JP6716138B2 - Terpyridine derivative, light emitting material comprising the same, and organic EL device using the same - Google Patents

Description

The present invention relates to a novel terpyridine derivative having high luminous efficiency, a light emitting material using the same, and an organic EL device.

In an organic EL ( electroluminescence ) element, by applying a voltage between a pair of electrodes, holes are injected from the anode, electrons are injected from the cathode, and electrons are injected into a light emitting layer containing an organic compound as a light emitting material. When the holes recombine with each other, excitons are formed in the light-emitting organic compound, and light emission can be obtained from the excited organic compound.

One of the means for improving the practicality of such an organic EL element is to increase the luminous efficiency. The excitons organic compound forms, there are singlet excitons (E _S) and triplet exciton (E _T), and the fluorescence emission from singlet excitons (E _S), triplet excitons (E Although there are a phosphorescence from _T), these statistical generation ratio in _{elements, E S: E T = 1} : 3, and limit the internal quantum efficiency of 25% on an organic EL element using the fluorescent emission It was said that. Therefore, in order to improve the conversion efficiency (internal quantum efficiency) of electrons to photons, a light-emitting element using a phosphorescent material capable of converting a triplet excited state into light emission has been actively developed in recent years. .. In a phosphorescent material, interatomic crossing is promoted by the heavy atom effect of heavy atoms such as iridium and platinum, and all excitons can be used for light emission. However, the complex of a noble metal such as iridium or platinum, which is used as a phosphorescent material, as a central metal is high in cost, and in addition, exciton deactivation under high current density and stability of a blue light emitting element are problems. was there.

Recently, studies have been conducted on a material that emits delayed fluorescence as a material capable of converting a part of the triplet excited state into light emission without using such a phosphorescent compound. Specifically, the triplet exciton (E _T1) of singlet excitons (E _S1) to be up-conversion, heat activated delayed fluorescence (thermally activated delayed fluorescence; TADF) organic EL element using a material have been developed ing. When this TADF material is used, the singlet excitons (E _S ) emit fluorescence, while the triplet excitons (E _T ) absorb heat of the device and the surroundings to cause an inverse singlet crossing to an excited singlet. As a result, the excitons generated by current excitation can be extracted as light energy, and at the same time, an internal quantum efficiency of 100% can be realized.

For example, Non-Patent Document 1 reports a carbazolyl dicyanobenzene (CDCB) derivative as a metal-free phosphorescent compound, and the CDCB derivative has an energy between a singlet excited state and a triplet excited state. It has been reported that the difference (ΔE _ST ) is small and promotes highly efficient upconversion from an excited triplet state to an excited singlet exciton while maintaining a high emission quantum yield.

Further, the TADF material can be expected not only to have a high internal quantum yield but also to improve an external quantum yield because of the above-described light emission mechanism. The external quantum efficiency of the conventional fluorescent material was about 7.5%, but the external quantum efficiency of the green TADF material is as high as 30%, which is comparable to that of the phosphorescent material.

Non-Patent Document 2 shows one of the design rules of a blue-emitting organic molecule exhibiting TADF, and an organic molecule based on the design rule has a HOMO (Highest Occupied Molecular Orbital) in which electrons are delocalized in a wide range. Orbit) and LUMO (Lowest Unoccupied Molecular Orbital; lowest unoccupied orbital), and it is reported that even when the overlap of two wavefunctions is small, high oscillator strength is induced and the emission quantum yield is increased. .. The organic molecule exhibits high emission quantum yield and efficient upconversion from triplet excitons to singlet excitons, and achieves a state in which both emission efficiency and internal quantum efficiency are close to 100%. There is disclosure.

It is considered that the organic EL device using the delayed fluorescent light emitting material in the light emitting layer exhibits high external quantum efficiency. In order to obtain the delayed fluorescence with high efficiency, it is necessary that not only the triplet level to the excited singlet level undergo intersystem reciprocal crossing, but also the excited singlet can efficiently emit light. In order to obtain such a light emitting material, for example, in order to reduce the energy difference (ΔE _ST ) between the singlet excited state and the triplet excited state, an electron donating group having a donor property in an organic compound, Precise molecular design is needed, such as selecting and combining an electron-withdrawing group having an acceptor property appropriately.

Patent Document 1 reports that a triazine compound having a carbazole structure or a terpyridine compound having a carbazole structure can be a TADF material as a light emitting material used for an organic EL device.

Furthermore, Non-Patent Document 3 describes a blue organic EL element using a 9,10-dihydroacridine/diphenylsulfone derivative as a TADF material, and has performance comparable to that of existing phosphorescent organic EL elements. It has been reported that the device containing the material exhibits an external quantum efficiency of 19.5% and suppresses a decrease in luminous efficiency at high brightness.

All of the above documents design molecules of TADF materials. However, at present, for example, in a blue TADF material that requires higher emission energy, the required emission efficiency has not been sufficiently achieved and remains at a low value. Therefore, further studies on TADF materials are desired.

Japanese Patent No. 56794996

H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi, Nature 2012, 492, 234. S. Hirata, Y. Sakai, K. Masui, H. Tanaka, SY Lee, H. Nomura, N. Nakamura, M. Yasumatsu, H. Nakanotani, Q. Zhang, K. Shizu, H. Miyazaki, C. Adachi , Nature Materials 2015, 14, 330. Q. Zhang, B. Li, S. P. Huang, H. Nomura, H. Tanaka, C. Adachi, Nature Photonics 2014, 8, 326.

In the present invention, the energy difference between the HOMO-LUMO (ΔE _HL), and focuses on energy difference between the singlet excited state and a triplet excited state (Delta] E _ST), triplet excitons of (E _T) as object to provide a light-emitting material and organic EL device using the singlet exciton (E _S) efficiently novel terpyridine derivatives as a heat activated delayed fluorescence (TADF) material capable of up-conversion, and this There is.

The present inventors have found that a specific terpyridine derivative in which a specific electron-donating site is introduced into a terpyridine skeleton that is a light-emitting site is effective as a thermally activated delayed fluorescence (TADF) material, and completed the present invention. It was
That is, the present invention comprises the following matters.

一般式（１）中、２つの置換基Ａがピリジン環を介して、下記のターピリジン基を形成し、

置換基Ｂは下記のとおりであり、

Ｘは−ＣＲ ^a Ｒ ^b −、−Ｏ−、−Ｓ−、又は−Ｓ（＝Ｏ） ₂ −を表し、Ｒ ^a 及びＲ ^b は、同一であって、メチル基、フェニル基、トリル基もしくはピリジル基であり、Ｒ ^a 及びＲ ^b は互いに連結して環を形成してもよく、Ｒ ¹ 及びＲ ² はそれぞれ独立に、カルバゾリル基又はジフェニルアミノ基である。 The terpyridine derivative of the present invention is characterized by being represented by the following general formula (1).

In the general formula (1), two substituents A form a terpyridine group below via a pyridine ring,

Substituent B is as follows:

X is ^{-CR a R b -, - O} -, - S-, or -S (= O) ₂ - represents, R ^a and R ^b are identical and methyl group, a phenyl group, a tolyl group or It is a pyridyl group, R ^a and R ^b may be linked to each other to form a ring, and R ¹ and R ² are each independently a carbazolyl group or a diphenylamino group.

Terpyridine derivative represented by the general formula (1) is preferably Rukoto represented by the following structural formulas.

The light emitting material of the present invention comprises the above terpyridine derivative.
The organic EL device of the present invention uses the above terpyridine derivative.

According to the terpyridine derivative of the present invention, by introducing a specific electron-donating site into the terpyridine skeleton, which is a light-emitting site, the energy difference (ΔE _ST ) between singlet and triplet shows a value close to 0.2 eV. Therefore, efficient up-conversion from triplet excitons to singlet excitons via inverse intersystem crossing is realized. Specifically, in the terpyridine derivative represented by the general formula (1), an electron donating moiety such as a carbazole moiety, an acridine moiety, a dialkylacridine derivative moiety, or an indole moiety is provided as the substituent B in the terpyridine skeleton which is a light emitting moiety. By introducing it, upconversion emission can be observed. That is, the terpyridine derivatives, from the result of quantum chemical calculation, excited singlet energy (E _S) - the energy difference between the triplet energy (E _T) (ΔE _ST) indicates a value close to 0.2 eV, a high emission Has quantum efficiency. Therefore, the terpyridine derivative is suitable as a thermally activated delayed fluorescence (TADF) material.

Further, in the terpyridine derivative, the terpyridine skeleton, and the carbazole moiety, dimethylacridine moiety, dialkylacridine derivative moiety, or indole moiety that is the substituent D each have a high triplet energy (E _T ). Therefore, as a result of quantum chemical calculation, the terpyridine derivative has a large energy difference (ΔE _HL ) between HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) of 3.3 eV or more, and is expected to emit blue light. It

The terpyridine derivative can be synthesized in a good yield by a relatively simple method. Further, since no precious metal such as Ir or Pt is contained, cost reduction of the light emitting material can be realized.

The thermally activated delayed fluorescence organic EL device of the present invention achieves a maximum external quantum efficiency of 30% or more at the theoretical upper limit by using the terpyridine derivative. Such external quantum efficiency is 4 times or more as compared with the conventional fluorescent material.

FIG. 1 is a diagram showing a ¹ H-NMR spectrum of Ac-2TP. FIG. 2 is a diagram showing a ¹ H-NMR spectrum of AcCz-2TP. FIG. 3 is a diagram showing a ¹ H-NMR spectrum of AcDPA-2TP. FIG. 4A shows the 5% decomposition temperature of Ac-2TP by TGA, and FIG. 4B shows the DSC thermogram of Ac-2TP. FIG. 5A shows the 5% decomposition temperature of AcCz-2TP by TGA, and FIG. 5B shows the DSC thermogram of AcCz-2TP. FIG. 6A shows a UV-vis absorption spectrum and a PL spectrum of the Ac-2TP single film, and FIG. 6B shows a PYS measurement result of the Ac-2TP single film. FIG. 7A shows a UV-vis absorption spectrum and a PL spectrum of a 10 wt% DPEPO-doped co-deposited film of Ac-2TP, and FIG. 7B shows 300K and 5K of a 10 wt% DPEPO-doped co-deposited film of Ac-2TP. 7(c) is a graph showing a PL spectrum at 5K of a 10 wt% DPEPO-doped co-evaporated film of Ac-2TP. FIG. 8 is a diagram showing a UV-vis absorption spectrum and a PL spectrum of a 10 ⁻⁵ M toluene solution of Ac-2TP. FIG. 9A shows the UV-vis absorption spectrum and PL spectrum of the AcCz-2TP single film, and FIG. 9B shows the PYS measurement result of the AcCz-2TP single film. FIG. 10A shows a UV-vis absorption spectrum and a PL spectrum of a 10 wt% DPEPO-doped co-evaporated film of AcCz-2TP, and FIG. 10B shows 300 K and 5 K of a 10 wt% DPEPO-doped co-evaporated film of AcCz-2TP. 10(c) is a diagram showing a PL spectrum at 5K of a 10 wt% DPEPO-doped co-evaporated film of AcCz-2TP. FIG. 11 is a diagram showing a UV-vis absorption spectrum and a PL spectrum of a 10 ⁻⁵ M toluene solution of AcCz-2TP. FIG. 12A shows the UV-vis absorption spectrum and PL spectrum of the AcDPA-2TP single film, and FIG. 12B shows the PYS measurement result of the AcDPA-2TP single film. FIG. 13A shows the UV-vis absorption spectrum and PL spectrum of the 10 wt% DPEPO-doped co-deposited film of AcDPA-2TP, and FIG. 13B shows the UV of the 10 wt% CBP-doped co-deposited film of AcDPA-2TP. It is a figure showing a -vis absorption spectrum and a PL spectrum. FIG. 14 is a diagram showing transient PL spectra of a 10 wt% DPEPO-doped co-deposited film of AcDPA-2TP at 300K and 5K. FIG. 15 is a diagram showing a PL spectrum of a 10 wt% DPEPO-doped co-evaporated film of AcDPA-2TP at 5K. FIG. 16 is a diagram showing transient PL spectra of a 10 wt% CBP-doped co-evaporated film of AcDPA-2TP at 300K and 5K. FIG. 17 is a diagram showing a PL spectrum of a 10 wt% CBP-doped co-evaporated film of AcDPA-2TP at 5K. FIG. 18 shows holes when the light-emitting layer is a 10 wt% DPEPO-doped co-deposited film of Ac-2TP (Device 1) or a 10 wt% DPEPO-doped co-deposited film of AcCz-2TP (Device 4) in Devices 1 and 4. An energy diagram of a transport layer, a light emitting layer, and an electron transport layer, and in devices 2 and 5, a layer in which the light emitting layer is a host material and a 10 wt% DPEPO-doped co-evaporated film of Ac-2TP (device 2), or a host material and AcCz. -2TP, an energy diagram of a hole transport layer, a light emitting layer, and an electron transport layer when a layer (device 5) is formed of a 10 wt% DPEPO-doped co-deposited film, and one of the light emitting layers in devices 3 and 6 is a host material. And a layer of Ac-2TP (device 3) or a layer of a host material and AcCz-2TP (device 6), and the other light-emitting layer is a 10 wt% DPEPO-doped co-deposited film of Ac-2TP (device 3) or AcCz. 2 is an energy diagram of a hole transport layer, a light emitting layer, a light emitting layer, and an electron transport layer when a −2TP 10 wt% DPEPO-doped co-deposited film (Device 6) is used. FIG. 19 shows that in devices 3, 6 and 7, when the light emitting layer was a 10 wt% mCP-doped co-evaporated film of Ac-2TP and a 10 wt% DPEPO-doped co-evaporated film of Ac-2TP (device 3), AcCz-2TP was used. 10 wt% mCP-doped co-deposited film and AcCz-2TP 10 wt% DPEPO-doped co-deposited film (Device 6), or AcDPA-2TP 10 wt% mCP-doped co-deposited film and AcDPA-2TP 10 wt% An energy diagram of the hole transport layer, the light emitting layer, the light emitting layer, and the electron transport layer of the DPEPO-doped co-deposited film (device 7), and in the devices 8 to 12, the light emitting layer was a 5 wt% TCTA-doped layer of AcDPA-2TP. When a vapor-deposited film and a 5 wt% CBP-doped co-evaporated film of AcDPA-2TP (device 8), a 10 wt% TCTA-doped co-evaporated film of AcDPA-2TP, and a 10 wt% CBP-doped co-evaporated film of AcDPA-2TP are formed. (Device 9), a 15 wt% TCTA-doped co-deposited film of AcDPA-2TP, and a 15 wt% CBP-doped co-deposited film of AcDPA-2TP (Device 10), a 20 wt% TCTA-doped co-deposited film of AcDPA-2TP, and When a 20 wt% CBP-doped co-deposited film of AcDPA-2TP (device 11), or a 30 wt% TCTA-doped co-deposited film of AcDPA-2TP and a 30 wt% CBP-doped co-deposited film of AcDPA-2TP (device) 12 is an energy diagram of a hole transport layer, a light emitting layer, a light emitting layer and an electron transport layer of 12). 20A illustrates an EL spectrum when a current of 1 mA is applied to the devices 1 to 3, and FIG. 20B illustrates an EL spectrum when a current of 5 mA is applied to the devices 1 to 3. 20C shows the power efficiency-luminance characteristic relationship of the devices 1 to 3, FIG. 20D shows the current density-voltage characteristic and luminance-voltage characteristic relationship of the devices 1 to 3, and FIG. FIG. 6E is a diagram illustrating a relationship between external quantum efficiency and luminance characteristics of the devices 1 to 3. FIG. 21A shows an EL spectrum when a current of 1 mA is applied to the devices 4 to 6, FIG. 21B shows a power efficiency-luminance characteristic relationship of the devices 4 to 6, and FIG. 21D shows the relationship between the current density-voltage characteristic and the luminance-voltage characteristic of the devices 4 to 6, and FIG. 21D is the diagram showing the relationship between the external quantum efficiency and the luminance characteristic of the devices 4 to 6. 22A shows an EL spectrum when a current of 1.0 mA was applied to the devices 3, 6 and 7, and FIG. 22B shows a current density-voltage characteristic and brightness-of the devices 3, 6 and 7. 22C shows the relationship of the voltage characteristics, FIG. 22C shows the relationship of the power efficiency-luminance characteristics of the devices 3, 6 and 7, and FIG. 22D shows the current efficiency-luminance characteristics of the devices 3, 6 and 7. 22E is a diagram showing the relationship of the external quantum efficiency-luminance characteristics of the devices 3, 6 and 7. 23A shows an EL spectrum when a current of 1 mA is applied to the devices 8 to 12, and FIG. 23B shows a relationship between current density-voltage characteristics and luminance-voltage characteristics of the devices 8-12. 23(c) shows the power efficiency-luminance characteristic relationship of the devices 8-12, and FIG. 23(d) shows the current efficiency-luminance characteristic relationship of the devices 8-12, and FIG. FIG. 4 is a diagram showing a relationship between external quantum efficiency and luminance characteristics of the devices 8 to 12. FIG. 24 is a diagram showing a typical configuration of an organic EL element.

Hereinafter, the present invention will be described in detail.
[Terpyridine derivative]
The terpyridine derivative of the present invention is represented by the following general formula (1).

In the general formula (1), R ^{1 to} R ⁶ each independently represent a hydrogen atom, an alkyl group or an aryl group.
In R ^{1 to} R ⁶ , specifically, the alkyl group includes a methyl group, an ethyl group, a 1-propyl group, a 2-propyl group and a t-butyl group, and the aryl group includes a phenyl group and a biphenyl group. Group, terphenyl group, pyridyl group, terpyridyl group, diphenylamino group, alkylamino group, carbazolyl group, naphthyl group and anthracenyl group.

In the general formula (1), X represents ^a dialkylmethylene (—CR ^a R ^b —) group, an ether bond (—O—), a thioether bond (—S—) or a sulfonyl group (—SO ₂ —). Specific examples of —CR ^a R ^b — in X include a dimethylmethylene group, a diphenylmethylene group, a ditolylmethylene group, and a dipyridylmethylene group. R ^a and R ^b may be linked to each other to form a 5- to 7-membered ring such as cyclopentene, cyclohexane and cycloheptane, and these rings are within a range not impairing the effects of the present invention. Thus, for example, it may have a substituent such as an alkoxy group, a thioalkoxy group, a carbonyl group and an ester group.

In the general formula (1), the two substituents A preferably form a terpyridyl group represented by the following formula via a pyridine ring. Of these, a 2,2′:6′,2″-terpyridyl group having a nitrogen atom inside the ring structure is particularly preferable from the viewpoint of widening the emission color (bluing).

Substituent B is preferably an electron donating site. By having the substituent B in the general formula (1), in the terpyridine derivative represented by the general formula (1), electrons can be appropriately supplied to the terpyridine skeleton that is a light emitting site, and singlet and triplet The energy difference (ΔE _ST ) from the term can be reduced. Substituent B is preferably ^a dimethylacridine derivative (R ^a and R ^b are methyl groups) or a carbazole skeleton-containing substituent from the viewpoint of having a high triplet energy.

The terpyridine derivative represented by the above general formula (1) is more specifically represented by the following structural formula.

The terpyridine derivative represented by the general formula (1) can be produced by various known methods. For example, Ac-2TP can be produced using a known cross coupling reaction.

That is, 4′-(4-bromophenyl)-2,2′:6′,2″-terpyridine and 9,10-dihydro-9,9-dimethylacridine were placed in a four-necked flask, and Pd( II) The compound can be synthesized in a yield of 81.8% by heating under reflux with a base such as sodium t-butoxide in the presence of a catalyst and phosphine.

However, the terpyridine derivative represented by the general formula (1) is not limited to the above method, and can be produced by combining various known methods.

Terpyridine derivative represented by the general formula (1) of the present invention obtained as described above, the energy difference between the excited singlet energy (E _S) and triplet excitation energy (E _T) (Delta] E _ST) Is 0.38 eV or less and has high emission quantum efficiency. The energy difference (ΔE _ST ) between the excitation singlet energy (E _S ) and the triplet excitation energy (E _T ) is, for example, a PL spectrum measured at low temperature (5 K) and room temperature (300 K), The excitation singlet energy (E _S1 ) and triplet excitation energy (E _T1 ) are estimated from the rise of the phosphorescence spectrum observed at low temperature (5K) and the rise of the fluorescence emission spectrum observed at room temperature (300K), respectively. , Triplet excitation energy ( _ET1 ) minus excitation singlet energy ( _ES1 ). Further, in the terpyridine derivative, an electron-donating site having a carbazole moiety, an acridine moiety, a dimethylacridine derivative moiety, or an indole moiety is introduced into the terpyridine skeleton that is a light-emitting site, whereby triplet excitons are converted to singlet excitons. The up-conversion emission can be observed due to the reciprocal intersystem crossing. Therefore, the above terpyridine derivative can be expected as a thermally activated delayed fluorescence (TADF) material.

Further, in the terpyridine derivative, the terpyridine skeleton, and the carbazole moiety, dimethylacridine moiety, dimethylacridine derivative moiety, or indole moiety, which are the substituents B, each have a high triplet energy (E _T1 ), and HOMO and LUMO. The energy difference (ΔE _HL ) with and tends to increase. Therefore, the terpyridine derivative can be expected to emit blue light, which is the emission color in the short wavelength region.

[Light emitting materials/organic EL devices]
The light emitting material of the present invention comprises the above terpyridine derivative.
The organic EL device of the present invention uses the above terpyridine derivative.
Here, FIG. 14 shows a typical layer structure of the organic EL element.
In the organic EL device, typically, as the anode 2, a film of, for example, ITO is formed on the substrate 1, and a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection are formed thereon. The layer and the cathode are laminated in this order.

As the substrate 1, a transparent and smooth substrate having a total light transmittance of at least 70% or more is used. Specifically, it is a flexible transparent substrate such as a glass substrate having a thickness of several μm or a special transparent substrate. Plastic or the like is used.

Thin films such as the anode 2, the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the electron transport layer 6, the electron injection layer 7, and the cathode 8 formed on the substrate are laminated by a vacuum deposition method or a coating method. To be done. When the vacuum deposition method is used, the deposition is usually heated in an atmosphere reduced to 10 ⁻³ Pa or less. The thickness of each layer varies depending on the type of layer and the material used, but is usually about 100 nm for the anode 2 and the cathode 8 and less than 50 nm for the other layers including the light emitting layer 5. The electron injection layer 7 and the like may be formed with a thickness of 1 nm or less, for example.

As the anode 2, one having a large work function and a total light transmittance of usually 80% or more is used. Specifically, in order to transmit the light emitted from the anode 2, the hole injection layer 3 has a transparent conductive ceramic such as ITO or ZnO, poly(ethylenedioxythiophene):polystyrenesulfonic acid (PEDOT/PSS). A transparent conductive polymer such as or polyaniline, or another transparent conductive material is used. The film thickness of the anode 2 is usually 10 to 200 nm.

In the light emitting layer 5, it is preferable to use a host compound together with the terpyridine derivative, which is the light emitting material of the present invention, like the other light emitting layers used in the organic EL device. The host compound is not particularly limited as long as it does not impair the emission characteristics based on fluorescence and TADF. For example, DPEPO, PO9,4,4′-bis(N-carbazolyl)-1,1′-biphenyl( CBP), 2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT), adamantane anthracene (Ad-Ant), rubrene, and 2,2′-bi(9,10-diphenylanthracene) (TPBA). To be The content of the light emitting material of the present invention (that is, the terpyridine derivative) and the host compound in the components constituting the light emitting layer 5 is usually 1 to 50 wt%, preferably 5 to 10 wt%.

A hole transport layer 4 is provided between the anode 2 and the light emitting layer 5 in order to efficiently transport holes from the anode 2 to the light emitting layer. Examples of the hole transport material forming the hole transport layer 4 include TAPC, N,N′-diphenyl-N,N′-di(m-tolyl)benzidine (TPD), N,N′-di(1 -Naphthyl)-N,N'-diphenylbenzidine (α-NPD), (4,4',4" tri-9-carbazolyltriphenylamine (TCTA)) and (4,4',4" tris. [Phenyl(m-tolyl)amino]triphenylamine)) and the like.
Further, a hole injection layer 3 as a buffer is provided between the anode 2 and the hole transport layer 4. Examples of the hole injection material forming the hole injection layer 3 include KLHIP:PPBi, 1,4,5,8,9,12-hexaazatriphenylenehexacarbonitrile in addition to the above PEDOT/PSS and polyaniline. (HATCN) and copper phthalocyanine (CuPc).

An electron transport layer 6 is provided between the cathode 8 and the light emitting layer 5 in order to efficiently transport electrons from the cathode to the light emitting layer. Examples of the electron transport material forming the electron transport layer 6 include B3PymPm, 2-(4-biphenylyl)-5-(pt-butylphenyl)-1,3,4-oxadiazole (tBu-PBD). , 1,3-Bis[5-(4-t-butylphenyl)-2-[1,3,4]oxadiazolyl]benzene (OXD-7), 3-(biphenyl-4-yl)-5-(4 -T-Butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ), bathocuproine (BCP), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl) Examples thereof include benzene (TPBi).
Since a metal such as Al is often used for the cathode, the electron injection layer 7 is provided between the electron transport layer 6 and the light emitting layer 5. Examples of the electron injection material forming the electron injection layer 7 include lithium fluoride (LiF), 8-hydroxyquinolinolato-lithium (Liq) and lithium 2-(2′,2″-bipyridine-6′-. Ilyl)phenolate (Libpp) and the like.

By selecting a material having an electron-transporting property as the electron-injecting material, electrons can be moved more quickly, or a material having a good electron-injecting property can be selected to play a role of further increasing the electron-injecting efficiency.

In addition to the above layers, layers such as a hole blocking layer, an electron blocking layer, and an exciton blocking layer are further formed as needed.

Hereinafter, the present invention will be described more specifically based on Examples, but the present invention is not limited to the following Examples.

[Identification of compound]
The equipment and measurement conditions used for identifying the compound are as follows.
(1) ¹ H Nuclear Magnetic Resonance (NMR) Apparatus JNM-EX270FT-NMR type (400 MHz) JNM-K9 [desktop GCQMS] manufactured by JEOL Ltd. and Waters Co., Ltd. Zspray (SQ detector 2))
(3) Elemental analyzer Perkin Elmer 2400II CHNS/O analyzer Measurement mode: CHN mode

[Optical property evaluation]
The equipment and measurement conditions used for optical property evaluation are as follows.
(1) Ultraviolet/visible (UV-vis) spectrophotometer UV-3150 manufactured by Shimadzu Corporation
Measurement conditions; scan speed medium speed, measurement range 200 to 800 nm, sampling pitch 0.5 nm, slit width 0.5 nm
(2) Photoluminescence (PL) measuring device Fluoro MAX-2 manufactured by Horiba, Ltd.
The PL spectrum and the time-resolved PL spectrum (transient PL spectrum) using a streak camera (C4334 manufactured by Hamamatsu Photonics KK) were measured at room temperature and low temperature.
(3) Photoelectron Yield Spectroscopy (PYS) Device Sumitomo Heavy Industries, Ltd. Ionization Potential Measuring Device Ionization potential (Ip) was measured in vacuum using an ionization potential measuring device.
(4) Luminescent quantum yield (PLQY) measuring device Absolute PL quantum yield measuring device manufactured by Hamamatsu Photonics KK

[Device performance evaluation]
The equipment used for the evaluation of the organic EL element is as follows.
EL (electroluminescence) measuring device PHOTONIC MULTI-CHANNEL ANALYZER PMA-1 manufactured by Hamamatsu Photonics KK

[ Reference Example 1]
[Synthesis of Ac-2TP]

0.627 g (3.00 mmol) of 9,10-dihydro-9,9-dimethylacridine (DMAC) in a 50 ml four-necked flask, 4'-(4-bromophenyl)-2,2':6,2'' -Terpyridine (Br2TP) 1.16 g (3.00 mmol) and sodium t-butoxide (t-BuONa) 0.865 g (9.00 mmol) were added, and nitrogen flow was performed for 15 minutes. After the nitrogen flow, 30 ml of xylene was added and nitrogen bubbling was performed for 1 hour. After bubbling with nitrogen, palladium (II) acetate (Pd(OAc) ₂ ) 0.0337 g (0.150 mmol) and tri(t-butylphosphine) (P(t-Bu) ₃ ) 0.106 ml (0.450 mmol) were added. In addition, the mixture was refluxed at 130° C. for 21 hours. The disappearance of the raw materials was confirmed by thin layer chromatography (TLC), and the reaction was completed (red-black solution). It was cooled to room temperature, suction filtered, and extracted with a separating funnel. After extraction, purification was performed by silica gel column chromatography (silica gel; 500 cc, developing solvent; chloroform:methanol=10:1). The fraction considered to be the target was collected to obtain a reddish black viscous body, which was dried at 60° C. under reduced pressure to obtain 1.48 g of a red solid. Since a small amount of dust was mixed, dispersion washing was performed with hexane, and after drying under reduced pressure at 60° C., 1.26 g (yield 81.8%) of a red solid was obtained.

The target product was identified by ¹ H-NMR (FIG. 1) and MS.
¹ H-NMR (400 MHz, DMSO-d ₆ ): 8.85 (s, 2H), 8.79 (d, 2H, J=3.6 Hz), 8.72 (d, 2H, J=8.4 Hz). ), 8.26 (d, 2H, J=8.4 Hz), 8.09-8.05 (m, 2H), 7.60-7.51 (m, 6H), 7.08-6.92. (M, 4H), 6.27 (d, 2H, 7.2Hz), 1.65 (s, 6H)
EIMS: m/z=517 [M ⁺ ]

Further, 600 mg of a red solid of Ac-2TP was subjected to sublimation purification under the conditions of nitrogen gas 100 cc/min, high temperature part 300° C. and low temperature part 150° C. using a sublimation analyzer, and 278 mg of a transparent yellow crystal (yield 46 .3%) was obtained.

Elemental analysis of the purified Ac-2TP was performed.
Anal. Calcd for C ₃₆ H ₂₈ N ₄ ; C, 83.69%; H, 5.46%; N, 10.84%. Found: C, 83.70%; H, 5.35%; N, 10.84%
The error between the theoretical value and the measured value was within 0.3% for all the elements, and it was confirmed that the target product could be sufficiently purified.

[Thermal property evaluation]
The thermal characteristics of Ac-2TP after sublimation purification were evaluated by TGA and DSC.
As shown in FIG. 3, the 5% decomposition temperature of Ac-2TP was 401° C., and an endothermic peak was observed at 238° C.

また、Ａｃ−２ＴＰの１．０×１０^-5Ｍトルエン溶液を調製し、ＵＶ−ｖｉｓ吸収スペクトル及びＰＬスペクトル測定を行った。測定結果を図８に示す。 [Optical property evaluation]
An Ac-2TP single film was prepared by a resistance heating vapor deposition method using a vacuum vapor deposition machine, and UV-vis absorption spectrum (Fig. 6a), PL spectrum (Fig. 6a), PYS (Fig. 6b), and PLQY were measured. went.
In addition, a doped film (Ac-2TP:DPEPO (10 wt%) co-deposited film) was prepared, and a UV-vis absorption spectrum (Fig. 7a), a PL spectrum (Fig. 7a), and a transient attenuation PL spectrum by a streak camera (Fig. 7b). , Low temperature phosphorescence spectrum (@5K) (Fig. 7c), and PLQY were measured.

Further, a 1.0×10 ⁻⁵ M toluene solution of Ac-2TP was prepared, and UV-vis absorption spectrum and PL spectrum measurement was performed. The measurement result is shown in FIG.

In FIGS. 6a, 7a and 8, the optical bandgap (E _g ) was determined to be 3.48 eV from the absorption edge of the UV-vis absorption spectrum and the rise of the PL spectrum, and the ionization potential (I _p ) was 5.55 eV from FIG. 6b. I asked.
From FIG. 7b, it can be seen that the strength is increased and the efficiency is increased by heat when the temperature is 300 K rather than when the temperature is 5 K. This suggests that TADF occurs in the device.
In FIG. 7c, the excited singlet energy (E _s1 ) is 3.09 eV and the excited triplet energy (E _T1 ) is 2.71 eV from the rising of each graph, and the singlet excited state and the triplet excited state are It can be seen that the energy difference (ΔE _ST ) between them is as small as 0.38 eV.

[Example 2]
[Synthesis of AcCz-2TP]
(1) Synthesis of AcCl

4.18 g (20 mmol) of 9,10-dihydro-9,9-dimethylacridine was added to a 200 ml four-necked flask equipped with a thermometer and a dropping funnel, and nitrogen flow was performed for 15 minutes. After the nitrogen flow, 170 ml of dichloromethane was added. The system was covered with aluminum foil and cooled in a water bath (ice, water, salt) to 0°C. While cooling, 5.34 g (40 mmol) of N-chlorosuccinimide (NCS) was dissolved in 230 ml of dichloromethane, and the NCS solution was added dropwise over 90 minutes. After the completion of dropping, the mixture was stirred at 0° C. for 3 hours. The disappearance of the raw materials was confirmed by TLC, and the reaction was completed. After completion of the reaction, the mixture was washed by liquid separation operation, concentrated by an evaporator to obtain a black-green viscous substance, and purified by silica gel column chromatography (silica gel; 450 cc, developing solvent; ethyl acetate:hexane=1:20). Since the target product and dust came out together, the product was re-purified by silica gel column chromatography (silica gel; 350 cc, developing solvent; ethyl acetate:hexane=1:20). The fraction considered to be the target was collected to obtain a yellow viscous substance, which was dried under reduced pressure to obtain 1.05 g (yield 19.0%) of yellow tea solid.

The target product was identified by ¹ H-NMR and MS.
¹ H-NMR (400 MHz, DMSO-d ₆ ): 9.13 (s, 1H), 7.32 (d, 2H, J=2.8 Hz), 7.07 (q, 2H, J=8. 6 Hz), 6.75 (d, 2H, J=8.8 Hz), 1.44 (s, 6H)
EIMS: m/z=278 [M ⁺ ]

(2) Synthesis of AcCl-2TP

In a 50 ml four-necked flask equipped with a reflux tube and a thermometer, 4'-(4-bromophenyl)-2,2':6',2"-terpyridine (Br2TP) 1.16 g (3 mmol), AcCl 0.834 g. (3 mmol) and 1.24 g (9 mmol) of potassium carbonate (K ₂ CO ₃ ) were added, and a nitrogen flow was performed for 15 minutes. After nitrogen flow, 50 ml of xylene was added and nitrogen bubbling was carried out for 2 hours. After bubbling nitrogen, 0.0337 g (0.15 mmol) of Pd(OAc) _{2 and} 0.106 ml (0.45 mmol) of P(t-Bu) ₃ were added and the mixture was refluxed at 120° C. for 4 hours. The disappearance of the raw materials was confirmed by TLC, and the reaction was completed. After completion of the reaction, unnecessary substances were removed by suction filtration and washed by a liquid separation operation, the obtained orange solution was concentrated to obtain a red viscous substance, which was purified by silica gel column chromatography (silica gel; 350 cc, developing solvent). Ethyl acetate:hexane=1:5). The fraction considered to be the target was collected to obtain a yellow viscous substance, which was dried under reduced pressure to obtain 1.34 g (yield 76.5%) of a yellow solid.

The target product was identified by ¹ H-NMR and MS.
¹ H-NMR (400 MHz, DMSO-d ₆ ): 8.77 (m, 6H), 8.25 (d, 2H, J=8.4 Hz), 8.06 (t, 2H, J=8 Hz), 7.55 (m, 6H), 7.07 (d, 2H, J = 8.8Hz), 6.26 (d, 2H, J = 8.8Hz), 1.65 (s, 6H)
EIMS: m/z=584 [M ⁺ ]

還流管、温度計を付した５０ｍｌ四つ口フラスコにＡｃＣｌ−２ＴＰ １．３４ｇ（２．３ｍｍｏｌ）、カルバゾール１．１５ｇ（６．９ｍｍｏｌ）、Ｋ₂ＣＯ₃ ０．９５３ｇ（６．９ｍｍｏｌ）を加えて１５分間窒素フローを行った。窒素フロー後、キシレン５０ｍｌを加えて１時間窒素バブリングを行った。窒素バブリング後、Ｐｄ(ＯＡｃ)₂ ０．０２５８ｇ（０．０１１５ｍｍｏｌ）、Ｐ(ｔ−Ｂｕ)₃ ０．０８１０ｍｌ（０．３４５ ｍｍｏｌ）を加えて１３０℃で７時間還流させた。ＴＬＣにより原料の消失を確認し、反応を終了した。反応終了後、吸引濾過により不要物を取り除き、分液操作により洗浄し、得られた透明橙色溶液を濃縮し、橙色粘体を得、シリカゲルカラムクロマトグラフィーにて精製を行った（シリカゲル；３５０ｃｃ、展開溶媒；酢酸エチル：ヘキサン＝１：１０）。目的物と思われるフラクションを回収し、黄色粘体を得、減圧下乾燥後、黄色固体０．７０ｇ（収率３６．１％）を得た。 (3) Synthesis of AcCz-2TP

AcCl-2TP 1.34 g (2.3 mmol), carbazole 1.15 g (6.9 mmol), and K ₂ CO ₃ 0.953 g (6.9 mmol) were added to a 50 ml four-necked flask equipped with a reflux tube and a thermometer. And a nitrogen flow was performed for 15 minutes. After nitrogen flow, 50 ml of xylene was added and nitrogen bubbling was carried out for 1 hour. After bubbling nitrogen, 0.0258 g (0.0115 mmol) of Pd(OAc) _{2 and} 0.0810 ml (0.345 mmol) of P(t-Bu) ₃ were added, and the mixture was refluxed at 130° C. for 7 hours. The disappearance of the raw materials was confirmed by TLC, and the reaction was completed. After completion of the reaction, unnecessary substances were removed by suction filtration and washed by liquid separation operation, and the obtained transparent orange solution was concentrated to obtain an orange viscous substance, which was purified by silica gel column chromatography (silica gel; 350 cc, development) Solvent; ethyl acetate:hexane=1:10). The fraction considered to be the target was collected to obtain a yellow viscous substance, which was dried under reduced pressure to obtain 0.70 g of a yellow solid (yield 36.1%).

The target product was identified by ¹ H-NMR (FIG. 2) and MS.
¹ H-NMR (400 MHz, DMSO-d ₆ ): 8.79 (m, 6H), 8.34 (s, 2H), 8.24 (d, 4H, J=7.6 Hz), 8.06 ( s, 2H), 7.80 (m, 4H), 7.55 (s, 2H), 7.50 (m, 14H), 6.61 (d, 2H, J=8.4Hz), 1.80. (S, 6H)
EIMS: m/z=846 [M ⁺ ]

(4) Purification of AcCz-2TP 519 mg of a yellow solid of AcCz-2TP was subjected to sublimation purification using a high vacuum sublimation purification device under conditions of a high temperature part of 390° C. and a low temperature part of 260° C. Rate 34.3%).

Elemental analysis of the purified AcCz-2TP was performed.
Anal. Calcd for C ₆₀ H ₄₂ N ₆ ; C, 85.08%; H, 5.00%; N, 9.92%. Found: C, 85.15%; H, 4.88%; N, 9.88%
The error between the theoretical value and the measured value was within 0.3% for all the elements, and it was confirmed that the target product could be sufficiently purified.

[Thermal property evaluation]
The thermal characteristics of AcCz-2TP after sublimation purification were evaluated by TGA and DSC.
As shown in FIG. 5, the 5% decomposition temperature of AcCz-2TP was 456° C., and an endothermic peak was observed at 367° C.

[Optical property evaluation]
An AcCz-2TP single film was prepared using a glass chamber, and UV-vis absorption spectrum (FIG. 9a), PL spectrum (FIG. 9a), PYS (FIG. 9b), and PLQY measurement were performed.
In addition, a doped film (AcCz-2TP:DPEPO (10 wt%) co-deposited film) was prepared, and a UV-vis absorption spectrum (FIG. 10a), a PL spectrum (FIG. 10a), a PLQY measurement, and a transient attenuation PL spectrum by a streak camera ( The measurement of FIG. 10b) and low temperature phosphorescence spectrum (@5K) (FIG. 10c) was performed.
Further, a 1.0×10 ⁻⁵ M toluene solution of AcCz-2TP was prepared, and UV-vis absorption spectrum and PL spectrum measurement was performed. The measurement result is shown in FIG.

In FIGS. 9a, 10a, and 11, the optical bandgap (E _g ) was determined to be 3.29 eV from the absorption edge of the UV-vis absorption spectrum and the rise of the PL spectrum, and the ionization potential (I _p ) was 5.62 eV from FIG. 9b. I asked.
From FIG. 10b, it can be seen that the strength is higher and the efficiency is increased by heat when the temperature is 300K than when the temperature is 5K. This suggests that TADF occurs in the device.
In FIG. 10c , the excited singlet energy (E _s ) is 3.00 eV and the excited triplet energy (E _T1 ) is 2.75 eV from the rising of each graph, and the singlet excited state and the triplet excited state are The energy difference (ΔE _ST ) between them was 0.25 eV, which was close to the target value of 0.2 eV.
The thermal and photophysical properties of Ac-2TP and AcCz-2TP were determined based on the measurement results of the optical characteristic evaluation of Reference Example 1 and Example 2. The results are shown in Table 1.

[Example 3]
(1) Synthesis of AcDPA-2TP In a 25 ml four-necked flask equipped with a reflux tube and a thermometer, 0.701 g (1.2 mmol) of AcCl-2TP, 0.406 g (2.4 mmol) of diphenylamine, and 0.04 g of sodium t-butoxide. 346 g (3.6 mmol) was added and nitrogen flow was performed for 15 minutes. After nitrogen flow, 25 ml of xylene was added and nitrogen bubbling was performed for 100 minutes. After bubbling with nitrogen, 0.0135 g (0.06 mmol) of Pd(OAc) _{2 and} 0.0423 ml (0.18 mmol) of P(t-Bu) ₃ were added, and the mixture was refluxed at 127° C. for 21 hours. The disappearance of the raw materials was confirmed by TLC, and the reaction was completed. After completion of the reaction, unnecessary substances were removed by suction filtration and washed by a liquid separation operation, and the obtained transparent orange solution was concentrated to obtain a red viscous substance, which was purified by silica gel column chromatography (silica gel; 350 cc, development) Solvent; ethyl acetate:hexane=1:5). The fraction considered to be the target was collected to obtain a yellow viscous substance, which was dried under reduced pressure to obtain 0.57 g (yield 57%) of a yellow solid.
The target product was identified by ¹ H-NMR (FIG. 3) and MS.

¹ H-NMR (400 MHz, DMSO-d ₆ ): 8.84-8.67 (m, 8H), 8.24 (t, 2H, J=7.8 Hz), 8.06 (t, 2H, J). =7.8 Hz), 7.66-7.47 (m, 5H), 7.22 (q, 9H, J=7.6 Hz), 6.95 (d, 12H, J=7.6 Hz), 6 .77 (d, 2H, J=9.2), 6.23 (t, 2H, J=7.8 Hz), 1.56 (s, 3H), 1.46 (s, 3H)
EIMS: m/z=851 [M ⁺ ]

(2) Purification of AcDPA-2TP Yellow solid of 257 mg of AcDPA-2TP was purified by sublimation using a high vacuum sublimation purification device under conditions of a high temperature part of 340° C., and 113 mg of yellow crystals (yield 43.9%). Got This was repeated several times to collect yellow crystals.
The obtained yellow crystals were further purified by sublimation to finally obtain 100 mg of yellow crystals.
Elemental analysis of the purified AcDPA-2TP was performed.
Anal. Calcd for C ₆₀ H ₄₆ N ₆ ; C, 84.68%; H, 5.45%; N, 9.87%. Found: C, 84.38%; H, 5.17%; N, 9.85%

[Optical property evaluation]
An AcDPA-2TP single film (neat thin film) was prepared using a glass chamber, and UV-vis absorption spectrum (Fig. 12a), PL spectrum (Fig. 12a), and PYS (Fig. 12b) were measured.
In addition, an AcDPA-2TP:DPEPO (10 wt%) co-deposited film (hereinafter also referred to as “DPEPO-doped film”) was prepared, and a UV-vis absorption spectrum (FIG. 13a), a PL spectrum (FIG. 13a), and a transient decay PL spectrum were prepared. (FIG. 14) and low temperature phosphorescence spectrum (FIG. 15) were measured. Similarly, an AcDPA-2TP:CBP (10 wt%) co-deposited film (hereinafter also referred to as “CBP-doped film”) was prepared, and a UV-vis absorption spectrum (FIG. 13b), a PL spectrum (FIG. 13b), and a transient decay PL were prepared. The spectrum (FIG. 16) and the low temperature phosphorescence spectrum (FIG. 17) were measured.

実施例３の光学特性評価の測定結果に基づき、ＡｃＤＰＡ−２ＴＰの熱的及び光物理的性質を求めた。結果を表２に示す。

The thermal and photophysical properties of AcDPA-2TP were determined based on the measurement results of the optical property evaluation of Example 3. The results are shown in Table 2.

[Example 4]
Devices using Ac-2TP (Devices 1, 2 and 3) and AcCz-2TP (Devices 4, 5 and 6) as light emitting layers were prepared in a glass chamber.
The configuration of each device is as follows.
(I) Device 1
[ITO/KLHIP:PPBi (20 nm)/TAPC (20 nm)/EML2 (20 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al]
(Ii) Device 2
[ITO/KLHIP:PPBi (20 nm)/TAPC (20 nm)/mCP (5 nm)/EML2 (20 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al]
(Iii) Device 3
[ITO/KLHIP:PPBi (20 nm)/TAPC (20 nm)/mCP (5 nm)/EML1 (10 nm)/EML2 (10 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al]

(Iv) Device 4
[ITO/KLHIP:PPBi (20 nm)/TAPC (20 nm)/EML4 (20 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al]
(V) Device 5
[ITO/KLHIP:PPBi (20 nm)/TAPC (20 nm)/mCP (5 nm)/EML4 (20 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al]
(Vi) Device 6
[ITO/KLHIP:PPBi (20 nm)/TAPC (20 nm)/mCP (5 nm)/EML3 (10 nm)/EML4 (10 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al]

(Vii) Device 7
[ITO/KLHIP:PPBi (20 nm)/TAPC (20 nm)/mCP (5 nm)/EML5 (10 nm)/EML6 (10 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al]
(Viii) Device 8
[ITO/KLHIP:PPBi (20 nm)/TAPC (30 nm)/EML7 (5 nm)/EML8 (5 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al (100 nm)]
(Ix) Device 9
[ITO/KLHIP:PPBi (20 nm)/TAPC (30 nm)/EML9 (5 nm)/EML10 (5 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al (100 nm)]

(X) device 10
[ITO/KLHIP:PPBi (20 nm)/TAPC (30 nm)/EML11 (5 nm)/EML12 (5 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al (100 nm)]
(Xi) Device 11
[ITO/KLHIP:PPBi (20 nm)/TAPC (30 nm)/EML13 (5 nm)/EML14 (5 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al (100 nm)]
(Xii) device 12
[ITO/KLHIP:PPBi (20 nm)/TAPC (30 nm)/EML15 (5 nm)/EML16 (5 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al (100 nm)]

KLHIP:PPBi constituting the above devices 1 to 6 is a triphenylamine-containing polymer: (4-isopropyl-4′-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (PPBI) (triphenylamine-containingpolymer: 4-isopropyl-4′). -methyldiphenyl-iodoniumtetrakis(pentafluorophenyl)borate (PPBI)), and mCPd, B3PyPB and TAPC are represented by the following structural formulas.

EML is a light emitting layer, and EML1 to 4 are made of the following materials.
EML1=10 wt% Ac-2TP:mCP
EML2=10 wt% Ac-2TP:DPEPO
EML3=10 wt% AcCz-2TP:mCP
EML4=10 wt% AcCz-2TP:DPEPO
EML5=10 wt% AcDPA-2TP:mCP
EML6=10 wt% AcDPA-2TP:DPEPO
EML7=5 wt% AcDPA-2TP:TCTA
EML8=5 wt% AcDPA-2TP:CBP
EML9=10 wt% AcDPA-2TP:TCTA
EML10=10 wt% AcDPA-2TP:CBP
EML11=15 wt% AcDPA-2TP:TCTA
EML12=15 wt% AcDPA-2TP:CBP
EML13=20 wt% AcDPA-2TP:TCTA
EML14=20 wt% AcDPA-2TP:CBP
EML15=30 wt% AcDPA-2TP:TCTA
EML16=30 wt% AcDPA-2TP:CBP

The energy diagram of devices 1-6 is shown in FIG.
The characteristics of Devices 1, 2 and 3 using Ac-2TP are shown in FIG.
The characteristics of devices 4, 5 and 6 using AcCz-2TP are shown in FIG.
Table 3 shows the element performance when the brightness of the devices 1 to 6 was 1 cd/m ² and 100 cd/m ² .
From Table 3, the voltage (V) at 1 cd/m ² is 3.06 to 3.23 V, the brightness (PE) is 6.37 to 18.7 m/W, and the external quantum efficiency (E.Q.E. .) is 3.55 to 10.2%, the voltage (V) at 100 cd/m ² is 4.20 to 5.04 V, and the brightness (PE) is 2.23 to 7.97 lm/W. , And the external quantum efficiency (E.Q.E.) was 1.84 to 6.03%. Further, the CIE o'clock 1 cd / m ² is CIE o'clock 0.16~0.19,0.21~0.30,100cd / m ² becomes 0.16～0.18,0.18～0.28 , Showing emission in the blue region. From these results, luminescence due to TADF was strongly suggested.

The energy diagrams for devices 3, 6-12 are shown in FIG.
The device performance when the brightness of the devices 3, 6 and 7 is 1 cd/m ² , 100 cd/m ² and 1000 cd/m ² is shown in Table 4, and the brightness of the devices 8 to 12 is 1 cd/m ² and 100 cd/m ^2. Table 5 shows the device performance in the case of 1000 cd/m ² .

なお、本発明は以下の態様を包含する。
［１］下記一般式（１）で表されるターピリジン誘導体。

（一般式（１）中、Ｘは−ＣＲ^aＲ^b−、−Ｏ−、−Ｓ−、又は−Ｓ（＝Ｏ）₂−を表し、Ｒ^a及びＲ^bは互いに連結して環を形成してもよく、Ｒ¹〜Ｒ⁶はそれぞれ独立に水素原子、アルキル基又はアリール基を表す。）
［２］前記一般式（１）中、２つの置換基Ａはピリジン環を介して、下記式で表されるターピリジン基を形成し、前記置換基Ｂが電子供与性部位である、［１］に記載のターピリジン誘導体。

［３］上記［１］又は［２］に記載のターピリジン誘導体よりなる発光材料。
［４］上記［１］又は［２］に記載のターピリジン誘導体を用いた有機ＥＬ素子。

The present invention includes the following aspects.
[1] A terpyridine derivative represented by the following general formula (1).

(In the general formula (1), X represents —CR ^a R ^b —, —O—, —S—, or —S(═O) ₂ —, and R ^a and R ^b are linked to each other to form a ring. Alternatively, R ^{1 to} R ⁶ each independently represent a hydrogen atom, an alkyl group or an aryl group.)
[2] In the general formula (1), the two substituents A form a terpyridine group represented by the following formula via a pyridine ring, and the substituent B is an electron-donating moiety. The terpyridine derivative according to 1.

[3] A luminescent material comprising the terpyridine derivative according to the above [1] or [2].
[4] An organic EL device using the terpyridine derivative according to the above [1] or [2].

1 substrate 2 anode 3 hole injection layer 4 hole transport layer 5 light emitting layer 6 electron transport layer 7 electron injection layer 8 cathode

Claims (4)

A terpyridine derivative represented by the following general formula (1).

(In the general formula (1), two substituents A form a terpyridine group described below via a pyridine ring,

Substituent B is as follows:

X is ^{-CR a R b -, - O} -, - S-, or -S (= O) ₂ - represents, R ^a and R ^b are identical and methyl group, a phenyl group, a tolyl group or It is a pyridyl group, R ^a and R ^b may be linked to each other to form a ring, and R ¹ and R ² are each independently a carbazolyl group or a diphenylamino group . ) The terpyridine derivative according to claim 1, wherein the terpyridine derivative represented by the general formula (1) is represented by the following structural formula .

A luminescent material comprising the terpyridine derivative according to claim 1. An organic EL device using the terpyridine derivative according to claim 1.

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