Light emitting device

Abstract

It is an object of the present invention to provide a light-emitting element having a long lifetime. Another object of one embodiment of the present invention is to provide a light-emitting element with high emission efficiency and low driving voltage. It is another object of the present invention to provide a light-emitting device, an electronic device, and a lighting device each having a long lifetime and low power consumption by using the light-emitting element of the present invention.SOLUTION: One embodiment of the present invention is a light-emitting element including at least a stacked-layer structure in which a first layer, a second layer, and a light-emitting layer are provided between an anode and a cathode in this order from the anode side, in which the first layer includes a first organic compound and an electron-accepting compound, and the second layer includes a second organic compound having a HOMO level within ± 0.2 eV of the HOMO level of the first organic compound; The light-emitting layer includes a third compound having a HOMO level within ± 0. 2eV of that of the second compound and a light-emitting material having a hole-trapping property with respect to the third compound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light-emitting element, a light-emitting device, an electronic device, and a lighting device. [Background technology]

[0002] In recent years, electroluminescence (EL) The basic structure of these light-emitting devices is as follows: A light-emitting material is sandwiched between a pair of electrodes. This allows light emission from the luminescent substance.

[0003] These light-emitting elements are self-luminous, so the pixels are more visible than those of LCDs. It has the advantage of being simple and does not require a backlight, making it suitable for use as a flat panel display element. Furthermore, such a light-emitting element can be manufactured to be thin and lightweight. Another major advantage is that it has an extremely fast response time.

[0004] Furthermore, these light-emitting elements can be formed into a film, making it easy to emit light in a planar form. Therefore, it is possible to form a large-area element utilizing surface light emission. This means that the light source is not uniform across the entire spectrum, even when it comes to point light sources such as incandescent bulbs and LEDs, or linear light sources such as fluorescent lamps. This is a feature that is difficult to obtain from other sources, making it highly useful as a surface light source that can be applied to lighting, etc.

[0005] In the case of light-emitting elements that utilize electroluminescence, the light-emitting substance is either an organic compound or They can be broadly divided into compounds based on whether they are inorganic or not.

[0006] When the light-emitting substance is an organic compound, light is emitted from the anode by applying a voltage to the light-emitting element. Holes are injected from the cathode and electrons are injected from the cathode into the layer containing the light-emitting organic compound, causing a current to flow. Then, the carriers (holes and electrons) recombine to form light-emitting organic The compound forms an excited state, and emits light when the excited state returns to the ground state. Current-excited light-emitting elements that use photo-active organic compounds are generally called organic EL elements. .

[0007] The types of excited states that organic compounds form are singlet excited states and triplet excited states. The organic compounds used in general organic EL devices have a singlet state in the ground state. Since the light emitted from the singlet excited state is called fluorescence, the light emitted from the triplet excited state is called phosphorescence. It's been discovered.

[0008] For such light-emitting devices, a heterostructure in which layers of different organic compounds are stacked has been proposed. This has led to significant developments (see Non-Patent Document 1). This is because the recombination efficiency of carriers increases, and the light emission efficiency improves. A hole transport layer and an electron transport light emitting layer are laminated.

[0009] Since then, many studies have been conducted on the relationship between heterostructure and driving voltage, or between heterostructure and lifetime. For example, in a device in which the hole transport layer is in contact with the anode, It has been reported that the ionization potential of the hole transport layer affects the lifetime (non In the device disclosed in Non-Patent Document 2, the ions in the hole transport layer It is said that the smaller the ionization potential, the longer the life. By inserting a hole injection layer with a small capacitance between the anode and the hole transport layer, the device can have a long life. There are also reports that this leads to the formation of erythrocytes (see Non-Patent Documents 3 and 4). [Prior art documents] [Non-patent literature]

[0010] [Non-Patent Document 1] C.W. Tang and 1 other collaborators, Applied Physics Letters, Vol. 51, No. 12, 913-915 (1987)

[0011] [Non-patent document 2] Chihaya Adachi and two others, Applied Physics Letters, Vol. 66, No. 20, 2679-2681 (1995)

[0012] [Non-patent document 3] Yasuhiko Shirota and seven others, Applied Physics Letters, Vol. 65, No. 7, 807-809 (1994)

[0013] [Non-patent document 4] SAVan Slyke and two others, Applied Physics Letters, Vol. 69, No. 15, pp. 2160-2162 (1996) Summary of the Invention [Problem to be solved by the invention]

[0014] Considering the reports in Non-Patent Documents 2 to 4, the ionic conductivity of the organic material of the hole injection layer in contact with the anode is The ionization potential (in other words, the HOMO level) should be as close as possible to the work function of the anode. As a result, it is desirable to laminate a hole injection layer, a hole transport layer, and a light-emitting layer. In the case of optical devices, as shown in FIG. 2 of Non-Patent Document 3, the emission is determined from the work function of the anode. The HOMO level is designed to be stepped up to the optical layer. The HOMO level gradually decreases from the positive Select materials for the hole injection layer and hole transport layer.

[0015] This type of stepped design has been the standard element design for organic EL elements up until now. Based on this device design, the materials for the hole injection layer, hole transport layer, and light-emitting layer were selected. By changing the type of material, we have been searching for the combination of materials that will give us the best lifespan and efficiency. This is the trend in element development and is still the mainstream today.

[0016] However, the larger the difference between the work function of the anode and the HOMO level of the light-emitting layer, However, this design presents difficulties because in this case, hole injection between the anode and the light-emitting layer In order to reduce the barrier to entry, it is necessary to create many steps in the HOMO level, i.e., to create many layers. This is because it is necessary to insert a layer between the anode and the light-emitting layer. Therefore, in many light-emitting devices, at most two layers, a hole injection layer and a hole transport layer, are formed. That's all.

[0017] Therefore, between the hole injection layer and the hole transport layer, or between the hole transport layer and the light emitting layer, Although the hole injection barrier in the blue semiconductor can be reduced, it is difficult to eliminate it substantially. In the case of color light-emitting devices and phosphorescent light-emitting devices, the energy of the material of the light-emitting layer (especially the host material of the light-emitting layer) The HOMO level tends to be quite low because of the large energy gap. Therefore, the difference between the work function of the anode and the HOMO level of the light-emitting layer becomes large, resulting in a large hole injection hindrance. In many cases, a large hole injection barrier occurs between the hole transport layer and the light emitting layer. Cheap.

[0018] The inventors have found that these hole injection barriers can be overcome by improving the materials and structure of the light-emitting layer. It was found that the wall is now becoming a problem for the life span. When the first reports of 4 were published, the light-emitting layer was the rate-limiting factor for the lifetime. Recently, the hole injection barrier designed in a stepped shape has become a problem. was recognized.

[0019] Furthermore, by introducing a conventional heterostructure, the light emission efficiency can be secured, but the lifetime is Depending on the heterostructure (type of material) introduced, it may improve or decrease dramatically. The cause of this phenomenon has not been clarified. Therefore, this phenomenon can be explained simply by the compatibility of materials. Currently, this is often overlooked, and no guidelines have been established regarding the combination of materials.

[0020] Therefore, the inventors have designed a device that differs from the conventional heterostructure, and have been able to reduce the driving voltage and We attempted to obtain a light-emitting element with a long life without sacrificing luminous efficiency. We also conducted a detailed study on how to combine materials in the product.

[0021] In view of the above, an object of the present invention is to obtain a light emitting element having a long life. An object of the present invention is to obtain a light-emitting element that is excellent in efficiency and driving voltage.

[0022] Furthermore, by using the light-emitting element of the present invention, a light-emitting device with a long life and low power consumption can be provided. The present invention also aims to provide electronic devices and lighting devices that have a long life and low power consumption. The goal is to [Means for solving the problem]

[0023] First, the inventors have developed a method for substantially eliminating the hole injection barrier from the anode to the light-emitting layer. Furthermore, after extensive research, we found that the following could be achieved with this device structure: This problem can be solved by adding a light-emitting substance that exhibits hole-trapping properties to the light-emitting layer. We found that...

[0024] That is, one aspect of the present invention is a laminate comprising a first layer and a second layer disposed between an anode and a cathode in this order from the anode side. The first layer has at least a laminated structure including a second layer and a light-emitting layer. The second layer contains an organic compound and an electron-accepting compound, and the second layer contains H of the first organic compound. a second organic compound having a HOMO level within ±0.2 eV of the OMO level; The light-emitting layer has a HOMO level within ±0.2 eV of the HOMO level of the second organic compound. a third organic compound having an O level and a compound exhibiting hole trapping properties with respect to the third organic compound; The light-emitting element is a light-emitting element containing a light-emitting material.

[0025] In this specification, the anode is an electrode from which holes are emitted, and the cathode is an electrode from which holes are emitted from the anode. The electrode that receives holes. Alternatively, the cathode is the electrode that emits electrons, and the anode is the cathode. The electrode that receives the electrons emitted from the

[0026] The hole transport skeleton of the organic compound used in the hole injection layer, the hole transport layer, and the light emitting layer is Therefore, one aspect of the present invention is to provide a cathode and an anode between the anode and the cathode. The semiconductor device has at least a laminated structure in which a first layer, a second layer, and a light-emitting layer are provided in this order from the electrode side. The first layer comprises a first organic compound having a first hole transport skeleton and an electron accepting compound. the second layer comprises a second organic compound having a second hole transport skeleton, The light-emitting layer comprises a third organic compound having a third hole transport skeleton, and a compound having a third hole transport skeleton. and a light-emitting substance that exhibits hole-trapping properties against the first hole-transporting skeleton, the second hole-transporting skeleton, The light-emitting device is one in which the hole transport skeleton and the third hole transport skeleton are the same.

[0027] Here, the present inventors have investigated the properties of the organic compounds used in the hole injection layer, hole transport layer, and light emitting layer. When a specific framework is applied to the hole transport framework, the hole injection barrier between each layer is reduced. Furthermore, by adding an electron-accepting compound to the hole injection layer, the anode and the hole injection layer It has been found that the hole injection barrier between the anode and the layer can also be reduced. Between the anode and the cathode, a first layer, a second layer, and a light-emitting layer are provided in this order from the anode side. The first layer has a laminated structure, and the first layer has a first organic compound having a first hole transport skeleton. and an electron accepting compound, and the second layer comprises a second hole transporting skeleton. the light-emitting layer comprises a third organic compound having a third hole-transporting skeleton, a light-emitting substance that exhibits hole-trapping properties with respect to the third organic compound, the transport skeleton, the second hole transport skeleton, and the third hole transport skeleton are each independently , π-excess heteroaromatic ring, 3-ring fused aromatic hydrocarbon ring, or 4-ring fused aromatic hydrocarbon The light-emitting device includes at least one skeleton of a monocyclic ring.

[0028] Examples of hole transport skeletons include carbazole, dibenzofuran, dibenzothiophene, Alternatively, at least one skeleton of anthracene is preferred.

[0029] In addition, even when the above-mentioned specific skeleton is used as the hole transport skeleton, It is preferable that the hole transport skeleton of the organic compound used in the transport layer and the light emitting layer is the same. Therefore, one aspect of the present invention is a laminate comprising a first layer and a second layer disposed between an anode and a cathode, in this order from the anode side: The first layer has at least a laminated structure including a second layer and a light-emitting layer. The second layer comprises a first organic compound having a hole transport skeleton and an electron accepting compound. a second organic compound having the first hole transport skeleton, and the light-emitting layer comprises the first a third organic compound having a hole transport skeleton; and a hole trap for the third organic compound. and a light-emitting substance exhibiting a π-excess heteroaromatic ring, ... A light-emitting device containing at least one skeleton of a fused aromatic ring or a fused tetracyclic aromatic ring. do.

[0030] Examples of hole transport skeletons include carbazole, dibenzofuran, dibenzothiophene, Alternatively, at least one skeleton of anthracene is preferred.

[0031] In the above-described configuration of the light-emitting element, the light-emitting substance is an aromatic amine compound. Pyrene diamine or an organometallic complex is preferred because of its high hole trapping ability. The compound or iridium complex has a high hole trapping property and also has a high luminous efficiency, and is therefore suitable. do.

[0032] Furthermore, the present inventors have found that the light-emitting element according to one embodiment of the present invention can be formed under certain specific conditions. By providing another light-emitting layer, the escape of holes to the cathode is further suppressed, improving the lifespan and luminous efficiency. It has been found that both the positive and negative photosensitivity can be dramatically improved. Between the anode and the cathode, a first layer, a second layer, a first light-emitting layer, and a third layer are disposed in this order from the anode side. The first layer has a laminated structure including a first light-emitting layer and a second light-emitting layer, and the first layer is a first organic compound. and an electron-accepting compound, and the second layer has a HOMO approximation of the first organic compound. a second organic compound having a HOMO level within ±0.2 eV of the first organic compound; The light-emitting layer has a HOMO level within ±0.2 eV of the HOMO level of the second organic compound. a third organic compound having a level, and a hole trapping property for the third organic compound. a first light-emitting material, and the second light-emitting layer has a HOMO level of the third organic compound. the HOMO level of the third organic compound is within ±0.2 eV of the LUMO level of the third organic compound. a fourth organic compound having a LUMO level within ±0.2 eV of the fourth organic compound; a second light-emitting substance that exhibits hole trapping properties with respect to the organic compound, and The object is a light-emitting element that is a compound different from the third organic compound.

[0033] In this specification, the escape of holes to the cathode refers to the escape of holes injected from the anode into electrons. This refers to passing through to the cathode side without recombining.

[0034] The organic compounds used in the hole injection layer, the hole transport layer, the first light-emitting layer, and the second light-emitting layer are It is preferable that the hole transport skeletons of the first and second light-emitting layers are the same. It is preferable that the electron transport skeletons are the same. Between the first layer, the second layer, the first light-emitting layer, and the second light-emitting layer, in this order from the anode side, and a first layer having a first hole transport skeleton. and an electron-accepting compound, and the second layer comprises a second hole-transporting compound. the first light-emitting layer comprises a second organic compound having a third hole-transporting skeleton and an electron transporting skeleton; a third organic compound having a hole transport skeleton, and a compound having hole trapping properties relative to the third organic compound; and the second light-emitting layer comprises a fourth hole-transporting skeleton and a first light-emitting material exhibiting the electron transporting property a fourth organic compound having a hole transport skeleton; and a compound having hole trapping properties relative to the fourth organic compound. and a second luminescent material that exhibits the following: a compound comprising the first hole transport skeleton, the second hole transport skeleton, the third hole transport skeleton, The light-emitting device is one in which the transport skeleton and the fourth hole-transport skeleton are the same.

[0035] Here, the present inventors have prepared a hole injection layer, a hole transport layer, a first light-emitting layer, and a second light-emitting layer. When a specific skeleton is applied to the hole transport skeleton of the organic compound used, hole injection between each layer Furthermore, it was found that the hole injection barrier was reduced by adding an electron-accepting compound to the hole injection layer. It was found that if this is done, the hole injection barrier between the anode and the hole injection layer can also be reduced. In one aspect of the present invention, a first layer, a second layer, and a second layer are disposed between an anode and a cathode in this order from the anode side. The light-emitting device has at least a laminated structure including a first light-emitting layer and a second light-emitting layer, comprises a first organic compound having a first hole transport skeleton and an electron accepting compound, The second layer comprises a second organic compound having a second hole transport skeleton, and the first light-emitting layer comprises a third organic compound having a third hole transport skeleton and an electron transport skeleton; a first light-emitting substance exhibiting hole-trapping properties with respect to a compound, and the second light-emitting layer a fourth organic compound having a hole transport skeleton and the electron transport skeleton; and a second light-emitting substance that exhibits hole trapping properties with respect to the fourth organic compound. , the third organic compound is a compound different from the first hole transport skeleton, the second the hole transport skeleton, the third hole transport skeleton, and the fourth hole transport skeleton are each independently In particular, at least one of a π-excess heteroaromatic ring, a 3-ring condensed aromatic ring, or a 4-ring condensed aromatic ring The light-emitting element includes any one of the skeletons.

[0036] Examples of hole transport skeletons include carbazole, dibenzofuran, dibenzothiophene, Alternatively, at least one skeleton of anthracene is preferred.

[0037] In addition, even when the above-mentioned specific skeleton is used as the hole transport skeleton, The hole transport skeletons of the organic compounds used in the transport layer, the first light-emitting layer, and the second light-emitting layer are the same. Therefore, in one aspect of the present invention, a cathode is provided between the anode and the cathode. A laminated structure in which a first layer, a second layer, a first light-emitting layer, and a second light-emitting layer are provided in this order. The first layer has at least a structure, and the first layer comprises a first organic compound having a first hole transport skeleton. and an electron accepting compound, and the second layer comprises a second hole transporting skeleton having the first hole transporting skeleton. the first light-emitting layer comprises an organic compound, and the first light-emitting layer comprises the first hole-transporting skeleton and the electron-transporting skeleton. a third organic compound having a hole trapping property with respect to the third organic compound; and a light-emitting material, and the second light-emitting layer comprises the first hole-transporting skeleton and the electron-transporting skeleton. a fourth organic compound having a hole trapping property with respect to the fourth organic compound; and a second luminescent material, wherein the fourth organic compound is a compound different from the third organic compound. The first hole transport skeleton is a π-excess heteroaromatic ring, a fused tricyclic aromatic ring, or is a light-emitting device containing at least one skeleton of a fused tetracyclic aromatic ring.

[0038] Examples of hole transport skeletons include carbazole, dibenzofuran, dibenzothiophene, Alternatively, at least one skeleton of anthracene is preferred.

[0039] In the above-described configuration having the first light-emitting layer and the second light-emitting layer, In order to increase the carrier recombination efficiency, the hole transport property of the first light-emitting layer is set to be higher than that of the second light-emitting layer. the hole transporting property of the first light-emitting layer is higher than the electron transporting property of the second light-emitting layer; It is preferable that the α-threshold value is lower than that of the α-threshold value.

[0040] The first luminescent material and the second luminescent material may be an aromatic amine compound, Alternatively, organometallic complexes are preferred because of their high hole trapping properties. The iridium complex or the iridium complex is preferable because it has a high hole trapping property and also has a high luminous efficiency.

[0041] Furthermore, even when the first luminescent material and the second luminescent material are the same material, the present invention This is one aspect of the present invention, as it provides the desired effect.

[0042] In the light-emitting element described above, the HOMO level of the light-emitting layer is close to that of the light-emitting layer. Organic compounds, in other words, organic compounds with a much deeper HOMO level than conventional ones, Therefore, one embodiment of the present invention is a light-emitting element comprising the above-described organic compound. In the compound, the HOMO level of the first organic compound is -6.0 eV or more, -5.7 eV or more The light-emitting device is characterized in that:

[0043] In the light-emitting device described above, the laminated structure (the first layer, the second layer, and the light-emitting layer) a laminated structure including a first layer, a second layer, a first light-emitting layer, and a second layer; A plurality of layers (a laminated structure in which a light-emitting layer is provided) may be provided between the anode and the cathode. good.

[0044] In one aspect of the present invention, a first layer and a second layer are disposed between an anode and a cathode in this order from the anode side. The first layer has a laminated structure including a first conductive layer and a light-emitting layer. the second layer contains the HO of the first organic compound and the electron-accepting compound; a second organic compound having a HOMO level within ±0.2 eV of the MO level; The light-emitting layer has a HOMO level within ±0.2 eV of the HOMO level of the second organic compound. a third organic compound having a level, and a hole trapping property for the third organic compound. The light-emitting element includes a light-emitting substance and a light-emitting substance.

[0045] The light-emitting substance may have an excitation energy equal to or less than that of the light-emitting substance exhibiting hole trapping properties. It is a light-emitting element that has excitation energy.

[0046] The above-described light-emitting element of one embodiment of the present invention is useful and applicable to various light-emitting devices. Therefore, a light-emitting device using a light-emitting element which is one embodiment of the present invention is also included in the present invention. In this specification, the term "light emitting device" refers to an image display device, a light emitting device, or It also refers to the light source. nted circuit) or TAB (Tape Automated Bond ing) tape or TCP (Tape Carrier Package) is attached modules with printed wiring boards at the end of TAB tape or TCP or a substrate on which a light emitting element is formed, by the COG (Chip On Glass) method. Therefore, all modules on which an IC (integrated circuit) is directly mounted are also included in the light-emitting device.

[0047] Furthermore, the light-emitting device according to one embodiment of the present invention can be used in a display portion or a light-emitting portion of various electronic devices. Therefore, the light-emitting device according to one embodiment of the present invention can be used as a light source or the like. The present invention also includes electronic devices that perform the above-described functions.

[0048] The light-emitting device according to one embodiment of the present invention is also useful as a light source for various lighting devices. Therefore, a lighting device including a light-emitting device according to one embodiment of the present invention is also included in the present invention. Let's say. [Effects of the Invention]

[0049] By using the present invention, a light-emitting element having a long life can be provided. An excellent light emitting element can be provided.

[0050] Furthermore, a light emitting device having a long life and low power consumption can be provided. It is possible to provide low-power electronic devices and lighting devices. [Brief explanation of the drawings]

[0051] [Figure 1] 1A to 1C illustrate a light-emitting element according to an embodiment. [Figure 2] 1A and 1B are diagrams illustrating a conventional light-emitting element. [Figure 3] 1A to 1C illustrate a light-emitting element according to an embodiment. [Figure 4] 1A to 1C illustrate a light-emitting element according to an embodiment. [Figure 5] 1A to 1C illustrate a light-emitting element according to an embodiment. [Figure 6] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 7] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 8] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 9] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 10] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 11] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 12] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 13] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 14] 1A to 1C illustrate compounds used in a light-emitting element according to an embodiment. [Figure 15] 1A to 1C illustrate a light-emitting element according to an embodiment. [Figure 16] 1A to 1C are diagrams illustrating compounds used in a light-emitting element according to an embodiment. [Figure 17] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 18] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 19] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 20] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 21] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 22] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 23] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 24] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 25] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 26] 1A to 1C illustrate a light-emitting device according to an embodiment. [Figure 27] 1A to 1C illustrate a light-emitting device according to an embodiment. [Figure 28] 1A to 1C illustrate a display device according to an embodiment. [Figure 29] 1A to 1C illustrate electronic devices according to an embodiment. [Figure 30] 1A and 1B are diagrams illustrating a lighting device according to an embodiment. [Figure 31] 1A to 1C illustrate a display device according to an embodiment. [Figure 32] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 33] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. [Figure 34] 1A to 1C are diagrams illustrating light-emitting elements according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0052] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and various modifications may be made without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications may be made to the details. The present invention should not be construed as being limited to the description of the following embodiments.

[0053] In this specification, when a substance A is dispersed in a matrix made of another substance B, Substance B that constitutes the matrix is ​​called the host material, and substance A that is dispersed in the matrix is ​​called the gel material. Substance A and substance B are each a single substance. It may be a mixture of two or more substances.

[0054] In this specification, the HOMO level refers to the highest occupied molecular orbital (HOMO). The LUMO level is the level possessed by the LUMO (Liquid Uplifted Molecular Orbital) The lowest unoccupied molecular orbital (Lowest Unoccupied Molecular Orbital) tal) has.

[0055] Furthermore, in this specification, the HOMO level or LUMO level is high. A low HOMO or LUMO level means that the energy level is high. For example, a substance with a HOMO level of -5.5 eV Material A has a HOMO level 0.3 eV lower than material B, which has a HOMO level of -5.2 eV. , which means that the HOMO level is 0.2 eV higher than that of material C, which has a HOMO level of -5.7 eV. It is possible.

[0056] (Embodiment 1) In this embodiment 1, materials to be used and a manufacturing method thereof will be described with respect to a structure of a light-emitting element which is one embodiment of the present invention. In the first embodiment, the area between the anode and the cathode is This is called the EL layer.

[0057] First, regarding a light-emitting element of one embodiment of the present invention, a conceptual diagram of the element structure is shown in FIG. 1( a ), and its bandgap is shown. The diagram is shown in Fig. 1(b). For comparison, the element structure of a conventional light-emitting device is shown in Fig. 1(c). The structure is shown in Figure 2(a) and its band diagram is shown in Figure 2(b).

[0058] FIG. 2(a) shows the device structure of a conventional light-emitting device as shown in, for example, Non-Patent Document 3. An EL layer 203 is provided between an anode 201 and a cathode 202. The EL layer 203 is In order from the anode 201 side, a hole injection layer 211, a hole transport layer 212, and a light emitting layer 221 are formed. The laminated structure is provided.

[0059] Conventionally, as shown in FIG. 2(b), the HOMO level of the hole injection layer 211 in contact with the anode 201 is It is desirable that the level 233 is as close as possible to the work function 231 of the anode 201. As a result, the HOMO level of the hole injection layer is 233, and the HOMO level of the hole transport layer is 23 4. The HOMO level 235 of the light-emitting layer is designed to be gradually lowered in a stepwise manner. The holes are conducted through these HOMO levels and are transferred to the light-emitting layer 221 together with the electrons injected from the cathode 202. The electrons recombine to emit light, where 232 is the work function of the cathode.

[0060] However, the energy gap of the material of the light-emitting layer (especially the host material of the light-emitting layer) is large. As the temperature increases, the HOMO level 235 of the light-emitting layer tends to decrease accordingly. In this case, the difference between the work function 231 of the anode and the HOMO level 235 of the light-emitting layer becomes large. In the conventional light-emitting device, the HOMO level 233 of the hole injection layer and the HO The hole injection barrier between the HOMO level 234 and the HOMO level 234 of the hole transport layer At least one of the hole injection barriers between the HOMO level 235 of the layer and the In many cases, a large hole injection between the hole transport layer 212 and the light emitting layer 221 occurs. Barriers are likely to arise.

[0061] In conventional light-emitting devices, this hole injection barrier is utilized to accumulate holes. It has been thought that it is important to prevent holes from passing through to the cathode and obtain high luminous efficiency. As a means for preventing holes from passing through to the cathode, for example, a hole blocking layer with a large hole injection barrier is used. The introduction of a barrier layer on the cathode side of the light-emitting layer is also being considered. The concept of conventional heterostructure light-emitting devices is to achieve high luminous efficiency by using .

[0062] However, as mentioned above, the present inventors have found that these hole injection barriers have a significant effect on lifetime. The present invention was developed based on the recognition that this was becoming a problem. The figure shows the concept of the element structure of the light-emitting element, and shows the structure of the anode 101 and the cathode 102. The EL layer 103 is provided. The EL layer 103 is formed by stacking a first layer 11 The light-emitting layer 121 has a laminated structure including at least a first layer 111, a second layer 112, and a light-emitting layer 121. The first layer 111 contains a first organic compound and an electron-accepting compound. The second layer 112 contains a second organic compound, and the light-emitting layer 121 contains a third organic compound and The third organic compound contains a light-emitting substance that exhibits hole-trapping properties.

[0063] First, as shown in FIG. 1(b), the inventors first investigated the H The OMO level 133 and the HOMO level 134 of the second organic compound in the second layer are In addition, the HOMO level of the second organic compound in the second layer is 1 The HOMO level 34 of the third organic compound in the light-emitting layer is approximately equal to the HOMO level 135 of the third organic compound in the light-emitting layer. As a result, the hole injection barrier between the first layer 111 and the second layer 112 and The hole injection barriers between the second layer 112 and the light-emitting layer 121 are both significantly reduced.

[0064] In this specification, the term "similar HOMO levels" specifically refers to the difference in the HOMO levels. Usually, when there are two kinds of substances, the energy of the electrochemical reaction is If the energy difference is within 0.2 eV, both electrochemical reactions occur. This is because the chemical energy can be considered roughly equivalent (on the other hand, the energy of an electrochemical reaction When the difference is much greater than 0.2 eV, the electrochemical reaction occurs selectively in only one direction. As will be described later in the examples, experimentally, if the difference in HOMO levels is within ±0.2 eV, the present invention can be realized. Furthermore, it is preferable that the difference in HOMO levels is within ±0.1 eV. This allows for greater benefits from the invention.

[0065] Here, when the energy gap of the third organic compound in the light-emitting layer 121 becomes large, As a result, the HOMO level 135 of the third organic compound tends to become lower. Therefore, with the above-described configuration, hole injection between the first layer 111 and the second layer 112 When the hole injection barrier between the second layer 112 and the light-emitting layer 121 is reduced, The HOM of any of the first organic compound, the second organic compound, and the third organic compound The O level is also significantly lower than the work function of the anode. There is a large hole injection barrier between the work function 131 and the HOMO level 133 of the first organic compound. is formed, making it difficult to inject holes from the anode 101 into the first layer 111.

[0066] Therefore, the present inventors have proposed a method for forming an electron-accepting layer 111 as a barrier at the anode interface. We thought that this problem could be overcome by adding an electron-accepting compound to the first layer 111. By this, the work function 131 of the anode and the first organic compound contained in the first layer 111 are Even if there is a gap between the HOMO level 133 and the The first layer 111 is made of an electron-accepting compound and a first organic compound. The electron-accepting compound and the first organic compound may be mixed, or the electron-accepting compound and the first organic compound may be mixed on the anode side. It may also be configured such that they are stacked in this order.

[0067] With the above-described configuration, the problem of the anode to the light-emitting layer, which is considered to be a problem in conventional devices, is solved. However, in this configuration, the hole injection barrier up to However, simply applying this makes it easier for holes to escape to the cathode, reducing the luminous efficiency. In addition, it was found that the electron transport layer was provided between the light-emitting layer 121 and the cathode 102. In this case, it was found that the electron transport layer emits light.

[0068] To prevent holes from passing through to the cathode without using a barrier (hole blocking), It is effective to add a hole-trapping substance, but the inventors have not yet found the type of hole-trapping substance. As a result, we have investigated the type and region of the luminescent material added to the luminescent layer. By providing trapping properties, this problem can be overcome without increasing the driving voltage. In order to trap holes using a light-emitting material, a third organic It is preferable to use a compound as a host material and a light-emitting substance with hole trapping properties as a guest material. In addition, the HOMO level 136 of the hole-trapping luminescent material is From the viewpoint of the HOMO level of the third organic compound, it is necessary to select a compound having a HOMO level of 135 that is 0.3 eV or more higher than that of the third organic compound. preferable.

[0069] To prevent holes from leaking to the cathode and increase luminous efficiency, a material that traps holes is used. This can also be achieved by adding between the anode 101 and the light-emitting layer 121. In such a method, the movement speed of holes from the light-emitting layer 121 to the light-emitting layer 121 is slow. Therefore, the drive voltage inevitably increases. The bonding area is attracted to the anode, and electrons escape to the anode, reducing the luminous efficiency. On the other hand, in the structure of one embodiment of the present invention as shown in FIG. The electrons are transported from the electrode 101 to the light-emitting layer 121 without encountering any barriers or traps. Therefore, the increase in the driving voltage can be minimized. Preferably, no sticky materials are added.

[0070] Furthermore, as shown in FIG. 1(b), the holes that reach the light-emitting layer 121 are trapped by the hole-trapping The electrons are trapped in the HOMO level 136 of the light-emitting material, and the speed of their movement within the light-emitting layer 121 is rapidly reduced. Then, the holes whose movement speed is reduced and the electrons injected from the cathode 102 are efficiently transferred. In Figure 1(b), 132 is the cathode. From the viewpoint of the driving voltage, it is necessary to sufficiently transport electrons in the light-emitting layer 121. Therefore, the third organic compound serving as the host material of the light-emitting layer 121 must have not only hole transport properties but also It is preferable that the material has not only a dielectric constant but also an electron transport property. In other words, it is preferable that the material is bipolar. I wish.

[0071] In this specification, the bipolar material is a material that has the ability to inject holes (electrons) into the EL layer. A material capable of electron injection (reaction in which electrons are taken) and electron scavenging (reaction in which electrons are received) It refers to a material that is relatively stable against chemical reactions and can transport both holes and electrons sufficiently. .

[0072] As described above, an important point in the light-emitting element of one embodiment of the present invention is that the The holes are smoothly transported without encountering any barriers or traps up to the emitting layer. The advantage of this method is that it reduces the hole transport rate without using a barrier, leading to efficient recombination. Since no barrier is used, holes and electrons accumulate and concentrate in a narrow area (around the barrier), causing degradation. This reduces the occurrence of the phenomenon that promotes hole injection, leading to a longer life. Since there are substantially no hole traps, the driving voltage can be reduced. By using a flip-top luminescent material in the luminescent layer, the speed of holes moving is controlled not by the outside of the luminescent layer but by the luminescent layer. Because the concentration is reduced within the layer, holes and electrons can be efficiently recycled without using a barrier. This allows realization of a light-emitting device with a long life and high luminous efficiency. The luminescent material itself traps holes, so the holes and the electrons This allows the electrons to be recombined more efficiently, thereby realizing a light-emitting device with high luminous efficiency.

[0073] From this viewpoint, the hole transport property of the light emitting layer 121 is determined by the hole transport property of the second layer 112. It is preferable that the hole transport property of the light-emitting layer 121 is lower than the hole transport property of the second layer 112. To make it lower than this, for example, the second organic compound and the third organic compound can be the same compound. By this method, the hole transporting property of the light emitting layer 121 can be obtained by adding a light emitting material having a hole trapping property. The second layer 112 is always lower than the second layer 112 by the amount of the overlap.

[0074] Based on the above points, the first organic compound, the second organic compound, and the third organic compound The concept and specific examples of materials that can be used are described below.

[0075] As described above, a hole injection barrier between the first organic compound and the second organic compound; and The present invention is based on the idea of ​​substantially eliminating the hole injection barrier between the second organic compound and the third organic compound. One of the methods is to develop a hole transport skeleton of the first organic compound. The hole transport skeleton of the second organic compound and the hole transport skeleton of the third organic compound are the same. The present inventors have devised a method for doing this.

[0076] The hole transport skeleton is a part of the skeleton in which the HOMO is distributed in the skeleton of the compound. The distribution of HOMOs can be determined using molecular orbital calculations. Each compound (in the first embodiment, the first organic compound, the second organic compound, and the third organic compound) By using the same hole transport skeleton for the organic compounds, the HOMO levels of each compound are As a result, the electrochemical barrier between the compounds is reduced.

[0077] Specific examples of hole transport skeletons will be described with reference to Figs. 6 to 14. 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazoline, respectively. CzPA, 3-phenyl-9-[4-(10-phenyl-9-anthryl) phenyl]-9H-carbazole (abbreviation: CzPAP), 9-phenyl-3-[4-(1 0-Phenyl-9-anthrylphenyl]-9H-carbazole (abbreviation: PCzPA) , 4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation Name: 2mPDBFPA-II), 4-[4-(9,10-diphenyl-2-anthryl) phenyl]dibenzofuran (abbreviation: 2PDBFPA-II), 4-[3-(triphenyl mDBTPTp-II), 9-[ 4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-ca Rubazole (abbreviation: CO11), 9-[4''-(5-phenyl-1,3,4-oxa Diazol-2-yl)-[1,1':2',1'':2'',1''']quaterphe Nyl-4-yl]-9H-carbazole (abbreviation: Z-CzPO11), 9-[4'''- (Benzoxazol-2-yl)-[1,1':2',1'':2'',1'''] Each compound of [4-(4-phenyl-4-yl)]-9H-carbazole (abbreviation: Z-CzPBOx) In each of Figures 6 to 14, (a) shows the chemical formula, and (b) and (c) show the The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were visualized using molecular orbital calculations. Shows something.

[0078] The molecular orbital calculations were carried out as follows: First, the ground state of each compound was calculated. The optimal molecular structure was calculated using density functional theory (DFT). The total energy of the DFT was Potential energy, electrostatic energy between electrons, kinetic energy of electrons and complex interelectronic In DFT, the exchange-correlation energy is expressed as the sum of all the exchange-correlation interactions. The function is approximated by a functional (meaning a function of a function) of the one-electron potential expressed in terms of electron density. Therefore, the calculation is fast and accurate. Here, we use the mixed functional B3LYP. , the weights of each parameter related to the exchange and correlation energy are specified. In addition, as the basis functions, 6-311 (triple split using three contraction functions for each valence orbital) The basis functions of the valence basis set were applied to all atoms. For example, for a hydrogen atom, the 1s to 3s orbitals are considered, and for a carbon atom, the 1 The orbitals s to 4s and 2p to 4p are considered. As a polar basis set, p-functions were added to hydrogen atoms, and d-functions were added to atoms other than hydrogen atoms. The chemical calculation program used was Gaussian03. The experiment was carried out using a computer (SGI, Altix 4700).

[0079] Then, the HOMO and LUMO of the optimal molecular structure of each compound calculated by the calculation are The results visualized by Gauss View 4.1 are shown in (b) and (c) of Figures 6 to 14. The spheres in the figure represent the atoms that make up each compound, and the clouds around the atoms are , HOMO or LUMO. From these figures, it is clear that in each compound, the HOMO The skeleton in which these groups exist can be called a hole-transport skeleton.

[0080] As shown in Figures 6 to 8, CzPA, CzPAP, and PCzPA have an anthracene skeleton. CzPA and PCzPA are compounds that combine a carbazole skeleton with HO MO is distributed in the anthracene skeleton, and the anthracene skeleton can be said to be a hole-transporting skeleton. On the other hand, in CzPAP, the HOMO is mostly distributed in the anthracene skeleton, but the carbazoline The anthracene and carbamates also contribute to the HOMO. Both the anthracene and benzothiazolinone skeletons can be considered hole-transporting skeletons (however, the contribution is greater for the anthracene skeleton). is large).

[0081] In addition, as shown in Figures 9 and 10, 2mPDBFPA-II and 2PDBFPA-II is a compound that combines an anthracene skeleton and a dibenzofuran skeleton. 2mPDB In FPA-II, the HOMO is distributed in the anthracene skeleton, and the anthracene skeleton is a hole On the other hand, the HOMO of 2PDBFPA-II is mostly anthracene. The dibenzofuran skeleton also contributes slightly to the HOMO. Therefore, both the anthracene skeleton and the dibenzofuran skeleton can be said to be hole-transporting skeletons ( However, the contribution is greater from the anthracene skeleton.

[0082] As shown in Figure 11, mDBTPTp-II has a triphenylene skeleton and a dibenzothiazolinone skeleton. mDBTPTp-II is a compound in which the HOMO is tri- It is distributed in both phenylene and dibenzothiophene skeletons, and triphenylene skeleton Both the benzothiophene and dibenzothiophene skeletons can be considered hole-transporting skeletons (their HOMO The amount of money given is roughly the same.

[0083] As shown in Figures 12 and 13, CO11 and Z-CzPO11 are 1, 3, 4 -It is a compound that combines an oxadiazole skeleton and a carbazole skeleton. In the compound, the HOMO is localized in the carbazole skeleton, so the carbazole skeleton acts as a hole transport It can be said to be a skeleton.

[0084] As shown in Figure 14, Z-CzPBOx has a benzoxazole skeleton and a carbazole skeleton. Z-CzPBOx is a compound in which the HOMO is a carbazole skeleton. Since the carbazole skeleton is localized in the lattice, it can be said that the carbazole skeleton is a hole-transporting skeleton.

[0085] As shown above, it is possible to estimate the hole transport skeleton from molecular orbital calculations. The hole transport skeletons of the first organic compound, the second organic compound, and the third organic compound are the same. This is one aspect of the present invention.

[0086] The hole transport skeleton is preferably a skeleton with high electron donating properties, typically an aromatic amine skeleton. In addition, π-excess heteroaromatic rings and condensed aromatic hydrocarbon rings are useful. The π-excess heteroaromatic ring is a monoheterocyclic five-membered aromatic ring (pyrrole, furan, thiophene), and a monoheterocyclic five-membered aromatic ring fused with an aromatic ring (typically a benzene ring) It refers to a skeleton having

[0087] Furthermore, the present inventors have found that a hole injection barrier between the first organic compound and the second organic compound, and and one of the methods for reducing the hole injection barrier between the second organic compound and the third organic compound. As a result, the following combination was found: a hole transport skeleton of the first organic compound (a hole transport skeleton of the first organic compound), a hole transport skeleton of the second organic compound (a second hole transport skeleton), and The hole transport skeletons of the three organic compounds (third hole transport skeletons) are each independently linked to the π-excess system. At least one of a tricyclic aromatic hydrocarbon ring, a tricyclic condensed aromatic hydrocarbon ring, and a tetracyclic condensed aromatic hydrocarbon ring In this case, the first hole transport skeleton and the second hole transport skeleton are The hole transporting framework, the second hole transporting framework, and the third hole transporting framework may be substantially hole transporting frameworks, even if they are different from each other. The present inventors have experimentally found that the injection barrier is eliminated. Combinations are also an aspect of the present invention.

[0088] Specific examples of π-excess heteroaromatic rings include pyrrole, furan, thiophene, and indole. benzoindole, isoindole, benzofuran, isobenzofuran, benzothiophene, isobenzo Examples include thiophene, carbazole, dibenzofuran, and dibenzothiophene skeletons. In addition, the three-ring fused aromatic hydrocarbon ring or the four-ring fused aromatic hydrocarbon ring may be specifically The compound may be any one of phenanthrene, anthracene, pyrene, chrysene, and triphenylene. The skeleton of

[0089] Among these, the hole transport skeleton is particularly carbazole, dibenzofuran, dibenzothio It is preferable that the compound contains at least one skeleton of phene or anthracene. These frameworks not only solve the hole injection barrier problem, but also have high electrochemical stability and This is because it also has excellent hole transport properties.

[0090] The hole transport skeletons of the first organic compound, the second organic compound, and the third organic compound As the π-excess heteroaromatic ring (preferably carbazole, dibenzofuran, or dibenzothiophene skeleton), or the above-mentioned three-ring fused aromatic hydrocarbon ring or four-ring At least one skeleton of the fused aromatic hydrocarbon ring (preferably an anthracene skeleton) Even when the above formula is applied, the hole transport skeleton of the first organic compound and the hole transport skeleton of the second organic compound are It is preferable that the hole transport skeleton of the organic compound and the hole transport skeleton of the third organic compound are the same. As mentioned above, the electrochemical barrier is reduced between the same skeletons.

[0091] In the light-emitting element of one embodiment of the present invention, the first organic compound, the second organic compound, It is preferred that the hole transporting skeleton alone is the same compound as the third organic compound. By using the same compound, the molecular orbitals tend to overlap, and the movement of holes becomes easier. In addition, since the same compound is continuously deposited, the device It also becomes easier to manufacture.

[0092] In the following, the first organic compound, the second organic compound, and the third organic compound are preferably As described above, the hole transport skeleton is an aromatic amine skeleton. A skeleton having one of a cyclic ring, a π-excessive heteroaromatic ring, and a fused aromatic hydrocarbon ring is useful. do.

[0093] Compounds having an aromatic amine skeleton as a hole transport skeleton include 4,4'-bis[N- (1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD) , 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H -Carbazole-3-amine (abbreviation: CzA1PA), 4-(9H-carbazole-9- yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGA PA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]phenyl ]-9H-carbazol-3-amine (abbreviation: PCAPA), N,9-diphenyl-N- {4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carba PCAPBA, N,9-diphenyl-N-(9,10-diphenyl) Phenyl-2-anthryl)-9H-carbazol-3-amine (abbreviation: 2PCAPA) , 4,4'-(quinoxaline-2,3-diyl)bis(N,N-diphenylaniline) ( Abbreviation: TPAQn), N,N'-(quinoxaline-2,3-diyldi-4,1-phenylene N-phenyl-1,1'-biphenyl-4-amine) (abbreviation: BPAPQ), N,N'-(quinoxaline-2,3-diyldi-4,1-phenylene)bis[bis(1, 1'-biphenyl-4-yl)amine] (abbreviation: BBAPQ), 4,4'-(quinoxaline) N-[4-(9H-carbazol-9-yl)phenyl]- N-phenylaniline} (abbreviation: YGAPQ), N,N'-(quinoxaline-2,3-di (N,9-diphenyl-9H-carbazole-3-yldi-4,1-phenylene)bis( ... amine) (abbreviation: PCAPQ), 4-(9H-carbazol-9-yl)-4'-(3-fluoropropanediol) N,9-phenylquinoxalin-2-yl)triphenylamine (abbreviation: YGA1PQ), Diphenyl-N-[4-(3-phenylquinoxalin-2-yl)phenyl]-9H-quinoxaline Rubazol-3-amine (abbreviation: PCA1PQ), N,N,N'-triphenyl-N'- [4-(3-phenylquinoxalin-2-yl)phenyl]-1,4-phenylenediamine DPA1PQ, 4-(9H-carbazol-9-yl)-4'-(5-phenyl)- Nyl-1,3,4-oxadiazol-2-yl)triphenylamine (abbreviation: YGAO 11), N,9-diphenyl-N-[4-(5-phenyl-1,3,4-oxadiazo] (2-yl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAO11), N,N,N'-triphenyl-N'-[4-(5-phenyl-1,3,4-oxadiazo [(2-(2-yl)phenyl]-1,4-phenylenediamine (abbreviation: DPAO11), 4 -(9H-carbazol-9-yl)-4'-(4,5-diphenyl-4H-1,2,4 -triazol-3-yl)triphenylamine (abbreviation: YGATAZ1), 4-(9H -carbazol-9-yl)-4'-(3,5-diphenyl-4H-1,2,4-triazol-9-yl)- 4-(4-phenyl-4-azolyl)triphenylamine (abbreviation: YGATAZ2) and the like.

[0094] In addition, the hole transport skeleton may be a π-excess heteroaromatic ring and / or a fused aromatic hydrocarbon ring. Examples of compounds having this property include 1,1',1''-(benzene-1,3,5-triyl)trimethylsilyl. Ripylene, 9,10-diphenylanthracene (abbreviation: DPAnth), 9-(2-naphthyl) phenyl)-10-[4-(1-naphthyl)phenyl]anthracene, 9-[4-(10- CzPA, 3-phenyl-9-anthrylphenyl]-9H-carbazole Phenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazo CzPAP, 3,6-diphenyl-9-[4-(10-phenyl-9-anthracene) tolyl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 3-(1-naphthyl )-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole ( Abbreviation: CzPAαN), 3-(biphenyl-3-yl)-9-[4-(10-phenyl- 9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPAmB), 3-[4- (1-naphthyl)phenyl]-9-[4-(10-phenyl-9-anthryl)phenyl ]-9H-carbazole (abbreviation: CzPAαNP), 9-phenyl-3-[4-(10- Phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 9 -(9,10-diphenyl-2-anthryl)-9H-carbazole (abbreviation: 2CzPA ), 9-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazo 4-[3-(9,10-diphenyl-2-anthryl)phenol] (abbreviation: 2CzPPA), phenyl]dibenzofuran (abbreviation: 2mPDBFPA-II), 4-[4-(9,10-diphenyl)dibenzofuran Phenyl-2-anthrylphenyl]dibenzofuran (abbreviation: 2PDBFPA-II) , 4-{3-[10-(2-naphthyl)-9-anthryl]phenyl}dibenzofuran, 4-[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzothiophene ( Abbreviation: 2mPDBTPA-II), 4-[3-(triphenylen-2-yl)phenyl] Dibenzothiophene (abbreviation: mDBTPTp-II), 9-[4-(5-phenyl-1, 3,4-Oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO1 1), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl ]-3-phenyl-9H-carbazole (abbreviation: CO11-II), 9-[4-(5-furan (phenyl-1,3,4-oxadiazol-2-yl)phenyl]-3,6-diphenyl- 9H-Carbazole (abbreviation: CO11-III), 9-[4'''-(5-phenyl-1 ,3,4-Oxadiazol-2-yl)-[1,1':2',1'':2'',1'' ']quaterphenyl-4-yl]-9H-carbazole (abbreviation: Z-CzPO11), 9-[4-(benzoxazol-2-yl)phenyl]-3-phenyl-9H-carba CzBOx-II, 9-[4-(benzoxazol-2-yl)phenyl]phenyl] Nyl]-3,6-diphenyl-9H-carbazole (abbreviation: CzBOx-III), 9- [4'''-(benzoxazol-2-yl)-[1,1':2',1'':2'', 1''']quaterphenyl-4-yl]-9H-carbazole (abbreviation: Z-CzPBO x) and others.

[0095] All of the compounds mentioned above are bipolar compounds, and the third organic compound This is a particularly preferred compound group.

[0096] Next, the hole-trapping luminescent material contained in the light-emitting layer 121 will be described. The light-emitting material with hole trapping properties exhibits hole trapping properties with respect to the third organic compound contained in the light-emitting layer 121. In other words, the third organic compound can be added to the Specifically, the third organic compound is a compound that can reduce the hole mobility of the material. A material with a HOMO level at least 0.3 eV higher is preferred.

[0097] Here, the present inventors have found that a light-emitting substance comprising an aromatic amine compound or an organometallic complex is Since it exhibits hole trapping properties for many organic compounds, it is suitable as a light-emitting material for the present invention. In particular, it has been found that a pyrene diamine compound or an iridium complex acts as a hole transporter. It has been found that this has high adhesion and is suitable.

[0098] In addition, pyrene diamine compounds and iridium complexes have hole transport skeletons of anthracene and carbene. At least one skeleton of dibenzofuran, dibenzothiophene, or dibenzobenzophenone It has been found that compounds containing ZnO exhibit very strong hole trapping properties. The third organic compound containing these skeletons and the pyrene diamine compound or iridium complex are It is preferable to combine it with a luminescent material consisting of the following:

[0099] Experimentally, pyrenediamine compounds have been shown to be more stable than other aromatic amines with similar HOMO levels. Compared to other compounds, it has a higher hole trapping ability (when added to the light-emitting layer, it prevents hole migration in the light-emitting layer). It has been found that the luminescence is significantly reduced), and is particularly suitable as a luminescent material in the present invention. .

[0100] As described above, the luminescent material is preferably , an aromatic amine compound, or an organometallic complex is suitable. , N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenyl Phenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol- (10-phenyl-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation :YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl N,9-diphenyl-2-anthryltriphenylamine (abbreviation: 2YGAPPA) N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole 3-Amine (abbreviation: PCAPA), 4-(10-phenyl-9-anthryl)-4'-( 9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAP) A), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1 -phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine]( Abbreviation: DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2- anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'- N,N,N',N-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA) ',N'',N'',N''',N'''-Octaphenyldibenzo[g,p]chrysene -2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,1 0-Diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazole-3-a amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)] )-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N' -Triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10 -bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-tri Phenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), N-[9,10- Bis(1,1'-biphenyl-2-yl)]-N-[4-(9H-carbazole-9-yl)] phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), 4-( 10-phenyl-9-anthryl)-4'-(9-phenyl-9H-fluorene-9-yl) N,N,N',N'-tetraphenyltriphenylamine (abbreviation: FLPAPA) Pyrene-1,6-diamine, N,N'-(3-methylphenyl)-N,N'-diphenyl Pyrene-1,6-diamine, N,N'-bis[4-(9-phenyl-9H-fluorene- 9-yl)phenyl)-N,N'-diphenylpyrene-1,6-diamine (abbreviation: 1,6 FLPAPrn), N,N'-bis(4-tert-butylphenyl)-N,N'-bis [4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diazomethane Examples include 1,6tBu-FLPAPrn (abbreviation: 1,6tBu-FLPAPrn).

[0101] As an organometallic complex, bis[2-(4',6'-difluorophenyl)pyridinium] Nat-N,C 2’ ]Iridium(III) acetylacetonate (abbreviation: FIracac ), tris(2-phenylpyridinato-N,C 2’ ) Iridium(III) (abbreviation: Ir (ppy)3), bis(2-phenylpyridinato-N,C 2’ ) Iridium(III) Cetylacetonate (abbreviation: Ir(ppy)2(acac)), tris(benzo[h]ky Iridium(III) (abbreviation: Ir(bzq)3), bis(benzo[h]quino Iridium(III) acetylacetonate (abbreviation: Ir(bzq)2(aca c)), bis(2,4-diphenyl-1,3-oxazolato-N,C 2’ )iridium( III) Acetylacetonate (abbreviation: Ir(dpo)2(acac)), bis(2-fluoromethyl) Phenylbenzothiazolato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation Name: Ir(bt)2(acac)), bis[2-(2'-benzo[4,5-α]thienyl ) Pyridinato-N,C3’ ]Iridium(III) acetylacetonate (abbreviation: Ir( btp)2(acac)), tris(1-phenylisoquinolinato-N,C 2’ ) Iriji Ir(III) (abbreviation: Ir(piq)3), bis(1-phenylisoquinolinato-N, C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir(piq)2(aca c)), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-poly Examples include rufirin platinum(II) (abbreviation: PtOEP).

[0102] Next, the electron-accepting compound contained in the first layer 111 will be described. The substance accepts electrons from the first organic compound simply by mixing (contacting) it with the first organic compound. Alternatively, the compound can readily accept electrons from the first organic compound by applying an electric field. For example, transition metal oxides and compounds of Groups 4 to 8 of the periodic table are usable. Specifically, vanadium oxide and niobium oxide are examples of oxides of metals belonging to the group , tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, oxide Rhenium is preferred because of its high electron-accepting property. In particular, molybdenum oxide has low hygroscopicity. In addition, 7,7,8,8-tetracyano-2,3, Organic conversion of 5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, etc. Examples of such compounds include:

[0103] In the first layer 111, the mass ratio of the first organic compound is 0.1 or more and 4. It is preferable to add the electron accepting compound at a ratio of 0 or less.

[0104] The electron-accepting compound can be converted into the first active compound simply by mixing (contacting) with the first organic compound. When an electron is accepted from an organic compound, a charge transfer complex is formed in the first layer. Absorption due to charge-transfer interactions is observed in the infrared region, but the first organic compound is an aromatic amine. In the case of compounds, absorption often occurs in the visible light region. This is undesirable from the viewpoint of transmittance. For example, in Japanese Patent Application Laid-Open No. 2003-272860, a compound having an aromatic amine skeleton is disclosed. By mixing vanadium oxide with the compound, New absorptions were observed. In addition, when compounds with aromatic amine skeletons were mixed with F4-TCNQ, By combining, new absorption occurs around 700nm, 900nm and 1200nm. In this case, the absorption peak in the visible light region in particular is a factor that reduces the luminous efficiency. Wow.

[0105] However, the present inventors have found that π-excess heteroaromatic rings (preferably carbazole, dibenzyl dibenzothiophene skeleton) and the above-mentioned tricyclic condensed aromatic hydrocarbons. A hole transport skeleton consisting of a ring or a fused 4-ring aromatic hydrocarbon ring (preferably an anthracene skeleton) When the first layer is formed using a first organic compound containing the formula: Although absorption based on charge transfer interaction does not occur, a hole injection barrier from the anode is realized. This resulted in the discovery that the absorption peak in the visible light region is not present. Since it is easy to form the first layer, it is possible to prevent a decrease in light-emitting efficiency due to a decrease in transmittance. can be done.

[0106] This brings about the following effects: By changing the film thickness of the EL layer 103, the optical design can be improved. When performing this, the first layer 111, which has little fluctuation in driving voltage, is made thicker, and the other layers are made thinner. However, the first layer having an absorption spectrum peak in the visible light region is preferable. If the thickness of the light emitting layer 121 is increased, the light emitted from the light emitting layer 121 will be absorbed by the first layer 111. This leads to a decrease in luminous efficiency. By applying the first layer 111 that does not have a luminous efficiency, the luminous efficiency can be maximized. In addition, by making the first layer 111 thicker, it is also effective in preventing short circuits in the light emitting element. do.

[0107] Therefore, from the viewpoint of combination with the above electron-accepting compound, the first organic compound The hole transport skeleton of the compound is a π-excess heteroaromatic ring, a fused tricyclic aromatic hydrocarbon ring, or a tetracyclic aromatic hydrocarbon ring. A skeleton having a fused aromatic hydrocarbon ring is preferred. In particular, carbazole and dibenzofuran are preferred. , dibenzothiophene, and anthracene are electrochemically very stable and have hole transport properties. It is also preferable because it has excellent properties.

[0108] In addition, when the first organic compound has an aromatic amine skeleton, the hole transport of the first organic compound In many cases, the backbone is an aromatic amine backbone. In this case, the backbone is an aromatic amine backbone. Therefore, it is preferable that the first organic compound does not have an aromatic amine skeleton. .

[0109] In addition, conventionally, the ionization potential of organic compounds is 5.7 eV or more (HOMO level is - 5.7 eV or less), oxidation-reduction reactions with electron-accepting compounds become difficult to occur. (See, for example, Japanese Patent Application Laid-Open No. 2003-272860). As an organic compound for causing an oxidation-reduction reaction with an ionic compound, Substances with a HOMO level lower than 5.7 eV (HOMO level higher than -5.7 eV), specifically aromatic It has been thought that a substance with high electron donating properties, such as aromatic amines, is necessary. In an embodiment, even if the first organic compound does not contain an aromatic amine skeleton, at least If the HOMO level is between -6.0 eV and -5.7 eV, the electron-accepting compound It was demonstrated that the first layer functions despite not showing absorption based on charge transfer interactions. It is known experimentally.

[0110] Therefore, in the light-emitting element of one embodiment of the present invention, the first organic compound HOM The O level is preferably −6.0 eV or more and −5.7 eV or less. The concept of the present invention can be realized even when the energy gap of the light-emitting layer is large and the HOMO is low. It becomes easier.

[0111] The compound not containing an amine skeleton is preferably the above-mentioned 9,10-diphenyl Anthracene (abbreviation: DPAnth), 9-(2-naphthyl)-10-[4-(1-naphthyl)- 9-[4-(10-phenyl-9-anthryl)phenyl]anthracene, 3-phenyl-9-[4-(10-phenyl)-9H-carbazole (abbreviation: CzPA), [Nyl-9-anthrylphenyl]-9H-carbazole (abbreviation: CzPAP), 3,6 -diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-chlor DPCzPA (abbreviation: DPCzPA), 3-(1-naphthyl)-9-[4-(10-phenyl -9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPAαN), 3-(biphenyl) Phenyl-3-yl)-9-[4-(10-phenyl-9-anthryl)phenyl]-9 H-Carbazole (abbreviation: CzPAmB), 3-[4-(1-naphthyl)phenyl]-9 -[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPAαNP), 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl] 9-(9,10-diphenyl-2- anthryl)-9H-carbazole (abbreviation: 2CzPA), 9-[4-(9,10-difluoromethyl) (phenyl-2-anthryl)phenyl]-9H-carbazole (abbreviation: 2CzPPA), 4 -[3-(9,10-diphenyl-2-anthryl)phenyl]dibenzofuran (abbreviation: 2mPDBFPA-II), 4-[4-(9,10-diphenyl-2-anthryl)phenyl] 4-[3-[10-(2-naphthyl)dibenzofuran (abbreviation: 2PDBFPA-II) 4-[3-(9,10-diphenyl)-9-anthryl]phenyl}dibenzofuran, [2-(2-anthryl)phenyl]dibenzothiophene (abbreviation: 2mPDBTPA-II) , 4-[3-(triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mD BTPTp-II), 9-[4-(5-phenyl-1,3,4-oxadiazole-2- 9-[4-(5-phenylyl)phenyl]-9H-carbazole (abbreviation: CO11), -1,3,4-oxadiazol-2-yl)phenyl]-3-phenyl-9H-carba azole (abbreviation: CO11-II), 9-[4-(5-phenyl-1,3,4-oxadiazolium nitrate]

[0023] -3,6-diphenyl-9H-carbazole (abbreviation: CO 11-III), 9-[4'''-(5-phenyl-1,3,4-oxadiazole-2 -yl)-[1,1':2',1'':2'',1'''']quaterphenyl-4-yl ]-9H-carbazole (abbreviation: Z-CzPO11), 9-[4-(benzoxazole -2-yl)phenyl]-3-phenyl-9H-carbazole (abbreviated as CzBOx-II ), 9-[4-(benzoxazol-2-yl)phenyl]-3,6-diphenyl-9 H-Carbazole (abbreviation: CzBOx-III), 9-[4'''-(benzoxazole) (2-yl)-[1,1':2',1'':2'',1''']quaterphenyl-4 -yl]-9H-carbazole (abbreviation: Z-CzPBOx). Polymers of carbazole derivatives such as (N-vinylcarbazole) (abbreviation: PVK) You can use it.

[0112] The specific configuration of the EL layer 103 has been described above. The cathode 102 will now be described.

[0113] The anode 101 preferably has a large work function (specifically, 4.0 eV or more). It is preferable to use metals, alloys, electrically conductive compounds, and mixtures thereof. For example, indium tin oxide (ITO) , indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide Lead (IZO: Indium Zinc Oxide), tungsten oxide and zinc oxide These electrically conductive metal oxide films include indium oxide (IWZO) and is usually formed by sputtering, but it is also possible to apply the sol-gel method to form an inkjet It may be formed by a jet method, a spin coating method, or the like. For example, indium oxide-oxide Indium oxide zinc oxide (IZO) is a target made by adding 1 to 20 wt% of zinc oxide to indium oxide. The film can be formed by sputtering using tungsten oxide and Indium oxide containing zinc oxide (IWZO) is a material that has a tungsten oxide content compared to indium oxide. A target containing 0.5 to 5 wt% zinc and 0.1 to 1 wt% zinc oxide was used for the spat. It can be formed by the quenching method. In addition, gold (Au), platinum (Pt), nickel Ni, Tungsten (W), Chromium (Cr), Molybdenum (Mo), Iron (Fe), Cobalt (Co), copper (Cu), palladium (Pd), titanium (Ti), or metallic materials nitrides (e.g., titanium nitride, etc.), molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, titanium oxide, etc. Poly(3,4-ethylenedioxythiophene) / Poly(styrenesulfonic acid) (PEDOT / PSS), polyaniline / poly(styrene sulfonate) (PAni / PSS), etc. A polymer having a high viscosity may also be used.

[0114] The cathode 102 should have a small work function (specifically, 3.8 eV or less). (preferably) metals, alloys, electrically conductive compounds, and mixtures thereof can be used. Specific examples of such cathode materials include those belonging to Group 1 or 2 of the periodic table. Elements, namely alkali metals such as lithium (Li) and cesium (Cs), and magnesium Alkaline earth metals such as magnesium (Mg), calcium (Ca), and strontium (Sr), and alloys containing these (MgAg, AlLi), europium (Eu), ytterbium Examples of rare earth metals include Yb and alloys containing these. compounds, alkaline earth metal compounds, or rare earth metal compounds (e.g., lithium fluoride ( LiF), lithium oxide (LiOx), cesium fluoride (CsF), calcium fluoride ( A thin film of CaF2, erbium fluoride (ErF3), etc., and a metal film such as aluminum It is also possible to form a cathode by laminating alkali metals and alkaline earth metals. Films of metals and alloys containing these can be formed by vacuum deposition. Alloys containing alkali metals or alkaline earth metals can also be formed by sputtering. It is also possible to form a film using silver paste or the like by an inkjet method. .

[0115] In the light-emitting element of one embodiment of the present invention, at least one of the anode and the cathode The light-transmitting property can be achieved by using a transparent electrode such as ITO or by using a thin film electrode. This can be ensured by reducing the film thickness.

[0116] In addition, a substrate for forming a light-emitting element according to one embodiment of the present invention is provided on the anode 101 side. The substrate may be provided on the cathode 102 side or on the cathode 102 side. The support of the light emitting element can be made of glass, plastic, metal, etc. Any other suitable material may be used as long as it functions as a light emitting element. When light is extracted to the outside through a plate, the substrate is preferably a light-transmitting substrate.

[0117] With the above-described structure, a light-emitting element of one embodiment of the present invention can be manufactured. It should be noted that other layers may be further introduced into the EL layer 103. Specifically, as shown in FIG. The device may have a structure in which an electron transport layer 113 and an electron injection layer 114 are introduced into the organic EL element.

[0118] The electron transport layer 113 may be formed of, for example, tris(8-quinolinolato)aluminum (abbreviated as : Alq), tris(4-methyl-8-quinolinolato)aluminum (abbreviated as Almq3 ), bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq2) , bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation The compounds consist of metal complexes with a quinoline or benzoquinoline skeleton, such as BAlq In addition, bis[2-(2-hydroxyphenyl)benzoxazolato] Zinc (abbreviation: Zn(BOX)2), bis[2-(2-hydroxyphenyl)benzothiazo oxazole-based and thiazole-based ligands such as tetrahydrozinc (abbreviated as Zn(BTZ)2) In addition to metal complexes, 2-(4-biphenyl) (4-tert-butylphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation PBD) and 1,3-bis[5-(p-tert-butylphenyl)-1,3,4- Oxadiazol-2-yl]benzene (abbreviation: OXD-7), 3-(4-biphenylyl) )-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), Bathophenanthroline (abbreviation: BPhen), Bathocuproine (abbreviation: The substances mentioned here are mainly 10 -6 cm 2 / V It is a substance that has an electron mobility of 1000 s or more. It is a substance that has a higher electron transporting property than a hole transporting property. If desired, a material other than the above may be used for the electron transport layer. The material may be not only a laminate of the above-mentioned materials but also a laminate of two or more layers of the above-mentioned materials.

[0119] Polymer compounds can also be used. For example, poly[(9,9-dihexylfluorene)] PF-Py ), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-biphenyl) pyridine-6,6'-diyl)] (abbreviation: PF-BPy), etc. can be used.

[0120] The electron injection layer 114 may be formed of, for example, lithium, calcium, magnesium, or lithium fluoride. Lithium (LiF), Lithium oxide (LiO x ), Cesium Fluoride (CsF), Calcium Fluoride Alkali metals, alkaline earth metals, or their compounds, such as sodium (CaF2) can be used.

[0121] In addition, the substance having electron transport properties includes alkali metals, alkaline earth metals, or Compounds containing magnesium (Mg) in Alq In this case, electrons can be injected from the cathode 102 more efficiently. It is possible.

[0122] Next, a method for manufacturing the light-emitting element of one embodiment of the present invention will be described. A dry process typified by an evaporation method is preferred because the light-emitting element of one embodiment of the present invention The dry process allows for laminating the first layer, second layer, and light-emitting layer. From this point of view, the first organic compound and the second organic compound The third organic compound and the light-emitting substance are preferably low molecular weight compounds.

[0123] However, the light-emitting element of one embodiment of the present invention can be formed by either a dry process or a wet process. The formation may be performed by using various methods. As a wet process, an ink jet method or A typical example of such a method is spin coating, but the method is not limited to this.

[0124] As described above, by applying the present invention, it is possible to provide a light emitting element with a long life. This makes it possible to provide a light-emitting element that is excellent in luminous efficiency and driving voltage.

[0125] (Embodiment 2) In the second embodiment, in a light-emitting element according to one aspect of the present invention, the recombination efficiency of carriers is A more preferable configuration from the viewpoint of improving the performance will be described below, along with the materials used and the manufacturing method. In the second embodiment, the region sandwiched between the anode and the cathode is called an EL layer.

[0126] Regarding the light-emitting element according to one embodiment of the present invention in this embodiment 2, the concept of the element structure is shown in FIG. The band diagram is shown in FIG. 4(a) and in FIG. 4(b). As shown in FIG. 4(a), In this light-emitting element, an EL layer 403 is provided between an anode 401 and a cathode 402. The EL layer 403 is made up of a first layer 411 and a second layer 412 in this order from the anode 401 side. The laminated structure in which the first light-emitting layer 421 and the second light-emitting layer 422 are provided is The first layer 411 contains a first organic compound and an electron-accepting compound. The second layer 412 contains a second organic compound, and the first light-emitting layer 421 contains a third organic compound. a first light-emitting substance that exhibits hole trapping properties with respect to a third organic compound; The second light-emitting layer 422 is a fourth organic compound and a hole transport layer for the fourth organic compound. The fourth organic compound and the third organic compound are They are different compounds.

[0127] First, as shown in FIG. 4(b), the inventors first The OMO level 433 and the HOMO level 434 of the second organic compound in the second layer are In addition, the HOMO level of the second organic compound in the second layer is 4 The HOMO level 34 of the first organic compound in the first light-emitting layer is aligned to the HOMO level 435 of the third organic compound in the first light-emitting layer. In addition, the HOMO level of the third organic compound in the first light-emitting layer is 435 and the HOMO level 437 of the fourth organic compound in the second light-emitting layer are aligned to the same extent. As a result, the hole injection barrier between the first layer 411 and the second layer 412, a hole injection barrier between the second layer 412 and the first light-emitting layer 421, and Any hole injection barrier between the second light-emitting layer 422 and the second light-emitting layer 422 is significantly reduced.

[0128] From the viewpoint of electrochemical selectivity described in the first embodiment, the same Specifically, the difference in HOMO levels is within ±0.2 eV. .

[0129] As described in Embodiment 1, the first layer 411 may be doped with an electron-accepting compound. As a result, the work function 431 of the anode and the HOM of the first organic compound contained in the first layer 411 Even if there is a gap between the O level 433, hole injection is smoothly performed and the The hole injection barrier disappears. The first layer 411 is a layer containing an electron-accepting compound and a first organic compound. The electron-accepting compound and the first organic compound may be mixed, or may be arranged in the order from the anode side. A laminated structure may also be used.

[0130] With the above-described configuration, from the anode to the first and second light-emitting layers, The hole injection barrier is almost eliminated.

[0131] Furthermore, for the same reason as in the first embodiment, a hole-trapping luminescent material is added to the luminescent layer. Specifically, the first light-emitting layer 421 has a third A first light-emitting substance exhibiting hole trapping properties is added to the organic compound. The second light-emitting layer 422 has a hole transporter for the fourth organic compound in the second light-emitting layer 422. A second luminescent material that exhibits flip-flop properties is added. This does not lead to an increase in the driving voltage. Therefore, the hole escape to the cathode can be prevented.

[0132] In order to trap holes using a light-emitting material, the first light-emitting layer 421 is The third organic compound is used as a host material, and the first light-emitting substance having hole trapping properties is used as a guest material. In the second light-emitting layer 422, the fourth organic compound is preferably a host material. It is preferable that the second light-emitting material has hole-trapping properties as the guest material.

[0133] Furthermore, the HOMO level 436 of the hole-trapping first luminescent material is From the viewpoint of practical selectivity, the HOMO level of the third organic compound is at least 0.3 eV higher than 435. In addition, the HOMO level 438 of the second light-emitting material having hole trapping properties is preferably From the viewpoint of the electrochemical selectivity mentioned above, the HOMO level of the fourth organic compound is 0 rather than 437. It is preferable that it is at least 0.3 eV higher.

[0134] To prevent holes from leaking to the cathode and increase luminous efficiency, a material that traps holes is used. This can also be achieved by adding between the anode 401 and the first light-emitting layer 421. However, in such a method, the migration time of holes from reaching the first light-emitting layer 421 to emitting light is On the other hand, as shown in Figure 4, In the structure of one embodiment of the present invention, holes are guided from the anode 401 to the first light-emitting layer 421. Since the transport is carried out without experiencing barriers or traps, the increase in driving voltage is minimized. That is, the second layer does not contain a hole-trapping material. is preferred.

[0135] Furthermore, as shown in FIG. 4(b), the holes that reach the light-emitting layer are trapped by the first 436 of the light-emitting material and 438 of the second light-emitting material. However, the movement speed rapidly slows down in the first light-emitting layer 421 and the second light-emitting layer 422. Then, the holes whose movement speed is reduced and the electrons injected from the cathode 402 are efficiently transferred. In Figure 4(b), 432 is the work function of the cathode. From the viewpoint of the driving voltage, the number of the first light-emitting layer 421 and the second light-emitting layer 42 Since electrons must be transported sufficiently within the first light-emitting layer 421, The third organic compound and the fourth organic compound serving as a host material for the second light-emitting layer 422 are It is preferable that each of them has not only hole transporting property but also electron transporting property. Preferably, the material is a non-ionic material.

[0136] In this specification, the bipolar material is a material that has hole injection (electron A material capable of electron injection (reaction in which electrons are taken away) and electron ion injection (reaction in which electrons are received), It refers to a material that is relatively stable against reactions and can transport both holes and electrons sufficiently. vinegar.

[0137] The LUMO level 439 of the first organic compound contained in the first layer 411 and the LUMO level 438 of the second organic compound contained in the second layer The LUMO level of the second organic compound in the luminescent material is 440, and the LUMO level of the first hole-trapping organic compound in the luminescent material is 441. O level 443, and the LUMO level 444 of the second emissive material.

[0138] Here, as a way to further increase the recombination efficiency in the light-emitting layer without using a barrier, In the second embodiment, a first light-emitting layer 421 using a third organic compound and a fourth organic compound are formed. A second light-emitting layer 422 using a third organic compound and a fourth organic compound are laminated on the second light-emitting layer 422. A distinctive feature is that the compounds are deliberately made different.

[0139] As described above, electrochemical hole injection occurs between the third organic compound and the fourth organic compound. The barrier to entry is essentially zero (HOMO levels are comparable), but the hole transfer between the same materials is In comparison, hole transfer between different materials is somewhat slower.

[0140] On the other hand, with regard to electrons, in one embodiment of the present invention shown in FIG. 4, the LUMO of the third organic compound is The LUMO level 441 of the fourth organic compound is set to be approximately equal to the LUMO level 442 of the fourth organic compound. There is virtually no electrochemical barrier to electron injection from the organic compound to the third organic compound. However, since the third and fourth organic compounds are different compounds, the hole Similarly, electron transfer is somewhat suppressed compared to between the same kind of substances. From the viewpoint of selectivity, the term "similar LUMO levels" as used herein specifically refers to LUMO levels of This refers to a state in which the difference in O levels is within ±0.2 eV.

[0141] Therefore, at the interface between the first light-emitting layer 421 and the second light-emitting layer 422, holes and electrons The movement of both molecules is inhibited. Since there is no electrochemical barrier at this interface, the inhibition effect However, since it affects both holes and electrons, The carrier recombination region is formed around this interface. Since the recombination is not caused by the electrons, the recombination region is not localized. The phenomenon of accumulating or concentrating in a small area (around the barrier) and promoting degradation is unlikely to occur.

[0142] With the above design, the inside of the light-emitting layer (first light-emitting layer 421) can be easily formed without using a barrier. and the second light-emitting layer 422) The inventors have found that a bipolar material that allows both holes and electrons to flow is The idea of ​​recombining carriers by applying different combinations of bonded light-emitting layers is This is a new concept that can be called bipolar heterojunction, and is one of the important ideas of the present invention. This makes it possible to prevent deterioration caused by the barrier and at the same time increase the luminous efficiency.

[0143] As described above, an important point in the light-emitting element of one embodiment of the present invention is that the The holes are smoothly transported without encountering any barriers or traps up to the emitting layer. It controls not only the speed of hole transport but also the speed of electron transport without using a barrier, resulting in efficient Since no barrier is used, holes and electrons are trapped in a narrow region (around the barrier). This reduces the risk of deterioration due to accumulation and concentration in the surrounding area, leading to a longer lifespan. There is virtually no hole injection barrier or hole trap up to the optical layer, which allows for low drive voltages. Furthermore, a hole-trapping luminescent material is used in the luminescent layer, and further, a bipolar heterojunction is used. By applying the coupling, holes and electrons can be efficiently recombined without using a barrier. This allows realization of a light emitting device with a long life and high luminous efficiency.

[0144] From this viewpoint, the hole transporting property of the first light-emitting layer 421 is set to be equal to that of the second layer 412. It is preferable that the hole transport property of the first light-emitting layer 421 is lower than that of the second layer 412. In order to lower the hole transport property of the organic compound, for example, the second organic compound and the third organic compound are By this method, the hole transporting property of the first light-emitting layer 421 can be obtained by using a hole trapping The temperature of the second layer 412 is necessarily lower than that of the second layer 412 by the amount of the first light-emitting material contained therein.

[0145] Based on the above points, the first organic compound, the second organic compound, the third organic compound, and The concepts and specific examples of materials that can be used for the fourth organic compound are as follows: explain.

[0146] As in the first embodiment, the hole transport skeleton of the first organic compound and the hole transport skeleton of the second organic compound are The skeleton, the hole transport skeleton of the third organic compound, and the hole transport skeleton of the fourth organic compound are the same. It is preferable that the hole transport skeleton is as described in the first embodiment with reference to FIGS. As explained.

[0147] Furthermore, in the second embodiment, the electric potential between the third organic compound and the fourth organic compound is One of the key points is to virtually eliminate the electron injection barrier. The electron transport skeleton of the first organic compound and the electron transport skeleton of the fourth organic compound are the same. The inventors came up with an idea.

[0148] The electron transport skeleton is the part of the skeleton in which the LUMO is distributed in the skeleton of the compound. The distribution of LUMO can be determined using molecular orbital calculations. The electrons of each compound (the third organic compound and the fourth organic compound in the second embodiment) By using the same transport skeleton, the LUMO levels of each compound are close to each other, resulting in The electrochemical barrier between the compounds is reduced.

[0149] Specific examples of the electron transport skeleton will be described with reference to FIGS. 6 to 14. CzPA, CzPAP, and PCzPA have an anthracene skeleton and a carbazole skeleton. In both compounds, the LUMO is distributed over the anthracene skeleton. Therefore, the anthracene skeleton can be said to be the electron transport skeleton.

[0150] As shown in Figures 9 and 10, 2mPDBFPA-II and 2PDBFPA-I I is a compound that combines an anthracene skeleton and a dibenzofuran skeleton. The LUMO of the compounds is mostly distributed in the anthracene skeleton, but the dibenzofuran skeleton is also distributed in the L There is some contribution to UMO, so the anthracene and dibenzofuran skeletons Both of these can be considered electron transport skeletons (however, the anthracene skeleton contributes more). .

[0151] As shown in Figure 11, mDBTPTp-II has a triphenylene skeleton and a dibenzothiazolinone skeleton. mDBTPTp-II is a compound that combines two phene structures. The LUMO of mDBTPTp-II is approximately The triphenylene skeleton is distributed, but the dibenzothiophene skeleton also has a slight LUMO Since the contribution of the electrons is seen, both the triphenylene skeleton and the dibenzothiophene skeleton are electron-rich. It can be said to be a transport skeleton (although the contribution of the triphenylene skeleton is greater).

[0152] As shown in Figures 12 and 13, CO11 and Z-CzPO11 are 1,3,4 -It is a compound that combines an oxadiazole skeleton and a carbazole skeleton. The LUMO of the compound is distributed around the 1,3,4-oxadiazole skeleton. The 3,4-oxadiazole skeleton can be said to be an electron transport skeleton.

[0153] As shown in Figure 14, Z-CzPBOx has a benzoxazole skeleton and a carbazole skeleton. Z-CzPBOx is a compound in which the LUMO is a benzoxazoline. Since the electron transport structure is distributed around the benzoxazole skeleton, the benzoxazole skeleton is said to be the electron transport structure. can.

[0154] As shown above, the hole transport skeleton and electron transport skeleton can be estimated from molecular orbital calculations. and a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound. The hole transport skeleton of the first organic compound is the same, and the electron transport skeleton of the third organic compound is the same as that of the fourth organic compound. In one embodiment of the present invention, the electron transport skeleton of the organic compound is the same as that of the organic compound of the present invention.

[0155] The hole transport skeleton is preferably a skeleton with high electron donating properties, typically an aromatic alkyl group. The amine structure is well known. Other examples include π-excess heteroaromatic rings and condensed aromatic hydrocarbon rings. The π-excess heteroaromatic ring is a monoheterocyclic five-membered aromatic ring (pyrrole, fluorine, etc.). lan, thiophene), and aromatic rings (typically benzene rings) fused to five-membered monoheterocycles It refers to a skeleton containing an aromatic ring.

[0156] Furthermore, the present inventors have found that a hole injection barrier between the first organic compound and the second organic compound, and and a hole injection barrier between the second organic compound and the third organic compound, and One method for reducing the hole injection barrier between the compound and the fourth organic compound is to use the following combination: That is, a hole transport skeleton of the first organic compound (first hole transport skeleton), a hole transport skeleton of the second organic compound (second hole transport skeleton), a hole transport skeleton of the third organic compound a third hole transporting skeleton, and a fourth hole transporting skeleton of an organic compound (fourth hole transporting skeleton). skeleton) are each independently a π-excessive heteroaromatic ring, a tricyclic fused aromatic hydrocarbon ring, or is a method for forming a structure containing at least one skeleton of a fused tetracyclic aromatic hydrocarbon ring. In this case, a first hole transport skeleton, a second hole transport skeleton, a third hole transport skeleton, and The fourth hole transport framework may be different from each other, but the hole injection barrier is substantially eliminated. The present inventors have experimentally found that such a combination is also included in the present invention. This is one aspect.

[0157] π-excess heteroaromatic rings, 3-ring fused aromatic hydrocarbon rings, and 4-ring fused aromatic hydrocarbon rings Specific and preferred examples of the ring are the same as those described in the first embodiment.

[0158] The first organic compound, the second organic compound, the third organic compound, and the fourth organic compound The hole transport skeleton of the compound is a π-excess heteroaromatic ring, a tricyclic fused aromatic hydrocarbon ring, or Even when at least one skeleton of a fused tetracyclic aromatic hydrocarbon ring is applied, , a hole transport skeleton of a first organic compound, a hole transport skeleton of a second organic compound, a third organic compound It is preferable that the hole transport skeleton of the first organic compound and the hole transport skeleton of the fourth organic compound are the same. As mentioned above, the electrochemical barrier is reduced between the same skeletons. .

[0159] In the light-emitting element of one embodiment of the present invention, the first organic compound, the second organic compound, It is preferred that the hole transporting skeleton alone is the same compound as the third organic compound. By using the same compound, the molecular orbitals tend to overlap, and the movement of holes becomes easier. In addition, since the same compound is continuously deposited, the device However, the fourth organic compound is not suitable for the bipolar heterojunction (barrier In order to form a carrier recombination region without using a first organic compound, a second organic compound, The first organic compound and the third organic compound are different compounds.

[0160] The first organic compound, the second organic compound, the third organic compound, and the fourth organic compound Specific examples of compounds suitable as the compound include those having the aromatic amine skeleton described in the first embodiment. Compounds with hole transport frameworks, π-excess heteroaromatic rings and / or fused aromatic carbons Examples include compounds having a hydrogen ring as a hole transport skeleton.

[0161] In order to increase the recombination efficiency in the light-emitting layer, the hole transport property of the first light-emitting layer 421 is The hole transporting property of the first light-emitting layer 421 is higher than that of the second light-emitting layer 422, and the electron transporting property of the first light-emitting layer 421 is higher than that of the second light-emitting layer 422. It is preferable that the electron transporting property of the emitting layer 422 is lower than that of the emitting layer 422. Formation of heterojunctions is also one of the features of the present invention.

[0162] Such properties are evident in, for example, PCzPA (HOMO level is -5.7 according to CV measurements). 9 eV) and 1,6-FLPAPrn (HOMO level is -5.40 eV) as the first emitting material. The first light-emitting layer was a layer doped with 5 wt% of CzPA (HOMO level is -5.79e V) 5 wt% of the same luminescent material, 1,6-FLPAPrn, was added as the second luminescent material. The layer formed by the ion implantation is used as the second light-emitting layer.

[0163] As described above, if the first luminescent material and the second luminescent material are the same compound, This is preferable because it is easy to control the hole transport property and electron transport property of the light-emitting layer and the second light-emitting layer. .

[0164] However, the first and second luminescent materials are luminescent materials with different luminescent colors, For example, the first luminescent material may be yellow and the second luminescent material may be yellow. By using a blue light-emitting substance, white light can be obtained.

[0165] Next, the first light-emitting material having hole trapping properties contained in the first light-emitting layer 421 and the second light-emitting material The second light-emitting material contained in the layer 422 and having hole-trapping properties will be described.

[0166] The first light-emitting material forms a hole transporter with respect to the third organic compound contained in the first light-emitting layer 421. There are no particular limitations on the substance as long as it exhibits a crystalline structure. Any material capable of reducing the hole mobility of the organic compound is acceptable. Specifically, the third organic compound A substance having a HOMO level at least 0.3 eV higher than that of the HOMO level ... is preferred.

[0167] Similarly, the second light-emitting material is a fourth organic compound contained in the second light-emitting layer 422. There are no particular limitations on the substance as long as it exhibits hole trapping properties. Any material that can reduce the hole mobility of the fourth organic compound may be used. A substance having a HOMO level at least 0.3 eV higher than that of the organic compound is preferred.

[0168] As in the first embodiment, the first and second luminescent materials are aromatic compounds. A luminescent material comprising an amine compound or an organometallic complex is preferred, and pyrenediamine is particularly preferred. Pyrene diamine compounds and iridium complexes are preferred. The hole transport skeleton is anthracene, carbazole, dibenzofuran, or dibenzothiophene. It has very strong hole trapping properties for compounds containing at least one of the olefin skeletons. Therefore, the third and fourth organic compounds are It is preferable that the hole transport skeleton contains these.

[0169] Experimentally, pyrenediamine compounds have been shown to be more stable than other aromatic amines with similar HOMO levels. Compared to other compounds, it has a higher hole trapping ability (when added to the light-emitting layer, it prevents hole migration in the light-emitting layer). It has been found that the first luminescent material and / or It is particularly suitable as the second luminescent material.

[0170] Specific examples of the first and second luminescent materials include the luminescent materials in the first embodiment. The same hole-trapping light-emitting materials as those mentioned above can be used.

[0171] Next, the electron-accepting compound contained in the first layer 411 will be described. The same compounds as those described in the first embodiment can also be used as the material. In the first layer 411, the mass ratio of the first organic compound to the first organic compound is 0.1 or more and 4.0 or less. It is preferable to include an electron accepting compound in a ratio of 1:1.

[0172] In the first layer 411, the first organic compound is a compound that does not contain an aromatic amine skeleton. The HOMO level of the first organic compound is preferably −6.0 eV or more. As in the first embodiment, it is also preferable that the potential is 5.7 eV or less.

[0173] The specific configuration of the EL layer 403 has been described above. The cathode 402 will now be described.

[0174] The specific configuration of the anode 401 and the cathode 402 is the same as that of the first embodiment. In the light-emitting element of one embodiment of the present invention, at least one of the anode and the cathode The light-transmitting property can be achieved by using a transparent electrode such as ITO or by using a Alternatively, this can be ensured by making the electrode film thinner.

[0175] In addition, a substrate for forming the light-emitting element of one embodiment of the present invention is provided on the anode 401 side. The substrate may be provided on the cathode 402 side or on the cathode 402 side. The support of the light emitting element can be made of glass, plastic, metal, etc. Any other suitable material may be used as long as it functions as a light emitting element. When light is extracted to the outside through a plate, the substrate is preferably a light-transmitting substrate.

[0176] With the above-described structure, a light-emitting element of one embodiment of the present invention can be manufactured. It should be noted that other layers may be further introduced into the EL layer 403. Specifically, as shown in FIG. The element may have a structure in which an electron transport layer 413 and an electron injection layer 414 are introduced into the electron transport layer 413. The layer 413 and the electron-injecting layer 414 may have the same structure as that described in Embodiment 1. This can be done.

[0177] Next, a method for manufacturing the light-emitting element of one embodiment of the present invention will be described. A dry process typified by an evaporation method is preferred because the light-emitting element of one embodiment of the present invention In order to stack the first layer, the second layer, the first light-emitting layer, and the second light-emitting layer, This is because it is easier to create each region separately using the process. a second organic compound, a third organic compound, a fourth organic compound, a first luminescent material, and The second luminescent substance is preferably a low molecular weight compound.

[0178] However, the light-emitting element of one embodiment of the present invention can be formed by either a dry process or a wet process. The formation may be performed by using various methods. As a wet process, an ink jet method or A typical example of such a method is spin coating, but the method is not limited to this.

[0179] As described above, by applying the present invention, it is possible to provide a light emitting element with a long life. This makes it possible to provide a light-emitting element that is excellent in luminous efficiency and driving voltage.

[0180] This embodiment can be combined with all other embodiments and examples. is.

[0181] (Embodiment 3) In this embodiment mode, another structure of the light-emitting layer in Embodiment Modes 1 and 2 will be described. The structure of the light-emitting element will be described with reference to FIG.

[0182] In this embodiment, in FIG. 1, the light-emitting layer 121 is made of a third organic compound and a third organic In the case where the compound contains a light-emitting substance that exhibits hole trapping properties, As described in 1, in this embodiment, a light-emitting material that exhibits a hole-trapping property is used. The case where a light-emitting substance (light-emitting substance) is contained will be described. The optical layer 121 contains a luminescent material in addition to a hole-trapping luminescent material. .

[0183] The configuration of this embodiment other than the light-emitting layer 121 in FIG. 1 is the same as that described in Embodiment 1. Therefore, detailed description will be omitted here.

[0184] The light-emitting layer 121 contains the third organic compound described in the first embodiment. The light-emitting layer contains a light-emitting substance that exhibits hole trapping properties, and further contains a light-emitting substance.

[0185] The light-emitting substance has an excitation energy lower than the excitation energy of the light-emitting substance that exhibits hole trapping properties. Any material having electromotive energy can be used.

[0186] The luminescent material may be a fluorescent material or a phosphorescent material. -Bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstyrene Ruben-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazole-9-yl) YGAP A), N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-ca 2PCAPA, N-[9,10-bis(1,1'-biphenyl)] (phenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazole- 3-Amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl) )-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA ), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N ,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA) , N-[9,10-bis(1,1'-biphenyl-2-yl)]-N-[4-(9H-carboxylate) 2-( ... YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPh APhA), rubrene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11 -Diphenyltetracene (abbreviation: BPT), N,N,N',N'-tetrakis(4-methyl (phenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-di Phenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2 -a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), bis[2-( 2'-benzo[4,5-α]thienyl)pyridinato-N,C 3 ')]Iridium(III ) acetylacetonate (abbreviation: Ir(btp)2(acac)), bis(1-phenyl Isoquinolinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: Ir (piq)2(acac)), (acetylacetonato)bis[2,3-bis(4-fluoro Iridium(III) (abbreviation: Ir(Fdpq)2(ac ac)), 2,3,7,8,12,13,17,18-octaethyl-21H,23H- Organometallic complexes such as platinum(II) porphyrin (abbreviation: PtOEP), perylene, 2,5, 8,11-tetra(tert-butyl)perylene (TBP), 4,4'-bis(2 ,2-diphenylvinyl)biphenyl (abbreviation: DPVBi), 4,4'-bis[2-(N -ethylcarbazol-3-yl)vinyl]biphenyl (abbreviation: BCzVBi), bis( 2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation: BA lq), bis(2-methyl-8-quinolinolato)gallium chloride (abbreviation: Gamq2C l), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N ,C 2’}Iridium(III) picolinate (abbreviation: Ir(CF3ppy)2(pic )), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]Iriji ammonium(III) acetylacetonate (abbreviation: FIr(acac)), bis[2-(4' ,6'-difluorophenyl)pyridinato-N,C 2’ ]Iridium(III) picolinate bis[2-(4',6'-difluorophenyl)pyridinyl]propionate (abbreviation: FIrpic), To-N,C 2’ ]Iridium(III) tetra(1-pyrazolyl)borate (abbreviation: FI r6), 2,3-bis(4-diphenylaminophenyl)quinoxaline (abbreviation: TPAQ n), 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation In addition to compounds with an arylamine skeleton such as NPB, 4,4'-di(N-carbamoyl) 4,4',4''-tri(N-carbazolyl)biphenyl (abbreviation: CBP), Carbazole derivatives such as bis[2-(2-hydroxybenzoyl) (2-hydroxyphenyl)pyridinato]zinc (abbreviation: Znpp2), bis[2-(2-hydroxyphenyl)pyridinato]zinc phenyl)benzoxazolato]zinc (abbreviation: ZnBOX), bis(2-methyl-8-oxo- (4-phenylphenolato)aluminum (abbreviation: BAlq), tris(8 -quinolinolato)aluminum (abbreviation: Alq3), and other metal complexes, poly(N-vinyl carboxylates) Polymer compounds such as PVK (abbreviated as PVK) can be used as appropriate.

[0187] By using such a light-emitting layer according to the present embodiment, light-emitting elements that emit different colors on the same substrate can be formed. When forming a layer, the materials constituting the first layer 111 and the second layer 112 and the process of forming them are This allows the manufacturing process to be simplified.

[0188] For example, if you want to emit two colors on the same substrate, you can use a light-emitting element that emits a first color and a light-emitting element that emits a second color. In the light-emitting element that emits light of two colors, the first layer 111 and the second layer 112 of each light-emitting element are The material of the second layer 112 is determined by the HOMO level and LUMO level of the hole-trapping light-emitting material. Therefore, the hole trapping luminescent material that emits the first color and the second color are determined by the When a hole-trapping luminescent material is used, the hole-trapping material that emits the first color of light is used. a light-emitting element including a light-emitting material with hole-trapping properties that emits light of a second color; In an optical element, the first layer 111 and the second layer 112 must be made of different materials. This makes the process more complicated.

[0189] However, as in the light-emitting layer of this embodiment, the light-emitting layer contains a light-emitting material having hole trapping properties as well. When a structure containing a luminescent material is used, the first layer 111 and the second layer 112 can be easily formed regardless of the luminescent color. The material of the layer 112 can be made common.

[0190] An important point in the light-emitting element of one embodiment of the present invention is that there are no barriers or barriers between the anode and the light-emitting layer. The holes are transported smoothly without encountering traps, while the light-emitting layer does not use barriers. The advantage of this is that it reduces the rate of hole migration and leads to efficient recombination. The trapping luminescent material traps the HOMO and LUMO levels of the third organic compound in the luminescent layer. This determines the level, and the materials of the first layer 111 and the second layer 112 are also determined accordingly. When two colors are to be emitted on the same substrate, a light-emitting element that emits the first color and a light-emitting element that emits the second color are used. In the light-emitting device that emits light, the HOMO level and the LUMO level of the third organic compound in the light-emitting layer are The levels are different, and it becomes necessary to change the materials of the first layer 111 and the second layer 112.

[0191] On the other hand, a light-emitting element that emits light of a first color and a light-emitting element that emits light of a second color using the light-emitting layer of this embodiment are In the light emitting device, the first layer 111, the second layer 112, and the first layer 121 The luminescent material that exhibits hole trapping properties for the organic compound 3 and the organic compound 3 is a common material. Then, the luminescent material added to the luminescent layer 121 can be made to emit light of the first color. By changing the light emitting element that emits the first color and the light emitting element that emits the second color, Different colors can be produced by using a light-emitting element that emits a first color and a light-emitting element that emits a second color.

[0192] In this case, the light emitting element that emits the first color and the light emitting element that emits the second color are However, the light-emitting layer of the first embodiment may be used for either one of them. The light emitting element for emitting the first color and the light emitting element for emitting the second color are the light emitting elements of the present embodiment. A light-emitting device using the light-emitting layer of the first embodiment is used in combination with a light-emitting device using the light-emitting layer of the first embodiment. is also good.

[0193] The light-emitting layer of this embodiment can also be applied to FIG. 4. In this case, the first light-emitting layer It can be applied to either the first light-emitting layer 421 or the second light-emitting layer 422, or it can be applied to both light-emitting layers. It is also possible.

[0194] In this case, similarly to the above explanation, light emitting elements that emit different colors are formed on the same substrate. In this case, the same effect as that shown in FIG. 1 is obtained. Furthermore, as explained above, the use of light-emitting elements of different colors The light-emitting layer of each element is a light-emitting element using the light-emitting layer of this embodiment and a light-emitting element using the light-emitting layer of embodiment 1. A light-emitting element may be used in combination with a light-emitting element. It is also acceptable to do so.

[0195] Although the case where two colors are to be emitted on the same substrate has been described, the present invention is not limited to this. It is also possible to have two or more colors appear on the same substrate. Alternatively, the light emitting element may be configured to emit a monochromatic light such as white light.

[0196] This embodiment can be combined with all other embodiments and examples. is.

[0197] (Fourth embodiment) In this embodiment 4, a structure of a light-emitting element which is one embodiment of the present invention will be described. In the fourth embodiment, the region sandwiched between the anode and the cathode is provided with the same structure as in the first and second embodiments. A light-emitting element having a plurality of EL layers as described above (hereinafter referred to as a tandem-type light-emitting element) This will be explained with reference to FIG.

[0198] FIG. 15(a) shows a structure in which two EL layers, i.e., a first EL layer, are disposed between an anode 501 and a cathode 502. This is an example of a tandem type light emitting device in which a first EL layer 503 and a second EL layer 504 are stacked. The L layer 503 and the second EL layer 504 are the EL layers disclosed in the first and second embodiments. can be applied.

[0199] As described in the first and second embodiments, the anode side of each EL layer (in the first and second embodiments) The first layer in 2) contains an electron-accepting compound. The included regions (511 and 512 in FIG. 15) function as charge generation layers. Therefore, by providing an appropriate electron injection layer 513 at the portion where each EL layer is connected, The first EL layer 503 and the second EL layer 504 are connected in series to function as a tandem light emitting element. The type of the electron injection layer 513 is the same as that of the electron injection layer disclosed in the first embodiment. Just use the following.

[0200] As shown in FIG. 15(b), the electron injection layer 513 and the EL layer (the first An auxiliary layer 514 may be further provided between the first and second EL layers 504. For example, a transparent conductive film such as ITO may be formed on the surface of the light emitting element to perform optical adjustment. An electron-accepting compound, typically molybdenum oxide, may be formed. An electron relay layer may be provided as the auxiliary layer 514.

[0201] The electron relay layer is formed by the charge generation layer (the region 51 containing the electron-accepting compound in FIG. 15(b)). 2) A layer that can quickly receive electrons extracted by an electron-accepting compound. Therefore, the electron relay layer is a layer containing a substance with high electron transport properties, and its LUMO The level is the acceptor level of the electron-accepting compound and the LUMO level of the first EL layer 503. It is preferable to form the layer using a material that occupies a level between about - It is preferable to use a material having a LUMO level of 5.0 eV or more, and a LUMO level of about -5.0 eV It is more preferable to use a material having a LUMO level of -3.0 eV or more. Examples of the material used for the layer include perylene derivatives and nitrogen-containing condensed aromatic compounds. Nitrogen-containing condensed aromatic compounds are stable compounds and are therefore suitable for use in electron relay layers. Furthermore, among nitrogen-containing condensed aromatic compounds, those containing cyano groups or fluoro groups are preferred. By using a compound having an electron-withdrawing group such as This is preferable because it makes it easier to remove.

[0202] Specific examples of perylene derivatives that can be used in the electron relay layer include 3, 4, 9, 1 0-Perylenetetracarboxylic dianhydride (PTCDA), 3,4,9,10-Perylenetetracarboxylic dianhydride Phenylenetetracarboxylic bisbenzimidazole (abbreviation: PTCBI), N,N'- Dioctyl-3,4,9,10-perylenetetracarboxylic acid diimide (abbreviation: PTCDI Specific examples of nitrogen-containing condensed aromatic compounds include pyrazino [2,3-f][1,10]phenanthroline-2,3-dicarbonitrile (PP DN), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexacyano HAT(CN)6, 2,3-diphenylpyrido[2,3 -b]pyrazine (abbreviation: 2PYPR), 2,3-bis(4-fluorophenyl)pyrido[ 2,3-b]pyrazine (abbreviation: F2PYPR), etc. Lopentacene, 7,7,8,8-tetracyanoquinodimethane (TCNQ), 1,4 ,5,8-Naphthalenetetracarboxylic dianhydride (abbreviation: NTCDA), copper hexadecafluorophosphate Fluorophthalocyanine (abbreviation: F 16 CuPc), N,N'-bis(2,2,3,3,4 ,4,5,5,6,6,7,7,8,8,8-Pentadecafluorooctyl)-1,4, 5,8-Naphthalenetetracarboxylic acid diimide (abbreviation: NTCDI-C8F), 3',4 '-Dibutyl-5,5''-bis(dicyanomethylene)-5,5''-dihydro-2,2 ':5',2''-terthiophene) (abbreviation: DCMT), methanofullerenes (e.g. , [6,6]-phenyl C 61 Butyric acid methyl ester (PCBM) and other substances are used as electronic relays. It can be used in layers.

[0203] The electron relay layer may also contain an electron donating compound. is an alkali metal, alkaline earth metal, or rare earth metal, or an alkali metal, alkaline Suitable for the treatment of rare earth metals or rare earth metal compounds (including oxides, halides, and carbonates) Specifically, lithium (Li), cesium (Cs), magnesium (Mg), Mg, Calcium (Ca), Strontium (Sr), Europium (Eu), Examples include metals such as ytterbium (Yb) and compounds of these metals. Metal compounds are preferred because they have high electron injection properties.

[0204] In this embodiment, a light emitting element having two EL layers has been described. The same can be applied to a light emitting device in which an L layer is stacked. DEM-type light-emitting devices are capable of emitting light in a high-brightness range while maintaining a low current density. In addition, when applied to lighting, the voltage due to the resistance of the electrode material Since the drop can be reduced, uniform light emission over a large area is possible. Therefore, the EL layer described in the first and second embodiments can be used to realize a device. By using this structure to fabricate a tandem light-emitting device, synergistic effects can be achieved in terms of lifespan and power consumption. This results in a beneficial effect.

[0205] In addition, by making the luminescent color of each EL layer different, the desired luminescence color can be obtained as a whole. For example, in a light-emitting element having two EL layers, the first By making the luminous color of the first EL layer and the luminous color of the second EL layer complementary to each other, It is also possible to obtain a light-emitting element that emits white light as a whole. In other words, the color that becomes achromatic when it is made of a substance that emits complementary colors. By mixing the resulting light, white light can be obtained. The same applies to the case of a light-emitting element in which, for example, the emission color of the first EL layer is red and the emission color of the second EL layer is red. When the emission color of the first EL layer is green and the emission color of the third EL layer is blue, the entire light-emitting element As a result, white light can be emitted.

[0206] This embodiment can be combined with all other embodiments and examples. is.

[0207] (Embodiment 5) In this embodiment mode, a light-emitting device manufactured using the light-emitting element described in the above embodiment mode will be described. Examples include a passive matrix light-emitting device and an active matrix light-emitting device. This article explains:

[0208] 26 and 27 show examples of passive matrix light emitting devices.

[0209] A passive matrix type (also called a simple matrix type) light-emitting device has a stripe-shaped A plurality of anodes arranged in parallel in a stripe pattern and a plurality of cathodes arranged in parallel in a stripe pattern are orthogonal to each other. The light-emitting layer is sandwiched between the two crossing points. The pixel at the intersection of the selected anode (to which voltage is applied) and the selected cathode lights up. This becomes the case.

[0210] 26A to 26C are top views of a pixel portion before sealing. FIG. 26(D) is a cross-sectional view taken along the chain line AA' in FIGS. 26(A) to 26(C).

[0211] An insulating layer 602 is formed on the substrate 601 as an insulating base layer. If insulating layer 602 is not required, it does not have to be formed. A number of first electrodes 603 are arranged at equal intervals (FIG. 26(A)). The first electrode 603 indicated by corresponds to the anode or cathode in this specification.

[0212] Moreover, on the first electrode 603, a partition wall 604 having an opening 605 corresponding to each pixel is provided. The partition wall 604 is made of an insulating material, such as polyimide or acrylic. photosensitive materials such as styrene, polyamide, polyimide amide, resist, or benzocyclobutene The insulating material is a photosensitive or non-photosensitive organic material, or an SOG film such as an SiOx film containing an alkyl group. The openings 605 corresponding to the respective pixels become light-emitting areas (see FIG. 26(B)).

[0213] A plurality of partitions 606 are provided on the partitions 604 having openings, and intersect with the first electrodes 603. The partition walls 606 are arranged parallel to each other (FIG. 26(C)). It has a reverse tapered shape.

[0214] An EL layer 607 and a second electrode 608 are sequentially stacked on the first electrode 603 and the partition wall 604. The second electrode 608 is also referred to as an anode or cathode in this specification (FIG. 26(D)). The combined height of the partition wall 604 and the partition wall 606 is equal to the height of the EL layer 607 and the second electrode. Since the thickness of the electrode 608 is set to be larger than that of the electrode 608, the thickness of the electrode 608 is increased as shown in FIG. The EL layer 607 and the second electrode 608 are formed in a number of separate regions. The separated regions are electrically independent from each other.

[0215] The second electrode 608 is a stripe-shaped electrode extending in a direction intersecting with the first electrode 603. The EL layer 607 and the second electrode 608 are also formed on the inversely tapered partition wall 606. However, the EL layer 607 and the second electrode 608 are separated from each other. There are.

[0216] If necessary, a sealing material such as a sealing can or a glass substrate is applied to the substrate 601. The light emitting element may be placed in a sealed space by bonding and sealing with an adhesive. This prevents the light emitting element from deteriorating. Filling may be performed with a filler or a dry inert gas. To prevent this, it is preferable to enclose a desiccant between the substrate and the sealing material. The small amount of moisture is removed by drying, and the material is thoroughly dried. The oxide of an alkaline earth metal such as aluminum, zeolite, or silica gel can be used. Yes, alkaline earth metal oxides have the property of absorbing moisture through chemical adsorption. Zeolite and silica gel also have the property of adsorbing moisture through physical adsorption.

[0217] Next, the passive matrix light-emitting devices shown in FIGS. 26(A) to 26(D) are Figure 27 shows a top view of the case where a flexible printed circuit (C) or the like is mounted.

[0218] In FIG. 27, the pixel portion that forms the image display has a group of scanning lines and a group of data lines that are perpendicular to each other. They intersect like this.

[0219] Here, the first electrode 603 in FIG. 26 corresponds to the scanning line 703 in FIG. 27. The second electrode 608 in FIG. 27 corresponds to the data line 708 in FIG. 27, and the inversely tapered partition wall 60 26. The EL layer 6 shown in FIG. 26 is disposed between the data line 708 and the scanning line 703. 07 are sandwiched between them, and the intersection shown as area 705 is one pixel.

[0220] The scanning line 703 is electrically connected to the connection wiring 709 at the wiring end, and the connection wiring 709 is connected to the input terminal The data line 708 is connected to the FPC 711b via the terminal 710. It is connected to FPC711a via

[0221] If necessary, a polarizing plate, a circular polarizing plate (including an elliptical polarizing plate), a retardation plate, etc. may be provided on the light exit surface. Optical films such as a λ / 4 plate, a λ / 2 plate, and a color filter may be provided as appropriate. In addition to the polarizing plate or the circular polarizing plate, an anti-reflection film may be provided. The uneven surface diffuses reflected light, reducing glare. It is possible.

[0222] Although FIG. 27 shows an example in which the driving circuit is not provided on the substrate, it is also possible to provide a driving circuit on the substrate. An IC chip for this purpose may be mounted.

[0223] In addition, when mounting an IC chip, the area around (outside) the pixel area is The data line side IC and the scanning line side IC, which are formed with the drive circuits that transmit signals, are mounted separately. The mounting method can be COG, TCP, wire bonding, etc. TCP is a device that mounts an IC on a TAB tape. The TAB tape is then attached to the layout board on which the device is formed. The data line side IC and the scan line side IC are mounted on a silicon substrate or SO It may be formed on a silicon-on-insulator (I) substrate. Alternatively, it may be formed on a glass substrate, a quartz substrate, or a plastic substrate. .

[0224] Next, an example of an active matrix light emitting device will be described with reference to FIG. 28(A) is a top view showing a light emitting device, and FIG. 28(B) is a top view showing the light emitting device as seen from the dashed line A in FIG. 28(A). 1 is a cross-sectional view taken along line A' of an active matrix light-emitting device according to an embodiment of the present invention. 8 includes a pixel section 802 provided on an element substrate 801 and a drive circuit section (source side drive circuit) 8 803 and a driver circuit section (gate side driver circuit) 804. The element substrate 801 and the sealing substrate 803 and the driver circuit portion 804 are sealed by a sealing material 805. 806.

[0225] On the element substrate 801, a driving circuit section 803 and a driving circuit section 804 are provided with external signals (beams). external signals that transmit voltages (video signals, clock signals, start signals, reset signals, etc.) A wiring 807 is provided to connect the input terminal. In this example, only the FPC is shown. However, the FPC may have a printed wiring board (PWB) attached to it. The light emitting device in this case is not just the light emitting device itself, but also the light emitting device itself to which the FPC or PWB is attached. This also includes items that are already attached.

[0226] Next, a cross-sectional structure of an active matrix light emitting device will be described with reference to FIG. 28(B). On the element substrate 801, a driver circuit portion 803, a driver circuit portion 804, and a pixel portion 28(B), the source side driver circuit 802 is formed. 8 shows a portion 803 and a pixel portion 802.

[0227] The driving circuit section 803 is a combination of an n-channel TFT 809 and a p-channel TFT 810. The example shows a CMOS circuit that combines the driver circuitry. The transistors can be formed of various CMOS, PMOS, or NMOS circuits. In this embodiment, a driver-integrated LCD in which a driver circuit is formed on a substrate on which a pixel portion is formed is used. However, the present invention is not limited to this configuration. A driving circuit can also be formed on the substrate.

[0228] The pixel section 802 includes a switching TFT 811, a current control TFT 812, and a The positive electrode is electrically connected to the wiring (source electrode or drain electrode) of the current control TFT812. The pixel is formed by a plurality of pixels including the anode 813. The edge of the anode 813 is covered with an insulating film. A border 814 is formed. Here, a positive photosensitive acrylic resin is used. The TFT811 for switching and the TFT812 for current control are formed. The structure of the TFT is not particularly limited. For example, it may be a staggered TFT or an inverted staggered TFT. The TFT may be a top gate type TFT or a bottom gate type TFT. The semiconductor material used for the TFT is not particularly limited, and silicon may be used. Alternatively, an oxide semiconductor such as an oxide containing indium, gallium, and zinc may be used. The crystallinity of the semiconductor used in the TFT is not particularly limited, and an amorphous semiconductor Alternatively, a crystalline semiconductor may be used.

[0229] The light-emitting element 817 is composed of an anode 813, an EL layer 815, and a cathode 816. The structure, materials, etc. of the light-emitting element have been described in the above embodiment, so detailed description will not be given here. The anode 813, the EL layer 815, and the cathode 816 in FIG. These correspond to the anode 101, the EL layer 103, and the cathode 102 in FIGS. Although not shown here, the cathode 816 is electrically connected to the FPC 808, which is an external input terminal. are.

[0230] The insulator 814 is provided on the end of the anode 813. In order to ensure good coverage of the cathode 816 to be formed, the upper end of the insulator 814 It is preferable that a curved surface having a curvature is formed at the upper or lower end. The upper or lower end of the object 814 has a curved surface with a radius of curvature (0.2 μm to 3 μm). It is preferable that the material of the insulator 814 is insoluble in the etchant when exposed to light. Negative photosensitive resin that becomes soluble in the etchant when exposed to light, or positive photosensitive resin that becomes soluble in the etchant when exposed to light. Organic compounds such as photosensitive resins and inorganic compounds such as silicon oxide and silicon oxynitride can be used. This can be done.

[0231] In addition, although only one light emitting element 817 is shown in the cross-sectional view of FIG. 28(B), In the pixel section 802, a plurality of light emitting elements are arranged in a matrix. 802, three types of light-emitting elements (R, G, B) are selectively formed, and In addition, a light-emitting device capable of displaying multiple colors can be formed by combining with a color filter. By using the same, a light emitting device capable of full color display may be obtained.

[0232] The light emitting element 817 is surrounded by the element substrate 801, the sealing substrate 806, and the sealing material 805. The space 818 is filled with a rare gas or nitrogen gas. Alternatively, the gap may be filled with a sealing material 805.

[0233] The sealing material 805 is preferably made of a material that is as impermeable to moisture and oxygen as possible. For example, it is preferable to use an epoxy resin. , quartz substrate, or FRP (Fiberglass-Reinforced Plast ics), PVF (polyvinyl fluoride), polyester, or acrylic A plastic substrate or the like can be used.

[0234] In this manner, an active matrix light emitting device can be obtained.

[0235] This embodiment can be combined with all other embodiments and examples. is.

[0236] (Sixth embodiment) In this embodiment mode, electronic devices manufactured using the light-emitting device described in the above embodiment mode, A specific example of the lighting device will be described with reference to FIGS. 29 and 30. FIG.

[0237] An example of an electronic device to which the present invention can be applied is a television device (television, or television (also known as TV receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones, portable game consoles, personal digital assistants, audio equipment These electronic devices and Specific examples of the lighting device are shown in Figs. 29 and 30.

[0238] FIG. 29(A) shows an example of a television device 9100. In the display device 100, a display portion 9103 is incorporated in a housing 9101. The manufactured light-emitting device can be used for the display portion 9103. In this case, the stand 9105 is used to hold the case 910 This shows a configuration that supports 1.

[0239] The television device 9100 can be operated using an operation switch provided on the housing 9101 or a separate remote control. This can be done by using the remote control operation device 9110. The channel and volume can be controlled by the -9109, and the information displayed on the display 9103 In addition, the remote control unit 9110 can be used to control the video. A display unit 9107 for displaying information output from the device 9110 may be provided.

[0240] A television device 9100 shown in FIG. 29(A) includes a receiver, a modem, and the like. The television device 9100 can receive general television broadcasts using a receiver. Furthermore, by connecting to a wired or wireless communication network via a modem, It can be directional (from sender to receiver) or bidirectional (between sender and receiver, or between receivers, etc.) ) information communication is also possible.

[0241] A light-emitting device manufactured using one embodiment of the present invention has high emission efficiency and a long lifetime. By using the light-emitting device in the display portion 9103 of the television set 9100, It is possible to display images with improved image quality in all cases.

[0242] FIG. 29(B) shows a computer, which includes a main body 9201, a housing 9202, a display portion 9203, It includes a keyboard 9204, an external connection port 9205, a pointing device 9206, etc. The computer displays a light-emitting device manufactured using one embodiment of the present invention on the display portion 9203. It is produced by using

[0243] Furthermore, a light-emitting device manufactured using one embodiment of the present invention has high emission efficiency and a long lifetime. Since the light-emitting device is an optical device, by using the light-emitting device in the display portion 9203 of the computer, It is possible to display an image with improved image quality compared to the conventional method.

[0244] FIG. 29C shows a portable game machine, which is composed of two housings, a housing 9301 and a housing 9302. The housing 9301 is connected by a connecting portion 9303 so as to be openable and closable. A display unit 9304 is built in, and a display unit 9305 is built in the housing 9302. The portable game machine shown in FIG. 29(C) includes an operation key 9309, a connection terminal 9310, a sensor 9311 (force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature , chemicals, voice, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, (including functions for measuring vibration, odor or infrared rays), microphone 9312, etc. Further, a speaker unit 9306, a recording medium insertion unit 9307, an LED light Of course, the configuration of the portable game machine is not limited to the above. The above embodiment may be applied to both or either of the display portion 9304 and the display portion 9305. It is sufficient that at least a light emitting device formed by applying the present invention is used.

[0245] The portable game machine shown in FIG. 29(C) is a game machine that uses a program or data recorded on a recording medium. It has the function of reading data and displaying it on the display, and wirelessly communicating with other portable game consoles to exchange information. The functions of the portable game machine shown in Figure 29(C) are as follows: The function is not limited to the above, and may have various functions.

[0246] Furthermore, a light-emitting device manufactured using one embodiment of the present invention has high emission efficiency and a long lifetime. Since it is a light emitting device, the light emitting device is used for the display part (9304, 9305) of the portable game machine. This makes it possible to display images with improved image quality compared to conventional methods.

[0247] FIG. 29D shows an example of a mobile phone. The mobile phone 9400 includes a housing 940 1, in addition to a display unit 9402, operation buttons 9403, an external connection port 9404, The mobile phone 9 includes a speaker 9405, a microphone 9406, an antenna 9407, and the like. 400 is a diagram showing a configuration in which a light-emitting device manufactured according to one embodiment of the present invention is used for the display portion 9402. It is made from.

[0248] In a mobile phone 9400 shown in FIG. 29(D), when a user touches the display portion 9402 with a finger or the like, You can enter information, make calls, or compose emails. .

[0249] The screen of the display unit 9402 has three main modes. The first mode is mainly for displaying images. The first mode is a display mode for inputting text and other information, and the second mode is an input mode for inputting text and other information. This is a display + input mode that combines two modes: display mode and input mode.

[0250] For example, when making a call or creating an email, the display portion 9402 is used for inputting characters. The main input mode is to input characters displayed on the screen. It is preferable to display a keyboard or number buttons on most of the screen of the display unit 9402. It's nice.

[0251] In addition, the mobile phone 9400 includes a sensor for detecting tilt such as a gyro or an acceleration sensor. By providing a detection device having the above, the orientation of the mobile phone 9400 (portrait or landscape) can be determined. The screen display on the display portion 9402 can be automatically switched by disconnecting the power supply.

[0252] The screen mode can be switched by touching the display portion 9402 or by operating the housing 9401. This is done by operating the button 9403. Also, depending on the type of image displayed on the display unit 9402, For example, if the image signal to be displayed on the display unit is a video signal, If it is data, the display mode is switched to, and if it is text data, the input mode is switched to.

[0253] In the input mode, a signal detected by an optical sensor of the display portion 9402 is detected and displayed. If there is no input by touch operation on the display unit 9402 for a certain period of time, the screen mode is changed to the input mode. Alternatively, the display mode may be switched from the normal mode to the display mode.

[0254] The display portion 9402 can also function as an image sensor. By touching the palm or fingers to the display unit 9402 and capturing an image of the palm print, fingerprint, etc., personal authentication can be performed. In addition, the display unit may be equipped with a backlight that emits near-infrared light or a sensor that emits near-infrared light. By using a scanning light source, it is also possible to capture images of finger veins, palm veins, etc.

[0255] A light-emitting device manufactured using one embodiment of the present invention has high emission efficiency and a long lifetime. Therefore, by using the light-emitting device in the display portion 9402 of a mobile phone, It is possible to display an image with improved image quality.

[0256] FIG. 29(E) shows a tabletop lighting device, which includes a lighting unit 9501, a shade 9502, and an adjustable arm 9503. 503, a support 9504, a base 9505, and a power supply 9506. The light-emitting device manufactured using one embodiment of the above is used for the lighting portion 9501 . The lighting equipment types are not limited to tabletop types, but also include ceiling-mounted types, wall-mounted types, and portable types. .

[0257] FIG. 30 shows a light-emitting device manufactured using one embodiment of the present invention as an indoor lighting device 1001. The light-emitting device manufactured according to one embodiment of the present invention can also have a large area. Therefore, it can be used as a large-area lighting device. The optical device can be made thin, so it can also be used as a roll-type lighting device 1002. As shown in FIG. 30, in a room equipped with an indoor lighting device 1001, ) may be used in combination with the tabletop lighting device 1003 described above.

[0258] The light-emitting device of one embodiment of the present invention can also be used as a lighting device. 3 is an example of a liquid crystal display device using a light-emitting device according to one embodiment of the present invention as a backlight. The liquid crystal display device shown in FIG. 1 comprises a housing 1101, a liquid crystal layer 1102, a backlight 1103, a housing The liquid crystal layer 1102 has a body 1104, and is electrically connected to a driver IC 1105. The backlight 1103 uses the light-emitting device of one embodiment of the present invention, and the terminal 11 Current is supplied by 06.

[0259] In this way, the light-emitting device of one embodiment of the present invention can be used as a backlight of a liquid crystal display device. In addition, the light-emitting device of one embodiment of the present invention has a surface Since it is a light-emitting lighting device and can be made large, it is also possible to make the backlight large. . Therefore, a liquid crystal display device with low power consumption and a large area can be obtained.

[0260] This embodiment can be combined with all other embodiments and examples. is.

[0261] As described above, electronic devices and lighting devices can be manufactured using a light-emitting device manufactured using one embodiment of the present invention. The range of application of a light-emitting device manufactured according to one embodiment of the present invention is extremely wide. The present invention can be applied to a wide range of electronic devices in a variety of fields. [Example]

[0262] In Example 1, a first organic compound and a second organic compound in a light-emitting element according to one embodiment of the present invention were Regarding compounds suitable as the compound, third organic compound, or fourth organic compound, The HOMO level was measured by cyclic voltammetry (CV). The measurements were carried out using an electrochemical analyzer (manufactured by BAS Co., Ltd., model No.: ALS model 600A or 600C) was used.

[0263] The 25 compounds measured are shown below. Compounds 1 and 2 are tricyclic fused aromatic rings. Compounds 3 and 4 are π-excess heteroaromatic compounds containing an anthracene skeleton. Compounds 5 to 12 are compounds containing a carbazole ring in the skeleton. Compounds 13 to 15 are compounds containing both anthracene and carbazole in the skeleton. It is a compound that contains both benzofuran and dibenzofuran, a π-excess heteroaromatic ring, in its skeleton. Compound 16 is a bifunctional compound consisting of anthracene and dibenzothiophene, a π-excess heteroaromatic ring. Compound 17 is a pyrene, which is a fused tetracyclic aromatic ring. Compounds 18 to 24 are compounds containing carbazole in the skeleton.

[0264] [ka]

[0265] [ka]

[0266] [ka]

[0267] [ka]

[0268] First, the specific measurement method is described below. The solution in the CV measurement is Water, dimethylformamide (DMF) (Aldrich Corporation, 99.8%, catalog no. :22705-6) was used, and tetra-n-butylammonium perchlorate was used as the supporting electrolyte. (n-Bu4NClO4) (Tokyo Chemical Industry Co., Ltd., Catalog No.: T0836) 100 ml The measurement target is dissolved to a concentration of 2 mmol / L. However, due to its low solubility, it was not possible to dissolve it at a concentration of 2 mmol / L. For the potato, the remaining residue was filtered off and the filtrate was used for measurement. The electrode was a platinum electrode (PTE platinum electrode, manufactured by BAS Co., Ltd.), and the auxiliary electrode was a A platinum electrode (Pt counter electrode (5 cm) for VC-3, manufactured by BAS Co., Ltd.) Ag / Ag as the reference electrode + Electrode (manufactured by BAS Co., Ltd., RE7 non-aqueous solvent system reference) The measurements were carried out at room temperature (20-25°C). The scan speed was standardized to 0.1 V / sec.

[0269] (Calculation of potential energy relative to the vacuum level of the reference electrode) First, the reference electrode (Ag / Ag + potential of the electrode relative to the vacuum level The electron energy (eV) was calculated. + The Fermi level of the electrode was calculated. The redox potential of ferrocene in methanol is +0.61 vs. the standard hydrogen electrode. 0 [V vs. SHE] (Reference: Christian R.Goldsmith et al., J.Am.Chem.Soc., Vol. 124, No.1, 83-96, 2002). On the other hand, the reference electrode used in this example The oxidation-reduction potential of ferrocene in methanol was found to be +0.11 V[ vs. Ag / Ag + Therefore, the potential of the reference electrode used in this example was The energy was found to be 0.50 eV lower than that of the standard hydrogen electrode.

[0270] Here, the potential energy of the standard hydrogen electrode from the vacuum level is -4.44 eV. It is known that (Reference: Toshihiro Onishi and Tamami Koyama, Polymer EL Materials (Kyoritsu Shuppan) , pp.64-67). From the above, the potential of the reference electrode used in this example relative to the vacuum level The potential energy can be calculated as -4.44-0.50=-4.94[eV]. Ta.

[0271] (Measurement example of compound 1 (DPAnth)) The method for calculating the HOMO level will be explained using Compound 1 (DPAnth) as an example. The potential was scanned from -0.20 V to 1.30 V against the solution, and then from 1.30 V to -0. The potential was scanned up to 20 V. As a result, the oxidation peak potential E pa is 0.97V, and the reduction peak potential E pc and 0.83 V, respectively. pc and E pa The intermediate potential between the two can be calculated as 0.90V. This means that DPAnth is 0.90[ V vs. Ag / Ag + ] is oxidized by the electrical energy of The energy corresponds to the HOMO level. The potential energy of the electrons relative to the vacuum level is -4.94 eV, so DPA The nth HOMO level is -4.94-(0.90)=-5.84[eV] Understood.

[0272] (Measurement results) The same measurement was carried out for the other compounds 2 to 24 to measure the HOMO levels. The results are shown in Figure 16. As shown in Figure 16, compounds having π-excess heteroaromatic rings and HO of compounds having three or four fused aromatic hydrocarbon rings It can be seen that the difference in MO level is generally within 0.2 eV. The HOMO levels of the compounds are also in the range of -5.7 to -6.0 eV (rounded to the second decimal place). From this result, it can be seen that a skeleton selected from this skeleton group is a hole transport skeleton. This suggests that there is almost no hole injection barrier between compounds having the same structure.

[0273] Therefore, the first organic compound, the second organic compound, and the third organic compound in the present invention and a compound in which the hole transport skeleton of the fourth organic compound has a π-excess heteroaromatic ring (particularly carbazole, dibenzofuran, or dibenzothiophene), and 3- or 4-ring fused rings By containing at least one of a synthetic aromatic hydrocarbon ring (particularly anthracene), A particularly preferred embodiment is realized. [Example]

[0274] In this Example 2, a manufacturing example of a light-emitting element according to one embodiment of the present invention and its characteristics will be described. The structural formulas of the materials used in Example 2 are shown below.

[0275] [ka]

[0276] First, a method for manufacturing a light-emitting element (light-emitting element 1) according to one embodiment of the present invention will be described below. The structure is shown in Figure 5.

[0277] (Light-emitting element 1) First, as the anode 401, a 110 nm thick film of indium tin oxide containing silicon oxide (abbreviation A glass substrate with a film of ITSO (Integrated Titanium Dioxide) was prepared. The ITSO surface was 2 mm square. The periphery was covered with a polyimide film so that the surface was exposed, and the electrode area was 2 mm × 2 mm. As a pretreatment for forming a light-emitting element on the substrate, the substrate surface was washed with water and heated at 200°C for 1 After baking for 1 hour, UV ozone treatment was performed for 370 seconds. -5 Inside up to Pa The substrate was introduced into a vacuum deposition apparatus with the pressure reduced, and the substrate was heated at 170°C for 30 minutes in a heating chamber of the vacuum deposition apparatus. The substrate was then left to cool for about 30 minutes.

[0278] Next, the glass substrate on which the anode 401 is formed is placed so that the surface on which the anode 401 is formed faces downward. The substrate was fixed to a substrate holder provided in a film formation chamber in a vacuum deposition apparatus.

[0279] First, 9-phenyl-3-[4-(10-phenyl-9-anthracene)] is applied to the anode 401. tolyl)phenyl]-9H-carbazole (abbreviation: PCzPA) and molybdenum oxide (VI ) is co-deposited with the first organic compound, and the electron-accepting compound, molybdenum oxide, is deposited on the first organic compound. A first layer 411 was formed by adding PCzPA, which is a material. Resistance heating was used for the deposition. The thickness of the first layer 411 is 50 nm, and the ratio of PCzPA to molybdenum (VI) oxide is The deposition ratio was 1:0.5 (=PCzPA:molybdenum(VI) oxide) by weight. The co-evaporation method involves simultaneous evaporation from multiple evaporation sources in one processing chamber. This is a vapor deposition method that performs the following.

[0280] Next, a 30 nm film of PCzPA was formed using a vapor deposition method using resistance heating. Thus, a second layer 412 made of PCzPA, which is the second organic compound, was formed.

[0281] Next, PCzPA and N,N'-bis[4-(9-phenyl-9H-fluorene-9-yl] (phenyl)phenyl)-N,N'-diphenylpyrene-1,6-diamine (abbreviation: 1,6FLP By co-evaporating the third organic compound, PCzPA and PCzP A first luminescent material 1,6FLPAPrn exhibiting hole trapping properties. The first light-emitting layer 421 was formed. The film thickness of the first light-emitting layer 421 was set to 20 nm, and it was composed of PCzPA and 1,6 The weight ratio of FLPAPrn was 1:0.05 (= PCzPA:1,6FLPAPrn). The deposition rate was adjusted so that

[0282] Furthermore, 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazo The fourth organic layer was formed by co-evaporating CzPA and 1,6FLPAPrn. The compound CzPA and the second luminescent material that exhibits hole trapping properties for CzPA The second light-emitting layer 422 containing 1,6FLPAPrn was formed. The thickness was 25 nm, and the ratio of CzPA to 1,6FLPAPrn was 1:0.05 ( The deposition rate was adjusted so that the composition was CzPA:1,6FLPAPrn.

[0283] The hole transport skeleton of the first to third organic compounds, PCzPA, and the fourth organic compound, As described in the embodiment, the hole transport skeleton of the compound CzPA is anthracene. In addition, although the electron transport skeleton of each compound is anthracene, the compounds are different. Therefore, a bipolar heterojunction is formed between the first light-emitting layer 421 and the second light-emitting layer 422. are.

[0284] Then, a 10 nm film of tris(8-quinolinolato)aluminum (abbreviation: Alq) was formed. Then, a 15 nm film of bathophenanthroline (abbreviated as BPhen) was formed. A electron transport layer 413 was formed. Furthermore, a lithium fluoride film was formed to a thickness of 1 nm. A layer 414 was formed.

[0285] Finally, aluminum was evaporated to a thickness of 200 nm using resistance heating. A cathode 402 was formed by film formation, and a light-emitting element 1 was fabricated.

[0286] (Comparative light-emitting element A) For comparison, the organic compound used in the first layer 411 and the second layer 412 in the light-emitting element 1 was A comparative light-emitting element A was fabricated by replacing the compound (PCzPA) with another compound.

[0287] The comparative light-emitting element A was fabricated as follows. First, 4-phenyl-4 '-(9-phenyl-9H-fluoren-9-yl)triphenylamine (abbreviation: BPA The first layer 411 is formed by co-evaporating FLP and molybdenum (VI) oxide. Resistance heating was used for the deposition. The thickness of the first layer 411 was set to 50 nm, and the BPAFL The weight ratio of P to molybdenum (VI) oxide was 1:0.5 (=BPAFLP:molybdenum oxide). The evaporation rate was adjusted to obtain the desired concentration of butyl butyl (VI).

[0288] Next, a 10 nm film of BPAFLP was formed using a vapor deposition method using resistance heating. Thus, the second layer 412 was formed.

[0289] Next, the first light-emitting layer 421 was formed using the same layer as that of the light-emitting element 1. The light-emitting element 22 had the same structure as the light-emitting element 1, except that the film thickness was changed from 25 nm to 30 nm.

[0290] Furthermore, the electron transport layer 413, the electron injection layer 414, and the cathode 402 are the same as those in the light-emitting element 1. The same configuration was used.

[0291] (Comparative light-emitting element B) For comparison, a comparative light-emitting element B was fabricated, which does not include the second layer 412 of the light-emitting element 1. .

[0292] The comparative light-emitting element B was fabricated as follows. First, the same organic compound as that of the light-emitting element 1 was deposited on the anode 401. Next, a first layer 411 having the above structure was formed without providing a second layer 412. The second light-emitting layer 421 was formed to have the same structure as the light-emitting element 1. The second light-emitting layer 422 had a thickness of 25 The structure was the same as that of the light-emitting element 1, except that the thickness was changed from 100 nm to 30 nm.

[0293] Furthermore, the electron transport layer 413, the electron injection layer 414, and the cathode 402 are the same as those in the light-emitting element 1. The same configuration was used.

[0294] The device structures of the fabricated light-emitting element 1, comparative light-emitting element A, and comparative light-emitting element B are shown in Table 1 below. I have summarized it below.

[0295] [Table 1]

[0296] (Element evaluation) The light-emitting element 1, the comparative light-emitting element A, and the comparative light-emitting element B obtained above were subjected to a nitrogen atmosphere. In a glove box, the light-emitting element is sealed to prevent it from being exposed to the atmosphere. After that, the operating characteristics of these light-emitting devices were measured. The event was held in an atmosphere maintained at a comfortable level.

[0297] The luminance-current efficiency characteristics of the light-emitting element 1, the comparative light-emitting element A, and the comparative light-emitting element B are shown in FIG. The luminance-external quantum efficiency characteristics are shown in Fig. 17(a) and Fig. 17(b), respectively. The properties are shown in Figure 18. 2 Emission spectrum when emitting light at a current density of is shown in Figure 19.

[0298] Light-emitting element 1 is 1000 cd / m 2 When emitting light at a brightness of 4.6V, the driving voltage is 4.6V and the current is It has an efficiency of 9.3cd / A, an external quantum efficiency of 7.5%, and a power efficiency of 6.3[lm / W]. In particular, the external quantum efficiency was higher than that of conventional fluorescent elements. As can be seen from FIG. 19, the light-emitting element 1 is a 1,6-FLPA A sharp emission spectrum originating from Prn was obtained, and the chromaticity was CIE(x,y) = Pure blue emission of (0.14,0.18) was obtained.

[0299] The external quantum efficiency of the comparative light-emitting element A is only in the 5% range, which is lower than that of the light-emitting element of one embodiment of the present invention. The light-emitting efficiency is not as high as that of the light-emitting element 1. In addition, the driving voltage is lower than that of the light-emitting element 1. It can be seen that all of the current efficiencies are high. As can be seen from Figure 9, a shoulder peak appears on the long wavelength side of the emission spectrum, and the color purity This is because the luminance is poor (CIE(x,y)=(0.16,0.25)).

[0300] The reasons why the comparative light-emitting element A is inferior to the light-emitting element 1 in terms of driving voltage and luminous efficiency are as follows: The following is considered to be the case. The HOMO level of BPAFLP is -5.51 eV according to CV measurements. The HOMO level of PCzPA used in the first light-emitting layer is −5 as disclosed in Example 1. That is, between the second layer and the first light-emitting layer, there is a hole There is an injection barrier, which is thought to be the cause of the deterioration of characteristics.

[0301] On the other hand, comparative light-emitting element B has relatively high external quantum efficiency and current efficiency in the low luminance region. However, the efficiency drops significantly on the high brightness side. This is thought to be because the recombination efficiency is reduced due to the electrons passing through to the anode side. In the optical element 1, the second layer 412, which is not doped with a hole-trapping material, plays an important role. It is fulfilling its role.

[0302] Next, for the light-emitting element 1, the comparative light-emitting element A, and the comparative light-emitting element B, the initial luminance was 1000 cd / m 2 A continuous lighting test was conducted under the conditions of constant current drive. The results are shown in Figure 20. In the graph, the vertical axis represents the normalized brightness, with the initial brightness set to 100%, and the horizontal axis represents the normalized brightness during driving. In addition, in Fig. 20(a), the horizontal axis (driving time) is in a logarithmic scale. 20(b) shows the horizontal axis (driving time) on a linear scale.

[0303] As can be seen from FIG. 20, Light-emitting element 1 maintained 92% or more of its initial luminance even after 1000 hours. On the other hand, the comparative light-emitting element A has a long operating life of 200 hours. The brightness has decreased to about 90% of the initial brightness. This is thought to be due to the hole injection barrier to zPA. As can be seen from 0(b), the long-term deterioration is not so bad, but the initial deterioration is large. There is a problem.

[0304] The above results indicate that the light-emitting element 1 of one embodiment of the present invention has very high emission efficiency and It was found that a long lifespan could be achieved.

[0305] Therefore, for the light-emitting element 1, the initial luminance is 1000 cd / m 2 The half-life of the brightness The accelerated luminance test was conducted on a device having the same structure as the light-emitting element 1. and set the initial brightness to 3000, 5000, 8000, 10000, 12000, and 150 00cd / m 2 The brightness was set to each value and a constant current test was performed. From the correlation plot of initial brightness vs. brightness half-life, the initial brightness was 1000 cd / m 2 To The half-life of the luminance was estimated.

[0306] The results of the accelerated luminance test are shown in Figure 21(a), and the correlation plot between initial luminance and luminance half-life is shown in Figure 2. 1(b) shows the initial luminance of 3000 and 5000 cd / m, respectively. 2 Regarding Since the brightness has not yet reached half its original value, the degradation curve was extrapolated to estimate the brightness half-life. The results of the speed test are summarized in Table 2 below.

[0307] [Table 2]

[0308] The results of Table 2 are plotted in the correlation plot of initial luminance vs. half-life of luminance in Figure 21(b). The brightness half life of the light-emitting element 1 is inversely proportional to the 1.7th power of the initial brightness, From these results, it can be seen that there is a correlation between the initial luminance of 1000 cd / m 2 To The half-life of the luminance is estimated to be 42,000 hours, which proves that this is an extremely long-life element. It was. [Example]

[0309] In this example 3, a manufacturing example of a light-emitting element according to one embodiment of the present invention and its characteristics will be described. The structural formulas of the materials used in Example 3 are shown below. The materials used in Example 2 are also shown below. This will be omitted.

[0310] [ka]

[0311] First, a method for manufacturing a light-emitting element (light-emitting element 2) according to one embodiment of the present invention will be described below. The structure is shown in Figure 5.

[0312] (Light-emitting element 2) First, an anode 401 was formed of indium tin silicon oxide (ITSO) with a thickness of 110 nm. The ITSO surface was exposed to a 2 mm square. The periphery of the substrate was covered with a polyimide film, and the electrode area was 2 mm x 2 mm. As a pretreatment for forming the substrate, the surface of the substrate was washed with water and baked at 200°C for 1 hour. UV ozone treatment was performed for 370 seconds. -5 The inside is decompressed to a vacuum of about Pa The substrate is introduced into the deposition apparatus and vacuum baked at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus. After that, the substrate was left to cool for about 30 minutes.

[0313] Next, the glass substrate on which the anode 401 is formed is placed so that the surface on which the anode 401 is formed faces downward. The substrate was fixed to a substrate holder provided in a film formation chamber in a vacuum deposition apparatus.

[0314] First, 9-phenyl-3-[4-(10-phenyl-9-anthracene)] is applied to the anode 401. tolyl)phenyl]-9H-carbazole (abbreviation: PCzPA) and molybdenum oxide (VI ) is co-deposited with the first organic compound, and the electron-accepting compound, molybdenum oxide, is deposited on the first organic compound. A first layer 411 was formed by adding PCzPA, which is a material. Resistance heating was used for the deposition. The thickness of the first layer 411 is 50 nm, and the ratio of PCzPA to molybdenum (VI) oxide is The deposition ratio was 1:0.5 (=PCzPA:molybdenum(VI) oxide) by weight. The co-evaporation method involves simultaneous evaporation from multiple evaporation sources in one processing chamber. This is a vapor deposition method that performs the following.

[0315] Next, 4-[3-(9,10-diphenyl-2- ( 2mPDBFPA-II) By depositing a film, a second layer consisting of a second organic compound, 2mPDBFPA-II, is formed. 412 was formed.

[0316] Next, 2mPDBFPA-II and N,N'-bis[4-(9-phenyl-9H-fluoro N,N'-diphenylpyrene-1,6-diamine (abbreviation: The third organic compound, 2mPDB, was co-evaporated with 1,6FLPAPrn. FPA-II and 2mPDB, the first luminescent material that exhibits hole-trapping properties for FPA-II The first light-emitting layer 421 containing 1,6FLPAPrn was formed. The thickness was 10 nm, and the weight ratio of 2mPDBFPA-II to 1,6FLPAPrn was The evaporation level was adjusted to 1:0.05 (=2mPDBFPA-II:1,6FLPAPrn). The rate was adjusted.

[0317] Furthermore, 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazo The fourth organic layer was formed by co-evaporating CzPA and 1,6FLPAPrn. The compound CzPA and the second luminescent material that exhibits hole trapping properties for CzPA The second light-emitting layer 422 containing 1,6FLPAPrn was formed. The thickness was 25 nm, and the ratio of CzPA to 1,6FLPAPrn was 1:0.05 ( The deposition rate was adjusted so that the composition was CzPA:1,6FLPAPrn.

[0318] The first organic compound, PCzPA, the second and third organic compounds, 2mPDB The hole transport skeleton of FPA-II and the fourth organic compound, CzPA, is As mentioned above, both are anthracene. Also, as in Example 2, bipolar heterojunction is formed.

[0319] Then, 2-[4-(10-phenyl-9-anthryl)phenyl]benzoxazo A 10 nm film of PABOx was then formed on the substrate. en) was deposited to a thickness of 15 nm to form an electron transport layer 413. An electron injection layer 414 was formed by depositing a 1 nm film of lithium.

[0320] Finally, aluminum was evaporated to a thickness of 200 nm using resistance heating. A cathode 402 was formed by film formation, and a light-emitting element 2 was fabricated.

[0321] (Element evaluation) The light-emitting element 2 obtained as described above was placed in a glove box with a nitrogen atmosphere. After sealing the element to prevent it from being exposed to the atmosphere, the operating characteristics of the light-emitting element 2 were measured. The measurements were carried out at room temperature (an atmosphere maintained at 25°C).

[0322] The luminance vs. current efficiency characteristics of the light-emitting element 2 are shown in FIG. 22(a) and the luminance vs. external quantum efficiency characteristics are shown in FIG. The voltage-luminance characteristics are shown in Figure 23. 2 The emission spectrum when light was emitted at a current density of 1000 kJ / s is shown in FIG.

[0323] Light-emitting element 2 is 1000 cd / m 2 When emitting light at a brightness of , the driving voltage is 3.4V and the current The efficiency is 11 cd / A, the external quantum efficiency is 8.0%, and the power efficiency is 10 [lm / W]. In particular, the external quantum efficiency was higher than that achieved by conventional fluorescent elements. As can be seen from FIG. 24, the light-emitting element 2 has a high luminous efficiency of 1,6-FLPAPr. The sharp emission spectrum derived from n is obtained, and the chromaticity is CIE(x,y)=(0 Blue luminescence (0.14,0.21) was obtained.

[0324] Next, regarding the light-emitting element 2, the initial luminance is 5000 cd / m 2 The constant current drive is performed under the condition of The results are shown in Figure 25. In Figure 25, the vertical axis represents the initial luminance as 100%. The horizontal axis is the normalized brightness normalized by the linear It's Asscale.

[0325] From FIG. 25, the initial luminance of the light-emitting element 2 is 5000 cd / m 2 The half-life of the brightness at This is estimated to be more than 500 hours, which is the initial luminance of the light-emitting element 1 disclosed in Example 2. 0 cd / m 2 Therefore, the luminance acceleration factor is the same as that of the Then, the initial brightness is 1000 cd / m 2 The half-life of the luminance at this temperature is 40 It is estimated to last more than 10,000 hours, making it an extremely long-life element.

[0326] The above results indicate that the light-emitting element 2 of one embodiment of the present invention has very high emission efficiency and In particular, it was found that the power efficiency exceeded 10 [lm / W]. However, it has a long lifespan, so it can withstand use as a blue light-emitting component in lighting. It is considered performance. [Example]

[0327] In this example 4, a manufacturing example of a light-emitting element according to one embodiment of the present invention and its characteristics will be described. The materials used in Examples 2 and 3 are omitted.

[0328] First, a method for manufacturing a light-emitting element (light-emitting element 3) according to one embodiment of the present invention will be described below. The structure is shown in Figure 3.

[0329] (Light-emitting element 3) First, an anode 101 was formed of indium tin silicon oxide (ITSO) with a thickness of 110 nm. The ITSO surface was exposed to a 2 mm square. The periphery of the substrate was covered with a polyimide film, and the electrode area was 2 mm x 2 mm. As a pretreatment for forming the substrate, the surface of the substrate was washed with water and baked at 200°C for 1 hour. UV ozone treatment was performed for 370 seconds. -5 The inside is decompressed to a vacuum of about Pa The substrate is introduced into the deposition apparatus and vacuum baked at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus. After that, the substrate was left to cool for about 30 minutes.

[0330] Next, the glass substrate on which the anode 101 is formed is placed with the surface on which the anode 101 is formed facing downwards. The substrate was fixed to a substrate holder provided in a film formation chamber in a vacuum deposition apparatus.

[0331] First, 9-phenyl-3-[4-(10-phenyl-9-anthracene)] is applied to the anode 101. tolyl)phenyl]-9H-carbazole (abbreviation: PCzPA) and molybdenum oxide (VI ) is co-deposited with the first organic compound, and the electron-accepting compound, molybdenum oxide, is deposited on the first organic compound. The first layer 111 was formed by adding PCzPA, which is a material. Resistance heating was used for the deposition. The thickness of the first layer 111 was set to 70 nm, and the ratio of PCzPA to molybdenum (VI) oxide was set to 100 nm. The deposition ratio was 1:0.5 (=PCzPA:molybdenum(VI) oxide) by weight. The co-evaporation method involves simultaneous evaporation from multiple evaporation sources in one processing chamber. This is a vapor deposition method that performs the following.

[0332] Next, a 30 nm film of PCzPA was formed using a vapor deposition method using resistance heating. Thus, a second layer 112 made of PCzPA, which is the second organic compound, was formed.

[0333] Next, 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol CzPA and N,N'-bis[4-(9-phenyl-9H-fluorene-9- 1,6-diphenyl)-N,N'-diphenylpyrene-1,6-diamine (abbreviation: 1,6FL By co-evaporating the third organic compound, CzPA and CzPA and a light-emitting layer 12 containing 1,6FLPAPrn, which is a light-emitting material exhibiting hole trapping properties. The light-emitting layer 121 had a thickness of 20 nm and was made of CzPA and 1,6FLPAPrn. The ratio of CzPA to 1,6FLPAPrn was 1:0.05 by weight. The rate was adjusted.

[0334] The first and second organic compounds, PCzPA, and the third organic compound, CzPA, As described in the embodiment, the hole transport skeleton is anthracene in all cases. , 3, forming a bipolar heterojunction.

[0335] Then, a 10 nm film of CzPA was formed, followed by bathophenanthroline (abbreviated as BPhen ) was deposited to a thickness of 15 nm to form an electron transport layer 113. The electron injection layer 114 was formed by depositing a 1 nm thick film of ZnSe.

[0336] Finally, aluminum was evaporated to a thickness of 200 nm using resistance heating. The cathode 102 was formed by film deposition, and the light-emitting device 3 was fabricated.

[0337] (Element evaluation) The light-emitting element 3 obtained as described above was placed in a glove box with a nitrogen atmosphere. After sealing the element to prevent it from being exposed to the atmosphere, the operating characteristics of the light-emitting element 3 were measured. The measurements were carried out at room temperature (an atmosphere maintained at 25°C).

[0338] The luminance-current efficiency characteristics and the external quantum efficiency of the light-emitting element 3 are shown in FIG. The properties are shown in Figure 33. 2 Emission spectrum when emitting light at a current density of is shown in Figure 34.

[0339] Light-emitting element 3 is 1000 cd / m 2 When emitting light at a brightness of , the driving voltage is 3.1V and the current It has an efficiency of 12cd / A, an external quantum efficiency of 10.0%, and a power efficiency of 13[lm / W]. Excellent characteristics were obtained. In particular, the external quantum efficiency was higher than that achieved by conventional fluorescent elements. As can be seen from FIG. 34, the light-emitting element 3 has an emission wavelength of 467nm. The sharp emission spectrum derived from m is obtained, and the chromaticity is CIE(x,y)=(0 Blue luminescence (0.14,0.17) was obtained.

[0340] Next, the initial brightness was set to 5000 cd / m 2 When the drive test was performed at a constant current, From the results of Examples 2 and 3, the brightness half life was 810 hours. Since it is inversely proportional to the 1.7th power, the initial brightness is 1000 cd / m 2 Half life is 12,000 hours It is calculated as follows.

[0341] The above results demonstrate that the light-emitting element 3 of one embodiment of the present invention has an extremely low driving voltage and It was found that the luminous efficiency was high and the lifespan was extremely long. It has achieved a long life while being power efficient, so it can be used as a blue light-emitting component in lighting. , and is considered to have sufficient durability. [Explanation of symbols]

[0342] 101 Anode 102 Cathode 103 EL layer 111 First Layer 112 Second Layer 113 Electron transport layer 114 Electron injection layer 121 Light-emitting layer

Claims

1. Between the anode and the cathode, there is a first layer, a second layer, a third layer, a light-emitting layer, and an electron transport layer. The first layer is located between the anode and the second layer. The second layer is located between the first layer and the third layer. The third layer is located between the second layer and the light-emitting layer. The light-emitting layer is located between the third layer and the electron transport layer. The electron transport layer is located between the light-emitting layer and the cathode. The first layer comprises an electron-accepting compound, The second layer comprises the first organic compound, The third layer comprises the second organic compound, The light-emitting layer comprises a third organic compound and a light-emitting substance that exhibits hole-trapping properties with respect to the third organic compound. The first organic compound and the second organic compound are different compounds from each other. The first organic compound, the second organic compound, and the third organic compound each independently contain at least one of a π-excess heteroaromatic ring, a tricyclic condensed aromatic ring, or a tetracyclic condensed aromatic ring. The π-excess heteroaromatic ring comprises a skeleton having a monohetero-five-membered aromatic ring formed by the fusion of aromatic rings, and is a light-emitting element.

2. Between the anode and the cathode, there is a first layer, a second layer, a third layer, a light-emitting layer, and an electron transport layer. The first layer is located between the anode and the second layer. The second layer is located between the first layer and the third layer. The third layer is located between the second layer and the light-emitting layer. The light-emitting layer is located between the third layer and the electron transport layer. The electron transport layer is located between the light-emitting layer and the cathode. The first layer comprises an electron-accepting compound, The second layer comprises the first organic compound, The third layer comprises the second organic compound, The light-emitting layer comprises a third organic compound and a light-emitting material having a HOMO level 0.3 eV or higher than that of the third organic compound. The first organic compound and the second organic compound are different compounds from each other. The first organic compound, the second organic compound, and the third organic compound each independently contain at least one of a π-excess heteroaromatic ring, a tricyclic condensed aromatic ring, or a tetracyclic condensed aromatic ring. The π-excess heteroaromatic ring comprises a skeleton having a monohetero-five-membered aromatic ring formed by the fusion of aromatic rings, and is a light-emitting element.

3. In claim 1 or claim 2, The aforementioned light-emitting material is an organometallic complex, which is a light-emitting element.

4. In any one of claims 1 to 3, The third organic compound is a light-emitting element having a pyrrole skeleton.

5. In any one of claims 1 to 3, The third organic compound is a light-emitting element having an anthracene skeleton.

6. In any one of claims 1 to 3, The third organic compound is a light-emitting element having an anthracene skeleton and a dibenzofuran skeleton.

7. In any one of claims 1 to 3, The first organic compound, the second organic compound, and the third organic compound each independently have a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an anthracene skeleton, respectively, in a light-emitting element.

8. In any one of claims 1 to 3, The first organic compound, the second organic compound, and the third organic compound each contain a pyrrole skeleton, respectively, in a light-emitting element.

9. In any one of claims 1 to 8, A light-emitting element in which the energy difference between the HOMO level of the first organic compound and the HOMO level of the second organic compound is within 0.2 eV.

10. A light-emitting device having a light-emitting element according to any one of claims 1 to 9.

11. An electronic device having the light-emitting device described in claim 10.

12. A lighting device having the light-emitting device described in claim 10.

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