JP7060670B2 - Assist dopant material, luminescent thin film, organic electroluminescence device, display device and lighting device - Google Patents

Description

The present invention relates to an assist dopant material, a luminescent thin film, an organic electroluminescence element, a display device and a lighting device provided with the organic electroluminescence element. More specifically, the present invention relates to an assist dopant material having improved luminous efficiency.

Organic EL devices (also referred to as "organic electroluminescent devices") that utilize electroluminescence (hereinafter abbreviated as "EL"), which is an organic material, have already been put into practical use as a new light emitting system that enables planar light emission. It is a technology that has been done. 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 emission 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 singlet exciter generation efficiency in TTA is only about 40%, so that phosphorescence is still emitted. It has a problem of high emission efficiency as compared with the above.

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, 100% internal quantum, which is theoretically equivalent to that of phosphorescent light emission, even in fluorescent light emission by electric field excitation. Efficiency is possible.

In order for the TADF phenomenon to occur, it is necessary to cause 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, the absolute value of the difference between the lowest excited singlet energy level (S ₁ ) and the lowest triplet excited energy level (T ₁ ) (hereinafter referred to as _ΔEST ) is extremely high. It is essential to be small.

Further, it is known that if a compound exhibiting TADF property is included in the light emitting layer as a third component (assist dopant) in the light emitting layer composed of a host compound and a light emitting compound, it is effective in exhibiting high luminous efficiency (non-). See Patent Document 3). By generating 25% singlet excitons and 75% triplet excitons on the assist dopant by field excitation, the triplet excitons generate singlet excitons with inverse intersystem crossing (RISC). be able to. The energy of the singlet excitons is transferred to the luminescent compound, and the luminescent compound can emit light by the transferred energy. Therefore, it is theoretically possible to make the luminescent compound emit light by using 100% exciton energy, and high luminous efficiency is exhibited.

In order to minimize _ΔEST in an organic compound, it is desirable to localize the highest occupied molecular orbital (HOMO) and the lowest empty molecular orbital (LUMO) in the molecule without mixing them.

1 and 2 are schematic diagrams showing energy diagrams of a compound exhibiting the TADF phenomenon (TADF compound) and a general fluorescent light emitting compound. For example, in 2CzPN having the structure shown in FIG. 1, HOMO is localized on the carbazolyl groups at the 1- and 2-positions on the benzene ring, and LUMO is localized on the cyano groups at the 4- and 5-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.

In the prior art, a method using a strong electron-donating group or an electron-withdrawing group is known in order to clearly separate HOMO and LUMO. However, the use of a strong electron donating group or electron attracting group forms a strong intramolecular charge transfer (CT) excited state, which causes the absorption spectrum and the emission spectrum to have a longer wavelength, and emits light. There is a problem that it is difficult to control the wavelength. On the contrary, if the electron donating property or the electron attracting property is weakened in order to control the emission wavelength, the expression of the TADF phenomenon is hindered. Therefore, a new method for expressing the TADF phenomenon while controlling the emission wavelength is desired.

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 increasing 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.

As a result of investigating the causes of the above problems in order to solve the above problems, the present inventor has as a result of examining the causes of the above problems, and as a result, the electron-donating groups D and the electron-withdrawing groups A, or the electron-donating groups D and the electron-withdrawing groups A. A π-conjugated compound having 2 or 3 ring structures in which 3 to 5 atoms are present and all of these 3 to 5 atoms are contained can improve the light emission efficiency of, for example, an organic electroluminescence element. Newly found and came to the present invention.
That is, the above-mentioned problem according to the present invention is solved by the following means.

（一般式（１）～（６）中、
ＬとＭは各々独立に、電子供与性基Ｄ又は電子求引性基Ａを表し、
前記電子供与性基Ｄは、電子供与性基で置換されたアリール基、置換されていてもよい電子供与性基の複素環基、及び置換されていてもよいアミノ基からなる群より選ばれる基であり、
前記電子求引性基Ａは、置換されていてもよいカルボニル基、置換されていてもよいスルホニル基、置換されていてもよいホスフィンオキサイド基、置換されていてもよいボリル基、電子求引性基で置換されていてもよいアリール基、電子求引性基で置換されている電子供与性の複素環基、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り、
Ｑは各々独立に、炭素原子又は窒素原子を表し、
一般式（３）中、
Ｒは炭素原子、酸素原子、窒素原子、硫黄原子、ホウ素原子又はケイ素原子を表す。）
［２］ 一般式（１）～（６）において、ＬとＭの一方が前記電子供与性基Ｄであり、他方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］ 前記電子供与性基Ｄは、電子供与性基で置換されたアリール基又は置換されていてもよい電子供与性基の複素環基である、［１］又は［２］に記載のπ共役系化合物。
［４］ 前記電子求引性基Ａは、電子求引性基で置換されていてもよいアリール基、電子求引性基で置換されている電子供与性の複素環基、又は置換されていてもよい電子求引性の複素環基である、［１］～［３］のいずれかに記載のπ共役系化合物。
［５］ 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］～［４］のいずれかに記載のπ共役系化合物。 [1] A π-conjugated compound having a structure represented by any one of the following general formulas (1) to (6).

(In the general formulas (1) to (6),
L and M each independently represent an electron-donating group D or an electron-withdrawing group A.
The electron-donating group D is a group selected from the group consisting of an aryl group substituted with an electron-donating group, a heterocyclic group of an electron-donating group which may be substituted, and an amino group which may be substituted. And
The electron-attracting group A includes a optionally substituted carbonyl group, a optionally substituted sulfonyl group, an optionally substituted phosphinoxide group, an optionally substituted boryl group, and an electron-attracting group. It is selected from the group consisting of an aryl group optionally substituted with a group, an electron donating heterocyclic group substituted with an electron attracting group, and an electron attracting heterocyclic group optionally substituted. Is the basis and
Q independently represents a carbon atom or a nitrogen atom.
In general formula (3),
R represents a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, a boron atom or a silicon atom. )
[2] The π-conjugated system according to [1], wherein one of L and M is the electron-donating group D and the other is the electron-withdrawing group A in the general formulas (1) to (6). Compound.
[3] The π according to [1] or [2], wherein the electron-donating group D is an aryl group substituted with an electron-donating group or a heterocyclic group of an electron-donating group which may be substituted. Conjugated compound.
[4] The electron-withdrawing group A is an aryl group optionally substituted with an electron-withdrawing group, an electron-donating heterocyclic group substituted with an electron-withdrawing group, or a substituted group. The π-conjugated compound according to any one of [1] to [3], which is a good electron-withdrawing heterocyclic group.
[5] The π-conjugated compound according to any one of [1] to [4], 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. ..

[6] An organic electroluminescence device material containing the π-conjugated compound according to any one of [1] to [5].
[7] A luminescent material containing the π-conjugated compound according to any one of [1] to [5], wherein the π-conjugated compound radiates fluorescence.

[8] The light emitting material according to [7], wherein the π-conjugated compound emits delayed fluorescence.
[9] A charge transport material containing the π-conjugated compound according to any one of [1] to [5], wherein the π-conjugated compound radiates delayed fluorescence.
[10] A luminescent thin film containing the π-conjugated compound according to any one of [1] to [5].
[11] The luminescent thin film according to [10], wherein the π-conjugated compound radiates delayed fluorescence.
[12] The anode, the cathode, and a light emitting layer provided between the anode and the cathode are included.
An organic electroluminescence device in which at least one layer of the light emitting layer contains the π-conjugated compound according to any one of [1] to [5].
[13] The organic electroluminescence device according to [12], wherein the π-conjugated compound produces excitons.
[14] The organic electroluminescence device according to [12] or [13], wherein the π-conjugated compound radiates fluorescence.
[15] The organic electroluminescence device according to [14], wherein the π-conjugated compound emits delayed fluorescence.
[16] The organic electroluminescence device according to any one of [12] to [15], wherein the light emitting layer contains the π-conjugated compound and the host compound.
[17] The organic electroluminescence element according to any one of [12] to [16], wherein the light emitting layer contains the π-conjugated compound and at least one of a fluorescent light emitting compound and a phosphorescent light emitting compound.
[18] The organic according to any one of [12] to [16], wherein the light emitting layer contains the π-conjugated compound, at least one of a fluorescent compound and a phosphorescent compound, and a host compound. Electroluminescence element.

（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。）
［２０］ 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、［１９］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。） [19] The organic electroluminescence device according to [16] or [18], wherein the host compound has a structure represented by the following general formula (I).

(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. )
[20] The organic electroluminescence device according to [19], wherein the host compound having the structure represented by the general formula (I) has a 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 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. )

[21] A display device including the organic electroluminescence device according to any one of [12] to [20].
[22] A lighting device comprising the organic electroluminescence device according to any one of [12] to [20].

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, a light emitting thin film, a light emitting material using the π-conjugated compound, 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 an 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 meaning which includes the numerical values described before and after it as the lower limit value and the upper limit value.

In the π-conjugated compound containing an electron-donating group D and / or an electron-withdrawing group A, the present inventor has an electron-donating group D with respect to each other, an electron-withdrawing group A with each other, or an electron-donating group D with an electron. A molecular design having two or three ring structures in which 3 to 5 atoms are present between the attractive group A and all of these 3 to 5 atoms are included as ring-constituting atoms is performed. So, I found that the TADF phenomenon can be more expressed. However, when 3 to 5 atoms are present between the two electron-donating groups D and two or three ring structures containing all of these atoms as ring-constituting atoms are formed, the ring structure is formed. Is an electron-withdrawing ring. Similarly, when 3 to 5 atoms are present between the two electron-withdrawing groups A and two or three ring structures containing all of these atoms as ring-constituting atoms are formed, the said. The ring structure is an electron-donating ring. The two or three ring structures mean a fused ring in which two or three monocyclic aromatic rings are condensed.
It is known that in order to further develop the TADF phenomenon, it is necessary to separate HOMO and LUMO to form a CT-like excited state. In the method of the present application, two or three atoms containing 3 to 5 atoms are contained between the electron-donating groups D, the electron-withdrawing groups A, or between the electron-donating group D and the electron-withdrawing group A. By arranging the ring structure of, HOMO and LUMO are separated, and _ΔEST has been successfully minimized. Further, in the specific structure in the present invention, the electron donating groups D and the electron attracting groups A, or the electron donating group D and the electron attracting group A face each other spatially at an angle close to parallel. Therefore, it is considered that non-radiative deactivation can be suppressed by effectively forming and stabilizing the CT-like excited state. It is considered that the luminous efficiency of the compound of the present application could be improved by minimizing _ΔEST and suppressing non-radiative deactivation.

Further, it is known that in the CT-like excited state expressing TADF, the electron donating part and the electron attracting part are charge-separated. In order for a compound to exhibit a high emission quantum yield, it is important to stabilize the charge separation state.

(Combination of the same species)
When the π-conjugated compound of the present invention has two electron-donating groups D or two electron-withdrawing groups A, 3 to 5 atoms are inserted between the electron-donating groups D or between the electron-withdrawing groups A. In a molecular design having a ring structure containing the electrons, electron-donating groups D or electron-withdrawing groups A resonate spatially in an excited state to stabilize positive or negative charges, and the molecule as a whole has CT properties. Since the excited state can be stably formed, it is considered that non-radiation deactivation can be suppressed and the light emission efficiency can be improved.

(Combination of different species)
When the π-conjugated compound of the present invention has an electron-donating group D and an electron-withdrawing group A, a ring structure containing 3 to 5 atoms between the electron-donating group D and the electron-withdrawing group A is formed. In the molecular design, the electron-donating group D and the electron-withdrawing group A can face each other spatially at an angle close to parallel in the excited state, so that the electron-donating group D and the electron-withdrawing group A can face each other. It is possible to effectively form and stabilize the CT-like excited state. As a result, it is considered that non-radiative deactivation can be suppressed and the luminous efficiency can be improved. Further, since such a π-conjugated compound can minimize _ΔEST , it is considered that the luminous efficiency can be further improved.

Specifically, it can be considered as follows. In the prior art, there is known a method of directly connecting an electron-donating group D and an electron-withdrawing group A and forming a CT-induced excited state only by a through bond by directly connecting them at a position where they are difficult to act spatially. Has been done. However, in such a conventional technique, since it does not contribute much to the stabilization of the excited state, the structure of the compound changes in the ground state, the singlet excited state, and the triplet excited state, respectively, and there is a problem that non-radiative deactivation occurs. be. On the other hand, when the electron-donating group D and the electron-withdrawing group A face each other at an angle close to parallel in space as in the present invention, the electron-donating group D and the electron-withdrawing group A located in the immediate vicinity become the same. It is considered that a CT-like excited state is formed between them (that is, through space). As a result, the excited state of the CT property is stabilized, and non-radiative deactivation can be suppressed as compared with the prior art, which is considered to be advantageous in the development of high luminous efficiency by the organic electroluminescence device.

Above all, in the π-conjugated compound of the present invention, in the general formulas (1) to (6), one of L and M is an electron-donating group D and the other is an electron-withdrawing group A, that is, It is preferable that the compound has both an electron-donating group D and an electron-withdrawing group A in order to reduce _ΔEST and achieve high luminous efficiency. Further, if the electron-donating group D and the electron-withdrawing group A face each other as in the π-conjugated compound of the present invention, it is not necessary to use a strong electron-donating group or an electron-withdrawing group. , It is preferable because high luminous efficiency can be achieved. As a result, it is considered that the lengthening of the absorption spectrum and the emission spectrum can be suppressed.

1. 1. π-conjugated compound The π-conjugated compound of the present invention is a compound having a structure represented by any one of the following general formulas (1) to (6).

In the general formulas (1) to (6), L and M independently represent an electron-donating group D or an electron-withdrawing group A, respectively.

(Electron donating group D)
In the general formulas (1) to (6), the electron donating group D represented by L or M is an "aryl group substituted with an electron donating group" or "an electron donating group optionally substituted". It can be a "heterocyclic group" or a "optionally substituted amino group".

The "aryl group" in the "aryl group substituted with an electron donating group" represented by D 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, pryaden ring, phenalene ring, fluoranthene ring, perylene ring, acephenanthrene ring, biphenyl ring, terphenyl ring, tetra Examples include a phenyl ring. More preferably, benzene ring, naphthalene ring, fluorene ring, phenanthrene ring, anthracene ring, biphenylene ring, chrysene ring, pyrene ring, triphenylene ring, chrysene ring, fluoranthene ring, perylene ring, biphenyl ring and terphenyl ring can be mentioned.

The "electron donating group" in the "aryl group substituted with an electron donating group" represented by D includes an alkyl group, an alkoxy group, an amino group which may be substituted, and an electron donating which may be substituted. Examples include sex heterocyclic groups. Preferred examples include a optionally substituted alkyl group and a optionally substituted electron-donating group heterocyclic group.

The "alkyl group" of the "electron donating group" in the "aryl group substituted with the electron donating group" represented by D may be linear, branched or cyclic, and may have, for example, 1 to 1 carbon atoms. Examples thereof include 20 linear, branched or cyclic alkyl groups, specifically 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, cyclohexyl group, 2-ethylhexyl group, n-heptyl group, n-octyl group, 2-hexyloctyl group, n-nonyl group, n-decyl group, n-undecyl Examples thereof include a group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group and an n-icosyl group. Preferred examples include a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclohexyl group, a 2-ethylhexyl group and a 2-hexyloctyl group.

The "arco-shiki group" of the "electron-donating group" of the "aryl group substituted with the electron-donating group" represented by D may be linear, branched, or cyclic, and may have, for example, 1 to 1 carbon atoms. Examples thereof include 20 linear, branched or cyclic alkyl groups, specifically methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, t-butoxy group, n. -Pentyloxy group, neopentyloxy group, n-hexyloxy group, cyclohexyloxy group, n-heptyloxy group, n-octyloxy group, 2-ethylhexyloxy group, nonyloxy group, decyloxy group, 3,7-dimethyloctyl Oxy 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-octadecyloxy group, n-nonadecyloxy group, n-icosyloxy group, methoxy group, ethoxy group, isopropoxy group, t-butoxy group, cyclohexyloxy group. , 2-Ethylhexyloxy group, 2-hexyloctyloxy group are preferable.

The substituent of the "optionally substituted amino group" of the "electron-donating group" of the "aryl group substituted with the electron-donating group" represented by D is substituted with an alkyl group or an alkyl group. Examples thereof include an aryl group, wherein the alkyl group and the aryl group are synonymous with the above-mentioned alkyl group and aryl group, respectively.

The "electron-donating heterocyclic group" in the "optionally substituted electron-donating heterocyclic group" represented by D is derived from an electron-donating heterocycle having 4 to 24 carbon atoms. It is preferably a group. Examples of such heterocycles include pyrrole ring, indole ring, carbazole ring, azacarbazole ring, diazacarbazole ring, indroindole ring, 9,10-dihydroacridin ring, 10,11-dihydrodibenzoazepine, 5 , 10-dihydrodibenzoazacillin, phenoxazine ring, phenothiazine ring, dibenzothiophene ring, benzofurylindole ring, benzothienodorindol ring, indolocarbazole ring, benzofurylcarbazole ring, benzothienocarbazole ring, benzothioenobenzothiophene ring, Examples thereof include a benzocarbazole ring and a dibenzocarbazole ring. More preferably, a carbazole ring, an indole indole ring, a 9,10-dihydroacridine ring, a phenoxazine ring, a phenothiazine ring, a dibenzothiophene ring, a benzofurylindole ring, and a benzocarbazole ring can be mentioned. The electron-donating heterocyclic group may be one in which two or more of the same or different heterocycles are bonded via a single bond.

The substituent in the "optionally substituted electron-donating heterocyclic group" represented by D may be an alkyl group, an alkoxy group, an aryl ring optionally substituted with an alkyl group, or a substituent may be substituted. Amino groups and the like can be mentioned. The alkyl group, alkoxy group, aryl group and amino group are synonymous with the above-mentioned alkyl group, alkoxy group, aryl group and amino group, respectively.

The "optionally substituted electron-donating heterocyclic group" of the "electron-donating group" of the "electron-donating aryl group substituted with the electron-donating group" represented by D is the above-mentioned "substituted heterocyclic group". It is synonymous with "good electron donating heterocyclic group".

Examples of the substituent in the "optionally substituted amino group" represented by D include an alkyl group and an aryl group optionally substituted with an alkyl group. The alkyl group and the aryl group can be the same as the above-mentioned alkyl group and aryl group, respectively.

Among these, since the electron donating group is high, the electron donating group D is substituted with a phenyl group substituted with an electron donating group, a carbazolyl group optionally substituted, an azacarbazolyl group optionally substituted. A diazacarbazolyl group which may be substituted, a 9,10-dihydroacrylidyl group which may be substituted, a phenoxadyl group which may be substituted, a phenothiazil group which may be substituted, and a phenothiazil group which may be substituted. It is preferably a 5,10-dihydrophenazyl group, a optionally substituted diphenylamino group, or an optionally substituted dialkylamino group. More preferably, a optionally substituted carbazolyl group, an optionally substituted azacarbazolyl group, an optionally substituted diazacarbazolyl group, an optionally substituted 9,10-dihydroacrylyl group, It is a diphenylamino group that may be substituted.

(Electronic withdrawing group A)
In the general formulas (1) to (6), the electron-attracting group A represented by L or M is a "optionally substituted carbonyl group", "optionally substituted sulfonyl group", or "substituted". Phosphine oxide group which may be substituted, "boryl group which may be substituted", "aryl group which may be substituted with an electron-attracting group", "electron substituted with an electron-withdrawing group". It can be a "donating heterocyclic group" or a "optionally substituted electron-withdrawing heterocyclic group".

The "aryl group" of the "aryl group optionally substituted with an electron-withdrawing group" represented by A has the same meaning as the above-mentioned aryl group.

The substituent of the "aryl group which may be substituted with an electron-attracting group" represented by A includes a fluorine atom, a cyano group, an alkyl group which may be substituted with a fluorine atom, and a substituent which may be substituted. Examples thereof include a good carbonyl group, a optionally substituted sulfonyl group, a optionally substituted phosphinoxide group, a optionally substituted boryl group, and an optionally substituted electron-withdrawing heterocyclic group. A fluorine atom, a cyano group, an alkyl group substituted with a fluorine atom, or an electron-withdrawing heterocyclic group which may be substituted is preferable.

The "electron-donating heterocyclic group" in the "electron-donating heterocyclic group substituted with the electron-withdrawing group" represented by A may be "substitutable" represented by the above-mentioned D. It is synonymous with "electron-donating heterocyclic group" in "electron-donating heterocyclic group".

The "electron-withdrawing group" which is the substituent of the "electron-donating heterocyclic group substituted with the electron-withdrawing group" represented by A is synonymous with the above-mentioned aryl group substituent. ..

The "heterocyclic group" in the "optionally substituted electron-withdrawing heterocyclic group" represented by A is a group derived from an electron-withdrawing heterocyclic group having 3 to 24 carbon atoms. preferable. Examples of such heterocycles include dibenzothiophene oxide ring, dibenzothiophene dioxide ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, isoquinoline ring, quinazoline ring, cinnoline ring, quinoxaline ring. , Phtalazine ring, pteridine ring, phenanthridazine ring, phenanthrolin ring, dibenzofuran ring, dibenzofuran ring, dibenzofuran ring, azadibenzofuran ring, diazadibenzofuran ring, dibenzophosphor oxide ring and the like. More preferably, a pyridine ring, a pyrimidine ring, a pyrazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, a phenanthridine ring, a phenanthroline ring, a dibenzofuran ring, an azadibenzofuran ring, a diazadibenzofuran ring, or a dibenzo Phosphor oxide ring can be mentioned. The electron-withdrawing heterocyclic group may be one in which two or more of the same or different heterocycles are bonded via a single bond.

The substituent in the "optionally substituted electron-attracting heterocyclic group" represented by A includes a deuterium atom, a fluorine atom, a cyano group, an alkyl group optionally substituted with a fluorine atom, and fluorine. Examples thereof include an aryl group which may be substituted with an alkyl group which may be substituted with an atom and an aryl group which may be substituted with a fluorine atom. Alkyl group and aryl group are synonymous with the above-mentioned alkyl group and aryl group.

The "substituted electron-withdrawing heterocyclic group" of the substituent of the "aryl group optionally substituted with an electron-withdrawing group" represented by A has the same meaning as described above.

In "optionally substituted carbonyl group", "optionally substituted sulfonyl group", "optionally substituted phosphine oxide group", "optionally substituted boryl group" represented by A Examples of substituents include a fluorine atom, a cyano group, an alkyl group optionally substituted with a fluorine atom, an aryl group optionally substituted, and an electron-attracting heterocycle optionally substituted. .. Alkyl group and aryl group are synonymous with the above-mentioned alkyl group and aryl group.

"Carbonyl group optionally substituted", "sulfonyl group optionally substituted", "substituted" of substituents of "aryl group optionally substituted with electron-attracting group" represented by A The "phosphine oxide group which may be present" and the "boryl group which may be substituted" have the same meanings as described above.

In the general formulas (1) to (6), L and M independently represent an electron-donating group D or an electron-withdrawing group A, respectively. Therefore, the π-conjugated compound having the structure represented by any of the general formulas (1) to (6) may have two electron donating groups D (or electron donating groups A). It may have both an electron donating group D and an electron donating group A. When both L and M are electron-donating groups D, it is assumed that the ring to which L and M are bonded is an electron-withdrawing ring; both L and M are electron-withdrawing groups A. Then, it is assumed that the ring to which L and M are bonded is an electron-donating ring.

Examples of the ring in which L and M are bonded in the general formulas (1) to (6) are "electron-donating rings" include a carbazole ring in the general formula (1) and a carbazole ring in the general formula (3). The indole ring in the general formula (5) and the indolocarbazole ring in the general formula (6) are included.
Examples of the ring in which L and M are bonded in the general formulas (1) to (6) are "electron-withdrawing rings" include the dibenzofuran ring (R = oxygen atom) and dibenzothiophene in the general formula (3). Includes a dioxide ring (R = SO ₂ ), a azadibenzofuran ring (R = oxygen atom, one of Q is a nitrogen atom), and a diazadibenzofuran ring (R = oxygen atom, two of Q are nitrogen atoms). ..

Above all, in the π-conjugated compound of the present invention, one of L and M is an electron-donating group D and the other is an electron-withdrawing group A, that is, the compound is an electron-donating group D and an electron-withdrawing group. Having both attractive groups A is preferable in order to make _ΔEST smaller and achieve high luminous efficiency. Further, if the electron-donating group D and the electron-withdrawing group A face each other as in the π-conjugated compound of the present invention, it is not necessary to use a strong electron-donating group or an electron-withdrawing group. , It is preferable because high luminous efficiency can be achieved. As a result, it is considered that the lengthening of the absorption spectrum and the emission spectrum can be suppressed.

In the above general formulas (1) to (6), Q independently represents a carbon atom or a nitrogen atom. The general formulas (1) to (6) include Q of 6 to 10, of which the number of nitrogen atoms is preferably 0 to 4, and more preferably 0 to 2. When the number of nitrogen atoms contained as Q is 2 or less, it is preferable from the viewpoint of controlling the emission wavelength.

In the above general formulas (1) to (6), when Q is a carbon atom, the substituent of the carbon atom may be a hydrogen atom, a heavy hydrogen atom, a fluorine atom, a cyano group, or an alkyl group which may be substituted with fluorine. , An aryl group optionally substituted with an electron-donating group or an electron-withdrawing group, a heterocyclic group of an electron-donating group optionally substituted, an amino group optionally substituted, and optionally substituted. From a group consisting of a heterocyclic group of an electron-withdrawing group, a carbonyl group which may be substituted, a sulfonyl group which may be substituted, a phosphinoxide group which may be substituted, and a boryl group which may be substituted. It is the group of choice, and each has the same meaning as described above. Preferably, it is substituted with a hydrogen atom, a heavy hydrogen atom, a fluorine atom, a cyano group, an alkyl group optionally substituted with fluorine, an aryl group optionally substituted with an electron donating group or an electron attracting group, and substituted. It is also a heterocyclic group of an electron-donating group, an amino group which may be substituted, a heterocyclic group of an electron-withdrawing group which may be substituted, and more preferably a hydrogen atom, a heavy hydrogen atom, or a cyano group. , A heterocyclic group of an electron-donating group which may be substituted, an amino group which may be substituted, and a heterocyclic group of an electron-withdrawing group which may be substituted.

Further, in the general formula (3), R represents a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, a boron atom, or a silicon atom, preferably a carbon atom, an oxygen atom, a nitrogen atom, or a silicon atom, and more preferably. Is an oxygen atom and a nitrogen atom. From the viewpoint of luminescence and synthesis, it is preferable that R is an oxygen atom or a nitrogen atom.

Further, when R is a carbon atom, a nitrogen atom, a boron atom or a silicon atom, R may be substituted. Since the π-conjugated compound having the structure represented by the general formula (3) has an electron-donating group D and / or an electron-withdrawing group A as L and M, the substituent of R is L. It is preferable that the electron-donating groups D as M and the electron-withdrawing groups A do not interfere with each other, or the interaction between the electron-donating group D and the electron-withdrawing group A is not hindered.

Specific examples of the substituent include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a dodecyl group, a tridecyl group, a tetradecyl group and a pentadecyl group. Etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), aryl group (eg, phenyl group, p-chlorophenyl group, mesityl group, trill group, xsilyl group, naphthyl group, anthryl group, azrenyl group, acenaftenyl group , Fluolenyl group, phenanthryl group, indenyl group, pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group (eg, pyridyl group, pyrimidinyl group, frill group, pyrrolyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, etc. Triazolyl group (eg 1,2,4-triazol-1-yl group, 1,2,3-triazole-1-yl group, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (eg, for example. Methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), amino group (eg, amino). Group, ethylamino group, dimethylamino group, diphenylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc., halogen atom (for example) , Fluorine atom, chlorine atom, bromine atom, etc.), Fluorinated hydrocarbon group (for example, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, Examples thereof include a mercapto group, a silyl group (for example, a trimethylsilyl group, a triisopropylsilyl group, a triphenylsilyl group, a phenyldiethylsilyl group, etc.), a phosphono group and the like.

Among these, R is preferably an aryl group or an alkyl group because the electronic perturbations of L and M are small.

Of the above general formulas (1) to (6), a particularly preferable structure is the formula (1). In the π-conjugated compound having the structure of the formula (1), an electron-donating group D and an electron-withdrawing group A, two electron-donating groups D with each other, or two electron-withdrawing groups A with each other are spatially present. It is easy to meet at a position close to and at an angle close to parallel. As a result, a CT-like excited state is likely to be formed between the electron-donating group D and the electron-withdrawing group A, and the _ΔEST can be reduced; the two electron-donating groups D can be attracted to each other or two electrons can be attracted. This is because the sex groups A are likely to resonate spatially with each other and the excited state is easily stabilized. The compound represented by the formula (1) includes a compound that achieves high luminous efficiency and has a minimum absolute value of _ΔEST when used as a light emitting material, a third component, or a host compound. Therefore, it is preferable.

The π-conjugated compound having the structure represented by any of the general formulas (1) to (6) includes an organic electroluminescence device material containing the π-conjugated compound and light emission containing the π-conjugated compound. It can be used as an organic thin film and an organic electroluminescence element containing the π-conjugated compound.

The π-conjugated compound having the structure represented by any of the general formulas (1) to (6) is excited by electric field excitation and can generate excitons. Therefore, the π-conjugated compound having the structure represented by any of the general formulas (1) to (6) 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 alone a π-conjugated compound having a structure represented by any of the general formulas (1) to (6); the general formulas (1) to (1) to Does it contain a π-conjugated compound having a structure represented by any of (6) and a host compound described later; π-conjugated having a structure represented by any of the general formulas (1) to (6). It contains a system compound and at least one of a fluorescent compound and a phosphorescent compound described later; or π-conjugated having a structure represented by any of the above general formulas (1) to (6). It is preferable to contain the system compound, at least one of the fluorescent and phosphorescent compounds described below, and the host compound described below.

The absolute value ( _ΔEST ) of the energy difference between the lowest excited singlet level and the lowest excited triplet level of the π-conjugated compound having the structure represented by any of the general formulas (1) to (6) is , 0.50 eV or less is preferable. The π-conjugated compound of the present invention 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. Here, showing delayed fluorescence means that there are two or more types of components having different decay rates of the emitted fluorescence when the 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.

Since these compounds have bipolarity and can cope with various energy levels, they can be used not only as light emitting materials and host materials, but also 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 is described in, for example, International Publication No. 2010/117355, Organic Letters, 2002, 4, 1783-1785. , Angew. Chem. Int. Ed. 2010, 49, 2014-2017. It can be synthesized by referring to the method described in 1 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: "phosphorescence emission" that emits light when returning from the triplet excited state to the ground state, and "fluorescence emission" that emits light when returning from the singlet excited state to the ground state. 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, triplet-triplet excitators, which are normally generated with a 75% probability and whose exciter energy is normally only heat due to non-radiation deactivation, are 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 light emitting element is placed A phenomenon (also referred to as thermally excited delayed fluorescence or thermally excited delayed fluorescence: "TADF") 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. 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 complexes 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 exciton energy 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 compounds do not have heavy atoms in the molecule, there is an inverse intersystem crossing from the triplet excited state to the singlet excited state, which is not normally possible due to the small _ΔEST . 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 emitting fluorescence 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-withdrawing 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.

The π-conjugated compound of the present invention contains 3 to 5 atoms between electron-donating groups D, electron-withdrawing groups A, or between electron-donating groups D and electron-withdrawing groups A. By arranging two or three ring structures, HOMO and LUMO have been successfully separated. In the specific structure in the present invention, the electron-donating groups D and the electron-withdrawing groups A, or the electron-donating groups D and the electron-withdrawing groups A face each other spatially at an angle close to parallel. Therefore, it is considered that a CT-like excited state can be effectively formed and stabilized. As a result, it is considered that the non-radiative deactivation of the compound of the present application could be suppressed and the luminous efficiency could be improved.

Further, in the π-conjugated compound of the present invention, since the electron-withdrawing group A and the electron-donating group D interact with each other in the through space instead of being linked by the through bond, the length of the absorption spectrum and the emission spectrum is long. It is considered that the wavelength change can be suppressed.

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 structural optimization and electron density distribution calculation by molecular orbital calculation of π-conjugated compound in the present invention, software for molecular orbital calculation using B3LYP as a general function and 6-31G (d) as a basis function is used as a calculation method. It can be calculated by using the software, and the software is not particularly limited, and any of them can be used in the same manner.
In the present invention, Gaussian 09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian, USA 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 functional and 6-31G (d) as the base function is further applied 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 sample is prepared by depositing a compound to be measured on a quartz substrate on a quartz substrate, 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 singlet energy level can be obtained from the lowest excited singlet 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 is according to any one of the general formulas (1) to (7). It is characterized by containing a π-conjugated compound having the represented structure.
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 / 1st light emitting unit / intermediate layer / 2nd light emitting unit / intermediate layer / 3rd 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, and US Pat. No. 6,107,734. Japanese Patent No. 6337492, International Publication No. 2005/009087, Japanese Patent Application Laid-Open No. 2006-229712, Japanese Patent Application Laid-Open No. 2006-24791, Japanese Patent Application Laid-Open No. 2006-49393, Japanese Patent Application Laid-Open No. 2006-49394. , Japanese Patent Application Laid-Open No. 2006-49396, Japanese Patent Application Laid-Open No. 2011-966679, Japanese Patent Application Laid-Open No. 2005-340187, Japanese Patent No. 4711424, Japanese Patent No. 349661, Japanese Patent No. 3884564, Japanese Patent No. 4213169, Japanese Patent Application Laid-Open No. Japanese Patent Application Laid-Open No. 2010-192719, Japanese Patent Application Laid-Open No. 2009-0762929, Japanese Patent Application Laid-Open No. 2008-078441, Japanese Patent Application Laid-Open No. 2007-059848, Japanese Patent Application Laid-Open No. 2003-272860, Japanese Patent Application Laid-Open No. 2003-045676, International Publication No. Examples thereof include the element configurations and constituent materials described in 2005/094130 and the like, but 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 in the range of 2 nm to 1 μm, more preferably in the range of 2 to 200 nm, and further preferably in the range of 3 to 150 nm. It will be adjusted.
The light emitting layer used in the present invention may be composed of 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 contains a light emitting dopant (a light emitting compound, a light emitting dopant, also simply referred to as a dopant), and further contains a host compound (a matrix material, a light emitting host compound, also simply referred to as a host). Is 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 assist dopant in the range of 0.1 to 50% by mass, and particularly in the range of 1 to 30% by mass. It is preferable to contain it within.

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 forming 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 assist 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 radiance 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.

(1.1) 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 in the light emitting layer of an organic EL element. It may be appropriately selected and used from sex dopants.

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 compounds described in International Publication No. 2011/156793, JP-A-2011-213643, JP-A-2010-93181, and Patent No. 5366106. However, the present invention is not limited to these.

(1.2) 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 the excited triplet 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. The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescence dopant used in the present invention achieves the above-mentioned phosphorescence quantum 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. , U.S. Patent Application Publication No. 2009/0108737, U.S. Patent Application Publication No. 2009/00397776, U.S. Patent No. 6921915, U.S. Patent No. 6687266, U.S. Patent Application Publication No. 2007/0190359 Specification, US Patent Application Publication No. 2006/0008670, US Patent Application Publication No. 2009/0165846, US Patent Application Publication No. 2008/0015355, US Patent No. 725226, 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. Japanese 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 / 07680, International Publication No. 2010/032663, International Publication No. 2008/140115, International Publication No. 2007/05/2431, 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 Japanese 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 -302671A, JP-A-2002-363552, and the like.
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 device.
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 cationic radical state, the anionic radical 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 ongstrom level.

Further, especially when the light emitting dopant used in combination exhibits TADF emission, the existence time of the triplet 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 excited complex, 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 device against heat generation during high temperature driving or device 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, USA Patent Application Publication No. 2005/0112407, US Patent Application Publication No. 2009/0017330, US Patent Application Publication No. 2009/0030202, US Patent Application Publication No. 2005/0238919, International Publication No. 2001/039234, International Publication No. 2009/021126, International Publication No. 2008/056746, International Publication No. 2004/093207, International Publication No. 2005/089025, International Publication No. 2007/0637996, International Publication No. 2007 / 063754, International Publication No. 2004/107822, International Publication No. 2005/030900, International Publication No. 2006/114966, International Publication No. 2009/0860228, International Publication No. 2009/003898, International Publication No. 2012/0293947 , JP-A-2008-074939, JP-A-2007-254297, European Patent No. 2034538, International Publication No. 2011/055933, International Publication No. 2012/035853, JP-A-2015-38941, etc. Ah To. 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 compound as 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 group derived from a ring, a carbazole ring, a carbolin ring, a diazacarbazole ring (a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carbazole ring is further substituted with a nitrogen atom, or the like. Also, a carbazole ring and a diaza. The carbazole ring may be collectively referred to as "azacarbazole ring".);
Non-aromatic hydrocarbon ring group (eg cyclopentyl group, cyclohexyl group, etc.);
Non-aromatic heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, 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 groups (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.);
Fluorocarbon group (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 directly taken out 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, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, for example, tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-). Dibromo-8-quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), 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 and 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 a (electron-rich) electron transport layer having a high n property. 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 Pat. No. 6,528,187, 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 Application Publication No. 2009/0101870, US Patent Application Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132805, 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 Patent No. 7964293, 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. 2011/086953, 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, Japanese Patent Application Laid-Open No. 2008-277810, Japanese Patent Application Laid-Open No. 2006-156445, Japanese Patent Application Laid-Open No. 2005-340122, Japanese Patent Application Laid-Open No. 2003-45662, Japanese Patent Application Laid-Open No. 2003-31367, Japanese Patent Application Laid-Open No. 2003-282270 No., International Publication No. 2012/11034, 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 emission brightness, and is an “organic EL element and its structure”. 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, acene derivative such as anthracene and naphthalene, fluorene derivative, fluorenone derivative, and polyvinylcarbazole, a polymer material or oligomer in which an aromatic amine is introduced into the main chain or side chain, polysilane, conductivity. 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-mentioned materials 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 the side chain. High molecular weight materials or oligomers are preferably used.

Specific examples of known and preferable hole transporting materials 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 transporting 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. , Polyaniline (emeraldine), polythiophene and other conductive polymers, tris (2-phenylpyridine) iridium complexes and the like, orthometallated 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 coating method, a casting method, an inkjet method, a printing method, a die coating method, a blade coating method, a roll coating method, a spray coating method, a curtain coating method, 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 mesitylene 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 a substrate, a base material, 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, polyetherketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones, polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyallylates, Arton (trade name: JSR) or Appel. Examples thereof include cycloolefin-based resins (trade name: manufactured by Mitsui Kagaku Co., Ltd.).

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 further, oxygen permeability measured by a method according to JIS K 7126-1987. However, it is preferable that the film has a high barrier property of 1 × 10 ^-3 ml / ^m 2.24 h · atm or less and a water vapor permeability of 1 × 10 ^-5 g / ^m 2.24 h or less.

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 be intaglio-shaped or flat-plate-shaped. 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 measured by a method according to JIS K 7126-1987 of 1 × 10 ^-3 ml / ^m 2.24 h or less, 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 thermosetting 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 preferable to coat 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) (Valium, 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 a 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, JP-A-63-314795), a method of forming a reflective surface on a side surface of an element (for example, JP-A 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), a method of introducing a flat layer having an intermediate refractive index between the substrate and the light emitter, which has a lower refractive index than the substrate. 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 lattice 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 light-collecting 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 the 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.
As the light emitting device, for example, a lighting device (household lighting, interior lighting), a backlight for a clock or a liquid crystal, a signboard advertisement, a signal device, a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processor, 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 illumination.
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 a plurality of pixels based on image information from the outside, and the scanning signal is used to send pixels 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 switching transistor 11 is driven 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 video 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 contain 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 Toagosei 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 having 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 coating method, a casting method, an inkjet method, a printing method, a die coating method, a blade coating method, a roll coating method, a spray coating method, a curtain coating method, 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 light-emitting material used in the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene and mesitylene. , Aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used.

Further, 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-14)
Angew. Chem. Int. Ed. , 2014, 53, 2701. 11H-benzo [a] carbazole synthesized by the method described in 1 above and 1-fluoro-2-nitrobenzene were reacted in N, N-dimethylformamide in the presence of sodium hydride at 120 ° C. to 11- (2). -Nitrophenyl) -11H-benzo [a] carbazole was obtained. Next, 11- (2-nitrophenyl) -11H-benzo [a] carbazole was heated in ethanol at 80 ° C. in the presence of tin chloride, and 2- (11H-benzo [a] carbazolyl-11-yl) aniline was heated. Got Subsequently, 2- (11H-benzo [a] carbazolyl-11-yl) aniline and 1-bromo-2-iodobenzene, palladium acetate, bis [2- (diphenylphosphino) phenyl] ether and t-butoxysodium. In the presence of, the mixture was heated at 100 ° C. in toluene to obtain N- (2- (11H-benzo [a] carbazolyl-11-yl) phenyl) -2-bromoaniline. Subsequently, N- (2- (11H-benzo [a] carbazolyl-11-yl) phenyl) -2-bromoaniline, palladium acetate, 1,1'-bis (diphenylphosphino) ferrocene and potassium carbonate are present. Below, the reaction was carried out in N, N-dimethylformamide at 140 ° C. to obtain 11- (9H-carbazolyl-1-yl) -11H-benzo [a] carbazole. Finally, 11- (9H-carbazolyl-1-yl) -11H-benzo [a] carbazole and 2-chloro-4,6-diphenyl-1,3,5-triazine were added to N, in the presence of sodium hydride. The reaction was carried out in N-dimethylformamide at 60 ° C. to obtain a crude product of the π-conjugated compound T-14. Then, column chromatography, recrystallization, and sublimation purification were performed to obtain a high-purity product of the π-conjugated compound T-14.

(Synthesis of other π-conjugated compounds)
In the same manner as described above, the π-conjugated compounds T-7, T-9, T-13, T-15, T-16, T-18, T-19, T-22, T-25, T-32, T-33, T-46, T-54, T-55, T-57, T-62, T-70, T-82, T-91, T-92, T-93, T-94, T- 95, T-96, T-97, T-98, T-99, T-100, T-101, T-102, T-103, T-104, T-105, T-106, T-107, T-108, T-130, T-131, and T-133 were synthesized.

The _ΔEST of the obtained π-conjugated compound and comparative compounds 1 and 2 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 basis function as the calculation method. As software for calculating the molecular orbital, Gaussian09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian, USA was used.
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)
An ITO (indium tin oxide) as an anode is formed 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 after patterning, a transparent substrate to which the ITO transparent electrode is attached. Was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone washed for 5 minutes, and 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 are 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. bottom.
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 1-42)
Organic EL devices 1-2 to 1-42 were produced in the same manner as the organic EL device 1-1 except that the luminescent compound was changed from Comparative Compound 1 as shown in Table 1.

(Measurement of luminous efficiency)
For each of the produced organic EL elements, the luminous efficiency of each sample during driving was evaluated by performing the following measurements.
Each organic EL element manufactured above is made to emit light under a constant current condition of room temperature (about 25 ° C.) and 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).

(Calculation of relative luminous efficiency)
The relative value of the obtained emission luminance (relative value with respect to the emission luminance of the organic EL element 1-1 in Example 1) was obtained and shown in Table 1.

As is clear from Table 1, the organic EL device using the compound of the present invention showed higher luminous efficiency than the comparative compound as the luminescent compound. In particular, compounds T-7, T-9, T-13, T-14, T-16, T-18, T-22, T-70, T-82, T-91, T-92, T-93, T-96, T-98, T-99, T-100, T-101, T-102, T-103, T-104, T-105, T-106, T-130 and T-131 were used. The organic EL element had an absolute value of _ΔEST of less than 0.1 and a high relative luminous efficiency of 148% or more.

[Example 2]
(Manufacturing of organic EL element 2-1)
A transparent support provided with this ITO transparent electrode after patterning on a substrate (NA45 manufactured by NH Technoglass Co., Ltd.) in which ITO (indium tin oxide) was deposited at 100 nm on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode. The substrate was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone washed 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, and each of the crucibles for vapor deposition in the vacuum vapor deposition apparatus was filled with the constituent materials of each layer in an optimum amount for manufacturing an element. 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. H-234 as the host compound and 2,5,8,11-tetra-t-butylperylene as the luminescent compound were deposited at a vapor deposition rate of 0.1 nm / sec so as to be 97% and 3% by volume, respectively. Co-deposited 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, 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 2-1.

(Manufacturing of organic EL element 2-2)
H-234 was used as the host compound, 2,5,8,11-tetra-t-butylperylene was used as the luminescent compound, and comparative compound 1 was used as the third component, and the volumes were 82%, 3%, and 15%, respectively. 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 be%.

(Manufacturing of organic EL elements 2-3 to 2-13)
Organic EL elements 2-3 to 2-13 were produced in the same manner as the organic EL element 2-2 except that the third component was changed as shown in Table 2.

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

As is clear from Table 2, the organic EL device using the compound of the present invention as the third component showed higher luminous efficiency than the compound of Comparative Example. In particular, organic EL devices using compounds T-9, T-13, T-18, T-22, T-91, T-99, T-105 and T-131 have an absolute value of _ΔEST of 0.1. It was less than that, and the relative luminous efficiency was as high as 149% or more.

[Example 3]
(Manufacturing of organic EL element 3-1)
ITO (indium tin oxide) as an anode is formed 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 after patterning, a transparent substrate to which the ITO transparent electrode is attached. Was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone washed for 5 minutes, and then this transparent substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus.

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. bottom.

Next, a resistance heating boat containing Comparative Compound 1 as a comparative host compound and GD-1 as a luminescent compound was energized and heated, and the holes were deposited at a vapor deposition rate of 0.1 nm / sec and 0.010 nm / sec, respectively. Co-deposited on the transport layer to form a light emitting layer with 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 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 3-24)
Organic EL devices 3-2 to 3-24 were prepared in the same manner as the organic EL device 3-1 except that the host compound was changed from Comparative Compound 1 as shown in Table 3.

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

As is clear from Table 3, the organic EL device using the compound of the present invention as the host compound showed higher luminous efficiency than the comparative example compound. In particular, organic EL devices using compounds T-13, T-16, T-82, T-100, T-103, T-105, T-147, T-156 and T-172 have absolute values of _ΔEST . Was less than 0.1, and the relative luminous efficiency was as high as 145% or more.

[Example 4]
(Manufacturing of organic EL element 4-1)
ITO (indium tin oxide) as an anode is formed 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 after patterning, a transparent substrate to which the ITO transparent electrode is attached. Was ultrasonically washed with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone washed for 5 minutes, and then this transparent substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus.

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 an 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 and TBPe (2,5,8,11-tetra-tert-butylperylene), which are comparative host compounds, was energized and heated, and the deposition rate was 0.1 nm / sec. , 0.010 nm / sec was co-deposited on the hole transport layer 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 (1,3,5-tris (1-phenyl-1H-benzimidazol-2-yl) benzene) is vapor-deposited on it at a vapor deposition rate of 0.1 nm / sec, and a second electron transport having a layer thickness of 30 m is carried out. Formed a layer.

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 4-12)
Organic EL devices 4-2 to 4-12 were prepared in the same manner as the organic EL device 4-1 except that the host compound was changed from Comparative Compound 1 as shown in Table 4.

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

As is clear from Table 4, the organic EL device using the compound of the present invention as the host compound showed higher luminous efficiency than the comparative example compound. In particular, the organic EL device using the compounds T-7, T-9, T-18, T-99, T-101 and T-131 has an absolute value of _ΔEST of less than 0.1 and a relative luminous efficiency. Was as high as 148% or more.

[Example 5]
When the organic EL element was lit at an initial brightness of 300 cd / m ² , the brightness half time was measured.

(Manufacturing of organic EL elements 5-1 to 5-7)
Organic EL devices 5-1 to 5-7 were produced in the same manner as in the organic EL devices 1-4 of Example 1 except that the host compound and the luminescent compound were changed as shown in Table 5.

(Measurement of relative brightness half time)
The organic EL elements 5-1 to 5-7 produced above and the organic EL elements 1-4, 1-5, 1-12, 1-13, 1-16, 1-40 and 1 produced in Example 1 For -42, the relative luminance half time was measured. Specifically, the lighting was performed under the condition that the brightness of each organic EL element was 300 cd / m ² , and the time required for the brightness to be halved to 150 cd / m ² was measured to obtain a half-luminance time. The relative value of the obtained luminance half time (relative value with respect to the luminance half time of the organic EL element 1-16) was obtained and is shown in Table 5.

As is clear from Table 5, the organic EL element of Example 5 in which the host compound is the compound represented by the above-mentioned general formula (I) uses the same luminescent compound, but uses another host compound. Compared with the organic EL element of Example 1, it showed a relative brightness half time longer than 10 times.

[Example 6]
(Preparation of co-deposited film 6-1)
A 50 mm × 50 mm, 0.7 mm thick quartz substrate is ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone washed for 5 minutes, and then this transparent substrate is 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 H-232 and the luminescent compound T-14. 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, H-232 and the luminescent compound T-14 were co-deposited at a vapor deposition rate of 0.1 nm / sec so as to be 94% and 6% by volume, respectively. A co-deposited film 5-1 having a layer thickness of 40 nm was formed.

(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 of 355 nm, and fluorescence attenuation was measured at the maximum emission wavelength.
FIG. 11 shows a graph showing the relationship between time and the number of photons for the co-deposited film 6-1.

As shown in FIG. 11, in the π-shared compound (T-14) of the present invention, two or more components having different fluorescence attenuation rates were confirmed, and it was confirmed that delayed fluorescence was emitted.

This application claims priority under Japanese Patent Application No. 2015-256970 filed on December 28, 2015. All the contents described in the application specification and drawings are incorporated herein by reference.

According to the present invention, it is possible to provide a novel 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, a light emitting material, a charge transport material, a light emitting thin film, an organic electroluminescence element, a display device and a lighting device using the π-conjugated compound.

1 Display 3 pixels 5 Scanning 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 equipment 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 (17)

It has a structure represented by the following general formula (1) or (3) , and 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.
Assist dopant material.

(In the general formula (1) or (3) ,
One of L and M is an electron-donating group D, and the other is an electron-withdrawing group A.
The electron-donating group D is a group selected from the group consisting of an aryl group substituted with an electron-donating group, a heterocyclic group of an electron-donating group which may be substituted, and an amino group which may be substituted. And
The electron-attracting group A includes a optionally substituted carbonyl group, a optionally substituted sulfonyl group, an optionally substituted phosphinoxide group, an optionally substituted boryl group, and an electron-attracting group. It is selected from the group consisting of an aryl group optionally substituted with a group, an electron donating heterocyclic group substituted with an electron attracting group, and an electron attracting heterocyclic group optionally substituted. Is the basis and
Q represents a carbon atom or a nitrogen atom which may be substituted independently, respectively.
The substituent of the carbon atom is a hydrogen atom, a heavy hydrogen atom, a fluorine atom, a cyano group, an alkyl group which may be substituted with fluorine, an electron-donating group or an aryl group which may be substituted with an electron-attracting group. , A heterocyclic group of an electron-donating group which may be substituted, an amino group which may be substituted, a heterocyclic group of an electron-withdrawing group which may be substituted, a carbonyl group which may be substituted, It is a group selected from the group consisting of a sulfonyl group which may be substituted, a phosphinoxide group which may be substituted, and a boryl group which may be substituted.
In general formula (3),
R represents a carbon atom that may be substituted, an oxygen atom, a nitrogen atom that may be substituted, a sulfur atom, a boron atom that may be substituted, or a silicon atom that may be substituted.
The substituent of R is an alkyl group, a cycloalkyl group, an aryl group, an aromatic heterocyclic group, an alkoxy group, a cycloalkoxy group, an amino group, a halogen atom, a fluorinated hydrocarbon group, a cyano group, a nitro group, or a hydroxy group. , A group selected from the group consisting of a mercapto group, a silyl group and a phosphono group. ) The electron donating group D is an aryl group substituted with an electron donating group or a heterocyclic group of an electron donating group optionally substituted.
The assist dopant material according to claim 1 . The electron-withdrawing group A is an aryl group that may be substituted with an electron-withdrawing group, an electron-donating heterocyclic group substituted with an electron-withdrawing group, or an electron that may be substituted. An attractive heterocyclic group,
The assist dopant material according to claim 1 or 2 . The _ΔEST of the assist dopant material is 0.10 eV or less.
The assist dopant material according to any one of claims 1 to 3 . The assist dopant material according to any one of claims 1 to 4 is included.
Luminous thin film. The assist dopant material emits delayed fluorescence.
The luminescent thin film according to claim 5 . 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 the assist dopant material according to any one of claims 1 to 4 .
Organic electroluminescence element. The assist dopant material produces excitons.
The organic electroluminescence device according to claim 7 . The assist dopant material radiates fluorescence.
The organic electroluminescence device according to claim 7 or 8 . The assist dopant material emits delayed fluorescence.
The organic electroluminescence device according to claim 9 . The light emitting layer contains the assist dopant material and a host compound.
The organic electroluminescence device according to any one of claims 7 to 10 . The light emitting layer contains the assist dopant material and at least one of a fluorescent compound and a phosphorescent compound.
The organic electroluminescence device according to any one of claims 7 to 10 . The light emitting layer contains the assist dopant material, at least one of a fluorescent compound and a phosphorescent compound, and a host compound.
The organic electroluminescence device according to any one of claims 7 to 10 . The host compound has a structure represented by the following general formula (I).
The organic electroluminescence device according to claim 11 or 13 .

(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 14 .

(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 organic electroluminescence device according to any one of claims 7 to 15 is included.
Display device. The organic electroluminescence device according to any one of claims 7 to 15 is included.
Lighting equipment.

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