JP2002324675A - Organic light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic light emitting device with a light output of high efficiency, high brightness and long life, which has durability, is easy to manufacture and of comparatively moderate in price. SOLUTION: With the organic light emitting device having a pair of electrodes that is a positive and a negative electrodes and a layer including one or a plurality of organic compounds pinched between the electrodes, one or more layers including the organic compounds contain a compound of formula 1. R1 to R6 either a substituted or non-substituted alkyl group, a substituted or non-substituted aryl group, a substituted or non-substituted aralkyl group, a substituted or non-substituted alkoxy group, or a substituted or non-substituted heterocyclic group, provided, R1 to R6 may be identical or different. Further, R1 and R2 , R3 and R4 , and R5 and R6 may form condensed rings.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic light emitting device, and more particularly, to a device that emits light by applying an electric field to a thin film containing an organic compound.

[0002]

2. Description of the Related Art In an organic light emitting device, a thin film containing a fluorescent organic compound is sandwiched between an anode and a cathode, and electrons and holes (holes) are injected from each electrode to exciton the fluorescent compound. It is an element that utilizes light emitted when this exciton is returned to the ground state.

In 1987, a study by Kodak Company (Appl.
Phys. Lett. 51, 913 (1987)), a function-separated type 2 using ITO as an anode, magnesium-silver alloy as a cathode, an aluminum quinolinol complex as an electron transporting material and a luminescent material, and a triphenylamine derivative as a hole transporting material. This device has a layered structure, and has an applied voltage of about 10 V and 1000 cd / m ^2.
A degree of luminescence has been reported. Related patents include U.S. Pat. No. 4,539,507 and U.S. Pat.
0,432, U.S. Pat. No. 4,885,211 and the like.

[0004] In addition, by changing the type of the fluorescent organic compound, light emission from ultraviolet to infrared can be achieved, and various compounds have recently been actively studied. For example, US Pat. No. 5,151,629 and US Pat.
409,783, U.S. Patent No. 5,382,477,
JP-A-2-247278, JP-A-3-25519
0, JP-A-5-202356, JP-A-9-206
JP-A-202878 and JP-A-9-227576.

[0005] In addition to the organic light-emitting device using the above low-molecular material, an organic light-emitting device using a conjugated polymer is also a group of Cambridge University (Nature,
347, 539 (1990)).
In this report, light emission was confirmed in a single layer by forming a film of polyphenylenevinylene (PPV) in a coating system.
Patents related to organic light-emitting devices using conjugated polymers include US Pat. No. 5,247,190 and US Pat.
No. 514,878, US Pat. No. 5,672,678,
JP-A-4-145192, JP-A-5-24746
No. 0 publication.

As described above, recent advances in organic light-emitting devices have been remarkable, and their characteristics are that high luminance, a variety of emission wavelengths, high-speed response, a thin and lightweight light-emitting device can be realized at a low applied voltage. It suggests potential for a wide range of applications.

However, at present, light output with higher luminance or higher conversion efficiency is required. In addition, there are still many problems in terms of durability such as a change with time due to long-term use and deterioration due to an atmospheric gas containing oxygen or moisture. Further, when application to a full-color display or the like is considered, light emission of blue, green, and red with good color purity is required, but this problem has not yet been sufficiently solved.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an organic light-emitting device having extremely high efficiency, high brightness, and long life light output has been developed. To provide. Another object of the present invention is to provide an organic light-emitting device that has various emission wavelengths, exhibits various emission hues, and is extremely durable. Another object of the present invention is to provide an organic light emitting device that can be easily manufactured and can be manufactured at relatively low cost.

[0009]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a pair of electrodes including an anode and a cathode and one or more electrodes sandwiched between the pair of electrodes are provided. In an organic light-emitting device having at least a layer containing an organic compound, at least one of the layers containing the organic compound contains a specific compound, thereby producing an organic light-emitting device having a higher efficiency and a higher luminance light output. It has been found that the present invention can be performed, and the present invention has been completed.

That is, the first aspect of the organic light emitting device of the present invention is an organic light emitting device having at least a pair of electrodes comprising an anode and a cathode, and a layer containing one or more organic compounds sandwiched between the pair of electrodes. Wherein at least one of the layers containing the organic compound contains a compound represented by the following general formula [1].

[0011]

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(In the formula [1], R _{1 to} R ₆ represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkoxy group, Represents any of unsubstituted heterocyclic groups, provided that R _{1 to} R ₆ may be the same or different, R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ May form a condensed ring.)

That is, the second aspect of the organic light emitting device of the present invention is an organic light emitting device having at least a pair of electrodes comprising an anode and a cathode, and a layer containing one or more organic compounds sandwiched between the pair of electrodes. Wherein at least one of the layers containing the organic compound contains a compound represented by the following general formula [2].

[0014]

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(In the formula [2], R _{7 to} R ₁₂ represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkoxy group, Represents any of unsubstituted heterocyclic groups, provided that R _{7 to} R ₁₂ may be the same or different, R ₇ and R ₈ , R ₉ and R ₁₀ , R ₁₁ and R ₁₂ May form a condensed ring.)

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

First, the above general formula [1] used in the present invention
The compound represented by [2] will be described.

[0018] Formula [1] [2] substituent in R ₁ ~
Specific examples of R ₁₂ given below.

Examples of the substituted or unsubstituted alkyl group and aralkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a ter-butyl group, an octyl group, a benzyl group and a phenethyl group.

Examples of the substituted or unsubstituted alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a 2-ethyl-octyloxy group, a phenoxy group, a 4-butylphenoxy group and a benzyloxy group.

Examples of the substituted or unsubstituted aryl groups include phenyl, 4-methylphenyl, 4-ethylphenyl, 3-chlorophenyl, 3,5-dimethylphenyl, triphenylamino, biphenyl, Examples include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and a pyrenyl group.

As the substituted or unsubstituted heterocyclic group,
Examples include a pyridyl group, a bipyridyl group, a methylpyridyl group, a thienyl group, a terthienyl group, a propylthienyl group, a furyl group, a quinolyl group, a carbazolyl group, and an N-ethylcarbazolyl group.

The substituents that R _{1 to} R ₁₂ may have include methyl, ethyl, n-propyl, iso-propyl, ter-butyl, octyl, benzyl, Alkyl group such as phenethyl group, aralkyl group, methoxy group, ethoxy group, propoxy group, 2-
Ethyl-octyloxy group, phenoxy group, 4-butylphenoxy group, alkoxy group such as benzyloxy group, phenyl group, 4-methylphenyl group, 4-ethylphenyl group, 3-chlorophenyl group, 3,5-dimethylphenyl group , Triphenylamino group, biphenyl group, terphenyl group, naphthyl group, anthryl group, phenanthryl group,
Aryl group such as pyrenyl group, pyridyl group, bipyridyl group, methylpyridyl group, thienyl group, terthienyl group,
Examples include, but are not limited to, heterocyclic groups such as propylthienyl group, furyl group, quinolyl group, carbazolyl group, and N-ethylcarbazolyl group.

Next, typical examples of the compounds represented by the general formulas [1] and [2] will be given. However, it is not limited to these compounds.

[0025]

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[0026]

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[0027]

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Next, the organic light emitting device of the present invention will be described 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, as the luminescent material, a material having one or both functions of a hole transporting property and an electron transporting property is used for each layer, and used in combination with a mere hole transporting substance having no light emitting property or an electron transporting substance. Useful in cases. Further, in this case, the light emitting layer is composed of either the hole transport layer 5 or 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 light emission, and is used in a timely combination with a compound having hole transport, electron transport, and light emitting properties. Can be used, so that the emission hue can be diversified. Further, it is possible to effectively confine each carrier or exciton in the central light emitting layer 3 to improve the luminous efficiency.

However, FIGS. 1 to 3 show only very basic device configurations, and the configuration of the organic light-emitting device using the compound of the present invention is not limited to these. For example, various layer configurations such as providing an insulating layer at the interface between the electrode and the organic layer, providing an adhesive layer or an interference layer, and forming the hole transport layer from two layers having different ionization potentials can be employed.

The compounds represented by the general formulas [1] and [2] used in the present invention are extremely excellent in electron injecting property, electron transporting property and light emitting property as compared with conventional compounds. Either form of FIG. 3 can be used.

In particular, the organic layer using the compounds represented by the general formulas [1] and [2] of the present invention is useful as an electron transport layer and also as a light emitting layer.

In the organic light emitting device of the present invention, the compound represented by the general formulas [1] and [2] is formed between the anode 2 and the cathode 4 by a vacuum deposition method or a solution coating method. The thickness of the organic layer is thinner than 10 μm, preferably 0.5 μm or less, more preferably 0.01 to 0.5 μm.

In the present invention, the compounds represented by the above general formulas [1] and [2] are used as constituents of the electron transporting and light emitting layer. If necessary, conventionally known hole transporting compounds may be used. A light-emitting compound, a light-emitting layer matrix compound, an electron-transport compound, a charge-transport polymer material, and a light-emitting polymer material (for example, compounds shown below) can be used together as necessary. However, it is needless to say that the present invention is not limited to these. Hole transport compound

[0037]

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Electron transporting luminescent material

[0039]

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Light emitting material

[0041]

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Light emitting layer matrix material and electron transport material

[0043]

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Polymer-based hole transporting material

[0045]

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Polymer light emitting material and charge transporting material

[0047]

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In the organic light emitting device of the present invention, the layer containing the compounds represented by the general formulas [1] and [2] and the layer containing other organic compounds are generally formed by vacuum evaporation or by dissolving in an appropriate solvent. To form a thin film by a coating method. In particular, when forming a film by a coating method, the film can be formed in combination with an appropriate binder resin.

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

The anode material preferably has a work function as large as possible. For example, simple metals such as gold, platinum, nickel, palladium, cobalt, selenium, and vanadium or alloys thereof, tin oxide, zinc oxide, indium tin oxide ( Metal oxides such as ITO) and indium zinc oxide can be used. Further, conductive polymers such as polyaniline, polypyrrole, polythiophene, and polyphenylene sulfide can also be used. These electrode substances may be used alone or in combination of two or more.

On the other hand, it is preferable that the cathode material has a small work function, such as lithium, sodium, potassium, calcium, magnesium, aluminum, indium, silver, and the like.
It can be used as a single metal or a plurality of alloys such as lead, tin and chromium. It is also possible to use metal oxidation such as indium tin oxide (ITO). Further, the cathode may have a single-layer structure or a multilayer structure.

The substrate used in the present invention is not particularly limited, but an opaque substrate such as a metal substrate and a ceramic substrate, and a transparent substrate such as glass, quartz and a plastic sheet are used. Further, it is also possible to control the emitted light by using a color filter film, a fluorescent color conversion filter film, a dielectric reflection film or the like on the substrate.

It is to be noted that a protective layer or a sealing layer may be provided on the fabricated device for the purpose of preventing contact with oxygen, moisture, or the like. Examples of the protective layer include an inorganic material film such as a diamond thin film, a metal oxide, and a metal nitride; a polymer film such as a fluorine resin, polyparaxylene, polyethylene, a silicone resin, and a polystyrene resin; and a photocurable resin. Can be Alternatively, the device itself can be covered with glass, a gas impermeable film, metal, or the like, and the element itself can be packaged with an appropriate sealing resin.

[0054]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 An element having the structure shown in FIG. 1 was prepared.

On a glass substrate as a substrate 1, indium tin oxide (ITO) as an anode 2 was
A film having a thickness of 0 nm was used as a transparent conductive support substrate. This was ultrasonically washed sequentially with acetone and isopropyl alcohol (IPA), boiled and washed with IPA, and dried. Further, the substrate subjected to UV / ozone cleaning was used as a transparent conductive support substrate.

The above-mentioned Compound No. 0.050g of 27
And 1.00 g of polyvinyl carbazole was dissolved in 75 ml of tetrahydrofuran to prepare a solution. Using this solution, a spin coating method (20
An organic layer film (light-emitting layer 3) having a thickness of 120 nm was formed at a speed of 00 rpm.

Next, a metal layer film (cathode 4) having a thickness of 150 nm was formed on the above organic layer by a vacuum deposition method using a deposition material composed of aluminum and lithium (lithium concentration: 1 atomic%). . The degree of vacuum during vapor deposition is 1.0 × 1
The film was formed under the conditions of 0 ^-4 Pa and a film formation speed of 1.0 to 1.2 nm / sec.

When a DC voltage of 8 V is applied to the device thus obtained with an ITO electrode serving as a positive electrode and an Al-Li electrode serving as a negative electrode, a current flows at a current density of 2.3 mA / cm ² and an initial luminance Blue light emission of 145 cd / m ² was observed.

Example 2 An element having the structure shown in FIG. 2 was prepared.

The hole transport layer 5 was formed on the same transparent conductive support substrate as in Example 1 by depositing α-NPD shown in Chemical formula 8 to a thickness of 70 nm by a vacuum evaporation method. Further, the above-mentioned exemplified compound No. 13 was formed into a film having a thickness of 50 nm by a vacuum evaporation method to form an electron transport layer 6. The degree of vacuum at the time of vapor deposition is 1.0 × 10 ⁻⁴ Pa, and the film formation rate is 0.2 to 0.3 n.
The film was formed under the conditions of m / sec.

Next, an Al—Li electrode was formed in the same manner as in Example 1.

When a DC voltage of 8 V was applied to the device thus obtained with an ITO electrode serving as a positive electrode and an Al-Li electrode serving as a negative electrode, a current flowed at a current density of 5.1 mA / cm ² , resulting in an initial luminance. Blue-green light emission of 320 cd / m ² was observed.

Example 3 An element having the structure shown in FIG. 3 was prepared.

On the same transparent conductive support substrate as in Example 1, a hole transporting layer 5 was formed by depositing TPD shown in Chemical formula 8 to a thickness of 70 nm by a vacuum evaporation method. The light emitting layer 3 was formed to a thickness of 25 nm by a vacuum evaporation method using aluminum trisquinolinol. Further, exemplary compound N
o. 1 was formed into a film having a thickness of 40 nm by a vacuum evaporation method to form an electron transport layer 6. The degree of vacuum during deposition is 1.0 × 10 ^-4
The film was formed under the conditions of Pa and a film formation rate of 0.2 to 0.3 nm / sec.

Next, an Al—Li electrode was formed in the same manner as in Example 1.

When a DC voltage of 8 V was applied to the device thus obtained with an ITO electrode as a positive electrode and an Al-Li electrode as a negative electrode, a current flowed at a current density of 5.4 mA / cm ² , Green light emission of 570 cd / m ² was observed.

Further, this element was placed under a nitrogen atmosphere.
When the voltage was applied for 1,000 hours while maintaining the current density at 5.0 mA / cm ² , the initial luminance was 450 cd / m ² to 10
After 00 hours, the luminance was 400 cd / m ² and the luminance deterioration was very small.

Comparative Example 1 A device of Comparative Example 1 was prepared in exactly the same manner as the device of Example 3 except that the compound used in the electron transport layer 6 of Example 3 was changed to a compound having the following structural formula. .

[0070]

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When a DC voltage of 8 V is applied to the device thus obtained with an ITO electrode serving as a positive electrode and an Al-Li electrode serving as a negative electrode, a current flows at a current density of 3.7 mA / cm ² , and an initial luminance is obtained. Green emission of 55 cd / m ² was observed.

Further, this element was placed in a nitrogen atmosphere.
When a voltage was applied for 1000 hours while maintaining the current density at 5.0 mA / cm ² , the initial luminance was 60 cd / m ² to 100.
No light emission was observed after 0 hour.

[0073]

The organic light-emitting device using the compound of the present invention, as shown in Examples and Comparative Examples, can emit light with high luminance at a low applied voltage and has excellent durability.

In particular, the organic layer using the compound of the present invention
It is useful as an electron transporting layer, and also useful as, for example, a light emitting layer that emits blue light.

Further, the device can be prepared by using a vacuum deposition method or a casting method, and a relatively inexpensive device having a large area can be easily prepared.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an organic light emitting device according to the present invention.

FIG. 2 is a cross-sectional view illustrating another example of the organic light emitting device according to the present invention.

FIG. 3 is a cross-sectional view illustrating another example of the organic light emitting device according to 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

Claims (2)

[Claims] A pair of electrodes comprising an anode and a cathode;
In an organic light-emitting element having at least a layer containing one or more organic compounds sandwiched between the pair of electrodes, at least one of the layers containing the organic compound contains a compound represented by the following general formula [1]. An organic light-emitting device, comprising: Embedded image (In the formula [1], R _{1 to} R ₆ represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted Represents any of heterocyclic groups, provided that R
_{1 to} R ₆ may be the same or different. Also, R
₁ and R ₂ , R ₃ and R ₄ , and R ₅ and R ₆ may form a condensed ring. ) 2. A pair of electrodes comprising an anode and a cathode,
In an organic light-emitting element having at least a layer containing one or more organic compounds sandwiched between the pair of electrodes, at least one of the layers containing the organic compound contains a compound represented by the following general formula [1]. An organic light-emitting device, comprising: Embedded image (In the formula [2], R _{7 to} R ₁₂ represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkoxy group,
Shows either a substituted or unsubstituted heterocyclic group. However,
R _{7 to} R ₁₂ may be the same or different. R ₇ and R ₈ , R ₉ and R ₁₀ , and R ₁₁ and R ₁₂ may form a condensed ring. )