JP2016103568A - Organic electroluminescent element material, organic electroluminescent element, display device and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element capable of increasing luminous efficacy and durability, a display device and a lighting device.SOLUTION: An embodiment contains a compound having a structure represented by the general formula (1) in the figure, where Rto Rare each independently a hydrogen atom or substituent, in which, if neighboring two of Rto Rare substituents, the substituents are different from each other.SELECTED DRAWING: None

Description

  The present invention relates to an organic electroluminescent element material capable of enhancing the luminous efficiency and durability of an organic electroluminescent element, and an organic electroluminescent element, a display device, and an illumination device using the organic electroluminescent element material.

An organic electroluminescence element is a solid element provided with a light emitting layer containing a light emitting organic compound between a pair of electrodes. When a voltage is applied to the pair of electrodes to inject holes and electrons into the light-emitting layer, excitons (excitons) are generated by recombination of the holes and electrons. When the exciton is deactivated, light is emitted from the light emitting layer.
An organic layer other than the light emitting layer may be formed between the electrodes, but each layer is a thin film of submicron order. In addition, since the light emitting layer can emit light at a voltage of about several volts to several tens of volts, the organic electroluminescence element is expected to be used for the next generation thin display, surface emitting illumination and the like.

  As for the development of organic electroluminescence devices for practical application, Princeton University has been actively developing materials that exhibit phosphorescence at room temperature since the report of organic electroluminescence devices using phosphorescence emission from excited triplets was reported. It is becoming. In addition, organic electroluminescence elements that utilize phosphorescence emission can in principle achieve a luminous efficiency that is approximately four times that of organic electroluminescence elements that utilize fluorescence emission. At the beginning, research and development of layer structure, electrodes, etc. are conducted all over the world.

Particularly problematic in the research and development process is the low durability due to the fact that the luminescent material itself is an organic compound, and many luminescent materials have been developed to improve the durability.
One means of improving durability is the use of condensed rings, and the development of materials having a wide π-conjugated structure is being promoted by combining three imidazole rings to form one condensed ring ( For example, see Patent Documents 1 and 2.)

However, a material having a wide π-conjugated structure tends to have high molecular planarity due to introduction of a substituent such as an aromatic ring.
When the planarity of the molecules is high, stacking of molecules occurs, and the molecules are easily aggregated and crystallized, resulting in insufficient interfacial bonding with the adjacent layer and lowering the light emission efficiency. Due to the aggregation and crystallization, the compatibility with other materials is also lowered, so that the durability when used in the organic electroluminescence device is low.
In addition, since the material having high molecular planarity has a low triplet energy level, it is difficult to apply it to a blue light emitting device.

JP 2007-63220 A International Publication No. 2005/037954

  The present invention has been made in view of the above problems and circumstances, and the problem to be solved is an organic electroluminescent element material capable of enhancing the luminous efficiency and durability of the organic electroluminescent element, and an organic material using the organic electroluminescent element material. An electroluminescence element, a display device, and a lighting device are provided.

In order to solve the above problems, the present inventor, in the process of studying the cause of the above problems, the improvement in the planarity of the molecules due to the wide π-conjugated structure of the compound, the luminous efficiency and durability of the organic electroluminescence device. I guessed it was a factor to decrease. That is, when a material having high molecular flatness is used for an organic electroluminescence device, the interaction between the same compound molecules in the film or the other compound molecules becomes stronger, and aggregation and crystallization occur. It is possible. Due to crystallization, interfacial bonding with the adjacent layer becomes insufficient, the luminous efficiency is lowered, and the film state becomes unstable, so that the durability is lowered. In addition, a high triplet energy level due to a wide π-conjugated structure is also lowered.
As a result of intensive studies, the present inventors have introduced the above-mentioned aggregation and the above-described aggregation by appropriately adjusting the interaction between molecules by introducing an appropriate substituent even when a material having a wide π-conjugated structure is used. The inventors have found that the luminescence efficiency and durability of the organic electroluminescence element can be improved by suppressing crystallization, and the present invention has been achieved.

〔一般式（１）において、Ｒ_１〜Ｒ_６は、それぞれ独立に、水素原子又は置換基である。Ｒ_１〜Ｒ_６のうちの隣接する二つが置換基である場合、各置換基は互いに異なる置換基である。ただし、Ｒ_１とＲ_２、Ｒ_３とＲ_４、Ｒ_５とＲ_６の全ての組み合わせにおいて、いずれか一方の置換基が直鎖アルキル基である場合、他方の置換基は、それぞれ独立に、置換基を有する単環の芳香環、縮合芳香環、ジアリールアミノ基、シリル基又はホスフィノ基である。〕 That is, the subject concerning this invention is solved by the following means.
1. An organic electroluminescent element material comprising a compound having a structure represented by the following general formula (1).

[In General formula (1), R < ₁ > -R < ₆ > is a hydrogen atom or a substituent each independently. When two adjacent ones of R _{1 to} R ₆ are substituents, each substituent is a different substituent. However, in any combination of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , when one of the substituents is a linear alkyl group, the other substituent is independently A monocyclic aromatic ring having a substituent, a condensed aromatic ring, a diarylamino group, a silyl group, or a phosphino group. ]

2. In the general formula (1), of the R ₁ to R _6, the organic electroluminescent device material as described in paragraph 1, wherein at least two are hydrogen atoms.

  3. In the general formula (1), when the imidazole ring is located at the center of the condensed ring formed by bonding and is rotated every 120 ° about the axis perpendicular to the surface of the condensed ring. The structure represented by the general formula (1) is different from each other in the materials for organic electroluminescence elements according to item 1 or 2.

4). An organic electroluminescence device comprising: a light emitting unit composed of a plurality of organic layers including at least a light emitting layer; and a pair of electrodes sandwiching the light emitting unit,
At least 1 layer of these organic layers contains the organic electroluminescent element material as described in any one of Claim 1- Claim 3. The organic electroluminescent element characterized by the above-mentioned.

  5. 5. The organic electroluminescent element according to item 4, wherein the light emitting layer contains the material for an organic electroluminescent element.

  6). 6. The organic electroluminescence device according to item 5, wherein the light emitting layer contains a blue phosphorescent compound.

  7). A display device comprising the organic electroluminescence element according to any one of items 4 to 6.

  8). An illuminating device comprising the organic electroluminescence element according to any one of items 4 to 6.

  An organic electroluminescent element material capable of enhancing the luminous efficiency and durability of an organic electroluminescent element by the above-described means of the present invention, an organic electroluminescent element using the organic electroluminescent element material, a display device, and an illumination apparatus. Can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
The organic electroluminescent element material of the present invention is an independent substituent in which R _{1 to} R ₆ bonded to the condensed ring of three imidazole rings are hydrogen atoms or are not bonded to each other to form a ring. When R _{1 to} R _{6 to} be substituted are substituents, different substituents are introduced. Such R _{1 to} R ₆ suppress the strength of interaction between molecules, cause steric hindrance between adjacent R _{1 to} R ₆ , and tilt with respect to the plane of the condensed ring, so that the molecular plane The spread of sex can be suppressed. As a result, the expansion of the π-conjugated system was suppressed, and the interaction between molecules was reduced. Therefore, it is presumed that intermolecular aggregation and crystallization could be suppressed.
By suppressing the spread of the planarity of the molecule, it is possible to prevent a high triplet energy level from being lowered due to the condensed ring and to maintain a high light emitting property. Further, since the interfacial bonding with the adjacent layer is improved by suppressing aggregation and crystallization, it is presumed that the carrier transportability and thus the light emission properties are improved, and high light emission efficiency is obtained. Further, it is presumed that the stability of the compound in the film is improved by suppressing aggregation and crystallization, and not only high luminous efficiency but also high durability can be achieved.

Side view of a three-dimensional molecular model of a compound having a structure represented by the formula (A) Top view of a three-dimensional molecular model of a compound having a structure represented by the formula (A) Side view of three-dimensional molecular model of exemplary compound 1 Top view of the three-dimensional molecular model of Example Compound 1 The perspective view which shows schematic structure of the display apparatus of one embodiment of this invention Sectional drawing which shows the manufacturing process of the organic EL element in a display apparatus Sectional drawing which shows the manufacturing process of the organic EL element in a display apparatus Sectional drawing which shows the manufacturing process of the organic EL element in a display apparatus Sectional drawing which shows the manufacturing process of the organic EL element in a display apparatus Sectional drawing which shows the manufacturing process of the organic EL element in a display apparatus Sectional drawing which shows schematic structure of the illuminating device of one embodiment of this invention.

The material for an organic electroluminescence device of the present invention contains a compound having a structure represented by the general formula (1). This feature is a technical feature common to the inventions according to claims 1 to 8.
As an embodiment of the present invention, from the viewpoint of enhancing the light emission efficiency and durability of the organic electroluminescence element, in the general formula (1), at least two of R _{1 to} R ₆ may be hydrogen atoms. preferable.
From the same viewpoint, in the above general formula (1), it is located at the center of a condensed ring formed by bonding three imidazole rings, and every 120 ° centered on an axis perpendicular to the surface of the condensed ring. It is preferable that the structures represented by the general formula (1) are different from each other.

  As for the organic electroluminescent element of this invention, at least 1 layer of the some organic layer with which a light emission unit is provided contains the said organic electroluminescent element material. Thereby, the effect which improves the luminous efficiency and durability of an organic electroluminescent element is acquired.

  The organic electroluminescence element of the present invention can be suitably included in a display device and a lighting device. Thereby, a display device and a lighting device with high luminous efficiency and durability can be provided.

Hereinafter, the present invention, its components, and modes for carrying out the present invention will be described in detail.
In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

〔一般式（１）において、Ｒ_１〜Ｒ_６は、それぞれ独立に、水素原子又は置換基である。Ｒ_１〜Ｒ_６のうちの隣接する二つが置換基である場合、各置換基は互いに異なる置換基である。ただし、Ｒ_１とＲ_２、Ｒ_３とＲ_４、Ｒ_５とＲ_６の全ての組み合わせにおいて、いずれか一方の置換基が直鎖アルキル基である場合、他方の置換基は、それぞれ独立に、置換基を有する単環の芳香環、縮合芳香環、ジアリールアミノ基、シリル基又はホスフィノ基である。〕 [Materials for organic electroluminescence elements]
The organic electroluminescent (EL) element material of the present invention contains a compound having a structure represented by the following general formula (1).

[In General formula (1), R < ₁ > -R < ₆ > is a hydrogen atom or a substituent each independently. When two adjacent ones of R _{1 to} R ₆ are substituents, each substituent is a different substituent. However, in any combination of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , when one of the substituents is a linear alkyl group, the other substituent is independently A monocyclic aromatic ring having a substituent, a condensed aromatic ring, a diarylamino group, a silyl group, or a phosphino group. ]

  The structure represented by the general formula (1) has a high-order π-conjugated structure formed by cyclization condensation of three imidazoles as a parent nucleus. A high-order π-conjugated structure refers to a conjugated structure in which π-conjugate is highly spread in the molecule. In general, it is known that the triplet energy level decreases as the π-conjugated system expands such as benzene, naphthalene, and anthracene. However, the higher-order π-conjugated structure having the parent nucleus of the compound of the present invention specifically exhibits almost the same triplet energy level as monocyclic imidazole. This is presumed to be because the central triazine ring in the condensed ring of higher-order π-conjugated structure, ie, three imidazoles, does not contribute to the expansion of the π-conjugated system while exhibiting aromatic characteristics.

In the general formula (1), each is independently a hydrogen atom or a substituent, and when adjacent R _{1 to} R ₆ are substituents, different substituents are introduced as R _{1 to} R _6. The interaction with substituents of other molecules can be moderately suppressed. Since adjacent R _{1 to} R ₆ are not bonded to each other to form a new ring, the expansion of the π-conjugated system by the aromatic ring is suppressed, the hydrophobicity is increased by the non-aromatic ring, and the compound molecules are aggregated. And the occurrence of orientation can be prevented. In this way, by adjusting the interaction between molecules moderately and suppressing the expansion of the π-conjugated system, it is the same or the cause of the decrease in luminous efficiency and durability when a compound is used in the organic EL element. Stacking with other kinds of molecules, aggregation of multiple molecules, crystallization, etc. can be suppressed.

Examples of the substituent for R _{1 to} R ₆ include an alkyl group, a cycloalkyl group, an arylalkyl group, an alkenyl group, an alkynyl group, an aryl group (an aromatic hydrocarbon group, an aromatic hydrocarbon ring group, an aromatic carbocyclic group, etc. ), Heteroaryl group (also referred to as aromatic heterocyclic group), heterocyclic group, carbonyl group such as alkoxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, acyl group, amide group, alkylsulfonyl group, arylsulfonyl group A heteroarylsulfonyl group, an amino group, a fluorinated hydrocarbon group, a silyl group, a phosphine oxide group, a fluorine atom and the like, and these may further have a substituent. Further, examples of the substituent which may be included include the same substituents as the substituents of R _{1 to} R ₆ .

Among the substituents listed as R _{1 to} R ₆ , an alkyl group, a fluorinated hydrocarbon group, a carbonyl group, an amino group, a silyl group, a phosphine oxide group, an arylalkyl group from the viewpoint of easy interaction adjustment. An aryl group or a heteroaryl group is preferable, an alkyl group, a silyl group, an aryl group or a heteroaryl group is more preferable, and an aryl group or a heteroaryl group is further preferable.
Moreover, it is preferable that at least one of R _{1 to} R ₆ has an aromatic heterocyclic ring having 14 or more π electrons. Examples of the substituent having an aromatic heterocyclic ring having 14 or more π electrons include a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, and the like, and among them, a carbazolyl group or a dibenzofuranyl group is preferable.

The alkyl group is preferably an alkyl group having 3 or more carbon atoms, and may be linear, branched or cyclic, but is preferably a branched alkyl group.
Specific examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, 2-ethylexyl group, cyclopentyl group, cyclohexyl group, n -Dodecyl group etc. are mentioned, Especially, an ethyl group, n-propyl group, isopropyl group or 2-methylbutyl group is preferable, isopropyl group or s-butyl group is more preferable, and isopropyl group is more preferable.
Among the above alkyl groups, a branched alkyl group is preferable for the purpose of controlling intermolecular interaction due to the bulkiness of the three-dimensional structure. Specifically, an isopropyl group, a 2-methylpropyl group, A t-butyl group or 2-ethylhexyl group is preferred. Further, from the viewpoint of adjusting the interaction between molecules due to the interaction between alkyl groups, an alkyl group having 5 or more carbon atoms is preferable. Specifically, a 2-ethylhexyl group, a cyclopentyl group, a cyclohexyl group, or n -A dodecyl group is preferred.

  The fluorinated hydrocarbon group is a substituent in which at least one hydrogen atom of the alkyl group is substituted with a fluorine atom. The fluorinated hydrocarbon group is preferably a trifluoromethyl group or a tetrafluoroethyl group, and more preferably a trifluoromethyl group. Since a fluorine atom has a sterically large van der Waals radius as compared with a hydrogen atom, the steric hindrance is large, which is preferable. In addition, since the electronegativity is large, the interaction with other substituents or other molecules bonded to the same imidazole ring can be adjusted to an appropriate range by introducing a fluorinated hydrocarbon group.

  Examples of the aryl group include a monocyclic aryl group, specifically, a phenyl group, a biphenylene group, a terphenylene group, and the like, and these may further have a substituent at an arbitrary position. As the substituent when the aryl group further has a substituent, an alkyl group, a heteroaryl group, or the like can be preferably used.

  Examples of the heteroaryl group include a pyridine group, a pyrimidine group, a triazine group, a carbazolyl group, a carbolinyl group, and a diazacarbazolyl group (one in which one of the carbon atoms constituting the carboline ring of the carbolinyl group is substituted with a nitrogen atom) , Imidazolyl group, pyrazolyl group, triazolyl group, benzoimidazolyl group, indolyl group, benzopyrazolyl group, furanyl group, thienyl group, benzofuranyl group, benzothienyl group, dibenzofuranyl group, dibenzothiophenyl group, azadibenzofuranyl group, aza A dibenzothiophenyl group etc. are mentioned, These may have a substituent. Among these, a monocyclic or tri-condensed heteroaryl group is preferable, and pyridyl group, pyrimidyl group, triazine group, carbazolyl group, azacarbazolyl group, diazacarbazolyl group, dibenzofuranyl group, dibenzothiophenyl group, azadibenzo group A furanyl group or an azadibenzothiophenyl group is more preferable, a triazine group, a carbazolyl group, a dibenzofuranyl group or a dibenzothiophenyl group is more preferable, and a triazine group or a 9-carbazolyl group is more preferable.

Examples of the amino group include a diarylamino group, which may further have a substituent, and the substituents may be bonded to each other to form a ring. Preferable examples of such an amino group include a substituent represented by the following general formula (A-1).

In the general formula (A-1), X _{1 to} X ₈ are CR _A or a nitrogen atom, and R _A is a hydrogen atom or the same substituent as R _{1 to} R ₆ in the general formula (1). Y _A is CR _B R _B , O, S, NR _B , SiR _B R _B or P (═O) R _B , and R _B is an alkyl group, an aryl group, or a heteroaryl group.

In the above general formula (1), the combination of R ₁ and R ₂ , R ₃ and R ₄ and R ₅ and R ₆ is not limited, but the branched positions are a branched alkyl group and an aryl group, a branched alkyl group and a heteroaryl. Group, a hydrogen atom and an aryl group, a hydrogen atom and a heteroaryl group, a hydrogen atom and an amino group, a hydrogen atom and a silyl group, or a combination of a hydrogen atom and a hydrogen atom, and a substituent other than a hydrogen atom further has a substituent It may be. Among them, out of the combinations of _{R 1} and _R 2, _{R 3} and _{R 4} and _{R 5} and _{R 6,} it is preferable that at least one of combinations is a hydrogen atom and a hydrogen atom.

As an aryl group that can be used in a preferable combination of R ₁ and R ₂ , R ₃ and R ₄ and R ₅ and R ₆ , a xylyl group, an isopropylphenyl group, an m-biphenylene group, or an m-terphenylene group is preferable. An m-biphenylene group or an m-terphenylene group is more preferable. In addition, preferred heteroaryl groups include 9-carbazolyl group, 3-carbazolyl group, dibenzofuranyl group, dibenzothiophenyl group, pyridyl group having a substituent, and triazine optionally having a substituent. And a pyrimidine group which may have a substituent, and the like. From the viewpoint of improving the light-emitting property, a 9-carbazolyl group, a triazine group having a substituent, or a pyrimidyl group having a substituent is preferable.

Furthermore, in the substitution position of the above combination, R ₁ , R ₃ and R ₅ are any of 9-carbazolyl group, dibenzofuranyl group, dibenzothiophenyl group, m-biphenylene group and m-terphenylene group. R ₂ , R ₄ and R ₆ are preferably m-biphenylene group, m-terphenylene group, 3-carbazolyl group or a triazine group having a substituent.

However, in any combination of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , when one of the substituents is a linear alkyl group, the other substituent is independently A monocyclic aromatic ring having a substituent, a condensed aromatic ring, a diarylamino group, a silyl group, or a phosphino group.
When one of the two substituents bonded to the same imidazole ring is a linear alkyl group, the steric hindrance to the other substituent is small, so the planarity of the molecule is increased and the luminous efficiency and durability are reduced. It becomes a factor to do. However, if the other substituent is a sterically bulky substituent as described above, the three-dimensional structure in which each of the substituents R _{1 to} R ₆ is inclined with respect to the plane of the condensed ring that is the parent nucleus of the compound Therefore, the spread of the planarity of the compound molecule can be suppressed.

1A and 1B are diagrams showing a three-dimensional molecular model of a compound having a structure represented by the following formula (A), from the side and the top, respectively.

In the structure represented by the above formula (A), in the general formula (1), R ₂ , R ₄ and R ₆ are all methyl groups, and R ₁ , R ₃ and R ₅ are all substituents. It is a structure which is a phenyl group which does not have. In this case, as shown in FIGS. 1A and 1B, the angle formed by each surface of the phenyl group and the higher-order π-conjugated structure (condensed ring of three imidazoles) becomes small, and the planarity of the whole molecule becomes high. When the planarity is high, the π-conjugated system expands to the phenyl group, and the high triplet energy level inherent in the higher-order π-conjugated structure is lowered.

  In addition, since high planarity enhances the interaction between molecules, a bimolecular stack and multimolecular aggregation tend to occur. Compared to a monomolecular body, a bimolecular stack body and a multimolecular aggregate body not only have a low triplet energy level, but may also reduce carrier transportability. When the compound is used in an organic EL device, crystallization occurs in the film as stacking and aggregation progress. Due to crystallization, interfacial bonding with an adjacent layer becomes insufficient, carrier transportability and compatibility with other types of molecules are lowered, and this is a factor that lowers the luminous efficiency and durability of the organic EL element.

2A and 2B are views showing a three-dimensional molecular model of Exemplary Compound 1 having a structure represented by the following formula, from the side and top, respectively.

Exemplified Compound 1 has the above general formula (1), wherein R ₂ , R ₄ and R ₆ are all methyl groups, and R ₁ , R ₃ and R ₅ are all phenyl groups having substituents (2, 6-xylyl group). As shown in FIGS. 2A and 2B, in the exemplified compound 1, the surface of the xylyl group is greatly twisted with respect to the surface of the higher-order π-conjugated structure. Thus, even if the steric hindrance action of one substituent is small, when the other substituent is sterically bulky, there is no spread of the planarity of the molecule. Molecular aggregation is unlikely to occur. Also, even if the substituent is an aromatic ring, if the angle formed between the higher-order π-conjugated structure and each surface of the substituent is kept large, the expansion of the π-conjugated system does not occur, and higher-order π-conjugated The high triplet energy level inherent in the structure can be maintained.

As described above, a compound having a higher-order π-conjugated structure of three condensed rings of imidazole has a great influence on the physical properties of the compound in the film. When this compound is used as a material for an organic EL device, high luminous efficiency and durability can be obtained by selecting R _{1 to} R ₆ described above as substituents capable of appropriately adjusting the interaction between molecules. It can be given to the EL element.

In the general formula (1), at least two of R _{1 to} R ₆ are hydrogen atoms, which increases the degree of freedom of the other substituents R _{1 to} R ₆ and increases the planarity of the molecule. It is preferable from a viewpoint of suppressing, It is more preferable that three are hydrogen atoms, and it is still more preferable that four are hydrogen atoms. Due to the increased degree of freedom, amorphousness in the film can be improved, crystallization can be suppressed, molecular vibration during vibration and vibration can be relaxed, and durability can be improved. From the viewpoint of ease of synthesis, it is preferable that three of R _{1 to} R ₆ are hydrogen atoms. From the viewpoint of improving durability, R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and In each combination of R ₆ , any one is preferably a hydrogen atom.

In the general formula (1), when R _{1 to} R ₆ are different from each other, the interaction between substituents between molecules is weakened, and aggregation and thus crystallization are suppressed, so that the compound can be used for an organic EL device. It is preferable because it can suppress a decrease in luminous efficiency and durability.

In the above general formula (1), the above general formula (1) is located at the center of three condensed rings of imidazole and rotated every 120 ° about an axis perpendicular to the plane of the condensed ring. It is preferable that the structures represented by are different from each other. Such compounds are said to have no C3 axis of rotation. The C3 rotation axis refers to a rotation axis when the respective structures when rotated every 120 ° are the same structure. A compound having no C3 rotation axis has low molecular symmetry, and the entropy when many molecules are assembled is larger than that of a compound having a C3 rotation axis. The greater the entropy, the more stable the compound molecules in the film and the greater the degree of freedom. Therefore, aggregation, orientation, crystallization, etc. of the compound molecules can be suppressed, and when the compound is used in an organic EL device. The luminous efficiency and durability can be improved.
In the general formula (1), the C3 rotational axis is such that R ₁ , R ₃ and R ₅ are all hydrogen atoms or the same substituent, and R ₂ , R ₄ and R ₆ are all hydrogen atoms. Or the same substituent.

  Although the compound represented by the said General formula (1) below is illustrated, this invention is not limited to these illustration compounds 1-43.

  The compounds of the present invention are disclosed in J. Am. Chem. Soc., 1994, 116, 391-392, J. Org. Chem., Vol. 44, No24, 1979, p4243, Japanese Patent No. 4259236, International Publication No. 2005/037954. It can be synthesized with reference to the number.

  Hereinafter, although the synthesis method of the exemplary compounds 4 and 19 is demonstrated as a synthesis example of the compound represented by the said General formula (1), this invention is not limited to this.

<Synthesis Example of Exemplary Compound 4>

  Step (S21): 5.0 g of intermediate a2 (2-bromo-5-isopropyl-4-phenylimidazole) is added to 500 mL of 0.1 M sodium hydroxide solution, and then 3.5 g of iodine monochloride is added. The mixture was stirred at room temperature for 4 hours and further at 50 ° C. for 1 hour. The precipitated solid was washed sequentially with water and hexane to obtain 3.0 g of intermediate b2. Intermediate b2 was directly used in the next step (S22).

  Step (S22): 1.5 g of intermediate b2 was put in a container and sealed in a nitrogen atmosphere. The container was irradiated with microwaves for 2 hours using a microwave reaction apparatus (200 W) and allowed to react. After cooling, the obtained solid was purified by GPC (Gel Permeation Chromatography) to obtain 90 mg of the target exemplified compound 4. The structure of Example Compound 4 was identified by NMR and mass spectrum.

<Synthesis Example of Exemplified Compound 19>

  Step (S11): 2.0 g of intermediate a1 obtained according to the description of J. Org. Chem., Vol.44, No24, 1979, p4243 was dissolved in 50 mL of chlorobenzene and cooled to −20 ° C. To this solution, 5.5 g of bromine was dropped while maintaining the temperature at 0 ° C. or lower. After stirring at 50 ° C. for 4 hours, purification yielded 1.2 g of intermediate b1. The structure of intermediate b1 was confirmed by NMR.

  Step (S12): 1.0 g of intermediate b1 was placed in a flask under a nitrogen stream, and 50 mL of dehydrated DMF (DiMethylFuran) was further added and dissolved. To this solution was added 2.0 g of 9H-carbazole, followed by 100 mg of copper (I) oxide and 100 mg of dipivaloylmethane. The obtained mixed solution was heated to reflux at 200 ° C. for 8 hours. After allowing to cool, dichloromethane was added, washed with water until neutrality, and purified by column chromatography to obtain 240 mg of the intended Exemplified Compound 19. The structure of Exemplified Compound 19 was identified by NMR and mass spectrum.

  When used as a material for an organic EL device, it is preferable to further perform sublimation purification twice on the compound obtained by synthesis.

[Organic electroluminescence device]
The organic EL element of the present invention includes a light emitting unit composed of a plurality of organic layers including at least a light emitting layer, and a pair of electrodes sandwiching the light emitting unit, and at least one of the plurality of organic layers is the above-described book. Contains the material for an organic electroluminescence element of the invention.
By using the organic EL device material of the present invention, which has high carrier transportability and moderate interaction between molecules in the film, in the organic layer, the light emission efficiency and durability of the organic EL device can be enhanced.

  As an organic layer other than the light emitting layer constituting the light emitting unit, an electron transport layer, a hole blocking layer, an electron injection layer, etc. can be provided between the light emitting layer and the cathode, or between the light emitting layer and the anode. A hole transport layer, an electron blocking layer, a hole injection layer, and the like can also be provided. From the role of transporting electrons, the hole blocking layer and the electron injection layer are also one type of the electron transport layer. From the role of transporting holes, the electron blocking layer and the hole injection layer are both of the hole transport layer. It can be said that it is one kind. Organic layers other than the light emitting layer can be provided as necessary.

As a typical configuration of the organic EL element of the present invention, the following configuration examples (2) to (7) may be mentioned in addition to the basic configuration shown in the following configuration example (1). Especially, although the structural example (7) is preferable, the structure of the organic EL element of this invention is not limited to these.
(1) Anode / light emitting layer / cathode (2) Anode / light emitting layer / electron transport layer / cathode (3) Anode / hole transport layer / light emitting layer / cathode (4) Anode / hole transport layer / light emitting layer / electron Transport layer / cathode (5) Anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (6) Anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode ( 7) Anode / hole injection layer / hole transport layer / electron blocking layer / light emitting layer / hole blocking method / electron transport layer / electron injection layer / cathode

[Light emitting layer]
The light emitting layer is a layer that emits light by recombination of electrons and holes transported from each of the pair of electrodes. Light emission may occur either in the light emitting layer or at the interface between the light emitting layer and the adjacent layer.
The organic EL device of the present invention can include one or more light emitting layers.

The total thickness of the light emitting layer is not particularly limited, but it is 2 nm to 5 μm from the viewpoint of improving the uniformity of the film, preventing the application of an excessively high voltage during light emission, and improving the stability of the emission color with respect to the driving current. It is preferably within the range, more preferably within the range of 2 to 500 nm, and even more preferably within the range of 5 to 200 nm.
When there are a plurality of light emitting layers, the thickness of each light emitting layer is preferably in the range of 2 nm to 1 μm, more preferably in the range of 2 to 200 nm, and in the range of 3 to 150 nm. Further preferred.

  The light-emitting layer preferably contains a light-emitting dopant (also referred to as a light-emitting dopant compound, a dopant compound, or a dopant) and a host compound (also referred to as a light-emitting host, a host, or a matrix material).

[Luminescent dopant]
As the light emitting dopant, a fluorescent light emitting dopant or a phosphorescent light emitting dopant can be preferably used, and at least one light emitting layer preferably contains a phosphorescent light emitting dopant.

The light emitting dopant can be used in combination of a plurality of types such as combining dopants having different structures, combining a fluorescent light emitting dopant and a phosphorescent light emitting dopant. Thereby, arbitrary luminescent colors can be obtained.
The emission color of the organic EL device of the present invention is spectral emission as described in FIG. 4.16 on page 108 of “New Color Material Chemistry Handbook” (edited by the Japan Color Material Society, University of Tokyo Press, 1985). It is determined by applying the result measured with a luminance meter CS-2000 (manufactured by Konica Minolta) to the CIE chromaticity coordinates.

In the present invention, it is also preferable that one or a plurality of light-emitting layers contain a plurality of light-emitting dopants having different emission colors and emit white light. Although it does not specifically limit about the combination of the light emission dopant which shows white, For example, the combination of blue and orange, blue, green, and red etc. are mentioned.
The white color of the luminescent color is chromaticity in the CIE1931 color system at 1000 cd / m ² when x2 viewing angle front luminance is measured with the above spectral radiance meter, x = 0.39 ± 0.09, y = 0.38 ± 0.08 is preferable.

  The concentration of the light emitting dopant in the light emitting layer can be arbitrarily determined. The light emitting layer can contain a light emitting dopant having a uniform concentration in the layer thickness direction of the light emitting layer, or can contain a light emitting dopant in an arbitrary concentration distribution in the layer thickness direction of the light emitting layer.

[Phosphorescent dopant]
A phosphorescent dopant is a compound in which light emission from an excited triplet is observed. Specifically, it is a phosphorescent compound that emits phosphorescence at room temperature (25 ° C.), and is defined as a compound having a phosphorescence quantum yield of 0.01 or more at 25 ° C. The photon yield is 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence emission dopant according to the present invention achieves the above phosphorescence quantum yield (0.01 or more) in any solvent. Just do it.

  The emission principle of the phosphorescent dopant includes two types of energy transfer type and carrier trap type. In the case of the energy transfer type, carrier recombination occurs on the host compound to which the carrier is transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent dopant to emit light from the phosphorescent dopant. Get. In the case of the carrier trap type, the phosphorescent light emitting dopant becomes a carrier trap, and carrier recombination occurs on the phosphorescent light emitting dopant, and light emission from the phosphorescent light emitting dopant is obtained. In either case, it is a condition that the excited state energy of the phosphorescent dopant is lower than the excited state energy of the host compound.

〔一般式（ＤＰ）中、Ｍは、Ｉｒ、Ｐｔ、Ｒｈ、Ｒｕ、Ａｇ、Ｃｕ又はＯｓである。Ａ_１、Ａ_２、Ｂ_１及びＢ_２は、それぞれ、炭素原子又は窒素原子である。環Ｚ_１は、Ａ_１及びＡ_２とともに形成される６員の芳香族炭化水素環又は５員若しくは６員の芳香族複素環である。環Ｚ_２は、Ｂ_１及びＢ_２とともに形成される５員又は６員の芳香族複素環である。環Ｚ_１及び環Ｚ_２は置換基を有していてもよく、さらに置換基同士が結合して縮環構造を形成していてもよい。また、各々の配位子の置換基が、互いに結合して、配位子同士が連結していてもよい。Ｌ′は、Ｍに配位したモノアニオン性の二座配位子である。ｍ′は、０〜２のいずれかの整数である。ｎ′は、１〜３のいずれかの整数である。ｍ′＋ｎ′は、２又は３である。ｍ′及びｎ′が２以上のとき、環Ｚ_１及び環Ｚ_２の配位子及びＬ′は、それぞれ同じでも異なっていてもよい。〕 The phosphorescent light emitting dopant can be appropriately selected from known materials used for the light emitting layer of the organic EL device.
In the present invention, a phosphorescent compound having a structure represented by the following general formula (DP) can be suitably used as a phosphorescent dopant.

[In General Formula (DP), M is Ir, Pt, Rh, Ru, Ag, Cu, or Os. A ₁ , A ₂ , B ₁ and B ₂ are each a carbon atom or a nitrogen atom. Ring Z ₁ is a 6-membered aromatic hydrocarbon ring or 5-membered or 6-membered aromatic heterocycle formed with A ₁ and A ₂ . Ring Z ₂ is a 5-membered or 6-membered aromatic heterocycle formed with B ₁ and B ₂ . Ring Z ₁ and ring Z ₂ may have a substituent, and the substituents may be bonded to each other to form a condensed ring structure. Moreover, the substituent of each ligand may couple | bond together and the ligands may connect. L ′ is a monoanionic bidentate ligand coordinated to M. m ′ is an integer of 0-2. n ′ is an integer from 1 to 3. m ′ + n ′ is 2 or 3. When m ′ and n ′ are 2 or more, the ligands and L ′ of ring Z ₁ and ring Z ₂ may be the same or different. ]

Among these, M is preferably Ir, Pt, Rh, Ru, or Os, and more preferably Ir, Pt, or Os.
Ring Z ₂ is preferably a 5-membered aromatic heterocyclic ring, and at least one of B ₁ and B ₂ is preferably a nitrogen atom.
Examples of the substituent that the ring Z ₁ and the ring Z ₂ may have include the same substituents as R _{1 to} R _{6 in} the general formula (1). In addition, the substituents of the ring Z ₁ and the ring Z ₂ may be bonded to each other to form a condensed ring structure, or the substituents of the respective ligands may be bonded to each other to coordinate. The children may be connected.

When the structure represented by the general formula (DP) is a structure represented by the following general formula (DP-1) or (DP-2), a long-lived phosphorescent compound exhibiting blue light emission is obtained. Obtained and preferred. Since the material containing the compound having the structure represented by the general formula (1) of the present invention has a high triplet energy level, such a blue phosphorescent compound is used as a host compound with respect to the luminescent dopant. As a result, a blue organic EL element with high luminous efficiency and durability can be obtained.

In the above general formula (DP-1), M, A ₁ , A ₂ , B ₁ , B ₂ , ring Z ₁ , L ′, m ′ and n ′ are M, A ₁ , A in the general formula (DP). ₂ , B ₁ , B ₂ , ring Z ₁ , L ′, m ′ and n ′ are synonymous.
In the general formula (DP-1), B _{3 to} B ₅ are an atomic group that forms an aromatic heterocyclic ring with B ₁ and B _2, and a carbon atom that may have a hydrogen atom or a substituent, A nitrogen atom, an oxygen atom or a sulfur atom. Examples of the substituent that B _{3 to} B ₅ may have include the same groups as the substituents that the ring Z ₁ and the ring Z ₂ in the general formula (DP) may have.

In the general formula (DP-1), the aromatic heterocycle formed by B _{1 to} B ₅ is represented by any _{one of the following} general formulas (DP-1a), (DP-1b), and (DP-1c). It is preferable to have a structure represented by the general formula (DP-1c).

In the above general formulas (DP-1a), (DP-1b), and (DP-1c), * 1 represents a binding site with A _{2 in the} general formula (DP-1), and * 2 represents a binding site with M. Represents.
In the general formulas (DP-1a), (DP-1b), and (DP-1c), Rb _{3 to} Rb ₅ are hydrogen atoms or substituents, and Rb _{3 to} Rb ₅ include the general formula (DP) ring Z ₁ and the ring Z ₂ is the same substituent group as the substituent which may have at.
B ₄ and B ₅ in the general formula (DP-1a) are a carbon atom or a nitrogen atom, and more preferably at least one is a carbon atom.
B ₃ and B ₄ in the general formula (DP-1c) are a carbon atom or a nitrogen atom, more preferably at least one is a carbon atom, and Rb ₃ and Rb ₄ are further bonded to each other to form a condensed ring structure. More preferably, the condensed ring structure newly formed at this time is an aromatic ring, and is preferably a benzimidazole ring, an imidazopyridine ring, an imidazopyrazine ring or a purine ring. Rb ₅ is preferably an alkyl group or an aryl group, and more preferably a phenyl group.

上記一般式（ＤＰ−２）において、Ｍ、Ａ_１、Ａ_２、Ｂ_１、Ｂ_２、環Ｚ_１、Ｌ′、ｍ′及びｎ′は、一般式（ＤＰ）におけるＭ、Ａ_１、Ａ_２、Ｂ_１、Ｂ_２、環Ｚ_１、Ｌ′、ｍ′及びｎ′と同義である。
上記一般式（ＤＰ−２）において、環Ｚ_２は、Ｂ_１〜Ｂ_３とともに形成される５員の芳香族複素環である。
上記一般式（ＤＰ−２）において、Ａ_３及びＢ_３は、炭素原子又は窒素原子であり、Ｌ″は２価の連結基である。Ｌ″の２価の連結基としては、例えばアルキレン基、アルケニレン基、アリーレン基、ヘテロアリーレン基、２価の複素環基、Ｏ、Ｓ、これらを任意に組み合わせた連結基等が挙げられる。
一般式（ＤＰ−２）で表される構造は、さらに下記一般式（ＤＰ−２ａ）で表されることが好ましい。

In the above general formula (DP-2), M, A ₁ , A ₂ , B ₁ , B ₂ , ring Z ₁ , L ′, m ′ and n ′ are M, A ₁ , A in the general formula (DP). ₂ , B ₁ , B ₂ , ring Z ₁ , L ′, m ′ and n ′ are synonymous.
In formula (DP-2), the ring _{Z 2 is} a 5-membered aromatic heterocyclic ring formed together with B 1 ~B _3.
In the general formula (DP-2), A ₃ and B ₃ are a carbon atom or a nitrogen atom, and L ″ is a divalent linking group. Examples of the divalent linking group of L ″ include an alkylene group. , Alkenylene group, arylene group, heteroarylene group, divalent heterocyclic group, O, S, a linking group in which these are arbitrarily combined, and the like.
The structure represented by the general formula (DP-2) is preferably further represented by the following general formula (DP-2a).

上記一般式（ＤＰ−２ａ）において、Ｍ、Ａ_１、Ａ_２、Ｂ_１、Ｂ_２、環Ｚ_１、環Ｚ_２、Ｌ′、ｍ′及びｎ′は、一般式（ＤＰ−２）におけるＭ、Ａ_１、Ａ_２、Ｂ_１、Ｂ_２、環Ｚ_１、環Ｚ_２、Ｌ′、ｍ′及びｎ′と同義である。
上記一般式（ＤＰ−２ａ）において、Ｌ″_１及びＬ″_２は、Ｃ−Ｒｂ_６又は窒素原子であり、Ｒｂ_６は、水素原子又は置換基である。Ｌ″_１及びＬ″_２がＣ−Ｒｂ_６の場合はＲｂ_６同士が互いに結合し環を形成してもよい。

In the above general formula (DP-2a), M, A ₁ , A ₂ , B ₁ , B ₂ , ring Z ₁ , ring Z ₂ , L ′, m ′ and n ′ are the same in general formula (DP-2) It is synonymous with M, A ₁ , A ₂ , B ₁ , B ₂ , ring Z ₁ , ring Z ₂ , L ′, m ′ and n ′.
In the general formula (DP-2a), L ″ ₁ and L ″ ₂ are C—Rb ₆ or a nitrogen atom, and Rb ₆ is a hydrogen atom or a substituent. When L ″ ₁ and L ″ ₂ are C—Rb ₆ , Rb ₆ may be bonded to each other to form a ring.

In the above general formulas (DP), (DP-1), (DP-2), and (DP-2a), A ₂ is preferably a carbon atom, and A ₁ is preferably a carbon atom. More preferably, the ring Z ₁ is a substituted or unsubstituted benzene ring or pyridine ring, and more preferably a benzene ring.

[Fluorescent emission dopant]
As the fluorescent light-emitting dopant, a compound capable of emitting light from excited singlet can be used, and is not particularly limited as long as light emission from excited singlet is observed.
Examples of the fluorescent emission dopant include anthracene derivatives, pyrene derivatives, chrysene derivatives, fluoranthene derivatives, perylene derivatives, fluorene derivatives, arylacetylene derivatives, styrylarylene derivatives, styrylamine derivatives, arylamine derivatives, boron complexes, squalium derivatives, oxobenzanthracene. Derivatives, fluorescein derivatives, perylene derivatives, polythiophene derivatives, rare earth complex compounds, and the like can be given.

  In addition, luminescent dopants using delayed fluorescence have been developed, and these may be used. Specific examples of the luminescent dopant using delayed fluorescence include, for example, compounds described in International Publication No. 2011/156793, Japanese Patent Application Laid-Open No. 2011-213743, Japanese Patent Application Laid-Open No. 2010-93181, and the like. Not.

[Host compound]
The host compound is preferably a compound having a phosphorescence quantum yield of phosphorescence emission at room temperature (25 ° C.) of less than 0.1, and more preferably a compound having a phosphorescence quantum yield of less than 0.01.
Moreover, it is preferable that the excited state energy of a host compound is higher than the excited state energy of the light emission dopant contained in the same layer.

Among the plurality of compounds contained in the light emitting layer, the mass ratio of the host compound in the light emitting layer is preferably 20% or more.
The host compound may be used alone or in combination. By using a plurality of types of host compounds, charge transfer can be adjusted and the light emission efficiency of the organic EL element can be increased.

  As the host compound that can be used in the present invention, the organic EL device material of the present invention having a high triplet energy level as described above can be preferably used, but there is no particular limitation, and even a low molecular compound can be used. A polymer compound having a repeating unit may be used, and a compound having a reactive group such as a vinyl group or an epoxy group may be used.

  As a known host compound, while having a hole transporting ability or an electron transporting ability, it prevents the wavelength of light emission from being increased, and allows the organic EL element to operate stably at a high temperature driving or during the driving of the element. From the viewpoint, it is preferable to have a high glass transition temperature (Tg). Tg is preferably 90 ° C. or higher, more preferably 120 ° C. or higher. Here, the glass transition point (Tg) is a value determined by a method based on JIS-K-7121 using DSC (Differential Scanning Calorimetry).

Specific examples of known host compounds that can be used in the organic EL device of the present invention include compounds described in the following documents, but the present invention is not limited thereto.
JP 2002-206833, JP 2002-363227, JP 2002-234888, JP 2002-280183, JP 2002-299060, JP 2002-302516, JP 2002-305083, 2002-305084, US Patent Publication No. 2009/0017330, US Patent Publication No. 2009/0030202, US Patent Publication No. 2005/0238919, International Publication No. 2001/039234, International Publication No. 2009/021126, International Publication No. 2008/056746, International Publication No. 2007/063796, International Publication No. 2007/063754, International Publication No. 2004/107822, International Publication No. 2006/114966, International Publication No. 2009 No. 086028, WO 2009/003898, WO 2012/023947, JP 2008-074939, JP 2007-254297, JP-like EP2034538.

(Electron transport layer)
The electron transport layer is a layer that transports electrons injected from the cathode to the light emitting layer.
The material for the electron transport layer may be any one of electron injection property, electron transport property, and hole barrier property, and as described above, the electron transport layer material may be the organic material of the present invention. An EL element material can be used.

  As a material for the electron transport layer, an arbitrary compound can be selected and used from conventionally known compounds. For example, nitrogen-containing aromatic heterocyclic derivatives (carbazole derivatives, azacarbazole derivatives (one or more carbon atoms constituting the carbazole ring are substituted with nitrogen atoms), pyridine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, Quinoxaline derivatives, phenanthroline derivatives, oxazole derivatives, thiazole derivatives, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, benzoxazole derivatives, etc.), dibenzofuran derivatives, dibenzothiophene derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, Triphenylene, etc.).

Further, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, such as tris (8-quinolinol) aluminum (Alq ₃ ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7- Dibromo-8-quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and these metal complexes A metal complex in which the central metal is replaced with In, Mg, Cu, Ca, Sn, Ga, or Pb can also be used as an electron transporting material.

  In addition, a phthalocyanine derivative and a distyrylpyrazine derivative can also be used as an electron transport material, and an inorganic semiconductor can be used as an electron transport material as well as a hole injection layer and a hole transport layer. Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

  A doping material may be doped as a guest material to form an electron transport layer having a high n property (electron rich). Examples of the doping material include n-type dopants such as metal compounds such as metal complexes and metal halides. Specific examples of the electron transport layer having such a structure include, for example, JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J. Pat. Appl. Phys. , 95, 5773 (2004) and the like.

Specific examples of known preferable electron transport materials used in the organic EL device of the present invention include compounds described in the following documents, but the present invention is not limited thereto.
US Patent Publication No. 2009/0115316, US Patent Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132805, Appl. Phys. Lett. 75, 4 (1999), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 79,156 (2001), US Patent Publication No. 2009/030202, International Publication No. 2004/080975, International Publication No. 2005/085387, International Publication No. 2006/069311, International Publication No. 2007/086552, International Publication. 2008/114690, International Publication No. 2009/069442, International Publication No. 2009/066779, International Publication No. 2009/054253, International Publication No. 2011/0886935, International Publication No. 2010/150593, International Publication No. 2010 No. 047707, JP 2010-251675 A, JP 2009-209133 A, JP 2009-124114 A, JP 2008-277810 A, JP 2006-156445 A, JP 2003-31367 A. Gazette, country Publication No. 2012/115034 and the like.

More preferable electron transport materials in the present invention include pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, azacarbazole derivatives, benzimidazole derivatives, and the like.
The electron transport material may be used alone or in combination of two or more.

Although there is no restriction | limiting in particular about the layer thickness of the electron carrying layer of this invention, Usually, it is the range of 2 nm-5 micrometers, More preferably, it is the range of 2-500 nm, More preferably, it is the range of 5-200 nm.
In an organic EL device, when light generated in the light emitting layer is extracted from the electrode, interference is caused between the light directly extracted from the light emitting layer and the light extracted after being reflected by the electrode from which the light is extracted and the electrode located at the counter electrode. It has been known. When light is reflected by the cathode, this interference effect can be efficiently utilized by appropriately adjusting the total thickness of the electron transport layer between several nanometers and several micrometers. On the other hand, when the electron transport layer is thickened, the voltage is likely to increase. Therefore, particularly when the layer thickness is thick, the electron mobility of the electron transport layer is preferably 10 ⁻⁵ cm ² / Vs or more.

(Hole blocking layer)
The hole blocking layer is preferably provided adjacent to the cathode side of the light emitting layer in order to improve the recombination probability of electrons and holes by blocking holes while transporting electrons.
As the material used for the hole blocking layer, the organic EL device material of the present invention can be used as described above, but the material used for the electron transport layer is also preferably used. Moreover, the material used as the above-mentioned host compound is also preferably used for the hole blocking layer.
The layer thickness of the hole blocking layer is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.

(Electron injection layer)
The electron injection layer can be provided in order to reduce drive voltage and improve light emission luminance.
Details of the electron injection layer are also described in JP-A-6-325871, JP-A-9-17574, and JP-A-10-74586.

As described above, the organic EL element material of the present invention can be used as the material for the electron injection layer. Specific examples of materials preferably used for other electron injection layers include metals (strontium, aluminum, etc.), alkali metal compounds (lithium fluoride, sodium fluoride, etc.), alkaline earth metal compounds (magnesium fluoride, fluoride). Calcium etc.), metal oxides (aluminum oxide etc.), metal complexes (lithium 8-hydroxyquinolate (Liq) etc.), etc. are mentioned. Further, the above-described electron transport material can also be used. These materials may be used alone or in combination of two or more.
The electron injection layer is preferably a very thin layer, and the layer thickness is preferably in the range of 0.1 to 5 nm, although it depends on the material. Moreover, the nonuniform film | membrane in which a constituent material exists intermittently may be sufficient.

(Hole transport layer)
As a material for the hole transport layer, any material can be selected from conventionally known compounds as long as it has any of hole injection property, hole transport property, and electron barrier property. Can be used.
Examples of the material for the hole transport layer include porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, phenylenediamine derivatives, stilbene derivatives, triarylamine derivatives, carbazole derivatives, indolocarbazole derivatives, acene derivatives such as anthracene and naphthalene, and fluorene derivatives. , A fluorenone derivative, polyvinylcarbazole, a polymer material or oligomer in which an aromatic amine is introduced into the main chain or side chain, polysilane, a conductive polymer or oligomer (for example, (xythiophene) -polystyrene sulfonate (hereinafter abbreviated as PEDOT: PSS) ), Aniline copolymers, polyaniline, polythiophene, etc.). As described above, the material for an organic EL device of the present invention can also be used as the material for the hole transport layer.

  Examples of the triarylamine derivative include benzidine type represented by (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) (hereinafter abbreviated as α-NPD) and representative of MTDATA. And a compound having fluorene or anthracene in the starburst type, triarylamine-linked core portion.

  In addition, hexaazatriphenylene derivatives such as those described in JP-T-2003-519432 and JP-A-2006-135145 can also be used as the material for the hole transport layer. Moreover, it is good also as a positive hole transport layer with high p property which doped the impurity. Examples thereof include JP-A-4-297076, JP-A-2000-196140, 2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

JP-A-11-251067, J. Org. Huang et. al. As materials for so-called p-type hole transport layers as described in the literature (Appl. Phys. Lett. 80 (2002), p. 139), inorganic materials such as p-type-Si and p-type-SiC are used. Compounds can also be used. Further, ortho-metalated organometallic complexes having Ir or Pt as a central metal as typified by Ir (ppy) ₃ are also preferably used.

Among the materials for the hole transport layer described above, triarylamine derivatives, carbazole derivatives, indolocarbazole derivatives, organometallic complexes, polymer materials or oligomers in which an aromatic amine is introduced into the main chain or side chain are preferably used. It is done.
The above-described materials may be used alone or in combination.

  Although there is no restriction | limiting in particular about the layer thickness of a positive hole transport layer, Usually, it is the range of 2 nm-5 micrometers, More preferably, it is the range of 5-500 nm, More preferably, it is the range of 5-200 nm.

(Electron blocking layer)
The electron blocking layer is preferably provided adjacent to the anode side of the light emitting layer in order to improve the recombination probability of electrons and holes by blocking electrons while transporting holes.

As the material for the electron blocking layer, as described above, the organic EL device material of the present invention can be used, and the material used for the hole transport layer or the host compound used for the light emitting layer is preferably used. Can do.
The thickness of the electron blocking layer is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.

[Hole injection layer]
The hole injection layer can be provided between the anode and the light emitting layer or between the anode and the hole transport layer in order to lower the driving voltage and improve the light emission luminance.

  As the material for the hole injection layer, as described above, the material for an organic EL device of the present invention can be used, and the material used for the hole transport layer can be used. Among these, phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives as described in JP-T-2003-519432, JP-A-2006-135145, etc., metal oxides typified by vanadium oxide, Preferred are conductive polymers such as amorphous carbon, polyaniline (emeraldine) and polythiophene, orthometalated complexes represented by tris (2-phenylpyridine) iridium complex, and triarylamine derivatives. The material for the hole injection layer may be used alone or in combination of two or more.

[Display device]
The display device of the present invention includes the above-described organic EL element of the present invention.

FIG. 3 shows a schematic configuration of an active matrix display device 10 as an embodiment of the present invention.
As illustrated in FIG. 3, the display device 10 includes a plurality of pixels 21 arranged in a matrix, a plurality of X-rays 22 and Y lines 23 provided so as to be orthogonal to each other between the pixels 21, and an X-ray. 22 and a plurality of active elements 24 provided at the intersections of the Y lines 23.

Each pixel 21 includes an organic EL element that emits red, green, or blue light. Full color display is possible by arranging the pixels 21 of each color to emit light.
One active element 24 corresponds to one pixel 21, and each active element 24 is connected to an electrode of an organic EL element included in each corresponding pixel 21. The active element 24 supplies current to the corresponding pixel 21 when current is supplied from the X-ray 22 and current is also supplied from the Y-line 23. The active element 24 can be composed of, for example, a capacitor, a TFT (Thin Film Transistor), or the like.

  At the time of displaying an image, a horizontal area signal indicating the effective area of the image is output to the X-ray 22 for each line, and an image signal is output to the Y line 23 in synchronization with the horizontal area signal. The active element 24 to which current is supplied from the X-ray 22 by output of the horizontal region signal and current from the Y-line 23 by output of the image signal supplies current to the corresponding pixel 21. When the organic EL element of each pixel 21 emits light by supplying current, light of each color of red, green, and blue is emitted in the direction of the arrow shown in FIG. 3, and a full-color image can be reproduced.

The plurality of pixels 21 can be manufactured as shown in FIGS. 4A to 4E.
As shown in FIG. 4A, an anode material film such as indium tin oxide (ITO) is formed on the substrate 11 and then etched, or an ITO film having a predetermined pattern is formed using a mask. Thus, the anode 1A of each pixel 21 is formed in a predetermined pattern.
Next, as shown in FIG. 4B, partition walls 12 (width 20 μm, thickness 2.0 μm) are formed by photolithography on the substrate 11 and between the anodes 1A. As a material of the partition 12, for example, non-photosensitive polyimide can be used.

As shown in FIG. 4C, the hole injection layer 1B is formed on the anode 1A and between the partition walls 12 by an inkjet head method or the like.
As shown in FIG. 4D, the hole injection layer 1B of each pixel 21, an ink jet method, to form a blue emitting layer 1C _B, green light-emitting layer 1C _G and red light-emitting layer 1C _R, respectively.
Furthermore, as shown in FIG. 4E, the light emitting layer _1C R of the pixels 21 formed so as to cover the entire 1C _G and 1C _B, by depositing aluminum or the like to form the cathode 1D.

  The display device of the present invention is not limited to the active matrix type described above, and may be a passive matrix type display device.

[Lighting device]
The illumination device of the present invention includes the above-described organic EL element of the present invention.

FIG. 5 shows a schematic configuration of the illumination device 30 according to the embodiment of the present invention.
As shown in FIG. 5, the illumination device 30 is provided with an organic EL element 1 including an anode 1 </ b> A, a light emitting layer 1 </ b> C, and a cathode 1 </ b> D on a substrate 31. A sealing material 32 is bonded onto the substrate 31 via an adhesive 33, and the organic EL element 1 on the substrate 31 is sealed with the sealing material 32. In order to prevent the deterioration of the organic EL element 1 due to oxygen gas, water vapor or the like, the inside of the sealing material 32 is filled with an inert gas 34 and a water catching agent 35 is provided.

  In the illumination device 30, by applying a voltage to the pair of electrodes 1A and 1E, the light emitting layer 1C emits light, and light is emitted in a direction indicated by an arrow in FIG.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless there is particular notice, it represents "mass part" or "mass%".

Example I
[Organic EL element 101]
On a 100 mm × 100 mm × 1.1 mm glass substrate, an anode having a thickness of 100 nm was formed with ITO in a predetermined pattern. This substrate was ultrasonically cleaned with isopropyl alcohol and dried with dry nitrogen gas, followed by UV ozone cleaning for 5 minutes.

  On the transparent substrate thus obtained, a coating solution comprising the composition of the hole injection layer was applied by spin coating, and dried at 200 ° C. to form a hole injection layer having a thickness of 20 nm. As a coating solution, a solution obtained by diluting PEDOT / PSS (Baytron P Al 4083 manufactured by Bayer) to 65% with pure water was used.

Next, the substrate having the hole injection layer was fixed to a substrate holder of a commercially available vacuum deposition apparatus. 200 mg of α-NPD, 200 mg of compound H-1, 200 mg of comparative compound 1, 100 mg of compound D-37, and 250 mg of Alq ₃ were placed in separate molybdenum resistance heating boats and attached to a vacuum deposition apparatus.

The compound H-1, the comparative compound 1, and the compound D-37 each have a structure represented by the following formula.

After depressurizing the vacuum tank of the vacuum evaporation system to 4 × 10 ⁻⁴ Pa, the heating boat containing α-NPD was energized and heated, and deposited on the hole injection layer at a deposition rate of 0.1 nm / second. Then, a hole transport layer having a thickness of 30 nm was provided. Subsequently, the heating boat containing the compound H-1 was energized and heated, and deposited on the hole transport layer at a deposition rate of 0.1 nm / second to provide an electron blocking layer having a thickness of 10 nm.

  Next, each heating boat of the comparative compound 1 and the compound D-37 was energized and heated, and co-deposited on the electron blocking layer at a deposition rate of 0.1 nm / second and 0.010 nm / second, respectively. A 40 nm light emitting layer was provided. Comparative compound 1 in the light emitting layer is a host compound, and compound D-37 is a phosphorescent dopant.

Further, a heating boat containing Alq ₃ was heated by energization, and was deposited on the light emitting layer at a deposition rate of 0.1 nm / second to provide an electron transport layer having a thickness of 30 nm.
Subsequently, lithium fluoride was vapor-deposited to form an electron injection layer having a thickness of 0.5 nm, and aluminum was further vapor-deposited to form a cathode having a thickness of 110 nm. Thus, an organic EL element 101 was produced.

[Organic EL elements 102 to 115]
In the production of the organic EL element 101, each of the organic EL elements 102 to 115 was produced in the same manner as the organic EL element 101 except that the combination of the host compound and the light-emitting dopant was changed as shown in Table 1 below.
In addition, the exemplary compounds in Table 1 are the exemplary compounds listed as the organic EL device material of the present invention.

Moreover, the comparative compound 2 and compound D-54 as described in Table 1 have a structure represented by a following formula. Comparative compounds 1 and 2 are compounds described in JP 2007-63220 A.

[Evaluation]
The light emission efficiency and durability of each organic EL element 101-115 were evaluated.

[Luminescence efficiency]
Using each of the organic EL elements 101 to 115, an illumination device having the same configuration as the illumination device shown in FIG. 5 was manufactured as follows.
Using a glass cover as a sealing material, an epoxy-based photo-curing type adhesive (Luxtrac LC0629B manufactured by Toagosei Co., Ltd.) is applied around the sealing material, and the sealing material is placed on the organic EL element. The coated portion was brought into close contact with the glass substrate of the organic EL element. The adhesive was cured by irradiating UV light around the organic EL element from the glass substrate side, and the organic EL element was sealed to produce a lighting device.
The organic EL element was energized under conditions of room temperature (25 ° C.) and a constant current of ^2.5 mA / cm ² to cause the organic EL element to emit light, and light emission luminance (L0) [cd / m ² immediately after the start of light emission. The external extraction quantum efficiency (η) was calculated. CS-2000 (manufactured by Konica Minolta Co., Ltd.) was used for measuring the emission luminance.

  The external extraction quantum efficiency of each of the organic EL elements 101 to 115 was expressed as a relative value when the external extraction quantum efficiency of the organic EL element 102 was 100, and this was evaluated as the light emission efficiency. The larger the value of the luminous efficiency, the higher the luminous efficiency as compared with the organic EL element 102.

[Half life]
The half life of each of the organic EL elements 101 to 115 was evaluated as follows as one of durability.
The organic EL device was driven at a constant current with a current giving an initial luminance of 4000 cd / m ² at room temperature (temperature 25 ° C.), and the time from the start of driving until the luminance became half the initial luminance was measured.
The measurement time of each organic EL element 101-115 was evaluated as a half life. The larger the half-life value, the longer the life and the higher the durability than the organic EL element 102.

[Thermal stability]
The thermal stability of each of the organic EL elements 101 to 115 was evaluated as follows as one of durability evaluation items.
The organic EL element was energized under a constant current condition of ^2.5 mA / cm ² , the luminous efficiency of the organic EL element was measured, and the current value when giving an initial luminance of 4000 cd / m ² was determined. Thereafter, the organic EL element was placed in a constant temperature bath at 60 ° C., and was driven with a low current at the current value previously obtained in the constant temperature bath. From the measured half-life, the thermal stability was calculated by the following formula. In addition, the half life measured in the said half life evaluation was used for the half life at room temperature.
Thermal stability (%) = Half life at 60 ° C./Half life at room temperature × 100
The closer the value of thermal stability is to 100, the better the thermal stability and the higher the durability.

Table 1 below shows the evaluation results.
In Table 1 below, the evaluation values of the organic EL elements 101 to 109 are expressed as relative values when the measurement time of the organic EL element 102 is 100, and the evaluation values of the organic EL elements 110 to 115 are expressed as organic EL elements. This is expressed as a relative value when the measurement time of 111 is 100.
In addition, “ND” in the thermal stability item of Table 1 below cannot be measured because the half-life at 60 ° C. measured in the thermal stability evaluation is remarkably short and the driving voltage at the time of measurement is significantly increased. It shows that there was. The cause of the inability to measure is not clear, but either one of the layers in the organic EL element has crystallized, or the interface junction with the adjacent layer has become defective and orientated, resulting in dark spots. It is estimated that

As shown in Table 1 above, when compound D-37 was used as the luminescent dopant, the organic EL elements 103 to 110 according to the examples of the present invention emitted light compared to the organic EL elements 101 and 102 of the comparative examples. High efficiency and long half life. Since the thermal stability is also improved by a factor of two or more, it can be seen that according to the present invention, an organic EL device excellent in luminous efficiency and durability can be obtained.
Further, according to the organic EL elements 102 and 111 of the comparative examples, when the emission dopant is changed from the compound D-37 to the compound D-54, the emission efficiency is reduced to about half, and the half life is also greatly reduced. I understand. On the other hand, the organic EL elements 112 to 115 according to the examples of the present invention show little reduction in luminous efficiency even when the luminescent dopant is changed to the compound D-54, show a good half-life, and have high thermal stability. It turns out that it is excellent.

Example II
In the manufacture of the organic EL device 101 of Example I above, the material of the electron transport layer was changed to Compound E-1, and the combination of the luminescent dopant and the host compound was changed as shown in Table 2 below. In the same manner as the element 101, the organic EL elements 201 to 210 were manufactured. In addition, the exemplary compounds in Table 2 are the exemplary compounds listed as the organic EL device material of the present invention.

The compound E-1 and the compounds D-20 and D-32 described in Table 2 below each have the following structure.

The luminous efficiency and durability of each of the produced organic EL elements 201 to 210 were evaluated in the same manner as in Example I.
Table 2 below shows the evaluation results. In Table 2, the values indicating the light emission efficiency, half-life and thermal stability of each of the organic EL elements 201 to 210 are relative values based on the value of the organic EL element 201.

  As shown in Table 2, the organic EL elements 202 to 205 and 207 to 210, which are examples of the present invention, are excellent in luminous efficiency and durability when the luminescent dopant is any of the compounds D-20 and D-32. I understand that

Example III
In the manufacture of the organic EL element 201 of Example II, each of the organic EL elements 301 to 310 was changed in the same manner as the organic EL element 201 except that the combination of the light emitting dopant and the host compound was changed as shown in Table 3 below. Manufactured. In addition, the exemplary compound in Table 3 is an exemplary compound enumerated as a material for organic EL elements of the present invention.

Compounds D-3 and D-14 shown in Table 3 below have the following structures, respectively.

The luminous efficiency and durability of each of the produced organic EL elements 301 to 310 were evaluated in the same manner as in Example I.
Table 3 below shows the evaluation results. In Table 3, the values indicating the light emission efficiency, half-life and thermal stability of each of the organic EL elements 301 to 310 are relative values based on the value of the organic EL element 301.

  As shown in Table 3, the organic EL elements 302 to 305 and 307 to 310, which are examples of the present invention, are excellent in luminous efficiency and durability when the luminescent dopant is any of the compounds D-3 and D-14. I understand that

Example IV
In the manufacture of the organic EL element 101 of Example I above, the organic EL element 101 and the organic EL element 101 were changed except that the materials of the hole transport layer, the electron blocking layer, the light emitting host and the electron transport layer were changed as shown in Table 4 below. Similarly, each organic EL element 401-405 was manufactured.

The luminous efficiency and durability of each of the produced organic EL elements 401 to 405 were evaluated in the same manner as in Example I.
Table 4 below shows the evaluation results. In Table 4, the values indicating the light emission efficiency, half life, and thermal stability of each of the organic EL elements 401 to 405 are relative values based on the value of the organic EL element 401.

As shown in Table 4, the organic EL elements 402 to 405 that are examples of the present invention have higher luminous efficiency and longer half-life than the organic EL element 401 of the comparative example. Moreover, it is a common feature that the thermal stability is improved about twice.
From the evaluation results shown in Table 4, the compound according to the present invention can be applied to a hole transport layer other than the light-emitting layer, an electron blocking layer, an electron transport layer, and the like, and is excellent in luminous efficiency and durability when applied. It can be seen that an organic EL element is obtained, and in particular, the thermal stability is improved.

[Example V]
The organic EL element used in the display device having the configuration shown in FIG. 3 was manufactured in the same manner as the manufacturing process shown in FIGS. 4A to 4E, and it was confirmed whether a full-color image could be displayed.

  After forming an ITO film on a glass substrate (NA45 manufactured by NH Techno Glass), etching was performed to form each anode 1A in the area of each pixel. The pattern of each anode 1A was a square having a thickness of 100 nm and a size of 100 μm × 100 μm. Next, a partition wall having a thickness of 2.0 μm and a width of 20 μm was formed by photolithography on each glass substrate and separating each pixel between the anodes. Non-photosensitive polyimide was used as a material for the partition walls.

Further, the composition of the following hole injection layer on the anode of each pixel and between each partition wall 12 was injected and injected using an inkjet head (MJ800C manufactured by Epson Corporation). Then, ultraviolet light was irradiated for 200 seconds, the drying process was performed for 10 minutes at 60 degreeC, and the 40-nm-thick hole injection layer was provided.
(Composition of hole injection layer)
Compound HT-1: 20 parts by mass Cyclohexylbenzene: 50 parts by mass Isopropyl biphenyl: 50 parts by mass

On the hole injection layer of each pixel, each composition of the following blue light emitting layer, green light emitting layer and red light emitting layer was discharged and injected by an inkjet head so that the pixels were arranged in the order of blue, green and red. Then, the drying process for 10 minutes was performed at 60 degreeC, and the light emitting layer of each color of blue, green, and red was provided.
(Composition of blue light emitting layer)
Compound D-63: 0.04 parts by mass Exemplary compound 35 of the present invention 35: 0.8 parts by mass Cyclohexylbenzene: 60 parts by mass Isopropyl biphenyl: 40 parts by mass (composition of green light-emitting layer)
Compound D-20: 0.04 parts by mass Exemplary compound 35 of the present invention 35: 0.7 parts by mass Cyclohexylbenzene: 50 parts by mass Isopropylbiphenyl: 50 parts by mass (composition of red light emitting layer)
Compound D-14: 0.04 parts by mass Exemplified compound 41 of the present invention 41: 0.7 parts by mass Cyclohexylbenzene: 50 parts by mass Isopropyl biphenyl: 50 parts by mass

The compounds HT-1 and D-63 have a structure represented by the following formula.

  Next, the compound E-1 is vapor-deposited on the light-emitting layer of each pixel, an electron transport layer having a thickness of 45 nm is provided, lithium fluoride is vapor-deposited on the electron transport layer, and an electron having a thickness of 0.5 nm is formed. An injection layer was provided. Furthermore, aluminum was vapor-deposited so as to cover the entire pixels, and a cathode having a thickness of 130 nm was provided to manufacture an organic EL element included in each pixel.

  When a voltage was applied to the pair of electrodes of the organic EL element of each pixel, blue, green and red light emission was observed from each organic EL element, and it was confirmed that a full color image could be displayed.

10 display device 21 pixel 10 organic EL element 11 substrate 12 partition wall 1A anode _{1C, 1C R, 1C G,} 1C B emission layer 1D cathode 30 illumination device 31 substrate 32 sealant

Claims (8)

An organic electroluminescent element material comprising a compound having a structure represented by the following general formula (1).

[In General formula (1), R < ₁ > -R < ₆ > is a hydrogen atom or a substituent each independently. When two adjacent ones of R _{1 to} R ₆ are substituents, each substituent is a different substituent. However, in any combination of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , when one of the substituents is a linear alkyl group, the other substituent is independently A monocyclic aromatic ring having a substituent, a condensed aromatic ring, a diarylamino group, a silyl group, or a phosphino group. ] In the general formula (1), of the R ₁ to R _6, the organic electroluminescence device material according to claim 1, wherein at least two or more is a hydrogen atom.   In the general formula (1), when the imidazole ring is located at the center of the condensed ring formed by bonding and is rotated every 120 ° about the axis perpendicular to the surface of the condensed ring. The structure represented by said general formula (1) of each differs, The organic electroluminescent element material of Claim 1 or Claim 2 characterized by the above-mentioned. An organic electroluminescence device comprising: a light emitting unit composed of a plurality of organic layers including at least a light emitting layer; and a pair of electrodes sandwiching the light emitting unit,
At least 1 layer of these organic layers contains the organic electroluminescent element material as described in any one of Claim 1- Claim 3. The organic electroluminescent element characterized by the above-mentioned.   The said light emitting layer contains the said organic electroluminescent element material, The organic electroluminescent element of Claim 4 characterized by the above-mentioned.   6. The organic electroluminescence device according to claim 5, wherein the light emitting layer contains a blue phosphorescent compound.   A display device comprising the organic electroluminescence element according to any one of claims 4 to 6.   An illuminating device comprising the organic electroluminescence element according to any one of claims 4 to 6.

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