CN113874467A

CN113874467A - Composition for organic electroluminescent element, method for producing organic electroluminescent element, and display device

Info

Publication number: CN113874467A
Application number: CN202080037101.XA
Authority: CN
Inventors: 梶山良子; 长山和弘; 饭田宏一朗
Original assignee: Mitsubishi Chemical Corp
Current assignee: Mitsubishi Chemical Corp
Priority date: 2019-05-20
Filing date: 2020-05-19
Publication date: 2021-12-31
Also published as: JPWO2020235562A1; TW202106696A; KR20220010598A; WO2020235562A1

Abstract

The present invention relates to a composition for an organic electroluminescent element, comprising: a compound represented by the following formula (1) in which a triazine ring is substituted at a specific position, a compound represented by the following formula (2) in which the maximum emission wavelength is shorter than that of the compound represented by the formula (1), and a solvent.

Description

Composition for organic electroluminescent element, method for producing organic electroluminescent element, and display device

Technical Field

The present invention relates to a composition for an organic electroluminescent element, which is useful for forming a light-emitting layer of an organic electroluminescent element (hereinafter, sometimes referred to as an "organic EL element"). The present invention also relates to an organic electroluminescent element having a light-emitting layer formed using the composition for an organic electroluminescent element, a method for producing the same, and a display device having the organic electroluminescent element.

Background

Various electronic devices using organic EL elements, such as organic EL lighting and organic EL displays, have been put to practical use. Organic electroluminescent elements have been used not only for large-sized display monitors but also for small-sized displays such as mobile phones and smartphones because they consume less power due to low applied voltage and can emit light of three primary colors.

An organic electroluminescent element is manufactured by laminating a plurality of layers such as a light-emitting layer, a charge injection layer, and a charge transport layer. Currently, organic electroluminescent elements are often manufactured by vacuum vapor deposition of organic materials, but in the case of the vacuum vapor deposition method, the vapor deposition process is complicated, and the productivity is poor. It is extremely difficult to realize illumination and an increase in the size of a panel of a display by an organic electroluminescent element manufactured by a vacuum deposition method.

In recent years, a wet film formation method (coating method) has been studied as a process for efficiently manufacturing an organic electroluminescent element that can be used for a large display or illumination. Since the wet film formation method has an advantage that a stable layer can be easily formed as compared with the vacuum deposition method, it is expected that the display and the lighting device can be mass-produced and applied to a large-sized device.

In order to produce an organic electroluminescent element by a wet film formation method, it is necessary that all materials used be dissolved in an organic solvent and used as an ink. When the solubility of the material used is low, the material may be deteriorated before use because an operation such as heating for a long time is required. Further, when the solution state cannot be maintained in a uniform state for a long time, precipitation of a material from the solution occurs, and film formation by an ink jet apparatus or the like cannot be performed. The material used in the wet film formation method is required to have solubility in 2 meanings that it is rapidly dissolved in an organic solvent and remains in a uniform state without precipitation after dissolution.

As an advantage of the wet film formation method over the vacuum deposition method, more kinds of materials can be used for 1 layer. In the vacuum deposition method, it is difficult to control the deposition rate to be constant when the number of types of materials is increased, whereas in the wet film formation method, even if the number of types of materials is increased, ink having a constant composition ratio can be produced as long as each material is dissolved in an organic solvent.

In recent years, the following attempts have been made: by taking advantage of this, 2 or more kinds of iridium complex compounds are used in the ink to improve the light emission efficiency of the organic electroluminescent element, or the driving voltage is reduced to improve the performance of the organic electroluminescent element (for example, patent documents 1 and 2).

On the other hand, when the chemical structure of the material is focused, an iridium complex compound in which a phenylpyridine having a triazine ring substituted at a specific position as a ligand is used as a red light-emitting material in a white light-emitting element has been attempted (for example, patent documents 3 and 4).

Documents of the prior art

Patent document

Patent document 1: international publication No. 2015/192939

Patent document 2: international publication No. 2016/015815

Patent document 3: international publication No. 2017/154884

Patent document 4: japanese patent laid-open publication No. 2018-83941

Disclosure of Invention

However, in the conventional techniques described above, the performance of the organic electroluminescent element is not sufficient for display applications, and further reduction in driving voltage, improvement in light emission efficiency, and improvement in driving life are required particularly for red elements.

The invention provides an organic electroluminescent element which can be produced by a wet film formation method particularly for a red element and has a lower driving voltage, higher luminous efficiency and longer driving life than the conventional one.

The present inventors have made intensive studies in view of the above-mentioned problems in order to take advantage of the advantage of a wet film formation method that can use more material types for 1 layer. As a result, the present inventors have found that an iridium complex compound having a relatively short maximum emission wavelength is used as an auxiliary dopant, an iridium complex compound having a phenyl pyridine with a triazine ring substituted at a specific position as a ligand is used as a light-emitting dopant in a red device, and an organic electroluminescent device composition in which the auxiliary dopant and the light-emitting dopant are dissolved in a solvent is prepared.

Further, it has been found that the performance of the organic electroluminescent element is further improved by using the iridium complex compound as a light-emitting dopant at a composition ratio larger than that of the auxiliary dopant.

The composition for an organic electroluminescent element of the present invention contains an iridium complex compound having a short wavelength relative to the maximum light-emitting wavelength of a light-emitting dopant as an auxiliary dopant, and an iridium complex compound having a ligand comprising phenylpyridine substituted with a triazine ring at a specific position as a light-emitting dopant. Therefore, an organic electroluminescent element having a lower driving voltage, higher light emission efficiency, and a longer driving life than those of the conventional organic electroluminescent elements can be manufactured. In addition, the composition for an organic electroluminescent element of the present invention can appropriately suppress light emission from the auxiliary dopant by increasing the composition ratio of the light-emitting dopant to be larger than the composition ratio of the auxiliary dopant, and can produce an organic electroluminescent element having a more vivid light-emitting color.

That is, the gist of the present invention is as follows.

[1] A composition for an organic electroluminescent element, comprising a compound represented by the following formula (1), a compound represented by the following formula (2) having a maximum light-emitting wavelength shorter than that of the compound represented by the formula (1), and a solvent.

[ in the above formula, R¹、R²Each independently an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, (hetero) alkoxy group having 1 to 20 carbon atoms, (hetero) aryloxy group having 3 to 20 carbon atoms, (hetero) alkylsilyl group having 1 to 20 carbon atoms, arylsilyl group having 6 to 20 carbon atoms, alkylcarbonyl group having 2 to 20 carbon atoms, arylcarbonyl group having 7 to 20 carbon atoms, alkylamino group having 1 to 20 carbon atoms, arylamino group having 6 to 20 carbon atoms, or (hetero) aryl group having 3 to 30 carbon atoms. These groups may further have a substituent. R¹、R²When a plurality of them exist, they may be respectively the same or different. R¹When plural, adjacent R¹May be bonded to each other to form a ring.

a is an integer of 0 to 4, and b is an integer of 0 to 3.

R³、R⁴Each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbon atoms, a (hetero) aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero) aryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, or a (hetero) aryl group having 3 to 20 carbon atoms. These groups may further have a substituent. R³、R⁴When a plurality of them exist, they may be respectively the same or different.

L¹Represents an organic ligand, and m is an integer of 1 to 3.]

[ in the above formula, R⁵The alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, (hetero) alkoxy group having 1 to 20 carbon atoms, (hetero) aryloxy group having 3 to 20 carbon atoms, (hetero) alkylsilyl group having 1 to 20 carbon atoms, arylsilyl group having 6 to 20 carbon atoms, alkylcarbonyl group having 2 to 20 carbon atoms, and the likeAn arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, or a (hetero) aryl group having 3 to 30 carbon atoms. These groups may further have a substituent. R⁵When plural, they may be the same or different.

c is an integer of 0 to 4.

The ring A is pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring,

An azole ring, a thiazole ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azabenzophenanthrene ring, a carboline ring, a benzothiazole ring, a benzo

Any one of the oxazole rings.

The ring A may have a substituent selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbon atoms, a (hetero) aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero) aryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, and a (hetero) aryl group having 3 to 20 carbon atoms. In addition, adjacent substituents bonded to the ring a may be bonded to each other to further form a ring. When a plurality of rings A are present, they may be the same or different.

L²Represents an organic ligand, and n is an integer of 1 to 3.]

[2] The composition for organic electroluminescent element according to the above [1], wherein the composition ratio of the compound represented by the above formula (1) is not less than the composition ratio of the compound represented by the above formula (2) in terms of parts by mass.

[3] The composition for an organic electroluminescent element according to the above [1] or [2], wherein the compound represented by the above formula (1) is a compound represented by the following formula (1-1).

[ in the above formula, R¹、R²、a、b、L¹M and R in the above formula (1)¹、R²、a、b、L¹And m are the same as each other.

R⁶、R⁷Each independently an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, (hetero) alkoxy group having 1 to 20 carbon atoms, (hetero) aryloxy group having 3 to 20 carbon atoms, (hetero) alkylsilyl group having 1 to 20 carbon atoms, arylsilyl group having 6 to 20 carbon atoms, alkylcarbonyl group having 2 to 20 carbon atoms, arylcarbonyl group having 7 to 20 carbon atoms, alkylamino group having 1 to 20 carbon atoms, arylamino group having 6 to 20 carbon atoms, or (hetero) aryl group having 3 to 30 carbon atoms. These groups may further have a substituent. R⁶、R⁷When a plurality of them exist, they may be respectively the same or different.

d. e is an integer of 0 to 5. ]

[4] The composition for an organic electroluminescent element according to the above [1] or [2], wherein the compound represented by the above formula (1) is a compound represented by the following formula (1-2).

[ in the above formula, R²～R⁴、b、L¹M and R in the above formula (1)²～R⁴、b、L¹And m are the same as each other.

R¹⁴～R¹⁶Is a substituent, R¹⁴～R¹⁶When a plurality of them exist, they may be respectively the same or different.

i is an integer of 0 to 4. ]

[5] The composition for an organic electroluminescent element according to the above [3], wherein the compound represented by the above formula (1-1) is a compound represented by the following formula (1-3).

[ in the above formula, R²、R⁶、R⁷、b、d、e、L¹M and R in the above formula (1-1)²、R⁶、R⁷、b、d、e、L¹And m are the same as each other.

i is an integer of 0 to 4. ]

[6] The composition for an organic electroluminescent element according to any one of the above [1] to [5], wherein the compound represented by the above formula (2) is a compound represented by the following formula (2-1).

[ in the above formula, ring A, L²N and ring A, L in formula (2)²And n are the same as each other.

R⁸The aryl group is an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, (hetero) alkoxy group having 1 to 20 carbon atoms, (hetero) aryloxy group having 3 to 20 carbon atoms, (hetero) alkylsilyl group having 1 to 20 carbon atoms, arylsilyl group having 6 to 20 carbon atoms, alkylcarbonyl group having 2 to 20 carbon atoms, arylcarbonyl group having 7 to 20 carbon atoms, alkylamino group having 1 to 20 carbon atoms, arylamino group having 6 to 20 carbon atoms, or (hetero) aryl group having 3 to 30 carbon atoms. These groups may further have a substituent. R⁸When plural, they may be the same or different.

f is an integer of 0 to 5. ]

[7]According to the above [1]～[6]The composition for an organic electroluminescent element as described in any one of the above, wherein m in the above formula (1) is less than 3, and L is¹Has at least one structure selected from the following formulae (3), (4) and (5).

[ in the above formulae (3) to (5), R⁹、R¹⁰And R in the above formula (1)¹Have the same meaning as R⁹、R¹⁰When a plurality of them exist, they may be respectively the same or different.

R¹¹～R¹³Each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may be substituted with a fluorine atom, a phenyl group which may be substituted with an alkyl group having 1 to 20 carbon atoms, or a halogen atom.

g is an integer of 0 to 4. h is an integer of 0 to 4.

Ring B is a pyridine ring, a pyrimidine ring, an imidazole ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azabenzophenanthrene ring, a carboline ring, a benzothiazole ring, or a benzo

An azole ring. Ring B may further have a substituent.]

[8]According to the above [1]～[7]The composition for organic electroluminescent element according to any one of the above items, wherein a in the formula (1) is 1, or a in the formula (1) is an integer of 2 or more and does not have adjacent R¹Rings bonded to each other.

[9] A method for manufacturing an organic electroluminescent element includes the steps of: a light-emitting layer is formed by a wet film-forming method using the organic electroluminescent element composition according to any one of the above [1] to [8 ].

[10] An organic electroluminescent element having a light-emitting layer formed using the organic electroluminescent element composition according to any one of the above [1] to [8 ].

[11] A display device having the organic electroluminescent element as described in [10 ].

According to the present invention, an organic electroluminescent element which can be produced by a wet film formation method particularly for a red element, and which has a lower driving voltage, higher luminous efficiency, and a longer driving life than conventional organic electroluminescent elements can be provided.

Drawings

Fig. 1 is a cross-sectional view schematically showing an example of the structure of an organic electroluminescent element according to the present invention.

Detailed Description

The present invention is not limited to the following embodiments, and can be carried out by being variously modified within the scope of the gist thereof.

In the present specification, the terms (hetero) aralkyl group, (hetero) aryloxy group, and (hetero) aryl group mean an aralkyl group which may contain a heteroatom, an aryloxy group which may contain a heteroatom, and an aryl group which may contain a heteroatom, respectively. "may contain a hetero atom" means that 1 or 2 or more carbon atoms among carbon atoms forming an aryl skeleton in a main skeleton of an aryl group, an aralkyl group or an aryloxy group are substituted with a hetero atom. Examples of the hetero atom include a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, a silicon atom, and the like, and among them, a nitrogen atom is preferable from the viewpoint of durability.

[ luminescent dopant ]

The composition for an organic electroluminescent element of the present embodiment contains a compound represented by the following formula (1), and the compound mainly functions as a light-emitting dopant. The compound represented by the formula (1) may include only 1 kind, or may include a plurality of kinds. In addition, the compound as the light-emitting dopant may include a compound as the light-emitting dopant other than the compound represented by formula (1), and in this case, the content of the total of the compounds represented by formula (1) is preferably 50% by mass or more, and more preferably 100% by mass, relative to the total of the compounds as the light-emitting dopant. That is, the compound represented by the formula (1) alone is more preferable.

In the above formula (1), R¹、R²Each independently an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms,An alkoxy group having 1 to 20 carbon atoms, a (hetero) aryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, or a (hetero) aryl group having 3 to 30 carbon atoms. These groups may further have a substituent. R¹、R²When a plurality of them exist, they may be respectively the same or different. R¹When plural, adjacent R¹May be bonded to each other to form a ring.

a is an integer of 0 to 4, and b is an integer of 0 to 3.

L¹Represents an organic ligand, and m is an integer of 1 to 3.

From the aspect of durability, R¹～R⁴Each independently of the other, more preferably an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, arylamino group having 6 to 20 carbon atoms, or (hetero) aryl group having 3 to 30 carbon atoms, or (hetero) aryl group having 3 to 20 carbon atoms, further preferably an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, or (hetero) aryl group having 3 to 20 carbon atoms, and further preferably an alkyl group having 1 to 20 carbon atoms, aralkyl group having 7 to 40 carbon atoms, or aryl group having 6 to 20 carbon atoms.

R¹～R⁴The substituent which may be further contained is preferably selected from the substituents described laterSubstituents in group Z.

When a is 2 or more, adjacent 2R¹May be bonded to each other to form a ring.

As R¹There are a plurality of and adjacent R¹Examples of the ring formed by bonding to each other include fluorene, naphthalene, dibenzothiophene, and dibenzofuran. From the viewpoint of stability, fluorene is particularly preferable.

From the viewpoint of making the emission wavelength longer, adjacent R's are preferable¹Bonded to each other to form a ring structure.

In addition, from the viewpoint of not making the emission wavelength longer, adjacent R is preferable¹Do not bond to each other and form a ring. That is, it is preferable that a in the formula (1) is 1, or a is 2 or more and does not have adjacent R¹Rings bonded to each other.

In view of ease of production, a is preferably 0, and in view of improvement in durability and solubility, it is preferably 1 or 2, and more preferably 1. B is preferably 0 in view of easy production, and 1 in view of improvement of solubility.

Since the LUMO is more stabilized by the presence of a plurality of triazine ring-containing structures having a high electron-accepting property, m is preferably 2 or 3, and more preferably 3.

L¹The organic ligand is not particularly limited, but is preferably a bidentate ligand having a valence of 1, and more preferably selected from the following chemical formulae. The dotted line in the chemical formula represents a coordinate bond. There are 2 organic ligands L¹When the organic ligand L is present¹May be different structures from each other. When m is 3, L is not present¹。

When m in the formula (1) is less than 3, L is preferably L¹Has at least one structure selected from the following formulae (3), (4) and (5).

In the above formulae (3), (4) and (5), R⁹、R¹⁰And R in the above formula (1)¹The meaning is the same. I.e. from and as R¹The substituents selected are selected from the same group, and preferred examples are also the same, and may further have a substituent. R⁹、R¹⁰When a plurality of them exist, they may be respectively the same or different.

g is an integer of 0 to 4. h is an integer of 0 to 4.

An azole ring. Ring B may further have a substituent.

R⁹、R¹⁰The substituent which the ring B may further have is preferably a substituent selected from substituent group Z described later.

Further preferred R⁹、R¹⁰Each independently an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 30 carbon atoms which may be substituted with an alkyl group having 1 to 20 carbon atoms. The aryl group having 6 to 30 carbon atoms is a monocyclic ring, a bicyclic fused ring, a tricyclic fused ring, or a group in which a plurality of monocyclic, bicyclic fused rings, or tricyclic fused rings are connected.

G and h are preferably 0 from the viewpoint of ease of production, and 1 or 2, more preferably 1, from the viewpoint of improvement of solubility.

R¹¹～R¹³Each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may be substituted with a fluorine atom, a phenyl group which may be substituted with an alkyl group having 1 to 20 carbon atoms, or a halogen atom, more preferably R¹¹And R¹³Is methyl or tert-butyl, R¹²Is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or a phenyl group.

From the viewpoint of durability, the ring B is preferably a pyridine ring, a pyrimidine ring, or an imidazole ring, and more preferably a pyridine ring.

From the viewpoint of durability and the viewpoint of improving solubility, it is preferable that the hydrogen atom on the ring B is substituted with an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, or (hetero) aryl group having 3 to 20 carbon atoms.

In addition, it is preferable that the hydrogen atom on the ring B is not substituted from the viewpoint of easy production.

Further, from the viewpoint of improving the light emission efficiency by easily generating excitons when used as an organic electroluminescent element, it is preferable that the hydrogen atom on the ring B is substituted with a phenyl group or a naphthyl group which may have a substituent. The substituent which the phenyl group or the naphthyl group may have is preferably selected from the substituents in substituent group Z described later.

In addition, the ring B is preferably a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azabenzophenanthrene ring, or a carboline ring, in view of the improvement in light emission efficiency due to the easy generation of an exciton on the auxiliary dopant. Among them, a quinoline ring, an isoquinoline ring, and a quinazoline ring are more preferable in terms of durability and in terms of exhibiting red light emission.

More preferably, the substituent of the ring B is an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms which may be substituted with an alkyl group having 1 to 20 carbon atoms. The aryl group having 6 to 20 carbon atoms is a monocyclic ring, a bicyclic fused ring, a tricyclic fused ring, or a group in which a plurality of monocyclic, bicyclic fused rings, or tricyclic fused rings are connected.

As the compound represented by the formula (1), which is the light-emitting dopant contained in the composition for an organic electroluminescent element of the present embodiment, R is preferable³、R⁴A compound which is a phenyl group which may have a substituent, that is, a compound represented by the following formula (1-1).

[ in the above formula, R¹、R²、a、b、L¹M and R in formula (1)¹、R²、a、b、L¹And m are the same as each other.

d. e is an integer of 0 to 5. ]

From the aspect of durability, R⁶、R⁷More preferably an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, (hetero) aryl group having 6 to 20 carbon atoms or (hetero) aryl group having 3 to 30 carbon atoms, still more preferably an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms or (hetero) aryl group having 3 to 20 carbon atoms, and still more preferably an alkyl group having 1 to 20 carbon atoms or aralkyl group having 7 to 40 carbon atoms.

R⁶、R⁷The substituent which may be further contained is preferably a substituent selected from substituent group Z described later.

D and e are preferably 0 from the viewpoint of ease of production, and are preferably 1 or 2, more preferably 1, from the viewpoint of improvement in durability and solubility. B is preferably 0 in view of easy production, and 1 in view of improvement of solubility.

The light-emitting dopant represented by formula (1) contained in the composition for an organic electroluminescent element according to the present embodiment preferably has a value of 2 or more and R adjacent thereto¹Bonded to each other to form a fluorene ring structure. Among them, preferred is a compound represented by the formula (1-2).

[ in the above formula, R²～R⁴、b、L¹M and R in formula (1)²～R⁴、b、L¹And m are the same as each other.

i is an integer of 0 to 4. ]

R¹⁴Is R¹Substituted for R in the case of phenyl¹The substituent (b) is more preferably a substituent selected from substituent group Z described later. More preferably an alkyl group having 1 to 20 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms which may be substituted with an alkyl group having 1 to 20 carbon atoms. Here, the C6-30 aromatic hydrocarbon group refers to a single ring, two to four ring condensed rings, or a single ring or two to four ring condensed rings connected to a plurality of groups. More preferably an alkyl group having 1 to 20 carbon atoms, and still more preferably an alkyl group having 1 to 8 carbon atoms.

R¹⁵、R¹⁶Is R¹A part of (A) or R¹Substituted for R in the case of methyl¹The substituents (B) are preferably each independently an alkyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 30 carbon atoms which may be substituted with an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms which may be substituted with an alkoxy group having 1 to 20 carbon atoms. Here, the C6-30 aromatic hydrocarbon group refers to a single ring, two to four ring condensed rings, or a single ring or two to four ring condensed rings connected to a plurality of groups. More preferably an alkyl group having 1 to 20 carbon atoms or an aromatic hydrocarbon group having 6 or 12 carbon atoms which may be substituted with an alkyl group having 1 to 20 carbon atoms, and still more preferably an alkyl group having 1 to 8 carbon atoms or an aromatic hydrocarbon group having 6 carbon atoms which may be substituted with an alkyl group having 1 to 8 carbon atoms. Here, the aromatic hydrocarbon structure having 6 carbon atoms is a benzene structure, and the aromatic hydrocarbon structure having 12 carbon atoms is a biphenyl structure.

As R¹⁴～R¹⁶Specific examples of the preferred alkyl group in (1) include methyl group and ethyl groupAnd (b) a group such as a phenyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-octyl group, isopropyl group, isobutyl group, isopentyl group, tert-butyl group, cyclohexyl group, 2-ethylhexyl group, etc.

As R¹⁴～R¹⁶Specific examples of the preferred aromatic hydrocarbon group in (B) include benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzopyrene ring, perylene ring, and aromatic hydrocarbon group,

A ring, a triphenylene ring, a fluoranthene ring, a biphenyl group, a terphenyl group, and the like.

As R¹⁵、R¹⁶Specific examples of the preferred alkoxy group include methoxy, ethoxy, propoxy, isopropoxy, hexyloxy, cyclohexyloxy, octadecyloxy and the like.

The compound as the light-emitting dopant represented by the formula (1-1) contained in the composition for an organic electroluminescent element according to the present embodiment is more preferably a compound represented by the formula (1-3).

[ in the above formula, R²、R⁶、R⁷、b、d、e、L¹M and R in the formula (1-1)²、R⁶、R⁷、b、d、e、L¹And m are the same as each other.

i is an integer of 0 to 4. ]

R¹⁴～R¹⁶The substituents are respectively as R in the formula (1-2)¹⁴～R¹⁶The substituents are the same in meaning, and the preferred ranges are also the same.

Specific preferred examples of the compound represented by the formula (1) as the light-emitting dopant contained in the composition for an organic electroluminescent element according to the present embodiment, other than the compounds shown in the examples, are shown below, but the present invention is not limited thereto.

[ auxiliary dopant ]

The composition for an organic electroluminescent element of the present embodiment contains a compound represented by the following formula (2), and the compound mainly functions as an auxiliary dopant. The maximum emission wavelength of the compound represented by formula (2) is shorter than that of the compound represented by formula (1) as the light-emitting dopant. Therefore, when the auxiliary dopant represented by formula (2) reaches the excited state, energy transfer to the light-emitting dopant represented by formula (1) having smaller excitation energy occurs, and thus light emission from the light-emitting dopant is observed after the light-emitting dopant reaches the excited state.

The compound represented by the formula (2) may include only 1 kind, or may include a plurality of kinds. In addition, the compound as the auxiliary dopant may include a compound as the auxiliary dopant other than the compound represented by formula (2), and in this case, the content of the total of the compounds represented by formula (2) is preferably 50% by mass or more, and more preferably 100% by mass, relative to the total of the compounds as the auxiliary dopant. That is, the compound represented by the formula (2) alone is more preferable.

Further, the composition ratio of the compound represented by formula (1) is preferably not less than the composition ratio of the compound represented by formula (2) in terms of parts by mass. This suppresses direct light emission from the auxiliary dopant represented by formula (2), and energy can be transferred from the auxiliary dopant represented by formula (2) to the light-emitting dopant represented by formula (1) with high efficiency. Therefore, light emission of the light emitting dopant is obtained with higher efficiency.

In the above formula, R⁵The aryl group is an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, (hetero) alkoxy group having 1 to 20 carbon atoms, (hetero) aryloxy group having 3 to 20 carbon atoms, (hetero) alkylsilyl group having 1 to 20 carbon atoms, arylsilyl group having 6 to 20 carbon atoms, alkylcarbonyl group having 2 to 20 carbon atoms, arylcarbonyl group having 7 to 20 carbon atoms, alkylamino group having 1 to 20 carbon atoms, arylamino group having 6 to 20 carbon atoms, or (hetero) aryl group having 3 to 30 carbon atoms. These groups may further have a substituent. R⁵When plural, they may be the same or different.

c is an integer of 0 to 4.

The ring A is pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring,

Any one of the oxazole rings.

Ring a may have a substituent.

The substituent is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbon atoms, a (hetero) aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero) aryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms in the alkyl group, an arylsilyl group having 6 to 20 carbon atoms in the aryl group, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, or a (hetero) aryl group having 3 to 20 carbon atoms. In addition, adjacent substituents bonded to the ring a may be bonded to each other to further form a ring. When a plurality of rings A are present, they may be the same or different.

L²Represents an organic ligand, and n is an integer of 1 to 3.

R⁵The substituent which may be further contained is preferably a substituent selected from substituent group Z described later.

From the aspect of durability, R⁵More preferably an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, (hetero) aryl group having 6 to 20 carbon atoms, or (hetero) aryl group having 3 to 30 carbon atoms, and still more preferably an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, or (hetero) aryl group having 3 to 20 carbon atoms. From the aspect of durability and the aspect of solubility, R⁵Preferably a phenyl group which may have a substituent and is bonded to ring A at the meta position and the para position to iridium. That is, the compound represented by the following formula (2-1) is preferably contained. The substituent which may be present is preferably a substituent selected from substituent group Z described later.

f is an integer of 0 to 5. ]

R⁸The substituent which may be further contained is preferably a substituent selected from substituent group Z described later.

F is preferably 0 from the viewpoint of ease of production, and is preferably 1 or 2, more preferably 1 from the viewpoint of durability and improvement of solubility.

The ring a is preferably a pyridine ring, a pyrimidine ring, or an imidazole ring, and more preferably a pyridine ring, from the viewpoint of durability.

The hydrogen atom on the ring A is preferably substituted with an alkyl group having 1 to 20 carbon atoms, (hetero) aralkyl group having 7 to 40 carbon atoms, or (hetero) aryl group having 3 to 20 carbon atoms, from the viewpoint of durability and from the viewpoint of improving solubility. In addition, the hydrogen atom on the ring a is preferably not substituted from the viewpoint of easy production. The hydrogen atom on ring a is preferably substituted with a phenyl group or a naphthyl group which may have a substituent, from the viewpoint of improving the light-emitting efficiency by easily generating an exciton when used as an organic electroluminescent element.

The ring a is preferably a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azabenzophenanthrene ring, or a carboline ring, in view of facilitating exciton generation in the auxiliary dopant and improving the light emission efficiency. Among them, quinoline rings, isoquinoline rings, and quinazoline rings are preferable in terms of durability.

L²The organic ligand is not particularly limited, and is preferably a bidentate ligand having a valence of 1, more preferably L¹The ligands shown in the preferred examples of (3) are the same. Note that there are 2 organic ligands L²When the organic ligand L is present²May be different structures from each other. When n is 3, L is not present²。

Preferred specific examples of the compound represented by the formula (2) as the auxiliary dopant contained in the composition for an organic electroluminescent element according to the present embodiment, other than the compounds shown in the examples, are shown below, but the present invention is not limited thereto.

[ substituent group Z ]

As the substituent, an alkyl group, an aralkyl group, a heteroaralkyl group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an alkylsilyl group, an arylsilyl group, an alkylcarbonyl group, an arylcarbonyl group, an alkylamino group, an arylamino group, an aryl group, or a heteroaryl group may be used.

Preferably, the group is an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 40 carbon atoms, a heteroaralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, a heteroaryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or a heteroaryl group having 3 to 30 carbon atoms, and more specifically, it is a substituent described in [ specific examples of substituents ] below.

More preferably an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, or an aryl group having 6 to 30 carbon atoms.

[ specific examples of substituents ]

Specific examples of the substituents in the structures of the respective compounds described above and the substituents in the substituent group Z described above are as follows.

The alkyl group having 1 to 20 carbon atoms may be any of a linear, branched or cyclic alkyl group. More specifically, examples thereof include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, isopropyl, isobutyl, isopentyl, tert-butyl, and cyclohexyl. Among them, a linear alkyl group having 1 to 8 carbon atoms such as a methyl group, an ethyl group, an n-butyl group, an n-hexyl group, an n-octyl group and the like is preferable.

The (hetero) aralkyl group having 7 to 40 carbon atoms is a group in which a part of hydrogen atoms constituting a linear alkyl group, a branched alkyl group or a cyclic alkyl group is substituted with an aryl group or a heteroaryl group. More specifically, 2-phenyl-1-ethyl, cumyl, 5-phenyl-1-pentyl, 6-phenyl-1-hexyl, 7-phenyl-1-heptyl, tetrahydronaphthyl, and the like are exemplified. Among them, 5-phenyl-1-pentyl, 6-phenyl-1-hexyl, and 7-phenyl-1-heptyl are preferable.

Specific examples of the alkoxy group having 1 to 20 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a hexyloxy group, a cyclohexyloxy group, an octadecyloxy group and the like. Among them, hexyloxy is preferable.

Specific examples of the (hetero) aryloxy group having 3 to 20 carbon atoms include a phenoxy group, a 4-methylphenoxy group and the like. Among them, phenoxy is preferred.

Specific examples of the alkylsilyl group having 1 to 20 carbon atoms include trimethylsilyl group, triethylsilyl group, triisopropylsilyl group, dimethylphenyl group, tert-butyldimethylsilyl group, tert-butyldiphenylsilyl group and the like. Among them, triisopropyl group, tert-butyldimethylsilyl group and tert-butyldiphenylsilyl group are preferable.

Specific examples of the arylsilyl group having 6 to 20 carbon atoms include a diphenylpyridyl silyl group and a triphenylsilyl group. Among them, triphenylsilyl is preferable.

Specific examples of the alkylcarbonyl group having 2 to 20 carbon atoms include acetyl group, propionyl group, pivaloyl group, hexanoyl group, decanoyl group, cyclohexylcarbonyl group and the like. Among them, acetyl and pivaloyl are preferable.

Specific examples of the arylcarbonyl group having 7 to 20 carbon atoms include benzoyl, naphthoyl, and anthracenoyl (アントライル group). Among them, benzoyl is preferred.

Specific examples of the alkylamino group having 1 to 20 carbon atoms include a methylamino group, a dimethylamino group, a diethylamino group, an ethylmethylamino group, a dihexylamino group, a dioctylamino group, and a dicyclohexylamino group. Among them, dimethylamino group and dicyclohexylamino group are preferable.

Specific examples of the arylamino group having 6 to 20 carbon atoms include a phenylamino group, a diphenylamino group, a di (4-tolyl) amino group, a di (2, 6-dimethylphenyl) amino group and the like. Among them, diphenylamino group and di (4-tolyl) amino group are preferable.

The (hetero) aryl group having 3 to 30 carbon atoms is an aromatic hydrocarbon group having 1 free valence, an aromatic heterocyclic group, a connecting aromatic hydrocarbon group in which a plurality of aromatic hydrocarbons are connected, a connecting aromatic heterocyclic group in which a plurality of aromatic heterocyclic groups are connected, or a group in which at least 1 or more aromatic hydrocarbons and aromatic heterocycles are arbitrarily connected.

Specific examples thereof include benzene rings, naphthalene rings, anthracene rings, phenanthrene rings, perylene rings, tetracene rings, pyrene rings, benzopyrene rings, perylene ring, and aromatic ring,

A ring, a triphenylene ring, a fluoranthene ring, a furan ring, a benzofuran ring, a dibenzofuran ring, a thiophene ring, a benzothiophene ring, a dibenzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a thiophene ring, a compound, a,

A diazole ring, an indole ring, a carbazole ring, a pyrroloimidazole ring, a pyrrolopyrazole ring, a pyrrolopyrrole ring, a thienopyrrole ring, a thienothiophene ring, a furopyrrole ring, a furofuran ring, a thienofuran ring, a benzisoxazole ring

An azole ring, a benzisothiazole ring, a benzimidazole ring, a pyridine ring, a pyrazine ring, a pyridazine ring, a pyrimidine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a cinnoline ring, a quinoxaline ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, an azulene ring, or the like. Examples of the linking aromatic hydrocarbon group to which a plurality of aromatic hydrocarbons are linked include a biphenyl group, a terphenyl group, and the like.

From the viewpoint of durability, among the (hetero) aryl groups, a benzene ring, a naphthalene ring, a dibenzofuran ring, a dibenzothiophene ring, a carbazole ring, a pyridine ring, a pyrimidine ring, and a triazine ring having 1 free valence are preferable, and among them, a 6 to 18 carbon atom aryl group such as a benzene ring, a naphthalene ring, and a phenanthrene ring, which may be substituted with an alkyl group having 1 to 8 carbon atoms, having 1 free valence, or a pyridine ring, which may be substituted with an alkyl group having 1 to 4 carbon atoms, having 1 free valence, is more preferable, and a 6 to 18 carbon atom aryl group such as a benzene ring, a naphthalene ring, and a phenanthrene ring, which may be substituted with an alkyl group having 1 to 8 carbon atoms, having 1 free valence is further preferable.

When a group in the compound has a plurality of substituents, combinations of these substituents include, for example, a combination of an aryl group and an alkyl group, a combination of an aryl group and an aralkyl group, or a combination of an aryl group and an alkyl group or an aralkyl group, but the present invention is not limited thereto. As the combination of the aryl group and the aralkyl group, for example, a combination of benzene, biphenyl group, terphenyl group, and 5-phenyl-1-pentyl group, 6-phenyl-1-hexyl group can be used.

[ maximum luminescence wavelength ]

The following shows a method for measuring the maximum emission wavelength of the compound in the present embodiment.

The maximum light emission wavelength of a compound can be determined from the photoluminescence spectrum of a solution in which a material is dissolved in an organic solvent or the photoluminescence spectrum of a thin film of a material alone.

In the case of photoluminescence from a solution, the compound was reacted at a concentration of 1X 10 at room temperature using a spectrophotometer (measurement apparatus for organic EL quantum yield C9920-02 made by Korsakoff photonics Co., Ltd.)^－4The phosphorescence spectrum of a solution obtained by dissolving 2-methyltetrahydrofuran in a concentration of mol/L or less was measured. The wavelength at which the obtained phosphorescence spectrum intensity exhibits the maximum value is set as the maximum light emission wavelength.

In the case of thin film photoluminescence, a material is vacuum-deposited or solution-coated to prepare a thin film, photoluminescence is measured by the spectrophotometer, and the wavelength at which the obtained emission spectrum intensity exhibits the maximum value is defined as the maximum emission wavelength.

The maximum light emission wavelengths of the compound used in the light-emitting dopant and the compound used in the auxiliary dopant need to be determined by the same method and compared.

The compound represented by formula (2) as the auxiliary dopant contained in the composition for an organic electroluminescent element according to the present embodiment has a shorter maximum emission wavelength than the compound represented by formula (1) as the light-emitting dopant.

The maximum emission wavelength of the compound as the light-emitting dopant is preferably 580nm or more, more preferably 590nm or more, further preferably 600nm or more, and further preferably 700nm or less, more preferably 680nm or less. When the maximum light emission wavelength is in this range, a preferable color suitable as a red light emitting material of the organic electroluminescent element tends to be exhibited.

It is preferable that the maximum emission wavelength of the compound as the auxiliary dopant is 10nm or more away from the maximum emission wavelength of the compound as the light-emitting dopant because energy can be efficiently exchanged.

The compound represented by formula (1) preferably contains the same amount as or a larger amount than the compound represented by formula (2). That is, the composition ratio of the compound represented by formula (1) is preferably not less than the composition ratio of the compound represented by formula (2) in terms of parts by mass. The compound represented by formula (1) preferably contains 1 to 3 times the compound represented by formula (2) in terms of parts by mass. In particular, the content is preferably 1 to 2 times from the viewpoint of the luminous efficiency and the long life of the element. The content is more preferably 2 times or more in order to obtain brighter light emission, and is more preferably less than 2 times in order to reduce the driving voltage of the element. Accordingly, energy from the auxiliary dopant is more efficiently transferred to the light-emitting dopant, and therefore, high light-emitting efficiency is obtained, and a long lifetime of the element can be expected.

[ Synthesis method of Iridium Complex ]

The compound represented by formula (2) as the auxiliary dopant and the compound represented by formula (1) as the light-emitting dopant contained in the composition for an organic electroluminescent element according to the present embodiment are both iridium complex compounds. The following shows a method for synthesizing an iridium complex compound.

The ligand of the iridium complex compound may be synthesized by a combination of known methods or the like. The ligand can be synthesized by suzuki-miyaura coupling reaction of an arylboronic acid with a haloheteroaryl group, friedlaerder cyclization reaction with a 2-formyl group or an anilide group or an acyl-aminopyridine group located at the ortho-position to each other (chem. rev.2009, 109, 2652, or Organic Reactions, 1982, 28(2), 37-201) and the like.

The iridium complex can be synthesized by a combination of known methods using the ligand obtained as described above and iridium chloride n hydrate or the like as raw materials. The following description is made.

For easy understanding, a method of crosslinking an iridium dinuclear complex via chlorine (M.G.Colombo, T.C.Brunald, T.Riedener, H.U.GudelInorg.Chem., 1994, 33, 545-550) as shown in the following formula [ A ], a method of obtaining a target by exchanging chlorine crosslinking with acetylacetone and converting into a mononuclear complex from a dinuclear complex as shown in the following formula [ B ] (S.Lamansky, P.Djurovich, D.Murphy, F.Abdel-Razzaq, R.Kwong, I.Tsyba, M.Borz, B.Mui, R.Bau, M.Thompson, Inorg.Chem.2001, 40, 1704, 1711) and the like can be exemplified, but not limited thereto.

For example, typical reaction conditions shown by the following formula [ A ] are as follows. In the present specification, Et represents an ethyl group, and Tf represents a trifluoromethylsulfonyl group.

As a first stage, a chloro-crosslinked iridium dinuclear complex is synthesized by the reaction of 2 equivalents of the first ligand with 1 equivalent of iridium chloride n-hydrate. The solvent is usually a mixed solvent of 2-ethoxyethanol and water, and may be used without solvent or in other solvents. An excess of ligand may also be used, or an additive such as a base may be used to promote the reaction. Other crosslinkable anionic ligands such as bromine may be used instead of chlorine.

The reaction temperature is not particularly limited, but is usually preferably 0 ℃ or higher, and more preferably 50 ℃ or higher. Further, it is preferably 250 ℃ or lower, and more preferably 150 ℃ or lower. When the reaction temperature is in this range, only the desired reaction proceeds without involving by-products or decomposition reactions, and high selectivity tends to be obtained.

[A]

In the second stage, a halogen ion capturing agent such as silver trifluoromethanesulfonate is added and brought into contact with the second ligand to obtain a target complex. The solvent is usually ethoxyethanol or diglyme, and depending on the type of ligand, either no solvent or another solvent may be used, or a mixture of a plurality of solvents may be used. Although the reaction may progress without adding a halogen ion scavenger, it is not always necessary, but it is advantageous to add the scavenger in order to increase the reaction yield and selectively synthesize a facial isomer having a higher quantum yield. The reaction temperature is not particularly limited, and is usually in the range of 0 ℃ to 250 ℃.

Typical reaction conditions shown by the following formula [ B ] will be described.

The dinuclear coordination compound of the first stage can be synthesized in the same manner as in the formula [ A ].

In the second stage, the dinuclear coordination compound is converted into a mononuclear coordination compound coordinated with a 1, 3-dione ligand by reacting the dinuclear coordination compound with a 1, 3-dione compound such as acetylacetone in an amount of 1 equivalent or more and a basic compound such as sodium carbonate in an amount of 1 equivalent or more, which can extract active hydrogen from the 1, 3-dione compound. In general, solvents such as ethoxyethanol and methylene chloride, which can dissolve the dinuclear complex of the raw material, are used, but the reaction may be carried out without a solvent when the ligand is in a liquid state. The reaction temperature is not particularly limited, and is usually in the range of 0 ℃ to 200 ℃.

[B]

The third stage reacts 1 equivalent or more of the second ligand. The kind and amount of the solvent are not particularly limited, and the second ligand may be liquid at the reaction temperature without solvent. The reaction temperature is also not particularly limited, and the reaction is often carried out at a relatively high temperature of 100 to 300 ℃ because the reactivity is somewhat insufficient. Therefore, a high boiling point solvent such as glycerin is preferably used.

The final reaction is followed by purification in order to remove unreacted starting materials, reaction by-products and solvents. Although a purification operation in general organic synthetic chemistry can be employed, purification is mainly performed by forward silica gel column chromatography as described in the above non-patent documents. The eluent can be hexane, heptane, dichloromethane, chloroform, ethyl acetate, toluene, methyl ethyl ketone, methanol or their mixture. Purification can be carried out several times with varying conditions. Other chromatographic techniques, such as reverse silica gel column chromatography, size exclusion chromatography, paper chromatography, liquid separation washing, reprecipitation, recrystallization, suspension washing of powder, reduced pressure drying, and the like, may be performed as necessary.

[ solvent, composition ratio ]

The composition for an organic electroluminescent element of the present embodiment contains a solvent.

The composition for an organic electroluminescent element is generally used for forming a layer or a film by a wet film formation method, and is particularly preferably used for forming a light-emitting layer of an organic electroluminescent element.

The content of the light-emitting dopant in the composition for an organic electroluminescent element is usually 0.01 mass% or more, preferably 0.1 mass% or more, and usually 20 mass% or less, preferably 10 mass% or less. When the content of the light-emitting dopant is within this range, when the composition is used for an organic electroluminescent element, transfer of excitation energy to an adjacent layer, for example, a hole transport layer or a hole blocking layer is less likely, and extinction due to interaction between excitons is less likely to occur, so that light emission efficiency can be improved. The content of the light-emitting dopant refers to the total content of the compounds represented by formula (1).

The content of the auxiliary dopant in the composition for an organic electroluminescent element is usually 0.005 mass% or more, preferably 0.05 mass% or more, and usually 10 mass% or less, preferably 5 mass% or less. When the content of the auxiliary dopant is in this range, holes and electrons can be efficiently injected from adjacent layers, for example, a hole transport layer and a hole blocking layer, into the light-emitting layer when the composition is used for an organic electroluminescent element, and the driving voltage can be reduced. The content of the auxiliary dopant refers to the total content of the compounds represented by formula (2).

The composition for an organic electroluminescent element may contain only 1 type of compound represented by formula (2) as an auxiliary dopant, or may contain 2 or more types in combination. However, when 2 or more compounds are contained, the maximum emission wavelength of all the compounds as the auxiliary dopant is shorter than the maximum emission wavelength of the compound as the light-emitting dopant represented by formula (1). In addition, when 2 or more compounds represented by formula (1) are contained as the light emitting dopant, the maximum light emitting wavelength of all the compounds as the auxiliary dopant is shorter than the maximum light emitting wavelength of all the compounds as the light emitting dopant.

The composition ratio (% by mass) of the compound represented by formula (1) as the light-emitting dopant in the composition for an organic electroluminescent element is preferably the same as or larger than the composition ratio (% by mass) of the compound represented by formula (2) as the auxiliary dopant. By increasing the composition ratio of the compound as the light-emitting dopant, the width of the emission spectrum becomes narrower when the organic electroluminescent element is produced, and more vivid light emission is obtained, and therefore, the organic electroluminescent element is suitable for display device applications. When 2 or more compounds as the auxiliary dopant are contained, the composition ratio (mass%) of the compounds as the light-emitting dopant is preferably larger than the total composition ratio (mass%) of all the compounds as the auxiliary dopant.

The compound as the light-emitting dopant is more preferably 1 to 3 times the amount of the compound as the auxiliary dopant in terms of parts by mass. Thereby, energy from the auxiliary dopant is more efficiently transferred to the light emitting dopant, and thus higher light emitting efficiency is obtained. Particularly preferably 1 to 2 times. From the viewpoint of obtaining more vivid light emission, the composition ratio (% by mass) of the compound as the light-emitting dopant is more preferably 2 times or more larger than the composition ratio (% by mass) of the compound as the auxiliary dopant. On the other hand, from the viewpoint of being able to reduce the driving voltage of the element, the composition ratio (% by mass) of the compound as the light-emitting dopant is preferably less than 2 times the composition ratio (% by mass) of the compound as the auxiliary dopant.

The solvent contained in the composition for an organic electroluminescent element is a volatile liquid component for forming a layer containing an auxiliary dopant and a light-emitting dopant by wet film formation.

The solvent is not particularly limited as long as the solute, that is, the compound as the auxiliary dopant and the compound as the light-emitting dopant is well dissolved in the solvent. Further, a solvent in which a charge transporting compound described later is dissolved is preferable.

Examples of the preferred solvent include alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, mesitylene, phenylcyclohexane, and tetrahydronaphthalene; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, trichlorobenzene and the like; aromatic ethers such as 1, 2-dimethoxybenzene, 1, 3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2, 3-dimethylanisole, 2, 4-dimethylanisole, and diphenyl ether; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; alicyclic ketones such as cyclohexanone, cyclooctanone and fenchone; alicyclic alcohols such as cyclohexanol and cyclooctanol; aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; aliphatic alcohols such as butanol and hexanol; and aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA). Among these, alkanes and aromatic hydrocarbons are more preferable, and phenylcyclohexane is particularly preferable because it has a preferable viscosity and a preferable boiling point in a wet film forming process.

These solvents may be used alone in 1 kind, and in addition, may also be used in any combination and ratio of 2 or more.

The boiling point of the solvent is usually 80 ℃ or higher, preferably 100 ℃ or higher, more preferably 150 ℃ or higher, and particularly preferably 200 ℃ or higher. When the amount is within this range, a decrease in film formation stability due to evaporation of the solvent from the composition for an organic electroluminescent element can be suppressed during wet film formation. The boiling point is usually 270 ℃ or lower, preferably 250 ℃ or lower, and more preferably 240 ℃ or lower.

The content of the solvent is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, and particularly preferably 80 parts by mass or more, and is preferably 99.95 parts by mass or less, more preferably 99.9 parts by mass or less, and particularly preferably 99.8 parts by mass or less, with respect to 100 parts by mass of the composition for organic electroluminescent elements.

When the light-emitting layer of the organic electroluminescent element is formed from the composition for organic electroluminescent elements, the thickness is usually about 3 to 200nm, and the content of the solvent is set to the lower limit or more, whereby the composition can be prevented from being excessively viscous and from deteriorating the film workability. On the other hand, when the amount is not more than the upper limit, a film obtained by removing the solvent after film formation can have a thickness not less than a certain level, and the film formation property is good.

[ Charge-transporting Compound ]

The composition for an organic electroluminescent element of the present embodiment preferably further contains a charge-transporting compound.

As the charge transporting compound, a compound conventionally used as a material for an organic electroluminescent element can be used. Examples thereof include triarylamines, biscarbazoles, triaryltriazines, triarylpyrimidines, derivatives thereof, naphthalenes substituted with arylamino or carbazolyl groups, perylenes, pyrenes, anthracenes, and the like,

Fused aromatic ring compounds such as tetracene, phenanthrene, coronene, fluoranthene, triphenylene, fluorene, and acetylnaphthofluoranthene.

The charge transporting compound may be a polymer, and examples of the charge transporting compound of the polymer include a polyfluorene material such as poly (9, 9-dioctylfluorene-2, 7-diyl), poly [ (9, 9-dioctylfluorene-2, 7-diyl) -co- (4,4 '- (N- (4-sec-butylphenyl)) diphenylamine) ], poly [ (9, 9-dioctylfluorene-2, 7-diyl) -co- (1, 4-benzo-2 {2, 1' -3 } -triazole) ], and a polystyrene material such as poly [ 2-methoxy-5- (2-ethylhexyloxy) -1, 4-phenylene vinylene ].

These charge transporting compounds may be used alone in 1 kind, or may be used in any combination and ratio in 2 or more kinds.

[ organic electroluminescent element ]

The organic electroluminescent element of the present embodiment includes a layer formed using the composition for an organic electroluminescent element, preferably by a wet film formation method.

The organic electroluminescent element preferably has at least an anode, a cathode, and at least 1 organic layer between the anode and the cathode on a substrate, and at least 1 of the organic layers is formed using the composition for an organic electroluminescent element of the present embodiment. The layer is more preferably formed by a wet film formation method. The organic layer includes a light-emitting layer, and more preferably, the light-emitting layer is formed using the composition for an organic electroluminescent element according to the present embodiment.

In the present specification, the wet film-forming method is a method of forming a film by applying a wet film-forming method such as a spin coating method, a dip coating method, a die coating method, a bar coating method, a blade coating method, a roll coating method, a spray coating method, a capillary coating method, an ink jet method, a nozzle printing method, a screen printing method, a gravure printing method, a flexographic printing method, or the like, as a coating method, and drying the film formed by these methods.

Fig. 1 is a schematic diagram showing a cross section of a preferred configuration example of an organic electroluminescent element 10 according to the present invention. In fig. 1, reference numeral 1 denotes a substrate, reference numeral 2 denotes an anode, reference numeral 3 denotes a hole injection layer, reference numeral 4 denotes a hole transport layer, reference numeral 5 denotes a light emitting layer, reference numeral 6 denotes a hole blocking layer, reference numeral 7 denotes an electron transport layer, reference numeral 8 denotes an electron injection layer, and reference numeral 9 denotes a cathode.

The material used in these structures is not particularly limited, and known materials can be used, and typical materials and production methods for each layer are described below as examples. Hereinafter, when a publication, a paper, or the like is referred to, the content can be appropriately adopted and applied within the scope of general knowledge of those skilled in the art.

< substrate 1 >

The substrate 1 is a support for the organic electroluminescent element, and is generally a quartz or glass plate, a metal foil, a film or sheet of synthetic resin, i.e., plastic, or the like. Among them, a transparent synthetic resin film such as a glass plate, polyester, polymethacrylate, polycarbonate, polysulfone, or the like is preferable. The substrate 1 is preferably made of a material having a high gas barrier property, since degradation of the organic electroluminescent element due to the outside air is less likely to occur. In particular, when a material having low gas barrier properties such as a synthetic resin substrate is used, it is preferable to provide a dense silicon oxide film or the like on at least one surface of the substrate 1 to improve the gas barrier properties.

< anode 2 >

The anode 2 has a function of injecting holes into a layer on the light-emitting layer side. The anode 2 is usually made of metal such as aluminum, gold, silver, nickel, palladium, platinum, etc.; metal oxides such as oxides of indium and/or tin; halogenated metals such as copper iodide; carbon black, conductive polymers such as poly (3-methylthiophene), polypyrrole, polyaniline, and the like.

The anode 2 is often formed by a dry method such as a sputtering method or a vacuum deposition method. When the anode 2 is formed using fine metal particles such as silver, fine particles such as copper iodide, carbon black, fine conductive metal oxide particles, fine conductive polymer powder, or the like, it may be formed by dispersing the fine metal particles, the fine carbon black, the fine conductive metal oxide particles, or the fine conductive polymer powder in an appropriate binder resin solution and coating the solution on the substrate 1. In the case of a conductive polymer, a thin film may be formed directly on a substrate by electrolytic polymerization, or the anode 2 may be formed by coating a conductive polymer on a substrate (appl. phys. lett., volume 60, page 2711, 1992).

The anode 2 is usually a single-layer structure, and may be suitably formed into a laminated structure. When the anode 2 has a laminated structure, different conductive materials may be laminated on the anode of the 1 st layer.

The thickness of the anode 2 may be determined according to the required transparency, material, and the like. When particularly high transparency is required, the thickness is preferably 60% or more in visible light transmittance, and more preferably 80% or more in visible light transmittance. The thickness of the anode 2 is usually 5nm or more, preferably 10nm or more, usually 1000nm or less, preferably 500nm or less.

In the case where transparency is not required, the thickness of the anode 2 may be any thickness depending on the required strength and the like, and in this case, the anode 2 may be the same thickness as the substrate 1.

When the next layer is formed on the surface of the anode 2 after the formation, it is preferable to remove impurities on the anode by performing treatment such as ultraviolet + ozone, oxygen plasma, or argon plasma and adjust the ionization potential thereof to improve the hole injecting property before the film formation.

< hole injection layer 3 >

A layer having a function of transporting holes from the anode 2 side to the light-emitting layer 5 side is generally called a hole injection transport layer or a hole transport layer. When the number of layers having a function of transporting holes from the anode 2 side to the light-emitting layer 5 side is 2 or more, the layer closer to the anode 2 side may be referred to as a hole injection layer 3.

Although the hole injection layer 3 is described below, the hole injection transport layer or the hole transport layer in the case where the layer having a function of transporting holes is 1 layer is also described as the hole injection layer 3 in the same manner. That is, the hole transport layer 4 described later is a name of a layer closer to the light emitting layer 5 when the layer having a function of transporting holes is 2 or more, unlike the hole transport layer when the layer is 1 layer, and is an arbitrary layer.

The hole injection layer 3 is preferably used in order to enhance the function of transporting holes from the anode 2 to the light-emitting layer 5 side. When the hole injection layer 3 is used, the hole injection layer 3 is usually formed on the anode 2.

The film thickness of the hole injection layer 3 is usually 1nm or more, preferably 5nm or more, usually 1000nm or less, preferably 500nm or less.

The method for forming the hole injection layer 3 may be a vacuum deposition method or a wet film formation method. In terms of excellent film-forming properties, it is preferably formed by a wet film-forming method.

The hole injection layer 3 preferably contains a hole-transporting compound, and more preferably contains a hole-transporting compound and an electron-accepting compound. Further, the hole injection layer 3 preferably contains a radical positive ion compound, and particularly preferably contains a radical positive ion compound and a hole-transporting compound.

(hole transporting Compound)

The composition for forming a hole injection layer generally contains a hole-transporting compound as the hole injection layer 3.

In the case of a wet film formation method, the composition usually further contains a solvent. The composition for forming a hole injection layer preferably has a high hole-transporting property and can efficiently transport injected holes. Therefore, it is preferable that the hole mobility is high and impurities to be traps are not easily generated at the time of manufacturing, use, or the like. Further, it is preferable that the composition has excellent stability, a small ionization potential, and high transparency to visible light. In particular, when the hole injection layer 3 is in contact with the light-emitting layer 5, that is, when the layer having the function of transporting holes from the anode 2 side to the light-emitting layer 5 side is 1 layer of the hole injection layer 3, a substance which does not quench light emission from the light-emitting layer 5 or a substance which does not form an exciplex with the light-emitting layer 5 and which decreases light emission efficiency is preferable.

The hole-transporting compound is preferably a compound having an ionization potential of 4.5eV to 6.0eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. Examples of the hole-transporting compound include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which fluorenyl groups are linked by a tertiary amine, hydrazone compounds, silazane compounds, quinacridone compounds, and the like.

Among the above-mentioned exemplary compounds, aromatic amine compounds are preferable, and aromatic tertiary amine compounds are particularly preferable, from the viewpoint of amorphousness and visible light transmittance. The aromatic tertiary amine compound refers to a compound having an aromatic tertiary amine structure, and also includes a compound having a group derived from an aromatic tertiary amine.

The type of the aromatic tertiary amine compound is not particularly limited, and a polymer compound (a polymerizable compound in which repeating units are linked) having a weight average molecular weight of 1000 to 1000000 is preferably used in terms of facilitating uniform light emission by the surface smoothing effect. Preferred examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (I).

In the formula (I), Ar¹And Ar²Each independently represents a 1-valent aromatic group which may have a substituent or a 1-valent heteroaromatic group which may have a substituent. Ar (Ar)³～Ar⁵Each independently represents an aromatic group having a valence of 2 which may have a substituent or a heteroaromatic group having a valence of 2 which may have a substituent. Q represents a linking group selected from the following linking group. In addition, Ar¹～Ar⁵Two groups bonded to the same N atom in (1) may be bonded to each other to form a ring.

The linking group is shown below.

(in the above formulae, Ar⁶～Ar¹⁶Each independently represents an aromatic group which may have a substituent or a heteroaromatic group which may have a substituent. R^aAnd R^bEach independently represents a hydrogen atom or an optional substituent. )

As Ar¹～Ar¹⁶The aromatic group and the heteroaromatic group in (b) are preferably groups derived from a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene ring, and a pyridine ring, and more preferably groups derived from a benzene ring and a naphthalene ring, from the viewpoints of solubility, heat resistance, and hole injection transport properties of the polymer compound.

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by formula (I) include the compounds described in international publication No. 2005/089024.

(Electron accepting Compound)

In order to improve the conductivity of the hole injection layer 3 by oxidation of the hole transporting compound, the hole injection layer 3 preferably contains an electron accepting compound.

The electron accepting compound is preferably a compound having an oxidizing ability and an ability to accept one electron from the hole transporting compound, more preferably a compound having an electron affinity of 4eV or more, and still more preferably a compound having an electron affinity of 5eV or more.

Examples of such an electron-accepting compound include compounds selected from triarylboron compounds, metal halides, Lewis acids, organic acids, and mixtures thereof,

And 1 or 2 or more compounds selected from salts of arylamines and metal halides and salts of arylamines and Lewis acids. Specifically, 4-isopropyl-4' -methyldiphenyliodide

Substituted with organic groups such as tetrakis (pentafluorophenyl) borate, triphenylsulfonium tetrafluoroborate and the like

Salt (international publication No. 2005/089024); iron (III) chloride (Japanese patent application laid-open No. 11-251067), ammonium persulfate, and other high-valence inorganic compounds; cyano compounds such as tetracyanoethylene; aromatic boron compounds such as tris (pentafluorophenyl) borane (Japanese patent application laid-open No. 2003-31365); fullerene derivatives and iodine, etc.

(radical positive ion Compound)

The radical cation compound is preferably an ionic compound composed of a radical cation which is a chemical species for removing one electron from the hole-transporting compound and a counter anion. When the radical cation is derived from a hole-transporting polymer compound, the radical cation has a structure obtained by removing one electron from a repeating unit of the polymer compound.

The radical cation is preferably a chemical species obtained by removing one electron from a compound preferable as the hole-transporting compound, from the viewpoints of amorphousness, visible light transmittance, heat resistance, solubility, and the like.

The radical positive ion compound can be produced by mixing the hole-transporting compound and the electron-accepting compound. By mixing the hole-transporting compound and the electron-accepting compound, electrons are transferred from the hole-transporting compound to the electron-accepting compound, and a radical positive ion compound composed of a radical positive ion of the hole-transporting compound and a counter anion is generated.

As the radical positive ion compound, for example, a radical positive ion compound derived from a polymer compound such as poly (3, 4-ethylenedioxythiophene) (PEDOT/PSS) (adv.mater., 2000, 12, 481 pages), emeraldine hydrochloride (j.phys.chem., 1990, 94, 7716 pages) doped with poly (4-styrenesulfonic acid) can be produced by oxidative polymerization (dehydropolymerization).

The oxidative polymerization herein refers to chemical or electrochemical oxidation of a monomer in an acidic solution using peroxodisulfate or the like. In the case of this oxidative polymerization (dehydrogenation polymerization), the monomer is oxidized to be polymerized into a polymer, and a radical cation in which one electron is removed from a repeating unit of the polymer is generated using an anion derived from an acidic solution as a counter anion.

(formation of hole injection layer 3 by Wet film formation method)

In the case of forming the hole injection layer 3 by a wet film formation method, a composition for film formation (composition for hole injection layer formation) is usually prepared by mixing a material to be the hole injection layer 3 and a solvent (solvent for hole injection layer) capable of dissolving the material, and the composition for hole injection layer formation is formed on the anode 2, which is usually a layer corresponding to a lower layer of the hole injection layer 3, by a wet film formation method, and dried to form the hole injection layer 3. The film formed may be dried in the same manner as the drying method in the formation of the light-emitting layer 5 by the wet film formation method.

The concentration of the hole-transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, and is preferably low in terms of uniformity of film thickness, and is preferably high in terms of difficulty in generating defects in the hole injection layer 3. The concentration of the hole-transporting compound in the composition for forming a hole injection layer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and further preferably 70% by mass or less, more preferably 60% by mass or less, particularly preferably 50% by mass or less.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, and amide solvents.

Examples of the ether solvent include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA), and aromatic ethers such as 1, 2-dimethoxybenzene, 1, 3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2, 3-dimethylanisole, and 2, 4-dimethylanisole.

Examples of the ester-based solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.

Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylbiphenyl, 1,2,3, 4-tetramethylbenzene, 1, 4-diisopropylbenzene, and methylnaphthalene.

Examples of the amide solvent include N, N-dimethylformamide and N, N-dimethylacetamide.

In addition, dimethyl sulfoxide or the like can be used.

The formation of the hole injection layer 3 by a wet film formation method is generally performed by preparing a composition for forming a hole injection layer, applying the composition to a layer corresponding to a lower layer of the hole injection layer 3, generally the anode 2, and drying the composition. The hole injection layer 3 is usually formed, and then the coating film is dried by heating, drying under reduced pressure, or the like.

(formation of hole injection layer 3 by vacuum deposition)

Forming voids by vacuum depositionIn the case of the hole injection layer 3, usually, 1 or 2 or more kinds of the above-mentioned hole-transporting compound, electron-accepting compound, and the like, which are constituent materials of the hole injection layer 3, are put in a crucible provided in a vacuum vessel. In this case, when 2 or more kinds of materials are used, the materials are usually placed in different crucibles. Thereafter, the vacuum vessel was evacuated to 10 degrees by a vacuum pump^－4After Pa, the crucible was heated and evaporated while controlling the amount of evaporation of the material in the crucible. When 2 or more kinds of materials are used, the respective crucibles are generally heated and evaporated while controlling the amount of evaporation independently of each other. The hole injection layer 3 is formed on the anode 2 on the substrate placed facing the crucible by the above operation. When 2 or more kinds of materials are used, they may be put in a crucible as a mixture, heated, and evaporated to form the hole injection layer 3.

The degree of vacuum at the time of vapor deposition is not particularly limited as long as the effect of the present invention is not significantly impaired, and is usually 0.1X 10^－ ⁶Torr(0.13×10^－4Pa)～9.0×10^－6Torr(12.0×10^－4Pa) is added. The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, and is usually

The film forming temperature during vapor deposition is not particularly limited as long as the effects of the present invention are not significantly impaired, and is preferably 10 to 50 ℃.

< hole transport layer 4 >

The hole transport layer 4 is a layer having a function of transporting holes from the anode 2 side to the light-emitting layer 5 side. The hole transport layer 4 is not an essential layer in the organic electroluminescent element of the present embodiment, but is preferably provided in view of enhancing the function of transporting holes from the anode 2 to the light-emitting layer 5. When the hole transport layer 4 is provided, the hole transport layer 4 is usually formed between the anode 2 and the light-emitting layer 5. With the hole injection layer 3, the hole transport layer 4 is formed between the hole injection layer 3 and the light-emitting layer 5.

The film thickness of the hole transport layer 4 is usually 5nm or more, preferably 10nm or more, usually 300nm or less, preferably 100nm or less.

The method for forming the hole transport layer 4 may be a vacuum deposition method or a wet film formation method. In view of excellent film forming properties, it is preferable to form the film by a wet film forming method.

The hole transport layer 4 generally contains a hole-transporting compound that serves as the hole transport layer 4. Examples of the hole-transporting compound contained in the hole-transporting layer 4 include aromatic amine compounds having a starburst structure (j.lumin., 72-74 vol., 985 p., 1997), such as aromatic diamines containing 2 or more tertiary amines and having 2 or more condensed aromatic rings substituted on the nitrogen atom, particularly represented by 4,4 '-bis [ N- (1-naphthyl) -N-phenylamino ] biphenyl (jp-a-5-234681), 4', 4 ″ -tris (1-naphthylphenylamino) triphenylamine, aromatic amine compounds composed of tetramers of triphenylamines (chem.commun., 2175 p., 1996), spiro compounds such as 2,2 ', 7,7 ' -tetrakis- (diphenylamino) -9, 9 ' -spirobifluorene (synth. metals, volume 91, page 209, 1997), and carbazole derivatives such as 4,4 ' -N, N ' -dicarbazolylbiphenyl. Polyvinyl carbazole, polyvinyl triphenylamine (jp 7-53953 a), and polyarylene ether sulfone containing tetraphenylbenzidine (polym. adv. tech., volume 7, page 33, 1996), and the like can also be preferably used.

(formation of hole transport layer 4 by Wet film formation method)

When the hole transport layer 4 is formed by a wet film formation method, it is generally formed by using a composition for forming a hole transport layer instead of the composition for forming a hole injection layer, as in the case of forming the hole injection layer 3 by a wet film formation method.

When the hole transport layer 4 is formed by a wet film formation method, the hole transport layer forming composition usually further contains a solvent. The solvent used in the composition for forming a hole transport layer may be the same as the solvent used in the composition for forming a hole injection layer.

The concentration of the hole-transporting compound in the composition for forming a hole-transporting layer may be in the same range as the concentration of the hole-transporting compound in the composition for forming a hole-injecting layer.

The formation of the hole transport layer 4 by a wet film formation method can be performed in the same manner as the film formation method of the hole injection layer 3 described above.

(formation of hole transport layer 4 by vacuum deposition)

When the hole transport layer 4 is formed by the vacuum vapor deposition method, it is generally possible to form the hole transport layer by using the constituent material of the hole transport layer 4 instead of the constituent material of the hole injection layer 3, similarly to the case of forming the hole injection layer 3 by the vacuum vapor deposition method described above. The film formation conditions such as the degree of vacuum at the time of vapor deposition, the vapor deposition rate, and the temperature can be the same as those at the time of vacuum vapor deposition of the hole injection layer 3.

< light emitting layer 5 >

The light-emitting layer 5 is a layer having a function of being excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 when an electric field is applied between the pair of electrodes, and emitting light.

The light-emitting layer 5 is a layer formed between the anode 2 and the cathode 9. The light-emitting layer 5 is formed between the hole injection layer 3 and the cathode 9 when the hole injection layer 3 is provided on the anode 2, and between the hole transport layer 4 and the cathode 9 when the hole transport layer 4 is provided on the anode 2.

The thickness of the light-emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, and is preferably thick in terms of being less likely to cause defects in the film, and is preferably thin in terms of being more likely to have a low driving voltage. The thickness of the light-emitting layer 5 is preferably 3nm or more, more preferably 5nm or more, and is usually preferably 200nm or less, more preferably 100nm or less.

The light-emitting layer 5 is preferably formed using the composition for an organic electroluminescent element according to the present embodiment, and more preferably formed by a wet coating method.

The organic electroluminescent element may contain another light-emitting material and a charge-transporting material in addition to the light-emitting layer formed by a wet coating method using the composition for an organic electroluminescent element of the present embodiment, and the other light-emitting material and the charge-transporting material will be described in detail below.

(luminescent Material)

The light-emitting material is not particularly limited as long as it emits light at a desired emission wavelength and does not impair the effects of the present invention, and a known light-emitting material can be used. The light-emitting material may be a fluorescent light-emitting material or a phosphorescent light-emitting material, and a material having good emission efficiency is preferable.

Examples of the fluorescent light-emitting material include the following materials.

Examples of the fluorescent light-emitting material emitting blue light (blue fluorescent light-emitting material) include naphthalene, perylene, pyrene, anthracene, coumarin, perylene, and perylene,

P-bis (2-phenylvinyl) benzene and derivatives thereof, and the like.

Examples of the fluorescent light-emitting material emitting green light (green fluorescent light-emitting material) include quinacridone derivatives, coumarin derivatives, and Al (C)₉H₆NO)₃And the like aluminum complexes.

Examples of the fluorescent light-emitting material that emits yellow light (yellow fluorescent light-emitting material) include rubrene, a perimidine (ペリミドン) derivative, and the like.

Examples of the fluorescent light-emitting material emitting red light (red fluorescent light-emitting material) include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) based compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azobenzothioxanthene, and the like.

Examples of the phosphorescent light-emitting material include organometallic complexes containing a metal of groups 7 to 11 of the long-period periodic table (hereinafter, unless otherwise specified, the term "periodic table" refers to the long-period periodic table), and the like. Preferred examples of the metal selected from groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, gold, and the like.

The ligand of the organometallic complex compound is preferably a ligand in which a (hetero) aryl group such as a (hetero) arylpyridine ligand or a (hetero) arylpyrazole ligand is bonded to pyridine, pyrazole, phenanthroline, or the like, and particularly preferably a phenylpyridine ligand or a phenylpyrazole ligand. Here, (hetero) aryl means at least one of aryl and heteroaryl.

Specific examples of preferable phosphorescent light-emitting materials include phenylpyridine coordination compounds such as tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, tris (2-phenylpyridine) osmium, and tris (2-phenylpyridine) rhenium, and porphyrin coordination compounds such as octaethylplatinum porphyrin, octaphenylplatinum porphyrin, octaethylpalladium porphyrin, and octaphenylpalladium porphyrin.

Examples of the polymer-based light-emitting material include a polyfluorene material such as poly (9, 9-dioctylfluorene-2, 7-diyl), poly [ (9, 9-dioctylfluorene-2, 7-diyl) -co- (4,4 '- (N- (4-sec-butylphenyl)) diphenylamine) ], poly [ (9, 9-dioctylfluorene-2, 7-diyl) -co- (1, 4-benzo-2 {2, 1' -3 } -triazole) ], and a polystyrene material such as poly [ 2-methoxy-5- (2-ethylhexyloxy) -1, 4-phenylene vinylene ].

(Charge-transporting Material)

The charge transporting material is a material having a positive charge (hole) or negative charge (electron) transport property, and is not particularly limited as long as the effect of the present invention is not impaired, and a known material can be used.

As the charge transporting material, a compound conventionally used in the light-emitting layer 5 of an organic electroluminescent element can be used, and a compound used as a host material of the light-emitting layer 5 is particularly preferable.

Specific examples of the charge transporting material include hole transporting compounds as the hole injection layer 3, such as aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds obtained by connecting tertiary amines with fluorenyl groups, hydrazone compounds, silazane compounds, phosphoramide compounds, and quinacridone compoundsExamples of the compound include anthracene compounds, pyrene compounds, carbazole compounds, pyridine compounds, phenanthroline compounds, and the like,

And electron-transporting compounds such as a diazole compound and a silacyclopentadiene compound.

As the charge transporting material, 4' -bis [ N- (1-naphthyl) -N-phenylamino ] group can be preferably used]Examples of the hole-transporting compound of the hole-transporting layer 4 include aromatic amine compounds having a starburst structure such as aromatic diamines in which 2 or more condensed aromatic rings containing 2 or more tertiary amines, represented by biphenyl, are substituted on a nitrogen atom (jp-a-5-234681), 4 ', 4 ″ -tris (1-naphthylphenylamino) triphenylamine (j.lumin., volume 72-74, page 985, 1997), aromatic amine compounds composed of a tetramer of triphenylamines (chem.commun., page 2175, 1996), fluorene compounds such as 2, 2', 7,7 '-tetrakis- (diphenylamino) -9, 9' -spirobifluorene (synth.metals, volume 91, page 209, 1997), and carbazole compounds such as 4,4 '-N, N' -dicarbazolylbiphenyl. Further, 2- (4-biphenylyl) -5- (p-tert-butylphenyl) -1, 3, 4-

Oxadiazole (tBu-PBD), 2, 5-bis (1-naphthyl) -1, 3, 4-

Oxadiazoles (BND) and the like

Oxadiazole-based compounds, silacyclopentadiene-based compounds such as 2, 5-bis (6 '- (2', 2 "-bipyridyl)) -1, 1-dimethyl-3, 4-diphenylsilacyclopentadiene (pypespypy), and phenanthroline-based compounds such as bathophenanthroline (BPhen) and 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline (BCP, bathocuproine).

(formation of light-emitting layer 5 by Wet film-Forming method)

The organic electroluminescent element preferably has a light-emitting layer formed by a wet film formation method using the composition for an organic electroluminescent element of the present embodiment.

The light-emitting layer 5 may have another light-emitting layer in addition to the light-emitting layer formed using the composition for an organic electroluminescent element of the present embodiment. The method for forming these light-emitting layers may be a vacuum deposition method or a wet film formation method, and a wet film formation method is preferable because of its excellent film formation properties.

In the case where the light-emitting layer 5 is formed by a wet film formation method, a light-emitting layer-forming composition prepared by mixing a material to be the light-emitting layer 5 and a solvent (light-emitting layer solvent) capable of dissolving the material is generally used in place of the hole-injecting layer-forming composition, as in the case where the hole-injecting layer 3 is formed by a wet film formation method.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, alkane solvents, halogenated aromatic hydrocarbon solvents, aliphatic alcohol solvents, alicyclic alcohol solvents, aliphatic ketone solvents, and alicyclic ketone solvents, which are exemplified for the formation of the hole injection layer 3. The solvent used is also exemplified as the solvent of the composition containing an iridium complex compound in the present embodiment. Specific examples of the solvent are not limited to the following examples unless the effects of the present invention are impaired.

Examples thereof include aliphatic ether solvents such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); aromatic ether solvents such as 1, 2-dimethoxybenzene, 1, 3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2, 3-dimethylanisole, 2, 4-dimethylanisole, and diphenyl ether; aromatic ester solvents such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; aromatic hydrocarbon solvents such as toluene, xylene, mesitylene, cyclohexylbenzene, tetrahydronaphthalene, 3-isopropylbiphenyl, 1,2,3, 4-tetramethylbenzene, 1, 4-diisopropylbenzene, and methylnaphthalene; amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide; alkane solvents such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; halogenated aromatic hydrocarbon solvents such as chlorobenzene, dichlorobenzene, trichlorobenzene and the like; aliphatic alcohol solvents such as butanol and hexanol; alicyclic alcohol solvents such as cyclohexanol and cyclooctanol; aliphatic ketone solvents such as methyl ethyl ketone and dibutyl ketone; and alicyclic ketone solvents such as cyclohexanone, cyclooctanone and fenchone. Among them, an alkane-based solvent and an aromatic hydrocarbon-based solvent are particularly preferable.

In order to obtain a more uniform film, it is preferable to evaporate the solvent at an appropriate rate from the liquid film immediately after the film formation. Therefore, the boiling point of the solvent used is usually 80 ℃ or higher, preferably 100 ℃ or higher, more preferably 120 ℃ or higher, and usually 270 ℃ or lower, preferably 250 ℃ or lower, more preferably 230 ℃ or lower, as described above.

The amount of the solvent to be used is arbitrary as long as the effect of the present invention is not significantly impaired, and the total content of the composition for forming a light-emitting layer, that is, the composition containing an iridium complex is preferably large in view of easiness of film formation due to low viscosity, and is preferably low in view of easiness of film formation in a thick film. As described above, the content of the solvent in the composition containing the iridium complex compound is preferably 1% by mass or more, more preferably 10% by mass or more, particularly preferably 50% by mass or more, preferably 99.99% by mass or less, more preferably 99.9% by mass or less, and particularly preferably 99% by mass or less.

As a method for removing the solvent after wet film formation, heating or reduced pressure may be used. As the heating mechanism used in the heating method, a cleaning oven or a heating plate is preferable in order to uniformly supply heat to the entire film.

The heating temperature in the heating step is arbitrary as long as the effect of the present invention is not significantly impaired, and is preferably low in view of shortening the drying time, the higher the temperature is, the more the material is damaged, and the less the material is damaged. The upper limit of the heating temperature is usually 250 ℃ or less, preferably 200 ℃ or less, and more preferably 150 ℃ or less. The lower limit of the heating temperature is usually 30 ℃ or more, preferably 50 ℃ or more, and more preferably 80 ℃ or more. When the amount is not more than the upper limit, the temperature is lower than the heat resistance of a charge transporting material or a phosphorescent material which is generally used, and decomposition and crystallization can be suppressed. By setting the heating temperature to the lower limit or more, it is possible to avoid a long time for removing the solvent. The heating time in the heating step is appropriately determined depending on the boiling point and vapor pressure of the solvent in the composition for forming a light-emitting layer, the heat resistance of the material, and the heating conditions.

(formation of light-emitting layer 5 by vacuum deposition)

When the light-emitting layer 5 is formed by the vacuum deposition method, usually, 1 or 2 or more of the light-emitting materials, the charge-transporting compounds, and the like, which are the constituent materials of the light-emitting layer 5, are placed in a crucible provided in a vacuum chamber. In this case, when 2 or more kinds of materials are used, the materials are usually placed in different crucibles. Thereafter, the vacuum vessel was evacuated to 10 degrees by a vacuum pump^－4After Pa, the crucible was heated and evaporated while controlling the amount of evaporation of the material in the crucible. When 2 or more kinds of materials are used, the respective crucibles are generally heated and evaporated while controlling the amount of evaporation independently of each other. The light-emitting layer 5 is formed on the hole injection layer 3 or the hole transport layer 4 placed facing the crucible by the above operation. When 2 or more kinds of materials are used, they may be put in a crucible as a mixture, heated, and evaporated to form the light-emitting layer 5.

The degree of vacuum at the time of vapor deposition is not particularly limited as long as the effect of the present invention is not significantly impaired, and is usually 0.1X 10^－ ⁶Torr(0.13×10^－4Pa)～9.0×10^－6Torr(12.0×10^－4Pa) is added. The deposition rate is not limited as long as the effect of the present invention is not impaired, and is usually

The film forming temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not impaired, and is preferably 10 to 50 ℃.

< hole blocking layer 6 >

The hole blocking layer 6 may be provided between the light emitting layer 5 and an electron injection layer 8 described later. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

The hole blocking layer 6 has a function of blocking holes transferred from the anode 2 from reaching the cathode 9 and a function of efficiently transporting electrons injected from the cathode 9 in the direction of the light-emitting layer 5. Physical properties required for the material constituting the hole-blocking layer 6 include high electron mobility and low hole mobility, a large energy gap, i.e., a large difference between HOMO and LUMO, and a high excited triplet level (T1).

Examples of the material of the hole-blocking layer 6 satisfying such conditions include metal complexes such as bis (2-methyl-8-quinolinolato) (phenol) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanol) aluminum, mixed ligand complexes such as bis (2-methyl-8-quinolinolato) aluminum- μ -oxo-bis- (2-methyl-8-quinolinolato) aluminum dinuclear metal complexes, styryl compounds such as distyrylbiphenyl derivatives (jp-a-11-242996 a), triazole derivatives such as 3- (4-biphenyl) -4-phenyl-5 (4-tert-butylphenyl) -1, 2, 4-triazole (jp-a-7-41759 a), and phenanthroline derivatives such as bathocuproine (jp-a-10-79297 a). A compound having a pyridine ring substituted at least at 1

position

2,4, or 6 as described in international publication No. 2005/022962 is also preferable as the material of the hole-blocking layer 6.

The method for forming the hole blocking layer 6 is not limited, and the hole blocking layer can be formed in the same manner as the method for forming the light emitting layer 5 described above.

The thickness of the hole-blocking layer 6 is arbitrary as long as the effect of the present invention is not significantly impaired, and is usually 0.3nm or more, preferably 0.5nm or more, usually 100nm or less, and preferably 50nm or less.

< electron transport layer 7 >

In order to further improve the current efficiency of the device, the electron transport layer 7 is provided between the light-emitting layer 5 or the hole blocking layer 6 and the electron injection layer 8.

The electron transport layer 7 is formed of a compound capable of efficiently transporting electrons injected from the cathode 9 to the direction of the light emitting layer 5 between the electrodes to which an electric field is applied. As the electron-transporting compound used in the electron transport layer 7, a compound having high electron injection efficiency from the cathode 9 or the electron injection layer 8, high electron mobility, and capable of transporting injected electrons efficiently is required.

Examples of the electron-transporting compound satisfying such a condition include a metal complex such as an aluminum complex of 8-hydroxyquinoline (Japanese patent application laid-open No. Sho 59-194393), and 10-hydroxybenzo [ h ]]Metal complexes of quinolines,

Oxadiazole derivatives, distyrylbiphenyl derivatives, silacyclopentadiene derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, and benzophenones

An azole metal complex compound, a benzothiazole metal complex compound, a triphenylimidazolylbenzene (see the specification of U.S. Pat. No. 5645948), a quinoxaline compound (Japanese patent application laid-open No. 6-207169), an orthophenylene derivative (Japanese patent application laid-open No. 5-331459), 2-tert-butyl-9, 10-N, N' -dicyanoanthraquinone diimine, N-type hydrogenated amorphous silicon carbide, N-type zinc sulfide, N-type zinc selenide, and the like.

The thickness of the electron transport layer 7 is usually 1nm or more, preferably 5nm or more, usually 300nm or less, preferably 100nm or less.

The electron transport layer 7 is formed by being laminated on the light emitting layer 5 or the hole blocking layer 6 by a wet film formation method or a vacuum deposition method, similarly to the light emitting layer 5. Vacuum evaporation is generally used in many cases.

< electron injection layer 8 >

The electron injection layer 8 functions to efficiently inject electrons injected from the cathode 9 into the electron transport layer 7 or the light emitting layer 5.

In order to efficiently inject electrons, a metal having a low work function is preferably used as a material for forming the electron injection layer 8. For example, alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium can be used.

The thickness of the electron injection layer 8 is preferably 0.1 to 5 nm.

Inserting LiF, MgF into the interface of cathode 9 and electron transport layer 7₂、Li₂O、Cs₂CO₃An extremely thin insulating film having a film thickness of about 0.1 to 5nm is also effective as the electron injection layer 8 for improving the device efficiency (appl. Phys. Lett., vol.70, p. 152, 1997; Japanese patent laid-open No. H10-74586; IEEE trans. Electron. devices, vol.44, p. 1245, 1997; SID 04Digest, p. 2004, p. 154).

Further, it is preferable that an organic electron-transporting material represented by a nitrogen-containing heterocyclic compound such as bathophenanthroline or a metal complex compound such as an aluminum complex compound of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium or rubidium (described in japanese patent application laid-open No. 10-270171, japanese patent application laid-open No. 2002-100478, japanese patent application laid-open No. 2002-100482, etc.), since both electron injection property and electron transport property can be improved and excellent film quality can be achieved. The film thickness in this case is usually 5nm or more, preferably 10nm or more, usually 200nm or less, preferably 100nm or less.

The electron injection layer 8 is formed by laminating on the light-emitting layer 5 or the hole blocking layer 6 or the electron transport layer 7 thereon by a wet film formation method or a vacuum deposition method, similarly to the light-emitting layer 5.

The details of the wet film formation method are the same as those of the light-emitting layer 5 described above.

< cathode 9 >

The cathode 9 functions to inject electrons into a layer on the light-emitting layer 5 side, such as the electron injection layer 8 or the light-emitting layer 5. As the material of the cathode 9, the material used for the anode 2 can be used, and it is preferable to use a metal having a low work function, for example, a metal such as tin, magnesium, indium, calcium, aluminum, or silver, or an alloy thereof, in terms of efficient electron injection. Examples of the material of the cathode 9 include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

In terms of element stability, it is preferable to protect the cathode 9 made of a metal having a low work function by stacking a metal layer having a high work function and stable to the atmosphere on the cathode 9. Examples of the metal to be laminated include metals such as aluminum, silver, copper, nickel, chromium, gold, and platinum.

The film thickness of the cathode is generally the same as that of the anode 2.

< other constituent layers >

As described above, the element having the layer structure shown in fig. 1 is mainly described, and any layer other than the above-described layers may be provided between the anode 2 and the cathode 9 and the light-emitting layer 5 in the organic electroluminescent element of the present embodiment as long as the performance is not impaired, or any layer other than the light-emitting layer 5 may be omitted.

For example, it is also effective to provide an electron blocking layer between the hole transport layer 4 and the light-emitting layer 5 for the same purpose as the hole blocking layer 6. The electron blocking layer has: the function of blocking the electrons transferred from the light-emitting layer 5 from reaching the hole-transporting layer 4, thereby increasing the probability of recombination with holes in the light-emitting layer 5 and confining the generated excitons in the light-emitting layer 5, and the function of efficiently transporting the holes injected from the hole-transporting layer 4 in the direction of the light-emitting layer 5.

The characteristics required for the electron-blocking layer include a high hole-transport property, a large energy gap difference between HOMO and LUMO, and a high excited triplet level (T1).

When the light-emitting layer 5 is formed by a wet film formation method, it is preferable that the electron blocking layer is also formed by a wet film formation method because element fabrication is easy.

Therefore, the electron blocking layer is also preferably suitable for wet film formation, and examples of the material used for such an electron blocking layer include a copolymer of dioctylfluorene and triphenylamine (international publication No. 2004/084260) typified by F8-TFB.

The structure may be the reverse of that shown in fig. 1, that is, the cathode 9, the electron injection layer 8, the electron transport layer 7, the hole blocking layer 6, the light-emitting layer 5, the hole transport layer 4, the hole injection layer 3, and the anode 2 may be sequentially stacked on the substrate 1. The organic electroluminescent element according to the present embodiment may be provided between 2 substrates at least one of which has high transparency.

A structure in which a plurality of layers shown in fig. 1 are repeated, that is, a structure in which a plurality of light emitting units are stacked may be employed. At this time, for example, V₂O₅And the like, when used as a charge generation layer instead of the interface layer between the segments, that is, between the light emitting cells, the barrier between the segments is reduced, and is more preferable from the viewpoint of light emission efficiency and driving voltage. The interface layer is referred to as 2 layers when the anode is ITO and the cathode is Al, for example.

The organic electroluminescent element of the present invention is applicable to a single element, an element having a structure in which the elements are arranged in an array, and a structure in which anodes and cathodes are arranged in an X-Y staggered manner.

[ display device ]

The display device and the lighting device of the present embodiment have the organic electroluminescent element described above. The form and structure of the display device are not particularly limited, and the organic electroluminescent element of this embodiment can be assembled by a conventional method.

For example, the display device of this embodiment can be formed by a method described in "organic EL display" (ohmi, published 8/20/2004, shich, yadak qian pu, hamata ying.

Examples

The present invention will be described in more detail with reference to the following examples. The present invention is not limited to the following examples, and can be carried out with any modification without departing from the spirit thereof.

[ example 1]

The organic electroluminescent element was produced as follows.

A transparent conductive film of Indium Tin Oxide (ITO) was deposited on a glass substrate to a thickness of 50nm (sputtering film-formed product, manufactured by mitsui vacuum corporation), and the anode was patterned into 2mm wide stripes by a general photolithography technique and hydrochloric acid etching. The substrate on which the ITO was patterned in this way was cleaned by ultrasonic cleaning with a surfactant aqueous solution, water cleaning with ultrapure water, ultrasonic cleaning with ultrapure water, and water cleaning with ultrapure water in this order, then dried in compressed air, and finally subjected to ultraviolet ozone cleaning.

As a composition for forming a hole injection layer, a composition was prepared in which 3.0 mass% of a hole-transporting polymer compound having a repeating structure represented by the following formula (P-1) and 0.6 mass% of an oxidizing agent represented by the following formula (HI-1) were dissolved in ethyl benzoate.

The solution was spin-coated on the substrate in the air, and dried at 240 ℃ for 30 minutes by a heating plate in the air to form a uniform film having a thickness of 40nm, thereby forming a hole injection layer.

Then, 100 parts by mass of a charge transporting polymer compound having a structure represented by the following formula (HT-1) was dissolved in cyclohexylbenzene to prepare a 3.0 mass% solution.

The solution was spin-coated on the substrate on which the hole injection layer was formed in a nitrogen glove box, and dried at 230 ℃ for 30 minutes by a heating plate in the nitrogen glove box to form a uniform thin film having a thickness of 40nm as a hole transport layer.

Then, as a material of the light-emitting layer, 60 parts by mass of a compound represented by the following formula (H-1), 40 parts by mass of a compound represented by the following formula (H-2), 15 parts by mass of a compound represented by the following formula (D-1) as a red light-emitting dopant, and 15 parts by mass of a compound represented by the following formula (D-2) as an auxiliary dopant were weighed and dissolved in cyclohexylbenzene to prepare a 7.8 mass% solution.

The solution was spin-coated on the substrate on which the hole transport layer was formed in a nitrogen glove box, and dried at 120 ℃ for 20 minutes by a heating plate in the nitrogen glove box to form a uniform thin film having a thickness of 80nm as a light-emitting layer. The compound represented by the formula (D-1) is a dopant having a maximum light emission wavelength of 613nm, and the compound represented by the formula (D-2) is a dopant having a maximum light emission wavelength of 555 nm.

The substrate on which the light-emitting layer was formed was set in a vacuum deposition apparatus, and the inside of the apparatus was evacuated to 2X 10^－4Pa or less.

Next, a compound represented by the following formula (HB-1) and 8-hydroxyquinoline lithium were deposited by vacuum deposition so as to obtain a film thickness ratio of 2:3

The hole blocking layer was formed at a film thickness of 30nm by co-evaporation at the same speed as above.

Next, a 2mm wide stripe shadow mask was set in another vacuum deposition apparatus as a mask for cathode deposition in close contact with the substrate so as to be orthogonal to the ITO stripes of the anode. Then, the molybdenum boat is used to heat the aluminum for evaporation speed

An aluminum layer having a thickness of 80nm was formed to form a cathode.

Thus, an organic electroluminescent element having a light-emitting area portion of a size of 2mm × 2mm was obtained.

When a voltage was applied to the obtained organic electroluminescent element, red light emission from the compound represented by the formula (D-1) was observed.

[ example 2]

An organic electroluminescent element was produced in the same manner as in example 1 except that the mass ratio of the compounds represented by each formula in the light-emitting layer composition was changed to (H-1): (H-2): (D-1): (D-3): 60:40:15: 15.

The structural formula of the compound represented by the formula (D-3) is shown below. The compound represented by the formula (D-3) is a dopant having a maximum emission wavelength of 560 nm.

[ example 3]

An organic electroluminescent element was produced in the same manner as in example 1 except that the mass ratio of the compounds represented by each formula in the light-emitting layer composition was changed to (H-1): (H-2): (D-1): (D-4): 60:40:15: 15.

The structural formula of the compound represented by the formula (D-4) is shown below. The compound represented by the formula (D-4) is a dopant having a maximum emission wavelength of 558 nm.

Comparative example 1

An organic electroluminescent element was produced in the same manner as in example 1, except that the compound represented by formula (D-5) was used as the red light-emitting dopant and the composition of the light-emitting layer was changed to (H-1): (H-2): (D-5): (D-2): 60:40:15:15 in terms of the mass ratio of the compounds represented by the formulae.

The structural formula of the compound represented by the formula (D-5) is shown below.

When a voltage was applied to the obtained organic electroluminescent element, red light emission from the compound represented by the formula (D-5) was observed.

Comparative example 2

An organic electroluminescent element was produced in the same manner as in example 1, except that the compound represented by the formula (D-5) was used as the red light-emitting dopant and the composition of the light-emitting layer was changed to 60:40:15 in the mass ratio of the compounds represented by each formula (H-1) to (H-2) to (D-5) to (D-3).

Comparative example 3

An organic electroluminescent element was produced in the same manner as in example 1, except that the compound represented by the formula (D-5) was used as the red light-emitting dopant and the composition of the light-emitting layer was changed to 60:40:15 in the mass ratio of the compounds represented by each formula (H-1) to (H-2) to (D-5) to (D-4).

[ evaluation of Components ]

The organic electroluminescent elements obtained in examples 1 to 3 and comparative examples 1 to 3 were measured for luminance of 1000cd/m²Current luminous efficiency (cd/a) and external quantum efficiency EQE (%) at the time of light emission. The ratios of the current luminous efficiencies of examples n (n is 1 to 3) were calculated as relative luminous efficiencies, respectively, assuming that the current luminous efficiencies of comparative examples n (n is 1 to 3) are 1, and are shown in table 1. Table 1 below also shows values of Δ EQE (example n) to EQE (comparative example n) obtained by subtracting the EQE of comparative example n (n is 1 to 3) from the EQE of example n (n is 1 to 3).

From the results in table 1, it can be seen that: an organic electroluminescent element using the compound represented by the formula (D-1) of the present embodiment as a light-emitting dopant for a light-emitting layer material has improved efficiency regardless of the structure of the compound as an auxiliary dopant, as compared with an organic electroluminescent element using the compound represented by the formula (D-5).

[ Table 1]

TABLE 1

	Luminescent dopants	Auxiliary dopant	Relative luminous efficiency	ΔEQE
					Example 1	D-1	D-2	2.7	+2.6
Comparative example 1	D-5	D-2	1	-
					Example 2	D-1	D-3	2.7	+2.0
Comparative example 2	D-5	D-3	1	-
					Example 3	D-1	D-4	2.6	+2.4
Comparative example 3	D-5	D-4	1	-

Comparative example 4

An organic electroluminescent element was produced in the same manner as in example 1, except that the compound represented by the formula (D-2) was not used as an auxiliary dopant, and the mass ratio of the compounds represented by each formula (H-1) to (H-2) to (D-1) was changed to 60:40: 15.

Comparative example 5

An organic electroluminescent element was fabricated in the same manner as in example 1, except that the compound represented by formula (D-5) was used as the red light-emitting dopant and the compound represented by formula (D-2) was not used as the auxiliary dopant, and the composition of the light-emitting layer was adjusted such that the mass ratio of the compounds represented by the formulae (H-1) to (H-2) to (D-5) was 60:40: 15.

[ evaluation of Components ]

The organic electroluminescent elements obtained in example 1, comparative example 4 and comparative example 5 were measured to have luminances of 1000cd/m²External quantum efficiency EQE when illuminated. The range of change in EQE of the organic electroluminescent element (example 1 or comparative example 1) containing a compound as an auxiliary dopant from the EQE of the organic electroluminescent element (comparative example 4 or comparative example 5) containing no compound as an auxiliary dopant was represented by Δ EQE, and is shown in table 2 or table 3 below.

From the results of tables 2 and 3, it can be seen that: in the organic electroluminescent element (example 1) using the compound represented by the formula (D-1) of the present embodiment as a light-emitting dopant for a light-emitting layer material, the external quantum efficiency is more greatly changed when the compound represented by the formula (D-5) is added as an auxiliary dopant than in the organic electroluminescent element (comparative example 1).

[ Table 2]

TABLE 2

	Luminescent dopants	Auxiliary dopant	ΔEQE
				Example 1	D-1	D-2	+2.3
Comparative example 4	D-1	Is free of	-

[ Table 3]

TABLE 3

	Luminescent dopants	Auxiliary dopant	ΔEQE
				Comparative example 1	D-5	D-2	+2.1
Example 5	D-5	Is free of	-

[ example 4]

An organic electroluminescent element was produced in the same manner as in example 1, except that the compound represented by the formula (D-6) was used as the red light-emitting dopant and the composition of the light-emitting layer was changed to 60:40:15 in the mass ratio of the compounds represented by each formula (H-1) to (H-2) to (D-6) to (D-2). The compound represented by the formula (D-6) is a dopant having a maximum light emission wavelength of 627 nm.

When a voltage was applied to the obtained organic electroluminescent element, red light emission from the compound represented by the formula (D-6) was observed.

[ example 5]

An organic electroluminescent element was produced in the same manner as in example 1 except that the mass ratio of the compounds represented by each formula was changed to (H-1): (H-2): (D-6): (D-7): 60:40: 15. The compound represented by the formula (D-7) is a dopant having a maximum light emission wavelength of 605 nm.

Comparative example 6

An organic electroluminescent element was produced in the same manner as in example 1, except that the mass ratio of the compounds represented by each formula in the light-emitting layer composition was changed to (H-1): (H-2): and (D-6): 60:40: 15.

Comparative example 7

An organic electroluminescent element was produced in the same manner as in example 1 except that the mass ratio of the compounds represented by each formula in the light-emitting layer composition was changed to (H-1), (H-2), (D-5), (D-7), and (D-7) was changed to 60:40:15: 15.

[ evaluation of Components ]

The organic electroluminescent elements obtained in examples 4, 5, 6 and 7 were measured to have luminances of 1000cd/m²The difference between the external quantum efficiency EQE during light emission and the EQE of comparative example 6 is denoted as Δ EQE. In addition, at 60mA/cm²The current density of (2) was calculated as the relative lifetime when the organic electroluminescent element was driven and the time LT80 at which the relative emission luminance reached 80% was measured and taken as LT80 of comparative example 6 as 100. Set forth in table 4 below.

From the results in Table 4, it is understood that an organic electroluminescent element using the compound represented by the formula (D-6) of the present embodiment as a light-emitting dopant in combination with a compound as an auxiliary dopant in a light-emitting layer is an element having high efficiency and long driving life. Among them, an organic electroluminescent element using the compound represented by the formula (D-7) as the compound serving as the auxiliary dopant is an element having higher luminous efficiency and longer driving life.

[ Table 4]

TABLE 4

	Luminescent dopants	Auxiliary dopant	ΔEQE	Relative life time
					Example 4	D-6	D-2	+1.7	222
Example 5	D-6	D-7	+2.4	227
					Comparative example 6	D-6	Is free of	-	100
Comparative example 7	D-5	D-7	-0.7	166

While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be added without departing from the spirit and scope thereof. The present application is based on the japanese patent application published on 20/5/2019 (japanese patent application 2019-094708), the content of which is incorporated herein by reference.

Description of the symbols

1 substrate

2 anode

3 hole injection layer

4 hole transport layer

5 light-emitting layer

6 hole blocking layer

7 electron transport layer

8 electron injection layer

9 cathode

10 organic electroluminescent element

Claims

1. A composition for an organic electroluminescent element, comprising a compound represented by the following formula (1), a compound represented by the following formula (2) having a maximum light-emitting wavelength shorter than that of the compound represented by the formula (1), and a solvent,

in the formula (1), R¹、R²Each independently an alkyl group having 1 to 20 carbon atoms, an aralkyl group or heteroaralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy group or heteroaryloxy group having 3 to 20 carbon atoms, or a carbon atomAn alkylsilyl group of 1 to 20 carbon atoms, an arylsilyl group of 6 to 20 carbon atoms, an alkylcarbonyl group of 2 to 20 carbon atoms, an arylcarbonyl group of 7 to 20 carbon atoms, an alkylamino group of 1 to 20 carbon atoms, an arylamino group of 6 to 20 carbon atoms or an aryl or heteroaryl group of 3 to 30 carbon atoms, which may further have a substituent, R¹、R²When plural, they may be the same or different, R¹When plural, adjacent R¹May be bonded to each other to form a ring,

a is an integer of 0 to 4, b is an integer of 0 to 3,

R³、R⁴each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbon atoms, an aralkyl or heteroaralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy or heteroaryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms or an aryl or heteroaryl group having 3 to 20 carbon atoms, which may further have a substituent, R³、R⁴When plural, they may be respectively the same or different,

L¹represents an organic ligand, m is an integer of 1 to 3,

in the formula (2), R⁵The alkyl group having 1 to 20 carbon atoms, the aralkyl or heteroaralkyl group having 7 to 40 carbon atoms, the alkoxy group having 1 to 20 carbon atoms, the aryloxy or heteroaryloxy group having 3 to 20 carbon atoms, the alkylsilyl group having 1 to 20 carbon atoms, the arylsilyl group having 6 to 20 carbon atoms, the alkylcarbonyl group having 2 to 20 carbon atoms, the arylcarbonyl group having 7 to 20 carbon atoms, the alkylamino group having 1 to 20 carbon atoms, the arylamino group having 6 to 20 carbon atoms, or the aryl or heteroaryl group having 3 to 30 carbon atoms, and these groups may beTo further have a substituent, R⁵When plural, they may be the same or different,

c is an integer of 0 to 4,

the ring A is pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring,

Any one of the azole rings may be used,

the ring A may have a substituent(s) such as a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbon atoms, an aralkyl or heteroaralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy or heteroaryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, or an aryl or heteroaryl group having 3 to 20 carbon atoms, and adjacent substituents bonded to the ring A may be bonded to each other to further form a ring, and when a plurality of rings A are present, they may be the same or different,

L²represents an organic ligand, and n is an integer of 1 to 3.

2. The composition for an organic electroluminescent element according to claim 1, wherein the composition ratio of the compound represented by the formula (1) is not less than the composition ratio of the compound represented by the formula (2) in terms of parts by mass.

3. The composition for organic electroluminescent element according to claim 1 or 2, wherein the compound represented by the formula (1) is a compound represented by the following formula (1-1),

in the formula (1-1), R¹、R²、a、b、L¹M and R in the formula (1)¹、R²、a、b、L¹And m are the same as each other in meaning,

R⁶、R⁷each independently an alkyl group having 1 to 20 carbon atoms, an aralkyl or heteroaralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy or heteroaryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, or an aryl or heteroaryl group having 3 to 30 carbon atoms, which may further have a substituent, R⁶、R⁷When plural, they may be respectively the same or different,

d. e is an integer of 0 to 5.

4. The composition for organic electroluminescent element according to claim 1 or 2, wherein the compound represented by the formula (1) is a compound represented by the following formula (1-2),

in the formula (1-2), R²～R⁴、b、L¹M and R in the formula (1)²～R⁴、b、L¹And m are the same as each other in meaning,

R¹⁴～R¹⁶is a substituent, R¹⁴～R¹⁶When plural, they may be respectively the same or different,

i is an integer of 0 to 4.

5. The composition for organic electroluminescent element according to claim 3, wherein the compound represented by the formula (1-1) is a compound represented by the following formula (1-3),

in the formula (1-3), R²、R⁶、R⁷、b、d、e、L¹M and R in the formula (1-1)²、R⁶、R⁷、b、d、e、L¹And m are the same as each other in meaning,

i is an integer of 0 to 4.

6. The composition for organic electroluminescent element according to any one of claims 1 to 5, wherein the compound represented by the formula (2) is a compound represented by the following formula (2-1),

in the above formula (2-1), ring A, L²N and ring A, L in said formula (2)²And n are the same as each other in meaning,

R⁸an alkyl group having 1 to 20 carbon atoms, an aralkyl group or a heteroaralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy group or a heteroaryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, or an aryl group or a heteroaryl group having 3 to 30 carbon atoms, which may further have a substituent, R⁸When plural, they may be the same or different,

f is an integer of 0 to 5.

7. The composition for organic electroluminescent element according to any one of claims 1 to 6, wherein m in the formula (1) is less than 3, L¹Has at least one structure selected from the following formulae (3), (4) and (5),

in the above formulae (3) to (5), R⁹、R¹⁰And R in the formula (1)¹Have the same meaning as R⁹、R¹⁰When plural, they may be respectively the same or different,

R¹¹～R¹³each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may be substituted with a fluorine atom, a phenyl group which may be substituted with an alkyl group having 1 to 20 carbon atoms, or a halogen atom,

g is an integer of 0 to 4, h is an integer of 0 to 4,

The azole ring, ring B may further have a substituent.

8. The composition for organic electroluminescent element according to any one of claims 1 to 7, wherein a in the formula (1) is 1, or a in the formula (1) is an integer of 2 or more and does not have adjacent R¹Rings bonded to each other.

9. A method of manufacturing an organic electroluminescent element, comprising: a step of forming a light-emitting layer by a wet film-forming method using the organic electroluminescent element composition according to any one of claims 1 to 8.

10. An organic electroluminescent element having a light-emitting layer formed using the organic electroluminescent element composition according to any one of claims 1 to 8.

11. A display device having the organic electroluminescent element according to claim 10.