JP2018170369A - Material for organic electroluminescent element and organic electroluminescent element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element having high efficiency and excellent life characteristics, and a compound suitable therefor.SOLUTION: A material for an organic electroluminescent element comprises a corannulene compound represented by general formula (1) and having a structure in which a carbazole-containing group is bonded to corannulene. The organic electroluminescent element contains the material for an organic electroluminescent element in an organic layer. In the formula, Cz is a divalent carbazole group; L is a single bond, a (p+1)-valent aromatic hydrocarbon group, an aromatic heterocyclic group, or a linked aromatic group constituted by linking 2-6 aromatic rings thereof; p and q each represent a substitution number; p is an integer of 1-4; q is an integer of 0-4; and m represents a repeating number and is an integer of 2-4.SELECTED DRAWING: None

Description

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

  In general, an organic electroluminescence element (hereinafter referred to as an organic EL element) has 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, an organic EL element using an organic thin film has been developed. In particular, in order to increase the luminous efficiency, the type of electrode is optimized for the purpose of improving the efficiency of carrier injection from the electrode, and the light emission consists of a hole transport layer made of aromatic diamine and 8-hydroxyquinoline aluminum complex (Alq ₃ ). The development of a device with a thin layer between the electrodes has led to a significant improvement in luminous efficiency compared to conventional devices using single crystals such as anthracene. It has been promoted with the aim of putting it into practical use for high-performance flat panels.

In addition, as an attempt to increase the light emission efficiency of the device, the use of phosphorescence instead of fluorescence has been studied. Many devices, including those provided with the hole transport layer composed of the aromatic diamine and the light-emitting layer composed of Alq ₃ described above, used fluorescent light emission. By using the light emission from the term excited state, it is expected that the efficiency is improved by about 3 to 4 times compared to the conventional device using fluorescence (singlet). And, it has been studied to use a coumarin derivative or a benzophenone derivative as a light emitting layer as a fluorescent light emitting material. In addition, as an attempt to utilize the triplet state, it has been studied to use a europium complex as a phosphorescent material, but this also has not led to highly efficient light emission. In recent years, as described in Patent Document 1, many studies have been conducted using an organometallic complex such as an iridium complex as a phosphorescent material for the purpose of increasing the efficiency of light emission and extending the lifetime.

WO01 / 041512 A1 JP 2001-313178 A JP 2007-55959 A 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 to be used is important simultaneously with the phosphorescent material. A representative example of the host material proposed 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 typified by tris (2-phenylpyridine) iridium complex (Ir (ppy) ₃ ), CBP is easy to flow holes, and it is difficult to flow electrons. The balance is lost, and excess holes flow out to the electron transport layer side. As a result, the light emission efficiency from Ir (ppy) ₃ decreases.

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

  In Patent Documents 2, 3, 4, 5 and Non-Patent Document 1, corannulene compounds as shown below are disclosed.

  However, these do not indicate 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 the 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 sufficiently ensure stability during driving. An object of this invention is to provide the practically useful organic EL element which has high efficiency and high drive stability in view of the said present condition, and a compound suitable for it.

  As a result of intensive studies, the present inventors have found that the use of a corannulene compound having a structure having a corannulene ring and a plurality of carbazole rings for an organic EL device has led to the completion of the present invention.

The present invention is an organic electroluminescent element material comprising a corannulene compound represented by the following 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 2-4. When p is an integer of 2 or more, the plurality of Cz may be the same or different.
L is a single bond, a 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 Or it is a connection aromatic group comprised by connecting 2-6 aromatic rings of an aromatic heterocyclic group.
R ¹ is independently a 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 group. This is a linked aromatic group constituted by connecting 2 to 6 aromatic rings of a heterocyclic group.
R ² is independently hydrogen, a 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 This is a linked aromatic group constituted by connecting 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 general formula (1), m is preferably 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 a 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 group. It is a connected aromatic group constituted by connecting 2 to 6 aromatic rings of an aromatic group.

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

(Here, R ³ is the same as the formula (2).)

R ³ in the above formula (2) or formulas (4) to (7) is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 3 to 17 carbon atoms. It is preferably a linked aromatic group formed by linking 2 to 6 aromatic rings selected from a cyclic group or the aromatic hydrocarbon group and the aromatic heterocyclic group, and is substituted or unsubstituted. The aromatic hydrocarbon group having 6 to 18 carbon atoms or a linked aromatic group constituted by connecting 2 to 6 aromatic rings selected from the aromatic hydrocarbon group is more preferable.

  According to another aspect of the present invention, there is provided an organic electroluminescent device comprising an anode, an organic layer and a cathode laminated on a substrate, wherein the organic electroluminescent device comprises the organic electroluminescent device material described above. It is.

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

The organic electroluminescent element material 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 the corannulene compound having such a structural feature, since the lowest unoccupied orbital (LUMO) that affects the electron injection and transport property is widely distributed throughout the corannulene ring, the type and number of substituents bonded to the corannulene ring are determined. By changing it, the electron injection / transport property of the device can be controlled at a high level. On the other hand, on the oligocarbazole ring, the highest occupied orbitals (HOMO) that affect the hole injection and transport properties are widely distributed, changing the number of carbazole groups and the type and number of substituents on the carbazole group. Thus, the hole injection / transport property of the device can be controlled at a high level. From these characteristics, the compound of the present invention becomes a material for an organic electroluminescence device that is balanced in both charge (hole / electron) injecting and transporting properties. By using this for an organic EL device, the driving voltage of the device is reduced. In addition, high luminous efficiency can be achieved.
In addition, since the organic electroluminescent element material of the present invention exhibits excellent amorphous characteristics and high thermal stability and is extremely stable in an excited state, an organic EL element using the organic EL element has a long driving life and a practical level. Of durability.

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

  The material for an organic electroluminescent element 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, and is a single bond, a 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 This is a linked aromatic group constituted by connecting 2 to 6 aromatic rings of an aromatic hydrocarbon group or an aromatic heterocyclic group. The case where L is a single bond is limited when L is a divalent group, that is, when p is 1. And when L is an aromatic heterocyclic group, it is good that it is groups other than a carbazole group.

R ¹ is independently a 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 group. This is a linked aromatic group constituted by connecting 2 to 6 aromatic rings of a heterocyclic group.
R ² is independently hydrogen, a 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 This is a linked aromatic group constituted by connecting 2 to 6 aromatic rings of an aromatic heterocyclic group.
R ³ is the same as 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 It is an integer of 0-2.
m represents the number of repetitions, and is an integer of 2 to 4, preferably 2 or 3, more preferably 2.
When m and p are 2 or more, the plurality of Cz may be the same or different.

A case where L and 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, fluoranthene, pyrene, chrysene. , 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, quinoxaline, quinazoline, naphthyridine, dibenzofuran, dibenzothiophene, acridine, azepine, tribenzazepine, phenazine, phenoxazine, phenothiazine, dibenzo Examples thereof include a group formed by removing hydrogen from an aromatic heterocyclic compound such as phosphole, dibenzoborol, carbazole, etc., preferably a group formed by removing hydrogen from pyridine, pyrimidine, triazine, quinazoline, dibenzofuran or dibenzothiophene. However, L and R ² are preferably groups other than the carbazole group.

In the present specification, a group generated 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 connected by a single bond is referred to as a linked aromatic group. The linked aromatic group is a group constituted by connecting 2 to 6 aromatic rings, and the connected 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 connected aromatic rings is preferably 2 to 4, more preferably 2 or 3. The number of carbon atoms of each aromatic group constituting the linked aromatic group is within the range of the number of carbon atoms when L and R ^{1 to} R ³ are an aromatic hydrocarbon group or an aromatic heterocyclic group, The number of carbon atoms is 60 or less, preferably 40 or less.

  Specific examples of the linked aromatic group include biphenyl, terphenyl, quaterphenyl, phenylnaphthalene, diphenylnaphthalene, phenylanthracene, diphenylanthracene, diphenylfluorene, bipyridine, bipyrimidine, vitriazine, bisdibenzofuran, bisdibenzothiophene, and phenylpyridine. Group obtained by removing hydrogen from phenylpyrimidine, phenyltriazine, phenylcarbazole, phenyldibenzofuran, diphenylpyridine, diphenyltriazine, bisdibenzofuranylbenzene and the like.

  The aromatic hydrocarbon group, aromatic heterocyclic group or linked aromatic group may have a substituent. When the aromatic hydrocarbon group has a substituent, the preferred substituent is a diallylamino group having 12 to 30 carbon atoms, It is a C1-C12 alkyl group, a C1-C12 alkoxy group, or an acetyl group. More preferably, they are 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. In the present specification, calculation of the carbon number is understood to include the carbon number of the substituent.

Similarly, the carbazole group may 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. In addition, when the N-position of the Cz ring is not used for bonding with an adjacent ring, it is desirable to have the above 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. As a preferable embodiment of the formula (2), there is any one 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 represents 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 group. A linked aromatic group constituted by connecting 2 to 6 aromatic rings selected from an aromatic group, more preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or This is a linked aromatic group constituted by connecting 2 to 6 aromatic rings selected from the aromatic hydrocarbon group.

（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 is represented, for example, by the following formula, and may be linked in a linear or branched form.

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

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

Intermediate A can be synthesized by the following reaction formula with reference to the synthesis example shown in Chem Commun, 2012, 48, p6298-6300. This intermediate A can be used to introduce a functional group by a known reaction (Suzuki coupling or Ullman coupling).

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

The organic electroluminescent element material 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) is formed by laminating an anode, a plurality of organic layers and a cathode on a substrate. By including it in at least one organic layer of the organic EL element, an excellent organic electroluminescence element is provided. As the organic layer to be contained, a light emitting layer, an electron transport layer or a hole blocking layer is suitable.
Here, when used in a light emitting layer, it can be used as a host material of a light emitting layer containing a fluorescent, delayed fluorescent 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 having at least one of excited singlet energy and excited triplet energy higher than that of the compound of the present invention is used as a host material. It is preferable. The compound of the present invention is particularly preferably contained as a host material for a light emitting layer containing a phosphorescent dopant.

  Next, the organic EL element using the organic electroluminescent element material 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 an anode and a cathode laminated on a substrate, and the at least one organic layer is for the organic electroluminescent device of the present invention. Contains materials. Advantageously, the organic electroluminescent device material of the present invention is included in the light emitting layer together with a phosphorescent dopant.

  Next, the structure of the organic EL element of the present invention will be described with reference to the drawings. However, the structure of the organic EL element of the present invention is not limited to the illustrated one.

  FIG. 1 is a cross-sectional view showing a structural example of a general organic EL device used in the present invention, wherein 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 represents 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, and may have an electron blocking layer between the light emitting layer and the hole injection layer. The exciton blocking layer can be inserted on either the anode side or the cathode side of the light emitting layer, or both can be inserted simultaneously. 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 to have a hole injecting and transporting layer and an electron injecting and transporting layer in layers other than the essential layers, and further emit light. It is preferable to have a hole blocking layer between the layer and the electron injecting and transporting layer. The hole injection / transport layer means either or both of a hole injection layer and a hole transport layer, and the electron injection / transport layer means either or both of an electron injection layer and an electron transport layer.

  In addition, it is also possible to laminate | stack the cathode 7, the electron carrying layer 6, the light emitting layer 5, the positive hole transport layer 4, and the anode 2 in order on the board | substrate 1 in the reverse structure, FIG. Layers can be added or omitted as necessary.

-Board-
The organic EL element of the present invention is preferably supported on a substrate. The substrate is not particularly limited as long as it is conventionally used for an organic EL element. 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, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is 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. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, these electrode materials may be formed into a thin film 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 the pattern accuracy is not required (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it 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 material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the light emission luminance is improved, which is convenient.

  Moreover, after producing the metal with a film thickness of 1 to 20 nm on the cathode, a transparent or translucent cathode can be produced by producing the conductive transparent material mentioned in the description of the anode on the cathode, By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

-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 the anode and the cathode, respectively, 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, the fluorescent light emitting material may be at least one kind of fluorescent light emitting material, but it is preferable to use the fluorescent light emitting material as a 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 be selected from them. For example, benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives, condensed aromatic compounds, perinone derivatives, oxadiazole derivatives , Oxazine derivatives, aldazine derivatives, cyclopentadiene derivatives, bisstyrylanthracene derivatives, quinacridone derivatives, pyrrolopyridine derivatives, thiadiazolopyridine derivatives, styrylamine derivatives, diketopyrrolopyrrole derivatives, aromatic dimethylidine compounds, 8-quinolinol derivatives Complexes, metal complexes of pyromethene derivatives, rare earth complexes, various metal complexes represented by transition metal complexes, etc., polythiophene, polyphenylene Polyphenylene vinylene polymer compounds such as, organic silane derivatives, and the like. Preferred examples include condensed aromatic compounds, styryl compounds, diketopyrrolopyrrole compounds, oxazine compounds, pyromethene metal complexes, transition metal complexes, and lanthanoid complexes, more preferably naphthacene, pyrene, chrysene, triphenylene, benzo [c] phenanthrene, Benzo [a] anthracene, pentacene, perylene, fluoranthene, acenaphthofluoranthene, dibenzo [a, j] anthracene, dibenzo [a, h] anthracene, benzo [a] naphthacene, hexacene, anthanthrene, naphtho [2,1 -f] isoquinoline, α-naphthaphenanthridine, phenanthrooxazole, quinolino [6,5-f] quinoline, benzothiophanthrene and the like. 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, a compound having a condensed aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, indene, or a derivative thereof, N, N′-dinaphthyl-N, N′-diphenyl-4 Aromatic amine derivatives such as 4,4'-diphenyl-1,1'-diamine, metal chelated oxinoid compounds such as tris (8-quinolinato) aluminum (III), bisstyryl derivatives such as distyrylbenzene derivatives, tetraphenyl Butadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, Carbazole derivatives, indolocarbazole derivatives, triazine derivatives, in polymer systems, a polyphenylene vinylene derivative, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives can be used is not particularly limited.

  When the fluorescent light emitting material is used as a fluorescent light emitting dopant and includes 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 range.

  Usually, an organic EL element injects electric charges into a luminescent material from both an anode and a cathode, generates an excited luminescent material, and emits light. In the case of a charge injection type organic EL device, it is said that 25% of the generated excitons are excited to a singlet excited state and the remaining 75% are excited to a triplet excited state. As shown in Advanced Materials 2009, 21, 4802-4806. Certain fluorescent materials emit triplet-triplet annihilation or heat after energy transition to triplet excited state due to intersystem crossing. It is known that, due to the absorption of energy, the singlet excited state is crossed back to back and emits fluorescence, thereby expressing thermally activated delayed fluorescence. The organic EL device of the present invention can also exhibit delayed fluorescence. In this case, both fluorescence emission and delayed fluorescence emission can be included. However, light emission from the host material may be partly or partly emitted.

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

  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 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 given. Specific examples include compounds described in the following non-patent documents and patent documents, but are not limited to these compounds.

  1) Adv. Mater. 2009, 21, 4802-4806, 2) Appl. Phys. Lett. 98, 083302 (2011), 3) JP 2011-213643, 4) J. Am. Chem. Soc. 2012 , 134, 14706-14709.

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

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

  As the delayed fluorescent host material in the light emitting layer, a coranulene compound represented by the general formula (1) can be used, but it can also be selected from compounds other than coranulene. For example, a compound having a condensed aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, indene, or a derivative thereof, N, N′-dinaphthyl-N, N′-diphenyl-4 Aromatic amine derivatives such as 4,4'-diphenyl-1,1'-diamine, metal chelated oxinoid compounds such as tris (8-quinolinato) aluminum (III), bisstyryl derivatives such as distyrylbenzene derivatives, tetraphenyl Butadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, In the rubazole derivative, indolocarbazole derivative, triazine derivative, and polymer system, polyphenylene vinylene derivative, polyparaphenylene derivative, polyfluorene derivative, polyvinylcarbazole derivative, polythiophene derivative, arylsilane derivative, 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 includes a phosphorescent light emitting dopant and a host material. The phosphorescent dopant material preferably contains an organometallic 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.

Preferable phosphorescent dopants include complexes such as Ir (ppy) ₃ having a noble metal element of Ir such as the central metal, Ir (bt) complexes such as ₂ · acac _3, complexes such as PtOEt ₃ and the like. 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 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 a host material in the light emitting layer. However, when the corannulene compound is used in 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, you may use together a carborane compound and another host material. Furthermore, a plurality of known host materials may be used in combination.

  The known host compound that can be used is preferably a compound that has a hole transporting ability and an electron transporting ability, prevents light emission from becoming longer, 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 include indole derivatives, carbazole derivatives, indolocarbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, Pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, porphyrins Compounds, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, etc. Tetracarboxylic anhydride, phthalocyanine derivatives, metal complexes of 8-quinolinol derivatives, metal phthalocyanines, various metal complexes represented by metal complexes of benzoxazole and benzothiazole derivatives, polysilane compounds, poly (N-vinylcarbazole) derivatives, Examples include aniline-based copolymers, thiophene oligomers, polythiophene derivatives, polyphenylene derivatives, polyphenylene vinylene derivatives, and polyfluorene derivatives.

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

-Injection layer-
The injection layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the luminance of light emission. 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 between the cathode and the light emitting layer or the electron transport layer. The injection layer can be provided as necessary.

-Hole blocking layer-
The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking.

  Although the corannulene compound of the present invention is preferably used for the hole blocking layer, a known hole blocking layer material may be used when the coranulene compound is used for any other organic layer. Moreover, as a hole-blocking layer material, the material of the electron carrying layer mentioned later can be used as needed.

-Electron blocking layer-
The electron blocking layer is made of a material that has a function of transporting holes and has a very small ability to transport electrons. The electron blocking layer blocks the electrons while transporting holes, and the probability of recombination of electrons and holes. Can be improved.

  As a material for the electron blocking layer, a material for a hole transport layer described later can be used as necessary. The 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 recombination of holes and electrons in the light emitting layer from diffusing into the charge transport layer. It becomes possible to efficiently confine in the light emitting layer, and the light emission efficiency of the device can be improved. The exciton blocking layer can be inserted on either the anode side or the cathode side adjacent to the light emitting layer, or both can be inserted simultaneously.

  As a material for the exciton blocking layer, a corannulene compound represented by the general formula (1) can be used. As other materials, for example, 1,3-dicarbazolylbenzene (mCP), bis ( 2-methyl-8-quinolinolato) -4-phenylphenolato aluminum (III) (BAlq).

-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 can be provided as a single layer or a plurality of layers.

  The hole transport material has any of hole injection or transport and electron barrier properties, and may be either organic or inorganic. As the known hole transporting material that can be used, a carborane compound represented by the general formula (1) is preferably used, but any one of conventionally known compounds 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, oxazole derivatives. , Styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. 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 can be provided as a single layer or a plurality of layers.

  The electron transport 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. Although it is preferable to use the corannulene compound of the present invention for the electron transport layer, any one of conventionally known compounds can be selected and used. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyrandi Examples thereof include oxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, 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. However, the present invention is of course not limited to these examples, and can be implemented in various forms as long as the gist thereof is not exceeded. .

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

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

Under a nitrogen atmosphere, Koranyuren 5.0 g (0.0199 mol), N- iodosuccinimide 4.5 g (0.0199 mol), AuCl 3 302 mg (0.998 mmol), 1,2- dichloroethane 400 mL was added and stirred overnight at room temperature. Thereafter, 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 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- 0.91 g (0.00797 mmol) of cyclohexanediamine and 40 mL of 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 distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain 3.20 g (4.87 mmol, 61% yield) of Compound 1 (APCI-TOFMS, m / z 657 [M + H] ⁺ ).

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

Example 2
Each thin film was laminated at a vacuum degree of 4.0 × 10 ⁻⁵ Pa by a vacuum evaporation method on a glass substrate on which an anode made of ITO having a thickness of 110 nm was formed. First, HAT-CN was formed as a hole injection layer with a thickness of 25 nm on ITO, and then NPD was formed as a hole transport layer with a thickness of 45 nm. 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-evaporated from different evaporation 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%. Further, 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 to a thickness of 1 nm as an electron injection layer on the electron transport layer. Finally, on the electron injection layer, Al was formed to a thickness of 70 nm as a cathode, and an organic EL device was produced.

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 in place of compound 1 as the host material of 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 the host material of the light emitting layer in Example 2.

The compounds used in the examples are shown below.

Table 1 shows the luminance, driving voltage, luminous efficiency, and luminance half-life of the produced organic EL device. In the table, luminance, driving voltage, and luminous efficiency are values at a driving current of 20 mA / cm ² , and are initial characteristics. LT95 is the time it takes for the luminance to decay to 95% of the initial luminance at an initial luminance of 3700 cd / m ² , and is a lifetime characteristic.

In addition, when the organic EL elements produced in Examples 2 to 8 and Comparative Examples 1 and 2 were connected to an external power source and applied with a DC voltage, an emission spectrum with a maximum wavelength of 620 nm was observed, and Ir ( pic) ₂ It was found that 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 remarkably 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)

An organic electroluminescent element material comprising 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 bond, a 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 Or it is a connection aromatic group comprised by connecting 2-6 aromatic rings of an aromatic heterocyclic group.
R ¹ is independently a 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 group. This is a linked aromatic group constituted by connecting 2 to 6 aromatic rings of a heterocyclic group.
R ² is independently hydrogen, a 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 This is a linked aromatic group constituted by connecting 2 to 6 aromatic rings of an aromatic heterocyclic group. )   The organic electroluminescent element material according to claim 1, wherein m is an integer of 2 in the general formula (1). The organic electroluminescent element material 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).

(Wherein R ³ is a 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 (This is a linked aromatic group constituted by connecting 2 to 6 aromatic rings of an aromatic heterocyclic group.) The organic electroluminescent element material according to claim 3, wherein the formula (2) is any one of the following formulas (4) to (7).

(Here, R ³ is the same as the formula (2).) R ³ represents 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 heterocyclic group. The organic electroluminescent element material according to claim 4, which is a linked aromatic group composed of 2 to 6 aromatic rings selected from a cyclic group. R ³ is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a linked aromatic group formed by connecting 2 to 6 aromatic rings selected from the aromatic hydrocarbon group. The organic electroluminescent element material according to claim 4.   An organic electroluminescence device comprising an anode, an organic layer and a cathode laminated on a substrate, wherein the organic electroluminescence device comprises an organic layer containing the material for an organic electroluminescence device according to claim 1. Electroluminescent device.   The organic electroluminescent element according to claim 7, wherein the organic layer containing the organic electroluminescent element material is at least one layer selected from the group consisting of a light emitting layer, an electron transport layer, and a hole blocking layer.   The organic electroluminescent device according to claim 7, wherein the organic layer containing the material for an organic electroluminescent device is a light emitting layer containing a phosphorescent dopant. The organic electroluminescent element according to claim 9, wherein the emission wavelength of the phosphorescent dopant has an emission maximum wavelength at 550 nm or more.

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