JP2016072377A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly practical organic EL element which is highly efficient even at a low voltage and has high driving stability.SOLUTION: The organic electroluminescent element includes one or more light-emitting layers between an anode and a cathode facing each other. At least one of the light-emitting layers contains a host material containing at least two compounds, and a luminescent dopant. The host material contains (i) an indolocarbazole compound having one or two indolocarbazole ring structures and (ii) a carborane compound having a carborane ring bonded to a dibenzofuran ring.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an organic electroluminescent device (hereinafter referred to as an organic EL device), and more particularly to an organic EL device having a light emitting layer containing a host material composed of a plurality of compounds.

  In general, the 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 light is emitted as energy when they are recombined in the light emitting layer. Use the phenomenon.

In recent years, an organic EL element using an organic thin film has been developed. In particular, in order to increase the luminous efficiency, the type of electrode is optimized for the purpose of improving the efficiency of carrier injection from the electrode, and the luminous layer is composed of an aromatic diamine hole transport layer and an 8-hydroxyquinoline aluminum complex (Alq ₃ ). With the development of a device in which a layer / electron transport layer is provided as a thin film between electrodes, the luminous efficiency has been greatly improved as compared with a conventional device using a single crystal such as anthracene. Therefore, development has been progressing with the aim of putting it into practical use as a high-performance flat panel having features such as self-luminance and high-speed response.

As an attempt to increase the luminous efficiency of the device, the use of a phosphorescent material instead of a fluorescent material has been studied. Many devices, including those provided with the hole transport layer composed of the aromatic diamine and the light-emitting layer composed of Alq ₃ , use fluorescence emission, but use phosphorescence emission, that is, triple By using the light emission from the term excited state, it is expected that the efficiency is improved by about 3 to 4 times compared to the conventional device using fluorescence (singlet). 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. Thereafter, the use of a europium complex has been studied as an attempt to utilize the triplet state, but this also did not lead to highly efficient light emission. In this research using phosphorescence, many studies have been conducted mainly on organometallic complexes such as iridium complexes listed in Patent Document 1 as phosphorescent dopants. Has been.

WO01 / 041512 A1 WO2008 / 056746 A1 Japanese Unexamined Patent Publication No. 2005-162709 JP 2005-166574 A US2012 / 0319088 A1 WO2013 / 094834 A1 US2009 / 0167162 A1 WO2009 / 136596 A1 WO2010 / 098246 A1

  Patent Document 2 discloses the use of an indolocarbazole compound as a host material. Patent Documents 3 to 7 disclose the use of a carborane compound as a host material. Patent Documents 8 and 9 disclose host materials in which two types of indolocarbazole compounds are mixed.

  However, there is no teaching that a specific indolocarbazole compound and a carborane compound are mixed to make a host material.

  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. In view of the above situation, an object of the present invention is to provide a practically useful organic EL device having high efficiency and high driving stability while being low in voltage.

The present invention relates to an organic electroluminescent device comprising one or more light emitting layers between an anode and a cathode facing each other, wherein at least one light emitting layer comprises at least one host material containing at least two types of host compounds and at least one light emitting property. It contains a dopant, and the host material contains (i) a compound represented by the following general formula (1) or (2) and (ii) a compound represented by the following general formula (3). The present invention relates to an organic electroluminescent element.

Here, ring a, ring c, and ring c ′ independently represent an aromatic ring represented by the formula (a1) that is condensed with two adjacent rings at an arbitrary position, and X ¹ represents C—R or N. ,
Ring b, Ring d, and Ring d ′ each independently represent a heterocyclic ring represented by Formula (b1) that is condensed with two adjacent rings at any position;
Ar ¹ independently represents a p + 1 valent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a p + 1 valent substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms,
Z is a divalent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a divalent substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or 2 of these aromatic rings. 10 to 10 linked divalent substituted or unsubstituted linked aromatic groups,
L ¹ is independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or an aromatic ring having 2 to 10 carbon atoms. A substituted or unsubstituted linked aromatic group formed by linking;
p is the number of substitutions and independently represents an integer of 0 to 7,
R and R ^{1 to} R ⁷ are independently hydrogen, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 38 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, carbon A dialkylamino group having 2 to 40 carbon atoms, a diarylamino group having 12 to 44 carbon atoms, a diaralkylamino group having 14 to 76 carbon atoms, an acyl group having 2 to 20 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, and a carbon number An alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonyloxy group having 2 to 20 carbon atoms, an alkylsulfonyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 30 carbon atoms, Or an aromatic heterocyclic group having 3 to 18 carbon atoms, and when it is a group other than hydrogen, it may have a substituent, and when R ¹ , R ² , R ^{4 to} R ⁷ are phenyl groups, , Aromatic ring substituted by phenyl group A condensed ring may be formed.
In Ar ¹ , Z, and L ¹ , when the aromatic hydrocarbon group, the aromatic hydrocarbon group, or the linked aromatic group has a substituent, the substituent is an alkyl group having 1 to 12 carbon atoms, or 1 to 12 carbon atoms. Or an acyl group having 2 to 13 carbon atoms, and in R and R ^{1 to} R ⁷ , the substituent in the case of having a substituent is an alkyl group having 1 to 12 carbon atoms, or a carbon atom having 1 to 12 carbon atoms. It is an alkoxy group, an acyl group having 2 to 13 carbon atoms, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 18 carbon atoms. These substituents may be the same or different.

Here, ring A independently represents a C ₂ B ₁₀ H ₁₀ divalent carborane group represented by formula (c1) or formula (d1).
s is the number of repetitions and is an integer of 1 to 4, n is the number of substitutions and is an integer of 0 to 4. However, when n = 1, s = 1.
L ² and L ³ are independently a single bond, an n + 1-valent or divalent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic ring having 3 to 30 carbon atoms. Or a substituted or unsubstituted linked aromatic group constituted by connecting 2 to 6 of these aromatic rings. However, when n = 0, it does not become a single bond, and when n = 1, it may contain at least one aromatic heterocyclic group, or when n = 1, L ² is at least It may be a group containing one aromatic heterocyclic group or a single bond.
L ⁴ is hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an acyl group having 2 to 13 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, A substituted or unsubstituted aromatic hydrocarbon group having 3 to 30 carbon atoms, or a substituted or unsubstituted linked aromatic group constituted by connecting 2 to 6 of these aromatic rings.
In L ^{2 to} L ⁴ , when the aromatic hydrocarbon group, the aromatic hydrocarbon group or the linked aromatic group has a substituent, the substituent is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. A group or an acyl group having 2 to 13 carbon atoms, the substituent may be plural, the plural substituents may be the same or different, and L ² -H present at the terminal and L ³ —H may be an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an acyl group having 2 to 13 carbon atoms.

In the general formulas (1), (2) and (3), when Z, L ¹ , L ² , L ³ and L ⁴ are linked aromatic groups, the linked aromatic rings may be the same or different. Good.

In the general formulas (1) and (2), X ¹ is C—R, Ar ¹ is an aromatic heterocyclic group having 3 to 16 carbon atoms, or Z is 3 to 16 carbon atoms. It is a preferable aspect that it is an aromatic heterocyclic group.

In the general formula (3), L ² and L ³ are each independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Or a linked aromatic group formed by linking these two or five, or L ² is each independently a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms or 2 It is a preferable aspect that it is the connection aromatic group comprised by -5 connection.

  Moreover, it is desirable that at least two host materials are a compound represented by the general formula (1) and a compound represented by the general formula (3). Furthermore, it is desirable that the light-emitting dopant is an organometallic complex containing at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold.

In order to improve device characteristics, it is important to suppress leakage of excitons and charges to the peripheral layer. In order to suppress the leakage of charge / exciton, it is effective to improve the bias of the light emitting region in the light emitting layer. For this purpose, it is necessary to control the injection amount of both charges (electrons / holes) within a preferable range.
Here, the indolocarbazole compound has high skeletal stability, and the electron / hole injection / transport properties can be controlled to some extent by isomers and substituents. However, with an indolocarbazole compound alone, it is difficult to control both charge injection amounts within a preferable range as described above. On the other hand, the specific carborane compound represented by the general formula (3) has a low vacancy orbit (LUMO) that affects the electron injection / transport property widely distributed throughout the molecule, so that the electron injection / transport property of the device is high. It can be controlled at a high level, and in addition, it has high skeletal stability like indolocarbazole compounds. Therefore, by using a carborane compound and an indolocarbazole compound as a mixed host, the amount of both charges injected into the light-emitting layer can be precisely adjusted, and can be controlled in a more preferable range than when they are used alone.

  The organic EL device of the present invention can achieve a low voltage by using a specific compound as a mixed host. In the case of a phosphorescent light-emitting EL element, since the lowest excited triplet energy (T1 energy) is sufficiently high to confine the lowest excited triplet energy, there is no energy outflow from the light emitting layer, High efficiency and long life can be achieved. The organic EL element of the present invention is a flat panel display (cell phone display element, in-vehicle display element, OA computer display element, television, etc.), and a light source (illumination, light source of a copying machine, liquid crystal display) utilizing the characteristics as a surface light emitter In addition, its technical value is great in applications to backlights for measuring instruments, display boards, indicator lamps, and the like.

The schematic cross section which showed an example of the organic EL element.

  The organic electroluminescent element of the present invention has at least one light emitting layer containing a host material containing at least two kinds of host compounds and at least one light emitting dopant between an anode and a cathode facing each other. The host material contained in the light emitting layer is represented by the first host material selected from the compounds represented by any one of the above general formulas (1) to (2) as the host compound and the above general formula (3). A mixture containing a second host material selected from the following compounds. Note that the first host compound and the second host compound may be a mixture of two or more compounds.

  Hereinafter, the general formulas (1) and (2) will be described. In general formulas (1) and (2), common symbols have the same meaning.

Ring a, ring c, and ring c ′ represent an aromatic ring represented by the formula (a1) condensed at an arbitrary position of two adjacent rings (meaning an aromatic hydrocarbon ring, an aromatic heterocyclic ring, or both). Show. Here, in the formula (a1), X ¹ represents C—R or N, and is preferably C—R.

  Ring b, ring d, and ring d 'each represent a heterocycle represented by the formula (b1) that is fused at an arbitrary position of two adjacent rings. Here, ring c and ring c ', and ring d and ring d' may be the same or different.

  The aromatic ring represented by the formula (a1) can be condensed with two adjacent rings at any position, but there is a position where it cannot be condensed structurally. The aromatic ring represented by the formula (a1) has six sides, but does not condense with two adjacent rings at two adjacent sides. Further, the heterocyclic ring represented by the formula (b1) can be condensed with two adjacent rings at an arbitrary position, but there are positions where it cannot be condensed structurally. That is, this heterocyclic ring has five sides, but is not condensed with two adjacent rings at two adjacent sides, and is not condensed with an adjacent ring at a side containing a nitrogen atom. Therefore, the types of isomers of the compounds represented by the general formulas (1) and (2) are limited.

Ar ¹ is independently a p + 1-valent substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group. Carbon number of an aromatic hydrocarbon group is 6-30, Preferably it is 6-22, More preferably, it is 6-18. The aromatic heterocyclic group preferably has 3 to 16 carbon atoms.

Specific examples of Ar ¹ include benzene, pentalene, indene, naphthalene, azulene, heptalene, octalene, indacene, acenaphthylene, phenalene, phenanthrene, anthracene, tridene, fluoranthene, acephenanthrylene, acanthrylene, triphenylene, pyrene, chrysene. , Tetraphen, tetracene, pleiaden, picene, perylene, pentaphen, pentacene, tetraphenylene, cholanthrylene, helicene, hexaphene, rubicene, coronene, trinaphthylene, heptaphene, pyranthrene, furan, benzofuran, isobenzofuran, xanthene, oxatolene, dibenzofuran, peri Xanthenoxanthene, thiophene, thioxanthene, thianthrene, phenoxathiin, thionaphthene, iso Anaphten, thiobutene, thiophantrene, dibenzothiophene, pyrrole, pyrazole, tellurazole, selenazole, thiazole, isothiazole, 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, phenazine, carboline, phenotelrazine, phenotherazine, phenothiazine, phenoxazine, Lysine, benzothiazole, benzimidazole, benzoxazole, And a group formed by removing p + 1 hydrogen from an aromatic compound such as benzoisoxazole or benzoisothiazole. Preferred is a group formed by removing p + 1 hydrogen from benzene, naphthalene, anthracene, pyridine, pyrazine, pyrimidine, pyridazine, triazine, carbazole, dibenzofuran, dibenzothiophene, quinoline, isoquinoline, quinoxaline, or naphthyridine.

L ¹ is independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or an aromatic ring having 2 to 2 A substituted or unsubstituted linked aromatic group formed by 10 linkages is shown. Preferably they are a C6-C18 aromatic hydrocarbon group, a C3-C16 aromatic heterocyclic group, or a connection aromatic group formed by connecting these aromatic rings in 2-7.

Specific examples of L ¹ include benzene, pentalene, indene, naphthalene, azulene, heptalene, octalene, indacene, acenaphthylene, phenalene, phenanthrene, anthracene, tridene, fluoranthene, acephenanthrylene, acanthrylene, triphenylene, pyrene, chrysene. , Tetraphen, tetracene, pleiaden, picene, perylene, pentaphen, pentacene, tetraphenylene, cholanthrylene, helicene, hexaphene, rubicene, coronene, trinaphthylene, heptaphene, pyranthrene, furan, benzofuran, isobenzofuran, xanthene, oxatolene, dibenzofuran, peri Xanthenoxanthene, thiophene, thioxanthene, thianthrene, phenoxathiin, thionaphthene, isothi Naphthene, thiobutene, thiophanthrene, dibenzothiophene, pyrrole, pyrazole, tellurazole, selenazole, thiazole, isothiazole, 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, phenazine, carboline, phenotelrazine, phenotherazine, phenothiazine, phenoxazine, Lysine, benzothiazole, benzimidazole, benzoxazole, Examples thereof include aromatic compounds such as nzoisoxazole and benzoisothiazole, or linked aromatic groups formed by removing one hydrogen from an aromatic compound in which a plurality of aromatic rings of these aromatic compounds are linked.

As used herein, a linked aromatic group is a group in which a plurality of aromatic rings (which are aromatic hydrocarbon rings, aromatic heterocycles, or both) of an aromatic compound having a single ring structure or a condensed ring structure are connected. is there. The term “aromatic ring linked” means that the aromatic rings of the aromatic group are linked by a direct bond. When the aromatic ring is a substituted aromatic ring, the substituent is not an aromatic ring.
The linked aromatic group may be linear or branched, and the aromatic rings to be linked may be the same or different, and either one of the aromatic hydrocarbon ring and the aromatic heterocyclic ring or You may have both and you may have a substituent.

When the linking aromatic group is a monovalent group, for example, the linking mode shown below can be mentioned.

  When the linking aromatic group is a divalent group, for example, a linking mode as shown below is exemplified. In the case of a trivalent or higher group, it is understood from the above.

In formulas (4) to (9), Ar ^{12 to} Ar ¹⁶ and Ar ^{21 to} Ar ²⁶ represent a substituted or unsubstituted aromatic ring (aromatic group), and the ring constituent atoms of the aromatic ring are bonded by a direct bond. To do. Bonds come out of the ring atoms of the aromatic ring. The aromatic ring (aromatic group) means an aromatic hydrocarbon group or an aromatic heterocyclic group, and can be a monovalent or higher group.
In formulas (4) to (9), the bond is from Ar ¹¹ , Ar ²¹ , or Ar ²³ , but can be from other aromatic rings. Moreover, when it is a bivalent or more group, two or more bonds may come out from one aromatic ring.

  Specific examples of the linked aromatic group include, for example, biphenyl, terphenyl, bipyridine, bipyrimidine, vitriazine, terpyridine, phenylterphenyl, binaphthalene, phenylpyridine, diphenylpyridine, phenylpyrimidine, diphenylpyrimidine, phenyltriazine, diphenyltriazine, phenylnaphthalene. 1 from aromatic compounds such as diphenylnaphthalene, carbazolylbenzene, biscarbazolylbenzene, biscarbazolyltriazine, dibenzofuranylbenzene, bisdibenzofuranylbenzene, dibenzothiophenylbenzene, bisdibenzothiophenylbenzene And groups formed by removing one or more hydrogens.

  The description regarding said connection aromatic group is common to the connection aromatic group which appears by description in General formula (1), (2) and (3).

  In the general formula (2), Z is a divalent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or 2 10 to 10 linked substituted or unsubstituted linked aromatic groups. Preferably, it is a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, an aromatic heterocyclic group having 3 to 16 carbon atoms, or a linked aromatic group formed by connecting 2 to 7 thereof.

Specific examples of Z include a divalent group generated by removing two hydrogens from the aromatic compound exemplified in the description of L ¹ , or an aromatic compound in which a plurality of these are connected.

In general formula (1) and formula (b1), p is the number of substitutions and independently represents an integer of 0 to 7. Preferably it is 0-5, More preferably, it is 0-3. When formula (b1) is incorporated into general formulas (1) and (2), there are two (L ¹ ) _p in general formula (1) and one in general formula (2). . When p is 0, L ¹ does not exist. However, in general formula (1), when one p is 0, the other p is preferably 1 or more.

When Ar ¹ , Z, and L ¹ are a substituted aromatic hydrocarbon group, a substituted aromatic heterocyclic group, or a substituted linked aromatic group, the substituent is an alkyl group having 1 to 12 carbon atoms, Preferred examples include an alkoxy group having 1 to 12 carbon atoms and an acyl group having 2 to 13 carbon atoms. More preferably, it is a C1-C10 alkyl group, a C1-C10 alkoxy group, or a C2-C11 acyl group. In addition, it is good that the number of substituents is 0-5, Preferably it is 0-2.
In this specification, calculation of carbon number is understood not to include the carbon number of the substituent. However, it can be said that the total number of carbon atoms including the carbon number of the substituent is preferably in the range of the carbon number. The number of carbon atoms of the linked aromatic group is understood as the total number of carbon atoms that each of the aromatic hydrocarbon group and aromatic heterocyclic group to be linked has.

Specific examples of the substituent are shown below.
The alkyl group may be saturated or unsaturated, linear, branched or cyclic, and may be a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group, Carbon number 1 such as saturated alkyl group having 1 to 10 carbon atoms such as pentyl group, hexyl group and octyl group, unsaturated alkyl group having 2 to 10 carbon atoms such as ethenyl group and propenyl group, cyclopentyl group and cyclohexyl group 10 to 10 cycloalkyl groups are preferred.

  The alkoxy group may be linear or branched, and is a methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, t-butoxy group, pentoxy group, 2-ethylbutoxy group, hexyloxy group, octoxy Preferable examples include an alkoxy group having 1 to 10 carbon atoms such as a group.

  The acyl group may be linear or branched, and may be a methylcarbonyl group (acetyl group), ethylcarbonyl group, propylcarbonyl group, isopropylcarbonyl group, butylcarbonyl group, t-butylcarbonyl group, pentylcarbonyl group, Preferable examples include an acyl group having 2 to 11 carbon atoms such as a 2-ethylbutylcarbonyl group, a hexylcarbonyl group, and an octylcarbonyl group.

R and R ^{1 to} R ⁷ are independently hydrogen, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 38 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, carbon A dialkylamino group having 2 to 40 carbon atoms, a diarylamino group having 12 to 44 carbon atoms, a diaralkylamino group having 14 to 76 carbon atoms, an acyl group having 2 to 20 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, and a carbon number An alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonyloxy group having 2 to 20 carbon atoms, an alkylsulfonyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or It is a C3-C18 aromatic heterocyclic group. Preferably, hydrogen, an alkyl group having 1 to 10 carbon atoms, an aralkyl group having 7 to 24 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an acyl group having 2 to 11 carbon atoms, and a diarylamino group having 12 to 36 carbon atoms , An aromatic hydrocarbon group having 6 to 18 carbon atoms or an aromatic heterocyclic group having 3 to 16 carbon atoms, more preferably hydrogen, an aromatic hydrocarbon group having 6 to 18 carbon atoms or 3 to 16 carbon atoms. An aromatic heterocyclic group.
Moreover, when R < ¹ > -R < ² > and R < ⁴ > -R < ⁷ > are phenyl groups, you may form the aromatic ring and condensed ring to substitute.

R and R ^{1 to} R ⁷ are alkyl groups having 1 to 20 carbon atoms, aralkyl groups having 7 to 38 carbon atoms, alkenyl groups having 2 to 20 carbon atoms, alkynyl groups having 2 to 20 carbon atoms, and 2 to 40 carbon atoms. Dialkylamino group having 12 to 44 carbon atoms, diaralkylamino group having 14 to 76 carbon atoms, acyl group having 2 to 20 carbon atoms, acyloxy group having 2 to 20 carbon atoms, and 1 to 20 carbon atoms. Specific examples in the case of an alkoxy group, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonyloxy group having 2 to 20 carbon atoms, and an alkylsulfonyl group having 1 to 20 carbon atoms are shown below.

  Methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, phenylmethyl, phenylethyl, phenylicosyl, Naphthylmethyl, anthranylmethyl, phenanthrenylmethyl, pyrenylmethyl, vinyl, propenyl, butenyl, pentenyl, decenyl, icocenyl, ethynyl, propargyl, butynyl, pentynyl, decynyl, icosinyl, dimethylamino, ethylmethylamino, diethylamino, dipropylamino , Dibutylamino, dipentynylamino, didecylamino, diicosylamino, diphenylamino, naphthylphenylamino, dinaphthyl Mino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, diphenylmethylamino, diphenylethylamino, phenylmethylphenylethylamino, dinaphthylmethylamino, dianthranylmethylamino, diphenanthrenylmethylamino, methylcarbonyl ( Acetyl), ethylcarbonyl, propylcarbonyl, isopropylcarbonyl, butylcarbonyl, t-butylcarbonyl, pentylcarbonyl, 2-ethylbutylcarbonyl, hexylcarbonyl, octylcarbonyl, valeryl, benzoyl, acetyloxy, propionyloxy, butyryloxy, valeryloxy, benzoyl Oxy, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycar Alkylsulfonyl, methoxycarbonyloxy, ethoxycarbonyloxy, propoxycarbonyloxy, butoxycarbonyloxy, pentoxycarbonyl oxy, methylsulfonyl, ethylsulfonyl, propylsulfonyl, butylsulfonyl, pentylsulfonyl and the like. Preferably, a C1-10 alkyl group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, phenylmethyl, phenylethyl, naphthylmethyl, anthranylmethyl, phenanthrenylmethyl, pyrenylmethyl C7-20 aralkyl groups such as, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, deoxy, etc., C1-10 alkoxy groups, methylcarbonyl (acetyl), ethylcarbonyl, propylcarbonyl, isopropyl C2-C11 acyl groups such as carbonyl, butylcarbonyl, t-butylcarbonyl, pentylcarbonyl, 2-ethylbutylcarbonyl, hexylcarbonyl, octylcarbonyl, diphenylamino, Examples thereof include diarylamino groups having two C6-15 aromatic hydrocarbon groups such as naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino and the like.

Specific examples in the case where R and R ^{1 to} R ⁷ are an aromatic hydrocarbon group having 6 to 30 carbon atoms or an aromatic heterocyclic group having 3 to 18 carbon atoms include benzene, pentalene, indene, naphthalene, and azulene , Indacene, acenaphthylene, phenalene, phenanthrene, anthracene, tridene, fluoranthene, acephenanthrylene, acanthrylene, triphenylene, pyrene, chrysene, tetraphen, tetracene, pleiaden, picene, perylene, pentaphene, pentacene, tetraphenylene, cholanthrylene , Furan, benzofuran, isobenzofuran, xanthene, oxatolene, dibenzofuran, perixanthenoxanthene, thiophene, thioxanthene, thianthrene, phenoxathiin, thionaphthene, isothianaphthene, thiobutene Thiophanthrene, dibenzothiophene, pyrrole, pyrazole, tellurazole, selenazole, thiazole, isothiazole, oxazole, furazane, thiadiazole, 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, phenazine, carboline, indolocarbazole, phenotelrazine, phenotherazine, phenothiazine, phenoxazine , Anti-lysine, benzothiazole, benzimidazole, benzo And a group formed by removing hydrogen from an aromatic compound such as oxazole, benzisoxazole, or benzoisothiazole. Preferably benzene, naphthalene, anthracene, pyridine, pyrazine, pyrimidine, pyridazine, triazine, isoindole, indazole, purine, isoquinoline, imidazole, naphthyridine, phthalazine, quinazoline, benzodiazepine, quinoxaline, cinnoline, quinoline, pteridine, phenanthridine, acridine , Groups formed by removing hydrogen from perimidine, phenanthroline, phenazine, carboline, indole, carbazole, dibenzofuran, or dibenzothiophene.

When R and R ^{1 to} R ⁷ are groups other than hydrogen, they may have a substituent. The substituent includes the same group as the substituent when Ar ¹ , Z, and L ¹ are a substituted aromatic hydrocarbon group or a substituted aromatic heterocyclic group, and 6 to 30 carbon atoms, Preferred examples include an aromatic hydrocarbon group having 6 to 18 carbon atoms and an aromatic heterocyclic group having 3 to 18 carbon atoms, preferably 3 to 15 carbon atoms. The number of substituents R, per one of R ¹ to R ^7, preferably 0-3, 0-2 is more preferable.

  Although the preferable specific example of a compound represented by General formula (1) and (2) is shown below, it is not limited to these.

Next, the compound (carborane compound) represented by the general formula (3) will be described.
Ring A represents a C ₂ B ₁₀ H ₈ divalent carborane group represented by Formula (c1) or Formula (d1), and a plurality of rings A in the molecule may be the same or different. Preferably, all the rings A are carborane groups represented by the formula (c1).

  s is the number of repetitions and represents an integer of 0 to 1, preferably s = 0. n is the number of substitutions and represents an integer of 0 to 2, preferably n = 0. However, when n = 1, s = 1.

L ² independently represents a single bond or an n + 1 valent group. In the case of an n + 1 valent group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or these aromatic rings are 2 to 2 6 or more substituted or unsubstituted linked aromatic groups, preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted 3 to 17 carbon atoms An aromatic heterocyclic group, or a substituted or unsubstituted linked aromatic group formed by connecting these aromatic rings in 2 to 5 units. In the case of a linked aromatic group, it may be linear or branched, and the aromatic rings to be linked may be the same or different.

L ³ independently represents a single bond or a divalent group. In the case of a divalent group, the substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, the substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or these aromatic rings are 2 to 2 6 or more substituted or unsubstituted linked aromatic groups, preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted carbon group having 3 to 17 carbon atoms. An aromatic heterocyclic group, or a substituted or unsubstituted linked aromatic group formed by linking them 2 to 5, more preferably a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or they Is a substituted or unsubstituted linked aromatic group formed by 2 to 5 linkages.

However, if L ² and L ³ is present at the end of the general formula (3), but each becomes L ² -H and L ³ -H, the L ² -H and L ³ -H is 1 to carbon atoms It may be a 12 alkyl group, an alkoxy group having 1 to 12 carbon atoms, or an acyl group having 2 to 13 carbon atoms.

L ⁴ is hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an acyl group having 2 to 13 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, A substituted or unsubstituted aromatic hydrocarbon group having 3 to 30 carbon atoms, or a substituted or unsubstituted linked aromatic group constituted by connecting 2 to 6 of these aromatic rings.

In L ^{2 to} L ⁴ , specific examples of the unsubstituted aromatic hydrocarbon group include benzene, pentalene, indene, naphthalene, fluorene, azulene, heptalene, octalene, indacene, acenaphthylene, phenalene, phenanthrene, anthracene, tridden, fluoranthene, Acephenanthrylene, acanthrylene, triphenylene, pyrene, chrysene, tetraphen, tetracene, preaden, picene, perylene, pentaphen, pentacene, tetraphenylene, cholantolylene, helicene, hexaphene, rubicene, coronene, trinaphthylene, heptaphene, pyranthrene, etc. Aromatic hydrocarbon group or a linked aromatic hydrocarbon group produced by removing hydrogen from a linked aromatic hydrocarbon compound in which a plurality of these are connected. It is, preferably benzene, naphthalene, anthracene, groups formed except fluorene, phenanthrene, or hydrogen from triphenylene.

Specific examples of the unsubstituted aromatic heterocyclic group include furan, benzofuran, isobenzofuran, xanthene, oxatolene, dibenzofuran, perixanthenoxanthene, thiophene, thioxanthene, thianthrene, phenoxathiin, thionaphthene, isothianaphthene, thiobutene, Thiophantrene, dibenzothiophene, pyrrole, pyrazole, tellurazole, selenazole, thiazole, isothiazole, oxazole, furazane, pyridine, pyrazine, pyrimidine, pyridazine, triazine, indolizine, indole, isoindole, indazole, purine, quinolidine, isoquinoline, Carbazole, imidazole, naphthyridine, phthalazine, quinazoline, azepine, benzodiazepine, tribenzoazepine, quinoxaline, Norin, quinoline, pteridine, phenanthridine, acridine, perimidine, phenanthroline, phenazine, carboline, phenotelrazine, phenoselenazine, phenothiazine, phenoxazine, antilysine, benzothiazole, benzimidazole, benzoxazole, benzoisoxazole, or benzoiso Aromatic heterocyclic compounds such as thiazole, dibenzophosphole, dibenzoborol, etc., or aromatic heterocyclic groups or linked aromatic groups generated by removing hydrogen from a linked aromatic heterocyclic compound in which a plurality of these are linked, are preferred, Is a group formed by removing hydrogen from pyridine, pyrimidine, triazine, dibenzofuran, dibenzothiophene, or carbazole.
The number of hydrogen removed is n + 1, 2 or 1, respectively.

  The substituent in the case of a substituted aromatic hydrocarbon group, a substituted aromatic heterocyclic group or a substituted linked aromatic group is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or the number of carbon atoms It is an acyl group of 2 to 13, and may be linear, branched or cyclic. More preferably, it is a C1-C10 alkyl group, a C1-C10 alkoxy group, or a C2-C11 acyl group. In addition, the number of substituents is 0-5, Preferably it is 0-2.

  The alkyl group may be saturated or unsaturated, linear, branched or cyclic, and specific examples include methyl, ethyl, propyl, isopropyl, butyl, C1-C10 saturated alkyl group such as t-butyl group, pentyl group, hexyl group, octyl group, etc., C2-C10 unsaturated alkyl group such as ethenyl group, propenyl group, cyclopentyl group, cyclohexyl group Preferred examples thereof include cycloalkyl groups having 5 to 10 carbon atoms.

  The alkoxy group may be linear or branched, and specific examples include methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, t-butoxy group, pentoxy group, 2-ethylbutoxy group. C1-C10 alkoxy groups such as hexyloxy group and octoxy group are preferred.

  The acyl group may be linear or branched. Specific examples include a methylcarbonyl group (acetyl group), an ethylcarbonyl group, a propylcarbonyl group, an isopropylcarbonyl group, a butylcarbonyl group, and a t-butylcarbonyl group. C2-C11 acyl groups such as pentylcarbonyl group, 2-ethylbutylcarbonyl group, hexylcarbonyl group and octylcarbonyl group are preferred.

An alkyl group in which L ⁴ , terminal L ² —H and L ³ —H are each an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an acyl group having 2 to 13 carbon atoms; The same applies to an alkoxy group and an acyl group.

  Although the preferable specific example of a compound represented by the said General formula (3) is shown below, it is not limited to these.

  The host material including the first host material (H1) and the second host material (H2) may be mixed and vapor-deposited using one vapor deposition source before forming the device. You may mix at the time of producing an element by operation, such as used co-evaporation. Although there is no restriction | limiting in particular about the mixing ratio (weight ratio) of a host material, The range of 95: 5-5: 95 is preferable.

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.

(1) Configuration of Organic EL Element FIG. 1 is a cross-sectional view schematically showing a structural example of a general organic EL element, where 1 is a substrate, 2 is an anode, 3 is a hole injection layer, and 4 is hole transport. Layers 5, 5 are light-emitting layers, 6 is an electron transport layer, 7 is an electron injection layer, and 8 is a cathode. The organic EL device of the present invention has an anode, a light emitting layer, and a cathode as essential layers, but other layers may be provided as necessary. Examples of other layers include, but are not limited to, a hole injection transport layer, an electron blocking layer, and a hole blocking layer. In addition, a positive hole injection transport layer means either a positive hole injection layer, a positive hole transport layer, or both. Preferably, the layer shown in FIG. 1 is provided as an essential layer.

(2) Substrate The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film or a sheet is used. In particular, glass plates and smooth and transparent synthetic resin plates such as polyester, polymethacrylate, polycarbonate and polysulfone are preferred. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

(3) Anode An anode 2 is provided on the substrate 1, and the anode plays a role of hole injection into the hole transport layer. This anode is usually a metal such as aluminum, gold, silver, nickel, palladium, platinum, a metal oxide such as an oxide of indium and / or tin, an oxide of indium and / or zinc, or a halogen such as copper iodide. Metal oxide, carbon black, or a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline. In general, the anode is often formed by a sputtering method, a vacuum deposition method, or the like. Also, in the case of fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., it is dispersed in an appropriate binder resin solution and placed on the substrate. An anode can also be formed by coating. Further, in the case of a conductive polymer, a thin film can be directly formed on a substrate by electrolytic polymerization, or an anode can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett., 60). (Vol. 2711, 1992). The anode can be formed by stacking different materials. The thickness of the anode varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness is usually 5 to 1000 nm, preferably 10 to It is about 500 nm. If it may be opaque, the anode may be the same as the substrate. Furthermore, it is also possible to laminate different conductive materials on the anode.

(4) Hole Transport Layer The hole transport layer 4 is provided on the anode 2. A hole injection layer 3 can also be provided between them. As conditions required for the material of the hole transport layer, it is necessary that the material has a high hole injection efficiency from the anode and can efficiently transport the injected holes. For this purpose, the ionization potential is low, the transparency to visible light is high, the hole mobility is high, the stability is high, and impurities that become traps are unlikely to be generated during manufacturing or use. Required. Further, in order to contact the light emitting layer 5, it is required not to quench the light emitted from the light emitting layer or to form an exciplex with the light emitting layer to reduce the efficiency. In addition to the above general requirements, when the application for in-vehicle display is considered, the element is further required to have heat resistance. Therefore, a material having a Tg value of 85 ° C. or higher is desirable.

As the hole transport material, known compounds conventionally used for this layer can be used. For example, an aromatic diamine containing two or more tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234681), 4,4 ', 4 "-tris (1- Aromatic amine compounds having a starburst structure such as naphthylphenylamino) triphenylamine (J. Lumin., 72-74, 985, 1997), aromatic amine compounds comprising a tetramer of triphenylamine ( Chem. Commun., 2175, 1996), spiro compounds such as 2,2 ', 7,7'-tetrakis- (diphenylamino) -9,9'-spirobifluorene (Synth. Metals, 91, 209) Page, 1997), etc. These compounds may be used alone or in combination as necessary.
In addition to the above compounds, polyarylene ether sulfone (Polym. Adv. Tech) containing polyvinylcarbazole, polyvinyltriphenylamine (Japanese Patent Laid-Open No. 7-53953), and tetraphenylbenzidine as a material for the hole transport layer. ., Vol. 7, p. 33, 1996).

  When forming the hole transport layer by a coating method, one or more hole transport materials and, if necessary, an additive such as a binder resin or a coating property improving agent that does not trap holes are added, Dissolve to prepare a coating solution, apply onto the anode by a method such as spin coating, and dry to form a hole transport layer. Examples of the binder resin include polycarbonate, polyarylate, and polyester. When the binder resin is added in a large amount, the hole mobility is lowered.

When forming by vacuum evaporation, put the hole transport material in a crucible installed in a vacuum vessel, evacuate the vacuum vessel to about 10 ^-4 Pa with a suitable vacuum pump, then heat the crucible The hole transport material is evaporated, and a hole transport layer is formed on the substrate on which the anode is formed, facing the crucible. The thickness of the hole transport layer is usually 1 to 300 nm, preferably 5 to 100 nm. In order to uniformly form such a thin film, a vacuum deposition method is generally used.

(5) Hole injection layer For the purpose of further improving the efficiency of hole injection and improving the adhesion of the whole organic layer to the anode, the hole injection layer is provided between the hole transport layer 4 and the anode 2. 3 is also inserted. By inserting the hole injection layer, the driving voltage of the initial element is lowered, and at the same time, an increase in voltage when the element is continuously driven with a constant current is suppressed. The conditions required for the material used for the hole injection layer are that the contact with the anode is good and a uniform thin film can be formed, which is thermally stable, that is, the glass transition temperature is high, and the glass transition temperature is 100 ° C. or higher. Is required. Furthermore, the ionization potential is low, hole injection from the anode is easy, and the hole mobility is high.

  For this purpose, phthalocyanine compounds such as copper phthalocyanine (Japanese Patent Laid-Open No. 63-295695), polyaniline (Appl. Phys. Lett., 64, 1245, 1994), polythiophene (Optical Materials, 9, 125, 1998) and other organic compounds, sputtered carbon films (Synth. Met., 91, 73, 1997), metals such as vanadium oxide, ruthenium oxide, molybdenum oxide P type such as oxide (J. Phys. D, 29, 2750, 1996), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) and hexanitrile hexaazatriphenylene (HAT) Organic substances (WO2005-109542) have been reported. These compounds may be used alone or in combination as necessary. In the case of the hole injection layer, a thin film can be formed in the same manner as the hole transport layer, but in the case of an inorganic material, a sputtering method, an electron beam evaporation method, or a plasma CVD method is further used. The thickness of the hole injection layer formed as described above is usually 1 to 300 nm, preferably 5 to 100 nm.

(6) Light-Emitting Layer The light-emitting layer 5 is provided on the hole transport layer 4. The light emitting layer may be formed from a single light emitting layer, or may be formed by laminating a plurality of light emitting layers so as to be in direct contact with each other. The light emitting layer includes a host material and a light emitting dopant. The luminescent dopant may be a fluorescent material, a delayed fluorescent material, or a phosphorescent material. Two or more luminescent dopants may be used in combination.

The host material is selected from the first host material (H1) selected from the compounds represented by any one of the general formulas (1) to (2) and the compound represented by the general formula (3). Contains a second host material (H2). Preferably, the compound of the general formula (1) or (2) is used as the first host material, and the compound of the general formula (3) is used as the second host material. These compounds may contain two or more compounds included in the above formula.
The use ratio (weight ratio) of the first host material (H1) and the second host material (H2) is preferably H1; H2 = 10 to 90:90 to 100, more preferably 20 to 80. : 80-20.

  In the case of a fluorescent light-emitting organic EL device, fluorescent light-emitting materials to be added to the host material include condensed ring derivatives such as perylene and rubrene, quinacridone derivatives, phenoxazone 660, DCM1, perinone, coumarin derivatives, pyromethene (diazaindacene) derivatives, cyanine dyes Etc. can be used.

  In the case of a delayed fluorescence organic EL device, examples of the delayed fluorescence material in the light emitting layer include carborane derivatives, tin complexes, indolocarbazole derivatives, copper complexes, carbazole derivatives, and the like. Specific examples include compounds described in the following non-patent documents and patent documents, but are not limited to these compounds.

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

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

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

  In the case of a phosphorescent organic EL device, the phosphorescent luminescent dopant contains an organometallic complex containing at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold. Is good. Specific examples include compounds described in the following patent publications, but are not limited to these compounds.

  WO2009-073245 Publication, WO2009-046266 Publication, WO2007-095118 Publication, WO2008-156879 Publication, WO2008-140657 Publication, US2008-261076 Publication, Special Table 2008-542203 Publication, WO2008-054584 Publication, Special Table 2008-505925, Special Table 2007-522126, Special Table 2004-506305, Special Table 2006-513278, Special 2006-50596, WO2006-046980, WO2005-113704 Publication, US2005-260449 publication, US2005-2260448 publication, US2005-214576 publication, WO2005-076380 publication, etc.

  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 2 to 40% by weight, preferably 5 to 30% by weight.

  Although there is no restriction | limiting in particular about the film thickness of a light emitting layer, Usually, 1-300 nm, Preferably it is 5-100 nm, and it forms a thin film with the method similar to a hole transport layer.

(7) Electron Transport Layer An electron transport layer 6 is provided between the light emitting layer 5 and the cathode 8 for the purpose of further improving the light emission efficiency of the device. As the electron transport layer, an electron transport material capable of smoothly injecting electrons from the cathode is preferable, and any commonly used material can be used. As an electron transport material satisfying such conditions, a metal complex such as Alq3 (JP 59-194393A), a metal complex of 10-hydroxybenzo [h] quinoline, an oxadiazole derivative, a distyrylbiphenyl derivative, a silole derivative, 3 -Or 5-hydroxyflavone metal complex, benzoxazole metal complex, benzothiazole metal complex, trisbenzimidazolylbenzene (USP 5,645,948), quinoxaline compound (JP6-207169A), phenanthroline derivative (JP5-331459A), 2-t-butyl- 9,10-N, N′-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide and the like can be mentioned.

  The film thickness of the electron transport layer is usually 1 to 300 nm, preferably 5 to 100 nm. The electron transport layer is formed by laminating on the light emitting layer by a coating method or a vacuum deposition method in the same manner as the hole transport layer. Usually, a vacuum deposition method is used.

(8) Cathode The cathode 8 plays a role of injecting electrons into the electron transport layer 6. As the material used as the cathode, the material used for the anode 2 can be used. However, a metal having a low work function is preferable for efficient electron injection, and tin, magnesium, indium, calcium, aluminum A suitable metal such as silver or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.
The thickness of the cathode is usually the same as that of the anode. For the purpose of protecting the cathode made of a low work function metal, further laminating a metal layer having a high work function and stable to the atmosphere on the cathode increases the stability of the device. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used.
Furthermore, it is also effective to improve the efficiency of the device by inserting an ultrathin insulating film (0.1-5 nm) such as LiF, MgF ₂ , Li ₂ O between the cathode 8 and the electron transport layer 6 as the electron injection layer 7. Is the method.

  1, that is, a cathode 8, an electron injection layer 7, an electron transport layer 6, a light emitting layer 5, a hole transport layer 4, a hole injection layer 3, and an anode 2 are laminated on the substrate 1 in this order. It is also possible to provide the organic EL element of the present invention between two substrates, at least one of which is highly transparent as described above. Also in this case, layers can be added or omitted as necessary.

  The organic EL element of the present invention can be any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. According to the organic EL device of the present invention, the light emitting layer is a mixed host composed of two host materials, and a specific compound is used as at least one of the host materials, so that the luminous efficiency is high even at a low voltage. In addition, a device with greatly improved driving stability can be obtained, and excellent performance can be exhibited in application to full-color or multi-color panels.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples, and can be implemented in various forms as long as the gist of the present invention is not exceeded. In addition, a 1st host means the host compound represented by General formula (1) or General formula (2), and a 2nd host means the host compound represented by General formula (3).

Example 1
Each thin film was laminated at a vacuum degree of 2.0 × 10 ⁻⁵ Pa by a vacuum deposition method on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 70 nm was formed. First, copper phthalocyanine (CuPC) was formed to a thickness of 30 nm on ITO as a hole injection layer. Next, 4,4-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPB) was formed to a thickness of 15 nm as a hole transport layer. Next, as the light emitting layer, compound 1-30 is used as the first host, compound 3-1 is used as the second host, and the iridium complex [iridium (III) bis (4,6-di- Fluorophenyl) -pyridinate-N, C2 ′] picolinate] (FIrpic) was co-evaporated from different deposition sources to form a light emitting layer with a thickness of 30 nm. At this time, the deposition rate ratio of the first host, the second host, and FIrpic was 47: 47: 6. Next, Alq ₃ was formed to a thickness of 25 nm as an electron transport layer. Further, on the electron transport layer, lithium fluoride (LiF) was formed to a thickness of 1.0 nm as an electron injection layer. Finally, aluminum (Al) was formed as an electrode to a thickness of 70 nm on the electron injection layer. The obtained organic EL device has a layer structure in which an electron injection layer is added between the cathode and the electron transport layer in the organic EL device shown in FIG.

Examples 2-10
In Example 1, the organic EL element was produced like Example 1 except having used the compound described in Table 1 as the 2nd host of a light emitting layer.

Examples 11-20
In Example 1, an organic EL device was produced in the same manner as in Example 1 except that Compound 1-99 was used as the first host of the light emitting layer and the compound described in Table 1 was used as the second host.
When an external power source was connected to the obtained organic EL device and a DC voltage was applied, an emission spectrum with a maximum wavelength of 475 nm was observed from any organic EL device, and it was found that light emission from FIrpic was obtained. . Table 1 shows the characteristics of the produced organic EL elements.

Comparative Examples 1-12
In Example 1, an organic EL device was produced in the same manner as in Example 1 except that the compound described in Table 2 was used alone as the light emitting layer host. The host amount was the same as the total of the first host and the second host in Example 1, and the guest amount was the same. When a power source was connected to the obtained organic EL element and a DC voltage was applied, an emission spectrum with a maximum wavelength of 475 nm was observed from any organic EL element, and it was found that light emission from FIrpic was obtained. Table 2 shows the characteristics of the produced organic EL elements.

In Tables 1 and 2, the luminance, voltage, and luminous efficiency are values at a driving current of 2.5 mA / cm ² , and the luminance half time is a value at an initial luminance of 1000 cd / m ² . Compound No. is the number given to the above chemical formula.

  From Tables 1 and 2, it can be seen that Examples 1 to 20 have improved luminance and lifetime characteristics and exhibit good characteristics.

Example 21
Each thin film was laminated at a vacuum degree of 2.0 × 10 ⁻⁵ Pa by a vacuum deposition method on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 70 nm was formed. First, CuPC was formed to a thickness of 30 nm on ITO as a hole injection layer. Next, NPB was formed to a thickness of 15 nm as a hole transport layer. Next, as the light emitting layer, compound 2-29 as the first host, compound 3-1 as the second host, and FIrpic as the light emitting layer guest are co-deposited from different vapor deposition sources, and the light emitting layer has a thickness of 30 nm. Formed. At this time, the deposition rate ratio of the first host, the second host, and FIrpic was 47: 47: 6. Next, Alq ₃ was formed to a thickness of 25 nm as an electron transport layer. Furthermore, LiF was formed to a thickness of 1.0 nm as an electron injection layer on the electron transport layer. Finally, Al was formed as an electrode to a thickness of 70 nm on the electron injection layer. The obtained organic EL device has a layer structure in which an electron injection layer is added between the cathode and the electron transport layer in the organic EL device shown in FIG.

Examples 22-30
In Example 21, an organic EL device was produced in the same manner as in Example 21 except that the compounds described in Table 1 were used as the second host of the light emitting layer.
When an external power source was connected to the obtained organic EL device and a DC voltage was applied, an emission spectrum with a maximum wavelength of 475 nm was observed from any organic EL device, and it was found that light emission from FIrpic was obtained. . Table 3 shows the characteristics of the produced organic EL elements.

Comparative Example 13
In Example 21, an organic EL device was produced in the same manner as in Example 21 except that the compounds listed in Table 3 were used alone as the light emitting layer host. The host amount was the same as the total of the first host and the second host in Example 21, and the guest amount was the same. When a power source was connected to the obtained organic EL element and a DC voltage was applied, an emission spectrum with a maximum wavelength of 475 nm was observed from any organic EL element, and it was found that light emission from FIrpic was obtained. Table 3 shows the characteristics of the produced organic EL elements.

In Table 3, the luminance, voltage, and light emission efficiency are values at a driving current of 2.5 mA / cm ² , and the luminance half time is a value at an initial luminance of 1000 cd / m ² .

  From Table 3, it can be seen that Examples 21 to 30 have improved luminance and lifetime characteristics and show good characteristics.

Example 31
Each thin film was laminated at a vacuum degree of 4.0 × 10 ⁻⁴ Pa by a vacuum deposition method on a glass substrate on which an anode made of ITO having a thickness of 150 nm was formed. First, CuPc was formed to a thickness of 20 nm on ITO as a hole injection layer, and then NPB was formed to a thickness of 20 nm as a hole transport layer. Next, as the light emitting layer, compound 1-2 as the first host, compound 3-1 as the second host, and tris (2-phenylpyridine) iridium (III) (Ir (PPy) ₃ ) as the light emitting layer guest, respectively. Co-deposited from different deposition sources and formed to a thickness of 30 nm. At this time, the deposition rate ratio of the first host, the second host, and Ir (PPy) ₃ was 47: 47: 6. Next, aluminum (III) bis (2-methyl-8-quinolinato) 4-phenylphenolate (BAlq) was formed to a thickness of 10 nm as a hole blocking layer. Next, Alq ₃ was formed to a thickness of 40 nm as an electron transport layer. Further, LiF was formed to a thickness of 0.5 nm as an electron injection layer on the electron transport layer. Finally, Al was formed as a cathode with a thickness of 100 nm on the electron injection layer, and an organic EL device was produced.
When an external power source was connected to the obtained organic EL element and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed, and it was found that light emission from Ir (PPy) ₃ was obtained. Table 4 shows the characteristics (luminance, voltage, external quantum efficiency, and luminance half-life) of the organic EL element produced.

Examples 32-40
In Example 31, an organic EL device was produced in the same manner as in Example 31 except that the compounds described in Table 4 were used as the second host of the light emitting layer.

Examples 41-50
In Example 31, an organic EL device was produced in the same manner as in Example 31, except that Compound 1-3 was used as the first host of the light emitting layer and the compound described in Table 1 was used as the second host.
When an external power source was connected to the obtained organic EL element and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed from any organic EL element, and light emission from Ir (PPy) ₃ was obtained. I understood. Table 4 shows the characteristics of the produced organic EL elements.

Comparative Examples 14-25
In Example 31, an organic EL device was produced in the same manner as in Example 31 except that the compound described in Table 5 was used alone as the light emitting layer host. The host amount was the same as the sum of the first host and the second host in Example 31, and the guest amount was the same. When a power source was connected to the obtained organic EL element and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed from any organic EL element, and light emission from Ir (PPy) ₃ was obtained. all right. Table 5 shows the characteristics of the produced organic EL elements.

In Tables 4 and 5, the luminance, voltage, and luminous efficiency are values at a driving current of 20 mA / cm ² , and the luminance half time is a value at an initial luminance of 1000 cd / m ² .

  From Tables 4 and 5, it can be seen that Examples 31 to 50 have improved luminance and life characteristics and show good characteristics.

Example 51
Each thin film was laminated at a vacuum degree of 4.0 × 10 ⁻⁴ Pa by a vacuum deposition method on a glass substrate on which an anode made of ITO having a thickness of 150 nm was formed. First, CuPc was formed to a thickness of 20 nm on ITO as a hole injection layer, and then NPB was formed to a thickness of 20 nm as a hole transport layer. Next, as a light emitting layer, the compound 2-5 as a first host, the compound 3-1 as a second host, and Ir (PPy) ₃ as a light emitting layer guest were co-deposited from different vapor deposition sources, respectively, to a thickness of 30 nm. Formed. At this time, the deposition rate ratio of the first host, the second host, and Ir (PPy) ₃ was 47: 47: 6. Next, BAlq was formed to a thickness of 10 nm as a hole blocking layer. Next, Alq ₃ was formed to a thickness of 40 nm as an electron transport layer. Further, LiF was formed to a thickness of 0.5 nm as an electron injection layer on the electron transport layer. Finally, Al was formed as a cathode with a thickness of 100 nm on the electron injection layer, and an organic EL device was produced.
When an external power source was connected to the obtained organic EL element and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed, and it was found that light emission from Ir (PPy) ₃ was obtained. Table 6 shows the characteristics of the produced organic EL elements.

Examples 52-60
In Example 51, an organic EL device was produced in the same manner as in Example 51 except that the compounds described in Table 6 were used as the light emitting layer second host.

Examples 61-70
In Example 51, an organic EL device was produced in the same manner as in Example 51 except that Compound 2-29 was used as the first host of the light emitting layer and the compound described in Table 6 was used as the second host (obtained). When an external power source was connected to the organic EL element and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed from any organic EL element, indicating that light emission from Ir (PPy) ₃ was obtained. It was.

Comparative Examples 26-27
In Example 51, an organic EL device was produced in the same manner as in Example 51 except that the compound described in Table 6 was used alone as the light emitting layer host. The host amount was the same as the total of the first host and the two hosts in Example 51. When an external power source was connected to the obtained organic EL element and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed from any organic EL element, and light emission from Ir (PPy) ₃ was obtained. I understood.

Table 6 shows the luminance, external quantum efficiency, and luminance half-life of the organic EL elements produced. The luminance and the external quantum efficiency are values at a driving current of 20 mA / cm ² , and the luminance half time is a value at an initial luminance of 1000 cd / m ² .

  From Table 6, it can be seen that Examples 51 to 70 have improved luminance and life characteristics and show good characteristics.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Electron injection layer 8 Cathode

Claims (10)

In an organic electroluminescent device including one or more light-emitting layers between an anode and a cathode facing each other, at least one light-emitting layer contains a host material and a light-emitting dopant, and the host material comprises (i) An organic electroluminescent device comprising a compound represented by formula (1) or (2) and (ii) a compound represented by the following general formula (3).

(Here, ring a, ring c, and ring c ′ independently represent an aromatic ring represented by the formula (a1) fused with two adjacent rings at an arbitrary position, and X ¹ represents C—R or N. Show
Ring b, Ring d, and Ring d ′ each independently represent a heterocyclic ring represented by Formula (b1) that is condensed with two adjacent rings at any position;
Ar ¹ independently represents a p + 1-valent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms,
Z is a divalent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or 2 to 10 linked aromatic rings. A substituted or unsubstituted linked aromatic group,
L ¹ is independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or an aromatic ring having 2 to 10 carbon atoms. A substituted or unsubstituted linked aromatic group formed by linking;
p is independently the number of substitutions and represents an integer of 0 to 7,
R and R ^{1 to} R ⁷ are independently hydrogen, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 38 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, carbon A dialkylamino group having 2 to 40 carbon atoms, a diarylamino group having 12 to 44 carbon atoms, a diaralkylamino group having 14 to 76 carbon atoms, an acyl group having 2 to 20 carbon atoms, an acyloxy group having 2 to 20 carbon atoms, and a carbon number An alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 20 carbon atoms, an alkoxycarbonyloxy group having 2 to 20 carbon atoms, an alkylsulfonyl group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 30 carbon atoms, Or an aromatic heterocyclic group having 3 to 18 carbon atoms, and when it is a group other than hydrogen, it may have a substituent, and when R ¹ , R ² , R ^{4 to} R ⁷ are phenyl groups, , Aromatic ring substituted by phenyl group A condensed ring may be formed.
In Ar ¹ , Z, and L ¹ , when the aromatic hydrocarbon group, the aromatic hydrocarbon group, or the linked aromatic group has a substituent, the substituent is an alkyl group having 1 to 12 carbon atoms, or 1 to 12 carbon atoms. Or an acyl group having 2 to 13 carbon atoms, and in R and R ^{1 to} R ⁷ , the substituent in the case of having a substituent is an alkyl group having 1 to 12 carbon atoms, or a carbon atom having 1 to 12 carbon atoms. It is an alkoxy group, an acyl group having 2 to 13 carbon atoms, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 18 carbon atoms. These substituents may be the same or different. )

(Here, ring A independently represents a C ₂ B ₁₀ H ₁₀ divalent carborane group represented by formula (c1) or formula (d1)).
s is the number of repetitions and is an integer of 0 to 1, n is the number of substitutions and is an integer of 0 to 2. However, when n = 1, s = 1.
L ² is independently a single bond, an n + 1-valent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or an aromatic thereof. A substituted or unsubstituted linked aromatic group constituted by connecting 2 to 6 group rings is represented. However, when n = 1, it is a group or a single bond containing at least one aromatic heterocyclic group.
L ³ is independently a single bond, a divalent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or an aromatic thereof. A substituted or unsubstituted linked aromatic group constituted by connecting 2 to 6 group rings is represented.
L ⁴ is hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an acyl group having 2 to 13 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted group Alternatively, it represents an unsubstituted aromatic hydrocarbon group having 3 to 30 carbon atoms, or a substituted or unsubstituted linked aromatic group constituted by connecting 2 to 6 these aromatic rings.
In L ² , L ³ and L ⁴ , the substituent when the aromatic hydrocarbon group, aromatic hydrocarbon group or linked aromatic group has a substituent is an alkyl group having 1 to 12 carbon atoms, 1 to 1 carbon atoms 12 alkoxy groups or C2-C13 acyl groups, which may be substituted plurally, and the plural substituents may be the same or different, and L ² − present at the terminal. H and L ³ —H may be an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an acyl group having 2 to 13 carbon atoms. ) The organic electroluminescent element according to claim ¹ , wherein X ^{1 in the} general formulas (1) and (2) is C—R. The organic electroluminescent device according to claim 1 or 2, wherein at least one of Ar ^{1 in} the general formula (1) or Z in the general formula (2) is an aromatic heterocyclic group having 3 to 16 carbon atoms.   In general formula (3), n is an integer of 0 or 1, The organic electroluminescent element in any one of Claims 1-3. The organic electroluminescent element according to claim 1, wherein in general formula (3), ring A is a C ₂ B ₁₀ H ₁₀ divalent carborane group represented by formula (c1). In General Formula (3), L ³ is a divalent substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or these The organic electroluminescent device according to any one of claims 1 to 5, which is a substituted or unsubstituted linked aromatic group constituted by connecting 2 to 5 aromatic rings. In General Formula (3), L ² is an n + 1 valent substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or a substituted or constituted of these aromatic rings linked to 2 to 5 or The organic electroluminescent element according to claim 1, which is an unsubstituted linked aromatic group.   The organic electroluminescent element according to claim 1, wherein in general formula (3), n is an integer of 0.   The organic electroluminescent device according to any one of claims 1 to 6, wherein the host material comprises (i) a compound represented by the general formula (1) and (ii) a compound represented by the general formula (3). .   The luminescent dopant is an organometallic complex containing at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold. The organic electroluminescent element as described.

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