JP2011198900A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element (organic EL element) that improves the efficiency of light emission of the element, ensures sufficient drive stability and has a simple configuration.SOLUTION: The organic EL element has an organic layer including a light emitting layer between an anode and a cathode which are laminated on a substrate, wherein the light emitting layer contains a polycyclic condensed compound in which a phosphorescent dopant and seven or more rings are condensed, as a host material. The polycyclic condensed compound is a compound formed by coupling three or more condensed rings having a structure in which two or more indole rings are condensed to a carbazole ring by an aromatic ring. An example thereof is a compound expressed by the formula.

Description

  The present invention relates to an organic electroluminescent element containing a polycyclic fused ring compound, and more particularly to a thin film device that emits light by applying an electric field to a light emitting layer made of an 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 luminous efficiency, the type of electrode was optimized for the purpose of improving the efficiency of carrier injection from the electrode. From the hole transport layer made of aromatic diamine and 8-hydroxyquinoline aluminum complex (hereinafter referred to as Alq3) As a result of the development of a device with a light emitting layer as a thin film between the electrodes, the luminous efficiency has been greatly improved 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 with these characteristics.

  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 above aromatic diamine and the light emitting layer composed of Alq3, used fluorescence emission, but use phosphorescence emission, that is, triplet. By using the light emission from the excited state, the efficiency is expected to be improved by about 3 to 4 times as compared with the conventional device using fluorescence (singlet). For this purpose, it has been studied to use a coumarin derivative or a benzophenone derivative as a light emitting layer, but only an extremely low luminance was obtained. Further, as an attempt to use the triplet state, use of a europium complex has been studied, but this has not led to highly efficient light emission. In recent years, as described in Patent Document 1, many studies have been conducted focusing on organometallic complexes such as iridium complexes for the purpose of increasing the efficiency of light emission and extending the lifetime.

Special Table 2003-515897 JP 2001-313178 A WO2007-063754 Publication JP 2006-193729 A WO2009-148015 Publication

  In order to obtain high luminous efficiency, the host material to be used is important simultaneously with the dopant material. A representative example of a host material proposed is 4,4′-bis (9-carbazolyl) biphenyl (hereinafter referred to as CBP), which is a carbazole compound 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 (hereinafter referred to as Ir (ppy) 3), CBP is easy to flow holes and not easily flow electrons. The charge injection 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.

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

Patent Document 3 discloses the following compounds as host materials. However, there is no disclosure of an acene-type indolocarbazole compound in which a plurality of indole rings are condensed like acene.

Patent Document 4 discloses an acene-type indolocarbazole compound as shown below. However, it only discloses its use as a thin film transistor.

Patent Document 5 discloses the following compounds. However, it only discloses an acene-type compound in which chalcogen-containing 5-membered rings and aromatic hydrocarbon 6-membered rings are condensed alternately.

  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 an acene-based compound in which a five-membered ring and a six-membered ring are alternately condensed exhibits excellent characteristics as an organic EL device, and the present invention has been completed. It was.

  The present invention relates to an organic electroluminescent device in which an anode, an organic layer including a phosphorescent light emitting layer and a cathode are laminated on a substrate, the light emitting layer, the hole transport layer, the electron transport layer, the hole blocking layer, and the electron blocking layer An organic electroluminescent device comprising a compound represented by the general formula (1) in at least one organic layer selected from the group consisting of:

一般式（１）中、Ｚ₁はそれぞれ独立して式（１ａ）で表わされるアセン型インドロカルバゾール化合物の窒素に置換する１個のＡが単結合である１価の基を表し、Ｚ₂はそれぞれ独立して式（１ａ）で表わされるアセン型インドロカルバゾール化合物の窒素に置換する２個のＡが単結合である２価の基を表し、Ｌ₁、Ｌ₂はそれぞれ独立して炭素数６〜５０の芳香族炭化水素基又は７環以上の縮合複素環を含まない炭素数３〜５０の芳香族複素環基を表し、ｍは１〜４の整数を表す。ｍが２以上の場合、Ｚ₂及びＬ₂はそれぞれ同一でも異なっていても良い。

In the general formula (1), Z ₁ represents a monovalent group one A substituting the nitrogen independently acene type indolocarbazole compound represented by the formula (1a) is a single bond, Z ₂ Each independently represents a divalent group in which two A's substituted with nitrogen in the acene-type indolocarbazole compound represented by the formula (1a) are single bonds, and L ₁ and L ₂ are each independently carbon. A C3-C50 aromatic heterocyclic group which does not contain a C6-C50 aromatic hydrocarbon group or 7 or more condensed heterocyclic rings is represented, and m represents an integer of 1-4. When m is 2 or more, Z ₂ and L ₂ may be the same or different.

式（１ａ）中、環Ａは隣接環と縮合する式（１ｂ）で表される炭化水素環を表し、環Ｂは隣接環と縮合する式（１ｃ）で表される複素環を表し、ｎは２〜４の整数を表す。式（１ａ）及び（１ｂ）中、Ｒはそれぞれ独立して水素、炭素数１〜１０のアルキル基、炭素数３〜１１のシクロアルキル基、炭素数６〜１８の芳香族炭化水素基又は炭素数３〜１８の芳香族複素環基を表す。式（１ａ）及び（１ｃ）中、Ａはそれぞれ独立して単結合、炭素数１〜１０のアルキル基、炭素数３〜１１のシクロアルキル基、炭素数６〜５０の芳香族炭化水素基又は７環以上の縮合複素環を含まない炭素数３〜５０の芳香族複素環基を表すが、１個又は２個は単結合である。

In formula (1a), ring A represents a hydrocarbon ring represented by formula (1b) fused with an adjacent ring, ring B represents a heterocycle represented by formula (1c) fused with an adjacent ring, and n Represents an integer of 2-4. In formulas (1a) and (1b), each R is independently hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or carbon. Represents an aromatic heterocyclic group of formula 3-18. In formulas (1a) and (1c), each A independently represents a single bond, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, an aromatic hydrocarbon group having 6 to 50 carbon atoms, or An aromatic heterocyclic group having 3 to 50 carbon atoms that does not contain 7 or more condensed heterocyclic rings is represented, but one or two are single bonds.

  Here, in the general formula (1), m is preferably 1 or 2, or n in the formula (1a) is preferably 2.

In the general formula (1), Z ₁ is preferably a monovalent group represented by any of the following formulas (2) to (5).

  In the formulas (2) to (5), R is the same as the formulas (1a), (1b) and (1c). A is an aromatic group having 3 to 50 carbon atoms not containing an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, an aromatic hydrocarbon group having 6 to 50 carbon atoms, or a condensed heterocyclic ring having 7 or more rings. Represents a heterocyclic group.

式（６）〜（８）中、Ａ及びＲは式（２）〜（５）と同意である。 In the general formula (1), Z ₂ is preferably a divalent group represented by any of the following formulas (6) to (8).

In formulas (6) to (8), A and R are the same as formulas (2) to (5).

  Moreover, this invention is said organic electroluminescent element characterized by the organic layer containing the compound represented by General formula (1) being a light emitting layer containing a phosphorescence dopant. In the organic electroluminescent element of the present invention, the organic layer containing the compound is preferably a light emitting layer containing a phosphorescent dopant.

  The compound represented by the general formula (1) used in the organic electroluminescence device of the present invention has three or more skeletons in which three or more indole rings and a benzene ring are condensed in a straight chain via a specific linking group. Take the connected form. By using this compound in an organic EL device, it is considered that it exhibits excellent hole and electron injection and transport properties and has high durability. The organic EL device using this has a low driving voltage. In particular, when this compound is contained in the light emitting layer, the recombination probability is improved because the balance of both charges is improved, and a high lowest excited triplet state is obtained. Therefore, it is considered that excellent light emission characteristics can be obtained because it has a feature that the transfer of triplet excitation energy from the dopant to the host molecule can be effectively suppressed. In addition, since it exhibits good amorphous characteristics and high thermal stability and is electrochemically stable, it is considered that an organic EL element having a long driving life and high durability can be realized.

  The organic EL device of the present invention has practically satisfactory levels of light emission characteristics, drive life and durability, and is a flat panel display (mobile phone display device, in-vehicle display device, OA computer display device, television, etc.), surface light emission. Its technical value is great in applications to light sources (lighting, light sources for copying machines, backlight light sources for liquid crystal displays and instruments), display boards, and sign lamps that make use of the characteristics of the body.

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

The organic electroluminescent element of this invention contains the compound represented by the said General formula (1). The compound represented by the general formula (1) has a structure in which Z ₁ and Z ₂ are linked by linking groups L ₁ and L ₂ . Z ₁ and Z ₂ have a skeleton obtained by further condensing 1 to 3 indole rings to the indolocarbazole ring represented by the formula (1a). And it is thought that the above excellent effects are brought about by having a structure in which three or more skeletons are bonded in a chain form on nitrogen via a linking group.

In the general formula (1), Z ₁ and Z ₂ are represented by the formula (1a), but Z ₁ is a monovalent group and Z ₂ is a divalent group. Therefore, one or two of A present in the formula (1a) is a single bond, and when there is one single bond, it becomes Z ₁ , and when there are _two, it becomes Z ₂ .

  In Formula (1a), Ring A represents a hydrocarbon ring represented by Formula (1b) that is condensed with an adjacent ring, and Ring B represents a heterocyclic ring represented by Formula (1c) that is condensed with an adjacent ring. The hydrocarbon ring represented by the formula (1b) can be condensed with an adjacent ring at an arbitrary position, but the position where structural condensation is possible is limited. That is, this hydrocarbon ring has six sides, but adjacent sides are not fused with two adjacent rings, respectively. In addition, the heterocyclic ring represented by the formula (1c) can be condensed with an adjacent ring at an arbitrary position, but in this case as well, the positions where structural condensation is possible are limited. This heterocyclic ring has five sides, but the adjacent sides are not condensed with two adjacent rings, respectively, and the side containing N is not condensed with the adjacent ring. Therefore, the number of skeletons of the compound represented by the formula (1a) is limited.

  In the formula (1a), n represents an integer of 2 to 4. Preferably n is an integer of 2 or 3, more preferably n is 2. In this case, the n rings A and B may be the same or different. Further, the positions at which rings A and B are condensed may be the same or different.

  In formulas (1a) and (1b), each R is independently hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or carbon. Represents an aromatic heterocyclic group of formula 3-18. Preferably, hydrogen, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aromatic hydrocarbon group having 6 to 12 carbon atoms, or an aromatic heterocyclic group having 3 to 12 carbon atoms, More preferred is hydrogen.

  In formulas (1a) and (1c), A is each independently a single bond, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, or an aromatic hydrocarbon having 6 to 50 carbon atoms. Represents an aromatic heterocyclic group having 3 to 50 carbon atoms which does not include a group or a condensed heterocyclic ring having 7 or more rings. As described above, the number of single bonds is 1 or 2, and the rest are groups other than single bonds. The group other than a single bond is preferably an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aromatic hydrocarbon group having 6 to 24 carbon atoms, or a condensed heterocyclic ring having 7 or more rings. It is a C3-C24 aromatic heterocyclic group which does not contain.

  Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group, preferably a methyl group, an ethyl group, and a propyl group. Group, butyl group, pentyl group, hexyl group, heptyl group and octyl group. The alkyl group may be linear or branched.

  Specific examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a methylcyclohexyl group, preferably a cyclohexyl group and a methylcyclohexyl group.

  Specific examples of the aromatic hydrocarbon group or the aromatic heterocyclic group not containing 7 or more condensed heterocyclic rings include benzene, pentalene, indene, naphthalene, azulene, heptalene, octalene, indacene, acenaphthylene, phenalene, phenanthrene, anthracene , Triindene, fluoranthene, acephenanthrylene, acanthrylene, triphenylene, pyrene, chrysene, tetraphen, tetracene, preaden, picene, perylene, pentaphen, pentacene, tetraphenylene, colanthrylene, helicene, hexaphen, rubicene, coronene, trinaphthylene , Heptaphene, pyranthrene, obalene, coranulene, fluorene, anthanthrene, zetrene, terylene, naphthacenonaphthacene, truxene, furan, benzofuran, i Benzofuran, xanthene, oxatolene, dibenzofuran, perixanthenoxanthene, thiophene, thioxanthene, thianthrene, phenoxathiin, thionaphthene, isothianaphthene, thiophanten, thiophanthrene, dibenzothiophene, pyrrole, pyrazole, tellurazole, selenazole, thiazole, iso Thiazole, oxazole, furazane, pyridine, pyrazine, pyrimidine, pyridazine, triazine, indolizine, indole, isoindole, indazole, purine, quinolidine, isoquinoline, carbazole, indolocarbazole, imidazole, naphthyridine, phthalazine, quinazoline, benzodiazepine, quinoxaline, Cinnoline, quinoline, pteridine, phenanthridine, acridine, perimidi , Phenanthroline, phenazine, carboline, phenotelrazine, phenoselenazine, phenothiazine, phenoxazine, anti-lysine, thebenidine, quindrine, quinindrine, aclindrine, phthaloperine, triphenodithiazine, triphenodioxazine, benzothiazole, benzimidazole, benzoxazole, benzo Examples include isoxazole, benzoisothiazole, and groups generated by removing hydrogen from an aromatic compound in which a plurality of these aromatic rings are connected. Preferably benzene, naphthalene, anthracene, pyridine, pyrazine, pyrimidine, pyridazine, triazine, isoindole, indazole, purine, isoquinoline, imidazole, naphthyridine, phthalazine, quinazoline, benzodiazepine, quinoxaline, cinnoline, quinoline, pteridine, phenanthridine, acridine , Perimidine, phenanthroline, phenazine, carboline, indole, carbazole, indolocarbazole, or a group formed by removing hydrogen from an aromatic compound in which a plurality of these aromatic rings are linked. In addition, when the aromatic ring is a group generated from a linked aromatic compound, the number to be linked is preferably 2 to 10, more preferably 2 to 7, and the linked aromatic rings may be the same. It may be different. In that case, the bonding position of A bonded to the nitrogen of the ring represented by the formula (1a) is not limited, and it may be a ring at the end of the linked aromatic ring or a ring at the center. Here, the aromatic ring is a generic term for an aromatic hydrocarbon ring and an aromatic heterocyclic ring. When the linked aromatic ring contains at least one heterocyclic ring, it is included in the aromatic heterocyclic group.

（式（１１）〜（１３）中、Ａｒ₁〜Ａｒ₆は、置換又は無置換の芳香環を示す） Here, the monovalent group generated by connecting a plurality of aromatic rings is represented by the following formula, for example.

(In formulas (11) to (13), Ar _{1 to} Ar ₆ represent a substituted or unsubstituted aromatic ring)

  Specific examples of the group formed by linking a plurality of the aromatic rings include, for example, biphenyl, terphenyl, bipyridine, bipyrimidine, vitriazine, terpyridine, bistriazylbenzene, dicarbazolylbenzene, carbazolylbiphenyl, dicarbazolylbiphenyl. , Phenylterphenyl, carbazolylterphenyl, binaphthalene, phenylpyridine, phenylcarbazole, diphenylcarbazole, diphenylpyridine, phenylpyrimidine, diphenylpyrimidine, phenyltriazine, diphenyltriazine, phenylnaphthalene, diphenylnaphthalene, indolocarbazolylbenzene, India And monovalent groups generated by removing hydrogen from locarbazolylpyridine, indolocarbazolyltriazine, and the like.

  The aromatic ring may have a substituent. When the aromatic ring has a substituent, examples of the substituent include an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and 1 to 2 carbon atoms. An alkoxy group, an acetyl group, or a diarylamino group having 6 to 24 carbon atoms. An alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or a diarylamino group having 6 to 24 carbon atoms is preferable. When having a plurality of substituents, they may be the same or different. In addition, when the said aromatic ring has a substituent, the calculation of the carbon number includes the carbon number of a substituent.

In the general formula (1), L ₁ and L ₂ are each independently an aromatic hydrocarbon group having 3 to 50 carbon atoms which does not include a divalent aromatic hydrocarbon group having 6 to 50 carbon atoms or a condensed heterocyclic ring having 7 or more rings. It is a heterocyclic group. Preferably it is a C6-C24 aromatic hydrocarbon group or a C3-C24 aromatic heterocyclic group which does not contain a 7 or more condensed heterocyclic ring. Specific examples of the aromatic heterocyclic group not containing an aromatic hydrocarbon group or a condensed heterocyclic ring having 7 or more rings are as follows. A is an aromatic hydrocarbon group or a condensed heterocyclic having 7 or more rings except that they are divalent. This is the same as in the case of an aromatic heterocyclic group containing no ring.

  In General formula (1), m is an integer of 1-4. Preferably it is an integer of 1-3, More preferably, m is 1 or 2.

In the general formula (1), when m is 2 or more, the number of n in the formula (1a) represented by Z ₂ and the positions where the rings A and B are condensed may be the same or different.

  In General formula (1), n is an integer of 2-4. Preferably it is 2 or 3, more preferably 2.

In the general formula (1), among Z ₁ , compounds represented by the above general formulas (2) to (5) are preferable compounds.

In the general formula (1), among Z ₂ , compounds represented by the above general formulas (6) to (8) are preferable compounds.

  In the general formulas (2) to (8), R is the same as the formula (1a). Since A to be a single bond is represented as a single bond in the formula, A in the general formulas (2) to (8) is a case where it is a single bond from A defined in the formula (1a). Meaning.

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

  For example, diindolo [2,3-a: 3 ′, 2′-i] carbazole skeleton (A), diindolo [2,3-a: 2 ′, 3′-h] carbazole skeleton (B), diindolo [3, 2-b: 2 ′, 3′-h] carbazole skeleton (C) is a compound of The Journal of Organic Chemistry, 2004, Vol. 69 (17), 5705 and ORGANIC LETTERS, 2004, Vol. 6, No. 19, 3413. Can be synthesized according to the following reaction formula with reference to the synthesis example shown in FIG.

Diindolo [2,3-a: 3 ', 2'-i] carbazole skeleton (A)
Diindolo [2,3-a: 2 ', 3'-h] carbazole skeleton (B)

  The diindolo [2,3-a: 3 ′, 2′-i] carbazole skeleton (A) and the diindolo [2,3-a: 2 ′, 3′-h] carbazole skeleton (B) were synthesized by the same scheme described above. , Extraction, column separation, crystallization, and the like, can be isolated by known separation techniques.

ジインドロ[3,2-b:2',3'-h]カルバゾール骨格（Ｃ）は、原料のニトロフェニルカルバゾール化合物をブロモ化し、ニトロ基を還元して縮合させる閉環位置を限定することで合成可能である。 Diindolo [3,2-b: 2 ', 3'-h] carbazole skeleton (C)

Diindolo [3,2-b: 2 ', 3'-h] carbazole skeleton (C) can be synthesized by brominating the starting nitrophenylcarbazole compound and reducing the nitro group to limit the ring closure position It is.

  A compound represented by the general formula (1) can be synthesized by substituting hydrogen on nitrogen of each skeleton obtained by the above reaction formula with a corresponding aromatic group according to a conventional method. For example, the compound represented by the following exemplary compound (17) can be synthesized by the following reaction formula.

  Although the specific example of a compound represented by General formula (1) is shown below, the material used for the organic electroluminescent element of this invention is not limited to these. The number given to the chemical formula is the compound number.

  The compound represented by the general formula (1) is excellent in an organic electroluminescence device by being contained in at least one organic layer of an organic EL device in which an anode, a plurality of organic layers and a cathode are laminated on a substrate. give. The organic layer to be contained is a light emitting layer, a hole transport layer, an electron transport layer, a hole blocking layer or an electron blocking layer. More preferably, it may be contained as a host material of a light emitting layer containing a phosphorescent dopant.

  Next, the organic EL 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 laminated on a substrate, and a light emitting layer, an electron transport layer, a hole blocking layer, or an electron blocking layer At least one organic layer selected from includes a compound represented by the general formula (1). The compound represented by the general formula (1) is preferably included in the light emitting layer together with the phosphorescent dopant.

  The indolocarbazole compound used in the present invention has good charge transport properties and can be used in any of the above organic layers.

  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 phosphorescent light emitting layer and includes a phosphorescent 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. Such organometallic complexes are known in the prior art documents and the like, and these can be selected and used.

  Preferable phosphorescent dopants include complexes such as Ir (ppy) 3 having a noble metal element such as Ir as a central metal, complexes such as Ir (bt) 2 · acac3, and complexes such as PtOEt3. Specific examples of these complexes are shown below, but are not limited to the following compounds.

  The amount of the phosphorescent dopant contained in the light emitting layer is preferably in the range of 1 to 50% by weight. More preferably, it is 5 to 30% by weight.

  As the host material in the light emitting layer, it is preferable to use the compound represented by the general formula (1). However, when the compound is used in any organic layer other than the light emitting layer, the host material other than the compound may be used for the light emitting layer. Moreover, you may use this compound and another host material together. 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, 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, porphyrin compounds, anthraquino Heterocyclic tetracarboxylic acid anhydrides such as dimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, Various metal complexes represented by metal complexes of Russianin derivatives, 8-quinolinol derivatives, metal phthalocyanines, metal complexes of benzoxazole and benzothiazole derivatives, polysilane compounds, poly (N-vinylcarbazole) derivatives, aniline copolymers, Examples thereof include polymer compounds such as thiophene oligomers, polythiophene derivatives, polyphenylene derivatives, polyphenylene vinylene derivatives, polyfluorene derivatives, and the like.

-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 it is preferable to use the compound represented by the general formula (1) for the hole blocking layer, when the compound is used for any other organic layer, a known hole blocking layer material may be used. Good. 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.

  Although it is preferable to use the compound represented by the general formula (1) for the electron blocking layer, a known electron blocking layer material may be used when the compound is used in any other organic layer. 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.

  Examples of the material for the exciton blocking layer include 1,3-dicarbazolylbenzene (mCP) and bis (2-methyl-8-quinolinolato) -4-phenylphenolato aluminum (III) (BAlq). It is done.

-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. Although it is preferable to use the compound represented by General formula (1) for a positive hole transport layer, arbitrary things can be selected and used from a conventionally well-known compound. Examples of known hole transport materials that can be used include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, Examples include styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. Porphyrin compounds, aromatic tertiary amine compounds, and styryl. It is preferable to use an amine 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 compound represented by the general formula (1) for the electron transport layer, any one of conventionally known compounds can be selected and used. For example, nitro-substituted fluorene derivatives, diphenylquinone Derivatives, thiopyran dioxide 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. . Compounds 1, 7, 13, 17 and 19 exemplified as the compound represented by the general formula (1) were prepared and used for the production of an organic EL device.

Example 1
In FIG. 1, an organic EL device having a configuration in which the hole transport layer was omitted and an electron injection layer was added was produced. Poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) as a hole injection layer on a glass substrate made of ITO having a thickness of 150 nm that has undergone UV ozone cleaning and drying steps: A 20 wt% ethanol solution of C. Stark Co., Ltd. (trade name: Clevios PCH8000) was spin-coated at a rotational speed of 3000 rpm for 60 seconds and dried at 200 ° C. for 60 minutes. The film thickness at this time was 25 nm. Next, as a light emitting layer, as a host material, compound 1 (38.0 parts by weight), as a phosphorescent dopant material, tris (2-phenylpyridine) iridium (Ir (ppy) 3) (2.0 parts by weight), dichloromethane (2840 parts by weight) ) Was spin-coated at a rotation speed of 4000 rpm for 30 seconds and dried at 120 ° C. for 30 minutes. The film thickness of the light emitting layer at this time was 70 nm. Next, as an electron transport layer, tris (8-hydroxyquinoline) aluminum (Alq3) was formed into a film with a thickness of 35 nm at a deposition rate of 0.1 nm / sec by a vacuum deposition method. Further, as an electron injection layer, lithium fluoride (LiF) was formed to a thickness of 0.5 nm by vacuum deposition. Finally, as an electrode on the electron injection layer, aluminum (Al) was formed to a thickness of 170 nm by vacuum vapor deposition to produce an organic EL device.

As an initial characteristic of the obtained organic EL element, an external power source was connected to the element, a DC voltage was applied so that a current of 100 mA / cm ² flowed, and current efficiency (cd / A) at that time was measured. The results are shown in Table 1. The same measurement was performed on the organic EL elements obtained in the following examples and comparative examples, and the results are shown in Table 1.

Example 2
An organic EL device was produced in the same manner as in Example 3 except that Compound 7 was used as the host material for the light emitting layer.

Example 3
An organic EL device was produced in the same manner as in Example 3 except that Compound 13 was used as the host material for the light emitting layer.

Example 4
An organic EL device was produced in the same manner as in Example 3 except that Compound 17 was used as the host material for the light emitting layer.

Example 5
An organic EL device was produced in the same manner as in Example 3 except that Compound 19 was used as the host material for the light emitting layer.

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

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

Claims (6)

In an organic electroluminescent device in which an anode, an organic layer including a phosphorescent light emitting layer and a cathode are laminated on a substrate, a group consisting of a light emitting layer, a hole transport layer, an electron transport layer, a hole blocking layer and an electron blocking layer An organic electroluminescent device comprising a compound represented by the general formula (1) in at least one selected organic layer.

In the general formula (1), Z ₁ represents a monovalent group one A substituting the nitrogen independently acene type indolocarbazole compound represented by the formula (1a) is a single bond, Z ₂ Each independently represents a divalent group in which two A's substituted with nitrogen in the acene-type indolocarbazole compound represented by the formula (1a) are single bonds, and L ₁ and L ₂ are each independently carbon. A C3-C50 aromatic heterocyclic group which does not contain a C6-C50 aromatic hydrocarbon group or 7 or more condensed heterocyclic rings is represented, and m represents an integer of 1-4. When m is 2 or more, Z ₂ and L ₂ may be the same or different.

In formula (1a), ring A represents a hydrocarbon ring represented by formula (1b) fused with an adjacent ring, ring B represents a heterocycle represented by formula (1c) fused with an adjacent ring, and n Represents an integer of 2-4. In formulas (1a) and (1b), each R is independently hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms, or carbon. Represents an aromatic heterocyclic group of formula 3-18. In formulas (1a) and (1c), each A independently represents a single bond, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, an aromatic hydrocarbon group having 6 to 50 carbon atoms, or An aromatic heterocyclic group having 3 to 50 carbon atoms that does not contain 7 or more condensed heterocyclic rings is represented, but one or two are single bonds.   The organic electroluminescent element according to claim 1, wherein m is 1 or 2 in the general formula (1).   The organic electroluminescent element according to claim 1, wherein n in the formula (1a) is 2 in the general formula (1). In the general formula (1), an organic electroluminescence device according to any one of claims 1 to 3, characterized in that Z ₁ is represented by any one of the following formulas (2) to (5).

In the formulas (2) to (5), R is the same as the formulas (1a), (1b) and (1c). A is an aromatic group having 3 to 50 carbon atoms not containing an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, an aromatic hydrocarbon group having 6 to 50 carbon atoms, or a condensed heterocyclic ring having 7 or more rings. Represents a heterocyclic group. In the general formula (1), an organic electroluminescence device according to any one of claims 1 to 4, characterized in that Z ₂ is represented by any one of the following formulas (6) to (8).

In formulas (6) to (8), A and R are the same as formulas (2) to (5).   The organic electroluminescent element according to claim 1, wherein the organic layer containing the compound represented by the general formula (1) is a light emitting layer containing a phosphorescent dopant.

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