KR102111535B1 - Material for organic electroluminescent elements and organic electroluminescent elements using same - Google Patents

Abstract

An organic electroluminescent element (organic EL element) having a simple configuration and a material for an organic EL element used therein are provided while improving luminous efficiency and sufficiently securing driving stability. This organic electroluminescent device has a light emitting layer between an anode and a cathode stacked on a substrate, and the light emitting layer contains a material for an organic EL device composed of a phosphorescent dopant and a carborane compound as a host material. The carborane compound as a material for an organic EL device is a compound having three or more carborane skeletons, and is represented by L ^2- (A) _p -L ¹ -AL ^1- (A) _q -L ² . A is a carborane ring, L ¹ is a direct bond or an aromatic group, L ² is a hydrogen or an aromatic group, and p and q are integers from 1 to 5.

Description

Materials for organic electroluminescent devices and organic electroluminescent devices using the same {MATERIAL FOR ORGANIC ELECTROLUMINESCENT ELEMENTS AND ORGANIC ELECTROLUMINESCENT ELEMENTS USING SAME}

The present invention relates to an organic electroluminescent element containing a carborane compound, and more details relates to a thin film type device that emits light by applying an electric field to a light emitting layer made of an organic compound.

In general, an organic electroluminescent element (hereinafter referred to as an organic EL element) has a simplest structure comprising a light emitting layer and a pair of counter electrodes covering the layer. That is, in the organic EL device, when an electric field is applied between both electrodes, electrons are injected from the cathode, holes are injected from the anode, and they recombine in the light emitting layer to emit light.

Recently, an organic EL device using an organic thin film has been developed. In particular, in order to improve the luminous efficiency, the electrode type is optimized for the purpose of improving the efficiency of carrier injection at the electrode, and a hole transport layer made of an aromatic diamine and a light emitting layer made of an 8-hydroxyquinoline aluminum complex (hereinafter referred to as Alq ₃ ) By developing the device prepared as a thin film between electrodes, compared to the device using a single crystal such as anthracene, a significant improvement in luminous efficiency has been achieved, and thus, for a high-performance flat panel having characteristics such as self-luminescence and high-speed response. It has been progressed with the goal of commercialization.

In addition, it has been studied to use phosphorescence rather than fluorescence as an attempt to increase the luminous efficiency of the device. A hole transport layer made of the aromatic diamine and Alq ₃ Many devices, including devices having a light emitting layer made of them, used fluorescent light emission, but they used phosphorescent light emission, that is, using light emitted from a triplet excited state, and devices using conventional fluorescence (single term). In comparison, it is expected to improve the efficiency by 3 to 4 times. For this purpose, it was considered to use a coumarin derivative or a benzophenone derivative as a light emitting layer, but only extremely low luminance was obtained. In addition, the use of the europium complex as an attempt to use the triplet state has been considered, but this also failed to achieve high efficiency luminescence. Recently, as suggested in Patent Document 1, a number of studies have been focused on organometallic complexes such as iridium complexes for the purpose of high efficiency and long life of light emission.

Japanese Patent Publication No. 2003-515897 Japanese Patent Application Publication No. 2001-313178 Japanese Patent Application Publication No. 2005-162709 Japanese Patent Application Publication No. 2005-166574

J. Am. Chem. Soc. 2012, 134, 17982-17990

In order to obtain high luminous efficiency, the host material used simultaneously with the dopant material is important. A representative 4,4'-bis (9-carbazolyl) biphenyl (hereinafter referred to as CBP) of the carbazole compound introduced in Patent Document 2 is suggested as a host material. When CBP is used as a host material of a green phosphorescence emitting material represented by tris (2-phenylpyridine) iridium complex (hereinafter referred to as Ir (ppy) ₃ ), CBP is easy to flow holes, and electrons are difficult to flow. The injection balance is disturbed, and excess holes flow out toward the electron transport layer, resulting in a decrease in luminous efficiency from Ir (ppy) ₃ .

As described above, in order to obtain high luminous efficiency with an organic EL device, a host material having high triplet excitation energy and balanced in two charge (hole and electron) injection transport characteristics is required. In addition, a compound having electrochemically stable, high heat resistance and excellent amorphous stability is required, and further improvement is required.

In patent documents 3, 4 and non-patent document 1, the carborane compound as shown below is disclosed.

However, the compound is a phenyl group or a fluorenyl group or a carbazolylphenyl group bonded to the carborane skeleton, or a carbolan skeleton and a phenyl group are cyclically bonded, and an aromatic group and a carborane skeleton are bonded in a straight chain. However, it does not disclose a compound having three or more carborane skeletons in a molecule.

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 sufficiently secure stability during driving. An object of the present invention is to provide a practically useful organic EL device having a high efficiency and high driving stability in consideration of the above-described situation, and a compound suitable therefor.

As a result of careful study, the present inventors found that the aromatic group and the carborane skeleton are bonded in a straight chain, and the carbolan compound having three or more carborane skeletons in the molecule is used as an organic EL device, thereby finding excellent properties. It came to completion.

The present invention relates to a material for an organic electroluminescent device composed of a carborane compound represented by the general formula (1).

In General Formula (1), ring A independently represents a tetravalent carbolan group of C ₂ B ₁₀ H ₈ represented by either Formula (1a) or Formula (1b). L ¹ is independently a direct 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 an aromatic group selected from the aromatic hydrocarbon group and the aromatic heterocyclic group Represents an aromatic group consisting of 2 to 6 aromatic rings. However, not all of L ¹ are direct bonds. L 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 an aromatic group selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. The aromatic ring represents a linked aromatic group consisting of 2 to 6 linked groups, and L ³ is independently hydrogen, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, substituted or unsubstituted An aromatic heterocyclic group having 3 to 30 carbon atoms or an aromatic ring selected from the aromatic hydrocarbon group and the aromatic heterocyclic group is a linking aromatic group composed of 2 to 6 aromatic rings. When L ¹ , L ² , and L ³ are a linked aromatic group, the aromatic rings to be connected may be the same or different. p and q independently represent an integer of 1 to 5, and in the general formula (1), part or all of hydrogen may be substituted with deuterium.

Among the carborane compounds represented by the general formula (1), the carborane compounds of the following general formula (2) are preferable, and the carborane compounds represented by general formulas (3) and (4) are more preferable compounds.

In general formula (2), L ¹ , L ² , L ³ , p and q have the same meanings as general formula (1). Ring A represents a tetravalent carbolan group of C ₂ B ₁₀ H ₈ represented by either Formula (2a) or Formula (2b), and may be the same or different when multiple rings A are present in the molecule.

In General Formulas (3) and (4), L ¹ , L ² , L ³ , p, and q have the same meanings as those in General Formula (1).

In General Formulas (1), (2), (3), and (4), L ¹ is independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic having 3 to 17 carbon atoms It is preferable that the heterocyclic group or the aromatic hydrocarbon group and the aromatic ring of the aromatic group selected from the aromatic heterocyclic group are two to five aromatic rings.

In General Formulas (1), (2), (3), and (4), L ² is independently substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, substituted or unsubstituted aromatic having 3 to 17 carbon atoms It is preferable that the heterocyclic group or the aromatic hydrocarbon group and the aromatic ring of the aromatic group selected from the aromatic heterocyclic group are two to five aromatic rings.

In addition, the present invention is an organic electroluminescent device having an organic layer containing the material for the organic electroluminescent device in an organic electroluminescent device comprising an anode, an organic layer and a cathode laminated on a substrate.

Moreover, in the present invention, it is preferable that the organic layer containing the material for an organic electroluminescent device contains a phosphorescent dopant. In addition, it is preferable that the emission wavelength of the phosphorescent dopant has a maximum emission wavelength of 550 nm or less.

The organic electroluminescent device material of the present invention has a structure in which three or more carborane skeletons are attached, and the carborane skeleton is linearly bonded through at least one aromatic ring. In the carborane compound having such a structural feature, the lowest co-orbit (LUMO) that affects electron injection transportability is widely distributed throughout the molecule to control the electron injection transportability of the device to a high level. In addition, since it has a T1 energy high enough to trap the lowest triplet excitation energy (T1 energy) of the dopant, efficient light emission from the dopant is possible. From the above characteristics, this was used for an organic EL device to achieve a reduction in driving voltage of the device and high luminous efficiency.

In addition, since the material for an organic electroluminescent device of the present invention exhibits good amorphous properties and high thermal stability and is very stable in an excited state, the organic EL device using this has a long driving life and durability at a practical level.

1 is a cross-sectional view showing an example of a structure of an organic EL device.
2 is an NMR chart of carborane compound 1.
3 is an NMR chart of the carborane compound 36.

The material for an organic electroluminescent device of the present invention is a carborane compound represented by the above general formula (1). It is thought that this carborane compound has a structure in which three or more carborane skeletons are connected in a straight chain through a direct bond or an aromatic ring, and thus it is thought to bring about excellent effects as described above.

In general formula (1), L ¹ is independently a direct bond or a divalent aromatic group. The divalent aromatic group 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 an aromatic ring of the aromatic group selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. It is a linked aromatic group consisting of 2 to 6 linked, and in the case of a linked aromatic group, the aromatic rings to be connected may be the same or different. However, not all of L ¹ are direct bonds. The preferred range of L ¹ 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 an aromatic group selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. It is a linked aromatic group consisting of 2 to 5 aromatic rings.

In General Formula (1), L ² is independently hydrogen or a monovalent aromatic group. The monovalent aromatic group 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 an aromatic ring of the aromatic group selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. It represents a linked aromatic group consisting of 2 to 6 linked, preferably substituted or unsubstituted aromatic hydrocarbon groups having 6 to 18 carbon atoms, substituted or unsubstituted aromatic heterocyclic groups having 3 to 17 carbon atoms, or the aromatic hydrocarbon group and the It is a linked aromatic group consisting of 2 to 5 aromatic rings of an aromatic group selected from aromatic heterocyclic groups.

In General Formula (1), L ³ is independently hydrogen or a monovalent C 1 to C 12 aliphatic hydrocarbon group or a monovalent aromatic group. The monovalent aromatic group 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 an aromatic ring of the aromatic group selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. It represents the linked aromatic group which consists of 2-6 pieces. L ³ is preferably hydrogen, 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 an aromatic group selected from the aromatic hydrocarbon group and the aromatic heterocyclic group Is an aromatic aromatic group consisting of 2 to 5 aromatic rings, and more preferably hydrogen.

Specific examples of the unsubstituted aromatic hydrocarbon group include a group formed by removing hydrogen from aromatic hydrocarbon compounds such as benzene, naphthalene, fluorene, anthracene, phenanthrene, fluoranthene, pyrene, chrysene, and triphenylene. It is a group formed by removing hydrogen from benzene, naphthalene, anthracene, phenanthrene, and triphenylene.

Specific examples of the unsubstituted aromatic heterocyclic group include pyridine, pyrimidine, triazine, quinoline, isoquinoline, quinoxaline, naphthyridine, carbazole, dibenzofuran, dibenzothiophene, acridine, azepine, tribenzoase And groups generated by removing hydrogen from aromatic heterocyclic compounds such as pin, phenazine, phenoxazine, phenothiazine, dibenzophosphol, and dibenzoborol. Preferred are pyridine, pyrimidine, triazine, carbazole, Dibenzofuran is a group formed by removing hydrogen from dibenzothiophene.

A group formed by removing hydrogen from an aromatic compound having a structure in which the aromatic hydrocarbon compound or aromatic heterocyclic compound is connected plurally is called a linked aromatic group. The linked aromatic group is a group consisting of 2 to 6 aromatic rings connected, and the connected aromatic rings may be the same or different, and may include two aromatic hydrocarbon groups and aromatic heterocyclic groups. The number of aromatic rings to be connected is preferably 2 to 5, and more preferably 2 or 3. The aromatic ring to be connected may be a condensed ring, and the condensed ring is calculated as 1 regardless of the number of rings in the condensed ring in the calculation of the number of connections.

Specific examples of the linking aromatic group include biphenyl, terphenyl, phenylnaphthalene, diphenylnaphthalene, phenylanthracene, diphenylanthracene, diphenylfluorene, bipyridine, bipyrimidine, vitriazine, biscarbazole, bisdibenzo Furan, bisdibenzothiophene, bisfluorene, phenylpyridine, phenylpyrimidine, phenyltriazine, phenylcarbazole, phenyldibenzofuran, phenyldibenzothiophene, diphenylpyridine, diphenyltriazine, biscarba And groups formed by removing hydrogen from zolylbenzene, bisdibenzofuranylbenzene, bisbenzothiophenylbenzene, pyridylcarbazole, and the like.

The aromatic hydrocarbon group, the aromatic heterocyclic group, and the linked aromatic group may have a substituent, and when having a substituent, preferred substituents are an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cyano group, or an acetyl group. More preferably, it is an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an acetyl group or a cyano group, and it is preferable that the substituent does not contain a silicon-containing group such as a silyl group. Specific examples include a methyl group, ethyl group, isopropyl group, butyl group, methoxy group, ethoxy group, acetyl group and cyano group.

Here, when the said connecting aromatic group is a divalent group, it is represented by the following formula, for example, and may be connected in linear or branched form.

(Ar ¹ to Ar ⁶ are unsubstituted aromatic hydrocarbon rings or aromatic heterocycles)

In General Formula (1), L ² is the same as L ¹ except that it is monovalent and contains hydrogen. L ³ is the same as L ¹ except that it is monovalent, hydrogen, and an aliphatic hydrocarbon group having 1 to 12 carbon atoms. Further, L ¹ is a direct bond or a divalent aromatic group, but the L ² and L ³ groups are not directly bonded.

Therefore, L ² and L ³ The description of the monovalent aromatic group is understood by looking at the divalent as monovalent in the description of the divalent aromatic group in L ¹ .

In addition, the aliphatic hydrocarbon group in L ³ may be saturated or unsaturated, and may be linear, branched or cyclic, and specific examples include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group and octyl group. And cycloalkyl groups such as cyclopentyl group and cyclohexyl group.

In general formula (1), p represents an integer of 1 to 5, preferably 1 to 2. q is an integer of 1-5, preferably 1-2. p + q is preferably an integer from 2 to 8, more preferably 2, 3 or 4.

In general formula (1), hydrogen may be substituted with deuterium.

Among the carborane compounds represented by the general formula (1), the carborane compounds represented by the general formula (2) are exemplified as preferred compounds, and more preferably, the carborane represented by the general formula (3) or (4) It is a compound.

In Formulas (1) to (4), except for Ring A, the same symbols and formulas are interpreted to have the same meaning unless otherwise specified. Therefore, the description of one symbol in the general formula (1) is also understood as the description of the symbols in the general formulas (2) to (4). About ring A, ring A of general formula (2) is more limited than general formula (1).

The carborane compounds represented by the general formulas (1) to (4) can be synthesized using a known technique by selecting a raw material according to the structure of the target compound.

For example, the carborane parent skeleton can be synthesized (A-1) by the following reaction scheme with reference to the synthesis examples presented in Journal of Organometallic Chemistry, 1993, 462, p19-29.

(A-2) can be synthesized by the following reaction formula with reference to the synthesis example of (A-1).

(A-3) may be synthesized by the following reaction scheme with reference to the synthesis examples presented in European Journal of Inorganic Chemistry, 2010, p2012-2024 and Inorganic Chemistry, 1995, 34, p2095-2100.

(A-4) can be synthesized by the following reaction scheme with reference to the synthesis example presented in Inorganica Chimica Acta, 1995, 240, p371-378.

Although the specific example of the carborane compound represented by general formula (1)-(4) is shown below, the material for organic electroluminescent elements of this invention is not limited to this.

The material for an organic electroluminescent device of the present invention (also referred to as a carborane compound) provides an excellent organic electroluminescent device by including it in at least one organic layer of an organic EL device in which an anode, a plurality of organic layers and a cathode are stacked on a substrate. 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, in addition to being used as a host material for a light emitting layer containing a dopant of fluorescence emission, delayed fluorescence emission or phosphorescence emission, the carborane compound of the present invention is used as an organic emission material emitting fluorescence and delayed fluorescence. Can be used. When used as an organic light emitting material that emits fluorescence and delayed fluorescence, it is preferable to use another organic compound having at least one of excitation singlet energy and excitation triplet energy having a higher value than the compound of the present invention as a host material. It is particularly preferable that the carborane compound of the present invention is contained as a host material of a light emitting layer containing a phosphorescent dopant.

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

Next, the structure of the organic EL device of the present invention will be described with reference to the drawings, but the structure of the organic EL device of the present invention is not limited to what is shown.

1 is a cross-sectional view showing a structural example of a general organic EL device used in the present invention, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer, 6 is an electron transport layer, 7 is Each cathode is shown. In the organic EL device of the present invention, an exciton blocking layer may be provided adjacent to the light emitting layer, and an electron blocking layer may be provided between the light emitting layer and the hole injection layer. The exciton blocking layer can be inserted into both the anode side and the cathode side of the light emitting layer, and both can be inserted simultaneously. In the organic EL device of the present invention, a substrate, an anode, a light emitting layer, and a cathode are essential layers, but it is preferable to have a hole injection transport layer and an electron injection transport layer in a layer other than the essential layer, and also a hole blocking layer between the light emitting layer and the electron injection transport layer. It is good to have. In addition, 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.

In addition, a structure opposite to that of FIG. 1, that is, a cathode 7, an electron transport layer 6, a light emitting layer 5, a hole transport layer 4, and an anode 2 may be stacked on the substrate 1 in order. In this case, layers may be added or omitted as necessary.

-Board-

It is preferable that the organic EL device of the present invention is supported on a substrate. There is no restriction | limiting in particular about this board | substrate, If it is conventionally used for the organic EL element, it is good, for example, what consists of glass, transparent plastic, quartz, etc. can be used.

-anode-

As an anode in an organic EL device, it is preferable to use a metal having a large work function (4 eV or more), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material. Specific examples of such electrode materials include metals such as Au, conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ and ZnO. Moreover, you may use material which is amorphous and can manufacture a transparent conductive film, such as IDIXO (In ₂ O ₃ -ZnO). The positive electrode may form a thin film of these electrode materials by a method such as vapor deposition or sputtering, and may form a pattern having a desired shape by a photolithography method, or when pattern precision is not required (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape during deposition or sputtering of the electrode material. Alternatively, when a material that can be applied, such as an organic conductive compound, is used, a wet film forming method such as a printing method or a coating method may be used. When light emission is extracted from this anode, it is preferable that the transmittance is greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, the film thickness varies depending on the material, but is usually 10 to 1000 nm, and 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-injecting metal), an alloy, an electrically conductive compound, and a mixture thereof are used as electrode materials. Specific examples of the electrode material 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 ) mixture, indium , Lithium / aluminum mixtures, rare earth metals, and the like. Among them, a mixture of an electron-injectable metal and a second metal, which is a stable metal having a higher work function value, from the viewpoint of electron injectability and durability against oxidation, for example, a magnesium / silver mixture, a magnesium / aluminum mixture, magnesium / Indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, lithium / aluminum mixture, aluminum, etc. are suitable. The cathode can be produced by forming a thin film of such an electrode material by a method such as vapor deposition or sputtering. In addition, the sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually 10 nm to 5 μm, preferably 50 to 200 nm. In addition, if either one of the anode or the cathode of the organic EL device is transparent or translucent in order to transmit the emitted light, the luminance of the light emission is improved, which is advantageous.

In addition, after fabricating the metal on the negative electrode with a film thickness of 1 to 20 nm, a transparent or semi-transparent negative electrode can be produced by fabricating the conductive transparent material described above on the positive electrode, and by applying this, both the positive electrode and the negative electrode are permeable. It is possible to manufacture a device having a.

-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, the fluorescent light emitting material may be used alone, or at least one type of fluorescent light emitting material may be used alone, but it is preferable that the fluorescent light emitting material is used as a fluorescent light emitting dopant to include a host material.

As the fluorescent light-emitting material in the light-emitting layer, a carborane compound represented by the general formula (1) can be used, but since it is known from a number of 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 derivatives, aldazine derivatives, pyrrazine derivatives, cyclopentadiene derivatives, bisstyrylanthracene derivatives, quinacridone derivatives, pyrrolopyridine derivatives, thiadiazolopyridines Derivatives, styrylamine derivatives, diketopyrrolopyrrole derivatives, aromatic dimethylidine compounds, metal complexes of 8-quinolinol derivatives or metal complexes of pyrromethene derivatives, rare earth complexes, various metal complexes represented by transition metal complexes, etc. And polymer compounds such as thiophene, polyphenylene, and polyphenylene vinylene, and organic silane derivatives. Preferably, a condensed aromatic compound, a styryl compound, a diketopyrrolopyrrole compound, an oxazine compound, a pyrromethene metal complex, a transition metal complex, a lanthanoide complex, and more preferably naphthacene, pyrene, and cree Sen, triphenylene, benzo [c] phenanthrene, benzo [a] anthracene, pentacene, perylene, fluoranthene, acenaphthofluoranthene, dibenzo [a, j] anthracene, dibenzo [a, h] Anthracene, benzo [a] naphthacene, hexacene, anthane, naphtho [2,1-f] isoquinoline, α-naphthaphenanthridine, phenanthrooxazole, quinolino [6,5-f] And quinoline and benzothiopanrene. These may have an alkyl group, an aryl group, an aromatic heterocyclic group, and a diarylamino group as a substituent.

As the fluorescent host material in the light emitting layer, a carborane compound represented by the general formula (1) can be used, but since it is known from a number of patent documents, it can also be selected from them. For example, compounds having condensed aryl rings, such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, and inden, derivatives thereof, N, N ' Aromatic amine derivatives such as -naphthyl-N, N'-diphenyl-4,4'-diphenyl-1,1'-diamine, metal chelates including tris (8-quinolinato) aluminum (III) Bisstyryl derivatives such as chelated oxynoid compounds and distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, blood Rollopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, polyphenylenevinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives for polymer systems, Polyvinyl Carbazole derivatives, polythiophene derivatives, and the like can be used, but are not particularly limited.

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

In general, an organic EL device emits light by injecting charge from both electrodes of an anode and a cathode into a light emitting material, and generating a light emitting material in an excited state. In the case of the charge injection type organic EL device, it is known that 25% of the generated excitons are excited by the singlet excited state, and the remaining 75% are excited by the triplet excited state. As suggested in Advanced Materials 2009, 21, 4802-4806, certain fluorescent light-emitting materials transfer energy to a triplet excitation state by inter-crossing or the like, and then triplet-triplet dissipation or absorption of thermal energy It is known to emit fluorescence by crossing inversely between singlet excitation states and expressing thermal activation delayed fluorescence. Delayed fluorescence can also be expressed in the organic EL device of the present invention. In this case, both fluorescence emission and delayed fluorescence emission may be included. However, light emission from the host material may be partly or partly of light emission.

When the light emitting layer is a delayed fluorescent light emitting layer, the delayed light emitting material may use at least one type of delayed light emitting material alone, but it is preferable to use a delayed fluorescent material as a delayed fluorescent light emitting dopant and to include a host material.

As the delayed fluorescent light emitting material in the light emitting layer, a carborane 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, etc. are mentioned. Specifically, the compounds described in the following non-patent documents and patent documents may be mentioned, but are not limited to these compounds.

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

Although a specific example of a delayed-emitting material is shown, it is not limited to the following compound.

When the delayed fluorescent light emitting material is used as a delayed fluorescent light emitting dopant, and when a host material is included, 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% by weight, more preferably 0.01 It is good to be in the range of ~ 10%.

As the delayed fluorescent host material in the light emitting layer, a carborane compound represented by the general formula (1) can be used, but it can also be selected from compounds other than carborane. For example, compounds having condensed aryl rings, such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, and inden, derivatives thereof, N, N ' Aromatic amine derivatives such as -naphthyl-N, N'-diphenyl-4,4'-diphenyl-1,1'-diamine, metal chelates including tris (8-quinolinato) aluminum (III) Bisstyryl derivatives such as chemical oxynoid compounds and distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, and pyrrolopyrrole derivatives , Thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, polyphenylenevinylene derivatives in polymer systems, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcar Bazol 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 includes a phosphorescent dopant and a host material. The phosphorescent dopant material preferably contains an organometallic complex comprising at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold. Specifically, the compounds described in the following patent publications may be mentioned, but are not limited to these compounds.

WO2009 / 073245 publication, WO2009 / 046266 publication, WO2007 / 095118 publication, WO2008 / 156879 publication, WO2008 / 140657 publication, US2008 / 261076 publication, Japanese published patent publication 2008-542203, WO2008 / 054584 Publication, Japanese Patent Publication No. 2008-505925, Japanese Publication Patent Publication 2007-522126, Japanese Publication Patent Publication 2004-506305, Japanese Publication Patent Publication 2006-513278, Japanese Publication Patent Publication 2006-50596 No. WO2006 / 046980, WO2005113704, US2005 / 260449, US2005 / 2260448, US2005 / 214576, etc.

Preferred phosphorescent dopants include complexes such as Ir (ppy) ₃ , complexes such as Ir (bt) ₂ · acac ₃ , and complexes such as PtOEt ₃ having a noble metal element such as Ir as a central metal. Although the specific example of such a complex is shown below, it is not limited to the following compound.

The amount of the phosphorescent dopant contained in the light emitting layer is preferably 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 a carborane compound represented by the general formula (1) according to the present invention as a host material in the light-emitting layer. However, when the carborane compound is used in any other organic layer than the light-emitting layer, the material used for the light-emitting layer may be a host material other than the carborane compound. Moreover, you may use together a carborane compound and another host material. Moreover, you may use together well-known host material in multiple types.

As a known host compound that can be used, it is preferable that the compound has a hole transport ability and an electron transport ability, prevents long-wavelength emission of luminescence, and has a high glass transition temperature.

These other host materials are known from a number of patent documents and the like and can be selected from them. Although it is not specifically limited as a specific example of a host material, Indole derivative, carbazole derivative, triazole derivative, oxazole derivative, oxadiazole derivative, imidazole derivative, polyaryl alkane derivative, pyrazoline derivative, pyrazolone derivative, phenyl Rendiamine 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 Metal complexes of heterocyclic tetracarboxylic anhydrides, phthalocyanine derivatives, and 8-quinolinol derivatives, such as, porphyrin compounds, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, and naphthaleneperylene B Metal phthalocyanine, gold of benzoxazole or benzothiazole derivatives Various metal complexes, polysilane-based compounds, poly (N-vinylcarbazole) derivatives, aniline-based copolymers, thiophene oligomers, polythiophene derivatives, polyphenylene derivatives, polyphenylenevinylene derivatives, etc. And polymer compounds such as polyfluorene derivatives.

The light emitting layer may be either 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 to lower the driving voltage or improve the luminescence brightness, and there is a hole injection layer and an electron injection layer, even if it is present between the anode and the emission layer or the hole transport layer and between the cathode and the emission layer or the electron transport layer. good. The injection layer can be provided as needed.

-Hole blocking layer-

The hole blocking layer has a function of an electron transport layer in a broad sense, has a function of transporting electrons, is made of a hole blocking material having a remarkably small ability to transport holes, and blocks electrons and holes by blocking holes while transporting electrons To improve the probability of recombination.

It is preferable to use a carborane compound represented by the general formula (1) according to the present invention for the hole blocking layer, but when a carborane compound is used in any other organic layer, a known hole blocking layer material may be used. Moreover, as a hole blocking layer material, the material of the electron transport layer mentioned later can be used as needed.

-Electronic blocking layer-

The electron blocking layer is made of a material having a function of transporting holes and having a remarkably small ability to transport electrons, and it is possible to improve the probability of recombination of electrons and holes by blocking electrons while transporting holes.

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

-Here's the lower 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, and it is possible to efficiently confine the excitons in the light emitting layer by insertion of this layer, and to emit light of the device. Efficiency can be improved. 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 simultaneously.

As the material for the exciton-blocking layer, a carborane 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-qui Nolinolato) -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 in a single layer or multiple layers.

As the hole transport material, it has either injection or transport of holes or barrier properties of electrons, and may be either organic or inorganic. As the well-known hole transport material that can be used, it is preferable to use a carborane compound represented by the general formula (1), but it can be arbitrarily selected from conventionally known compounds and used. Known hole transport materials that can be used include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyaryl alkane 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-based copolymers may also include conductive polymer oligomers, especially thiophene oligomers, etc., but porphyrin compounds , It is preferable to use an aromatic tertiary amine compound and a styrylamine compound, and it is more preferable to use an aromatic tertiary amine compound.

-Electronic 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 with a single layer or multiple layers.

As the electron transporting layer material (sometimes also serving as a hole blocking material), it is only necessary to have a function of transferring electrons injected from the cathode to the light emitting layer. As the electron transport layer, it is preferable to use a carborane derivative represented by the general formula (1) according to the present invention, but it can be arbitrarily selected from conventionally known compounds and used, for example, a nitro-substituted fluorene derivative, a diphenylquinone derivative , Thiopyrandioxide derivatives, carbodiimide, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. In addition, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom in the oxadiazole derivative, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Moreover, these materials may be introduced into a polymer chain, or a polymer material using these materials as a main chain of a polymer may be used.

Example

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

A carborane compound serving as a material for an organic electroluminescent device was synthesized by the route shown below. In addition, the compound number corresponds to the number given to the above formula.

Example 1

Compound 1 was synthesized according to the following scheme.

Under nitrogen atmosphere, 35.0 g (0.243 mol) of m-carborane and 926 mL of 1,2-dimethoxyethane (DME) were added to cool the DME solution to 0 ° C. 154.6 mL of 1.65 M n-butyl lithium hexane solution was added dropwise and stirred at room temperature for 1 hour. 24.1 g (0.243 mol) of copper (I) chloride was added and stirred at room temperature for 15 minutes, and then 136 mL of pyridine was added. After stirring at room temperature for 5 minutes, 64.2 g (0.243 mol) of iodine benzene was added and stirred at 95 ° C overnight. The solvent of the obtained reaction solution was distilled off under reduced pressure, and the obtained residue was purified by silica gel column chromatography to obtain 18.6 g (91.7 mmol, yield 38%) of intermediate A.

Under nitrogen atmosphere, 18.2 g (0.09 mol) of intermediate A and 343 mL of DME were added to cool the DME solution to 0 ° C. 57.2 mL of 1.65 M n-butyl lithium hexane solution was added dropwise and stirred at room temperature for 1 hour. 8.9 g (0.09 mol) of copper (I) chloride was added and stirred at room temperature for 15 minutes, and then 50.6 mL of pyridine was added. After stirring at room temperature for 5 minutes, 25.5 g (0.09 mol) of 1-bromo-3-iodinebenzene was added and stirred at 95 ° C overnight. The solvent of the obtained reaction solution was distilled off under reduced pressure, and the obtained residue was purified by silica gel column chromatography to obtain 18.0 g (48.0 mmol, yield 53%) of intermediate B.

Under nitrogen atmosphere, 3.11 g (0.0216 mol) of m-carborane and 82.4 mL of DME were added to cool the DME solution to 0 ° C. 27.5 mL of 1.65 M n-butyl lithium hexane solution was added dropwise and stirred at room temperature for 1 hour. 4.28 g (0.0432 mol) of copper (I) chloride was added and stirred at room temperature for 15 minutes, and then 12.1 mL of pyridine was added. After stirring at room temperature for 5 minutes, 17.0 g (0.453 mol) of Intermediate B was added and stirred at 95 ° C for one week. The solvent of the obtained reaction solution was distilled off under reduced pressure, and the obtained residue was purified by silica gel column chromatography and recrystallization to obtain 1.8 g of compound 1 (2.45 mmol, yield 11%).

FD-MS, m / z 735 [M] +, and 1H-NMR measurement results (measurement solvent: CDCI3) are shown in FIG. 2.

Example 2

Compound 36 was synthesized according to the following scheme.

Under nitrogen atmosphere, 35.0 g (0.243 mol) of m-carborane and 350 mL of DME were added, and the resulting DME solution was cooled to 0 ° C. 96.8 mL of 2.69 M n-butyllithium hexane solution was added dropwise and stirred for 30 minutes under ice cooling. After adding pyridine 67 mL and stirring at room temperature for 10 minutes, 75.6 g (0.763 mol) of copper (I) chloride was added and stirred at 65 ° C for 30 minutes. Thereafter, 76.4 g (0.260 mol) of 2-iododibenzofuran was added and stirred at 95 ° C overnight. After cooling the reaction solution to room temperature, the precipitated crystals were filtered out and the solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain 25.0 g (3.22 mmol, yield 33%) of Intermediate C.

Under nitrogen atmosphere, the DME solution obtained by adding 200 mL of m-carborane 20.0 g (0.240 mol) and DME was cooled to 0 ° C. 113 mL of 2.69 M n-butyllithium hexane solution was added dropwise and stirred for 30 minutes under ice cooling. After adding pyridine 76.9 g (0.96 mol) and stirring at room temperature for 10 minutes, copper chloride (I) was added 87.8 g (0.880 mol) and stirred at 65 ° C for 30 minutes. Then, 98.9 g (0.300 mol) of p-diiodobenzene was added and stirred overnight at 95 ° C. After cooling the reaction solution to room temperature, the precipitated crystals were filtered out and the solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain 18.6 g (33.9 mmol, yield 24%) of Intermediate C.

Under nitrogen atmosphere, DME solution obtained by adding 5.0 g (16.1 mmol) of intermediate C and 36.0 mL of DME was cooled to 0 ° C. 2.69 M of n-butyl lithium hexane solution was added dropwise and stirred for 30 minutes under ice cooling. After adding pyridine 4.4mL and stirring at room temperature for 10 minutes, 4.9g (49.5mmol) of copper (I) chloride was added and stirred at 65 ° C for 30 minutes. Thereafter, 3.5 g (6.38 mmol) of Intermediate D was added and stirred at 95 ° C for 2 days. After cooling the reaction solution to room temperature, the precipitated crystals were filtered out and the solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain 0.63 g of compound 36 (0.69 mmol, yield 11%). APCI-TOFMS, m / z 913 [M] +, 1H-NMR measurement results (measurement solvent: CDCI3) are shown in FIG. 3.

Compounds H-1 to H-3 for comparison with compounds 4, 6, 11, 17, 23 and 27 were synthesized according to the above synthesis method. The chemical formulas of the compounds H-1 to H-3 are shown below.

An organic EL device was produced using compounds 1, 4, 6, 11, 17, 23, 27, 36 and compounds H-1, H-2, H-3.

Example 3

Each thin film was laminated with a vacuum degree of 2.0 × 10 ⁻⁵ Pa on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 70 nm was formed. First, copper phthalocyanine (CuPC) was formed as a hole injection layer on ITO to a thickness of 30 nm. Next, diphenylnaphthyldiamine (NPD) was formed as a hole transport layer to a thickness of 15 nm. Next, on the hole transport layer, compound 1 as the host material of the light emitting layer and the iridium complex [iridium (III) bis (4,6-difluorophenyl) -pyridinato-N, C2 '] picolig, which is the blue phosphorescent material of the dopant NATO] (FIrpic) was co-deposited from another evaporation source to form a light emitting layer with a thickness of 30 nm. The concentration of FIrpic was 10%. Next, Alq3 was formed to a thickness of 25 nm as an electron transporting layer. Further, lithium fluoride (LiF) was formed as an electron injection layer on the electron transport layer to a thickness of 1.0 nm. Finally, aluminum (Al) was formed as an electrode on the electron injection layer to a thickness of 70 nm. The obtained organic EL device has a layer configuration in which an electron injection layer is added between the cathode and the electron transport layer in the organic EL device shown in FIG. 1.

As a result of applying a DC voltage by connecting an external power supply to the obtained organic EL device, it was confirmed that it has light-emitting characteristics as shown in Table 1. In Table 1, luminance, voltage, and luminous efficiency indicate values (initial characteristics) at 2.5 ㎃ / cm 2. In addition, it was found that the maximum wavelength of the device emission spectrum was 475 nm, and light emission from FIrpic was obtained.

Examples 4-9

An organic EL device was prepared in the same manner as in Example 2 except that Compound 4, 6, 11, 23, 27 or 36 was used instead of Compound 1 as the host material for the light emitting layer in Example 3.

Comparative Example 1

An organic EL device was prepared in the same manner as in Example 3 except that mCP was used as the host material for the light emitting layer in Example 3.

Comparative Examples 2-4

An organic EL device was prepared in the same manner as in Example 3 except that Compound H-1, H-2 or H-3 was used as the host material for the light emitting layer in Example 3.

The organic EL devices obtained in Examples 4 to 9 and Comparative Examples 1 to 4 were evaluated in the same manner as in Example 3, and as a result, it was confirmed that they had the luminescence properties shown in Table 1. Further, the maximum wavelength of the emission spectrum of the organic EL device obtained in Examples 4 to 9 and Comparative Examples 1 to 4 was 475 nm, and it was confirmed that light emission from FIrpic was obtained.

In Table 1, the luminous efficiency of Examples 3 to 9 in which the carborane compound of the present invention was used for the light emitting layer shows better properties than Comparative Examples 1 to 4.

Example 10

Each thin film was laminated with a vacuum degree of 2.0 × 10 ⁻⁵ Pa on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 70 nm was formed. First, copper phthalocyanine (CuPC) was formed as a hole injection layer on ITO to a thickness of 30 nm. Next, diphenylnaphthyldiamine (NPD) was formed as a hole transport layer to a thickness of 15 nm. Next, on the hole transport layer, compound 1 and Ir (ppy) ₃ as a dopant as host materials for the light emitting layer were co-deposited from other deposition sources to form a light emitting layer with a thickness of 30 nm. The concentration of Ir (ppy) ₃ was 10%. Next, Alq3 was formed to a thickness of 25 nm as an electron transport layer. Further, lithium fluoride (LiF) was formed as an electron injection layer on the electron transport layer to a thickness of 1 nm. Finally, aluminum (Al) was formed as an electrode on the electron injection layer to a thickness of 70 nm to produce an organic EL device.

As a result of applying a DC voltage by connecting an external power supply to the obtained organic EL device, it was confirmed that it has light-emitting characteristics as shown in Table 2. In Table 2, luminance, voltage, and luminous efficiency indicate values (initial characteristics) when driven at 20 mA / cm 2. The maximum wavelength of the device emission spectrum was 530 nm, and it was found that light emission from Ir (ppy) ₃ was obtained.

Examples 11-17

An organic EL device was prepared in the same manner as in Example 10 except that Compound 4, 6, 11, 17, 23, 27 or 36 was used in place of Compound 1 as the host material for the light emitting layer in Example 10.

Comparative Example 5

An organic EL device was prepared in the same manner as in Example 10 except that CBP was used as the host material for the light emitting layer in Example 10.

Comparative Examples 6-8

An organic EL device was prepared in the same manner as in Example 10 except that Compound H-1, H-2 or H-3 was used as the host material for the light emitting layer in Example 10.

The organic EL devices obtained in Examples 11 to 17 and Comparative Examples 5 to 8 were evaluated in the same manner as in Example 10, and as a result, it was confirmed that they had the luminescence properties shown in Table 2. Further, the maximum wavelength of the emission spectrum of the organic EL devices obtained in Examples 11 to 17 and Comparative Examples 5 to 8 was 530 nm, and it was identified that light emission from Ir (ppy) ₃ was obtained.

In Table 2, Examples 10 to 17 using the carborane compound of the present invention in the light emitting layer were found to exhibit better luminous efficiency than Comparative Examples 5 to 8.

Example 18

Each thin film was laminated with a vacuum degree of 2.0 × 10 ⁻⁵ Pa on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 70 nm was formed. First, copper phthalocyanine (CuPC) was formed as a hole injection layer on ITO to a thickness of 30 nm. Next, diphenylnaphthyldiamine (NPD) was formed as a hole transport layer to a thickness of 15 nm. Next, a CBP and Ir (ppy) ₃ as a dopant were co-evaporated on the hole transport layer as a host material in another evaporation source to form a light emitting layer with a thickness of 30 nm. The concentration of Ir (ppy) ₃ was 10%. Next, compound 1 was formed to a thickness of 5 nm as a hole blocking layer on the light emitting layer. Next, Alq3 was formed as an electron transport layer to a thickness of 20 nm. Further, lithium fluoride (LiF) was formed as an electron injection layer on the electron transport layer to a thickness of 1.0 nm. Finally, aluminum (Al) was formed as an electrode on the electron injection layer to a thickness of 70 nm. The obtained organic EL device has a layer configuration in which an electron injection layer between the cathode and the electron transport layer and a hole blocking layer are added between the light emitting layer and the electron transport layer in the organic EL device shown in FIG. 1.

As a result of applying a DC voltage by connecting an external power supply to the obtained organic EL device, it was confirmed that it has light-emitting characteristics as shown in Table 3. In Table 3, luminance, voltage, and luminous efficiency indicate values (initial characteristics) when driven at 20 mA / cm 2. The maximum wavelength of the device emission spectrum was 530 nm, and it was found that light emission from Ir (ppy) ₃ was obtained.

Examples 19-25

An organic EL device was prepared in the same manner as in Example 18 except that Compound 4, 6, 11, 17, 23, 27 or 36 was used instead of Compound 1 as the hole blocking material in Example 18.

Comparative Example 9

An organic EL device was prepared in the same manner as in Example 18, except that the film thickness of Alq3 as the electron transporting layer in Example 18 was 25 nm and no hole blocking layer was provided.

Comparative Examples 10-12

An organic EL device was prepared in the same manner as in Example 18 except that Compound H-1, H-2, or H-3 was used as the hole blocking material in Example 18.

The organic EL devices obtained in Examples 19 to 25 and Comparative Examples 9 to 12 were evaluated in the same manner as in Example 18, and as a result, it was confirmed that they had the luminescence properties shown in Table 3. In addition, the maximum wavelength of the emission spectrum of the organic EL devices obtained in Examples 19 to 25 and Comparative Examples 9 to 12 was 530 nm, and it was confirmed that light emission from Ir (ppy) ₃ was obtained. The light-emitting layer host materials used in Examples 19-25 and Comparative Examples 9-12 are all CBP.

In Table 3, the improvement in initial properties was observed in all systems compared to those in Comparative Example 9 (when no hole blocking material was used). Especially, when the carborane compound of this invention is used for a hole blocking layer, it shows favorable characteristics compared with the other cases (Comparative Examples 10-12).

The organic EL device according to the present invention has a practically satisfactory level in light emission characteristics, driving life and durability, and features as a flat panel display (mobile phone display device, vehicle display device, OA computer display device or television, etc.), surface light emitter Its technical value is great in applications such as light sources utilizing illumination (lighting, copier light sources, liquid crystal displays or instrument backlight lights), signs and signs.

Claims (9)

A material for an organic electroluminescent device comprising a carborane compound represented by the following general formula (1).

Here, ring A independently represents a tetravalent carborane group of C ₂ B ₁₀ H ₈ represented by either of formula (1a) or formula (1b). L ¹ is independently a direct 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 an aromatic selected from the aromatic hydrocarbon group and the aromatic heterocyclic group It represents the linked aromatic group which consists of 2-6 aromatic rings of a group connected. However, not all of L ¹ are direct bonds. L 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 an aromatic selected from the aromatic hydrocarbon group and the aromatic heterocyclic group The aromatic ring of the group represents 2 to 6 linked aromatic groups, and L ³ is independently hydrogen, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, substituted or unsubstituted A substituted aromatic group consisting of 2 to 6 aromatic rings of a substituted aromatic heterocyclic group having 3 to 30 carbon atoms, or an aromatic group selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. When L ¹ , L ² and L ³ are a linked aromatic group, the aromatic rings to be connected may be the same or different. p and q represent the integer of 1-5 independently. According to claim 1,
A material for an organic electroluminescent device which is a carborane compound represented by the following general formula (2).

Here, L ¹ , L ² , L ³ , p and q have the same meaning as in the general formula (1). Ring A represents a tetravalent carbolan group of C ₂ B ₁₀ H ₈ represented by either Formula (2a) or Formula (2b), and multiple rings A in the molecule may be the same or different. According to claim 1,
A material for an organic electroluminescent device which is a carborane compound represented by the following general formula (3) or (4).

Here, L ¹ , L ² , L ³ , p and q have the same meaning as in the general formula (1). According to claim 3,
In the formulas (3) and (4), L ¹ is each independently 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. A material for an organic light emitting device which is a linked aromatic group consisting of 2 to 5 aromatic rings of an aromatic group selected from the group and the aromatic heterocyclic group. According to claim 3,
In the formulas (3) and (4), L ² is each independently 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. A material for an organic light emitting device which is a linked aromatic group consisting of 2 to 5 aromatic rings of an aromatic group selected from the group and the aromatic heterocyclic group. An organic electroluminescent device comprising an organic layer comprising the material for an organic electroluminescent device according to any one of claims 1 to 5 in an organic electroluminescent device comprising an anode, an organic layer and a cathode laminated on a substrate. The method of claim 6,
An organic electroluminescent device wherein the organic layer including the material for the organic electroluminescent device 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 method of claim 7,
The organic electroluminescent device, characterized in that the organic layer containing the material for the organic electroluminescent device is a light emitting layer containing a phosphorescent dopant. The method of claim 8,
An organic electroluminescent device having a phosphorescence emission dopant emission wavelength with a maximum emission wavelength of 550 nm or less.

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