JP6264001B2 - ORGANIC ELECTROLUMINESCENT ELEMENT, LIGHT-EMITTING THIN FILM, DISPLAY DEVICE AND LIGHTING DEVICE - Google Patents

Description

  The present invention relates to an organic electroluminescence element. The present invention also relates to a light-emitting thin film, a display device, and a lighting device provided with the organic electroluminescence element. More specifically, the present invention relates to an organic electroluminescence element with improved luminous efficiency.

  An organic EL element (also referred to as “organic electroluminescence element”) using an organic material electroluminescence (hereinafter abbreviated as “EL”) has already been put into practical use as a new light emitting system that enables planar light emission. Technology. Organic EL elements are not only applied to electronic displays but also recently applied to lighting equipment, and their development is expected.

There are two types of organic EL emission methods: “phosphorescence emission” that emits light when returning from the triplet excited state to the ground state and “fluorescence emission” that emits light when returning from the singlet excited state to the ground state. There is.
When an electric field is applied to the organic EL element, holes and electrons are injected from the anode and the cathode, respectively, and recombine in the light emitting layer to generate excitons. At this time, since singlet excitons and triplet excitons are generated at a ratio of 25%: 75%, phosphorescence using triplet excitons is theoretically higher in internal quantum than fluorescence. It is known that efficiency can be obtained.
However, in order to actually obtain high quantum efficiency in the phosphorescence emission method, it is necessary to use a complex using a rare metal such as iridium or platinum as a central metal. There is concern that price will be a major industrial issue.

On the other hand, various developments have been made to improve the light emission efficiency in the fluorescent light emitting type, and a new movement has recently been made.
For example, Patent Document 1 discloses a phenomenon in which singlet excitons are generated by collision of two triplet excitons (hereinafter referred to as “triplet-triplet annihilation”, hereinafter abbreviated as “TTA” as appropriate. Triplet-Triplet Fusion: Focusing on “TTF”), a technique for efficiently increasing the efficiency of a fluorescent element by efficiently causing TTA is disclosed. This technology improves the power efficiency of fluorescent materials (hereinafter also referred to as fluorescent materials), up to 2-3 times that of conventional fluorescent materials, but the theoretical singlet excitons in TTA. Since the generation efficiency is limited to about 40%, there is still a problem of higher light emission efficiency than phosphorescence emission.
Further, in recent years, Adachi et al. Have developed a fluorescent material using a thermally activated delayed fluorescence (also referred to as “thermally activated delayed fluorescence”: hereinafter, abbreviated as “TADF” as appropriate) mechanism. The possibility of use for organic EL elements has been reported (for example, see Non-Patent Documents 1 to 7 and Patent Document 2).

  As shown in FIG. 1, the TADF mechanism is a compound having a smaller difference (ΔEst) between the singlet excitation energy level and the triplet excitation energy level (ΔEst (TADF) in FIG. 1) as compared with a normal fluorescent compound. Is smaller than ΔEst (F).), A light emission mechanism utilizing a phenomenon in which a reverse intersystem crossing from a triplet exciton to a singlet exciton occurs. That is, since ΔEst is small, triplet excitons generated with a probability of 75% due to electric field excitation cannot contribute to light emission originally, but transition to a singlet excited state by thermal energy at the time of driving an organic EL element, From this state to the ground state, radiation is deactivated (also referred to as “radiation transition” or “radiation deactivation”) to cause fluorescence emission. If delayed fluorescence due to the TADF mechanism is used, it is considered that 100% internal quantum efficiency is theoretically possible even in fluorescence emission.

However, a fluorescent compound using the TADF mechanism generally tends to have a deep LUMO level due to its intramolecular CT strength consisting of a strong donor site and a strong acceptor site.
Molecules in such a state are considered to tend to trap electrons when used in an organic EL light-emitting layer. That is, the balance between the hole transport property and the electron transport property, that is, the balance of the charge transport property is deteriorated in the light emitting layer, and in many cases, it is considered that light is emitted at the electron transport layer interface.

When the charge transport property is poor, the range where recombination occurs in the light emitting layer is narrow or the recombination position shifts over time, resulting in a decrease in luminous efficiency and a decrease in luminance over time, that is, the device lifetime. It causes deterioration.
Among the fluorescent compounds, indoloindole compounds have recently attracted attention as parts responsible for adjusting the charge balance in the light-emitting layer due to their high hole transport properties, and are used as host compounds for phosphorescent compounds. (See Patent Documents 3 to 6.)
In these prior documents, indoloindole compounds have been used as host compounds, but no examples have been used as luminescent materials.

International Publication No. 2012/133188 JP2013-116975A International Publication No. 2011/055933 International Publication No. 2011/132866 International Publication No. 2012/035853 JP 2013-58560 A

"Development of phosphorescent organic EL technology for lighting" Applied Physics Vol. 80, No. 4, 2011 H. Uoyama, et al. , Nature, 2012, 492, 234-238. S. Y. Lee et al. , Applied Physics Letters, 2012, 101, 093306-093309. Q. Zhang et al. , J .; Am. Chem. Soc. 2012, 134, 14706-14709 T.A. Nakagawa et al. , Chem. Commun. , 2012, 48, 9580-9582 A. Endo et al. , Adv. Mater. , 2009, 21, 4802-4806 Proceedings of the 10th Annual Meeting of Organic EL Discussion p11-12, 2010

  The present invention has been made in view of the above problems and situations, and a problem to be solved is to provide an organic electroluminescence element capable of improving the light emission efficiency. Another object of the present invention is to provide a light-emitting thin film containing a light-emitting material used for the organic electroluminescent element, and a display device and a lighting device including the organic electroluminescent element or the light-emitting thin film.

As a result of studying the cause of the above problems in order to solve the above problems, the present inventor has found that an indoloindole compound having a specific structure can be applied to an organic electroluminescence device as an effective light emitting material. It came.
That is, the said subject which concerns on this invention is solved by the following means.

（式中、Ｒ_１及びＲ_２は、各々独立に、水素原子又は置換基を表す。Ｒａ及びＲｂは、各々独立に、置換基を表す。ｐ及びｑは、各々、０から４の整数を表す。Ｒａ及びＲｂが置換基を表し、複数存在するとき、各々の置換基は同一でも異なっていてもよく、また各々の置換基同士が結合して環を形成していてもよい。また、Ｒ_１、Ｒ_２、Ｒａ及びＲｂのうち少なくとも一つは電子求引性基又は電子求引性基で置換された基を表す。）

（式中、Ｒ _５ は、置換基を表す。Ｌ _１ 及びＬ _２ は、各々、２価の連結基又は単結合を表す。Ｒａ及びＲｂは、各々、置換基を表す。ｐ及びｑは、各々、０から４の整数を表す。Ｒａ及びＲｂが置換基を表し、複数存在するとき、各々の置換基は同一でも異なっていてもよく、また各々の置換基同士が結合して環を形成していてもよい。ｎは、１から３の整数を表す。また、Ｒ _５ 、Ｌ _１ 、Ｌ _２ 、Ｒａ及びＲｂのうち少なくとも一つは電子求引性基又は電子求引性基で置換された基を表す。） 1. An organic electroluminescent device having an organic layer including a light emitting layer of at least one layer between the anode and the cathode, at least one layer of the light emitting layer is represented by the following formula (1-a) as a luminescent material Containing at least one of fluorescent compounds having a structure ;
The organic electroluminescent device, wherein the fluorescent compound has a structure represented by the following general formula (3).

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a substituent. Ra and Rb each independently represent a substituent. P and q each represents an integer of 0 to 4. Ra and Rb each represent a substituent, and when there are a plurality of substituents, each substituent may be the same or different, and each substituent may be bonded to form a ring. (At least one of R ₁ , R ₂ , Ra and Rb represents an electron withdrawing group or a group substituted with an electron withdrawing group.)

(In the formula, R ₅ represents a substituent. L ₁ and L ₂ each represent a divalent linking group or a single bond. Ra and Rb each represent a substituent. P and q are Each represents an integer of 0 to 4. When Ra and Rb represent a substituent, when there are a plurality of substituents, each substituent may be the same or different, and each substituent is bonded to form a ring. N represents an integer of 1 to 3. Further, at least one of R ₅ , L ₁ , L ₂ , Ra and Rb is substituted with an electron withdrawing group or an electron withdrawing group. Represents a group formed by

（式中、Ｒ _１ 及びＲ _２ は、各々独立に、水素原子又は置換基を表す。Ｒａ及びＲｂは、各々独立に、置換基を表す。ｐ及びｑは、各々、０から４の整数を表す。Ｒａ及びＲｂが置換基を表し、複数存在するとき、各々の置換基は同一でも異なっていてもよく、また各々の置換基同士が結合して環を形成していてもよい。また、Ｒ _１ 、Ｒ _２ 、Ｒａ及びＲｂのうち少なくとも一つは電子求引性基又は電子求引性基で置換された基を表す。） 2 . An organic electroluminescence device having an organic layer including at least one light emitting layer between an anode and a cathode, wherein at least one of the light emitting layers has the following general formula (1-a) or (1- containing at least one of the fluorescent compounds having the structure represented by b),
Wherein at least one layer of the organic layer, in addition to said fluorescent compound, organic electroluminescent device characterized by containing a host compound having a structure represented by the following general formula (I).

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a substituent. Ra and Rb each independently represent a substituent. P and q each represents an integer of 0 to 4. Ra and Rb each represent a substituent, and when there are a plurality of substituents, each substituent may be the same or different, and each substituent may be bonded to form a ring. (At least one of R ₁ , R ₂ , Ra and Rb represents an electron withdrawing group or a group substituted with an electron withdrawing group.)

(In the general formula (I), X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R _103. y ₁ to y ₈ each represent CR ₁₀₄ or a nitrogen atom. _{101 to} R ₁₀₄ each represent a hydrogen atom or a substituent, and may combine with each other to form a ring, and Ar ₁₀₁ and Ar ₁₀₂ each represent an aromatic ring, and may be the same or different. n101 and n102 is each an integer of 0 to _4, when _{R 101} is a hydrogen atom, n101 represents an integer of 1-4.)

3 . 3. The organic electroluminescence device according to item 2 , wherein the host compound having a structure represented by the general formula (I) has a structure represented by the following general formula (II).

(In the general formula (II), X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R _103. R _{101 to} R ₁₀₃ each represents a hydrogen atom or a substituent, (Ar ₁₀₁ and Ar ₁₀₂ may each represent an aromatic ring and may be the same or different, and n102 represents an integer of 0 to 4).

4). 4. The organic electroluminescence device according to any one of items 1 to 3, wherein the electron withdrawing group of the fluorescent compound is an aromatic heterocyclic group.
5 . A luminescent thin film comprising the fluorescent luminescent compound according to item 1 .

6 . The characterized in that it contains a fluorescing compound and the host compound represented by the general formula (II) according to the general formula (I) or the third term according to paragraph 2 of paragraph 1, wherein 5 The light-emitting thin film according to Item.

7 . A display device comprising the organic electroluminescence element according to any one of items 1 to 4 .

8 . A display device, wherein the light-emitting thin film according to item 5 or 6 is used.

9 . The organic electroluminescent element as described in any one of Claim 1 to 4 is provided, The illuminating device characterized by the above-mentioned.

1 0 . An illuminating device using the light-emitting thin film according to item 5 or 6 .

  By the above means of the present invention, an organic electroluminescence device capable of improving the light emission efficiency, the light emission lifetime and the stability can be provided. Moreover, the luminescent thin film containing the luminescent material used for the said organic electroluminescent element, the display apparatus provided with the organic electroluminescent element or the said luminescent thin film, and an illuminating device can be provided.

  The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

It has long been known that some organic molecules have a certain overlap between HOMO and LUMO, which correlates with the intensity of light emission (oscillator strength). However, there are many organic molecules in which HOMO and LUMO are separated.
For example, a molecule having both a donor site and an acceptor site in the molecule. In such a case, HOMO is often localized at the donor site, and LUMO is often localized at the acceptor site. In particular, when the macromolecule has a donor and acceptor site at both ends, HOMO and LUMO are located at both ends of the molecule. Will exist.
In such a case, the organic molecule is synonymous with performing its own charge during the HOMO-LUMO transition, that is, it can be said that the intramolecular charge transfer (CT) property is strong.

Such a phenomenon is noticeable when the donor property of the donor site is strong and the acceptor property of the acceptor site is strong.
Since the acceptor strength represents the electron withdrawing strength of the site, the LUMO level becomes deeper than that of a normal host compound having no electron withdrawing group.
On the other hand, arylamines and carbazoles generally known as electron donating groups are known as partial skeletons of hosts. That is, the HOMO level does not change greatly compared to a normal host compound.

In such a case, when the light-emitting compound is used in an electronic device such as an organic EL element, holes can move smoothly (hopped) via the HOMO level of the molecule, but the LUMO level is deep and trapping property is increased. Therefore, it is considered that electron hopping is prevented as compared with holes, and as a result, the charge transport property is biased.
Although indoloindole has been known for its hole transporting strength for a long time, it is not known that the HOMO level is relatively shallow compared to carbazole and diphenylamine.

The following table shows the results of structure optimization calculations using semi-empirical molecular orbital calculation methods for indoloindole, diphenylamine, and carbazole as donor sites.
The structure optimization and the calculation of electron density distribution by molecular orbital calculation of a fluorescent compound are carried out by using molecular orbital calculation software Gaussian09 using M06-2X as a functional and 6-31G (d) as a basis function. Using.

  From Table 1, it can be seen that indoloindole has a shallower HOMO level than other general electron donating groups. Therefore, it can be said that the hole injection balance is easier to match than when an electron donating group such as carbazole or diphenylamine is used. Therefore, the light emission efficiency is improved and the lifetime is increased due to the expansion of the recombination region in the light emitting layer.

Schematic diagram showing energy diagrams of normal fluorescent compounds and TADF compounds Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram of an active matrix display device Schematic showing the pixel circuit Schematic diagram of a passive matrix display device Schematic of lighting device Schematic diagram of lighting device

The organic electroluminescent device of the present invention is an organic electroluminescent device having an organic layer including at least one light emitting layer between an anode and a cathode, wherein at least one of the light emitting layers is the above general formula as a light emitting material. contains at least one of (1-a) fluorescent compound having a structure represented by, the fluorescent compound is a feature that have a structure represented by the general formula (3) To do .

In addition, in the organic electroluminescence element of the present invention, at least one layer of the organic layers has a structure represented by the general formula (1-a) or (1-b) , characterized in that it contains a host compound having a structure represented by the general formula (I). Moreover, it is preferable that the host compound which has a structure represented by the said general formula (I) has a structure represented by the said general formula (II).
In the present invention, the electron withdrawing group of the fluorescent compound is preferably an aromatic heterocyclic group.

The fluorescent compound according to the present invention, or the fluorescent compound and the host compound represented by the general formula (I) or (II) can be preferably applied to a light-emitting thin film.
Furthermore, the organic electroluminescence element and the light-emitting thin film of the present invention can be preferably applied to a display device or a lighting device.

Hereinafter, the present invention, its components, and modes 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.
Before going into this discussion, an organic EL light emitting system and a light emitting material related to the technical idea of the present invention will be described.

<Light emitting method of organic EL>
There are two types of organic EL emission methods: “phosphorescence emission” that emits light when returning from the triplet excited state to the ground state, and “fluorescence emission” that emits light when returning from the singlet excited state to the ground state. is there.
When excited by an electric field such as an organic EL, triplet excitons are generated with a probability of 75% and singlet excitons are generated with a probability of 25%. Therefore, phosphorescence is more efficient than fluorescence. This is an excellent method for realizing low power consumption.
On the other hand, in the fluorescence emission, the triplet excitons that are generated with a probability of 75% ordinarily, and the exciton energy becomes only heat due to non-radiation deactivation, are present at high density. There is a system using a TTA (triplet-triplet annealing: abbreviated as “TTF”) mechanism that generates singlet excitons from two triplet excitons to improve luminous efficiency. Has been found.

  Furthermore, in recent years, the discovery of Adachi et al. Has reduced the energy gap between the singlet excited state and the triplet excited state. Reverse intersystem crossing from the singlet excited state to the singlet excited state, and as a result, a phenomenon that enables nearly 100% fluorescence emission (also referred to as thermally excited delayed fluorescence or thermally excited delayed fluorescence: “TADF”) And a fluorescent substance that makes this possible have been found (for example, see Non-Patent Document 1).

<Phosphorescent compound>
As described above, phosphorescence is theoretically 3 times more advantageous than fluorescence in terms of light emission efficiency, but energy deactivation (= phosphorescence) from triplet excited state to singlet ground state is forbidden. Similarly, since the intersystem crossing from the singlet excited state to the triplet excited state is also a forbidden transition, the rate constant is usually small. That is, since the transition is difficult to occur, the exciton lifetime is increased from millisecond to second order, and it is difficult to obtain desired light emission.
However, when a complex using a heavy metal such as iridium or platinum emits light, the rate constant of the forbidden transition increases by three orders of magnitude or more due to the heavy atom effect of the central metal. % Phosphorescence quantum yield can be obtained.
However, in order to obtain such ideal light emission, it is necessary to use a rare metal called a white metal such as iridium, palladium, or platinum, which is a rare metal. The price of the metal itself is a major industrial issue.

<Fluorescent compound>
A general fluorescent compound is not necessarily a heavy metal complex like a phosphorescent compound, and is a so-called organic compound composed of a combination of general elements such as carbon, oxygen, nitrogen and hydrogen. In addition, other non-metallic elements such as phosphorus, sulfur, and silicon can be used, and complexes of typical metals such as aluminum and zinc can be used.
However, since only 25% of excitons can be applied to light emission as described above with conventional fluorescent compounds, high efficiency light emission such as phosphorescence emission cannot be expected.

<Delayed fluorescent compound>
[Excited triplet-triplet annihilation (TTA) delayed fluorescent compound]
In order to solve the problems of fluorescent compounds, a light emission method using delayed fluorescence has appeared. The TTA method that originates from collisions between triplet excitons can be described by the following general formula. That is, there is a merit that a part of triplet excitons, in which the energy of excitons has been converted only to heat due to non-radiation deactivation, can cross back to singlet excitons that can contribute to light emission. Even in an actual organic EL device, it is possible to obtain an external extraction quantum efficiency approximately twice that of a conventional fluorescent light emitting device.
General formula: T ^* + T ^* → S ^* + S
(In the formula, T ^* represents a triplet exciton, S ^* represents a singlet exciton, and S represents a ground state molecule.)
However, as can be seen from the above equation, since only one singlet exciton that can be used for light emission is generated from two triplet excitons, it is theoretically impossible to obtain 100% internal quantum efficiency by this method.

[Thermal activated delayed fluorescence (TADF) compound]
The TADF method, which is another highly efficient fluorescent emission, is a method that can solve the problems of TTA.
As described above, the fluorescent compound has the advantage that the molecule can be designed infinitely. That is, among the molecularly designed compounds, there is a compound in which the energy level difference between the triplet excited state and the singlet excited state (hereinafter referred to as ΔEst) is extremely close (see FIG. 1). .
Although such a compound does not have a heavy atom in the molecule, a reverse intersystem crossing from a triplet excited state to a singlet excited state, which cannot normally occur due to a small ΔEst, occurs. Furthermore, since the rate constant of deactivation from singlet excited state to ground state (= fluorescence emission) is extremely large, triplet excitons themselves are thermally deactivated to ground state (non-radiative deactivation). It is more kinetically advantageous to return to the ground state while emitting fluorescence via the singlet excited state. Therefore, TADF can ideally emit 100% fluorescence.

<Molecular design concept for ΔEst>
The molecular design for reducing the ΔEst will be described.
In order to reduce ΔEst, in principle, it is most effective to reduce the spatial overlap between the highest occupied orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in the molecule. It is.
In general, it is known that HOMO is distributed in electron donating sites and LUMO is distributed in electron withdrawing sites in the electron orbit of the molecule. By introducing an electron donating and electron withdrawing skeleton into the molecule, HOMO is distributed. It is possible to move away the position where LUMO exists.

For example, in Non-Patent Document 1 described above, by introducing an electron-withdrawing skeleton such as a cyano group, a sulfonyl group, or a triazine and an electron-donating skeleton such as a carbazole or a diphenylamino group, LUMO and HOMO Are localized.
It is also effective to reduce the change in molecular structure between the ground state and triplet excited state of the compound. As a method for reducing the structural change, for example, making the compound rigid is effective. Rigidity described here means that there are few sites that can move freely in the molecule, for example, by suppressing free rotation in the bond between rings in the molecule or by introducing a condensed ring with a large π conjugate plane. means. In particular, it is possible to reduce the structural change in the excited state by making the portion involved in light emission rigid.

<General problems with TADF compounds>
TADF compounds have various problems in terms of their light emission mechanism and molecular structure.
The following describes some of the problems generally associated with TADF compounds.
In the TADF compound, it is necessary to separate the HOMO and LUMO sites as much as possible in order to reduce ΔEst. Therefore, the electronic state of the molecule is a donor / acceptor type molecule in which the HOMO and LUMO sites are separated. It becomes a state close to the inner CT (intramolecular charge transfer state).

  When a plurality of such molecules are present, stabilization is achieved by bringing the donor part of one molecule and the acceptor part of the other molecule close to each other. Such a stabilization state is not limited to the formation between two molecules, but can also be formed between a plurality of molecules, such as between three or five molecules, resulting in various stable distributions with a wide distribution. Therefore, the shape of the absorption spectrum and the emission spectrum is broad. In addition, even when a multimolecular assembly exceeding two molecules is not formed, various existence states can be taken depending on the direction and angle of interaction between the two molecules. The shape of the emission spectrum becomes broad.

The broad emission spectrum creates two major problems.
One problem is that the color purity of the emitted color is lowered. This is not a big problem when applied to lighting applications, but when used for electronic displays, the color gamut is small and the color reproducibility of pure colors is low. It becomes difficult.

Another problem is the rising wavelength on the short wavelength side of the emission spectrum ( "fluorescence Zero - Zero Band". Referred to as) of shorter wavelength, that is, high S ₁ (higher energy of the lowest excited singlet energy) It is to end.
Naturally, when the fluorescence zero-zero band is shortened, the phosphorescence zero-zero band derived from T ₁ having lower energy than S ₁ is also shortened (higher T ₁ ). Therefore, the compound used in the host compound in order not to cause reverse energy transfer from the dopant, arises the need to ₁ reduction and high T ₁ of high S.
This is a very big problem. A host compound consisting essentially of an organic compound takes a plurality of active and unstable chemical species such as a cation radical state, an anion radical state, and an excited state in an organic EL device. By expanding the π-conjugated system, it can exist relatively stably.

However, in order to achieve high S ₁ and high T ₁ , it is necessary to reduce or cut off the π-conjugated system in the molecule, which makes it difficult to achieve both stability and as a result. The life of the light emitting element is shortened.
In addition, in a TADF compound that does not contain a heavy metal, a transition that is deactivated from a triplet excited state to a ground state is a forbidden transition, and therefore the existence time (exciton lifetime) in the triplet excited state is from several hundred microseconds to millisecond. It is very long with second order. Therefore, even if the T ₁ energy of the host compound is higher than that of the fluorescent compound, the reverse energy from the triplet excited state of the fluorescent compound to the host compound is determined from the length of the existence time. The probability of causing movement increases. As a result, the reverse reverse energy transfer from the triplet excited state to the singlet excited state of the originally intended TADF compound does not occur sufficiently, and unfavorable reverse energy transfer to the host compound becomes the mainstream, resulting in sufficient luminous efficiency. Inconvenience that cannot be obtained.

In order to solve the above problems, it is necessary to sharpen the emission spectrum shape of the TADF compound and reduce the difference between the emission maximum wavelength and the rising wavelength of the emission spectrum. This can be basically achieved by reducing the change in the molecular structure of the singlet excited state and the triplet excited state.
In order to suppress reverse energy transfer to the host compound, it is effective to shorten the existence time (exciton lifetime) of the triplet excited state of the TADF compound. To achieve this, it is necessary to take measures such as reducing the molecular structure change between the ground state and the triplet excited state and introducing suitable substituents and elements to undo the forbidden transition. Can be solved.

The present invention includes, as a design concept, a fluorescent compound that suppresses the structural change of the excited state as described above and a fluorescent compound that has a short triplet excited state.
Hereinafter, various measurement methods relating to the fluorescent compound according to the present invention will be described.

[Electron density distribution]
In the fluorescent compound according to the present invention, it is preferable that HOMO and LUMO are substantially separated in the molecule from the viewpoint of reducing ΔEst. The distribution states of these HOMO and LUMO can be obtained from the electron density distribution when the structure is optimized obtained by semi-empirical molecular orbital calculation.
In the present invention, structure optimization and electron density distribution calculation by semi-empirical molecular orbital calculation of a fluorescent compound in the present invention are performed using molecular orbital calculation using B3LYP as a functional and 6-31G (d) as a basis function. There is no particular limitation on the software, and any of them can be similarly calculated.
In the present invention, Gaussian 09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian, USA was used as molecular orbital calculation software.

Further, “HOMO and LUMO are substantially separated” means that the HOMO orbital distribution calculated by the above molecular calculation and the central part of the LUMO orbital distribution are separated, more preferably the HOMO orbital distribution and the LUMO orbital. This means that the distributions of do not overlap.
As for the separation state of HOMO and LUMO, from the above-described structure optimization calculation using B3LYP as the functional and 6-31G (d) as the basis function, the time-dependent density functional method (Time-Dependent DFT) is used. It is also possible to calculate the energy of S ₁ and T ₁ (respectively E (S ₁ ) and E (T ₁ )) by calculating the excited state and calculate ΔEst = E (S ₁ ) −E (T ₁ ). It is. As the calculated ΔEst is smaller, HOMO and LUMO are more separated. In the present invention, ΔEst calculated using the same calculation method as described above is preferably 0.5 eV or less, more preferably 0.2 eV or less, and further preferably 0.1 eV or less.

[Minimum excitation singlet energy S ₁ ]
The lowest excited singlet energy S ₁ of the fluorescent compound in the present invention is defined in the present invention as calculated in the same manner as in a normal method. That is, a sample to be measured is deposited on a quartz substrate to prepare a sample, and the absorption spectrum (vertical axis: absorbance, horizontal axis: wavelength) of this sample is measured at room temperature (300 K). A tangent line is drawn with respect to the rising edge of the absorption spectrum on the long wavelength side, and is calculated from a predetermined conversion formula based on the wavelength value at the intersection of the tangent line and the horizontal axis.
However, when the aggregation property of the molecule of the fluorescent compound used in the present invention is relatively high, an error due to aggregation may occur in the measurement of the thin film. In consideration of the fact that the fluorescent compound in the present invention has a relatively small Stokes shift and that the structural change between the excited state and the ground state is small, the lowest excited singlet energy S ₁ in the present invention is at room temperature (25 ° C.). The peak value of the maximum emission wavelength in the solution state of the fluorescent compound was used as an approximate value.
Here, as the solvent to be used, a solvent that does not affect the aggregation state of the fluorescent compound, that is, a solvent having a small influence of the solvent effect, for example, a nonpolar solvent such as cyclohexane or toluene can be used.

[Minimum excitation triplet energy T ₁ ]
The lowest excited triplet energy (T ₁ ) of the fluorescent compound in the present invention was calculated from the photoluminescence (PL) characteristics of the solution or thin film. For example, as a calculation method in a thin film, after making a dispersion of a fluorescent fluorescent compound in a dilute state into a thin film, by using a streak camera and measuring transient PL characteristics, the fluorescent component and the phosphorescent component are separated, The lowest excited triplet energy can be obtained from the lowest excited singlet energy with the energy difference as ΔEst.
In measurement / evaluation, an absolute PL quantum yield measurement apparatus C9920-02 (manufactured by Hamamatsu Photonics) was used for measurement of the absolute PL quantum yield. The light emission lifetime was measured using a streak camera C4334 (manufactured by Hamamatsu Photonics) while exciting the sample with laser light.

<< Constituent layers of organic EL elements >>
As typical element structures in the organic EL element of the present invention, the following structures can be exemplified, but the invention is not limited thereto.
(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 layer /) electron transport layer / electron injection layer / cathode Among the above, the configuration of (7) is Although used preferably, it is not limited to this.
The light emitting layer used in the present invention is composed of a single layer or a plurality of layers. When there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the light emitting layers.

If necessary, a hole blocking layer (also referred to as a hole blocking layer) or an electron injection layer (also referred to as a cathode buffer layer) may be provided between the light emitting layer and the cathode. An electron blocking layer (also referred to as an electron barrier layer) or a hole injection layer (also referred to as an anode buffer layer) may be provided therebetween.
The electron transport layer used in the present invention is a layer having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. Moreover, you may be comprised by multiple layers.
The hole transport layer used in the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. Moreover, you may be comprised by multiple layers.
In the above-described typical element configuration, the layer excluding the anode and the cathode is also referred to as “organic layer”.

(Tandem structure)
The organic EL element of the present invention may be a so-called tandem element in which a plurality of light emitting units including at least one light emitting layer are stacked.
As typical element configurations of the tandem structure, for example, the following configurations can be given.
Anode / first light emitting unit / intermediate layer / second light emitting unit / intermediate layer / third light emitting unit / cathode Here, the first light emitting unit, the second light emitting unit and the third light emitting unit are all the same, May be different. Two light emitting units may be the same, and the remaining one may be different.
A plurality of light emitting units may be laminated directly or via an intermediate layer, and the intermediate layer is generally an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, an intermediate layer. A known material structure can be used as long as it is also called an insulating layer and has a function of supplying electrons to the anode-side adjacent layer and holes to the cathode-side adjacent layer.

Examples of materials used for the intermediate layer include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiO _x , VO _x , CuI, InN, GaN, Conductive inorganic compound layers such as CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ and Al, two-layer films such as Au / Bi ₂ O ₃ , SnO ₂ / Ag / SnO ₂ , ZnO / Multi-layer film such as Ag / ZnO, Bi ₂ O ₃ / Au / Bi ₂ O ₃ , TiO ₂ / TiN / TiO ₂ , TiO ₂ / ZrN / TiO ₂ , fullerenes such as C ₆₀ , conductivity such as oligothiophene Examples include organic material layers, conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, and metal-free porphyrins. The present invention is not limited thereto.
As a preferable configuration in the light emitting unit, for example, a configuration in which the anode and the cathode are excluded from the configurations (1) to (7) described in the above-described typical element configurations, and the like is described. It is not limited.

  Specific examples of the tandem organic EL element include, for example, US Pat. No. 6,337,492, US Pat. No. 7,420,203, US Pat. No. 7,473,923, US Pat. No. 6,872,472, US Pat. No. 6,107,734, US Pat. No. 6,337,492, International JP 2005/009087, JP 2006-228712, JP 2006-24791, JP 2006-49393, JP 2006-49394, JP 2006-49396, JP 2011. No. -96679, JP 2005-340187, JP 47114424, JP 34096681, JP 3884564, JP 431169, JP 2010-192719, JP 2009-076929, JP Open 2008-0784 No. 4, JP 2007-059848 A, JP 2003-272860 A, JP 2003-045676 A, International Publication No. 2005/094130, and the like. The present invention is not limited to these.

  Hereinafter, each layer which comprises the organic EL element of this invention is demonstrated.

<Light emitting layer>
The light-emitting layer used in the present invention is a layer that provides a field in which electrons and holes injected from an electrode or an adjacent layer are recombined to emit light via excitons, and the light-emitting portion is the light-emitting layer. Even in the layer, it may be the interface between the light emitting layer and the adjacent layer. If the light emitting layer used for this invention satisfy | fills the requirements prescribed | regulated by this invention, there will be no restriction | limiting in particular in the structure.
The total thickness of the light emitting layer is not particularly limited, but it prevents the uniformity of the film to be formed, the application of unnecessary high voltage during light emission, and the improvement of the stability of the emission color against the drive current. From a viewpoint, it is preferable to adjust to the range of 2 nm-5 micrometers, More preferably, it adjusts to the range of 2-500 nm, More preferably, it adjusts to the range of 5-200 nm.
Further, the thickness of each light emitting layer used in the present invention is preferably adjusted to a range of 2 nm to 1 μm, more preferably adjusted to a range of 2 to 200 nm, and further preferably in a range of 3 to 150 nm. Adjusted.
The light-emitting layer used in the present invention contains a light-emitting dopant (a light-emitting compound, a light-emitting dopant compound, a dopant compound, also simply referred to as a dopant), and further, the above-described host compound (matrix material, light-emitting host compound, simply host). It is also preferable to contain.

(1) Luminescent dopant As the luminescent dopant, a fluorescent luminescent dopant (also referred to as a fluorescent luminescent compound, a fluorescent dopant, or a fluorescent compound) and a phosphorescent dopant (phosphorescent compound, phosphorescent dopant, phosphorescence). It is also referred to as a functional compound). In the present invention, at least one light emitting layer contains the above-described fluorescent compound.
In this invention, it is preferable that a light emitting layer contains a fluorescent compound in the range of 5-40 mass%, and contains in the range of 10-30 mass% especially.
The concentration of the fluorescent compound in the light emitting layer can be arbitrarily determined based on the specific fluorescent compound used and the requirements of the device, and is uniform in the thickness direction of the light emitting layer. It may be contained in a concentration and may have any concentration distribution.
In addition, the fluorescent compound according to the present invention may be used in combination of two or more kinds, a combination of fluorescent compounds having different structures, or a combination of a fluorescent compound and a phosphorescent compound. May be. Thereby, arbitrary luminescent colors can be obtained.

The light emission color of the organic EL device of the present invention and the compound used in the present invention is shown in FIG. It is determined by the color when the result measured with the luminance meter CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.
In the present invention, it is also preferable that the light emitting layer of one layer or a plurality of layers contains a plurality of light emitting dopants having different emission colors and emits white light.
There are no particular limitations on the combination of the light-emitting dopants that exhibit white, and examples include blue and orange, and a combination of blue, green, and red.
The white color in the organic EL device of the present invention means that the chromaticity in the CIE 1931 color system at 1000 cd / m ² is x = 0.39 ± 0.09 when the 2 ° viewing angle front luminance is measured by the method described above. Y = 0.38 ± 0.08.

(1.1) Fluorescent compound As a luminescent material according to the present invention, at least one of fluorescent compounds having a structure represented by the following general formula (1-a) or (1-b) is contained. It is characterized by that.

In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a substituent. Ra and Rb each independently represent a substituent. p and q each represents an integer of 0 to 4. When Ra and Rb represent a substituent and a plurality thereof are present, each substituent may be the same or different, and each substituent may be bonded to form a ring. Further, at least one of R ₁ , R ₂ , Ra and Rb represents an electron withdrawing group or a group substituted with an electron withdrawing group.

When R ₁ , R ₂ , Ra and Rb represent a substituent, examples of the substituent include an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, Octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl) Group, propargyl group, etc.), aromatic hydrocarbon group (aromatic hydrocarbon ring group, aromatic carbocyclic group, aryl group, etc.), for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group , Naphthyl, anthryl, azulenyl, acenaphthenyl, fluorenyl, phenanthryl, in Denyl group, pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group (for example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1, 2,4-triazol-1-yl group, 1,2,3-triazol-1-yl group, etc.), oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, thienyl group, A quinolyl group, a benzofuryl group, a dibenzofuryl group, a benzothienyl group, a dibenzothienyl group, an indolyl group, a carbazolyl group, a carbolinyl group, a diazacarbazolyl group (one of the carbon atoms constituting the carboline ring of the carbolinyl group is a nitrogen atom ), Quinoxalinyl group, Ridazinyl group, triazinyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy group, pentyl) Oxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (Eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group ( For example, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, Phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group) , Dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, aceto Til group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group ( For example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonyl) Amino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcal Nylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexyl) Aminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido) Group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyri Sulfinyl group (eg, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group) Group), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (for example, phenyl) Sulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, diphenylamine) Mino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (for example, fluorine atom, chlorine atom, bromine atom, etc.) , Fluorinated hydrocarbon group (for example, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, Triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.), phosphono group and the like. Preferably, an alkyl group, an aromatic hydrocarbon group, an aromatic heterocyclic group, an alkoxy group, an amino group, and a cyano group are exemplified.

  Furthermore, indole ring, indazole ring, benzothiazole ring, benzoxazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, isoindole ring, naphthyridine ring, phthalazine ring, carbazole ring, carboline ring, diaza Substituents such as a carbazole ring (in which one of the carbon atoms constituting the carboline ring is replaced by a nitrogen atom), acridine ring, phenanthridine ring, phenanthroline ring, phenazine ring, azadibenzofuran ring, azadibenzothiophene ring Can also be suitably used. These substituents can also be suitably used as electron withdrawing groups.

  Moreover, these substituents may be further substituted with the above substituents. Further, these substituents may be bonded together to form a ring.

  Moreover, it is preferable that the fluorescent compound according to the present invention has a structure represented by the following general formula (2-a) or (2-b).

In the formula, R ₃ and R ₄ each independently represent a hydrogen atom or a substituent. k and m each represents an integer of 1 to 5. When R ₃ and R ₄ represent a substituent and a plurality thereof are present, each substituent may be the same or different, and each substituent may be bonded to form a ring. L ₁ and L ₂ each represent a divalent to hexavalent linking group or a single bond. Ra and Rb each represents a substituent. p and q each represents an integer of 0 to 4. When Ra and Rb represent a substituent and a plurality thereof are present, each substituent may be the same or different, and each substituent may be bonded to form a ring. Further, at least one of R ₃ , R ₄ , Ra and Rb represents an electron withdrawing group or a group substituted with an electron withdrawing group.

When R ₃ , R ₄ , Ra and Rb represent a substituent, the substituents represented by the general formulas (1-a) and (1-b) can be similarly used as the substituent.
When L ₁ and L ₂ represent a linking group, a hydrocarbon group, an aromatic hydrocarbon group, an aromatic heterocyclic group, or the like can be preferably used. These linking groups may be further substituted with the above substituents.
In addition, these substituents and linking groups may be further substituted with the above substituents. Further, these substituents may be bonded together to form a ring.

  Further, the fluorescent compound having the structure represented by the general formula (2-a) or (2-b) has a structure represented by the following general formula (2-a ′) or (2-b ′). It is also preferable to have it.

In the formula, R ₃ ′ represents a divalent or trivalent group. R ₄ represents a hydrogen atom or a substituent. m represents an integer of 1 to 5. When R ₄ represents a substituent and a plurality of substituents are present, each substituent may be the same or different, and each substituent may be bonded to form a ring. L ₁ represents a divalent linking group or a single bond. L ₂ represents a divalent to hexavalent linking group or a single bond. Ra and Rb each represents a substituent. p and q each represents an integer of 0 to 4. When Ra and Rb represent a substituent and a plurality thereof are present, each substituent may be the same or different, and each substituent may be bonded to form a ring. t represents an integer of 2 or 3. At least one of R ₃ ′, R ₄ , Ra and Rb represents an electron withdrawing group or a group substituted with an electron withdrawing group.

The fluorescent compound represented by the general formula (2-a ′) or (2-b ′) is a fluorescent compound having a structure represented by the general formula (2-a) or (2-b). Of these, R ₃ represents a repeating structure.
In the general formula (2-a ′) or (2-b ′), when R ₄ , Ra and Rb represent a substituent, the substituents represented by the general formulas (1-a) and (1-b) Can be used as well.
When R ₃ ′ represents a divalent or trivalent group, a hydrocarbon group, an aromatic hydrocarbon group, an aromatic heterocyclic group, or the like can be preferably used. These groups may be further substituted with the above substituents.
In the case R 3 _'is representative of a divalent or trivalent group, which is an example of formula (2-a) and fluorescent compound having a structure represented by (2-b). Regarding the general formulas (2-a) and (2-b), a fluorescent compound having a structure in which Ra or Rb is Ra ′ or Rb ′ representing a divalent or trivalent group is also included. As the substituents represented by Ra ′ and Rb ′, the same substituents as represented by R ₃ ′ can be used.

  Moreover, it is also preferable that the fluorescent compound according to the present invention has a structure represented by the following general formula (3).

In the formula, R ₅ represents a substituent. L ₁ and L ₂ each represent a divalent linking group or a single bond. Ra and Rb each represents a substituent. p and q each represents an integer of 0 to 4. When Ra and Rb represent a substituent and a plurality thereof are present, each substituent may be the same or different, and each substituent may be bonded to form a ring. n represents an integer of 1 to 3. In addition, at least one of R ₅ , L ₁ , L ₂ , Ra and Rb represents an electron withdrawing group or a group substituted with an electron withdrawing group.

In the general formula (3), when R ₅ , Ra and Rb represent a substituent, the substituents represented by the general formulas (1-a) and (1-b) may be used in the same manner. it can.
Moreover, these substituents may be further substituted with the above substituents. Further, these substituents may be bonded together to form a ring.

  The general formulas (1-a), (1-b), (2-a), (2-b), (2-a ′), (2-b ′) and (3) preferably used in the present invention are as follows. ) Is taken as an example, but the present invention is not limited to this.

  By using these compounds, as described above, indoloindole has a relatively shallow HOMO level as compared with carbazole and diphenylamine, so that it is considered that intramolecular charge transfer is likely to occur. Furthermore, since it has higher electron donating property than a commonly used carbazole derivative, it is considered to promote intramolecular charge transfer.

<Synthesis method>
The fluorescent compound is, for example, a method described in International Publication No. 2011/055933, International Publication No. 2011/132866 and International Publication No. 2012/035853, or a reference described in these references. It can be synthesized by referring to the method.

(1.2) Phosphorescent dopant The phosphorescent dopant used in the present invention will be described.
The phosphorescent dopant used in the present invention is a compound in which light emission from an excited triplet is observed, specifically, a compound that emits phosphorescence at room temperature (25 ° C.), and a phosphorescence quantum yield. Is defined as a compound of 0.01 or more at 25 ° C., but a preferable phosphorescence quantum 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 dopant used in the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. Just do it.

The phosphorescent dopant can be appropriately selected from known materials used for the light emitting layer of the organic EL device. Specific examples of known phosphorescent dopants that can be used in the present invention include compounds described in the following documents.
Nature 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19, 739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17, 1059 (2005), International Publication No. 2009/100991, International Publication No. 2008/101842, International Publication No. 2003/040257, US Patent Application Publication No. 2006/835469, US Patent Application Publication No. 2006 /. No. 0202194, U.S. Patent Application Publication No. 2007/0087321, U.S. Patent Application Publication No. 2005/0244673, Inorg. Chem. 40, 1704 (2001), Chem. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chem. lnt. Ed. 2006, 45, 7800, Appl. Phys. Lett. 86, 153505 (2005), Chem. Lett. 34, 592 (2005), Chem. Commun. 2906 (2005), Inorg. Chem. 42, 1248 (2003), International Publication No. 2009/050290, International Publication No. 2002/015645, International Publication No. 2009/000673, US Patent Application Publication No. 2002/0034656, US Pat. No. 7,332,232, US Patent Application Publication No. 2009/0108737, United States Patent Application Publication No. 2009/0039776, United States Patent No. 6921915, United States Patent No. 6,687,266, United States Patent Application Publication No. 2007/0190359, United States Patent Application Publication No. 2006/0008670, United States Patent Application Publication No. 2009/0165846, United States Patent Application Publication No. 2008/0015355, United States Patent No. 7250226, United States Patent No. 7396598, United States Patent Application Publication No. 200 / 0263635 Pat, U.S. Patent Application Publication No. 2003/0138657, U.S. Patent Application Publication No. 2003/0152802, U.S. Patent No. 7090928, Angew. Chem. lnt. Ed. 47, 1 (2008), Chem. Mater. 18, 5119 (2006), Inorg. Chem. 46, 4308 (2007), Organometallics 23, 3745 (2004), Appl. Phys. Lett. 74, 1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/009024, International Publication No. 2006/056418, International Publication No. 2005/019373, International Publication No. 2005/123873, International Publication No. 2005/123873, International Publication No. 2007/004380, International Publication No. 2006/082742, US Patent Application Publication No. 2006/0251923, US Patent Application Publication No. 2005/0260441, US Pat. No. 7,393,599. , US Pat. No. 7,534,505, US Pat. No. 7,445,855, US Patent Application Publication No. 2007/0190359, US Patent Application Publication No. 2008/0297033, US Pat. No. 7,338,722, US Patent Application Publication No. 2002 / No. 134984, U.S. Pat. No. 7,279,704, U.S. Patent Application Publication No. 2006/098120, U.S. Patent Application Publication No. 2006/103874, International Publication No. 2005/076380, International Publication No. 2010/032663 International Publication No. 2008140115, International Publication No. 2007/052431, International Publication No. 2011/134013, International Publication No. 2011/157339, International Publication No. 2010/086089, International Publication No. 2009/113646, International Publication No. 2012/020327, International Publication No. 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149, US Patent Application Publication No. 2012/228583, US Patent Application Publication No. 2012/21211. No. 26, JP 2012-069737 A, Japanese Patent Application No. 2011-181303, JP 2009-114086, JP 2003-81988, JP 2002-302671, JP 2002-363552. No. gazette.
Among these, a preferable phosphorescent dopant includes an organometallic complex having Ir as a central metal. More preferably, a complex containing at least one coordination mode of a metal-carbon bond, a metal-nitrogen bond, a metal-oxygen bond, or a metal-sulfur bond is preferable.

(2) Host compound The host compound used in the present invention is a compound mainly responsible for charge injection and transport in the light emitting layer, and its own light emission is not substantially observed in the organic EL device.
The host compound preferably has a mass ratio in the layer of 20% or more among the compounds contained in the light emitting layer.
A host compound may be used independently or may be used in combination of multiple types. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient.
The host compound that is preferably used in the present invention will be described below.

The host compound used together with the fluorescent compound in the present invention is not particularly limited, but from the viewpoint of reverse energy transfer, those having an excitation energy larger than the excitation singlet energy of the fluorescent compound according to the present invention are preferable. Further, those having an excitation triplet energy larger than the excitation triplet energy of the fluorescent compound according to the present invention are more preferable.
The host compound is responsible for carrier transport and exciton generation in the light emitting layer. Therefore, it can exist stably in all active species states such as cation radical state, anion radical state, and excited state, and does not cause chemical changes such as decomposition and addition reaction. It is preferable not to move at the angstrom level.

In particular, when the light-emitting dopant used in combination exhibits TADF light emission, since the existence time of the triplet excited state of the TADF compound is long, the T ₁ energy of the host compound itself is high, and the host compounds are associated with each other. in prevention of generation of a low T ₁ state, that the TADF compound and the host compound does not form a exciplex, such that the host compound does not form a electro-mer by the electric field, the host compound is a molecular structure such as not to lower T ₁ of Appropriate design is required.
In order to satisfy these requirements, the host compound itself must have high electron hopping mobility, high hole hopping movement, and small structural change when it is in a triplet excited state. It is. Representative examples of host compounds that satisfy these requirements include high π-energy conjugated skeletons having high T ₁ energy such as carbazole skeleton, azacarbazole skeleton, dibenzofuran skeleton, dibenzothiophene skeleton, or azadibenzofuran skeleton. What has as a partial structure is mentioned preferably. In particular, when the light-emitting layer contains a carbazole derivative, it is possible to promote appropriate carrier hopping and dispersion of the light-emitting material in the light-emitting layer, and the effect of improving the light-emitting performance of the device and the stability of the thin film can be obtained. Therefore, it is preferable.

Further, representative examples include compounds in which these rings have a biaryl and / or multiaryl structure. As used herein, “aryl” includes not only an aromatic hydrocarbon ring but also an aromatic heterocyclic ring.
More preferably, it is a compound in which a carbazole skeleton and a 14π-electron aromatic heterocyclic compound having a molecular structure different from that of the carbazole skeleton are directly bonded, and further a 14π-electron aromatic heterocyclic compound is incorporated in the molecule. A carbazole derivative having at least one is preferred. In particular, the carbazole derivative is preferably a compound having two or more conjugated structures having 14π electrons or more in order to further enhance the effects of the present invention.

Moreover, as a host compound used for this invention, the compound represented by the following general formula (I) is also preferable. This is because the compound represented by the following general formula (I) has a condensed ring structure, and therefore a π electron cloud spreads, the carrier transportability is high, and the glass transition temperature (Tg) is high. Further, generally, the condensed aromatic ring tends to have a small triplet energy (T ₁ ), but the compound represented by the general formula (I) has a high T ₁ and has a short emission wavelength (that is, T _1). and larger S ₁₎ it can be suitably used also for the light emitting material.

In the general formula (I), X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R ₁₀₃ . y _{1 to} y ₈ each represents CR ₁₀₄ or a nitrogen atom.
R _{101 to} R ₁₀₄ each represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring.
Ar ₁₀₁ and Ar ₁₀₂ each represent an aromatic ring and may be the same or different.
n101 and n102 are each an integer of 0 to _4, when _{R 101} is a hydrogen atom, n101 represents an integer of 1-4.
R _{101 to} R ₁₀₄ in the general formula (I) represent hydrogen or a substituent, and the substituent referred to here refers to what may be contained within a range not inhibiting the function of the host compound used in the present invention, for example, In the case where a substituent is introduced in the synthetic scheme, the compound having the effect of the present invention is defined as being included in the present invention.

Examples of the substituent represented by each of R _{101 to} R ₁₀₄ include a linear or branched alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group). Group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring group (aromatic Also called carbocyclic group, aryl group, etc. For example, benzene ring, biphenyl, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysene ring, naphthacene ring, triphenylene ring, o-terphenyl ring, m- Terphenyl ring, p-terphenyl ring, acenaphthene ring, coronene ring, indene ring, fluorene ring A group derived from a fluoranthrene ring, a naphthacene ring, a pentacene ring, a perylene ring, a pentaphen ring, a picene ring, a pyrene ring, a pyrantolen ring, an anthraanthrene ring, tetralin, etc.), an aromatic heterocyclic group (for example, a furan ring) , Dibenzofuran ring, thiophene ring, dibenzothiophene ring, oxazole ring, pyrrole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, benzimidazole ring, oxadiazole ring, triazole ring, imidazole ring, pyrazole ring, Thiazole ring, indole ring, indazole ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, cinnoline ring, quinoline ring, isoquinoline ring, phthalazine ring, naphthyridine ring, carbazole ring, Borin ring, diazacarbazole ring (group derived from a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is further substituted with a nitrogen atom, etc. In addition, combining the carboline ring and the diazacarbazole ring Sometimes referred to as “azacarbazole ring”), non-aromatic hydrocarbon ring group (eg, cyclopentyl group, cyclohexyl group, etc.), non-aromatic heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl) Group), alkoxy group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (for example, cyclopentyloxy group, cyclohexyloxy group) Etc.), aryloxy group (for example, phenoxy group, naphthyloxy group) Etc.), alkylthio groups (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio groups (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio groups ( For example, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, Phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group) Group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group) Group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group) Ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), Mido group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group) Group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylamino) Carbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl Rubonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylamino group) Ureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc. ), Alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl) , Dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (eg, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (eg, amino group, ethylamino group, dimethylamino group, Butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom), fluoride Hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, thiol group, silyl group (eg, trimethylsilyl group, triisopropylsilyl group) Group, trifeni Silyl group, a phenyl diethyl silyl group and the like), or the like deuterium atom.

These substituents may be further substituted with the above substituents. In addition, a plurality of these substituents may be bonded to each other to form a ring.
As y _{1 to} y ₈ in the general formula (I), preferably at least three of y _{1 to} y ₄ or at least three of y _{5 to} y ₈ are represented by CR ₁₀₂ , more preferably y _{1 to} y ₈ are all CR ₁₀₂ . Such a skeleton is excellent in hole transport property or electron transport property, and can efficiently recombine and emit holes / electrons injected from the anode / cathode in the light emitting layer.
Among them, a compound in which X ₁₀₁ is NR ′, an oxygen atom, or a sulfur atom in general formula (I) is preferable as a structure having a low LUMO energy level and excellent electron transport properties. More preferably, the condensed ring formed with X ₁₀₁ and y _{1 to} y ₈ is a carbazole ring, an azacarbazole ring, a dibenzofuran ring or an azadibenzofuran ring.

Further, considering that it is preferable to make the host compound rigid, when X ₁₀₁ is NR ₁₀₁ , R ₁₀₁ is an aromatic hydrocarbon ring which is a π-conjugated skeleton among the substituents mentioned above. It is preferably a group or an aromatic heterocyclic group. Further, these R ₁₀₁ may be further substituted with a substituent represented by the aforementioned R _{101 to} R ₁₀₄ .
In the general formula (I), examples of the aromatic ring represented by Ar ₁₀₁ and Ar ₁₀₂ include an aromatic hydrocarbon ring and an aromatic heterocyclic ring. The aromatic ring may be a single ring or a condensed ring, and may be unsubstituted or may have a substituent similar to the substituents represented by R _{101 to} R ₁₀₄ described above.
In the general formula (I), examples of the aromatic hydrocarbon ring represented by Ar ₁₀₁ and Ar ₁₀₂ include the aromatic hydrocarbon rings exemplified as the substituents represented by the aforementioned R _{101 to} R _104. Examples include the same ring as the group.

In the partial structure represented by the general formula (I), examples of the aromatic heterocycle represented by Ar ₁₀₁ and Ar ₁₀₂ include the substituents represented by R _{101 to} R ₁₀₄ described above. The same ring as an aromatic heterocyclic group is mentioned.
In view of the purpose that the host compound represented by the general formula (I) has a large T ₁ , the aromatic ring itself represented by Ar ₁₀₁ and Ar ₁₀₂ preferably has a high T ₁ , and the benzene ring (Including polyphenylene skeletons (biphenyl, terphenyl, quarterphenyl, etc.) with multiple benzene rings), fluorene ring, triphenylene ring, carbazole ring, azacarbazole ring, dibenzofuran ring, azadibenzofuran ring, dibenzothiophene ring, dibenzothiophene ring A pyridine ring, a pyrazine ring, an indoloindole ring, an indole ring, a benzofuran ring, a benzothiophene ring, an imidazole ring or a triazine ring is preferable. More preferred are a benzene ring, a carbazole ring, an azacarbazole ring and a dibenzofuran ring.
When Ar ₁₀₁ and Ar ₁₀₂ are a carbazole ring or an azacarbazole ring, it is more preferable that they are bonded at the N-position (or 9-position) or the 3-position.
When Ar ₁₀₁ and Ar ₁₀₂ are dibenzofuran rings, they are more preferably bonded at the 2-position or 4-position.
In addition to the above purpose, when considering the use of an organic EL element mounted in a vehicle, the environment temperature in the vehicle is assumed to be high, so the Tg of the host compound is high. Is also preferable. Therefore, for the purpose of increasing the Tg of the host compound represented by the general formula (I), each of the aromatic rings represented by Ar ₁ and Ar ₂ is preferably a condensed ring of 3 or more rings. .

Specific examples of the aromatic hydrocarbon condensed ring in which three or more rings are condensed include naphthacene ring, anthracene ring, tetracene ring, pentacene ring, hexacene ring, phenanthrene ring, pyrene ring, benzopyrene ring, benzoazulene ring, chrysene ring , Benzochrysene ring, acenaphthene ring, acenaphthylene ring, triphenylene ring, coronene ring, benzocoronene ring, hexabenzocoronene ring, fluorene ring, benzofluorene ring, fluoranthene ring, perylene ring, naphthoperylene ring, pentabenzoperylene ring, benzoperylene ring, pentaphen A ring, a picene ring, a pyranthrene ring, a coronene ring, a naphtho- coronene ring, an ovalen ring, an anthraanthrene ring, and the like. In addition, these rings may further have the above substituent.
Specific examples of the aromatic heterocycle condensed with three or more rings include an acridine ring, a benzoquinoline ring, a carbazole ring, a carboline ring, a phenazine ring, a phenanthridine ring, a phenanthroline ring, a carboline ring, a cyclazine ring, Kindin ring, tepenidine ring, quinindrin ring, triphenodithiazine ring, triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, diazacarbazole ring (any one of the carbon atoms constituting the carboline ring is a nitrogen atom Phenanthroline ring, dibenzofuran ring, dibenzothiophene ring, naphthofuran ring, naphthothiophene ring, benzodifuran ring, benzodithiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring, A Tiger thiophene ring, anthradithiophene ring, thianthrene ring, phenoxathiin ring, such as thio fan Tren ring (naphthaldehyde thiophene ring), and the like. In addition, these rings may further have a substituent.

In general formula (I), n101 and n102 are each preferably an integer of 0 to 2, and more preferably n101 + n102 is an integer of 1 to 3. _Furthermore, since _{the R 101} is the n101 and n102 when the hydrogen atom is 0 at the same time, the general formula (I) only a low Tg small molecular weight of the host compounds represented by not _achievable, when _{R 101} is a hydrogen atom N101 represents an integer of 1 to 4.

  As the host compound used in the present invention, the host compound having a structure represented by the general formula (I) is preferably a compound having a structure represented by the general formula (II). This is because such a compound tends to have particularly excellent carrier transportability.

In formula _{(II), X 101, Ar} 101, Ar 102, n102 have the same meanings as _{X 101, Ar 101, Ar 102} , n102 in the formula (I).
n102 is preferably an integer of 0 to 2, more preferably 0 or 1.
In the general formula (II), the condensed ring formed containing X ₁₀₁ may further have a substituent other than Ar ₁₀₁ and Ar ₁₀₂ as long as the function of the host compound used in the present invention is not inhibited. .
Furthermore, it is preferable that the compound represented by general formula (II) is represented by the following general formula (III-1), (III-2), or (III-3).

In the general formula (III-1) ~ (III -3), X 101, Ar 102, n102 have the same meanings as _{X 101,} Ar 102, n102 in the general formula (II). In the general formula _{(III-2), R 104} has the same meaning as _{R 104} in formula (I).
In the general formulas (III-1) to (III-3), the condensed ring, carbazole ring and benzene ring formed containing X ₁₀₁ are further substituted within a range not inhibiting the function of the host compound used in the present invention. You may have.
Examples of the host compound used in the present invention include compounds represented by the general formulas (I), (II), (III-1) to (III-3) and other structures. It is not limited to these.

The preferred host compound used in the present invention may be a low molecular compound having a molecular weight that can be purified by sublimation or a polymer having a repeating unit.
In the case of a low molecular weight compound, sublimation purification is possible, so that there is an advantage that purification is easy and a high-purity material is easily obtained. The molecular weight is not particularly limited as long as sublimation purification is possible, but the preferred molecular weight is 3000 or less, more preferably 2000 or less.
In the case of a polymer or oligomer having a repeating unit, there is an advantage that it is easy to form a film by a wet process, and since a polymer generally has a high Tg, it is preferable from the viewpoint of heat resistance.
The polymer used as the host compound used in the present invention is not particularly limited as long as the desired device performance can be achieved, but preferably the general formulas (I), (II), (III-1) to (III-) What has the structure of 3) in a principal chain or a side chain is preferable. Although there is no restriction | limiting in particular as molecular weight, Molecular weight 5000 or more is preferable or a thing with 10 or more repeating units is preferable.

In addition, the host compound has a hole transporting ability or an electron transporting ability, prevents the emission of light from being long-wavelength, and is stable with respect to heat generated when the organic EL element is driven at a high temperature or during the element driving. From the viewpoint of operation, 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 obtained by a method based on JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

《Electron transport layer》
In the present invention, the electron transport layer is made of a material having a function of transporting electrons, and may have a function of transmitting electrons injected from the cathode to the light emitting layer.
Although there is no restriction | limiting in particular about the total layer thickness of the electron carrying layer which concerns on this invention, Usually, it is the range of 2 nm-5 micrometers, More preferably, it is 2-500 nm, More preferably, it is 5-200 nm.
Further, in the organic EL element, when the light generated in the light emitting layer is extracted from the electrode, the light extracted directly from the light emitting layer interferes with the light extracted after being reflected by the electrode from which the light is extracted and the electrode located at the counter electrode. It is known to wake up. 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 thickness of the electron transport layer is increased, the voltage is likely to increase. Therefore, particularly when the layer thickness is large, the electron mobility of the electron transport layer is 10 ⁻⁵ cm ² / V · s or more. Is preferred.
The material used for the electron transport layer (hereinafter referred to as an electron transport material) may be any of electron injecting or transporting properties and hole blocking properties, and can be selected from conventionally known compounds. Can be selected and used.

  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, pyrazine derivatives, pyridazine derivatives, Triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, azatriphenylene derivatives, oxazole derivatives, thiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, etc.), dibenzofuran derivatives, Dibenzothiophene derivatives, silole derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, triphenylene derivatives, etc.) That.

In addition, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, for example, tris (8-quinolinol) aluminum (Alq), 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) and the like, and their 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 the electron transport material.
In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transport material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer. Can also be used as an electron transporting material.
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.

  In the electron transport layer according to the present invention, the electron transport layer may be doped with a doping material 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 complexes and metal compounds such as 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 Pat. No. 6,528,187, US Pat. No. 7,230,107, US Patent Application Publication No. 2005/0025993, US Patent Application Publication No. 2004/0036077, US Patent Application Publication No. 2009/0115316, US Patent Application Publication No. 2009/0101870, United States Patent Application Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132805, Appl. Phys. Lett. 75, 4 (1999), Appl. Phys. Lett. 79, 449 (2001), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 79, 156 (2001), U.S. Patent No. 7964293, U.S. Patent Application Publication No. 2009/030202, International Publication No. 2004/080975, International Publication No. 2004/063159, International Publication No. 2005/085387, International Publication No. Public Publication No. 2006/067931, International Publication No. 2007/086552, International Publication No. 2008/114690, International Publication No. 2009/066942, International Publication No. 2009/066779, International Publication No. 2009/054253, International Publication No. 2011/086935, International Publication No. 2010/150593, International Publication No. 2010/047707, EP23111826, JP2010-251675A, JP2009-209133A, JP2009-124114A, JP JP-A-2008-277810, JP-A-2006-156445, JP-A-2005-340122, JP-A-2003-45662, JP-A-2003-31367, JP-A-2003-282270, International Publication No. 2012. / 115034.

More preferable electron transport materials in the present invention include aromatic heterocyclic compounds containing at least one nitrogen atom. For example, pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, azadibenzofuran derivatives. , Azadibenzothiophene 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.

《Hole blocking layer》
The hole blocking layer is a layer having a function of an electron transport layer in a broad sense, and is preferably made of a material having a function of transporting electrons and a small ability to transport holes, and transporting electrons while transporting holes. By blocking this, the recombination probability of electrons and holes can be improved.
Moreover, the structure of the electron carrying layer mentioned above can be used as a hole-blocking layer concerning this invention as needed.
The hole blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the cathode side of the light emitting layer.
The layer thickness of the hole blocking layer according to the present invention is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.
As the material used for the hole blocking layer, the material used for the above-described electron transport layer is preferably used, and the material used as the above-described host compound is also preferably used for the hole blocking layer.

《Electron injection layer》
The electron injection layer (also referred to as “cathode buffer layer”) according to the present invention is a layer provided between the cathode and the light emitting layer in order to lower the driving voltage and improve the light emission luminance. It is described in detail in Chapter 2 “Electrode Materials” (pages 123 to 166) of the second edition of “The Forefront of Industrialization” (issued by NTT Corporation on November 30, 1998).
In the present invention, the electron injection layer may be provided as necessary, and may be present between the cathode and the light emitting layer or between the cathode and the electron transport layer as described above.
The electron injection layer is preferably a very thin film, and the layer thickness is preferably in the range of 0.1 to 5 nm, although it depends on the material. Moreover, the nonuniform layer (film | membrane) in which a constituent material exists intermittently may be sufficient.

The details of the electron injection layer are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specific examples of materials preferably used for the electron injection layer are as follows. , Metals typified by strontium and aluminum, alkali metal compounds typified by lithium fluoride, sodium fluoride, potassium fluoride, etc., alkaline earth metal compounds typified by magnesium fluoride, calcium fluoride, etc., oxidation Examples thereof include metal oxides typified by aluminum, metal complexes typified by 8-hydroxyquinolinate lithium (Liq), and the like. Further, the above-described electron transport material can also be used.
Moreover, the material used for said electron injection layer may be used independently, and may be used in combination of multiple types.

《Hole transport layer》
In the present invention, the hole transport layer is made of a material having a function of transporting holes and may have a function of transmitting holes injected from the anode to the light emitting layer.
Although there is no restriction | limiting in particular about the total layer thickness of the positive hole transport layer which concerns on this invention, Usually, it is the range of 5 nm-5 micrometers, More preferably, it is 2-500 nm, More preferably, it is 5-200 nm.
As a material used for the hole transport layer (hereinafter referred to as a hole transport material), any material that has either a hole injection property or a transport property or an electron barrier property may be used. Any one can be selected and used.
For example, porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives , Indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, and polyvinyl carbazole, polymeric materials or oligomers with aromatic amines introduced into the main chain or side chain, polysilane, conductive And polymer (for example, PEDOT / PSS, aniline copolymer, polyaniline, polythiophene, etc.).

Examples of the triarylamine derivative include benzidine type represented by α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl), starburst type represented by MTDATA, Examples include compounds having fluorene or anthracene in the triarylamine-linked core.
In addition, hexaazatriphenylene derivatives such as those described in JP-A-2003-519432 and JP-A-2006-135145 can also be used as a hole transport material.
Furthermore, a hole transport layer having a high p property doped with impurities can also be used. 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. It is also possible to use so-called p-type hole transport materials and inorganic compounds such as p-type-Si and p-type-SiC, as described in the literature (Applied Physics Letters 80 (2002), p. 139). Further, ortho-metalated organometallic complexes having Ir or Pt as the central metal as typified by Ir (ppy) ₃ are also preferably used.
Although the above-mentioned materials can be used as the hole transport material, a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organometallic complex, or an aromatic amine is introduced into the main chain or side chain. The polymer materials or oligomers used are preferably used.

Specific examples of known preferred hole transport materials used in the organic EL device of the present invention include the compounds described in the following documents in addition to the documents listed above, but the present invention is not limited thereto. Not.
For example, Appl. Phys. Lett. 69, 2160 (1996), J. MoI. Lumin. 72-74, 985 (1997), Appl. Phys. Lett. 78, 673 (2001), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 51, 913 (1987), Synth. Met. 87, 171 (1997), Synth. Met. 91, 209 (1997), Synth. Met. 111, 421 (2000), SID Symposium Digest, 37, 923 (2006), J. Am. Mater. Chem. 3, 319 (1993), Adv. Mater. 6, 677 (1994), Chem. Mater. 15, 3148 (2003), US Patent Application Publication No. 2003/0162053, US Patent Application Publication No. 2002/0158242, US Patent Application Publication No. 2006/0240279, US Patent Application Publication No. 2008 / No. 0220265, U.S. Patent No. 5061569, International Publication No. 2007/002683, International Publication No. 2009/018009, EP650955, U.S. Patent Application Publication No. 2008/0124572, U.S. Patent Publication No. 2007/0278938. Specification, US Patent Application Publication No. 2008/0106190, US Patent Application Publication No. 2008/0018221, International Publication No. 2012/115034, Japanese Translation of PCT International Publication No. 2003-519432, Japanese Patent Application Laid-Open No. 2006-135145 , US Patent Application No. 13/585981 and the like.
The hole transport material may be used alone or in combination of two or more.

《Electron blocking layer》
The electron blocking layer is a layer having a function of a hole transport layer in a broad sense, and is preferably made of a material having a function of transporting holes and a small ability to transport electrons, while transporting holes. By blocking electrons, the probability of recombination of electrons and holes can be improved.
Moreover, the structure of the positive hole transport layer mentioned above can be used as an electron blocking layer according to the present invention, if necessary.
The electron blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the anode side of the light emitting layer.
The layer thickness of the electron blocking layer according to the present invention is preferably in the range of 3 to 100 nm, and more preferably in the range of 5 to 30 nm.
As the material used for the electron blocking layer, the material used for the above-described hole transport layer is preferably used, and the above-mentioned host compound is also preferably used for the electron blocking layer.

《Hole injection layer》
The hole injection layer (also referred to as “anode buffer layer”) according to the present invention is a layer provided between the anode and the light emitting layer for the purpose of lowering the driving voltage and improving the light emission luminance. It is described in detail in Chapter 2 “Electrode Materials” (pages 123 to 166) of the second edition of “The Forefront of Industrialization” (issued by NTT Corporation on November 30, 1998).
In the present invention, the hole injection layer may be provided as necessary, and may be present between the anode and the light emitting layer or between the anode and the hole transport layer as described above.
The details of the hole injection layer are also described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069, etc. Examples of the material used for the hole injection layer include: Examples thereof include materials used for the above-described hole transport layer.
Among them, phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives as described in JP-T-2003-519432 and JP-A-2006-135145, metal oxides typified by vanadium oxide, amorphous carbon Preferred are conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometalated complexes represented by tris (2-phenylpyridine) iridium complex, and triarylamine derivatives.
The materials used for the hole injection layer described above may be used alone or in combination of two or more.

"Additive"
The organic layer in the present invention described above may further contain other additives.
Examples of the additive include halogen elements such as bromine, iodine and chlorine, halogenated compounds, alkali metals and alkaline earth metals such as Pd, Ca, and Na, transition metal compounds, complexes, and salts.
The content of the additive can be arbitrarily determined, but is preferably 1000 ppm or less, more preferably 500 ppm or less, and further preferably 50 ppm or less with respect to the total mass% of the contained layer. .
However, it is not within this range depending on the purpose of improving the transportability of electrons and holes or the purpose of favoring the exciton energy transfer.

<Method for forming organic layer>
A method for forming an organic layer (hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) according to the present invention will be described.
The method for forming the organic layer according to the present invention is not particularly limited, and a conventionally known method such as a vacuum deposition method or a wet method (also referred to as a wet process) can be used.
Examples of the wet method include a spin coating method, a casting method, an ink jet method, a printing method, a die coating method, a blade coating method, a roll coating method, a spray coating method, a curtain coating method, and an LB method (Langmuir-Blodgett method). From the viewpoint of obtaining a homogeneous thin film easily and high productivity, a method with high roll-to-roll method suitability such as a die coating method, a roll coating method, an ink jet method and a spray coating method is preferable.

Examples of the liquid medium for dissolving or dispersing the organic EL material used in the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, Aromatic hydrocarbons such as mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used.
Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.
Further, different film forming methods may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a vacuum degree of 10 ⁻⁶ to 10 ⁻² Pa, and a vapor deposition rate of 0.01 to It is desirable to select appropriately within a range of 50 nm / second, a substrate temperature of −50 to 300 ° C., and a layer (film) thickness of 0.1 nm to 5 μm, preferably 5 to 200 nm.
The organic layer according to the present invention is preferably formed from the hole injection layer to the cathode consistently by a single evacuation, but it may be taken out halfway and subjected to different film formation methods. In that case, it is preferable to perform the work in a dry inert gas atmosphere.

"anode"
As the anode in the organic EL element, a material having a work function (4 eV or more, preferably 4.5 eV or more) of a metal, an alloy, an electrically conductive compound, or a mixture thereof is preferably used. Specific examples of such electrode substances include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used.
The anode may be formed by depositing a thin film of these electrode materials by vapor deposition or sputtering, and a pattern having a desired shape may be formed by photolithography, or when pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material.
Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less.
The film thickness of the anode depends on the material, but is usually selected within the range of 10 nm to 1 μm, preferably 10 to 200 nm.

"cathode"
As the cathode, a material having a work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, aluminum, rare earth metals and the like. Among these, in terms of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.
In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the emission luminance is advantageously improved.
Moreover, after producing the above metal with a film thickness of 1 to 20 nm on the cathode, a transparent or translucent cathode can be produced by producing a conductive transparent material mentioned in the description of the anode on the cathode. By applying the above, it is possible to manufacture a device in which both the anode and the cathode are transparent.

[Support substrate]
The support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention is not particularly limited in the type of glass, plastic, etc., and is transparent. Or opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element.

  Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate ( CAP), cellulose esters such as cellulose acetate phthalate, cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones, Cycloolefin resins such as polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned.

An inorganic film, an organic film, or a hybrid film of both may be formed on the surface of the resin film, and the water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. , Relative humidity (90 ± 2)% RH) is preferably 0.01 g / m ² · 24 h or less of a barrier film, and further, oxygen permeability measured by a method according to JIS K 7126-1987. However, it is preferable that the film has a high barrier property of 1 × 10 ⁻³ ml / m ² · 24 h · atm or less and a water vapor permeability of 1 × 10 ⁻⁵ g / m ² · 24 h or less.

As a material for forming the barrier film, any material may be used as long as it has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.
The method for forming the barrier film is not particularly limited. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma polymerization A plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films, opaque resin substrates, and ceramic substrates.
The external extraction quantum efficiency at room temperature (25 ° C.) of light emission of the organic EL device of the present invention is preferably 1% or more, and more preferably 5% or more.
Here, external extraction quantum efficiency (%) = number of photons emitted to the outside of the organic EL element / number of electrons flowed to the organic EL element × 100.
In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor may be used in combination.

[Sealing]
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of bonding a sealing member, an electrode, and a support substrate with an adhesive. As a sealing member, it should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and it may be concave plate shape or flat plate shape. Moreover, transparency and electrical insulation are not particularly limited.
Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the organic EL element can be thinned. Furthermore, the polymer film has an oxygen permeability measured by a method according to JIS K 7126-1987 of 1 × 10 ⁻³ ml / m ² · 24 h or less, and measured by a method according to JIS K 7129-1992. The water vapor permeability (25 ± 0.5 ° C., relative humidity 90 ± 2%) is preferably 1 × 10 ⁻³ g / m ² · 24 h or less.
For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used.

Specific examples of adhesives include photocuring and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. be able to. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.
In addition, since an organic EL element may deteriorate by heat processing, what can be adhesive-hardened from room temperature to 80 degreeC is preferable. A desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print like screen printing.

In addition, it is also preferable that the electrode and the organic layer are coated on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and an inorganic or organic layer is formed in contact with the support substrate to form a sealing film. . In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can.
Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. There are no particular limitations on the method of forming these films. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

In the gap between the sealing member and the display area of the organic EL element, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil can be injected in the gas phase and liquid phase. preferable. A vacuum can also be used. Moreover, a hygroscopic compound can also be enclosed inside.
Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide etc.), perchloric acids (eg perchloric acid) Barium, magnesium perchlorate and the like), and anhydrous salts are preferably used in sulfates, metal halides and perchloric acids.

[Protective film, protective plate]
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided outside the sealing film or the sealing film on the side facing the support substrate with the organic layer interposed therebetween. In particular, when sealing is performed by the sealing film, the mechanical strength is not necessarily high, and thus it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, etc. used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

[Light extraction improvement technology]
The organic EL element emits light inside a layer having a refractive index higher than that of air (within a refractive index of about 1.6 to 2.1), and is about 15% to 20% of light generated in the light emitting layer. It is generally said that it can only be taken out. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the device, This is because light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the side surface of the device.

  As a technique for improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the transparent substrate and the air interface (for example, US Pat. No. 4,774,435), A method for improving efficiency by providing light condensing property (for example, JP-A-63-314795), a method for forming a reflective surface on a side surface of an element (for example, JP-A-1-220394), a substrate, etc. A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light emitter (for example, Japanese Patent Application Laid-Open No. 62-172691), lower refraction than the substrate between the substrate and the light emitter A method of introducing a flat layer having a refractive index (for example, Japanese Patent Application Laid-Open No. 2001-202827), and a method of forming a diffraction grating between any one of the substrate, the transparent electrode layer and the light emitting layer (including between the substrate and the outside world) ( JP-A-11 No. 283,751 Publication), and the like.

In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, transparent A method of forming a diffraction grating between any layers of the electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used.
In the present invention, by combining these means, it is possible to obtain an element having higher luminance or durability.

When a low refractive index medium is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the light extracted from the transparent electrode has a higher extraction efficiency to the outside as the refractive index of the medium is lower. Become.
Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally in the range of about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Furthermore, it is preferable that it is 1.35 or less.
The thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave exuded by evanescent enters the substrate.

  The method of introducing a diffraction grating into an interface that causes total reflection or in any medium has a feature that the effect of improving the light extraction efficiency is high. This method uses the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction, such as first-order diffraction or second-order diffraction. The light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating into any layer or medium (in the transparent substrate or transparent electrode). , Trying to extract light out.

The introduced diffraction grating desirably has a two-dimensional periodic refractive index. This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution only in a certain direction, only light traveling in a specific direction is diffracted. The light extraction efficiency does not increase so much.
However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and light extraction efficiency is increased.
The position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or the transparent electrode), but is preferably in the vicinity of the organic light emitting layer where light is generated. At this time, the period of the diffraction grating is preferably within a range of about 1/2 to 3 times the wavelength of light in the medium. The arrangement of the diffraction gratings is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

[Condensing sheet]
The organic EL element of the present invention can be processed to provide a structure on a microlens array, for example, on the light extraction side of a support substrate (substrate) or combined with a so-called condensing sheet, for example, in a specific direction, for example, the element Condensing light in the front direction with respect to the light emitting surface can increase the luminance in a specific direction.
As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are arranged two-dimensionally on the light extraction side of the substrate. One side is preferably within a range of 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.
As the condensing sheet, for example, a sheet that is put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, the base material may be formed by forming a △ -shaped stripe having a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex angle is rounded and the pitch is changed randomly. Other shapes may be used.
Moreover, in order to control the light emission angle from an organic EL element, you may use a light-diffusion plate and a film together with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

[Usage]
The organic EL element of the present invention can be used as an electronic device such as a display device, a display, and various light emitting devices.
Examples of light-emitting devices include lighting devices (home lighting, interior lighting), clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, Especially, it can use effectively for the use as a backlight of a liquid crystal display device, and a light source for illumination.
In the organic EL element of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like as needed during film formation. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned. In the fabrication of the element, a conventionally known method is used. Can do.

<Display device>
The display device including the organic EL element of the present invention may be single color or multicolor, but here, the multicolor display device will be described.

In the case of a multicolor display device, a shadow mask is provided only at the time of forming a light emitting layer, and a film can be formed on one surface by vapor deposition, casting, spin coating, ink jet, printing, or the like.
In the case of patterning only the light emitting layer, there is no limitation on the method, but a vapor deposition method, an inkjet method, a spin coating method, and a printing method are preferable.

  The configuration of the organic EL element provided in the display device is selected from the above-described configuration examples of the organic EL element as necessary.

  Moreover, the manufacturing method of an organic EL element is as having shown to the one aspect | mode of manufacture of the organic EL element of said invention.

  When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.

  The multicolor display device can be used as a display device, a display, or various light emission sources. In a display device or display, full-color display is possible by using three types of organic EL elements of blue, red, and green light emission.

  Examples of the display device or display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in an automobile. In particular, it may be used as a display device for reproducing still images and moving images, and the driving method when used as a display device for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.

  Light-emitting devices include household lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, optical storage media light sources, electrophotographic copying machine light sources, optical communication processor light sources, optical sensor light sources, etc. However, the present invention is not limited to these.

Hereinafter, an example of a display device having the organic EL element of the present invention will be described with reference to the drawings.
FIG. 2 is a schematic view showing an example of a display device composed of organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element.

The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, a wiring unit C that electrically connects the display unit A and the control unit B, and the like.
The control unit B is electrically connected to the display unit A via the wiring unit C, and sends a scanning signal and an image data signal to each of a plurality of pixels based on image information from the outside. Sequentially emit light according to the image data signal, scan the image, and display the image information on the display unit A.

FIG. 3 is a schematic diagram of a display device using an active matrix method.
The display unit A includes a wiring unit C including a plurality of scanning lines 5 and data lines 6, a plurality of pixels 3 and the like on a substrate. The main members of the display unit A will be described below.
FIG. 3 shows a case where the light emitted from the pixel 3 is extracted in the direction of the white arrow (downward).

The scanning line 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a grid pattern and are connected to the pixels 3 at the orthogonal positions (details are illustrated). Not)
When a scanning signal is applied from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data.
Full-color display is possible by appropriately arranging pixels in the red region, the green region, and the blue region on the same substrate.

Next, the light emission process of the pixel will be described. FIG. 4 is a schematic diagram showing a pixel circuit.
The pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. A full color display can be performed by using red, green, and blue light emitting organic EL elements as the organic EL elements 10 in a plurality of pixels, and juxtaposing them on the same substrate.

  In FIG. 4, an image data signal is applied from the control unit B to the drain of the switching transistor 11 through the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is supplied to the capacitor 13 and the driving transistor 12. Is transmitted to the gate.

  By transmitting the image data signal, the capacitor 13 is charged according to the potential of the image data signal, and the drive of the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10, and the power supply line 7 connects to the organic EL element 10 according to the potential of the image data signal applied to the gate. Current is supplied.

When the scanning signal is moved to the next scanning line 5 by the sequential scanning of the control unit B, the driving of the switching transistor 11 is turned off. However, since the capacitor 13 holds the charged potential of the image data signal even if the driving of the switching transistor 11 is turned off, the driving of the driving transistor 12 is kept on and the next scanning signal is applied. Until then, the light emission of the organic EL element 10 continues. When the scanning signal is next applied by sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.
That is, the organic EL element 10 emits light by the switching transistor 11 and the drive transistor 12 that are active elements for the organic EL element 10 of each of the plurality of pixels, and the light emission of the organic EL element 10 of each of the plurality of pixels 3. It is carried out. Such a light emitting method is called an active matrix method.

Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or by turning on / off a predetermined light emission amount by a binary image data signal. Good. The potential of the capacitor 13 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.
In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

FIG. 5 is a schematic diagram of a passive matrix display device. In FIG. 5, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice shape so as to face each other with the pixel 3 interposed therebetween.
When the scanning signal of the scanning line 5 is applied by sequential scanning, the pixels 3 connected to the applied scanning line 5 emit light according to the image data signal.
In the passive matrix system, the pixel 3 has no active element, and the manufacturing cost can be reduced.
By using the organic EL element of the present invention, a display device with improved luminous efficiency was obtained.

<Lighting device>
The organic EL element of the present invention can also be used for a lighting device.
The organic EL element of the present invention may be used as an organic EL element having a resonator structure. Examples of the purpose of use of the organic EL element having such a resonator structure include a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processing machine, and a light source of an optical sensor. It is not limited. Moreover, you may use for the said use by making a laser oscillation.
Further, the organic EL element of the present invention may be used as a kind of lamp for illumination or exposure light source, a projection device for projecting an image, or a type for directly viewing a still image or a moving image. It may be used as a display device (display).
The driving method when used as a display device for reproducing a moving image may be either a passive matrix method or an active matrix method. Alternatively, it is possible to produce a full-color display device by using two or more organic EL elements of the present invention having different emission colors.

  Further, the fluorescent compound used in the present invention can be applied to an organic EL element that emits substantially white light as a lighting device. For example, when a plurality of light emitting materials are used, white light emission can be obtained by simultaneously emitting a plurality of light emission colors and mixing the colors. The combination of a plurality of emission colors may include three emission maximum wavelengths of three primary colors of red, green, and blue, or two of the complementary colors such as blue and yellow, blue green and orange, etc. The thing containing the light emission maximum wavelength may be used.

In addition, the organic EL device forming method of the present invention may be simply arranged by providing a mask only when forming a light emitting layer, a hole transport layer, an electron transport layer, or the like, and separately coating with the mask. Since the other layers are common, patterning of a mask or the like is unnecessary, and for example, an electrode film can be formed on one surface by a vapor deposition method, a cast method, a spin coating method, an ink jet method, a printing method, or the like, and productivity is improved.
According to this method, unlike a white organic EL device in which light emitting elements of a plurality of colors are arranged in parallel in an array, the elements themselves emit white light.

[One Embodiment of Lighting Device of the Present Invention]
One aspect of the lighting device of the present invention that includes the organic EL element of the present invention will be described.
The non-light emitting surface of the organic EL device of the present invention is covered with a glass case, a 300 μm thick glass substrate is used as a sealing substrate, and an epoxy photocurable adhesive (LUX The track LC0629B) is applied, and this is overlaid on the cathode and brought into close contact with the transparent support substrate, irradiated with UV light from the glass substrate side, cured, sealed, and illuminated as shown in FIGS. A device can be formed.
FIG. 6 shows a schematic diagram of the lighting device, and the organic EL element of the present invention (organic EL element 101 in the lighting device) is covered with a glass cover 102 (note that the sealing operation with the glass cover is performed by lighting. This was performed in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) without bringing the organic EL element 101 in the apparatus into contact with the air.
FIG. 7 is a cross-sectional view of the lighting device, 105 is a cathode, 106 is an organic layer, and 107 is a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.
By using the organic EL element of the present invention, an illumination device with improved luminous efficiency was obtained.

<Light emitting material>
The luminescent material used in the present invention is characterized by containing at least one of the fluorescent compounds having the structure represented by the general formula (1-a) or (1-b).
As a result, the electron mobility in the organic EL element is improved, and as a result, the emission efficiency is reduced at a high current density in the organic EL element, that is, the effect of improving the roll-off is obtained. An improvement effect is obtained.

  Further, in addition to the fluorescent compound, a host compound having a structure represented by the general formula (I), the general formula (II) or / and the general formulas (III-1) to (III-3) is contained. It is preferable to do. As a result, the effects of further improving the luminous efficiency and improving the lifetime can be obtained.

Furthermore, the fluorescent compound used in the present invention as the light emitting material can also be used for a light emitting thin film, a display device and a lighting device.
Here, the luminescent thin film of the present invention will be described.

<Luminescent thin film>
The light-emitting thin film of the present invention can be produced in the same manner as the organic layer forming method.
The method for forming the light-emitting thin film of the present invention is not particularly limited, and a conventionally known method such as a vacuum deposition method or a wet method (also referred to as a wet process) can be used.
Examples of the wet method include a spin coating method, a casting method, an ink jet method, a printing method, a die coating method, a blade coating method, a roll coating method, a spray coating method, a curtain coating method, and an LB method (Langmuir-Blodgett method). From the viewpoint of obtaining a homogeneous thin film easily and high productivity, a method with high roll-to-roll method suitability such as a die coating method, a roll coating method, an ink jet method and a spray coating method is preferable.

  Examples of the liquid medium for dissolving or dispersing the light emitting material used in the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, and mesitylene. Aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used.

Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.
Further, different film forming methods may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally the boat heating temperature is in the range of 50 to 450 ° C., and the degree of vacuum is in the range of 10 ⁻⁶ to 10 ⁻² Pa. Of these, the deposition rate is appropriately selected within the range of 0.01 to 50 nm / second, the substrate temperature within the range of −50 to 300 ° C., the layer thickness within the range of 0.1 nm to 5 μm, and preferably within the range of 5 to 200 nm. desirable.
When a spin coat method is employed for film formation, it is preferable to perform the spin coater within a range of 100 to 1000 rpm and within a range of 10 to 120 seconds in a dry inert gas atmosphere.

Moreover, the luminescent thin film of this invention can also be used for a display apparatus and an illuminating device.
As a result, a display device and a lighting device with improved luminous efficiency can be obtained.

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 otherwise indicated, "part by mass" or "mass%" is represented.
Moreover, the volume% of the compound in each Example is calculated | required from specific gravity by measuring the layer thickness to produce by the quartz crystal microbalance method, and calculating mass.

[Example 1]
<< Production of thin film >>
(Method for producing thin film 1-A)
A quartz substrate having a size of 50 mm × 50 mm and a thickness of 0.7 mm was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes. After coating for 30 seconds, it was baked at 120 ° C. for 30 minutes and dried. The thin film was sealed by covering it with a can-shaped glass case in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more, to produce a thin film 1-A having a thickness of 40 nm.

Fluorescent compound 1-4 5 parts by mass DPEPO 95 parts by mass Chlorobenzene 20000 parts by mass

(Method for producing thin films 1-B to 1-G)
Thin films 1-B to 1-G were prepared in the same manner as thin film 1-A, except that the dopant used was changed as shown in Table 2.
(Evaluation of thin film)
UV-970 (Hitachi, Ltd.) was used for the thin film 1-A to 1-G samples, the UV spectrum was measured, the excitation wavelength was determined, and the PL spectrum of each thin film was measured. For PL measurement, an absolute PL quantum yield measuring device C9920-02 (manufactured by Hamamatsu Photonics) was used.
The peak intensity at the emission maximum wavelength of the fluorescent compound 1-4 as a dopant was set to 1, and the peak intensity at the emission maximum wavelength when each dopant was used is shown in Table 2 as a relative value.

(result)
When the fluorescent compound according to the present invention was used as a dopant, specific light emission was observed in each. When the compound of the present invention having an electron withdrawing group in the molecule was used, the emission intensity was increased as compared with the case of using a comparative compound. Although the reason is not clear, it is presumed that the light emission from the singlet was promoted by the improvement of the CT property in the molecule.

[Example 2]
(Method for producing organic EL element 2-A)
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached After ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen gas and UV ozone cleaning for 5 minutes, this transparent substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.
After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 1.0 nm / second. A hole transport layer was formed.

Subsequently, the host compound UGH2 and the fluorescent compound 2-6 were co-deposited at a deposition rate of 0.1 nm / second so as to be 90% and 10% by volume, respectively, to form a light emitting layer having a layer thickness of 35 nm. Next, α-NPD was deposited at a deposition rate of 1.0 nm / second to form a hole transport layer having a layer thickness of 70 nm.
Furthermore, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-light-emitting surface side of the above element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 2-A.

(Method for producing organic EL elements 2-B to 2-I)
Organic EL elements 2-B to 2-H were prepared in the same manner as organic EL element 2-A, except that the compounds used in organic EL element 2-A were changed to the compounds shown in Table 3. Organic EL device 2-I was produced in the same manner as device 2-A, except that no fluorescent compound was used.

(Evaluation of organic EL elements 2-A to 2-I)
The hole transport characteristics in the light emitting layers of the organic EL elements 2-A to 2-I can be obtained by applying a voltage of −10 V to 15 V using a minute current measuring device manufactured by Keithley Instruments Co., Ltd. evaluated. From the obtained IV characteristics, the rising voltage was obtained from a tangent drawn from a straight line with a constant slope of the current value. The rising voltage of the organic EL element 2-I of Comparative Example was set to 1, and the rising voltage of each element was shown as a relative value. This result corresponds to the electron mobility in the light emitting layer, and a smaller value indicates a better result.

(result)
The rising voltage of the organic EL element (2-A to 2-G) using the compound of the present invention is lower than the organic EL element 2-I which is a device to which no fluorescent compound is added. Recognize. This is considered to be the effect that charge injection is promoted by adding a fluorescent compound as a dopant, that is, holes are directly injected into the dopant, compared to the case of using only the host compound. On the other hand, in the organic EL element 2-H using the comparative compound B-2 as a dopant, since the HOMO level with the host is almost the same, holes cannot directly enter the dopant, and the voltage becomes high. It is thought that.

[Example 3]
(Preparation of organic EL element 3-A)
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached After ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen gas and UV ozone cleaning for 5 minutes, this transparent substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection transport layer was formed.
Next, the host compound DPEPO and the dopant compound 2-51 were co-deposited at a deposition rate of 0.1 nm / second so as to be 90% and 10% by volume, respectively, to form a light-emitting layer having a layer thickness of 35 nm.
Thereafter, BCP (electron transport material) was deposited at a deposition rate of 0.1 nm / second to form an electron transport layer having a layer thickness of 30 nm.
Furthermore, after forming lithium fluoride with a film thickness of 0.5 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-light-emitting surface side of the above element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 3-A.

(Preparation of organic EL elements 3-B to 3-J)
Organic EL elements 3-B to 3-J were produced in the same manner as the organic EL element 3-A except that the dopant compound 2-51 was changed as shown in Table 4.

(Evaluation)
The following evaluation was performed on the organic EL elements 3-A to 3-J.

(Roll-off characteristics during high brightness light emission)
Each of the produced organic EL elements was evaluated for roll-off characteristics at room temperature (about 25 ° C.). First, a graph of luminance-external quantum yield obtained when voltage was applied to each element to emit light from 0 to 10000 cd / A was prepared. The emission luminance was measured using a spectral radiance meter CS-2000 (manufactured by Konica Minolta).
The roll-off characteristic R is observed with respect to the emission luminance at which the maximum value of the external quantum yield of each organic EL element was obtained, and the emission luminance at which a decrease in the external quantum yield of 20% was observed. The relative value is shown.
Roll-off characteristic R = (value of emission luminance at which a decrease in external quantum yield of 20% was observed from the maximum value) / (value of emission luminance at which the maximum value of external quantum yield was obtained)
A larger value indicates better roll-off characteristics (less roll-off).

(Evaluation of external quantum yield (emission brightness))
Each of the produced organic EL elements was allowed to emit light at room temperature (about 25 ° C.) under a constant current condition of ^2.5 mA / cm ² , and the emission luminance immediately after the start of emission was measured using a spectral radiance meter CS-2000 (Konica Minolta). The measurement was performed using
Subsequently, the relative light emission luminance which set the light emission luminance of the organic EL element 3-J of the comparative example to 1 was calculated | required, and this was made into the scale of luminous efficiency (external quantum yield). It represents that it is excellent in luminous efficiency, so that a numerical value is large.

(Evaluation of half-life (continuous drive stability))
While continuously driving each sample at an initial luminance of 3000 cd / m ² , the luminance was measured using the spectral radiance meter CS-2000, and the time for which the measured luminance was reduced by half (LT50) was determined.
The relative value which set LT50 of the organic EL element 3-J of the comparative example to 1 was calculated | required, and this was made into the scale of continuous drive stability. The evaluation results are shown in Table 4. In the table, the larger the value, the better the continuous drive stability (long life).

(result)
It can be seen that the organic EL elements 3-A to 3-H are superior in roll-off characteristics and external quantum yield as compared with the organic EL element of the comparative example.
This is thought to be because the energy level of the indoloindole compound is relatively shallow, so that the hole injection property is improved, and as a result, the range in which charges can be recombined when driving the organic EL element is widened. It can be considered that the widening of the range where charges can be recombined greatly contributes to the improvement of the lifetime by suppressing the decrease in luminance (roll-off) due to the deviation of the light emission position that occurs when driving at a high current density.

[Example 4]
(Preparation of organic EL element 4-A)
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached After ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen gas and UV ozone cleaning for 5 minutes, this transparent substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection transport layer was formed.
Next, the host compound UGH2 and the dopant 3-1 were co-deposited at a deposition rate of 0.1 nm / second so as to be 90% and 10% by volume, respectively, to form a light emitting layer having a layer thickness of 35 nm.
Thereafter, BAlq (hole blocking material) was deposited at a deposition rate of 0.1 nm / second to form a hole blocking with a layer thickness of 10 nm. Further, Alq ₃ (electron transport material) was deposited thereon at a deposition rate of 0.1 nm / second to form a hole blocking with a layer thickness of 30 nm.
Furthermore, after forming lithium fluoride with a film thickness of 0.5 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-light-emitting surface side of the element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 4-A.

(Preparation of organic EL elements 4-B to 4-R)
Organic EL elements 4-B to 4-R were produced in the same manner as the organic EL element 4-A except that the dopant 3-1 and the host compound UGH2 were changed as shown in Table 5.

(Evaluation)
The following evaluation was performed on the organic EL elements 4-A to 4-R.
(Evaluation of external quantum yield (emission brightness))
Each of the produced organic EL elements was allowed to emit light at room temperature (about 25 ° C.) under a constant current condition of ^2.5 mA / cm ² , and the emission luminance immediately after the start of emission was measured using a spectral radiance meter CS-2000 (Konica Minolta). The measurement was performed using
Subsequently, the relative light emission luminance which set the light emission luminance of the organic EL element 4-P of the comparative example to 1 was calculated | required, and this was made into the scale of luminous efficiency (external quantum yield). It represents that it is excellent in luminous efficiency, so that a numerical value is large.

(Evaluation of half-life (continuous drive stability))
While continuously driving each sample at an initial luminance of 3000 cd / m ² , the luminance was measured using the spectral radiance meter CS-2000, and the time for which the measured luminance was reduced by half (LT50) was determined.
The relative value which set LT50 of the organic EL element 4-P of the comparative example to 1 was calculated | required, and this was made into the scale of continuous drive stability. The evaluation results are shown in the table. In the table, the larger the value, the better the continuous drive stability (long life).

(Voltage increase during driving)
The voltage increase of each sample when driving the organic EL element was evaluated by performing the following measurement.

(A) Measurement of initial driving voltage For each sample, the emission luminance of each sample was measured at room temperature (about 25 ° C.) using a spectral radiance meter CS-2000 (manufactured by Konica Minolta), and the emission luminance was 1000 cd. The initial drive voltage at / m ² was determined.

(B) Measurement of voltage after half-life With respect to the sample for which the above half-life evaluation has been completed, emission of each sample is performed at room temperature (about 25 ° C.) using a spectral radiance meter CS-2000 (manufactured by Konica Minolta). The luminance was measured, and the driving voltage at an emission luminance of 1000 cd / m ² was obtained.

(Voltage increase during driving)
The drive voltage was evaluated by the following formula.
Voltage rise = (B) Measurement of drive voltage at emission luminance 1000 cd / m ² after half-life / (A) Initial drive voltage at emission luminance 1000 cd / m ^{2 In} Table 5, the smaller the value of voltage rise, the better It is shown that.

(result)
It can be seen that the organic EL elements 4-A to 4-L are superior in external quantum yield and half-life compared to the organic EL element of the comparative example.
This is because, as described above, the energy level of the indoloindole compound is relatively shallow, so that the hole injection property is improved, and as a result, the range in which charges can be recombined when the organic EL element is driven is widened. it is conceivable that. Along with this, voltage increase before and after driving in each element is also suppressed. Furthermore, these effects are enhanced by using the preferred host group of the present invention. Although the exact reason is not clear, this is presumed to be due to a favorable interaction between the host and the dopant (indoloindole compound).

[Example 5]
(Preparation of organic EL element 5-A)
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached Was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes. On this substrate, a solution of poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (abbreviated as PEDOT / PSS, manufactured by Bayer, Baytron P Al 4083) diluted to 70% with pure water at 3000 rpm for 30 seconds. After film formation by spin coating, the film was dried at 200 ° C. for 1 hour to provide a hole injection layer having a layer thickness of 30 nm.

This substrate was transferred to a nitrogen atmosphere using nitrogen gas (grade G1), and a solution obtained by dissolving 0.5% of exemplary compound A-1 (Mw = 80000) as a hole transport material in chlorobenzene was obtained at 1500 rpm, 30%. After forming a film by spin coating in seconds, the film was held at 160 ° C. for 30 minutes to form a hole transport layer having a layer thickness of 30 nm.
A light emitting material having the following composition was coated on the hole transport layer using a spin coater under conditions of 500 rpm and 30 seconds, and then baked at 120 ° C. for 30 minutes and dried to produce a light emitting layer.
Fluorescent compound 2-70 6 parts by mass H-209 94 parts by mass TFPO (2,2,3,3-tetrafluoro-1-propanol) 20000 parts by mass

Subsequently, the substrate was attached to a vacuum deposition apparatus without being exposed to the atmosphere. Moreover, what put exemplary compound A-2 in the resistance heating boat made from molybdenum was attached to a vacuum evaporation system, and after reducing the vacuum tank to 4 × 10 ⁻⁵ Pa, the boat was energized and heated to heat exemplary compound A. An electron transport layer having a layer thickness of 30 nm was formed on the light emitting layer at a rate of 1 nm / second.

続いて、前記電子輸送層上に層厚１ｎｍのフッ化ナトリウムの薄膜を０．０２ｎｍ／秒で形成し、続けて同様にフッ化ナトリウム上に層厚１．５ｎｍのフッ化カリウムの電子注入層を０．０２ｎｍ／秒で形成した。引き続き、アルミニウム１００ｎｍを蒸着して陰極を形成した。
上記素子の非発光面側を、純度９９．９９９％以上の高純度窒素ガスの雰囲気下で、缶状ガラスケースで覆い、電極取り出し配線を設置して、有機ＥＬ素子５−Ａを作製した。

Subsequently, a thin film of sodium fluoride having a layer thickness of 1 nm is formed on the electron transport layer at 0.02 nm / second, and then an electron injection layer of potassium fluoride having a layer thickness of 1.5 nm is similarly formed on the sodium fluoride. Was formed at 0.02 nm / sec. Subsequently, 100 nm of aluminum was deposited to form a cathode.
The non-light-emitting surface side of the above element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 5-A.

(Evaluation of organic EL element 5-A)
When a voltage was applied to each of the produced organic EL elements at room temperature (about 25 ° C.) so as to satisfy a constant current condition of ^2.5 mA / cm ² , strong luminescence derived from the fluorescent compound 2-70 as a dopant was emitted. was gotten.

[Example 6]
(Preparation of organic EL element 6-A)
A transparent substrate with an ITO (Indium Tin Oxide) film having a thickness of 150 nm formed on a glass substrate of 50 mm × 50 mm and a thickness of 0.7 mm, patterned, and this ITO transparent electrode was attached After ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen gas and UV ozone cleaning for 5 minutes, this transparent substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection transport layer was formed.
Next, the host compound H-156 and the fluorescent compounds 1-25, 2-3 and Ir (piq) ₃ as the dopant are 90%, 9%, 9.9% and 0.1% by volume, respectively. Thus, co-evaporation was performed at a deposition rate of 0.1 nm / second to form a light-emitting layer having a layer thickness of 35 nm.
Thereafter, BAlq (hole blocking material) was deposited at a deposition rate of 0.1 nm / second to form a hole blocking with a layer thickness of 10 nm. Further, Alq ₃ (electron transport material) was deposited thereon at a deposition rate of 0.1 nm / second to form a hole blocking with a layer thickness of 30 nm.
Furthermore, after forming lithium fluoride with a film thickness of 0.5 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-light-emitting surface side of the above element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 6-A.

(Evaluation of organic EL element 6-A)
When a voltage was applied to each of the produced organic EL elements at room temperature (about 25 ° C.) so as to satisfy a constant current condition of ^2.5 mA / cm ² , strong white light emission was obtained.
It turned out that the same white light is obtained also when the following exemplary compound A-3 is used instead of Ir (piq) ₃ .

DESCRIPTION OF SYMBOLS 1 Display 3 Pixel 5 Scan line 6 Data line 7 Power supply line 10 Organic EL element 11 Switching transistor 12 Drive transistor 13 Capacitor 101 Organic EL element 102 in an illuminating device Glass cover 105 Cathode 106 Organic layer 107 Glass substrate 108 with a transparent electrode Nitrogen gas 109 Water capturing agent A Display part B Control part C Wiring part

Claims (10)

An organic electroluminescent device having an organic layer including a light emitting layer of at least one layer between the anode and the cathode, at least one layer of the light emitting layer is represented by the following formula (1-a) as a luminescent material Containing at least one of fluorescent compounds having a structure ;
The organic electroluminescent device, wherein the fluorescent compound has a structure represented by the following general formula (3).

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a substituent. Ra and Rb each independently represent a substituent. P and q each represents an integer of 0 to 4. Ra and Rb each represent a substituent, and when there are a plurality of substituents, each substituent may be the same or different, and each substituent may be bonded to form a ring. (At least one of R ₁ , R ₂ , Ra and Rb represents an electron withdrawing group or a group substituted with an electron withdrawing group.)

(In the formula, R ₅ represents a substituent. L ₁ and L ₂ each represent a divalent linking group or a single bond. Ra and Rb each represent a substituent. P and q are Each represents an integer of 0 to 4. When Ra and Rb represent a substituent, when there are a plurality of substituents, each substituent may be the same or different, and each substituent is bonded to form a ring. N represents an integer of 1 to 3. Further, at least one of R ₅ , L ₁ , L ₂ , Ra and Rb is substituted with an electron withdrawing group or an electron withdrawing group. Represents a group formed by An organic electroluminescence device having an organic layer including at least one light emitting layer between an anode and a cathode, wherein at least one of the light emitting layers has the following general formula (1-a) or (1- containing at least one of the fluorescent compounds having the structure represented by b),
Wherein at least one layer of the organic layer, in addition to said fluorescent compound, organic electroluminescent device characterized by containing a host compound having a structure represented by the following general formula (I).

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a substituent. Ra and Rb each independently represent a substituent. P and q each represents an integer of 0 to 4. Ra and Rb each represent a substituent, and when there are a plurality of substituents, each substituent may be the same or different, and each substituent may be bonded to form a ring. (At least one of R ₁ , R ₂ , Ra and Rb represents an electron withdrawing group or a group substituted with an electron withdrawing group.)

(In the general formula (I), X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R _103. y ₁ to y ₈ each represent CR ₁₀₄ or a nitrogen atom. _{101 to} R ₁₀₄ each represent a hydrogen atom or a substituent, and may combine with each other to form a ring, and Ar ₁₀₁ and Ar ₁₀₂ each represent an aromatic ring, and may be the same or different. n101 and n102 is each an integer of 0 to _4, when _{R 101} is a hydrogen atom, n101 represents an integer of 1-4.) The organic electroluminescence device according to claim 2 , wherein the host compound having a structure represented by the general formula (I) has a structure represented by the following general formula (II).

(In the general formula (II), X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R _103. R _{101 to} R ₁₀₃ each represents a hydrogen atom or a substituent, (Ar ₁₀₁ and Ar ₁₀₂ may each represent an aromatic ring and may be the same or different, and n102 represents an integer of 0 to 4).   4. The organic electroluminescent element according to claim 1, wherein the electron withdrawing group of the fluorescent compound is an aromatic heterocyclic group. 5. A luminescent thin film comprising the fluorescent compound according to claim 1 . Claims, characterized in that it contains a fluorescent compound as defined in Claim 2 formulas according to (I) or the host compound represented by the general formula (II) according to claim 3 of claim 1 5. The luminescent thin film according to 5 . A display device comprising the organic electroluminescence element according to any one of claims 1 to 4 . A light emitting thin film according to claim 5 or 6 is used. The organic electroluminescent element as described in any one of Claim 1- Claim 4 is comprised, The illuminating device characterized by the above-mentioned. An illuminating device comprising the luminescent thin film according to claim 5 or 6 .

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