JP2000123973A - Organic light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize light output of high luminance and long service life by comprising a specific compound in at least one layer out of layers formed of an organic compound. SOLUTION: A light emitting element comprises a compound expressed by a formula. In the formula, a, b, c, d, e represent a carbon atom or a nitrogen atom, R1-R5 represent groups selected from a group comprising a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, an aralkyl group, a nitro group, a substitutive or nonsubstitutive amino group, a carbonyl group, an ether group, a thioether group, a silyl group and a nitryl group. R1 and R2, R2 and R3, R3 and R4, R4 and R5 can be respectively integrated to form a condensed ring. M represents alkaline metal. This compound is formed between a positive electrode and a negative electrode by a vacuum deposition method or a solution applying method, and it is preferable to form its organic layer in a thin film with a thickness of 0.05-0.5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device having a light emitting layer made of a light emitting substance and capable of directly converting electric field applied energy to light energy by applying an electric field.

More specifically, unlike conventional incandescent lamps, fluorescent lamps, inorganic light-emitting diodes, and the like, they have the characteristics of large area, high resolution, thin, light weight, high-speed operation, and complete solid-state devices, and are likely to meet high demands. The present invention relates to an organic light-emitting device used for an electroluminescent (EL) panel having a characteristic.

[0003]

2. Description of the Related Art An electroluminescent phenomenon of an organic material was observed in an anthracene single crystal by Pope et al. In 1963 (J. Chem. Phys. 38 (1963) 2).
042), followed by Helfrich (He) in 1965.
lfinch) and Schneider
Has succeeded in observing a relatively strong injection type EL by using a solution electrode system having high injection efficiency (Phys. Re.
v. Lett. 14 (1965) 229).

Since then, US Pat. No. 3,172,862
No. 3,173,050, U.S. Pat.
0,167, J.M. Chem. Phys. 44 (196
6) 2902; Chem. Phys. 50 (196
9) 14364; Chem. Phys. 58 (19
73) 1542, or Chem. Phys. Let
t. 36 (1975) 345 etc.
Studies have been conducted on the formation of an organic luminescent material with a conjugated organic host material and a conjugated organic activator having a fused benzene ring. Naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzopyrene, chrysene, picene, carbazole, fluorene, biphenyl, terphenyl,
Triphenylene oxide, dihalobiphenyl, trans-stilbene, 1,4-diphenylbutadiene and the like are shown as examples of organic host materials, and anthracene, tetracene, pentacene and the like are mentioned as examples of activators. However, each of these organic luminescent substances is 1 μm
It existed as a single layer having a thickness exceeding the above, and a high electric field was required for light emission. For this reason, research on a thin film element by a vacuum deposition method has been advanced (for example, Thin Solid).
Films 94 (1982) 171, Polyme
r 24 (1983) 748, Jpn. J. Appl.
Phys. 25 (1986) L773). However, although thinning was effective in reducing the driving voltage, it did not lead to obtaining a high-brightness element on a practical level.

[0005] However, Tang et al. (App
l. Phys. Lett. 51 (1987) 913 or U.S. Pat. No. 4,356,429), devising an EL element in which two extremely thin layers (a charge transport layer and a light emitting layer) are stacked by vacuum deposition between an anode and a cathode, and low driving is performed. High brightness was achieved with voltage. This type of stacked organic EL device has been actively studied thereafter, and is disclosed in, for example, JP-A-59-194393.
No. 4,539,507, Japanese Unexamined Patent Publication No.
194393, U.S. Pat. No. 4,720,432,
JP-A-63-264692, Appl. Phys
s. Lett. 55 (1989) 1467;
163188.

Further, Jpn. J. Appl. Phys
s. 27 (1988) L269. L713 reports a three-layered EL device in which the functions of carrier transport and light emission are separated from each other. In selecting a dye for the light-emitting layer that determines the emission color, the restrictions on carrier transport performance are relaxed, and the degree of freedom in selection is increased. It is also suggested that there is a possibility of improving the light emission by effectively confining holes and electrons (or excitons) in the central light emitting layer.

Although a vacuum evaporation method is generally used for producing a stacked organic EL device, it has been reported that a device having a considerably high brightness can be obtained by a casting method (for example, the 50th application). Proceedings of academic conference
006 (1989) and Proceedings of the 50th Annual Meeting of the Japan Society for Materials Science 1041 (1990)).

Further, even a mixed single-layer organic EL device formed by a dip coating method from a solution in which polyvinyl carbazole as a hole transport compound, an oxadiazole derivative as an electron transport compound, and coumarin 6 as a luminous body is considerably high luminous efficiency. Is reported to be obtained (for example, 1038
(1991)). As noted above, recent advances in organic EL devices have shown remarkably widespread application possibilities.

[0009] However, the history of these researches is still short, and research on materials and devices has not yet been sufficiently performed. At present, there is still a problem in terms of durability, such as light output with higher luminance, a change over time due to long-term use, and deterioration due to an atmospheric gas containing oxygen or moisture. In addition, when considering application to full color display, etc., blue, green,
Problems such as diversification of emission wavelengths for accurately selecting a red emission hue have not yet been sufficiently solved.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art.
The first object is to provide an organic light emitting device having an extremely high luminance and a long life light output. Secondly, it is an object of the present invention to provide an organic light-emitting device having various emission wavelengths, exhibiting various emission hues, and being extremely durable. Thirdly, it is an object of the present invention to provide an organic light emitting device which is easy to manufacture and can be provided at relatively low cost.

[0011]

That is, the present invention relates to an organic light-emitting device having at least a pair of electrodes comprising an anode and a cathode, and at least one organic compound layer sandwiched between the pair of electrodes. An organic light-emitting device, wherein at least one of the organic compound layers contains a compound represented by the following general formula [1].

[0012]

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(Wherein a, b, c, d, and e represent a carbon atom or a nitrogen atom; R _{1 to} R ₅ represent a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, an aralkyl group, a nitro group, R represents a group selected from the group consisting of a group, a substituted or unsubstituted amino group, a carbonyl group, an ether group, a thioether group, a silyl group, and a nitrile group.
₁ and R ₂ , R ₂ and R ₃ , R ₃ and R ₄ , and R ₄ and R ₅ may be integrated to form a condensed ring. M represents an alkali metal. )

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An organic light-emitting device according to the present invention is an organic light-emitting device having at least a pair of electrodes comprising an anode and a cathode, and at least a layer comprising one or more organic compounds sandwiched between the pair of electrodes. At least one of the layers comprising the organic compound contains a compound represented by the following general formula [1].

[0015]

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In the general formula [1], a, b, c, d,
e represents a carbon atom or a nitrogen atom. For example, a, b,
When c, d, and e are all carbon atoms, the general formula [1] is represented by a metal phenolate.

R _{1 to} R ₅ represent a substituent, and include a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, an aralkyl group, a nitro group, a substituted or unsubstituted amino group,
Represents a group selected from the group consisting of a carbonyl group, an ether group, a thioether group, a silyl group and a nitrile group. In the general formula [1], R ₁ and R ₂ , R ₂ and R ₃ , R ₃
And R ₄ , or R ₄ and R ₅ may be integrated to form a condensed ring. M represents an alkali metal such as Li, Na, and K.

Hereinafter, the substituents R _{1 to} R ₅ will be specifically described. In the substituents R _{1 to} R ₅ , a linear or branched alkyl group having 1 to 22 carbon atoms is preferable as the alkyl group, for example, a linear alkyl group such as a methyl group, an ethyl group, a propyl group, a hexyl group, and a nonyl group; Isopropyl group,
Examples include a branched alkyl group such as an isobutyl group and a 2-methylheptyl group.

The alkenyl group is represented by the following formula:

[0020]

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The groups represented by Wherein R ₆ ,
R ₇ and R ₈ are selected from the group consisting of a hydrogen atom, an alkyl group, an aryl group, an alkenyl group, an alkylamino group, a nitrile group, a monoarylamino group, a diarylamino group, an alkyloyl group, an aryloyl group, and an aralkyloyl group. Group.

Examples of the aryl group include substituted or unsubstituted aromatic compounds such as phenyl, naphthyl, anthranyl, pyridyl, quinolyl, acridinyl, indolyl, pyrrolyl, thienyl, and furyl. Six- and five-membered heteroaromatic compounds are also included.

The aralkyl group is represented by the following formula:

[0024]

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The following groups may be mentioned. In the formula, Ar includes a substituted or unsubstituted aromatic group or heteroaromatic group. Examples of the unsubstituted aromatic group include a monocyclic ring and a condensed ring such as a phenyl group, a naphthyl group and an anthranyl group. As the substituted aromatic group, an alkyl group,
Halogen atom, nitrile group, nitro group, carbonyl group,
A monocyclic or condensed ring aromatic group substituted by a hydroxy group,
For example, a tolyl group, a nitrophenyl group, a 3-cyanonaphthyl group and the like can be mentioned.

Examples of the substituted or unsubstituted heteroaromatic group include a monocyclic or condensed heterocyclic group substituted with an alkyl group, a halogen atom, a nitrile group, a nitro group, a carbonyl group, a hydroxy group, and the like. Thienyl, furyl, pyridyl, 4-methylpyridyl, acridinyl, indonyl, 5-aminoquinolyl and the like.

In the general formula [1], R ₁ and R ₂ ,
R ₂ and R ₃ , R ₃ and R ₄ , R ₄ and R ₅ are each integrated,
When a condensed ring is formed, for example, compounds represented by the following formulas are exemplified, but not limited thereto.

[0028]

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In the above formula, f, g, h, and i represent atoms,
It is selected from the group of carbon atom, nitrogen atom, sulfur atom, silicon atom and the like.

R ₉ , R ₁₀ , R ₁₁ and R ₁₂ represent a substituent on the condensed ring. R ₉ , R ₁₀ , R ₁₁ , and R _{12 each} represent a hydrogen atom, an alkyl group, an aryl group, an alkenyl group, an alkylamino group, a nitrile group, a monoarylamino group, a diarylamino group, an alkyloyl group, an aryloyl group, an aralkyloyl group Is a group selected from the group consisting of Further, a condensed ring may be formed by adjacent substituents.

Further, in the general formula [1], when a polycyclic condensed ring is formed, for example, when a condensed ring is formed by R _{1 to} R ₂ and R _{3 to} R ₄ , compounds represented by the following formulas are exemplified. However, the present invention is not limited to these.

[0032]

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In the above equation, f, g, h, i, j, k, l,
m represents an atom, and is selected from a group such as a carbon atom, a nitrogen atom, a sulfur atom, and a silicon atom.

R ₉ , R ₁₀ , R ₁₁ and R ₁₂ , R
₁₃ , R ₁₄ , R ₁₅ , and R ₁₆ represent substituents on the condensed ring portion. Substituents R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ ,
R ₁₄ , R ₁₅ , and R ₁₆ each represent a group consisting of a hydrogen atom, an alkyl group, an aryl group, an alkenyl group, an alkylamino group, a nitrile group, a monoarylamino group, a diarylamino group, an alkilloyl group, an aryloyl group, and an aralkylyl group. Is a group selected from Adjacent substituents may form a condensed ring.

Examples of the compound represented by the general formula [1] described above include the following, but are not limited thereto.

However, in the following exemplified compounds, M is one metal selected from alkali metals.

[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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The organic light-emitting device of the present invention has one or more organic compound layers sandwiched between an anode and a cathode, and at least one of the organic compound layers has the general formula [1] At least one compound selected from the group consisting of:

In the organic light emitting device of the present invention, the compound represented by the above general formula [1] is formed between the anode and the cathode by a vacuum deposition method, a solution coating method, or the like. The thickness of the organic layer is thinner than 2 μm, preferably 0.5 μm or less, more preferably 0.05 to 0.5 μm.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a sectional view showing an example of the organic light emitting device of the present invention. FIG. 1 shows a structure in which an anode 2, a light emitting layer 3 and a cathode 4 are sequentially provided on a substrate 1. The light-emitting element used here is useful when it has a single hole-transporting ability, electron-transporting ability, and light-emitting performance, or when a mixture of compounds having the respective properties is used.

FIG. 2 is a sectional view showing another example of the organic light emitting device of the present invention. FIG. 2 shows a configuration in which an anode 2, a hole transport layer 5, an electron transport layer 6, and a cathode 4 are sequentially provided on a substrate 1. In this case, the light-emitting substance is a material having either a hole-transporting property or an electron-transporting property or both, and is used in combination with a simple hole-transporting substance or an electron-transporting substance having no light-emitting property Useful in cases. In this case, the light emitting layer 3 is composed of the hole transport layer 5 and the electron transport layer 6.

FIG. 3 is a sectional view showing another example of the organic light emitting device of the present invention. FIG. 3 shows a structure in which an anode 2, a hole transport layer 5, a light emitting layer 3, an electron transport layer 6, and a cathode 4 are sequentially provided on a substrate 1. It separates the functions of carrier transport and luminescence, and is used in a timely combination with a compound having each of hole transport, electron transport, and luminescent properties. Since various compounds having different wavelengths can be used, the emission hue can be diversified. Further, it is also possible to effectively confine holes and electrons (or excitons) in the central light emitting layer to improve the light emission efficiency.

The compound represented by the general formula [1] used in the present invention is a compound having extremely excellent luminous properties as compared with the conventional compound, and may have any of the forms shown in FIGS. Light emitting elements can also be used.

The compound represented by the general formula [1] used in the present invention has one or both of a hole transporting property and an electron transporting property depending on the structure.
In any of the forms of FIG. 3, one or more of the compounds represented by the general formula [1] may be used.

In particular, an organic layer using the compound represented by the general formula [1] of the present invention is useful as an electron injection layer.
It is also useful as, for example, a light emitting layer that emits blue light.

In the present invention, the compound represented by the above general formula [1] is used as a component of the light emitting layer. If necessary, a hole transporting compound which has been studied in the electrophotographic photoreceptor field or the like may be used. Hitherto known hole-transporting luminescent compounds (for example, compounds shown in Tables 1 to 4)
Alternatively, an electron transporting compound or a conventionally known electron transporting luminescent compound (for example, the compounds listed in Tables 5 to 6) can be used together if necessary.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

[0056]

[Table 4]

[0057]

[Table 5]

[0058]

[Table 6]

In the organic light emitting device of the present invention, the layer containing the compound represented by the general formula [1] and the layer composed of another organic compound are generally formed into a thin film by vacuum deposition or by combining with an appropriate binder resin. Form.

The binder can be selected from a wide range of binder resins, for example, polyvinyl carbazole resin, polycarbonate resin, polyester resin, polyarylate resin, butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin , Methacrylic resin, phenolic resin, epoxy resin,
Examples include, but are not limited to, silicone resins, polysulfone resins, urea resins, and the like. These may be used alone or as a copolymer in one kind or as a mixture of two or more kinds.

The anode material preferably has a work function as large as possible. For example, nickel, gold, platinum, palladium, selenium, rhenium, iridium and alloys thereof, or tin oxide, indium tin oxide (ITO), copper iodide Is preferred. Further, a conductive polymer such as poly (3-methylthiophene), polyphenylene sulfide, or polypyrrole can also be used.

On the other hand, as a cathode material, silver, lead, tin, magnesium, aluminum, calcium, manganese, indium, chromium, lithium, sodium, or an alloy thereof having a small work function is used.

At least one of the materials used for the anode and the cathode is 50% in the emission wavelength region of the device.
Preferably, more than% of light is transmitted. Further, as the transparent substrate used in the present invention, glass, plastic film, or the like is used.

The organic light-emitting device of the present invention is characterized by having a large area, being thin, being lightweight, operating at high speed, and being a complete solid-state device, and is a light-emitting device that can satisfy high requirements.

[0065]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Tin oxide-indium (ITO) coating (1200 mm thick)
On a transparent anode of a glass substrate provided with N, N′-bis- (3-methylphenyl) -1,1 as a hole transport material.
l'-biphenyl-4,4-diamine (hereinafter abbreviated as TPD) at 500 °, the above-mentioned exemplary compound 2 (M = Li in this example) at 500 °, and Mg / A as a cathode.
g (10/1) was sequentially vacuum-deposited to a thickness of 1500 ° to form a device. The degree of vacuum during deposition is 3 × 10 ⁻⁶ To
rr, and the film formation rate is 2-3 °. This device emits blue light, and its voltage-luminance characteristics are shown in FIG.

Example 2 Tin oxide-indium (ITO) coating (1200 mm thick)
On a transparent anode of a glass substrate provided with TPD, 500 μm of TPD was used as a hole transporting material, and tris (8-quinolinolate) was used.
The aluminum complex was added at 500 °
(In this example, M = Li) was vacuum-deposited to a thickness of 20 ° and Al as a cathode in a thickness of 1500 ° to prepare a device. This device emits green light, and its voltage-luminance characteristics are shown in FIG.

Example 3 Tin oxide-indium (ITO) coating (1200 mm thick)
Is provided on a transparent anode of a glass substrate provided with, for example, 500 ° of TPD as a hole transporting material, then 500 ° of the exemplified compound 16 (M = Li in this example), and M as a cathode.
g / Ag (10/1) was sequentially vacuum-deposited to a thickness of 1500 ° to form a device. This device emits blue light, and its voltage-luminance characteristics are shown in FIG.

In this embodiment, the device of the present invention is useful as a blue light source because blue light can be emitted.

Example 4 Tin oxide-indium (ITO) coating (1200 mm thick)
On a transparent anode of a glass substrate provided with, a TPD of 500 ° as a hole transport material, a tris (8-quinolinolato) aluminum complex of 500 °, and then the exemplified compound 16
(In this example, M = Li) was vacuum-deposited to a thickness of 20 ° and Al as a cathode in a thickness of 1500 ° to prepare a device. This device emits green light, and its voltage-luminance characteristics are shown in FIG.

Comparative Example 1 A device was produced in the same manner as in Example 4 except that the layer of the exemplified compound 16 was not provided. The voltage-luminance characteristics are shown in FIG.

FIG. 7 shows that the exemplified compound 1 of Example 4 was obtained.
It was confirmed that 6 exhibited very good characteristics as an electron injection layer.

Example 5 On a transparent anode of tin oxide-indium (ITO) coated (1200 °) glass, 50 TPD was used as a hole transport material.
0Å, 150 wt.% Of tris (8-quinolinolate) aluminum complex doped with Nile Red.
{, Tris (8-quinolinolato) aluminum complex at 350 °, 20% at the above-mentioned exemplified compound 16 (M = Li in this example), and 1500 ° at Al as a cathode.
Vacuum evaporation was sequentially performed to a thickness of 3 to produce a device. This device emits orange light, and its voltage-luminance characteristics are shown in FIG.

[0074]

As described above, the light-emitting device using the compound represented by the general formula [1] of the present invention can obtain extremely high-luminance light emission at a low applied voltage, and has high durability. Very good. In particular, the organic layer using the compound represented by the general formula [1] of the present invention is useful as an electron injection layer, and is also useful, for example, as a light emitting layer that emits blue light. Also, the device can be prepared by a vacuum deposition method or a casting method, and a relatively inexpensive and large-area device can be easily prepared.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the organic light emitting device of the present invention.

FIG. 2 is a sectional view showing another example of the organic light emitting device of the present invention.

FIG. 3 is a sectional view showing another example of the organic light emitting device of the present invention.

FIG. 4 is a graph showing voltage-luminance characteristics of the organic light emitting device of Example 1 of the present invention.

FIG. 5 is a graph showing voltage-luminance characteristics of the organic light emitting device of Example 2 of the present invention.

FIG. 6 is a graph showing voltage-luminance characteristics of the organic light emitting device of Example 3 of the present invention.

FIG. 7 is a graph showing voltage-luminance characteristics of the organic light emitting devices of Example 4 and Comparative Example 1 of the present invention.

FIG. 8 is a graph showing voltage-luminance characteristics of the organic light emitting device of Example 5 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Light emitting layer 4 Cathode 5 Hole transport layer 6 Electron transport layer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akihiro Senoo 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 3K007 AB00 AB02 AB04 AB18 CA01 CA06 CB01 DA00 DB03 EB00 FA01 FA03

Claims (1)

[Claims] 1. An organic light-emitting element having at least a pair of electrodes composed of an anode and a cathode and one or more organic compound layers sandwiched between the pair of electrodes, wherein at least one of the organic compound layers An organic light-emitting device wherein one layer contains a compound represented by the following general formula [1]. Embedded image (In the formula, a, b, c, d, and e represent a carbon atom or a nitrogen atom. R _{1 to} R ₅ represent a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, an aralkyl group, a nitro group, or an unsubstituted amino group, a carbonyl group, an ether group, a thioether group, a group selected from the group consisting of silyl group and nitrile group. Further, R ₁ and R _2, R ₂
And R ₃ , R ₃ and R ₄ , and R ₄ and R ₅ may be integrated to form a condensed ring. M represents an alkali metal. )