JP2008166538A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element of high brightness and high durability by incorporating an organic material having high film formation property, high carrier mobility and thermal stability. <P>SOLUTION: The organic EL element exhibits high light output and high durability by incorporating a compound No.1-1, for example (a compound expressed by a general formula (1) wherein R1 to R4 are methyl group). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent element used for a display, an illumination light source, an exposure light source of a copying machine, a display board, a marker lamp, and the like.

An organic electroluminescent element (hereinafter abbreviated as an organic EL element) is a fluorescent compound formed by sandwiching a thin film material containing a fluorescent organic compound between an anode and a cathode and injecting holes and electrons from each electrode. An element that generates excitons and uses light emitted when the excitons return to the ground state. The electroluminescent phenomenon of organic materials was first observed by Pope et al. In 1963 in anthracene single crystals (Non-Patent Document 1), followed by 1965 Helfinch and Schneider in a solution electrode system with good injection efficiency and relatively strong injection type EL. Has been successfully observed (Non-patent Document 2). Since then, organic fluorescent substances consisting of conjugated organic host compounds and conjugated organic activators having condensed benzene rings have been actively researched. Naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzopyrene, chrysene are used as organic host compounds. Various organic fluorescent substances using, for example, anthracene, tetracene, pentacene and the like as organic activators have been tried (Patent Document 1), picene, carbazole, fluorene, biphenyl, terphenyl and the like. However, all of these organic fluorescent materials are single layers having a thickness exceeding 1 μm, and a high electric field is required for light emission. Therefore, research on a thin film element was advanced (Non-patent Document 3).

In recent years, Tang et al. Have devised an organic EL element in which a very thin charge transport layer and a light emitting layer are stacked by vacuum deposition between a pair of electrodes, and have achieved high luminance with a low driving voltage (Non-Patent Document 4). Currently, with the growing demand for flat panel displays, music players, etc., various display elements are being developed and put to practical use. Of these, organic EL elements with high resolution, high brightness, and high visibility are particularly focused. Gathered. Organic EL elements have the disadvantage of a shorter lifetime than inorganic EL elements, but they can be driven at a low voltage, can be applied to a wide range of wavelengths, can have a large area, and have high brightness. There are advantages such as that, and applications such as displays, various light sources, and illumination are being studied.

The characteristics required for the organic material used for the organic EL element are (1) heat stable and stable amorphous state, (2) a good quality thin film without pinholes, (3) electrical, Examples thereof include chemical stability, (4) no decomposition during vapor deposition, and (5) excellent charge transport ability or light emission ability. In order to obtain a light output with a high luminance and a device with a long lifetime, a material having a high charge injection efficiency, a material having a high charge transport capability, and a material having a high quantum yield of light emission, or a material having both of them is suitable. Need to be combined in a proper contact state.
The charge transport capability is evaluated by the moving speed per unit electric field of carriers, and is called carrier drift mobility. The higher the carrier drift mobility, the more efficiently the holes can move in the charge transport layer, so that there is a possibility that light emission with high luminance can be obtained. The drift mobility is specific to the charge transport material under a certain temperature and applied voltage condition. Therefore, it is preferable to use a material having a high carrier mobility in order to achieve a high luminance light output of the organic EL element. However, at present, no compound having high mobility, film-forming property, and sufficient thermal stability has been found.
Conventionally, some organic materials for organic EL devices using a p-terphenyl compound having excellent carrier mobility have been proposed (for example, Patent Documents 2 to 6). However, carrier mobility and thermal stability cannot be said to be sufficient, and even if the thermal stability is improved, the solubility in the solvent becomes extremely low and purification is difficult. Yes.

“Journal of Physical Chemistry” 1963, 38, 2042 “Physical Review Letters” 1965, 14, 229 “Thin Solid Films” 1982, 94, 171 “Applied Physics Letters” 1987, 51, 913 U.S. Pat. No. 3,170,167 JP-A-11-35532 JP 11-167991 A JP 2001-52868 A JP 2004-339134 A International Publication No. 2005/063684

An object of the present invention is to provide an organic EL device excellent in high luminance and durability by containing an organic material having high film forming property, high carrier mobility and thermal stability.
As a result of diligent efforts, the present inventors have not disclosed the compound in the prior literature, and among the p-terphenyl compounds, only those having a structure limited to the compound of the present invention exhibit extremely high carrier transport ability. I found out for the first time. And by containing the compound of this invention in an organic EL element, high-intensity light output and lifetime improvement were achieved, and this invention was completed.

That is, the above object of the present invention is achieved by the following configuration.
(I) In an organic electroluminescent device in which one or more organic thin film layers including at least a light emitting layer are formed between a pair of electrodes, at least one layer of the organic thin film layer is represented by the general formula (1) An organic electroluminescent device comprising an amine compound.

式中、Ｒ１〜Ｒ４は各々独立して直鎖または環状アルキル基、アリールアルキル基、アリールアルケニル基を表す。
（ｉｉ）一般式（１）で示されるアリールアミン化合物を含有する有機薄膜層が発光層、ホール輸送層、ホール注入層からなる群より選択されることを特徴とする（ｉ）の有機電界発光素子。
（ｉｉｉ）一般式（１）で示されるアリールアミン化合物のＲ１〜Ｒ４が炭素数１〜４の低級アルキル基から選択されることを特徴とする（ｉ）〜（ｉｉ）の有機電界発光素子。

In the formula, R1 to R4 each independently represent a linear or cyclic alkyl group, an arylalkyl group, or an arylalkenyl group.
(Ii) The organic electroluminescence according to (i), wherein the organic thin film layer containing the arylamine compound represented by the general formula (1) is selected from the group consisting of a light emitting layer, a hole transport layer, and a hole injection layer element.
(Iii) The organic electroluminescent device according to (i) to (ii), wherein R1 to R4 of the arylamine compound represented by the general formula (1) are selected from lower alkyl groups having 1 to 4 carbon atoms.

  The organic EL device of the present invention exhibits high light output, is highly durable, and has excellent characteristics.

Hereinafter, the present invention will be described in more detail.
The organic electroluminescent element of the present invention has one or more organic thin film layers between a pair of electrodes, and at least one layer of the organic thin film layer contains an arylamine compound represented by the above general formula (1) It is.
In the general formula (1), R1 to R4 are specifically linear alkyl groups having 1 to 20 carbon atoms such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, hexadecyl, octadecyl, and the like; Cyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl; arylalkyl groups such as benzyl, naphthylmethyl, phenethyl, anthrylethyl, phenylpropyl, naphthylbutyl, phenanthrylpentyl, phenylhexyl, naphthyloctyl; An arylalkenyl group such as styryl, diphenylvinyl, naphthylvinyl, phenylbutadienyl, diphenylbutadienyl, phenylhexatrienyl, naphthyloctatetraenyl and the like is represented.
The compound represented by the general formula (1) exhibits extremely high carrier mobility, but if R1 to R4 are long chain alkyl groups, the glass transition temperature is lowered, and the heat resistance tends to be lowered accordingly. The glass transition temperature is an upper limit temperature at which the material can exist in an amorphous state. Generally, when the glass transition temperature of the material is low, the element is rapidly deteriorated and it is difficult to obtain a highly durable element. Therefore, from the point of durability of the device, R1 to R4 are preferably a linear alkyl group having 1 to 8 carbon atoms, and more preferably a linear alkyl group having 1 to 4 carbon atoms.

The combination of R1 to R4 is preferably a combination in which R1 and R3, R2 and R4 are the same, or all of R1 to R4 are the same. From the viewpoint of durability, in the present invention, at least one of R1 to R4 is preferably a linear alkyl group having 4 or less carbon atoms.
Specific examples of the compound (1) are shown in Table 1 below. However, this is an example of the compound (1) of the present invention, and the present invention is not limited to the compounds shown in Table 1 below. In Table 1, Me represents methyl, Et represents ethyl, n-Pr represents n-propyl, and n-Bu represents n-butyl.

Next, the manufacturing method of the compound (1) of this invention is demonstrated. Compound (1) of the present invention can be synthesized by combining conventionally known methods. As an example of the synthesis method, a synthesis example in the case where R1 and R3 and R2 and R4 are the same is shown below.

In the above formula, R1 and R2 represent the same meaning as described above. X represents a chlorine, bromine, or iodine atom.
In the above synthesis method, first, the aniline compound (2) is reacted with acetic anhydride to synthesize the amide derivative (3). Next, the resulting amide derivative (3) and halogenobenzene compound (4) are led to the compound (5) by the Ullmann reaction, and then hydrolyzed with a base to obtain the diarylamine compound (6). Next, a method of reacting dihalo-p-terphenyl (7) in the presence of a copper catalyst (Japanese Patent Application Laid-Open No. 2005-350416, etc.), or a coupling reaction with dihalo-p-terphenyl (7) using a palladium catalyst (J. Org. Chem., 2000, 65, 5327) and the like, the target compound (1A) can be obtained.
In the above, various starting aniline compounds (2) are commercially available and are readily available. The other starting material, dihalo-p-terphenyl (7), can also be easily derived from p-terphenyl by a known method (JP-A-11-128739, etc.).
On the other hand, when all the substituents of R1 to R4 are the same, the aniline compound (2) is condensed with each other in the presence of an aluminum chloride catalyst to obtain a diarylamine compound (6a). -By reacting terphenyl (7), the target compound (1a) can be synthesized more easily.

In the above formula, R 1 and X represent the same meaning as described above.
Conditions such as raw material molar ratio, reaction solvent, reaction temperature and the like in the above two reactions may be carried out according to known methods.
In addition, even when R1 to R4 are all different or a combination of R1 to R4 other than the above, they can be synthesized according to the above synthesis method.
Furthermore, the compound of the present invention can be easily purified in the production process, and by using it, an organic EL device having high luminance and high durability can be obtained.

Next, the organic electroluminescent element containing the compound of the present invention will be described in detail.
In the organic electroluminescent element of the present invention, the organic thin film layer to be formed may be a layer having one function or a layer having another function. For example, when the compound used for the light emitting layer also has a hole injection function, a hole transport function (and / or an electron injection function), an electron transport function, etc., a hole injection / transport function (and / or an electron in the light emitting layer) It is possible to obtain a single-layer element configuration including an injection transport function. On the other hand, when the compound used for the light emitting layer is poor in the hole injection function and / or the hole transport function, a two-layer device configuration in which a hole injection transport layer is provided on the anode side of the light emitting layer can be obtained. If the electron transport function is poor, a two-layer device structure in which an electron injection transport layer is provided on the cathode side of the light emitting layer can be obtained. Furthermore, a three-layer type device configuration in which the light emitting layer is sandwiched between a hole injection transport layer and an electron injection transport layer may be used. Each of the hole injecting and transporting layer, the electron injecting and transporting layer, and the light emitting layer may have a single layer structure or a multilayer structure, and the hole injecting and transporting layer and the electron injecting and transporting layer each have a charge injection function. A structure in which a layer and a layer having a charge transporting function are provided separately can also be employed.

Further, the element configuration will be described in detail.
The element structure in the organic electroluminescent element of the present invention is not particularly limited. For example, anode / hole injection / transport layer / light emitting layer / electron injection / transport layer / cathode type element (FIG. 1), anode / hole injection / transport layer / Light emitting layer / cathode type element (FIG. 2), anode / light emitting layer / electron injection / transport layer / cathode type element (FIG. 3), anode / light emitting layer / cathode type element (FIG. 4), and the like. In the single-layer element configuration of FIG. 4, for example, an element in which a light-emitting component is sandwiched between a pair of electrodes as a light-emitting layer, and a pair of electrodes in a single-layer form in which a hole injection transport component and a light-emitting component are mixed as a light-emitting layer. Examples include an element sandwiched between a pair of electrodes in a single layer form in which a light emitting component and an electron injecting and transporting component are mixed as a light emitting layer.

In the present invention, the object can be achieved by incorporating the compound (1) in the organic thin film layer. This is because the object compound (1) is a light emitting layer provided between a pair of electrodes of an anode and a cathode, and further required. The hole injection layer, the hole transport layer, the electron transport layer, the electron injection layer, and the like provided according to the above may be contained at least one kind, and two or more kinds may be used in appropriate combination.
Among these, the compound (1) of the present invention is particularly useful as an organic material for forming a hole injection layer, a hole transport layer, and a light emitting layer, and is preferably contained in the hole injection layer and / or the hole transport layer. Further, the compound (1) of the present invention and a known hole transporting compound can be mixed and used in a hole injection layer and / or a hole transporting layer. Can be used alone in each layer.

The known hole transporting compound that can be used alone or mixed with the compound (1) of the present invention is not particularly limited, but for example, tertiary such as 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane Aromatic diamine compounds in which aromatic amine units are linked (Japanese Patent Laid-Open No. 59-194393, etc.); two or more typified by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl An aromatic amine having a starburst structure with a triphenylbenzene derivative (US Pat. No. 5,234,681); 4,923,774 etc.); aromatic diamines such as N, N′-diphenyl-N, N′-bis (3-methylphenyl) biphenyl-4,4′-diamine (rice Patent No. 4,764,625, etc.); a sterically asymmetric triphenylamine derivative as a whole molecule (JP-A-4-129271, etc.); a compound in which a pyrenyl group is substituted with a plurality of aromatic diamino groups (JP-A-4 1994) Aromatic diamines in which tertiary aromatic amine units are linked by ethylene groups (JP-A-4-264189, etc.); aromatic diamines having styryl groups (JP-A-4-290851, etc.); tertiary Aromatic amine units linked by a thiophene group (JP-A-4-304466, etc.); Starburst type aromatic triamine (JP-A-4-308688, etc.); Benzylphenyl compound (JP-A-4-364153, etc.); A tertiary amine linked by a fluorene group (JP-A-5-25473, etc.); a triamine compound (JP-A-5-23945) Bisdipyridylaminobiphenyl (JP-A-5-320634, etc.); N, N, N-triphenylamine derivatives (JP-A-6-1972, etc.); Aromatic diamines having a phenoxazine structure (JP-A-5-1993) Diaminophenylphenanthridine derivatives (JP-A-7-252474, etc.); hydrazone compounds (JP-A-2-311591, etc.); silazane compounds (US Pat. No. 4,950,950, etc.); Examples thereof include silanamine derivatives (JP-A-6-49079, etc.); phosphamine derivatives (JP-A-6-25659, etc.); quinacridone compounds and the like. These compounds may be used alone or in combination of two or more.

In addition to the above-mentioned compounds, polyvinylcarbazole, polysilane (Appl. Phys. Lett., 59, 2760, 1991), polyphosphazene (JP-A-5-310949, etc.), polyamide (JP-A-5-315) -310949, JP-A-5-310949, etc.), polyvinyltriphenylamine (JP-A-7-53953, etc.), a polymer in which triphenylamine units are linked by a methylene group or the like (Synthetic Metals, 55-57, 4163). Hole transport polymer compounds such as polymethacrylates containing aromatic amines (J. Polym. Sci., Polym. Chem. Ed., 21, 969, 1983) can be used. .
The thicknesses of the hole injection layer and the hole transport layer are not particularly limited, but are usually 1 nm to 3 μm, preferably 5 nm to 1 μm, and more preferably 10 nm to 500 nm.

The light emitting layer material used in the present invention is a compound that exhibits high fluorescence or phosphorescence quantum yield in the solid state and efficiently transports holes and / or electrons, and has been used in conventional organic EL devices. Can do. For example, a metal complex such as an aluminum complex of 8-hydroxyquinoline, a metal complex of 10-hydroxybenzo [h] quinoline, a bisstyrylbenzene derivative, a metal complex of (2-hydroxyphenyl) benzothiazole, a bipyridyl metal complex, phenyl, pyridine Examples include metal complexes and silole derivatives.

The electron injection layer and the electron transport layer used in the present invention may have any one of the function of injecting electrons from the cathode, the function of transmitting injected electrons, and the function of blocking holes injected from the anode. Those conventionally used in organic EL elements can be used. For example, a fluorenone derivative, an anthraquinodimethane derivative, a diphenylquinone derivative, a thiopyrandioxide derivative, an oxadiazole derivative, a triazole derivative, a fluorenylidenemethane derivative, an anthrone derivative, and the like can be given. Although the film thickness of an electron injection layer and an electron carrying layer is not specifically limited, Usually, 1 nm-3 micrometers, Preferably they are 5 nm-1 micrometer, More preferably, they are 10 nm-500 nm.
Further, it can be sensitized by adding an electron accepting substance to the hole transport material and an electron donating substance to the electron transport material.

Examples of the material constituting the support substrate include glass, transparent plastic, and quartz.
As a material constituting the anode, materials conventionally used in organic EL elements such as metals, alloys, metal oxides, electrically conductive compounds having a work function smaller than 4 eV can be used. For example, metal oxides such as indium tin oxide (ITO), tin oxide and zinc oxide; metals such as gold, silver, chromium and nickel; inorganic conductive materials such as copper iodide and copper sulfide; polyaniline, polythiophene and polypyrrole Examples include, but are not limited to, organic conductive materials. Of these, ITO is preferred. Since the anode emits light from the electrode, the light transmittance is preferably 10% or more, and the sheet resistance as the anode is preferably several hundred Ω / cm ² or less. The film thickness of the anode varies depending on the material, but is usually 1 nm to 5 μm, preferably 5 nm to 1 μm, more preferably 10 to 500 nm.

As a material constituting the cathode, materials conventionally used in organic EL elements such as metals, alloys, metal oxides, and electrically conductive compounds having a work function larger than 4 eV can be used. Specifically, alkali metals such as lithium, sodium and potassium or fluorides thereof; alkaline earth metals such as magnesium and calcium or fluorides thereof; metals such as gold, silver, lead and aluminum; sodium-potassium, lithium-aluminum And alloys such as magnesium-silver or mixed metals thereof; rare earth metals such as indium and ytterbium; and preferably aluminum, lithium-aluminum alloy, magnesium-silver alloy, and the like. The sheet resistance as the cathode is preferably several hundred Ω / cm ² or less. Although the film thickness of a cathode changes with materials, it is 1 nm-5 micrometers normally, Preferably it is 5 nm-1 micrometer, More preferably, it is 10-500 nm.

When manufacturing the organic EL device of the present invention, as a method for thinning, a coating method such as a spin coating method or a casting method, a vacuum deposition method, an LB method, a printing method, an ink jet method, or the like is used. Vapor deposition or spin coating is preferred. In the vacuum deposition method, for example, each material may be sequentially deposited on a support substrate on which ITO as an anode is formed in advance using, for example, a general vacuum deposition apparatus. Deposition conditions vary depending on the type of compound used, but the temperature of the supporting substrate is usually −50 to 300 ° C., the degree of vacuum is 1 × 10 ⁻⁶ to 1 × 10 ⁻² Pa, and the deposition rate is 0.01 to 50 nm / It is desirable to select appropriately within the range of minutes. In the case of the spin coating method, the coating solvent can be freely selected depending on the polymer, for example, alcohols such as methanol and ethanol, acids such as acetic acid, glycol solvents such as ethylene glycol,
Examples thereof include water, other highly polar solvents, aromatic hydrocarbons, halogenated hydrocarbons, and other low polarity solvents.

EXAMPLES Next, although this invention is further demonstrated using an Example, this invention is not limited to this.

Synthesis Example 1 Synthesis of Exemplary Compound No. 1-1 88.9 g (0.83 mol) of p-toluidine, 56 ml of 1,2,3,4-tetrahydronaphthalene, 25.6 g (0.23 mol) of anhydrous calcium chloride, Anhydrous aluminum chloride 30.8 g (0.23 mol) was charged and reacted at 210 to 220 ° C. for 4 hours in a nitrogen atmosphere. After the completion of the reaction, the reaction solution was cooled, and 130 ml of toluene was added to the reaction solution. The organic layer was washed with 100 ml of 5% aqueous sodium hydrogen carbonate solution and further washed with 100 ml of water, and the organic solvent was distilled off under reduced pressure. 70 ml of methanol was added thereto for crystallization, followed by filtration to obtain 56.2 g (yield 68.7%) of di (p-tolyl) amine as white crystals.

Next, glacial acetic acid 120 ml, water 60 ml, p-terphenyl 57.6 g (0.25 mol), iodine 32.5 g (0.26 mol), sodium chlorate 3.9 g (0.036 mol), concentrated sulfuric acid 9 ml was charged and reacted at 95-100 ° C. for 5 hours. After the reaction, 100 ml of toluene was added, and the organic layer was washed with 60 ml of 5% sodium thiosulfate. After washing with 100 ml of water and adding 150 ml of methanol for crystallization, the mixture was filtered to obtain 87.1 g (yield 72.3%) of diiodo-p-terphenyl as yellow crystals.

29.6 g (0.15 mol) of di (p-tolyl) amine, 24.7 g (0.05 mol) of diiodo-p-terphenyl, 0.098 g (0.40 mmol) of copper sulfate pentahydrate, carbonic acid Potassium (14.0 g, 0.10 mol) was charged, and the reaction was performed at an internal temperature of 220 to 230 ° C. for 3 hours under a nitrogen atmosphere. After the reaction, 120 ml of toluene and 60 ml of water were added and stirred. After standing, the organic layer and the aqueous layer were separated. After the organic layer was distilled off under reduced pressure, 120 ml of ethyl acetate was added for crystallization, followed by filtration to obtain crude crystals as slightly yellow crystals. The crude crystals were recrystallized from ethyl acetate to obtain 25.8 g (yield 83.2%) of the target compound.

Synthesis Example 2 Preparation of Exemplified Compound No. 1-4 70 ml of toluene and 78.7 g (0.53 mol) of 4-n-butylaniline were added, and 55.5 g (0.54 mol) of acetic anhydride was added dropwise under cooling. Thereafter, the reaction was carried out at an internal temperature of 90 to 95 ° C. for 1 hour. After cooling, 160 ml of water was added and stirred, and after standing, the organic layer and the aqueous layer were separated. The organic layer was distilled off under reduced pressure, and 200 ml of ethanol and 200 ml of water were added and separated after crystallization to obtain 91.1 g (yield 90.3%) of 4- (n-butyl) acetanilide as white crystals.

4- (n-butyl) acetanilide 83.7 g (0.44 mol), 4-bromotoluene 121.4 g (0.71 mol), copper sulfate pentahydrate 1.09 g (0.004 mol), sodium carbonate 35.3 g (0.33 mol) was charged, the temperature was raised to 210-220 ° C., and further, 255.1 g (1.49 mol) of 4-bromotoluene was added dropwise and reacted for 8 hours in a nitrogen atmosphere. After the reaction, 92 ml of water was added, stirred and allowed to stand, and then the organic layer and the aqueous layer were separated. 40 ml of ethanol and 51.6 g (0.92 mol) of potassium hydroxide were added thereto, and the mixture was further reacted at 90 to 95 ° C. for 1 hour. 76 ml of water and 100 ml of hexane were added and stirred and allowed to stand, and then the organic layer and the aqueous layer were separated. The organic layer was distilled off under reduced pressure, and N- {4- (n-butyl) phenyl} -N- (p-tolyl) amine as a fraction having a degree of vacuum of 1 to 2 Torr and a tower temperature of 166 to 170 ° C. by distillation under reduced pressure. 0 g (yield 79.6%) was obtained.

Diiodo-p-terphenyl 14.8 g (0.03 mol), N- {4- (n-butyl) phenyl} -N- (p-tolyl) amine 21.5 g (0.09 mol), copper sulfate five 0.059 g (0.24 mmol) of hydrate, 8.4 g (0.06 mol) of potassium carbonate, 0.042 g (0.24 mmol) of L-ascorbic acid were charged, and the internal temperature was 220 to 230 ° C. under a nitrogen atmosphere. For 5 hours. 80 ml of toluene and 40 ml of water were added and stirred, and after standing, the organic layer and the aqueous layer were separated. The organic layer was distilled off under reduced pressure, crystallized by adding 90 ml of ethyl acetate and 40 ml of methanol, and filtered to obtain crude crystals as slightly yellow crystals. The crude crystals were recrystallized from ethyl acetate to obtain 16.7 g (yield 76.8%) of the target compound.

Example 1 Mobility Measurement Amorphous selenium was vacuum-deposited to a thickness of 0.5 μm on an aluminum substrate, and a solution in which a mixture of the exemplified compound (1-1) and polycarbonate A was dissolved in dichloromethane was coated thereon. . It was dried under reduced pressure at 40 ° C. for 2 hours to form a photosensitive layer having a thickness of 10 μm. A gold electrode was deposited on the surface of the photosensitive layer to a thickness of 150 mm, irradiated with 5 ns pulse light with a 510 nm laser, and the hole mobility μ was measured by a time-of-flight method. The measurement conditions were in accordance with the method described in the literature (Philosophy Magazine B, 1988, Vol. 58, No. 5, 539; J. Phys. Chem., 1984, Vol. 88, No. 20, 4707).
It is known that the electric field strength dependence of the hole mobility μ can be quantitatively arranged by the following equation. In Equation 1, μ ₀ represents zero field mobility, β represents a Pool-Frenkel parameter, and E represents electric field strength.

Examples 2 to 20 Measurement of mobility The following exemplary compounds were synthesized in the same manner as in Synthesis Examples 1 and 2, a photosensitive layer was prepared in the same manner as in Example 1, and the mobility was measured under the same measurement conditions. . Table 2 shows the hole mobility μ, β value, and zero field mobility μ ₀ in Table 2.

Comparative Examples 1-15
Using a comparative compound represented by the following general formula (X) instead of the compound of the present invention, a photosensitive layer was formed in the same manner as in Example 1, and the mobility was measured. In general formula (X), n1-n4 represents 1 or 2, and when n1-n4 is 2, each R5-R8 may be the same or different. Specific substituents for R5 to R8 are shown in Table 3. Table 3 shows the hole mobility μ, β value, and zero field mobility μ ₀ of Comparative Compounds X-1 to X-15.

Comparative Examples 16-20
Using a known positive charge transporting compound shown below instead of the compound of the present invention, a photosensitive layer was formed in the same manner as in Example 1, and the mobility was measured. Table 4 shows the results.

<Known positive charge transporting compound>

Zero field mobility μ ₀ calculated from Equation 1 means hole mobility that does not include carrier behavior under a high electric field. From the above results, it can be seen that among the terphenyl positive charge transport materials known as high mobility, compounds having a structure limited to the present invention have extremely high mobility. Further, it can be seen that the compound of the present invention has extremely higher mobility than conventional positive charge transport materials and can transport carriers efficiently.

Example 21 Preparation and characteristic evaluation of organic EL device
An organic EL device containing the compound of the present invention was prepared by the following method, and the light emission characteristics and durability were evaluated. As shown in FIG. 2, an ITO electrode, a hole injection layer, and an exemplary compound No. A hole transport layer 3 using 1-1, a light emitting layer (also serving as an electron transport layer) 4, and an aluminum electrode 6 as a cathode were sequentially deposited to prepare an organic EL device. Deposition is performed by cleaning the ITO-coated glass substrate with UV and ozone and mounting it in the vapor deposition machine, followed by copper phthalocyanine as the hole injection material, exemplary compound 1-1 as the hole transport material, aluminum quinolinol complex as the light emitting material, cathode The aluminum was sequentially deposited. Vapor deposition was performed up to a hole injection layer of 25 nm, a hole transport layer of 35 nm, a light emitting layer of 50 nm, and a cathode of 100 nm while monitoring the film thickness. The light emission characteristics of the device were evaluated by the initial light emission luminance when the applied current was 100 mA / cm ² .

Examples 22-29
A device was prepared in the same manner as in Example 21 except that the exemplified compounds shown in Table 5 were used for the hole transport layer, and performance evaluation was performed.

Comparative Examples 21-30
A device was prepared in the same manner as in Example 21 except that a comparative compound shown in Table 5 or a known hole transport material was used for the hole transport layer, and performance evaluation was performed. Table 5 shows the results of Examples 21 to 29 and Comparative Examples 21 to 30.

It can be seen from Table 5 that the organic EL device containing the hole transport material of the present invention exhibits high light output, is highly durable, and has excellent characteristics.

It is a partial schematic diagram of the organic EL element which shows an example of the laminated constitution of the laminated organic EL element using the hole transport material of this invention. It is a partial schematic diagram of the organic EL element which shows the other example of the laminated constitution of the laminated organic EL element using the hole transport material of this invention. It is a partial schematic diagram of the organic EL element which shows the other example of the laminated constitution of the laminated organic EL element using the hole transport material of this invention. It is a partial schematic diagram of a single layer type organic EL device showing a layer structure of a single layer type organic EL device using the hole transport material of the present invention.

Explanation of symbols

1: Support substrate 2: Anode 3: Hole injection / transport layer 4: Light emitting layer 5: Electron injection / transport layer 6: Cathode

Claims (3)

In an organic electroluminescent device in which one or more organic thin film layers including at least a light emitting layer are formed between a pair of electrodes, at least one layer of the organic thin film layer includes an arylamine compound represented by the general formula (1) An organic electroluminescent element characterized by containing.

In the formula, R1 to R4 each independently represent a linear or cyclic alkyl group, an arylalkyl group, or an arylalkenyl group. The organic electroluminescent device according to claim 1, wherein the organic thin film layer containing the compound represented by the general formula (1) is selected from the group consisting of a light emitting layer, a hole transport layer, and a hole injection layer. In the said General formula (1), R1-R4 is respectively independently a C1-C4 linear alkyl group, The organic electroluminescent element of Claims 1-2 characterized by the above-mentioned.

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