Organic light-emitting diodes

Abstract

To provide an organic light-emitting element with improved durability characteristics.SOLUTION: An organic light-emitting element includes an anode, a light-emitting layer, a first organic compound layer in contact with the light-emitting layer, and a cathode in this order. The light-emitting layer includes a host material and a guest material. The host material is configured only of SP2 carbon and is any of the formulae [1-1] to [1-6]. The guest material is a luminescent material including a fluoranthene skeleton.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an organic light-emitting element. [Background technology]

[0002] In recent years, research and development of full-color displays using organic electroluminescent (OLED) elements, which emit light by passing an electric current through an OLED layer containing a light-emitting layer sandwiched between a pair of electrodes, has been actively pursued. When fabricating full-color displays, there are two methods: one in which the light-emitting layer is painted separately for each pixel (element), and another using white OLED elements where the light-emitting layer emits white light and a color filter is painted separately for each pixel. In the case of white OLED elements, two or more types of light-emitting materials are often used. Patent Document 1 discloses a blue organic light-emitting device using the following organic compound 1-a as the host for the light-emitting layer.

[0003] [ka] [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-255099 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the organic EL element disclosed in Patent Document 1 still has room for further improvement in terms of durability. This invention was made to solve the above problems and provides an organic light-emitting element with improved durability. [Means for solving the problem]

[0006] This invention NoThe organic light-emitting element comprises an anode, a light-emitting layer, a first organic compound layer in contact with the light-emitting layer, and a cathode in this order, the light-emitting layer comprises a host material and a guest material, the host material is SP 2 a hydrocarbon compound composed only of carbon and represented by any one of the following general formulas [1-1] to [1-6],

[0007]

Chemical Formula

Chemical Formula

Effects of the Invention

[0008] According to the present invention, an organic light-emitting element with improved durability characteristics can be provided.

Brief Description of the Drawings

[0009] [Figure 1](a) is a schematic cross-sectional view illustrating an example of a pixel of a display device according to an embodiment of the present invention. (b) is a schematic cross-sectional view illustrating an example of a display device using an organic light-emitting element according to an embodiment of the present invention. [Figure 2] It is a schematic diagram illustrating an example of a display device according to an embodiment of the present invention. [Figure 3] (a) is a schematic diagram illustrating an example of an imaging device according to an embodiment of the present invention. (b) is a schematic diagram illustrating an example of an electronic device according to an embodiment of the present invention. [Figure 4] (a) is a schematic diagram illustrating an example of a display device according to an embodiment of the present invention. (b) is a schematic diagram illustrating an example of a bendable display device. [Figure 5] (a) is a schematic diagram illustrating an example of a lighting device according to an embodiment of the present invention. (b) is a schematic diagram illustrating an example of a moving body including a vehicular lamp according to an embodiment of the present invention. [Figure 6] (a) is a schematic diagram illustrating an example of a wearable device according to an embodiment of the present invention. (b) is a schematic diagram illustrating another example of a wearable device according to an embodiment of the present invention. [Figure 7] (a) is a schematic diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. (b) is a schematic diagram illustrating an example of an exposure light source of an image forming apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

[0010] Hereinafter, the present invention will be described in detail. <1> Organic light-emitting element The organic light-emitting element of the present embodiment includes an anode, a light-emitting layer, a first organic compound layer in contact with the light-emitting layer, and a cathode in this order, and the light-emitting layer includes a host material and a guest material.

[0011] The host material is SP 2 A hydrocarbon compound composed of only carbon and represented by any one of the following general formulas [1-1] to [1-6].

[0012]

Chemical

[0013] The organic light-emitting element of this embodiment comprises an anode, a light-emitting layer, a first organic compound layer in contact with the light-emitting layer, and a cathode in this order. A specific element configuration is a multilayer element configuration in which the electrode layers and organic compound layers shown in (1) to (6) below are sequentially stacked on a substrate. In any element configuration, the organic compound layer always includes a light-emitting layer having a light-emitting material. (1) Anode / Emitting layer / Electron transport layer / Cathode (2) Anode / Hole transport layer / Emitting layer / Electron transport layer / Cathode (3) Anode / Hole transport layer / Emitting layer / Electron transport layer / Electron injection layer / Cathode (4) Anode / Hole injection layer / Hole transport layer / Emitting layer / Electron transport layer / Cathode (5) Anode / Hole injection layer / Hole transport layer / Emitting layer / Electron transport layer / Electron injection layer / Cathode (6) Anode / Hole transport layer / Electron blocking layer / Emitting layer / Hole blocking layer / Electron transport layer / Cathode However, these examples of element configurations are merely very basic configurations, and the element configuration of the organic light-emitting element of the present invention is not limited to these. For example, a variety of layer configurations can be adopted, such as providing an insulating layer, an adhesive layer, or an interference layer at the interface between the electrode and the organic compound layer, having an electron transport layer or hole transport layer composed of two layers with different ionization potentials, or having a light-emitting layer composed of two layers of different light-emitting materials.

[0014] The method of extracting light from the light-emitting layer (device configuration) can be either a so-called bottom emission method, where light is extracted from the electrode on the substrate side, or a so-called top emission method, where light is extracted from the opposite side of the substrate. A double-sided extraction method, where light is extracted from both the substrate side and the opposite side of the substrate, can also be employed.

[0015] The light-emitting layer may be a single layer or a multi-layer layer. In this embodiment, the light-emitting layer emits blue light, and by including light-emitting materials with other colors, it is possible to mix colors. A multi-layer layer means that one light-emitting layer is stacked on top of another light-emitting layer. In this case, the light-emitting color of the organic light-emitting element is not limited to blue. More specifically, it may be white or an intermediate color. In the case of white, the other light-emitting layer emits a color other than blue, i.e., green or red. Furthermore, the film is formed by vapor deposition or coating. Details of this will be explained in detail in the examples described later.

[0016] The other light-emitting layer preferably comprises a host material and a guest material and is positioned between the light-emitting layer and the anode. The host material included in the other light-emitting layer is SP 3 It is preferable that the material does not contain carbon. It is preferable that the host material contained in the light-emitting layer and the host material contained in another light-emitting layer are the same material.

[0017] In the organic light-emitting element of this embodiment, it is preferable that the light-emitting layer contains a naphthalene compound represented by any one of the general formulas [1-1] to [1-6], and that the first organic compound layer adjacent to the light-emitting layer on the cathode side contains a compound having at least one condensed polycyclic hydrocarbon skeleton of 3 to 5 rings.

[0018] In this case, the light-emitting layer has a light-emitting material containing a fluorantene skeleton. A characteristic of light-emitting materials containing a fluorantene skeleton is that they have electron-deficient five-membered rings, which results in low HOMO and LUMO energies (far from the vacuum level). This yields two effects.

[0019] The first advantage is that the light-emitting material itself becomes more stable against oxidation and reactions. In organic light-emitting devices, the light-emitting material contained in the light-emitting layer undergoes repeated excitation and emission during operation. Therefore, higher stability of the light-emitting material improves the continuous operation durability characteristics.

[0020] Secondly, the difference in LUMO energy between the host material and the fluorite layer becomes larger, improving electron trapping capabilities. Furthermore, having two or more fluoritene skeletons can enhance electron trapping capabilities. As a result, the number of electrons reaching the layer in contact with the light-emitting layer (such as EBL) on the anode side can be reduced, providing an organic EL element with excellent durability.

[0021] The compounds contained in the light-emitting layer have different uses depending on their concentration within the layer. Specifically, they are divided into main components and minor components depending on their concentration within the light-emitting layer.

[0022] The main component compound is the compound with the highest mass ratio (concentration) among the compounds contained in the light-emitting layer, and is also called the host compound. The host compound is a compound that exists as a matrix around the light-emitting material in the light-emitting layer, and is mainly responsible for the transport of carriers to the light-emitting material and the provision of excitation energy to the light-emitting material. The concentration of the host is preferably 50% by mass or more and 99.99% by mass or less, and more preferably 80% by mass or more and 99.9% by mass or less, based on the total amount of constituent materials of the light-emitting layer.

[0023] Furthermore, the minor components are compounds other than the main component, and depending on their function, they can be called guests (dopants), luminescence assisting materials, or charge injection materials. A guest, a type of minor component, is the compound (luminescent material) that is primarily responsible for luminescence in the luminescent layer. A luminescence assisting material, also a type of minor component, is a compound that assists the luminescence of the guest, and is a compound whose mass ratio (concentration) in the luminescent layer is smaller than that of the host. Due to its function, the luminescence assisting material is also called a secondary host.

[0024] The concentration of the guest relative to the host is preferably 0.01% by mass or more and 50% by mass or less, and more preferably 0.1% by mass or more and 20% by mass or less, based on the total amount of constituent material of the light-emitting layer. From the viewpoint of preventing density quenching, the concentration of the guest is particularly preferably 10% by mass or less.

[0025] The guest material may be uniformly distributed throughout the entire layer where the host matrix is ​​located, or it may be distributed in a concentration gradient. Alternatively, the guest material may be partially distributed in specific regions within the layer, so that the luminescent layer has regions containing only the host and no guest material.

[0026] In the present invention, it is preferable to include an organic compound containing a naphthalene skeleton represented by any one of general formulas [1-1] to [1-6] as a host material and a luminescent material containing a fluorantene skeleton as a guest material, both in the luminescent layer. In this case, for the purpose of assisting the transfer of excitons and carriers, other luminescent materials may be further included in the luminescent layer in addition to the above-mentioned luminescent material. Furthermore, for the purpose of assisting the transfer of excitons and carriers, a compound other than the compound represented by any one of general formulas [1-1] to [1-6] may be further included in the luminescent layer as a second host.

[0027] <2> Combined effect of the luminescent layer and the adjacent first organic compound layer In organic light-emitting devices, the presence of a fluorantene-containing luminescent material as a guest material increases the LUMO energy difference with the host material, resulting in higher electron trapping properties. In other words, the electron mobility within the luminescent layer is slower than the hole mobility. To put it another way, the charge mobility in the luminescent layer is faster than the electron mobility due to the hole mobility. Therefore, we found that charge tends to accumulate at the interface between the luminescent layer and the organic compound layer adjacent to the cathode, causing quenching and reactions between excitons and charges, which degrades durability.

[0028] The organic light-emitting element of this embodiment focuses on the compatibility between the organic compound represented by any of the general formulas [1-1] to [1-6] contained in the light-emitting layer and the organic compound contained in the first organic compound layer adjacent to the cathode side of the light-emitting layer. Specifically, it was found that by improving the compatibility between the light-emitting layer and the adjacent organic compound layer, charge transfer proceeds more smoothly, charge accumulation is improved and durability is enhanced.

[0029] To enhance compatibility, we designed the film to maximize intermolecular interactions while maintaining good film properties. While ππ interactions between aromatic rings are generally known, we found that the closer the number of condensed rings, the stronger the intermolecular interactions become in the thin film state, resulting in higher compatibility.

[0030] Table 1 shows examples of condensed polycyclic hydrocarbon skeletons with 3 to 5 rings.

[0031] [Table 1]

[0032] Furthermore, Table 2 shows the relationship between the number of fused rings of Ar1 and Ar2 in the host material contained in the light-emitting layer and the number of fused rings of the organic compound contained in the first organic compound layer adjacent to the light-emitting layer on the cathode side, and the effect of improving the durability of the device. In addition, Table 3 shows the effect of improving the durability of the device for specific compound combinations. The effect of improving the durability of the device in Tables 2 and 3 was calculated by determining the brightness degradation rate ratio during continuous operation of the organic light-emitting element in the same manner as in the examples, and was described according to the following criteria. A...Brightness degradation ratio is 2.5 or higher B...Brightness degradation ratio is 2.0 or higher and less than 2.5 C...Brightness degradation ratio is 1.5 or higher and less than 2.0 D...Brightness degradation ratio is 1.0 or less

[0033] [Table 2]

[0034] [Table 3]

[0035] As shown in Tables 2 and 3, it is even more preferable that the number of fused rings of Ar1 and Ar2 in the host material is the same as the number of fused rings of the organic compound contained in the first organic compound layer. Furthermore, a significant effect can be obtained regardless of whether the number of fused rings of the organic compound contained in the first organic compound layer is 3 to 5, but it is even more preferable that the number of fused rings of Ar1 and Ar2 in the host material contained in the luminescent layer is 4.

[0036] Furthermore, it is preferable to use combinations with four or more fused rings, as this leads to higher thermal stability, such as the glass transition temperature. In particular, combinations with four fused rings result in higher planarity and a lower possibility of excessive intermolecular π-stacking. This makes partial crystallization less likely to occur during the operation of the organic light-emitting device, and the compatibility effect can be maximized, making combinations with four fused rings more preferable.

[0037] Further, if the host material has a group that suppresses intermolecular interactions such as an alkyl group or a fluorine group, or if the fused polycycle of the compound contained in the first organic compound layer is a heterocycle whose electronic state changes greatly, the above effect cannot be obtained. For comparison, Table 3 shows the durability characteristics of the combination described in Patent Document 1. In the comparative example, the organic compound contained in the light-emitting layer has an alkyl group, and the organic compound contained in the first organic compound layer does not have a fused polycyclic hydrocarbon skeleton of 3 or more and 5 or less rings, so the compatibility effect cannot be obtained, and the durability characteristics do not improve.

[0038] The first organic compound layer may be functionally separated into two layers. For example, the organic electroluminescent element may further include a second organic compound layer disposed between the first organic compound layer and a cathode and in contact with the first organic compound layer, and the second organic compound layer may contain a compound having at least one fused polycyclic hydrocarbon skeleton of 3 or more and 5 or less rings similar to that of the first organic compound layer.

[0039] <3>Host material (organic compound contained in light-emitting layer) The organic compound used as the host material of the light-emitting layer will be described. The host material is SP 2 a hydrocarbon compound composed only of carbon and represented by any one of the following general formulas [1-1] to [1-6]. The host material is preferably a compound represented by the following general formula [1-3].

[0040]

Chemical Formula

[0041] <Ar1 and Ar2> In general formulas [1-1] to [1-6], Ar1 and Ar2 are each independently selected from an anthracene residue, a phenanthrene residue, a pyrene residue, a fluoranthene residue, a chrysene residue, a triphenylene residue, a benzanthracene residue, a benzophenanthrene residue, a benzopyrene residue, a benzofluoranthene residue, a benzochrysene residue, and a picene residue. Ar1 and Ar2 are preferably 4-ring condensed rings, more preferably a pyrene residue, a fluoranthene residue, a chrysene residue, or a triphenylene residue.

[0042] Ar1 and Ar2 may further have a phenyl group, a biphenyl group, a terphenyl group, or a naphthyl group.

[0043] <R1, R2 to R8> R1, R2 to R8 are each independently selected from a hydrogen atom, and a substituted or unsubstituted aryl group.

[0044] Examples of the aryl group include, but are not limited to, a phenyl group, a naphthyl group, an indenyl group, a biphenyl group, a terphenyl group, a fluorenyl group, a phenanthryl group, a pyrenyl group, a triphenylenyl group, and the like. Among these, aryl groups having 6 to 18 carbon atoms are preferred.

[0045] <Characteristic> The host material represented by general formulas [1-1] to [1-6] has the following two characteristics. (1)SP 2 It is a hydrocarbon compound composed exclusively of carbon. (2) It has a partial structure that reduces linearity. These characteristics are described below.

[0046] (1)SP 2 It is a hydrocarbon compound composed exclusively of carbon.

[0047] In inventing the organic light-emitting device of the present invention, the present inventors focused on the bond strength of the structure of the host compound. Specifically, the host material is SP2 We attempted to design the molecule to be a hydrocarbon compound consisting solely of carbon, without including any structures with low bond stability. This is because compounds with unstable bonds (i.e., bonds with low bond energy) in their molecular structure are prone to degradation during device operation, which is likely to negatively impact the lifespan of the organic EL device.

[0048] Here, taking the compound CBP ([4,4'-bis(carbazole-9-yl)biphenyl]) shown below as an example, the bond with low bond stability is the bond connecting the carbazole ring and the phenylene group (nitrogen-carbon bond). Below, a comparison of calculated bond energies between CBP and the example host material compound A2 is shown. The calculation method used was b3-lyp / def2-SV(P).

[0049] [ka]

[0050] The results above indicate that the nitrogen-carbon bond in CBP is an unstable bond. Such a bond is undesirable, especially in the host material structure of the luminescent layer. On the other hand, example compound A2 is composed solely of carbon-carbon bonds, demonstrating its high bond stability.

[0051] Furthermore, we attempted to design the molecules to enhance bond stability using substituents (R1, R2 to R8, Ar1 to Ar2) present in the host material. Here, Table 4 shows the bond dissociation energies of carbon-hydrogen bonds as described in ACC.Chem.Res.36,255-263,(2003).

[0052] [Table 4]

[0053] A higher bond dissociation energy indicates a stronger bond, while a lower value indicates a weaker bond. This means that SP (split-isolated) groups such as methyl, ethyl, and benzyl groups are stronger.3 A carbon-containing substituent is not preferred because it is a substituent from which hydrogen atoms are easily eliminated and generates radicals.

[0054] From the above, the host material is SP 2 Since it is composed only of carbon, it is a compound with excellent durability properties, and an organic light-emitting device using the same has excellent durability properties. Further, SP 2 Since it is composed only of carbon, electron mobility is increased. Therefore, an effect on reducing the driving voltage of the device can also be expected.

[0055] (2) It has a partial structure that reduces linearity.

[0056] As described in feature (1) above, the host material is SP 2 It is composed only of carbon. For this reason, there is a concern that molecules tend to cause molecular aggregation via π-π stacking, which deteriorates film properties and sublimability.

[0057] Therefore, as feature (2), in order to suppress molecular aggregation, the host material has the structures of general formulas [1-1] to [1-6] that reduce the linearity of the molecular structure. As a comparative structure, it has been found that the structure of the following general formula [1-7] has high molecular linearity, tends to cause molecular aggregation, and deteriorates film properties and sublimability. In addition, in general formula [1-7], Ar1, Ar2, R1, R3 to R5, and R7 to R8 are the same as those in general formulas [1-1] to [1-6].

[0058]

Chemical Formula

[0059] Here, as shown in Table 5, a solubility test comparison was performed between the exemplary compound A2 of the host material and comparative compound 2 represented by general formula [1-7]. The solubility test was performed by heating 100 mg of the host material under reflux with toluene under stirring, and comparing the amount of toluene solvent used for dissolution. The value shown is the amount of solvent required to completely dissolve comparative compound 2 when the amount of toluene solvent required to completely dissolve exemplary compound A2 is defined as 1.

[0060] [Table 5]

[0061] Table 5 shows that although both example compound A2 and comparative compound 2 are compounds composed of pyrene and naphthalene, their solubility differs significantly depending on the substitution positions.

[0062] Comparative compound 2 has a highly linear structure because pyrene is bonded to the 2,6 positions of naphthalene. In contrast, example compound A2 has pyrene bonded to the 2,7 positions of naphthalene, resulting in a bent molecular structure, which is thought to contribute to its solubility.

[0063] In the case of highly linear molecular structures, molecules tend to overlap easily, leading to molecular aggregation. This results in poor solubility, making them unsuitable for mass production from a materials synthesis perspective. Furthermore, they are undesirable as materials for organic light-emitting devices because they lead to deterioration of film properties and reduced sublimation. On the other hand, host materials represented by general formulas [1-1] to [1-6] have a bent structure, which inhibits molecular overlapping and reduces molecular aggregation. Therefore, they offer improved solubility, enhanced film amorphousness, and improved sublimation.

[0064] In organic light-emitting devices, the film properties of the organic compound constituting the device are crucial. This is because high amorphous properties reduce the likelihood of grain boundaries, trap levels, and quenchers forming due to minute crystallization during device operation, thus maintaining good carrier transport and highly efficient light emission characteristics. As a result, it is possible to provide organic light-emitting devices with excellent durability and efficiency.

[0065] Similarly, in organic light-emitting devices, the sublimation properties of the organic compounds constituting the device are important. This is because high sublimation properties allow for stable sublimation purification without decomposition during sublimation. This also translates to high deposition stability when fabricating organic light-emitting devices. In other words, it is possible to fabricate high-purity deposited films without decomposition during deposition, providing long-life organic light-emitting devices.

[0066] In other words, the host material used in the present invention is an SP molecular structure with high bonding stability. 2 It has a structure consisting solely of carbon and possesses a structure that enhances film properties. Therefore, it can be said to be a compound that combines molecular chemical stability with film stability and sublimation properties suitable for use in organic EL devices.

[0067] <Preferred Compounds> Among the compounds represented by general formulas [1-1] to [1-6], preferably the compounds represented by general formulas [1-2] to [1-5], and more preferably the compounds represented by general formula [1-3].

[0068] The host material is preferably highly planar. Therefore, the dihedral angles were calculated when Ar1 and Ar2 are phenyl groups. The results are shown in Table 6. As a result, it was found that the dihedral angles of the compounds represented by general formulas [1-2] to [1-5] are small, and the dihedral angle of the compound represented by general formula [1-3] is particularly small, indicating high planarity. In other words, organic compounds represented by general formulas [1-2] to [1-5] are preferable, and organic compounds represented by general formula [1-3] are even more preferable, exhibiting higher compatibility and better durability.

[0069] [Table 6]

[0070] The above calculation of the dihedral angle was performed using molecular orbital calculations. The molecular orbital calculation method used was Density Functional Theory (DFT), which is widely used today. The functional was B3LYP, and the basis set was 6-31G. *It is also a smooth-flowing waveguide and is based on Gaussian09(Gaussian09, RevisionC.01,MJFrisch,GWTrucks,HBSchlegel,GEScuse ria, MARobb,JRCheeseman,G.Scalmani,V.Barone,B.Mennucci,GAPetersson,H.Nakatsuji,M.Caricato,X.Li,HPHra tchian, AFIzmaylov, J. Bloino, G. Zheng, JLSonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishi da,T.Nakajima,Y.Honda,O.Kitao,H.Nakai,T.Vreven,JAMontgomery,Jr.,JEPeralta,F.Ogliaro,M.Bearpark,JJHe yd, E. Brothers, KNKudin, VNS Taroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, JCBurant ,SSIyengar,J.Tomasi,M.Cossi,N.Rega,JMMillam,M.Klene,JEKnox,JBCross,V.Bakken,C.Adamo,J.Jaramillo,R.G omperts,REStratmann,O.Yazyev,AJAustin,R.Cammi,C.Pomelli,JWOchterski,RLMartin,K.Morokuma,VGZakrzews ki,GAVoth,P.Salvador,JJDannenberg,S.Dapprich,ADDaniels,O.Farkas,JBForesman,JVOrtiz,JCioslowski,and DJFox,Gaussian,Inc.,Wallingford CT,2010.)

[0071] <Outside> Next, specific examples of host materials are shown. However, these compounds are merely examples, and the present invention is not limited thereto.

[0072] [ka]

[0073] [ka]

[0074] [ka]

[0075] The exemplary compounds belonging to Group A are the organic compounds shown in formula [1-3]. Among the compounds according to this embodiment, the compounds belonging to Group A have higher planarity and higher compatibility with the first organic compound layer. In other words, Group A is a group of compounds that have better durability characteristics when used in organic light-emitting devices. Furthermore, A1 to A28 are a group of compounds having a four-ring fused skeleton, and their compatibility with the first organic compound layer can be easily adjusted.

[0076] Examples of compounds belonging to Group B are the organic compounds shown in formulas [1-2], [1-4], and [1-5]. Compounds belonging to Group B have lower molecular symmetry than the compounds in this embodiment, resulting in higher solubility in organic solvents and easier improvement of purity through purification. In other words, Group B is a group of compounds that are likely to yield good durability when used in organic light-emitting devices.

[0077] Examples of compounds belonging to group C are the organic compounds shown in formulas [1-1] and [1-6]. Compounds belonging to group C have a bulkier molecular structure and a higher glass transition temperature compared to the compounds in this embodiment. In other words, group C is a group of compounds that, when used in organic light-emitting devices, provide uniform light emission characteristics even during longer operating times.

[0078] <4> Compounds contained in the first organic compound layer the above <2> As explained in the section above, the compounds contained in the first organic compound layer adjacent to the light-emitting layer on the cathode side have at least one condensed polycyclic hydrocarbon skeleton with 3 to 5 rings, which improves compatibility with the light-emitting layer host material and improves the durability characteristics of the organic light-emitting element. Preferably, the compounds contained in the first organic compound layer are compounds having at least one 4-ring condensed polycyclic hydrocarbon skeleton. Furthermore, the compounds having at least one condensed polycyclic hydrocarbon skeleton with 3 to 5 rings are preferably hydrocarbons.

[0079] The following are specific examples of compounds having at least one condensed polycyclic hydrocarbon skeleton with 3 to 5 rings. However, these compounds are merely examples and the invention is not limited to them. Furthermore, a compound represented by any of the general formulas [1-1] to [1-6] may be used in the first organic compound layer adjacent to the light-emitting layer on the cathode side.

[0080] [ka]

[0081] <5> Guest materials The guest material is a light-emitting material containing a fluorantene skeleton, preferably a hydrocarbon containing a fluorantene skeleton. As mentioned above, a characteristic of light-emitting materials containing a fluorantene skeleton is that, due to the presence of an electron-deficient five-membered ring, the HOMO and LUMO energies are low (far from the vacuum level). This makes the light-emitting material itself stable against oxidation and reactions, and improves the electron-trapping properties when used as an organic light-emitting element. Therefore, it is possible to provide an organic EL element with excellent durability.

[0082] Furthermore, to provide sufficient electron trapping properties, it is preferable to have a substructure containing two or more fluorantene skeletons. This is because adding more fluorantene skeletons containing electron-deficient five-membered rings results in a smaller LUMO energy (further from the vacuum level). This increases the LUMO energy difference with the host material, further improving electron trapping properties.

[0083] The following are specific examples of substructures containing two or more fluorantene skeletons. However, these substructures are merely examples and are not limiting. The fluorantene skeletons may be condensed with each other, for example, by forming a fused ring with benzene rings that form the fluorantene skeleton, as in FF1; by forming a fused ring with benzene rings other than those that form the fluorantene skeleton, as in FF8; or by bonding with benzene rings that form the fluorantene skeleton to form a fused ring, as in FF17. Furthermore, the fluorantene skeletons may share benzene rings that form the fluorantene skeleton, as in FF5 and FF11.

[0084] [ka]

[0085] Next, specific examples of guest materials that exhibit blue light emission are shown. However, these compounds are merely examples and are not limiting. Among the blue light-emitting guest materials listed below, SP 2 A structure composed solely of carbon is particularly preferred.

[0086] [ka]

[0087] [ka]

[0088] Next, we will show specific examples of guest materials that exhibit green emission. However, these compounds are merely examples and are not the only ones that can be used.

[0089] [ka]

[0090] Next, specific examples of guest materials exhibiting red emission are shown. However, these compounds are merely examples and the material is not limited to them. Among the red emission guest materials listed below, RD1 to RD26, which have a substructure containing two or more fluorantene skeletons, are particularly preferred.

[0091] [ka]

[0092] <6> Other materials for organic light-emitting diodes In addition to the compounds described above, conventionally known low-molecular-weight and high-molecular-weight hole-injecting or hole-transporting compounds, host compounds, luminescent compounds, electron-injecting or electron-transporting compounds, etc., can be used together as needed. Examples of these compounds are listed below.

[0093] As hole-implantation transport materials, materials with high hole mobility are preferred to facilitate hole injection from the anode and to transport the injected holes to the light-emitting layer. Furthermore, materials with a high glass transition temperature are preferred to suppress deterioration of the film quality, such as crystallization, in the organic light-emitting element. Examples of low-molecular-weight and high-molecular-weight materials with hole-implantation transport properties include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly(vinylcarbazole), poly(thiophene), and other conductive polymers. Moreover, the above-mentioned hole-implantation transport materials are also suitably used in electron-blocking layers. Specific examples of compounds used as hole-implantation transport materials are shown below, but are not limited to these.

[0094] [ka]

[0095] In addition to the luminescent material containing the fluorantene skeleton of this embodiment, other luminescent materials primarily involved in the luminescence function include fused ring compounds (e.g., fluorene derivatives, naphthalene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, anthracene derivatives, rubrene, etc.), quinacridone derivatives, coumarin derivatives, stilbene derivatives, organoaluminum complexes such as tris(8-quinolinolate)aluminum, iridium complexes, platinum complexes, rhenium complexes, copper complexes, europium complexes, ruthenium complexes, and polymer derivatives such as poly(phenylenevinylene) derivatives, poly(fluorene) derivatives, and poly(phenylene) derivatives. Specific examples of other compounds used as luminescent materials are shown below, but are of course not limited to these.

[0096] [ka]

[0097] [ka]

[0098] In addition to the compounds represented by any of the general formulas [1-1] to [1-6] mentioned above, other examples of luminescent layer hosts or luminescence assist materials included in the luminescent layer include aromatic hydrocarbon compounds or their derivatives, as well as carbazole derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, organoaluminum complexes such as tris(8-quinolinolate)aluminum, and organoberylium complexes.

[0099] In particular, materials having a carbazole skeleton, materials having an azine ring as a skeleton, or materials having a xanthone as a skeleton are preferred as assisting materials. This is because these materials have high electron-donating and electron-withdrawing properties, making it easy to adjust the HOMO and LUMO. When these assisting materials are combined with the organic compounds of the present invention, a good carrier balance can be achieved.

[0100] The following are specific examples of compounds used as light-emitting assist materials in the light-emitting layer, but of course, they are not the only ones that can be used.

[0101] [ka]

[0102] Other electron-transporting materials than those compounds having at least one condensed polycyclic hydrocarbon skeleton of three to five rings in this embodiment can be arbitrarily selected from those capable of transporting electrons injected from the cathode to the light-emitting layer, and are selected considering the balance with the hole mobility of the hole-transporting material. Examples of materials having electron-transporting properties include oxadiazole derivatives, oxazole derivatives, pyrazine derivatives, triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, organoaluminum complexes, and fused ring compounds (e.g., fluorene derivatives, naphthalene derivatives, chrysene derivatives, anthracene derivatives, etc.). Furthermore, the above electron-transporting materials are also suitably used in the hole-blocking layer. Specific examples of compounds used as electron-transporting materials are shown below, but are of course not limited to these.

[0103] [ka]

[0104] Electron injection materials can be arbitrarily selected from those that allow for easy electron injection from the cathode, taking into consideration the balance with hole injection properties. Organic compounds include n-type dopants and reducing dopants. Examples include alkali metal compounds such as lithium fluoride, lithium complexes such as lithium quinolinol, benzimidazolidene derivatives, imidazolidene derivatives, fluvalene derivatives, and acridine derivatives. They can also be used in combination with the above-mentioned electron transport materials.

[0105] <Configuration of an organic light-emitting element> An organic light-emitting element is provided on a substrate by forming an insulating layer, a first electrode, an organic compound layer, and a second electrode. A protective layer, a color filter, a microlens, etc., may be provided on the second electrode. If a color filter is provided, a planarization layer may be provided between it and the protective layer. The planarization layer can be made of acrylic resin or the like. The same applies when a planarization layer is provided between the color filter and the microlens.

[0106] [substrate] Examples of substrates include quartz, glass, silicon wafers, resins, and metals. The substrate may also be equipped with switching elements such as transistors and wiring, and an insulating layer may be provided on top of them. The insulating layer can be made of any material that allows for the formation of contact holes between it and the first electrode, while ensuring insulation from wiring that is not connected. For example, resins such as polyimide, silicon oxide, and silicon nitride can be used.

[0107] [electrode] A pair of electrodes can be used. The pair of electrodes may be an anode and a cathode. When an electric field is applied in the direction in which the organic light-emitting element emits light, the electrode with the higher potential is the anode, and the other is the cathode. Alternatively, the electrode that supplies holes to the light-emitting layer can be the anode, and the electrode that supplies electrons can be the cathode.

[0108] For the anode, materials with the largest possible work function are preferable. For example, elemental metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, and tungsten, or mixtures containing these, or alloys combining them, as well as metal oxides such as tin oxide, zinc oxide, indium oxide, tin-indium oxide (ITO), and zinc-indium oxide can be used. Conductive polymers such as polyaniline, polypyrrole, and polythiophene can also be used.

[0109] These electrode materials may be used individually or in combination of two or more types. Furthermore, the anode may consist of a single layer or multiple layers.

[0110] When used as a reflective electrode, materials such as chromium, aluminum, silver, titanium, tungsten, molybdenum, or alloys or laminates thereof can be used. It is also possible to use the above materials as a reflective film without serving as an electrode. Furthermore, when used as a transparent electrode, oxide transparent conductive layers such as indium tin oxide (ITO) or indium zinc oxide can be used, but are not limited to these. Photolithography can be used to form the electrodes.

[0111] On the other hand, materials with a small work function are preferred for the cathode. Examples include alkali metals such as lithium, alkaline earth metals such as calcium, and elemental metals or mixtures containing aluminum, titanium, manganese, silver, lead, and chromium. Alternatively, alloys combining these elemental metals can also be used. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper, and zinc-silver can be used. Metal oxides such as indium tin oxide (ITO) can also be used. These electrode materials may be used individually or in combination of two or more. The cathode may also be a single-layer or multi-layer structure. Among these, silver is preferred, and a silver alloy is even more preferred to reduce silver aggregation. The alloy ratio is not important as long as silver aggregation is reduced. For example, the ratio of silver to other metals may be 1:1, 3:1, etc.

[0112] The cathode may be a top-emission element using an oxide conductive layer such as ITO, or a bottom-emission element using a reflective electrode such as aluminum (Al), and is not particularly limited. The method for forming the cathode is not particularly limited, but using DC and AC sputtering methods is more preferable because it provides good film coverage and makes it easier to reduce resistance.

[0113] [Organic compound layer] The organic compound layer may have layers other than the light-emitting layer and the first organic compound layer. The layers other than the light-emitting layer and the first organic compound layer may be formed as a single layer or as multiple layers. If there are multiple layers, they may be called a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer, or an electron injection layer, depending on their function. The organic compound layer is mainly composed of organic compounds, but may also contain inorganic atoms and inorganic compounds. For example, it may contain copper, lithium, magnesium, aluminum, iridium, platinum, molybdenum, zinc, etc. The organic compound layer may be placed between the first electrode and the second electrode, or it may be placed in contact with the first electrode and the second electrode.

[0114] The organic compound layer (hole injection layer, hole transport layer, electron blocking layer, light-emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) constituting the organic light-emitting element according to one embodiment of the present invention is formed by the method shown below.

[0115] The organic compound layer constituting the organic light-emitting element according to one embodiment of the present invention can be formed using a dry process such as vacuum deposition, ionization deposition, sputtering, or plasma deposition. Alternatively, instead of a dry process, a wet process can be used in which the layer is formed by dissolving the compound in a suitable solvent and applying a known coating method (e.g., spin coating, dipping, casting, LB method, inkjet method, etc.).

[0116] When layers are formed using methods such as vacuum deposition or solution coating, crystallization is less likely to occur, resulting in excellent stability over time. Furthermore, when forming films using coating methods, it is possible to combine the film with an appropriate binder resin.

[0117] Examples of the binder resins mentioned above include, but are not limited to, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenolic resin, epoxy resin, silicone resin, and urea resin.

[0118] Furthermore, these binder resins may be used individually as homopolymers or copolymers, or as a mixture of two or more types. Additionally, known additives such as plasticizers, antioxidants, and UV absorbers may be used in combination as needed.

[0119] [Protective layer] A protective layer may be provided on the second electrode. For example, by bonding glass with a desiccant to the second electrode, the intrusion of water and other substances into the organic compound layer can be reduced, thereby reducing the occurrence of display defects. In another embodiment, a passivation film such as silicon nitride may be provided on the second electrode to reduce the intrusion of water and other substances into the organic compound layer. For example, after forming the second electrode, it may be transported to another chamber without breaking the vacuum and a silicon nitride film with a thickness of 2 μm may be formed by the CVD method to serve as a protective layer. A protective layer may also be provided using atomic deposition (ALD) after film formation by the CVD method. The material of the film formed by the ALD method is not limited, but may be silicon nitride, silicon oxide, aluminum oxide, etc. Silicon nitride may be further formed on the film formed by the ALD method by the CVD method. The film formed by the ALD method may have a thinner film thickness than the film formed by the CVD method. Specifically, it may be 50% or less, or even 10% or less.

[0120] [Color Filter] A color filter may be provided on top of the protective layer. For example, a color filter that takes into account the size of the organic light-emitting element may be provided on a separate substrate and bonded to the substrate on which the organic light-emitting element is provided, or a color filter may be patterned on the protective layer as described above using photolithography technology. The color filter may be made of polymer.

[0121] [Planarization layer] A planarizing layer may be provided between the color filter and the protective layer. The planarizing layer is provided to reduce the unevenness of the layer below. It may also be called a material resin layer without limiting its purpose. The planarizing layer may be composed of an organic compound, which may be low molecular weight or high molecular weight, but high molecular weight is preferred.

[0122] The planarization layer may be provided above or below the color filter, and its constituent materials may be the same or different. Specifically, examples include polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenolic resin, epoxy resin, silicone resin, urea resin, etc.

[0123] [Microlens] An organic light-emitting element or organic light-emitting device may have optical elements such as microlenses on its light-emitting side. Microlenses may be made of acrylic resin, epoxy resin, or the like. Microlenses may be used to increase the amount of light extracted from the organic light-emitting element or organic light-emitting device, or to control the direction of the extracted light. Microlenses may have a hemispherical shape. If they have a hemispherical shape, among the tangents tangent to the hemisphere, there is a tangent parallel to the insulating layer, and the point of contact between that tangent and the hemisphere is the vertex of the microlens. The vertex of the microlens can be similarly determined in any cross-sectional view. That is, among the tangents tangent to the semicircle of the microlens in the cross-sectional view, there is a tangent parallel to the insulating layer, and the point of contact between that tangent and the semicircle is the vertex of the microlens.

[0124] Furthermore, the midpoint of a microlens can also be defined. In the cross-section of a microlens, a line segment can be imagined from the point where one arc ends to the point where another arc ends, and the midpoint of this line segment can be called the midpoint of the microlens. The cross-section used to determine the vertices and midpoints may be a cross-section perpendicular to the insulating layer.

[0125] [Opposite substrate] A counter substrate may be provided on the planarized layer. The counter substrate is called a counter substrate because it is provided in a position corresponding to the aforementioned substrate. The constituent material of the counter substrate may be the same as that of the aforementioned substrate. The counter substrate may be the second substrate if the aforementioned substrate is referred to as the first substrate.

[0126] [Pixel circuit] An organic light-emitting device having an organic light-emitting element may have a pixel circuit connected to the organic light-emitting element. The pixel circuit may be an active-matrix type that independently controls the light emission of a first light-emitting element and a second light-emitting element. The active-matrix type circuit may be voltage-programmed or current-programmed. The driving circuit has a pixel circuit for each pixel. The pixel circuit may include a light-emitting element, a transistor that controls the light emission brightness of the light-emitting element, a transistor that controls the light emission timing, a capacitor that holds the gate voltage of the transistor that controls the light emission brightness, and a transistor for connecting to GND without going through the light-emitting element.

[0127] The light-emitting device has a display area and a peripheral area arranged around the display area. The display area has a pixel circuit, and the peripheral area has a display control circuit. The mobility of the transistors constituting the pixel circuit may be smaller than the mobility of the transistors constituting the display control circuit. The slope of the current-voltage characteristic of the transistors constituting the pixel circuit may be smaller than the slope of the current-voltage characteristic of the transistors constituting the display control circuit. The slope of the current-voltage characteristic can be measured by the so-called Vg-Ig characteristic. The transistors constituting the pixel circuit are transistors connected to the light-emitting element, such as the first light-emitting element.

[0128] [Pixels] An organic light-emitting device having an organic light-emitting element may have a plurality of pixels. Each pixel may have subpixels that emit light of a different color from the others. The subpixels may each have, for example, RGB light-emitting colors.

[0129] A pixel emits light from a region also called the pixel aperture. This region is the same as the first region. The pixel aperture may be 15 μm or less, or 5 μm or more. More specifically, it may be 11 μm, 9.5 μm, 7.4 μm, 6.4 μm, etc. The distance between subpixels may be 10 μm or less, and specifically, it may be 8 μm, 7.4 μm, 6.4 μm.

[0130] Pixels can take on known arrangements in a plan view. For example, they may be in a stripe arrangement, delta arrangement, pentile arrangement, or Bayer arrangement. The shape of subpixels in a plan view may be any known shape. For example, rectangles, rhombuses, hexagons, etc. Of course, even if it is not a precise shape, if it is close to a rectangle, it is included in the category of rectangles. The shape of subpixels and the pixel arrangement can be used in combination.

[0131] <Applications of organic light-emitting diodes> The organic light-emitting element according to this embodiment can be used as a component of a display device or lighting device. Other applications include exposure light sources for electrophotographic image forming apparatuses, backlights for liquid crystal display devices, and light-emitting devices with a color filter in a white light source.

[0132] The display device may also be an image information processing device having an image input unit that receives image information from an area CCD, linear CCD, memory card, etc., an information processing unit that processes the input information, and displays the input image on a display unit. The display device may have a plurality of pixels, and at least one of the plurality of pixels may have the organic light-emitting element of this embodiment and a transistor connected to the organic light-emitting element.

[0133] Furthermore, the display unit of the imaging device or inkjet printer may have a touch panel function. The driving method for this touch panel function may be infrared, capacitive, resistive, or electromagnetic induction, and is not particularly limited. The display device may also be used as the display unit of a multifunction printer.

[0134] Next, a display device according to this embodiment will be described with reference to the drawings. Figure 1 is a schematic cross-sectional view showing an example of a display device having an organic light-emitting element and a transistor connected to the organic light-emitting element. The transistor is an example of an active element. The transistor may be a thin-film transistor (TFT).

[0135] Figure 1(a) shows an example of a pixel, which is a component of the display device according to this embodiment. The pixel has sub-pixels 10. The sub-pixels are divided into 10R, 10G, and 10B based on their light emission. The light emission color may be distinguished by the wavelength emitted from the light-emitting layer, or the light emitted from the sub-pixel may be selectively transmitted or color-converted by a color filter or the like. Each sub-pixel 10 has a reflective electrode which is a first electrode 2 on an interlayer insulating layer 1, an insulating layer 3 covering the end of the first electrode 2, an organic compound layer 4 covering the first electrode 2 and the insulating layer 3, a transparent electrode which is a second electrode 5, a protective layer 6, and a color filter 7.

[0136] The interlayer insulating layer 1 may have transistors and capacitive elements placed in the layer below or inside it. The transistor and the first electrode 2 may be electrically connected via a contact hole or the like (not shown).

[0137] The insulating layer 3 is also called a bank or pixel isolation layer. It covers the edge of the first electrode 2 and surrounds the first electrode 2. The portion not covered by the insulating layer 3 is in contact with the organic compound layer 4 and becomes the light-emitting region.

[0138] The organic compound layer 4 includes a hole injection layer 41, a hole transport layer 42, a first light-emitting layer 43, a second light-emitting layer 44, and an electron transport layer 45.

[0139] The second electrode 5 may be a transparent electrode, a reflective electrode, or a semi-transparent electrode.

[0140] The protective layer 6 reduces the penetration of moisture into the organic compound layer 4. Although the protective layer 6 is shown as a single layer, it may consist of multiple layers. Each layer may contain an inorganic compound layer and an organic compound layer.

[0141] The color filter 7 is classified into 7R, 7G, and 7B according to its color. The color filter 7 may be formed on a planarization film (not shown). The color filter 7 may also have a resin protective layer (not shown). Alternatively, the color filter 7 may be formed on a protective layer 6. Or it may be bonded to an opposing substrate such as a glass substrate after being placed on it.

[0142] The display device 100 in Figure 1(b) has an organic light-emitting element 26 and a TFT 18 as an example of a transistor. A substrate 11 made of glass, silicon, or the like is provided, with an insulating layer 12 on top of it. An active element such as the TFT 18 is placed on the insulating layer 12, and the gate electrode 13, gate insulating film 14, and semiconductor layer 15 of the active element are arranged therein. The TFT 18 is also composed of a drain electrode 16 and a source electrode 17. An insulating film 19 is provided on top of the TFT 18. The anode 21 and the source electrode 17 that constitute the organic light-emitting element 26 are connected via a contact hole 20 provided in the insulating film 19.

[0143] Note that the method of electrical connection between the electrodes (anode 21, cathode 23) included in the organic light-emitting element 26 and the electrodes (source electrode 17, drain electrode 16) included in the TFT 18 is not limited to the configuration shown in Figure 1(b). In other words, it is sufficient if either the anode 21 or the cathode 23 is electrically connected to either the source electrode 17 or the drain electrode 16 of the TFT 18. TFT refers to a thin-film transistor.

[0144] In the display device 100 shown in Figure 1(b), the organic compound layer 22 is depicted as a single layer, but the organic compound layer 22 may consist of multiple layers. A first protective layer 24 and a second protective layer 25 are provided on the cathode 23 to reduce the degradation of the organic light-emitting element 26.

[0145] In the display device 100 shown in Figure 1(b), a transistor is used as the switching element, but other switching elements may be used instead.

[0146] Furthermore, the transistor used in the display device 100 in Figure 1(b) is not limited to a transistor using a single-crystal silicon wafer, but may also be a thin-film transistor having an active layer on an insulating surface of the substrate. Examples of active layers include non-single-crystal silicon such as single-crystal silicon, amorphous silicon, and microcrystalline silicon, and non-single-crystal oxide semiconductors such as indium zinc oxide and indium gallium zinc oxide. Thin-film transistors are also called TFT elements.

[0147] The transistors included in the display device 100 in Figure 1(b) may be formed within a substrate such as a Si substrate. Here, "formed within a substrate" means that the transistors are manufactured by processing the substrate itself, such as a Si substrate. In other words, having transistors within a substrate can be seen as the substrate and transistors being formed as a single unit.

[0148] The organic light-emitting element according to this embodiment has its luminescence controlled by a TFT, which is an example of a switching element, and by providing multiple organic light-emitting elements on the surface, an image can be displayed using the luminescence of each element. The switching element according to this embodiment is not limited to a TFT, but may also be a transistor made of low-temperature polysilicon, or an active matrix driver formed on a substrate such as a Si substrate. "On the substrate" can also mean "within the substrate." Whether to provide a transistor within the substrate or to use a TFT is selected depending on the size of the display area; for example, if the size is about 0.5 inches, it is preferable to provide the organic light-emitting element on a Si substrate.

[0149] Figure 2 is a schematic diagram showing an example of a display device according to this embodiment. The display device 1000 may have a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 1007, and a battery 1008 between an upper cover 1001 and a lower cover 1009. Flexible printed circuits FPCs 1002 and 1004 are connected to the touch panel 1003 and the display panel 1005. Transistors are printed on the circuit board 1007. The battery 1008 may not be provided if the display device is not a portable device, or it may be provided in a different location even if it is a portable device.

[0150] The display device according to this embodiment may have a color filter having red, green, and blue colors. The color filter may have the red, green, and blue colors arranged in a delta array.

[0151] The display device according to this embodiment may be used in the display unit of a mobile terminal. In that case, it may have both display and operation functions. Examples of mobile terminals include smartphones and other mobile phones, tablets, and head-mounted displays.

[0152] The display device according to this embodiment may be used in the display unit of an imaging device having an optical unit with multiple lenses and an image sensor that receives light that has passed through the optical unit. The imaging device may have a display unit that displays information acquired by the image sensor. Furthermore, the display unit may be a display unit exposed to the outside of the imaging device or a display unit located inside the viewfinder. The imaging device may be a digital camera or a digital video camera.

[0153] Figure 3(a) is a schematic diagram showing an example of an imaging device according to this embodiment. The imaging device 1100 may include a viewfinder 1101, a rear display 1102, an operation unit 1103, and a housing 1104. The viewfinder 1101 may have a display device according to this embodiment. In that case, the display device may display not only the image to be captured, but also environmental information, imaging instructions, etc. Environmental information may include the intensity of ambient light, the direction of ambient light, the speed at which the subject is moving, the possibility of the subject being obscured by an obstacle, etc.

[0154] Since the optimal timing for imaging is very short, it is best to display the information as quickly as possible. Therefore, it is preferable to use a display device using the organic light-emitting element of this embodiment, because organic light-emitting elements have a fast response speed. Display devices using organic light-emitting elements can be used more suitably than liquid crystal display devices, which require a fast display speed.

[0155] The imaging device 1100 has an optical section (not shown). The optical section has multiple lenses that form an image on the image sensor housed in the housing 1104. The focus can be adjusted by adjusting the relative positions of the multiple lenses. This operation can also be performed automatically. The imaging device may also be called a photoelectric converter. The photoelectric converter may not capture images sequentially, but may include imaging methods such as detecting the difference from the previous image or extracting from an image that is always being recorded.

[0156] Figure 3(b) is a schematic diagram showing an example of an electronic device according to this embodiment. The electronic device 1200 has a display unit 1201, an operation unit 1202, and a housing 1203. The housing 1203 may have a circuit, a printed circuit board having the circuit, a battery, and a communication unit. The operation unit 1202 may be a button or a touch panel type response unit. The operation unit 1202 may also be a biometric recognition unit that recognizes a fingerprint to unlock the device, etc. An electronic device having a communication unit can also be called a communication device. The electronic device 1200 may further have a camera function by including a lens and an image sensor. The image captured by the camera function is displayed on the display unit 1201. Examples of electronic devices 1200 include smartphones and laptop computers.

[0157] Figure 4 is a schematic diagram showing an example of a display device according to this embodiment. Figure 4(a) is a display device such as a television monitor or a PC monitor. The display device 1300 has a frame 1301 and a display unit 1302. The display unit 1302 may use a light-emitting element according to this embodiment. It has a frame 1301 and a base 1303 that supports the display unit 1302. The base 1303 is not limited to the form shown in Figure 4(a). The lower edge of the frame 1301 may also serve as the base. In addition, the frame 1301 and the display unit 1302 may be curved. The radius of curvature may be 5000 mm or more and 6000 mm or less.

[0158] Figure 4(b) is a schematic diagram showing another example of the display device according to this embodiment. The display device 1310 in Figure 4(b) is configured to be foldable and is a so-called foldable display device. The display device 1310 has a first display unit 1311, a second display unit 1312, a housing 1313, and a bending point 1314. The first display unit 1311 and the second display unit 1312 may have light-emitting elements according to this embodiment. The first display unit 1311 and the second display unit 1312 may be a single display device without seams. The first display unit 1311 and the second display unit 1312 can be separated by a bending point. The first display unit 1311 and the second display unit 1312 may each display different images, or the first and second display units may together display a single image.

[0159] Figure 5(a) is a schematic diagram showing an example of a lighting device according to this embodiment. The lighting device 1400 may include a housing 1401, a light source 1402, a circuit board 1403, and an optical filter 1404 and a light diffusion unit 1405 that transmit light emitted from the light source 1402. The light source 1402 may have an organic light-emitting element according to this embodiment. The optical filter 1404 may be a filter that improves the color rendering of the light source. The light diffusion unit 1405 can effectively diffuse the light from the light source, such as for lighting up, and deliver light over a wide area. The optical filter 1404 and the light diffusion unit 1405 may be provided on the light-emitting side of the lighting. A cover may be provided on the outermost part as needed.

[0160] The lighting device is, for example, a device for illuminating a room. The lighting device may emit white light, cool white light, or any other color from blue to red. It may have a dimming circuit to adjust the brightness of these lights. The lighting device may have the organic light-emitting element of this embodiment and a power supply circuit connected thereto. The power supply circuit is a circuit that converts AC voltage to DC voltage. White light has a color temperature of 4200K, and cool white light has a color temperature of 5000K. The lighting device may have a color filter.

[0161] Furthermore, the lighting device according to this embodiment may have a heat dissipation section. The heat dissipation section releases heat from inside the device to the outside, and examples include metals with high specific heat, liquid silicon, etc.

[0162] Figure 5(b) is a schematic diagram of an automobile, which is an example of a mobile body according to this embodiment. The automobile has a taillight, which is an example of a lighting device. The automobile 1500 has a taillight 1501, and may be configured to illuminate when the brakes are applied or the like.

[0163] The taillight 1501 may have an organic light-emitting element according to this embodiment. The taillight 1501 may have a protective member to protect the organic light-emitting element. The protective member has a reasonably high strength and can be made of any transparent material, but it is preferably made of polycarbonate or the like. A frangic acid derivative, an acrylonitrile derivative, or the like may be mixed with the polycarbonate.

[0164] The automobile 1500 may have a body 1503 and windows 1502 attached thereto. The windows 1502 may be transparent displays, unless they are windows for checking the front and rear of the automobile. The transparent displays may have organic light-emitting elements according to this embodiment. In this case, the constituent materials such as electrodes of the organic light-emitting element are made of transparent members.

[0165] The mobile body according to this embodiment may be a ship, aircraft, drone, etc. The mobile body may have a body and a lighting device provided on the body. The lighting device may emit light to indicate the position of the body. The lighting device has an organic light-emitting element according to this embodiment.

[0166] Referencing Figure 6, examples of applications of the display devices of each embodiment described above will be explained. The display device can be applied to systems that can be worn as wearable devices such as smart glasses, HMDs, and smart contact lenses. The imaging display device used in such applications comprises an imaging device capable of photoelectric conversion of visible light and a display device capable of emitting visible light.

[0167] Figure 6(a) is a schematic diagram showing an example of a wearable device according to one embodiment of the present invention. Using Figure 6(a), we will explain a pair of glasses 1600 (smart glasses) according to one application example. An imaging device 1602, such as a CMOS sensor or SPAD, is provided on the front surface side of the lens 1601 of the glasses 1600. In addition, the display devices of each embodiment described above are provided on the back surface side of the lens 1601.

[0168] The eyeglasses 1600 further include a control device 1603. The control device 1603 functions as a power supply that provides power to the imaging device 1602 and the display device. The control device 1603 also controls the operation of the imaging device 1602 and the display device. The lens 1601 has an optical system formed therein for focusing light onto the imaging device 1602.

[0169] Figure 6(b) is a schematic diagram showing another example of a wearable device according to one embodiment of the present invention. Using Figure 6(b), we will describe a pair of glasses 1610 (smart glasses) according to one application example. The glasses 1610 have a control device 1612, which is equipped with an imaging device corresponding to the imaging device 1602 in Figure 6(a) and a display device. The lens 1611 has an optical system formed therein for projecting light emitted from the imaging device and the display device in the control device 1612, and an image is projected onto the lens 1611. The control device 1612 functions as a power supply that supplies power to the imaging device and the display device, and also controls the operation of the imaging device and the display device.

[0170] The control device 1612 may have a gaze detection unit that detects the wearer's gaze. Gaze detection may use infrared light. The infrared light emitter emits infrared light towards the user's eyeball that is fixated on the displayed image. An imaging unit having a photodetector detects the reflected light from the eyeball of the emitted infrared light, thereby obtaining an image of the eyeball. By having a reduction means that reduces the light from the infrared light emitter to the display unit in a planar view, the degradation of image quality is reduced. The user's gaze toward the displayed image is detected from the image of the eyeball obtained by imaging with infrared light. Any known method can be applied to gaze detection using the image of the eyeball. As an example, a gaze detection method based on the Purkinje image obtained by the reflection of irradiated light from the cornea can be used. More specifically, gaze detection processing based on the pupil-corneal reflection method is performed. Using the pupil-corneal reflection method, the user's gaze is detected by calculating a gaze vector representing the orientation (rotation angle) of the eyeball based on the pupil image and Purkinje image included in the image of the eyeball.

[0171] A display device according to one embodiment of the present invention has an imaging device having a light-receiving element, and may control the display image of the display device based on the user's gaze information from the imaging device. Specifically, the display device determines a first field of view area that the user is fixated on and a second field of view area other than the first field of view area, based on the gaze information. The first field of view area and the second field of view area may be determined by the control device of the display device, or they may be determined by an external control device and received by the display device. In the display area of ​​the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than that of the first field of view area.

[0172] Furthermore, the display area has a first display area and a second display area different from the first display area, and based on gaze information, the area with higher priority is determined from the first display area and the second display area. The first and second view areas may be determined by the control device of the display device, or they may be determined by an external control device and received. The resolution of the high-priority area may be controlled to be higher than the resolution of the areas other than the high-priority area. In other words, the resolution of areas with relatively lower priority may be set lower.

[0173] AI may be used to determine the primary field of view and high-priority areas. The AI ​​may be a model configured to estimate the angle of gaze and the distance to the target object at the end of the line of sight from the image of the eye, using the image of the eye and the direction the eye was actually looking in that image as training data. The AI ​​program may be installed in the display device, the imaging device, or an external device. If installed in an external device, it will be transmitted to the display device via communication.

[0174] When display control is based on visual detection, this method is preferably applicable to smart glasses that further include an imaging device for capturing images of the surrounding environment. The smart glasses can display the captured external information in real time.

[0175] Figure 7(a) is a schematic diagram showing an example of an image forming apparatus according to one embodiment of the present invention. The image forming apparatus 40 is an electrophotographic image forming apparatus and includes a photoreceptor 27, an exposure light source 28, a charging unit 30, a developing unit 31, a transfer unit 32, a transport roller 33, and a fuser 35. Light 29 is irradiated from the exposure light source 28, and an electrostatic latent image is formed on the surface of the photoreceptor 27. This exposure light source 28 has an organic light-emitting element according to this embodiment. The developing unit 31 contains toner or the like. The charging unit 30 charges the photoreceptor 27. The transfer unit 32 transfers the developed image to a recording medium 34. The transport roller 33 transports the recording medium 34. The recording medium 34 is, for example, paper. The fuser 35 fixes the image formed on the recording medium 34.

[0176] Figures 7(b) and 7(c) are diagrams showing the exposure light source 28, schematic diagrams showing how multiple light-emitting units 36 are arranged on a long substrate. The arrow 37 is parallel to the axis of the photoreceptor and represents the column direction in which the organic light-emitting elements are arranged. This column direction is the same as the direction of the axis in which the photoreceptor 27 rotates. This direction can also be called the long axis direction of the photoreceptor 27. Figure 7(b) shows a configuration in which the light-emitting units 36 are arranged along the long axis direction of the photoreceptor 27. Figure 7(c) is a different configuration from Figure 7(b), in which the light-emitting units 36 are arranged alternately in the column direction in the first and second columns. The first and second columns are located at different positions in the row direction. In the first column, multiple light-emitting units 36 are arranged with intervals between them. In the second column, light-emitting units 36 are located at positions corresponding to the intervals between the light-emitting units 36 in the first column. That is, multiple light-emitting units 36 are also arranged with intervals between them in the row direction. The arrangement in Figure 7(c) can also be described as a grid pattern, a houndstooth pattern, or a checkerboard pattern.

[0177] As described above, by using the device employing the organic light-emitting element according to this embodiment, stable display with good image quality is possible even during long-term display. [Examples]

[0178] [Example 1] An organic light-emitting device with a bottom-emission structure was fabricated on a substrate, in which an anode, hole injection layer, hole transport layer, electron blocking layer, light-emitting layer, hole blocking layer (first organic compound layer), electron transport layer, electron injection layer, and cathode were sequentially formed.

[0179] First, an ITO film was deposited on a glass substrate, and an ITO electrode (anode) was formed by applying the desired patterning process. At this time, the film thickness of the ITO electrode was set to 100 nm. The substrate on which the ITO electrode was formed in this way was used as the ITO substrate in the following process. Next, 1.33 × 10 -4 Vacuum deposition was performed by resistance heating in a Pa vacuum chamber to continuously deposit the organic compound layer and electrode layer shown in Table 7 onto an ITO substrate. Note that the electrode area of ​​the opposing electrodes (metal electrode layer, cathode) was 3 mm². 2 I made it so that it would be like that.

[0180] [Table 7]

[0181] The characteristics of the obtained device were measured and evaluated. The light-emitting element emitted blue light, and the maximum external quantum efficiency (EQE) was 5%. Furthermore, the current density was 100 mA / cm². 2 A continuous operation test was conducted, and the time it took for the brightness degradation rate to reach 5% was measured. When the time it took for the brightness degradation rate to reach 5% in Comparative Example 1 was set to 1.0, the brightness degradation rate ratio in this example was 2.7.

[0182] In this embodiment, the measuring device specifically measured the current-voltage characteristics with a Hewlett-Packard 4140B micro-ammeter, and the luminous intensity with a Topcon BM7.

[0183] [Examples 2 to 31, Comparative Examples 1 to 4] (Examples 17, 19, 23, 25, 27, and 31 are for reference only.) ] Organic light-emitting devices were fabricated in the same manner as in Example 1, except that the compounds shown in Tables 8 and 9 were appropriately changed. The characteristics of the obtained devices were measured and evaluated in the same manner as in Example 1. The measurement results are shown in Tables 8 and 9. Comparative compound 1-a is organic compound 1-a described in Patent Document 1. Comparative compound 1-b is a dopant described in Patent Document 1, and its molecular structure is shown below.

[0184] [ka]

[0185] [Table 8]

[0186] [Table 9]

[0187] As shown in Examples 1 to 31, the organic light-emitting element of this embodiment demonstrated excellent durability. On the other hand, Comparative Examples 1 to 4 did not exhibit superior durability.

[0188] In Comparative Example 1 and Comparative Example 2, comparative compound 1-a, which is the host material of the light-emitting layer, SP 3 Because it contains multiple carbon atoms, it is thought that bond cleavage and radical generation occurred during the operation of the device, and that the reduced compatibility with guest materials negatively affected the device's operation durability.

[0189] Furthermore, in the case of Comparative Example 1, the adjacent layer ETL of the light-emitting layer is compound ET1, which does not have a condensed polycyclic hydrocarbon skeleton of 3 to 5 rings. Therefore, the compatibility was greatly reduced, and it is thought that this negatively affected the device's driving durability due to charge accumulation and quenching of excitons and charges.

[0190] In the case of Comparative Example 3, the guest material is comparative compound 1-b, which does not contain a fluorantene skeleton, and therefore exhibits inferior durability. Furthermore, comparative compound 1-b is an amine compound and has a carbon-nitrogen bond with low bond stability. It is thought that this makes it prone to bond cleavage during device operation, which negatively affected the device's operation durability.

[0191] In the case of Comparative Example 4, the light-emitting layer host material is comparative compound 2, represented by formula [1-7], which has high linearity and is prone to suppressing molecular aggregation. Therefore, it is thought that the deterioration of film properties negatively affected the device characteristics.

[0192] Furthermore, as shown in Examples 1 to 8, any guest material having a fluorantene skeleton exhibits excellent durability.

[0193] Furthermore, in Examples 9 to 11, we compared combinations in which the host material Ar1 and Ar2 had 4 rings, and the HBL material, which is the first organic compound layer, had 3 to 5 rings. As a result, the combination in which both the host material Ar1 and Ar2 and the HBL material had 4 rings exhibited the best durability characteristics.

[0194] Furthermore, as in Examples 12 to 15, when the combination of the number of fused rings of Ar1 and Ar2 in the host material and the number of fused rings in the HBL material is 3 rings and 5 rings, the effect of improving durability is certainly obtained, but the effect is slightly inferior compared to the case with only 4 rings.

[0195] Furthermore, in Examples 16 to 31, the positions of Ar1 and Ar2 in the host material were compared. Examples 16 to 21, 30, and 31, which used a compound represented by general formula [1-3] with a small dihedral angle with the naphthalene plane as the host material, showed a greater improvement in durability compared to Examples 22 to 29.

[0196] [Example 32] An organic light-emitting element was fabricated in the same manner as in Example 1, except that the organic compound layer and electrode layer shown in Table 10 were continuously deposited on an ITO substrate. The characteristics of the obtained element were measured and evaluated in the same manner as in Example 1.

[0197] [Table 10]

[0198] The light-emitting element emitted white light, and its maximum external quantum efficiency (EQE) was 7%. Furthermore, when the time at which the brightness degradation rate of Comparative Example 1 reached 5% was set to 1.0, the brightness degradation rate ratio of this embodiment was 2.6.

[0199] [Examples 33 to 46, Comparative Example 5] (Examples 34, 36, and 45 are for reference only) ] Organic light-emitting devices were fabricated in the same manner as in Example 32, except that the compounds shown in Table 11 were appropriately changed. The characteristics of the obtained devices were measured and evaluated in the same manner as in Example 32. The measurement results are shown in Table 11.

[0200] [Table 11]

[0201] As shown in Examples 32 to 46, the white organic light-emitting element of this embodiment demonstrated excellent durability. On the other hand, Comparative Example 5 did not exhibit excellent durability. In the case of Comparative Example 5, comparative compound 1-a, which is the host material of the light-emitting layer, was SP 3 Because the host material contains multiple carbon atoms, it is thought that bond cleavage and radical generation during device operation, as well as a decrease in compatibility with the guest material, negatively affected the device's operation durability.

[0202] [Example 47] In this embodiment, an organic EL element with a top-emission structure was fabricated on a substrate, in which an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a first light-emitting layer, a second light-emitting layer, a hole blocking layer (first organic compound layer), an electron transport layer, an electron injection layer, and a cathode were sequentially formed.

[0203] First, a 40nm Ti film was deposited on the substrate using the sputtering method, and the anode was formed by patterning using known photolithography techniques. The pixel area of ​​the opposing electrodes (metal electrode layer, cathode) at this time was 3mm². 2 Next, the substrate with the washed electrodes and the material were attached to the vacuum deposition apparatus (manufactured by ULVAC), and 1.33 × 10 -4 Pa(1 × 10) -6 After exhausting to Torr, UV / ozone cleaning was performed. Subsequently, each layer was deposited with the layer configuration shown in Table 12.

[0204] [Table 12]

[0205] After forming the electron transport layer, a 0.5 nm thin film of lithium fluoride was deposited as the electron injection layer. Subsequently, a 10 nm thin film of MgAg alloy was deposited as the cathode layer. The ratio of Mg to Ag was 1:1. Finally, a 1.5 μm thick film of SiN was deposited as the encapsulation layer using the CVD method.

[0206] The characteristics of the obtained organic EL elements were measured and evaluated. 1000 cd / m² 2 The efficiency, voltage, and CIE chromaticity coordinates during display were 7.2 cd / A, 3.6 V, and (0.25, 0.31), respectively, indicating a high-efficiency, low-voltage white organic EL element. Furthermore, the current density was 100 mA / cm². 2 A continuous operation test was conducted, and the time it took for the brightness degradation rate to reach 5% was measured. When the time it took for the brightness degradation rate to reach 5% in Comparative Example 1 was set to 1.0, the brightness degradation rate ratio in this example was 2.7.

[0207] [Examples 48 to 55, Comparative Example 6] (Examples 48 and 49 are for reference only) ] A white organic EL element was fabricated in the same manner as in Example 47, except that the first and second light-emitting layers were appropriately changed to the compounds shown in Table 13. The characteristics of the obtained organic EL element were measured and evaluated in the same manner as in Example 47. The measurement results are shown in Table 13.

[0208] [Table 13]

[0209] As shown in Examples 47 to 55, the white organic light-emitting element of this embodiment demonstrated excellent durability. On the other hand, Comparative Example 6 did not exhibit excellent durability. In the case of Comparative Example 60, comparative compound 1-a, which is the host material of the light-emitting layer, was SP 3 Because the host material contains multiple carbon atoms, it is thought that bond cleavage and radical generation during device operation, as well as a decrease in compatibility with the guest material, negatively affected the device's operation durability. [Explanation of Symbols]

[0210] 1: Interlayer insulating layer, 2: First electrode, 3: Insulating layer, 4: Organic compound layer, 5: Second electrode, 6: Protective layer, 7: Color filter, 10: Sub-pixel, 11: Substrate, 12: Insulating layer, 13: Gate electrode, 14: Gate insulating film, 15: Semiconductor layer, 16: Drain electrode, 17: Source electrode, 18: TFT, 19: Insulating film, 20: Contact hole, 21: Anode, 22: Organic compound layer, 23: Cathode, 24: First protective layer, 25: Second protective layer, 26: Organic light-emitting element, 100: Display device

Claims

1. The device comprises an anode, a light-emitting layer, a first organic compound layer in contact with the light-emitting layer, and a cathode, in this order. The light-emitting layer comprises a host material and a guest material. The host material is SP 2 A hydrocarbon compound composed solely of carbon, represented by one of the following general formulas [1-1] to [1-6], 【Transformation 5】 (In general formulas [1-1] to [1-6], Ar 1 and Ar 2 The following are independently selected from anthracene residues, phenanthrene residues, pyrene residues, fluorantene residues, triphenylene residues, benzoanthracene residues, benzophenanthrene residues, benzopyrene residues, benzofluorantene residues, benzochrysene residues, and picene residues. 1 and Ar 2 It may further have a phenyl group, a biphenyl group, a terphenyl group, or a naphthyl group. R 1 , R 3 ~R 8 (These are independently selected from a hydrogen atom and a substituted or unsubstituted aryl group, and the aryl group is a phenyl group, naphthyl group, indenyl group, biphenyl group, terphenyl group, fluorenyl group, phenanthryl group, pyrenyl group, or triphenylenyl group.) The guest material is a fluorescent material containing a fluorantene skeleton and has one of the following substructures: FF1 to FF11, FF13 to FF23. 【Transformation 6】 The organic light-emitting element is characterized in that the first organic compound layer contains a hydrocarbon compound having at least one condensed polycyclic hydrocarbon skeleton with three to five rings.

2. The organic light-emitting element according to claim 1, characterized in that the host material is a hydrocarbon compound represented by the general formula [1-3].

3. Said Ar 1 and Ar 2 The organic light-emitting device according to claim 1 or 2, characterized in that each is independently selected from the group consisting of a pyrene residue, a fluoranthene residue and a triphenylene residue.

4. The organic light-emitting element according to claim 3, characterized in that the first organic compound layer contains a compound having at least one tetracyclic condensed polycyclic hydrocarbon skeleton.

5. The organic light-emitting element according to any one of claims 1 to 4, characterized in that the light-emitting layer is a light-emitting layer that emits blue light.

6. Furthermore, the organic light-emitting element according to any one of claims 1 to 5 is characterized in that it further comprises another light-emitting layer having a host material and a guest material between the light-emitting layer and the anode.

7. The host material included in the aforementioned other light-emitting layer is SP 3 The organic light-emitting element according to claim 6, characterized in that it does not contain carbon.

8. The organic light-emitting element according to claim 6 or 7, characterized in that the host material contained in the light-emitting layer and the host material contained in the other light-emitting layer are the same material.

9. The organic light-emitting element according to any one of claims 6 to 8, characterized in that the light-emitting layer and the other light-emitting layer emit white light.

10. The organic light-emitting element according to any one of claims 1 to 9, further comprising a second organic compound layer disposed between the first organic compound layer and the cathode and in contact with the first organic compound layer, wherein the second organic compound layer contains a compound having at least one condensed polycyclic hydrocarbon skeleton of three to five rings.

11. The organic light-emitting element according to claim 10, characterized in that the HOMO of the first organic compound layer is smaller than the HOMO of the light-emitting layer.

12. A display device having a plurality of pixels, wherein at least one of the plurality of pixels is an organic light-emitting element according to any one of claims 1 to 11, and a transistor connected to the organic light-emitting element.

13. It comprises an optical unit having multiple lenses, an image sensor that receives light that has passed through the optical unit, and a display unit that displays the image captured by the image sensor. The photoelectric conversion device is characterized in that the display unit has an organic light-emitting element as described in any one of claims 1 to 11.

14. An electronic device comprising: a display unit having an organic light-emitting element as described in any one of claims 1 to 11; a housing on which the display unit is provided; and a communication unit provided in the housing for communicating with the outside.

15. A lighting device comprising a light source having an organic light-emitting element as described in any one of claims 1 to 11, and a light-diffusing section or optical filter that transmits light emitted by the light source.

16. A mobile body characterized by comprising a lamp having an organic light-emitting element according to any one of claims 1 to 11, and a body on which the lamp is provided.

17. An image forming apparatus characterized by comprising an exposure light source having an organic light-emitting element according to any one of claims 1 to 11, and a photoreceptor exposed to the exposure light source.

18. An exposure light source having a plurality of organic light-emitting elements according to any one of claims 1 to 11, wherein the organic light-emitting elements are arranged in a row.

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