High molecular weight compound and light emitting diode containing the high molecular weight compound

Abstract

The purpose of the present invention is to provide: a high molecular weight compound that has excellent hole injection / transportation capability, has electron stopping capability, and is highly stable in a thin film state; and a light emitting diode that has an organic layer (thin film) formed by said high molecular weight compound, that has a high luminous efficiency, and that provides a long service life.　The high molecular weight compound according to the present invention includes repeating units formed by a specific triarylamine structural unit and a specific linkage structural unit, and has a weight average molecular weight not less than 10,000 but less than 1,000,000 in polystyrene equivalent.

Description

[Technical Field]

[0001] The present invention relates to a high molecular weight compound suitable for an organic electroluminescence element (organic EL element), which is a type of light-emitting diode suitable for various display devices and is a self-emitting element, and to the element. [Background technology]

[0002] Organic EL elements are self-luminous elements, and therefore are brighter and more visible than liquid crystal elements, enabling clearer displays, and therefore have been the subject of active research.

[0003] Organic EL elements are constructed by sandwiching a thin film (organic layer) of organic compounds between an anode and a cathode. Thin film formation methods can be broadly divided into vacuum deposition and coating methods. Vacuum deposition is a technique that mainly uses low-molecular-weight compounds to form a thin film on a substrate by evaporating it in a vacuum, and is a technology that has already been put to practical use. On the other hand, coating is a technique that mainly uses high-molecular-weight compounds to form a thin film on a substrate using a solution such as inkjet or printing. It is highly efficient in the use of materials and is suitable for larger areas and higher resolution, making it an essential technology for future large-area organic EL displays.

[0004] The vacuum deposition method using low-molecular-weight materials has extremely low material utilization efficiency, and as the substrate size increases, the shadow mask bends more, making uniform deposition on large substrates difficult. It also has other problems, such as high manufacturing costs.

[0005] On the other hand, polymeric materials can be dissolved in organic solvents and applied to form uniform films on large substrates, and thin films can be formed using coating methods such as inkjet printing, etc. This allows for increased material utilization efficiency and significantly reduced manufacturing costs for device fabrication.

[0006] Various organic EL devices using polymer materials have been investigated to date, but there have been problems in that device characteristics such as luminous efficiency and life span are not necessarily sufficient (see, for example, Patent Documents 1 to 5).

[0007] The most important technology for improving the performance of polymer organic EL devices is the technology to laminate upper layers by coating without disturbing the underlying thin film. Polymer organic EL devices are fabricated by dissolving materials in an organic solvent and coating the solution, so there is a risk that the lower thin film will dissolve in the solvent that dissolved the upper layer material, and this has the disadvantage that lamination is more difficult than with vacuum deposition methods.

[0008] There are two main types of lamination technology for polymer organic EL elements. One is a method of adding a crosslinker to the base material. After the base material is applied, heat treatment is used to promote crosslinking, making it insoluble in organic solvents. The other is a method of selecting the type of solvent used to dissolve the upper layer material. By selecting an organic solvent that does not dissolve the base material, it is possible to prevent the base from leaching out when the upper layer is applied.

[0009] A typical hole-transporting material used in polymer organic EL devices to date is a fluorene polymer called TFB, which does not have a crosslinker (see Patent Documents 6 and 7). However, TFB has insufficient hole-transporting and electron-blocking properties, which means that some electrons pass through the emissive layer, preventing improvements in luminous efficiency. Furthermore, TFB has poor film adhesion to adjacent layers, preventing device lifespans from being extended. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-272834 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-119763 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-162009 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-177225 [Patent Document 5] International Publication WO2005 / 049546 [Patent Document 6] International Publication WO99 / 54385 [Patent Document 7] International Publication WO2005 / 059951 Summary of the Invention

[0011] The object of the present invention is to provide a polymer material that has excellent hole injection / transport properties, electron blocking ability, and high stability in a thin film state, and to provide a light-emitting diode, particularly a polymer organic EL device, that has an organic layer (thin film) formed from the polymer material and has a low driving voltage, high luminous efficiency, and long life.

[0012] The present inventors have noticed that triarylamines containing a fluorene structure have high hole injection and transport capabilities and are also expected to have a wide gap. As a result of synthesizing and examining various high molecular weight compounds having triarylamine structural units containing a fluorene structure, they have discovered a high molecular weight compound with a novel structure that not only has hole injection and transport capabilities but also a wide gap, excellent heat resistance, and thin film stability, and have completed the present invention.

[0013] According to the present invention, there is provided a high molecular weight compound comprising a repeating unit represented by the following general formula (3), which is composed of a triarylamine structural unit represented by the following general formula (1) and a linking structural unit represented by the following general formula (2).

[0014] According to the present invention, there is provided a light-emitting diode having a pair of electrodes and at least one organic layer sandwiched between them, wherein the organic layer contains the above-mentioned high molecular weight compound as a constituent material.

[0015] In the light-emitting diode of the present invention, the organic layer is preferably a hole transport layer, an electron blocking layer, a hole injection layer or a light-emitting layer.

[0016] That is, the present invention is as follows.

[0017] [1] A high molecular weight compound containing a repeating unit represented by the following general formula (3), which is composed of a triarylamine structural unit represented by the following general formula (1) and a linking structural unit represented by the following general formula (2), and having a weight average molecular weight of 10,000 or more but less than 1,000,000 in terms of polystyrene.

[0018] [ka]

[0019] [ka]

[0020] [ka]

[0021] In the above formula, R1 each independently represents a deuterium atom, a cyano group, a nitro group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an alkyl group or an alkyloxy group having 1 to 8 carbon atoms, a cycloalkyl group or a cycloalkyloxy group having 5 to 10 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryloxy group; R2 each independently represents an alkyl group or alkyloxy group having 1 to 8 carbon atoms, or a cycloalkyl group or cycloalkyloxy group having 5 to 10 carbon atoms; X represents a hydrogen atom, an amino group, a monovalent aryl group, or a monovalent heteroaryl group; L represents a divalent phenyl group; n represents an integer of 0 to 3, a represents an integer of 0 to 3; b represents an integer of 0 to 4.

[0022] [2] The high molecular weight compound according to [1], wherein a and b are 0.

[0023] [3] The high molecular weight compound according to [1] or [2], wherein R2 is an alkyl group having 1 to 8 carbon atoms.

[0024] [4] The high molecular weight compound according to any one of [1] to [3], wherein X is a hydrogen atom.

[0025] [5] The high molecular weight compound according to any one of [1] to [3], wherein X is a diphenylamino group, a phenyl group, a naphthyl group, a dibenzofuranyl group, a dibenzothienyl group, a phenanthrenyl group, a fluorenyl group, a carbazolyl group, an indenocarbazolyl group, or an acridinyl group.

[0026] [6] A light-emitting diode having a pair of electrodes and at least one organic layer sandwiched between them, wherein the organic layer contains the high molecular weight compound according to any one of [1] to [5] as a constituent material.

[0027] [7] The light-emitting diode according to [6], wherein the organic layer is a hole transport layer.

[0028] [8] The light-emitting diode according to [6], wherein the organic layer is an electron blocking layer.

[0029] [9] The light-emitting diode according to [6], wherein the organic layer is a hole injection layer.

[0030]

[10] The light-emitting diode according to [6], wherein the organic layer is a light-emitting layer.

[0031]

[11] The light-emitting diode according to any one of [6] to

[10] , which is an organic electroluminescence element.

[0032] The high molecular weight compound of the present invention having the triarylamine structural unit (divalent group) represented by the above-mentioned general formula (1) and the linking structural unit (divalent group) represented by the general formula (2) is, for example, a polymer having the structural unit as a repeating unit, and preferably has a weight average molecular weight in the range of 10,000 or more and less than 1,000,000 in terms of polystyrene, as measured by GPC (gel permeation chromatography).

[0033] The high molecular weight compound according to the present invention is (1) Good hole injection characteristics, (2) High hole mobility, (3) Wide gap and excellent electron blocking ability. (4) The thin film state is stable. (5) Excellent heat resistance It has the following characteristics.

[0034] An organic EL device in which an organic layer formed from the high molecular weight compound of the present invention, for example, a hole transport layer, an electron blocking layer, a hole injection layer, or a light emitting layer, is formed between a pair of electrodes, is (1) High luminous efficiency and power efficiency (2) Low practical driving voltage (3) Long life. This has the advantage that: [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a diagram showing the chemical structures of structural units 1 to 11 suitable as linking structural units represented by general formula (2) according to the present invention. [Figure 2] FIG. 1 is a diagram showing the chemical structures of structural units 12 to 21 suitable as linking structural units represented by general formula (2) according to the present invention. [Figure 3] FIG. 2 is a diagram showing the chemical structures of structural units 22 to 31 suitable as linking structural units represented by general formula (2) according to the present invention. [Figure 4] FIG. 2 is a diagram showing the chemical structures of structural units 32 to 38, which are suitable as linking structural units represented by general formula (2) according to the present invention. [Figure 5] FIG. 1 is a diagram showing an example of the layer structure of an organic EL element of the present invention. [Figure 6] 1 is a 1H-NMR chart of the high molecular weight compound (Compound A) synthesized in Example 1 of the present invention. [Figure 7] 1H-NMR chart of the high molecular weight compound (Compound B) synthesized in Example 2 of the present invention. [Figure 8] 1H-NMR chart of the high molecular weight compound (Compound C) synthesized in Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] <Triarylamine structural unit and linking structural unit> The triarylamine structural unit and the linking structural unit contained in the high molecular weight compound of the present invention are both divalent groups and are represented by the following general formulas (1) and (2), respectively.

[0037] [ka]

[0038] [ka]

[0039] In the general formulas (1) and (2), R1 each independently represents a hydrogen atom, a deuterium atom, a cyano group, a nitro group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an alkyl group or an alkyloxy group having 1 to 8 carbon atoms, a cycloalkyl group or a cycloalkyloxy group having 5 to 10 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryloxy group.

[0040] In the above R1, examples of the alkyl group, alkyloxy group, cycloalkyl group, cycloalkyloxy group, alkenyl group, and aryloxy group include the following groups.

[0041] Examples of the alkyl group (having 1 to 8 carbon atoms) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, an isohexyl group, a neohexyl group, an n-heptyl group, an isoheptyl group, a neoheptyl group, an n-octyl group, an isooctyl group, and a neooctyl group.

[0042] Examples of the alkyloxy group (having 1 to 8 carbon atoms) include a methyloxy group, an ethyloxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, a tert-butyloxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, and an n-octyloxy group.

[0043] Examples of the cycloalkyl group (having 5 to 10 carbon atoms) include a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, and a 2-adamantyl group.

[0044] Examples of the cycloalkyloxy group (having 5 to 10 carbon atoms) include a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, a 1-adamantyloxy group, and a 2-adamantyloxy group.

[0045] Examples of the alkenyl group (having 2 to 6 carbon atoms) include a vinyl group, an allyl group, an isopropenyl group, and a 2-butenyl group.

[0046] Examples of the aryloxy group include a phenyloxy group and a tolyloxy group.

[0047] In the general formulae (1) and (2), a represents an integer of 0 to 3, and b represents an integer of 0 to 4.

[0048] In the high molecular weight compound of the present invention, when a or b is not 0, the above R1 is preferably a deuterium atom, and it is most preferable that a and b are 0 from the viewpoint of synthesis.

[0049] In the general formula (1), R2's each independently represent an alkyl group or alkyloxy group having 1 to 8 carbon atoms, or a cycloalkyl group or cycloalkyloxy group having 5 to 10 carbon atoms.

[0050] In the above R2, examples of the alkyl group, alkyloxy group, cycloalkyl group and cycloalkyloxy group include the same groups as those shown in R1.

[0051] In the high molecular weight compound of the present invention, the above R2 is preferably an alkyl group having 1 to 8 carbon atoms, and most preferably an n-hexyl group or an n-octyl group, in order to enhance solubility.

[0052] In the general formula (2), X represents a hydrogen atom, an amino group, a monovalent aryl group, or a monovalent heteroaryl group.

[0053] In the above X, examples of the monovalent aryl group and the monovalent heteroaryl group include the following groups.

[0054] Examples of the aryl group include a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a fluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, and a fluoranthenyl group.

[0055] Examples of heteroaryl groups include a pyridyl group, a pyrimidinyl group, a triazinyl group, a furyl group, a pyrrolyl group, a thienyl group, a quinolyl group, an isoquinolyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a carbazolyl group, an indenocarbazolyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, a naphthyridinyl group, a phenanthrolinyl group, an acridinyl group, and a carbolinyl group.

[0056] The amino group, aryl group, and heteroaryl group may have a substituent, such as a deuterium atom, a cyano group, a nitro group, or the following groups:

[0057] halogen atoms, for example, fluorine atom, chlorine atom, bromine atom, and iodine atom; alkyl groups, particularly those having 1 to 8 carbon atoms, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, n-hexyl group, isohexyl group, neohexyl group, n-heptyl group, isoheptyl group, neoheptyl group, n-octyl group, isooctyl group, and neooctyl group; alkyloxy groups, particularly those having 1 to 8 carbon atoms, for example, methyloxy group, ethyloxy group, and propyloxy group; alkenyl groups, for example, vinyl group and allyl group; aryloxy groups, for example, phenyloxy group and tolyloxy group; and aryl groups, for example, phenyl group and biphenylyl group. , terphenylyl group, naphthyl group, anthracenyl group, phenanthrenyl group, fluorenyl group, indenyl group, pyrenyl group, perylenyl group, fluoranthenyl group, triphenylenyl group; heteroaryl groups such as pyridyl group, pyrimidinyl group, triazinyl group, thienyl group, furyl group, pyrrolyl group, quinolyl group, isoquinolyl group, benzofuranyl group, benzothienyl group, indolyl group, carbazolyl group, indenocarbazolyl group, benzoxazolyl group, benzothiazolyl group, quinoxalinyl group, benzimidazolyl group, pyrazolyl group, dibenzofuranyl group, dibenzothienyl group, carbolinyl group; arylvinyl groups such as styryl group, naphthylvinyl group; acyl groups such as acetyl group, benzoyl group, and the like.

[0058] These substituents may further have the substituents exemplified above. Furthermore, these substituents preferably exist independently of each other, but these substituents may be bonded to each other via a single bond, a methylene group which may have a substituent, an oxygen atom, or a sulfur atom to form a ring.

[0059] For example, the aryl group or heteroaryl group may have a phenyl group as a substituent, and the phenyl group may further have a phenyl group as a substituent, i.e., taking the aryl group as an example, the aryl group may be a biphenylyl group, a terphenylyl group, or a triphenylenyl group.

[0060] In the general formula (1), L represents a divalent phenyl group, and n represents an integer of 0 to 3. In the present invention, n is preferably 0 from the viewpoint of synthesis.

[0061] Furthermore, the above L may have a substituent. Examples of the substituent include the same groups as the substituents that the above X may have, and these substituents may further have a substituent.

[0062] In the present invention, specific examples of the linking structural unit represented by the above-mentioned general formula (2) are shown as structural units 1 to 38 in Figures 1 to 4. In the chemical formulae shown in Figures 1 to 4, dashed lines indicate bonds to adjacent structural units, and solid lines extending from a ring with free ends indicate that a methyl group is substituted. Although preferred specific examples of the linking structural unit are shown, the linking structural unit used in the present invention is not limited to these structural units.

[0063] <High molecular weight compounds> The high molecular weight compound of the present invention, which contains a repeating unit represented by general formula (3) consisting of the triarylamine structural unit represented by general formula (1) and the linking structural unit represented by general formula (2), has excellent properties such as hole injection characteristics, hole mobility, electron blocking ability, thin film stability, and heat resistance, as already mentioned above. From the viewpoint of further enhancing these properties and ensuring film formability, for example, the weight average molecular weight in terms of polystyrene measured by GPC is preferably in the range of 10,000 or more and less than 1,000,000, more preferably 10,000 or more and less than 500,000, and even more preferably 10,000 or more and less than 200,000.

[0064] In the high molecular weight compound of the present invention, when the structural unit represented by general formula (1) is represented by I and the linking structural unit represented by general formula (2) is represented by II, it is preferable that the structural unit I and the structural unit II are each contained in an amount of 50 mol %, and a binary copolymer containing structural units I and II so as to satisfy such conditions is most suitable for forming the organic layer of an organic EL device.

[0065] Such high molecular weight compounds of the present invention can be synthesized by linking the structural units together through the Suzuki polymerization reaction or the Hartwig-Buchwald polymerization reaction, respectively, by forming a C—C bond or a C—N bond. Specifically, the high molecular weight compounds of the present invention can be synthesized by preparing unit compounds having the structural units, appropriately converting the unit compounds into boric acid esters or halogenating them, and then subjecting them to a polycondensation reaction using an appropriate catalyst.

[0066] For example, a triarylamine derivative represented by the following general formula (1a) can be used as a compound for introducing the structural unit of general formula (1).

[0067] [ka]

[0068] In the formula, Q is a hydrogen atom, a halogen atom or a borate ester group, and R1, R2 and L are all the same as defined in general formula (1).

[0069] That is, in the above general formula (1a), those in which Q is a hydrogen atom are unit compounds for introducing the structural unit of general formula (1), and those in which Q is a halogen atom or a borate ester group are halides or borate ester compounds used to synthesize polymers, respectively. The halogen atom is preferably Br.

[0070] For example, a copolymer containing 50 mol % of structural units I represented by general formula (1) and 50 mol % of structural units II represented by general formula (2) is represented by the following general formula (4).

[0071] [ka]

[0072] Such high molecular weight compounds can be synthesized by a polycondensation reaction between a boric acid ester and a halogenated borate, but it is necessary that the intermediate for introducing structural unit I is a boric acid ester and the intermediate for introducing structural unit II is a halogenated borate, or that the intermediate for introducing structural unit I is a halogenated borate and the intermediate for introducing structural unit II is a boric acid ester. In other words, the molar ratio of the halogenated borate to the boric acid ester must be equal.

[0073] The high molecular weight compound of the present invention described above is dissolved in an aromatic organic solvent such as benzene, toluene, xylene, or anisole to prepare a coating solution, which is then coated on a predetermined substrate and dried by heating, to form a thin film excellent in properties such as hole injection, hole transport, and electron blocking properties. Such a thin film also has good heat resistance and good adhesion to other layers.

[0074] The high-molecular-weight compound can be used as a constituent material of a hole injection layer and / or a hole transport layer of an organic EL device. A hole injection layer or a hole transport layer formed from such a high-molecular-weight compound has higher hole injection properties, higher mobility, and higher electron blocking properties than those formed from conventional materials, and can confine excitons generated in the light-emitting layer. It also improves the probability of hole and electron recombination, resulting in high luminous efficiency. It also reduces the driving voltage and improves the durability of the organic EL device.

[0075] Furthermore, the high molecular weight compound of the present invention having the above-described electrical properties has a wider gap than conventional materials and is effective in confining excitons, and therefore can naturally be suitably used in electron blocking layers and light-emitting layers.

[0076] <Organic EL element> An organic EL device having an organic layer formed using the above-described high molecular weight compound of the present invention has, for example, a structure shown in Fig. 5. That is, a transparent anode 2, a hole injection layer 3, a hole transport layer 4, a light-emitting layer 5, an electron transport layer 6, and a cathode 7 are provided on a glass substrate 1 (which may be a transparent substrate such as a transparent resin substrate).

[0077] Of course, the organic EL device to which the high molecular weight compound of the present invention is applied is not limited to the above-mentioned layer structure. A hole-blocking layer may be provided between the light-emitting layer 5 and the electron-transporting layer 6, an electron-blocking layer may be provided between the hole-transporting layer 4 and the light-emitting layer 5, or an electron-injection layer may be provided between the cathode 7 and the electron-transporting layer 6. Furthermore, some layers may be omitted. For example, a simple layer structure may be used in which an anode 2, a hole-transporting layer 4, a light-emitting layer 5, an electron-transporting layer 6, and a cathode 7 are provided on a substrate 1. Alternatively, a two-layer structure in which layers having the same function are stacked may be used.

[0078] The high molecular weight compound of the present invention is suitably used as a material for forming an organic layer (e.g., a hole injection layer 3, a hole transport layer 4, an emitting layer 5, or an electron blocking layer) provided between the anode 2 and the cathode 7, taking advantage of its properties such as hole injection property and hole transport property.

[0079] In the above organic EL element, the transparent anode 2 may be formed from a known electrode material, and is formed by depositing an electrode material with a large work function, such as ITO or gold, on the substrate 1 (a transparent substrate such as a glass substrate).

[0080] The hole injection layer 3 provided on the transparent anode 2 can be formed using a coating liquid prepared by dissolving the high molecular weight compound of the present invention in an aromatic organic solvent such as toluene, xylene, or anisole. That is, the hole injection layer 3 can be formed by coating the transparent anode 2 with this coating liquid by spin coating, inkjet printing, or the like.

[0081] In an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, the hole injection layer 3 can also be formed using a conventionally known material, such as the following material, without using the high molecular weight compound of the present invention. Porphyrin compounds, such as copper phthalocyanine; Starburst triphenylamine derivatives; Arylamines having structures linked by single bonds or divalent groups that do not contain heteroatoms (e.g., triphenylamine trimers and tetramers); Acceptor heterocyclic compounds such as hexacyanoazatriphenylene; Coating-type polymer materials, such as poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(styrene sulfonate) (PSS).

[0082] Layers (thin films) made of such materials can be formed by vapor deposition or coating using spin coating, inkjet printing, etc. This also applies to other layers, and films are formed by vapor deposition or coating depending on the type of film-forming material.

[0083] The hole transport layer 4 provided on the hole injection layer 3 can also be formed by coating using the high molecular weight compound of the present invention by spin coating, inkjet or the like, similar to the hole injection layer 3.

[0084] In an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, the hole transport layer 4 can also be formed using a conventionally known hole transport material. Representative examples of such hole transport materials are as follows.

[0085] Benzidine derivatives, for example: N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (hereinafter abbreviated as TPD); N,N'-diphenyl-N,N'-di(α-naphthyl)benzidine (hereinafter abbreviated as NPD); N,N,N',N'-tetrabiphenylylbenzidine; Amine derivatives, for example: 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane (hereinafter abbreviated as TAPC); various triphenylamine trimers and tetramers; Coating polymer materials that are also used for hole injection layers.

[0086] The compounds for the hole transport layer described above, including the high molecular weight compound of the present invention, may be used alone to form a film, or two or more of them may be mixed to form a film. Furthermore, one or more of the compounds may be used to form multiple layers, and a multilayer film formed by laminating such layers may be used as the hole transport layer.

[0087] In an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, the hole injection layer 3 and the hole transport layer 4 may be combined, and such a hole injection / transport layer can be formed by coating using a polymer material such as PEDOT.

[0088] The hole transport layer 4 (and the hole injection layer 3) may be made of a material typically used for the layer, but doped with P, such as trisbromophenylaminehexachloroantimony or a radialene derivative (see, for example, WO2014 / 009310).The hole transport layer 4 (or the hole injection layer 3) may also be made of a polymer compound having a TPD basic skeleton.

[0089] Furthermore, the electron blocking layer (which can be provided between the hole transport layer 4 and the light emitting layer 5) can also be formed by coating using the high molecular weight compound of the present invention by spin coating, ink jet or the like.

[0090] In an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, the electron blocking layer can also be formed using a known electron blocking compound having an electron blocking effect, such as a carbazole derivative or a compound having a triphenylsilyl group and a triarylamine structure. Specific examples of carbazole derivatives and compounds having a triarylamine structure are as follows:

[0091] Examples of carbazole derivatives 4,4',4''-tri(N-carbazolyl)triphenylamine (hereafter abbreviated as TCTA); 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene; 1,3-bis(carbazol-9-yl)benzene (hereafter abbreviated as mCP); 2,2-bis[4-(carbazol-9-yl)phenyl]adamantane (hereinafter abbreviated as Ad-Cz) Examples of compounds with a triarylamine structure 9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene

[0092] The electron-blocking layer may be formed using a single compound, including the high-molecular-weight compound of the present invention, or a mixture of two or more compounds. Alternatively, multiple layers may be formed using one or more of the compounds, and a multilayer film formed by stacking such layers may be used as the electron-blocking layer.

[0093] In an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, the light-emitting layer 5 can be formed using light-emitting materials such as metal complexes of quinolinol derivatives such as Alq3, as well as various metal complexes of zinc, beryllium, aluminum, etc., anthracene derivatives, bisstyrylbenzene derivatives, pyrene derivatives, oxazole derivatives, and polyparaphenylenevinylene derivatives.

[0094] The light-emitting layer 5 can also be composed of a host material and a dopant material. In this case, in addition to the light-emitting materials described above, thiazole derivatives, benzimidazole derivatives, polydialkylfluorene derivatives, etc. can be used as the host material, and the high-molecular-weight compound of the present invention described above can also be used. As the dopant material, quinacridone, coumarin, rubrene, perylene, and derivatives thereof, benzopyran derivatives, rhodamine derivatives, aminostyryl derivatives, etc. can be used.

[0095] Such a light-emitting layer 5 may also have a single layer structure using one or more types of light-emitting materials, or may have a multilayer structure in which a plurality of layers are laminated.

[0096] Furthermore, the light-emitting layer 5 can be formed using a phosphorescent material as the light-emitting material. Examples of phosphorescent materials that can be used include phosphorescent emitters of metal complexes such as iridium and platinum. For example, green phosphorescent emitters such as Ir(ppy)3, blue phosphorescent emitters such as FIrpic and FIr6, and red phosphorescent emitters such as Btp2Ir(acac) can be used. These phosphorescent materials are used by doping into a hole-injecting / transporting host material or an electron-transporting host material.

[0097] In order to avoid concentration quenching, the phosphorescent light-emitting material is preferably doped into the host material by co-evaporation in an amount ranging from 1 to 30 weight percent based on the entire light-emitting layer.

[0098] It is also possible to use materials that emit delayed fluorescence, such as CDCB derivatives such as PIC-TRZ, CC2TA, PXZ-TRZ, and 4CzIPN, as light-emitting materials (see Appl. Phys. Let., 98, 083302 (2011)).

[0099] By forming the light-emitting layer 5 by loading the high molecular weight compound of the present invention with a fluorescent light-emitting material, a phosphorescent light-emitting material, or a material that emits delayed fluorescence, which is called a dopant, an organic EL device with a reduced driving voltage and improved luminous efficiency can be realized.

[0100] In an organic EL device having an organic layer formed using the high-molecular-weight compound of the present invention, the high-molecular-weight compound of the present invention can be used as a hole-injecting / transporting host material. In addition, carbazole derivatives such as 4,4'-di(N-carbazolyl)biphenyl (hereinafter abbreviated as CBP), TCTA, and mCP can also be used.

[0101] In addition, in an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, p-bis(triphenylsilyl)benzene (hereinafter abbreviated as UGH2) or 2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole) (hereinafter abbreviated as TPBI) can be used as an electron-transporting host material.

[0102] In an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, a hole-blocking layer (not shown) provided between the light-emitting layer 5 and the electron-transporting layer 6 can be formed using a known compound having a hole-blocking effect. Examples of such known compounds having a hole-blocking effect include the following:

[0103] phenanthroline derivatives such as bathocuproine (hereafter abbreviated as BCP); Metal complexes of quinolinol derivatives such as aluminum(III) bis(2-methyl-8-quinolinato)-4-phenylphenolate (hereinafter abbreviated as BAlq); Various rare earth complexes; Triazole derivatives; Triazine derivatives; Oxadiazole derivatives, etc.

[0104] These materials can also be used to form the electron transport layer 6 described below, and can also be used as a hole blocking layer and electron transport layer.

[0105] Such a hole blocking layer may also have a single layer or a multi-layer laminate structure, and each layer is formed using one or more of the above-mentioned compounds having hole blocking properties.

[0106] In an organic EL device having an organic layer formed using the high-molecular-weight compound of the present invention, the electron-transporting layer 6 is formed using a known electron-transporting compound, for example, a metal complex of a quinolinol derivative such as Alq3 or BAlq, as well as various metal complexes, pyridine derivatives, pyrimidine derivatives, triazole derivatives, triazine derivatives, oxadiazole derivatives, thiadiazole derivatives, carbodiimide derivatives, quinoxaline derivatives, phenanthroline derivatives, silole derivatives, and benzimidazole derivatives.

[0107] This electron transport layer 6 may also have a single layer or a multi-layer laminate structure, and each layer is formed using one or more of the above-mentioned electron transport compounds.

[0108] Furthermore, in an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, an electron injection layer (not shown) that is provided as needed can also be formed using a known compound, for example, an alkali metal salt such as lithium fluoride or cesium fluoride, an alkaline earth metal salt such as magnesium fluoride, a metal oxide such as aluminum oxide, or an organometallic complex such as lithium quinoline.

[0109] For the cathode 7 of an organic EL device having an organic layer formed using the high molecular weight compound of the present invention, an electrode material having a low work function such as aluminum, or an alloy having an even lower work function such as a magnesium-silver alloy, a magnesium-indium alloy, or an aluminum-magnesium alloy is used as the electrode material.

[0110] As described above, by forming at least one of the hole injection layer, hole transport layer, light-emitting layer, and electron blocking layer using the high molecular weight compound of the present invention, an organic EL device having high luminous efficiency and power efficiency, low practical driving voltage, low light-emission onset voltage, and extremely excellent durability can be obtained. In particular, this organic EL device has high luminous efficiency, a reduced driving voltage, improved current resistance, and an increased maximum luminous brightness. [Example]

[0111] The present invention will now be described with reference to the following experimental examples. In the following description, the structural unit represented by general formula (1) contained in the high molecular weight compound of the present invention is referred to as "structural unit I," and the linking structural unit represented by general formula (2) is referred to as "structural unit II."

[0112] The synthesized compounds were purified by column chromatography and solvent crystallization, and identified by NMR analysis.

[0113] <Synthesis of Intermediate 1> To produce the high molecular weight compound of the present invention, intermediate 1 for introducing structural unit I was synthesized.

[0114] [ka]

[0115] The following components were added to a reaction vessel whose atmosphere had been replaced with nitrogen, and nitrogen gas was bubbled through the vessel for 30 minutes. N,N-bis(3-bromophenyl)-9,9-dioctyl-9H-fluoren-2-amine: 43.4g Bis(pinacolato)diboron: 32.3g Potassium acetate: 17.9g 1,4-dioxane: 220 ml Next, 1.0 g of a dichloromethane adduct of {1,1'-bis(diphenylphosphino)ferrocene}palladium(II) dichloride was added, and the mixture was heated and stirred at 100°C for 13 hours. After cooling to room temperature, water and toluene were added, and the organic layer was separated and washed three times with saturated brine. This organic layer was dehydrated with anhydrous sodium sulfate and then concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (ethyl acetate / n-hexane = 1 / 20) to obtain 22.9 g (45% yield) of white powder of intermediate 1.

[0116] Example 1 (Synthesis of high molecular weight compound A) The following components were added to a reaction vessel whose atmosphere had been replaced with nitrogen, and nitrogen gas was bubbled through the vessel for 30 minutes. N,N-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-9,9-dioctyl-9H-fluoren-2-amine: 5.6g 1,3-dibromobenzene: 1.6g Tripotassium phosphate: 7.7g Toluene: 9 ml Water: 5ml 1,4-dioxane: 27 ml

[0117] Next, 1.6 mg of palladium(II) acetate and 12.9 mg of tri-o-tolylphosphine were added, heated, and stirred at 85°C for 11 hours. After this, 19 mg of phenylboronic acid was added and stirred for 1 hour, followed by 271 mg of bromobenzene and stirring for 1 hour. 50 ml of toluene and 50 ml of a 5 wt% aqueous solution of sodium N,N-diethyldithiocarbamate were added, heated, and stirred under reflux for 2 hours. After cooling to room temperature, the organic layer was separated and washed three times with saturated brine. The organic layer was dehydrated over anhydrous magnesium sulfate and concentrated under reduced pressure to obtain a crude polymer. The crude polymer was dissolved in toluene, silica gel was added, and the mixture was purified by adsorption. The silica gel was removed by filtration. The resulting filtrate was concentrated under reduced pressure, and the dried product was dissolved in 100 ml of toluene. This was then added dropwise to 300 ml of n-hexane, and the resulting precipitate was collected by filtration. This procedure was repeated three times and dried to obtain 3.2 g of high molecular weight compound A (70% yield).

[0118] The average molecular weight and dispersity of the high molecular weight compound A measured by GPC were as follows: Number average molecular weight Mn (polystyrene equivalent): 56,000 Weight average molecular weight Mw (polystyrene equivalent): 89,000 Dispersion degree (Mw / Mn): 1.6

[0119] Further, NMR measurement was carried out on the high molecular weight compound A. 1 The results of H-NMR measurement are shown in Figure 6. The structure of high molecular weight compound A is as follows.

[0120] [ka]

[0121] As can be seen from the above structural formula, this high molecular weight compound A contained 50 mol % of structural unit I represented by general formula (1) and 50 mol % of structural unit II represented by general formula (2).

[0122] <Example 2> (Synthesis of high molecular weight compound B) The following components were added to a reaction vessel whose atmosphere had been replaced with nitrogen, and nitrogen gas was bubbled through the vessel for 30 minutes. Intermediate 1: 6.6g 1,3-dibromobenzene: 1.9g Tripotassium phosphate: 9.1g Toluene: 12 ml Water: 7ml 1,4-dioxane: 36 ml

[0123] Next, 1.9 mg of palladium(II) acetate and 15.1 mg of tri-o-tolylphosphine were added, heated, and stirred at 85°C for 11.5 hours. After this, 23 mg of phenylboronic acid was added and stirred for 1 hour, followed by 319 mg of bromobenzene and stirring for 1 hour. 50 ml of toluene and 50 ml of a 5 wt% aqueous solution of sodium N,N-diethyldithiocarbamate were added, and the mixture was heated and stirred under reflux for 2 hours. After cooling to room temperature, the organic layer was separated and washed three times with saturated brine. The organic layer was dehydrated with anhydrous sodium sulfate and then concentrated under reduced pressure to obtain a crude polymer. The crude polymer was dissolved in toluene, silica gel was added, and the mixture was purified by adsorption. The silica gel was removed by filtration. The resulting filtrate was concentrated under reduced pressure, and 30 ml of toluene was added to the dried product to dissolve it. The solution was then added dropwise to 400 ml of n-hexane, and the resulting precipitate was collected by filtration. This procedure was repeated once more and dried to obtain 1.6 g of high molecular weight compound B (yield 30%).

[0124] The average molecular weight and dispersity of polymer compound B measured by GPC were as follows: Number average molecular weight Mn (polystyrene equivalent): 38,000 Weight average molecular weight Mw (polystyrene equivalent): 50,000 Dispersion degree (Mw / Mn): 1.3

[0125] In addition, NMR measurement was carried out on the high molecular weight compound B. 1 The results of H-NMR measurement are shown in Figure 7. The structure of high molecular weight compound B is as follows.

[0126] [ka]

[0127] As can be seen from the above structural formula, this high molecular weight compound B contained 50 mol % of structural unit I represented by general formula (1) and 50 mol % of structural unit II represented by general formula (2).

[0128] Example 3 (Synthesis of high molecular weight compound C) The following components were added to a reaction vessel whose atmosphere had been replaced with nitrogen, and nitrogen gas was bubbled through the vessel for 30 minutes. N,N-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-9,9-dioctyl-9H-fluoren-2-amine: 5g 9-(3,5-dibromophenyl)-3,6-diphenyl-9H-carbazole: 1.6g Tripotassium phosphate: 3.4g Toluene: 7 ml Water: 4ml 1,4-dioxane: 21 ml

[0129] Next, 1.4 mg of palladium(II) acetate and 11.5 mg of tri-o-tolylphosphine were added, heated, and stirred at 85°C for 12 hours. After this, 17 mg of phenylboronic acid was added and stirred for 1 hour, followed by 242 mg of bromobenzene and stirring for 1 hour. 50 ml of toluene and 50 ml of a 5 wt% aqueous solution of sodium N,N-diethyldithiocarbamate were added, heated, and stirred under reflux for 2 hours. After cooling to room temperature, the organic layer was separated and washed three times with saturated brine. The organic layer was dehydrated with anhydrous sodium sulfate and concentrated under reduced pressure to obtain a crude polymer. The crude polymer was dissolved in toluene, silica gel was added, and the mixture was purified by adsorption. The silica gel was removed by filtration. The resulting filtrate was concentrated under reduced pressure, and the dried product was dissolved in 100 ml of toluene. This was then added dropwise to 300 ml of n-hexane, and the resulting precipitate was collected by filtration. This procedure was repeated three times and dried to obtain 1.8 g of high molecular weight compound C (30% yield).

[0130] The average molecular weight and dispersity of the high molecular weight compound C measured by GPC were as follows: Number average molecular weight Mn (polystyrene equivalent): 45,000 Weight average molecular weight Mw (polystyrene equivalent): 73,000 Dispersion degree (Mw / Mn): 1.6

[0131] In addition, NMR measurement was carried out on the high molecular weight compound C. 1 The results of H-NMR measurement are shown in Figure 8. The structure of high molecular weight compound C is as follows.

[0132] [ka]

[0133] As can be seen from the above structural formula, this high molecular weight compound C contained 50 mol % of structural unit I represented by general formula (1) and 50 mol % of structural unit II represented by general formula (2).

[0134] Example 4 (Work function measurement) Using the high molecular weight compounds A, B, and C synthesized in Examples 1, 2, and 3, coating films with a thickness of 80 nm were formed on ITO substrates, and the work functions were measured using an ionization potential measurement device (PYS-202 model, manufactured by Sumitomo Heavy Industries, Ltd.). The results are as follows:

[0135] [Table 1]

[0136] It is clear that the high molecular weight compounds A, B, and C of the present invention have a preferable energy level compared with the work function of 5.4 eV of common hole transport materials such as NPD and TPD, and have good hole transport ability.

[0137] <Example 5> (Fabrication and evaluation of organic EL devices) An organic EL device having the layer structure shown in FIG. 5 was fabricated by the following method.

[0138] A glass substrate 1 on which a 50 nm thick ITO film was formed was washed with an organic solvent, and then the ITO surface was cleaned by UV / ozone treatment. A 50 nm thick PEDOT / PSS (manufactured by HERAEUS) film was formed by spin coating to cover the transparent anode 2 (ITO) provided on this glass substrate 1, and dried on a hot plate at 200°C for 10 minutes to form a hole injection layer 3.

[0139] A coating solution was prepared by dissolving 0.6 wt % of the high molecular weight compound A obtained in Example 1 in toluene. The substrate on which the hole injection layer 3 had been formed as described above was transferred into a glove box purged with dry nitrogen, and the coating solution was spin-coated on the hole injection layer 3 to form a coating layer with a thickness of 25 nm. This was then dried on a hot plate at 220°C for 30 minutes to form a hole transport layer 4.

[0140] The substrate on which the hole transport layer 4 was formed as described above was placed in a vacuum deposition machine, and the pressure was reduced to 0.001 Pa or less. On the hole transport layer 4, a 34 nm-thick light-emitting layer 5 was formed by binary deposition of a blue light-emitting material (EMD-1) having the following structural formula and a host material (EMH-1). In the binary deposition, the deposition rate ratio was EMD-1:EMH-1=4:96.

[0141] [ka]

[0142] As electron transport materials, compounds ETM-1 and ETM-2 having the following structural formulas were prepared.

[0143] [ka]

[0144] On the light-emitting layer 5 formed above, an electron-transporting layer 6 having a thickness of 20 nm was formed by binary deposition using the electron-transporting materials ETM-1 and ETM-2. In the binary deposition, the deposition rate ratio of ETM-1:ETM-2 was set to 50:50.

[0145] Finally, aluminum was evaporated to a thickness of 100 nm to form a cathode 7 . The glass substrate having the transparent anode 2, hole injection layer 3, hole transport layer 4, light-emitting layer 5, electron transport layer 6, and cathode 7 formed thereon was transferred into a glove box purged with dry nitrogen, and another glass substrate for sealing was attached using a UV-curable resin to form an organic EL device. The characteristics of the fabricated organic EL device were measured in air at room temperature. Furthermore, the light-emitting characteristics of the fabricated organic EL device were measured when a DC voltage was applied. The measurement results are shown in Table 2.

[0146] Example 6 An organic EL device was fabricated in the same manner as in Example 5, except that the hole transport layer 4 was formed using a coating solution prepared by dissolving 0.6 wt % of the compound of Example 2 (high molecular weight compound B) in toluene instead of high molecular weight compound A. The characteristics of the fabricated organic EL device were measured in the air at room temperature. The measurement results of the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device are summarized in Table 2.

[0147] Example 7 An organic EL device was fabricated in the same manner as in Example 5, except that the hole transport layer 4 was formed using a coating solution prepared by dissolving 0.6 wt % of the compound of Example 3 (high molecular weight compound C) in toluene instead of high molecular weight compound A. The characteristics of the fabricated organic EL device were measured in the air at room temperature. The measurement results of the light-emitting characteristics when a DC voltage was applied to the fabricated organic EL device are summarized in Table 2.

[0148] <Comparative Example 1> An organic EL device was produced in the same manner as in Example 5, except that the hole transport layer 4 was formed using a coating solution prepared by dissolving 0.6 wt % of the following TFB (hole transport polymer) in toluene instead of the high molecular weight compound A.

[0149] [ka]

[0150] The TFB (hole transport polymer) was poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine] (Hole Transport Polymer ADS259BE, manufactured by American Dye Source). The organic EL device of Comparative Example 1 was evaluated for various characteristics in the same manner as in Example 5, and the results are shown in Table 2.

[0151] In evaluating various characteristics, the device life is measured when the luminance at the start of light emission (initial luminance) is 700 cd / m 2 When driven at a constant current, the luminance was 560 cd / m 2 The time it took for the brightness to decay to 80% (equivalent to 80% of the initial brightness of 100%) was measured.

[0152] [Table 2]

[0153] As shown in Table 2, both the example and the comparative example had a low practical driving voltage and a current density of 10 mA / cm 2 The luminous efficiency when a current of 1000 kJ / s was passed was 5.52 cd / A for the organic EL element of Comparative Example 1, 8.65 cd / A for the organic EL element of Example 5, 7.62 cd / A for the organic EL element of Example 6, and 10.34 cd / A for the organic EL element of Example 7, all of which were high efficiencies. Furthermore, the element lifetime (at 80% decay) was 440 hours for the organic EL element of Example 5, which was an unexpectedly large improvement compared to 5.9 hours for the organic EL element of Comparative Example 1, and both the organic EL element of Example 6 and the organic EL element of Example 7 were long lifetimes of 9.9 hours and 63.9 hours, respectively. [Industrial Applicability]

[0154] The high-molecular-weight compound of the present invention has high hole-transporting ability and excellent electron-blocking ability, making it an excellent compound for various light-emitting diodes, particularly organic EL devices, which are self-emitting elements, and more preferably for coating-type organic EL devices. By using the compound to prepare coating-type organic EL devices, high luminous efficiency and power efficiency can be achieved, and durability can be improved. This allows for a wide range of applications, such as in home appliances and lighting. [Explanation of symbols]

[0155] 1. Glass substrate 2...Transparent anode 3. Hole injection layer 4. Hole transport layer 5. Emitting layer 6...Electron transport layer 7...Cathode

Claims

1. A high molecular weight compound containing only repeating units represented by the following general formula (3), which consists of a triarylamine structural unit represented by the following general formula (1) and a linking structural unit represented by the following general formula (2), wherein the linking structural unit represented by the following general formula (2) is a structural unit selected from the group consisting of the following structural units 1 to 24 and structural units 32 to 37, and having a weight average molecular weight of 10,000 or more and less than 1,000,000 in terms of polystyrene. 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 During the ceremony, R １ each independently represent a deuterium atom, a cyano group, a nitro group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an alkyl group or an alkyloxy group having 1 to 8 carbon atoms, a cycloalkyl group or a cycloalkyloxy group having 5 to 10 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryloxy group, R ２ represents an octyl group, X represents a hydrogen atom, an amino group, a monovalent aryl group, or a monovalent heteroaryl group; L represents a divalent phenyl group; n represents an integer of 0 to 3; a is 0, b represents an integer of 0 to 4; 【Chemistry 4】 The dashed lines indicate bonds to adjacent structural units. 【Transformation 5】 The dashed lines indicate bonds to adjacent structural units. 【Transformation 6】 The dashed lines indicate bonds to adjacent structural units. 【Transformation 7】 The dashed lines indicate bonds to adjacent structural units.

2. 2. The high molecular weight compound of claim 1, wherein a and b are 0.

3. A light-emitting diode having a pair of electrodes and at least one organic layer sandwiched therebetween, wherein the organic layer contains the high molecular weight compound according to claim 1 or 2 as a constituent material.

4. 4. The light-emitting diode of claim 3, wherein the organic layer is a hole-transporting layer.

5. 4. The light-emitting diode of claim 3, wherein the organic layer is an electron-blocking layer.

6. 4. The light-emitting diode of claim 3, wherein the organic layer is a hole-injection layer.

7. 7. The light-emitting diode according to claim 3, which is an organic electroluminescence element.

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