JPH10228983A - Electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an element having a large light emitting intensity and excellent durability by including a specified di-styryl compound as a charge transporting material in a charge transfer layer of an organic electroluminescent element. SOLUTION: A di-styryl compound expressed with a formula (R1 means an alkyl group or an aryl group, which can have a substituent group: R2 means an alkyl group, aralkyl group or an aryl group, which can have a substituent group; R3 means alkyl, vinyl, ethinyl, benzyl, an aryl group, which can have a substituent group, furil, chenyl, alcoxy. aralkyloxy, phenoxy, thioalkyl. thioaralkyl or thiophenyl group) is used. In the case of forming with deposition, thickness is formed at 0.01-0.3μm in usual, and in the case of forming with spin-coating, di-styryl compound is included at 20-80wt.% in relation to the binder resin, and thickness is formed at about 0.05-1.0μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electroluminescence device containing a novel distyryl compound as a charge transporting substance.

[0002]

2. Description of the Related Art Conventionally, various organic compounds usable as a photoconductive material are known, such as anthracene derivatives, anthraquinone derivatives, imidazole derivatives, carbazole derivatives, hydrazone derivatives, styryl derivatives and the like. Asymmetric distyryl compounds are disclosed in JP 175052 or JP-A-62-120346. However, at present, satisfactory characteristics have not been obtained.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an electroluminescent device which is different from any of the above-mentioned structures and contains a novel distyryl compound as a charge transport material. The purpose is to:

[0004]

Means for Solving the Problems The present invention provides the following general formula [I]:

Embedded image [Wherein, R ₁ represents an alkyl group or an aryl group which may have a substituent; R ₂ represents an alkyl group, an aralkyl group or an aryl group which may have a substituent; R ₃ represents an alkyl group; Represents a vinyl group, an ethynyl group, a benzyl group, an aryl group which may have a substituent, a furyl group, a thienyl group, an alkoxy group, an aralkyloxy group, a phenoxy group, a thioalkyl group, a thioaralkyl or a thiophenyl group. An electroluminescent device containing the distyryl compound represented by the formula (1) as a charge transporting material.

[0005] The distyryl compound represented by the general formula [I] has excellent charge transportability.

In the general formula [I], R ₁ represents an alkyl group such as a methyl group or an ethyl group, or an aryl group such as a phenyl group or a naphthyl. The aryl group may have a substituent such as a lower alkyl group, a lower alkoxy group, a phenyl group, and a halogen atom. R ₂ represents an alkyl group such as a methyl group or an ethyl group, an aralkyl group such as benzyl or phenethyl, or an aryl group such as a phenyl group or a naphthyl group. The aryl group may have a substituent such as a lower alkyl group, a lower alkoxy group, a phenyl group, and a halogen atom. R ₃ is an alkyl group such as a methyl group, an ethyl group or a propyl group, an alkenyl group such as a vinyl group,
Alkynyl group such as ethynyl group, aralkyl group such as benzyl group or phenethyl group, aryl group such as phenyl group or naphthyl group, furan, thiophene or 1,
A heterocyclic residue such as 3-dioxaindane, an alkoxy group such as methoxy or ethoxy, a benzyloxy group, an aralkyloxy group such as a phenethyloxy group, a phenoxy group, a thiomethyl group, and a thioalkyl group such as a thioethyl group;
Represents a thioaralkyl or thiophenyl group such as a thiobenzyl group. The aryl group may have one or more substituents such as a C1 to C4 alkyl or alkoxy group, a halogen atom, a hydroxyl group, and the like.

Specific examples of the distyryl compound represented by the general formula [I] include those having the following structural formulas.

[0008]

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[0009]

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[0010]

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[0011]

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[0012]

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[0013]

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[0014]

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[0015]

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[0016]

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[0017]

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The distyryl compound represented by the general formula [I] can be synthesized by the following two methods.
That is, the distyryl compound represented by the general formula [I] is represented by the following general formula [II]:

Embedded image [In the formula, R ₁ is the general formula [same meaning as R ₁ in I], R ₄
Represents a lower alkyl group] and the following general formula [III]

Embedded image [Wherein, R ₂ and R ₃ have the same meanings as R ₂ and R ₃ in formula [I]. And an aldehyde compound represented by the following general formula [IV] or [V]:

Embedded image [Wherein, R ₃ has the same meaning as R ₃ in formula [I]; R ₅ represents a lower alkyl group. ]

Embedded image [Wherein, R ₃ has the same meaning as R ₃ in formula [I]; X represents a halogen atom] and the following formula [VI]:

Embedded image [Wherein, R _1, R ₂ have the same meanings as R _1, R ₂ in the general formula [I]. By reacting with an aldehyde compound represented by the following formula: The phosphorus compound represented by the general formula [II] or [IV] used in the synthesis of the present invention can be easily prepared by heating the corresponding halomethyl compound and trialkyl phosphite directly or in a solvent such as toluene or xylene. Can be manufactured. Trialkyl phosphite as an alkyl group having 1 to 4 carbon atoms,
Particularly, a methyl group and an ethyl group are preferable. The phosphorus compound represented by the general formula [V] can be easily produced by heating the corresponding halomethyl compound and triphenylphosphine directly or in a solvent such as toluene or xylene. The general formula [I obtained as described above
I], [IV] or [a phosphorus compound of the general formula represented by V] [III] or [an aldehyde compound represented by VI], the presence of a basic catalyst, a temperature of about 100 ⁰ C from room temperature To react. As a solvent in the reaction,
For example, hydrocarbons, alcohols, ethers are good,
Methanol, ethanol, isopropanol, butanol, 2-methoxyethanol, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, dioxane, tetrahydrofuran, toluene, xylene, dimethylsulfoxide, N, N-dimethylformamide, N-
Methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like can be mentioned. Among them, polar solvents such as N,
N-dimethylformamide and dimethylsulfoxide are preferred. As the basic catalyst (condensing agent), an alcoholate such as sodium hydroxide, potassium hydroxide, sodium amide, sodium hydrogen and sodium methylate, and potassium tert-butoxide is used. The reaction temperature is about ⁰ C
It can be selected from a wide range of up to about 100 ⁰ C.
Preferably from ¹⁰ 0 Celsius to about 80 ⁰ C. The distyryl-based compound represented by the general formula [I] of the present invention can be used for a charge transport layer of an electroluminescence element by utilizing charge transport properties, particularly high photoconductivity at the time of light irradiation.

The organic electroluminescent element is composed of at least an organic light emitting layer and a charge transport layer containing a distyryl compound between electrodes. FIG. 1 schematically shows an electroluminescent element. In the figure, (1) is an anode,
The charge transport layer (2), the organic light emitting layer (3) and the cathode
(4) is sequentially laminated, and the charge transport layer contains a distyryl compound represented by the above general formula [I]. When a voltage is applied to the anode (1) and the cathode (4), the organic light emitting layer (3) develops color.

Anode of organic electroluminescence element
As the conductive material used as (1), those having a work function of more than 4 eV are preferable, and carbon, aluminum, vanadium, iron, cobalt, nickel, copper, zinc,
Tungsten, silver, tin, gold and their alloys,
Tin oxide and indium oxide are used. As the metal forming the cathode (4), a metal having a work function smaller than 4 eV is preferable, and magnesium, calcium, titanium,
Yttrium, lithium, gadolinium, ytterbium, ruthenium, manganese, and alloys thereof are used. In the organic electroluminescence device,
At least the anode (1) or the cathode (4) is a transparent electrode so that light emission can be seen. At this time, if a transparent electrode is used for the cathode, the transparency is likely to be impaired. Therefore, it is preferable to use the anode as the transparent electrode. When forming a transparent electrode, on a transparent substrate, using a conductive substance as described above, evaporation,
What is necessary is just to form so that desired translucency may be ensured by means, such as sputtering. The transparent substrate is not particularly limited as long as it has a proper strength, is not adversely affected by heat due to vapor deposition or the like at the time of producing the electroluminescent element, and is not particularly limited as long as it is transparent. It is also possible to use various resins, for example, polyethylene, polypropylene, polyethersulfone, polyetheretherketone, and the like. As a transparent electrode formed on a glass substrate, commercially available products such as ITO and NESA are known, and those may be used.

The charge transport layer (2) may be formed by vapor deposition of the distyryl compound represented by the above general formula [I], or by spin coating an appropriate resin solution of the distyryl compound. You may. When formed by the vapor deposition method, the thickness is usually 0.01 to 0.3 μm, and when formed by the spin coating method, the content of the distyryl compound to the binder resin is about 20 to 80% by weight. The thickness may be about 0.05 to 1.0 μm.

An organic light emitting layer is formed on the charge transport layer (2) thus formed. As the organic light-emitting material used for the organic light-emitting layer, known materials can be used. For example, epidolidine, 2,5-bis [5,7-di-t-pentyl-2-benzoxazolyl] thiophene, 2,2′- (1,4
-Phenylenedivinylene) bisbenzothiazole, 2,
2 ′-(4,4′-biphenylene) bisbenzothiazole,
5-methyl-2- {2- [4- (5-methyl-2-benzoxazolyl) phenyl] vinyl} benzoxazole,
5-bis (5-methyl-2-benzoxazolyl) thiophene, anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, perinone, 1,4-diphenylbutadiene, tetraphenylbutadiene, coumarin,
Macridine stilbene, 2- (4-biphenyl) -6-phenylbenzoxazole, aluminum trisoxine, magnesium bisoxin, bis (benzo-8-quinolinol) zinc, bis (2-methyl-8quinolinolate) aluminum oxide, indium tris Oxine, aluminum tris (5-methyloxin), lithium oxine, gallium trioxin, calcium bis
(5-chlorooxin), polyzinc-bis (8-hydroxy-5-quinolinonyl) methane) dilithium epindridione, zinc bisoxin, 1,2-phthaloperinone,
Examples thereof include 2-naphthaloperinone. Also, common fluorescent dyes such as fluorescent coumarin dye, fluorescent perylene dye, fluorescent pyran dye, fluorescent thiopyran dye,
Fluorescent polymethine dyes, fluorescent merocyanine dyes, fluorescent imidazole dyes and the like can also be used. Among them, particularly preferred are chelated oxinoid compounds. The organic light-emitting layer may have a single-layer structure of the above-described light-emitting substance, or in order to adjust characteristics such as the color of light emission and the intensity of light emission,
It may have a multilayer structure. Next, the above-described cathode is formed on the organic light emitting layer.

The case where the charge transport layer (2), the light emitting layer (3) and the cathode (4) are sequentially laminated on the anode (1) to form an organic luminescent element has been described. A light emitting layer (5), a charge transport layer (2) and an anode may be sequentially laminated thereon. One set of transparent electrodes has nichrome wire, gold wire,
An appropriate lead wire (5) such as a copper wire or a platinum wire is connected, and the organic luminescence element emits light by applying an appropriate voltage (Vs) to both electrodes. The organic electroluminescence device of the present invention is applicable to various display devices, display devices, and the like. Hereinafter, the present invention will be described with reference to specific examples. In the following examples, “parts” means “parts by weight” unless otherwise specified.

Synthesis Example Synthesis Example of Compound [1] The following formula:

Embedded image 4.51 g (0.01 mol) of the aldehyde compound and 2.28 g (0.09 g) of diethyl benzylphosphonate
(1 mol) was added and dissolved in 50 ml of dimethylformamide (DMF). While the resulting solution was cooled to 5 ⁰ C and a suspension containing potassium -t- butoxide 1.68g in dimethyl formamide 50 ml, was added dropwise to the solution. The resulting solution was stirred for 4 hours at room temperature, 80 ⁰ C
For 2 hours to complete the reaction. The obtained mixture was added to 500 ml of water, and neutralized with dilute hydrochloric acid. After 30 minutes, the precipitated crystals were filtered. The filtered product was washed with water, dissolved in toluene, and separated and purified by silica gel column chromatography. After distilling off toluene from the effluent, recrystallization from ethanol gave 3.8 g (yield 72.4%) of pale yellow crystals. The melting point was 76 to 78 ⁰ C. The results of the elemental analysis are as follows (as C ₄₀ H ₃₁ N).

[0025]

[Table 1] Table 1 {C (%) H (%) N (%)} ────────── Calculated value 91.43 5.90 2.67 ───────────────────── Experimental value 91.40 5.85 2.75 ───────── ────────────

FIG. 2 shows the infrared absorption spectrum (KBr tablet method) of the product. The infrared absorption spectrum was measured using a model 1710FTIR (manufactured by PerkinElmer) under the conditions of a resolution of 4 cm ^-1 and five scans.

Synthesis Examples 2 to 17 The present invention was carried out in the same manner as in Synthesis Example 1 except that the aldehyde compounds and phosphorus compounds shown in Tables 2 to 5 were used instead of the aldehyde compounds and phosphorus compounds used in Synthesis Example 1. A distyryl compound was synthesized. In the table, the melting point, recrystallization solvent, and elemental analysis results of each product are shown. Compounds [2], [4], [9], [21], [23], [2]
4], [27], and [39], the infrared absorption spectra are shown in FIGS. 3 to 10, respectively.

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5] Example 1 A thin film having a thickness of 500 ° was formed on an indium tin oxide-coated glass by vapor deposition of a distyryl compound [2]. Next, aluminum trisoxin was vapor-deposited at 500Å.
A thin film was formed to have a thickness of. Next, as the cathode,
A thin film having a thickness of 2000 ° was formed using Mg and Ag at an atomic ratio of 0: 1. Thus, an organic electroluminescence device was manufactured.

Examples 2 to 7 In Example 1, instead of using the distyryl compound [2], the distyryl compounds [3], [9], [1]
5], [21], [23], and [30], except that the organic electroluminescent device was manufactured in exactly the same manner as in Example 1.

Comparative Examples 1 to 3 Organic electroluminescent devices were produced in the same manner as in Example 1, except that the following compound was used instead of the distyryl compound [2]. (Comparative Example 1): N-ethylcarbazole-3-carbaldehyde-N-methyl, N-phenylhydrazone (Comparative Example 2): 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadi Azole (Comparative Example 3): N, N, N-tri (p-tolyl) amine

The electroluminescence device obtained in Evaluation Example 1 was operated at a current density of 5 mA / cm ² for 1 hour while applying a bias voltage using the glass electrode as an anode. The initial output was lowered from 0.1 mW / cm ² to 0.095mW / cm ^2. When operated for an additional hour, it decreased to 0.090 mW / cm ² . Similarly, operation tests were performed on the electroluminescent devices of Examples 2 to 7 and Comparative Examples 1 to 3. Table 6 shows the results.

[0035]

[Table 6]

According to the present invention, when a specific distyryl compound is contained in the charge transporting layer, an organic electroluminescence device having high light emission intensity and excellent durability can be obtained.

[0037]

The electroluminescent device containing the distyryl compound of the present invention as a charge transport material has a high emission intensity and excellent durability.

[Brief description of the drawings]

FIG. 1 shows a schematic sectional view of an electroluminescent element.

FIG. 2 is a diagram showing an infrared absorption spectrum of a distyryl compound example of the present invention.

FIG. 3 is a view showing an infrared absorption spectrum of an example of a distyryl compound of the present invention.

FIG. 4 is a view showing an infrared absorption spectrum of an example of a distyryl compound of the present invention.

FIG. 5 is a diagram showing an infrared absorption spectrum of a distyryl compound example of the present invention.

FIG. 6 is a diagram showing an infrared absorption spectrum of a distyryl compound example of the present invention.

FIG. 7 is a view showing an infrared absorption spectrum of a distyryl compound example of the present invention.

FIG. 8 is a view showing an infrared absorption spectrum of a distyryl compound example of the present invention.

FIG. 9 is a view showing an infrared absorption spectrum of a distyryl compound example of the present invention.

FIG. 10 is a view showing an infrared absorption spectrum of a distyryl compound example of the present invention.

Claims (1)

[Claims] 1. The following general formula [I]: [Wherein, R ₁ represents an alkyl group or an aryl group which may have a substituent; R ₂ represents an alkyl group, an aralkyl group or an aryl group which may have a substituent; R ₃ is an alkyl group , A vinyl group, an ethynyl group, a benzyl group, an aryl group which may have a substituent, a furyl group, a thienyl group, an alkoxy group, an aralkyloxy group, a phenoxy group, a thioalkyl group, a thioaralkyl group or a thiophenyl group. ] The electroluminescent element containing the distyryl compound represented by these as a charge transporting substance.