WO2014024447A1

WO2014024447A1 - Compound having triphenylene ring structure, and organic electroluminescent element

Info

Publication number: WO2014024447A1
Application number: PCT/JP2013/004684
Authority: WO
Inventors: 安達　千波矢; 和法富樫
Original assignee: 保土谷化学工業株式会社; 国立大学法人九州大学
Priority date: 2012-08-08
Filing date: 2013-08-02
Publication date: 2014-02-13
Also published as: JP2015214491A; TW201412718A

Abstract

Provided is a material for use in a high-efficiency organic electroluminescent element, namely a light-emitting-layer host compound that has a high excited-triplet level and is capable of completely sealing in triplet excitons from a phosphorescent light-emitting body. Said compound has a triphenylene ring structure represented by general formula (1). Also provided is a high-efficiency, high-luminance organic electroluminescent element using said compound. Said organic electroluminescent element, which has a pair of electrodes and one or more organic layers sandwiched therebetween, is characterized in that the aforementioned compound is used as a constituent material for at least one organic layer.

Description

Compound having triphenylene ring structure and organic electroluminescence device

The present invention relates to a compound suitable for an organic electroluminescence element which is a self-luminous element suitable for various display devices and the element, and more specifically, a compound having a triphenylene ring structure, and an organic electroluminescence using the compound. It relates to an element.

Since organic electroluminescence elements are self-luminous elements, they have been actively researched because they are brighter and more visible than liquid crystal elements and can display clearly.

In recent years, as an attempt to increase the luminous efficiency of an element, an element that generates phosphorescence using a phosphorescent material, that is, uses light emission from a triplet excited state has been developed. According to the theory of the excited state, when phosphorescent light emission is used, a remarkable improvement in light emission efficiency is expected in that light emission efficiency about four times that of conventional fluorescent light emission becomes possible.
In 1993, M.P. A. Baldo et al. Achieved an external quantum efficiency of 8% with a phosphorescent device using an iridium complex.
An element utilizing light emission by thermally activated delayed fluorescence (TADF) has also been developed. In 2011, Adachi et al. Of Kyushu University realized an external quantum efficiency of 5.3% with a device using a thermally activated delayed fluorescent material (see, for example, Non-Patent Document 1).

Since the phosphorescent material causes concentration quenching, it is supported by doping a charge transporting compound generally called a host compound. The supported phosphorescent emitter is called a guest compound. As this host compound, 4,4′-di (N-carbazolyl) biphenyl (hereinafter abbreviated as CBP) represented by the following formula has been generally used (see, for example, Non-Patent Document 2).

However, it has been pointed out that CBP has a low glass transition point (Tg) as low as 62 ° C. and strong crystallinity, so that it has poor stability in a thin film state. Therefore, satisfactory device characteristics have not been obtained in scenes where heat resistance is required, such as high luminance light emission.

As research on phosphorescent devices progresses, the elucidation of the energy transfer process between phosphorescent emitters and host compounds advances, and in order to increase luminous efficiency, the excited triplet level of the host compound is higher than the excited triplet level of the phosphorescent emitter. It has become clear that it must be high.

When FIrpic, which is a blue phosphorescent light emitting material represented by the following formula, is doped into the CBP to form a host compound of the light emitting layer, the external quantum efficiency of the phosphorescent light emitting element remains at about 6%. This is because the excited triplet level of FIrpic is 2.67 eV, whereas the excited triplet level of CBP is as low as 2.57 eV, so that confinement of triplet excitons by FIrpic is insufficient with CBP. It was considered. This is demonstrated by the fact that the photoluminescence intensity of a thin film in which FIrpic is doped into CBP shows temperature dependence (see, for example, Non-Patent Document 3).

As a host compound having a higher triplet level of excitation than CBP, 1,3-bis (carbazol-9-yl) benzene (hereinafter abbreviated as mCP) shown below is known. Since the point (Tg) is as low as 55 ° C. and the crystallinity is strong, the stability in the thin film state is poor. Therefore, satisfactory element characteristics have not been obtained in scenes where heat resistance is required, such as high-luminance light emission (see Non-Patent Document 3, for example).

In addition, it has been found that when a host compound having a higher excited triplet level is studied, when an iridium complex is doped into an electron transporting or bipolar transporting host compound, high luminous efficiency can be obtained (for example, Non-Patent Document 4).

Thus, in order to increase the luminous efficiency of a phosphorescent light emitting device in a practical situation, a host compound of a light emitting layer having a high excitation triplet level and high thin film stability has been required.

An object of the present invention is to provide a host compound of a light emitting layer having a high excited triplet level and capable of completely confining triplet excitons of a phosphorescent emitter as a material for a highly efficient organic electroluminescence device. Furthermore, another object of the present invention is to provide a high-efficiency, high-brightness organic electroluminescence device using this compound. The physical properties that the organic compound to be provided by the present invention should have include (1) high excitation triplet level, (2) bipolar transportability, and (3) stable thin film state. I can give you. In addition, physical properties to be provided by the organic electroluminescence device to be provided by the present invention include (1) high luminous efficiency and (2) low practical driving voltage.

Therefore, in order to achieve the above object, the present inventors designed a compound using the energy level as an index, paying attention to the possibility that the triphenylene ring, dibenzofuran ring and dibenzothiophene ring have a high excited triplet level. Thus, the energy level of the compound was confirmed by actually synthesizing and actually measuring the work function, and a compound having a novel triphenylene ring structure having characteristics suitable for a phosphorescent light emitting device was found. Then, various organic electroluminescence devices were prototyped using the compound, and the characteristics of the devices were evaluated. As a result, the present invention was completed.

1) That is, the present invention is a compound having a triphenylene ring structure represented by the general formula (1).

(1)

(Wherein R ₁ to R ₆ may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent) 1 to 6 linear or branched alkyl groups, substituted or unsubstituted aromatic hydrocarbon groups, substituted or unsubstituted aromatic heterocyclic groups or substituted or unsubstituted condensed polycyclic aromatic groups, A ₁ to A ₆ may be the same or different and each represents a substituted or unsubstituted aromatic heterocyclic group.

2) Moreover, this invention is a compound which has the triphenylene ring structure of the said 1) description represented by the following general formula (1 ').

(1 ')

3) According to the present invention, in the general formula (1), A 1 _~ A ₆ are represented by a monovalent group represented by the following structural formula (B), being a compound having a triphenylene ring structure of the above 1), wherein .

(B)

(Wherein R ₇ to R ₁₁ may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or an optionally substituted carbon atom) 1 to 6 linear or branched alkyl group, optionally substituted linear or branched alkenyl group having 2 to 6 carbon atoms, substituted or unsubstituted aromatic hydrocarbon group , A substituted or unsubstituted aromatic heterocyclic group or a substituted or unsubstituted condensed polycyclic aromatic group, V, W, X, Y, Z represents a carbon atom or a nitrogen atom, and V, W, X, (It is assumed that one to three of Y and Z are nitrogen atoms, and the nitrogen atom in this case does not have a substituent of R ₇ to R _11. )

4) Moreover, this invention is a compound which has a triphenylene ring structure of said 3) description in which any one of V, W, X, Y, and Z is a nitrogen atom in the said structural formula (B).

5) Moreover, this invention is a compound which has a triphenylene ring structure of said 3) description in which any two of V, W, X, Y, and Z are nitrogen atoms in the said structural formula (B).

6) Moreover, this invention is a compound which has a triphenylene ring structure of said 3) description in which any three of V, W, X, Y, and Z are nitrogen atoms in the said structural formula (B).

7) In the organic electroluminescence device having a pair of electrodes and at least one organic layer sandwiched therebetween, at least one of the organic layers has a triphenylene ring structure represented by the general formula (1). It is an organic electroluminescent element containing the compound which has.

8) Further, according to the present invention, the organic layer described above is a hole blocking layer, and the compound having a triphenylene ring structure represented by the general formula (1) includes at least one constituent material in the hole blocking layer. The organic electroluminescence device according to 7) above, wherein the organic electroluminescence device is used.

9) In the present invention, the organic layer described above is a light emitting layer, and the compound having a triphenylene ring structure represented by the general formula (1) is used as at least one constituent material in the light emitting layer. 7) The organic electroluminescence device as described in 7) above.

10) Further, the present invention is characterized in that the organic layer described above is a light emitting layer, and a compound having a triphenylene ring structure represented by the general formula (1) is used as a host material of the light emitting layer. The organic electroluminescent device according to 9) above.

11) Further, the present invention provides an organic electroluminescent device having a light emitting layer containing a phosphorescent light emitting material and at least one organic layer sandwiched between a pair of electrodes and represented by the general formula (1). The organic electroluminescent device according to 7) above, wherein the compound having a triphenylene ring structure is used as at least one constituent material in the light emitting layer.

12) Moreover, this invention is an organic electroluminescent element of said 11) description whose said phosphorescent luminescent material is a metal complex containing iridium or platinum.

13) Moreover, this invention is an organic electroluminescent element of said 11) description whose above-mentioned phosphorescent luminescent material is a green luminescent material.

As the “aromatic heterocyclic group” in the “substituted or unsubstituted aromatic heterocyclic group” represented by A ₁ to A ₆ in the general formula (1) and general formula (1 ′), specifically, Pyridyl group, bipyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, furyl group, pyrrolyl group, thienyl group, imidazolyl group, pyrazolyl group, oxazolyl group, thiazolyl group, isothiazolyl group, isoxazolyl group, quinolyl group, isoquinolyl group Quinoxalyl group, pteridinyl group, benzofuranyl group, benzothienyl group, indolyl group, isoindolyl group, benzoimidazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalyl group, carbazolyl group, pyrazolyl group, pyridoindolyl group, dibenzofuranyl group , Dibenzothienyl group, naphthylidini And a group such as an alkyl group, a phenanthrolinyl group, an acridinyl group, and a xanthenyl group.
A ₁ to A _{6 in the} general formula (1) and general formula (1 ′) are pyridyl group, bipyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, oxazolyl group. Group, thiazolyl group, isothiazolyl group, isoxazolyl group, quinolyl group, isoquinolyl group, quinoxalyl group, pteridinyl group, indolyl group, isoindolyl group, benzoimidazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalyl group, carbazolyl group, pyrazolyl group, Nitrogen-containing aromatic heterocyclic groups such as a pyridoindolyl group, a naphthyridinyl group, a phenanthrolinyl group, and an acridinyl group are preferable, and a monovalent group represented by the structural formula (B) is more preferable. Pyrimidinyl and triazinyl groups are Particularly preferred.

Specific examples of the “substituent” in the “substituted aromatic heterocyclic group” represented by A ₁ to A ₆ in the general formula (1) and general formula (1 ′) include a deuterium atom and a fluorine atom. , Chlorine atom, cyano group, trifluoromethyl group, nitro group, linear or branched alkyl group having 1 to 6 carbon atoms, cyclopentyl group, cyclohexyl group, linear or branched group having 1 to 6 carbon atoms Alkyloxy group, dialkylamino group substituted by linear or branched alkyl group having 1 to 6 carbon atoms, phenyl group, biphenylyl group, terphenylyl group, tetrakisphenyl group, styryl group, naphthyl group, fluorenyl Group, phenanthryl group, indenyl group, pyrenyl group, pyridyl group, bipyridyl group, triazyl group, pyrimidyl group, quinolyl group, isoquinolyl group, And a group such as a quindolyl group, a pyridoindolyl group, a carbazolyl group, a quinoxalyl group, and a pyrazolyl group. These substituents may be further substituted by the above-exemplified substituents.
The “substituent” in the “substituted aromatic heterocyclic group” represented by A ₁ to A ₆ in the general formula (1) or general formula (1 ′) is the nitrogen-containing aromatic heterocyclic group exemplified above. Is preferred.

“The linear or optionally having 1 to 6 carbon atoms which may have a substituent represented by R ₁ to R ₁₁ in the general formula (1), the general formula (1 ′) and the structural formula (B)” As the “alkyl group” in the “branched alkyl group”, specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, Examples thereof include an isopentyl group, a neopentyl group, and an n-hexyl group.

“A linear or branched alkyl group having 1 to 6 carbon atoms having a substituent, represented by R ₁ to R ₁₁ in the general formula (1), the general formula (1 ′) and the structural formula (B)” As the “substituent” in the above, specifically, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, a nitro group, a cyclopentyl group, a cyclohexyl group, a straight chain having 1 to 6 carbon atoms Or a branched alkyloxy group, a dialkylamino group substituted with a linear or branched alkyl group having 1 to 6 carbon atoms, phenyl group, biphenylyl group, terphenylyl group, tetrakisphenyl group, styryl group, naphthyl group Fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, pyridyl group, bipyridyl group, triazyl group, pyrimidyl group, quinolyl group, isoquinol group Examples include a group such as a noryl group, an indolyl group, a pyridoindolyl group, a carbazolyl group, a quinoxalyl group, and a pyrazolyl group, and these substituents may be further substituted by the above-exemplified substituents. The substituents may be bonded to each other to form a ring.

“Substituted or unsubstituted aromatic hydrocarbon group” or “substituted or unsubstituted aromatic” represented by R ₁ to R ₁₁ in the general formula (1), general formula (1 ′) and structural formula (B) As the “aromatic hydrocarbon group”, “aromatic heterocyclic group” or “fused polycyclic aromatic group” in the “aromatic heterocyclic group” or “substituted or unsubstituted condensed polycyclic aromatic group”, specifically, Phenyl, biphenylyl, terphenylyl, tetrakisphenyl, styryl, naphthyl, anthryl, acenaphthenyl, fluorenyl, phenanthryl, indenyl, pyrenyl, pyridyl, bipyridyl, triazyl, pyrimidyl, furyl Group, pyrrolyl group, thienyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, benzoo group Examples thereof include xazolyl group, benzothiazolyl group, quinoxalyl group, benzimidazolyl group, pyrazolyl group, pyridoindolyl group, dibenzofuranyl group, dibenzothienyl group, naphthyridinyl group, phenanthrolinyl group and acridinyl group.

“Substituted aromatic hydrocarbon group”, “substituted aromatic heterocyclic group” or “substituted” represented by R ₁ to R ₁₁ in formula (1), formula (1 ′) and structural formula (B) Specific examples of the “substituent” in the “condensed polycyclic aromatic group” include a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, a nitro group, and a straight chain having 1 to 6 carbon atoms. Or substituted with a branched alkyl group, a cyclopentyl group, a cyclohexyl group, a linear or branched alkyloxy group having 1 to 6 carbon atoms, or a linear or branched alkyl group having 1 to 6 carbon atoms Dialkylamino, phenyl, biphenylyl, terphenylyl, tetrakisphenyl, styryl, naphthyl, fluorenyl, phenanthryl, indenyl, pyrenyl, pyridyl Group, bipyridyl group, triazyl group, pyrimidyl group, quinolyl group, isoquinolyl group, indolyl group, pyridoindolyl group, carbazolyl group, quinoxalyl group, pyrazolyl group, and these substituents can be further The substituents exemplified above may be substituted.

As the “alkenyl group” in the “linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent” represented by R ₇ to R ₁₁ in the structural formula (B), Specific examples include vinyl group, allyl group, isopropenyl group, 2-butenyl group, isobutenyl group, 2-pentenyl group, isopentenyl group, 2-hexenyl group, 4-methyl-3-pentenyl group, and the like. And adjacent groups may be bonded to each other to form a ring.

As the “substituent” in the “straight-chain or branched alkenyl group having 2 to 6 carbon atoms having a substituent” represented by R ₇ to R ₁₁ in the structural formula (B), specifically, Deuterium atom, fluorine atom, chlorine atom, cyano group, trifluoromethyl group, nitro group, linear or branched alkyl group having 1 to 6 carbon atoms, cyclopentyl group, cyclohexyl group, 1 to 6 carbon atoms A linear or branched alkyloxy group, a dialkylamino group substituted with a linear or branched alkyl group having 1 to 6 carbon atoms, phenyl group, biphenylyl group, terphenylyl group, tetrakisphenyl group, styryl Group, naphthyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, pyridyl group, bipyridyl group, triazyl group, pyrimidyl group , Quinolyl group, isoquinolyl group, indolyl group, pyridoindolyl group, carbazolyl group, quinoxalyl group, pyrazolyl group, and the like. These substituents may be bonded to each other to form a ring.

The compound having a triphenylene ring structure represented by the general formula (1) or the general formula (1 ′) of the present invention is a novel compound, has an energy level suitable as a host compound of the light emitting layer, and has a triplet. Has excellent ability to confine excitons.

The compound having a triphenylene ring structure represented by the general formula (1) or general formula (1 ′) of the present invention is a light-emitting layer or a hole blocking layer of an organic electroluminescence element (hereinafter abbreviated as an organic EL element). It can be used as a constituent material of the layer. By using the compound of the present invention, which is superior in bipolar transportability compared to conventional materials, it has the effect of improving the power efficiency and lowering the practical driving voltage.

The compound having a triphenylene ring structure of the present invention is useful as a compound for a hole blocking layer of an organic EL device or a host compound for a light emitting layer. By producing an organic EL device using the compound, high efficiency, An organic EL element with a low driving voltage can be obtained.

1 is a ¹ H-NMR chart of the compound of Example 1 of the present invention (Compound 2). FIG. 6 is a diagram showing EL element configurations of Example 4 and Comparative Example 1. 6 is a diagram showing an EL element configuration of Comparative Example 2. FIG.

The compound having a triphenylene ring structure of the present invention is a novel compound, and these compounds can be synthesized, for example, as follows. A compound having a triphenylene ring structure is synthesized by performing a cross-coupling reaction such as Suzuki coupling between a boronic acid or boronic acid ester of an aromatic heterocyclic ring having various substituents and a halide of a corresponding triphenylene compound. be able to.

Specific examples of preferable compounds among the compounds having the triphenylene ring structure represented by the general formula (1) and the general formula (1 ′) are shown below, but the present invention is not limited to these compounds. Absent.

(Compound 2)

(Compound 3)

(Compound 4)

(Compound 5)

(Compound 6)

(Compound 7)

(Compound 8)

(Compound 9)

(Compound 10)

(Compound 11)

(Compound 12)

(Compound 13)

(Compound 14)

(Compound 15)

(Compound 16)

These compounds were purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization using a solvent, crystallization method, and the like. The compound was identified by NMR analysis. As physical property values, melting point, glass transition point (Tg) and work function were measured. The melting point is an index of vapor deposition, the glass transition point (Tg) is an index of stability in a thin film state, and the work function is an index of energy level as a light-emitting host material. .

Melting point and glass transition point (Tg) were measured with a high sensitivity differential scanning calorimeter (Bruker AXS, DSC3100S) using powder.

The work function was measured using an atmospheric photoelectron spectrometer (AC-3 type, manufactured by Riken Keiki Co., Ltd.) by forming a 100 nm thin film on the ITO substrate.

As the structure of the organic EL device of the present invention, on the substrate sequentially, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, a hole blocking layer, an electron transport layer, a cathode, Further, those having an electron injection layer between the electron transport layer and the cathode, and those having an exciton blocking layer on the anode side and / or the cathode side of the light emitting layer can be mentioned. In these multilayer structures, several organic layers can be omitted. For example, an anode, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode can be sequentially formed on the substrate. , Anode, hole transport layer, light emitting layer, electron transport layer, and cathode.

The light emitting layer, the hole transport layer, and the electron transport layer may have a structure in which two or more layers are laminated.

As the anode of the organic EL element of the present invention, an electrode material having a large work function such as ITO or gold is used. As a hole injection layer of the organic EL device of the present invention, in addition to a porphyrin compound typified by copper phthalocyanine, a naphthalenediamine derivative, a starburst type triphenylamine derivative, a molecule having three or more triphenylamine structures, Triphenylamine trimers and tetramers such as arylamine compounds having a structure linked by a divalent group containing no bond or hetero atom, acceptor heterocyclic compounds such as hexacyanoazatriphenylene, and coating-type polymers Materials can be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As a hole transport layer of the organic EL device of the present invention, in addition to a compound containing an m-carbazolylphenyl group, N, N′-diphenyl-N, N′-di (m-tolyl) -benzidine (hereinafter referred to as “a”) N, N′-diphenyl-N, N′-di (α-naphthyl) -benzidine (hereinafter abbreviated as NPD), N, N, N ′, N′-tetrabiphenylylbenzidine, etc. Benzidine derivatives, 1,1-bis [(di-4-tolylamino) phenyl] cyclohexane (hereinafter abbreviated as TAPC), various triphenylamine trimers and tetramers, and carbazole derivatives can be used. . These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. In addition, as a hole injection / transport layer, a coating type such as poly (3,4-ethylenedioxythiophene) (hereinafter abbreviated as PEDOT) / poly (styrene sulfonate) (hereinafter abbreviated as PSS) is used. These polymer materials can be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

Further, in the hole injection layer or the hole transport layer, a material in which trisbromophenylamine hexachloroantimony is further P-doped to a material usually used in the layer, or a polymer having a TPD structure in its partial structure A compound or the like can be used.

As an electron blocking layer of the organic EL device of the present invention, 4,4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine (hereinafter abbreviated as TCTA), 9,9-bis [4- (carbazole- 9-yl) phenyl] fluorene, 1,3-bis (carbazol-9-yl) benzene (hereinafter abbreviated as mCP), 2,2-bis (4-carbazol-9-ylphenyl) adamantane (hereinafter Ad) Carbazole derivatives such as 9- [4- (carbazol-9-yl) phenyl] -9- [4- (triphenylsilyl) phenyl] -9H-fluorene And a compound having an electron blocking action such as a compound having a triarylamine structure can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As the light emitting layer of the organic EL device of the present invention, various metal complexes such as metal complexes of quinolinol derivatives including tris (8-hydroxyquinoline) aluminum (hereinafter abbreviated as Alq ₃ ), anthracene derivatives, bisstyrylbenzene derivatives , Pyrene derivatives, oxazole derivatives, polyparaphenylene vinylene derivatives, and the like can be used. The light emitting layer may be composed of a host material and a dopant material. In this case, the host material is a compound having a triphenylene ring structure represented by the general formula (1) of the present invention, mCP, thiazole derivative, benzimidazole. Derivatives, polydialkylfluorene derivatives and the like can be used. As the dopant material, quinacridone, coumarin, rubrene, anthracene, perylene and derivatives thereof, benzopyran derivatives, rhodamine derivatives, aminostyryl derivatives, and the like can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used.

Further, a phosphorescent light emitting material can be used as the light emitting material. As the phosphorescent emitter, a phosphorescent emitter of a metal complex such as iridium or platinum can be used. Green phosphorescent emitters such as Ir (ppy) ₃ , blue phosphorescent emitters such as FIrpic and FIr6, and red phosphorescent emitters such as Btp ₂ Ir (acac) and Ir (piq) ₃ are used. As the host material, a carbazole derivative such as CBP, TCTA, or mCP can be used as a hole injecting / transporting host material. As an electron transporting host material, p-bis (triphenylsilyl) benzene (hereinafter abbreviated as UGH2) or 2,2 ′, 2 ″-(1,3,5-phenylene) -tris (1-phenyl) -1H-benzimidazole) (hereinafter abbreviated as TPBI) and the like can be used.
In order to avoid concentration quenching, the doping of the phosphorescent light emitting material to the host material is preferably performed by co-evaporation in the range of 1 to 30 weight percent with respect to the entire light emitting layer.

It is also possible to use a thermally activated delayed fluorescent material as the material of the light emitting layer. As the thermally activated delayed fluorescent material, PIC-TRZ (see, for example, Non-Patent Document 1), compounds described in Japanese Patent Application No. 2012-088615, and the like can be used.

These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

In addition, an element having a structure in which a light-emitting layer manufactured using a compound having a different work function as a host material is stacked adjacent to a light-emitting layer manufactured using the compound of the present invention can be manufactured (for example, non-patented). Reference 5).

As the hole blocking layer of the organic EL device of the present invention, in addition to the compound having the triphenylene ring structure represented by the general formula (1) of the present invention, phenanthroline derivatives such as bathocuproine (hereinafter abbreviated as BCP), aluminum (III) In addition to metal complexes of quinolinol derivatives such as bis (2-methyl-8-quinolinate) -4-phenylphenolate (hereinafter abbreviated as BAlq), various rare earth complexes, oxazole derivatives, triazole derivatives, triazine derivatives For example, a compound having a hole blocking action can be used. These materials may also serve as the material for the electron transport layer. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As an electron transport layer of the organic EL device of the present invention, various metal complexes, triazole derivatives, triazine derivatives, oxadiazole derivatives, thiadiazole derivatives, carbodiimide derivatives, quinoxaline, in addition to metal complexes of quinolinol derivatives including Alq ₃ and BAlq. Derivatives, phenanthroline derivatives, silole derivatives and the like can be used. These may be formed alone, but may be used as a single layer formed by mixing with other materials, layers formed alone, mixed layers formed, or A stacked structure of layers formed by mixing with a layer formed alone may be used. These materials can be formed into a thin film by a known method such as a spin coating method or an ink jet method in addition to a vapor deposition method.

As the electron injection layer of the organic EL device of the present invention, an alkali metal salt such as lithium fluoride and cesium fluoride, an alkaline earth metal salt such as magnesium fluoride, and a metal oxide such as aluminum oxide can be used. In the preferred selection of the electron transport layer and the cathode, this can be omitted.

Furthermore, in the electron injecting layer or the electron transporting layer, a material usually used for the layer and further doped with a metal such as cesium can be used.

As the cathode of the organic EL device of the present invention, an electrode material having a low work function such as aluminum or an alloy having a lower work function such as a magnesium silver alloy, a magnesium indium alloy, or an aluminum magnesium alloy is used as the electrode material.

Hereinafter, embodiments of the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

[Example 1]
<Synthesis of 2,3,6,7,10,11-hexa (pyridin-3-yl) triphenylene (Compound 2)>
To a reaction vessel purged with nitrogen, 5.0 g of triphenylene, 0.49 g of iron powder and 10.1 ml of bromine were added and heated, followed by stirring at 170 ° C. for 10 hours. After cooling to room temperature, 100 ml of tetrahydrofuran was added and the mixture was further stirred for 0.5 hour. By filtration, 13.5 g (yield 84%) of 2,3,6,7,10,11-hexabromotriphenylene gray powder was obtained.

3.46 g of the obtained 2,3,6,7,10,11-hexabromotriphenylene and 4.0 g of 3-pyridineboronic acid, 22.4 ml of 2M aqueous potassium carbonate solution, tetrakis (triphenylphosphine) palladium (0) 0.57 g, 180 ml of toluene and 45 ml of ethanol were added to a reaction vessel purged with nitrogen, heated, and refluxed for 28 hours with stirring. After cooling to room temperature and adding 100 ml of water and 500 ml of chloroform, the organic layer was collected by performing a liquid separation operation. The organic layer was washed with 100 ml of water, dehydrated with anhydrous magnesium sulfate, and concentrated to obtain a crude product. The resulting crude product was purified by recrystallization from 1,2-dichlorobenzene to obtain 2,3,6,7,10,11-hexa (pyridin-3-yl) triphenylene (compound 2) as white 0.9 g (yield 26%) of powder was obtained.

The structure of the obtained white powder was identified using NMR. ^The results of ¹ H-NMR measurement are shown in FIG.

^The following 30 hydrogen signals were detected by ¹ H-NMR (CDCl 3). δ (ppm) = 8.76 (6H), 8.65 (6H), 8.57-8.59 (6H), 7.59-7.61 (6H), 7.27-7.29 (6H) ).

[Example 2]
About the compound of this invention, melting | fusing point and the glass transition point were calculated | required with the highly sensitive differential scanning calorimeter (The product made from Bruker AXS, DSC3100S).
Melting point Glass transition point Compound of Invention Example 1 380 ° C. or higher None

Since the glass transition point of the compound of the present invention was not confirmed, it indicates that the thin film state is stable.

[Example 3]
Using the compound of the present invention, a 50 nm-thick deposited film was formed on an ITO substrate, and the work function was measured with an atmospheric photoelectron spectrometer (AC-3 type, manufactured by Riken Keiki Co., Ltd.).
Work Function Compound of Invention Example 1 6.40 eV
CBP 6.00eV

Thus, the compound of the present invention has a suitable energy level as compared with CBP generally used as a host compound in the light emitting layer.

[Example 4]
As shown in FIG. 2, the organic EL element has a hole transport layer 3, a light emitting layer 4, an electron transport layer 6, and an electron injection layer 7 on a glass substrate 1 on which an ITO electrode is previously formed as a transparent anode 2. The cathode (aluminum electrode) 8 was deposited in this order.

Specifically, the glass substrate 1 on which ITO having a thickness of 100 nm was formed was washed with an organic solvent, and then the surface was washed by UV ozone treatment. Then, this glass substrate with an ITO electrode was mounted in a vacuum vapor deposition machine and the pressure was reduced to 0.001 Pa or less. Subsequently, a compound (Tris-PCz) having the following structural formula was formed so as to cover the transparent anode 2 so as to have a film thickness of 50 nm at a deposition rate of 2 蒸着 / s. On this hole transport layer 3, the compound (Compound 2) of Example 1 of the present invention and the green phosphorescent emitter Ir (ppy) ₃ are used as the light emitting layer 4, and the deposition rate ratio is Compound 2: Ir (ppy) ₃ = Binary vapor deposition was performed at a vapor deposition rate of 94: 6 to form a film thickness of 20 nm. On this light emitting layer 4 was formed to a thickness 30nm as an electron-transporting layer 6 Alq ₃ at a deposition rate of 2 Å / s. On the electron transport layer 6, lithium fluoride was formed as the electron injection layer 7 so as to have a film thickness of 1 nm at a deposition rate of 0.1 Å / s. Finally, aluminum was deposited to a thickness of 100 nm to form the cathode 8. About the produced organic EL element, the characteristic measurement was performed at normal temperature in air | atmosphere.

(Tris-PCz)

The measurement results of the light emission characteristics when a DC voltage was applied to the organic EL device produced using the compound of Example 1 of the present invention (Compound 2) are shown in Table 1.

[Comparative Example 1]
For comparison, the material of the light-emitting layer 4 in Example 4 was changed from the compound of Example 1 (Compound 2) to CBP, and an organic EL device was produced under the same conditions as in Example 4. About the produced organic EL element, the characteristic measurement was performed at normal temperature in air | atmosphere. Table 1 summarizes the measurement results of the light emission characteristics when a DC voltage was applied to the produced organic EL element.

[Comparative Example 2]
As shown in FIG. 3, the organic EL element has a hole transport layer 3, a light emitting layer 4, a hole blocking layer 5, an electron transport layer on a glass substrate 1 on which an ITO electrode is previously formed as a transparent anode 2. 6, an electron injection layer 7 and a cathode (aluminum electrode) 8 were deposited in this order.

Specifically, the glass substrate 1 on which ITO having a thickness of 100 nm was formed was washed with an organic solvent, and then the surface was washed by UV ozone treatment. Then, this glass substrate with an ITO electrode was mounted in a vacuum vapor deposition machine and the pressure was reduced to 0.001 Pa or less. Subsequently, as a hole transport layer 3 so as to cover the transparent anode 2, the compound of the structural formula (Tris-PCz) was formed to a film thickness of 50 nm at a deposition rate of 2 Å / s. On this hole transport layer 3, CBP and green phosphorescent emitter Ir (ppy) ₃ are used as the light emitting layer 4, and binary deposition is performed at a deposition rate such that the deposition rate ratio is CBP: Ir (ppy) ₃ = 94: 6. To form a film thickness of 20 nm. On this light emitting layer 4, BCP was formed as a hole blocking layer 5 so as to have a film thickness of 10 nm at a deposition rate of 2 Å / s. On the hole blocking layer 5, Alq ₃ was formed as the electron transport layer 6 so as to have a film thickness of 30 nm at a deposition rate of 2 Å / s. On the electron transport layer 6, lithium fluoride was formed as the electron injection layer 7 so as to have a film thickness of 1 nm at a deposition rate of 0.1 Å / s. Finally, aluminum was deposited to a thickness of 100 nm to form the cathode 8. About the produced organic EL element, the characteristic measurement was performed at normal temperature in air | atmosphere.

As shown in Table 1, the maximum external quantum efficiency at a current density of 10 mA / cm ² is 14.0% in Example 4 compared to 4.4% in Comparative Example 1 using CBP as the material of the light emitting layer. Increased efficiency. Furthermore, the maximum external quantum efficiency higher than 13.3% of the comparative example 2 which has the element structure which used CBP as a material of a light emitting layer, and added the hole-blocking layer using BCP was shown.

As is clear from these results, the organic EL device using the compound having a triphenylene ring structure of the present invention can achieve an improvement in external quantum efficiency as compared with CBP which is a general light-emitting host material. It was also found that the external quantum efficiency can be improved even when compared with an organic EL device having a device configuration in which a hole blocking layer using BCP, which is a general hole blocking layer material, is added.

As described above, the compound having a triphenylene ring structure of the present invention has a suitable energy level and has an ability to confine a suitable triplet energy.

Since the compound having a triphenylene ring structure of the present invention has a suitable energy level and has the ability to confine a suitable triplet energy, it can be used as a host compound and a hole blocking compound for a light-emitting layer. Are better. Moreover, the brightness | luminance and luminous efficiency of the conventional organic EL element can be improved by producing an organic EL element using this compound.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Transparent anode 3 Hole transport layer 4 Light emitting layer 5 Hole blocking layer 6 Electron transport layer 7 Electron injection layer 8 Cathode

Claims

A compound having a triphenylene ring structure represented by the following general formula (1).

(1)
(Wherein R 1 to R 6 may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent) 1 to 6 linear or branched alkyl groups, substituted or unsubstituted aromatic hydrocarbon groups, substituted or unsubstituted aromatic heterocyclic groups or substituted or unsubstituted condensed polycyclic aromatic groups, A 1 to A 6 may be the same or different and each represents a substituted or unsubstituted aromatic heterocyclic group.
The compound which has a triphenylene ring structure of Claim 1 represented by the following general formula (1 ').

(1 ')
(Wherein R 1 to R 6 may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent) 1 to 6 linear or branched alkyl groups, substituted or unsubstituted aromatic hydrocarbon groups, substituted or unsubstituted aromatic heterocyclic groups or substituted or unsubstituted condensed polycyclic aromatic groups, A 1 to A 6 may be the same or different and each represents a substituted or unsubstituted aromatic heterocyclic group.
The compound having a triphenylene ring structure according to claim 1, wherein in the general formula (1), A 1 to A 6 are represented by a monovalent group represented by the following structural formula (B).

(B)
(Wherein R 7 to R 11 may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or an optionally substituted carbon atom) 1 to 6 linear or branched alkyl group, optionally substituted linear or branched alkenyl group having 2 to 6 carbon atoms, substituted or unsubstituted aromatic hydrocarbon group , A substituted or unsubstituted aromatic heterocyclic group or a substituted or unsubstituted condensed polycyclic aromatic group, V, W, X, Y, Z represents a carbon atom or a nitrogen atom, and V, W, X, (It is assumed that one to three of Y and Z are nitrogen atoms, and the nitrogen atom in this case does not have a substituent of R 7 to R 11. )
The compound having a triphenylene ring structure according to claim 3, wherein in the structural formula (B), any one of V, W, X, Y, and Z is a nitrogen atom.
The compound having a triphenylene ring structure according to claim 3, wherein in the structural formula (B), any two of V, W, X, Y and Z are nitrogen atoms.
The compound having a triphenylene ring structure according to claim 3, wherein in the structural formula (B), any three of V, W, X, Y and Z are nitrogen atoms.
In an organic electroluminescence device having a pair of electrodes and at least one organic layer sandwiched between them, a compound having a triphenylene ring structure represented by the following general formula (1) is used as a constituent material of at least one organic layer: An organic electroluminescence device characterized by being used.

(1)
(Wherein R 1 to R 6 may be the same or different and each represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, or a carbon atom which may have a substituent) 1 to 6 linear or branched alkyl groups, substituted or unsubstituted aromatic hydrocarbon groups, substituted or unsubstituted aromatic heterocyclic groups or substituted or unsubstituted condensed polycyclic aromatic groups, A 1 to A 6 may be the same or different and each represents a substituted or unsubstituted aromatic heterocyclic group.
The organic layer is a hole blocking layer, and the compound represented by the general formula (1) is used as at least one constituent material in the hole blocking layer. 8. The organic electroluminescence device according to 7.
8. The organic material according to claim 7, wherein the organic layer is a light emitting layer, and the compound represented by the general formula (1) is used as at least one constituent material in the light emitting layer. Electroluminescence element.
10. The organic electroluminescence device according to claim 9, wherein the organic layer is a light emitting layer, and the compound represented by the general formula (1) is used as a host material of the light emitting layer.
In the organic electroluminescence device having a light emitting layer containing a phosphorescent light emitting material and at least one organic layer sandwiched between a pair of electrodes, the compound represented by the general formula (1) is formed of the light emitting layer. 8. The organic electroluminescence device according to claim 7, wherein the organic electroluminescence device is used as at least one constituent material.
The organic electroluminescence device according to claim 11, wherein the phosphorescent light emitting material is a metal complex containing iridium or platinum.
The organic electroluminescent device according to claim 11, wherein the phosphorescent light emitting material is a green light emitting material.