JP6846256B2 - Materials for organic electroluminescent devices and organic electroluminescent devices using them - Google Patents

Description

The present invention relates to an organic electroluminescent device using a coranulene compound as a material for an organic electroluminescent device, and more particularly to a thin film type device that emits light by applying an electric field to a light emitting layer containing the organic compound.

Generally, an organic electroluminescent device (hereinafter referred to as an organic EL device) is composed of a light emitting layer and a pair of counter electrodes sandwiching the layer as its simplest structure. That is, in an organic EL element, when an electric field is applied between both electrodes, electrons are injected from the cathode, holes are injected from the anode, and these are recombined in the light emitting layer to emit light. ..

In recent years, organic EL devices using organic thin films have been developed. In particular, in order to improve the luminous efficiency, the type of electrode was optimized for the purpose of improving the efficiency of carrier injection from the electrode, and the luminous efficiency was composed of a hole transport layer composed of aromatic diamine and an 8-hydroxyquinolin aluminum complex (Alq ₃ ). By developing an element in which a layer is provided as a thin film between the electrodes, the luminous efficiency has been significantly improved compared to the conventional element using a single crystal such as anthracene. It has been promoted with the aim of putting it into practical use in a high-performance flat panel with.

Further, as an attempt to increase the luminous efficiency of the device, the use of phosphorescence instead of fluorescence is also being studied. Many elements, including those provided with a hole transport layer made of aromatic diamine and _{a light emitting layer made of Alq 3} , used fluorescence emission, but use phosphorescence emission, that is, triplet. By utilizing the light emission from the term excited state, it is expected that the efficiency will be improved by about 3 to 4 times as compared with the device using the conventional fluorescence (singlet term). Then, it has been studied to use a coumarin derivative or a benzophenone derivative as a light emitting layer as a fluorescent light emitting material, but only extremely low brightness can be obtained. Further, as an attempt to utilize the triplet state, the use of a europium complex as a phosphorescent light emitting material has been studied, but this also did not lead to highly efficient light emission. In recent years, as mentioned in Patent Document 1, many studies have been conducted using an organometallic complex such as an iridium complex as a phosphorescent light emitting material for the purpose of improving the efficiency of light emission and extending the service life.

WO01 / 041512 A1 Japanese Unexamined Patent Publication No. 2001-313178 Japanese Unexamined Patent Publication No. 2007-55959 Japanese Unexamined Patent Publication No. 2016-162982 US2015 / 0060830 A1

Org. Lett., Vol. 6, No. 9, 2004, 1397-1400

In order to obtain high luminous efficiency, the host material used at the same time as the phosphorescent material is important. A typical example of the proposed host material is 4,4'-bis (9-carbazolyl) biphenyl (CBP) introduced in Patent Document 2. When CBP is used as a host material for a green phosphorescent material represented by a tris (2-phenylpyridine) iridium complex (Ir (ppy) ₃ ), CBP is charged because it is easy for holes to flow and it is difficult for electrons to flow. The balance is lost, and excess holes flow out to the electron transport layer side, resulting in a decrease in emission efficiency from _{Ir (ppy) 3.}

That is, in order to obtain high luminous efficiency in an organic EL device, a host material having a good balance in both charge (hole / electron) injection and transport characteristics is required, and it is electrochemically stable and has high heat resistance. A compound having excellent amorphous stability is desired, and further improvement is required.

Patent Documents 2, 3, 4, 5 and Non-Patent Document 1 disclose the following corannulene compounds.

However, these do not show the usefulness of an organic EL device using a corannulene compound having a structure in which a plurality of carbazole rings are bonded to a corannulene ring.

In order to apply an organic EL element to a display element such as a flat panel display, it is necessary to improve the luminous efficiency of the element and at the same time ensure sufficient stability during driving. In view of the above situation, it is an object of the present invention to provide a practically useful organic EL device having high efficiency and high drive stability and a compound suitable for the organic EL device.

As a result of diligent studies, the present inventors have found that a corannulene compound having a structure having a corannulene ring and a plurality of carbazole rings exhibits excellent properties by using a corannulene compound having a structure having a corannulene ring and a plurality of carbazole rings, and have completed the present invention.

The present invention is a material for an organic electroluminescent device, which comprises a corannulene compound represented by the following general formula (1).

Here, Cz represents a divalently substituted or unsubstituted carbazole group. p and q represent the number of substitutions, p is an integer of 1 to 4, and q is an integer of 0 to 4. m is the number of repetitions and is an integer of 2-4. When p is an integer of 2 or more, a plurality of Cz may be the same or different.
L is a single-bonded, p + 1-valent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or the aromatic hydrocarbon group. Alternatively, it is a linked aromatic group formed by linking 2 to 6 aromatic rings of an aromatic heterocyclic group.
R ¹ is independently an aromatic hydrocarbon group having 6 to 30 carbon atoms substituted or unsubstituted, an aromatic heterocyclic group having 3 to 30 carbon atoms substituted or unsubstituted, or the aromatic hydrocarbon group or aromatic group. It is a linked aromatic group composed of 2 to 6 linked aromatic rings of a heterocyclic group.
R ² is independently hydrogen, an aromatic hydrocarbon group having 6 to 30 carbon atoms substituted or unsubstituted, an aromatic heterocyclic group having 3 to 30 carbon atoms substituted or unsubstituted, or the aromatic hydrocarbon group or the aromatic hydrocarbon group. It is a linked aromatic group formed by linking 2 to 6 aromatic rings of an aromatic heterocyclic group.

ここで、Ｒ³は、置換若しくは未置換の炭素数６〜３０の芳香族炭化水素基、置換若しくは未置換の炭素数３〜３０の芳香族複素環基、又は該芳香族炭化水素基若しくは芳香族複素環基の芳香族環が２〜６つ連結して構成される連結芳香族基である。 In the above general formula (1), m is often an integer of 2, and − (Cz) _m − is preferably a biscarbazole group represented by the formula (2) or the formula (3).

Here, R ³ is an substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or the aromatic hydrocarbon group or aromatic. It is a linked aromatic group formed by linking 2 to 6 aromatic rings of a group heterocyclic group.

（ここで、Ｒ³は式（２）と同意である。） As a preferred embodiment of the above formula (2), there is any of the following formulas (4) to (7).

(Here, R ³ agrees with equation (2).)

^{R 3} in the above formula (2) or formulas (4) to (7) is an substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or an substituted or unsubstituted aromatic complex having 3 to 17 carbon atoms. A ring group or a linked aromatic group composed of 2 to 6 linked aromatic rings selected from the aromatic hydrocarbon group and the aromatic heterocyclic group is preferable, and the aromatic group is substituted or unsubstituted. More preferably, it is an aromatic hydrocarbon group having 6 to 18 carbon atoms, or a linked aromatic group composed of 2 to 6 aromatic rings selected from the aromatic hydrocarbon groups.

Further, the present invention is an organic electroluminescent device in which an anode, an organic layer and a cathode are laminated on a substrate, wherein the organic electroluminescent device includes the above-mentioned organic electroluminescent device material. Is.

The organic layer containing the material for an organic electroluminescent device can be at least one layer selected from the group consisting of a light emitting layer, an electron transporting layer, and a hole blocking layer, and is a light emitting layer containing a phosphorescent dopant. Is preferable. In this case, it is preferable that the emission wavelength of the phosphorescent dopant has a maximum emission wavelength of 550 nm or more.

The material for an organic electroluminescent device of the present invention has a structure composed of a corannulene ring and an oligocarbazole ring in which a plurality of carbazole rings are bonded. In corannulene compounds having such structural characteristics, the lowest empty orbital (LUMO) that affects electron injection transportability is widely distributed throughout the corannulene ring, so the type and number of substituents bonded to the corannulene ring can be determined. By changing it, the electron injection transportability of the device can be controlled at a high level. On the other hand, the highest occupied orbitals (HOMO) that affect hole injection transportability are widely distributed on the oligocarbazole ring, and the number of carbazole groups and the type / number of substituents on the carbazole groups are changed. Therefore, the hole injection transportability of the device can be controlled at a high level. Due to these characteristics, the compound of the present invention becomes a material for an organic electroluminescent device in which both charge (hole / electron) injection and transport characteristics are balanced, and by using this in an organic EL device, the drive voltage of the device can be reduced. Moreover, high emission efficiency can be achieved.
Further, since the material for an organic electroluminescent device of the present invention exhibits good amorphous characteristics and high thermal stability and is extremely stable in an excited state, an organic EL device using this has a long drive life and is at a practical level. Has the durability of.

It is sectional drawing which shows one structural example of an organic EL element.

The material for an organic electroluminescent device of the present invention is a corannulene compound represented by the general formula (1).

In the general formula (1), Cz represents a divalent carbazole group. Here, the carbazole group is understood to mean a substituted or unsubstituted carbazole group. The same applies hereinafter.
L is a p + 1 valent group, which is a single-bonded, substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or the same. It is a linked aromatic group composed of 2 to 6 aromatic rings of an aromatic hydrocarbon group or an aromatic heterocyclic group. When L is a single bond, it is limited to when L is a divalent group, i.e. p is 1. When L is an aromatic heterocyclic group, it may be a group other than the carbazole group.

R ¹ is independently an aromatic hydrocarbon group having 6 to 30 carbon atoms substituted or unsubstituted, an aromatic heterocyclic group having 3 to 30 carbon atoms substituted or unsubstituted, or the aromatic hydrocarbon group or aromatic group. It is a linked aromatic group composed of 2 to 6 linked aromatic rings of a heterocyclic group.
R ² is independently hydrogen, an aromatic hydrocarbon group having 6 to 30 carbon atoms substituted or unsubstituted, an aromatic heterocyclic group having 3 to 30 carbon atoms substituted or unsubstituted, or the aromatic hydrocarbon group or the aromatic hydrocarbon group. It is a linked aromatic group formed by linking 2 to 6 aromatic rings of an aromatic heterocyclic group.
R ³ agrees with R ^1.

In the general formula (1), p and q represent the number of substitutions, p is an integer of 1 to 4, q is an integer of 0 to 4, preferably p is an integer of 1 to 2, and q is an integer of 1 to 2. It is an integer of 0 to 2.
m represents the number of repetitions and is an integer of 2-4, preferably 2 or 3, more preferably 2.
When m and p are 2 or more, a plurality of Cz may be the same or different.

The case where L, R ^{1 to} R ³ are an aromatic hydrocarbon group, an aromatic heterocyclic group, or a linked aromatic group will be described. L is a p + 1 valent group, and R ^{1 to} R ³ are monovalent groups.

Specific examples of the unsubstituted aromatic hydrocarbon group include groups formed by removing hydrogen from aromatic hydrocarbon compounds such as benzene, naphthalene, fluorene, anthracene, phenanthrene, triphenylene, tetraphenylene, fluorantene, pyrene and chrysen. , Preferably a group formed by removing hydrogen from benzene, naphthalene, fluorene, phenanthrene, or triphenylene.

Specific examples of the unsubstituted aromatic heterocyclic group include pyridine, pyrimidine, triazine, quinoline, isoquinoline, quinoxalin, quinazoline, naphthylidine, dibenzofuran, dibenzothiophene, aclysine, azepine, tribenzoazepine, phenazine, phenoxazine, phenothiazine, and dibenzo. Examples thereof include groups generated by removing hydrogen from aromatic heterocyclic compounds such as phosphor, dibenzofuran and carbazole, and preferably groups generated by removing hydrogen from pyridine, pyrimidine, triazine, quinazoline, dibenzofuran or dibenzothiophene. However, L and R ² may be groups other than the carbazole group.

In the present specification, a group formed by removing hydrogen from an aromatic compound in which a plurality of aromatic rings of an aromatic hydrocarbon compound or an aromatic heterocyclic compound are linked by a single bond is referred to as a linked aromatic group. A linked aromatic group is a group composed of 2 to 6 aromatic rings linked together, and the linked aromatic rings may be the same or different, and an aromatic hydrocarbon group and an aromatic heterocyclic group. Both may be included. The number of aromatic rings linked is preferably 2-4, more preferably 2 or 3. The carbon number of each aromatic group constituting the linked aromatic group is ^{within the range of the carbon number when L, R 1 to} R ³ are an aromatic hydrocarbon group or an aromatic heterocyclic group, and is the total. The number of carbon atoms is preferably 60 or less, preferably 40 or less.

Specific examples of the above-mentioned linked aromatic groups include biphenyl, terphenyl, quaterphenyl, phenylnaphthalene, diphenylnaphthalene, phenylanthracene, diphenylanthracene, diphenylfluorene, bipyridine, bipyrimidine, vitriazine, bisdibenzofuran, bisdibenzothiophene and phenylpyridine. , Phenylpyrimidine, phenyltriazine, phenylcarbazole, phenyldibenzofuran, diphenylpyridine, diphenyltriazine, bisdibenzofuranylbenzene and the like, which are groups formed by removing hydrogen.

The aromatic hydrocarbon group, aromatic heterocyclic group or linked aromatic group may have a substituent, and when it has a substituent, a preferred substituent is a diallylamino group having 12 to 30 carbon atoms. It is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an acetyl group. More preferably, it is a diallylamino group having 12 to 30 carbon atoms, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, or an acetyl group. As used herein, it is understood that the calculation of the number of carbon atoms includes the number of carbon atoms of the substituent.

Similarly, the carbazole group may also have a substituent, and this substituent is the same as described above. In the general formula (1), the terminal carbazole group (Cz) has R ² as a substituent, which is preferably an aromatic hydrocarbon group, an aromatic heterocyclic group or a linked aromatic group. Further, when the N-position of the Cz ring is not used for the bond with the adjacent ring, it is desirable to have the above-mentioned substituent. This substituent is the same as ^{R 3} in the above formula (2).

In the general formula (1), − (Cz) _m − is preferably a biscarbazole group represented by the above formula (2) or formula (3). These are examples where m is 2. A preferred embodiment of the formula (2) is any of the formulas (4) to (7). ^{R 3} in the formulas (2) and (4) to (7) is the same as the description ^{of R 1} in the general formula (1). Preferably, R ³ is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or the aromatic hydrocarbon group and the aromatic. A linked aromatic group composed of 2 to 6 aromatic rings selected from the group heterocyclic groups, more preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or an aromatic hydrocarbon group having 6 to 18 carbon atoms. It is a linked aromatic group composed of 2 to 6 aromatic rings selected from the aromatic hydrocarbon groups.

（Ａｒ¹〜Ａｒ⁶は置換又は未置換の芳香族炭化水素環又は芳香族複素環） Here, in the case of a divalent group, the linked aromatic group referred to in the present specification may be represented by, for example, the following formula, and may be linked in a linear or branched manner.

(Ar ^{1 to} Ar ⁶ are substituted or unsubstituted aromatic hydrocarbon rings or aromatic heterocycles)

The corannulene compound represented by the general formula (1) can be synthesized by selecting a raw material according to the structure of the target compound and using a known method.

Intermediate A can be synthesized by the following reaction formula with reference to the synthesis examples shown in ChemComm, 2012, 48, p6298-6300. Using this intermediate A, a functional group can be introduced by a known reaction (Suzuki coupling or Ulman coupling).

Specific examples of the corannulene compound represented by the general formula (1) are shown below, but the material for the organic electroluminescent device of the present invention is not limited thereto.

The material for an organic electroluminescent device of the present invention (also referred to as a compound of the present invention or a compound represented by the general formula (1) or a corannulene compound) comprises an anode, a plurality of organic layers, and a cathode laminated on a substrate. By containing it in at least one organic layer of the organic EL element, an excellent organic electroluminescent element is provided. As the organic layer to be contained, a light emitting layer, an electron transporting layer or a hole blocking layer is suitable.
Here, when used in a light emitting layer, it can be used as a host material for a light emitting layer containing a fluorescent light emitting, delayed fluorescent light emitting or phosphorescent dopant, and the compound of the present invention emits fluorescence and delayed fluorescence. It can be used as an organic light emitting material. When used as an organic light emitting material that emits fluorescence and delayed fluorescence, another organic compound in which at least one of the excitation singlet energy and the excitation triplet energy has a value higher than that of the compound of the present invention is used as the host material. Is preferable. It is particularly preferable that the compound of the present invention is contained as a host material for a light emitting layer containing a phosphorescent dopant.

Next, an organic EL device using the material for an organic electroluminescent device of the present invention will be described.

The organic EL device of the present invention has an organic layer having at least one light emitting layer between the anode and the cathode laminated on the substrate, and at least one organic layer is for the organic electroluminescent device of the present invention. Including material. Advantageously, the material for an organic electroluminescent device of the present invention is contained in the light emitting layer together with the phosphorescent dopant.

Next, the structure of the organic EL element of the present invention will be described with reference to the drawings, but the structure of the organic EL element of the present invention is not limited to the one shown in the drawing.

FIG. 1 is a cross-sectional view showing a structural example of a general organic EL device used in the present invention, in which 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, and 5 is a light emitting layer. , 6 represent an electron transport layer, and 7 represents a cathode. The organic EL device of the present invention may have an exciton blocking layer adjacent to the light emitting layer, or may have an electron blocking layer between the light emitting layer and the hole injection layer. The exciton blocking layer can be inserted into either the anode side or the cathode side of the light emitting layer, and both can be inserted at the same time. The organic EL device of the present invention has a substrate, an anode, a light emitting layer, and a cathode as essential layers, but it is preferable that a hole injection transport layer and an electron injection transport layer are provided in layers other than the essential layers, and light emission is further provided. It is preferable to have a hole blocking layer between the layer and the electron injection transport layer. The hole injection transport layer means either or both of the hole injection layer and the hole transport layer, and the electron injection transport layer means either or both of the electron injection layer and the electron transport layer.

It should be noted that the structure opposite to that of FIG. 1, that is, the cathode 7, the electron transport layer 6, the light emitting layer 5, the hole transport layer 4, and the anode 2 can be laminated in this order on the substrate 1, and in this case as well. Layers can be added or omitted as needed.

-Board-
The organic EL device of the present invention is preferably supported by a substrate. The substrate is not particularly limited as long as it is conventionally used for organic EL elements, and for example, a substrate made of glass, transparent plastic, quartz, or the like can be used.

− Anode −
As the anode in the organic EL element, a metal having a large work function (4 eV or more), an alloy, an electrically conductive compound, or a mixture thereof as an electrode material is preferably used. Specific examples of such an electrode material include metals such as Au and conductive transparent materials such as _{CuI, indium zinc oxide (ITO), SnO 2, and ZnO.} Further, a material such as IDIXO (In ₂ O _3- ZnO) which is amorphous and can produce a transparent conductive film may be used. For the anode, a thin film may be formed by depositing 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). ), A 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. Further, the film thickness depends on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

− Cathode −
On the other hand, 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 include mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. 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 this, it is possible to manufacture an element in which both the anode and the cathode are transparent.

-Light emitting layer-
The light emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from each of the anode and the cathode, and the light emitting layer includes an organic light emitting material and a host material.
When the light emitting layer is a fluorescent light emitting layer, at least one kind of fluorescent light emitting material may be used alone as the fluorescent light emitting material, but it is preferable to use the fluorescent light emitting material as the fluorescent light emitting dopant and include a host material. ..

As the fluorescent light emitting material in the light emitting layer, a corannulene compound represented by the general formula (1) can be used, but since it is known from many patent documents and the like, it can also be selected from them. For example, benzoxazole derivatives, benzothiazole derivatives, benzoimidazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives, condensed aromatic compounds, perinone derivatives, oxadiazole derivatives. , Oxazine derivative, aldazine derivative, cyclopentadiene derivative, bisstyrylanthracene derivative, quinacridone derivative, pyrolopyridine derivative, thiadiazolopyridine derivative, styrylamine derivative, diketopyrrolopyrrole derivative, aromatic dimethyridine compound, metal of 8-quinolinol derivative Examples thereof include metal complexes of complexes and pyromethene derivatives, rare earth complexes, various metal complexes typified by transition metal complexes, polymer compounds such as polythiophene, polyphenylene and polyphenylene vinylene, and organic silane derivatives. Preferred examples thereof include condensed aromatic compounds, styryl compounds, diketopyrrolopyrrole compounds, oxazine compounds, pyromethene metal complexes, transition metal complexes and lanthanoid complexes, and more preferably naphthalcene, pyrene, chrysene, triphenylene and benzo [c] phenanthrene. Benzo [a] anthracene, pentacene, perylene, fluorantene, acenafsofluoranthene, dibenzo [a, j] anthrene, dibenzo [a, h] anthanthrene, benzo [a] naphthacene, hexacene, anthanthrene, naphtho [2,1] -f] Isoquinoline, α-naphthaphenanthridin, phenanthrooxazole, quinolino [6,5-f] quinoline, benzothiophanthrene and the like can be mentioned. These may have an alkyl group, an aryl group, an aromatic heterocyclic group, or a diarylamino group as a substituent.

As the fluorescent host material in the light emitting layer, a corannulene compound represented by the general formula (1) can be used, but since it is known from many patent documents and the like, it can also be selected from them. For example, compounds having a fused aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysen, naphthacene, triphenylene, perylene, fluorantene, fluorene, and inden and their derivatives, N, N'-dinaphthyl-N, N'-diphenyl-4. , 4'-Diphenyl-1,1'-Diamine and other aromatic amine derivatives, Tris (8-quinolinate) aluminum (III) and other metal chelated oxynoid compounds, distyrylbenzene derivatives and other bisstyryl derivatives, tetraphenyl Butadiene derivative, inden derivative, coumarin derivative, oxadiazole derivative, pyrolopyridine derivative, perinone derivative, cyclopentadiene derivative, pyrolopyrrole derivative, thiadiazolopyridine derivative, dibenzofuran derivative, carbazole derivative, indolocarbazole derivative, triazine derivative, polymer In the system, a polyphenylene vinylene derivative, a polyparaphenylene derivative, a polyfluorene derivative, a polyvinylcarbazole derivative, a polythiophene derivative and the like can be used, but are not particularly limited.

When the fluorescent light emitting material is used as the fluorescent light emitting dopant and contains a host material, the amount of the fluorescent light emitting dopant contained in the light emitting layer is 0.01 to 20% by weight, preferably 0.1 to 10% by weight. It should be in the range.

Normally, an organic EL element injects an electric charge into a luminescent substance from both electrodes of an anode and a cathode to generate an excited luminescent substance to emit light. In the case of a charge injection type organic EL device, it is said that 25% of the generated excitons are excited to the singlet excited state, and the remaining 75% are excited to the triplet excited state. As shown in Advanced Materials 2009, 21, 4802-4806., A specific fluorescent substance has triplet-triplet annihilation or heat after the energy transitions to the triplet-excited state due to intersystem crossing or the like. It is known that by absorption of energy, the singlet-triplet excited state crosses the inverse intersystem crossing to emit fluorescence, and the thermal activation delayed fluorescence is exhibited. The organic EL device of the present invention can also exhibit delayed fluorescence. In this case, both fluorescent emission and delayed fluorescence emission can be included. However, some or part of the light emission may be emitted from the host material.

When the light emitting layer is a delayed fluorescent light emitting layer, at least one delayed light emitting material may be used alone, but the delayed fluorescent material may be used as the delayed fluorescent light emitting dopant and include a host material. Is preferable.

As the delayed fluorescent light emitting material in the light emitting layer, a corannulene compound represented by the general formula (1) can be used, but it can also be selected from known delayed fluorescent light emitting materials. For example, a tin complex, an indolocarbazole derivative, a copper complex, a carbazole derivative and the like can be mentioned. Specific examples thereof include the following non-patent documents and compounds described in the patent documents, but the present invention is not limited to these compounds.

1) Adv. Mater. 2009, 21, 4802-4806, 2) Appl. Phys. Lett. 98, 083302 (2011), 3) Japanese Patent Application Laid-Open No. 2011-213643, 4) J. Am. Chem. Soc. 2012 , 134, 14706-14709.

Specific examples of the delayed light emitting material are shown, but the present invention is not limited to the following compounds.

When the delayed fluorescent light emitting material is used as the delayed fluorescent light emitting dopant and contains a host material, the amount of the delayed fluorescent light emitting dopant contained in the light emitting layer is 0.01 to 50% by weight, preferably 0.1 to 20%. It is preferably in the range of% by weight, more preferably 0.01-10%.

As the delayed fluorescence host material in the light emitting layer, a corannulene compound represented by the general formula (1) can be used, but a compound other than corannulene can also be selected. For example, compounds having a fused aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysen, naphthacene, triphenylene, perylene, fluorantene, fluorene, and inden and their derivatives, N, N'-dinaphthyl-N, N'-diphenyl-4. , 4'-Diphenyl-1,1'-Diamine and other aromatic amine derivatives, Tris (8-quinolinate) aluminum (III) and other metal chelated oxynoid compounds, distyrylbenzene derivatives and other bisstyryl derivatives, tetraphenyl Butadiene derivative, inden derivative, coumarin derivative, oxadiazole derivative, pyrolopyridine derivative, perinone derivative, cyclopentadiene derivative, pyrolopyrrole derivative, thiadiazolopyridine derivative, dibenzofuran derivative, carbazole derivative, indolocarbazole derivative, triazine derivative, polymer In the system, polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives, arylsilane derivatives and the like can be used, but are not particularly limited.

When the light emitting layer is a phosphorescent light emitting layer, the light emitting layer contains a phosphorescent light emitting dopant and a host material. The phosphorescent dopant material preferably contains an organic metal complex containing at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold. A phosphorescent dopant material having an emission wavelength of 550 nm or more is preferable.

_{Preferred phosphorescent dopants include complexes such as Ir (ppy) 3} having a noble metal element such as Ir as a central metal, complexes such as Ir (bt) ₂ and acac ₃ , and complexes such as PtOEt ₃ . Specific examples of these complexes are shown below, but are not limited to the following compounds.

The amount of the phosphorescent dopant contained in the light emitting layer is preferably in the range of 2 to 40% by weight, preferably 5 to 30% by weight.

When the light emitting layer is a phosphorescent light emitting layer, it is preferable to use the corannulene compound of the present invention as the host material in the light emitting layer. However, when the corannulene compound is used for any organic layer other than the light emitting layer, the material used for the light emitting layer may be a host material other than the corannulene compound. Moreover, the carborane compound and other host materials may be used in combination. Further, a plurality of known host materials may be used in combination.

As the known host compound that can be used, it is preferable that the compound has a hole transporting ability and an electron transporting ability, prevents the wavelength of light emission from being lengthened, and has a high glass transition temperature.

Such other host materials are known from numerous patent documents and the like and can be selected from them. Specific examples of the host material are not particularly limited, but are indol derivatives, carbazole derivatives, indolocarbazole derivatives, triazole derivatives, oxazole derivatives, oxaziazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, Pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilben derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, porphyrin Metal complexes of system compounds, anthraquinodimethane derivatives, anthron derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, heterocyclic tetracarboxylic acid anhydrides such as naphthalene perylene, phthalocyanine derivatives, 8-quinolinol derivatives, metal phthalocyanine, benzoxazole Various metal complexes typified by metal complexes of benzothiazole derivatives, polysilane compounds, poly (N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, polythiophene derivatives, polyphenylene derivatives, polyphenylene vinylene derivatives, polyfluorene derivatives And the like, such as high molecular weight compounds.

The light emitting layer may be a fluorescent light emitting layer, a delayed fluorescent light emitting layer, or a phosphorescent light emitting layer, but a phosphorescent light emitting layer is preferable.

-Injection layer-
The injection layer is a layer provided between the electrode and the organic layer in order to reduce the driving voltage and improve the emission brightness. There are a hole injection layer and an electron injection layer, and between the anode and the light emitting layer or the hole transport layer, And may be present between the cathode and the light emitting layer or the electron transporting layer. The injection layer can be provided as needed.

-Hole blocking layer-
The hole blocking layer has the function of an electron transporting layer in a broad sense, and is made of a hole blocking material having a function of transporting electrons and a significantly small ability to transport holes. It is possible to improve the recombination probability of electrons and holes by blocking the above.

It is preferable to use the corannulene compound of the present invention for the hole blocking layer, but when the corannulene compound is used for any other organic layer, a known hole blocking layer material may be used. Further, as the hole blocking layer material, a material for an electron transport layer, which will be described later, can be used as needed.

-Electronic blocking layer-
The electron blocking layer is made of a material that has a function of transporting holes but has a significantly small ability to transport electrons, and the probability that electrons and holes are recombined by blocking electrons while transporting holes is increased. Can be improved.

As the material of the electron blocking layer, a material of the hole transport layer described later can be used as needed. The film thickness of the electron blocking layer is preferably 3 to 100 nm, more preferably 5 to 30 nm.

-Exciton blocking layer-
The exciton blocking layer is a layer for preventing excitons generated by the recombination of holes and electrons in the light emitting layer from diffusing into the charge transport layer, and the excitons are inserted by inserting this layer. It is possible to efficiently confine it in the light emitting layer, and it is possible to improve the light emitting efficiency of the element. The exciton blocking layer can be inserted into either the anode side or the cathode side adjacent to the light emitting layer, and both can be inserted at the same time.

As the material of the exciton blocking layer, a corannulene compound represented by the general formula (1) can be used, but as other materials, for example, 1,3-dicarbazolylbenzene (mCP) or bis ( 2-Methyl-8-quinolinolato) -4-phenylphenylatoaluminum (III) (BAlq) can be mentioned.

-Hole transport layer-
The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer may be provided as a single layer or a plurality of layers.

The hole transporting material has either injection or transport of holes or an electron barrier property, and may be either an organic substance or an inorganic substance. As a known hole transporting material that can be used, it is preferable to use a carborane compound represented by the general formula (1), but any conventionally known compound can be selected and used. Known hole transporting materials that can be used include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, and oxazole derivatives. , Styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stylben derivatives, silazane derivatives, aniline-based copolymers, conductive polymer oligomers, especially thiophene oligomers, etc., including porphyrin compounds, aromatic tertiary amine compounds and It is preferable to use a styrylamine compound, and it is more preferable to use an aromatic tertiary amine compound.

-Electron transport layer-
The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer may be provided with a single layer or a plurality of layers.

The electron transporting material (which may also serve as a hole blocking material) may have a function of transmitting electrons injected from the cathode to the light emitting layer. The coranulene compound of the present invention is preferably used for the electron transport layer, but any of conventionally known compounds can be selected and used, for example, a nitro-substituted fluorene derivative, a diphenylquinone derivative, and thiopyranji. Examples thereof include oxide derivatives, carbodiimides, freolenidene methane derivatives, anthracinodimethane and anthrone derivatives, and oxadiazole derivatives. Further, among the oxadiazole derivatives, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is replaced with a sulfur atom, and a quinoxalin derivative having a quinoxalin ring known as an electron-withdrawing group can also be used as an electron transport material. Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is, of course, not limited to these Examples, and can be carried out in various forms as long as the gist thereof is not exceeded. ..

A corannulene compound used as a material for an organic electroluminescent device was synthesized by the route shown below. The compound number corresponds to the number assigned to the above chemical formula.

Example 1 (Synthesis example)
Compound 1 was synthesized according to the following reaction formula.

Under a nitrogen atmosphere, 5.0 g (0.0199 mol) of coranulene, 4.5 g (0.0199 mol) of N-iodosuccinimide _{, 400 mL of AuCl 3} 302 mg (0.998 mmol), and 1,2-dichloroethane were added, and the mixture was stirred overnight at room temperature. Then, the precipitated crystals were collected by filtration, and the solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel chromatography to obtain 5.3 g (0.014 mol, yield 70%) of Intermediate A.

Under a nitrogen atmosphere, intermediate A 3.0 g (0.00797 mol), intermediate B 3.26 g (0.00797 mol) copper iodide 45.5 mg (0.239 mmol), tripotassium phosphate 5.07 g (0.0239 mol), trans-1,2- 40 mL of cyclohexanediamine 0.91 g (0.00797 mmol) and 1,4-dioxane were added, and the mixture was stirred at 115 ° C. overnight. After cooling the reaction solution to room temperature, the precipitated crystals were collected by filtration and the solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain 3.20 g (4.87 mmol, yield 61%) of Compound 1 (APCI-TOFMS, m / z 657 [M + H] ⁺ ).

In addition to compound 1, compounds 3, 29, 35, 36, 42 and 57 were synthesized according to the above synthesis example. In addition, compounds H-1 and r1 for comparison were synthesized.

Example 2
Each thin film was laminated with a ^{vacuum degree of 4.0 × 10 -5} Pa by a vacuum vapor deposition method on a glass substrate on which an anode made of ITO having a film thickness of 110 nm was formed. First, HAT-CN was formed on the ITO to a thickness of 25 nm as a hole injection layer, and then NPD was formed to a thickness of 45 nm as a hole transport layer. Next, HT-1 was formed to a thickness of 10 nm as an electron blocking layer. Then, compound 1 as a host material and Ir (piq) ₂ acac as a dopant were co-deposited from different vapor deposition sources to form a light emitting layer with a thickness of 40 nm.
At this time, _{the concentration of Ir (piq) 2} acac was 6.0 wt%. Furthermore, ET-1 was formed to a thickness of 10 nm as a hole blocking layer. Next, ET-2 was formed to a thickness of 27.5 nm as an electron transport layer. Then, LiF was formed on the electron transport layer as an electron injection layer to a thickness of 1 nm. Finally, Al was formed as a cathode on the electron injection layer to a thickness of 70 nm to fabricate an organic EL device.

Examples 3-8
An organic EL device was produced in the same manner as in Example 2 except that compounds 3, 29, 35, 36, 42 and 57 were used instead of compound 1 as the host material for the light emitting layer in Example 2.

Comparative Examples 1 and 2
An organic EL device was produced in the same manner as in Example 2 except that H-1 and r1 were used as host materials for the light emitting layer in Example 2.

The compounds used in the examples are shown below.

Table 1 shows the brightness, drive voltage, luminous efficiency, and half-life of the manufactured organic EL element. In the table, the brightness, drive voltage, and luminous efficiency are ^{the values when the drive current is 20 mA / cm 2} and are the initial characteristics. The LT95 is the time required for the brightness to decay to 95% of the initial brightness at an initial brightness of 3700 cd / m ^{2, which is a lifetime characteristic.}

Further, when the organic EL devices manufactured in Examples 2 to 8 and Comparative Examples 1 and 2 were connected to an external power source and a DC voltage was applied to them, an emission spectrum having a maximum wavelength of 620 nm was observed, and Ir ( pic) ₂ It was found that the luminescence from acac was obtained.

From Table 1, it can be seen that when the compound represented by the general formula (1) is used as the host material, the initial characteristics and the life characteristics are significantly extended as compared with the comparative compound.

1 substrate, 2 anode, 3 hole injection layer, 4 hole transport layer, 5 light emitting layer, 6 electron transport layer, 7 cathode

Claims (10)

A material for an organic electroluminescent device, which comprises a corannulene compound represented by the general formula (1).

(Here, Cz represents a divalent substituted or unsubstituted carbazole group. P and q represent the number of substitutions, p is an integer of 1 to 4, and q is an integer of 0 to 4. m. Is the number of repetitions and is an integer of 2 to 4. When p is an integer of 2 or more, a plurality of Cz may be the same or different.
L is a single-bonded, p + 1-valent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or the aromatic hydrocarbon group. Alternatively, it is a linked aromatic group formed by linking 2 to 6 aromatic rings of an aromatic heterocyclic group.
R ¹ is independently an aromatic hydrocarbon group having 6 to 30 carbon atoms substituted or unsubstituted, an aromatic heterocyclic group having 3 to 30 carbon atoms substituted or unsubstituted, or the aromatic hydrocarbon group or aromatic group. It is a linked aromatic group composed of 2 to 6 linked aromatic rings of a heterocyclic group.
R ² is independently hydrogen, an aromatic hydrocarbon group having 6 to 30 carbon atoms substituted or unsubstituted, an aromatic heterocyclic group having 3 to 30 carbon atoms substituted or unsubstituted, or the aromatic hydrocarbon group or the aromatic hydrocarbon group. It is a linked aromatic group formed by linking 2 to 6 aromatic rings of an aromatic heterocyclic group. ) The material for an organic electroluminescent device according to claim 1, wherein m is an integer of 2 in the general formula (1). The material for an organic electroluminescent device according to claim 1 or 2, wherein in the general formula (1), − (Cz) _m − is a biscarbazole group represented by the formula (2) or the formula (3).

(Here, R ³ is an substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or the aromatic hydrocarbon group or the aromatic hydrocarbon group. It is a linked aromatic group composed of 2 to 6 aromatic rings of an aromatic heterocyclic group linked together.) The material for an organic electroluminescent device according to claim 3, wherein the formula (2) is any of the following formulas (4) to (7).

(Here, R ³ agrees with equation (2).) R ³ is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or the aromatic hydrocarbon group and the aromatic complex. The material for an organic electric field light emitting element according to claim 4, which is a linked aromatic group composed of 2 to 6 aromatic rings selected from the ring groups. R ³ is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a linked aromatic group composed of 2 to 6 aromatic rings selected from the aromatic hydrocarbon groups. The material for an organic electric field light emitting element according to claim 4. An organic electroluminescent device in which an anode, an organic layer, and a cathode are laminated on a substrate includes an organic layer containing the material for an organic electroluminescent device according to any one of claims 1 to 6. Electroluminescent element. The organic electroluminescent device according to claim 7, wherein the organic layer containing the material for the organic electroluminescent device is at least one layer selected from a group consisting of a light emitting layer, an electron transporting layer, and a hole blocking layer. The organic electroluminescent device according to claim 7, wherein the organic layer containing the material for the organic electroluminescent device is a light emitting layer containing a phosphorescent dopant. The organic electroluminescent device according to claim 9, wherein the phosphorescent dopant has a maximum emission wavelength of 550 nm or more.

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