Materials for organic electroluminescent devices, and organic electroluminescent devices.

Abstract

The present invention provides an organic EL element which has low-voltage drivability, high luminous efficiency and a long service life. An organic EL element having low voltage, high luminous efficiency and a long service life is able to be obtained by a material for organic electroluminescent elements, the material being represented by general formula (1). (In the formula, Ar1 represents a group that is represented by general formula (2) or the like; and * represents a binding point. Some or all hydrogen atoms in the compounds represented by general formula (1), general formula (2) or the like may be substituted by deuterium atoms; and n represents an integer of 0 to 1.)

Description

[Technical Field]

[0001] This invention relates to an organic electroluminescent element (referred to as an organic EL element) that can convert electrical energy into light, and to a material for such an organic electroluminescent element.

[0002] When a voltage is applied to an organic EL element, holes are injected from the anode and electrons from the cathode into the light-emitting layer. In the light-emitting layer, the injected holes and electrons recombine to generate excitons. At this time, according to the statistical laws of electron spin, singlet excitons and triplet excitons are generated in a ratio of 1:3. Fluorescent organic EL elements that use emission from singlet excitons are said to have an internal quantum efficiency limited to 25%. On the other hand, phosphorescent organic EL elements that use emission from triplet excitons are known to have an internal quantum efficiency of up to 100% if intersystem crossing from singlet excitons is performed efficiently.

[0003] In recent years, advancements have been made in technologies for extending the lifespan of phosphorescent organic light-emitting diodes (OLEDs), and these are being applied to displays in mobile phones and other devices. However, no practical phosphorescent OLEDs have been developed for blue OLEDs, and there is a need for the development of highly efficient and long-lasting blue OLEDs.

[0004] More recently, highly efficient delayed fluorescence type organic EL elements have been developed using delayed fluorescence. For example, Patent Document 1 discloses an organic EL element that utilizes the TTF (Triplet-Triplet Fusion) mechanism, one of the mechanisms of delayed fluorescence. The TTF mechanism utilizes the phenomenon in which a singlet exciton is generated by the collision of two triplet excitons, and it is theoretically thought that the internal quantum efficiency can be increased to 40%. However, since its efficiency is lower compared to phosphorescent type organic EL elements, further improvements in efficiency are needed.

[0005] On the other hand, Patent Document 2 discloses an organic EL device utilizing the thermally activated delayed fluorescence (TADF) mechanism. The TADF mechanism utilizes the phenomenon in which reverse intersystem crossing occurs from triplet excitons to singlet excitons in materials where the energy difference between the singlet and triplet levels is small, and it is theoretically thought that the internal quantum efficiency can be increased to 100%.

[0006] The driving voltage, luminous efficiency, and lifetime characteristics of organic EL elements are greatly influenced by the charge transport material that transports charges such as holes and electrons to the light-emitting layer, and the host material in the light-emitting layer. Among these, materials having a carbazole skeleton are known as hole transport materials (see, for example, Patent Documents 3-5). Furthermore, the above-mentioned materials having a carbazole skeleton are also known as host materials for the light-emitting layer (see, for example, Patent Documents 4-7 and Non-Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] WO2010 / 134350 publication [Patent Document 2] WO2011 / 070963 publication [Patent Document 3] Japanese Patent Application Publication No. 8-3547 [Patent Document 4] WO2012 / 153725 publication [Patent Document 5] WO2014 / 017484 publication [Patent Document 6] EP3611240 publication [Patent Document 7] WO2019 / 132545 publication [Non-patent literature]

[0008] [Non-Patent Document 1] Molecules 2018, 23, 847

Summary of the Invention

Problems to be Solved by the Invention

[0009] In order to apply an organic EL element as a display element such as a flat panel display or a light source, it is necessary to improve the light emission efficiency of the element and at the same time sufficiently ensure the stability during driving. The present invention has been made in view of such a situation, and provides a material for an organic electroluminescent element capable of obtaining an organic EL element that emits light with high efficiency and has high driving stability and is useful in practical applications, and an organic EL element using the same.

Means for Solving the Problems

[0010] The present invention is a material for an organic electroluminescent element, which is represented by the following general formula (1).

[0011]

Chemical formula

[0012] Here, Ar 1 is a group represented by any one of the following general formulas (2) to (11), and * represents a bonding point. Some or all of the hydrogen atoms in the compound represented by the general formula (1) and the following general formulas (2) to (11) may be substituted with deuterium atoms.

[0013]

Chemical formula

[0014] Here, Ar 2 represents an unsubstituted phenyl group or an unsubstituted biphenyl group. X 1 represents oxygen or sulfur. X 2 represents an unsubstituted N-phenyl, an unsubstituted N-biphenyl, an unsubstituted N-terphenyl, oxygen, or sulfur.

[0015] Here, n represents an integer between 0 and 1, preferably 0.

[0016] It is preferable that the above general formula (1) is represented by the following general formula (12). [ka]

[0017] Here, Ar 1 This is the same as defined in general formula (1) above. The hydrogen atom in the compound represented by general formula (12) above may be substituted with a deuterium atom.

[0018] In the above general formulas (1) and (12), Ar 1 However, it is preferable that it be represented by the general formula (2) or (3) above.

[0019] It is preferable that the above general formulas (1) and (12) are represented by the following general formula (13).

[0020] [ka]

[0021] Here, Ar 2 This is the same as defined in general formula (3) above. The hydrogen atom in the compound represented by general formula (13) above may be substituted with a deuterium atom.

[0022] Furthermore, the present invention relates to an organic electroluminescent device comprising one or more organic layers between opposing anodes and cathodes, wherein at least one organic layer contains the above-mentioned organic electroluminescent device material.

[0023] In the organic electroluminescent element of the present invention, it is preferable that at least one organic layer of the organic layer is a light-emitting layer, and that the light-emitting layer separately contains a thermally activated delayed fluorescence light-emitting material.

[0024] In the organic electroluminescent device of the present invention, at least one of the organic layers is a light-emitting layer, and it is preferable that a phosphorescent light-emitting material is separately contained in the light-emitting layer.

[0025] In the organic electroluminescent device of the present invention, at least one of the organic layers is a light-emitting layer, the light-emitting layer contains one or more host materials, and it is preferable that at least one of the host materials is the material for the organic electroluminescent device described above.

[0026] In the organic electroluminescent device of the present invention, at least one of the organic layers is a light-emitting layer, the light-emitting layer contains two or more host materials, it is preferable to use the material for the organic electroluminescent device described above as the first host, and to use a compound represented by any of the following general formulas (14) to (20) as the second host.

[0027] [Chemical formula]

[0028] Here, Ar 3 ~Ar 20 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. Ar 21 and Ar 22 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. The hydrogen atoms in the compound represented by the general formulas (14) to (20) may be substituted with deuterium atoms.

[0029] Furthermore, in the organic electroluminescent element of the present invention, at least one of the organic layers is an electron blocking layer or a hole transport layer, and the above-mentioned organic electroluminescent element material can be contained in the electron blocking layer or the hole transport layer. [Effects of the Invention]

[0030] The present invention makes it possible to obtain a practically useful organic EL element that emits light with high efficiency and possesses high driving stability and long lifespan characteristics. [Brief explanation of the drawing]

[0031] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of the structure of an organic EL element used in the present invention. [Modes for carrying out the invention]

[0032] The compound represented by general formula (1) in this invention will be described in detail.

[0033] Ar 1 is a group represented by any of the general formulas (2) to (11), and * represents a bond point, preferably a group represented by either the general formula (2) or (3), and more preferably a group represented by the general formula (3).

[0034] Ar 2 represents an unsubstituted phenyl group or an unsubstituted biphenyl group, preferably an unsubstituted phenyl group.

[0035] X 1 represents oxygen or sulfur, preferably oxygen.

[0036] X 2 X represents unsubstituted N-phenyl, unsubstituted N-biphenyl, unsubstituted N-terphenyl, oxygen, or sulfur, and preferably represents N-phenyl. 2 When represents an unsubstituted N-terphenyl, the terphenyl may be linear or branched.

[0037] In general formulas (2) to (11), * represents a bond point, Ar 1 The compound can be bonded at any position on the carbazole ring in the general formula (1), preferably at the 3-position of the carbazole ring in the general formula (1).

[0038] Some or all of the hydrogen atoms in the compounds represented by the general formulas (1) and (2) to (11) can be substituted with deuterium atoms.

[0039] The t-Bu group in the compound represented by the general formula (1) can be substituted at the ortho, meta, or para position, but meta or para substitution is preferred.

[0040] In addition, the t-Bu group in the compound represented by the general formula (1) refers to a tert-butyl group substituted for a specific phenyl group in the general formula (1).

[0041] Conventional compounds with a carbazole skeleton have not always possessed sufficient performance as light-emitting element materials. For example, 9-[1,1'-biphenyl]-4-yl-9'-pheneyl-3,3'-bi-9H-carbazole, which has a skeleton in which two carbazoles are linked, is known to improve lifetime characteristics when used as a hole-transporting host in phosphorescent light-emitting elements. However, it has problems such as a high driving voltage and a relatively low glass transition temperature, which reduces the heat resistance of organic EL elements. In response to this, the inventors hypothesized that introducing t-Bu groups into conventional carbazole compounds would improve hole injection properties, reduce the driving voltage when used as an electron blocking layer or hole-transporting host, and increase the glass transition temperature, thereby improving the heat resistance of organic EL elements. Furthermore, the inventors considered that the lifetime characteristics might change depending on the position and number of t-Bu groups introduced into the carbazole compound, leading to the invention of the compound represented by general formula (1).

[0042] Specific examples of organic electroluminescent material represented by general formula (1) are shown below, but the material is not limited to these example compounds.

[0043] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0044] By incorporating the organic electroluminescent element material represented by the general formula (1) into the organic layer, it is possible to create an organic EL element that emits light with high efficiency and has high driving stability, making it practically superior.

[0045] The aforementioned organic EL element is preferably an organic EL element in which at least one organic layer is a light-emitting layer and the light-emitting layer contains a thermally activated delayed fluorescence material or a phosphorescent material, and more preferably an organic EL element in which the light-emitting layer contains a thermally activated delayed fluorescence material.

[0046] Furthermore, if necessary, the light-emitting layer may contain at least one host material together with a thermally activated delayed fluorescence light-emitting material or a phosphorescent light-emitting material to create a superior organic EL element, and it is preferable that the at least one host material is an organic electroluminescent element material represented by the general formula (1).

[0047] Next, the structure of the organic EL element of the present invention will be described with reference to the drawings, but the structure of the organic EL element of the present invention is not limited thereto.

[0048] Figure 1 is a cross-sectional view showing an example of the structure of a typical organic EL element used in the present invention, where 1 is the substrate, 2 is the anode, 3 is the hole injection layer, 4 is the hole transport layer, 5 is the light-emitting layer, 6 is the electron transport layer, and 7 is the cathode. The organic EL element of the present invention has an anode, a light-emitting layer, and a cathode as essential layers, but it is common to have a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the essential layers, and furthermore, an electron blocking layer may be included between the hole transport layer and the light-emitting layer, and a hole blocking layer may be included between the light-emitting layer and the electron transport layer.

[0049] It is also possible to stack the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, hole injection layer 3, and anode 2 on the substrate 1 in the reverse order of Figure 1. In this case as well, layers can be added or omitted as needed. In organic EL elements as described above, layers other than electrodes such as anodes and cathodes that constitute the stacked structure on the substrate are sometimes collectively referred to as organic layers.

[0050] -substrate- The organic EL element of the present invention is preferably supported on a substrate. There are no particular restrictions on this substrate; any substrate that has been conventionally used in organic EL elements may be used, such as glass, transparent plastic, or quartz.

[0051] -anode- For the anode material in an organic EL device, materials consisting of metals, alloys, electrically conductive compounds, or mixtures thereof with a large work function (4 eV or more) are preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO2, and ZnO. Amorphous materials such as IDIXO (In2O3-ZnO), which can be used to fabricate transparent conductive films, may also be used. The anode may be formed by creating a thin film from these electrode materials using methods such as vapor deposition or sputtering, and then forming a pattern of the desired shape using photolithography. Alternatively, if high pattern accuracy is not required (around 100 μm or more), the pattern may be formed via a mask of the desired shape during vapor deposition or sputtering of the electrode material. When using a coatable substance such as an organic conductive compound, wet film formation methods such as printing or coating can also be used. When extracting light from this anode, it is desirable to have a transmittance greater than 10%, and the sheet resistance of the anode is preferably several hundred Ω / □ or less. The film thickness depends on the material, but is usually selected within the range of 10 to 1000 nm, preferably 10 to 200 nm.

[0052] -cathode- On the other hand, cathode materials consist of metals with a low work function (4 eV or less) (referred to as electron-injection metals), alloys, electrically conductive compounds, or mixtures thereof. Specific examples of such electrode materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) mixtures, indium, lithium / aluminum mixtures, and rare earth metals. Among these, from the viewpoint of electron injection and durability against oxidation, mixtures of electron-injection metals with metalloids that have a higher work function and are more stable, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) mixtures, lithium / aluminum mixtures, and aluminum, are preferred. Cathodes can be fabricated by forming thin films of these cathode materials by methods such as vapor deposition or sputtering. Furthermore, the sheet resistance of the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. Furthermore, to allow the emitted light to pass through, it is advantageous if either the anode or cathode of the organic EL element is transparent or semi-transparent, as this improves the luminescence brightness.

[0053] Furthermore, by forming the above-mentioned metal on the cathode with a film thickness of 1 to 20 nm, and then forming the conductive transparent material mentioned in the description of the anode on top of it, a transparent or translucent cathode can be fabricated. By applying this, it is possible to fabricate an element in which both the anode and cathode are transparent.

[0054] -Emitting layer- The light-emitting layer is a layer that emits light after excitons are generated by the recombination of holes and electrons injected from the anode and cathode, respectively. The light-emitting layer may be a single layer or multiple layers, each containing an organic light-emitting dopant material and a host material.

[0055] The organic luminescent dopant may contain only one type or two or more types in the luminescent layer. The content of the organic luminescent dopant is preferably 0.1 to 50 w% relative to the host material, and more preferably 0.1 to 40 wt%.

[0056] When using phosphorescent dopants (also called phosphorescent materials) as organic luminescent dopant materials, the phosphorescent dopant should preferably contain an organometallic complex comprising at least one metal selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Specifically, iridium complexes described in J.Am.Chem.Soc.2001,123,4304 and JP 2013-530515 are preferably used, but are not limited to these.

[0057] Phosphorescent dopant materials are not particularly limited, but specific examples include the following:

[0058] [ka] [ka]

[0059] When using a fluorescent dopant as a luminescent dopant material, the fluorescent dopant is not particularly limited, but examples include condensed polycyclic aromatic derivatives, styrylamine derivatives, condensed ring amine derivatives, boron-containing compounds, pyrrole derivatives, indole derivatives, carbazole derivatives, and indrocarbazole derivatives. Among these, condensed ring amine derivatives, boron-containing compounds, carbazole derivatives, and indrocarbazole derivatives are preferred. Examples of condensed ring amine derivatives include diaminepyrene derivatives, diaminochrysene derivatives, diaminoanthracene derivatives, diaminofluorenone derivatives, and diaminofluorene derivatives having one or more benzoflo skeletons fused together. Examples of boron-containing compounds include pyromethene derivatives and triphenylborane derivatives.

[0060] Fluorescent dopant materials are not particularly limited, but specific examples include the following:

[0061] [ka] [ka]

[0062] When using a thermally activated delayed fluorescence dopant (also called a thermally activated delayed fluorescence material) as a luminescent dopant material, examples of thermally activated delayed fluorescence dopants are not particularly limited, but include metal complexes such as tin complexes and copper complexes, indolocarbazole derivatives described in WO2011 / 070963, cyanobenzene derivatives and carbazole derivatives described in Nature 2012, 492, 234, phenazine derivatives, oxadiazole derivatives, triazole derivatives, sulfone derivatives, phenoxazine derivatives, acridine derivatives described in Nature Photonics 2014, 8, 326, and arylborane derivatives described in Adv. Mater. 2016, 28, 2777.

[0063] Thermally activated delayed fluorescence dopant materials are not particularly limited, but specific examples include the following:

[0064] [ka] [ka]

[0065] It is preferable to use a compound represented by the general formula (1) as the host material in the light-emitting layer. It is preferable that the glass transition temperature of the compound represented by the general formula (1) is 120°C or higher. When the compound represented by the general formula (1) is used in any organic layer other than the light-emitting layer, known host materials used in phosphorescent light-emitting devices and fluorescent light-emitting devices can be used in addition to the compound represented by the general formula (1). Known host materials that can be used are compounds that have hole transport ability, electron transport ability, and a high glass transition temperature, and it is preferable that they have a triplet excitation energy (T1) that is greater than the triplet excitation energy (T1) of the light-emitting dopant material. In addition, a compound with TADF activity may be used as the host material, in which case a compound in which the difference between the singlet excitation energy (S1) and the triplet excitation energy (T1) (ΔEST = S1 - T1) is 0.20 eV or less is preferred. Furthermore, the compound represented by the general formula (1) may be used in combination with other known host materials. Moreover, multiple types of known host materials may be used in combination.

[0066] Here, S1 and T1 are measured as follows: Vacuum deposition is performed on a quartz substrate at a vacuum level of 10 -4 A sample compound (thermally activated delayed fluorescence material) is deposited under conditions of Pa or less to form a deposited film with a thickness of 100 nm. S1 is calculated by measuring the emission spectrum of this deposited film, drawing a tangent to the rising edge on the short wavelength side of the emission spectrum, and substituting the wavelength value λedge [nm] at the intersection of the tangent and the horizontal axis into the following equation (i). S1[eV] = 1239.85 / λedge (i)

[0067] On the other hand, T1 is calculated by measuring the phosphorescence spectrum of the deposited film, drawing a tangent to the rising edge of the short-wavelength side of this phosphorescence spectrum, and substituting the wavelength value λedge [nm] at the intersection of the tangent and the horizontal axis into equation (ii). T1[eV] = 1239.85 / λedge (ii)

[0068] Known host materials are available through numerous patent documents and other sources, and can be selected from among them. Specific examples of host materials are not limited to indole compounds, carbazole compounds, indrocarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, triazole compounds, oxazole compounds, oxadiazole compounds, imidazole compounds, phenylenediamine compounds, arylamine compounds, anthracene compounds, fluorenone compounds, stilbene compounds, triphenylene compounds, carborane compounds, porphyrin compounds, phthalocyanine compounds, metal complexes of 8-quinolinol compounds and metal phthalocyanines, various metal complexes represented by metal complexes of benzoxazole and benzothiazole compounds, poly(N-vinylcarbazole) compounds, aniline copolymers, thiophene oligomers, polythiophene compounds, polyphenylene compounds, polyphenylene vinylene compounds, polyfluorene compounds, and other polymer compounds. Preferably, examples include carbazole compounds, indrocarbazole compounds, pyridine compounds, pyrimidine compounds, triazine compounds, anthracene compounds, triphenylene compounds, carborane compounds, and porphyrin compounds.

[0069] While there are no specific limitations to what constitutes a desirable host, some examples include the following: [ka] [ka] [ka]

[0070] Furthermore, when using the compound represented by general formula (1) in combination with other known host materials, it is preferable to use the compound represented by general formula (1) as the first host and combine it with an electron-transporting compound as the second host, since the compound represented by general formula (1) has good hole injection transport properties. The electron-transporting compound is not particularly limited, but triazine compounds are preferred. Suitable triazine compounds for such second hosts will be described later.

[0071] When using multiple types of hosts, each host can be deposited from a different deposition source, or multiple types of hosts can be deposited simultaneously from a single deposition source by pre-mixing them into a premixture before deposition.

[0072] When using a pre-mixed first and second host, in order to reproducibly fabricate organic EL elements with good characteristics, the 50% weight loss temperature (T) is used. 50 A small difference in weight is desirable. The 50% weight loss temperature is the temperature at which the weight decreases by 50% when the temperature is raised from room temperature to 550°C at a rate of 10°C per minute in TG-DTA measurements under reduced pressure with a nitrogen flow (1 Pa). Around this temperature, vaporization by evaporation or sublimation is thought to occur most actively.

[0073] Preferably, the difference in the 50% weight loss temperature between the first host and the second host in the premixture is within 20°C. By vaporizing this premixture from a single evaporation source and depositing it, a uniform deposited film can be obtained. In this case, the premixture may contain luminescent dopant material necessary for forming the luminescent layer or other hosts used as needed, but if there is a large difference in the temperature at which the desired vapor pressure is reached, it is preferable to deposit it from a different deposition source.

[0074] Furthermore, the mixing ratio (weight ratio) of the first host to the second host is preferably 40-70%, with the first host making up 40-80% of the total volume of the first and second hosts.

[0075] For pre-mixing, a method that allows for as uniform a mixture as possible is desirable. Examples include grinding and mixing, heating and melting under reduced pressure or inert gas atmosphere such as nitrogen, and sublimation, but the method is not limited to these.

[0076] The host and its premixture may be in the form of a powder, stick, or granules.

[0077] Here, when the light-emitting layer contains two or more host materials and the compound represented by general formula (1) is used as the first host, the second host can be a compound represented by any of the following general formulas (14) to (20), and it is preferable that the compound represented by the following general formulas (14) to (20) is an electron-transporting compound. [ka]

[0078] Here Ar 3 ~Ar 20 Each of these independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of two to three aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. Preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of two to three aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. More preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of two to three aromatic groups selected from the aromatic hydrocarbon group and the aromatic hydrocarbon group.

[0079] Unsubstituted Ar 3 ~Ar 20Specific examples include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzoisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or linked aromatic groups in which 2 to 3 of these aromatic groups are linked together. Preferably, the aromatic groups include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzoisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or linked aromatic groups in which 2 to 3 of these aromatic groups are linked together. More preferably, the aromatic groups include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, or linked aromatic groups in which 2 to 3 of these aromatic groups are linked together.

[0080] Ar 21 and Ar 22Each of these independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of two to three aromatic groups selected from the aromatic heterocyclic group. Preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of two to three aromatic groups selected from the aromatic heterocyclic group. More preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 15 carbon atoms, or a substituted or unsubstituted linked aromatic group composed of two to three aromatic groups selected from the aromatic hydrocarbon group.

[0081] Unsubstituted Ar 21 and Ar 22 A specific example is the unsubstituted Ar, except that the aromatic heterocyclic group has 2 to 17 carbon atoms. 3 ~Ar 20 The same applies as described above. Preferably, examples include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, thiadiazole, phthalazine, tetrazole, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzoisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or linked aromatic groups in which 2 to 3 of these aromatic groups are linked together. More preferably, the aromatic groups include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, phenanthrene, fluorene, or linked aromatic groups in which 2 to 3 of these aromatic groups are linked together.

[0082] The above-mentioned unsubstituted aromatic hydrocarbon groups, aromatic heterocyclic groups, or linked aromatic groups may each have substituents. If substituents are present, preferred substituents are deuterium, halogens, cyano groups, C1-C10 alkyl groups, C9-C30 triarylsilyl groups, C2-C5 alkenyl groups, C1-C5 alkoxy groups, or C12-C44 diarylamino groups.

[0083] The number of substituents is preferably 0 to 5, more preferably 0 to 2. When calculating the number of carbon atoms in an aromatic hydrocarbon group, aromatic heterocyclic group, or linked aromatic group that has substituents, the number of carbon atoms of the substituents is not included. However, it is preferable that the total number of carbon atoms including the number of carbon atoms of the substituents satisfies the above range.

[0084] Specific examples of the above substituents include deuterium, cyano, bromo, fluorine, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, triphenylsilyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenylenylamino, dipyrenylamino, etc. Preferably, deuterium, cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, vinyl, propenyl, butenyl, pentenyl, methoxy, ethoxy, propoxy, butoxy, and pentoxy are used.

[0085] In this specification, a linked aromatic group refers to an aromatic group formed by the single bond between the carbon atoms of the aromatic rings of two or more aromatic groups. These linked aromatic groups may be linear or branched. The linking position when benzene rings are linked may be ortho, meta, or para, but para or meta linking is preferred. The aromatic groups may be aromatic hydrocarbon groups or aromatic heterocyclic groups, and the multiple aromatic groups may be the same or different.

[0086] In the present invention and known host materials that can be used in combination, the hydrogen in the compounds used may be deuterium. That is, in addition to the hydrogen on the aromatic ring and the hydrogen in the t-Bu group in compounds represented by general formulas (1) to (20), Ar 1 ~Ar 22 The hydrogen atoms on the aromatic ring, and furthermore, some or all of the hydrogen atoms on the aromatic ring or in the substituents of known host materials that can be used in combination, may be deuterium.

[0087] -Injection layer- An injection layer is a layer provided between the electrode and the organic layer to reduce the driving voltage and improve the luminescence brightness. There are hole injection layers and electron injection layers, and they may be present between the anode and the light-emitting layer or hole transport layer, and between the cathode and the light-emitting layer or electron transport layer. The injection layer can be provided as needed.

[0088] -Hole blocking layer- In a broad sense, a hole-blocking layer functions as an electron-transport layer. It consists of a hole-blocking material that has the ability to transport electrons while significantly reducing its ability to transport holes. By blocking holes while transporting electrons, it can improve the probability of electron-hole recombination in the light-emitting layer. Known hole-blocking materials can be used for the hole-blocking layer. Multiple types of hole-blocking materials may also be used in combination.

[0089] -Electron blocking layer- In a broad sense, an electron blocking layer functions as a hole transport layer, improving the probability of electron-hole recombination in the light-emitting layer by blocking electrons while transporting holes. While it is preferable to use a compound represented by general formula (1) as the material for the electron blocking layer, known electron blocking layer materials can also be used. When using a compound represented by general formula (1) as the electron blocking layer, the host material may be the compound represented by general formula (1), the known host materials mentioned above, or a combination of several of these.

[0090] Layers adjacent to the light-emitting layer include hole blocking layers and electron blocking layers. However, if these layers cannot be provided, hole transport layers and electron transport layers become the adjacent layers.

[0091] - Hole transport layer - A hole transport layer consists of a hole transport material that has the function of transporting holes, and the hole transport layer can be a single layer or multiple layers.

[0092] The hole transport material has either hole injection or transport, or electron barrier properties, and may be either organic or inorganic. While it is preferable to use a compound represented by the general formula (1) in the hole transport layer, any compound from conventionally known compounds can also be selected and used. Examples of such hole transport materials include porphyrin derivatives, arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. When using a compound represented by the general formula (1) in the hole transport layer, the host material may be the compound represented by the general formula (1), the known host materials mentioned above, or a combination of several of these.

[0093] -Electron transport layer- An electron transport layer consists of a material that has the function of transporting electrons, and the electron transport layer can consist of a single layer or multiple layers.

[0094] The electron transport material (which may also serve as a hole-blocking material) only needs to have the function of transferring electrons injected from the cathode to the light-emitting layer. Any compound from conventionally known compounds can be selected and used for the electron transport layer. Examples include polycyclic aromatic derivatives such as naphthalene, anthracene, and phenanthroline; tris(8-quinolinolate)aluminum(III) derivatives; phosphine oxide derivatives; nitro-substituted fluorene derivatives; diphenylquinone derivatives; thiopyrandioxide derivatives; carbodiimide; phreolenylidenemethane derivatives; anthraquinodimethane and anthrone derivatives; bipyridine derivatives; quinoline derivatives; oxadiazole derivatives; benzimidazole derivatives; benzothiazole derivatives; and indolocarbazole derivatives. Furthermore, polymer materials can be used in which these materials are incorporated into polymer chains, or in which these materials are used as the main chain of the polymer.

[0095] The method for fabricating each layer of the organic EL element of the present invention is not particularly limited, and may be fabricated using either a dry process or a wet process. [Examples]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [ka] [ka]

[0097] Synthesis Example 1 [ka]

[0098] As shown in the reaction equation above, under a nitrogen atmosphere, 5.0 g of starting material (A), 5.0 g of starting material (B), 5.0 g of copper, 18.6 g of potassium carbonate, and 100 ml of DMI (1,3-dimethyl-2-imidazolidinone) were placed in a three-necked flask and stirred at 200°C for 66 hours. After the reaction solution was cooled to room temperature, the reaction solution was placed in a flask containing 800 ml of water and stirred for 1 hour. The precipitated solid was filtered off, dissolved in dichloromethane, washed with water, and then concentrated. The concentrate was purified by silica gel column chromatography and recrystallization, and the resulting solid was dried to obtain 6.5 g of compound (1) (yield: 86%). APCI-TOFMS m / z 617 [M+1]

[0099] Synthesis Example 2 [ka]

[0100] As shown in the reaction equation above, under a nitrogen atmosphere, 5.0 g of starting material (A), 13.2 g of starting material (C), 5.0 g of copper, 18.6 g of potassium carbonate, and 200 ml of DMI were placed in a three-necked flask and stirred at 200°C for 39 hours. After the reaction solution was cooled to room temperature, the reaction solution was placed in a flask containing 800 ml of water and stirred for 1 hour. After filtering off the precipitated solid, it was dissolved in dichloromethane, washed with water, and concentrated. The concentrate was purified by silica gel column chromatography and recrystallization, and the resulting solid was dried to obtain compound (47) 2.4 g (yield: 32%). APCI-TOFMS m / z 617 [M+1]

[0101] Table 1 shows the glass transition temperatures of the aforementioned compound and the following compound. [ka]

[0102] [Table 1]

[0103] Example 1 On a glass substrate on which an anode made of ITO with a thickness of 70 nm has been formed, the following thin films are deposited by vacuum deposition at a vacuum of 4.0 × 10⁻⁶ -5 The layers were stacked using Pa. First, the previously shown HAT-CN was formed on ITO to a thickness of 10 nm as a hole injection layer, and then HT-1 was formed to a thickness of 25 nm as a hole transport layer. Next, HT-2 was formed to a thickness of 5 nm as an electron blocking layer. Then, compound (1) was co-deposited as a host and BD-1 as a thermally activated delayed fluorescence dopant from different deposition sources to form an emissive layer with a thickness of 30 nm. At this time, co-depositing was performed under deposition conditions that resulted in a BD-1 concentration of 2 wt%. Next, ET-2 was formed to a thickness of 5 nm as a hole blocking layer. Next, ET-1 was formed to a thickness of 40 nm as an electron transport layer. Furthermore, lithium fluoride (LiF) was formed to a thickness of 1 nm as an electron injection layer on the electron transport layer. Finally, aluminum (Al) was formed to a thickness of 70 nm as a cathode on the electron injection layer to fabricate the organic EL device according to Example 1.

[0104] Comparative Example 1 Except for using BH-1 as the host, an organic EL element was fabricated in the same manner as in Example 1.

[0105] Example 2 On a glass substrate on which an anode made of ITO with a thickness of 70 nm has been formed, the following thin films are deposited by vacuum deposition at a vacuum of 4.0 × 10⁻⁶ -5The layers were stacked using Pa. First, the previously shown HAT-CN was formed on ITO to a thickness of 10 nm as a hole injection layer, and then HT-1 was formed to a thickness of 25 nm as a hole transport layer. Next, HT-2 was formed to a thickness of 5 nm as an electron blocking layer. Then, compound (1) was co-deposited as the first host, BH-6 as the second host, and BD-1 as a thermally activated delayed fluorescence dopant from different deposition sources to form an emissive layer with a thickness of 30 nm. At this time, co-depositing was performed under deposition conditions where the concentration of BD-1 was 2 wt% and the weight ratio of the first host to the second host was 70:30. Next, ET-2 was formed to a thickness of 5 nm as a hole blocking layer. Next, ET-1 was formed to a thickness of 40 nm as an electron transport layer. Furthermore, lithium fluoride (LiF) was formed to a thickness of 1 nm as an electron injection layer on the electron transport layer. Finally, an aluminum (Al) cathode was formed on the electron injection layer to a thickness of 70 nm to create the organic EL device according to Example 1.

[0106] Examples 3-12, Comparative Examples 2-5 An organic EL device was fabricated in the same manner as in Example 2, except that the electron blocking layer material, the first host, and the second host were the compounds shown in Table 2.

[0107] [Table 2]

[0108] Table 3 shows the emission color, voltage, power efficiency, and lifespan of the organic EL elements fabricated in the examples and comparative examples. The emission color, voltage, and luminous efficiency are based on a current density of 2.5 mA / cm². 2 This is the value at time and represents the initial characteristics. The lifespan is determined by a current density of 2.5 mA / cm². 2 The time it took for the brightness to decay to 50% of the initial brightness was measured.

[0109] [Table 3]

[0110] From the examples and comparative examples in Table 2, it can be seen that an organic electroluminescent element using the material for organic electroluminescent elements of the present invention as an electron blocking layer or host in an organic EL element containing a thermally activated delayed fluorescence emitting material in the light-emitting layer emits blue light and has characteristics of low voltage, high efficiency, and long lifespan.

[0111] Example 13 Each thin film is deposited on a glass substrate with an anode made of ITO with a thickness of 110 nm using vacuum deposition at a vacuum level of 4.0 × 10⁻⁶. -5 The layers were stacked using Pa. First, a 25nm thick layer of HAT-CN was formed on ITO as a hole injection layer, followed by a 30nm thick layer of HT-3 as a hole transport layer. Next, a 10nm thick layer of BH-1 was formed as an electron blocking layer. Compound (1) was co-deposited as the first host, BH-5 as the second host, and GD-1 as a phosphorescent dopant from different deposition sources to form a 40nm thick light-emitting layer. At this time, the co-deposit conditions were such that the concentration of GD-1 was 5wt% and the weight ratio of the first and second hosts was 50:50. Then, an ET-1 layer was formed to a 20nm thick electron transport layer. Furthermore, a 1nm thick layer of lithium fluoride (LiF) was formed on the electron transport layer as an electron injection layer. Finally, a 70nm thick layer of aluminum (Al) was formed on the electron injection layer as a cathode to fabricate an organic EL device.

[0112] Examples 14-18, Comparative Examples 6-9 An organic EL device was fabricated in the same manner as in Example 13, except that the electron blocking layer material, the first host, and the second host were the compounds shown in Table 4.

[0113] [Table 4]

[0114] Table 5 shows the emission color, voltage, power efficiency, and lifespan of the organic EL elements fabricated in the examples and comparative examples. The emission color, voltage, and luminous efficiency are determined at a current density of 20 mA / cm². 2 This is the value at time and represents the initial characteristics. The lifespan is based on a current density of 20 mA / cm². 2The time it took for the brightness to decay to 95% of the initial brightness was measured.

[0115] [Table 5]

[0116] From the examples and comparative examples in Table 4, it can be seen that an organic electroluminescent element using the organic electroluminescent element material of the present invention as an electron blocking layer or host in an organic EL element containing a phosphorescent material in the light-emitting layer emits green light and has characteristics of low voltage, high efficiency, and long lifespan.

[0117] Example 19 Each thin film is deposited on a glass substrate with an anode made of ITO with a thickness of 110 nm using vacuum deposition at a vacuum level of 4.0 × 10⁻⁶. -5 The layers were stacked using Pa. First, a 25nm thick layer of HAT-CN was formed on ITO as a hole injection layer, followed by a 45nm thick layer of HT-3 as a hole transport layer. Next, a 10nm thick layer of BH-1 was formed as an electron blocking layer. Compound (1) was co-deposited as the first host, BH-5 as the second host, and RD-1 as a phosphorescent dopant from different deposition sources to form a 40nm thick light-emitting layer. At this time, the co-deposit conditions were such that the concentration of RD-1 was 3wt% and the weight ratio of the first and second hosts was 50:50. Then, an ET-1 layer was formed to a 40nm thick electron transport layer. Furthermore, a 1nm thick layer of lithium fluoride (LiF) was formed on the electron transport layer as an electron injection layer. Finally, a 70nm thick layer of aluminum (Al) was formed on the electron injection layer as a cathode to fabricate an organic EL device.

[0118] Examples 20-24, Comparative Examples 10-13 An organic EL device was fabricated in the same manner as in Example 19, except that the electron blocking layer material, the first host, and the second host were the compounds shown in Table 6.

[0119] [Table 6]

[0120] Table 7 shows the emission color, voltage, power efficiency, and lifespan of the organic EL elements fabricated in the examples and comparative examples. The emission color, voltage, and luminous efficiency are based on a current density of 20 mA / cm². 2 This is the value at time and represents the initial characteristics. The lifespan is based on a current density of 40 mA / cm². 2 The time it took for the brightness to decay to 95% of the initial brightness was measured.

[0121] [Table 7]

[0122] From the examples and comparative examples in Table 7, it can be seen that an organic electroluminescent element using the organic electroluminescent element material of the present invention as an electron blocking layer or host in an organic EL element containing a phosphorescent material in the light-emitting layer emits red light and has characteristics of low voltage, high efficiency, and long lifespan. [Industrial applicability]

[0123] The present invention makes it possible to obtain a practically useful organic EL element that emits light with high efficiency and possesses high driving stability and long lifespan characteristics. [Explanation of symbols]

[0124] 1. Substrate, 2. Anode, 3. Hole injection layer, 4. Hole transport layer, 5. Light-emitting layer, 6. Electron transport layer, 7. Cathode

Claims

1. A material for an organic electroluminescent device, represented by the following general formula (1). 【Chemistry 1】 (Ar １ is a group represented by any of the following general formulas (2) to (11), where * represents a bond point. Some or all of the hydrogen atoms in the compounds represented by general formula (1) and general formulas (2) to (11) may be substituted with deuterium atoms. n represents an integer between 0 and 1. 【Chemistry 2】 (Ar ２ X represents an unsubstituted phenyl group or an unsubstituted biphenyl group. １ This represents sulfur. X ２ (This represents unsubstituted N-phenyl, unsubstituted N-biphenyl, unsubstituted N-terphenyl, oxygen, or sulfur.)

2. The material for an organic electroluminescent element according to claim 1, characterized in that n is 0 in the general formula (1).

3. The material for an organic electroluminescent element according to claim 2, characterized in that the general formula (1) is represented by the following general formula (12). 【Transformation 3】 (Here, Ar １ This is equivalent to the above general formula (1). The hydrogen atoms in the compound represented by the above general formula (12) may be substituted with deuterium atoms.

4. Ar in the general formula (1) １ However, the material for an organic electroluminescent element according to claim 1, characterized by being represented by the general formula (2) or (3).

5. Ar in the general formula (12) １ However, the material for an organic electroluminescent element according to claim 3, characterized by being represented by the general formula (2) or (3).

6. The material for an organic electroluminescent element according to claim 1, characterized in that the general formula (1) is represented by the following general formula (13). 【Chemistry 4】 (Here, Ar ２ This is equivalent to the above general formula (1). The hydrogen atoms in the compound represented by the above general formula (13) may be substituted with deuterium atoms.

7. An organic electroluminescent element comprising one or more organic layers between opposing anodes and cathodes, characterized in that at least one organic layer contains the organic electroluminescent element material described in claim 1.

8. The organic electroluminescent element according to claim 7, characterized in that at least one of the organic layers is a light-emitting layer, and the light-emitting layer separately contains a thermally activated delayed fluorescence light-emitting material.

9. The organic electroluminescent element according to claim 7, characterized in that at least one of the organic layers is a light-emitting layer, and the light-emitting layer separately contains a phosphorescent light-emitting material.

10. The organic electroluminescent device according to claim 7, characterized in that at least one of the organic layers is an emissive layer, the emissive layer contains one or more host materials, and at least one host material is the organic electroluminescent device material according to claim 1.

11. The organic electroluminescent device according to claim 7, characterized in that at least one of the organic layers is an emissive layer, the emissive layer contains two or more host materials, the first host is the organic electroluminescent device material according to claim 1, and the second host is a compound represented by any of the following general formulas (14) to (20). 【Transformation 5】 (Here, Ar ３ ~Ar ２０ each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 20 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. Ar ２１ and Ar ２２ each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 20 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 2 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 aromatic groups selected from the aromatic hydrocarbon group and the aromatic heterocyclic group. The hydrogen atoms in the compounds represented by the general formulas (14) to (20) may be substituted with deuterium atoms.)

12. The organic electroluminescent element according to claim 7, characterized in that at least one of the organic layers is an electron blocking layer or a hole transport layer, and the electron blocking layer or the hole transport layer contains the organic electroluminescent element material according to claim 1.

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