WO2014126241A1

WO2014126241A1 - Light emitting material and organic el element

Info

Publication number: WO2014126241A1
Application number: PCT/JP2014/053642
Authority: WO
Inventors: 清水　正毅; 裕介稲本; 井上　健二; 岳夫大塚; 昌也日高
Original assignee: 国立大学法人京都工芸繊維大学; 株式会社カネカ
Priority date: 2013-02-18
Filing date: 2014-02-17
Publication date: 2014-08-21
Also published as: JP6313742B2; JPWO2014126241A1

Abstract

This light emitting material contains a silicon crosslinked indole derivative represented by formula (I). In formula (I), each of R¹ and R² independently represents a lower alkyl group having 1-6 carbon atoms, an aryl group, an amino group or an unsaturated heterocyclic group; R³ represents a hydrogen atom, a lower alkyl group having 1-6 carbon atoms, an aryl group or an unsaturated heterocyclic group; R⁴ is a substituent bonded to a benzene ring, R⁵ is a substituent bonded to an indole ring, and each of R⁴ and R⁵ independently represents a halogen atom, a cyano group, a lower alkyl group having 1-6 carbon atoms, a lower alkoxy group having 1-6 carbon atoms, a lower alkylthio group having 1-6 carbon atoms, a halogen-substituted lower alkyl group having 1-6 carbon atoms, a halogen-substituted lower alkoxy group having 1-6 carbon atoms, an amino group, an aryl group or an unsaturated heterocyclic group; and a plurality of R⁴ moieties may combine together to form a ring structure.

Description

Luminescent material and organic EL device

The present invention relates to a light emitting material and an organic EL element using the light emitting material.

Organic EL elements are attracting attention as light emitting elements used in flat display panels and lighting devices. The organic EL element can emit light of various wavelengths by appropriately selecting the material constituting the light emitting layer. Various π-conjugated compounds have been studied as organic light-emitting materials used for organic EL devices, and anthracene derivatives, distyrylarylene derivatives, fluorene derivatives, pyrene derivatives, and the like have already been developed as blue light-emitting materials.

Recently, a silicon-bridged indole derivative has been found as a novel blue light-emitting material, and it has been reported that it has excellent light-emitting efficiency in a solid state (Patent Document 1). Patent Document 2 reports that when a silicon-bridged indole derivative is used together with a light-emitting host material such as an anthracene derivative, an organic EL element having a high light emission efficiency and a long life can be obtained. Further, Non-Patent Document 1 reports that the following silicon-bridged 2- (2-naphthyl) indole compound is applicable as a blue light-emitting dopant material or a light-emitting host material.

WO2010 / 047335 International Publication Pamphlet JP 2012-87187 A

As described above, various blue light emitting materials have been developed. However, there remains a problem in improving the light emission efficiency of the organic EL element, and it has a desired light emission wavelength and light emission spectrum shape, and has high light emission efficiency. There is a need for the development of materials with a long emission lifetime. The organic light emitting material can change the light emission characteristics such as the shape of the light emission spectrum and the light emission wavelength by derivatization by introducing a substituent. On the other hand, if the π-conjugated structure of the compound changes, the light emission characteristics change greatly, and it is difficult to predict the light emission characteristics and the light emission lifetime.

In view of the above-described present situation, an object of the present invention is to provide a novel blue light emitting material exhibiting high light emission efficiency and an organic EL element using the light emitting material.

As a result of investigations by the present inventors, it was found that a silicon-bridged indole derivative having an aryl group introduced on the naphthalene ring is excellent in luminous efficiency, leading to the present invention. That is, this invention relates to the luminescent material containing the silicon bridge | crosslinking indole derivative represented by following formula (I).

In formula (I),
R ¹ to R ³ each independently represents a lower alkyl group having 1 to 6 carbon atoms, an aryl group or an unsaturated heterocyclic group. R ⁴ is a substituent bonded to the benzene ring, and R ⁵ is a substituent bonded to the indole ring. p is an integer of 0 to 5, and q is an integer of 0 to 4. R ⁴ and R ⁵ are each independently a halogen atom, cyano group, amino group, aryl group, unsaturated heterocyclic group, lower alkyl group having 1 to 6 carbon atoms, lower alkoxy group having 1 to 6 carbon atoms, carbon number It represents a lower alkylthio group having 1 to 6 carbon atoms, a halogen-substituted lower alkyl group having 1 to 6 carbon atoms, a halogen-substituted lower alkoxy group having 1 to 6 carbon atoms, an amino group, an aryl group or an unsaturated heterocyclic group. If R ⁴ and R ⁵ are present in plural, the plurality of R ⁴ and R ^5, may each be the same or different. A plurality of R ⁴ may be bonded to each other to form a ring structure.

In particular, in the luminescent material of the present invention, in the above formula (I), p is preferably 0 or 1, and q = 0 is preferable. When p is 1, the substituent R ⁴ is preferably bonded to the para-position of the benzene ring (the following formula (II)). R ⁴ is preferably a methoxy group, for example.

In one embodiment, the luminescent material of the present invention contains a host material and a dopant material. The dopant material is preferably a compound of the above formula (I) or formula (II), and the host material is preferably an anthracene derivative. By using the above compound as a dopant material for an anthracene derivative host, an organic EL device having a long emission lifetime can be produced.

Furthermore, the present invention relates to an organic EL device having at least a light emitting layer between a pair of electrodes consisting of an anode and a cathode. As for the organic EL element of this invention, a light emitting layer has the said light emitting material.

The light emitting material of the present invention is a blue light emitting material having a light emission maximum wavelength in a blue region having a wavelength shorter than 500 nm, and an organic EL device having high light emission efficiency can be produced.

It is a typical sectional view showing an example of layer composition of an organic EL device. It is typical sectional drawing which shows an example of the layer structure of the organic EL element in the organic EL apparatus of FIG.

[Structure of compound]
The light emitting material of the present invention contains a silicon bridged 2- (2-naphthyl) indole derivative represented by the following formula (I).

In formula (I), R ¹ and R ² each independently represents a lower alkyl group having 1 to 6 carbon atoms, an aryl group or an unsaturated heterocyclic group. R ³ represents a lower alkyl group having 1 to 6 carbon atoms, an aryl group, or an unsaturated heterocyclic group. R ⁴ is a substituent bonded to the benzene ring, and R ⁵ is a substituent bonded to the indole ring. p is an integer of 0 to 5, and q is an integer of 0 to 4. R ⁴ and R ⁵ are each independently a halogen atom, a cyano group, a lower alkyl group having 1 to 6 carbon atoms, a lower alkoxy group having 1 to 6 carbon atoms, a lower alkylthio group having 1 to 6 carbon atoms, or 1 to 6 represents a halogen-substituted lower alkyl group, an amino group, an aryl group or an unsaturated heterocyclic group. When a plurality of R ⁴ and R ⁵ are present (when p and q are each 2 or more), the plurality of R ⁴ and R ⁵ may be the same or different. A plurality of R ⁴ may be bonded to each other to form a ring structure.

[Substituent examples]
<R ¹ and R ² >
In the formula (I), R ¹ and R ² represent a lower alkyl group having 1 to 6 carbon atoms, an aryl group, or an unsaturated heterocyclic group.

Examples of the lower alkyl group include linear or branched alkyl groups having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. Specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, sec-butyl group, n-pentyl group, 1-ethylpropyl group, isopentyl group And neopentyl group, n-hexyl group, 1,2,2-trimethylpropyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, isohexyl group, 3-methylpentyl group, and the like.

Examples of the aryl group include a phenyl group, a biphenyl group, and a naphthyl group. The aryl group has a substituent such as a lower alkyl group, a lower alkoxy group, a halogen-substituted lower alkyl group, a lower alkoxycarbonyl group, a lower alkylcarbonyl group, an amino group, an aminocarbonyl group, or a halogen atom on the phenyl ring or naphthalene ring. One or more may be included.

The amino group may have one or two substituents in addition to the unsubstituted amino group (—NH ₂ ). Moreover, when an amino group has two substituents, these may be the same or different. When the amino group has a substituent, the substituent is preferably the lower alkyl group or aryl group exemplified above. Specific examples of the amino group include unsubstituted amino group, methylamino group, ethylamino group, n-propylamino group, isopropylamino group, n-butylamino group, tert-butylamino group, n-pentylamino group, n -Hexylamino, arylamino, dimethylamino, diethylamino, di-n-propylamino, di-n-butylamino, di-n-pentylamino, di-n-hexylamino, N- Methyl-N-ethylamino group, N-ethyl-Nn-propylamino group, N-methyl-Nn-butylamino group, N-methyl-Nn-hexylamino group, diarylamino group, etc. Can be mentioned.

In addition, when an amino group can form a hydrogen bond, concentration quenching occurs and the light emission efficiency tends to decrease. Therefore, the amino group preferably has two substituents, and a diarylamino group is particularly preferable.

The unsaturated heterocyclic ring of the unsaturated heterocyclic group includes a 5- to 10-membered ring, preferably a 5- to 6-membered ring. Specifically, pyridine ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, furazane ring, imidazole ring, pyrazole ring, pyrazine ring, pyrimidine ring, pyridazine ring, dihydrooxazole ring, thiophene ring, A furan ring, a pyrazole ring, etc. are mentioned.

<R ³ >
In the formula (I), R ³ represents a hydrogen atom, a lower alkyl group having 1 to 6 carbon atoms, an aryl group or an unsaturated heterocyclic group. Examples of the lower alkyl group, aryl group and unsaturated heterocyclic group include the same substituents as those described above as examples of R ¹ and R ² . Among them, as R ³ , a lower alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group is particularly preferable.

^{<R 4} and ^R 5>
In the formula (I), R ⁴ and R ⁵ each independently represent a halogen atom, a cyano group, a lower alkyl group having 1 to 6 carbon atoms, a lower alkoxy group having 1 to 6 carbon atoms, or a lower group having 1 to 6 carbon atoms. It represents an alkylthio group, a halogen-substituted lower alkyl group having 1 to 6 carbon atoms, a halogen-substituted lower alkoxy group having 1 to 6 carbon atoms, an amino group, an aryl group or an unsaturated heterocyclic group. When a plurality of R ⁴ are present (when p is 2 or more), the plurality of R ⁴ may be bonded to each other to form a ring structure.

Examples of the lower alkyl group, amino group, aryl group or unsaturated heterocyclic group include the same substituents as those described above as examples of R ¹ and R ² .
Examples of the halogen atom include a fluorine atom and a chlorine atom.

Examples of the lower alkoxy group include straight or branched lower alkoxy groups having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, having straight or branched chains. Specifically, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, tert-butoxy group, sec-butoxy group, n-pentyloxy group, isopentyloxy group, neo A pentyloxy group, an n-hexyloxy group, an isohexyloxy group, a 3-methylpentyloxy group, and the like can be given.

Examples of the lower alkylthio group include linear or branched alkylthio groups having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. Specific examples include a methylthio group, an ethylthio group, an n-propylthio group, an isopropylthio group, an n-butylthio group, a tert-butylthio group, an n-pentylthio group, and an n-hexylthio group.

Examples of the halogen-substituted alkyl group include the above-exemplified alkyl groups substituted with 1 to 7, more preferably 1 to 3 halogen atoms. Specifically, fluoromethyl group, difluoromethyl group, trifluoromethyl group, chloromethyl group, dichloromethyl group, trichloromethyl group, bromomethyl group, dibromomethyl group, dichlorofluoromethyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, pentafluoroethyl group, 2-fluoroethyl group, 2-chloroethyl group, 3,3,3-trifluoropropyl group, heptafluoropropyl group, 2,2,3,3 , 3-pentafluoropropyl group, heptafluoroisopropyl group, 3-chloropropyl group, 2-chloropropyl group, 3-bromopropyl group, 4,4,4-trifluorobutyl group, 4,4,4,3, 3-pentafluorobutyl group, 4-chlorobutyl group, 4-bromobutyl group, 2-chlorobutyl group, 5, 5, 5 Trifluoro-pentyl group, 5-chloropentyl group, 6,6,6-trifluoro hexyl, 6-chloro-hexyl group, perfluorohexyl group, and the like.

Examples of the halogen-substituted alkoxy group include the alkoxy groups exemplified above substituted with 1 to 7, more preferably 1 to 3 halogen atoms. Specific examples include those in which an oxygen atom (—O—) is added to the halogen-substituted alkyl group exemplified above.

Ring structure in which a plurality of R ⁴ are bonded to each other to form may be a fused aromatic ring to the benzene ring, it may be an aliphatic ring. The ring structure formed by bonding a plurality of R ^{4 s} may be a heterocyclic ring.

[Examples of preferred compounds]
In the above formula (I), q is preferably 0. That is, the carbon atom of the indole ring preferably has no substituent. Further, p is preferably 0 or 1. When p = 1, R ⁴ is preferably bonded to the para position of the benzene ring. When these are put together, it is preferable that the luminescent material of the present invention contains a compound represented by the following formula (II).

As described above, the substituent R ⁴ is preferably an alkoxy group, an alkyl group, a halogen-substituted alkoxy group, a halogen-substituted alkyl group, an amino group, an alkylthio group, an aryl group, or an unsaturated heterocyclic group. Among these, from the viewpoint of obtaining a material having high blue light emission efficiency, R ⁴ is preferably an alkoxy group, and particularly preferably a methoxy group.

R ¹ and R ² are preferably both lower alkyl groups. R ¹ and R ² are preferably the same substituent. In particular, it is preferable that both R ¹ and R ² are isopropyl groups.
R ³ is preferably a lower alkyl group, and particularly preferably a methyl group.

In summary, the light-emitting material of the present invention preferably contains a compound represented by the following formula (III), and particularly preferably contains a compound represented by the following formula (IV).

[Synthesis method]
The method for synthesizing the above compound is not particularly limited, and a target compound can be obtained by combining various known reactions. For example, using 6-aryl-1-bromo-2-naphthol (1) as a starting material, As shown in scheme 1, compound (A) can be synthesized in four steps.

[Usage example as luminescent material]
The silicon-bridged 2- (2-naphthyl) indole derivative can be used alone as a light emitting material. The silicon-bridged 2- (2-naphthyl) indole derivative can also be used as a light emitting dopant material or a light emitting host material as a light emitting material together with another light emitting dopant material or a light emitting host material. In particular, by using the silicon-bridged 2- (2-naphthyl) indole derivative as a light emitting dopant material, an organic EL light emitting layer having excellent light emission efficiency and a longer light emission lifetime can be formed.

When the silicon bridged 2- (2-naphthyl) indole derivative is used as a light emitting dopant material, the host material is not particularly limited, but an anthracene derivative is preferably used. The anthracene derivative is not particularly limited as long as it can be used as a light emitting material, and various known compounds can be used. Examples of anthracene derivatives include 9,10-di (naphth-2-yl) anthracene (abbreviation: ADN), 2-tert-butyl-9,10-di (naphth-2-yl) anthracene (abbreviation: TBADN) 2-methyl-9,10-bis (naphthalen-2-yl) anthracene (abbreviation: MADN), 2,2′-di (9,10-diphenylanthracene) (abbreviation: TPBA), 4,4′-di (10- (naphthalen-1-yl) anthracen-9-yl) biphenyl (abbreviation: BUBH-3), and the like.

When a silicon-bridged 2- (2-naphthyl) indole derivative is used as the dopant material and an anthracene derivative is used as the host material, the addition ratio of the silicon-bridged 2- (2-naphthyl) indole derivative to the anthracene derivative (host compound) Is not particularly limited. The content of the silicon-bridged 2- (2-naphthyl) indole derivative is preferably 1 to 50 parts by weight, more preferably 2 to 30 parts by weight, still more preferably 2.5 to 100 parts by weight based on 100 parts by weight of the anthracene derivative. 25 parts by weight, particularly preferably 3 to 20 parts by weight.

An organic light emitting layer can be formed by depositing a silicon-crosslinked 2- (2-naphthyl) indole derivative on a support such as a substrate. When a silicon-bridged 2- (2-naphthyl) indole derivative is used as a dopant, an organic light emitting layer can be formed by co-evaporation with a host material such as an anthracene derivative.

[Organic EL device]
The above light emitting material is suitable as a material for the light emitting layer of the organic EL element.
FIG. 1 is an example of a layer configuration of an organic EL device. The organic EL device shown in FIG. 1 has a configuration called “bottom emission type” in which light is extracted from the transparent substrate 3 side. The organic EL device 1 has an organic EL element 2 on a transparent substrate 3, and the organic EL element is sealed by a sealing portion 7. The organic EL element 2 includes a functional layer 5 having at least one light emitting layer between a pair of electrodes composed of a transparent electrode layer (anode) 4 and a back electrode layer (cathode) 6.

The functional layer 5 is formed by laminating a plurality of organic compound thin films. FIG. 2 is an example of a layer configuration of the functional layer 5. In the organic EL element 2 shown in FIG. 2, the functional layer 5 includes a hole injection layer 10, a hole transport layer 11, a light emitting layer 12, an electron transport layer 15, and an electron injection layer 16. That is, in the organic EL element 2, the light emitting layer 12 is located between the transparent electrode layer 4 and the back electrode layer 6.

(Transparent substrate)
In the bottom emission type organic EL device, the transparent substrate 3 is not particularly limited as long as it is made of a material having translucency. In the embodiment of the bottom emission method shown in FIG. 1, since light is extracted from the transparent substrate 3 side, the transparent substrate 3 preferably has a transmittance in the visible light region of 80% or more, and preferably 90% or more. More preferably, it is more preferably 95% or more. As the transparent substrate 3, a glass substrate, a flexible transparent film substrate, or the like may be used. When the organic EL device adopts a top emission method, the substrate may be opaque.

(Transparent electrode)
A transparent electrode layer (anode) 4 is laminated on the transparent substrate 3. The material which comprises the transparent electrode layer 4 is not specifically limited, A well-known thing can be used. Examples thereof include those made of materials such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), and zinc oxide (ZnO). Among these, ITO or IZO is preferably used from the viewpoint of the light extraction efficiency from the light emitting layer 12 and the ease of electrode patterning.

The transparent electrode layer 4 may be doped with one or more dopants such as aluminum, gallium, silicon, boron, and niobium as necessary. The transmittance of the transparent electrode layer 4 is preferably 70% or more, more preferably 80% or more, and further preferably 90% or more in the visible light region. The transparent electrode layer 4 is formed on the transparent substrate 3 by a dry process such as sputtering or CVD. The film thickness of the transparent electrode layer 4 may be appropriately selected in consideration of light transmittance and electrical conductivity, and is, for example, 80 to 300 nm, preferably 100 to 150 nm, more preferably 130 to 150 nm.

(Back electrode layer)
A functional layer 5 is formed on the transparent electrode layer 4, and a back electrode layer (cathode) 6 is formed thereon. The material used for the back electrode layer is preferably a metal having a low work function, or an alloy or metal oxide thereof. Examples of the metal having a low work function include Li for alkali metals and Mg, Ca, etc. for alkaline earth metals. In addition, a single metal made of rare earth metal or an alloy such as Al, In, or Ag may be used. Further, as disclosed in Japanese Patent Application Laid-Open No. 2001-102175, etc., an organic metal complex compound containing at least one selected from the group consisting of alkaline earth metal ions and alkali metal ions as an organic layer in contact with the cathode Can also be used. In this case, it is preferable to use a metal capable of reducing metal ions in the complex compound to a metal in a vacuum, such as Al, Zr, Ti, Si, or an alloy containing these metals, as the cathode.

(Functional layer)
Next, the functional layer 5 will be described. The functional layer 5 has at least one light emitting layer 12. Each layer constituting the functional layer is generally composed of an amorphous film containing an organic compound, a polymer compound, a transition metal complex, or the like. The functional layer 5 generally has a laminated structure composed of a plurality of layers. In FIG. 2, the functional layer 5 includes a hole injection layer 10, a hole transport layer 11, a light emitting layer 12, an electron transport layer 15, and an electron injection layer 16. The functional layer 5 only needs to have the light emitting layer 12, and the hole injection layer 10, the hole transport layer 11, the electron transport layer 15, and the electron injection layer 16 are provided as necessary.

(Light emitting layer)
In the organic EL device of the present invention, the light emitting layer 12 contains the above silicon-bridged 2- (2-naphthyl) indole derivative. Further, as described above, the light emitting material of the light emitting layer 12 preferably contains an anthracene derivative as a host material. In this case, the light emitting layer 12 preferably contains 1 to 50 parts by weight of a silicon-bridged 2- (2-naphthyl) indole derivative as a dopant material with respect to 100 parts by weight of an anthracene derivative as a host material. The content of the silicon-crosslinked 2- (2-naphthyl) indole derivative is more preferably 2 to 30 parts by weight, still more preferably 2.5 to 25 parts by weight, and particularly preferably 3 to 20 parts by weight. By using the above light emitting material as a material constituting the light emitting layer, a blue light emitting layer having excellent light emission efficiency can be obtained.

The formation method of the light emitting layer is not particularly limited, and a dry process such as a vacuum deposition method or a transfer method, or a wet process such as a coating method or a printing method can be employed. In particular, since the luminescent material of the present invention exhibits good film forming properties, a vacuum deposition method is preferably used. In the vacuum vapor deposition method, a desired vapor deposition ratio (dope concentration) can be realized by co-depositing a host material and a dopant material and controlling the vapor deposition rate at that time.

(Hole injection layer and hole transport layer)
As shown in FIG. 2, the functional layer 5 may have a hole injection layer 10 or a hole transport layer 11 between the light emitting layer 12 and the anode 4. Although not shown, an electron blocking layer or the like may be further provided between the hole transport layer 11 and the light emitting layer 12.

Examples of the material constituting the hole injection layer 10 include metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, and manganese oxide, and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano. -Quinodimethane (abbreviation: F4-TCNQ). Further, a mixed layer of molybdenum trioxide and N, N-bis (naphthalen-1-yl) -N, N′-bis (phenyl) -benzidine (abbreviation: NPB) may be used as the hole injection layer 10. it can.

(Hole transport layer)
Materials constituting the hole transport layer include arylamine compounds, imidazole compounds, oxadiazole compounds, oxazole compounds, triazole compounds, chalcone compounds, styrylanthracene compounds, stilbene compounds, tetraarylethenes. Compounds, triarylamine compounds, triarylethene compounds, triarylmethane compounds, phthalocyanine compounds, fluorenone compounds, hydrazine compounds, carbazole compounds, N-vinylcarbazole compounds, pyrazoline compounds, pyrazolone compounds Examples include compounds, phenylanthracene compounds, phenylenediamine compounds, polyarylalkane compounds, polysilane compounds, polyphenylene vinylene compounds, and the like.

Particularly, in the hole transport layer containing an arylamine compound, since the arylamine compound is easily radically cationized, the hole transport efficiency from the hole transport layer to the light emitting layer can be effectively increased. Of the arylamine compounds that can constitute the hole transport layer material, triarylamine derivatives are preferred, and in particular, 4,4′-bis [N- (2-naphthyl) -N-phenyl-amino] biphenyl (“α-NPD Or “NPB”) is particularly preferred.

(Electron transport layer and electron injection layer)
As shown in FIG. 2, the functional layer 5 may have an electron injection layer 16 and an electron transport layer 15 between the light emitting layer 12 and the cathode 6. Although not shown, a hole blocking layer or the like may be further provided between the electron transport layer 15 and the light emitting layer 12. Examples of the material constituting the hole blocking layer include 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (common name: butocuproine, BCP).

Materials constituting the electron transport layer 15 include tris (8-hydroxy-quinolinato) aluminum (abbreviation: Alq ₃ ), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 1,3-bis [2- (2,2′-bipyridin-6-yl) -1,3,4-oxadiazo-5-yl] benzene (Bpy-OXD), 4,7-diphenyl-1,10-phenanthroline (Bphen), 2,2 ′, 2 ″-(1,3,5-Benzinetriyl) -tris (1-phenyl-1-H-benzimidazole) (TPBi), 2- (4-biphenyl) -5- (4 -Tert-Butifphenyl) -1,3,4-oxadiazole (PBD), bis (2-methyl 1-8-quinolinolato) -4- (phenylphenolato) aluminum (BAlq), 3- (4 Biphenyl) -4-phenyl -5-tert-butylphenyl-1,2,4-triazole (TAZ), and the like.

Examples of the material constituting the electron injection layer 16 include alkali metals such as Li; alkaline earth metals such as Mg and Ca; alloys containing one or more of the metals; oxides, halides, and carbonates of the metals; As well as mixtures thereof. Specific examples include 8-hydroxyquinolinolato (lithium) (Liq), lithium fluoride (LiF), and the like.

The organic EL element 2 shown in FIG. 2 has a hole injection layer 10, a hole transport layer 11, a light emitting layer 12, an electron on the transparent electrode layer 4 formed on the transparent substrate 3 by a technique such as vacuum deposition. It can be manufactured by laminating the transport layer 15, the electron injection layer 16, and the back electrode layer 6 sequentially. The organic EL element 2 manufactured in this way is sealed by the sealing portion 7 to become the organic EL device 1.

In addition, although FIG. 2 demonstrated the structure in which the functional layer 5 consists of five layers, this invention is not limited to the said embodiment. For example, a configuration in which some or all of the hole injection layer 10, the hole transport layer 11, the electron transport layer 15, and the electron injection layer 16 are omitted may be employed. Further, as described above, a hole blocking layer and an electron blocking layer may be provided before and after the light emitting layer 12.

The method for forming each layer constituting the functional layer 5 is not particularly limited, and can be formed by an appropriate method such as a vacuum deposition method, a coating method, or a printing method.

Hereinafter, the present invention will be described more specifically with reference to compound synthesis examples and organic EL device fabrication examples, but the present invention is not limited to these examples.

[Example 1] Synthesis of Compound A1 In this example, Compound A1 was synthesized in four stages by the above scheme 1 using 6-phenyl-1-bromo-2-naphthol (1) as a starting material. It should be noted that schem 1 is described in Efficient blue electroluminescence of silylene-bridged 2- (2-naphthyl) indole (M. Shimizu et al. J. Mater. Chem. 2012, Vol. 22, pages 4337-4342) except that the starting materials are different. This is similar to the synthetic scheme described.

The resulting compound A1 had a melting point of 250 ° C. and a thermal decomposition temperature of 306 ° C. (the temperature at which mass loss by thermogravimetric analysis (TGA) was 5% was defined as the thermal decomposition temperature).
Compound ¹ was measured for ¹ H-NMR, and the following results were obtained.
¹ H-NMR (400 MHz, CDCl ₃ ): δ (ppm) = 0.92 (d, J = 7.6 Hz, 6H), 1.39 (d, J = 7.6 Hz, 6H), 1.63 ( heptet, J = 7.6 Hz, 6H), 7.17 (ddd, J = 7.4, 1.2 Hz, 1H), 7.24 (ddd, J = 8.0, 1.2 Hz, 1H), 7 .36 to 7.42 (m, 2H), 7.50 (dd, J = 7.6 Hz, 2H), 7.65 (d, J = 8.0 Hz, 1H), 7.73 to 7.79 ( m, 3H), 7.88 (d, J = 8.8 Hz, 1H), 7.95 (d, J = 8.4 Hz, 1H), 8.03 to 8.08 (m, 2H).

[Example 2] Synthesis of Compound A2 Compound A2 was synthesized in the same manner as in Example 1 except that 6- (4-methoxyphenyl) -1-bromo-2-naphthol was used as a starting material.

The resulting compound A2 had a melting point of 256 ° C. and a thermal decomposition temperature of 321 ° C.
Compound ¹ was measured for ¹ H-NMR, and the following results were obtained.
¹ H-NMR (CDCl ₃ , 300 MHz): δ (ppm) = 0.91 (d, 6H, J = 7.2 Hz), 1.28 (d, 6H, J = 7.2 Hz), 1.55 ( heptet, 2H, J = 7.2, 7.2 Hz), 3.89 (s, 3H), 4.23 (s, 3H), 7.40 (d, 2H, J = 9 Hz), 7. 18 (d, 2H, J = 8.1 Hz), 7.40 (d, 1H, J = 8.7 Hz), 7.64 (d, 1H, J = 7.8 Hz), 7.69 (d, 2H) , J = 9.0 Hz), 7.73 (d, 1H, J = 6.9 Hz), 7.85 (d, 1H, J = 8.7 Hz), 7.93 (d, 1H, J = 9. 0 Hz), 7.99 (s, 1 H), 8.05 (d, 1 H, J = 8.4 Hz).

[Example 3] Synthesis of Compound A3 Compound A3 was synthesized in the same manner as in Example 1 except that 6- (4-trifluoromethylphenyl) -1-bromo-2-naphthol was used as a starting material. did.

[Comparative Example 1]
The following compound (thermal decomposition temperature: 244 ° C.) was obtained in the same manner as in Example 1 except that 1-bromo-2-naphthol was used as a starting material.

[Evaluation of Luminescent Properties of Compounds]
Using the crystallites of the respective compounds obtained in the above Examples and Comparative Examples as samples, using an absolute PL quantum yield measuring apparatus (model number: C9920-02, manufactured by Hamamatsu Photonics), fine crystals at room temperature (25 ° C.) were used. The emission quantum yield and emission maximum wavelength of the crystal were measured. Moreover, the light emission quantum yield and the light emission maximum wavelength in the film which disperse | distributed each compound in PMMA were measured. The results are shown in Table 1.

[Example 4] Production of organic EL device using compound A1 Bottom emission type evaluation device having a light emitting region of 2 mm x 2 mm on a glass substrate having a patterned ITO electrode (film thickness 150 nm) by the following procedure. Was made.

Molybdenum trioxide (MoO ₃ ) was vapor-deposited on the ITO electrode (anode) to form a hole injection layer (film thickness 0.8 nm). On the hole injection layer, N, N-bis (naphthalen-1-yl) -N, N′-bis (phenyl) -benzidine (NPB) was vacuum deposited to form a hole transport layer (film thickness 60 nm). Formed.

Next, the compound A1 obtained in Example 1 was vacuum deposited on the hole transport layer to form a light emitting layer (film thickness 20 nm).

On the light emitting layer, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was vacuum-deposited to form a hole blocking layer (thickness 10 nm). Next, tris (8-hydroxy-quinolinato) aluminum (Alq ₃ ) was vacuum-deposited on the hole blocking layer to form an electron transport layer (thickness 30 nm). On the electron transport layer, LiF was vacuum-deposited to form an electron injection layer (film thickness: 1 nm). On the electron injection layer, aluminum was formed to a thickness of 100 nm as a cathode.

After forming the cathode, the organic EL element after vapor deposition was moved to an inert glow box, a two-component curable resin was applied to the glass cap, and the substrate and the cap were bonded together. After the curing of the resin was completed, the bonded substrate was taken out under atmospheric pressure, a current was applied, and current-voltage-luminance (IVL) characteristics and emission intensity spectrum were measured.

[Example 5] Production of organic EL device using compound A1 As a material for the light emitting layer, instead of compound A1, compound A2 obtained in Example 2 was vacuum-deposited to form a light emitting layer (film thickness 20 nm). Formed. Otherwise, an organic EL device was produced in the same manner as in Example 4, and the IVL characteristics and emission intensity spectrum were measured under atmospheric pressure.

[Comparative Example 2]
On a glass substrate having a patterned ITO electrode (film thickness 150 nm), a bottom emission type evaluation element having a light emitting region of 2 mm × 2 mm was produced by the following procedure.

MoO ₃ and NPB were co-evaporated on the ITO electrode (anode) to form a hole injection layer (film thickness 60 nm). On the hole injection layer, NPB was vacuum deposited to form a hole transport layer (film thickness 20 nm).

Next, the compound obtained in Comparative Example 1 was vacuum deposited on the hole transport layer to form a light emitting layer (film thickness 5 nm).

An electron transporting material (ETM-033 manufactured by Merck & Co., Inc.) was vacuum deposited on the light emitting layer to form an electron transporting layer (60 nm). Next, LiF was vacuum-deposited on the electron transport layer to form an electron injection layer (film thickness 1 nm). On the electron injection layer, aluminum was formed to a thickness of 100 nm as a cathode. Thereafter, in the same manner as in Example 4, after the substrate and the cap were bonded and cured, the IVL characteristics and emission intensity spectrum were measured under atmospheric pressure.

[Example 6] Preparation of organic EL device using compound A1 as dopant material Compound A1 and 2-methyl-9,10-bis (naphthalen-2-yl) anthracene (MADN) in a weight ratio of 10:90 Was co-evaporated to form a light emitting layer (film thickness 20 nm). Otherwise, an organic EL device was produced in the same manner as in Example 4 above, and the IVL characteristics and emission intensity spectrum were measured under atmospheric pressure.

[Example 7] Production of organic EL device using compound A2 as dopant material Compound A2 and MADN were co-evaporated at a weight ratio of 10:90 to form a light emitting layer (film thickness 20 nm). Otherwise, an organic EL device was produced in the same manner as in Example 4 above, and the IVL characteristics and emission intensity spectrum were measured under atmospheric pressure.

[Comparative Example 3]
The compound obtained in Comparative Example 1 and MADN were co-evaporated at a weight ratio of 7:93 to form a light emitting layer (film thickness 20 nm). An electron transporting material (ETM-033 manufactured by Merck & Co., Inc.) was vacuum deposited thereon to form an electron transporting layer (40 nm). Otherwise, an organic EL device was produced in the same manner as in Comparative Example 2 above, and the IVL characteristics and emission intensity spectrum were measured under atmospheric pressure.

[Evaluation results of organic EL elements]
Table 2 shows the maximum light emission wavelength, the maximum current light emission efficiency, and the maximum power light emission efficiency of the organic EL devices prepared in Examples 4 to 7 and Comparative Examples 2 and 3.

From the above results, in the organic EL device using the compound A1 of Example 1 as the luminescent material and the organic EL device using the compound A2 of Example 2 as the luminescent material, when the compound A1 and the compound A2 are used alone (Example 4 and Example 5) and when A1 and A2 are used together with anthracene derivatives as dopant materials (Example 6 and Example 7), the luminous efficiency is higher than that of the comparative example. It has been shown.

In Examples 4 and 5 and Comparative Example 2, part of the element configuration such as the film thickness of the light emitting layer is different. However, the PL fluorescence quantum efficiencies of the film made of the compound A1 and the film made of the compound A2 are both substantially constant in the film thickness range of 5 nm to 20 nm. Therefore, the light emission efficiencies of the devices of Examples 4 and 5 and Comparative Example 2 This difference is not due to the difference in the thickness of the light emitting layer, but to the difference in the characteristics of the material. In Examples 6 and 7 and Comparative Example 3, the co-evaporation ratio of the dopant material in the light emitting layer is different, but the co-evaporation ratio (weight ratio) of Compound A1 and Compound A2 to MADN is 1:99 to In the range of 10:90, since the fluorescence quantum yield of the film is substantially constant, the difference in emission characteristics between Examples 6 and 7 and Comparative Example 3 is not due to the difference in the co-evaporation ratio. This can be attributed to the difference in characteristics.

[Evaluation of luminous lifetime]
The organic EL elements prepared in Examples 4 to 7 were continuously lit at a constant driving current density of 10 mA / cm ² at room temperature, and the time until the luminance became half of the initial value (light emission lifetime) was measured. The light emission time of the device of Example 4 was 5.2 hours, and the light emission time of the device of Example 5 was 4.8 hours. On the other hand, the light emission lifetime of the device of Example 6 is 280 hours, the light emission life of the device of Example 7 is 320 hours, and when the compound A1 and the compound A2 are used as the dopant material of the light emitting layer, the organic EL device It was confirmed that the light emission lifetime of the was significantly improved. From these results, it is understood that a blue light-emitting material with high luminous efficiency and long life can be obtained by using a silicon-bridged indole derivative having an aryl group introduced on the naphthalene ring as a dopant material for an anthracene derivative host.

2 Organic EL element 4 Transparent electrode layer (anode)
5 Functional layer 6 Back electrode layer (cathode)
12 Light emitting layer

Claims

Luminescent material containing a silicon-bridged indole derivative represented by the following formula (I):

In formula (I),
R 1 and R 2 each independently represents a lower alkyl group having 1 to 6 carbon atoms, an aryl group, or an unsaturated heterocyclic group,
R 3 represents a lower alkyl group having 1 to 6 carbon atoms, an aryl group, or an unsaturated heterocyclic group,
R 4 is a substituent bonded to the benzene ring, R 5 is a substituent bonded to the indole ring, p is an integer of 0 to 5, q is an integer of 0 to 4,
R 4 and R 5 are each independently a halogen atom, a cyano group, a lower alkyl group having 1 to 6 carbon atoms, a lower alkoxy group having 1 to 6 carbon atoms, a lower alkylthio group having 1 to 6 carbon atoms, or 1 to 6 halogen-substituted lower alkyl groups, halogen-substituted lower alkoxy groups having 1 to 6 carbon atoms, amino groups, aryl groups or unsaturated heterocyclic groups,
If R 4 there are a plurality, the plurality of R 4 may be the same or different, a plurality of R 4 may be bonded to form a ring structure,
If R 5 there are a plurality, the plurality of R 5, may be the same or different.
The luminescent material according to claim 1, wherein p is 0 or 1 in the formula (I).
The luminescent material according to claim 1, wherein, in the formula (I), p is 1 and R 4 is bonded to the para-position of the benzene ring.
The luminescent material according to claim 3, wherein R 4 is a methoxy group.
The luminescent material according to any one of claims 1 to 4, wherein q is 0 in the formula (I).
The luminescent material according to any one of claims 1 to 5, wherein, in the formula (I), R 1 and R 2 are the same substituent.
The light emitting material according to claim 6, wherein in the formula (I), R 1 and R 2 are both isopropyl groups and R 3 is a methyl group.
Contains a host material and a dopant material,
A luminescent material, wherein the dopant material is the luminescent material according to any one of claims 1 to 7, and the host material is an anthracene derivative.
At least a light emitting layer is provided between a pair of electrodes consisting of an anode and a cathode,
9. An organic EL device, wherein the light emitting layer comprises the light emitting material according to claim 1.