compound

Abstract

To provide a compound with suitable HOMO-LUMO levels, in particular optimal Eg values for organic electroluminescent device materials in hole-transporting materials, and exhibits excellent solvent resistance after deposition.SOLUTION: An aromatic compound is represented by the formula (1). (In the formula (1), R1-R5, n1-n5, a1-a5, and A1-A5 are as defined in the specifications).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to compounds that can be used in organic electroluminescent devices (hereinafter sometimes referred to as "OLEDs" or "devices"). [Background technology]

[0002] In recent years, the development of organic electroluminescent devices using organic thin films has shifted from those using inorganic materials to organic electroluminescent devices. Organic electroluminescent devices (OLEDs) typically have a charge injection layer, a charge transport layer, an organic light-emitting layer, and an electron transport layer between the anode and cathode. Materials suitable for each of these layers are being developed, and development is progressing on the emission colors, including red, green, and blue.

[0003] While the common method for manufacturing organic electroluminescent devices involves depositing organic materials into films using vacuum deposition and then stacking them, in recent years, research has been actively pursuing wet deposition methods, which involve depositing dissolved organic materials into films using inkjet technology and other methods, as a manufacturing method with superior material utilization efficiency.

[0004] To form an organic electroluminescent element by laminating multiple layers using wet deposition, the coated thin film must be insoluble in the composition coated on top. Generally, the most stable method is to incorporate crosslinking groups or polymerizable functional groups into the composition coated on the bottom layer, and then create bonds and make it insoluble through post-coating processing.

[0005] Patent Document 1 discloses specific asymmetric bis(1,2-diarylamino)benzenes having suitable HOMO-LUMO levels and particularly suitable Eg (energy gap) values ​​for use as organic electroluminescent materials such as hole transport materials.

[0006] When the diamine derivative disclosed in Patent Document 1 is used in the hole injection layer or hole transport layer, its solvent resistance is insufficient. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2021 / 201287 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] The present invention has been made in view of the above-described conventional circumstances, and an object thereof is to provide a compound having a HOMO-LUMO level and a suitable Eg value suitable for use as a hole-transporting material in an organic electroluminescent device material, and having excellent solvent resistance after film formation. [Means for Solving the Problems]

[0009] As a result of intensive studies, the present inventors have found that a specific asymmetric bis(1,2-diarylamino)benzene compound having a specific crosslinking group can solve the above problems, and have reached the present invention.

[0010] That is, the gist of the present invention is as follows [1] to [5]. [1] An aromatic compound represented by the following formula (1).

[0011] ; [Chemical Formula]

[0012] (In formula (1), R 5 ~R 5 are each independently a divalent aromatic hydrocarbon group having 6 to 60 carbon atoms which may have a substituent, n1 to n4 are each independently an integer of 0 to 5, n5 is an integer of 0 to 4, a1 to a5 are each independently 0 or 1, A 1 ~A 5 are each independently a hydrogen atom or represented by the following formula (2). However, A 1~A 5 Among them, at least one is represented by formula (2).)

[0013] [Chemical formula]

[0014] (In formula (2), the asterisk (*) represents the bond with formula (1), R 11 represents a hydrogen atom or an alkyl group.) [2] R 1 ~R 5 In R [3] R 1 ~R 5 each independently represents a 1,3-phenylene group or a 1,4-phenylene group, the aromatic compound according to [1] or [2]. [4] Formula (1) is represented by any one of the following formulas (2) to (5), the aromatic compound according to any one of [1] to [3].

[0015] [Chemical formula]

[0016] [5] A 1 ~A 5 Among them, at least four are represented by formula (2), the aromatic compound according to any one of [1] to [4]. [Advantages of the Invention]

[0017] According to the present invention, it is possible to provide a compound having a suitable HOMO-LUMO level and a suitable Eg value for use as a hole-transporting material in an organic electroluminescent device material, and having excellent solvent resistance after film formation.​​​​

[0018] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of the structure of the organic electroluminescent element of the present invention. [Modes for carrying out the invention]

[0019] The embodiments of the present invention will be described in detail below, but the present invention is not limited to the embodiments described below and can be implemented in various ways within the scope of its gist.

[0020] In the present invention, "may have substituents" means that it may have one or more substituents.

[0021] <Aromatic compounds represented by formula (1)> The compound of the present invention is represented by the following formula (1).

[0022] [ka]

[0023] (In formula (1), R 1 ~R 5 Each of these is independently a divalent aromatic hydrocarbon group having 6 to 60 carbon atoms, which may have substituents. n1 to n4 are each independent integers between 0 and 5. n5 is an integer between 0 and 4. a1 to a5 are each independently either 0 or 1. A 1 ~A 5 Each of these can be independently represented by a hydrogen atom or by the following formula (2). However, A 1 ~A 5 At least one of these can be expressed by equation (2).

[0024] [ka]

[0025] (In equation (2), the asterisk (*) indicates a combination with equation (1), R 11 (This represents a hydrogen atom or an alkyl group.)

[0026] Furthermore, the statement "In equation (2), the asterisk (*) represents a combination with equation (1)" is more precisely, A 1 When expressed by equation (2), if a1 is 0, the asterisk (*) is R in equation (1). 1 This represents a bond with a benzene ring, and when a1 is not 0, the asterisk (*) is R 1 This represents a combination with A. 2 ~A 5 If it is expressed by equation (2), then A 1 a1 and R 1 a2~a5 and R 2 ~R 5 These can be replaced with the respective terms and interpreted similarly.

[0027] The compounds of the present invention function as charge transport materials. That is, because the compounds of the present invention have a diamine structure, they can be made to function as hole transport materials. Therefore, the compound of the present invention is preferably a charge transport compound and is preferably used as a hole injection layer material or hole transport layer material in an organic field light-emitting device.

[0028] In the above equation (1), R 1 ~R 5 The substituents that may be present on the divalent aromatic hydrocarbon group having 6 to 60 carbon atoms are preferably selected from the substituent group Z described below.

[0029] The above formula (1) is preferably expressed by one of the following formulas (2) to (5).

[0030] [ka]

[0031] <R 1 ~R5 > R in equation (1) above 1 ~R 5 Each of these independently represents a divalent aromatic hydrocarbon group having 6 to 60 carbon atoms, which may have substituents.

[0032] Examples of divalent aromatic hydrocarbon groups with 6 to 60 carbon atoms include the divalent groups of benzene, naphthalene, anthracene, phenanthrene, tetraphenylene, chrysene, pyrene, benzoanthracene, perylene, biphenyl, or terphenyl rings.

[0033] R 1 ~R 5 From the viewpoint of the solubility and durability of the compound, a divalent group of a benzene ring and a divalent group of a naphthalene ring are preferred, independently of each other, a divalent group of a benzene ring is more preferred, and a 1,3-phenylene group and a 1,4-phenylene group are even more preferred.

[0034] <n1~n5> n1 to n4 each independently represent an integer from 0 to 5. n5 represents an integer between 0 and 4.

[0035] From the viewpoint of the solubility and durability of the compound, n1 to n5 are preferably 4 or less, more preferably 3 or less, even more preferably 2 or less, and particularly preferably 1 or less.

[0036] If n1 is 2 or greater, multiple R 1 They may be the same or different. If n2 is 2 or more, multiple R 2 They may be the same or different. If n3 is 2 or more, multiple R 3 They may be the same or different. If n4 is 2 or more, multiple R 4 They may be the same or different. If n5 is 2 or more, multiple R 5 They may be the same or different.

[0037] <a1~a5> a1 to a5 each independently represent either 0 or 1. From the viewpoint of the solubility and durability of the compound, 1 is preferred for a1 to a5.

[0038] 1 ~A 5 > A 1 ~A 5 Each of these can be independently represented by a hydrogen atom or by the following formula (2). However, A 1 ~A 5 Of these, at least one is represented by formula (2). From the viewpoint of solvent resistance, A 1 ~A 5 Of these, at least four are preferably structures represented by formula (2).

[0039] [ka]

[0040] (In equation (2), the asterisk (*) indicates a combination with equation (1), R 11 (This represents a hydrogen atom or an alkyl group.)

[0041] The structure represented by formula (2) above provides a crosslinking group to the compound represented by formula (1). This crosslinking group allows the compound represented by formula (1) to exhibit excellent solvent resistance after film formation, while maintaining a suitable HOMO-LUMO level and a suitable Eg value for use as an organic electroluminescent material for hole transport.

[0042] <R 11 > In the above formula, R 11 ​R represents a hydrogen atom or an alkyl group. Examples of alkyl groups include linear, branched, or cyclic alkyl groups having typically 1 or more carbon atoms, preferably 4 or more, and typically 24 or less, preferably 10 or less, such as methyl, ethyl, branched, linear, or cyclic propyl, branched, linear, or cyclic butyl, branched, linear, or cyclic pentyl, branched, linear, or cyclic hexyl, branched, linear, or cyclic octyl, branched, linear, or cyclic nonyl, and branched, linear, or cyclic dodecyl groups. 11 From the viewpoint of durability, hydrogen atoms and methyl groups are preferred, and methyl groups are particularly preferred.

[0043] <Substituent> R 1 ~R 5 The substituents that may be present can be selected from the group of substituents Z listed below.

[0044] <Substituent group Z> Examples of substituent group Z include alkyl groups, alkenyl groups, alkynyl groups, alkoxy groups, aryloxy groups, alkoxycarbonyl groups, acyl groups, halogen atoms, haloalkyl groups, alkylthio groups, arylthio groups, silyl groups, siloxy groups, cyano groups, aralkyl groups, or aromatic hydrocarbon groups.

[0045] Examples of alkyl groups include linear, branched, or cyclic alkyl groups having typically 1 or more carbon atoms, preferably 4 or more, and typically 24 or less, preferably 10 or less, such as methyl, ethyl, branched, linear, or cyclic propyl, branched, linear, or cyclic butyl, branched, linear, or cyclic pentyl, branched, linear, or cyclic hexyl, branched, linear, or cyclic octyl, branched, linear, or cyclic nonyl, and branched, linear, or cyclic dodecyl groups. From the viewpoint of compound stability, methyl, ethyl, branched, linear, or cyclic propyl, and branched, linear, or cyclic butyl groups are preferred, and branched propyl groups are particularly preferred.

[0046] Examples of alkenyl groups include vinyl groups and other alkenyl groups that typically have 2 or more carbon atoms, usually 24 or fewer, and preferably 12 or fewer.

[0047] Examples of alkynyl groups include ethynyl groups and other alkynyl groups that typically have 2 or more carbon atoms, usually 24 or fewer, and preferably 12 or fewer.

[0048] Examples of alkoxy groups include methoxy groups, ethoxy groups, and other alkoxy groups that typically have one or more carbon atoms, and usually 24 or fewer, preferably 12 or fewer.

[0049] Examples of aryloxy groups include phenoxy groups, naphthoxy groups, pyridyloxy groups, etc., which typically have 4 or more carbon atoms, preferably 5 or more, and typically 36 or fewer carbon atoms, preferably 24 or fewer carbon atoms, as well as aryloxy or heteroaryloxy groups.

[0050] Examples of alkoxycarbonyl groups include methoxycarbonyl groups and ethoxycarbonyl groups, which typically have 2 or more carbon atoms, usually 24 or fewer, and preferably 12 or fewer.

[0051] Examples of acyl groups include acetyl groups, benzoyl groups, and other acyl groups that typically have 2 or more carbon atoms, usually 24 or fewer, and preferably 12 or fewer.

[0052] Examples of halogen atoms include fluorine atoms and chlorine atoms.

[0053] Examples of haloalkyl groups include trifluoromethyl groups and other haloalkyl groups that typically have one or more carbon atoms, usually 12 or fewer, and preferably 6 or fewer.

[0054] Examples of alkylthio groups include methylthio groups, ethylthio groups, and other alkylthio groups that typically have one or more carbon atoms, usually 24 or fewer, and preferably 12 or fewer.

[0055] Examples of arylthio groups include phenylthio groups, naphthylthio groups, pyridylthio groups, etc., which typically have 4 or more carbon atoms, preferably 5 or more, and typically 36 or fewer carbon atoms, preferably 24 or fewer carbon atoms, and are either arylthio or heteroarylthio groups.

[0056] Examples of silyl groups include trimethylsilyl groups and triphenylsilyl groups, which typically have 2 or more carbon atoms, preferably 3 or more, and typically 36 or fewer carbon atoms, preferably 24 or fewer.

[0057] Examples of siloxy groups include trimethylsiloxy groups and triphenylsiloxy groups, which typically have 2 or more carbon atoms, preferably 3 or more, and typically 36 or fewer carbon atoms, preferably 24 or fewer.

[0058] Examples of aralkyl groups include benzyl group, 2-phenylethyl group, 2-phenylpropyl-2-yl group, 2-phenylbutyl-2-yl group, 3-phenylpentyl-3-yl group, 3-phenyl-1-propyl group, 4-phenyl-1-butyl group, 5-phenyl-1-pentyl group, 6-phenyl-1-hexyl group, 7-phenyl-1-heptyl group, and 8-phenyl-1-octyl group, which typically have 7 or more carbon atoms, preferably 9 or more, typically 30 or less, preferably 18 or less, and more preferably 10 or less.

[0059] Examples of aromatic hydrocarbon groups include benzene rings, naphthalene rings, anthracene rings, tetraphenylene rings, phenanthrene rings, chrysene rings, pyrene rings, benzoanthracene rings, or perylene rings, which typically have 6 or more carbon atoms, typically 30 or fewer, preferably 18 or fewer, and more preferably 10 or fewer.

[0060] Among the substituent group Z described above, alkyl groups and alkoxy groups are preferred, more preferably alkyl groups having 10 or fewer carbon atoms and alkoxy groups having 10 or fewer carbon atoms, and even more preferably alkyl groups having 10 or fewer carbon atoms.

[0061] Furthermore, each substituent in the substituent group Z may have further substituents. The same substituents as those in the substituent group Z can be used as these further substituents.

[0062] <Specific example> The following are specific examples of compounds having a crosslinking group according to the present invention, but the present invention is not limited to these.

[0063] [ka]

[0064] [ka]

[0065] [ka]

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] [ka]

[0070] [ka]

[0071] <Method for producing diamine compounds> The diamine compounds of the present invention can be produced, for example, by the method described in the examples.

[0072] <Uses of Diamine Compounds> The diamine compound of the present invention is preferably used in the organic layer of an organic electroluminescent device, and this organic layer is preferably a hole injection layer or a hole transport layer.

[0073] The organic layer containing the diamine compound of the present invention may be formed by vapor deposition or by a wet film deposition method. Forming the organic layer containing the diamine compound of the present invention by a wet film deposition method is particularly preferable because it allows for the formation of a more uniform film.

[0074] <Organic solvents> The organic solvent is a volatile liquid component used to form a layer containing the compound of the present invention by wet film formation.

[0075] The organic solvent is not particularly limited as long as it is an organic solvent that readily dissolves the compound of the present invention, which is the solute.

[0076] Examples of preferred organic solvents include aromatic hydrocarbon solvents, ether solvents, and ester solvents.

[0077] [Method for forming a film using the compound of the present invention] When forming a film using the compound of the present invention, the compound of the present invention is preferably a solution containing an organic solvent, and it is preferable to wet-form the composition of the present invention. Wet film deposition refers to a method of forming a film by coating a substrate with a solvent-containing composition and then drying and removing the solvent. While there are no particular limitations on the coating method, examples include spin coating, dip coating, die coating, bar coating, blade coating, roll coating, spray coating, capillary coating, inkjet printing, screen printing, gravure printing, and flexographic printing.

[0078] The solvent is typically removed by drying, usually by heating. Examples of heating methods used in the heating process include clean ovens, hot plates, and infrared heating. For infrared heating, halogen heaters, ceramic-coated halogen heaters, and ceramic heaters can be used.

[0079] The thickness of the organic layer formed by the wet deposition method using the compound of the present invention is typically 5 nm or more, preferably 10 nm or more, and more preferably 20 nm or more. Furthermore, the thickness is typically 1000 nm or less, preferably 500 nm or less, and more preferably 300 nm or less.

[0080] [Organic electroluminescent element] A film using the compound of the present invention can be suitably used as a charge transport layer. This charge transport layer is particularly preferably used as a charge transport film in an organic electroluminescent device.

[0081] As an example of the structure of the organic electroluminescent element of the present invention, Figure 1 shows a schematic diagram (cross-section) of an example of the structure of an organic electroluminescent element 8. In Figure 1, 1 represents the substrate, 2 the anode, 3 the hole injection layer, 4 the hole transport layer, 5 the light-emitting layer, 6 the electron transport layer, and 7 the cathode.

[0082] [substrate] The substrate 1 serves as a support for the organic electroluminescent element, and is typically made of quartz, glass, metal, plastic film, or sheet. Of these, glass plates and transparent synthetic resin plates such as polyester, polymethacrylate, polycarbonate, or polysulfone are preferred. The substrate should preferably be made of a material with high gas barrier properties to prevent degradation of the organic electroluminescent element by the outside air. Therefore, especially when using a material with low gas barrier properties, such as a synthetic resin substrate, it is preferable to provide a dense silicon oxide film or the like on at least one side of the substrate to improve its gas barrier properties.

[0083] [anode] Anode 2 is responsible for injecting holes into the layer on the light-emitting layer 5 side.

[0084] Anode 2 is typically composed of metals such as aluminum, gold, silver, nickel, palladium, and platinum; metal oxides such as indium and / or tin oxides; metal halides such as copper iodide; carbon black; and conductive polymers such as poly(3-methylthiophene), polypyrrole, and polyaniline.

[0085] The formation of anode 2 is usually carried out by dry methods such as sputtering or vacuum deposition. When forming the anode using metal nanoparticles such as silver, nanoparticles such as copper iodide, carbon black, conductive metal oxide nanoparticles, or conductive polymer fine powder, it can also be formed by dispersing them in a suitable binder resin solution and coating it onto a substrate. In the case of conductive polymers, the anode can also be formed by directly forming a thin film on the substrate by electrolytic polymerization, or by coating the substrate with conductive polymer (Appl. Phys. Lett., Vol. 60, p. 2711, 1992).

[0086] Anode 2 is usually a single-layer structure, but may be a multilayer structure as appropriate. If anode 2 is a multilayer structure, different conductive materials may be laminated on the first layer of anode.

[0087] The thickness of anode 2 can be determined according to the required transparency and material. When particularly high transparency is required, a thickness that allows for a visible light transmittance of 60% or more is preferable, and a thickness that allows for a visible light transmittance of 80% or more is even more preferable. The thickness of anode 2 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less. On the other hand, if transparency is not required, the thickness of anode 2 can be arbitrarily set according to the required strength, etc., and in this case, anode 2 may be the same thickness as the substrate.

[0088] When depositing other layers on the surface of anode 2, it is preferable to remove impurities from anode 2 and adjust its ionization potential to improve hole injection properties by treating it with ultraviolet / ozone, oxygen plasma, argon plasma, etc., before deposition.

[0089] [Hole injection layer] The layer responsible for transporting holes from the anode 2 to the light-emitting layer 5 is usually called a hole injection transport layer or hole transport layer. When there are two or more layers responsible for transporting holes from the anode 2 to the light-emitting layer 5, the layer closer to the anode is sometimes called the hole injection layer 3. It is preferable to form the hole injection layer 3 in order to enhance the function of transporting holes from the anode 2 to the light-emitting layer 5. When forming the hole injection layer 3, it is usually formed on the anode 2.

[0090] The hole injection layer 3 contains the diamine compound of the present invention.

[0091] The method for forming the hole injection layer 3 is not particularly limited and can be described as vacuum deposition or wet deposition. In the case of layer formation by wet deposition, the composition of the present invention is prepared, applied to the anode 2 by a wet deposition method such as spin coating or dip coating, and dried to form the hole injection layer 3.

[0092] The thickness of the hole injection layer 3 formed in this manner is typically in the range of 5 nm or more, preferably 10 nm or more, and typically 1000 nm or less, preferably 500 nm or less.

[0093] The hole injection layer can be formed by either vacuum deposition or wet deposition. Wet deposition is preferable because it offers superior film formation properties. Examples of solvents include ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0094] The hole injection layer 3 is typically formed by a wet deposition method, which involves preparing a hole injection layer formation composition, coating it onto the layer below the hole injection layer 3 (usually the anode 2), and then drying it.

[0095] The hole injection layer 3 is typically dried after film formation by heating or reduced-pressure drying.

[0096] [Hole transport layer] The hole transport layer 4 is a layer responsible for transporting holes from the anode 2 to the light-emitting layer 5. Although the hole transport layer 4 is not an essential layer in the organic electroluminescent device of the present invention, it is preferable to form this layer in order to enhance the function of transporting holes from the anode 2 to the light-emitting layer 5. When the hole transport layer 4 is formed, it is usually formed between the anode 2 and the light-emitting layer 5. Also, if the hole injection layer 3 described above is present, it is formed between the hole injection layer 3 and the light-emitting layer 5.

[0097] The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and on the other hand, it is usually 300 nm or less, preferably 100 nm or less.

[0098] The material forming the hole transport layer 4 is preferably a material that has high hole transport properties and can efficiently transport the injected holes. For this reason, it is preferable that the material has a low ionization potential, high transparency to visible light, high hole mobility, excellent stability, and is less likely to generate trapping impurities during manufacturing or use. In addition, since the hole transport layer 4 is often in contact with the light-emitting layer 5, it is preferable that it does not quench the light emission from the light-emitting layer 5 or form an excyplex with the light-emitting layer 5, thereby reducing efficiency.

[0099] The material for such a hole transport layer 4 can be any material that has been conventionally used as a constituent material for hole transport layers, for example, those exemplified as hole transport compounds used in the hole injection layer 3. Other examples include arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatic derivatives, and metal complexes.

[0100] Other examples include polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ethersulfone derivatives containing tetraphenylbenzidine, polyarylenevinylene derivatives, polysiloxane derivatives, polythiophene derivatives, and poly(p-phenylenevinylene) derivatives. These may be alternating copolymers, random polymers, block polymers, or graft copolymers. They may also be polymers with branched main chains and three or more terminal ends, or so-called dendrimers.

[0101] Among these, polyarylamine derivatives and polyarylene derivatives are preferred. Polymers are preferred as polyarylamine derivatives.

[0102] When forming the hole transport layer 4 by a wet film deposition method, the hole transport layer forming composition is prepared in the same manner as for forming the hole injection layer 3, followed by wet film deposition and then heat drying.

[0103] The hole transport layer formation composition contains a solvent in addition to the hole transport compound described above. The solvent used is the same as that used in the hole injection layer formation composition. The film formation conditions, heating and drying conditions, etc., are also the same as those for the formation of hole injection layer 3.

[0104] When forming a hole transport layer by vacuum deposition, the film deposition conditions are the same as those for forming the hole injection layer 3 described above.

[0105] The hole transport layer 4 may contain, in addition to the hole transport compound mentioned above, various light-emitting materials, electron transport compounds, binder resins, coating property modifiers, and the like.

[0106] Furthermore, the hole transport layer 4 may be a layer formed by crosslinking a crosslinkable compound. The crosslinkable compound is a compound having a crosslinkable group, and by crosslinking, it forms a network polymer compound.

[0107] Examples of these crosslinkable groups include groups derived from cyclic ethers such as oxetanes and epoxy; groups derived from unsaturated double bonds such as vinyl groups, trifluorovinyl groups, styryl groups, acrylic groups, methacryloyl, and cinnamoyl; and groups derived from benzocyclobutene.

[0108] The crosslinkable compound may be a monomer, oligomer, or polymer. The crosslinkable compound may consist of only one type, or two or more types in any combination and ratio.

[0109] As the crosslinkable compound, it is preferable to use a hole-transporting compound having a crosslinkable group. Examples of hole-transporting compounds include those exemplified above, and as the crosslinkable compound, it is preferable that the crosslinkable group is bonded to the main chain or side chain of these hole-transporting compounds. In particular, it is preferable that the crosslinkable group is bonded to the main chain via a linking group such as an alkylene group. Furthermore, it is particularly preferable that the hole-transporting compound is a polymer containing repeating units having a crosslinkable group.

[0110] To form a hole transport layer 4 by crosslinking a crosslinkable compound, a hole transport layer forming composition is usually prepared by dissolving or dispersing the crosslinkable compound in a solvent, and then the film is formed and crosslinked by wet deposition.

[0111] The thickness of the hole transport layer 4 formed in this manner is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 150 nm or less.

[0112] [Luminous layer] The light-emitting layer 5 is a layer that is excited and emits light when an electric field is applied between a pair of electrodes, by the recombination of holes injected from the anode 2 and electrons injected from the cathode 7. The light-emitting layer 5 is formed between the anode 2 and the cathode 7. If there is a hole injection layer above the anode, the light-emitting layer is formed between the hole injection layer and the cathode. If there is a hole transport layer above the anode, the light-emitting layer is formed between the hole transport layer and the cathode. As described above, the organic electroluminescent device in the present invention preferably includes a light-emitting layer forming material suitable as a light-emitting layer.

[0113] The film thickness of the light-emitting layer 5 is arbitrary as long as it does not significantly impair the effects of the present invention. However, a thicker film is preferable in that defects are less likely to occur in the film, while a thinner film is preferable in that it is easier to achieve a low driving voltage. For this reason, it is preferably 3 nm or more, more preferably 5 nm or more, and usually preferably 200 nm or less, and even more preferably 100 nm or less.

[0114] The light-emitting layer 5 includes at least a material having light-emitting properties (light-emitting material), and preferably includes one or more host materials.

[0115] [Suitable materials for forming light-emitting layers] The light-emitting layer of the present invention comprises a light-emitting material and a charge transport material. The light-emitting material may be a phosphorescent material or a fluorescent material. Preferably, the red light-emitting material and the green light-emitting material are phosphorescent materials, and the blue light-emitting material is a fluorescent material.

[0116] (Luminescent material) The luminescent material is not particularly limited as long as it emits light at a desired emission wavelength and does not impair the effects of the present invention; known luminescent materials can be used. The luminescent material may be a fluorescent material or a phosphorescent material, but a material with good luminescence efficiency is preferred, and a phosphorescent material is preferred from the viewpoint of internal quantum efficiency.

[0117] Examples of fluorescent materials include the following: Examples of fluorescent materials that emit blue light (blue fluorescent materials) include naphthalene, perylene, pyrene, anthracene, coumarin, chrysene, p-bis(2-phenylethenyl)benzene, and their derivatives.

[0118] Examples of fluorescent materials that emit green light (green fluorescent materials) include quinacridone derivatives, coumarin derivatives, and aluminum complexes such as Al(C9H6NO)3.

[0119] Examples of fluorescent materials that emit yellow light (yellow fluorescent materials) include rubrene and perimidone derivatives.

[0120] Examples of fluorescent materials that emit red light (red fluorescent materials) include DCM(4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran) compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, and azabenzothioxanthene.

[0121] Furthermore, examples of phosphorescent materials include organometallic complexes containing metals selected from groups 7 to 11 of the long-period periodic table (hereinafter, unless otherwise specified, "periodic table" refers to the long-period periodic table). Preferred metals selected from groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

[0122] Preferred ligands for organometallic complexes include (hetero)arylpyridine ligands and (hetero)arylpyrazole ligands, which are ligands in which a (hetero)aryl group is linked to pyridine, pyrazole, phenanthroline, etc., with phenylpyridine ligands and phenylpyrazole ligands being particularly preferred. Here, (hetero)aryl refers to an aryl group or a heteroaryl group.

[0123] Preferred phosphorescent materials include, specifically, phenylpyridine complexes such as tris(2-phenylpyridine)iridium, tris(2-phenylpyridine)ruthenium, tris(2-phenylpyridine)palladium, bis(2-phenylpyridine)platinum, tris(2-phenylpyridine)osmium, and tris(2-phenylpyridine)rhenium, as well as porphyrin complexes such as octaethylplatinum porphyrin, octaphenylplatinum porphyrin, octaethylpalladium porphyrin, and octaphenylpalladium porphyrin.

[0124] Examples of polymer-based light-emitting materials include polyfluorene-based materials such as poly(9,9-dioctylfluorene-2,7-diyl), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)], and poly[(9,9-dioctylfluorene-2,7-diyl)-co-(1,4-benzo-2{2,1'-3}-triazole)], and polyphenylene vinylene-based materials such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene].

[0125] (Charge transport material) A charge-transporting material is a material that has the ability to transport positive charges (holes) or negative charges (electrons), and there are no particular limitations as long as the effects of the present invention are not impaired; known materials can be used.

[0126] The charge transport material can be a compound that has been conventionally used in the light-emitting layer 5 of an organic electroluminescent device, and in particular, a compound used as the host material for the light-emitting layer 5 is preferred.

[0127] Examples of charge-transporting materials include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by fluorene groups, hydrazone compounds, silazane compounds, silanamine compounds, phosphatamine compounds, quinacridone compounds, and other compounds exemplified as hole-transporting compounds for hole injection layer 3. In addition, examples of electron-transporting compounds include anthracene compounds, pyrene compounds, carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds, and silole compounds.

[0128] Furthermore, for example, aromatic diamines containing two or more tertiary amines, such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, in which two or more condensed aromatic rings are substituted with nitrogen atoms (Japanese Patent Publication No. 5-234681), and aromatic amine compounds having a starburst structure such as 4,4',4''-tris(1-naphthylphenylamino)triphenylamine (J. Lumin., Vol. 72-74, p. 985, 1997), and triphenyl Compounds exemplified as hole-transporting compounds for hole transport layer 4, such as aromatic amine compounds consisting of tetramers of mine (Chem. Commun., p. 2175, 1996), fluorene compounds such as 2,2',7,7'-tetrakis-(diphenylamino)-9,9'-spirobifluorene (Synth. Metals, Vol. 91, p. 209, 1997), and carbazole compounds such as 4,4'-N,N'-dicarbazole biphenyl, can also be preferably used. In addition, other examples include oxadiazole compounds such as 2-(4-biphenylyl)-5-(p-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD) and 2,5-bis(1-naphthyl)-1,3,4-oxadiazole (BND), silole compounds such as 2,5-bis(6'-(2',2”-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), and phenanthroline compounds such as vasophenanthroline (BPhen) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, vasocuproine).

[0129] When forming the light-emitting layer 5 by a wet film deposition method, the light-emitting layer forming composition is prepared in the same manner as for forming the hole injection layer 3 described above, followed by wet film deposition and then heat drying.

[0130] The composition for forming the light-emitting layer contains a solvent in addition to the light-emitting layer forming material described above. The solvent used is the same as that used in the composition for forming the hole-injection layer. The film formation conditions, heating and drying conditions, etc., are also the same as those for forming the hole-injection layer 3.

[0131] When forming the light-emitting layer by vacuum deposition, the film deposition conditions are the same as those for forming the hole injection layer 3 described above.

[0132] [Hole Blocking Layer] A hole-blocking layer may be provided between the light-emitting layer 5 and the electron injection layer described later. The hole-blocking layer is a layer laminated on top of the light-emitting layer 5 so as to be in contact with the interface of the light-emitting layer 5 on the cathode 7 side.

[0133] This hole-blocking layer has two roles: preventing holes moving from anode 2 from reaching cathode 7, and efficiently transporting electrons injected from cathode 7 towards the light-emitting layer 5. The required properties for the material constituting the hole-blocking layer include high electron mobility and low hole mobility, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1).

[0134] Examples of hole blocking layer materials that satisfy these conditions include mixed ligand complexes such as bis(2-methyl-8-quinolinolato)(phenolato)aluminum and bis(2-methyl-8-quinolinolato)(triphenylsilanolato)aluminum, metal complexes such as bis(2-methyl-8-quinolato)aluminum-μ-oxo-bis-(2-methyl-8-quinolinolato)aluminum dinuclear metal complexes, styryl compounds such as distyrylbiphenyl derivatives (Japanese Patent Publication No. 11-242996), triazole derivatives such as 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (Japanese Patent Publication No. 7-41759), and phenanthroline derivatives such as basocproine (Japanese Patent Publication No. 10-79297). Furthermore, compounds having at least one pyridine ring substituted at the 2,4, and 6 positions, as described in International Publication No. 2005 / 022962, are also preferred as materials for hole blocking layers.

[0135] There are no restrictions on the method of forming the hole blocking layer. Therefore, it can be formed by wet deposition, vapor deposition, or other methods.

[0136] The thickness of the hole blocking layer is arbitrary as long as it does not significantly impair the effects of the present invention, but is usually 0.3 nm or more, preferably 0.5 nm or more, and is usually 100 nm or less, preferably 50 nm or less.

[0137] [Electron transport layer] The electron transport layer 6 is provided between the light-emitting layer 5 and the cathode 7 with the aim of further improving the current efficiency of the device.

[0138] The electron transport layer 6 is formed from a compound that can efficiently transport electrons injected from the cathode 7 towards the light-emitting layer 5 between electrodes under an applied electric field. The electron transport compound used in the electron transport layer 6 must have high electron injection efficiency from the cathode 7, high electron mobility, and be able to efficiently transport the injected electrons.

[0139] Examples of electron-transporting compounds used in the electron transport layer include, for example, metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Publication No. 59-194393), metal complexes of 10-hydroxybenzo[h]quinoline, oxadiazole derivatives, distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolbenzene (U.S. Patent No. 5645948), quinoxaline compounds (Japanese Patent Publication No. 6-207169), phenanthroline derivatives (Japanese Patent Publication No. 5-331459), 2-tert-butyl-9,10-N,N'-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide, and the like.

[0140] The film thickness of the electron transport layer 6 is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

[0141] The electron transport layer 6 is formed by laminating it onto the hole blocking layer using either a wet deposition method or a vacuum deposition method, as described above. Vacuum deposition is typically used. In the present invention, as described above, an electron transport layer can be formed on a light-emitting layer containing a suitable light-emitting layer forming material by a wet film deposition method.

[0142] [Electron injection layer] An electron injection layer may be provided to efficiently inject electrons injected from the cathode 7 into the electron transport layer 6 or the light-emitting layer 5.

[0143] To efficiently perform electron injection, the material forming the electron injection layer is preferably a metal with a low work function. Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. The film thickness is usually preferably between 0.1 nm and 5 nm.

[0144] Furthermore, doping organic electron transport materials, such as nitrogen-containing heterocyclic compounds like bathophenanthroline and metal complexes like aluminum complexes of 8-hydroxyquinoline, with alkali metals such as sodium, potassium, cesium, lithium, and rubidium (as described in Japanese Patent Publication No. 10-270171, Japanese Patent Publication No. 2002-100478, Japanese Patent Publication No. 2002-100482, etc.) is also preferable because it improves electron injection and transport properties and enables the achievement of excellent film quality.

[0145] The thickness of the electron injection layer is typically 5 nm or more, preferably 10 nm or more, and typically 200 nm or less, preferably 100 nm or less.

[0146] The electron injection layer is formed by laminating it onto the light-emitting layer 5 or the hole-blocking layer or electron transport layer 6 located thereon, using a wet deposition method or a vacuum deposition method. The details for the wet film deposition method are the same as those for the luminescent layer described above.

[0147] In some cases, the hole blocking layer, electron transport layer, and electron injection layer are combined into a single layer by co-doping the electron transport material with a lithium complex.

[0148] [cathode] The cathode 7 plays the role of injecting electrons into the layer on the light-emitting layer 5 side (such as the electron injection layer or light-emitting layer).

[0149] As the material for the cathode 7, the same material used for the anode 2 can be used. However, for efficient electron injection, it is preferable to use a metal with a low work function. For example, metals such as tin, magnesium, indium, calcium, aluminum, and silver, or alloys thereof, can be used. Specific examples include low-work-function alloy electrodes such as magnesium-silver alloys, magnesium-indium alloys, and aluminum-lithium alloys.

[0150] In terms of the stability of organic electroluminescent devices, it is preferable to protect the cathode, which is made of a metal with a low work function, by laminating a metal layer with a high work function and stability to the atmosphere on top of the cathode. Examples of metals that can be laminated include aluminum, silver, copper, nickel, chromium, gold, and platinum.

[0151] The film thickness of the cathode is usually the same as that of the anode.

[0152] [Other layers] The organic electroluminescent element of the present invention may have other layers as long as they do not significantly impair the effects of the present invention. That is, it may have any other layer between the anode and the cathode as described above.

[0153] [Other component configurations] The organic electroluminescent element of the present invention can also have a structure reversed from the above description, that is, for example, stacked on a substrate in the order of cathode, electron injection layer, electron transport layer, hole blocking layer, light-emitting layer, hole transport layer, hole injection layer, and anode.

[0154] When applying the organic electroluminescent element of the present invention to an organic electroluminescent device, it may be used as a single organic electroluminescent element, in a configuration in which multiple organic electroluminescent elements are arranged in an array, or in a configuration in which the anode and cathode are arranged in an XY matrix. [Examples]

[0155] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. The various conditions and evaluation result values ​​in the following examples are meant as preferred upper or lower limits in the embodiments of the present invention, and the preferred range may be defined by a combination of the aforementioned upper or lower limits and the values ​​in the following examples or between examples.

[0156] In this specification, Ac means acetyl group, Ph means phenyl group, dba means dibenzylideneacetone, and Amphos means [4-(N,N-dimethylamino)phenyl]di-tert-butylphosphine. t Bu stands for tert-butyl group.

[0157] <Example 1> (Synthesis of intermediates 1-3)

[0158] [ka]

[0159] To intermediates 1-1 (0.50 g, 0.77 mmol) and 1-2 (1.23 g, 3.83 mmol), nitrogen-bubbled toluene (20 mL), ethanol (10 mL), and tripotassium phosphate aqueous solution (2.0 mol / L, 10 mL) were sequentially added and heated to 50°C. Then, Pd(PPh3)4 (44 mg, 0.038 mmol) was added and the mixture was stirred at 90°C for 6 hours. After cooling to room temperature, saturated sodium chloride aqueous solution was added and extraction was performed using toluene. The organic layer was washed with saturated sodium chloride aqueous solution, dried over magnesium sulfate, and the solvent was removed under reduced pressure. The residue was subjected to silica gel column chromatography to obtain intermediate 1-3 (yield 0.62 g, yield 73%).

[0160] (Synthesis of Compound 1)

[0161] [ka]

[0162] Intermediate 1-3 (0.62 g, 0.56 mmol), bromobenzene (0.18 g, 1.12 mmol), and tert-butoxysodium (0.15 g, 1.51 mmol) were mixed with toluene (20 mL) that had been bubbling with nitrogen (Solution A1). To a solution of Pd2(dba)3 (51 mg, 0.056 mmol) in toluene (5 mL), Amphos (0.12 g, 0.45 mmol) was added and heated to 50 °C (Solution B1). Solution B1 was added to Solution A1 under a nitrogen stream and heated under reflux for 7.5 hours. After cooling to room temperature, the solvent was removed under reduced pressure. The residue was subjected to silica gel column chromatography to obtain compound 1 (yield 0.21 g, yield 32%).

[0163] [ka]

[0164] (Evaluation of solvent resistance) The solvent resistance of the obtained compound 1 after film formation was evaluated as follows. First, a solution was prepared by dissolving compound 1 at 2.0% by mass and compound (P-1), which has the structure shown below, at 0.4% by mass in ethyl benzoate.

[0165] [ka]

[0166] The solution was dropped onto an ITO substrate in air and spin-coated, then dried on a 100°C hot plate for 1 minute. Next, ultraviolet irradiation was performed using a Hamamatsu Photonics LC8 spot light source. The ultraviolet irradiation was 46 mW / cm². 2 The test was performed at this intensity for 90 seconds. The substrate was dried on a hot plate at 230°C for 10 minutes to form a compound 1 film. The thickness of the formed compound 1 film is shown in Table 1. Next, the substrate on which the compound 1 film was deposited was placed in a spin coater, 150 μL of toluene, the test solvent, was dropped onto the substrate, and the substrate was left to stand for 90 seconds after dropping to perform the solvent resistance test. Subsequently, the substrate was rotated at 1500 rpm for 30 seconds, and then at 4000 rpm for 30 seconds to spin out the dropped solvent. This substrate was dried on a hot plate at 145°C for 15 minutes. Solvent resistance was estimated from the change in film thickness before and after the solvent resistance test.

[0167] The solvent resistance of the compound after film formation was evaluated based on the following criteria. ○: No reduction in film thickness was observed. ××: The membrane dissolved and disappeared.

[0168] <Example 2> Solvent resistance was evaluated in the same manner as in Example 1, except that anisole was used instead of toluene.

[0169] <Comparative Example 1> The solvent resistance was evaluated in the same manner as in Example 1, except that comparative compound 1 was used instead of compound 1.

[0170] [ka]

[0171] <Comparative Example 2> Solvent resistance was evaluated in the same manner as in Comparative Example 1, except that anisole was used instead of toluene. Table 1 shows the evaluation results of solvent resistance for Examples 1 and 2 and Comparative Examples 1 and 2.

[0172] [Table 1] [Industrial applicability]

[0173] The compounds of the present invention are industrially useful as charge transport materials. [Explanation of Symbols]

[0174] 1 circuit board 2 Anode 3. Hole injection layer 4. Hole transport layer 5. Emitting layer 6 Electron transport layer 7 Cathode 8 Organic electroluminescent element

Claims

[Claim 1] An aromatic compound represented by the following formula (A). 【Chemistry 1】 (In the above formula (A), A １ ~A ５ Each of these can be independently represented by a hydrogen atom or by the following formula (2). However, A １ ~A ５ At least four of these can be expressed by the following formula (2). 【Chemistry 2】 (In equation (2), the asterisk (*) indicates a combination with equation (A) above, R １１ (This represents a hydrogen atom or an alkyl group.)

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