JP5577122B2 - Organic electroluminescence device - Google Patents

Description

  The present invention relates to an organic electroluminescent element containing an indolocarbazole 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 JP 2006-193729 A JP 2004-204234 A WO2007-063754 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's holes can flow easily and electrons do not flow easily. Then, the charge balance in the light emitting layer is lost, and excess holes flow out to the electron transporting 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.

In Patent Document 3, the following indolocarbazole compounds are disclosed, but only peripheral substitutes useful as organic semiconductors are disclosed.

In Patent Document 4, although the following indolocarbazole compounds are disclosed, only a copolymer with fluorene is disclosed as a blue light emitting polymer.

Patent Document 5 discloses the following indolocarbazole compounds, but only discloses compounds in which the indolocarbazole skeleton is linked in a branched manner.

  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 indolocarbazole skeleton exhibits excellent characteristics by using a compound in which a chain is bonded on nitrogen via a specific linking group as an organic EL device. The invention has been completed.

  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 an indolocarbazole 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は独立して式（２）で表される１価の基を、Ｚ₂は独立して式（２）で表される２価の基を表し、Ｌ₁、Ｌ₂はそれぞれ独立して２価の炭素数６〜５０の芳香族炭化水素基又は５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、ｎは１〜４の整数を表す。ｎ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 General Formula (1), Z ₁ independently represents a monovalent group represented by Formula (2), Z ₂ independently represents a divalent group represented by Formula (2), and L ₁ , L ₂ each independently represents a divalent aromatic hydrocarbon group having 6 to 50 carbon atoms or an aromatic heterocyclic group having 3 to 50 carbon atoms that does not contain 5 or more condensed heterocyclic rings, and n is 1 Represents an integer of ~ 4. When n is 2 or more, Z ₂ and L ₂ may be the same or different.

式（２）中、環Ａ₁は隣接環と縮合する式（２ａ）で表される芳香族炭化水素環を表し、環Ｂ₁は隣接環と縮合する式（２ｂ）で表される複素環を表す。式（２）、（２ａ）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３〜１７の芳香族複素環基を表す。Ｚ₁が式（２）で表される１価の基である場合、式（２ｂ）中、Ａは炭素数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５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、Ｚ₂が式（２）で表される２価の基である場合、Ａは単結合を表わす。

In formula (2), ring A ₁ represents an aromatic hydrocarbon ring represented by formula (2a) fused with an adjacent ring, and ring B ₁ represents a heterocyclic ring represented by formula (2b) fused with an adjacent ring. Represents. In formulas (2) and (2a), 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 3-17. When Z ₁ is a monovalent group represented by the formula (2), in the formula (2b), A is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, and 6 to 6 carbon atoms. When the aromatic hydrocarbon group having 3 to 50 carbon atoms not containing 50 aromatic hydrocarbon groups or five or more condensed heterocyclic rings, and Z ₂ is a divalent group represented by the formula (2) , A represents a single bond.

Among the indolocarbazole compounds represented by the general formula (1), a compound in which Z ₁ is a monovalent group represented by any _one of the formulas (3) to (6) can be mentioned as a preferred compound.

Among the indolocarbazole compounds represented by the general formula (1), compounds in which Z ₂ is a divalent group represented by any one of the formulas (7) to (9) are preferable compounds.

  In the formulas (3) to (9), R is the same as the formulas (2) and (2a). In the formulas (3) to (6), A is the same as the formula (2b), but since the single bond is represented in the above formula, it is not a single bond.

  In the organic electroluminescent element of the present invention, the organic layer containing the indolocarbazole compound is preferably a light emitting layer containing a phosphorescent dopant.

  In the phosphorescent light emitting device of the present invention, the organic layer containing the indolocarbazole compound is preferably an electron blocking layer.

  The indolocarbazole compound used in the organic electroluminescent device of the present invention is characterized in that a plurality of indolocarbazole skeletons are linearly linked on nitrogen via a specific linking group. The indolocarbazole compound is considered to exhibit good hole and electron injection and transport properties and high durability. The organic EL device using this has a low driving voltage. In particular, when this indolocarbazole compound is contained in the light emitting layer, the recombination probability is improved because the balance of both charges is improved, and high minimum excitation is achieved. Since it has triplet state energy, it has features such as effectively suppressing the transfer of triplet excitation energy from the dopant to the host molecule. It is done. In addition, since it exhibits good amorphous characteristics and high thermal stability and is electrochemically stable, it is considered to realize an organic EL element having a long driving life and high durability.

  The organic EL device according to the present invention has practically satisfactory levels in terms of light emission characteristics, driving life and durability, flat panel display (mobile phone display device, in-vehicle display device, OA computer display device, television, etc.), surface light emission, etc. 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 the present invention contains an indolocarbazole compound represented by the general formula (1). By having a structure in which three or more indolocarbazole skeletons are bonded in a chain form on nitrogen via a specific linking group, it is considered that the excellent effects as described above are brought about.

In the general formula (1), Z ₁ represents a monovalent group represented by the formula (2). In general formula (1), there are two Z _{1 s} , which may be the same or different. In the general formula (1), Z ₂ represents a divalent group represented by the formula (2). Formula (2) may represent a monovalent group or a divalent group, but when it represents a divalent group, A is a single bond, and when it represents a monovalent group, A is A substituent other than a single bond. When A is a substituent other than a single bond, the substituent is 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 5-ring. It is a C3-C50 aromatic heterocyclic group which does not contain the above condensed heterocyclic ring.

In formula (2), ring A ₁ represents an aromatic hydrocarbon ring represented by formula (2a) fused with an adjacent ring, and ring B ₁ represents a heterocyclic ring represented by formula (2b) fused with an adjacent ring. Represents.

  In the indolocarbazole skeleton represented by the formula (2), the aromatic hydrocarbon ring represented by the formula (2a) can be condensed with two adjacent rings at any position, but cannot be structurally condensed. There is. The aromatic hydrocarbon ring represented by the formula (2a) has six sides, but does not condense with two adjacent rings at two adjacent sides. Further, the heterocyclic ring represented by the formula (2b) can be condensed with two adjacent rings at an arbitrary position, but there are positions where it cannot be condensed structurally. That is, the heterocyclic ring represented by the formula (2b) has five sides, but does not condense with two adjacent rings at two adjacent sides, and also condenses with an adjacent ring at a side including a nitrogen atom. Never do. Therefore, the types of indolocarbazole skeleton are limited.

  In the general formula (2), the indolocarbazole skeleton is preferably represented by the following form. From this example, the preferred condensation positions of the aromatic hydrocarbon ring and the heterocyclic ring in the indolocarbazole skeleton are understood.

  In formulas (2) and (2a), 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 3-17. 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 the case where Formula (2) is a monovalent group, each A is independently an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, or an aromatic carbon atom having 6 to 50 carbon atoms. An aromatic heterocyclic group having 3 to 50 carbon atoms that does not contain a hydrogen group or five or more condensed heterocyclic rings. Preferably, the alkyl group having 1 to 8 carbon atoms, the cycloalkyl group having 3 to 7 carbon atoms, the aromatic hydrocarbon group having 6 to 24 carbon atoms, or 3 to 24 carbon atoms not containing 5 or more condensed heterocyclic rings. An aromatic heterocyclic group.

  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 which does not include an aromatic hydrocarbon group or five 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, imidazole, naphthyridine, phthalazine, quinazoline, benzodiazepine, quinoxaline, cinnoline, quinoline, Pteridine, phenanthridine, acridine, perimidine, phenanthroline, Enazine, carboline, phenotelrazine, phenoselenazine, phenothiazine, phenoxazine, antilysine, thebenidine, kindrin, quinindrine, benzothiazole, benzimidazole, benzoxazole, benzisoxazole, benzoisothiazole, or a fragrance in which multiple aromatic rings are connected And monovalent groups generated by removing hydrogen from a group compound or the like. 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, or a monovalent group generated 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 (2) is not limited, and it may be a ring at a terminal portion or a central ring of the linked aromatic rings. 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 the 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. , Monovalent formed by removing hydrogen from phenylterphenyl, carbazolylterphenyl, binaphthalene, phenylpyridine, phenylcarbazole, diphenylcarbazole, diphenylpyridine, phenylpyrimidine, diphenylpyrimidine, phenyltriazine, diphenyltriazine, phenylnaphthalene, diphenylnaphthalene, etc. The group of is mentioned.

  The aromatic hydrocarbon group or the aromatic heterocyclic group not containing a condensed heterocyclic ring having 5 or more rings may have a substituent. When these have a substituent, the substituent has 1 to 4 carbon atoms. An alkyl group, a cycloalkyl group having 3 to 6 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, and an acetyl group. Preferably they are a C1-C4 alkyl group and a C3-C6 cycloalkyl group. However, in this case, the aromatic group branched and linked is not treated as a substituent.

In the general formula (1), L ₁ and L ₂ are each independently a divalent aromatic hydrocarbon group having 6 to 50 carbon atoms or an aromatic group having 3 to 50 carbon atoms that does not contain 5 or more condensed heterocyclic rings. It is a heterocyclic group. Preferably, it is an aromatic hydrocarbon group having 6 to 24 carbon atoms or an aromatic heterocyclic group having 3 to 24 carbon atoms that does not contain a condensed heterocyclic ring having 5 or more rings. Specific examples of the aromatic heterocyclic group not containing an aromatic hydrocarbon group or a condensed heterocyclic ring having 5 or more rings are as follows. A is an aromatic hydrocarbon group or a condensed heterocyclic group having 5 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), n is an integer of 1-4. Preferably it is an integer of 1-3, More preferably, it is 1 or 2. In the general formula (1), when n is 2 or more, Z ₂ and L ₂ may be the same or different.

In the general formula (1), Z ₁ is preferably a monovalent group represented by the above general formulas (3) to (6). Z ₂ is preferably a divalent group represented by the general formulas (7) to (9).

  In the general formulas (1) to (9), the same symbols and formulas are understood to have the same meaning unless otherwise specified.

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

For example, the indolocarbazole skeleton (IC-1) possessed by the groups represented by the general formulas (3) and (7) is shown in Archiv der Pharmazie (Weinheim, Germany), 1987, 320 (3), p280-2. It can be synthesized by the following reaction formula with reference to the synthesis example.

Further, the indolocarbazole skeleton (IC-2) possessed by the groups represented by the general formulas (4) and (8) is synlett, 2005, no. 1, p42-48 can be synthesized according to the following reaction formula with reference to the synthesis example.

  Further, the indolocarbazole skeleton (IC-3) possessed by the groups represented by the general formulas (5), (6) and (9) is The Journal of Organic Chemistry, 2007, 72 (15) 5886, and Tetrahedron, It can be synthesized by the following reaction formula with reference to the synthesis example shown in 1999, 55, p2371.

  By synthesizing the indolocarbazole compound represented by the general formula (1) by substituting the hydrogen on the nitrogen of each indolocarbazole skeleton obtained by the above reaction formula with a corresponding aromatic group according to a conventional method. Can do.

  Specific examples of the indolocarbazole compound represented by the general formula (1) are shown below, but the indolocarbazole compound used in the organic electroluminescence device of the present invention is not limited thereto.

  The organic electroluminescent element of the present invention contains the indolocarbazole compound represented by the general formula (1) in 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 or an electron blocking layer of the light emitting layer containing a 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 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 the at least one organic layer is represented by the general formula (1). Contains indolocarbazole compounds. Advantageously, an indolocarbazole compound is included in the light emitting layer together with a phosphorescent dopant.

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

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

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

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

-Anode-
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when the pattern accuracy is not required (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

-Cathode-
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the light emission luminance is improved, which is convenient.

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

-Light emitting layer-
The light emitting layer is a 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 a host material in the light emitting layer, an indolocarbazole compound represented by the general formula (1) is preferably used. However, when the indolocarbazole compound is used in any organic layer other than the light emitting layer, the material used for the light emitting layer may be a host material other than the indolocarbazole compound. An indolocarbazole compound and another host material may be used in combination. 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.

  It is preferable to use the indolocarbazole compound represented by the general formula (1) for the hole blocking layer. However, when the indolocarbazole compound is used for any other organic layer, a known hole blocking layer is used. Materials may be used. Moreover, as a hole-blocking layer material, the material of the electron carrying layer mentioned later can be used as needed.

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

  As the material for the electron blocking layer, an indolocarbazole compound represented by the general formula (1) is preferably used, but 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. As the known hole transporting material that can be used, an indolocarbazole compound represented by the general formula (1) is preferably used, but any conventionally known compound can be selected and used. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. Porphyrin compounds, aromatic tertiary amine compounds, and styrylamine compounds are preferably used. It is more preferable to use a 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 indolocarbazole 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, a nitro-substituted fluorene derivative , 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. .

Synthesis example 1
Compound 25 was synthesized according to the following formula.

  Under nitrogen atmosphere, IC-3 10.0 g (0.039 mol), 1-bromo-3-iodobenzene 11.1 g (0.039 mol), copper iodide 0.3 g (0.0013 mol), tripotassium phosphate 42.3 g (0.20 mol), While stirring 300 ml of dehydrated 1,4-dioxane, 1.50 g (0.013 mol) of trans-1,2-cyclohexanediamine was added, followed by stirring for 18 hours while heating at 115 ° C. After the reaction solution was cooled to room temperature, the inorganic salt was filtered off. The obtained filtrate was dried with a vacuum dryer after the solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography to obtain 11.5 g of Intermediate A (0.028 mol yield: 72%) as a white solid.

  Under nitrogen atmosphere, IC-1 2.50 g (0.0097 mol), Intermediate A 10.0 g (0.024 mol), Copper 9.6 g (0.15 mol), Potassium carbonate 51.6 g (0.24 mol), 1,3-Dimethyl-2-imidazo 300 g of lizinone was added and stirred at 185 ° C. for 30 hours. After the reaction solution was cooled to room temperature, the inorganic substance was filtered off. The obtained filtrate was added to 2000 ml of water and stirred, and the precipitated crystals were separated by filtration. This was dried under reduced pressure and then purified by column chromatography to obtain 7.6 g (0.0083 mol, yield 86%) of Intermediate B as a white powder.

  Under a nitrogen atmosphere, add Intermediate B 7.0 g (0.0076 mol), Copper iodide 2.9 g (0.015 mol), Potassium carbonate 4.2 g (0.031 mol), Iodobenzene 100 g (0.49 mol), and stir at 185 ° C for 30 hours. did. After the reaction solution was cooled to room temperature, the inorganic substance was filtered off. The obtained filtrate was added to 1000 ml of water and stirred, and the precipitated crystals were separated by filtration. This was dried under reduced pressure and purified by column chromatography to obtain 5.0 g (0.0047 mol, yield 62%) of the desired product (Compound 25) as a white powder.

  Further, according to the synthesis examples and the synthesis methods described in the specification, the exemplified compounds 10, 14, 15, 24, 36, 38 and 40 were synthesized 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, compound 25 (38.0 parts by weight) obtained in the above synthesis example as a host material and tris (2-phenylpyridine) iridium (Ir (ppy) 3) (2.0 weights) as a phosphorescent dopant material Part) and a mixed solution of tetrahydrofuran (2840 parts by weight) were 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 a vacuum deposition method, and an organic EL element was produced.

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. It measured similarly about the organic EL element obtained by the following examples and comparative examples. The results are shown in Table 1.

Example 2
An organic EL device was produced in the same manner as in Example 1 except that Compound 10 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 1 except that Compound 15 was used as the host material for the light emitting layer.

Example 4
An organic EL device was prepared in the same manner as in Example 1 except that Compound 38 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 1 except that Compound 40 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 1 except that the following compound H-1 was used as the host material for the light emitting layer.

Example 6
In FIG. 1, an organic EL device having a configuration in which the hole transport layer was omitted and an electron blocking layer and an electron injection layer were added was produced. On a glass substrate made of ITO having a film thickness of 150 nm that has been subjected to UV ozone cleaning and drying steps, a 20 wt% ethanol solution of PEDOT / PSS as a hole injection layer is spin-coated at a rotational speed of 3000 rpm for 60 seconds, and 200 Dry at 60 ° C. for 60 minutes. The film thickness at this time was 25 nm. Next, as an electron blocking layer, a 20 wt% tetrahydrofuran mixed solution of Compound 14 was spin-coated at a rotational speed of 4000 rpm for 30 seconds and dried at 120 ° C. for 30 minutes. At this time, the thickness of the light emitting layer was 20 nm. Next, as a light emitting layer, 2,6-di (4-carbazolylphenyl) pyridine as a host material and tris (2-phenylpyridine) iridium (Ir (ppy) 3) as a phosphorescent dopant material are formed by vacuum deposition. Co-deposited at a deposition rate of 0.1 nm / sec. The film thickness of the light emitting layer at this time was 50 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 a vacuum deposition method, and an organic EL element was produced.

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. It measured similarly about the organic EL element obtained by the following examples and comparative examples. The results are shown in Table 2.

Example 7
An organic EL device was produced in the same manner as in Example 6 except that Compound 24 was used as the electron blocking layer material.

Example 8
An organic EL device was prepared in the same manner as in Example 6 except that Compound 36 was used as the electron blocking layer material.

Comparative Example 2
An organic EL device was produced in the same manner as in Example 6 except that the electron blocking layer was omitted and the thickness of the light emitting layer was changed to 70 nm.

Comparative Example 3
An organic EL device was produced in the same manner as in Example 6 except that Compound H-1 was used as the electron blocking layer material.

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

Claims (5)

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 element comprising an indolocarbazole compound represented by the general formula (1) in at least one selected organic layer.

In the general formula (1), Z ₁ independently represents a monovalent group represented by the formula (2), Z ₂ represents a divalent group represented by the formula (2), L ₁ , L ₂ independently represents a divalent aromatic hydrocarbon group having 6 to 50 carbon atoms or an aromatic heterocyclic group having 3 to 50 carbon atoms that does not include a condensed heterocyclic ring having 5 or more rings, and n represents 1 to 4 Represents an integer. When n is 2 or more, Z ₂ and L ₂ may be the same or different.

In formula (2), ring A ₁ represents an aromatic hydrocarbon ring represented by formula (2a) fused with an adjacent ring, and ring B ₁ represents a heterocyclic ring represented by formula (2b) fused with an adjacent ring. Represents. In formulas (2) and (2a), 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 3-17. When Formula (2) is a monovalent group, in Formula (2b), A is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 11 carbon atoms, and 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 5 or more rings . However, when Z ₂ is a divalent group represented by the formula (2), A in the formula (2b) represents a single bond bonded to L ₁ or L ₂ . 2. The organic electroluminescent element according to claim 1, wherein in the general formula (1), Z ₁ is a monovalent group represented by any _one of the formulas (3) to (6).

In the formulas (3) to (6), R is the same as the formulas (2) and (2a), and A is the same as the formula (2b). 3. The organic electroluminescent element according to claim 1, wherein in the general formula (1), Z ₂ is a divalent group represented by any one of the formulas (7) to (9).

In formulas (7) to (9), R is the same as formulas (2) and (2a).   The organic electroluminescent device according to claim 1, wherein the organic layer containing an indolocarbazole compound is a light emitting layer containing a phosphorescent dopant.   The organic electroluminescent element according to claim 1, wherein the organic layer containing an indolocarbazole compound is an electron blocking layer.

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