阅读说明：本技术 有机电致发光元件 (Organic electroluminescent element ) 是由 平山雄太 望月俊二 山本刚史 林秀一 朴永焕 于 2020-02-28 设计创作，主要内容包括：本发明的课题在于,为了与以单层形成了封盖层的有机EL元件相比,改善光的取出效率,提供包括由第一封盖层和折射率比第一封盖层高的第二封盖层这两层构成的封盖层的有机EL元件。本发明为有机电致发光元件,其依次至少具有阳极、空穴传输层、发光层、电子传输层、阴极和封盖层,所述封盖层为具有第一封盖层及第二封盖层这两层的结构,在波长450nm～650nm的整个范围中,所述第二封盖层的折射率比所述第一封盖层的折射率大,所述第二封盖层包含具有特定结构的芳基胺化合物。(An object of the present invention is to provide an organic EL device including a capping layer composed of two layers, i.e., a first capping layer and a second capping layer having a higher refractive index than the first capping layer, in order to improve light extraction efficiency as compared with an organic EL device in which a capping layer is formed in a single layer. The invention relates to an organic electroluminescent element, which at least comprises an anode, a hole transport layer, a luminescent layer, an electron transport layer, a cathode and a capping layer in sequence, wherein the capping layer has a structure comprising two layers, namely a first capping layer and a second capping layer, the refractive index of the second capping layer is larger than that of the first capping layer in the whole range of wavelength of 450 nm-650 nm, and the second capping layer comprises arylamine compound with a specific structure.)

1. An organic electroluminescent element comprising at least an anode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode and a capping layer in this order, wherein the capping layer has a structure comprising two layers, a first capping layer and a second capping layer in this order from the cathode side, the refractive index of the second capping layer is higher than that of the first capping layer over the entire wavelength range of 450 to 650nm, and the second capping layer comprises an arylamine compound represented by the following general formula (1),

in the formula, Ar₁、Ar₂、Ar₃And Ar₄May be the same or different from each other, and represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

Ar₁、Ar₂、Ar₃and Ar₄At least one of which is a 1-valent group represented by the following structural formula (B), or a group having the 1-valent group as a substituent,

n represents an integer of 0 to 4,

in the formula, R₁、R₂、R₃And R₄The same or different from each other, represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a silyl group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkoxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkoxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group,

R₁、R₂、R₃and R₄May form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom,

Ar₅and Ar₆May be the same or different from each other, and represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

R₁、R₂、R₃、R₄、Ar₅and Ar₆At least one of which is a linking group as a bonding site,

x represents a carbon atom or a nitrogen atom,

y represents a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom,

however, when Y is an oxygen atom or a sulfur atom, Y does not have Ar₆，

When X and Y are nitrogen atoms, X or Y does not have Ar₅Or Ar₆，

When X is a nitrogen atom and Y is a carbon atom, X or Y does not have Ar₅Or Ar₆，

There are no cases where X and Y are carbon atoms, X is a nitrogen atom and Y is an oxygen atom, and X is a nitrogen atom and Y is a sulfur atom.

2. The organic electroluminescent element according to claim 1, wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-1),

in the formula, R₁、R₂、R₃And R₄The same or different from each other, represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a silyl group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkoxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkoxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group,

R₁、R₂r and R₄May form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom,

the dotted line indicates the bonding site.

3. The organic electroluminescent element according to claim 1, wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-2),

in the formula, R₁、R₃And R₄Is the same as R in the general formula (B-1)₁、R₃And R₄The same meaning is given to the same person,

R₃and R₄May form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom,

Ar₅represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

the dotted line indicates the bonding site.

4. The organic electroluminescent element according to claim 1, wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-3),

in the formula, R₁、R₂、R₃And R₄Is the same as R in the general formula (B-1)₁、R₂、R₃And R₄The same meaning is given to the same person,

the dotted line indicates the bonding site.

5. The organic electroluminescent element according to claim 1, wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-4),

in the formula, R₁、R₃And R₄Is the same as R in the general formula (B-1)₁、R₃And R₄The same meaning is given to the same person,

R₃and R₄The same substituted benzene ring may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom to form a ring,

Ar₅represents a substituted or unsubstituted aromatic hydrocarbonA substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

the dotted line indicates the bonding site.

6. The organic electroluminescent element according to claim 1, wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-5),

in the formula, R₁、R₂、R₃And R₄Is the same as R in the general formula (B-1)₁、R₂、R₃And R₄The same meaning is given to the same person,

the dotted line indicates the bonding site.

7. The organic electroluminescent element according to claim 1, wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B'),

in the formula, R₃、R₄、R₅、R₆、R₇And R₈The same or different from each other, represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a silyl group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkoxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkoxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group,

R₃、R₄、R₅、R₆、R₇and R₈May form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom,

Ar₅and Ar₆May be the same or different from each other, and represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

R₃、R₄、R₅、R₆、R₇、R₈、Ar₅and Ar₆At least one of which is a linking group as a bonding site,

x represents a carbon atom or a nitrogen atom,

y represents a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom,

however, when Y is an oxygen atom or a sulfur atom, Y does not have Ar₆，

When X and Y are nitrogen atoms, X or Y does not have Ar₅Or Ar₆，

There are no cases where X and Y are carbon atoms, X is a nitrogen atom and Y is an oxygen atom, and X is a nitrogen atom and Y is a sulfur atom.

8. The organic electroluminescent element according to any one of claims 1 to 7, wherein n is 0 in the general formula (1).

9. The organic electroluminescent element according to any one of claims 1 to 7, wherein n is 1 in the general formula (1).

10. The organic electroluminescent element according to any one of claims 1 to 7, wherein n is 2 in the general formula (1).

11. The organic electroluminescent element according to any one of claims 1 to 10, wherein the organic electroluminescent element is provided in the organic electroluminescent elementIn the general formula (1), Ar₁、Ar₂、Ar₃And Ar₄Any two of them are a 1-valent group represented by the structural formula (B), or a group having the 1-valent group as a substituent.

12. The organic electroluminescent element according to any one of claims 1 to 10, wherein in the general formula (1), Ar₁And Ar₄Is a 1-valent group represented by the structural formula (B), or a group having the 1-valent group as a substituent.

13. The organic electroluminescent element according to any one of claims 1 to 12, wherein the electron transport layer has a refractive index (n)₂) And refractive index (n) of the first capping layer₁) Satisfying the following general formula (I) in the whole range of wavelength 450 nm-550 nm,

0.005≤n₁-n₂≤0.15(I)。

14. the organic electroluminescent element according to any one of claims 1 to 13, wherein the total thickness of the first capping layer and the second capping layer is in a range of 30nm to 120 nm.

15. The organic electroluminescent element according to any one of claims 1 to 14, wherein the refractive index of the second capping layer is 1.85 or more over the entire wavelength range of 450nm to 750 nm.

Technical Field

The present invention relates to an organic electroluminescent element (hereinafter, simply referred to as an organic EL element) as a self-luminous element suitable for various display devices, and more particularly, to an organic EL element in which a capping layer is laminated, and particularly, to an organic EL element with improved efficiency.

Background

Since the organic EL element is a self-luminous element, it is bright and excellent in visibility as compared with a liquid crystal element, and can perform a clear display, and thus active research is being conducted.

In 1987, c.w.tang of the company of eastman kodak (イーストマン & コダック) developed a laminated structure element in which various functions are shared among materials, and thus an organic EL element using an organic material was put to practical use. They laminated a phosphor capable of transporting electrons and an organic material capable of transporting holes, and injected charges of both into a phosphor layer to emit light, thereby obtaining 1000cd/m with a voltage of 10V or less²The above high luminance (see, for example, patent document 1 and patent document 2).

Conventionally, a number of improvements have been made for practical use of organic EL elements, and various functions of a stacked structure have been subdivided into a light-emitting element having a bottom emission structure in which light is extracted from the bottom of an electroluminescent element having an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode provided in this order on a substrate, thereby achieving high efficiency and durability (see, for example, non-patent document 1).

In recent years, a light-emitting element of a top emission structure in which a metal having a high work function is used for an anode and light is emitted from above is used. Unlike a light-emitting element of a bottom emission structure in which the area of light extraction is limited by a pixel circuit, a light-emitting element of a top emission structure has an advantage of enlarging the area of light extraction. In a light-emitting element having a top-emission structure, a translucent electrode such as LiF/Al/Ag (see, for example, non-patent document 2), Ca/Mg (see, for example, non-patent document 3), LiF/MgAg, or the like is used as a cathode.

In such a light-emitting element, when light emitted from the light-emitting layer enters another layer, if the light enters the other layer at a certain angle or more, total reflection occurs at the interface between the light-emitting layer and the other layer. Thus, only a portion of the emitted light can be utilized. In recent years, in order to improve light extraction efficiency, a light-emitting element has been proposed in which a "cover layer (キャッピング run body)" having a high refractive index is provided on the outer side of a translucent electrode having a low refractive index (see, for example, non-patent documents 2 and 3).

As for the effect of the capping layer in the light emitting element of the top emission structure, Ir (ppy)₃The current efficiency of the light-emitting element used for the light-emitting material was 38cd/A without a capping layer, and the current efficiency of the light-emitting element using ZnSe having a film thickness of 60nm as a capping layer was 64cd/A, and an efficiency improvement of about 1.7 times was confirmed. Further, it is shown that the maximum point of the transmittance of the translucent electrode and the capping layer does not necessarily coincide with the maximum point of the efficiency, and the maximum point of the light extraction efficiency is determined by the interference effect (for example, see non-patent document 3).

Although it has been proposed to use a metal mask with high fineness for forming a capping layer, there are problems as follows: when used under high temperature conditions, the alignment accuracy is deteriorated due to deformation caused by heat. For example, ZnSe has a melting point as high as 1100 ℃ or higher (see, for example, non-patent document 3), and a metal mask with high fineness cannot be deposited at an accurate position, and many other inorganic substances have a high deposition temperature, and therefore, it is not suitable for using a metal mask with high fineness for the same reason. Further, the light emitting element itself may be damaged. In addition, since film formation by sputtering damages the light-emitting element, it is not suitable to use a capping layer containing an inorganic substance as a constituent material.

It has also been proposed to use tris (8-hydroxyquinoline) aluminum (hereinafter abbreviated as Alq) as a capping layer for adjusting the refractive index₃) (see, for example, non-patent document 2). Known as Alq₃The organic EL material is generally used as a green light-emitting material or an electron-transporting material, and has a weak absorption near 450nm used in a cyan light-emitting element. Therefore, when used in a cyan light-emitting element, there is a problem that both color purity and light extraction efficiency are reduced.

Documents of the prior art

Patent document

Patent document 1: US5792557

Patent document 2: US 569914

Patent document 3: WO2015-001726

Non-patent document

Non-patent document 1: 9 th lecture conference presortment set of applied physics society pages 55 to 61 (2001)

Non-patent document 2: appl.phys.lett., 78, 544(2001)

Non-patent document 3: appl.phys.lett., 82, 466(2003)

Non-patent document 4: aust.j.chem., 45, 371(1992)

Non-patent document 5: j.org.chem., 60, 7508(1995)

Non-patent document 6: commun, 11, 513(1981)

Non-patent document 7: appl.phys.let., 98, 083302(2011)

Disclosure of Invention

The present invention provides a light-emitting device including a first capping layer having a high refractive index and excellent stability, durability and light resistance; and a second capping layer having a higher refractive index than the first capping layer and excellent in stability, durability and light resistance.

As physical properties in the material suitable for the second capping layer of the present invention, there can be mentioned (1) vapor-depositable without thermal decomposition; (2) the film state is stable; (3) the glass transition temperature is high; (4) the refractive index is high. In addition, as physical properties of the element suitable for the present invention, there can be mentioned (1) high light extraction efficiency; (2) no reduction in color purity; (3) the light can not change with time and can be transmitted; (4) and the service life is long.

In order to achieve the above object, the present inventors have focused on the fact that an arylamine compound having excellent stability and durability of a thin film of an arylamine material and a high refractive index is selected to produce an organic EL element used as a material constituting the second capping layer, and have conducted extensive evaluations of characteristics of the element, and as a result, have completed the present invention.

According to the present invention, the following organic EL element is provided.

1) An organic electroluminescent element comprising at least an anode, a hole transport layer, a light-emitting layer, an electron transport layer, a cathode, and a capping layer in this order, wherein the capping layer has a two-layer structure comprising a first capping layer and a second capping layer in this order from the cathode side, the refractive index of the second capping layer is higher than that of the first capping layer over the entire wavelength range of 450nm to 650nm, and the second capping layer contains an arylamine compound represented by the following general formula (1).

[ solution 1]

(wherein Ar is₁、Ar₂、Ar₃And Ar₄May be the same or different from each other, and represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

Ar₁、Ar₂、Ar₃and Ar₄At least one of which is a 1-valent group represented by the following structural formula (B), or a group having the 1-valent group as a substituent,

n represents an integer of 0 to 4. )

[ solution 2]

(in the formula, R₁、R₂、R₃And R₄The same or different from each other, represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a silyl group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkoxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkoxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group,

R₁、R₂、R₃and R₄May form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom,

Ar₅and Ar₆May be the same or different from each other, and represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

R₁、R₂、R₃、R₄、Ar₅and Ar₆At least one of which is a linking group as a bonding site,

x represents a carbon atom or a nitrogen atom,

y represents a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom,

however, when Y is an oxygen atom or a sulfur atom, Y does not have Ar₆，

In the case where X and Y are nitrogen atoms, X or Y does not have Ar₅Or Ar₆，

In which X is a nitrogen atom andwhen Y is a carbon atom, X or Y does not have Ar₅Or Ar₆，

There are no cases where X and Y are carbon atoms, X is a nitrogen atom and Y is an oxygen atom, and X is a nitrogen atom and Y is a sulfur atom. )

2) The organic EL element according to 1), wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-1).

[ solution 3]

(in the formula, R₁、R₂、R₃And R₄The same or different from each other, represents a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a silyl group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkoxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkoxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, or a substituted or unsubstituted aryloxy group,

R₁、R₂、R₃and R₄May form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom,

the dotted line indicates the bonding site. )

3) The organic EL element according to 1), wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-2).

[ solution 4]

(in the formula, R₁、R₃And R₄Is the same as R in the above general formula (B-1)₁、R₃And R₄The same meaning is given to the same person,

R₃and R₄May form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom,

Ar₅represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

the dotted line indicates the bonding site. )

4) The organic EL element according to 1), wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-3).

[ solution 5]

(in the formula, R₁、R₂、R₃And R₄Is the same as R in the above general formula (B-1)₁、R₂、R₃And R₄The same meaning is given to the same person,

the dotted line indicates the bonding site. )

5) The organic EL element according to 1), wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-4).

[ solution 6]

(in the formula, R₁、R₃And R₄Is the same as R in the above general formula (B-1)₁、R₃And R₄The same meaning is given to the same person,

then R₃And R₄With respect to the same substituted benzene ring, there may be mentioned via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atomAre bonded to each other to form a ring,

Ar₅represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

the dotted line indicates the bonding site. )

6) The organic EL element according to 1), wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B-5).

[ solution 7]

(in the formula, R₁、R₂、R₃And R₄Is the same as R in the above general formula (B-1)₁、R₂、R₃And R₄The same meaning is given to the same person,

the dotted line indicates the bonding site. )

7) The organic EL element according to 1), wherein the structural formula (B) is a 1-valent group represented by the following structural formula (B').

[ solution 8]

(in the formula, R₃、R₄、R₅、R₆、R₇And R₈The substituents may be the same or different and each represent a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, a silyl group, a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 10 carbon atoms which may have a substituent, a linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent, a linear or branched alkoxy group having 1 to 6 carbon atoms which may have a substituent, a cycloalkoxy group having 5 to 10 carbon atoms which may have a substituent, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted condensed polycyclic aromatic group, orA substituted or unsubstituted aryloxy group which is substituted or unsubstituted,

R₃、R₄、R₅、R₆、R₇and R₈May form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom,

Ar₅and Ar₆May be the same or different from each other, and represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, or a substituted or unsubstituted condensed polycyclic aromatic group,

R₃、R₄、R₅、R₆、R₇、R₈、Ar₅and Ar₆At least one of which is a linking group as a bonding site,

x represents a carbon atom or a nitrogen atom,

y represents a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom,

however, when Y is an oxygen atom or a sulfur atom, Y does not have Ar₆，

When X and Y are nitrogen atoms, X or Y does not have Ar₅Or Ar₆，

There are no cases where X and Y are carbon atoms, X is a nitrogen atom and Y is an oxygen atom, and X is a nitrogen atom and Y is a sulfur atom. )

8) The organic EL element according to any one of the above 1) to 7), wherein n is 0 in the general formula (1).

9) The organic EL element according to any one of the above 1) to 7), wherein n is 1 in the general formula (1).

10) The organic EL element according to any one of the above 1) to 7), wherein n is 2 in the general formula (1).

11) The organic EL element according to any one of the above 1) to 10), wherein Ar is represented by the general formula (1)₁、Ar₂、Ar₃And Ar₄Any two of them are a 1-valent group represented by the above structural formula (B), or a group having the 1-valent group as a substituent.

12) The organic EL element according to any one of the above 1) to 10), wherein Ar is represented by the general formula (1)₁And Ar₄Is a 1-valent group represented by the above structural formula (B), or a group having the 1-valent group as a substituent.

13) The organic electroluminescent element according to any one of 1) to 12), wherein the electron transport layer has a refractive index (n)₂) And refractive index (n) of the first capping layer₁) Satisfying the following general formula (I) in the whole range of wavelength 450 nm-550 nm,

0.005≤n₁-n₂≤0.15(I)。

14) the organic EL device according to any one of 1) to 13), wherein a total thickness of the first capping layer and the second capping layer is in a range of 30nm to 120 nm.

15) The organic EL device according to any one of 1) to 14), wherein the refractive index of the second capping layer is 1.85 or more over the entire wavelength range of 450nm to 750 nm.

In the organic EL device of the present invention, since the capping layer is provided on the outer side of the transparent or translucent electrode and has a laminated structure of the first capping layer and the second capping layer having a higher refractive index than the electrode, the light extraction efficiency is significantly improved. Further, by using the arylamine compound represented by the above general formula (1) for the second capping layer, a film can be formed at a temperature of 400 ℃ or lower, and thus, the light-emitting element is not damaged, and the light extraction efficiency of each color can be optimized by using a high-definition mask, and therefore, the light-emitting element can be suitably used for a full-color display, and a clear and bright image with high color purity can be displayed.

In the organic EL device of the present invention, since the material for the organic EL device having a high refractive index and excellent stability of the thin film, durability and light resistance is used as the material of the second capping layer, the color purity can be maintained and the light extraction efficiency can be greatly improved as compared with the conventional organic EL device. Further, an organic EL element having high efficiency and long life can be realized.

Drawings

Fig. 1 is a diagram showing the structure of organic EL devices of examples 10 to 15 and comparative examples 1 to 3.

Detailed Description

As Ar in the general formula (1)₁、Ar₂、Ar₃And Ar₄The "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic aromatic group" may specifically include phenyl, biphenyl, terphenyl, naphthyl, anthryl, phenanthryl, fluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl, benzo [9,10] benzo]Phenanthryl, pyridyl, furyl, pyrrolyl, thienyl, quinolyl, isoquinolyl, benzofuryl, benzothienyl, indolyl, carbazolyl, benzotriazolyl, benzoxazolyl, benzothiazolyl, quinoxalyl, benzimidazolyl, pyrazolyl, dibenzofuryl, dibenzothienyl, spirofluorenyl, and carbolinyl, and the like.

As Ar in the general formula (1)₁、Ar₂、Ar₃And Ar₄The "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group" or "substituted condensed polycyclic aromatic group" may specifically include a heavy hydrogen atom, a trifluoromethyl group, a cyano group, and a nitro group; halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; silyl groups such as trimethylsilyl and triphenylsilyl; a straight-chain or branched alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a tert-butyl group, a n-pentyl group, an isopentyl group, a neopentyl group, or a n-hexyl group; a linear or branched alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an ethoxy group, or a propoxy group; alkenyl groups such as allyl; aralkyl groups such as benzyl, naphthylmethyl, and phenethyl; aryloxy groups such as phenoxy and tolyloxy; arylalkoxy groups such as benzyloxy and phenethyloxy; phenyl, biphenyl, terphenyl, naphthyl, anthryl, phenanthryl, fluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl, benzo [9,10]]Aromatic hydrocarbon groups such as phenanthryl group and spirofluorenyl group, or condensed polycyclic aromatic groups; pyridine (II)An aromatic heterocyclic group such as pyridyl, furyl, thienyl, pyrrolyl, quinolyl, isoquinolyl, benzofuryl, benzothienyl, indolyl, carbazolyl, benzotriazolyl, benzoxazolyl, benzothiazolyl, quinoxalyl, benzimidazolyl, pyrazolyl, dibenzofuryl, dibenzothienyl, carbolinyl and the like; arylvinyl groups such as styryl and naphthylvinyl; acyl groups such as acetyl and benzoyl; dialkylamino groups such as dimethylamino group and diethylamino group; a disubstituted amino group substituted with an aromatic hydrocarbon group or a condensed polycyclic aromatic group such as a diphenylamino group or a dinaphthylamino group; a diaralkylamino group such as a dibenzylamino group or a di (phenylethyl) amino group; disubstituted amino groups substituted with an aromatic heterocyclic group such as dipyridyl amino, dithienylamino and the like; a dienylamino group such as a diallylamino group; a disubstituted amino group substituted with a substituent selected from the group consisting of an alkyl group, an aromatic hydrocarbon group, a condensed polycyclic aromatic group, an aralkyl group, an aromatic heterocyclic group and an alkenyl group, and these substituents may be further substituted with the substituents exemplified above. These substituents may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom, or a sulfur atom to form a ring.

As R in the structural formulae (B), (B-1), (B-2), (B-3), (B-4), (B-5) and (B')₁、R₂、R₃、R₄、R₅、R₆、R₇And R₈Examples of the "linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent", "cycloalkyl group having 5 to 10 carbon atoms which may have a substituent" or "linear or branched alkenyl group having 2 to 6 carbon atoms which may have a substituent" include "linear or branched alkyl group having 1 to 6 carbon atoms", "cycloalkyl group having 5 to 10 carbon atoms" and "linear or branched alkenyl group having 2 to 6 carbon atoms", and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, vinyl, allyl, isopropenyl and 2-butenyl groups, and the likeAnd may form a ring by bonding to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom or a sulfur atom.

As R in the structural formulae (B), (B-1), (B-2), (B-3), (B-4), (B-5) and (B')₁、R₂、R₃、R₄、R₅、R₆、R₇And R₈The "substituent" in the "substituted group" represented by "linear or branched alkyl group having 1 to 6 carbon atoms having a substituent", "cycloalkyl group having 5 to 10 carbon atoms having a substituent" or "linear or branched alkenyl group having 2 to 6 carbon atoms having a substituent" may be exemplified as the substituent represented by Ar in the general formula (1)₁、Ar₂、Ar₃And Ar₄The same groups as those shown as the "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group" or "substituted condensed polycyclic aromatic group" can be used in the same manner.

As R in the structural formulae (B), (B-1), (B-2), (B-3), (B-4), (B-5) and (B')₁、R₂、R₃、R₄、R₅、R₆、R₇And R₈The "linear or branched alkoxy group having 1 to 6 carbon atoms" or "cycloalkoxy group having 5 to 10 carbon atoms" in the "linear or branched alkoxy group having 1 to 6 carbon atoms which may have a substituent" or "cycloalkoxy group having 5 to 10 carbon atoms which may have a substituent" specifically includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, n-pentoxy, n-hexoxy, cyclopentoxy, cyclohexyloxy, cycloheptoxy, cyclooctoxy, 1-adamantoxy, and 2-adamantoxy groups, and these groups may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom, or a sulfur atom to form a ring.

As R in the structural formulae (B), (B-1), (B-2), (B-3), (B-4), (B-5) and (B')₁、R₂、R₃、R₄、R₅、R₆、R₇And R₈The "substituent" in the "substituted linear or branched alkoxy group having 1 to 6 carbon atoms having a substituent" or the "substituted cycloalkoxy group having 5 to 10 carbon atoms" represented by the above formula (1) may be mentioned₁、Ar₂、Ar₃And Ar₄The same groups as those shown as the "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group" or "substituted condensed polycyclic aromatic group" can be used in the same manner.

As R in the structural formulae (B), (B-1), (B-2), (B-3), (B-4), (B-5) and (B')₁、R₂、R₃、R₄、R₅、R₆、R₇And R₈The "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic aromatic group" may be the same as that of Ar in the general formula (1)₁、Ar₂、Ar₃And Ar₄The same groups as those shown in the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic aromatic group" can be used in the same manner.

As R in the structural formulae (B), (B-1), (B-2), (B-3), (B-4), (B-5) and (B')₁、R₂、R₃、R₄、R₅、R₆、R₇And R₈The "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group" or "substituted condensed polycyclic aromatic group" may be the same as that of Ar in the general formula (1)₁、Ar₂、Ar₃And Ar₄The "substituted aromatic hydrocarbon group" or the "substituted aromatic heterocycle" representedThe same groups as those indicated by the "substituent" in the group "or the" substituted condensed polycyclic aromatic group "may be used in the same form.

As R in the structural formulae (B), (B-1), (B-2), (B-3), (B-4), (B-5) and (B')₁、R₂、R₃、R₄、R₅、R₆、R₇And R₈The "aryloxy group" in the "substituted or unsubstituted aryloxy group" may specifically include a phenoxy group, a tolyloxy group, a biphenyloxy group, a terphenyloxy group, a naphthyloxy group, an anthracenyloxy group, a phenanthrenyloxy group, a fluorenyloxy group, an indenyloxy group, a pyreneoxy group, a peryleneoxy group, and the like, and these groups may be bonded to each other via a single bond, a substituted or unsubstituted methylene group, a substituted or unsubstituted amino group, an oxygen atom, or a sulfur atom to form a ring.

As R in the structural formulae (B), (B-1), (B-2), (B-3), (B-4), (B-5) and (B')₁、R₂、R₃、R₄、R₅、R₆、R₇And R₈The "substituent" in the "substituted aryloxy group" may be represented by Ar in the general formula (1)₁、Ar₂、Ar₃And Ar₄The same groups as those shown as the "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group" or "substituted condensed polycyclic aromatic group" can be used in the same manner.

As Ar in the structural formulae (B), (B-2), (B-4) and (B')₅And Ar₆The "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic aromatic group" may be the same as that of Ar in the general formula (1)₁、Ar₂、Ar₃And Ar₄The "substituted or unsubstituted aromatic hydrocarbon group", "substituted or unsubstituted aromatic heterocyclic group" or "substituted or unsubstituted condensed polycyclic group" representedThe same groups as those shown in the "aromatic hydrocarbon group", "aromatic heterocyclic group" or "condensed polycyclic aromatic group" in the "aromatic group" may be used in the same manner.

As Ar in the structural formulae (B), (B-2), (B-4) and (B')₅And Ar₆The "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group" or "substituted condensed polycyclic aromatic group" may be the same as that of Ar in the general formula (1)₁、Ar₂、Ar₃And Ar₄The same groups as those shown as the "substituent" in the "substituted aromatic hydrocarbon group", "substituted aromatic heterocyclic group" or "substituted condensed polycyclic aromatic group" can be used in the same manner.

R in the above structural formula (B)₁、R₂、R₃、R₄、Ar₅And Ar₆At least one of which is a linking group as a bonding site. Namely, R in the above structural formula (B)₁、R₂、R₃、R₄、Ar₅And Ar₆At least one of the two groups is a linking group which bonds the nitrogen atom of the arylamine compound represented by the above general formula (1) and the group represented by the above structural formula (B), or a linking group which bonds the group bonded to the nitrogen atom of the arylamine compound and the group represented by the above structural formula (B). The linking group as the bonding site also includes a single bond.

In the general formula (1), n represents an integer of 0 to 4, and n is preferably 0, 1 or 2, more preferably 0 or 1, from the viewpoint of the refractive index, stability of the thin film and durability.

In the general formula (1), Ar₁、Ar₂、Ar₃And Ar₄At least one of them is a 1-valent group represented by the above structural formula (B), or a group having the 1-valent group represented by the above structural formula (B) as a substituent thereof. For example, Ar can be mentioned₁、Ar₂、Ar₃And Ar₄At least one of which is represented by the above structural formula (B)A 1-valent radical, and Ar₁、Ar₂、Ar₃And Ar₄At least one of which has a 1-valent group represented by the above structural formula (B) as a substituent thereof, Ar₁、Ar₂、Ar₃And Ar₄Any two of them are a 1-valent group represented by the structural formula (B), Ar₁、Ar₂、Ar₃And Ar₄Any two of them are a group having a 1-valent group represented by the above structural formula (B) as a substituent thereof.

In the present invention, Ar is preferred from the viewpoint of refractive index, stability of thin film and durability₁And Ar₄A scheme of a 1-valent group represented by the above structural formula (B); ar (Ar)₁And Ar₄A group having a 1-valent group represented by the above structural formula (B) as a substituent thereof; and Ar₁Is a 1-valent group represented by the structural formula (B), Ar₄For the embodiment having a group having a 1-valent group represented by the above structural formula (B) as a substituent thereof, Ar is more preferred₁And Ar₄A group having a 1-valent group represented by the above structural formula (B-1), (B-3) or (B-5) as a substituent and a group having a 1-valent group represented by the above structural formula (B-2) or (B-4), and Ar is particularly preferable₁And Ar₄A group having a 1-valent group represented by the above structural formula (B-1), (B-3) or (B-5) as a substituent.

As the group substituted by the 1-valent group represented by the above structural formulae (B-1), (B-3) and (B-5), an aromatic hydrocarbon group, a condensed polycyclic aromatic group, a thienyl group, a benzothienyl group, a dibenzofuranyl group and a dibenzothienyl group are preferable, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a phenanthryl group, a fluorenyl group, a thienyl group, a benzothienyl group, a dibenzofuranyl group and a dibenzothienyl group are more preferable, a phenyl group, a biphenyl group, a fluorenyl group, a dibenzofuranyl group and a dibenzothienyl group are particularly preferable, and a phenyl group is most preferable.

That is, in the present invention, Ar is preferred₁And Ar₄Is an aromatic hydrocarbon group, a condensed polycyclic group having as a substituent a 1-valent group represented by the above structural formula (B-1), (B-3) or (B-5)Aromatic group, thienyl group, benzothienyl group, dibenzofuranyl group and dibenzothienyl group, more preferably phenyl group, biphenyl group, terphenyl group, naphthyl group, phenanthryl group, fluorenyl group, thienyl group, benzothienyl group, dibenzofuranyl group and dibenzothienyl group, particularly preferably phenyl group, biphenyl group, fluorenyl group, dibenzofuranyl group and dibenzothienyl group, and most preferably phenyl group.

Ar other than the 1-valent group represented by the above structural formula (B) and the group having the 1-valent group represented by the above structural formula (B) as a substituent thereof₁、Ar₂、Ar₃And Ar₄Preferred are aromatic hydrocarbon groups, fused polycyclic aromatic groups, thienyl groups, benzothienyl groups, dibenzofuranyl groups, and dibenzothienyl groups, more preferred are phenyl groups, biphenyl groups, terphenyl groups, naphthyl groups, phenanthryl groups, fluorenyl groups, thienyl groups, benzothienyl groups, dibenzofuranyl groups, and dibenzothienyl groups, particularly preferred are phenyl groups, biphenyl groups, fluorenyl groups, dibenzofuranyl groups, and dibenzothienyl groups, and most preferred are phenyl groups.

As Ar in the above-mentioned structural formulae (B), (B-2), (B-4) and (B')₅And Ar₆Preferred are aromatic hydrocarbon groups, fused polycyclic aromatic groups, thienyl groups, benzothienyl groups, dibenzofuranyl groups and dibenzothienyl groups, and more preferred are phenyl groups, biphenyl groups, terphenyl groups, naphthyl groups, phenanthryl groups, fluorenyl groups, thienyl groups, benzothienyl groups, dibenzofuranyl groups and dibenzothienyl groups.

In the above formula (B), only R is preferred₁、R₂、R₃、R₄、Ar₅、Ar₆Any of which is a linking group.

In the structural formulae (B) and (B'), X represents a carbon atom or a nitrogen atom, and Y represents a carbon atom, an oxygen atom, a sulfur atom or a nitrogen atom. Wherein, when Y is an oxygen atom or a sulfur atom, Y does not have Ar₆(absence of Ar)₆) When X and Y are nitrogen atoms, X or Y does not have Ar₅Or Ar₆(absence of Ar)₅Or Ar₆Any of the above), X or Y does not have Ar when X is a nitrogen atom and Y is a carbon atom₅Or Ar₆(absence of Ar)₅Or Ar₆Any of the above).

In the structural formulae (B) and (B'), when X is a nitrogen atom, Y is preferably a nitrogen atom, and in this case, Ar is preferably used from the viewpoint of stability of the compound₅Or Ar₆To a linking group with Ar₁、Ar₂、Ar₃Or Ar₄The carbon atom of the group represented is bonded (the 1-valent group represented by the structural formula (B) or (B') is Ar)₁、Ar₂、Ar₃Or Ar₄A substituent of (a).

In the structural formulae (B) and (B'), when X is a carbon atom, Y is preferably a carbon atom, an oxygen atom or a sulfur atom, and more preferably an oxygen atom or a sulfur atom. In the structural formulae (B) and (B'), the case where X is a nitrogen atom and Y is an oxygen atom or a sulfur atom is excluded from the present invention.

Specific examples of particularly preferred compounds among the arylamine compounds represented by the general formula (1) which are preferably used in the organic EL device of the present invention are shown below, but the present invention is not limited to these compounds.

[ solution 9]

[ solution 10]

[ solution 11]

[ solution 12]

The arylamine compound can be synthesized by a known method (for example, see patent document 3).

Purification of these compounds can be performed by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, or the like, recrystallization using a solvent, crystallization, or the like. In the present invention, it is preferable that purification by sublimation purification is finally performed after these purifications are performed.

As the physical property values of these compounds, it is preferable to measure the glass transition temperature (Tg) and the refractive index. The glass transition temperature (Tg) is an index of stability in a thin film state, and the refractive index is an index of improvement in light extraction efficiency.

The glass transition temperature (Tg) can be measured using a powder by a high-sensitivity differential scanning calorimeter (manufactured by ブルカー · エイエックスエス, DSC 3100S).

The refractive index can be measured by preparing a thin film of 80nm on a silicon substrate and using a spectrometer (F10-RT-UV, manufactured by フィルメトリクス Co.).

The arylamine compound represented by the general formula (1) which is preferably used in the organic EL device of the present invention can be used as a constituent material of a hole injection layer, a hole transport layer, a light-emitting layer, an electron blocking layer, or a capping layer of the organic EL device.

Examples of the light-emitting element having a top-emission structure as the structure of the organic EL element of the present invention include a structure including an anode made of a metal, a hole-transporting layer, a light-emitting layer, an electron-transporting layer, a semitransparent cathode, a first capping layer, and a second capping layer in this order on a glass substrate, a structure including a hole-injecting layer between the anode and the hole-transporting layer, a structure including an electron-blocking layer between the hole-transporting layer and the light-emitting layer, a structure including a hole-blocking layer between the light-emitting layer and the electron-transporting layer, and a structure including an electron-injecting layer between the electron-transporting layer and the cathode. In these multilayer structures, one organic layer can function as a certain layer or layers, and for example, a structure in which one organic layer functions as both a hole transport layer and an electron blocking layer, or a structure in which one organic layer functions as both an electron transport layer and a hole blocking layer can be provided. The total film thickness of the layers of the organic EL element is preferably about 200nm to 750nm, more preferably about 350nm to 600 nm. The total film thickness of the first capping layer and the second capping layer is, for example, preferably 30nm to 120nm, more preferably 40nm to 80 nm. In this case, a good light extraction efficiency is obtained. The film thicknesses of the first capping layer and the second capping layer can be appropriately changed depending on the kind of light-emitting material used in the light-emitting element, the thickness of the organic EL element other than the capping layer, and the like.

As the anode of the organic EL device of the present invention, an electrode material having a large work function such as ITO or gold is used.

As the material of the hole injection layer of the organic EL element of the present invention, arylamine compounds having a structure in which 3 or more triphenylamine structures are present in the molecule and are linked by a single bond or a 2-valent group containing no hetero atom, for example, starburst-type triphenylamine derivatives, various triphenylamine 4-mers, porphyrin compounds typified by copper phthalocyanine, acceptor-type heterocyclic compounds such as hexacyanoazabenzo [9,10] phenanthrene, coating-type polymer materials, and the like can be used.

As the material of the hole transport layer of the organic EL element of the present invention, N '-diphenyl-N, N' -di (m-tolyl) benzidine (hereinafter abbreviated as TPD), N '-diphenyl-N, N' -di (α -naphthyl) benzidine (NPD), 1-bis [4- (di-4-tolylamino) phenyl ] cyclohexane (TAPC), and the like can be used, and particularly, an arylamine compound having a structure in which 2 triphenylamine structures are present in the molecule and are linked by a single bond or a 2-valent group containing no hetero atom, for example, N, N, N ', N' -tetrabiphenylylbenzidine, and the like are preferably used. Further, arylamine compounds having a structure in which 3 or more triphenylamine structures are present in the molecule and are linked by a single bond or a 2-valent group containing no hetero atom, such as various triphenylamine 3-mers and 4-mers, are preferably used.

As materials for the hole injection layer and the hole transport layer, a product obtained by P-doping antimony tris (bromophenyl) amine hexachloride or the like with a material generally used for these layers, a polymer compound having a structure of a benzidine derivative such as TPD in a partial structure thereof, or the like can be used.

As the material of the electron-blocking layer of the organic EL element of the present invention, compounds having an electron-blocking effect, such as 4, 4', 4 ″ -tris (N-carbazolyl) triphenylamine (hereinafter abbreviated as TCTA), 9-bis [4- (carbazol-9-yl) phenyl ] fluorene, 1, 3-bis (carbazol-9-yl) benzene (hereinafter abbreviated as mCP), carbazole derivatives such as 2, 2-bis (4-carbazol-9-ylphenyl) adamantane (Ad-Cz), and compounds having a triphenylsilyl or triarylamine structure, such as 9- [4- (carbazol-9-yl) phenyl ] -9- [4- (triphenylsilyl) phenyl ] -9H-fluorene, can be used.

Alq can be used as a material for a light-emitting layer of an organic EL element of the present invention₃And metal complexes of quinolyl phenol derivatives, various metal complexes, anthracene derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, polyparaphenylene vinylene derivatives, and the like. The light-emitting layer may be composed of a host material and a dopant material, and a thiazole derivative, a benzimidazole derivative, a polydialkylfluorene derivative, or the like can be used as the host material in addition to the light-emitting material. As the dopant material, quinacridone, coumarin, rubrene, perylene, a derivative thereof, a benzopyran derivative, a rhodamine derivative, an aminostyryl derivative, or the like can be used.

In addition, as the light-emitting material, a phosphorescent light-emitting material can also be used. As the phosphorescent emitter, a phosphorescent emitter of a metal complex such as iridium or platinum can be used. Using Ir (ppy)₃Green phosphorescent emitters such as FIrpic and FIr6, and Btp₂Red phosphorescent emitters such as ir (acac) and the like, and in this case, carbazole derivatives such as 4, 4' -bis (N-Carbazolyl) Biphenyl (CBP), TCTA, mCP and the like can be used as a host material having hole injection and transport properties. In addition, as the electron-transporting host material, p-bis (triphenylsilyl) benzene (UGH2), 2', 2 ″ - (1, 3, 5-phenylene) -tris (1-phenyl-1H-benzimidazole) (TPBI), and the like can be used, and by using them, it is possible to useA high-performance organic EL element was produced.

Doping of the phosphorescent light-emitting material into the host material is preferably performed by co-evaporation in a range of 1 to 30 wt% with respect to the entire light-emitting layer in order to avoid concentration quenching.

Further, as the light-emitting material, a material emitting delayed fluorescence, such as CDCB derivatives, e.g., PIC-TRZ, CC2TA, PXZ-TRZ, and 4CzIPN, can be used (see, for example, non-patent document 7).

As the material of the hole-blocking layer of the organic EL element of the present invention, a compound having a hole-blocking effect, such as a phenanthroline derivative such as Bathocuproine (BCP), a metal complex of a quinolyl derivative such as bis (2-methyl-8-quinolinolato) -4-phenylphenolate aluminum (III) (hereinafter abbreviated as BAlq), various rare earth complexes, a triazole derivative, a triazine derivative, or an oxadiazole derivative, can be used. These materials may double as the material of the electron transport layer.

As the material of the electron transport layer of the organic EL element of the present invention, Alq can be used₃And metal complexes of quinolyl phenol derivatives including BAlq, various metal complexes, triazole derivatives, triazine derivatives, oxadiazole derivatives, thiadiazole derivatives, pyridoindole derivatives, carbodiimide derivatives, quinoxaline derivatives, phenanthroline derivatives, and silole derivatives. In addition, they are preferably compounds capable of forming an electron transport layer satisfying the above general formula (I).

As a material of the electron injection layer of the organic EL element of the present invention, an alkali metal salt such as lithium fluoride or cesium fluoride, an alkaline earth metal salt such as magnesium fluoride, a metal oxide such as alumina, or the like can be used, and the electron injection layer can be omitted depending on the preferable selection of the electron transport layer and the cathode.

Further, as the material of the electron injection layer and the electron transport layer, a material obtained by N-doping a metal such as cesium to a material generally used for these layers can be used.

As the translucent cathode of the organic EL element of the present invention, an electrode material having a low work function such as aluminum, an alloy having a low work function such as a magnesium silver alloy, a magnesium calcium alloy, a magnesium indium alloy, or an aluminum magnesium alloy, ITO, IZO, or the like is used as the electrode material.

As a material of the first capping layer of the organic EL element of the present invention, an arylamine compound or the like is preferably used.

As the second capping layer of the organic EL device of the present invention, an arylamine compound represented by the above general formula (1) or the like is preferably used.

These materials used for each layer constituting the organic EL element of the present invention can be formed into a thin film by a known method such as a vapor deposition method, a spin coating method, or an ink jet method.

These materials may be used alone or in combination as a single layer. Further, a laminated structure of layers formed by separately forming these materials, a laminated structure of layers formed by mixing them, or a laminated structure of layers formed by separately forming these materials and layers formed by mixing a plurality of these materials may be employed.

In the above description, the organic EL element having the top emission structure is described, but the present invention is not limited to this, and the present invention is also applicable to an organic EL element having a bottom emission structure and an organic EL element having a dual emission structure that emits light from both the upper side and the bottom side. In these cases, the electrode positioned in the direction of extracting light from the light-emitting element to the outside needs to be transparent or translucent.

The refractive index of the second capping layer is preferably higher than that of the adjacent first capping layer in the entire range of wavelengths 450nm to 650nm, and the refractive index of the first capping layer is preferably higher than that of the electron transport layer in the entire range of wavelengths 450nm to 550 nm. That is, the second capping layer having a high refractive index improves the light extraction efficiency in the organic EL element, and is effective in that the effect of light interference is large when the reflectance at the second capping layer and the first capping layer and the reflectance at the first capping layer and the electron transport layer are high. Therefore, the refractive index of the second capping layer is preferably higher than that of the adjacent first capping layer, and the refractive index of the entire wavelength range of 450nm to 750nm may be 1.70 or more, preferably 1.80 or more, particularly preferably 1.85 or more, and most preferably 1.90 or more.

As described above, the refractive index of the second capping layer is preferably higher than that of the first capping layer in the entire range of wavelengths of 450nm to 650nm, specifically, is preferably higher than that of the first capping layer by 0.05 or more, and more preferably higher by 0.1 or more.

In addition, as described above, the refractive index of the first capping layer is preferably higher than the refractive index of the electron transit layer, and specifically, the refractive index (n) of the electron transit layer is preferably₂) Refractive index (n) of the first capping layer₁) The following general formula (I) is satisfied in the whole range of wavelength 450 nm-550 nm.

0.005≤n₁-n₂≤0.15 (I)

The organic EL element of the present invention has a structure having two layers of the first capping layer and the second capping layer as described above, and the refractive index of the first capping layer and the refractive index of the electron transport layer satisfy the above conditions, so that the color purity is maintained and the light extraction efficiency is greatly improved. In particular, when the organic EL element of the present invention is a cyan light emitting element, the effects of maintaining color purity and improving light extraction efficiency become remarkable.

The materials constituting these layers may be selected from materials satisfying the above general formula (I) and materials capable of constituting the electron transport layer, for example, from materials having a lower refractive index than the second capping layer containing the arylamine compound represented by the above general formula (1).

The embodiments of the present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples below.

Examples

(example 1)

Synthesis of < N, N '-bis {4- (2H-benzo [1, 2, 3] triazol-2-yl) phenyl } -N, N' -diphenyl-4, 4 '-diamino-1, 1' -biphenyl (Compound (1-1))

4.2g of 2- (4-bromophenyl) -2H-benzo [1, 2, 3] triazole, 2.3g of N, N' -diphenylbenzidine, 2.0g of sodium tert-butoxide, and 50ml of toluene were charged into a reaction vessel purged with nitrogen, and nitrogen gas was introduced while ultrasonic wave irradiation was performed for 30 minutes. 62.0mg of palladium acetate and 0.2ml of tri-t-butylphosphine were added thereto, and the mixture was heated and stirred at 91 ℃ for 5 hours. After cooling to room temperature, 50ml of toluene was added to conduct extraction, whereby an organic layer was obtained. The organic layer was concentrated and purified by column chromatography (carrier: NH silica gel, eluent: toluene/N-hexane), and further subjected to dispersion washing using 100ml of N-hexane to obtain 3.3g (yield 66%) of N, N '-bis {4- (2H-benzo [1, 2, 3] triazol-2-yl) phenyl } -N, N' -diphenyl-4, 4 '-diamino-1, 1' -biphenyl (compound (1-1)) as a yellow powder.

The structure of the obtained yellow powder was identified by NMR.

By using¹H-NMR(THF-d₈) The following 34 hydrogen signals were detected.

δ(ppm)＝8.26(4H)、7.89(4H)、7.60(4H)、7.39(4H)、7.33(4H)、7.24(4H)、7.21(8H)、7.10(2H)

[ solution 13]

(example 2)

< N, N '-bis {4- (2H-benzo [1, 2, 3] triazol-2-yl) phenyl } -N, N' -diphenyl-4, 4 '-diamino-1, 1': synthesis of 4 ', 1' -terphenyl (Compound (1-2) >)

A reaction vessel substituted with nitrogen was charged with 4, 4 ″ -diiodo-1, 1': 4 ', 1' -terphenyl 14.0g, {4- (2H-benzo [1, 2, 3] triazol-2-yl) phenyl } phenyl amine 18.3g, potassium carbonate 13.2g, copper powder 0.3g, sodium hydrogen sulfite 0.9g, 3, 5-di-tert-butylsalicylic acid 0.7g, and dodecylbenzene 30ml were heated and stirred at 210 ℃ for 44 hours. After naturally cooling to room temperature, 50ml of toluene was added, and a precipitate was obtained by filtration. To the precipitate was added 230ml of 1, 2-dichlorobenzene, and the mixture was heated to dissolve the precipitate, and insoluble matter was removed by hot filtration. The filtrate was concentrated, and crystallization purification using 1, 2-dichlorobenzene was performed, followed by dispersion washing using methanol, whereby N, N ' -bis {4- (2H-benzo [1, 2, 3] triazol-2-yl) phenyl } -N, N ' -diphenyl-4, 4 ″ -diamino-1, 1 ': 22.2g (yield: 96%) of 4 ', 1' -terphenyl (compound (1-2)) was obtained as a yellow powder.

The structure of the obtained yellow powder was identified by NMR.

By using¹H-NMR(CDCl₃) The following 38 hydrogen signals were detected.

δ(ppm)＝8.24(4H)、7.99-7.92(4H)、7.72-7.58(7H)、7.50-7.12(23H)

[ solution 14]

(example 3)

< N, N ' -bis {4- (benzoxazol-2-yl) phenyl } -N, N ' -diphenyl-4, 4 "-diamino-1, 1 ': synthesis of 4 ', 1' -terphenyl (Compound (1-22) >)

In example 3, by using {4- (benzoxazol-2-yl) phenyl } phenylamine instead of {4- (2H-benzo [1, 2, 3] triazol-2-yl) phenyl } phenylamine and carrying out the reaction under the same conditions, N ' -bis {4- (benzoxazol-2-yl) phenyl } -N, N ' -diphenyl-4, 4 ″ -diamino-1, 1 ': 12.4g (yield: 47%) of 4 ', 1' -terphenyl (compound (1-22)) was obtained as a yellow powder.

The structure of the obtained yellow powder was identified by NMR.

By using¹H-NMR(CDCl₃) The following 38 hydrogen signals were detected.

δ(ppm)＝8.13(4H)、7.80-7.55(11H)、7.50-7.16(23H)

[ solution 15]

(example 4)

< Synthesis of N, N '-bis {4- (benzoxazol-2-yl) phenyl } -N, N' -diphenyl-4, 4 '-diamino-1, 1' -biphenyl (Compound (1-23) >)

In example 1, a reaction was carried out using 2- (4-bromophenyl) -benzoxazole in place of 2- (4-bromophenyl) -2H-benzo [1, 2, 3] triazole under the same conditions, whereby 8.8g (yield 54%) of N, N '-bis {4- (benzoxazol-2-yl) phenyl } -N, N' -diphenyl-4, 4 '-diamino-1, 1' -biphenyl (compound (1-23)) was obtained as a pale yellow powder.

For the obtained pale yellow powder, the structure was identified using NMR.

By using¹H-NMR(CDCl₃) The following 34 hydrogen signals were detected.

δ(ppm)＝8.12(4H)、7.80-7.72(2H)、7.60-7.53(5H)、7.41-7.14(23H)

[ solution 16]

(example 5)

< Synthesis of N, N '-bis {4- (benzothiazol-2-yl) phenyl } -N, N' -diphenyl-4, 4 '-diamino-1, 1' -biphenyl (Compound (1-25))

In example 1, a reaction was carried out using 2- (4-bromophenyl) -benzothiazole instead of 2- (4-bromophenyl) -2H-benzo [1, 2, 3] triazole under the same conditions, whereby 9.3g (yield 62%) of N, N '-bis {4- (benzothiazol-2-yl) phenyl } -N, N' -diphenyl-4, 4 '-diamino-1, 1' -biphenyl (compound (1-25)) was obtained as a pale yellow powder.

For the obtained pale yellow powder, the structure was identified using NMR.

By using¹H-NMR(CDCl₃) The following 34 hydrogen signals were detected.

δ(ppm)＝8.10-7.88(8H)、7.60-7.13(26H)

[ solution 17]

(example 6)

< N, N ' -bis {4- (benzothiazol-2-yl) phenyl } -N, N ' -diphenyl-4, 4 "-diamino-1, 1 ': synthesis of 4 ', 1' -terphenyl (Compound (1-27) >)

To a reaction vessel purged with nitrogen, 9.3g of N- {4- (benzothiazol-2-yl) phenyl } phenylamine, 4 ″ -diiodo-1, 1': 4 ', 1' -terphenyl 7.1g, tert-butoxy sodium 4.6g, toluene 140ml, irradiation 30 minutes ultrasonic wave while introducing nitrogen. 0.20g of palladium acetate and 0.5g of a 50% (v/v) toluene solution of tert-butylphosphine were added thereto, and the mixture was heated under reflux for 3 hours while stirring. After cooling to room temperature and obtaining a precipitate by filtration, the precipitate was purified by repeated crystallization using a mixed solvent of 1, 2-dichlorobenzene and methanol to obtain N, N ' -bis {4- (benzothiazol-2-yl) phenyl } -N, N ' -diphenyl-4, 4 ″ -diamino-1, 1 ': 7.0g (yield 58%) of 4 ', 1' -terphenyl (compound (1-27)) was obtained as a green powder.

The structure of the obtained green powder was identified by NMR.

By using¹H-NMR(CDCl₃) The following 38 hydrogen signals were detected.

δ(ppm)＝8.05(2H)、7.98(4H)、7.90(2H)、7.70(4H)、7.61(4H)、7.50(2H)、7.42-7.31(6H)、7.30-7.11(14H)

[ solution 18]

(example 7)

The arylamine compound represented by the general formula (1) was measured for its glass transition temperature by a high-sensitivity differential scanning calorimeter (manufactured by ブルカー & エイエックスエス, DSC 3100S). The results are shown in table 1.

[ Table 1]

The arylamine compound represented by the general formula (1) has a glass transition temperature of 100 ℃ or higher, and shows that the thin film state is stable.

(example 8)

A vapor-deposited film having a thickness of 80nm was formed on a silicon substrate using an arylamine compound represented by the above general formula (1), and the refractive index n was measured using a spectroscopic measuring apparatus (F10-RT-UV, manufactured by フィルメトリクス Co.). For comparison, for Alq₃And comparative compound (2-1) and comparative compound (2-2) of the following structural formulae were also measured. The measurement results are shown in table 2.

[ solution 19]

[ Table 2]

Thus, the arylamine compound represented by the general formula (1) has a ratio of Alq to Alq₃And the refractive index of the comparative compound (2-1) and the comparative compound (2-2) was large. In addition, comparative compound (2-1) had a refractive index ratio Alq₃Small values, satisfying the above general formula (I).

(example 9)

For using Alq₃The optical characteristics of the first capping layer and the second capping layer using the above-mentioned compounds (1 to 22) were simulated by using the following procedure of semiconductor Emissive Thin Film Optics Simulation (Setfos 3.2) for the device structure of example 11. In order to examine the correlation between the refractive indices of the electron transit layer and the first capping layer, the refractive index of the first capping layer was fixed, and then the conversion efficiency at a peak wavelength of 460nm of the cyan light emitting dopant was calculated for the value of the refractive index of the electron transit layer using the compound (2-1), the compound (2-2), and the compounds a to E having different refractive indices. The calculation results are summarized in table 3.

[ Table 3]

Thus, for an electron transport layer having a low refractive index at a wavelength of 460nm, the conversion efficiency has a large value, which means: if an electron transport layer having a low refractive index is used, the light extraction efficiency is improved.

(example 10)

As shown in fig. 1, the organic EL element is produced by depositing a hole injection layer 3, a hole transport layer 4, a light-emitting layer 5, an electron transport layer 6, an electron injection layer 7, a cathode 8, a first capping layer 9, and a second capping layer 10 in this order on a glass substrate 1 on which a reflective ITO electrode as a metal anode 2 is formed in advance.

Specifically, the glass substrate 1 on which ITO having a thickness of 50nm, a reflective film of a silver alloy having a thickness of 100nm, and an ITO film having a thickness of 5nm were formed in this order was ultrasonically cleaned in isopropyl alcohol for 20 minutes, and then dried on a hot plate heated to 250 ℃ for 10 minutes. After 2 minutes of UV ozone treatment, the ITO-coated glass substrate was mounted in a vacuum evaporator and reduced in pressure to 0.001Pa or less. Next, as the hole injection layer 3, an electron acceptor (acceptor-1) of the following structural formula and a compound (3-1) of the following structural formula were formed at a deposition rate ratio to cover the transparent anode 2 to be (acceptor-1): compound (3-1) ═ 3: the film was formed by binary vapor deposition at a vapor deposition rate of 97 so that the film thickness became 10 nm.

On the hole injection layer 3, a compound (3-1) of the following structural formula was formed as a hole transport layer 4 so that the film thickness became 140 nm.

On the hole transport layer 4, as the light emitting layer 5, a compound (EMD-1) of the following structural formula and a compound (EMH-1) of the following structural formula were deposited at a deposition rate ratio of (EMD-1): (EMH-1) ═ 5: the vapor deposition rate was 95, and binary vapor deposition was performed so that the film thickness became 20 nm.

On the light-emitting layer 5, as the electron transport layer 6, a compound (2-1) of the following structural formula and a compound (ETM-1) of the following structural formula were formed at a vapor deposition rate ratio of (2-1): (ETM-1) ═ 50: the film was formed by binary vapor deposition at a vapor deposition rate of 50nm so that the film thickness became 30 nm.

On the electron transport layer 6, lithium fluoride was deposited as an electron injection layer 7 so that the film thickness became 1 nm.

On the electron injection layer 7, a magnesium-silver alloy was formed as a cathode 8 so that the film thickness became 12 nm.

On the cathode 8, as a first capping layer 9, Alq is formed₃So that the film thickness became 30nm, and finally, as the second capping layer 10, the compound (1-1) of example 3 was formed so that the film thickness became 30 nm.

The characteristics of the organic EL element thus produced were measured in the air at normal temperature. The results of measuring the light emission characteristics when a dc voltage was applied to the fabricated organic EL element are shown in table 4.

[ solution 20]

(example 11)

In example 10, an organic EL device was produced under the same conditions except that the compound (1-2) of example 2 was formed as the second capping layer 10 in place of the compound (1-1) of example 1 so that the film thickness became 30 nm. The characteristics of the organic EL element thus produced were measured in the air at normal temperature. The results of measuring the light emission characteristics when a dc voltage was applied to the fabricated organic EL element are shown in table 3.

(example 12)

In example 10, an organic EL device was produced under the same conditions except that the compound (1-22) of example 3 was formed as the second capping layer 10 in place of the compound (1-1) of example 1 so that the film thickness became 30 nm. The characteristics of the organic EL element thus produced were measured in the air at normal temperature. The results of measuring the light emission characteristics when a dc voltage was applied to the fabricated organic EL element are shown in table 3.

(example 13)

In example 10, an organic EL device was produced under the same conditions except that the compound (1-23) of example 4 was formed as the second capping layer 10 in place of the compound (1-1) of example 1 so that the film thickness became 30 nm. The characteristics of the organic EL element thus produced were measured in the air at normal temperature. The results of measuring the light emission characteristics when a dc voltage was applied to the fabricated organic EL element are shown in table 3.

(example 14)

In example 10, an organic EL device was produced under the same conditions except that the compound (1-25) of example 5 was formed as the second capping layer 10 in place of the compound (1-1) of example 1 so that the film thickness became 30 nm. The characteristics of the organic EL element thus produced were measured in the air at normal temperature. The results of measuring the light emission characteristics when a dc voltage was applied to the fabricated organic EL element are shown in table 3.

(example 15)

In example 10, an organic EL device was produced under the same conditions except that the compound (1-27) of example 6 was formed as the second capping layer 10 in place of the compound (1-1) of example 1 so that the film thickness became 30 nm. The characteristics of the organic EL element thus produced were measured in the air at normal temperature. The results of measuring the light emission characteristics when a dc voltage was applied to the fabricated organic EL element are shown in table 3.

Comparative example 1

For comparison, in example 10, as the first capping layer 9, Alq was formed₃The organic EL element not including the second capping layer 10 was manufactured so that the film thickness became 60 nm. The characteristics of the organic EL element thus produced were measured in the air at normal temperature. The results of measuring the light emission characteristics when a dc voltage was applied to the fabricated organic EL element are shown in table 3.

Comparative example 2

For comparison, in example 12, Alq was used in place of the compound (2-1) as the electron transport layer 6₃Otherwise, an organic EL element was produced under the same conditions. The characteristics of the organic EL element thus produced were measured in the air at normal temperature. Will be paired withThe measurement results of the light emission characteristics of the produced organic EL device when a dc voltage was applied are summarized in table 3.

Comparative example 3

For comparison, in example 12, an organic EL device was produced under the same conditions except that compound (2-2) was used in place of compound (2-1) as the electron transport layer 6. The characteristics of the organic EL element thus produced were measured in the air at normal temperature. The results of measuring the light emission characteristics when a dc voltage was applied to the fabricated organic EL element are shown in table 3.

The results of measuring the device lifetime using the organic EL devices produced in examples 10 to 15 and comparative examples 1 to 3 are summarized in table 3. In terms of the lifetime of the device, 10mA/cm was carried out²The constant current driving time of (3) was measured as a time until the luminance decayed to 95% when the initial luminance was set to 100%.

As shown in Table 4, with respect to the current density, 10mA/cm²The driving voltage at the time of driving was substantially the same between the device of comparative example 1 in which the second capping layer was not used and the devices of examples 10 to 15 in which the arylamine compound represented by the general formula (1) was used as the second capping layer, but the devices of examples 10 to 15 were improved in luminance, light emission efficiency, power efficiency, conversion efficiency, and lifetime. This means that: the light extraction efficiency can be greatly improved by adopting a laminated structure in which a second capping layer containing an arylamine compound represented by the general formula (1) is laminated. In addition, in the use of Alq₃And the compound (2-2) as an electron transporting layer, the devices of examples 10 to 15 were improved in luminance, light emission efficiency, power efficiency, conversion efficiency, and lifetime in the devices of comparative examples 2 and 3 and the devices of examples 10 to 15. This means that: in the element having the laminated structure, the refractive index of the electron transport layer is lower than that of the first capping layer, and thus the light extraction efficiency can be significantly improved.

Industrial applicability

As described above, the organic EL element in which the electron transport layer satisfying the general formula (I), the first capping layer, and the second capping layer containing the arylamine compound represented by the general formula (1) are stacked can obtain high efficiency. The use of the compound having no absorption in each of the wavelength regions of cyan, green and red is particularly preferable when a clear and bright image having high color purity is displayed. For example, the method can be developed to the use of household electrochemical products and lighting.