JP6795728B2 - Electron transport materials, organic electroluminescence devices, display devices and lighting devices - Google Patents

Description

The present invention relates to compounds for organic electroluminescent devices, electron transport materials, organic electroluminescent devices, display devices and lighting devices.

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

There are two light emitting methods for organic EL elements: "phosphorescence", which emits light when returning from the triplet excited state to the ground state, and "fluorescent emission", which emits light when returning from the singlet excited state to the ground state. There is a street.

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 the singlet-exciter and the triplet-exciter are generated at a ratio of 25%: 75%, the phosphorescence emission using the triplet-exciter has a theoretically higher internal quantum than the fluorescence emission. It is known that efficiency can be obtained. However, in order to actually obtain high quantum efficiency in the phosphorescence method, it is necessary to use a complex using a rare metal such as iridium or platinum as the central metal, and in the future, the reserve of the rare metal and the metal itself There is concern that price will be a major industrial issue.

On the other hand, various developments have been made to improve the luminous efficiency of the fluorescent light emitting type, and new movements have emerged in recent years. For example, in Patent Document 1, a phenomenon in which singlet excitons are generated by collision of two triplet excitons (Triplet-Triplet Animation: hereinafter, abbreviated as “TTA” as appropriate. Further, Triplet-Triplet Fusion: “TTF”. (Also referred to as)), a technique for efficiently causing TTA to improve the efficiency of the fluorescent element is disclosed. Although the luminous efficiency of the fluorescent light emitting material is improved to 2 to 3 times that of the conventional fluorescent light emitting material by this technology, the theoretical singlet exciter generation efficiency in TTA is only about 40%, so that the phosphorescent light emission is still performed. It has a problem of high luminous efficiency.

Further, in recent years, fluorescent materials using thermally activated delayed fluorescence (“Thermally Activated Delayed Fluorescence”, hereinafter abbreviated as “TADF” as appropriate) and organic EL elements have been introduced. The possibility of use has been reported (see, for example, Non-Patent Documents 1-3).

1 and 2 are schematic diagrams showing energy diagrams of a compound exhibiting the TADF phenomenon (TADF compound) and a general fluorescent light emitting material. TADF mechanism, compared with the conventional fluorescent material, singlet excitation energy level and when the difference between the triplet excited energy level (Delta] E _ST) was used a material having a low singlet excitons from triplet excitons This is a light emitting mechanism that utilizes the phenomenon of cross-term intersection to. That is, by Delta] E _ST is small, triplet excitons generated at 75% probability by the electric field excitation, where not contribute to light emission would otherwise, a transition to the singlet excited state with thermal energy during the organic EL device driving , Radiation deactivation (also referred to as "radiation transition" or "radiation deactivation") from that state to the ground state causes fluorescence emission. It is believed that the use of delayed fluorescence by this TADF mechanism can theoretically achieve 100% internal quantum efficiency even in fluorescence emission.

Furthermore, if a compound exhibiting TADF properties is included in the light emitting layer as a third component (also referred to as a light emitting auxiliary material or an assist dopant) in the light emitting layer containing the host compound and the light emitting compound, it is effective in exhibiting high luminous efficiency. It is known to exist (see, for example, Non-Patent Document 4). By generating 25% singlet excitons and 75% triplet excitons by electric field excitation on a compound that acts as an assist dopant, the triplet excitons are singlet excitons with inverse intersystem crossing (RISC). Can be generated.

The energy of the singlet exciter is transferred to the luminescent compound by fluorescence resonance energy transfer (Fluorescence Resonance Energy Transfer: hereinafter, abbreviated as "FRET" as appropriate), and the luminescent compound can emit light by the transferred energy. It becomes. Therefore, it is possible to make the luminescent compound emit light by theoretically using 100% exciton energy, and high luminous efficiency can be realized.

Examples of the organic EL material generally include a compound having a skeleton based on a benzene ring having a π electron cloud. Specific examples include a dibenzofuran compound having a cyano group (Patent Document 1), a compound in which a benzofuran skeleton and a triazine skeleton are directly linked (Patent Document 2), and a triazine skeleton in which a dibenzofuran skeleton is linked to the para position via a phenylene group. Examples thereof include a compound (Patent Document 3) and a compound in which a phenyl group is linked to the meta position via a phenylene group (Non-Patent Document 5).

Japanese Unexamined Patent Publication No. 2012-49523 International Publication No. 2007/069569 International Publication No. 2013/07732

H. Uoyama, et. al. , Nature 2012, 492, 234. Q. Zhang et al. , J. Am. Chem. Soc. 2012, 134, 14706. H. Kaji, et. al. , Nature Communications 2015, 6, 8476. H. Nakanotani, et. al. , Nature Communications 2014, 5, 4016. H. Nakanotani, et. al. , Scientific Reports 2013, 3, 2127.

As described above, the luminous efficiency of the organic EL element has been improved by using various kinds of materials and by using a phenomenon such as TTA. However, there are many problems in the driving durability of the element, and further improvement is required particularly in the driving durability under high temperature conditions.

Drive durability in a high temperature environment is one of the extremely important element performances in an outdoor environment exposed to direct sunlight and in-vehicle applications, and it is essential to improve this performance in order to expand the applications of organic EL. I can say.

The high temperature tolerance of a device is often discussed in terms of the glass transition temperature of the material contained in the organic EL device. The higher the glass transition temperature, the less likely it is that the amorphous layers of various organic materials contained in the organic EL element will crystallize, so that stable long-term driving becomes possible.
This glass transition temperature is generally said to increase as the molecular weight of the organic material increases.

Further, in an organic EL device using a phosphorescent material or TADF material, which is said to have high luminous efficiency, triplet excitons are involved in the light emitting process. Excitons with high triplet level energies are known to transfer energy to surrounding molecules with lower triplet energies through a mechanism called the Dexter mechanism. Since this phenomenon causes a decrease in the luminous efficiency of the phosphorescent material or TADF material, the phosphorescent material or TADF material is contained in order to suppress the decrease in the luminous efficiency of such a phosphorescent material or TADF material. The material used for the light emitting layer or its adjacent layer is required to have a higher excitation triplet energy than the phosphorescent material or TADF material.

As described above, in order to realize an organic EL device having high heat resistance and high luminous efficiency, it is necessary to develop a material having both a high glass transition temperature and a high triplet excitation energy as described above.

However, as a general skeleton of an organic EL material, in the case of a compound having a benzene ring having a π electron cloud as a basic skeleton, the benzene ring skeleton is simply connected for the purpose of increasing the molecular weight in order to improve the glass transition temperature. Conjugated elongation of the π-electron cloud will occur, and the excitation triplet energy of the material will decrease. Therefore, it is not easy to develop a material that has both a high glass transition temperature and a high triplet excitation energy.

Patent Document 1 describes that a dibenzofuran compound having a cyano group is useful for improving chromaticity deviation when an organic EL device is stored at a high temperature. However, there is no description about the element characteristics when the organic EL element is driven in a high temperature environment. In addition, it is only stated that the cyano group is important for the effect on high temperature storage, and there is no description regarding the triazine skeleton.

Patent Document 2 describes that a compound in which a benzofuran skeleton and a triazine skeleton are directly linked is useful for improving the performance of an organic EL device. However, as a result of the examination by the present inventor, the compound in which the dibenzofuran skeleton is directly linked to the triazine skeleton has a small spread of the π-conjugated surface and the molecular weight is not so high, so that the carrier transport property and the triplet energy are likely to decrease. The glass transition temperature is also considered to be low.

Patent Document 3 describes a compound in which a dibenzofuran skeleton is linked to a triazine skeleton at the para position via a phenylene group. However, as a result of the examination by the present inventor, it is considered that the triplet energy tends to decrease in the compound because the electrons are delocalized and stabilized, and the organic EL using the above-exemplified compound described in Patent Document 3 is considered. The performance of the element was insufficient.

Non-Patent Document 5 describes a compound in which a phenyl group is linked to the meta position via a phenylene group in a triazine skeleton. However, there is no description of a material having dibenzofuran in the document, and as a result of examination by the present inventor, not only the triplet energy tends to decrease, but also the molecular weight is not so high, so that the glass transition temperature is considered to be low. ..

The present invention has been made in view of the above circumstances, and provides a compound for an organic EL device having a high glass transition temperature and a high triplet energy level, thereby having high heat resistance and high luminous efficiency. An object of the present invention is to provide an organic EL element.

As a result of diligent studies to solve the above problems, the present inventor has found that a compound in which a dibenzofuranyl group substituted or unsubstituted at the meta position is linked to a triazine skeleton via a phenylene group is an existing organic EL device. It has been found that it has both higher glass transition temperature and higher triplet energy than the compound for use. Further, they have found that an organic EL device using a compound for an organic EL device having such a structure has both high luminous efficiency and high heat resistance (high temperature resistance), and have reached the present invention.
That is, the above problem according to the present invention is solved by the following means.
[1] A compound for an organic electroluminescence device having a structure represented by the following general formula (1).
(In general formula (1),
A _{1 to} A ₃ are substituted or unsubstituted dibenzofuranyl groups independently represented by the general formula (2).
In general formula (2),
At least one of B _{1 to} B ₈ is a bond that binds to the structure of the general formula (1), and the rest represents a hydrogen atom or a substituent. )
[2] The compound for an organic electroluminescence device according to [1], wherein A _{1 to} A ₃ of the general formula (1) are the same group.
[3] The compound for an organic electroluminescence device according to [1] or [2], wherein the structure represented by the general formula (1) is a structure represented by the following formula E-1 or E-2.
[4] The compound for an organic electroluminescence device according to any one of [1] to [3], wherein the glass transition point (Tg) of the compound for an organic electroluminescence device is 100 ° C. or higher.
[5] the difference between the lowest excited singlet energy level and the lowest excited triplet energy level of the organic electroluminescence element compound (Delta] E _ST) is less than 0.8 eV, of [1] to [4] The compound for an organic electroluminescence element according to any one.
[6] The compound for an organic electroluminescence device according to any one of [1] to [5], wherein the compound for an organic electroluminescence device has a molecular weight of 700 or more.
[7] The molecular weight of the organic electroluminescence element compound, the value obtained by dividing the difference (Delta] E _ST) with its lowest excited singlet energy level and the lowest excited triplet energy level, 1,000 or more, [1 ] To [6], the compound for an organic electroluminescence element.
[8] An electron transporting material comprising the compound for an organic electroluminescence device according to any one of [1] to [7].
[9] With the anode
With the cathode
A first layer provided between the anode and the cathode and having a function of emitting light,
A second layer provided between the cathode and the first layer is provided.
The second layer is an organic electroluminescence device containing the compound for an organic electroluminescence device according to any one of [1] to [7].
[10] The organic electroluminescence device according to [9], wherein the first layer and the second layer are in contact with each other.
[11] A display device including the organic electroluminescence device according to [9] or [10].
[12] A lighting device including the organic electroluminescence device according to [9] or [10].

By the above means of the present invention, for example, it is possible to provide a new compound for an organic EL element capable of improving the luminous efficiency and heat resistance of the organic EL element. Furthermore, by the above means of the present invention, it is possible to provide a new organic EL element that has realized high durability and heat resistance. Further, it is possible to provide a display device and a lighting device provided with the organic EL element of the present invention.

It is a schematic diagram which showed the energy diagram of the TADF compound. It is a schematic diagram which showed the energy diagram of a general fluorescent compound. It is a schematic diagram which showed the energy diagram when the π-conjugated compound functions as a host material.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "~" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

The present inventors have linked a triazine skeleton and a dibenzofuran skeleton via a phenylene group so as to have a mutual positional relationship at the meta position (hereinafter, "compound for organic EL element of the present invention" or "compound of the present invention". However, it was found that an organic EL element having high glass transition temperature and high triplet energy, thereby having high heat resistance, little decrease in light emission efficiency, and high durability can be obtained. It was. The reason is not always clear, but it is presumed as follows.

(Wide π electron conjugated system)
It is considered preferable as the organic EL device material that the compound for an organic EL device of the present invention has a plurality (3 or more) dibenzofuran skeletons which have a wide π-electron conjugated system but do not easily reduce triplet energy. Be done. When electric charges are transported by a low-molecular-weight organic EL material, a mechanism called hopping conduction works, and it is said that the greater the overlap of π-electron clouds between molecules, the more efficient conduction is. Dibenzofuran is a skeleton in which 14 π electrons are conjugated, and has a wide π electron cloud spread, so that it is suitable as an organic EL device material. In addition, dibenzofuran is a skeleton capable of maintaining a high triplet energy, although the triplet energy of a compound usually decreases due to the extension of the conjugated system. Therefore, when used together with TADF materials and phosphorescent materials in which triplet excitons are involved in light emission, it is possible to suppress the transfer of those triplet energies to the compound for organic EL elements of the present invention, and thus the light emission efficiency. It is considered that this contributed to the improvement of the durability of the organic EL element.

(Introduction of phenylene linking group)
In the compound for an organic EL device of the present invention, a triazine skeleton and a dibenzofuran skeleton are linked via a phenylene group. It is considered that the presence of this phenylene group raises the glass transition temperature and enhances heat resistance by bringing about an appropriate increase in molecular weight. Further, since the phenylene group has π electrons, its conductivity is not impaired by its introduction, so that it is considered that the luminous efficiency is improved and the durability of the organic EL element is also improved. However, the introduction of phenylene groups is preferable from the viewpoint of increasing the molecular weight without adversely affecting the charge transport characteristics, but since the extension of the π-electron conjugated system causes a decrease in the triplet energy of the compound, it is randomly introduced. However, favorable results are not always obtained as a peripheral material used together with a phosphorescent material or a TADF material. In the present invention, the triazine skeleton and the dibenzofuran skeleton are linked via the meta position of the phenylene group that links them, thereby localizing the electric charge and suppressing the decrease in triplet energy, resulting in high luminescence efficiency. It is considered that the provision of the organic EL element showing the above can be realized. The present invention has been made based on such findings. Hereinafter, the compound for an organic EL device of the present invention will be specifically described.

<Compound for organic EL device of the present invention>
The compound for an organic EL device of the present invention has a structure represented by the following general formula (1).

A _{1 to} A ₃ in the general formula (1) are substituted or unsubstituted dibenzofuranyl groups independently represented by the general formula (2).

At least one of B _{1 to} B ₈ in the general formula (2) is a bond that binds to the structure of the general formula (1), and the rest represents a hydrogen atom or a substituent. Examples of the substituent substituting the dibenzofuranyl group include an aryl group, an alkyl group, a heteroaryl group and the like.

The aryl group to be substituted with the dibenzofuranyl group is preferably a group derived from an aromatic hydrocarbon ring having 6 to 24 carbon atoms. Examples of such aromatic hydrocarbon rings include benzene ring, inden ring, naphthalene ring, azulene ring, fluorene ring, phenanthrene ring, anthracene ring, acenaphtylene ring, biphenylene ring, naphthalene ring, pyrene ring, pentalene ring, and acetylene ring. Trilene ring, heptalene ring, triphenylene ring, as-indacene ring, chrysene ring, s-indacene ring, pleiaden ring, phenalene ring, fluoranthene ring, perylene ring, acephenanthrene ring, biphenyl ring, terphenyl ring, and Includes tetraphenyl ring and the like. Of these, benzene ring, naphthalene ring, fluorene ring, phenanthrene ring, anthracene ring, biphenylene ring, chrysene ring, pyrene ring, triphenylene ring, chrysene ring, fluoranthene ring, perylene ring, biphenyl ring, and terphenyl ring are preferable.

The alkyl group substituted with the dibenzofuranyl group may be linear, branched or cyclic, for example, a linear or branched alkyl group having 1 to 20 carbon atoms, or a cyclic group having 5 to 20 carbon atoms. Can be an alkyl group of. Examples of alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, n-pentyl group, neopentyl group, n-hexyl group and cyclohexyl. Group, 2-ethylhexyl group, n-heptyl group, n-octyl group, 2-hexyloctyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n- Includes tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecil group, n-icosyl group and the like; preferably methyl group, ethyl group, isopropyl group, t -Butyl group, cyclohexyl group, 2-ethylhexyl group and 2-hexyloctyl group.

The heteroaryl group substituted with the dibenzofuranyl group is preferably a group derived from an electron-donating heterocycle having 4 to 24 carbon atoms. Examples of such heterocycles include pyrrole ring, indole ring, carbazole ring, indoleindole ring, 9,10-dihydroacrine ring, 5,10-dihydrophenazine ring, 5,10-dihydrodibenzoazacillin ring, Phenoxazine ring, phenothiazine ring, dibenzothiophene ring, benzofurylindole ring, benzothienoindole ring, indolocarbazole ring, benzofurylcarbazole ring, benzothienocarbazole ring, benzothienobenzothiophene ring, benzocarbazole ring, dibenzocarbazole ring, Azacarbazole ring, diazacarbazole ring and the like are included. Among them, carbazole ring, azacarbazole ring, diazacarbazole ring, indoleindole ring, 9,10-dihydroacridine ring, 5,10-dihydrophenazine ring, phenothiazine ring, phenothiazine ring, dibenzothiophene ring, and benzofuryl indole. Rings are preferred. More preferably, an optionally substituted carbazole ring, an optionally substituted azacarbazole ring, an optionally substituted diazacarbazole ring, an optionally substituted 9,10-dihydroacridine ring, substituted. Phenothiazine ring which may be present, phenothiazine ring which may be substituted, 5,10-dihydrophenazine ring which may be substituted, dibenzothiophene oxide ring, dibenzothiophene dioxide ring, pyridine ring, pyridazine ring, pyrimidine ring. , Pyrazine ring, triazine ring, quinoline ring, isoquinoline ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, phenothiazine ring, phenanthrolin ring, dibenzofuran ring, dibenzosilol ring, dibenzoborol ring, dibenzophos Includes whole oxide rings and the like. Among them, pyridine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, phenanthridine ring, phenanthridine ring, dibenzofuran ring, dibenzoborol ring and dibenzophosphor oxide ring can be mentioned. .. Alternatively, the same or different two or more heterocycles may be bonded via a single bond.

The aryl group and heteroaryl group substituted with the dibenzofuranyl group may be further substituted with another substituent. Examples of such substituents include alkyl groups and aryl groups that may be substituted with alkyl groups. The alkyl group and the aryl group are synonymous with the above-mentioned alkyl group and aryl group, respectively.

The binding agent of the substituted or unsubstituted dibenzofuranyl group represented by the general formula (2) to the structure represented by the general formula (1) may be any of B _{1 to} B ₈ . It is preferably B ₃ or B ₆ . A compound in which the substituted or unsubstituted dibenzofuranyl group represented by the general formula (2) is bonded to the structure represented by the general formula (1) in B ₃ or B ₆ is triplet because the π conjugation does not spread too much. This is because the term energy can be made higher.

A _{1 to} A ₃ of the general formula (1) may be the same group or different groups, but it is preferable that all of A _{1 to} A ₃ are the same group. Furthermore, it is more preferable that the bonding positions of these groups are also the same as each other. As described above, a compound having a symmetric structure is considered to be more advantageous for packing molecules in a thin film than a compound having an asymmetric structure, and is therefore preferable from the viewpoint of improving conductivity and the like. Further, among the exemplary compounds shown below because they do not contain an alkyl group and have high symmetry, the exemplary compounds E-1 and E-2 are preferable, and in particular, the exemplary compounds in which the π-electron system of the molecule is widely spread spatially. E-2 is preferable from the viewpoint of improving conductivity.

Hereinafter, preferred specific examples of the compound for an organic EL device of the present invention will be given, but these compounds may further have a substituent or may have a structural isomer or the like, and are limited to this description. Not done.

(Synthesis method)
The compound for an organic EL device of the present invention is described in, for example, Non-Patent Document 5, International Publication No. 2010/117355, Organic Letters, 2002, 4, 1783-1785. , Angew. Chem. Int. Ed. 2010, 49, 2014-2017. It can be synthesized by referring to the method described in 1 or the method described in the references described in these documents.

(Glass-transition temperature)
It is considered that the higher the glass transition temperature (Tg) of the compound for an organic EL device of the present invention, the better the heat resistance (high temperature durability) of the organic EL device containing the compound. Therefore, the Tg is preferably 100 ° C. or higher, and more preferably 110 or higher. Further, it is preferably 400 ° C. or lower. When the Tg of the compound for an organic EL device of the present invention is 100 ° C. or higher, it is considered that the heat resistance of the organic EL device containing the compound is also improved. Further, when the organic EL element is manufactured by the coating method, a step of drying the residual solvent from the formed thin film is required. When a thin film is produced using the compound for an organic EL device of the present invention, it is considered that the stability of the thin film during the heating step for drying is also high because the glass transition temperature is high. The glass transition temperature can be measured using differential scanning calorimetry (DSC), for example, a differential scanning calorimeter DSC204F1 / Phoenix (manufactured by Netzsch).

(ΔE _ST )
Delta] E _ST of compound for organic EL device of the present invention, it is preferable in view of durability or less 0.8 eV. If Delta] E _ST of compound for organic EL device is large, because it possible to achieve both stability and high triplet energy of the compound itself becomes difficult, it is preferable Delta] E _ST is less than 0.8 eV. Delta] E _ST that is higher large and triplet energy level would that singlet energy level yet much greater than that. While the organic EL device is driven, it is desirable that charges are recombined in the light emitting material, but an undesired charge recombination pattern may occur on other materials. If this occurs in a material having a high singlet energy, the probability of going through a process of self-decomposition other than the non-radiation deactivation process from the excited state increases, which causes a decrease in the drive life of the device. Therefore, in order to achieve both the range and a high triplet energy of preferred singlet energy, Delta] E _ST is preferably not more than 0.8 eV, more preferably not more than 0.7 eV.

Delta] E _ST of compound for organic EL device performs a quantum chemical calculation by time-dependent density functional theory _{(TD-DFT), S 1} , T 1 energy level values (respectively _{E (S 1), E (} T After calculating ₁ )), it can be calculated by applying it to the following formula.
ΔE _ST = | E (S ₁ ) -E (T ₁ ) |
For quantum chemistry calculations, Gaussian rev. Manufactured by Gaussian, USA. Using 9.0c, the functional is set to B3LYP and the basis set is set to 6-31 g (d).

Delta] E _ST of compound for organic EL device can be adjusted for example in the general formula (1), the binding position of a substituted or unsubstituted dibenzofuranyl group represented by the general formula (2). To reduce the Delta] E _ST is preferably, for example, the binding position of a substituted or unsubstituted dibenzofuranyl group represented by the general formula (2) and B _3, or B _6.

(Molecular weight)
In order to improve the thermal stability of the compound for an organic EL device of the present invention, it is considered preferable to increase the molecular weight to some extent or more. Specifically, the molecular weight of the compound for an organic EL device is preferably 700 or more. If the molecular weight is 700 or more, even if the compound for an organic EL device is exposed to a high temperature environment including heat during driving, there is a possibility that a state change such as crystallization of an organic thin film composed of the compound for an organic EL device may occur. Is low, so it is considered that deterioration of the element is unlikely to occur. The molecular weight of the compound for an organic EL device is more preferably 800 or more, and further preferably 1200 or less. When the molecular weight is 1200 or less, the sublimation property of the compound does not decrease and the solubility in a solvent does not decrease, so that a film can be formed. In the compound for an organic EL device of the present invention, it is considered that the number of dibenzofuran skeletons is three, which is suitable for realizing an appropriate molecular weight, and contributes to the improvement of heat resistance.

The method for measuring the molecular weight of the compound for an organic EL element is not particularly limited, and examples thereof include known mass spectrometry methods (electron ionization method, fast atom bombardment method, matrix-assisted laser desorption method, etc.), chromatographic method (GPC method), and the like. Examples include a light scattering method. For compounds for organic EL devices, it is preferable to use a number average molecular weight. Further, the number average molecular weight of the monodisperse material can be uniquely calculated from the structure.

The molecular weight of the compound for an organic EL device can be adjusted, for example, by the type and number of substituents substituted with the substituted or unsubstituted dibenzofuranyl group represented by the general formula (2).

(Value of molecular weight divided by Delta] E _ST)
Molecular weight of compound for organic EL device as described above is large, contributing to the improvement of heat resistance, it Delta] E _ST is small is considered to contribute to the extension of the operation life. However, not always the molecular weight is only just large necessarily improved heat resistance may not always be a significant contribution to the extension of the operation life with only Delta] E _ST is small. In order to improve the durability of the organic EL element in a high temperature environment, it is preferable to satisfy both of these within a certain range, in particular the value obtained by dividing the molecular weight of the compound in Delta] E _ST 1,000 or more Is preferable, and 1200 or more is more preferable.

The molecular weight of the compound for organic EL device divided by Delta] E _ST can be adjusted by the molecular weight of the compound and Delta] E _ST. The molecular weight of the compound in order to increase the value obtained by dividing the Delta] E _ST is, for example preferable to reduce the Delta] E _ST in the same manner as described above.

The compound for an organic EL device having a structure represented by the general formula (1) can be used as an organic EL device.

The compound for an organic EL device of the present invention is particularly preferably used as an electron transport material because both the triazine skeleton and the dibenzofuran skeleton contain an element having a high electronegativity. Further, since the compound for an organic EL element has a high triplet excitation energy, a layer having a light emitting function containing either or both of a phosphorescent compound and a TADF luminous compound (first layer described later). It is also preferable that it is contained in a layer adjacent to (a second layer described later). However, the compound for an organic EL element has a wide π-conjugated system and is considered to exhibit sufficient charge transport property for both holes and electrons. Therefore, the compound for an organic EL element of the present invention. The application is not limited to this, and may be used for a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer, an electron injection layer, an intermediate layer, an exciton blocking layer and the like.

The organic EL element of the present invention can be suitably provided in a lighting device and a display device.

Next, the light emitting method and the light emitting material of the organic EL element related to the present invention will be described.

<Light emission method of organic EL element>
There are two types of emission methods for organic EL: "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 excitators are generated with a 75% probability and singlet excitors are generated with a 25% probability, so phosphorescence emission is more efficient than fluorescence emission. It is an excellent method to realize low power consumption.

On the other hand, even in fluorescence emission, triplet exciters, which are normally generated with a 75% probability and whose energy of the exciter is normally only heat due to non-radiation deactivation, are present at high density. A method using a TTA (Triplet-Triplet Annihilation, or Triplet-Triplet Fusion: abbreviated as "TTF") mechanism that generates one singlet-excited element from two triplet-excited states to improve light emission efficiency is available. It has been found.

Furthermore, in recent years, by reducing the energy gap between the single-term excited state and the triple-term excited state by the discovery of Adachi et al., The triplet with a low energy level due to Joule heat during light emission and / or the ambient temperature at which the light-emitting element is placed A phenomenon in which inverse intertermic intersection occurs from a term-excited state to a single-term excited state, and as a result, fluorescence emission close to 100% is possible (also referred to as thermal-excited delayed fluorescence or thermally excited delayed fluorescence: "TADF"). Fluorescent substances that make this possible have been found (see, for example, Non-Patent Document 1 and the like).

<< Phosphorescent compound >>
As mentioned above, phosphorescence emission is theoretically three times more advantageous than fluorescence emission in terms of emission efficiency, but energy deactivation (= phosphorescence emission) from the triplet excited state to the singlet base state is prohibited. Since it is a transition, and similarly, the crossing between terms from the singlet excited state to the triplet excited state is also a forbidden transition, its velocity constant is usually small. That is, since the transition is unlikely to occur, the exciton lifetime becomes long on the order of milliseconds to seconds, 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 3 orders of magnitude or more due to the heavy atom effect of the central metal, and depending on the selection of the ligand, 100 It is also possible to obtain a phosphorus photon yield of%.
However, in order to obtain such ideal luminescence, it is necessary to use precious metals such as iridium, palladium, and platinum, which are rare metals, so-called white metals, and when they are used in large quantities, their reserves and The price of the metal itself becomes a major industrial problem.

《Fluorescent compound》
A general fluorescent compound does not particularly need to be 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-metal elements such as phosphorus, sulfur, and silicon can be used, and complexes of typical metals such as aluminum and zinc can also be used, so that the variety can be said to be almost infinite.
However, since only 25% of excitons can be applied to light emission with a conventional fluorescent compound as described above, high-efficiency light emission such as phosphorescence light emission cannot be expected.

<< Delayed fluorescent compound >>
[Excited triplet-triplet annihilation (TTA) delayed fluorescent compound]
A light emission method using delayed fluorescence has been introduced to solve the problems of fluorescent compounds. The TTA method originating from collisions between triplet excitons can be described by the following general formula. That is, there is an advantage that a part of triplet excitons, in which the exciton energy is conventionally converted only into heat by non-radiation deactivation, can cross the singlet excitons that can contribute to light emission. Even in an actual organic EL element, it is possible to obtain an external extraction quantum efficiency about twice that of a conventional fluorescent light emitting element.

General formula: T ^* + T ^* → S ^* + S
(In the equation, 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 the two triplet excitons, it is not possible in principle 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.
Fluorescent compounds have the advantage of being able to design an infinite number of molecules as described above. That is, among the molecularly designed compounds, there are compounds in which the energy level differences between the triplet excited state and the singlet excited state are extremely close to each other.
Such compounds, even though in the molecule does not have a heavy atom, reverse intersystem crossing from a triplet excited state is usually not occur because Delta] E _ST is smaller to the singlet excited state occurs. Furthermore, since the rate constant of deactivation (= fluorescence emission) from the singlet excited state to the ground state is extremely large, the triplet excited state itself is thermally deactivated to the ground state (non-radiation deactivation). It is more rhythmically advantageous to return to the ground state while emitting fluorescence via the singlet excited state. Therefore, TADF can theoretically emit 100% fluorescent light.

<Organic EL element of the present invention>
Next, an organic EL device using the compound for an organic EL device of the present invention will be described.

<< Constituent layer of organic EL element >>
The organic EL element of the present invention includes a first layer provided between the anode and the cathode and having a light emitting function, and a second layer provided between the cathode and the first layer. The organic EL element, the second layer contains the compound for the organic EL element of the present invention.

Typical element configurations in the organic EL device of the present invention include, but are not limited to, the following configurations.
Anode / light emitting layer / electron transport layer / cathode anode / hole transport layer / light emitting layer / electron transport layer / cathode anode / hole injection layer / hole transport layer / (electron blocking layer /) light emitting layer / (hole blocking) Layer /) Electron transport layer / Electron injection layer / Anode

The first layer in the organic EL device of the present invention, that is, the first layer having a function of emitting light is a layer generally called a "light emitting layer". The light emitting layer is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the light emitting layers.

In the present invention, a second layer is provided between the first layer (light emitting layer) having a function of emitting light and the cathode. Examples of the second layer include a hole blocking layer (also referred to as a hole barrier layer), an electron transport layer, an electron injection layer (also referred to as a cathode buffer layer), and the like. Further, an electron blocking layer (also referred to as an electron barrier layer), a hole transport layer, a hole injection layer (also referred to as an anode buffer layer), or the like may be provided between the light emitting layer and the anode.

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. Further, it may be composed of a plurality of 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. Further, it may be composed of a plurality of layers.

The second layer containing the compound for an organic EL device of the present invention may be only one layer, or may have two or more layers. Above all, the compound for the organic EL element of the present invention has a high triplet energy, and it is difficult to reduce the light emitting efficiency of the luminescent compound contained in the first layer (light emitting layer). The compound is preferably contained in a second layer that is in contact with the first layer.

Hereinafter, each layer constituting the organic EL device of the present invention will be described.

《Light emitting layer》
The light emitting layer used in the present invention is a layer that provides a place where electrons and holes injected from an electrode or an adjacent layer are recombined and emit light via excitons, and the light emitting portion is a layer of the light emitting layer. It may be inside or at the interface between the light emitting layer and the adjacent layer.

The total thickness of the light emitting layer is not particularly limited, but the homogeneity of the formed film, prevention of applying an unnecessary high voltage at the time of light emission, and improvement of the stability of the emission color with respect to the drive current are improved. From the viewpoint, it is preferably adjusted to the range of 2 nm to 5 μm, more preferably to the range of 2 to 500 nm, and further preferably to the range of 5 to 200 nm.
The thickness of the individual light emitting layers used in the present invention is preferably adjusted to the range of 2 nm to 1 μm, more preferably adjusted to the range of 2 to 200 nm, and further preferably adjusted to the range of 3 to 150 nm. Be adjusted.

The light emitting layer used in the present invention may be one layer or may be composed of a plurality of layers. For example, at least one layer of the light emitting layer contains a light emitting dopant (a light emitting compound, a light emitting dopant, also simply referred to as a dopant), and further contains a host compound (a matrix material, a light emitting host compound, also simply referred to as a host). It can be a layer.

(1) Light-emitting dopant As the light-emitting dopant, a fluorescent light-emitting dopant (also referred to as a fluorescent light-emitting compound or a fluorescent dopant) and a phosphorescent light-emitting dopant (also referred to as a phosphorescent light-emitting compound or a phosphorescent dopant) are preferably used. Be done.

In the present invention, the light emitting layer preferably contains the luminescent compound in the range of 0.1 to 50% by mass, and particularly preferably in the range of 1 to 30% by mass.
The concentration of the luminescent compound in the light emitting layer can be arbitrarily determined based on the specific luminescent compound used and the requirements of the device, and the concentration is uniform with respect to the layer thickness direction of the light emitting layer. It may be contained or may have an arbitrary concentration distribution.
Further, the luminescent compound used in the present invention may be used in combination of a plurality of types, and may be used in combination of fluorescent compounds having different structures or in combination of a fluorescent compound and a phosphorescent compound. You may. Thereby, an arbitrary emission color can be obtained.

FIG. 3 shows a schematic diagram of the host compound. FIG. 3 is an example, and the process of generating triplet excitons generated on the host compound is not limited to electric field excitation, but also includes energy transfer and electron transfer within the light emitting layer or from the interface of the peripheral layer.
Further, in FIG. 3, a fluorescent compound is used as the light emitting material, but the present invention is not limited to this, and a phosphorescent compound or a TADF fluorescent compound may be used. However, a plurality of these may be used at the same time.

When the light emitting layer contains a host compound, the light emitting layer contains a fluorescent compound and / or a phosphorescent compound and / or a TADF fluorescent compound in a mass ratio of 0.1 to 50% with respect to the host compound. It is preferable to contain it within. Further, it is preferable that the emission spectrum of the host compound and the absorption spectrum of the luminescent compound overlap.

The color emitted by the organic EL element of the present invention is shown in FIG. 3.16 on page 108 of the "New Color Science Handbook" (edited by the Japan Color Society, edited by the University of Tokyo Press, 1985), and the spectral radiance meter CS-1000 (Konica). It is determined by the color when the result measured by a measuring instrument such as Minolta Co., Ltd.) or the spectroradiance meter SR3-AR (manufactured by Topcon Techno House) 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 light emitting colors and exhibits white light emission.
The combination of light emitting dopants showing white color is not particularly limited, and examples thereof include a combination of blue and orange, a combination of blue and green and red, and the like.
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 degree viewing angle front luminance is measured by the above method. , Y = 0.38 ± 0.08, preferably within the region.

(1.1) Fluorescent Luminescent Dopant The fluorescent luminescent dopant (fluorescent dopant) is one of known fluorescent dopants and delayed fluorescent dopants (also referred to as TADF fluorescent luminescent compounds) used in the light emitting layer of an organic EL element. You may use it by appropriately selecting from.

Specific examples of known fluorescent dopants that can be used in the present invention include, for example, anthracene derivatives, pyrene derivatives, chrysene derivatives, fluorantene derivatives, perylene derivatives, fluorene derivatives, arylacetylene derivatives, styrylarylene derivatives, styrylamine derivatives, and arylamine derivatives. , Boron complex, coumarin derivative, pyran derivative, cyanine derivative, croconium derivative, squalium derivative, oxobenzanthracene derivative, fluorescein derivative, rhodamine derivative, pyrylium derivative, perylene derivative, polythiophene derivative, rare earth complex compound and the like. Further, in recent years, light emitting dopants using delayed fluorescence have also been developed, and these may be used. Specific examples of the light emitting dopant using delayed fluorescence include compounds described in International Publication No. 2011/156793, Japanese Patent Application Laid-Open No. 2011-213643, Japanese Patent Application Laid-Open No. 2010-93181, Japanese Patent No. 5366106, and the like. However, the present invention is not limited to these.

(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 phosphorescent 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 phosphorus photon yield can be measured by the method described on page 398 (1992 edition, Maruzen) of Spectroscopy II of the 4th edition Experimental Chemistry Course 7. The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescence dopant used in the present invention achieves the above phosphorescence quantum yield (0.01 or more) in any of any solvents. Just do it.

The phosphorescent dopant can be appropriately selected from known ones used for the light emitting layer of the organic EL element. 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), Apple. Phys. Lett. 78, 1622 (2001), Adv. Mater. 19,739 (2007), Chem. Mater. 17, 3532 (2005), Adv. Mater. 17,1059 (2005), International Publication No. 2009/10991, International Publication No. 2008/101842, International Publication No. 2003/040257, US Patent Application Publication No. 2006/835469, US Patent Application Publication No. 2006 / 020194, US Patent Application Publication No. 2007/0087321, US 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, Apple. 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 Patent No. 7332232 , US Patent Application Publication No. 2009/01087737, US Patent Application Publication No. 2009/00397776, US Patent Application Publication No. 6921915, US Patent No. 6687266, US Patent Application Publication No. 2007/0190359 Specification, US Patent Application Publication No. 2006/0008670, US Patent Application Publication No. 2009/0165846, US Patent Application Publication No. 2008/0015355, US Patent No. 7250226, US Patent No. 7396598, US Patent Application Publication No. 2006/0263635, US Patent Application Publication No. 2003/0138657, US Patent Application Publication No. 2003/0152802, US Patent Application Publication No. 70090928, Angew .. Chem. lnt. Ed. 47, 1 (2008), Chem. Mater. 18,5119 (2006), Inorg. Chem. 46,4308 (2007), Organometallics 23,3745 (2004), Apple. Phys. Lett. 74,1361 (1999), International Publication No. 2002/002714, International Publication No. 2006/090024, 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. 2005/02060441, US Patent No. 73935999 Specification, US Patent No. 7534505, US Patent No. 7445855, US Patent Application Publication No. 2007/0190359, US Patent Application Publication No. 2008/0297033, US Patent No. 7338722. , US Patent Application Publication No. 2002/0134984, US Patent No. 7279704, US Patent Application Publication No. 2006/098120, US Patent Application Publication No. 2006/103874, International Publication No. 2005 / 07680, International Publication No. 2010/032663, International Publication No. 2008/140115, International Publication No. 2007/05/2431, International Publication No. 2011/134013, International Publication No. 2011/157339, International Publication No. 2010/086089 , International Publication No. 2009/113646, International Publication No. 2012/20327, International Publication No. 2011/051404, International Publication No. 2011/004639, International Publication No. 2011/073149, US Patent Application Publication No. 2012/228583 Specification, US Patent Application Publication No. 2012/212126, Japanese Patent Application Laid-Open No. 2012-069737, Japanese Patent Application Laid-Open No. 2011-181303, Japanese Patent Application Laid-Open No. 2009-114086, Japanese Patent Application Laid-Open No. 2003-81988, Japanese Patent Application Laid-Open No. 2002 −302671A, JP-A-2002-363552, and the like.
Among them, preferred phosphorescent dopants include organometallic complexes having Ir as the central metal. More preferably, a complex containing at least one coordination mode of metal-carbon bond, metal-nitrogen bond, metal-oxygen bond and metal-sulfur bond is preferable.

The luminescent compound contained in the light emitting layer is preferably a fluorescent luminescent compound in that high luminous efficiency can be easily obtained when combined with the second layer containing the compound for an organic EL element of the present invention, and is delayed. More preferably, it is a fluorescent compound. It is also preferable that the luminescent compound contained in the light emitting layer is a phosphorescent compound.

(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.
Among the compounds contained in the light emitting layer, the host compound preferably has a mass ratio of 20% or more in the layer.
The host compound may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of electric charges, and it is possible to improve the efficiency of the organic EL device.

Further, the host compound has a hole transporting ability or an electron transporting ability, prevents the wavelength of light emission from being lengthened, and is stable against heat generation when the organic EL device is driven at a high temperature or during the device driving. From the viewpoint of operation, it is preferable to have a high glass transition temperature (Tg). Tg is preferably 90 ° C. or higher, and 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: differential scanning calorimetry).

The host compound may be a compound for an organic EL device of the present invention, or may be another known host compound.

When a known host compound is used for the organic EL device of the present invention, specific examples thereof include the compounds described in the following documents, but the present invention is not limited thereto.
JP 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786, 2002-8860, 2002-334787A, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002. 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003 No. 3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-260861, No. 2002-280183, No. 2002-299060, No. 2002- 302516, 2002-305083, 2002-305084, 2002-308837, US Patent Application Publication No. 2003/0175553, US Patent Application Publication No. 2006/0280965, USA Publication of Patent Application Publication No. 2005/0112407, Publication of US Patent Application Publication No. 2009/0017330, Publication of US Patent Application Publication No. 2009/0030202, Publication of US Patent Application Publication No. 2005/0238919, International Publication No. 2001/039234, International Publication No. 2009/021126, International Publication No. 2008/056746, International Publication No. 2004/093207, International Publication No. 2005/089025, International Publication No. 2007/0637996, International Publication No. 2007 / 063754, International Publication No. 2004/107822, International Publication No. 2005/030900, International Publication No. 2006/114966, International Publication No. 2009/086028, International Publication No. 2009/003898, International Publication No. 2012/0293947 , Japanese Patent Application Laid-Open No. 2008-074939, Japanese Patent Application Laid-Open No. 2007-254297, European Patent No. 2034538, International Publication No. 2011/055933, International Publication No. 2012/035853, Japanese Patent Application Laid-Open No. 2015-38941, etc. Ah To. Examples of host compounds described in JP-A-2015-38941 include compounds H-1 to H-230 described in [0255] to [0293] of the specification.

Specific examples of the compound as the host compound used in the present invention are shown below, but the present invention is not limited thereto.

《Electron transport layer》
In the present invention, the electron transport layer may be 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.
The total thickness of the electron transport layer is not particularly limited, but is usually in the range of 2 nm to 5 μm, more preferably 2 to 500 nm, and further preferably 5 to 200 nm.

The material used for the electron transport layer (hereinafter referred to as an electron transport material) may have any of electron injection property, transport property, and hole barrier property, and is used for the organic EL device of the present invention. It is preferable to use a compound. The electron transport material contained in the electron transport layer may be one kind or two or more kinds. For example, the electron transport layer may further contain not only the compound for an organic EL device of the present invention as an electron transport material, but also other conventionally known electron transport materials.

Conventionally known electron transporting materials include, for example, nitrogen-containing aromatic heterocyclic derivatives (carbazole derivatives, azacarbazole derivatives (one or more carbon atoms constituting the carbazole ring substituted with nitrogen atoms), pyridine derivatives, and the like. Pyrimidine derivative, pyrazine derivative, pyridazine derivative, triazine derivative, quinoline derivative, quinoxalin derivative, phenanthroline derivative, azatriphenylene derivative, oxazole derivative, thiazole derivative, oxadiazole derivative, thiadiazol derivative, triazole derivative, benzimidazole derivative, benzoxazole derivative, Benzthiazole derivatives, etc.), dibenzofuran derivatives, dibenzothiophene derivatives, silol derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, triphenylene derivatives, etc.) and the like.

Further, 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), etc., and metal complexes thereof. A metal complex in which the central metal is replaced with In, Mg, Cu, Ca, Sn, Ga or Pb can also be used as an electron transport material.
In addition, metal-free or metal phthalocyanine, or those whose terminals are substituted with an alkyl group, a sulfonic acid group, or the like can also be preferably used as an electron transport material. Further, 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 or n-type-SiC is used like the hole injection layer and the hole transport layer. Can also be used as an electron transport material.
Further, it is also possible to use a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain.

In the electron transport layer, 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 compounds and metal compounds such as metal halides. Specific examples of the electron transport layer having such a structure include, for example, JP-A-4-2970776, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175, J. Mol. Apple. Phys. , 95, 5773 (2004) and the like.

Specific examples of known and preferable electron transport materials other than the compound for the organic EL device of the present invention used for the organic EL device of the present invention include the compounds described in the following documents, and the present invention includes these. Not limited.
US Patent No. 6528187, US Patent No. 7230107, US Patent Application Publication No. 2005/0025993, US Patent Application Publication No. 2004/0036077, US Patent Application Publication No. 2009/0115316. Books, US Patent Application Publication No. 2009/0101870, US Patent Application Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132805, Appl. Phys. Lett. 75, 4 (1999), Apple. Phys. Lett. 79,449 (2001), Apple. Phys. Lett. 81, 162 (2002), Apple. Phys. Lett. 81, 162 (2002), Apple. Phys. Lett. 79,156 (2001), US Patent No. 7964293, US Patent Application Publication No. 2009/030202, International Publication No. 2004/080975, International Publication No. 2004/063159, International Publication No. 2005/085387 , International Publication No. 2006/067931, International Publication No. 2007/0865552, International Publication No. 2008/114690, International Publication No. 2009/0694242, International Publication No. 2009/066797, International Publication No. 2009/054253, International Publication No. 2011/086935, International Publication No. 2010/150593, International Publication No. 2010/047707, European Patent No. 2311826, JP-A-2010-251675, JP-A-2009-209133, JP-A-2009. -124114, 2008-277810, 2006-156445, 2005-340122, 2003-45662, 2003-31367, 2003-282270. No., International Publication No. 2012/11034, etc.
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 transporting 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 is positive while transporting electrons. By blocking the holes, the probability of recombination of electrons and holes can be improved.
In addition, the above-mentioned structure of the electron transport layer can be used as a hole blocking layer, if necessary.
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 thickness of the hole blocking layer 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 hole blocking layer, the material used for the electron transport layer described above is preferably used, and the material used as the host compound described above is also preferably used for the hole blocking layer.

《Electron injection layer》
The electron injection layer (also referred to as "cathode buffer layer") is a layer provided between the cathode and the light emitting layer in order to reduce the driving voltage and improve the emission brightness, and is "organic EL element and its forefront of industrialization". It is described in detail in Volume 2, Chapter 2, "Electrode Materials" (pages 123-166) of "November 30, 1998, published by NTS".
The electron injection layer may be provided as needed 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. Further, it may be a non-uniform layer (film) in which the constituent material is intermittently present.

The details of the electron-injected layer are also described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like, and specific examples of materials preferably used for the electron-injected layer include , Metals such as strontium and aluminum, alkali metal compounds such as lithium fluoride, sodium fluoride and potassium fluoride, alkaline earth metal compounds such as magnesium fluoride and calcium fluoride, oxidation Examples thereof include metal oxides typified by aluminum, metal complexes typified by 8-hydroxyquinolinate lithium (Liq), and the like. It is also possible to use the above-mentioned electron transport material.
Further, the material used for the above-mentioned electron injection layer may be used alone or in combination of two or more.

《Hole transport layer》
The hole transport layer may be made of a material having a function of transporting holes (hereinafter referred to as a hole transport material) and may have a function of transmitting holes injected from the anode to the light emitting layer.
The total thickness of the hole transport layer is not particularly limited, but is usually in the range of 5 nm to 5 μm, more preferably 2 to 500 nm, and further preferably 5 to 200 nm.

The material used for the hole transport layer may have any of hole injectability, transportability, and electron barrier property, and any conventionally known compound may be selected and used. be able to.
For example, porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stillben derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives. , Indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, and polymer materials or oligomers in which polyvinylcarbazole and aromatic amines are introduced into the main chain or side chains, polysilane, conductivity. Examples thereof include sex polymers or oligomers (for example, PEDOT / PSS, aniline-based copolymers, polyaniline, polythiophene, etc.).

Examples of the triarylamine derivative include a benzidine type represented by α-NPD (4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) and a starburst type represented by MTDATA. Examples thereof include compounds having fluorene or anthracene in the triarylamine linking core portion.
Hexaazatriphenylene derivatives as described in JP-A-2003-591432 and JP-A-2006-135145 can also be used as the hole transport material in the same manner.
Further, 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, and JP-A-2001-102175. Apple. Phys. , 95, 5773 (2004) and the like.

In addition, JP-A-11-251667, J. Am. Hung et. al. So-called p-type hole transport materials and inorganic compounds such as p-type-Si and p-type-SiC, as described in the authored literature (Applied Physics Letters 80 (2002), p.139), can also be used. Further, an orthometalated organometallic complex having Ir or Pt in the central metal as represented by Ir (ppy) 3 is also preferably used.
As the hole transport material, the above-mentioned materials can be used, but a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organic metal complex, and an aromatic amine are introduced into the main chain or the side chain. High molecular weight materials or oligomers are preferably used.

Specific examples of known and preferable hole transporting materials used in the organic EL device of the present invention include the compounds described in the following documents in addition to the above-mentioned documents, but the present invention is limited thereto. Not done.
For example, Apple. Phys. Lett. 69,2160 (1996), J. Mol. Lumin. 72-74,985 (1997), Apple. Phys. Lett. 78,673 (2001), Apple. Phys. Lett. 90,183503 (2007), Apple. Phys. Lett. 90,183503 (2007), Apple. Phys. Lett. 51,913 (1987), Synth. Met. 87,171 (1997), Synth. Met. 91,209 (1997), Synth. Met. 111,421 (2000), SID Symposium Digist, 37,923 (2006), J. Mol. 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 / 0220265, US Patent No. 5061569, International Publication No. 2007/002683, International Publication No. 2009/01809, EP650955, US Patent Application Publication No. 2008/01245772, US Patent Application Publication No. 2007/0278938 Specification, US Patent Application Publication No. 2008/0106190, US Patent Application Publication No. 2008/0018221, International Publication No. 2012/115342, Japanese Patent Application Laid-Open No. 2003-591432, JP-A-2006-135145. , US Patent Application No. 13/585981, etc.
The hole transporting material may be used alone or in combination of two or more.

《Electronic blocking layer》
The electron blocking layer is a layer having a function of a hole transporting 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 the electrons, the probability of recombination of electrons and holes can be improved.
In addition, the structure of the hole transport layer described above can be used as an electron blocking layer, 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 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 hole transporting layer described above is preferably used, and the host compound described above is also preferably used for the electron blocking layer.

《Hole injection layer》
The hole injection layer (also referred to as “anode buffer layer”) is a layer provided between the anode and the light emitting layer in order to reduce the driving voltage and improve the emission brightness, and is “organic EL element and its forefront of industrialization”. (Published by NTS Co., Ltd., November 30, 1998) ”, Volume 2, Chapter 2,“ Electrode Materials ”(pages 123-166).
In the present invention, the hole injection layer may be provided as needed 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, 9-2660062, 8-288609, etc., and examples of the material used for the hole injection layer include. Examples thereof include materials used for the hole transport layer described above.
Among them, phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives as described in JP-A-2003-591432 and JP-A-2006-135145, metal oxides typified by vanadium oxide, amorphous carbon. , Polyaniline (emeraldine), polythiophene and other conductive polymers, tris (2-phenylpyridine) iridium complexes and the like, orthometallated complexes, triarylamine derivatives and the like are preferable.
The material used for the hole injection layer described above may be used alone or in combination of two or more.

"Additive"
Each of the above-mentioned layers 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, compounds and complexes of transition metals, salts and the like.
The content of the additive can be arbitrarily determined, but is preferably 1000 ppm or less, more preferably 500 ppm or less, still more preferably 50 ppm or less, based on 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 and the purpose of favoring the energy transfer of excitons.

<< How to form each layer >>
A method for forming each of the above-mentioned layers (hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, intermediate layer, etc.) will be described.
The method for forming each layer described above is not particularly limited, and a conventionally known forming method such as a vacuum vapor deposition method or a wet method (also referred to as a wet process) can be used.
The wet method includes a spin coating method, a casting method, an inkjet method, a printing method, a die coating method, a blade coating method, a roll coating method, a spray coating method, a curtain coating method, an LB method (Langmuir-Blogget method), and the like. From the viewpoint of easy obtaining a uniform thin film and high productivity, a method having high suitability for the roll-to-roll method such as a die coating method, a roll coating method, an inkjet method, and a spray coating method is preferable.

Examples of the liquid medium for dissolving or dispersing the organic EL element 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 and 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.
Further, as a dispersion method, dispersion can be performed by a dispersion method such as ultrasonic waves, high shear force dispersion, or media dispersion.
Further, a different film forming method may be applied to each layer. The case of employing an evaporation method in the deposition, the deposition conditions may vary due to kinds of materials used, generally boat temperature 50 to 450 ° C., vacuum of ¹⁰ -6 ^{to 10} -2 Pa, deposition rate 0.01 It is desirable to appropriately select within the range of 50 nm / sec, substrate temperature -50 to 300 ° C., layer (film) thickness 0.1 nm to 5 μm, preferably 5 to 200 nm.
The formation of each of the above-mentioned layers is preferably carried out consistently from the hole injection layer to the cathode by one vacuuming, but it may be taken out in the middle and a different film forming method may be applied. In that case, it is preferable to carry out the work in a dry inert gas atmosphere.

"anode"
As the anode in the organic EL element, a metal, an alloy, an electrically conductive compound having a large work function (4 eV or more, preferably 4.5 eV or more) and a mixture thereof as an electrode material are preferably used. Specific examples of such electrode materials include metals such as Au and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Further, a material such as IDIXO (In ₂ O _3- ZnO) that is amorphous and can produce a transparent conductive film may be used.
For the anode, a thin film may be formed by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not required so much (about 100 μm or more). The pattern may be formed through a mask having a desired shape during vapor deposition or sputtering of the electrode material.
Alternatively, when a coatable substance such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can also be used. When light emission is taken out from this anode, it is desirable to increase the transmittance to more 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 metal having a small work function (4 eV or less) (referred to as an electron-injectable metal), an alloy, an electrically conductive compound, or 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 ) Examples thereof include a mixture, indium, a lithium / aluminum mixture, aluminum, and a rare earth metal. Among these, from the viewpoint of electron injectability and durability against oxidation and the like, a mixture of an electron injectable 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 mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, lithium / aluminum mixture, aluminum and the like are suitable.

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 of 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, it is convenient that the emission brightness is improved if either the anode or the cathode of the organic EL element is transparent or translucent.
Further, a transparent or translucent cathode can be produced by producing the above metal on the cathode having a film thickness of 1 to 20 nm and then producing the conductive transparent material mentioned in the description of the anode on the cathode. By applying the above, it is possible to manufacture an element in which both the anode and the cathode are transparent.

[Support board]
The type of support substrate (hereinafter, also referred to as substrate, substrate, etc.) that can be used for the organic EL element of the present invention is not particularly limited, and even if it is transparent, it is opaque. You may. When light is taken out 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.

The external extraction quantum efficiency of the light emission of the organic EL device of the present invention at room temperature (25 ° C.) is preferably 1% or more, and more preferably 5% or more.
Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons passed through the organic EL element × 100.
Further, a hue improving 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 adhering a sealing member, an electrode, and a support substrate with an adhesive. The sealing member may be arranged so as to cover the display area of the organic EL element, and may be intaglio-shaped or flat-plate-shaped. Further, transparency and electrical insulation are not particularly limited.
Specific examples thereof 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.

[Protective film, protective plate]
A protective film or protective plate may be provided on the outer side of the sealing film or the sealing film on the side facing the support substrate with the constituent layer of the organic EL element sandwiched in order to increase the mechanical strength of the element. In particular, when the sealing is performed by the sealing film, its mechanical strength is not necessarily high, so it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, a glass plate, a polymer plate / film, a metal plate / film, etc. similar to those used for the sealing can be used, but the polymer film is lightweight and thin. It is preferable to use.

[Use]
The organic EL element of the present invention can be used as an electronic device, for example, a display device, a display, and various light emitting devices.
As the light emitting device, for example, a lighting device (household lighting, in-car lighting), a backlight for a clock or a liquid crystal, a signboard advertisement, a traffic light, a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processor, light Examples thereof include, but are not limited to, a light source of a sensor, but the light source can be effectively used as a backlight of a liquid crystal display device and a light source for lighting.

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

In the case of a multicolor display device, a shadow mask is provided only when the light emitting layer is formed, and a film can be formed on one surface by a vapor deposition method, a casting method, a spin coating method, an inkjet method, a printing method, or the like.
When patterning only the light emitting layer, the method is not limited, 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-mentioned configuration examples of the organic EL element, if necessary.

The method for manufacturing the organic EL device is as shown in the above-described aspect of manufacturing the organic EL device of the present invention.

The multicolor display device can be used as a display device, a display, or various light emitting light sources. Full-color display is possible by using three types of organic EL elements that emit blue, red, and green in a display device or display.

Examples of the display device or display include televisions, personal computers, mobile devices, AV devices, teletext displays, information displays in automobiles, and the like. In particular, it may be used as a display device for reproducing a still image or a moving image, and the drive system when used as a display device for reproducing a moving image may be either a simple matrix (passive matrix) system or an active matrix system.

Light emitting devices include household lighting, interior lighting, backlights for clocks and liquid crystals, signboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. However, the present invention is not limited thereto.

<Lighting device of the present invention>
The organic EL element of the present invention can also be used in a lighting device.
The organic EL element of the present invention may be used as an organic EL element having a resonator structure. The purpose of using the organic EL element having such a resonator structure includes a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processor, a light source of an optical sensor, and the like. Not limited. Further, it may be used for the above purpose by oscillating a laser.
Further, the organic EL element of the present invention may be used as a kind of lamp such as for lighting or an exposure light source, a projection device of a type for projecting an image, or a type for directly visually recognizing a still image or a moving image. It may be used as a display device (display).
When used as a display device for moving image playback, the drive system may be either a passive matrix system or an active matrix system. Alternatively, a full-color display device can be manufactured by using two or more kinds of organic EL elements of the present invention having different emission colors.

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

Further, in the method for forming the organic EL element of the present invention, a mask may be provided only when the light emitting layer, the hole transport layer, the electron transport layer, or the like is formed, and the mask may be applied separately. Since the other layers are common, patterning such as a mask is not required, and an electrode film can be formed on one surface by a vapor deposition method, a casting method, a spin coating method, an inkjet method, a printing method, or the like, and productivity is also 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.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. Although the display of "%" is used in the examples, it represents "mass%" unless otherwise specified. Further, the compound of the present invention was used for producing an organic EL device after being sublimated and purified after synthesis.

The compounds used in Examples and Comparative Examples are shown below.

<Synthesis of compound E-1>

2,4,6-Tris (m-bromophenyl) -1,3,5-triazine (1.62 g), dibenzofuran-4-boronic acid (2.08 g), potassium carbonate (4.16 g), 1,3 -Bis (2,6-diisopropylphenyl) imidazole-2-iriden] (3-chloropyridyl) palladium (II) dichloride (0.40 g) in a mixture of 1,4-dioxane (649 ml), pure water (64.9 ml) ) Was added, and the mixture was stirred at 90 ° C. for 5 days under a nitrogen atmosphere. After completion of the reaction, the mixture was allowed to cool to room temperature, water was added, and the reaction solution was filtered. Chlorobenzene was added to the collected solid, and the mixture was heated and stirred. Then, hot filtration was performed, and the filtrate was concentrated under reduced pressure. The solid obtained by concentration was washed with chloroform, dried, and then sublimated and purified to obtain 0.69 g of compound E-1 as a white solid.
Anal. calcd for C ₅₇ H ₃₃ N ₃ O ₃ : C, 84.74; H, 4.12; N, 5.20; O, 5.94. Found: C, 84.92; H, 4.14; N, 5.24; O, 5.70.

<Synthesis of compound E-2>

2,4,6-Tris (m-bromophenyl) -1,3,5-triazine (1.35 g), dibenzofuran-2-boronic acid (3.67 g), potassium carbonate (5.13 g), 1,3 -Bis (2,6-diisopropylphenyl) imidazole-2-iriden] (3-chloropyridyl) palladium (II) dichloride (0.84 g), 1,4-dioxane (676 ml), pure water (67.6 ml) ) Was added, and the mixture was stirred at 95 ° C. for 2 days under a nitrogen atmosphere. After completion of the reaction, the mixture was allowed to cool to room temperature, water was added, and the reaction solution was filtered. Chlorobenzene was added to the collected solid, and the mixture was heated and stirred. Then, hot filtration was performed, and the filtrate was concentrated under reduced pressure. The solid obtained by concentration was washed with chloroform, dried, and then sublimated and purified. Further, the obtained solid was washed with THF and chloroform to obtain Compound E-2 as 0.91 g of a white solid.
Anal. calcd for C ₅₇ H ₃₃ N ₃ O ₃ : C, 84.74; H, 4.12; N, 5.20; O, 5.94. Found: C, 84.97; H, 4.14; N, 4.99; O, 5.90.

<Synthesis of comparative compound T2T>
As a comparative compound, 2,4,6-tris (biphenyl-3-yl) -1,3,5-triazine (hereinafter referred to as T2T) was added according to the description of Journal of Material Chemistry 2009, 19, 8112-8118. Synthesized.

The glass transition temperatures of the obtained compounds E-1 and E-2 were determined by the following methods.

<Measurement of glass transition temperature (Tg)>
The glass transition temperature was measured by differential scanning calorimetry (DSC). DSC was measured using a differential scanning calorimeter DSC204F1 / Phoenix (manufactured by Netzsch). The results are shown in Table 1.

From the results in Table 1 above, it can be seen that the compound of the present invention has a higher glass transition temperature than the comparative compound.

_{<E S1, E T1,} measurement of ΔE _ST>
Quantum chemical calculations by the time-dependent density functional theory (TD-DFT) were performed for each of the compounds E-1 and E-2 and the comparative compound T2T, and the energy levels of HOMO, LUMO, S ₁ , and T ₁ were calculated. Was calculated. The results are shown in Table 2. For quantum chemistry calculations, Gaussian rev. Manufactured by Gaussian, USA. Using 9.0c, the functional was set to B3LYP and the basis function was set to 6-31 g (d).

The molecular weight described in the above table is calculated from the structure.

<Manufacturing of organic EL element 1>
A 25 mm x 25 mm glass substrate on which ITO (indium tin oxide) is patterned as an anode to a thickness of 100 nm is subjected to ultrapure water, ultrapure water, acetone, and isopropyl containing a detergent (semicoclean manufactured by Furuuchi Chemical Co., Ltd.). Ultrasonic cleaning was performed in the order of alcohol. Then, it was dried with dry nitrogen gas, and UV ozone washing was performed for 15 minutes.
On the substrate obtained above, a 1.5 mass% PEDOT: PSS (poly (3,4-ethylenedioxythiophene): poly (4-styrene sulfonate)) aqueous dispersion was applied at 1500 rpm using a spin coater. , Was applied under the condition of 30 seconds. Then, it was calcined in the air at 120 ° C. for 30 minutes to dry it, and a hole injection (transport) layer having a film thickness of 50 nm was formed.

Next, the substrate with the thin film was transferred to a nitrogen atmosphere, and a 1.2% by mass toluene solution of a mixture of the following luminescent material and host material was applied at 2500 rpm for 30 seconds using a spin coater. Then, it was calcined at 90 degreeC for 30 minutes and dried to form a light emitting layer having a film thickness of 30 nm.
Luminescent material: 2,4,5,6-tetrakis (carbazole-9-yl) isophthalonitrile 15 parts by mass Host material: 9- (4-tert-butylphenyl) -3,6-bis (triphenylsilyl)- 9H-carbazole 85 parts by mass

The material for forming each layer described later was packed in a molybdenum or tungsten vapor deposition heater, and set in a vacuum vapor deposition apparatus together with the above-mentioned thin-film glass substrate. Each of the vapor deposition heaters in the vacuum vapor deposition apparatus was filled with the constituent materials of each layer in an optimum amount for manufacturing the device. As the vapor deposition heater, a heater made of a resistance heating material made of molybdenum or tungsten was used.

After depressurizing to a vacuum degree of 1 × 10 ^-4 Pa, a heater for vapor deposition containing compound E-1 is energized and heated, and a film is deposited on the above-mentioned light emitting layer at a vapor deposition rate of 0.1 nm / sec. A first electron transport layer having a thickness of 10 nm was formed.

Next, a vapor deposition heater containing 2,7-bis (2,20-bipyridine-5-yl) triphenylene was energized and heated, and vapor deposition was performed on the first electron transport layer at a vapor deposition rate of 0.1 nm / sec. A second electron transport layer having a thickness of 40 nm was formed.

Further, after forming lithium fluoride with a film thickness of 1.0 nm by vapor deposition, aluminum 100 nm was vapor-deposited to form a cathode to obtain an element.

The non-light emitting surface side of the device was covered with a can-shaped glass case in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more to prepare an organic EL device 1.

<Manufacturing of organic EL elements 2 and 3>
Organic EL devices 2 and 3 were produced in the same manner as in Example 1 except that compound E-1 of the organic EL device 1 was replaced with compound E-2 or comparative compound T2T.

<Measurement of maximum external quantum efficiency and drive life test>
Using a spectral radiance meter SR3-AR (manufactured by Topcon Techno House), the maximum external quantum efficiency of the manufactured organic EL devices 1 to 3 was measured, and a drive life test was performed in an environment of 30 ° C. or 85 ° C.

(Measurement of maximum external quantum efficiency)
The maximum external quantum efficiency was measured when the organic EL element was placed in an environment of 30 ° C. and driven by a dry nitrogen gas atmosphere. The maximum external quantum efficiency was taken as the value of the highest external quantum efficiency obtained when the voltage was applied from 0V to 10V.

(Drive life test in an environment of 30 ° C)
The organic EL element was placed in an environment of 30 ° C. and driven in a dry nitrogen gas atmosphere, and the 80% reduced luminance life (LT80) was measured. The 80% brightness reduction life is the life (time) required for the front brightness of the organic EL element to be reduced to 80% of the initial front brightness. Here, the initial front luminance at the start of measurement was measured as 1000 cd / m ² .

(Drive life test in high temperature environment)
Next, the following steps (1) to (4) were carried out, and a drive life test was conducted in a high temperature environment. The organic EL element was driven in a dry nitrogen gas atmosphere.
(1) The organic EL element was placed in an environment of 30 ° C., and the measurement was started with the initial front luminance of 1000 cd / m ² .
(2) The driving environment of the organic EL element was raised to 85 ° C. and the driving was continued.
(3) The driving environment of the organic EL element was lowered to 30 ° C. once every few hours, and the front luminance was measured.
(4) The operations (2) to (3) were repeated until the front luminance of the organic EL element became 80% or less of the initial value, and the LT80 was obtained.

The characteristics of the obtained organic EL elements 1 to 3 are shown in Table 3. The result of the 80% brightness reduction life is shown as a relative value when the value of the organic EL element 1 in each environment is 100.

From the results in Table 3, the organic EL devices 1 and 2 using the compound E-1 or E-2, which are the compounds for the organic EL device of the present invention, are as high as the organic EL device 3 using the comparative compound T2T. In addition to showing the external quantum efficiency, it was confirmed that the brightness reduction life (LT80) was improved by 80% under both normal temperature conditions (30 ° C.) and high temperature conditions (85 ° C.). From this, it can be seen that the compound of the present invention is excellent as an organic EL device material and greatly contributes to the improvement of the durability of the organic EL device in a high temperature environment.

In consideration of the results of Table 2, compound for organic EL device of the present invention, as compared with a comparative compound T2T, large molecular weight, high glass transition temperature, small Delta] E _ST, further the molecular weight Delta] E It is considered that this is because the value divided by _ST is sufficiently large as 1000 or more.

According to the present invention, it is possible to provide a new compound for an organic EL element capable of improving the durability and heat resistance of the organic EL element. Further, it is possible to provide a new organic EL element material and an organic EL element that have realized high durability and heat resistance. Further, it is possible to provide a display device and a lighting device provided with the organic EL element of the present invention.

Claims (11)

An electron transporting material comprising a compound for an organic electroluminescence device having a structure represented by the following general formula (1).
(In general formula (1),
A _{1 to} A ₃ are substituted or unsubstituted dibenzofuranyl groups independently represented by the general formula (2).
In general formula (2),
At least one of B _{1 to} B ₈ is a bond that binds to the structure of the general formula (1), and the rest represents a hydrogen atom or a substituent. ) The electron transport material according to claim 1, wherein A _{1 to} A ₃ of the general formula (1) are the same group. The electron transport material according to claim 1 or 2, wherein the structure represented by the general formula (1) is a structure represented by the following formula E-1 or E-2.
The electron transport material according to any one of claims 1 to 3, wherein the glass transition point (Tg) of the compound for an organic electroluminescence device is 100 ° C. or higher. The difference between the lowest excited singlet energy level and the lowest excited triplet energy level of the organic electroluminescence element compound (Delta] E _ST) is less than 0.8 eV, to any one of claims 1-4 The electronic transport material described. The electron transport material according to any one of claims 1 to 5, wherein the compound for an organic electroluminescence device has a molecular weight of 700 or more. The molecular weight of the organic electroluminescence element compound, the value obtained by dividing the difference (Delta] E _ST) with its lowest excited singlet energy level and the lowest excited triplet energy level, 1,000 or more, according to claim 1 to 6 The electronic transport material according to any one of the above. With the anode
With the cathode
A first layer provided between the anode and the cathode and having a function of emitting light,
A second layer provided between the cathode and the first layer is provided.
The second layer is an organic electroluminescence device containing the electron transport material according to any one of claims 1 to 7. The organic electroluminescence device according to claim 8 , wherein the first layer and the second layer are in contact with each other. A display device comprising the organic electroluminescence device according to claim 8 or 9 . A lighting device comprising the organic electroluminescence device according to claim 8 or 9 .