JP5002758B2 - Organic EL device - Google Patents

Description

  The present invention relates to an organic EL (electroluminescence) device, and more particularly to a device that emits light by applying an electric field to a thin film made of an organic compound.

  The organic EL element has a configuration in which a thin film containing a fluorescent organic compound is sandwiched between an electron injection electrode (cathode) and a hole injection electrode (anode), and electrons and holes are injected into the thin film to be recombined. This is an element that emits light by utilizing the emission of light (fluorescence / phosphorescence) when excitons are generated by the excitons and the excitons are deactivated.

  In the organic EL element, in addition to the light emitting layer made of a thin film containing a fluorescent organic compound, the electrons or holes injected into the light emitting layer are optimized between the electrodes to improve the light emission efficiency. As an injection and / or transport layer, a layer called an electron injection layer, an electron transport layer, or an electron transport layer, or as a hole injection and / or transport layer, a hole injection layer, a hole transport layer, or a hole injection transport A layer called a layer is generally provided.

  Examples of electron injection / transport materials include metal complex compounds (see, for example, Patent Document 1) and heterocyclic compounds. Examples of heterocyclic compounds include phenanthroline-based compounds (for example, see Patent Documents 2 and 3), indole ( Pyrrole) compounds (for example, see Patent Documents 4 to 7), quinoxaline compounds (for example, see Patent Documents 8 to 12), oxadiazole compounds (for example, see Patent Documents 13 to 19), carbazole compounds (for example, In addition, examples using a layer doped with a donor dopant or an alkali metal in these electron injecting and transporting materials (see, for example, Patent Documents 22 to 24), Examples in which a hydrocarbon compound is contained (for example, see Patent Documents 25 and 26) are disclosed.

  Also disclosed are examples in which two or more electron injection / transport layers are provided (for example, see Patent Document 27) and examples in which an adhesion improving layer is provided between the electron injection layer and the electron injection cathode (for example, see Patent Document 28). In some cases, the material used for the adhesion improving layer is limited by the surface energy.

  On the other hand, with respect to the light-emitting layer, as a means for improving the efficiency and extending the life, many methods for doping a small amount of a fluorescent dye having a high fluorescence quantum yield have been reported and disclosed. For example, a red light-emitting element in which a perylene derivative is doped with an organometallic complex such as tris (8-quinolinolato) aluminum (Alq3) or an arylamine, oxadiazole, carbazole derivative, or the like is disclosed (for example, Patent Documents 29 and 30). reference). In addition, an example is also disclosed in which a preferable combination of a host and a dopant is limited by an ionization potential (IP) and an electron affinity (Ea) in order to obtain a highly efficient device (see, for example, Patent Document 31).

  However, in the prior art as described above, it is possible to inject electrons more efficiently than the cathode by using a material having a good electron injecting property for the electron injecting and transporting layer. Many have low mobility (electron transportability). When the carrier mobility (electron transport property) of the electron transport layer is low, a strong electric field is required to move the carriers in the electron transport layer to the light emitting layer. As a result, the driving voltage of the device is increased, and the light emission of the device It has become a cause of lowering efficiency.

  In addition, in order to obtain optically optimum external extraction efficiency, it is necessary to control the distance between the light emitting layer and the cathode, and the distance between the light emitting layer and the cathode is controlled by changing the film thickness of the electron transport layer. be able to. However, since the carrier transport property of the electron transport layer is low in the conventional device, the drive voltage changes greatly when the thickness of the electron transport layer is changed, and both optimization of the optical external extraction efficiency and low voltage drive are compatible. It was difficult. Furthermore, when the carrier mobility (electron transportability) of the electron transport layer is small, the carrier concentration of the electron transport layer increases and holes enter the electron transport layer, so that the carriers recombine in the electron transport layer. In some cases, the color purity obtained when the electron transport material emits light and only the light emitting layer emits light cannot be obtained. In addition, recombination of carriers other than the light emitting layer adversely affects the device lifetime.

  In addition, there are many polar molecules with a large dipole moment in materials with high electron-injection properties, and when these molecules come into contact with the light-emitting layer, interaction with the light-emitting material may occur and the exciton energy may be lost. .

  On the other hand, materials having high electron transporting properties do not have both adhesion to the electron injection cathode and electron injection properties. When such materials are used for the electron injection transport layer, uniform light emission is often not obtained. .

  In addition, even when the functions of the electron transport layer and the electron injection layer are separated, a combination of materials that optimally performs the respective functions has not been found, and sufficient device characteristics have not been obtained.

  Further, with respect to the light emitting layer, in the conventional technique, the concentration quenching of the light emitting material can be suppressed by doping to improve the efficiency, and the combination of the host and the dopant is limited by the IP and Ea values of those materials. It is also possible to improve the recombination efficiency by trapping carriers.

  However, when the carrier mobility (electron transport property) of the host material is small, the carrier in the light emitting layer is localized in the host material and the probability of recombination on the host material molecule increases. In this case, in order for the dopant to emit light, energy transfer from the host in the excited state to the dopant is necessary. If the energy transfer efficiency in the process is low, a loss occurs. In addition, the balance with the hole transportability may not be achieved, and the holes may penetrate to the electron transport layer, resulting in a decrease in the light emission efficiency of the device. In addition, when the energy transfer from the host to the dopant is insufficient, the host itself emits light, which may deteriorate the color purity of the device.

  Therefore, improvement of the above points is required.

JP-A-5-214333 Japanese Patent Laid-Open No. 7-82551 JP-A-5-331459 JP-A-5-339565 JP 2000-91075 A Japanese Patent Laid-Open No. 10-237442 JP 2003-17271 A Japanese Patent Laid-Open No. 9-3342 JP-A-9-13025 JP-A-7-102250 JP-A-6-207169 JP-A-9-188874 JP 2000-281663 A JP-A-9-104679 JP-A-8-193075 JP-A-8-3149 JP-A-8-3148 JP-A-7-179394 JP-A-6-140156 JP-A-8-60144 JP-A-8-88083 Japanese Patent No. 2926845 Japanese Patent No. 2846503 Japanese Patent Laid-Open No. 4-297076 JP 2000-344691 A JP-A-4-335087 JP 2000-340364 A JP-A-6-330034 Japanese Patent Laid-Open No. 10-330295 JP-A-11-233261 Japanese Patent No. 3069139

  An object of the present invention is to provide an organic EL device having high efficiency, excellent durability, and high color purity.

The above object is achieved by the present invention described below.
(1) In an organic EL device having a structure in which at least one light emitting layer, an electron transport layer, and an electron injection layer are sequentially laminated from the anode side, the electron transport layer contains a naphthacene derivative and / or an anthracene derivative Organic EL element to be used.
(2) The organic EL device according to (1) above, which has at least one hole injecting and transporting layer on the anode side of the light emitting layer.
(3) The organic EL device according to (1) or (2), wherein the electron injection layer contains an organic compound.
(4) The organic EL element according to any one of (1) to (3), wherein the electron injection layer has a thickness of 0.6 to 20 nm.
(5) The organic EL device according to (4) above, wherein the electron injection layer has a thickness of 1 to 10 nm.
(6) The organic EL device according to any one of (1) to (5), wherein the electron injection layer contains a heterocyclic compound.
(7) The organic EL device according to any one of (1) to (6), wherein the electron injection layer contains a nitrogen-containing heterocyclic compound.
(8) The electron injection layer is 1,10-phenanthroline, 1,9-phenanthroline, 1,8-phenanthroline, 1,7-phenanthroline, 2,9-phenanthroline, 2,8-phenanthroline, 2,7-phenanthroline, 3 , 8-phenanthroline, 3,7-phenanthroline, 4,7-phenanthroline and phenanthroline derivatives having one or more of these phenanthroline skeletons in the molecule, the above (1) to (7) Any organic EL element.
(9) The organic EL device according to (8), wherein the phenanthroline or phenanthroline derivative contained in the electron injection layer is represented by the following formula (1a) or (1b).

[In Formula (1a), Y _{2 to} Y ₉ may be the same or different, and each of hydrogen, aryl group, alkyl group, aralkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, and alkenyl group. Represents an amino group or a heterocyclic group, and two or more adjacent groups thereof may be bonded to each other to form a ring. In the formula (1b), A and B may be the same or different and each represents a group represented by the formula (1c), and L represents a single bond or a divalent linking group. In formula (1c), Y _{12 to} Y ₁₉ may be the same as or different from each other, and have the same meaning as Y ₂ to Y ₉ in formula (1a). However, one of Y ₁₂ to Y ₁₉ in the formula (1c) constitutes L, and Y ₁₂ to Y ₁₉ constituting L may be the same or different in A and B. Good. ]
(10) The organic EL element according to any one of (1) to (9), wherein the electron transport layer contains a naphthacene derivative.
(11) The organic EL device according to (10), wherein the naphthacene derivative contained in the electron transport layer is represented by the following formula (2).

[In the formula (2), Q ¹⁰ , Q ²⁰ , Q ³⁰ , Q ⁴⁰ , Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ , Q ⁸⁰ , Q ¹¹⁰ , Q ¹²⁰ , Q ¹³⁰ and Q ¹⁴⁰ are hydrogen, an alkyl group, An aryl group, an amino group, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an alkenyl group, an aralkyl group or a heterocyclic group, which may be the same or different. ]
(12) At least one or more of Q ¹⁰ , Q ²⁰ , Q ³⁰ , Q ⁴⁰ , Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ and Q ^{80 in} the naphthacene derivative represented by the formula (2) contained in the electron transport layer is The organic EL device according to the above (11), which is an aryl group.
(13) The above (11) or (12), wherein at least one of Q ¹⁰ , Q ²⁰ , Q ³⁰ and Q ^{40 in} the naphthacene derivative represented by the formula (2) contained in the electron transport layer is an aryl group Organic EL element.
(14) The organic EL device according to any one of (9) to (13), wherein the naphthacene derivative contained in the electron transport layer is represented by the following formula (2a).

[In the formula (2a), Q ^{5 to} Q ⁸ and Q ^{11 to} Q ¹⁶ are each hydrogen, alkyl group, aryl group, amino group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkenyl group, aralkyl group or Represents a heterocyclic group, which may be the same or different. Q ^{21 to} Q ²⁵ and Q ^{51 to} Q ⁵⁵ each represent hydrogen, an alkyl group, an aryl group, an amino group, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an alkenyl group, an aralkyl group, or a heterocyclic group, These may be the same or different, and two or more adjacent ones may be bonded to each other to form a ring. ]
(15) The organic EL device according to any one of (9) to (14), wherein the naphthacene derivative contained in the electron transport layer is a hydrocarbon compound.
(16) The organic EL device according to any one of (1) to (15), wherein the light-emitting layer contains a host material and a dopant material, and the host material contains a naphthacene derivative.
(17) The organic EL device according to (16), wherein the naphthacene derivative contained in the light emitting layer is represented by the following formula (2).

[In the formula (2), Q ¹⁰ , Q ²⁰ , Q ³⁰ , Q ⁴⁰ , Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ , Q ⁸⁰ , Q ¹¹⁰ , Q ¹²⁰ , Q ¹³⁰ and Q ¹⁴⁰ are hydrogen, alkyl group, An aryl group, an amino group, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an alkenyl group, an aralkyl group or a heterocyclic group, which may be the same or different. ]
(18) In the naphthacene derivative represented by the formula (2) contained in the light emitting layer, at least one of Q ¹⁰ , Q ²⁰ , Q ³⁰ , Q ⁴⁰ , Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ and Q ⁸⁰ is aryl. The organic EL device according to (17), which is a group.
(19) In the above (17) or (18), at least one of Q ¹⁰ , Q ²⁰ , Q ³⁰ and Q ^{40 in} the naphthacene derivative represented by the formula (2) contained in the light emitting layer is an aryl group Organic EL element.
(20) The organic EL device according to any one of (16) to (19), wherein the naphthacene derivative contained in the host material of the light emitting layer is represented by the following formula (2a).

[In the formula (2a), Q ^{5 to} Q ⁸ and Q ^{11 to} Q ¹⁶ are each hydrogen, alkyl group, aryl group, amino group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkenyl group, aralkyl group or Represents a heterocyclic group, which may be the same or different. Q ^{21 to} Q ²⁵ and Q ^{51 to} Q ⁵⁵ each represent hydrogen, an alkyl group, an aryl group, an amino group, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an alkenyl group, an aralkyl group, or a heterocyclic group, These may be the same or different, and two or more adjacent ones may be bonded to each other to form a ring. ]
(21) The organic EL device according to any one of (16) to (20), wherein the naphthacene derivative contained in the light emitting layer is a hydrocarbon compound.
(22) The organic EL device according to any one of (16) to (21), wherein the dopant material of the light emitting layer contains a fluoranthene derivative.
(23) The organic EL device according to (22), wherein the fluoranthene derivative is an indenoperylene derivative represented by the following formula (3a).

[In the formula (3a), Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ and Z ₂₀ are hydrogen, halogen, alkyl group, alkoxy group, alkylthio group, alkenyl group, alkenyl, respectively. Oxy group, alkenylthio group, aromatic ring-containing alkyl group, aromatic ring-containing alkyloxy group, aromatic ring-containing alkylthio group, aromatic ring group, aromatic ring oxy group, aromatic ring thio group, aromatic ring alkenyl group, alkenyl aromatic ring group, An amino group, a cyano group, a hydroxyl group, —COOR ₁ (where R ₁ represents hydrogen, an alkyl group, an alkenyl group, an aromatic ring-containing alkyl group or an aromatic ring group), —COR ₂ (where R ₂ is a hydrogen atom) , alkyl group, alkenyl group, aromatic ring-containing alkyl group, an aromatic group or an amino group), or -OCOR ₃ (wherein, _{R 3} is an alkyl group, alkenyl Group, represents an aromatic ring-containing alkyl group or aromatic ring group), _further, adjacent groups among _{Z 1 ~Z 6, Z 9,} Z 10, Z 11 ~Z 16, Z 19, Z 20 is They may be bonded to each other to form a ring with substituted carbon atoms. ]
(24) The organic EL device of any one of the electron transporting mu _a defined below the electron-transporting layer is 80 nm / V or more (1) to (23) (Note that the electron transporting mu _a is the In the organic EL element of (1), the parameter is defined as follows according to a change in driving voltage required to flow a current of 100 mA / cm ² when the thickness of the electron transport layer is changed. When the driving voltage (V) at the time of driving 100 mA / cm ² when the thickness (nm) of the transport layer is d ₁ and d ₂ (where d ₁ > d ₂ ) is V ₁ and V ₂ , respectively. _{μ a = (d 1 -d 2} ) is represented by the _{/ (V 1 -V 2))} .
(25) The organic EL device according to any one of (1) to (24), wherein a difference in ionization potential between the electron transport layer and the light emitting layer is 0.1 eV or less.
(26) The organic EL device according to any one of the above (1) to (25), wherein the material used for the electron transport layer has a dipole moment value of 1.0 Debye or less.
(27) The organic EL device according to any one of (16) to (26), wherein the light emitting layer contains a host material and a dopant material, and the value of the dipole moment of the host material is 1.0 Debye or less.

  In the configuration of the present invention, a material excellent in adhesion to the electrode and the electron transport layer is used for the electron injection layer, and a material having a high electron transport property is used for the electron transport layer, so that the electron transport to the light emitting layer is efficient. Thus, low voltage driving can be achieved, and high luminous efficiency with respect to current density can be obtained. Further, since the voltage change when the film thickness of the electron transport layer is changed is small and the optical film thickness can be adjusted without increasing the voltage, high external extraction efficiency can be obtained. Furthermore, a high-color purity device that hardly emits light from the electron transport layer can be obtained. In addition, a highly durable and long-life element can be obtained in which the drive voltage rise and the brightness drop during continuous driving are extremely small.

Hereinafter, the present invention will be described in detail.
The organic EL device of the present invention has an anode, and at least one layer, preferably a hole injecting and transporting layer, a light emitting layer, an electron transporting layer, and an electron injecting layer are sequentially stacked from the anode (hole injecting electrode) side. A cathode (electron injection electrode) is provided on the electron injection layer. Thus, by providing the electron transport layer and the electron injection layer separately, it is possible to select the best material having characteristics suitable for each layer. Therefore, in the present invention, the electron transport layer contains a naphthacene derivative and / or an anthracene derivative, and the electron injection layer contains a material excellent in adhesion to the cathode material or the electron transport layer. The injection layer contains an organic compound.

  As described above, in the present invention, a high-efficiency organic EL device can be obtained by defining a device structure, selecting a suitable compound as a material for an electron injection layer and an electron transport layer, and selecting a combination thereof. Obtainable. That is, according to the configuration of the present invention, the electric field strength applied to the electron transport layer can be reduced and low voltage driving can be achieved. In addition, this can reduce the voltage change when the thickness of the electron transport layer is changed, so that the optical film thickness can be adjusted without changing the voltage to obtain the optimum external extraction efficiency of light emission. And a highly efficient organic EL device can be obtained. Furthermore, since the carrier (electron) concentration in the electron transport layer can be lowered, the penetration of holes into the electron transport layer can be prevented, and the generation of excitons in the electron transport layer can be suppressed. Thus, an organic EL device having a high color purity with almost no emission can be obtained. For the same reason, the lifetime of the element can be extended.

  In particular, by using a nonpolar molecule having a small dipole moment as a material for the electron transport layer, an electron transport layer having a high electron transport property as described above can be obtained.

  In addition, by using nonpolar molecules in the electron transport layer, interaction with the light emitting material at the light emitting layer interface can be suppressed, and thus it is considered that there is an effect of preventing energy loss of excitons at the interface.

  On the other hand, the light emitting layer used in combination with such an electron transport layer preferably contains a host material and a dopant material, and a naphthacene derivative preferably used as a material for the electron transport layer is used as the host material. preferable.

  As described above, in the present invention, a material having a high electron transporting property is used as the host material of the light-emitting layer, and a material capable of trapping electrons in the host material is used as the dopant material. Can be localized in the trap order of the dopant with high probability, and an organic EL element with high efficiency and high color purity can be obtained. Further, it is preferable that the host material of the light emitting layer has a small dipole moment and a high electron transport property. That is, by using a material having a high electron transporting property as the host material of the light emitting layer and doping a compound having a higher electron affinity than the host material, the probability that the carriers (electrons) in the light emitting layer are localized in the dopant molecules is increased. It is possible to improve the efficiency, and the dopant excitons are efficiently generated, and the host excitons are hardly generated. Therefore, an organic EL element having high efficiency and color purity can be obtained. In addition, by using a non-polar molecule as a host material, interaction with the dopant material can be suppressed, so that it is considered that there is an effect of preventing efficiency and color purity from being lowered due to the interaction.

  The electron transport layer in the present invention contains a naphthacene derivative (including naphthacene) and / or an anthracene derivative.

  As an anthracene derivative, what is represented by following formula (4) is preferable.

In formula (4), n ₁₀₁ is 1 or 2. A ₁₀₁ represents a monophenylanthryl group or a diphenylanthryl group, and when n ₁₀₁ is 2, these may be the same or different. L ₁₀₁ represents hydrogen, a single bond or a divalent linking group.

The monophenylanthryl group or diphenylanthryl group represented by A ₁₀₁ may be unsubstituted or may have a substituent. In the case of having a substituent, examples of the substituent include an alkyl group, an aryl group, and a complex. A cyclic group, an alkoxy group, an aryloxy group, an amino group and the like can be mentioned, and these substituents may be further substituted. These substituents will be described later, but an aryl group is particularly preferable. The substitution position of such a substituent is not particularly limited, but is preferably not a anthracene ring but a phenyl group bonded to the anthracene ring.

  Moreover, it is preferable that the bonding position of the phenyl group in the anthracene ring is the 9th or 10th position of the anthracene ring.

In Formula (4), L ₁₀₁ represents hydrogen, a single bond or a divalent linking group, and the divalent linking group represented by L ₁₀₁ is preferably an arylene group in which an alkylene group or the like may be interposed. Such an arylene group will be described later.

  Among the phenylanthracene derivatives represented by the formula (4), those represented by the formula (4a) and the formula (4b) are preferable.

Describing the formula (4a), in the formula (4a), M ₁ and M ₂ each represents an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group or a heterocyclic group, particularly preferably An aryl group.

The alkyl group represented by M ₁ and M ₂ may have a substituent, may be linear or branched, and has 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms. A substituted or unsubstituted alkyl group is preferred. Particularly, an unsubstituted alkyl group having 1 to 4 carbon atoms is preferable, and specifically, a methyl group, an ethyl group, a (n-, i-) propyl group, (n-, i-, s-, t-) butyl. Groups and the like.

The cycloalkyl group represented by M ₁ and M ₂ may have a substituent, and examples thereof include a cyclohexyl group and a cyclopentyl group.

The aryl group represented by M ₁ and M ₂ is preferably an aryl group having 6 to 20 carbon atoms, and may further have a substituent such as a phenyl group or a tolyl group. Specific examples include a phenyl group, (o-, m-, p-) tolyl group, pyrenyl group, naphthyl group, anthryl group, biphenyl group, phenylanthryl group, and tolylanthryl group.

The alkenyl group represented by M ₁ and M ₂ is preferably one having a total carbon number of 6 to 50 and may be unsubstituted, but may have a substituent. It is preferable to have it. In this case, the substituent is preferably an aryl group such as a phenyl group. Specific examples include a triphenyl vinyl group, a tolyl vinyl group, and a tribiphenyl vinyl group.

As the alkoxy group represented by M ₁ or M ₂ , an alkyl group having 1 to 6 carbon atoms is preferable, and specific examples include a methoxy group and an ethoxy group. The alkoxy group may be further substituted.

The aryloxy group represented by M ₁ and M ₂ may have a substituent, and examples thereof include a phenoxy group.

The amino group represented by M ₁ or M ₂ may be unsubstituted or may have a substituent, but preferably has a substituent. In this case, the substituent is an alkyl group (methyl group, ethyl Group), an aryl group (phenyl group, etc.), and the like. Specific examples include a diethylamino group, a diphenylamino group, and a di (m-tolyl) amino group.

Examples of the heterocyclic group represented by M ₁ and M ₂ include a bipyridyl group, a pyrimidyl group, a quinolyl group, a pyridyl group, a thienyl group, a furyl group, and an oxadiazoyl group. These may have a substituent such as a methyl group or a phenyl group.

In the formula (4a), q1 and q2 each represent 0 or an integer of 1 to 5, and particularly preferably 0 or 1. When q1 and q2 are each an integer of 1 to 5, particularly 1 or 2, M ₁ and M ₂ are each preferably an aryl group.

In the formula (4a), it may be one that is different even in the same and _{M 1} and _{M 2,} when the _{M 1} and _{M 2} there are a plurality each, _{M 1} each other, _{M 2} each other in each different even in the same M ₁ or M ₂ may be bonded to each other to form a ring such as a benzene ring, and a ring is also preferable.

n has the same meaning as n _{101 in} formula (4).

In the formula (4a), L ₁₀ represents hydrogen, a single bond or an arylene group. The arylene group represented by L ₁₀ may have a substituent, but is preferably unsubstituted, specifically, other than a normal arylene group such as a phenylene group, a biphenylene group, and an anthrylene group. Examples include those in which two or more arylene groups are directly linked. L ₁₀ is preferably a single bond, a p-phenylene group, a 4,4′-biphenylene group, or the like.

The arylene group represented by L ₁₀ may have a substituent, and two or more arylene groups may be linked via an alkylene group, —O—, —S—, or —NR—. You may do. Here, R represents an alkyl group or an aryl group. Examples of the alkyl group include a methyl group and an ethyl group, and examples of the aryl group include a phenyl group. Among these, an aryl group is preferable, and in addition to the above phenyl group, A ₁₀₁ may be used, and further, A ₁₀₁ may be substituted on the phenyl group. The alkylene group is preferably a methylene group or an ethylene group.

  Specific examples of such an arylene group are shown below.

Next, formula (4b) will be described. In formula (4b), M ₃ and M ₄ are M ₁ and M ₂ in formula (4a), q3 and q4 are q1 and q2 in formula (4a), and Further, L ₂₀ has the same meaning as L ₁₀ in formula (4a), and the preferred ones are also the same.

In the formula (4b), may be one that is different even in the same and _{M 3} and _{M 4, when M 3} and _{M 4} there are a plurality each, _{M 3} each other, _{M 4} each other, different from in each identical M ₃ or M ₄ may be bonded to form a ring such as a benzene ring, and it is also preferable when a ring is formed.

Although the compound represented by Formula (4a) and Formula (4b) is illustrated below, this invention is not limited to these. Chemical formula 17, chemical formula 19, chemical formula 21, chemical formula 23, chemical formula 25, chemical formula 27, chemical formula 29, chemical formula 32 show general formulas, chemical formula 18, chemical formula 20, chemical formula 22, chemical formula 24, chemical formula 26, chemical formula 28, chemical formula 28. Specific examples corresponding to each of 30, 31, and 33 are represented by combinations of M _{11 to} M ₁₅ , M _{21 to} M _25, or M _{31 to} M ₃₅ , and M _{41 to} M ₄₅ .

  As a naphthacene derivative used for this invention, what is represented by following formula (2) is preferable.

In formula (2), Q ¹⁰ , Q ²⁰ , Q ³⁰ , Q ⁴⁰ , Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ , Q ⁸⁰ , Q ¹¹⁰ , Q ¹²⁰ , Q ¹³⁰ and Q ¹⁴⁰ are hydrogen, alkyl group, aryl, respectively. Represents a group, amino group, alkoxy group, alkylthio group, aryloxy group, arylthio group, alkenyl group, aralkyl group or heterocyclic group, which may be the same or different.

In formula (2), Q ¹⁰ , Q ²⁰ , Q ³⁰ and Q ⁴⁰ (collectively represented as Q ^{10 to} Q ⁴⁰ ) are any of hydrogen, an alkyl group, an aryl group, an amino group, a heterocyclic group and an alkenyl group. It is preferable that More preferably, it is an aryl group. Particularly preferred are those wherein Q ¹⁰ and Q ⁴⁰ are hydrogen and Q ²⁰ and Q ³⁰ are the above substituents.

Q ¹⁰ and Q ⁴⁰ , and Q ²⁰ and Q ³⁰ are preferably the same, but may be different.

Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ and Q ⁸⁰ (collectively represented as Q ^{50 to} Q ⁸⁰ ) are preferably any of hydrogen, an alkyl group, an aryl group, an amino group, an alkenyl group and a heterocyclic group, particularly preferably Is hydrogen or an aryl group. Further, Q ⁵⁰ and Q ⁶⁰ , and Q ⁷⁰ and Q ⁸⁰ are preferably the same, but may be different. Further, Q ¹¹⁰ , Q ¹²⁰ , Q ¹³⁰ and Q ¹⁴⁰ (collectively represented as Q ^{110 to} Q ¹⁴⁰ ) are preferably hydrogen.

The alkyl group represented by Q ^{10 to} Q ⁴⁰ , Q ^{50 to} Q ⁸⁰ , and Q ^{110 to} Q ¹⁴⁰ may have a substituent, preferably has 1 to 6 carbon atoms, and is linear. Or it may have a branch. Preferable specific examples of the alkyl group include a methyl group, an ethyl group, a (n, i) -propyl group, a (n, i, sec, tert) -butyl group, a (n, i, neo, tert) -pentyl group, and the like. Is mentioned.

The aryl group represented by Q ^{10 to} Q ⁴⁰ , Q ^{50 to} Q ⁸⁰ , and Q ^{110 to} Q ¹⁴⁰ may be monocyclic or polycyclic, and includes condensed rings and ring assemblies. The total carbon number is preferably 6 to 30, and may have a substituent. The aryl group represented by ^{Q 10 ~Q 40, Q 50 ~Q} 80, Q 110 ~Q 140, preferably a phenyl group, (o-, m-, p-) tolyl group, pyrenyl group, perylenyl group, Coronenyl group, (1- and 2-) naphthyl group, anthryl group, (o-, m-, p-) biphenylyl group, terphenyl group, phenanthryl group and the like.

The amino group represented by Q ^{10 to} Q ⁴⁰ , Q ^{50 to} Q ⁸⁰ , and Q ^{110 to} Q ¹⁴⁰ may be unsubstituted, but preferably has a substituent, an alkylamino group, an arylamino group , An aralkylamino group or the like may be used. These preferably have an aliphatic group having 1 to 6 carbon atoms in total and / or an aromatic carbocyclic ring having 1 to 4 rings. Specific examples include a dimethylamino group, a diethylamino group, a dibutylamino group, a diphenylamino group, a ditolylamino group, a bisdiphenylylamino group, and a bisnaphthylamino group.

The heterocyclic group represented by Q ^{10 to} Q ⁴⁰ , Q ^{50 to} Q ⁸⁰ , and Q ^{110 to} Q ¹⁴⁰ may have a substituent and is a 5-membered member containing O, N, and S as a hetero atom. Alternatively, a 6-membered ring, preferably an aromatic heterocyclic group, and a condensed polycyclic aromatic heterocyclic group having 2 to 20 carbon atoms can be used. Examples of the aromatic heterocyclic group and the condensed polycyclic aromatic heterocyclic group include a thienyl group, a furyl group, a pyrrolyl group, a pyridyl group, a quinolyl group, and a quinoxalyl group.

As the alkenyl group represented by Q ^{10 to} Q ⁴⁰ , Q ^{50 to} Q ⁸⁰ , and Q ^{110 to} Q ¹⁴⁰ , (1- and 2-) phenylalkenyl groups having a phenyl group as at least one substituent, ( 1,2- and 2,2-) diphenylalkenyl groups, (1,2,2-) triphenylalkenyl groups and the like are preferred, but may be unsubstituted.

The alkoxy group and alkylthio group represented by Q ^{10 to} Q ⁴⁰ , Q ^{50 to} Q ⁸⁰ , and Q ^{110 to} Q ¹⁴⁰ may have a substituent, and those having the aforementioned alkyl group are preferable.

The aryloxy group and arylthio group represented by Q ^{10 to} Q ⁴⁰ , Q ^{50 to} Q ⁸⁰ , and Q ^{110 to} Q ¹⁴⁰ may have a substituent and have an aryl group having 6 to 18 carbon atoms in total. Specifically, the aryloxy group is (o-, m-, p-) phenoxy group or the like, and the arylthio group is (o-, m-, p-) phenylthio group or the like.

The aralkyl group represented by Q ^{10 to} Q ⁴⁰ , Q ^{50 to} Q ⁸⁰ , and Q ^{110 to} Q ¹⁴⁰ may have a substituent, and those having a total carbon number of 7 to 30 are preferable. Are a benzyl group, a phenethyl group, and the like.

If ^{Q 10 ~Q 40, Q 50 ~Q} 80, Q 110 ~Q 140 has a substituent, the particular ^Q 10 ^{to Q 40} at least two aryl groups of these substituents, an amino group, a heterocyclic group , An alkenyl group and an aryloxy group are preferable, and an aryl group is particularly preferable. The aryl group, amino group, heterocyclic group and alkenyl group are the same as those described above for Q ^{10 to} Q ⁴⁰ .

  Two or more of these substituents may form a condensed ring. Further, it may be further substituted, and preferred substituents in that case are the same as described above.

If ^{Q 10 ~Q 40, Q 50 ~Q} 80, Q 110 ~Q 140 has a substituent, particularly ^preferably it has at least the two or more the above substituents of Q 10 ^{to Q 40.} The substitution position is not particularly limited, and when Q ^{10 to} Q ⁴⁰ have a phenyl group, any of the meta, para, and ortho positions may be used.

In Formula (2), it is preferable that at least one or more of Q ^{10 to} Q ⁸⁰ , more preferably at least one of Q ^{10 to} Q ⁴⁰ , is a substituted or unsubstituted aryl group.

  In particular, the naphthacene derivative is preferably represented by the following formula (2a), and is also preferably represented by the formula (2b). First, equation (2a) will be described.

In formula (2a), Q ^{5 to} Q ⁸ , Q ^{11 to} Q ¹⁶ are each hydrogen, alkyl group, aryl group, amino group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkenyl group, aralkyl group, or complex. Represents a cyclic group, which may be the same or different. Q ^{21 to} Q ²⁵ and Q ^{51 to} Q ⁵⁵ each represent hydrogen, an alkyl group, an aryl group, an amino group, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an alkenyl group, an aralkyl group, or a heterocyclic group, These may be the same or different, and two or more adjacent ones may be bonded to each other to form a ring.

Specific examples of these groups have the same meanings as Q ¹⁰ in formula (2).

In the formula (2a), Q ^{51 to} Q ⁵⁵ and Q ^{21 to} Q ²⁵ are each preferably hydrogen, an aryl group, an amino group, a heterocyclic group, an aryloxy group or an alkenyl group, particularly preferably an aryl group. Further, at least one of these groups preferably has any of an aryl group, an amino group, a heterocyclic group and an aryloxy group, particularly preferably an aryl group as a substituent. Two or more adjacent groups may form a condensed ring. Preferable embodiments of the aryl group, amino group, heterocyclic group and aryloxy group are the same as those in Q ^{10 to} Q ⁴⁰ above.

In addition, Q ^{51 to} Q ⁵⁵ and Q ^{21 to} Q ²⁵ are preferably the same, but may be different. The amino group that serves as a substituent for Q ^{51 to} Q ⁵⁵ and Q ^{21 to} Q ²⁵ may be an alkylamino group, an arylamino group, an aralkylamino group, or the like. These preferably have an aliphatic group having 1 to 6 carbon atoms in total and / or an aromatic carbocyclic ring having 1 to 4 rings. Specific examples include a dimethylamino group, a diethylamino group, a dibutylamino group, a diphenylamino group, a ditolylamino group, and a bisbiphenylylamino group.

  Examples of the condensed ring formed include indene, naphthalene, anthracene, phenanthrene, quinoline, isoquinoline, quinoxaline, phenazine, acridine, indole, carbazole, phenoxazine, phenothiazine, benzothiazole, benzothiophene, benzofuran, acridone, benzimidazole, and coumarin. And flavones.

Q ^{5 to} Q ⁸ in the formula (2a) have the same meanings as Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ , and Q ⁸⁰ in the formula (2), respectively. The particular hydrogen are preferred as ^Q 11 ^{to Q 16.}

Wherein ^{(2b), Q 5 ~Q 8} , Q 11 ~Q 14, Q 31 ~Q 35, Q 41 ~Q 45, Q 61 ~Q 65, Q 71 ~Q 75 is ^{Q 10,} etc. of formula (2) Is synonymous with

In formula (2b), Q ^{71 to} Q ⁷³ , Q ^{61 to} Q ⁶³ , Q ^{31 to} Q ³³ and Q ^{41 to} Q ⁴³ are any of hydrogen, aryl group, amino group, heterocyclic group, aryloxy group and alkenyl group And particularly preferably an aryl group. Further, at least one of these groups preferably has any of an aryl group, an amino group, a heterocyclic group and an aryloxy group as a substituent, and particularly preferably an aryl group. Two or more of these may combine to form a ring. Preferable embodiments of the aryl group, amino group, heterocyclic group, and aryloxy group are the same as Q ^{10 to} Q ⁴⁰ in formula (2). Further, Q ^{71 to} Q ⁷³ and Q ^{41 to} Q ⁴³ , Q ^{61 to} Q ⁶³ and Q ^{31 to} Q ³³ are preferably the same, but may be different.

As an amino group serving as a substituent for Q ^{71 to} Q ⁷³ , Q ^{61 to} Q ⁶³ , Q ^{31 to} Q ³³ and Q ^{41 to} Q ⁴³ , any of an alkylamino group, an arylamino group, an aralkylamino group and the like may be used. These preferably have an aliphatic group having 1 to 6 carbon atoms in total and / or an aromatic carbocyclic ring having 1 to 4 rings. Specific examples include a dimethylamino group, a diethylamino group, a dibutylamino group, a diphenylamino group, a ditolylamino group, and a bisbiphenylylamino group.

  Examples of the ring formed include indene, naphthalene, anthracene, phenanthrene, quinoline, isoquinoline, quinoxaline, phenazine, acridine, indole, carbazole, phenoxazine, phenothiazine, benzothiazole, benzothiophene, benzofuran, acridone, benzimidazole, and coumarin. And flavones.

Q ^{5 to} Q ⁸ in the formula (2b) are synonymous with Q ^{50 to} Q ⁸⁰ in the formula (2), and Q ^{11 to} Q ¹⁴ , Q ⁷⁴ , Q ⁷⁵ , Q ⁶⁴ , Q ⁶⁵ , Q ⁴⁴ , Q ⁴⁵ , Q ³⁴ and Q ³⁵ are particularly preferably hydrogen.

  In particular, the naphthacene derivative is preferably a hydrocarbon compound.

A particularly preferred specific example of the naphthacene derivative in the present invention is a combination of Q ¹⁰ , Q ²⁰ , Q ³⁰ , Q ⁴⁰ , Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ , and Q ^{80 in} the formula (2) (however, Q ^{110 to} Q ¹⁴⁰ Is hydrogen, and is shown below, but is not limited thereto.

  Such naphthacene derivatives and anthracene derivatives may be used alone or in combination of two or more in the electron transport layer. When two or more kinds are used, they may be naphthacene derivatives or anthracene derivatives, or a combination of a naphthacene derivative and an anthracene derivative.

  The content of the naphthacene derivative and / or anthracene derivative in the electron transport layer is preferably 80% (mass percentage) or more, and other electron transport materials (for example, metal complex compounds, quinoxaline compounds, azole compounds, diazole compounds) are used in combination. However, it is preferable that the electron transport layer is made of only a naphthacene derivative and / or an anthracene derivative. Of these, use of a naphthacene derivative is preferable, and in particular, use of a naphthacene derivative represented by the formula (2) (further, the formulas (2a) and (2b), particularly the formula (2a)) is preferable.

  The materials used for the electron transport layer, including naphthacene derivatives and / or anthracene derivatives, preferably have a dipole moment value of 1.0 Dybye or less, and more preferably 0.1 to 0.3 Dybye. . The dipole moment in this case is obtained by the AM1 method using a semi-empirical molecular orbital method program (MPAC).

By using a nonpolar molecule having a small dipole moment for the electron transport layer, the electron transport property is enhanced. Electron transporting mu _a is a change in the drive voltage required to using an organic EL element flowing a current of 100 mA / cm ² when changing the thickness of the electron transport layer configuration of the present invention, the following When the driving voltage (V) when the thickness (nm) of the electron transport layer is d ₁ and d ₂ (where d ₁ > d ₂ ) is V ₁ and V ₂ , mu _a = represented by _{(d 1 -d 2) / (} V 1 -V 2). The mu _a is 80 nm / V or more, and further preferably not 100 nm / V or more. The higher the electron transport property, the more the device that can be driven at a lower voltage can be created.There is no particular limitation on this upper limit, but the electron transport property is too high depending on the structure of the hole injection / transport layer and the light emitting layer, so the carrier balance is lost. Since there is a possibility, in the element configuration of the present invention, the upper limit is preferably about 600 nm / V.

  Thus, by using an electron transport layer having a high electron transport property, low voltage driving is possible, and light emission efficiency is improved. In the present invention, the electron injection layer, the electron transport layer, and the light-emitting layer are laminated in this order from the cathode side, which is the electron injection electrode. By selecting the electron transport layer of the present invention, the electric field strength applied to the electron transport layer is increased. Therefore, even when the optical external extraction efficiency is optimized by changing the film thickness of the electron transport layer, there is almost no change in the driving voltage, and an element that achieves both low driving voltage and high external extraction efficiency. Can be created. Further, the probability of carrier recombination occurring in the electron transport layer is reduced due to the penetration of holes, so that light emission other than in the light emitting layer is suppressed, and deterioration in color purity and device lifetime is prevented.

  Furthermore, since the electron transport layer material of the present invention is a nonpolar molecule, interaction with the light emitting material at the light emitting layer interface is unlikely to occur, and it is considered that there is an effect of preventing energy loss of excitons at the interface.

  Although the thickness of a preferable electron carrying layer changes with luminescent colors of an element, 5-100 nm is preferable, More preferably, it is 10-60 nm. By setting it to such a thickness, an optimum optical interference effect can be obtained, and good external extraction efficiency can be obtained. In addition, since the driving voltage does not change significantly even if the thickness of the electron transport layer is changed within the above range, the efficiency and color purity can be easily adjusted by optical interference.

  In addition, a material having a larger ionization potential (IP) than the light-emitting layer is used between the light-emitting layer and the electron-transporting layer as a means for preventing the escape of holes to the electron-transporting layer and improving efficiency, color purity, and device lifetime. There is a method of providing it as a hole blocking layer. However, in this method, generation of excitons is concentrated on the electron transport layer side of the light emitting layer. In the combination of the electron transport layer and the light-emitting layer of the present invention, the electron transport layer of the electron transport layer is high and can inject electrons well into the light-emitting layer, and the injected electrons are localized in the dopant molecule. It is possible to efficiently recombine with holes injected from the side. As a result, holes are not injected into the electron transport layer without providing a barrier that blocks holes between the light emitting layer and the cathode. Therefore, it is possible to prevent the above-described adverse effects by reducing the difference in ionization potential (IP) between the light emitting layer and the electron transport layer.

  For this reason, the difference in ionization potential (IP) between the electron transport layer and the light emitting layer is preferably 0.1 eV or less, particularly preferably 0 to 0.1 eV.

  In the present invention, as the electron injection layer used in combination with the electron transport layer, a material that has good adhesion to both the cathode and the electron transport layer, can efficiently inject electrons from the cathode, and can obtain a high carrier concentration is used. It is preferable. In this case, an electron injection layer made of an inorganic compound is also conceivable, but it is preferable to select and use an organic compound. Depending on the organic compound, in particular, when an alkali metal, an alkali metal compound, or the like is used for the electron injection electrode, it can be complexed with an alkali metal atom, further improving the adhesion and obtaining a high electron injection property. The organic compound in this case may contain a metal such as a metal complex in addition to a general carbon compound.

  In the electron injection layer, quinoline derivatives such as organometallic complexes having 8-quinolinol or a derivative thereof such as tris (8-quinolinolato) aluminum (Alq3) as a ligand, phenanthroline or phenanthroline derivatives, indole derivatives (including indole) Carbazole derivatives (including carbazole), oxadiazole derivatives (including oxadiazole), perylene derivatives, pyridine derivatives, acridine derivatives, pyrimidine derivatives, quinoxaline derivatives, phenazine derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, etc. These materials can be used.

  Thus, a compound having a heterocyclic ring is preferable, and a compound having a nitrogen-containing heterocyclic ring is particularly preferable.

  Of these, tris (8-quinolinolato) aluminum is generally used, but phenanthroline or a phenanthroline derivative is preferred because of its good adhesion to the cathode and good electron injection. The use of phenanthroline or a phenanthroline derivative is most preferable, but good characteristics can be obtained even when an indole derivative, a carbazole derivative, a quinoxaline derivative, a phenazine derivative, an acridine derivative, an oxadiazole derivative, or the like is used.

  Hereinafter, these compounds will be described more specifically.

  Examples of phenanthroline derivatives or phenanthroline derivatives include 1,10-phenanthroline, 1,9-phenanthroline, 1,8-phenanthroline, 1,7-phenanthroline, 2,9-phenanthroline, 2,8-phenanthroline, 2,7-phenanthroline, 3,8-phenanthroline, 3,7-phenanthroline, 4,7-phenanthroline and organic compounds having one or more of these phenanthroline skeletons in the molecule are preferred.

  As the phenanthroline or the phenanthroline derivative, those disclosed in JP-A-5-331459 and JP-A-2001-267080 can be used, and those represented by the formulas (1a) and (1b) are particularly preferable. preferable.

In formula (1a), Y _{2 to} Y ₉ may be the same as or different from each other, and hydrogen, aryl group, alkyl group, aralkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkenyl group, Represents an amino group or a heterocyclic group, and two or more adjacent groups thereof may form a ring, but preferably an aryl group, alkyl group, aralkyl group, alkoxy group, aryloxy group, alkyl group, amino group, heterocyclic ring And particularly preferably an aryl group or an aromatic heterocyclic group.

Specific examples of these aryl groups, an alkyl group, an aralkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an amino group, an alkenyl group, a heterocyclic group, those represented by Q ¹⁰ or the like of the formula (2) It is the same.

Y ₉ is preferably hydrogen, a phenyl group, a biphenylyl group, or a pyridyl group.

In formula (1b), A and B may be the same or different and each represents a group represented by formula (1c), and Y ₁₂ to Y ₁₉ in formula (1c) are represented by formula (1a). ) Are the same as Y ₂ to Y ₉ in FIG. However, one of Y ₁₂ to Y ₁₉ in the formula (1c) constitutes L. L represents a single bond or a divalent linking group, and the divalent linking group represented by L is described in the anthracene derivatives represented by the formula (4), the formula (4a), and the formula (4b). _{L 101,} L 10, L ₂₀ include those similar to, preferable ones are also same. Examples of the divalent linking group also include a divalent aromatic heterocyclic group (for example, a pyridinediyl group).

In Formula (1c), Y ₁₂ to Y ₁₉ constituting L may be the same or different in A and B. That is, in the formula (1b), there are no particular restrictions on the bonding positions of the rings A and B having two phenanthroline skeletons, and the bond between Y ₂ (2nd position), Y ₃ (3rd position), and Y ₄ (4th position) Bonding is common, but bonding at different sites such as Y ₂ (position 2) and Y ₄ (position 4) may also be used. Further, the rings A and B having two phenanthroline skeletons may be the same or different, and the substituents thereof may be the same or different.

  Specific examples of the phenanthroline or phenanthroline derivative used in the present invention are shown below, but the present invention is not limited thereto. A specific example is shown according to the display in Formula (f-1)-Formula (f-4).

  As described above, the electron injection layer material in the present invention is most preferably a phenanthroline derivative, but it is also preferable to use a nitrogen-containing heterocyclic compound having a basic skeleton as shown below.

Here, Rn (R _{1 to} R ₆ ) represents a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkenyl group, a heterocyclic group, a halogen atom, and a cyano group. But it can be different. Further, adjacent groups may form an aliphatic ring or an aromatic ring together with carbon atoms that are bonded or condensed to each other and substituted.

  Specific examples of these nitrogen-containing heterocyclic compounds are shown below, but a good electron injection material in the present invention is not limited thereto.

  As the indole derivative, an indole derivative having a skeleton represented by the formula (5) is preferable.

In the formula (5), R ^{1 to} R ⁷ are hydrogen, halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, amino group, alkyl group (for example, methyl group, ethyl group, propyl group, butyl group, etc.) An alkenyl group (for example, ethynyl group), an aryl group (for example, phenyl group, biphenyl group, terphenyl group, etc.), an aryloxy group (for example, phenyloxy group), an alkyloxy group (for example, methoxy group, ethoxy) Group), an arylcarbonyl group (for example, phenylcarbonyl group) or an alkylcarbonyl group (for example, acetyl group, propionyl group, etc.), and each of the groups is an alkyloxy group, an alkyl group, an aryl group, a nitro group, One or more substituents such as a cyano group, an amino group, and a halogen atom may be included.

And at least one of R ^{1 to} R ³ is preferably an aryl group or a group having an aryl group, and more preferably all of them are aryl groups.

  For example, a compound having a skeleton represented by the formula (5a) is preferable.

In the formula (5a), R ⁴¹ , R ⁴² and R ⁴³ are each an alkoxy group (preferably having 1 to 5 carbon atoms, particularly 1 carbon atom), an alkyl group (preferably having 1 to 5 carbon atoms), a dialkylamino group (Preferably an alkyl having 1 to 5 carbon atoms) or a nitro group. p, q, and r are integers of 0 to 3, and p + q + r ≧ 1, preferably p + q + r ≦ 6. R ⁴¹ , R ⁴² and R ⁴³ are usually bonded to the para position, but may be bonded to the ortho position.

R ^{1 to} R ⁷ which are adjacent to each other may be bonded to each other to form a 5- or 6-membered, particularly 6-membered condensed ring.

  Note that the alkyl group and the alkenyl group preferably have 1 to 5 carbon atoms. The aryl group is preferably a phenyl group.

  Examples of compounds in which substituents are bonded to each other to form a condensed ring include compounds represented by formulas (5b) and (5c). A compound having a skeleton represented by the formula (5d) is also preferable.

In the formula (5b), R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ are preferably selected from the same as R ^{1 to} R ⁷ described above, specifically, for example, R ^{1 to} R ³ , R It is preferable that all of ^{11 to} R ¹⁴ and R ^{6 to} R ⁷ are hydrogen.

In the formula (5c), R ²¹ , R ²² , R ²³ , and R ²⁴ are preferably selected from the same as R ^{1 to} R ⁷ described above, and specifically, for example, R ^{1 to} R ⁵ , R Those in which all of ^{21 to} R ²⁴ are hydrogen are preferred.

In the formula (5d), R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁵ , and R ³⁶ are preferably selected from the same as R ^{1 to} R ⁷ . X is a bond, 1,4-phenylene, 4,4′-biphenylene, and the like. Specifically, for example, X is a bond, 1,4-phenylene, or 4,4′-biphenylene. , R ^{2 to} R ⁷ , and R ^{31 to} R ³⁶ are all preferably hydrogen.

  Although the specific example of an indole derivative is shown below, it is not limited to these. Specific examples are shown according to the indications in the formulas (Id-1) to (Id-4).

As the quinoxaline derivative, one represented by the formula (6) is preferable.
Q _m -L100 (6)

  Referring to formula (6), Q represents a pyrazinyl group condensed with a 6-membered aromatic ring containing 0 to 2 nitrogen atoms. m is 2 or 3, and the m Qs in this case may be the same or different. As the six-membered aromatic ring forming Q, a benzene ring, a pyridine ring, a pyrimidine ring, a pyridazine ring and the like are preferable. Although there is no restriction | limiting in particular in the condensation position of such a 6-membered aromatic ring and a pyrazine ring, It is preferable that a carbon atom exists in a condensation position and it is more preferable that a nitrogen atom does not exist. Therefore, in the pyrazine ring, it is preferable to condense at the side of position number 2 or 3 or the side of position number 5 or 6, and in the pyridine ring, the side of position number 2 or 3 (or 5, 6) or position number 3 or 4 ( Or the side of position number 4, 5 (or 5, 6) in the pyrimidine ring, the side of position number 3, 4 (or 5, 6) or the side of position number 5, 4 in the pyridazine ring. Condensation is preferred.

  L100 represents a single bond or an m-valent group, that is, a divalent or trivalent group. As the divalent group, an arenediyl group is preferable. Specifically, a phenylene group, a biphenyldiyl group, a naphthalenediyl group, an anthracenediyl group, a pyrenediyl group, and the like are preferable. As the trivalent group, an arenetriyl group (specifically Specifically, a benzenetriyl group or the like), a nitrogen atom, a triarylamine triyl group (specifically, a triphenylamine triyl group or the like) and the like are preferable.

  Q and L100 may each further have a substituent, and as such a substituent, Q may be included, and the total number of Q in one molecule is preferably 2 to 10, Two to four are preferred.

  As described above, two or more Qs may be the same or different from each other, but are usually preferably the same for the convenience of synthesis.

  Of the quinoxaline derivatives represented by the formula (6) used in the present invention, the compound represented by the formula (VIII) is preferable.

  The formula (VIII) will be described. In the formula (VIII), Z represents an atomic group necessary for forming a benzene ring, a pyridine ring, a pyrimidine ring or a pyridazine ring together with two carbon atoms of the pyrazine ring.

  The ring completed with Z may further have a substituent and may have a condensed ring. Preferred examples of the condensation position of the ring completed with Z with respect to the pyrazine ring include the same condensation positions as those described in the description of formula (6).

A ₁ represents a monovalent substituent bonded to the pyrazine ring, and k is 0, 1 or 2. Preferred examples of the substituent of the ring completed by Z and the substituent represented by A ₁ are the same as A _{13 and the} like in formula (VIII-a) to formula (VIII-m) to be described later. Describe.

  m is 2 or 3. When m is 2, L100 represents a single bond, a phenylene group, a biphenyldiyl group or a naphthalenediyl group, and when m is 3, L100 represents a benzenetriyl group, a nitrogen atom or a triphenylaminetriyl group. This will be described in detail with reference to formula (VIII-a) to formula (VIII-n).

  The fused rings completed with Z may be the same or different, but are preferably the same as described for formula (6).

  The fused position of L100 in the fused pyrazine ring having a ring completed with Z may be any.

  Of the quinoxaline compounds represented by the formula (VIII), compounds represented by the formulas (VIII-a) to (VIII-n) are preferable.

  First, formula (VIII-a) to formula (VIII-f) and formula (VIII-m) in the case where L100 is a divalent group L111 or a single bond will be described. In Formula (VIII-a) to Formula (VIII-f) and Formula (VIII-m), L111 represents a phenylene group, a biphenyldiyl group, or a naphthalenediyl group.

  The phenylene group represented by L111 may be any of o-, m-, and p-phenylene groups, and a p-phenylene group is particularly preferable.

  As the biphenyldiyl group represented by L111, 4,4′-biphenyl-1,1′-diyl group and the like are preferable.

  The naphthalenediyl group represented by L111 is preferably a 1,5-naphthalenediyl group.

  These divalent groups are preferably unsubstituted but may optionally have a substituent such as an alkyl group or an aryl group.

Formula (VIII-a) in the _{A 13, A 15 ~A 18,} A 23, A 25 ~A 28, wherein (VIII-b) in the _{A 13, A 16 ~A 18,} A 23, A 26 ~A ₂₈ , A ₁₃ in formula (VIII-c), A ₁₅ , A ₁₇ , A ₁₈ , A ₂₃ , A ₂₅ , A ₂₇ , A ₂₈ , A ₁₃ in formula (VIII-d), A ₁₆ , A ₁₈ , A ₂₃ , A ₂₆ , A ₂₈ , A ₁₃ in formula (VIII-e), A ₁₇ , A ₁₈ , A ₂₃ , A ₂₇ , A ₂₈ , A ₁₃ in formula (VIII-f), A ₁₅ , A ₁₈ , A ₂₃ , A ₂₅ , A ₂₈ , and A ₁₂ , A ₁₃ , A ₁₅ , A ₁₇ , A ₁₈ , A ₂₂ , A ₂₃ , A ₂₅ , A ₂₇ , A _{28 in the} formula (VIII-m) Are each a hydrogen atom, a halogen atom, a hydroxy group, a carboxy group, Toromoto, cyano group, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group or a heterocyclic group, which may be different even in the same at in each formula.

The halogen atom represented by A ₁₃ or the like, a fluorine atom, a chlorine atom.

Alkyl group preferably has a total carbon number of 1 to 6, represented by A ₁₃ or the like, may have a branched be linear. Further, an unsubstituted one is preferable, but it may have a substituent (for example, a halogen atom such as F or Cl). Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a pentyl group, and a hexyl group.

The aryl group preferably has a total carbon number of 6 to 30 represented by A ₁₃ or the like, may be also be a single or polycyclic (condensed polycyclic and ring assembly), substituted Also good. Examples of the substituent include a halogen atom such as F and Cl, an alkyl group such as a methyl group, and a heterocyclic group. In this case, the heterocyclic group is, for example, a quinoxalinyl group in the formula (VIII-a). As described above, the same one as the condensed pyrazinyl group bonded to L111 is preferable. Specific examples of the aryl group, such as A ₁₃ are members, phenyl group, 1-naphthyl, 2-naphthyl, 2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group or the like, furthermore condensates such as those in quinoxalinyl group Examples include those substituted with a pyrazinyl group.

Alkoxy group represented by A ₁₃ or the like, it preferably has 1 to 6 carbon atoms in the alkyl moiety, may be substituted, those are preferably unsubstituted. Specific examples include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, and a t-butoxy group.

The aryloxy group represented by A ₁₃ or the like, and a phenoxy group.

Amino group represented by A ₁₃ or the like may have a substituent, examples of the substituent include an alkyl group, an aryl group, and the like. Specific examples include an amino group, a methylamino group, a dimethylamino group, a phenylamino group, and a diphenylamino group.

The alkylthio group represented by A ₁₃ or the like methylthio group, and ethylthio group.

The arylthio group represented by A ₁₃ or the like include a phenylthio group.

Fururi group as the heterocyclic group represented by A ₁₃ or the like, thienyl group, pyrrole group, pyridyl group, quinolyl group, and the like. In addition, the same condensed pyrazinyl group as that bonded to L ₁ such as a quinoxalinyl group in the formula (VIII-a) may be used.

In the formula (VIII-a), adjacent ones of A _{15 to} A ₁₈ and A _{25 to} A ₂₈ ,
In formula (VIII-b), adjacent ones of A _{16 to} A ₁₈ , A _{26 to} A ₂₈ ,
In the formula (VIII-c), A ₁₇ and A ₁₈ , A ₂₇ and A ₂₈ ,
In the formula (VIII-e), A ₁₇ and A ₁₈ , A ₂₇ and A ₂₈ ,
In formula (VIII-m), A ₁₂ and A ₁₃ , A ₁₇ and A ₁₈ , A ₂₂ and A ₂₃ , A ₂₇ and A ₂₈ may be bonded to each other to form a ring. As the ring in this case, a benzene ring or the like is preferable, and the benzene rings formed may be condensed with each other, and the benzene ring formed by these may further have a condensed ring.

In Formula (VIII-a) to Formula (VIII-f), A ₁₃ and A ₂₃ are preferably A ₁₂ , A ₁₃ , A ₂₂ and A ₂₃ in Formula (VIII-m), and an aryl group is preferable. In addition, A _{15 to} A ₁₈ and A _{25 to} A ₂₈ in the formula (VIII-a) are preferably a hydrogen atom, an alkyl group, an alkoxy group, or a group in which adjacent ones are bonded to form a benzene ring. Also, _A 16 _{to A} 18 of the formula _{(VIII-b), A 26} ~A 28, A 15 of the formula _{(VIII-c), A 17} , A 18, A 25, A 27, A 28, formula (VIII - d) A ₁₆ , A ₁₈ , A ₂₆ , A ₂₈ , A ₁₇ , A ₁₈ , A ₂₇ , A _{28 of} formula (VIII-e), A ₁₅ , A ₁₈ , A _{25 of} formula (VIII-f), A ₂₈ and A ₁₅ , A ₁₇ , A ₁₈ , A ₂₅ , A ₂₇ , A _{28 in} formula (VIII-m) are each preferably a hydrogen atom or the like.

  Next, formula (VIII-g) to formula (VIII-l) and formula (VIII-n) in the case where L100 is a trivalent group L112 will be described. In the formula (VIII-g) to the formula (VIII-1) and the formula (VIII-n), L112 represents a benzenetriyl group, a nitrogen atom or a triphenylamine triyl group.

  The benzenetriyl group represented by L112 is preferably a 1,3,5-benzenetriyl group.

  As the triphenylamine triyl group represented by L112, 4,4 ′, 4 ″ -triphenyl-1,1 ′, 1 ″ -triyl group and the like are preferable.

  These trivalent groups are preferably unsubstituted, but may optionally have a substituent such as an alkyl group or an aryl group.

A < ₁₃ >, A < ₁₅ > -A < ₁₈ >, A < ₂₃ >, A < ₂₅ > -A < ₂₈ >, A < ₃₃ >, A < ₃₅ > -A < ₃₈ > in Formula (VIII-g),
A < ₁₃ >, A < ₁₆ > -A < ₁₈ >, A < ₂₃ >, A < ₂₆ > -A < ₂₈ >, A < ₃₃ >, A < ₃₆ > -A < ₃₈ > in Formula (VIII-h),
_A 13 in formula _{(VIII-i), A 15} , A 17, A 18, A 23, A 25, A 27, A 28, A 33, A 35, A 37, A 38,
A ₁₃ , A ₁₆ , A ₁₈ , A ₂₃ , A ₂₆ , A ₂₈ , A ₃₃ , A ₃₆ , A ₃₈ in formula (VIII-j)
_{A 13,} A ₁₇ in formula _{(VIII-k), A 18} , A 23, A 27, A 28, A 33, A 37, A 38,
_A 13 in formula _{(VIII-l), A 15} , A 18, A 23, A 25, A 28, A 33, A 35, A 38,
_A 12 in formula _{(VIII-n), A 13} , A 15, A 17, A 18, A 22, A 23, A 25, A 27, A 28, A 32, A 33, A 35, A 37, A ₃₈ each represents a hydrogen atom, a halogen atom, a hydroxy group, a carboxy group, a nitro group, a cyano group, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, an alkylthio group, an arylthio group or a heterocyclic group, In each formula, these may be the same or different. Specific examples of these groups include the same groups as those described in the formulas (VIII-a) to (VIII-f). In the formula (VIII-g), adjacent ones of A _{15 to} A ₁₈ , A _{25 to} A ₂₈ , A _{35 to} A ₃₈ ,
In the formula _(VIII-h), between the adjacent ones of among _{A 16 ~A 18, A 26 ~A} 28, A 36 ~A 38,
In the formula (VIII-i), A ₁₇ and A ₁₈ , A ₂₇ and A ₂₈ , A ₃₇ and A ₃₈ ,
In the formula (VIII-k), A ₁₇ and A ₁₈ , A ₂₇ and A ₂₈ , A ₃₇ and A ₃₈ ,
In the formula (VIII-n), A ₁₂ and A ₁₃ , A ₁₇ and A ₁₈ , A ₂₂ and A ₂₃ , A ₂₇ and A ₂₈ , A ₃₂ and A ₃₃ , A ₃₇ and A ₃₈ are bonded to each other. A ring may be formed, and specific examples thereof include the same ones as in formulas (VIII-a) to (VIII-f). In Formulas (VIII-a) to (VIII-l), A ₁₃ , A ₂₃ , and A ₃₃ are preferably a hydrogen atom, an aryl group such as a phenyl group, or the like.

In addition, A _{15 to} A ₁₈ , A _{25 to} A ₂₈ , and A _{35 to} A ₃₈ in the formula (VIII-g) are preferably hydrogen atoms or those adjacent to each other to form a benzene ring.

_{Also, A 16 ~A 18, A 26} ~A 28 of formula (VIII-h), A 36 ~A 38,
_{A 15,} A ₁₇ of the formula _{(VIII-i), A 18} , A 25, A 27, A 28, A 35, A 37, A 38,
A ₁₆ , A ₁₈ , A ₂₆ , A ₂₈ , A ₃₆ , A ₃₈ in formula (VIII-j)
A ₁₇ , A ₁₈ , A ₂₇ , A ₂₈ , A ₃₇ , A ₃₈ in formula (VIII-k)
A < ₁₅ >, A <_18> , A < _{25 >} , A _{< 28 >} , A _{< 35>} , A _<38 > of Formula (VIII-1),
A ₁₂ , A ₁₃ , A ₁₅ , A ₁₇ , A ₁₈ , A ₂₂ , A ₂₃ , A ₂₅ , A ₂₇ , A ₂₈ , A ₃₂ , A ₃₃ , A ₃₅ , A ₃₇ , A in Formula (VIII-n) Each of ₃₈ is preferably a hydrogen atom or the like.

Specific examples of the quinoxaline derivative represented by the formula (6) preferably used in the present invention are shown below, but the present invention is not limited to these. Here, it displays a combination of L111, _{L112, A 13,} etc. in the formula (VIII-a) ~ formula _{(VIII-m), when A 13} and _{A 23} are different is shown separately in the table. In addition, since the display in Formula (VIII-a)-Formula (VIII-m) is a typical example, the compound actually obtained is a mixture of structural isomers normally on a synthetic pathway, Therefore These display correspond It is intended to include structural isomers.

  As an oxadiazole derivative, what is represented by Formula (7) is preferable.

In Formula (7), Z ₀ is hydrogen, an alkyl group (eg, methyl group, ethyl group, etc.), an aryl group (eg, phenyl group, naphthyl group, etc.), an alkoxy group (eg, methoxy group, ethoxy group, etc.), An aryloxy group (for example, phenoxy group), a heterocyclic group (for example, pyridyl group, thienyl group, etc.), a nitro group, a cyano group, an amino group, a hydroxyl group, a carboxyl group, or an alkenyl group, an alkyl group, an aryl group, an alkoxy group The group, aryloxy group, heterocyclic group, amino group, and alkenyl group may further have a substituent. Specific examples of these groups have been described above, but Q ^{10 in the} formula (2), etc. The same thing is mentioned. Z ₀ is preferably an aryl group such as a phenyl group, and may further have a substituent. In this case, examples of the substituent include a substituent represented by Z ₀ (an alkyl group, an aryl group, An alkoxy group, an aryloxy group, a heterocyclic group, etc.). n ₅₀ is 1, 2 or 3, 2,3 are preferred.

X ₅₀ is the same substituent or hydrogen as Z ₀ when n ₅₀ = 1, and when n ₅₀ = 2, a divalent linking group that connects two oxadiazolyl groups (for example, phenylene group, biphenyldiyl) Group), when n ₅₀ = 3, a trivalent linking group for linking three oxadiazolyl groups (for example, a benzenetriyl group). When n ₅₀ = 2 or 3, the plurality of oxadiazolyl groups linked by X ₅₀ may be the same or different.

  Specific examples of the oxadiazole derivative are shown below, but are not limited thereto. A specific example is shown according to the display in Formula (7-1) and Formula (7-2).

  As the carbazole derivative, those represented by the formula (8) are preferable.

In the formula (8), R _{52 to} R ₅₉ are hydrogen, an alkyl group (eg, methyl group, ethyl group, etc.), an aryl group (eg, phenyl group, naphthyl group, etc.), an alkoxy group (eg, methoxy group, ethoxy group). Etc.), aryloxy group (eg phenoxy group etc.), heterocyclic group (eg pyridyl group, thienyl group etc.), nitro group, cyano group, amino group, hydroxyl group, carboxyl group or alkenyl group, alkyl group, aryl group , An alkoxy group, an aryloxy group, a heterocyclic group, an amino group, and an alkenyl group may further have a substituent. Specific examples of these groups are as described above, but in the formula (2), those similar to Q ^10, and the like. n ₅₁ is 1 or 2, and 2 is preferable. X ₅₁ is the same substituent or hydrogen as R _{52 to} R ₅₉ when n ₅₁ = 1, and a divalent linking group that connects two carbazolyl groups when n ₅₂ = 2 (for example, a phenylene group) Etc.). In addition, when n = 2, the carbazolyl groups linked by X ₅₁ may be the same or different.

  Specific examples of the carbazole derivative are shown below, but are not limited thereto. A specific example is shown according to the display in Formula (8-1).

  The effects of the present invention can also be obtained by using general electron injection materials such as boron compounds and silacyclopentadiene derivatives as shown below.

  Examples of the boron compound include the following.

Here, Rn (R ₁₁ , R ₁₂ ) is a hydrogen atom, alkyl group, aryl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkenyl group, heterocyclic group, halogen atom, cyano group, alkylboryl group, An arylboryl group is shown. Ar represents an aryl group or a heterocyclic group.

  Although a specific example is shown below, it is not limited to this. These compounds are disclosed in JP-A No. 2001-233882, Polymer Preprints, Japan, Vol. 48, no. 9, 2047-2048, 1999, International Symp. on functional dyes, 36, 1999, and the like.

  Examples of the silacyclopentadiene derivative include the following.

Here, Rn (R ₂₁ , R ₂₆ ) is a hydrogen atom, alkyl group, aryl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkenyl group, heterocyclic group, halogen atom, cyano group, alkylboryl group, An arylboryl group is shown. Further, adjacent groups may form an aliphatic ring or an aromatic ring together with carbon atoms that are substituted or fused together.

  Although a specific example is shown below, it is not limited to this. These compounds are described in JP-A No. 2002-338581, JP-A No. 2002-216972, and the like.

  In addition, JP 2000-103786 A, JP 2000-306670 A, JP 2002-38141 A, JP 2001-57292 A, JP 2001-244076 A, JP 5-21165 A. JP-A-2001-335776, JP-A-7-82552, JP-A-10-251634, JP-A-9-3448 and the like can be used. The compound which can be used for this invention including these compounds is illustrated.

  In the electron injection layer, only one organic compound may be used, or two or more organic compounds may be used in combination. When using 2 or more types, the same type or different types may be used.

  Among these, it is preferable to use a phenanthroline derivative, particularly a phenanthroline or phenanthroline derivative represented by the formula (1a) or (1b), and preferably contains 80% (mass percentage) or more of the phenanthroline or phenanthroline derivative. In particular, it is preferably composed of phenanthroline or a phenanthroline derivative.

  The thickness of the electron injection layer is preferably 0.6 to 20 nm, more preferably 1 to 10 nm. In such a thickness range, the driving voltage can be reduced. On the other hand, when the electron injection layer becomes thin, the drive voltage rises critically, and the drive voltage rises even when the electron injection layer becomes thick. This is because if the electrode is too thin, the adhesion to the cathode is lowered and the electron injecting property is deteriorated. Also, since the material for the electron injecting layer has a low electron transporting property, the voltage is considered to increase if it is too thick. .

  The total thickness of the electron injection layer and the electron transport layer is preferably 5 to 100 nm. By setting it as such a total thickness, injection | pouring and transport of an electron can be performed efficiently, and optically favorable external extraction efficiency is obtained. On the other hand, when these total thicknesses are increased, the drive voltage is increased, and even when the drive voltage is decreased by reducing the thickness, external extraction efficiency is decreased if the film thickness is not optically optimal.

  In the present invention, the light emitting layer provided in contact with the electron transport layer preferably contains a host material and a dopant material.

  Examples of host materials in this case include naphthacene derivatives, anthracene derivatives, tetraaryldiamine derivatives, quinoxaline derivatives, metal complex compounds, and the like. Anthracene derivatives and naphthacene derivatives are preferably used, and naphthacene derivatives are particularly preferable.

  As the naphthacene derivative, the same naphthacene derivatives as those for the electron transport layer can be used, and preferable ones are also the same, particularly preferably the formula (2) (further, the formulas (2a) and (2b), especially It is a naphthacene derivative represented by the formula (2a)).

  The host material preferably has a dipole moment of 1.0 Dybe or less, and more preferably 0.5 to 0 Dybe. By using such a nonpolar molecule, the electron transporting property is improved, and the trapping of electrons by the dopant material is prevented. Since it becomes easy to occur and electrons are localized in the dopant, light emission of the dopant material is promoted and light emission from the host material can be suppressed. In addition, the interaction between the host molecule and the dopant can be suppressed. For this reason, an element with high efficiency and high color purity can be obtained.

  It is desirable that the electron affinity of the host material contained in the light-emitting layer, particularly the naphthacene derivative that is preferably used is greater than or equal to the electron affinity of the electron transport layer. Moreover, when providing a hole injection transport layer, it is preferable that it is larger than the electron affinity of a hole injection transport layer. If the electron affinity of the host material contained in the light emitting layer is greater than the electron affinity of the electron transport layer, the efficiency of electron injection into the light emitting layer is improved, and if it is greater than the electron affinity of the hole injection transport layer, hole injection transport is achieved. Since electrons are blocked at the interface of the layers, the light emission efficiency is improved and the device life is also improved.

  In addition, the light-emitting layer requires a hole and electron injection function, a transport function thereof, and a function of generating excitons by recombination of holes and electrons. By using a neutral compound, electrons and holes can be injected and transported easily and in a balanced manner.

  The host material in the light emitting layer is preferably contained in the light emitting layer in an amount of 80 to 99.9% (mass percentage), particularly 90 to 99.9% (mass percentage), more preferably 95.0 to 99.5%. (Mass percentage) is preferably contained.

  In addition, the thickness of the light emitting layer is preferably less than the total thickness of the organic compound layer in the element from the thickness corresponding to one molecular layer, specifically 1 to 85 nm, and more preferably 5 It is preferably ˜60 nm, particularly 5˜50 nm.

  On the other hand, the dopant material may be any material as long as it emits light by itself and can trap electrons in the host material, but a fluoranthene derivative is preferably used.

  As a fluoranthene derivative, what is represented by Formula (3) is preferable.

In formula (3), n ₁₀ is 1 or 2. L ₁₁ and L ₁₂ when Z _{1 to} Z ₁₀ and n ₁₀ = 1 are hydrogen, halogen, a linear, branched or cyclic alkyl group which may have a substituent, and a substituent. An alkoxy group having a linear, branched or cyclic alkyl moiety, a linear chain optionally having a substituent, an alkylthio group having a branched or cyclic alkyl moiety, or a linear chain optionally having a substituent A branched or cyclic alkenyl group, an optionally substituted straight chain, a branched or cyclic alkenyl moiety having an alkenyloxy group, an optionally substituted linear, branched or cyclic alkenyl moiety An alkenylthio group, a substituted or unsubstituted aromatic ring-containing alkyl group, a substituted or unsubstituted aromatic ring alkyl-containing oxy group, a substituted or unsubstituted aromatic ring-containing alkylthio group, Unsubstituted aromatic ring group, a substituted or unsubstituted aromatic ring oxy group, a substituted or unsubstituted aromatic ring thio group, a substituted or unsubstituted amino group, a cyano group, a hydroxyl group, -COOR 1 _(wherein, R ₁ Contains hydrogen, a linear, branched or cyclic alkyl group which may have a substituent, a linear, branched or cyclic alkenyl group which may have a substituent, a substituted or unsubstituted aromatic ring group An alkyl group, or a substituted or unsubstituted aromatic ring group), —COR ₂ (wherein R ₂ represents hydrogen, a linear, branched or cyclic alkyl group which may have a substituent, a substituent; A linear, branched or cyclic alkenyl group which may have, a substituted or unsubstituted aromatic ring-containing alkyl group, a substituted or unsubstituted aromatic ring group, or an amino group), or -OCOR ₃ (wherein , _{R 3} is a substituent A linear, branched or cyclic alkyl group that may be substituted, a linear, branched or cyclic alkenyl group that may have a substituent, a substituted or unsubstituted aromatic ring-containing alkyl group, or a substituted or unsubstituted group In addition, two or more adjacent groups selected from Z _{1 to} Z ₁₀ and L ₁₁ and L ₁₂ are bonded to each other to form a substituted or unsubstituted group together with a substituted carbon atom. A substituted aliphatic carbocycle, an aromatic ring, or a condensed ring of an aliphatic carbocycle and an aromatic ring may be formed. When n ₁₀ = 2 and at least one of L ₁₁ and L ₁₂ is a single bond, the other represents the same group as when n ₁₀ = 1, and forms a ring in the same manner as above. The same may be said. Further, both L ₁₁ and L ₁₂ may be a single bond, and in this case as well, a ring may be formed in the same manner as described above.

Further, in formula (3), two or more adjacent groups selected from Z _{1 to} Z ₁₀ and L ₁₁ and L ₁₂ are bonded to each other, and together with the substituted carbon atom, a substituted or unsubstituted aliphatic group It is preferable to form a condensed ring of a carbocyclic ring, an aromatic ring, or an aliphatic carbocyclic ring and an aromatic ring. Further, when n ₁₀ = 2, it is also preferable that both L ₁₁ and L ₁₂ are single bonds.

  Of the compounds represented by formula (3), diindeno [1,2,3-cd: 1 ′, 2 ′, 3′-lm] perylene derivatives represented by formula (3a) are particularly preferable.

In the formula (3a), Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ and Z ₂₀ are hydrogen, halogen, linear, branched or cyclic which may have a substituent. An alkyl group, an alkoxy group having an optionally substituted linear, branched or cyclic alkyl moiety, an alkylthio group having an optionally substituted linear, branched or cyclic alkyl moiety, and a substituent A linear, branched or cyclic alkenyl group which may have a group, an alkenyloxy group having a linear, branched or cyclic alkenyl part which may have a substituent, and a substituent. Good alkenylthio group having a linear, branched or cyclic alkenyl moiety, substituted or unsubstituted aromatic ring-containing alkyl group, substituted or unsubstituted aromatic ring-containing alkyloxy group, substituted or unsubstituted aromatic ring Alkylthio group, substituted or unsubstituted aromatic ring group, substituted or unsubstituted aromatic ring oxy group, substituted or unsubstituted aromatic ring thio group, substituted or unsubstituted aromatic ring alkenyl group, substituted or unsubstituted alkenyl aromatic A cyclic group, a substituted or unsubstituted amino group, a cyano group, a hydroxyl group, —COOR ₁ (where R ₁ represents hydrogen, a linear, branched or cyclic alkyl group which may have a substituent, a substituent; A linear, branched or cyclic alkenyl group which may have, a substituted or unsubstituted aromatic ring-containing alkyl group, or a substituted or unsubstituted aromatic ring group), —COR ₂ (wherein R ₂ represents Hydrogen, optionally substituted linear, branched or cyclic alkyl group, optionally substituted linear, branched or cyclic alkenyl group, substituted or unsubstituted aromatic ring-containing alkyl group , Place A substituted or unsubstituted aromatic ring group or an amino group, or —OCOR ₃ (wherein R ₃ has a linear, branched or cyclic alkyl group which may have a substituent, or a substituent. An optionally substituted linear, branched or cyclic alkenyl group, a substituted or unsubstituted aromatic ring-containing alkyl group, or a substituted or unsubstituted aromatic ring group), and Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ , and a group selected from adjacent groups selected from Z ₂₀ are bonded to each other, together with a substituted carbon atom, a substituted or unsubstituted aliphatic carbocyclic ring, An aromatic ring or a condensed ring of an aliphatic carbon ring and a condensed aromatic ring may be formed.

  The aromatic ring group means, for example, an aromatic hydrocarbon group (aryl group) such as a phenyl group or a naphthyl group and an aromatic heterocyclic group such as a furyl group, a thienyl group or a pyridyl group. Of these, an aryl group is preferred. The same applies to the following.

In the formulas (3) and (3a), a linear, branched or cyclic alkyl group represented by Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ , Z ₂₀ , Chain, branched or cyclic alkoxy groups, linear, branched or cyclic alkylthio groups, linear, branched or cyclic alkenyl groups, linear, branched or cyclic alkenyloxy groups, and linear, branched or cyclic alkenylthio groups Each group may further have a substituent, for example, halogen, an aromatic ring group having 4 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkoxy group having 2 to 20 carbon atoms, C2-C20 alkenyloxy group, C4-C20 aromatic ring-containing alkyloxy group, C5-C20 aromatic ring-containing alkyloxyalkoxy group, C3-C20 aromatic ring oxy group C4-C20 aromatic ring oxyalkoxy group, C5-C20 aromatic ring alkenyl group, C6-C20 aromatic ring-containing alkyl alkenyl group, C1-C20 alkylthio group, C2-C20 Alkoxyalkylthio group, carbon number 2-20 alkylthioalkylthio group, carbon number 2-20 alkenylthio group, carbon number 4-20 aromatic ring-containing alkylthio group, carbon number 5-20 aromatic ring-containing alkyloxyalkylthio group C5-C20 aromatic ring-containing alkylthioalkylthio group, C3-C20 aromatic ring thio group, C4-C20 aromatic oxyalkylthio group, C4-C20 aromatic ring thioalkylthio group, carbon It may be mono-substituted or poly-substituted with an alicyclic heterocyclic group of 4-20. Furthermore, the aromatic ring group contained in these substituents is further halogen, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aromatic ring group having 3 to 10 carbon atoms, and 4 to 10 carbon atoms. The aromatic ring-containing alkyl group may be substituted.

In the formulas (3) and (3a), an aromatic ring-containing alkyl group represented by Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ , Z ₂₀ , an aromatic ring-containing alkyloxy group, The aromatic ring group in the aromatic ring-containing alkylthio group, aromatic ring group, aromatic ring oxy group, and aromatic ring thio group may have a substituent, for example, an alkyl group having 1 to 20 carbon atoms, 2 carbon atoms -20 alkenyl group, C4-C20 aromatic ring-containing alkyl group, C3-C20 aromatic ring group, C1-C20 alkoxy group, C2-C20 alkoxyalkyl group, C2-carbon -20-alkoxyalkyloxy group, C2-C20 alkenyloxy group, C3-C20 alkenyloxyalkyl group, C3-C20 alkenyloxyalkyloxy group, C4-C20 aromatic ring Al Ruoxy group, C5-C20 aromatic ring-containing alkyloxyalkyl group, C5-C20 aromatic ring-containing alkyloxyalkyloxy group, C3-C20 aromatic ring oxy group, C4-C20 fragrance Ring oxyalkyl group, C4-20 aromatic ring oxyalkyloxy group, C2-20 alkylcarbonyl group, C3-20 alkenylcarbonyl group, C5-20 aromatic ring-containing alkylcarbonyl group C4-C20 aromatic ring carbonyl group, C2-C20 alkoxycarbonyl group, C3-C20 alkenyloxycarbonyl group, C5-C20 aromatic ring-containing alkyloxycarbonyl group, C4 -20 aromatic ring oxycarbonyl group, C2-C20 alkylcarbonyloxy group, C3-C20 alkenylcarbonyl A xy group, a C5-C20 aromatic ring-containing alkylcarbonyloxy group, a C4-C20 aromatic ring carbonyloxy group, a C1-C20 alkylthio group, a C4-C20 aromatic ring-containing alkylthio group, C3-C20 aromatic ring thio group, nitro group, cyano group, formyl group, halogen, halogenated alkyl group, hydroxyl group, amino group, C1-C20 N-monosubstituted amino group, C2-C40 The N, N-disubstituted amino group may be monosubstituted or polysubstituted.

  Furthermore, the aromatic ring group contained in these substituents is further halogen, a C1-10 alkyl group, a C1-10 alkoxy group, a C6-10 aryl group, a C7-10 carbon group. It may be substituted with an aralkyl group.

In formulas (3) and (3a), the amino group represented by Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ , Z ₂₀ may have a substituent, For example, it may be mono-substituted or di-substituted with an alkyl group having 1 to 20 carbon atoms, an alkyl group having 4 to 20 carbon atoms, or an aromatic ring group having 3 to 20 carbon atoms.

In the formulas (3) and (3a), the alkyl group, alkenyl group, aromatic ring-containing alkyl group and aryl group represented by R ₁ , R ₂ and R ₃ in the ester group or acyl group have a substituent. For example, it may be mono-substituted or poly-substituted with the substituents mentioned for Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ , Z ₂₀ .

Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ and Z ₂₀ are preferably Z ₅ , Z ₆ , Z ₉ , Z ₁₀ , Z ₁₅ , Z ₁₆ , Z ₁₉ and Z. ₂₀ is hydrogen, and Z _{1 to} Z ₄ , Z _{11 to} Z ₁₄ are hydrogen, halogen, a linear, branched or cyclic alkyl group having 1 to 24 carbon atoms which may have a substituent, substituted A linear, branched or cyclic alkyl moiety having 1 to 24 carbon atoms which may have a group, a straight chain having 2 to 24 carbon atoms which may have a substituent, a branched chain or a A cyclic alkenyl group, or an alkenylaryl group having such an alkenyl group or an arylalkenyl group (total carbon number 8-30), a substituted or unsubstituted aralkyl group having a total carbon number 7-24, a substituted or unsubstituted total Ants with 6 to 24 carbon atoms Le group or an aryloxy group, a cyano group, a heterocyclic group, a hydroxyl _group, -COOR 1, -COR ₂ or -OCOR _3, (provided that _wherein, R 1 to R ₃ have the same meanings as defined above) is.

Further, in Formula (3), L ₁₁ , L ₁₂ , Z _{1 to} Z ₆ , Z ₉ and Z ₁₀ , and in Formula (3a), Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z Adjacent groups selected from ₁₉ and Z ₂₀ are bonded to each other to form a substituted or unsubstituted aliphatic carbocyclic ring, an aromatic ring, or a condensed ring of an aliphatic carbocyclic ring and an aromatic ring together with a substituted carbon atom. The form to form is also preferable.

  The compound represented by the formula (3a) is further a compound represented by the following formula (3b), particularly dibenzo [f, f ′] diindeno [1,2,3-cd: 1 ′, 2 ′, 3 It is preferable that it is a '-lm] perylene derivative.

In the formula (3b), Z _{1 to} Z ₄₄ are synonymous with Z _{1 to} Z ₂₀ in the formula (3a).

In the compound represented by the formula (3a), Z _{1 to} Z ₂₀ , or in the compound represented by the formula (3b), Z _{1 to} Z ₄₄ are a substituted or unsubstituted aryl group, alkyl group, alkenyl group. , An alkoxy group or an aryloxy group is preferable.

Furthermore, in the compound represented by Formula (3a), at _{least one} of Z _{1 to} Z _{44 in} the compound represented by Z _{1 to} Z ₂₀ or Formula (3b) is an ortho-substituted phenyl group. Is preferred.

In particular, in the compound represented by formula (3a) or the compound represented by formula (3b), either one or both of Z ₁ and Z ₄ and / or one or both of Z ₁₁ and Z ₁₄ Is preferably an ortho-substituted phenyl group.

  Thus, by introducing a substituent at the ortho position, the decomposability during sublimation purification can be suppressed. In addition, fluorescence is improved by introducing a substituent at the ortho position.

  By using such an ortho-substituted compound, the fluorescence brightness of the EL element is improved and the concentration quenching property is suppressed, so that the margin as an EL dopant is improved and the design flexibility is improved.

  That is, by introducing an ortho-substituted phenyl group, the associative property of the perylene skeleton can be controlled by the steric hindrance, the solubility in a solvent is improved, and the purification can be performed with high purity. Further, for the same reason, sublimation purification can be performed at a lower temperature, decomposition during sublimation purification hardly occurs, and this point is also effective for obtaining a high-purity material. When an element is manufactured, exciton is hardly deactivated by impurities, and high light emission efficiency can be obtained.

  Another reason why high luminous efficiency can be obtained is to suppress concentration quenching by suppressing association between the same molecules or different molecules in the light emitting layer.

  Specific examples of the fluoranthene derivative of the present invention are shown below, but the present invention is not limited thereto. Particularly preferred specific examples of the compound represented by the formula (3b) are those shown in Chemical formula 289 to Chemical formula 295 (G-1 to G-100) and Chemical formula 313 to Chemical formula 317. Specific examples follow the display of the structural formulas shown. Ph represents a phenyl group.

  Such fluoranthene derivatives may be used alone or in combination of two or more. In particular, the use of the compound of formula (3a) is preferred.

  When such a fluoranthene derivative is used as a light-emitting component in a light-emitting layer, an organic EL device having high brightness and excellent durability, which has not been conventionally used, can be obtained. In addition, there is little decrease in luminous efficiency due to the temperature during driving, and the temperature characteristics are excellent.

  In the organic EL device of the present invention, it is preferable to use a naphthacene derivative as a host material. In particular, a combination of a naphthacene derivative and a fluoranthene derivative is preferable, and strong light emission can be obtained.

  The reason why such strong luminescence can be obtained is considered that the naphthacene derivative and the fluoranthene derivative are an ideal combination in which an interaction such as the formation of an exciplex does not occur. In addition to the generation and emission of dopant excitons by dopant carrier traps as described above, when a host exciton is generated, the energy is efficiently transferred to the dopant, and the emission mechanism by which the dopant emits light is also provided. Conceivable. The reason why such efficient energy transfer from the host to the dopant occurs in this combination is that the energy gap is relatively close to that of the dopant material. It is considered that such a high emission intensity can be obtained.

  Further, the combination of the host material and the dopant can suppress the concentration quenching of the dopant to a very low level, which contributes to such strong emission intensity.

  Such a very good light emission efficiency when an organic EL device is produced is not only the above-mentioned mechanism for obtaining a strong fluorescence intensity, but also an improvement in the carrier recombination probability in the light emitting layer, and further a naphthacene triplet. It is considered that there are also some effects such as generation of a singlet excited state of the dopant by energy transfer from the excited state.

  Further, in a general organic EL element, the driving voltage becomes high due to the carrier trap by the dopant, whereas the driving voltage of the organic EL element using the light emitting layer is very low. This is because, in addition to high performance, in addition to the dopant carrier trap, highly efficient light emission is realized by the mechanism described above. Furthermore, it is conceivable that carriers can be easily injected into the light emitting layer. In addition, since the host has a high electron transport property, it is also conceivable that carriers can be localized in the dopant without a large drive voltage increase.

  In addition, since a naphthacene derivative is very stable and has high durability against carrier injection, a combination element using a naphthacene derivative as a host material and a fluoranthene derivative as a dopant material has a very long lifetime.

  The hole injection / transport layer provided in the present invention has a function of facilitating the injection of holes from the hole injection electrode, a function of stably transporting holes, and a function of blocking electrons, thereby increasing the number of holes injected into the light emitting layer. And confinement, optimizing the recombination region, and improving luminous efficiency.

  Examples of the hole injecting and transporting layer include, for example, Japanese Patent Application Laid-Open No. 63-295695, Japanese Patent Application Laid-Open No. 2-191694, Japanese Patent Application Laid-Open No. 3-792, Japanese Patent Application Laid-Open No. Various organic compounds described in JP-A No. 5-299174, JP-A No. 7-126225, JP-A No. 7-126226, JP-A No. 8-100192, EP0650955A1, and the like can be used. For example, tetraarylbenzidine compounds (triaryldiamine or triphenyldiamine: TPD), aromatic tertiary amines, hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having amino groups, polythiophenes, etc. . Two or more of these compounds may be used in combination, and when used in combination, they may be laminated as separate layers or mixed.

  The hole injecting and transporting layer may be divided into a hole injecting layer and a hole transporting layer, and in this case, a preferred combination can be selected and used from the compounds for the hole injecting and transporting layer. At this time, it is preferable to laminate in order of a compound layer having a small ionization potential from the hole injection electrode (ITO or the like) side. Further, it is preferable to use a compound having a good thin film property on the surface of the hole injection electrode. Such a stacking order is the same when two or more hole injecting and transporting layers are provided. By adopting such a stacking order, the drive voltage is lowered, and the occurrence of current leakage and the generation / growth of dark spots can be prevented. In addition, in the case of elementization, since vapor deposition is used, a thin film of about 1 to 10 nm can be made uniform and pinhole free, so that the ion injection potential is small in the hole injection layer and the visible portion has absorption. Even if such a compound is used, it is possible to prevent a decrease in efficiency due to a change in color tone of light emission and reabsorption.

  The thickness of the hole injecting and transporting layer depends on the design of the recombination / light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. The thickness of the hole injecting and transporting layer is not particularly limited and varies depending on the forming method, but is usually about 5 to 500 nm, and preferably 10 to 300 nm. When the injection layer and the transport layer are separated, the injection layer is preferably 1 nm or more, and the transport layer is preferably 1 nm or more. The upper limit of the thickness of the injection layer and the transport layer at this time is usually about 500 nm for the injection layer and about 500 nm for the transport layer. Such a film thickness is the same when two injection transport layers are provided.

  For the formation of the electron injection layer, the electron transport layer, the light emitting layer, and the hole injection transport layer, it is preferable to use a vacuum deposition method because a homogeneous thin film can be formed. When the vacuum deposition method is used, a homogeneous thin film having an amorphous state or a crystal grain size of 0.1 μm or less can be obtained. When the crystal grain size exceeds 0.1 μm, non-uniform light emission occurs, the driving voltage of the element must be increased, and the hole injection efficiency is significantly reduced.

Although the conditions of vacuum deposition are not specifically limited, It is preferable to set it as the vacuum degree of 10 < ^-4 > Pa or less, and a vapor deposition rate to be about 0.01-1 nm / sec. Moreover, it is preferable to form each layer continuously in a vacuum. If formed continuously in a vacuum, impurities can be prevented from adsorbing to the interface of each layer, so that high characteristics can be obtained. Further, the driving voltage of the element can be lowered, and the growth / generation of dark spots can be suppressed.

  In the case of using a vacuum deposition method for forming each of these layers, when a plurality of compounds are contained in one layer, it is preferable to co-deposit each boat containing the compounds by individually controlling the temperature.

  In addition, as a method for forming the mixed layer in the light emitting layer, co-evaporation by evaporating from different vapor deposition sources is preferable. However, when the vapor pressure (evaporation temperature) is the same or very close, they are mixed in advance in the same vapor deposition board. In addition, vapor deposition can also be performed. In the mixed layer, it is preferable that the compounds are uniformly mixed, but in some cases, the compounds may be present in an island shape.

  The electron injection electrode (cathode) is preferably made of a metal, alloy or intermetallic compound having a work function of 4 eV or less. When the work function exceeds 4 eV, the electron injection efficiency decreases, and as a result, the light emission efficiency also decreases. Examples of the constituent metal of the electron injection electrode film having a work function of 4 eV or less include alkaline metals such as Li, Na, and K, alkaline earth metals such as Mg, Ca, Sr, and Ba, rare earth metals such as La and Ce, Al, In, Ag, Sn, Zn, Zr, and the like. Examples of the constituent alloy of the film having a work function of 4 eV or less include Ag · Mg (Ag: 0.1 to 50% in atomic ratio), Al·Li (Li: 0.01 to 12% in atomic ratio), In · Examples include Mg (Mg: 50 to 80% in atomic ratio), Al · Ca (Ca: 0.01 to 20% in atomic ratio), and the like. These may be present singly or as a combination of two or more, and the mixing ratio when two or more of these are combined is arbitrary. Alternatively, an oxide or halide of an alkali metal, alkaline earth metal, or rare earth metal may be thinly formed, and a support electrode (auxiliary electrode, wiring electrode) such as aluminum may be used.

  This electron injection electrode can be formed by vapor deposition or sputtering.

  The thickness of such an electron injection electrode may be a certain thickness that can sufficiently perform electron injection, and may be 0.1 nm or more. Moreover, although there is no restriction | limiting in particular in the upper limit, Usually, a film thickness should just be about 0.1-500 nm.

For the hole injection electrode (anode), it is preferable to determine the material and thickness so that the transmittance of the emitted light is preferably 80% or more. Specifically, an oxide transparent conductive thin film is preferable. For example, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), and zinc oxide ( Those having any of the main compositions of ZnO) are preferred. These oxides may deviate somewhat from their stoichiometric composition. The mixing ratio of SnO ₂ to In ₂ O ₃ is preferably 1 to 20% (mass percentage), and more preferably 5 to 12% (mass percentage). The mixing ratio of ZnO to In ₂ O ₃ is preferably 12 to 32% (mass percentage).

  The hole injecting electrode preferably has an emission wavelength band, usually 350 to 800 nm, and particularly has a light transmittance of 80% or more, particularly 90% or more for each emitted light. Usually, since emitted light is extracted through the hole injection electrode, if the transmittance is lowered, the light emitted from the light emitting layer itself is attenuated, and there is a tendency that luminance necessary for the light emitting element cannot be obtained. However, it is sufficient that the side from which the emitted light is extracted is 80% or more.

  The thickness of the hole injection electrode is sufficient if it has a certain thickness that can sufficiently inject holes, and is preferably in the range of 50 to 500 nm, more preferably 50 to 300 nm. The upper limit is not particularly limited, but if it is too thick, there is a concern about peeling. If the thickness is too thin, there are problems in terms of film strength, hole transport capability, and resistance value during manufacture.

  A sputtering method is preferable for forming the hole injection electrode. As the sputtering method, a high-frequency sputtering method using an RF power source or the like is possible, but the DC sputtering method is used in consideration of easy control of film physical properties of the hole injection electrode to be formed, smoothness of the film formation surface, and the like. It is preferable.

Moreover, you may form a protective film as needed. The protective film can be formed using an inorganic material such as SiO _X or an organic material such as Teflon (registered trademark). The protective film may be transparent or opaque, and the thickness of the protective film is about 50 to 1200 nm. The protective film may be formed by a general sputtering method, vapor deposition method or the like in addition to the reactive sputtering method described above.

  Furthermore, it is preferable to provide a sealing layer on the element in order to prevent oxidation of the organic layer and electrode of the element. The sealing layer is an adhesive resin layer such as a commercially available low-hygroscopic photocurable adhesive, epoxy adhesive, silicone adhesive, cross-linked ethylene-vinyl acetate copolymer adhesive sheet, etc. in order to prevent moisture from entering. Is used to adhere and seal a sealing plate such as a glass plate. Besides a glass plate, a metal plate, a plastic plate, etc. can also be used.

  As the substrate material, a transparent or translucent material such as glass, quartz, resin, or the like is used in the case where the light emitted from the substrate side is extracted. Further, the emission color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate. In the case of the reverse lamination, the substrate may be transparent or opaque, and if it is opaque, ceramics or the like may be used.

  For the color filter film, a color filter used in a liquid crystal display or the like may be used, but it is only necessary to adjust the characteristics of the color filter according to the light emitted from the organic EL to optimize the extraction efficiency and the color purity. . In addition, if a color filter that can cut off short-wavelength external light that is absorbed by the EL element material or the fluorescence conversion layer is used, the light resistance and display contrast of the element can be improved. Further, an optical thin film such as a dielectric multilayer film may be used instead of the color filter.

  The organic EL element of the present invention is usually used as a direct current drive type or a pulse drive type EL element, but may be an alternating current drive. The applied voltage is usually about 2 to 30V.

  Hereinafter, the present invention will be described specifically by way of examples. A comparative example is also shown. The compounds used in the following examples and comparative examples are shown below.

Reference example 1
The glass substrate with an ITO transparent electrode was subjected to ultrasonic cleaning using a neutral detergent, acetone and ethanol, and then pulled up from boiling ethanol and dried. After the surface of the transparent electrode was washed with UV / O _3, it was fixed to a substrate holder of a vacuum vapor deposition apparatus, and the inside of the tank was decompressed to 1 × 10 ⁻⁴ Pa or less. Next, N, N′-diphenyl-N, N′-bis [N- (4-methylphenyl) -Nmonophenyl- (4-aminophenyl)]-1, as a hole injection layer while maintaining the reduced pressure state 1′-biphenyl-4,4′-diamine was deposited to a thickness of 60 nm at a deposition rate of 0.1 nm / sec. Next, N, N, N ′, N′-tetrakis (m-biphenyl) -1,1′-biphenyl-4,4′-diamine is deposited as a hole transport layer at a thickness of 10 nm at a deposition rate of 0.1 nm / sec. Vapor deposited.

  Further, while maintaining the reduced pressure, the compound I (Naph) serving as the host material and the compound II (indenoperylene) serving as the dopant material were mixed at a mass ratio of 99: 1, with an overall deposition rate of 0.15 to 0.20 nm. / Sec was deposited to a thickness of 40 nm to form a light emitting layer.

  Next, while maintaining the reduced pressure state, Compound I (Naph) was deposited at a deposition rate of 0.1 nm / sec to a thickness of 25 nm to form an electron transport layer.

  Further, while maintaining the reduced pressure state, Compound III (B-phen) was evaporated to a thickness of 5 nm at a deposition rate of 0.1 nm / sec to form an electron injection layer.

  Subsequently, LiF was vapor-deposited at a deposition rate of 0.01 nm / sec to a thickness of 0.3 nm to form an electron injection electrode, and Al was deposited as a protective electrode to a thickness of 150 nm to obtain an organic EL device.

A direct current voltage was applied to the organic EL element, and light emission of 660 cd / m ² was confirmed at an initial current density of 10 mA / c ² at a driving voltage of 3.9 V. At this time, the emission maximum wavelength λmax = 610 nm, and the chromaticity coordinates were (x, y) = (0.66, 0.34). The efficiency at this time was 5.3 1 m / W.

In addition, when a constant current of 50 mA / cm ² was passed through the device to continuously emit light, the initial luminance was 3100 cd / m ² and the luminance attenuation after 2000 hours was 15%.

Example 3, Reference Examples 2 , 4, 5, Comparative Examples 1-4
In the organic EL device of Reference Example 1, the compounds used for the electron transport layer and the electron injection layer were changed as shown in Table 1, and otherwise, an organic EL device was obtained in the same manner. About these, it carried out similarly to the reference example 1, and evaluated the characteristic. The evaluation results are shown in Table 1 together with Reference Example 1.

  In addition, the dipole moment of the electron transport material shown in Table 1 is obtained by a semi-empirical molecular orbital method program (MOPAC). The same applies to the dipole moment of Compound I which is the host material of the light emitting layer.

  Further, the ionization potential (IP) of the electron transport layer and the light emitting layer was measured by atmospheric photoelectron spectroscopy or by cyclic voltammetry, and the difference was obtained and shown in Table 1.

Further, the electron transporting mu _a electron transport layer, an element in which the thickness of the electron transport layer to 25nm and 60nm constitute respectively, obtains the driving voltage required to flow the current of 100mA / cm ² (V), It is calculated from the above relational expression. Among them, Table 2 shows values of the drive voltage (V) when the film thickness is changed in Reference Example 1 and Comparative Example 2.

In Example 3 and Reference Examples 2 , 4 and 5, λmax and chromaticity coordinates are almost the same as in Reference Example 1, and in Comparative Examples 2 and 3, the electron transport layer emits light, so (x, y ) = (0.65, 0.35), and Comparative Example 1 was the same as Reference Example 1.

Reference Example 6
In Reference Example 1, an element was obtained when the thickness of the electron injection layer was changed as shown in Table 3 while keeping the total thickness of the electron transport layer and the electron injection layer at 30 nm. These are designated as Sample No. 1-1-No. 1-7. Sample No. 1-5 is the same as Reference Example 1. Table 3 shows the results of evaluating the initial characteristics of these in the same manner as in Reference Example 1. FIG. 1 shows the relationship of the driving voltage with respect to the thickness of the electron injection layer.

Comparative Example 5
A device was prepared and evaluated in the same manner as in Reference Example 1 except that compound VI (Alq) was used as the host material for the light emitting layer, compound IX (pyran) was used as the dopant material, and compound VI (Alq) was used as the electron transport material. The results are shown below.

Initial characteristic drive voltage at 10 mA / cm ² drive: 8.2 V
Luminance: 380 cd / m ²
Efficiency: 1.58lm / W
Continuous drive characteristics: Half by 1000 hr

The chromaticity coordinates were (x, y) = (0.61, 0.39). Incidentally, mu _a electron transport layer is 19.4nm / V, dipole moment 6.57Debye, Ip difference between the light-emitting layer was 0 eV.

It is a graph which shows the relationship with respect to the thickness of the electron injection layer of a drive voltage.

Claims (22)

In the organic EL element having a structure in which at least one light emitting layer, an electron transport layer, and an electron injection layer are sequentially laminated from the anode side,
The electron transport layer contains an anthracene derivative represented by the following formula (4),
The electron injection layer contains a nitrogen-containing heterocyclic compound;
The organic EL element in which the light emitting layer contains a host material and a dopant material, and the host material contains a naphthacene derivative.

[In the formula (4), n ₁₀₁ is 1 or 2. A ₁₀₁ represents a monophenylanthryl group having an aryl group as an unsubstituted or substituted group or a diphenylanthryl group having an aryl group as an unsubstituted or substituted group, and when n ₁₀₁ is 2, these are the same It may be different. L ₁₀₁ represents hydrogen, a single bond or an arylene group . ]   The organic EL device according to claim 1, further comprising at least one hole injecting and transporting layer on the anode side of the light emitting layer.   The organic EL device according to claim 1 or 2, wherein the electron injection layer has a thickness of 0.6 to 20 nm.   The organic EL device according to claim 3, wherein the electron injection layer has a thickness of 1 to 10 nm. The organic EL device according to any one of claims 1 to 4, wherein the anthracene derivative represented by the formula (4) is an anthracene derivative represented by the following formula (4a) or (4b).

Wherein (4a), _{M 1} and _{M 2} represent each the aryl group. L ₁₀ represents hydrogen, a single bond or an arylene group. q1 and q2 each represents 0 or an integer of 1 to 5. n is 1 or 2. ]

Wherein (4b), _{M 3} and _{M 4} represent each the aryl group. L ₂₀ represents hydrogen, a single bond or an arylene group. q3 and q4 each represents 0 or an integer of 1 to 5. ] 6. The organic EL device according to claim 5, wherein the anthracene derivative represented by the formula (4a) or (4b) is an anthracene derivative represented by the following formula (A), (B), (C) or (D).

[In the formula (A), M ₁₁ , M ₁₂ , M ₁₃ , M ₁₄ , M ₁₅ , M ₂₁ , M ₂₂ , M ₂₃ , M ₂₄ and M ₂₅ each represents a hydrogen atom or an aryl group . ]

Wherein _{(B), M 31, M} 32, M 33, M 34, M 35, M 41, M 42, M 43, M 44 and _{M 45} each represents a hydrogen atom or an aryl group. ]

[In the formula (C), M ₃₁ , M ₃₂ , M ₃₃ , M ₃₄ , M ₃₅ , M ₄₁ , M ₄₂ , M ₄₃ , M ₄₄ and M ₄₅ each represents a hydrogen atom or an aryl group . ]

[In the formula (D), M ₁₁ , M ₁₂ , M ₁₃ , M ₁₄ , M ₁₅ , M ₂₁ , M ₂₂ , M ₂₃ , M ₂₄ and M ₂₅ each represents a hydrogen atom or an aryl group . ]   The organic EL device according to claim 6, wherein the anthracene derivative represented by the formula (4a) or (4b) is an anthracene derivative represented by the formula (C). The organic EL device according to any one of claims 5 to 7, wherein the anthracene derivative represented by the formula (4) is an anthracene derivative represented by the following formula IV.

  1,10-phenanthroline, 1,9-phenanthroline, 1,8-phenanthroline, 1,7-phenanthroline, 2,9-phenanthroline, 2,8-phenanthroline, 2,7-phenanthroline, 3,8- The organic according to any one of claims 1 to 8, which contains one or more of phenanthroline, 3,7-phenanthroline, 4,7-phenanthroline and phenanthroline derivatives having one or more of these phenanthroline skeletons in the molecule. EL element. The organic EL device according to claim 9, wherein the phenanthroline or phenanthroline derivative contained in the electron injection layer is represented by the following formula (1a) or (1b).

[In Formula (1a), Y _{2 to} Y ₉ may be the same or different, and each of hydrogen, aryl group, alkyl group, aralkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, and alkenyl group. Represents an amino group or a heterocyclic group, and two or more adjacent groups thereof may be bonded to each other to form a ring. In the formula (1b), A and B may be the same or different and each represents a group represented by the formula (1c), and L represents a single bond or a divalent linking group. In formula (1c), Y _{12 to} Y ₁₉ may be the same as or different from each other, and have the same meaning as Y ₂ to Y ₉ in formula (1a). However, one of Y ₁₂ to Y ₁₉ in the formula (1c) constitutes L, and Y ₁₂ to Y ₁₉ constituting L may be the same or different in A and B. Good. ] The organic EL device according to any one of claims 1 to 10, wherein the naphthacene derivative contained in the light emitting layer is represented by the following formula (2).

[In the formula (2), Q ¹⁰ , Q ²⁰ , Q ³⁰ , Q ⁴⁰ , Q ⁵⁰ , Q ⁶⁰ , Q ⁷⁰ , Q ⁸⁰ , Q ¹¹⁰ , Q ¹²⁰ , Q ¹³⁰ and Q ¹⁴⁰ are hydrogen, alkyl group, An aryl group, an amino group, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an alkenyl group, an aralkyl group or a heterocyclic group, which may be the same or different. ] At least one of Q ¹⁰ , Q ²⁰ , Q ³⁰ , Q ⁴⁰ , Q ⁵⁰ , Q ⁶⁰ , Q ^70, and Q ^{80 in} the naphthacene derivative represented by the formula (2) contained in the light emitting layer is an aryl group. The organic EL device according to claim 11. The organic EL device according to claim 11 or 12, wherein at least one of Q ¹⁰ , Q ²⁰ , Q ³⁰ and Q ^{40 in} the naphthacene derivative represented by the formula (2) contained in the light emitting layer is an aryl group. The organic EL device according to claim 1, wherein the naphthacene derivative contained in the host material of the light emitting layer is represented by the following formula (2a).

[In the formula (2a), Q ^{5 to} Q ⁸ and Q ^{11 to} Q ¹⁶ are each hydrogen, alkyl group, aryl group, amino group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkenyl group, aralkyl group or Represents a heterocyclic group, which may be the same or different. Q ^{21 to} Q ²⁵ and Q ^{51 to} Q ⁵⁵ each represent hydrogen, an alkyl group, an aryl group, an amino group, an alkoxy group, an alkylthio group, an aryloxy group, an arylthio group, an alkenyl group, an aralkyl group, or a heterocyclic group, These may be the same or different, and two or more adjacent ones may be bonded to each other to form a ring. ]   The organic EL device according to claim 1, wherein the naphthacene derivative contained in the light emitting layer is a hydrocarbon compound.   The organic EL device according to claim 1, wherein the dopant material of the light emitting layer contains a fluoranthene derivative. The organic EL device according to claim 16, wherein the fluoranthene derivative is an indenoperylene derivative represented by the following formula (3a).

[In the formula (3a), Z _{1 to} Z ₆ , Z ₉ , Z ₁₀ , Z _{11 to} Z ₁₆ , Z ₁₉ and Z ₂₀ are hydrogen, halogen, alkyl group, alkoxy group, alkylthio group, alkenyl group, alkenyl, respectively. Oxy group, alkenylthio group, aromatic ring-containing alkyl group, aromatic ring-containing alkyloxy group, aromatic ring-containing alkylthio group, aromatic ring group, aromatic ring oxy group, aromatic ring thio group, aromatic ring alkenyl group, alkenyl aromatic ring group, An amino group, a cyano group, a hydroxyl group, —COOR ₁ (where R ₁ represents hydrogen, an alkyl group, an alkenyl group, an aromatic ring-containing alkyl group or an aromatic ring group), —COR ₂ (where R ₂ is a hydrogen atom) , alkyl group, alkenyl group, aromatic ring-containing alkyl group, an aromatic group or an amino group), or -OCOR ₃ (wherein, _{R 3} is an alkyl group, alkenyl Group, represents an aromatic ring-containing alkyl group or aromatic ring group), _further, adjacent groups among _{Z 1 ~Z 6, Z 9,} Z 10, Z 11 ~Z 16, Z 19, Z 20 is They may be bonded to each other to form a ring with substituted carbon atoms. ] Any one of the organic EL element according to claim 1 to 17 electron transporting mu _a defined below the electron-transporting layer is 80 nm / V or more (Note that the electron transporting mu _a is of claim 1 Organic In the EL element, the parameter is defined as follows according to a change in driving voltage required to flow a current of 100 mA / cm ² when the thickness of the electron transport layer is changed, and the thickness of the electron transport layer: When the drive voltage (V) at the time of driving 100 mA / cm ² when (nm) is d ₁ and d ₂ (where d ₁ > d ₂ ) is V ₁ and V ₂ , μ _a = (d ₁ -d ₂ ) / (V ₁ -V ₂ )).   The organic EL device according to claim 1, wherein a difference in ionization potential between the electron transport layer and the light emitting layer is 0.1 eV or less.   The organic EL element according to any one of claims 1 to 19, wherein a material used for the electron transport layer has a dipole moment value of 1.0 Debye or less.   The organic EL device according to any one of claims 1 to 20, wherein the light emitting layer contains a host material and a dopant material, and the value of the dipole moment of the host material is 1.0 Debye or less.   The organic EL device according to any one of claims 1 to 21, wherein the content of the anthracene derivative represented by the formula (4) in the electron transport layer is 80% (mass percentage) or more.

Images