JP2015214490A - Compound having triphenylene ring structure, and organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: as a material for use in a high-efficiency organic electroluminescent element, 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; and a high-efficiency, high-luminance organic electroluminescent element using the compound.SOLUTION: The present invention provides: a compound having a triphenylene ring structure represented by general formula (1); and an organic electroluminescent element which has a pair of electrodes and at least one organic layer sandwiched therebetween and is characterized in that the compound is used as a constituent material for at least one organic layer.

Description

  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 electroluminescent 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 light emitter 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 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 device 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 excited triplet level 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).

  Moreover, 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, refer nonpatent literature 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 excited triplet level and high thin film stability has been required.

Appl. Phys. Let. 98,083302 (2011) Appl. Phys. Let. , 75, 4 (1999) Development and Evaluation Technology of Organic EL Lighting Materials p102-106 Science & Technology Co., Ltd. (2010) Organic EL display p90, Ohm Corporation (2005) J. et al. Org. Chem. , 60, 7508 (1995) Synth. Commun. , 11, 513 (1981) Proceedings of the 1st regular meeting of organic EL debate, 19 (2005)

  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).

(Wherein R _{1 to} R ₁₀ 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 and A ₂ may be the same or different and represent a monovalent group represented by the following structural formula (B).

(In the formula, R _{11 to} R ₁₇ 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, X represents an oxygen atom, a sulfur atom or a selenium atom.)

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

(Wherein R _{1 to} R ₁₀ 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 and A ₂ may be the same or different and each represents a monovalent group represented by the structural formula (B).

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

(Wherein R _{1 to} R ₁₀ 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 and A ₂ may be the same or different and each represents a monovalent group represented by the structural formula (B).

  4) Moreover, this invention is a compound which has the triphenylene ring structure of said 1) description whose said Structural formula (B) is represented by the monovalent group shown by following Structural formula (B ') in General formula (1). It is.

(In the formula, R _{11 to} R ₁₇ 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, X represents an oxygen atom, a sulfur atom or a selenium atom.)

  5) Moreover, this invention has the triphenylene ring structure of said 1) description in which the said structural formula (B) is represented by the monovalent group shown by the following structural formula (B '') in General formula (1). A compound.

(In the formula, R _{11 to} R ₁₇ 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, X represents an oxygen atom, a sulfur atom or a selenium atom.)

  6) 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.

  7) Further, according to the present invention, the organic layer 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 6) above, wherein the organic electroluminescence device is used.

  8) 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. 6) The organic electroluminescence device as described in 6) above.

  9) Further, the present invention is characterized in that the organic layer 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 electroluminescence device according to 8) above.

  10) Further, the present invention relates to an 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 and represented by the general formula (1). The organic electroluminescent device according to 6) above, wherein the compound having a triphenylene ring structure is used as at least one constituent material in the light emitting layer.

  11) Moreover, this invention is an organic electroluminescent element of said 10) whose above-mentioned phosphorescent luminescent material is a metal complex containing iridium or platinum.

  12) Moreover, this invention is an organic electroluminescent element of the said 10) description whose above-mentioned phosphorescent luminescent material is a red luminescent material.

R _{1 to} R ₁₇ in the general formula (1), the general formula (1 ′), the general formula (1 ″), the structural formula (B), the structural formula (B ′), and the structural formula (B ″). Specific examples of the “alkyl group” in the “optionally substituted linear or branched alkyl group having 1 to 6 carbon atoms” specifically include a methyl group, an ethyl group, and n-propyl. Group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group and the like.

R _{1 to} R ₁₇ in the general formula (1), the general formula (1 ′), the general formula (1 ″), the structural formula (B), the structural formula (B ′), and the structural formula (B ″). Specific examples of the “substituent” in the “straight-chain or branched alkyl group having 1 to 6 carbon atoms” include a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, Substituted with a fluoromethyl group, a nitro 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 group, phenyl group, biphenylyl group, terphenylyl group, tetrakisphenyl group, styryl group, naphthyl group, fluorenyl group, phenanthryl group, indenyl group, pyrenyl group, pyridyl group, bipyridyl group, Examples thereof include a riadyl group, a pyrimidyl group, a quinolyl group, an isoquinolyl group, an indolyl group, a pyridoindolyl group, a carbazolyl group, a quinoxalyl group, and a pyrazolyl group, and these substituents may be further substituted. These substituents may be bonded to each other to form a ring.

R _{1 to} R ₁₇ in the general formula (1), the general formula (1 ′), the general formula (1 ″), the structural formula (B), the structural formula (B ′), and the structural formula (B ″). "Aromatic hydrocarbon group" in "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic aromatic group" , "Aromatic heterocyclic group" or "condensed polycyclic aromatic group" specifically includes phenyl group, biphenylyl group, terphenylyl group, tetrakisphenyl group, styryl group, naphthyl group, anthryl group, acenaphthenyl group, fluorenyl group Phenanthryl group, indenyl group, pyrenyl group, pyridyl group, bipyridyl group, triazyl group, pyrimidyl group, furanyl group, pyrrolyl group, thienyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothiyl Nyl group, indolyl group, carbazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalyl group, benzoimidazolyl group, pyrazolyl group, pyridoindolyl group, dibenzofuranyl group, dibenzothienyl group, naphthyridinyl group, phenanthrolinyl group, A group such as an acridinyl group can be exemplified.

R _{1 to} R ₁₇ in the general formula (1), the general formula (1 ′), the general formula (1 ″), the structural formula (B), the structural formula (B ′), and the structural formula (B ″). Specific examples of the “substituent” in the “substituted aromatic hydrocarbon group”, “substituted aromatic heterocyclic group” or “substituted condensed polycyclic aromatic group” include 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, linear or branched group having 1 to 6 carbon atoms An 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, Fena List groups such as tolyl, indenyl, pyrenyl, pyridyl, bipyridyl, triazyl, pyrimidyl, quinolyl, isoquinolyl, indolyl, pyridoindolyl, carbazolyl, quinoxalyl, pyrazolyl These substituents may be further substituted.

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

  The compound having a triphenylene ring structure represented by the general formula (1), the general formula (1 ′), and the general formula (1 ″) of the present invention is referred to as an organic electroluminescence device (hereinafter, abbreviated as an organic EL device). ) Of the light emitting layer or the hole blocking 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). ^{1 is} a ¹ H-NMR chart of a compound of Example 2 of the present invention (Compound 3). It is the figure which showed the EL element structure of Examples 5-6 and Comparative Examples 1-2.

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. First, the corresponding boronate ester form is synthesized by subjecting the corresponding triphenylene compound dihalide to boronic esterification with bis (pinacolato) diboron or the like (see, for example, Non-Patent Document 5), and further, the corresponding boron. A compound having a triphenylene ring structure is synthesized by performing a cross-coupling reaction such as Suzuki coupling between an acid ester and halogenodibenzofuran or halogenodibenzothiophene having various substituents (see, for example, Non-Patent Document 6). be able to.
On the other hand, by carrying out boronic esterification of halogenodibenzofuran or halogenodibenzothiophene having various substituents with bis (pinacolato) diboron or the like, a boronic ester of dibenzofuran or dibenzothiophene having various substituents is synthesized, Further, a compound having a triphenylene ring structure is synthesized by conducting a cross-coupling reaction such as Suzuki coupling between the boronic ester of dibenzofuran or dibenzothiophene having various substituents and a corresponding diphenylene halide of a triphenylene compound. be able to.

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

(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)

(Compound 17)

(Compound 18)

(Compound 19)

(Compound 20)

(Compound 21)

  These compounds were purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization using a solvent, 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 | fusing point and glass transition point (Tg) were measured with the high sensitivity differential scanning calorimeter (The Bruker AXS make, DSC3100S) using powder.

  The work function was measured using an atmospheric photoelectron spectrometer (manufactured by Riken Keiki Co., Ltd., AC-3 type) after 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.

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

  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, NPD, abbreviated as TPD), 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. Further, 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) A triphenylsilyl group represented by 9- [4- (carbazol-9-yl) phenyl] -9- [4- (triphenylsilyl) phenyl] -9H-fluorene, and the like. 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) and 2,2 ′, 2 ″-(1,3,5-phenylene) -tris (1-phenyl) -1H-benzimidazole) (hereinafter abbreviated as TPBI) or the like.
In order to avoid concentration quenching, the host material of the phosphorescent light emitting material is preferably doped by co-evaporation in the range of 1 to 30 weight percent with respect to the entire light emitting layer.

  Moreover, it is also possible to use a heat activated delayed fluorescent material as the material of the light emitting layer. As the thermally activated delayed fluorescent material, PIC-TRZ (for example, see 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 7).

  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-quinolinato) -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.

  Further, 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.

<Synthesis of 2,7-bis (8-phenyldibenzo [b, d] furan-2-yl) triphenylene (Compound 2)>
To a reaction vessel purged with nitrogen, 10 g of 2,8-dibromodibenzofuran, 4.1 g of phenylboronic acid, 20 ml of 2M aqueous potassium carbonate solution, 1.8 g of tetrakis (triphenylphosphine) palladium (0), 100 ml of toluene, and 25 ml of ethanol were added. Heated and stirred at 60 ° C. for 15 hours. After cooling to room temperature, 100 ml of water and 100 ml of toluene were added, and a liquid separation operation was performed to collect an organic layer. The organic layer was washed twice with 50 ml of water, dried over anhydrous magnesium sulfate, and concentrated to obtain a crude product. The crude product was purified by column chromatography [carrier: silica gel, eluent: n-hexane] to obtain 3.3 g (yield 33%) of 2-bromo-8-phenyldibenzo [b, d] furan white powder. It was.

  The resulting 2-bromo-8-phenyldibenzo [b, d] furan (3.0 g) and 2,7-bis (4,4,5,5-tetramethyl- [1,3,2] dioxaborolane-2- Yl) 2.2 g of triphenylene, 7.0 ml of 2M aqueous potassium carbonate solution, 0.3 g of tetrakis (triphenylphosphine) palladium (0), 40 ml of toluene, and 10 ml of ethanol were added to a nitrogen-substituted reaction vessel and heated with stirring. Reflux for hours. After cooling to room temperature, the precipitate was collected by filtration. To the precipitate was added 300 ml of tetrahydrofuran, the insoluble matter was removed by filtration, and then recrystallization from 1,2-dichlorobenzene was performed, whereby 2,7-bis (8-phenyldibenzo [b, d] furan-2- Il) Triphenylene (compound 2) white powder 1.1 g (yield 34%) was obtained.

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

^The following 32 hydrogen signals were detected by ¹ H-NMR (DMSO-d ₆ ). δ (ppm) = 9.14 (2H), 9.02-9.04 (2H), 8.93-8.95 (2H), 8.82 (2H), 8.60 (2H), 8. 16-8.18 (2H), 8.11-8.14 (2H), 7.77-7.86 (12H), 7.50-7.54 (4H), 7.37-7.42 ( 2H).

<Synthesis of 2,7-bis {(8-phenyl) -2-dibenzo [b, d] thienyl} triphenylene (Compound 3)>
To a reaction vessel purged with nitrogen, 10 g of 2,8-dibromodibenzothiophene, 4.6 g of phenylboronic acid, 22 ml of 2M aqueous potassium carbonate solution, 1.7 g of tetrakis (triphenylphosphine) palladium (0), 100 ml of toluene, and 25 ml of ethanol were added. And heated at 60 ° C. for 7 hours. After cooling to room temperature, the organic layer was collected by performing a liquid separation operation. The organic layer was washed with 30 ml of water three times, dried over anhydrous sodium sulfate, and concentrated to obtain a crude product. The crude product was purified by column chromatography [carrier: silica gel, eluent: n-hexane] to obtain 1.8 g of 2-bromo-8-phenyldibenzo [b, d] thiophene white powder (yield 18%). It was.

  1.7 g of the obtained 2-bromo-8-phenyldibenzo [b, d] thiophene and 2,7-bis (4,4,5,5-tetramethyl- [1,3,2] dioxaborolane-2- Yl) 1.2 g of triphenylene, 3.9 ml of 2M aqueous potassium carbonate solution, 0.2 g of tetrakis (triphenylphosphine) palladium (0), 20 ml of toluene, and 5 ml of ethanol were added to a nitrogen-substituted reaction vessel, heated and stirred for 5 Reflux for hours. After cooling to room temperature, the precipitate was collected by filtration. To the precipitate was added 350 ml of tetrahydrofuran, insolubles were removed by filtration, and then recrystallized from 1,2-dichlorobenzene, whereby 2,7-bis {(8-phenyl) -2-dibenzo [b, d ] 0.8 g (yield 41%) of a white powder of thienyl} triphenylene (compound 3) 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 32 hydrogen signals were detected by ¹ H-NMR (DMSO-d ₆ ). δ (ppm) = 9.19 (2H), 9.04-9.07 (4H), 8.94-8.96 (2H), 8.88 (2H), 8.23-8.26 (2H) ), 8.09-8.18 (6H), 7.83-7.89 (6H), 7.78-7.81 (2H), 7.51-7.55 (4H), 7.39- 7.43 (2H).

[Comparative Synthesis Example 1]
<Synthesis of 2,7-bis (9-phenyl-9H-carbazol-3-yl) triphenylene (Comparative Compound 1)>
To a reaction vessel purged with nitrogen, 3.0 g of 2,7-bis (trifluoromethanesulfonyl) triphenylene, 3- (4,4,5,5-tetramethyl- [1,3,2] dioxaborolan-2-yl)- 4.4 g of N-phenylcarbazole, 8.9 ml of 2M aqueous potassium carbonate solution, 0.3 g of tetrakis (triphenylphosphine) palladium (0), 60 ml of toluene and 15 ml of ethanol were added and heated, and the mixture was refluxed for 10 hours with stirring. After cooling to room temperature, the precipitate was collected by filtration. To the precipitate was added 350 ml of tetrahydrofuran, and the insoluble matter was removed by filtration. Then, the precipitate was purified by reflux washing with toluene, and 2,7-bis (9-phenyl-9H-carbazol-3-yl) triphenylene (Comparative Compound 1) was purified. White powder 3.0g (yield 74%) was obtained.

(Comparative Compound 1)

  The structure of the resulting white powder was identified using NMR.

^The following 34 hydrogen signals were detected by ¹ H-NMR (DMSO-d ₆ ). δ (ppm) = 9.11 (2H), 8.99-9.02 (2H), 8.86-8.88 (2H), 8.81 (2H), 8.41-8.43 (2H ), 8.13-8.15 (2H), 7.99-8.02 (2H), 7.77-7.79 (2H), 7.70-7.73 (4H), 7.64- 7.66 (4H), 7.55-7.58 (2H), 7.45-7.51 (4H), 7.38-7.40 (2H), 7.32-7.36 (2H) .

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 1 360 ° C None Compound of Invention Example 2 380 ° C or higher None

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

Using the compound of the present invention, a deposited film having a thickness of 50 nm 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 6.00 eV
Compound of Example 2 of the present invention 5.80 eV
CBP 6.00eV

  Thus, the compound of the present invention has an energy level equivalent to that of CBP that is generally used as a host compound in the light emitting layer.

  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, a compound (Tris-PCz) having the following structural formula was formed as a hole transport layer 3 so as to cover the transparent anode 2 so as to have a film thickness of 50 nm at a deposition rate of 2 Å / s. On this hole transport layer 3, the compound (Compound 2) of Example 1 of the present invention and the red phosphorescent body Ir (piq) ₃ are used as the light emitting layer 4, and the deposition rate ratio is Compound 2: Ir (piq) 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, 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 an 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 70 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)

  Table 1 summarizes 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 (Compound 2) of the present invention.

  An organic EL device was produced under the same conditions as in Example 5, except that the material of the light emitting layer 4 in Example 5 was changed from the compound of Example 1 (Compound 2) to the compound of Example 2 of the present invention (Compound 3). 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 1]
For comparison, the material of the light emitting layer 4 in Example 5 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 5. 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]
For comparison, the material of the light-emitting layer 4 in Example 5 was changed from the compound of Example 1 (Compound 2) to Comparative Compound 1, and an organic EL device was produced under the same conditions as in Example 5. 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.

As shown in Table 1, the driving voltage at a current density of 10 mA / cm ² was found to be that of Example 5 compared to 9.8 V of Comparative Example 1 using CBP and 9.6 V of Comparative Example 2 using Comparative Compound 1. In Example 6, the voltage was lowered to 9.0 V, and in Example 6, the voltage was 8.2 V.

As shown in Table 1, the external quantum efficiency at a current density of 10 mA / cm ² is 6.7% of Comparative Example 1 using CBP and 6.5% of Comparative Example 2 using Comparative Compound 1. The efficiency was increased to 7.0% in Example 5 and 7.2% in Example 6.

  As is clear from these results, the organic EL device using the compound having a triphenylene ring structure of the present invention has a lower driving voltage and an improved external quantum efficiency than CBP which is a general light-emitting host material. It was found that can be achieved.

  As described above, the compound of the present invention has a suitable energy level and has the 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 (12)

A compound having a triphenylene ring structure represented by the following general formula (1).
(Wherein R _{1 to} R ₁₀ 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 and A ₂ may be the same or different and represent a monovalent group represented by the following structural formula (B).
(In the formula, R _{11 to} R ₁₇ 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, X represents an oxygen atom, a sulfur atom or a selenium atom.) The compound which has a triphenylene ring structure of Claim 1 represented by the following general formula (1 ').
(Wherein R _{1 to} R ₁₀ 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 and A ₂ may be the same or different and each represents a monovalent group represented by the structural formula (B). The compound which has the triphenylene ring structure of Claim 1 represented by the following general formula (1 '').
(Wherein R _{1 to} R ₁₀ 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 and A ₂ may be the same or different and each represents a monovalent group represented by the structural formula (B). The compound having a triphenylene ring structure according to claim 1, wherein, in the general formula (1), the structural formula (B) is represented by a monovalent group represented by the following structural formula (B ').
(In the formula, R _{11 to} R ₁₇ 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, X represents an oxygen atom, a sulfur atom or a selenium atom.) The compound having a triphenylene ring structure according to claim 1, wherein in the general formula (1), the structural formula (B) is represented by a monovalent group represented by the following structural formula (B '').
(In the formula, R _{11 to} R ₁₇ 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, X represents an oxygen atom, a sulfur atom or a selenium atom.) 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.
(Wherein R _{1 to} R ₁₀ 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 and A ₂ may be the same or different and represent a monovalent group represented by the following structural formula (B).
(In the formula, R _{11 to} R ₁₇ 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, X represents an oxygen atom, a sulfur atom or a selenium atom.)   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. 6. The organic electroluminescence device according to 6.   The organic layer according to claim 6, 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.   The organic electroluminescence device according to claim 8, 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. 7. The organic electroluminescence device according to claim 6, wherein the organic electroluminescence device is used as at least one constituent material.   The organic electroluminescence device according to claim 10, wherein the phosphorescent light emitting material is a metal complex containing iridium or platinum.   The organic electroluminescent element according to claim 10, wherein the phosphorescent light emitting material is a red light emitting material.