよいフェノキサジン環からなる群より選ばれる置換されていてもよい電子供与性の含窒素芳香族複素環基であり、且つ該含窒素芳香族複素環基の窒素原子が前記Ｑ^１～Ｑ^３を含む環と結合しているか、又は前記置換されたアミノ基である、［１］～［５］のいずれかに記載のπ共役系化合物。
［７］ 前記電子供与性基Ｄは、置換されていてもよいアザカルバゾリル基、又は置換されていてもよいジアザカルバゾリル基である、［１］～［５］のいずれか一項に記載のπ共役系化合物。
［８］ 前記電子求引性基Ａは、シアノ基、シアノ基で置換されたアリール基、無置換の含窒素芳香族六員環基、フッ素原子で置換された含窒素芳香族六員環基、シアノ基で置換された含窒素芳香族六員環基、フッ素置換アルキル基で置換された含窒素芳香族六員環基、及び置換されていてもよいアリール基で置換された含窒素芳香族六員環基、アザジベンゾフリル基、及びジアザジベンゾフリル基からなる群より選ばれる基である、［１］～［７］のいずれか一項に記載のπ共役系化合物。
［９］ 前記電子求引性基Ａは、無置換のアリール基である、［１］～［７］のいずれか一項に記載のπ共役系化合物。
［１０］ 最低励起一重項準位と最低励起三重項準位とのエネルギー差の絶対値ΔＥ_ＳＴが０．５０ｅＶ以下である、［１］～［９］のいずれか一項に記載のπ共役系化合物。
［１１］［１］～［１０］のいずれか一項に記載のπ共役系化合物を含む、有機エレクトロルミネッセンス素子材料。
［１２］ ［１］～［１０］のいずれか一項に記載のπ共役系化合物を含み、前記π共役系化合物が蛍光を放射する、発光材料。
［１３］ 前記π共役系化合物が、遅延蛍光を放射する、［１２］に記載の発光材料。
［１４］［１］～［１０］のいずれか一項に記載のπ共役系化合物を含み、前記π共役系化合物が蛍光を放射する、電荷輸送材料。
［１５］ 前記π共役系化合物が、遅延蛍光を放射する、［１４］に記載の電荷輸送材料。
［１６］ ［１］～［１０］のいずれか一項に記載のπ共役系化合物を含む、発光性薄膜。
［１７］ 陽極と、陰極と、前記陽極と前記陰極との間に設けられた発光層とを含み、前記発光層の少なくとも一層が、［１］～［１０］のいずれか一項に記載のπ共役系化合物を含む、有機エレクトロルミネッセンス素子。
［１８］ 前記発光層が、ホスト化合物をさらに含む、［１７］に記載の有機エレクトロルミネッセンス素子。
［１９］ 前記発光層は、蛍光発光性化合物及びリン光発光性化合物の少なくとも一方をさらに含む、［１７］に記載の有機エレクトロルミネッセンス素子。
［２０］ 前記発光層は、蛍光発光性化合物及びリン光発光性化合物の少なくとも一方と、ホスト化合物とをさらに含む、［１７］に記載の有機エレクトロルミネッセンス素子。
［２１］ 前記ホスト化合物が、下記一般式（Ｉ）で表される構造を有する、［１８］又は［２０］に記載の有機エレクトロルミネッセンス素子。

（一般式（Ｉ）中、Ｘ_１０１は、ＮＲ_１０１、酸素原子、硫黄原子、スルフィニル基、スルホニル基、ＣＲ_１０２Ｒ_１０３又はＳｉＲ_１０４Ｒ_１０５を表し、ｙ_１～ｙ_８は、それぞれ独立に、ＣＲ_１０６又は窒素原子を表し、Ｒ_１０１～Ｒ_１０６は、それぞれ独立に、水素原子又は置換基を表し、互いに結合して環を形成してもよく、Ａｒ_１０１及びＡｒ_１０２は、それぞれ独立に、置換されていてもよいアリール基、又は置換されていてもよいヘテロアリール基を表し、ｎ１０１及びｎ１０２は、各々０～４の整数を表す。ただし、Ｒ_１０１が水素原子の場合は、ｎ１０１は１～４の整数を表す。）
［２２］ 前記一般式（Ｉ）で表される構造を有するホスト化合物が、下記一般式（II）で表される構造を有する、［２１］に記載の有機エレクトロルミネッセンス素子。

（一般式（II）中、Ｘ_１０１は、ＮＲ_１０１、酸素原子、硫黄原子、スルフィニル基、スルホニル基、ＣＲ_１０２Ｒ_１０３又はＳｉＲ_１０４Ｒ_１０５を表し、Ｒ_１０１～Ｒ_１０５は、各々水素原子又は置換基を表し、互いに結合して環を形成してもよく、Ａｒ_１０１及びＡｒ_１０２は、それぞれ独立に、置換されていてもよいアリール基、又は置換されていてもよいヘテロアリール基を表し、ｎ１０２は０～４の整数を表す。）
［２３］ ［１７］～［２２］のいずれかに記載の有機エレクトロルミネッセンス素子を含む、表示装置。
［２４］ ［１７］～［２２］のいずれか一項に記載の有機エレクトロルミネッセンス素子を含む、照明装置。 [1] A π-conjugated compound represented by the following general formula (1).

(In the general formula ( ¹ ), ^Q1 to ^Q3 represent —CH or a nitrogen atom, ^respectively , and L1, L2 and M represent an electron donating group D or an electron attracting group A, respectively. L ¹ and L ² are the electron donating group D and the M is the electron attracting group A, or L ¹ and L ² are the electron attracting group A and said. M is said electron-donating group D, where the electron-donating group D is substituted with a optionally substituted 10,11-dihydrodibenzoazepine ring, optionally substituted 9,10-dihydroacridine ring. May be 5,10-dihydrophenazine ring, optionally substituted 5,10-dihydrophenazacillin ring, optionally substituted phenoxadin ring, optionally substituted phenothiazine ring, substituted. May be benzofuryl indol ring, optionally substituted benzothienoindole ring, optionally substituted benzothienobenzothiophene ring, optionally substituted benzocarbazole ring, optionally substituted dibenzocarbazole ring. , A optionally substituted electron-donating heterocyclic group selected from the group consisting of a optionally substituted azacarbazole ring and an optionally substituted diazacarbazole ring, or a substituted amino group. The electron-attracting group A includes a fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, a substituted carbonyl group, a substituted sulfonyl group, a substituted phosphine oxide group, and a substituted boryl group. A group selected from the group consisting of an aryl group which may be substituted with an electron-attracting group and an electron-attracting heterocyclic group which may be substituted).
[2] The π-conjugated compound according to [1], wherein L ¹ and L ² are the electron-donating group D and M is the electron-withdrawing group A.
[3] In [1], the L ¹ and L ² are the electron-withdrawing group A, the M is the electron-donating group D, and the L ¹ and L ² are not cyano groups at the same time. The described π-conjugated compound.
[4] The π-conjugated compound according to any one of [1] to [3], wherein Q ¹ to Q ³ are all −CH.
[5] The π-conjugated compound according to any one of [1] to [3], wherein Q ¹ to Q ³ are all nitrogen atoms.
[6] The electron donating group D may be substituted 9,10-dihydroacridin ring, optionally substituted 5,10-dihydrophenazacillin ring, and optionally substituted phenoxadin. A optionally substituted nitrogen-containing aromatic heterocyclic group selected from the group consisting of rings, wherein the nitrogen atom of the nitrogen-containing aromatic heterocyclic group contains the above ^Q1 to ^Q3 . The π-conjugated compound according to any one of [1] to [5], which is an attached or substituted amino group.
[7] Described in any one of [1] to [5], wherein the electron donating group D is a substituted azacarbazolyl group or a optionally substituted diazacarbazolyl group. Π-conjugated compound.
[8] The electron-attracting group A is a cyano group, an aryl group substituted with a cyano group, an unsubstituted nitrogen-containing aromatic six-membered ring group, and a nitrogen-containing aromatic six-membered ring group substituted with a fluorine atom. , A nitrogen-containing aromatic six-membered ring group substituted with a cyano group, a nitrogen-containing aromatic six-membered ring group substituted with a fluorine-substituted alkyl group, and a nitrogen-containing aromatic group substituted with an optionally substituted aryl group. The π-conjugated compound according to any one of [1] to [7], which is a group selected from the group consisting of a six-membered ring group, a azadibenzofuryl group, and a diazadibenzofuryl group.
[9] The π-conjugated compound according to any one of [1] to [7], wherein the electron-withdrawing group A is an unsubstituted aryl group.
[10] The π-conjugated system according to any one of [1] to [9], wherein the absolute value _ΔEST of the energy difference between the lowest excited singlet level and the lowest excited triplet level is 0.50 eV or less. System compound.
[11] An organic electroluminescence device material containing the π-conjugated compound according to any one of [1] to [10].
[12] A luminescent material containing the π-conjugated compound according to any one of [1] to [10], wherein the π-conjugated compound radiates fluorescence.
[13] The light emitting material according to [12], wherein the π-conjugated compound emits delayed fluorescence.
[14] A charge transport material comprising the π-conjugated compound according to any one of [1] to [10], wherein the π-conjugated compound radiates fluorescence.
[15] The charge transport material according to [14], wherein the π-conjugated compound emits delayed fluorescence.
[16] A luminescent thin film containing the π-conjugated compound according to any one of [1] to [10].
[17] The item according to any one of [1] to [10], wherein the light emitting layer includes an anode, a cathode, and a light emitting layer provided between the anode and the cathode, and at least one layer of the light emitting layer is described in any one of [1] to [10]. An organic electroluminescence device containing a π-conjugated compound.
[18] The organic electroluminescence device according to [17], wherein the light emitting layer further contains a host compound.
[19] The organic electroluminescence element according to [17], wherein the light emitting layer further contains at least one of a fluorescent light emitting compound and a phosphorescent light emitting compound.
[20] The organic electroluminescence element according to [17], wherein the light emitting layer further contains at least one of a fluorescent light emitting compound and a phosphorescent light emitting compound, and a host compound.
[21] The organic electroluminescence device according to [18] or [20], wherein the host compound has a structure represented by the following general formula (I).

(In the general formula (I), X ₁₀₁ represents NR ₁₀₁ , oxygen atom, sulfur atom, sulfinyl group, sulfonyl group, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₄ R ₁₀₅ , and y ₁ to y ₈ are independent of each other. CR ₁₀₆ or a nitrogen atom, R ₁₀₁ to R ₁₀₆ each independently represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring, and Ar ₁₀₁ and Ar ₁₀₂ each independently. It represents an optionally substituted aryl group or a optionally substituted heteroaryl group, where n101 and n102 each represent an integer of 0-4, where n101 is 1 if R ₁₀₁ is a hydrogen atom. Represents an integer of ~ 4.)
[22] The organic electroluminescence device according to [21], wherein the host compound having the structure represented by the general formula (I) has a structure represented by the following general formula (II).

(In the general formula (II), X ₁₀₁ represents NR ₁₀₁ , oxygen atom, sulfur atom, sulfinyl group, sulfonyl group, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₄ R ₁₀₅ , and R ₁₀₁ to R ₁₀₅ are hydrogen atoms or hydrogen atoms, respectively. It represents a substituent and may be bonded to each other to form a ring, and Ar ₁₀₁ and Ar ₁₀₂ each independently represent an aryl group which may be substituted or a heteroaryl group which may be substituted. n102 represents an integer from 0 to 4.)
[23] A display device including the organic electroluminescence device according to any one of [17] to [22].
[24] A lighting device comprising the organic electroluminescence device according to any one of [17] to [22].

By the above means of the present invention, for example, a new π-conjugated compound capable of improving the luminous efficiency of an organic electroluminescence device can be provided. Further, by the above means of the present invention, it is possible to provide a new organic electroluminescence device which has improved luminous efficiency. Further, it is possible to provide an organic electroluminescence element material using the π-conjugated compound, a light emitting thin film, a light emitting material, and a display device and a lighting device provided with the organic electroluminescence element.

It is a schematic diagram which showed the energy diagram of the TADF compound. It is a schematic diagram which showed the energy diagram of a general fluorescent light emitting compound. It is a schematic diagram which showed the energy diagram when the π-conjugated compound functions as an assist dopant material. It is a schematic diagram which showed the energy diagram when the π-conjugated compound functions as a host material. It is a schematic diagram which showed an example of the display device composed of an organic EL element. It is a schematic diagram of the display device by the active matrix system. It is a schematic diagram which showed the circuit of a pixel. It is a schematic diagram of the display device by the passive matrix system. It is a schematic diagram of a lighting device. It is a schematic diagram of a lighting device. It is a graph which shows the relationship between the time from the excitation light irradiation and the number of photons when the fluorescence attenuation measurement was performed about the co-deposited film 6-1 using the π-conjugated compound of this invention produced in the Example.

Hereinafter, the present invention, its constituent elements, and modes and embodiments for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the sense that the numerical values described before and after it are included as the lower limit value and the upper limit value.

The present inventors 1) in an aromatic 6-membered ring containing a carbon atom or a nitrogen atom as a ring-constituting atom, one electron attracting group A and two electron donating groups D (or two electron attracting groups). Group A and one electron-donating group D) are placed in meta positions with each other, and 2) electron-donating group D is "a specific electron-donating heterocyclic group that may be substituted" or "substituted." It has been found that the emission efficiency of the organic EL element can be remarkably increased by using the "amino group".

The reason for this is not clear, but it is thought to be as follows. That is, in the aromatic 6-membered ring, when the electron-withdrawing group A and the electron-donating group D are in the meta-position with each other, the electron-withdrawing group A and the electron-donating group are more than in the para-position and the ortho-position. The distribution of the orbits of HOMO and LUMO at the connecting portion of D is small, and it is easy to separate HOMO and LUMO. Furthermore, the electron-donating group D "a specific electron-donating heterocyclic group (other than the azacarbazolyl group and the diazacarbazolyl group)" and the "substituted amino group" are more moderate than the "carbazolyl group". Has a high electron donating property. As a result, it is considered that _ΔEST can be reduced and the luminous efficiency of the organic EL element can be improved.

On the other hand, among the heterocyclic groups of the specific electron donating group, the "azacarbazolyl group and the diazacarbazolyl group" have a slightly lower electron donating property than the "carbazolyl group". However, the "azacarbazolyl group and the diazacarbazolyl group" can suppress the lengthening of the absorption spectrum and the emission spectrum more than the "carbazolyl group" by that amount. Furthermore, "azacarbazolyl group and diazacarbazolyl group" do not have too high HOMO as compared with "carbazolyl group". Therefore, high luminous efficiency can be obtained by allowing the π-conjugated compound having "azacarbazolyl group or diazacarbazolyl group" as the electron donating group D to function as the host compound or the assist dopant compound. The present invention has been made based on such findings.

<Pi-conjugated compound>
The π-conjugated compound of the present invention is preferably a compound represented by the following general formula (1).

^Q1 to ^Q3 of the general formula (1) represent -CH or a nitrogen atom, respectively. From the viewpoint that the higher the molecular symmetry, the easier it is to increase the quantum yield, it is preferable that all of ^Q1 to ^Q3 are −CH, or all of ^Q1 to ^Q3 are nitrogen atoms.

L ¹ , L ² and M of the general formula (1) represent an electron-donating group D or an electron-withdrawing group A, respectively. Specifically, L ¹ and L ² are electron-donating groups D and M is an electron-withdrawing group A, or L ¹ and L ² are electron-withdrawing groups A and M. Is the electron donating group D. L ¹ and L ² may be the same or different from each other, but are preferably the same because they are easy to synthesize and have good luminous efficiency.

(Electron donating group D)
The electron donating group D is a "specific electron donating heterocyclic group which may be substituted" or a "substituted amino group".

The "specific heterocyclic group having an electron donating property" in the "specific heterocyclic group having an electron donating property which may be substituted" represented by D has an electron donating property having 4 to 24 carbon atoms other than the carbazole ring. It is preferably a group derived from the aromatic heterocycle of. Examples of such electron-donating aromatic heterocycles include 10,11-dihydrodibenzoazepine, 9,10-dihydroacridine ring, 5,10-dihydrophenothiazine ring, 5,10-dihydrophenazacillin ring, Includes a phenoxazine ring, a phenothiazine ring, a benzofurylindole ring, a benzothienoindole ring, a benzothienobenzothiophene ring, a benzocarbazole ring, a dibenzocarbazole ring, an azacarbazole ring, a diazacarbazole ring and the like.
Among them, 9,10-dihydroacridin ring, 5,10-dihydrophenazacillin ring, phenoxazine ring, azacarbazole ring, diazacarbazole ring, 5,10-dihydrophenazine ring, phenoxazine ring, phenoxazine ring, and benzo. A frilled indole ring is preferable, and a nitrogen-containing aromatic heterocycle such as a 9,10-dihydroaclydin ring, a 5,10-dihydrophenazaciline ring, a phenoxazine ring, an azacarbazole ring, or a diazacarbazole ring is more preferable. The electron-donating aromatic heterocycle may be one in which two or more of the same or different aromatic heterocycles are bonded via a single bond. Further, the bonding position of these heterocyclic groups with the ring containing ^Q1 to ^Q3 is not particularly limited, but for example, when the heterocyclic group is an electron-donating nitrogen-containing aromatic heterocyclic group, Q1 to ^Q1 to The electron-donating nitrogen ^- containing aromatic heterocyclic group is bonded to the ring containing ^Q1 to ^Q3 via its nitrogen atom in that electrons can be easily transferred to the ring containing Q3. Is preferable.

Examples of substituents that the particular heterocyclic group may have include an alkyl group, an alkoxy group, an aryl group optionally substituted with an alkyl group, a heterocyclic group optionally substituted, and substituted. Also contains good amino groups.

The alkyl group may be linear, branched or cyclic, and may be, for example, a linear or branched alkyl group having 1 to 20 carbon atoms or a cyclic alkyl group having 5 to 20 carbon atoms. Examples of alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, n-pentyl group, neopentyl group, n-hexyl group and cyclohexyl. Group, 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- Includes tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group and the like; preferably methyl group, ethyl group, isopropyl group, t. -Butyl group, cyclohexyl group, n-octyl group, 2-ethylhexyl group and 2-hexyloctyl group.

The alkoxy group may be linear, branched or cyclic, and may be, for example, a linear or branched alkoxy group having 1 to 20 carbon atoms, or a cyclic alkoxy group having 6 to 20 carbon atoms. Examples of alkoxy groups include 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 -It contains an octadecyloxy group, an n-nonadecyloxy group, an n-icosyloxy group and the like, preferably a methoxy group, an ethoxy group, an isopropoxy group, a t-butoxy group, a cyclohexyloxy group, an n-octyloxy group and a 2-ethylhexyloxy group. Group, 2-hexyloctyloxy group.

The aryl group in the "aryl group optionally substituted with an alkyl group" is preferably a group derived from an aromatic hydrocarbon ring having 6 to 24 carbon atoms. Examples of such aromatic hydrocarbon rings include benzene ring, inden ring, naphthalene ring, azulene ring, fluorene ring, phenanthrene ring, anthracene ring, acenaphtylene ring, biphenylene ring, naphthalene ring, pyrene ring, pentalene ring, acetylene ring. Trilene ring, heptalene ring, triphenylene ring, as-indacene ring, chrysene ring, s-indacene ring, pleiaden ring, phenalene ring, fluoranthene ring, perylene ring, acephenanthrene ring, biphenyl ring, terphenyl ring, and Includes tetraphenyl ring and the like.
Of these, a benzene ring, a naphthalene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, a biphenylene ring, a chrysene ring, a pyrene ring, a triphenylene ring, a chrysene ring, a fluoranthene ring, a perylene ring, a biphenyl ring, and a terphenyl ring are preferable. Is more preferable.
The aryl group may be substituted with the above-mentioned alkyl group or alkoxy group.

The heterocyclic group in the "optionally substituted heterocyclic group" is a group derived from an aromatic heterocycle having 4 to 24 carbon atoms, preferably a group derived from an electron-donating aromatic heterocycle. be. Examples of such electron-donating aromatic heterocycles include pyrrole ring, indole ring, indoloindole ring, 10,11-dihydrodibenzoazepine, 9,10-dihydroacrydin ring, 5,10-dihydrophenazine ring. , 5,10-dihydrophenazacillin ring, phenoxazine ring, phenothiazine ring, dibenzothiophene ring, benzofurylindole ring, benzothienoindole ring, benzofurylcarbazole ring, benzothienocarbazole ring, benzothienobenzothiophene ring, benzocarbazole Ring, dibenzocarbazole ring, azacarbazole ring, diazacarbazole ring, carbazole ring, dibenzothiophene oxide ring, dibenzothiophene dioxide ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, isoquinoline ring, Kinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, phenanthridine ring, phenanthroline ring, dibenzofuran ring, azadibenzofuran ring, diazadibenzofuran ring, dibenzosilol ring, dibenzobolol ring, dibenzophosphor oxide ring, etc. Is included.

Examples of the substituent in the "optionally substituted heterocyclic group" include the above-mentioned alkyl group, alkoxy group, and aryl group optionally substituted with an alkyl group.

Examples of the substituent in the "optionally substituted amino group" include an alkyl group, an aryl group optionally substituted with an alkyl group, and a heterocyclic group optionally substituted. The alkyl group, the aryl group, and the optionally substituted heterocyclic group are synonymous with the above-mentioned alkyl group, aryl group, and optionally substituted heterocyclic group, respectively.

The substituent in the "substituted amino group" represented by D is synonymous with the above-mentioned substituent in the "optionally substituted amino group".

Above all, from the viewpoint of controlling the emission wavelength, the electron-donating group D is preferably an "electron-donating heterocyclic group which may be substituted" and "contains an electron-donating property which may be substituted". It is more preferably a nitrogen aromatic heterocyclic group. Substituted 9,10-dihydroacridin ring, optionally substituted 5,10-dihydrophenazacillin ring, which has high electron donating property and can reduce _ΔEST . Groups derived from the phenoxazine ring may be more preferred; azacarbazoles which may be substituted in that they have moderately high electron donating properties and can highly suppress the lengthening of the absorption spectrum and emission spectrum. It is more preferred that the ring is a group derived from a diazacarbazole ring which may be substituted. The electron-donating nitrogen-containing aromatic heterocyclic group which may be substituted is preferably bonded to the ring containing ^Q1 to ^Q3 via its nitrogen atom.

The molecular weight of the electron donating group D is preferably 100 or more, more preferably 150 or more. The electron donating group D having a molecular weight of 150 or more easily emits an electron due to the introduction of the electron donating group D or a substituent that enhances the electron donating property of the unpaired electron on the nitrogen atom, and is high. It may have an electron donating property. The upper limit of the molecular weight of the electron donating group D is, for example, 1000. The molecular weight of the electron donating group D can be determined as a formula based on the composition formula.

(Electronic withdrawing group A)
The electron-attracting group A is a "fluorine atom", a "cyano group", an "alkyl group substituted with a fluorine atom", a "substituted carbonyl group", a "substituted sulfonyl group", or a "substituted phosphine". An "oxide group", a "substituted boryl group", an "aryl group optionally substituted with an electron-attracting group", or an "electron-attracting heterocyclic group optionally substituted". However, from the viewpoint that if the electron-withdrawing performance is too strong, it may be difficult to control the emission wavelength and the like, it is preferable that both L ¹ and L ² are not cyano groups at the same time as the electron-withdrawing group A.

The alkyl group in the "alkyl group substituted with a fluorine atom" represented by A has the same meaning as the above-mentioned alkyl group. Examples of fluorine-substituted alkyl groups include -CF ₃ , -CF ₂ H, -CH ₂ F, -CF ₂ CF ₃ , and the like.

Examples of the substituents in the "substituted carbonyl group", "substituted sulfonyl group", "substituted phosphine oxide group" and "substituted boryl group" represented by A include a heavy hydrogen atom and fluorine. It includes an alkyl group which may be substituted with an atom, a cyano group and a fluorine atom, an aryl group which may be substituted, and an electron-withdrawing heterocyclic group which may be substituted.

The aryl group in the "optionally substituted aryl group" represented by A is a substituent that can be possessed by the above-mentioned "optionally substituted electron-donating heterocyclic group" represented by D. Synonymous with aryl group.

Examples of the substituents that the aryl group may have include a heavy hydrogen atom, a fluorine atom, a cyano group, an alkyl group which may be substituted with fluorine, a carbonyl group which may be substituted, and a substituent which may be substituted. It includes a sulfonyl group, an optionally substituted phosphinoxide group, an optionally substituted boryl group, an optionally substituted electron-withdrawing heterocyclic group, and an optionally substituted amino group.
Among them, the substituent that the aryl group can have is preferably an electron-attracting group, a fluorine atom, a cyano group, an alkyl group which may be substituted with fluorine, a carbonyl group which may be substituted, and the like. Preferred are substituted sulfonyl groups, optionally substituted phosphinoxide groups, optionally substituted boryl groups, and optionally substituted electron-withdrawing heterocyclic groups; fluorine atom, cyano. More preferred are a group, an alkyl group optionally substituted with fluorine, and an electron-attracting heterocyclic group optionally substituted.

The "optionally substituted electron-withdrawing heterocyclic group" represented by A is preferably a group derived from an electron-withdrawing aromatic heterocycle having 3 to 24 carbon atoms. Examples of such electron-attracting aromatic heterocycles include dibenzothiophene oxide ring, dibenzothiophene dioxide ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, isoquinoline ring, quinazoline. Rings, cinnoline rings, quinoxaline rings, phthalazine rings, pteridine rings, phenanthridazine rings, phenanthroline rings, dibenzofuran rings, azadibenzofuran rings, diazadibenzofuran rings, dibenzosilol rings, dibenzoborol rings, dibenzophosphor oxide rings, etc. included. Among them, a pyridine ring, a pyrimidine ring, a pyrazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxalin ring, a phenanthridin ring, a phenanthroline ring, a dibenzofuran ring, an azadibenzofuran ring, and a diazadibenzofuran ring are preferable. Aromatic heterocycles are more preferred, and nitrogen-containing aromatic six-membered rings, azadibenzofuran rings, and diazadibenzofuran rings are even more preferred. The electron-withdrawing aromatic heterocycle may be a combination of two or more identical or different aromatic heterocycles.

Examples of substituents that the electron-withdrawing heterocyclic group may have include a dehydrogen atom, a fluorine atom, a cyano group, an alkyl group optionally substituted with fluorine, and an alkyl optionally substituted with fluorine. It contains an aryl group which may be substituted with a group, an aryl group which may be substituted with fluorine, and is preferably substituted with a fluorine atom, a cyano group, an alkyl group which may be substituted with fluorine, and fluorine. It is an aryl group which may be used.

Among them, when 2 or more of ^Q1 to ^Q3 , preferably all of them are −CH, the electron-withdrawing group A is preferably a group having high electron-withdrawing property. Examples of the electron-attracting group A having high electron-attracting properties include a cyano group, an aryl group substituted with a cyano group, an unsubstituted nitrogen-containing aromatic six-membered ring group, and a nitrogen-containing group substituted with a fluorine atom. Fragrant 6-membered ring group, nitrogen-containing aromatic 6-membered ring group substituted with cyano group, nitrogen-containing aromatic 6-membered ring group substituted with fluorine-substituted alkyl group, substituted with optionally substituted aryl group It is preferably a nitrogen-containing aromatic six-membered ring group, an azadibenzofuryl group, or a diazadibenzofuryl group, preferably a cyano group, an aryl group substituted with a cyano group, or an unsubstituted nitrogen-containing aromatic six-membered ring group. , A nitrogen-containing aromatic six-membered ring group substituted with an optionally substituted aryl group, a azadibenzofuryl group, or a diazadibenzofuryl group is more preferable. More preferably, it is a cyano group, a cyano group substituted with a cyano group, a pyridyl group substituted with a cyano group, a pyrazil group optionally substituted, a pyrimidyl group optionally substituted, a triazil group optionally substituted. , Azadibenzofuryl group, or diazadibenzofuryl group, more preferably cyanophenyl group, m-dicyanophenyl group, 2-cyanopyridyl group, 3-cyanopyridyl group, 2,6-dicyanopyridyl group, 2 -Cyanopyrazyl group, 2-cyanopyrimidyl group, 5-cyanopyrimidyl group, optionally substituted 2,4-diphenylpyrimidyl group, optionally substituted diphenyltriazyl group, azadibenzofuryl group, or diazadibenzo It is a frill group.

On the other hand, when 2 or more of ^Q1 to ^Q3 , preferably all of them are nitrogen atoms, the electron-withdrawing group A is preferably a group having an appropriate electron-withdrawing property. This is because the ring itself containing ^Q1 to ^Q3 has a certain level of electron-withdrawing property. Examples of the electron-withdrawing group A having an appropriate electron-withdrawing property include an unsubstituted aryl group.

The molecular weight of the electron-withdrawing group A can be about 19 to 900. The molecular weight of the electron-withdrawing group A can be determined by the same method as the molecular weight of the electron-donating group D.

The π-conjugated compound represented by the general formula (1) is an organic electroluminescence element material containing the π-conjugated compound, a luminescent thin film containing the π-conjugated compound, and an organic containing the π-conjugated compound. It can be used as an electroluminescence element.

The π-conjugated compound represented by the general formula (1) is excited by electric field excitation and can generate excitons. Therefore, the π-conjugated compound represented by the general formula (1) is preferably contained in the light emitting layer of the organic electroluminescence device. That is, from the viewpoint of high light emission, the light emitting layer uses the π-conjugated compound represented by the general formula (1) alone; or the π-conjugated compound represented by the general formula (1) and the π-conjugated compound described later. Whether it contains a host compound; a π-conjugated compound represented by the general formula (1) and at least one of a fluorescent light emitting compound and a phosphorescent light emitting compound described later; or the general formula ( It is preferable to contain the π-conjugated compound represented by 1), at least one of the fluorescent and phosphorescent compounds described below, and the host compound described below.

In the π-conjugated compound represented by the general formula (1), the absolute value ( _ΔEST ) of the energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound is 0.50 eV. It is preferably contained in the organic electroluminescence element, the element material, or the luminescent thin film.

The organic electroluminescence device of the present invention may be suitably provided in a lighting device and a display device.

Hereinafter, preferred specific examples of the π-conjugated compound according to the present invention will be given, but these compounds may further have a substituent or may have a structural isomer or the like, and are limited to this description. Not done.

Among these compounds, materials having an absolute value of _ΔEST of 0.50 eV or less may exhibit TADF property (delayed fluorescence), that is, may emit delayed fluorescence. Showing delayed fluorescence means that there are two or more types of components having different decay rates of the emitted fluorescence when fluorescence attenuation measurement is performed. In addition, although the decay time of a component having a slow decay is generally sub-microsecond or more, the decay time is not limited because the decay time differs depending on the material.

Fluorescence attenuation measurement can generally be performed as follows. A solution or thin film of a π-conjugated compound (luminescent compound) or a co-deposited film of the π-conjugated compound and the second component is irradiated with excitation light under a nitrogen atmosphere, and the number of photons at a certain emission wavelength is measured. At this time, when there are two or more types of components having different decay rates of the emitted fluorescence, the π-conjugated compound exhibits delayed fluorescence. The preparation conditions and measurement conditions of the measurement sample may be the same as in the examples described later.

Since these compounds have bipolarity and can cope with various energy levels, they can be used not only as a light emitting material or a host material but also as a compound suitable for hole transport and electron transport, that is, Since it can be used as a charge transport material, it is not limited to use in a light emitting layer, and is not limited to the above-mentioned hole injection layer, hole transport layer, electron blocking layer, hole blocking layer, electron transport layer, and electron injection layer. , May be used for an intermediate layer or the like.

<Synthesis method>
The above-mentioned π-conjugated compound can be synthesized, for example, by referring to the method described in International Publication No. 2010/117355 or the method described in the references described in these documents.

Next, the light emitting method and the light emitting material of the organic EL related to the technical idea of the present invention will be described.

<Light emission method of organic EL>
There are two types of light emission methods for organic EL: "phosphorus light emission" that emits light when returning from the triplet excited state to the ground state, and "fluorescent emission" that emits light when returning from the singlet excited state to the ground state. be.
When excited by an electric field such as an organic EL, triplet excitators are generated with a 75% probability and singlet excitors are generated with a 25% probability, so phosphorescence emission is more efficient than fluorescence emission. It is an excellent method to realize low power consumption.
On the other hand, even in fluorescence emission, the triplet-triplet exciter, which is normally generated with a probability of 75% and whose energy is only heat due to non-radiation deactivation, is present at high density. A method using a TTA (Triplet-Triplet Annihilation, or Triplet-Triplet Fusion: abbreviated as "TTF") mechanism that generates one singlet exciter from two triplet excitors to improve light emission efficiency is available. It has been found.

Furthermore, in recent years, by reducing the energy gap between the single-term excited state and the triple-term excited state by the discovery of Adachi et al., Triple with a low energy level due to Joule heat during emission and / or the environmental temperature at which the emitting element is placed A phenomenon in which inverse crossing occurs from the term-excited state to the single-term excited state, and as a result, fluorescence emission close to 100% is possible (also referred to as thermal-excited delayed fluorescence or thermal-excited delayed fluorescence: "TADF"). Fluorescent substances that make this possible have been found (see, for example, Non-Patent Document 1 and the like).

<Phosphorescent compound>
As mentioned above, phosphorus light emission is theoretically three times more advantageous than fluorescence emission in terms of emission efficiency, but energy deactivation (= phosphorus light emission) from the triplet excited state to the singlet ground state is prohibited. Since it is a transition and the intersystem crossing from the singlet excited state to the triplet excited state is also a forbidden transition, its velocity constant is usually small. That is, since the transition is unlikely to occur, the exciton lifetime becomes long from milliseconds to seconds, and it is difficult to obtain desired light emission.
However, when a complex using a heavy metal such as iridium or platinum emits light, the rate constant of the forbidden transition increases by 3 orders of magnitude or more due to the heavy atom effect of the central metal, and 100 depending on the selection of the ligand. It is also possible to obtain a phosphorus photon yield of%.
However, in order to obtain such ideal light emission, it is necessary to use precious metals such as iridium, palladium, and platinum, which are rare metals, so-called white metals. The price of metal itself becomes a big problem in industry.

<Fluorescent luminescent compound>
The general fluorescent compound does not need to be a heavy metal complex like a phosphorus light-emitting compound, and is a so-called organic compound composed of a combination of general elements such as carbon, oxygen, nitrogen and hydrogen. In addition, other non-metal elements such as phosphorus, sulfur, and silicon can be used, and compounds of typical metals such as aluminum and zinc can also be used, so that the variety can be said to be almost infinite.
However, since only 25% of excitons can be applied to light emission with a conventional fluorescent compound as described above, high-efficiency light emission such as phosphorescent light emission cannot be expected.

<Delayed fluorescent compound>
[Excited triplet-triplet annihilation (TTA) delayed fluorescent compound]
An emission method using delayed fluorescence has emerged to solve the problems of fluorescent compounds. The TTA method originating from the collision between triplet excitons can be described by the following general formula. That is, there is an advantage that a part of triplet excitons, in which the energy of excitons is conventionally converted only into heat by non-radiation deactivation, can cross the singlet excitons that can contribute to light emission. Even in an actual organic EL element, it is possible to obtain an external extraction quantum efficiency that is about twice that of a conventional fluorescent light emitting element.
General formula: T ^* + T ^* → S ^* + S
(In the equation, T ^* represents a triplet exciton, S ^* represents a singlet exciton, and S represents a ground state molecule.)
However, as can be seen from the above equation, since only one singlet exciton that can be used for light emission is generated from two triplet excitons, it is not possible in principle to obtain 100% internal quantum efficiency by this method.

[Thermal Activated Delayed Fluorescence (TADF) Compound]
The TADF method, which is another high-efficiency fluorescent emission, is a method that can solve the problems of TTA.
Fluorescent compounds have the advantage of being able to design an infinite number of molecules as described above. That is, among the molecularly designed compounds, there are compounds in which the energy level differences between the triplet excited state and the singlet excited state are extremely close to each other.
Although such a compound does not have a heavy atom in the molecule, an intersystem crossing from a triplet excited state to a singlet excited state, which cannot normally occur due to a small _ΔEST , occurs. Furthermore, since the rate constant of deactivation (= fluorescence emission) from the singlet excited state to the ground state is extremely large, the triplet excitator itself is thermally deactivated to the ground state (non-radiative deactivation). It is more rhythmically advantageous to return to the ground state while fluorescing via the singlet excited state. Therefore, TADF can theoretically emit 100% fluorescent light.

<Molecular design concept for _ΔEST >
The molecular design for reducing the above _ΔEST will be described.
In principle, 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 the molecule. It is a target.
It is generally known that HOMO is distributed in an electron-donating site and LUMO is distributed in an electron-withdrawing site in the electron orbit of a molecule. By introducing an electron-donating and electron-withdrawing skeleton into the molecule, it is known. , HOMO and LUMO can be moved away from each other.

For example, in "Organic Optoelectronics Reaching the Practical Use Stage" Applied Physics Vol. 82, No. 6, 2013, electron-attracting skeletons such as cyano groups and triazines and electrons such as carbazole and diphenylamino groups LUMO and HOMO are localized by introducing a donor skeleton.
It is also effective to reduce the change in molecular structure between the ground state and triplet excited state of the compound. As a method for reducing the structural change, for example, it is effective to make the compound rigid. Rigidity described here means that there are few sites that can move freely in the molecule, such as suppressing free rotation in the bond between rings in the molecule and introducing a fused ring with a large π-conjugated surface. means. In particular, it is possible to reduce the structural change in the excited state by making the portion involved in light emission rigid.

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

[Electron density distribution]
In the π-conjugated compound according to the present invention, it is preferable that HOMO and LUMO are substantially separated in the molecule from the viewpoint of reducing _ΔEST . The distribution state of these HOMO and LUMO can be obtained from the electron density distribution when the structure is optimized obtained by the molecular orbital calculation.
For the structural optimization and the calculation of the electron density distribution by the molecular orbital calculation of the π-conjugated compound in the present invention, software for molecular orbital calculation using B3LYP as a general function and 6-31G (d) as a base function is used as a calculation method. It can be calculated by using it, and the software is not particularly limited, and it can be calculated in the same manner by using any of them.
In the present invention, Gaussian 09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian Co., Ltd. in the United States was used as the software for calculating the molecular orbital.

Further, "HOMO and 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 separated, and more preferably, the HOMO orbital distribution and the LUMO orbital are separated. It means that the distributions of are almost non-overlapping.
Regarding the separated state of HOMO and LUMO, the structure optimization calculation using B3LYP as the general function and 6-31G (d) as the base function is further performed by the time-dependent density functional theory (Time-Dependent DFT). Excited state calculation is performed to obtain the energy levels of S ₁ and T ₁ (E (S ₁ ) and E (T ₁ ), respectively), and ΔE _ST = | E (S ₁ ) -E (T ₁ ) | It is also possible to calculate. The smaller the calculated _ΔEST , the more separated HOMO and LUMO are. In the present invention, the _ΔEST calculated by using the same calculation method as described above is 0.50 eV or less, preferably 0.30 eV or less, and more preferably 0.10 eV or less.

[Lowest excited singlet energy level S ₁ ]
The lowest excited singlet energy level S1 of the π _- conjugated compound in the present invention is defined in the same invention as in the usual method. That is, a compound to be measured is vapor-deposited on a quartz substrate to prepare a sample, and the absorption spectrum (vertical axis: absorbance, horizontal axis: wavelength) of this sample is measured at room temperature (300 K). A tangent line is drawn with respect to the rising edge of the absorption spectrum on the long wavelength side, and the calculation is performed from a predetermined conversion formula based on the wavelength value at the intersection of the tangent line and the horizontal axis.
However, if the molecule itself of the π-conjugated compound used in the present invention has a relatively high cohesiveness, an error due to cohesion may occur in the measurement of the thin film. Considering that the π-conjugated compound in the present invention has a relatively small Stokes shift and that the structural changes between the excited state and the ground state are small, the lowest excited _single -term energy level S1 in the present invention is set to room temperature (25 ° C.). ), The peak value of the maximum emission wavelength in the solution state of the π-conjugated compound was used as an approximate value.
Here, as the solvent used, a solvent that does not affect the aggregated state of the π-conjugated compound, that is, a solvent that is less affected by the solvent effect, for example, a non-polar solvent such as cyclohexane or toluene can be used.

[Lowest excited triplet energy level T ₁ ]
The lowest excited triplet energy level (T ₁ ) of the π-conjugated compound used in the present invention was calculated from the photoluminescence (PL) characteristics of the solution or thin film. For example, as a calculation method for a thin film, a dispersion of a dilute π-conjugated compound is made into a thin film, and then the transient PL characteristics are measured using a streak camera to separate the fluorescent component and the phosphorescent component. The lowest excited triple-term energy level can be obtained from the lowest excited single-term energy level with the absolute value of the energy difference as _ΔEST .
In the measurement and evaluation, the absolute PL quantum yield measuring device C9920-02 (manufactured by Hamamatsu Photonics Co., Ltd.) was used for the measurement of the absolute PL quantum yield. The emission lifetime was measured using a streak camera C4334 (manufactured by Hamamatsu Photonics Co., Ltd.) while exciting the sample with a laser beam.

<< Constituent layer of organic EL element >>
The organic EL element of the present invention is an organic electroluminescence element having at least a light emitting layer between an anode and a cathode, and at least one layer of the light emitting layer has a structure represented by the general formula (1). It is characterized by containing a conjugated compound.
Typical element configurations in the organic EL device of the present invention include, but are not limited to, the following configurations.
(1) anode / light emitting layer / cathode (2) anode / light emitting layer / electron transport layer / cathode (3) anode / hole transport layer / light emitting layer / cathode (4) anode / hole transport layer / light emitting layer / electron Transport layer / cathode (5) Anodic / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (6) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode (6) 7) Anodic / hole injection layer / hole transport layer / (electron blocking layer /) light emitting layer / (hole blocking layer /) electron transport layer / electron injection layer / cathode Among the above, the configuration of (7) is preferable. Used, but not limited to.
The light emitting layer used in the present invention is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the light emitting layers.

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

(Tandem structure)
Further, the organic EL element of the present invention may be an element having a so-called tandem structure in which a plurality of light emitting units including at least one light emitting layer are laminated.
As a typical element configuration of the tandem structure, for example, the following configuration can be mentioned.
Anode / first light emitting unit / intermediate layer / second light emitting unit / intermediate layer / third light emitting unit / cathode Here, even if the first light emitting unit, the second light emitting unit and the third light emitting unit are all the same, It may be different. Further, the two light emitting units may be the same, and the remaining one may be different.
The plurality of light emitting units may be directly laminated or laminated via an intermediate layer, and the intermediate layer is generally an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, or an intermediate layer. A known material structure can be used as long as it is also called an insulating layer and has a function of supplying electrons to the adjacent layer on the anode side and holes to the adjacent layer on the cathode side.

Examples of the material used for the intermediate layer include ITO (inorganic tin oxide), IZO (indium / zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiOx, VOx, CuI, InN, GaN, and CuAlO ₂ . Conductive inorganic compound layers such as CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ , 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 , Multilayer film such as _{TIO 2} / ZrN / TIO ₂ , Fullerenes such as C60, Conductive organic material layer such as oligothiophene, Examples thereof include conductive organic compound layers such as metallic phthalocyanines, metal-free phthalocyanines, metal porphyrins, and metal-free porphyrins, but the present invention is not limited thereto.
Preferred configurations in the light emitting unit include, for example, configurations in which the anode and the cathode are removed from the configurations (1) to (7) mentioned in the above typical element configurations, and the present invention includes these. Not limited.

Specific examples of the tandem organic EL element include, for example, US Pat. No. 6,337,492, US Pat. No. 7,420,203, US Pat. No. 7,473,923, US Pat. No. 6,872,472, US Pat. No. 6,107,734, US Pat. No. 6,337,492, International. Publication No. 2005/009087, JP-A-2006-228712, JP-A-2006-24791, JP-A-2006-49393, JP-A-2006-49394, JP-A-2006-49396, JP-A-2011 -96679, Japanese Patent Application Laid-Open No. 2005-340187, Japanese Patent No. 4711424, Japanese Patent No. 3496681, Japanese Patent No. 3884564, Japanese Patent No. 4213169, Japanese Patent Application Laid-Open No. 2010-192719, Japanese Patent Application Laid-Open No. 2009-07629, Japanese Patent Publication No. The element configurations and constituent materials described in JP-A-2007-07844, JP-A-2007-059848, JP-A-2003-272860, JP-A-2003-045676, International Publication No. 2005/094130, etc. are listed. However, the present invention is not limited thereto.

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

《Light emitting layer》
The light emitting layer used in the present invention is a layer that provides a place where electrons and holes injected from an electrode or an adjacent layer are recombined and emit light via excitons, and the light emitting portion is a light emitting layer. It may be in the layer or at the interface between the light emitting layer and the adjacent layer. The structure of the light emitting layer used in the present invention is not particularly limited as long as it satisfies the requirements specified in the present invention.
The total thickness of the light emitting layer is not particularly limited, but the homogeneity of the film to be formed, the prevention of applying an unnecessary high voltage at the time of light emission, and the improvement of the stability of the light emission color with respect to the drive current are improved. From the viewpoint, it is preferably adjusted to the range of 2 nm to 5 μm, more preferably to the range of 2 to 500 nm, and further preferably to the range of 5 to 200 nm.
Further, the layer thickness of each light emitting layer used in the present invention is preferably adjusted to the range of 2 nm to 1 μm, more preferably adjusted to the range of 2 to 200 nm, and further preferably adjusted to the range of 3 to 150 nm. It will be adjusted.
The light emitting layer used in the present invention may be one layer or may be composed of a plurality of layers. When the π-conjugated compound of the present application is used for the light emitting layer, it may be used alone or mixed with a host material, a fluorescent light emitting material, a phosphorescent light emitting material and the like described later. At least one layer of the light emitting layer may contain a light emitting dopant (a light emitting compound, a light emitting dopant, also simply referred to as a dopant), and further contain a host compound (a matrix material, a light emitting host compound, also simply referred to as a host). preferable. It is preferable that at least one layer of the light emitting layer of the π-conjugated compound of the present application contains the π-conjugated compound of the present application and the host compound because the luminous efficiency is improved. It is preferable that at least one layer of the light emitting layer contains the π-conjugated compound of the present application and at least one of the fluorescent light emitting compound and the phosphorescent light emitting compound because the luminous efficiency is improved. It is preferable that at least one layer of the light emitting layer contains at least one of the π-conjugated compound of the present application, a fluorescent light emitting compound and a phosphorescent light emitting compound, and a host compound because the luminous efficiency is improved.

(1) Light-emitting dopant As the light-emitting dopant, a fluorescent light-emitting dopant (also referred to as a fluorescent light-emitting compound or a fluorescent dopant) and a phosphorescent light-emitting dopant (also referred to as a phosphorescent light-emitting compound or a phosphorescent dopant) are preferably used. Be done. In the present invention, the light emitting layer contains the π-conjugated compound according to the present invention as a fluorescent light emitting compound or an assisted dopeant in the range of 0.1 to 50% by mass, particularly 1 to 30% by mass. It is preferably contained within the range.

In the present invention, it is preferable that the light emitting layer contains the luminescent 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 luminescent compound in the light emitting layer can be arbitrarily determined based on the specific luminescent compound used and the requirements of the device, and at a uniform concentration with respect to the layer thickness direction of the light emitting layer. It may be contained or may have an arbitrary concentration distribution.
Further, the luminescent compound used in the present invention may be used in combination of a plurality of types, and may be used in combination of fluorescent compounds having different structures or in combination of a fluorescent compound and a phosphorescent compound. You may. This makes it possible to obtain an arbitrary emission color.

The π-conjugated compound, the luminescent compound, and the host compound according to the present invention in which the absolute value ( _ΔEST ) of the difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.50 eV or less. When contained in the light emitting layer, the π-conjugated compound according to the present invention acts as an assist dopant. On the other hand, when the light emitting layer contains the π-conjugated compound and the luminescent compound according to the present invention and does not contain the host compound, the π-conjugated compound according to the present invention acts as the host compound. When the light emitting layer contains only the π-conjugated compound according to the present invention, the π-conjugated compound according to the present invention acts as a host compound and a luminescent compound.
The mechanism by which the effect is exhibited is the same in all cases, and the triplet excitons generated on the π-conjugated compound according to the present invention are converted into singlet excitons by an intersystem crossing (RISC). It is in.
As a result, theoretically all exciton energies generated on the π-conjugated compound according to the present invention can be transferred to the luminescent compound by fluorescence resonance energy transfer (FRET), and high luminous efficiency can be achieved.
Therefore, when the light emitting layer contains the three components of the π-conjugated compound, the luminescent compound, and the host compound according to the present invention, the energy levels of S ₁ and T ₁ of the π-conjugated compound are the S of the host compound. It is preferably lower than the energy levels of ₁ and T ₁ and higher than the energy levels of the luminescent compounds S ₁ and T ₁ .
Similarly, when the light emitting layer contains two components of the π-conjugated compound and the luminescent compound according to the present invention, the energy levels of S ₁ and T ₁ of the π-conjugated compound are S ₁ of the luminescent compound. It is preferable that the energy level is higher _than the energy level of T1.

3 and 4 show schematic views of the case where the π-conjugated compound of the present invention acts as an assist dopant and a host compound, respectively. 3 and 4 are examples, and the process of generating triplet excitons generated on the π-conjugated compound according to the present invention is not limited to electric field excitation, and energy transfer within the light emitting layer or from the interface of the peripheral layer. And electron transfer are also included.
Further, in FIGS. 3 and 4, a fluorescent light emitting compound is used as the light emitting material, but the present invention is not limited to this, and a phosphorescent light emitting compound may be used, and the fluorescent light emitting compound and the phosphorescent light emitting compound may be used. Both sex compounds may be used.

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

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

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

The emission colors of the organic EL element of the present invention and the compound used in the present invention are shown in FIG. 3.16 on page 108 of the "New Color Science Handbook" (edited by the Japan Color Society, Tokyo University Press, 1985). It is determined by the color when the result measured by the brightness meter CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.
In the present invention, it is also preferable that the light emitting layer of one layer or a plurality of layers contains a plurality of light emitting dopants having different light emitting colors and exhibits white light emission.
The combination of light emitting dopants showing white color is not particularly limited, and examples thereof include a combination of blue and orange, and a combination of blue and green and red.
The white color in the organic EL element of the present invention means that the chromaticity in the CIE 1931 color system at 1000 cd / m ² is x = 0.39 ± 0.09 when the 2 degree viewing angle front luminance is measured by the above method. , Y = 0.38 ± 0.08, preferably within the region.

(1.2) Fluorescent Luminous Dopant As the fluorescent luminescent dopant (fluorescent dopant), the π-conjugated compound of the present invention may be used, or a known fluorescent dopant or delayed fluorescence used for the light emitting layer of the organic EL element. It may be appropriately selected from sex dopants and used.

Specific examples of known fluorescent dopants that can be used in the present invention include, for example, anthracene derivatives, pyrene derivatives, chrysene derivatives, fluorentene derivatives, perylene derivatives, fluorene derivatives, arylacetylene derivatives, styrylarylene derivatives, styrylamine derivatives, and arylamine derivatives. , Boron complex, coumarin derivative, pyran derivative, cyanine derivative, croconium derivative, squalium derivative, oxobenzanthracene derivative, fluorescein derivative, rhodamine derivative, pyrylium derivative, perylene derivative, polythiophene derivative, rare earth complex compound and the like. Further, in recent years, light emitting dopants using delayed fluorescence have also been developed, and these may be used. Specific examples of the light emitting dopant using delayed fluorescence include the compounds described in International Publication No. 2011/156793, Japanese Patent Laid-Open No. 2011-213643, Japanese Patent Application Laid-Open No. 2010-93181, Japanese Patent No. 5366106, and the like. However, the present invention is not limited to these.

(1.3) Phosphorescent Dopant A phosphorescent dopant used in the present invention will be described.
The phosphorescent dopant used in the present invention is a compound in which light emission from an excited triple term is observed, specifically, a compound that emits phosphorescent light at room temperature (25 ° C.), and has a phosphorescent quantum yield. Is defined as a compound of 0.01 or more at 25 ° C., but a preferable phosphorescence quantum yield is 0.1 or more.
The phosphorus photon yield can be measured by the method described on page 398 (1992 edition, Maruzen) of Spectroscopy II of the 4th Edition Experimental Chemistry Course 7. Although the phosphorus photon yield in a solution can be measured using various solvents, the phosphorus photon dopant used in the present invention achieves the above-mentioned phosphorus photon yield (0.01 or more) in any of any solvents. Just do it.

The phosphorescent dopant can be appropriately selected and used from known ones used for the light emitting layer of the organic EL element. Specific examples of known phosphorescent dopants that can be used in the present invention include compounds described in the following documents.
Nature 395, 151 (1998), Appl. Phys. Let. 78, 1622 (2001), Adv. Mater. 19,739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17, 1059 (2005), International Publication No. 2009/100991, International Publication No. 2008/101842, International Publication No. 2003/040257, US Patent Application Publication No. 2006/835469, US Patent Application Publication No. 2006 / 0202194, US Patent Application Publication No. 2007/0087321, US Patent Application Publication No. 2005/0244673, Inorg. Chem. 40,1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chem. lnt. Ed. 2006, 45, 7800, Appl. Phys. Let. 86,153505 (2005), Chem. Let. 34,592 (2005), Chem. Commun. 2906 (2005), Inorg. Chem. 42,1248 (2003), International Publication No. 2009/050290, International Publication No. 2002/015645, International Publication No. 2009/000673, US Patent Application Publication No. 2002/0034656, US Patent No. 7332232, USA Patent Application Publication No. 2009/01087737, US Patent Application Publication No. 2009/00397776, US Patent No. 6921915, US Patent No. 6688266, US Patent Application Publication No. 2007/0190359, US Patent Application Publication No. 2006/0008670, US Patent Application Publication No. 2009/0165846, US Patent Application Publication No. 2008/0015355, US Patent No. 7250226, US Patent No. 7396598, US Patent Application Publication No. 2006/0263635, US Patent Application Publication No. 2003/0138657, US Patent Application Publication No. 2003/0152802, US Patent No. 70090928, Angew. Chem. lnt. Ed. 47, 1 (2008), Chem. Mater. 18, 5119 (2006), Inorg. Chem. 46,4308 (2007), Organometallics 23,3745 (2004), Apple. Phys. Let. 74,1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/009024, International Publication No. 2006/056418, International Publication No. 2005/019373, International Publication No. 2005/123873, International Publication No. 2005/123873, International Publication No. 2007/004380, International Publication No. 2006/082742, US Patent Application Publication No. 2006/0251923, US Patent Application Publication No. 2005/02060441, US Patent No. 73935999. , US Patent No. 7534505, US Patent No. 7445855, US Patent Application Publication No. 2007/0190359, US Patent Application Publication No. 2008/0297033, US Patent No. 7338722, US Patent Application Publication No. 2002 / 0134984, US Patent No. 7279704, US Patent Application Publication No. 2006/098120, US Patent Application Publication No. 2006/103874, International Publication No. 2005/07638380, International Publication No. 2010/032663 , International Publication No. 2008140115, International Publication No. 2007/052431, International Publication No. 2011/134013, International Publication No. 2011/157339, International Publication No. 2010/086089, International Publication No. 2009/113646, International Publication No. 2012/20327, International Publication No. 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149, US Patent Application Publication No. 2012/228583, US Patent Application Publication No. 2012/212126 Japanese Patent Application Laid-Open No. 2012-069737, Japanese Patent Application Laid-Open No. 2011-181303, Japanese Patent Application Laid-Open No. 2009-1140886, Japanese Patent Application Laid-Open No. 2003-81988, Japanese Patent Application Laid-Open No. 2002-302671 and Japanese Patent Application Laid-Open No. 2002-363552 And so on.
Among them, preferred phosphorescent dopants include organometallic complexes having Ir as the central metal. More preferably, a complex containing at least one coordination mode of a metal-carbon bond, a metal-nitrogen bond, a metal-oxygen bond, and a metal-sulfur bond is preferable.

(2) Host compound The host compound used in the present invention is a compound mainly responsible for charge injection and transport in the light emitting layer, and its own light emission is not substantially observed in the organic EL element.
Among the compounds contained in the light emitting layer, the host compound preferably has a mass ratio of 20% or more in the layer.
The host compound 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 charge transfer, and it is possible to improve the efficiency of the organic electroluminescence device.
Hereinafter, the host compound preferably used in the present invention will be described.

As the host compound, the π-conjugated compound used in the present invention may be used as described above, but there is no particular limitation. From the viewpoint of reverse energy transfer, those having an excitation energy larger than the excitation singlet energy of the dopant are preferable, and those having an excitation triplet energy larger than the excitation triplet energy of the dopant are more preferable.
The host compound is responsible for carrier transport and exciton generation in the light emitting layer. Therefore, it can exist stably in all active species in the cation radical state, the angstrom state, and the excited state, does not cause chemical changes such as decomposition and addition reaction, and further, the host molecule is generated in the layer over time of energization. It is preferable not to move at the angstrom level.

Further, especially when the light emitting dopant used in combination exhibits TADF emission, the existence time of the triple-term excited state of the _TADF compound is long, so that the T1 energy level of the host compound itself is high, and the host compounds are associated with each other. Molecules that do not reduce the T ₁ of the host compound, such as not forming a low T ₁ state in the state of being in the state, the TADF compound and the host compound not forming an exciplex, and the host compound not forming an electromer by an electric field. Appropriate design of the structure is required.
In order to meet these requirements, it is necessary that the host compound itself has high electron hopping mobility, high hole hopping mobility, and a small structural change when it is in a triplet excited state. Is. As a representative of the host compound satisfying such a requirement, those having _a high T1 energy level such as a carbazole skeleton, an azacarbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton or a azadibenzofuran skeleton are preferably mentioned.

Further, the host compound has a hole transporting ability or an electron transporting ability, prevents the wavelength of light emission from being lengthened, and further stabilizes the organic electroluminescence element against heat generation during high temperature driving or element driving. It is preferable to have a high glass transition temperature (Tg) from the viewpoint of operation. Tg is preferably 90 ° C. or higher, and more preferably 120 ° C. or higher.
Here, the glass transition point (Tg) is a value obtained by a method based on JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

Further, as the host compound used in the present invention, it is also preferable to use the π-conjugated compound according to the present invention as described above. Since the π-conjugated compound according to the present invention has a high T ₁ , it can be suitably used for a light emitting material having a short emission wavelength (that is, a high energy level of T ₁ and S ₁ ). Is.

When a known host compound is used for the organic EL device of the present invention, specific examples thereof include the compounds described in the following documents, but the present invention is not limited thereto.
Japanese Patent Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75445, 2002-338579, 2002. 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003. -3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002- 302516, 2002-305083, 2002-305084, 2002-308837, US Patent Application Publication No. 2003/01755553, US Patent Application Publication No. 2006/0280965, US Patent Application Publication No. 302. 2005/0112407, US Patent Application Publication No. 2009/0017330, US Patent Application Publication No. 2009/0030202, US Patent Application Publication No. 2005/0238919, International Publication No. 2001/039234, International Publication No. 2009/021126 , International Publication No. 2008/056746, International Publication No. 2004/093207, International Publication No. 2005/0890225, International Publication No. 2007/0637996, International Publication No. 2007/0637554, International Publication No. 2004/107822, International Publication No. Publication No. 2005/030900, International Publication No. 2006/114966, International Publication No. 2009/086028, International Publication No. 2009/003898, International Publication No. 2012/0293947, JP-A-2008-074939, JP-A-2007. 254297A, European Patent No. 2034538, International Publication No. 2011/055933, International Publication No. 2012/035853, Japanese Patent Application Laid-Open No. 2015-38941 and the like. Examples of the host compound described in JP-A-2015-38941 include the compounds H-1 to H-230 described in [0255] to [0293] of the specification.

Specific examples of the host compound used in the present invention are shown below, but the present invention is not limited thereto.

上記一般式（Ｉ）中、Ｘ_１０１は、ＮＲ_１０１、酸素原子、硫黄原子、スルフィニル基、スルホニル基、ＣＲ_１０２Ｒ_１０３又はＳｉＲ_１０４Ｒ_１０５を表す。また、ｙ_１～ｙ_８は、それぞれ独立に、ＣＲ_１０６、又は窒素原子を表す。ここで、Ｒ_１０１～Ｒ_１０６は、それぞれ独立に、水素原子又は置換基を表し、互いに結合して環を形成してもよい。Ｒ_１０１～Ｒ_１０６でありうる置換基の例には、以下の基が含まれる。 Further, the host compound used in the present invention is preferably a compound represented by the following general formula (I). The compound represented by the following general formula (I) has bipolarity and is very stable. Therefore, if the host compound is a compound represented by the following general formula (I), the life of the organic EL device tends to be long.

In the above general formula (I), X ₁₀₁ represents NR ₁₀₁ , oxygen atom, sulfur atom, sulfinyl group, sulfonyl group, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₄ R ₁₀₅ . Further, y ₁ to y ₈ independently represent CR ₁₀₆ or a nitrogen atom. Here, R ₁₀₁ to R ₁₀₆ each independently represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring. Examples of substituents that may be R ₁₀₁ -R ₁₀₆ include the following groups:

Linear or branched alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc. );
Alkenyl group (eg vinyl group, allyl group, etc.);
Alkynyl group (eg, ethynyl group, propargyl group, etc.);
Aromatic hydrocarbon ring group (also referred to as aromatic carbon ring group, aryl group, etc. For example, benzene ring, biphenyl, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysen ring, naphthalene ring, triphenylene. Ring, o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaften ring, coronen ring, inden ring, fluorene ring, fluorantrene ring, naphthalene ring, pentacene ring, perylene ring, pentaphene ring, picene Groups derived from rings, pyrene rings, pyranthrene rings, anthrantone rings, tetralins, etc.);
Aromatic heterocyclic groups (eg, furan ring, dibenzofuran ring, thiophene ring, dibenzothiophene ring, oxazole ring, pyrrole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, benzoimidazole ring, oxadiazole ring , Triazole ring, imidazole ring, pyrazole ring, thiazole ring, indole ring, indole ring, benzoimidazole ring, benzothiazole ring, benzoxazole ring, quinoxalin ring, quinazoline ring, cinnoline ring, quinoline ring, isoquinoline ring, phthalazine ring, naphthylidine. A ring, a carbazole ring, a carboline ring, a diazacarbazole ring (a group derived from a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is further substituted with a nitrogen atom, etc., and a carboline ring and a diazacarbazole ring. The rings are sometimes collectively referred to as the "azacarbazole ring".);
Non-aromatic hydrocarbon ring group (eg cyclopentyl group, cyclohexyl group, etc.);
Non-aromatic heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholic group, oxazolidyl group, etc.);
Alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.);
Cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.);
Aryloxy groups (eg, phenoxy groups, naphthyloxy groups, etc.);
Alkylthio group (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.);
Cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.);
Arylthio groups (eg, phenylthio groups, naphthylthio groups, etc.);
Alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.);
Aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.);
Sulfamoyl groups (eg, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthyl) Aminosulfonyl group, 2-pyridylaminosulfonyl group, etc.);
Acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc. );
Acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.);
Amid groups (eg, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino Group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.);
Carbamoyl group (eg aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group , Phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.);
Ureid group (eg, methyl ureido group, ethyl ureido group, pentyl ureido group, cyclohexyl ureido group, octyl ureido group, dodecyl ureido group, phenyl ureido group naphthyl ureido group, 2-pyridyl amino ureido group, etc.);
Sulfinyl group (eg, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.);
Alkyl sulfonyl group (eg, methyl sulfonyl group, ethyl sulfonyl group, butyl sulfonyl group, cyclohexyl sulfonyl group, 2-ethylhexyl sulfonyl group, dodecyl sulfonyl group, etc.);
Arylsulfonyl or heteroarylsulfonyl group (eg, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.);
Amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, diphenylamino group, etc. );
Halogen atoms (eg, fluorine atoms, chlorine atoms, bromine atoms, etc.);
Fluorinated hydrocarbon groups (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.);
Cyano group;
Nitro group;
Hydroxy group;
Thiol group;
Cyril group (eg, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.);
Deuterium atom

Among the above, preferable groups include a linear or branched alkyl group, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, an amino group, a fluorine atom, a fluorinated hydrocarbon group, a cyano group, and a silyl group.

Further, Ar ₁₀₁ and Ar ₁₀₂ each independently represent an aryl group which may be substituted or a heteroaryl group which may be substituted. The aryl group in the "optionally substituted aryl group" is preferably a group derived from an aromatic hydrocarbon ring having 6 to 24 carbon atoms. Examples of such aromatic hydrocarbon rings include benzene ring, inden ring, naphthalene ring, azulene ring, fluorene ring, phenanthrene ring, anthracene ring, acenaphtylene ring, biphenylene ring, naphthalene ring, pyrene ring, pentalene ring, acetylene ring. Trilene ring, heptalene ring, triphenylene ring, as-indacene ring, chrysene ring, s-indacene ring, pleiaden ring, phenalene ring, fluoranthene ring, perylene ring, acephenanthrene ring, biphenyl ring, terphenyl ring, and Includes tetraphenyl ring and the like. Preferred are a benzene ring, a biphenyl ring and a terphenyl ring.

Further, the heteroaryl group in the "optionally substituted heteroaryl group" is preferably a group derived from various aromatic heterocycles. Examples of such aromatic heterocycles are pyrrole ring, indole ring, carbazole ring, indroindole ring, 9,10-dihydroacridine ring, 5,10-dihydrophenazine ring, phenoxazine ring, phenothiazine ring, dibenzothiophene. Ring, benzofurylindole ring, benzothienoindole ring, indolocarbazole ring, benzofurylcarbazole ring, benzothienocarbazole ring, benzothienobenzothiophene ring, benzocarbazole ring, dibenzocarbazole ring, azacarbazole ring, azadibenzofuran ring, diah Zcarbazole ring, diazadibenzofuran ring, dibenzothiophene oxide ring, dibenzothiophene oxide ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, isoquinoline ring, quinazoline ring, cinnoline ring, quinoxalin ring, Includes a phthalazine ring, a pteridine ring, a phenanthridine ring, a phenanthroline ring, a dibenzofuran ring, a dibenzosilol ring, a dibenzobolol ring, a dibenzophosphol oxide ring and the like. Preferred are carbazole ring, benzocarbazole ring, azacarbazole ring, azadibenzofuran ring, diazacarbazole ring, diazadibenzofuran ring, pyridine ring, pyrimidine ring, and triazine ring.

Examples of substituents that an aryl group or a heteroaryl group may have include an aryl group that may be substituted with an alkyl group, a fluorine atom, a cyano group, an alkyl group that may be substituted with fluorine, and substituted groups. May be carbonyl group, optionally substituted sulfonyl group, optionally substituted phosphinoxide group, optionally substituted boryl group, optionally substituted heterocyclic group, optionally substituted amino A group, a silyl group which may be substituted, and the like are included.
The above-mentioned "alkyl group" may be linear, branched or cyclic, and may be, for example, a linear or branched alkyl group having 1 to 20 carbon atoms or a cyclic alkyl group having 5 to 20 carbon atoms. It is possible. Examples of alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, n-pentyl group, neopentyl group, n-hexyl group and cyclohexyl. Group, 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- Includes a tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, an n-icosyl group and the like. Further, the "aryl group" and the "heterocyclic group" can be the same as the aryl group represented by Ar ₁₀₁ and Ar ₁₀₂ or the heteroaryl group.

Further, in the above general formula (I), n101 and n102 each represent an integer of 0 to 4, but when R ₁₀₁ is a hydrogen atom, n101 represents an integer of 1 to 4.

一般式（II）において、Ｘ_１０１は、ＮＲ_１０１、酸素原子、硫黄原子、スルフィニル基、スルホニル基、ＣＲ_１０２Ｒ_１０３又はＳｉＲ_１０４Ｒ_１０５を表す。Ｒ_１０１～Ｒ_１０５は、それぞれ独立して水素原子又は置換基を表し、互いに結合して環を形成してもよい。なお、Ｒ_１０１～Ｒ_１０５は、一般式（Ｉ）のＲ_１０１～Ｒ_１０５と同義である。 The host compound having the structure represented by the general formula (I) is more preferably having the structure represented by the following general formula (II).

In general formula (II), X ₁₀₁ represents NR ₁₀₁ , oxygen atom, sulfur atom, sulfinyl group, sulfonyl group, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₄ R ₁₀₅ . R ₁₀₁ to R ₁₀₅ each independently represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring. In addition, R ₁₀₁ to R ₁₀₅ are synonymous with R ₁₀₁ to R ₁₀₅ of the general formula (I).

Ar ₁₀₁ and Ar ₁₀₂ independently represent an aryl group which may be substituted and a heteroaryl group which may be substituted, respectively, and Ar ₁₀₁ and Ar ₁₀₂ are Ar ₁₀₁ and Ar ₁₀₂ of the general formula (I). Is synonymous with.

Further, n102 represents an integer of 0 to 4.

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

In the general formulas (III-1) to (III-3), X ₁₀₁ , Ar ₁₀₂ , and n 102 are synonymous with X ₁₀₁ , Ar ₁₀₂ , and n 102 in the general formula (II). Further, in the general formula (III-2), R ₁₀₄ is synonymous with R ₁₀₄ in the general formula (I).
In the general formulas (III-1) to (III-3), the condensed ring, the carbazole ring and the benzene ring formed by containing X ₁₀₁ may further have a substituent as long as the function of the host compound is not impaired. good.

Preferred specific examples of the host compounds represented by the above general formulas (I), (II), or (III-1) to (III-3) are given, and these compounds further have a substituent or may have a substituent. Structural isomers may be present and are not limited to this description.

《Electron transport layer》
In the present invention, the electron transport 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 transport layer according to the present invention is not particularly limited, but is usually in the range of 2 nm to 5 μm, more preferably 2 to 500 nm, and further preferably 5 to 200 nm.
Further, in the organic EL element, when the light generated in the light emitting layer is taken out from the electrode, the light taken out directly from the light emitting layer and the light taken out after being reflected by the electrode located opposite to the electrode from which the light is taken out interfere with each other. It is known to wake up. When light is reflected by the cathode, this interference effect can be efficiently utilized by appropriately adjusting the total thickness of the electron transport layer between several nm and several μm.
On the other hand, if the layer thickness of the electron transport layer is increased, the voltage tends to increase. Therefore, especially when the layer thickness is thick, 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 electron transport material) may have any of electron injection property, electron transport property, and hole barrier property, and is arbitrary from conventionally known compounds. Can be selected and used.

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

Further, metal complexes having a quinolinol skeleton or a dibenzoquinolinol skeleton as ligands, 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), etc., and their metal complexes. A metal complex in which the central metal is replaced with In, Mg, Cu, Ca, Sn, Ga or Pb can also be used as an electron transport material.
In addition, metal-free or metal phthalocyanines, or those whose terminals are substituted with an alkyl group, a sulfonic acid group, or the like can also be preferably used as an electron transport material. Further, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transporting material, and like the hole injection layer and the hole transporting layer, an inorganic semiconductor such as n-type-Si or n-type-SiC can be used. Can also be used as an electron transport material.
Further, it is also possible to use a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain.

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

Specific examples of known and preferable electron transporting materials used in the organic EL device of the present invention include, but are not limited to, the compounds described in the following documents.
US Patent No. 6528187, US Patent No. 7230107, US Patent Application Publication No. 2005/0025993, US Patent Application Publication No. 2004/0036077, US Patent Application Publication No. 2009/0115316, US Patent Publication No. 2009/0101870, US Patent Application Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/32085, Appl. Phys. Let. 75, 4 (1999), Appl. Phys. Let. 79,449 (2001), Appl. Phys. Let. 81, 162 (2002), Appl. Phys. Let. 81, 162 (2002), Appl. Phys. Let. 79,156 (2001), US Pat. No. 7,964,293, US Patent Application Publication No. 2009/030202, International Publication No. 2004/080975, International Publication No. 2004/063159, International Publication No. 2005/08537, International. Publication No. 2006/067931, International Publication No. 2007/086552, International Publication No. 2008/114690, International Publication No. 2009/0694242, International Publication No. 2009/066779, International Publication No. 2009/054253, International Publication No. 2011/086935, International Publication No. 2010/150593, International Publication No. 2010/047707, European Patent No. 2311826, JP-A-2010-251675, JP-A-2009-209133, JP-A-2009-124114 No., JP-A-2008-277810, JP-A-2006-156445, JP-A-2005-340122, JP-A-2003-45662, JP-A-2003-31367, JP-A-2003-282270. , International Publication No. 2012/115034, etc.

More preferred known electron transport materials in the present invention include aromatic heterocyclic compounds containing at least one nitrogen atom and compounds containing a phosphorus atom, such as pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives and dibenzofurans. Examples thereof include derivatives, dibenzothiophene derivatives, azadibenzofuran derivatives, azadibenzothiophene derivatives, carbazole derivatives, azacarbazole derivatives, benzimidazole derivatives, arylphosphine oxide derivatives and the like.
The electron transport material may be used alone or in combination of two or more.

《Hole blocking layer》
The hole blocking layer is a layer having the function of an electron transporting layer in a broad sense, and is preferably made of a material having a function of transporting electrons and a small ability to transport holes, and holes while transporting electrons. It is possible to improve the recombination probability of electrons and holes by blocking the above.
Further, the structure of the electron transport layer described above can be used as the hole blocking layer according to the present invention, if necessary.
The hole blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the cathode side of the light emitting layer.
The layer thickness of the hole blocking layer according to the present invention is preferably in the range of 3 to 100 nm, 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 as the host compound described above is also preferably used for the hole blocking layer.

《Electron injection layer》
The electron injection layer (also referred to as “cathode buffer layer”) according to the present invention is a layer provided between the cathode and the light emitting layer in order to reduce the driving voltage and improve the light emitting brightness, and is referred to as “organic EL element and its light emitting layer”. It is described in detail in Volume 2, Chapter 2, "Electrode Materials" (pages 123-166) of "Forefront of Industrialization (Published by NTS, November 30, 1998)".
In the present invention, the electron injection layer may be provided as needed and may be present between the cathode and the light emitting layer or between the cathode and the electron transport layer as described above.
The electron injection layer is preferably a very thin film, and the layer thickness is preferably in the range of 0.1 to 5 nm, although it depends on the material. Further, it may be a non-uniform layer (film) in which the constituent material is intermittently present.

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

《Hole transport layer》
In the present invention, the hole transport layer 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 according to the present invention is not particularly limited, but is usually in the range of 5 nm to 5 μm, more preferably 2 to 500 nm, and further preferably 5 to 200 nm.
The material used for the hole transport layer (hereinafter referred to as a hole transport material) may have any of hole injection property, hole transport property, and electron barrier property, and is among conventionally known compounds. Any one can be selected and used from.
For example, porphyrin derivative, phthalocyanine derivative, oxazole derivative, oxadiazole derivative, triazole derivative, imidazole derivative, pyrazoline derivative, pyrazolone derivative, phenylenediamine derivative, hydrazone derivative, stilben derivative, polyarylalkane derivative, triarylamine derivative, carbazole derivative. , Indrocarbazole derivative, Isoindole derivative, Asen derivative such as anthracene and naphthalene, Fluolene derivative, Fluolenone derivative, Polyvinylcarbazole, Polymer material or oligomer in which aromatic amine is introduced into the main chain or side chain, Polysilane, Conductive Examples thereof include sex polymers or oligomers (eg, PEDOT / PSS, aniline-based copolymers, 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) and a starburst type represented by MTDATA. Examples thereof include compounds having fluorene or anthracene in the triarylamine linking core portion.
Further, hexaazatriphenylene derivatives as described in JP-A-2003-591432 and JP-A-2006-135145 can also be used as the hole transport material in the same manner.
Further, a hole transport layer having a high p property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, and JP-A-2001-102175. Apple. Phys. , 95, 5773 (2004) and the like.

Further, Japanese Patent Application Laid-Open No. 11-251067, J. Mol. Hung et. al. So-called p-type hole transport materials and inorganic compounds such as p-type-Si and p-type-SiC, as described in the authored literature (Applied Physics Letters 80 (2002), p. 139), can also be used. Further, an orthometalated organometallic complex having Ir or Pt in the central metal as typified by Ir (ppy) 3 is also preferably used.
As the hole transport material, the above can be used, but a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organic metal complex, and an aromatic amine are introduced into the main chain or side chain. The polymer material or oligomer is preferably used.

Specific examples of the known and preferable hole transporting material used in the organic EL device of the present invention include the compounds described in the following documents in addition to the above-mentioned documents, but the present invention is limited thereto. Not done.
For example, Appl. Phys. Let. 69,2160 (1996), J. Mol. Lumin. 72-74,985 (1997), Appl. Phys. Let. 78,673 (2001), Appl. Phys. Let. 90,183503 (2007), Appl. Phys. Let. 90,183503 (2007), Appl. Phys. Let. 51,913 (1987), Synth. Met. 87,171 (1997), Synth. Met. 91,209 (1997), Synth. Met. 111,421 (2000), SID Symposium Digital, 37,923 (2006), J. Mol. Mater. Chem. 3,319 (1993), Adv. Mater. 6,677 (1994), Chem. Mater. 15, 3148 (2003), US Patent Application Publication No. 2003/0162053, US Patent Application Publication No. 2002/0158242, US Patent Application Publication No. 2006/0240279, US Patent Application Publication No. 2008/ 022265, US Patent No. 5061569, International Publication No. 2007/002683, International Publication No. 2009/01809, EP650955, US Patent Application Publication No. 2008/01245772, US Patent Application Publication No. 2007/0278938 Japanese Patent Application Publication No. 2008/01061190, US Patent Application Publication No. 2008/0018221, International Publication No. 2012/115034, Japanese Patent Application Laid-Open No. 2003-591432, JP-A-2006-135145. , US Patent Application No. 13/585981, etc.
The hole transport material may be used alone or in combination of two or more.

《Electronic blocking layer》
The electron blocking layer is a layer having a function of a hole transporting layer in a broad sense, and is preferably made of a material having a function of transporting holes but having a small ability to transport electrons, while transporting holes. By blocking the electrons, the probability of recombination of electrons and holes can be improved.
Further, the structure of the hole transport layer described above can be used as an electron blocking layer according to the present invention, if necessary.
The electron blocking layer provided in the organic EL element of the present invention is preferably provided adjacent to the anode side of the light emitting layer.
The layer thickness of the electron blocking layer according to the present invention is preferably in the range of 3 to 100 nm, and more preferably in the range of 5 to 30 nm.
As the material used for the electron blocking layer, the material used for the hole transporting layer described above is preferably used, and the host compound described above is also preferably used for the electron blocking layer.

《Hole injection layer》
The hole injection layer (also referred to as “anode buffer layer”) according to the present invention is a layer provided between the anode and the light emitting layer in order to reduce the driving voltage and improve the emission brightness, and is referred to as an “organic EL element”. It is described in detail in Volume 2, Chapter 2, "Electrode Materials" (pages 123-166) of "The Forefront of Industrialization (Published by NTS, November 30, 1998)".
In the present invention, the hole injection layer may be provided as needed and may be present between the anode and the light emitting layer or between the anode and the hole transport layer as described above.
The details of the hole injection layer are described in JP-A-9-45479, 9-2660062, 8-288609, etc., and examples of the material used for the hole injection layer include. Examples thereof include materials used for the hole transport layer described above.
Among them, phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives as described in JP-A-2003-591432 and JP-A-2006-135145, metal oxides typified by vanadium oxide, and amorphous carbon. , Conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometallated complexes typified by tris (2-phenylpyridine) iridium complexes, triarylamine derivatives and the like are preferred.
The material used for the hole injection layer described above may be used alone or in combination of two or more.

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

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

Examples of the liquid medium for dissolving or dispersing the organic EL material used in the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene and xylene. Aromatic hydrocarbons such as mecitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used.
Further, as the dispersion method, it can be dispersed by a dispersion method such as ultrasonic wave, high shear force dispersion or media dispersion.
Further, a different film forming method may be applied to each layer. When a thin-film deposition method is used for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally the boat heating temperature is 50 to 450 ° C, the vacuum degree is ^10-6 to ^10-2 Pa, and the vapor deposition rate is 0.01 to. It is desirable to appropriately select within the range of 50 nm / sec, substrate temperature -50 to 300 ° C., layer (film) thickness 0.1 nm to 5 μm, preferably 5 to 200 nm.
The formation of the organic layer according to the present invention is preferably carried out consistently from the hole injection layer to the cathode by one vacuuming, but it may be taken out in the middle and a different film forming method may be applied. In that case, it is preferable to carry out the work in a dry inert gas atmosphere.

"anode"
As the anode in the organic EL element, a metal having a large work function (4 eV or more, preferably 4.5 eV or more), an electrically conductive compound, or a mixture thereof as an electrode material is preferably used. Specific examples of such an electrode material include metals such as Au and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Further, a material such as IDIXO (In ₂ O ₃ -ZnO) that is amorphous and can produce a transparent conductive film may be used.
For the anode, a thin film may be formed by forming a thin film of these electrode materials by a method such as thin film deposition or sputtering, and a pattern of a desired shape may be formed by a photolithography method, or when pattern accuracy is not required so much (about 100 μm or more). The pattern may be formed through a mask having a desired shape during vapor deposition or sputtering of the electrode material.
Alternatively, when a coatable substance such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can also be used. When light emission is taken out from this anode, it is desirable to increase the transmittance to more than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less.
The film thickness of the anode depends on the material, but is usually selected within the range of 10 nm to 1 μm, preferably 10 to 200 nm.

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

The cathode can be produced by forming a thin film of these electrode materials by a method such as thin film deposition or sputtering. The sheet resistance of the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.
In order to transmit the emitted light, it is convenient if either the anode or the cathode of the organic EL element is transparent or translucent because the emission brightness is improved.
Further, a transparent or translucent cathode can be produced by producing the above metal on the cathode having a thickness of 1 to 20 nm and then producing the conductive transparent material mentioned in the description of the anode on the cathode. By applying the above, it is possible to manufacture an element in which both the anode and the cathode have transparency.

[Support board]
The type of support substrate (hereinafter, also referred to as substrate, substrate, etc.) that can be used for the organic EL element of the present invention is not particularly limited, and even if it is transparent, it is opaque. You may. When light is taken out from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of imparting flexibility to the organic EL element.

Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, and cellulose acetate propionate. CAP), cellulose ester phthalates, cellulose esters such as cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyether sulfone (PES), Polyphenylene sulfide, Polysulfones, Polyetherimide, Polyetherketoneimide, Polyamide, Fluororesin, Nylon, Polymethylmethacrylate, Acrylic or Polyallylates, Arton (trade name: JSR) or Appel Cycloolefin-based resins such as (trade name: manufactured by Mitsui Kagaku Co., Ltd.) can be mentioned.

A film of an inorganic substance, an organic substance, or a hybrid film thereof may be formed on the surface of the resin film, and the water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. , Relative humidity (90 ± ² )% RH) is preferably 0.01 g / m 2.24 h or less, and moreover, oxygen permeability measured by a method according to JIS K 7126-1987. However, it is preferable that the film is a high barrier film having 1 × 10 ^-3 ml / ^m 2.24 h · atm or less and a water vapor permeability of 1 × 10 ^-5 g / ^m 2.24 h or less.

As the material for forming the barrier film, any material may be used as long as it has a function of suppressing the infiltration of a material that causes deterioration of the element such as moisture and oxygen, and for example, silicon oxide, silicon dioxide, silicon nitride and the like can be used. Further, in order to improve the vulnerability of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of an organic material. The stacking order of the inorganic layer and the organic layer is not particularly limited, but it is preferable to stack the inorganic layer and the organic layer alternately a plurality of times.
The method for forming the barrier film is not particularly limited, and for example, a vacuum vapor 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. , Plasma CVD method, laser CVD method, thermal CVD method, coating method and the like can be used, but the atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

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

[Sealing]
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of adhering a sealing member, an electrode, and a support substrate with an adhesive. The sealing member may be arranged so as to cover the display area of the organic EL element, and may have a concave plate shape or a flat plate shape. Further, transparency and electrical insulation are not particularly limited.
Specific examples thereof include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, polysulfone and the like. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium and tantalum.

In the present invention, a polymer film or a metal film can be preferably used because the organic EL element can be made into a thin film. Furthermore, the polymer film had 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 was measured by a method according to JIS K 7129-1992. It is preferable that the water vapor transmission rate (25 ± 0.5 ° C., relative humidity 90 ± ² %) is 1 × 10 ^-3 g / m 2.24 h or less.
Sandblasting, chemical etching, etc. are used to process the sealing member into a concave shape.

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

Further, it is also possible to preferably cover the electrode and the organic layer on the outside of the electrode on the side facing the support substrate by sandwiching the organic layer, and form a layer of an inorganic substance or an organic substance in contact with the support substrate to form a sealing film. .. In this case, the material for forming the film may be any material having a function of suppressing infiltration of a material that causes deterioration of the element such as moisture and oxygen, and for example, silicon oxide, silicon dioxide, silicon nitride or the like may be used. can.
Further, in order to improve the vulnerability of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of an organic material. The method for forming these films is not particularly limited, and for example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma weight. Legal, plasma CVD method, laser CVD method, thermal CVD method, coating method and the like can be used.

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

[Protective film, protective plate]
A protective film or a protective plate may be provided on the outside of the sealing film or the sealing film on the side facing the support substrate with the organic layer sandwiched in order to increase the mechanical strength of the element. In particular, when the sealing is performed by the sealing film, the mechanical strength thereof is not necessarily high, so it is preferable to provide such a protective film and a protective plate. As the material that can be used for this, a glass plate, a polymer plate / film, a metal plate / film, etc. similar to those used for the sealing can be used, but the polymer film is lightweight and thin. It is preferable to use.

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

As a method for improving the efficiency of light extraction, for example, a method of forming irregularities on the surface of a transparent substrate to prevent total reflection at the interface between the transparent substrate and the air (for example, US Pat. No. 4,774,435), the substrate. A method of improving efficiency by providing light-collecting property (for example, Japanese Patent Application Laid-Open No. 63-314795), a method of forming a reflective surface on a side surface of an element (for example, Japanese Patent Application Laid-Open No. 1-220394), a substrate. A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the light emitter and the light emitter (for example, Japanese Patent Application Laid-Open No. 62-172691), which has a lower refractive index than the substrate between the substrate and the light emitter. A method of introducing a flat layer having a refractive index (for example, Japanese Patent Application Laid-Open No. 2001-202827), a method of forming a diffraction grating between layers (including, between the substrate and the outside world) of a substrate, a transparent electrode layer, or a light emitting layer (inclusive). Japanese Unexamined Patent Publication No. 11-283751) and the like.

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

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

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

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

[Condensing sheet]
The organic EL element of the present invention is frontal to a specific direction, for example, the light emitting surface of the element, by processing to provide a structure on a microlens array on the light extraction side of the support substrate (board) or by combining with a so-called condensing sheet. By condensing light in a direction, the brightness in a specific direction can be increased.
As an example of a microlens array, a quadrangular pyramid having a side of 30 μm and an apex angle of 90 degrees is arranged two-dimensionally on the light extraction side of the substrate. One side is preferably in the range of 10 to 100 μm. If it is smaller than this, the effect of diffraction is generated and it is colored, and if it is too large, the thickness becomes thick, which is not preferable.
As the condensing sheet, for example, a light-collecting sheet that has been put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a luminance increasing film (BEF) manufactured by Sumitomo 3M Ltd. can be used. The shape of the prism sheet may be, for example, a base material having a Δ-shaped stripe having an apex angle of 90 degrees and a pitch of 50 μm, or a shape having a rounded apex angle and a random change in pitch. It may have a shape like a stripe or another shape.
Further, a light diffusing plate / film may be used in combination with a light collecting sheet in order to control the light emission angle from the organic EL element. For example, a diffusion film (lighted up) manufactured by Kimoto Co., Ltd. can be used.

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

<Display device>
The display device provided with the organic EL element of the present invention may be monochromatic or multicolored, but here, a multicolor display device will be described.

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

The configuration of the organic EL element provided in the display device is selected from the above-mentioned configuration examples of the organic EL element, if necessary.

Further, the method for manufacturing the organic EL device is as shown in the above-mentioned aspect of manufacturing the organic EL device of the present invention.

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

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

Examples of the display device or display include televisions, personal computers, mobile devices, AV devices, teletext displays, information displays in automobiles, and the like. In particular, it may be used as a display device for reproducing a still image or a moving image, and the drive method when used as a display device for reproducing a moving image may be either a simple matrix (passive matrix) method or an active matrix method.

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

Hereinafter, an example of the display device having the organic EL element of the present invention will be described with reference to the drawings.
FIG. 5 is a schematic diagram showing an example of a display device composed of an organic EL element. It is a schematic diagram of a display such as a mobile phone which displays image information by light emission of an organic EL element.

The display 1 has a display unit A having a plurality of pixels, a control unit B that scans an image of the display unit A based on image information, a wiring unit C that electrically connects the display unit A and the control unit B, and the like.
The control unit B is electrically connected via the display unit A and the wiring unit C, sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside, and the scanning signal is used to send a pixel for each scanning line. Lights up sequentially according to the image data signal, scans the image, and displays the image information on the display unit A.

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

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

Next, the light emitting process of the pixel will be described. FIG. 7 is a schematic diagram showing a pixel circuit.
The pixel includes an organic EL element 10, a switching transistor 11, a drive transistor 12, a capacitor 13, and the like. As the organic EL element 10 for a plurality of pixels, red, green, and blue light emitting organic EL elements are used, and by arranging them side by side on the same substrate, full-color display can be performed.

In FIG. 7, an image data signal is applied from the control unit B to the drain of the switching transistor 11 via the data line 6. Then, when a scanning signal is applied from the control unit B to the gate of the switching transistor 11 via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is the capacitor 13 and the driving transistor 12. It is transmitted to the gate of.

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

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

Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations by a multi-valued image data signal having a plurality of gradation potentials, or may be on or off of a predetermined light emission amount by a binary image data signal. good. Further, the potential of the capacitor 13 may be continuously maintained until the next scan signal is applied, or may be discharged immediately before the next scan signal is applied.
In the present invention, the present invention is not limited to the active matrix method described above, and may be a passive matrix type light emission drive in which the organic EL element emits light in response to the data signal only when the scanning signal is scanned.

FIG. 8 is a schematic diagram of a display device using a passive matrix method. In FIG. 8, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a grid pattern so as to face each other with the pixel 3 interposed therebetween.
When the scanning signal of the scanning line 5 is applied by the sequential scanning, the pixel 3 connected to the applied scanning line 5 emits light according to the image data signal.
In the passive matrix method, the pixel 3 does not have an active element, and the manufacturing cost can be reduced.
By using the organic EL element of the present invention, a display device having improved luminous efficiency was obtained.

<Lighting device>
The organic EL element of the present invention can also be used in a lighting device.
The organic EL element of the present invention may be used as an organic EL element having a resonator structure. The purpose of using the organic EL element having such a resonator structure includes 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-mentioned applications by oscillating a laser.
Further, the organic EL element of the present invention may be used as a kind of lamp such as for lighting or an exposure light source, a projection device of a type for projecting an image, or a type for directly visually recognizing a still image or a moving image. It may be used as a display device (display).
When used as a display device for moving image reproduction, the drive method may be either a passive matrix method or an active matrix method. Alternatively, a full-color display device can be manufactured by using two or more kinds of organic EL elements of the present invention having different emission colors.

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

Further, in the method for forming the organic EL element of the present invention, a mask may be provided only when the light emitting layer, the hole transport layer, the electron transport layer, or the like is formed, and the mask may be applied separately. Since the other layers are common, patterning such as a mask is not required, and for example, an electrode film can be formed on one surface by a vapor deposition method, a casting method, a spin coating method, an inkjet method, a printing method, or the like, and productivity is also improved.
According to this method, unlike a white organic EL device in which light emitting elements of a plurality of colors are arranged in parallel in an array, the elements themselves emit white light.

[One aspect of the lighting device of the present invention]
An aspect of the lighting device of the present invention provided with the organic EL element of the present invention will be described.
The non-light emitting surface of the organic EL element of the present invention is covered with a glass case, a glass substrate having a thickness of 300 μm is used as a sealing substrate, and an epoxy-based photocurable adhesive (Lux manufactured by Toa Synthetic Co., Ltd.) is used as a sealing material around the glass substrate. Track LC0629B) is applied, which is placed on the cathode and brought into close contact with the transparent support substrate, irradiated with UV light from the glass substrate side, cured, sealed, and illuminated as shown in FIGS. 9 and 10. The device can be formed.
FIG. 9 shows a schematic view of the lighting device, and the organic EL element (organic EL element 101 in the lighting device) of the present invention is covered with a glass cover 102 (note that the sealing work with the glass cover is lighting. The organic EL element 101 in the apparatus was carried out in a glove box under a nitrogen atmosphere (under an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) without contacting the atmosphere.)
10A and 10B show a cross-sectional view of a lighting device, 105 is a cathode, 106 is an organic layer, and 107 is a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108, and a water catching agent 109 is provided.
By using the organic EL element of the present invention, a lighting device with improved luminous efficiency can be obtained.

<Luminescent material>
The π-conjugated compound of the present invention can radiate fluorescence by electric field excitation or the like. Therefore, it can be used as various light emitting materials. The luminescent material may contain other components, if necessary, in addition to the π-conjugated compound. Further, the light emitting material may be used in the form of powder, or may be processed into a desired shape and used. The luminescent material can be applied to, for example, a material for forming a luminescent thin film described later, a fluorescent paint, and a bioimaging fluorescent dye.

Further, when the absolute value of _ΔEST of the π-conjugated compound is 0.50 eV or less, the π-conjugated compound may emit delayed fluorescence, and such a compound should be applied to a bioimaging fluorescent dye. Can be done. Furthermore, delayed fluorescence is known to be quenched by oxygen, so it can also be applied to oxygen sensing materials.

<Light emitting thin film>
The luminescent thin film according to the present invention is characterized by containing the above-mentioned π-conjugated compound according to the present invention, and can be produced in the same manner as in the method for forming the organic layer.
The luminescent thin film and the luminescent thin film of the present invention can be produced in the same manner as in the method for forming the organic layer.

The method for forming the luminescent thin film of the present invention is not particularly limited, and conventionally known methods such as a vacuum vapor deposition method and a wet method (also referred to as a wet process) can be used.
Examples of the wet method include a spin coat method, a cast method, an inkjet method, a printing method, a die coat method, a blade coat method, a roll coat method, a spray coat method, a curtain coat method, and an LB method (Langmuir-Bloget method). From the viewpoint of easy obtaining a uniform thin film and high productivity, a method having high suitability for a roll-to-roll method such as a die coating method, a roll coating method, an inkjet method, and a spray coating method is preferable.

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

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

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in the examples, it represents "mass%" unless otherwise specified.

The compounds used in Examples and Comparative Examples are shown below.

(Synthesis of π-conjugated compound T-25)
(3,5-Dibromophenyl) boric acid and 2-chloro-4,6-diphenyl-1,3,5-triazine in the presence of tetrakis (triphenylphosphine) palladium and potassium carbonate in toluene, ethanol, and water. , Heated and stirred at 100 ° C. to obtain 2- (3,5-dibromo) -4,6-diphenyl-1,3,5-triazine. Next, 2- (3,5-dibromo) -4,6-diphenyl-1,3,5-triazine and diphenylamine were added to tris (dibenzylideneacetone) dipalladium, tri (t-butyl) phosphine, and t-butoxy. In the presence of sodium, the mixture was heated and stirred in xylene at 140 ° C. to obtain a crude product of the π-conjugated compound T-25. Then, column chromatography, recrystallization, and sublimation purification were performed to obtain a high-purity product of the π-conjugated compound T-25.

(Synthesis of other π-conjugated compounds)
Compounds T-1, T-8, T-13, T-15, T-16, T-22, T-26, T-33, T-34 in the same manner as described above except that the raw materials were mainly changed. , T-35, T-36, T-37, T-40, T-48, T-49, T-52, T-53, and T-56 were synthesized.

The _ΔEST of the obtained compound and the comparative compounds 1 to 4 was calculated and obtained by the following method.

(Calculation of _ΔEST )
The structural optimization and the calculation of the electron density distribution by the molecular orbital calculation of the compound were calculated using the molecular orbital calculation software using B3LYP as the general function and 6-31G (d) as the base function as the calculation method. Gaussian09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian Co., Ltd. in the United States was used as the software for calculating the molecular orbital.
From the structure optimization calculation using B3LYP as this functional and 6-31G (d) as the base function, the excited state calculation by the time-dependent density functional theory (Time-Dependent DFT) is further performed, and S ₁ , T ₁ The energy levels of (E (S ₁ ) and E (T ₁ ), respectively) were obtained and calculated as ΔE _ST = | E (S ₁ ) -E (T ₁ ) |.

[Example 1]
(Manufacturing of organic EL element 1-1)
ITO (indium tin oxide) was formed as an anode on a glass substrate having a thickness of 50 mm × 50 mm and a thickness of 0.7 mm to a thickness of 150 nm, and patterning was performed. Then, the transparent substrate to which the ITO transparent electrode was attached was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes. Then, this transparent substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus.
Each of the crucibles for vapor deposition in the vacuum vapor deposition apparatus was filled with the constituent materials of each layer in the optimum amount for manufacturing the device. As the crucible for vapor deposition, a crucible made of molybdenum or tungsten made of a resistance heating material was used.

After depressurizing to a vacuum degree of 1 × 10 ^-4 Pa, the crucible for vapor deposition containing HI-1 is energized and heated, and the film is vapor-deposited on an ITO transparent electrode at a vapor deposition rate of 0.1 nm / sec to a positive layer thickness of 10 nm. A hole injection transport layer was formed.
Next, α-NPD (4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) was deposited on the hole injection layer at a vapor deposition rate of 0.1 nm / sec, and the layer thickness was 40 nm. A hole transport layer was formed. H-232 as a host compound and Comparative Compound 1 as a luminescent compound were co-deposited at a vapor deposition rate of 0.1 nm / sec so as to have a volume of 94% and 6%, respectively, to form a light emitting layer having a layer thickness of 30 nm. ..
Then, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) was vapor-deposited at a vapor deposition rate of 0.1 nm / sec to form an electron transport layer having a layer thickness of 30 nm.
Further, after forming lithium fluoride with a film thickness of 0.5 nm, aluminum 100 nm was vapor-deposited to form a cathode.
The non-light emitting surface side of the element was covered with a can-shaped glass case in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more, and an electrode take-out wiring was installed to manufacture an organic EL element 1-1.

(Manufacturing of organic EL elements 1-2 to 1-23)
Organic EL devices 1-2 to 1-23 were produced in the same manner as the organic EL device 1-1 except that the luminescent compound was changed as shown in Table 1.

(Measurement of relative luminous efficiency)
Each of the above-produced organic EL elements is made to emit light at room temperature (about 25 ° C.) under a constant current condition of 2.5 mA / cm ² , and the emission brightness immediately after the start of emission is measured by the spectral radiance meter CS-2000 (Konica Minolta). It was measured using (manufactured by the company). Table 1 shows the relative value of the obtained emission luminance (in Example 1, the relative value with respect to the emission luminance of the organic EL element 1-1).

[Example 2]
(Manufacturing of organic EL element 2-1)
Patterning was performed on a substrate (NA45 manufactured by NH Techno Glass Co., Ltd.) in which ITO (indium tin oxide) was deposited at 100 nm on a glass substrate having a size of 100 mm × 100 mm × 1.1 mm as an anode. Then, the transparent support substrate provided with the ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.
On this transparent support substrate, poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) diluted to 70% with pure water was used at 3000 rpm. After forming a thin film by a spin coating method under the condition of 30 seconds, it was dried at 200 ° C. for 1 hour to provide a hole injection layer having a layer thickness of 20 nm. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus.
Each of the crucibles for vapor deposition in the vacuum vapor deposition apparatus was filled with the constituent materials of each layer in the optimum amount for manufacturing the device. As the crucible for vapor deposition, a crucible made of molybdenum or tungsten made of a resistance heating material was used.

After depressurizing to a vacuum degree of 1 × 10 ^-4 Pa, α-NPD was deposited on the hole injection layer at a vapor deposition rate of 0.1 nm / sec to form a hole transport layer having a layer thickness of 40 nm. The vapor deposition rate of H-234 as the host compound and TBPe (2,5,8,11-tetra-tert-butylperylene) as the luminescent compound was 0.1 nm / sec so as to be 97% and 3% by volume, respectively. To form a light emitting layer having a layer thickness of 30 nm.
Then, TPBi (1,3,5-tris (N-phenylbenzimidazol-2-yl)) was vapor-deposited at a vapor deposition rate of 0.1 nm / sec to form an electron transport layer having a layer thickness of 30 nm.
Further, after forming sodium fluoride with a film thickness of 1 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-light emitting surface side of the element was covered with a can-shaped glass case in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more, and an electrode take-out wiring was installed to manufacture an organic EL element 2-1.

(Manufacturing of organic EL element 2-2)
H-234 was used as the host compound, TBPe (2,5,8,11-tetra-tert-butylperylene) was used as the luminescent compound, and comparative compound 1 was used as the third component, and the respective ratios were 82%, 3%, and 15. The organic EL element 2-2 was produced in the same manner as in the production of the organic EL element 2-1 except that the light emitting layer was formed so as to have a volume% of%.

(Manufacturing of organic EL elements 2-3 to 2-8)
As shown in Table 2, the organic EL elements 2-3 to 2-8 were produced in the same manner as the organic EL element 2-2 except that the third component was changed.

The relative luminous efficiency of each of the produced organic EL elements during driving was measured in the same manner as in Example 1. Table 2 shows the relative value of the obtained emission luminance (in Example 2, the relative value with respect to the emission luminance of the organic EL element 2-1).

[Example 3]
(Manufacturing of organic EL element 3-1)
ITO (indium tin oxide) was formed as an anode on a glass substrate having a thickness of 50 mm × 50 mm and a thickness of 0.7 mm to a thickness of 150 nm, and patterning was performed. Then, the transparent substrate with the ITO transparent electrode was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, UV ozone washed for 5 minutes, and then the transparent substrate was placed in a substrate holder of a commercially available vacuum vapor deposition apparatus. Fixed.
Each of the resistance heating boats for vapor deposition in the vacuum vapor deposition apparatus was filled with the constituent materials of each layer in the optimum amount for manufacturing the device. The resistance heating boat was made of molybdenum or tungsten.

After depressurizing to a vacuum degree of 1 × 10 ^-4 Pa, the resistance heating boat containing HI-1 is energized and heated, and the film is vapor-deposited on an ITO transparent electrode at a vapor deposition rate of 0.1 nm / sec to a positive layer thickness of 15 nm. A hole injection layer was formed.

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

Next, a resistance heating boat containing Comparative Compound 1 as a host compound and GD-1 as a luminescent compound was energized and heated, and the hole transport layer was heated at a vapor deposition rate of 0.1 nm / sec and 0.010 nm / sec, respectively. To form a light emitting layer having a layer thickness of 40 nm.

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

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

Then, after vapor-filming lithium fluoride to a thickness of 0.5 nm, aluminum 100 nm was vapor-deposited to form a cathode, thereby producing an organic EL element 3-1.

(Manufacturing of organic EL elements 3-2 to 3-8)
Organic EL devices 3-2 to 3-8 were produced in the same manner as the organic EL device 3-1 except that the host compound was changed as shown in Table 3.

The relative luminous efficiency of each of the organic EL elements produced above was measured in the same manner as in Example 1.
Table 3 shows the relative value of the obtained emission luminance (in Example 3, the relative value with respect to the emission luminance of the organic EL element 3-1).

[Example 4]
(Manufacturing of organic EL element 4-1)
ITO (indium tin oxide) was formed as an anode on a glass substrate having a thickness of 50 mm × 50 mm and a thickness of 0.7 mm to a thickness of 150 nm, and patterning was performed. Then, the transparent substrate with the ITO transparent electrode was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, UV ozone washed for 5 minutes, and then the transparent substrate was placed in a substrate holder of a commercially available vacuum vapor deposition apparatus. Fixed.
Each of the resistance heating boats for vapor deposition in the vacuum vapor deposition apparatus was filled with the constituent materials of each layer in the optimum amount for manufacturing the device. The resistance heating boat was made of molybdenum or tungsten.

After depressurizing to a vacuum degree of 1 × 10 ^-4 Pa, the resistance heating boat containing α-NPD (4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) is energized and heated. Then, the film was deposited on the ITO transparent electrode at a vapor deposition rate of 0.1 nm / sec to form a hole injection layer having a layer thickness of 30 nm.

Next, TCTA (tris (4-carbazoyl-9-ylphenyl) amine) was vapor-deposited at a vapor deposition rate of 0.1 nm / sec to form a first hole transport layer having a layer thickness of 20 nm.

Further, H-233 was vapor-deposited at a vapor deposition rate of 0.1 nm / sec to form a second hole transport layer having a layer thickness of 10 nm.

Next, a resistance heating boat containing Comparative Compound 1 as the host compound and TBPe (2,5,8,11-tetra-tert-butylperylene) as the luminescent compound was energized and heated, and the vapor deposition rate was 0.1 nm / each. Co-deposited on the hole transport layer at 0.010 nm / sec to form a light emitting layer having a layer thickness of 20 nm.

Next, H-232 was vapor-deposited at a vapor deposition rate of 0.1 nm / sec to form a first electron transport layer having a layer thickness of 10 nm.

Further, TBPi was vapor-deposited on it at a vapor deposition rate of 0.1 nm / sec to form a second electron transport layer having a layer thickness of 30 m.

Then, after vapor-filming lithium fluoride to a thickness of 0.5 nm, aluminum 100 nm was vapor-deposited to form a cathode, thereby producing an organic EL element 4-1.

(Manufacturing of organic EL elements 4-2 to 4-6)
Organic EL devices 4-2 to 4-6 were produced in the same manner as the organic EL device 4-1 except that the host compound was changed as shown in Table 4.

The relative luminous efficiency of each of the organic EL elements produced above was measured in the same manner as in Example 1.
Table 4 shows the relative value of the obtained emission luminance (in Example 4, the relative value with respect to the emission luminance of the organic EL element 4-1).

In all of the elements 1 to 4, the compound of the present invention showed higher luminous efficiency than the compound of Comparative Example.

In Table 1, from the comparison of the organic EL elements 1-3, 1-7 and 1-8, the organic EL using the compound T-13 in which the electron donating group D is the “dihydroacrydinyl group” as the luminescent compound. The organic EL element 1-8 using the element 1-7 and the compound T-15 which is a “phenoxadinyl group” is an organic EL element 1-3 using the comparative compound 3 whose electron donating group D is a “carbazolyl group”. It is shown that ΔEst is smaller than that and the relative emission efficiency is high.

In Table 1, from the comparison of the organic EL elements 1-7 and 1-23, the organic EL element 1-23 using the compound T-56 in which both L ¹ and L ² are azadibenzofuranyl groups as the luminescent compound is used. Shows that ΔEst is smaller and the relative emission efficiency is higher than that of the organic EL element 1-7 using the compound T-13 in which both L ¹ and L ² are cyano groups.

In Table 1, from the comparison of the organic EL elements 1-10 and 1-22, the organic EL element 1-10 using the compound T-22 in which ^Q1 to ^Q3 are all carbon atoms as the luminescent compound is Q. It is shown that ΔEst is smaller and the relative emission efficiency is higher than that of the organic EL element 1-22 using the compound T-53 in which a part of ¹ to ^Q3 is a nitrogen atom.

In Table 1, from the comparison of the organic EL elements 1-5 and 1-21, the organic EL element 1-5 using the compound T-1 in which Q ¹ to Q ³ are all nitrogen atoms as the luminescent compound is Q. It is shown that the relative emission efficiency is higher than that of the organic EL element 1-21 using the compound T-52 in which a part of ¹ to ^Q3 is a nitrogen atom.

In Table 1, from the comparison of the organic EL elements 1-7 and 1-9, the organic EL element 1-7 using the compound T-13 in which the electron donating group D is the “dihydroacrydinyl group” as the luminescent compound is used. It is shown that the relative emission efficiency is higher than that of the organic EL element 1-9 using the compound T-16 in which the electron donating group D is a "phenothiazinyl group".

In Table 2, from the comparison of the organic EL elements 2-3, 2-4 and 2-8, the compounds T-8 and T-49 in which the electron donating group D is a "diazacarbazolyl group" as the third component are shown. The organic EL elements 2-4 and 2-8 using the above have a smaller ΔEst than the organic EL elements 2-3 using the compound T-1 in which the electron donating group D is a “dihydroacrydinyl group”, and are relative to each other. It is shown that the emission efficiency is high.

In Table 4, from the comparison of the organic EL elements 4-2 and 4-6, the organic EL element 4-6 using the compound T-49 in which the electron donating group D is the “diazacarbazolyl group” as the host compound is used. Has a smaller ΔEst and higher relative emission efficiency than the organic EL element 4-2 using the compound T-1 in which the electron donating group D is a “dihydroacrydinyl group”.

[Example 5]
(Manufacturing of organic EL elements 5-1 to 5-6)
The organic EL elements 5-1 to 5-6 were prepared in the same manner as the organic EL element 1-5 except that the host compound and the luminescent compound were changed from the element 1-5 of Example 1 as shown in Table 5. Made.
Further, the above-mentioned organic EL elements 1-5, 1-6, 1-11, 1-15, 1-18 and 1-19 were prepared.

(Measurement of relative brightness half time)
The brightness half-time (time required for the brightness to decrease from 300 cd / m ₂ to 150 cd / m ² ) when each of the prepared elements was lit at an initial brightness of 300 cd / m ² was measured.
Then, Table 5 shows the relative value of the luminance half time of each element with respect to the luminance half time of the organic EL element 1-19).

It is shown that in the element 5, the element using the compound represented by the general formula (I) as the host compound has a longer relative luminance half time than the element using H-232.

[Example 6]
(Preparation of co-deposited film 6-1)
A 50 mm × 50 mm, 0.7 mm thick quartz substrate was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone washed for 5 minutes, and then this transparent substrate was used as a substrate holder for a commercially available vacuum vapor deposition apparatus. Fixed to.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with 1,3-bis (N-carbazolyl) benzene (mCP) and compound T-25. As the crucible for vapor deposition, a crucible made of molybdenum or tungsten made of a resistance heating material was used.

After depressurizing to a vacuum degree of 1 × 10 ^-4 Pa, 1,3-bis (N-carbazolyl) benzene (mCP) as a host compound and compound T-25 as a luminescent compound were added at 94% and 6% by volume, respectively. The co-evaporation was carried out at a vapor deposition rate of 0.1 nm / sec so as to form a co-evaporation film 6-1 having a layer thickness of 40 nm.

(Measurement of delayed fluorescence of co-deposited film 6-1)
Under a nitrogen atmosphere, the co-deposited film 6-1 was irradiated with excitation light having a wavelength of 355 nm, and fluorescence attenuation was measured at each maximum emission wavelength. FIG. 11 shows a graph showing the relationship between time and the number of photons for each co-deposited film 6-1. As shown in FIG. 11, in the π-conjugated compound (T-25) of the present invention, two or more components having different fluorescence attenuation rates were confirmed, and it was confirmed that delayed fluorescence was emitted.

According to the present invention, for example, it is possible to provide a new π-conjugated compound capable of improving the luminous efficiency of an organic electroluminescence device. Further, it is possible to provide an organic electroluminescence element material using the π-conjugated compound, a light emitting thin film, a light emitting material, an organic electroluminescence element, and a display device and a lighting device provided with the organic electroluminescence element.

1 Display 3 pixels 5 Scan line 6 Data line 7 Power supply line 10 Organic EL element 11 Switching transistor 12 Drive transistor 13 Condenser 101 Organic EL element in lighting device 102 Glass cover 105 Cathode 106 Organic layer 107 Glass substrate with transparent electrode 108 Nitrogen gas 109 Water trapping agent A Display unit B Control unit C Wiring unit

Claims (11)

It comprises an anode, a cathode, and a light emitting layer provided between the anode and the cathode.
At least one layer of the light emitting layer contains an assist dopant, at least one of a fluorescent compound and a phosphorescent compound, and a host compound.
The assist dopant contains a π-conjugated compound represented by the following general formula (1), and the absolute value ΔE of the energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound. _ST is 0.50 eV or less,
Organic electroluminescence element.

(In general formula (1),
1) Q ¹ to Q ³ represent -CH, respectively.
L ¹ and L ² are electron-donating groups D and M is an electron-withdrawing group A, or L ¹ and L ² are electron-withdrawing groups A and M is an electron-donating group. In both cases, L ¹ and L ² are D and are the same as each other .
The electron donating group D is a optionally substituted 9,10-dihydroacridin ring, an optionally substituted phenoxazine ring, an optionally substituted phenothiazine ring, or an optionally substituted azacarbazole ring. , And an optionally substituted electron-donating heterocyclic group selected from the group consisting of optionally substituted diazacarbazole rings.
The electron-attracting group A is a phenyl group, a naphthalene group, a fluorenyl group, a phenanthrenyl group, an anthrasenyl group, a chrysenyl group, a pyrenyl group, a triphenylenyl group, a peryleneyl group, a fluortenylene group, or a biphenylene substituted with a cyano group or a cyano group. An aryl group selected from the group consisting of a group and a terphenylene group, or a pyridyl group substituted with a cyano group, a pyrazil group optionally substituted, a pyridimidyl group optionally substituted, a triazil group optionally substituted, aza. Is it an electron-withdrawing heterocyclic group selected from the group consisting of a dibenzofuryl group and a diazadibenzofuryl group?
or,
2) Q ¹ and Q ³ are nitrogen atoms, Q ² is -CH, or all of Q ¹ to Q ³ are nitrogen atoms.
L ¹ and L ² are electron-donating groups D and M is an electron-withdrawing group A, or L ¹ and L ² are electron-withdrawing groups A and M is an electron-donating group. In both cases, L ¹ and L ² are D and are the same as each other.
The electron donating group D may be substituted 9,10-dihydroacridin ring (provided that, if all of ^Q1 to ^Q3 are nitrogen atoms, 9,9-dimethyl-9,10- From the group consisting of a phenoxazine ring that may be substituted, a phenothiazine ring that may be substituted, an azacarbazole ring that may be substituted, and a diazacarbazole ring that may be substituted. An electron-donating heterocyclic group of choice that may be substituted,
The electron-withdrawing group A is a phenyl group. ) The above 1) is satisfied, and the L ¹ and L ² are the electron donating group D, and the M is the electron withdrawing group A.
The organic electroluminescence device according to claim 1. The above 2) is satisfied, and the L ¹ and L ² are the electron-withdrawing group A, and the M is the electron-donating group D.
The organic electroluminescence device according to claim 1. The above 2) is satisfied, and all of the above ^Q1 to ^Q3 are nitrogen atoms.
The organic electroluminescence device according to claim 1 or 3. The electron donating group D may be substituted 9,10-dihydroacridin ring (provided that, if all of ^Q1 to ^Q3 are nitrogen atoms, 9,9-dimethyl-9,10- A nitrogen-containing aromatic heterocyclic group that is optionally substituted and is an electron-donating nitrogen-containing aromatic heterocycle selected from the group consisting of a phenoxazine ring that may be substituted (excluding dihydroacridin). The nitrogen atom of the group is bonded to the ring containing ^Q1 to ^Q3 .
The organic electroluminescence device according to any one of claims 1 to 4. The electron donating group D is an optionally substituted azacarbazolyl group or an optionally substituted diazacarbazolyl group.
The organic electroluminescence device according to any one of claims 1 to 4. The host compound has a structure represented by the following general formula (I).
The organic electroluminescence device according to any one of claims 1 to 6.

(In general formula (I),
X ₁₀₁ represents NR ₁₀₁ , oxygen atom, sulfur atom, sulfinyl group, sulfonyl group, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₄ R ₁₀₅ .
y ₁ to y ₈ independently represent CR ₁₀₆ or a nitrogen atom, respectively.
R ₁₀₁ to R ₁₀₆ each independently represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring.
Ar ₁₀₁ and Ar ₁₀₂ each independently represent an optionally substituted aryl group or an optionally substituted heteroaryl group.
n101 and n102 each represent an integer of 0 to 4.
However, when R ₁₀₁ is a hydrogen atom, n 101 represents an integer of 1 to 4. ) The host compound having the structure represented by the general formula (I) has the structure represented by the following general formula (II).
The organic electroluminescence device according to claim 7.

(In general formula (II),
X ₁₀₁ represents NR ₁₀₁ , oxygen atom, sulfur atom, sulfinyl group, sulfonyl group, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₄ R ₁₀₅ .
R ₁₀₁ to R ₁₀₅ each represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring.
Ar ₁₀₁ and Ar ₁₀₂ each independently represent an optionally substituted aryl group or an optionally substituted heteroaryl group.
n102 represents an integer from 0 to 4. ) The content of the π-conjugated compound is 1 to 30% by mass with respect to the light emitting layer.
The organic electroluminescence device according to any one of claims 1 to 8. The organic electroluminescence device according to any one of claims 1 to 9 is included.
Display device. The organic electroluminescence device according to any one of claims 1 to 9 is included.
Lighting equipment.

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