JP7125324B2 - Organic electroluminescence device, display device, and lighting device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an organic electroluminescence (hereinafter, electroluminescence (electroluminescence) may be referred to as "EL") element, a display device, and a lighting device.

Triazine-containing compounds are attracting attention as materials for functional electronic devices due to their electronic properties. For example, it is expected to be used as a light-emitting material for organic EL (electroluminescence) devices that require properties such as electron-accepting properties and as an electron-transporting material. In particular, since organic EL elements have various excellent characteristics as display devices, the development of materials capable of achieving even higher performance is being actively pursued (for example, Patent Document 1, Non-Patent Document 1 12). Organic EL elements are also expected to be used as lighting devices.

Several examples of triazine-containing compounds that have been investigated for use in organic EL devices have been known so far. is substituted with benzene or pyridine. Although these compounds are known to exhibit excellent electron transport properties, they cannot be dissolved in solutions due to strong intermolecular interactions, and film formation was possible only by vacuum deposition (e.g. , Non-Patent Document 1).

The organic EL element described above has a structure in which a plurality of layers including a light-emitting layer are laminated between a cathode and an anode. An organic EL device has a structure in which a plurality of layers such as an electron transport layer, a light emitting layer, and a hole transport layer are laminated between a cathode and an anode. Organic EL elements are classified into so-called forward-structured organic EL elements in which such a laminated structure is formed, and so-called inverted-structured organic EL elements in which such a laminated structure is formed on a cathode placed on a substrate. As for some organic EL elements having an inverted structure, an organic-inorganic hybrid type (Hybrid Organic Inorganic LED: HOILED) in which a part of the layers constituting the organic EL element is made of an inorganic material has been reported. The characteristics of this hybrid device are that it uses an inorganic oxide as the electron injection layer, which enables electron injection without using an alkali metal, and has the advantage of being highly resistant to oxygen and moisture compared to ordinary organic EL devices. be.

In the reverse structure organic EL device, the electron injection layer can be formed before forming the light emitting layer on the substrate. Therefore, for example, even if an electron injection layer of inorganic oxide or the like is formed using a sputtering method, the light-emitting layer is not damaged, and the organic EL element having the reverse structure is preferable for manufacturing the hybrid type element.

The inorganic oxide layer of the organic EL element having the reverse structure is used as an electron injection layer (see, for example, Non-Patent Document 3), but the inorganic oxide layer has insufficient electron injection properties into the organic layer. be. Therefore, there is known a technique for improving the electron injection properties of an organic EL element by further forming an electron injection layer on the inorganic oxide layer. For example, Non-Patent Document 11 below reports that good electron injection characteristics can be obtained by coating a specific electron-transporting compound (triazine-containing compound) to form a film.

Japanese Patent No. 5124785

Shi-Jian Su, 4 others, "Advanced Materials", 2010, Vol. 22, p3311-3316 Tae Jin Park, 7 others, "Applied Physics Letters", Vol.92, 2008, p113308 Woo Sik Jeon, 6 others, Applied Physics Letters, Vol.92, 2008, p113311 Henk J. Henk J. Bolink, et al., "Advanced Materials", 2010, Vol. 22, p2198-2201 Henk J. Henk J. Bolink, et al., "Chemistry of Materials", 2009, Vol. 21, p439-441 Hyosung Choi, 8 others, "Advanced Materials", Vol. 23, 2011, p2759 Yinhua Zho, 21 others, "Science", Vol.336, 2012, p327 Young-Hoon Kim, 5 others, "Advanced Functional Materials", 2014, DOI: 10.1002/adfm. 201304163 Stephan Forfle, et al., "Advanced Materials", 2014, DOI: 10.1002/adma. 201304666 Stephan Forfle, et al., Advanced Materials, Vol. 26, 2014, DOI: 10.1002/adma. 201400332 Penn Way, et al., "Journal of American Chemical Society", Vol. 132, 2010, p8852 Hirohiko Fukagawa, 8 others, "Advanced Materials", DOI: 10.1002/adma. 201706768

A triazine-containing compound having a high electron-transporting property is also expected to be applied to the electron injection layer of the reverse structure organic EL device.
However, as described above, most of the triazine-containing compounds cannot be dissolved in solvents, making film formation by coating difficult. In order to enable film formation by coating, it is necessary to review the basic design of triazine-containing compounds.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an organic EL device that uses a compound that can be coated and has excellent electron injection properties, has a low driving voltage, and has excellent luminous efficiency. Make it an issue.

The present inventors conducted various studies on compounds that can be coated and formed and have excellent electron injection properties. The present inventors have arrived at the present invention based on the idea that the above-described problems can be solved by combining the two layers, thereby making it possible to form a film by coating.
The gist and configuration of the present invention for solving the above problems are as follows.

［式（１）中のＸは、下記式（２）：

中のＲと任意の位置で結合しており、
式（２）中の環Ａは、隣接環と任意の位置で縮合する、下記式（２ａ）：

で表される芳香環を表し、
式（２）中の環Ｂ及び環Ｂ’は、隣接環と任意の位置で縮合する、下記式（２ｂ－１）、式（２ｂ－２）、式（２ｂ－３）：

のいずれかで表される環構造を表し、
式（１）、式（２ａ）、及び式（２ｂ－１）中のＲは、独立に水素、又は炭素数１～１０のアルキル基、炭素数１～１０のアルコキシ基、炭素数１～１０のアルキルチオ基、炭素数１～１０のアルキルアミノ基、炭素数２～１０のアシル基、炭素数７～２０のアラルキル基、置換若しくは未置換の炭素数６～３０の芳香族炭化水素基、及び置換若しくは未置換の炭素数３～３０の芳香族６員複素環基からなる群から選択される１価の置換基であり、隣接する置換基が一体となって環を形成してもよく、
式（２）中のＲであって、式（１）中のＸと結合していないＲは、独立に水素、又は炭素数１～１０のアルキル基、炭素数１～１０のアルコキシ基、炭素数１～１０のアルキルチオ基、炭素数１～１０のアルキルアミノ基、炭素数２～１０のアシル基、炭素数７～２０のアラルキル基、置換若しくは未置換の炭素数６～３０の芳香族炭化水素基、置換若しくは未置換の炭素数３～３０の芳香族６員複素環基、ハロゲン基、及びシアノ基からなる群から選択される１価の置換基であり、隣接する置換基が一体となって環を形成してもよく、
式（２）中のｎは、１以上４以下の整数を示す。］で表されるトリアジン構造を有する化合物からなる層を有することを特徴とする。
かかる本発明の有機エレクトロルミネッセンス素子は、前記トリアジン構造を有する化合物からなる層の塗布成膜可能であり、駆動電圧が低く、発光効率に優れる。 The organic electroluminescence element of the present invention is an organic electroluminescence element in which a cathode, a light-emitting layer and an anode are provided in this order on a substrate,
Between the cathode and the light-emitting layer, the following formula (1):

[X in formula (1) is the following formula (2):

is bound at any position with R in
Ring A in formula (2) is fused to the adjacent ring at any position, the following formula (2a):

Represents an aromatic ring represented by
Ring B and ring B' in formula (2) are condensed at any position with the adjacent ring, the following formula (2b-1), formula (2b-2), formula (2b-3):

Represents a ring structure represented by either
R in formula (1), formula (2a), and formula (2b-1) is independently hydrogen, or an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or 1 to 10 carbon atoms. an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and A monovalent substituent selected from the group consisting of substituted or unsubstituted aromatic 6-membered heterocyclic groups having 3 to 30 carbon atoms, and adjacent substituents may be united to form a ring,
R in formula (2), R not bonded to X in formula (1) is independently hydrogen, or an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, carbon Alkylthio groups of 1 to 10 carbon atoms, alkylamino groups of 1 to 10 carbon atoms, acyl groups of 2 to 10 carbon atoms, aralkyl groups of 7 to 20 carbon atoms, substituted or unsubstituted aromatic carbonization of 6 to 30 carbon atoms A monovalent substituent selected from the group consisting of a hydrogen group, a substituted or unsubstituted 6-membered aromatic heterocyclic group having 3 to 30 carbon atoms, a halogen group, and a cyano group, wherein adjacent substituents are combined together may form a ring,
n in Formula (2) represents an integer of 1 or more and 4 or less. ] is characterized by having a layer made of a compound having a triazine structure represented by .
The organic electroluminescence element of the present invention can be coated with a layer comprising the compound having the triazine structure, has a low driving voltage, and is excellent in luminous efficiency.

In a preferred embodiment of the organic electroluminescence device of the present invention, the layer of the compound having a triazine structure contains a reducing agent. In this case, since electrons are sufficiently supplied from the cathode to the light-emitting layer, the driving voltage of the organic electroluminescence device is further lowered, and the light-emitting efficiency is further improved.

In another preferred embodiment of the organic electroluminescence device of the present invention, the layer of the compound having a triazine structure contains a basic compound having an acid dissociation constant pKa of 1 or more. In this case, the electron injection property of the layer composed of the compound having a triazine structure is improved, so that the drive voltage of the organic electroluminescence device is further lowered, and the luminous efficiency is further improved.

The organic electroluminescence device of the present invention preferably has an electron injection layer made of metal oxide between the cathode and the light emitting layer. In this case, the storage stability of the organic electroluminescence element is improved, and the drive stability is improved.

In another preferred embodiment of the organic electroluminescent device of the present invention, one of the ring B and the ring B' in the formula (2) is the formula (2b-1) in which one is condensed with an adjacent ring at an arbitrary position. and the other represents a ring structure represented by formula (2b-2) condensed at any position with the adjacent ring. In this case, the electron transport property of the layer made of the compound having a triazine structure is improved, the driving voltage is further lowered, and the luminous efficiency is further improved.

A display device of the present invention is characterized by comprising the organic electroluminescence element described above. Such a display device of the present invention is excellent in driving stability.

Further, a lighting device of the present invention is characterized by comprising the organic electroluminescence element described above. Such a lighting device of the present invention is excellent in driving stability.

According to the present invention, an organic EL device having a so-called inverted structure, which has a cathode on a substrate, uses a compound that can be coated and has excellent electron injection properties, has a low driving voltage, and has excellent luminous efficiency. It is possible to provide an organic EL device.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which showed an example of the structure of the organic EL element of this invention. 1 is an NMR spectrum of a compound having a triazine structure represented by formula (19). 1 is an NMR spectrum of a compound having a benzothiazole structure represented by formula (20). 4 is a graph showing the results of measuring (a) luminance-voltage characteristics and (b) external quantum efficiency-current density characteristics of various organic EL devices manufactured in Example 1 and Comparative Example 1-2.

The organic electroluminescence element, the display device, and the lighting device of the present invention will be illustrated and described in detail below based on the embodiments thereof.
A combination of two or more of the individual preferred embodiments of the invention described below is also a preferred embodiment of the invention.

<Organic electroluminescence element>
The organic electroluminescence device of the present invention is an organic electroluminescence device in which a cathode, a light-emitting layer and an anode are provided in this order on a substrate, and between the cathode and the light-emitting layer, the above formula (1) It is characterized by having a layer made of a compound having a triazine structure represented by.

In the organic electroluminescence device of the present invention, since the triazine structure of the compound having the triazine structure represented by the formula (1) has electron-transporting properties, the layer composed of the compound having the triazine structure has excellent electron-transporting properties. . Therefore, the organic electroluminescence device of the present invention has a low driving voltage and excellent luminous efficiency.
Further, in the compound having a triazine structure represented by the formula (1), a weakly electron-donating substituent represented by the formula (2) is bonded to the ortho position (X) of the aryl group bonded to the triazine structure. Therefore, it has excellent solubility. Therefore, when forming a layer composed of a compound having a triazine structure represented by the formula (1), there is also the advantage that film formation by coating is possible.

で表される。式（１）で表わされる化合物は、トリアジン環にアリール基が結合してなる化合物である。式（１）において、トリアジン環に結合している２つのＲは、独立に水素、又は炭素数１～１０のアルキル基、炭素数１～１０のアルコキシ基、炭素数１～１０のアルキルチオ基、炭素数１～１０のアルキルアミノ基、炭素数２～１０のアシル基、炭素数７～２０のアラルキル基、置換若しくは未置換の炭素数６～３０の芳香族炭化水素基、及び置換若しくは未置換の炭素数３～３０の芳香族６員複素環基からなる群から選択される１価の置換基であり、隣接する置換基が一体となって環を形成してもよい。 The compound having a triazine structure used in the organic electroluminescence device of the present invention has the following formula (1):

is represented by The compound represented by Formula (1) is a compound in which an aryl group is bonded to a triazine ring. In formula (1), the two Rs bonded to the triazine ring are independently hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an alkylamino group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted is a monovalent substituent selected from the group consisting of aromatic 6-membered heterocyclic groups having 3 to 30 carbon atoms, and adjacent substituents may be united to form a ring.

中のＲと任意の位置で結合している。
上記式（２）中のｎは、１以上４以下の整数を示す。ここで、ｎは１であることが好ましい。
上記式（２）中のＲであって、式（１）中のＸと結合していないＲは、独立に水素、又は炭素数１～１０のアルキル基、炭素数１～１０のアルコキシ基、炭素数１～１０のアルキルチオ基、炭素数１～１０のアルキルアミノ基、炭素数２～１０のアシル基、炭素数７～２０のアラルキル基、置換若しくは未置換の炭素数６～３０の芳香族炭化水素基、置換若しくは未置換の炭素数３～３０の芳香族６員複素環基、ハロゲン基、及びシアノ基からなる群から選択される１価の置換基であり、隣接する置換基が一体となって環を形成してもよい。 X in the above formula (1) is located at the ortho position of the aryl group bonded to the triazine structure, and the following formula (2):

It is bound to R in any position.
n in the above formula (2) represents an integer of 1 or more and 4 or less. Here, n is preferably 1.
R in the above formula (2), which is not bonded to X in formula (1), is independently hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, Alkylthio group having 1 to 10 carbon atoms, alkylamino group having 1 to 10 carbon atoms, acyl group having 2 to 10 carbon atoms, aralkyl group having 7 to 20 carbon atoms, substituted or unsubstituted aromatic group having 6 to 30 carbon atoms A monovalent substituent selected from the group consisting of a hydrocarbon group, a substituted or unsubstituted 6-membered aromatic heterocyclic group having 3 to 30 carbon atoms, a halogen group, and a cyano group, wherein adjacent substituents are united may form a ring.

で表される芳香環を表す。ここで、２つのＲの内の、一方のＲは、もう一方のＲに対して、パラ位に位置していても、メタ位に位置していても、オルト位に位置していてもよい。式（２ａ）中のＲは、独立に水素、又は炭素数１～１０のアルキル基、炭素数１～１０のアルコキシ基、炭素数１～１０のアルキルチオ基、炭素数１～１０のアルキルアミノ基、炭素数２～１０のアシル基、炭素数７～２０のアラルキル基、置換若しくは未置換の炭素数６～３０の芳香族炭化水素基、及び置換若しくは未置換の炭素数３～３０の芳香族６員複素環基からなる群から選択される１価の置換基であり、隣接する置換基が一体となって環を形成してもよい。 Further, the ring A in the above formula (2) is condensed with the adjacent ring at any position, the following formula (2a):

Represents an aromatic ring represented by Here, one R of the two R may be located at the para-position, the meta-position, or the ortho-position with respect to the other R. . R in formula (2a) is independently hydrogen, or an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, or an alkylamino group having 1 to 10 carbon atoms. , an acyl group having 2 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and a substituted or unsubstituted aromatic group having 3 to 30 carbon atoms It is a monovalent substituent selected from the group consisting of 6-membered heterocyclic groups, and adjacent substituents may be united to form a ring.

のいずれかで表される環構造を表す。式（２ｂ－１）中のＲは、独立に水素、又は炭素数１～１０のアルキル基、炭素数１～１０のアルコキシ基、炭素数１～１０のアルキルチオ基、炭素数１～１０のアルキルアミノ基、炭素数２～１０のアシル基、炭素数７～２０のアラルキル基、置換若しくは未置換の炭素数６～３０の芳香族炭化水素基、及び置換若しくは未置換の炭素数３～３０の芳香族６員複素環基からなる群から選択される１価の置換基であり、隣接する置換基が一体となって環を形成してもよい。
ここで、式（２）中の環Ｂ及び環Ｂ’は、一方が、隣接環と任意の位置で縮合する上記式（２ｂ－１）で表される環構造を表し、もう一方が、隣接環と任意の位置で縮合する上記式（２ｂ－２）で表される環構造を表すことが好ましい。この場合、トリアジン構造を有する化合物からなる層の電子輸送性が向上し、駆動電圧が更に低くなり、発光効率が更に向上する。 Further, the ring B and ring B' in the above formula (2) are condensed at any position with the adjacent ring, the following formula (2b-1), formula (2b-2), formula (2b-3):

Represents a ring structure represented by either R in formula (2b-1) is independently hydrogen, or an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms. amino group, acyl group having 2 to 10 carbon atoms, aralkyl group having 7 to 20 carbon atoms, substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and substituted or unsubstituted 3 to 30 carbon atoms It is a monovalent substituent selected from the group consisting of aromatic 6-membered heterocyclic groups, and adjacent substituents may be united to form a ring.
Here, ring B and ring B' in formula (2) represent a ring structure represented by the above formula (2b-1) condensed at any position with the adjacent ring, and the other is adjacent It preferably represents a ring structure represented by the above formula (2b-2) condensed at any position on the ring. In this case, the electron transport property of the layer made of the compound having a triazine structure is improved, the driving voltage is further lowered, and the luminous efficiency is further improved.

R in the above formula (1), formula (2a), and formula (2b-1) is independently hydrogen, or an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and 1 to 1 carbon atoms. 10 alkylthio groups, alkylamino groups having 1 to 10 carbon atoms, acyl groups having 2 to 10 carbon atoms, aralkyl groups having 7 to 20 carbon atoms, substituted or unsubstituted aromatic hydrocarbon groups having 6 to 30 carbon atoms, and a monovalent substituent selected from the group consisting of a substituted or unsubstituted aromatic 6-membered heterocyclic group having 3 to 30 carbon atoms, and adjacent substituents may form a ring together. , Also, R in the above formula (2), which is not bonded to X in formula (1), is independently hydrogen, or an alkyl group having 1 to 10 carbon atoms, or alkoxy group, alkylthio group having 1 to 10 carbon atoms, alkylamino group having 1 to 10 carbon atoms, acyl group having 2 to 10 carbon atoms, aralkyl group having 7 to 20 carbon atoms, substituted or unsubstituted 6 to 30 carbon atoms A monovalent substituent selected from the group consisting of an aromatic hydrocarbon group, a substituted or unsubstituted 6-membered aromatic heterocyclic group having 3 to 30 carbon atoms, a halogen group, and a cyano group, and adjacent substituents The groups may together form a ring.
Here, the alkyl group having 1 to 10 carbon atoms includes methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group and the like. Examples of the alkoxy group include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, pentyloxy, hexyloxy, heptyloxy, and octyloxy groups. , The alkylthio group having 1 to 10 carbon atoms includes a methylthio group, ethylthio group, propylthio group, butylthio group, pentylthio group, hexylthio group, heptylthio group, octylthio group, nonylthio group and the like. Examples of the amino group include methylamino group, ethylamino group, propylamino group, butylamino group, pentylamino group, hexylamino group, heptylamino group, octylamino group, nonylamino group and the like. The acyl group includes acetyl group, propionyl group, butyryl group and the like, and the aralkyl group having 7 to 20 carbon atoms includes benzyl group, phenethyl group, phenylpropyl group, naphthylmethyl group and the like. Examples of substituted aromatic hydrocarbon groups having 6 to 30 carbon atoms include phenyl group, 2,6-xylyl group, mesityl group, duryl group, biphenyl group, terphenyl group, naphthyl group, anthryl group, pyrenyl group and toluyl group. , anisyl group, fluorophenyl group, diphenylaminophenyl group, dimethylaminophenyl group, diethylaminophenyl group, pyridylphenyl group, phenanthrenyl group and the like, and substituted or unsubstituted aromatic 6-membered heterocyclic ring having 3 to 30 carbon atoms. Examples of groups include pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, and triazinyl groups. Halogen groups for R in formula (2) include fluorine, chlorine, bromine, and iodine.

Specific examples of the compound having a triazine structure represented by the above formula (1) include compounds represented by the following formulas (3-1) to (3-10).

A compound having a triazine structure represented by the formula (1) can be obtained by synthesizing by a known method. Although the method for synthesizing the compound having a triazine structure represented by formula (1) is not particularly limited, an example thereof is shown below.

First, prepare a compound represented by formula (2) in which none of R is bonded to X in formula (1) (hereinafter sometimes referred to as "compound represented by formula (2)"). Then, a dihydroxyboryl group [-B(OH) ₂ group] is introduced at the target position (R) of the compound to obtain a boronic acid compound. Here, the reaction for introducing the dihydroxyboryl group is carried out by reacting the compound represented by the formula (2) with a boric acid ester such as triisopropyl borate [(iPrO) ₃ B] with t-butyl titanium (t-BuLi) or the like. can be carried out by reacting in the presence of an organic lithium compound.

Next, the boronic acid compound obtained as described above and a dihalogenated benzene such as 1,2-dibromobenzene are subjected to Suzuki coupling to replace the dihydroxyboryl group of the boronic acid compound with a bromophenyl group. Here, the reaction for substituting a dihydroxyboryl group with a bromophenyl group involves combining a compound having a dihydroxyboryl group and a dihalogenated benzene such as 1,2-dibromobenzene with [1,1′-bis(diphenylphosphino) in the presence of a palladium catalyst such as ferrocene]palladium(II) dichloride [Pd(dppf) _Cl2 ] or tetrakis(triphenylphosphine)palladium(0)[Pd( _Ph3P ) ₄ ] and a base such as sodium carbonate. , can be carried out by reacting.

Next, the bromine in the bromophenyl group of the compound having a bromophenyl group obtained as described above is substituted with a boryl group such as a pinacolatoboryl group to obtain an organic boron compound. Here, the reaction for substituting the bromine of the bromophenyl group with a boryl group involves a compound having a bromophenyl group, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane [( iPrO)Bpin] and other pinacol esters in the presence of an organic lithium compound such as n-butyl titanium (n-BuLi).

Next, the organoboron compound obtained as described above and a compound having a triazine structure and having a halogen element bonded to the triazine ring are subjected to Suzuki coupling to obtain a triazine structure represented by formula (1). can be prepared. Here, Suzuki coupling between a compound having a halogen element bonded to the triazine ring and an organic boron compound having a boryl group is performed by combining a compound having a halogen element bonded to the triazine ring and an organic boron compound having a boryl group. in the presence of a palladium catalyst such as Pd(dppf)Cl ₂ and a base such as sodium carbonate. Compounds having a triazine structure and having a halogen element bonded to the triazine ring include 2-chloro-4,6-diphenyl-1,3,5-triazine and the like.

Next, one aspect of the organic electroluminescence element of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing an example of the structure of the organic EL device of the present invention.

In the organic EL device 1 shown in FIG. 1, a cathode 3, a light emitting layer 6, and an anode 9 are provided on a substrate 2 in this order. It has layer 5.
Here, in the organic EL device shown in FIG. 1, the electron injection/transport layer 5 contains the compound having the above triazine structure, that is, is a layer made of the compound having the above triazine structure. As described above, by providing the electron injection/transport layer 5 made of the compound having the triazine structure between the cathode 3 and the light emitting layer 6, the driving voltage of the organic EL element having the reverse structure is reduced, and the light emission efficiency is improved. can be improved.

The layers constituting the organic EL element 1 include an anode 9, a cathode 3, a light-emitting layer 6, an electron injection/transport layer 5, a hole transport layer 7, a hole injection layer 8, and the like. The organic EL element 1 is constructed by appropriately selecting and stacking them.
As long as the organic electroluminescence device of the present invention has a structure in which a plurality of layers are laminated between the anode 9 and the cathode 3 formed on the substrate 2, the structure of the laminated layers is Although not particularly limited, it is an element in which each layer of a cathode 3, an electron injection/transport layer 5, a light emitting layer 6, and optionally a hole transport layer 7, a hole injection layer 8, and an anode 9 are laminated in this order adjacent to each other. Preferably.

Examples of materials for the substrate 2 include resin materials and glass materials. Resin materials used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyether sulfone, polymethyl methacrylate, polycarbonate, and polyarylate. When a resin material is used as the material of the substrate 2, it is preferable because the organic EL element 1 having excellent flexibility can be obtained. On the other hand, examples of glass materials used for the substrate 2 include quartz glass and soda glass.

When the organic EL element 1 is of the bottom emission type, a transparent substrate is used as the material of the substrate 2 . On the other hand, when the organic EL element 1 is of the top emission type, the material of the substrate 2 may be not only a transparent substrate but also an opaque substrate. Examples of opaque substrates include substrates made of ceramic materials such as alumina, substrates made of metal plates such as stainless steel with an oxide film (insulating film) formed thereon, and substrates made of resin materials.

The average thickness of the substrate 2 can be determined according to the material of the substrate 2, and is preferably 0.1 to 30 mm, more preferably 0.1 to 10 mm. The average thickness of the substrate 2 can be measured with a digital multimeter and vernier calipers.

In the organic electroluminescence device of the present invention, known conductive materials can be appropriately used for the cathode 3 and the anode 9, but at least one of them is preferably transparent for light extraction. Examples of known transparent conductive materials include ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), FTO (fluorine-doped indium oxide). etc. On the other hand, examples of opaque conductive materials include calcium, magnesium, aluminum, tin, indium, copper, silver, gold, platinum and alloys thereof.
Among these, ITO, IZO, and FTO are preferable as the cathode 3 .
As the anode 9, among these, Au, Ag, and Al are preferable.

As described above, since the metal generally used for the anode 9 can be used for the cathode 3 and the anode 9, it is possible to easily achieve light extraction from the upper electrode (in the case of a top emission structure). Various electrodes can be selected and used for each electrode. For example, Al is used for the lower electrode, and ITO is used for the upper electrode.

Although the average thickness of the cathode 3 is not particularly limited, it is preferably 10 to 500 nm, more preferably 100 to 200 nm. The average thickness of the cathode 3 can be measured by a stylus profilometer or spectroscopic ellipsometry.

Although the average thickness of the anode 9 is not particularly limited, it is preferably 10 to 1000 nm, more preferably 30 to 150 nm. Even when an opaque material is used, it can be used as the top emission type and transparent type anode 9 by setting the average thickness to about 10 to 30 nm, for example. Incidentally, the average thickness of the anode 9 can be measured during film formation by a crystal oscillator film thickness meter.

The organic electroluminescence device of the present invention preferably has a metal oxide layer 4 between the anode 9 and the cathode 3 . When a metal oxide is used as the material of the laminated structure between the anode 9 and the cathode 3, the continuous driving life and storage stability are superior to those of an organic EL device that does not have a layer made of metal oxide. .

The metal oxide layer 4 is a layer that functions as part of the cathode 3 or as an electron injection layer.
The metal oxide layer 4 is a layer consisting of a single layer of a single metal oxide film, or a layer of a semiconductor or insulator laminated thin film that is a layer in which single metal oxides or two or more kinds of metal oxides are laminated and/or mixed. . Metal elements constituting metal oxides include magnesium, calcium, strontium, barium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, indium, gallium, iron, cobalt, nickel, and copper. , zinc, cadmium, aluminum and silicon. Among these, at least one of the metal elements constituting the laminated or mixed metal oxide layer is preferably a layer composed of magnesium, aluminum, calcium, zirconium, hafnium, silicon, titanium, and zinc. If it is an oxide, it preferably contains a metal oxide selected from the group consisting of magnesium oxide, aluminum oxide, zirconium oxide, hafnium oxide, silicon oxide, titanium oxide and zinc oxide.

Examples of the layer obtained by stacking and/or mixing single metal oxides or two or more kinds of metal oxides include titanium oxide/zinc oxide, titanium oxide/magnesium oxide, titanium oxide/zirconium oxide, titanium oxide/aluminum oxide, titanium oxide/ Laminates and/or metal oxide combinations such as hafnium oxide, titanium oxide/silicon oxide, zinc oxide/magnesium oxide, zinc oxide/zirconium oxide, zinc oxide/hafnium oxide, zinc oxide/silicon oxide, calcium oxide/aluminum oxide titanium oxide/zinc oxide/magnesium oxide, titanium oxide/zinc oxide/zirconium oxide, titanium oxide/zinc oxide/aluminum oxide, titanium oxide/zinc oxide/hafnium oxide, titanium oxide/zinc oxide/silicon oxide, A combination of three kinds of metal oxides such as indium oxide/gallium oxide/zinc oxide is laminated and/or mixed. Among these, IGZO, which is an oxide semiconductor exhibiting good characteristics as a special composition, and _{12CaO7Al2O3 ,} which is an electride, are also included.
In the present invention, a material with a sheet resistance lower than 100Ω/□ is classified as a conductor, and a material with a sheet resistance higher than 100Ω/□ is classified as a semiconductor or an insulator. Therefore, ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), FTO (fluorine-doped indium oxide), etc., known as transparent electrodes Since the thin film has high conductivity and is not included in the category of semiconductors or insulators, it does not correspond to one layer constituting the metal oxide layer 4 of the present invention.

The average thickness of the metal oxide layer 4 is allowable from about 1 nm to several μm, but from the viewpoint of an organic EL device that can be driven at a low voltage, it is preferably 1 to 1000 nm, and 2 to 100 nm. is more preferred. The average thickness of the metal oxide layer 4 can be measured by a stylus profilometer and spectroscopic ellipsometry.

It is more preferable that the organic electroluminescence device of the present invention has an electron injection layer (metal oxide layer 4 ) made of metal oxide between the cathode 3 and the light emitting layer 6 . The electron injection layer improves the speed of injection of electrons from the cathode 3 to the light emitting layer 6 and the electron transport property. By having, the storage stability of the organic EL element is improved, and the driving stability is further improved.

In the organic EL device shown in FIG. 1, the electron injection/transport layer 5 formed between the cathode 3 and the light emitting layer 6 contains the compound having the above triazine structure. The electron injection/transport layer 5 is preferably formed by applying a solution containing a compound having a triazine structure. Since the electron injection/transport layer 5 is a layer made of the above-described compound having a triazine structure, the electron injection and electron transport properties of the electron injection/transport layer 5 are improved, and the injection of holes from the anode and The injection of electrons from the cathode is balanced, the driving voltage of the organic EL element 1 is lowered, and the luminous efficiency is improved.
In FIG. 1, the metal oxide layer 4 is laminated on the cathode 3, and the electron injection/transport layer 5 is laminated on the metal oxide layer 4. In the electroluminescence device, the stacking order of the metal oxide layer 4 and the electron injection/transport layer 5 may be reversed.

In the organic electroluminescence device of the present invention, the electron injection/transport layer 5 (layer made of a compound having a triazine structure) preferably contains a reducing agent.
Here, since the reducing agent acts as an n-dopant, the electron injection/transport layer 5 containing the reducing agent sufficiently supplies electrons from the cathode 3 to the light-emitting layer 6, so that the organic EL element is driven. The voltage is lowered and the luminous efficiency is further improved.

The reducing agent is preferably an electron-donating compound such as 1,3-dimethyl-2,3-dihydro-1H-benzo[d]imidazole, 1,3-dimethyl-2-phenyl-2,3- Dihydro-1H-benzo[d]imidazole, (4-(1,3-dimethyl-2,3-dihydro-1H-benzimidazol-2-yl)phenyl)dimethylamine (N-DMBI), 1,3,5 2,3-dihydrobenzo[d]imidazole compounds such as -trimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole; 3-methyl-2-phenyl-2,3-dihydrobenzo[d ] 2,3-dihydrobenzo[d]thiazole compounds such as thiazole; 2,3-dihydrobenzo[d]oxazole compounds such as 3-methyl-2-phenyl-2,3-dihydrobenzo[d]oxazole; leuco crystals Violet (=tris(4-dimethylaminophenyl)methane), leucomalachite green (=bis(4-dimethylaminophenyl)phenylmethane), triphenylmethane compounds such as triphenylmethane; 2,6-dimethyl-1,4 One or more of dihydropyridine compounds such as diethyl-dihydropyridine-3,5-dicarboxylate (Hanchu ester) can be used. Among these, 2,3-dihydrobenzo[d]imidazole compounds and dihydropyridine compounds are preferred, and (4-(1,3-dimethyl-2,3-dihydro-1H-benzimidazol-2-yl)phenyl)dimethyl Amines (N-DMBI) or diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (Hantu ester) are particularly preferred.

The amount of the reducing agent is preferably 0.1 to 15 mass % with respect to 100 mass % of the compound having a triazine structure forming the electron injection/transport layer 5 . When the reducing agent is contained in such a ratio, the luminous efficiency of the organic EL device can be made sufficiently high. The amount of the reducing agent is more preferably 0.5 to 10% by mass, more preferably 0.5 to 5% by mass, relative to 100% by mass of the compound having a triazine structure.

In the organic electroluminescence device of the present invention, the electron injection/transport layer 5 (layer made of a compound having a triazine structure) preferably contains a basic compound having an acid dissociation constant pKa of 1 or more. The basic compound having an acid dissociation constant pKa of 1 or more is preferably a tertiary amine, a phosphazene compound, a guanidine compound, a heterocyclic compound containing an amidine structure, a hydrocarbon compound having a ring structure, and a ketone compound. These compounds may be used singly or in combination of two or more.

A basic compound having an acid dissociation constant pKa of 1 or more has the ability to abstract protons (H ⁺ ) from a compound having a triazine structure. The basic compound preferably has a pKa of 5 or more, more preferably 11 or more. The higher the pKa, the higher the ability to abstract protons from the compound having a triazine structure. As a result, the electron injection property of the electron injection/transport layer 5 is further improved. In addition, since the basic compound is suitably coordinated to the defect site of the inorganic compound, it also has the effect of preventing the reaction at the interface with oxygen and water that enter from the outside and increasing the atmospheric stability of the element.
In the present invention, "pKa" usually means "acid dissociation constant in water", but what cannot be measured in water means "acid dissociation constant in dimethyl sulfoxide (DMSO)", and cannot be measured even in DMSO. One means "acid dissociation constant in acetonitrile". It preferably means "acid dissociation constant in water".

The tertiary amine (tertiary amine derivative) may be a chain or cyclic amine compound, and when it is cyclic, it may be a heterocyclic amine compound. It may also be a heterocyclic amine compound such as a group amine. The tertiary amine preferably has 1 to 4 amino groups, more preferably 1 or 2 amino groups. Further, the amine compound may be a compound having an alkyl group, an alkylamino group, or an alkoxy group. Specific examples include (mono-, di-, and tri)alkylamines; aromatic amines having 1 to 3 alkylamino groups; and aromatic amines having 1 to 3 alkoxy groups.

As the tertiary amine, one containing no primary amine or secondary amine is preferable. Specifically, as the tertiary amine, a dialkylaminopyridine such as dimethylaminopyridine (DMAP) represented by the following general formula (4-1) or (4-2), or a dialkylaminopyridine represented by the following general formula (4-3) Amines having a structure represented by NR ¹ R ² R ³ such as triethylamine (wherein R ¹ , R ² and R ³ are the same or different and represent a hydrocarbon group which may have a substituent. ), acridine orange (AOB) represented by the following general formula (4-4), and the like.

The hydrocarbon group preferably has 1 to 30 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms. . When the hydrocarbon group has a substituent, it is preferable that the total number of carbon atoms including the substituent is the above. Examples of hydrocarbon groups include alkyl groups, alkenyl groups, and alkynyl groups, with alkyl groups being preferred. Examples of substituents in the substituted hydrocarbon group include halogen atoms, heterocyclic groups, cyano groups, hydroxyl groups, alkoxy groups, aryloxy groups, amino groups and the like. As for dimethylaminopyridine, the position of bonding to the pyridine ring of the dimethylamino group, which is an electron-donating group, is preferably the 2-position (2-DMAP) or the 4-position (4-DMAP). In particular, 4-dimethylaminopyridine, in which a dimethylamino group is bonded to the 4-position of the pyridine ring, has a high pKa, and when an organic thin film containing this is used as the electron injection/transport layer 5 of an organic EL device, It is preferable because a long life can be obtained.

As the tertiary amine, alkoxypyridine derivatives such as methoxypyridine derivatives can also be used. The alkoxy group is preferably an alkoxy group having 1 to 30 carbon atoms, more preferably an alkoxy group having 1 to 8 carbon atoms, still more preferably an alkoxy group having 1 to 4 carbon atoms, and still more preferably an alkoxy group having 1 or 2 carbon atoms. . Alkoxypyridine derivatives also include compounds having a structure in which one or more hydrogen atoms of alkoxypyridine are substituted with substituents. Examples of the substituent include those similar to those of the hydrocarbon group of the tertiary amine.
As the methoxypyridine derivative, 4-methoxypyridine (4-MeOP) represented by the following general formula (5-1) in which the position of the methoxy group bonded to the pyridine ring is at the 4-position or the following general formula at the 3-position: 3-Methoxypyridine (3-MeOP) represented by (5-2) is preferred. In particular, 4-methoxypyridine in which a methoxy group is bonded to the 4-position of the pyridine ring is preferred because of its high pKa.

As the tertiary amine, it is preferable to use one or more selected from heterocyclic aromatic amines and trialkylamines having a dialkylamino group and/or an alkoxy group. , and alkoxypyridine derivatives, it is particularly preferable to use one or more of them from the viewpoint of improving electron injection properties and life.

In the heterocyclic compound containing an amidine structure, the amidine structure is a structure represented by R ⁴ -C(=NR ⁵ )-NR ⁶ R ⁷ (provided that R ⁴ to R ⁷ are the same or different, represents a hydrogen atom or a hydrocarbon group). Heterocyclic compounds containing an amidine structure include diazabicyclononene derivatives and diazabicycloundecene derivatives.

Examples of the diazabicyclononene derivative include 1,5-diazabicyclo[4.3.0]nonene-5 (DBN) represented by the following general formula (6-1). DBN is preferable because a long life can be obtained when an organic thin film containing DBN is used as the electron injection/transport layer 5 of an organic EL device.
Examples of the diazabicycloundecene derivative include 1,8-diazabicyclo[5.4.0]undecene-7 (DBU) represented by the following general formula (6-2).

The diazabicyclononene derivatives include compounds having a structure in which one or more of the hydrogen atoms of diazabicyclononene are substituted with substituents. Also included are compounds having a structure in which one or more of the hydrogen atoms are substituted with a substituent. Examples of the substituent include those similar to those of the hydrocarbon group of the tertiary amine.

The phosphazene compound (phosphazene base derivative) is, for example, a compound containing a structure represented by the following general formula (7).

In the above formula (7), R ⁸ represents a hydrogen atom or a hydrocarbon group, R ⁹ to R ¹¹ represent a hydrogen atom, a hydrocarbon group, or -NR'R'', where R' and R'' are each independent represents a hydrogen atom or a hydrocarbon group. ), or a group represented by the following formula (8), where n represents a number from 1 to 5.

In the above formula (8), R ¹² to R ¹⁴ each represent a hydrogen atom, a hydrocarbon group, or -NR'R''(R' and R'' each independently represent a hydrogen atom or a hydrocarbon group. ) and m represents a number from 1 to 5.

As the hydrocarbon group in the above formulas (7) and (8), a group having 1 to 8 carbon atoms is preferable, and a group having 1 to 4 carbon atoms is preferable. Moreover, as a hydrocarbon group, an alkyl group is preferable. A tertiary butyl group is particularly preferred as R ¹¹ .

Examples of the phosphazene base derivative include compounds represented by the following general formula (9).

The guanidine compound is a compound containing a structure represented by the following general formula (10).

In the above formula (17), R ¹⁵ to R ¹⁹ are the same or different and represent a hydrogen atom or a hydrocarbon group, and two or more of R ¹⁵ to R ¹⁹ may combine to form a cyclic structure. good.

A guanidine cyclic derivative or the like can be used as the guanidine compound. As the guanidine cyclic derivative, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) represented by the following formula (11-1), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) shown in 2).

As the hydrocarbon compound having a ring structure, a compound having a 5-membered ring or a 6-membered ring as a ring structure is preferable, and a ring structure in which a 5-membered ring and a 6-membered ring are fused, Compounds with cyclic ring structures are also preferred. The 5-membered ring includes a cyclopentane ring, cyclopentadiene ring and the like, and the 6-membered ring includes a benzene ring and the like.
Examples of the hydrocarbon compound having a ring structure include a compound having only a ring structure, a compound having a structure in which an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms is bonded to the ring structure, and a plurality of A compound having a structure in which the ring structure is directly or bonded via a hydrocarbon linking group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms is preferred. Specific examples of hydrocarbon compounds having a ring structure include compounds represented by the following formulas (12-1) to (12-14). Ph in the formula represents a phenyl group.

The ketone compound is preferably a ketone having 2 to 30 carbon atoms and may have a cyclic structure. Specifically, methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), diisobutyl ketone (DIBK), 3,5,5-trimethylcyclohexanone, diacetone alcohol, cyclopenta non, cyclohexanone, and the like.

The mass ratio of the compound having a triazine structure to the basic compound having a pKa of 1 or more (compound having a triazine structure: basic compound having a pKa of 1 or more) is 1:0.01 to 1: A range of 10 is preferred, and a range of 1:0.5 to 1:5 is more preferred. If the mass ratio is within this range, the effect of the compound having a triazine structure and the basic compound having a pKa of 1 or more is sufficiently exhibited, and the effect of improving the electron transport property and the electron injection property becomes remarkable.

The electron injection/transport layer 5 may be formed by laminating the compound having the triazine structure and a plurality of materials. Other materials that can be used include, in addition to the above-described reducing agents and basic compounds having an acid dissociation constant pKa of 1 or more, tris-1,3,5-(3′-(pyridine-3″ -yl)phenyl)benzene (TmPyPhB) and other pyridine derivatives, 2-(3-(9-carbazolyl)phenyl)quinoline (mCQ) and other quinoline derivatives, 2-phenyl-4,6-bis(3,5-dipyridyl) Pyrimidine derivatives such as phenyl)pyrimidine (BPyPPM), pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen), 2,4-bis(4-biphenyl)-6-(4'-(2-pyridinyl)-4-biphenyl )-[1,3,5]triazine (MPT) and other triazine derivatives, 3-phenyl-4-(1′-naphthyl)-5-phenyl-1,2,4-triazole (TAZ) and other triazole derivatives, Oxazole derivatives, oxadiazole derivatives such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), 2,2′,2″-( 1,3,5-Benzoyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI) and other imidazole derivatives, naphthalene, aromatic ring tetracarboxylic acid anhydrides such as perylene, bis[2-(2- various metal complexes represented by hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ) ₂ ), tris(8-hydroxyquinolinato)aluminum (Alq ₃ ), 2,5-bis(6'-(2',2 ``-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy) and other silole derivatives.

The average thickness of the electron injection/transport layer 5 is preferably 5 to 100 nm. When the average thickness of the electron injection/transport layer 5 is 5 nm or more, the effect of blocking holes is large, and the driving stability of the organic EL element is further improved. When the average thickness of the electron injection/transport layer 5 is 100 nm or less, the driving voltage is low, which is practically preferable. The average thickness of the electron injection/transport layer 5 is more preferably 10 to 60 nm. Further, considering the continuous driving life of the organic EL element of the present invention, the average thickness of the electron injection/transport layer 5 is more preferably 10 to 30 nm. The average thickness of the electron injection/transport layer 5 can be measured by a stylus profilometer or spectroscopic ellipsometry.

In the organic EL device of the present invention, the material for forming the light-emitting layer 6 may be a low-molecular-weight compound or a high-molecular-weight compound, or a mixture thereof.

Examples of the polymer material forming the light-emitting layer 6 include polyacetylene-based compounds such as trans-polyacetylene, cis-polyacetylene, poly(di-phenylacetylene) (PDPA), and poly(alkyl, phenylacetylene) (PAPA); Poly(para-phenvinylene) (PPV), poly(2,5-dialkoxy-para-phenylenevinylene) (RO-PPV), cyano-substituted-poly(para-phenvinylene) (CN-PPV), poly( 2-dimethyloctylsilyl-para-phenylene vinylene) (DMOS-PPV), poly(2-methoxy,5-(2'-ethylhexoxy)-para-phenylene vinylene) (MEH-PPV) and other poly-paraphenylene vinylene compounds ; Polythiophene compounds such as poly(3-alkylthiophene) (PAT) and poly(oxypropylene) triol (POPT); poly(9,9-dialkylfluorene) (PDAF), poly(dioctylfluorene-alto-benzothiadiazole) (F8BT), α,ω-bis[N,N′-di(methylphenyl)aminophenyl]-poly[9,9-bis(2-ethylhexyl)fluorene-2,7-dyl] (PF2/6am4), Polyfluorene compounds such as poly(9,9-dioctyl-2,7-divinylenefluorenyl-ortho-co(anthracene-9,10-diyl); poly(para-phenylene) (PPP), poly(1 ,5-dialkoxy-para-phenylene) (RO-PPP) and other polyparaphenylene compounds; polycarbazole compounds such as poly(N-vinylcarbazole) (PVK); poly(methylphenylsilane) (PMPS); Polysilane-based compounds such as poly (naphthylphenylsilane) (PNPS) and poly (biphenylylphenylsilane) (PBPS); etc.

Examples of low-molecular-weight materials forming the light-emitting layer 6 include metal complexes functioning as hosts, phosphorescent light-emitting materials, thermally activated delayed fluorescent materials, and the like, which will be described later. More specifically, low-molecular-weight materials forming the light-emitting layer 6 include 8-hydroxyquinoline aluminum (Alq ₃ ), tris(4-methyl-8-quinolinolate) aluminum (III) (Almq ₃ ), 8-hydroxyquinoline zinc (Znq ₂ ), (1,10-phenanthroline)-tris-(4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dionate) europium (III) (Eu(TTA) ₃ (phen)), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphineplatinum (II), various metal complexes; distyrylbenzene (DSB), diaminodistyrylbenzene Benzene compounds such as (DADSB), naphthalene, naphthalene compounds such as Nile Red, phenanthrene compounds such as phenanthrene, chrysene, chrysene compounds such as 6-nitrochrysene, perylene, N,N'-bis(2,5 -Di-t-butylphenyl)-3,4,9,10-perylene-di-carboximide (BPPC) and other perylene compounds, coronene compounds such as coronene, anthracene, bisstyrylanthracene and other anthracene compounds, Pyrene compounds such as pyrene, pyran compounds such as 4-(di-cyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM), acridine compounds such as acridine, stilbene 4,4'-bis[9-dicarbazolyl]-2,2'-biphenyl (CBP), 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl (BCzVBi) and other carbazole compounds, thiophene compounds such as 2,5-dibenzoxazolethiophene, benzoxazole compounds such as benzoxazole, benzimidazole compounds such as benzimidazole, 2,2′-(para-phenylene benzothiazole compounds such as vinylene)-bisbenzothiazole; butadiene compounds such as bistyryl (1,4-diphenyl-1,3-butadiene) and tetraphenylbutadiene; naphthalimide compounds such as naphthalimide; Coumarin compounds, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole, aldazine compounds, 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP), etc. cyclo pentadiene compounds, quinacridone compounds such as quinacridone and quinacridone red; pyridine compounds such as pyrrolopyridine and thiadiazolopyridine; Metal or metal-free phthalocyanine compounds such as spiro compounds, phthalocyanine (H ₂ Pc), and copper phthalocyanine, and boron compound materials described in JP-A-2009-155325 and JP-A-5660371. 1 type(s) or 2 or more types can be used.
Quantum dots and perovskite materials can also be used as the light-emitting layer 6 .

Although the average thickness of the light-emitting layer 6 is not particularly limited, it is preferably 10 to 150 nm, more preferably 20 to 100 nm. The average thickness of the light-emitting layer 6 may be measured with a stylus profilometer, or may be measured at the time of film formation of the light-emitting layer 6 with a crystal oscillator film thickness meter.

As the material for the hole transport layer 7, any compound that can be normally used as a material for the hole transport layer can be used. Or they can be used in combination.
Examples of p-type polymer materials (organic polymers) include polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly(N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, Polyalkylthiophene, polyhexylthiophene, poly(p-phenylene vinylene), polytinylene vinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin or derivatives thereof, and the like.
These compounds can also be used as mixtures with other compounds. As an example, mixtures containing polythiophenes include poly(3,4-ethylenedioxythiophene/styrenesulfonic acid) (PEDOT/PSS) and the like.

Examples of the p-type low molecular weight materials include 1,1-bis(4-di-para-triaminophenyl)cyclohexane, 1,1′-bis(4-di-para-tolylaminophenyl)-4- Arylcycloalkane compounds such as phenyl-cyclohexane, 4,4′,4″-trimethyltriphenylamine, N,N,N′,N′-tetraphenyl-1,1′-biphenyl-4,4′-diamine , N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD1), N,N′-diphenyl-N,N′- Bis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD2), N,N,N',N'-tetrakis(4-methoxyphenyl)-1,1'-biphenyl- 4,4'-diamine (TPD3), N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD), TPTE, etc. arylamine compounds, N,N,N',N'-tetraphenyl-para-phenylenediamine, N,N,N',N'-tetra(para-tolyl)-para-phenylenediamine, N,N, Phenylenediamine compounds such as N',N'-tetra(meta-tolyl)-meta-phenylenediamine (PDA), carbazole compounds such as carbazole, N-isopropylcarbazole, N-phenylcarbazole, stilbene, 4-di- Stilbene compounds such as para-tolylaminostilbene, oxazole compounds such as OxZ, triphenylmethane, 4,4′,4″-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m- MTDATA) and other triphenylmethane-based compounds, 1-phenyl-3-(para-dimethylaminophenyl)pyrazoline and other pyrazoline-based compounds, benzene (cyclohexadiene)-based compounds, triazole-based compounds such as triazole, imidazole-based compounds such as imidazole compounds, oxadiazole compounds such as 1,3,4-oxadiazole, 2,5-di(4-dimethylaminophenyl)-1,3,4-oxadiazole, anthracene, 9-(4-diethylamino anthracene compounds such as styryl)anthracene; Lenone compounds, aniline compounds such as polyaniline, silane compounds, pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo-(3,4-c)pyrrolopyrrole, fluorene compounds such as fluorene compounds, porphyrins, porphyrin compounds such as metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, metal or metal-free phthalocyanine compounds such as phthalocyanine, copper phthalocyanine, tetra(t-butyl) copper phthalocyanine, iron phthalocyanine, copper sodium Metal or metal-free naphthalocyanine compounds such as phthalocyanine, vanadyl naphthalocyanine, monochlorogallium naphthalocyanine, N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine, N,N,N Examples include benzidine compounds such as ',N'-tetraphenylbenzidine, and the like, and one or more of these can be used.
Among these, arylamine compounds such as α-NPD and TPTE are preferred.

When the organic EL device of the present invention has the hole transport layer 7 as an independent layer, the average thickness of the hole transport layer 7 is not particularly limited, but is preferably 10 to 150 nm, more preferably 40 to 100 nm. is more preferred. The average thickness of the hole transport layer 7 can be measured by a crystal oscillator film thickness meter in the case of a low-molecular-weight compound, and by a contact-type profilometer in the case of a high-molecular-weight compound.

The hole injection layer 8 is not particularly limited, but one or more of metal oxides such as vanadium oxide ( _V2O5 ), molybdenum oxide ( _MoO3 ), ruthenium oxide _{( RuO2} ), etc. may be used. can be done. Among these, it is preferable to use vanadium oxide or molybdenum oxide as the main component. When the hole injection layer 8 contains vanadium oxide or molybdenum oxide as a main component, the hole injection layer 8 injects holes from the anode 9 and transports them to the light emitting layer 6 or the hole transport layer 7. function as a better one. In addition, since vanadium oxide or molybdenum oxide itself has a high hole-transporting property, it is possible to suitably prevent the efficiency of hole injection from the anode 9 to the light-emitting layer 6 or the hole-transporting layer 7 from decreasing. The hole injection layer 8 is more preferably made of vanadium oxide and/or molybdenum oxide.

Further, as the hole injection layer 8, 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-, which is an acceptor material capable of promoting hole injection, Hexacarbonitrile (HAT-CN), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), hexafluorotetracyanonaphthoquinodimethane (F6-TNAP) etc. can also be used.

Although the average thickness of the hole injection layer 8 is not particularly limited, it is preferably 1 to 1000 nm, more preferably 5 to 50 nm. Incidentally, the average thickness of the hole injection layer 8 can be measured by a crystal oscillator film thickness meter at the time of film formation.

In the organic EL device of the present invention, the method for forming all the layers is not particularly limited, and chemical vapor deposition (CVD) such as plasma CVD, thermal CVD, and laser CVD, which are vapor deposition methods, vacuum deposition, and sputtering. , dry plating methods such as ion plating, thermal spraying methods, and wet plating methods such as electrolytic plating, immersion plating, and electroless plating, which are liquid phase deposition methods, sol-gel methods, MOD methods, spray pyrolysis methods, fine particles A doctor blade method using a dispersion liquid, a spin coating method, an inkjet method, a printing technique such as a screen printing method, or the like can be used, and an appropriate method can be selected and used according to the material.
These methods are preferably selected according to the characteristics of the material of each layer, and the manufacturing method may be different for each layer.

In the organic EL device of the present invention, the color of emitted light can be changed by appropriately selecting the material of the light emitting layer 6, and a desired color of emitted light can be obtained by using a color filter or the like in combination. Therefore, the organic EL element of the present invention can be suitably used for display devices and lighting devices.

<Display device>
A display device of the present invention is characterized by comprising the organic electroluminescence element described above. Since the display device of the present invention includes the above-described organic EL element with low driving voltage and excellent luminous efficiency, the driving voltage is low and luminous efficiency is excellent. The display device of the present invention can comprise, in addition to the organic electroluminescent elements described above, other components commonly used in display devices.

<Lighting device>
A lighting device of the present invention is characterized by comprising the organic electroluminescence element described above. Since the lighting device of the present invention includes the above-described organic EL element with low driving voltage and excellent luminous efficiency, it has a low driving voltage and excellent luminous efficiency. The lighting device of the present invention can comprise, in addition to the organic electroluminescent elements described above, other components commonly used in lighting devices.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, "part" means "mass part" and "%" means "mass %".

<Measurement method of NMR>
AL400 manufactured by JEOL was used. The spectrometer is an AL-Series spectrometer, and the probe is a TH5ATFG2 probe. Also, the solvent is _CDCl3 .

<Synthesis of compound having triazine structure>
A 200 mL reactor was charged with a compound represented by the following formula (13) (4.0 g, 13.2 mmol, 1.0 eq.) and dehydrated diethyl ether (Et ₂ O, 40 mL). This solution was cooled to −78° C., CH ₃ Li (1.12 mol/L Et ₂ O solution) (35.4 mL, 39.7 mmol, 3.0 eq.) was added dropwise over about 5 minutes, and then After stirring for 0.5 hour at , the cooling bath was removed and the temperature was raised to room temperature. The resulting brown suspension was quenched with 5% aqueous ammonium chloride solution (100 mL), diethyl ether (100 mL) was added and the mixture was separated into two layers. The aqueous layer was extracted with diethyl ether (30 mL), and the organic layers were combined, washed successively with city water and saturated brine, dried over anhydrous sodium sulfate, and concentrated to give a beige solid (4.68 g). rice field. This was column-purified (SiO ₂ =120 g, hexane/toluene=1/1→1/2→toluene only) to obtain a colorless solid ketone body represented by the following formula (14′) (1.41 g, 4 .92 mmol, 37%) and the target alcohol represented by the following formula (14) (2.38 g, 8.37 mmol, 63%) were obtained. A reaction scheme is shown below.

The alcohol (2.3 g, 8.09 mmol, 1.0 eq.) represented by the above formula (14) and 70% polyphosphoric acid (PPA, 92 g) were added to a 200 mL reactor, and the temperature was raised to 130°C. After stirring at the same temperature for 30 minutes, the temperature was raised to 150° C., and the mixture was vigorously stirred for an additional 15 minutes. The resulting light brown solution was quenched with ice water (100 mL), extracted with ethyl acetate (100 mL), washed successively with 5% aqueous sodium bicarbonate, city water and saturated brine, dried and concentrated to give a brown liquid. (2.56 g) was obtained. This was column-purified (SiO ₂ =80 g, hexane/toluene=10/1) to obtain a colorless solid compound represented by the following formula (15) (2.17 g, 7.63 mmol, 94%). A reaction scheme is shown below.

A 100 mL reactor was charged with the compound represented by the above formula (15) (1.35 g, 4.75 mmol, 1.0 eq.) and anhydrous diethyl ether (Et ₂ O, 15 mL) and cooled to about -50°C. . t-BuLi (1.64 mol / L pentane solution) (4.34 mL, 7.12 mmol, 1.5 eq.) was added dropwise to this solution over about 3 minutes, and the temperature was slowly increased from the same temperature to -15 ° C. over 30 minutes. After warming to −78° C., the resulting pale yellow solution was treated with (iPrO) ₃ B (1.35 g, 13.0 mmol, 3.0 eq.) diluted in anhydrous diethyl ether (2 mL). added. After stirring at the same temperature for 15 minutes, the cooling bath was removed and the temperature was raised to room temperature. 0.5N Hydrochloric acid (10 mL) was added to this solution, and after stirring for 10 minutes, the mixture was extracted with ethyl acetate (20 mL), washed with city water and brine (50 mL x 3) in that order, dried over anhydrous sodium sulfate, Concentration gave a light brown viscous liquid (1.56 g). This was column-purified (SiO ₂ =60 g, hexane/ethyl acetate=3/1→2/1→1/1) to recover the compound (0.39 g) represented by the above formula (15) as a raw material, A mixture (0.39 g) containing a compound represented by the following formula (16) and a compound (0.73 g) represented by the following formula (16) were obtained. A reaction scheme is shown below.

A mixture containing the compound represented by the above formula (16) (0.39 g, 1.18 mmol, 1.0 eq.) and 1,2-dibromobenzene (1.4 g, 5.94 mmol, 5.0 eq.) were placed in a 50 mL reactor. 0 eq.), Pd(dppf) _Cl2 (43 mg, 0.0594 mmol, 0.05 eq.), sodium carbonate (0.38 g, 3.56 mmol, 3.0 eq.), degassed toluene (4 mL), degassed water. (4 mL) and degassed ethanol (2 mL) were added, and the mixture was heated and stirred at a bath temperature of 95° C. for 3 hours. To the resulting suspension, 5% aqueous ammonium chloride (4 mL) and toluene (4 mL) were added and stirred, the precipitated solid was filtered, the filtrate was divided into two layers, and the organic layer was concentrated to give a brown liquid. Liquid (i) (2.1 g) was obtained.

On the other hand, in a 100 mL reactor, the compound represented by the above formula (16) (0.73 g, 2.22 mmol, 1.0 eq.), 1,2-dibromobenzene (2.62 g, 11.1 mmol, 5.0 eq.) .), Pd(dppf) _Cl2 (81 mg, 0.111 mmol, 0.05 eq.), sodium carbonate (0.706 g, 6.66 mmol, 3.0 eq.), degassed toluene (7 mL), degassed water ( 7 mL) and degassed ethanol (3 mL) were added, and the mixture was heated with stirring at a bath temperature of 95° C. for 4 hours. To the resulting suspension, 5% aqueous ammonium chloride (10 mL) and toluene (10 mL) were added and stirred, the precipitated solid was filtered, the filtrate was separated into two layers, and the organic layer was washed with city water and saturated brine. , dried over anhydrous magnesium sulfate and concentrated to give a brown liquid (ii) (3.55 g). The obtained liquid (ii) was combined with the liquid (i) obtained above and subjected to column purification (SiO ₂ =60 g, hexane/toluene=5/1) to obtain a colorless solid of the following formula ( A compound represented by 17) (1.06 g, 2.41 mmol, 70%) was obtained. A reaction scheme is shown below.

A 100 mL reactor was charged with the compound represented by the above formula (17) (1.0 g, 2.27 mmol, 1.0 eq.) and THF (10 mL) and cooled to -78°C. To this solution, n-BuLi (1.55 mol/L hexane solution) (1.76 mL, 2.73 mmol, 1.2 eq.) was added dropwise over about 5 minutes, and stirred at the same temperature for 0.5 hours. (iPrO)Bpin (0.55 g, 2.97 mmol, 1.3 eq.) was added to the resulting pale yellow solution. After stirring at the same temperature for 30 minutes, the cooling bath was removed, the temperature was raised to room temperature, and the mixture was stirred for 3 hours. After adding a 5% aqueous ammonium chloride solution (60 mL) to this solution, it was extracted with ethyl acetate (40 mL), washed with city water and brine in that order, dried over anhydrous sodium sulfate, and concentrated to give a dark brown sticky residue. A liquid (1.42 g) was obtained. This was column-purified (SiO ₂ =50 g, heptane/toluene=2/1→1/1) to obtain a colorless amorphous compound represented by the following formula (18) (0.76 g, 1.56 mmol, 68% ). A reaction scheme is shown below.

A 100 mL reactor was charged with the compound represented by the above formula (18) (0.58 g, 1.19 mmol, 1.0 eq.), 2-chloro-4,6-diphenyl-1,3,5-triazine (0.58 g, 1.19 mmol, 1.0 eq.). 638 g, 2.38 mmol, 2.0 eq.), Pd(dppf) _Cl2 (26 mg, 0.0357 mmol, 0.03 eq.), sodium carbonate (0.378 g, 3.57 mmol, 3.0 eq.), toluene ( 6 mL), distilled water (6 mL) and ethanol (3 mL) were added. The resulting suspension was heated to a bath temperature of 90° C. and stirred at the same temperature for 18 hours. A 5% ammonium chloride aqueous solution (10 mL) was added to this suspension, ethyl acetate (20 mL) was added, the precipitated solid was separated by filtration, and the filtrate was separated into two layers. The aqueous layer was extracted with toluene (10 mL), the organic layers were combined, washed with city water and saturated brine, dried over anhydrous sodium sulfate and concentrated to give a brown liquid (0.95 g). This was column-purified (SiO ₂ =50 g, hexane/toluene=2/1→1/1) to obtain a colorless solid (0.66 g). This was heated and dispersed and washed with acetonitrile (12 mL) and dried at 80° C. under high vacuum. %) was obtained. A ¹ H-NMR spectrum of the product is shown in FIG. Moreover, a reaction scheme is shown below.

<Synthesis of compound having benzothiazole structure>
A compound represented by the above formula (18) was prepared in the same manner as described above. In a 50 mL reactor, the compound represented by the above formula (18) (0.96 g, 1.97 mmol, 1.0 eq.), 5-bromobenzo[c][1,2,5]thiadiazole (0.85 g, 3 .94 mmol, 2.0 eq.), Pd(dppf) _Cl2 (72 mg, 0.0985 mmol, 0.05 eq.), sodium carbonate (0.626 g, 5.91 mmol, 3.0 eq.), toluene (10 mL), Distilled water (10 mL) and ethanol (5 mL) were added. The resulting suspension was heated to a bath temperature of 95° C. and stirred at the same temperature for 24 hours. This suspension was filtered through celite, a 5% aqueous ammonium chloride solution (20 mL) was added to the filtrate, and the mixture was extracted with toluene (20 mL). Dry and concentrate to give a brown viscous liquid (1.69 g). This was column-purified (SiO ₂ =80 g, hexane/toluene=1/1→1/2) to obtain a colorless solid (1.16 g). This solid was suspended in ethanol (15 mL) at a bath temperature of 95° C., washed with heating, filtered, and dried under high vacuum. The compound (0.88 g, 1.78 mmol, 90%) was obtained. A ¹ H-NMR spectrum of the product is shown in FIG. Moreover, a reaction scheme is shown below.

<Production of organic EL element 1>
An organic EL element 1 was manufactured by the method shown below.

[Step 1]
As the substrate 2, a commercially available transparent glass substrate having an average thickness of 0.7 mm and having a patterned electrode (cathode 3) made of ITO and having a thickness of 150 nm was prepared. Then, the substrate 2 having the cathode 3 was subjected to ultrasonic cleaning in acetone and isopropanol, followed by UV ozone cleaning for 20 minutes.

[Step 2]
A zinc oxide (ZnO) layer with an average thickness of 10 nm is formed on the ITO electrode (cathode 3) prepared in [Step 1] by a sputtering method using zinc metal as a target and oxygen as a reaction gas and argon as a carrier gas. formed. After that, it was washed with isopropanol and acetone. Furthermore, this substrate was set on a spin coater, and a 1 mass% magnesium acetate solution (water/ethanol = 1/3) was spin-coated at 1600 rpm for 60 seconds. Annealing was performed for 1 hour. Subsequently, after washing the substrate with water, it was dried at 250.degree.

[Step 3]
Next, an electron injection/transport layer 5 was formed by the method described below.
Note that Example 1, Comparative Example 1, and Comparative Example 2 differ only in the electron injection/transport layer 5, and the other layers are the same. Methods for forming the electron injection/transport layer 5 in Example 1, Comparative Example 1, and Comparative Example 2 are shown below.

(Example 1)
The compound (1% by mass) having a triazine structure represented by the formula (19) synthesized as described above and 1,5-diazabicyclo[4.3.0]nonene represented by the above formula (6-1) -5 (DBN, 2% by mass) was dissolved in cyclopentanone to obtain a mixed solution. Next, the substrate 2 having the cathode 3 and the metal oxide layer 4 formed in the above [Step 2] was placed in a spin coater. Then, while dropping the mixed solution onto the metal oxide layer 4, the substrate 2 was rotated at 3000 rpm for 30 seconds to form a coating film. Annealing treatment was then performed at 120° C. for 2 hours in a nitrogen atmosphere using a hot plate to form an electron injection/transport layer 5 . The average thickness of the obtained electron injection/transport layer 5 was 30 nm.

(Comparative example 1)
The compound (1% by mass) having a benzothiazole structure represented by the formula (20) synthesized as described above and 1,5-diazabicyclo[4.3.0] represented by the above formula (6-1) Nonene-5 (DBN, 2% by mass) was dissolved in cyclopentanone to obtain a mixed solution. Next, the substrate 2 having the cathode 3 and the metal oxide layer 4 formed in the above [Step 2] was placed in a spin coater. Then, while dropping the mixed solution onto the metal oxide layer 4, the substrate 2 was rotated at 3000 rpm for 30 seconds to form a coating film. Annealing treatment was then performed at 120° C. for 2 hours in a nitrogen atmosphere using a hot plate to form an electron injection/transport layer 5 . The average thickness of the obtained electron injection/transport layer 5 was 30 nm.

で表わされる化合物［２’－（４，６－ジフェニル－１，３，５－トリアジン－２－イル）－Ｎ，Ｎ－ジフェニルビフェニル－２－アミン、Ｌｕｍｉｎｅｓｃｅｎｃｅ Ｔｅｃｈｎｏｌｏｇｙ Ｃｏｒｐ．製、ＬＴ－Ｎ５５５ ＰＡ－ｏｒｔ－２Ｐｈ－ＴＲＺ］（１質量％）と、上記式（６－１）で表わされる１，５－ジアザビシクロ［４．３．０］ノネン－５（ＤＢＮ、２質量％）をシクロペンタノンに溶解し、混合溶液を得た。次に、前記［工程２］で作製した陰極３および金属酸化物層４の形成されている基板２をスピンコーターに設置した。そして、混合溶液を金属酸化物層４上に滴下しながら、基板２を毎分３０００回転で３０秒間回転させて塗膜を形成した。その後、ホットプレートを用いて窒素雰囲気下で１２０℃、２時間のアニール処理を施し、電子注入・輸送層５を形成した。得られた電子注入・輸送層５の平均厚さは３０ｎｍであった。 (Comparative example 2)
Formula (21) below:

A compound represented by [2′-(4,6-diphenyl-1,3,5-triazin-2-yl)-N,N-diphenylbiphenyl-2-amine, Luminescence Technology Corp. manufactured by LT-N555 PA-ort-2Ph-TRZ] (1% by mass) and 1,5-diazabicyclo[4.3.0]nonene-5 (DBN, 2 mass%) represented by the above formula (6-1) %) was dissolved in cyclopentanone to obtain a mixed solution. Next, the substrate 2 formed with the cathode 3 and the metal oxide layer 4 prepared in the above [Step 2] was placed in a spin coater. Then, while dropping the mixed solution onto the metal oxide layer 4, the substrate 2 was rotated at 3000 rpm for 30 seconds to form a coating film. Annealing treatment was then performed at 120° C. for 2 hours in a nitrogen atmosphere using a hot plate to form an electron injection/transport layer 5 . The average thickness of the obtained electron injection/transport layer 5 was 30 nm.

[Step 4]
Next, the substrate 2 on which the layers up to the electron injection/transport layer 5 were formed was fixed to a substrate holder of a vacuum vapor deposition apparatus.
Further, bis[2-(2-benzothiazolyl)phenolato]zinc(II) (Zn(BTZ) ₂ ) represented by the following formula (22),
tris[1-phenylisoquinoline]iridium (III) (Ir(piq) ₃ ) represented by the following formula (23);
N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) represented by the following formula (24);
N4,N4'-bis(dibenzo[b,d]thiophen-4-yl)-N4,N4'-diphenylbiphenyl-4,4'-diamine (DBTPB) represented by the following formula (25);
Al and Al were placed in alumina crucibles, respectively, and set to the vapor deposition source.

Then, the pressure in the vacuum deposition apparatus is reduced to about 1×10 ⁻⁵ Pa, and Zn(BTZ) ₂ as a host and Ir(piq) ₃ as a dopant are co-evaporated to a thickness of 20 nm to form a light-emitting layer 6 . did. At this time, the doping concentration was such that Ir(piq) ₃ was 6 mass % with respect to the entire light emitting layer 6 .
Next, on the substrate 2 formed up to the light-emitting layer 6, a hole-transporting layer 7 was formed by vapor-depositing DBTPB and α-NPD to a thickness of 10 nm and 30 nm, respectively.
Further, a film of molybdenum trioxide MoO ₃ was vacuum deposited to form a hole injection layer 8 with a thickness of 10 nm.

[Step 5]
Next, on the substrate 2 formed up to the hole injection layer 8, aluminum (anode 9) was evaporated to a thickness of 100 nm to obtain an organic EL device.

(Measurement of emission characteristics of organic EL element)
A voltage was applied to all the devices using a Keithley Model 2400 Source Meter, and luminance was measured using a Konica Minolta LS-100. After that, it was continuously driven with an initial luminance of 1000 cd/m ² and the change in luminance with respect to the elapsed time was examined.

(Importance of a layer composed of a compound having a triazine structure in a reverse structure organic EL device)
FIG. 4A shows luminance-voltage characteristics of Example 1, Comparative Examples 1 and 2. FIG.
The main difference between the molecular structure of the compound having a triazine structure represented by formula (19) and the molecular structure of the compound having a benzothiazole structure represented by formula (20) is that the electron transport moiety is a triazine structure or The difference is that they have a benzothiazole structure, and this difference appears in the device characteristics. That is, Example 1 in which the electron injection/transport layer 5 is made of a compound having a triazine structure can be driven at a low voltage, whereas Comparative Example 1 has a high driving voltage.
Furthermore, a large difference was observed between Example 1 and Comparative Example 1 in the external quantum efficiency shown in FIG. In Example 1, a maximum external quantum efficiency of about 15% is obtained, whereas in Comparative Example 1 the luminous efficiency is extremely low. From this, it can be said that a compound having a triazine structure is extremely effective for electron injection/transport.

(Importance of substituents combined with triazine structure)
The main difference between the molecular structure of the compound represented by formula (19) and the molecular structure of the compound represented by formula (21) is the substituents combined with the triazine structure. Compared to Example 1, Comparative Example 2 using the compound represented by formula (21) has a higher driving voltage and a lower luminous efficiency. A possible reason for this is that the compound represented by the formula (21) has a smaller ionization energy than the compound represented by the formula (19). Table 1 shows the ionization energy and electron affinity of each material.

The compound represented by the formula (21) has a triphenylamine skeleton that is excellent in electron-donating properties, and the energy of the highest occupied orbital localized in this triphenylamine skeleton is reduced, so that the element blocks holes. diminished sexuality. Presumably, this caused the holes that reached the electron injection/transport layer 5 to flow into the cathode side, resulting in a decrease in luminous efficiency.
On the other hand, the compound represented by Formula (19) combines a weakly electron-donating substituent with a triazine structure, and has high ionization energy. It is believed that this high ionization energy leads to efficient hole blocking in the device, resulting in high luminous efficiency. Therefore, it can be seen that a substituent with weak electron-donating properties, such as the compound represented by formula (19), is suitable for combination with the triazine structure.
From these results, it was found that the material used for the electron injection/transport layer 5 in the reverse structure organic EL device shown in FIG. I know there is.

1: Organic EL (Electroluminescence) Element 2: Substrate 3: Cathode 4: Metal Oxide Layer 5: Electron Injection/Transport Layer 6: Light Emitting Layer 7: Hole Transport Layer 8: Hole Injection Layer 9: Anode

Claims (6)

An organic electroluminescence element in which a cathode, a light-emitting layer and an anode are provided in this order on a substrate,
Between the cathode and the light-emitting layer, the following formulas (3-1) to (3-7) and (3-10) :

An organic electroluminescence device characterized by having a layer made of a compound having a triazine structure represented by any one of: 2. The organic electroluminescence device according to claim 1, wherein said layer comprising a compound having a triazine structure contains a reducing agent. 2. The organic electroluminescence device according to claim 1, wherein said layer comprising a compound having a triazine structure contains a basic compound having an acid dissociation constant pKa of 1 or more. 4. The organic electroluminescence device according to claim 1, further comprising an electron injection layer made of a metal oxide between said cathode and said light emitting layer. A display device comprising the organic electroluminescence element according to any one of claims 1 to 4 . A lighting device comprising the organic electroluminescence device according to any one of claims 1 to 4 .

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