JP2000306670A - Organic luminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminescent element having high luminance and a long life by containing pyrazine compound in at least one of layers containing organic compound sandwitched by a positive electrode and a negative electrode. SOLUTION: At least one of layers composed of organic compound is this organic luminescent element containing pyrazine compound represented by a formula (where R1-4 are H, a halogen atom, a cyano group, a nitro group, an ester group, an amino group, an alkyl group, an alkoxy group, an aryl group, or an aromatic complex ring group; Ar1-4 are an aryl group or an aromatic heterocyclic group). Ar1-4 are preferably polyphenylene such as a biphenyl group, triphenylamino group, a tarphenyl group, or an aromatic condensation multi-ring group such as a bipyridyl group or a carbazolyl group. A pyrazine compound film is formed in thickness less than 0.05-0.5 μm between a positive electrode and a negative electrode, in a vacuum deposition method or a solution coating method combined with bonding resin. An organic layer containing a compound represented by a formula is suitable for an electron injection layer, an electron transportation layer, and a luminescent layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device that emits light by applying an electric field to a thin film made of 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 using ITO as an anode, an alloy of magnesium and silver as a cathode, using an aluminum quinolinol complex as an electron transporting material and a luminescent material, and using a triphenylamine derivative as a hole transporting material. This element has a two-layer structure and is applied at a voltage of about 10 V at a voltage of 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 and U.S. Pat. No. 4,885,211.

[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-
No. 2,028,782, 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, emission of blue, green, and red light with good color purity is required, but this problem has not yet been sufficiently solved.

Further, as patents related to light emitting devices using a pyrazine compound, there are, for example, JP-A-4-46987, JP-A-4-103688, and JP-A-4-117.
No. 485, for example, when these compounds are used, there is a problem in the stability of the thin film, and particularly, the durability of the element is not sufficient.

[0009]

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.

[0010]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention.

That is, the present invention provides 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. An organic light-emitting device wherein at least one of the layers contains a pyrazine compound represented by the following general formula [1].

[0012]

Embedded image

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, a halogen atom, a cyano group, a nitro group, a substituted or unsubstituted ester group, a substituted or unsubstituted amino group, Represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group or a substituted or unsubstituted aromatic heterocyclic group, and Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ each represent Independently represents a substituted or unsubstituted aryl group or a substituted or unsubstituted aromatic heterocyclic group.)

[0014]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to 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. By making at least one of the layers comprising the pyrazine compound represented by the following general formula [1], an organic light-emitting device having higher efficiency and higher luminance light output can be produced.

[0015]

Embedded image

In the above general formula [1], R ¹ , R ² , R ³ , R ⁴
Is independently a hydrogen atom, a halogen atom, a cyano group,
Nitro group, substituted or unsubstituted ester group, substituted or unsubstituted amino group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted aryl group, and substituted or unsubstituted aromatic group Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ each independently represent a substituted or unsubstituted aryl group or a substituted or unsubstituted aromatic heterocyclic group.

Next, the above substituents R ¹ , R ² , R ³ , R ⁴
Specific examples of Ar ¹ , Ar ² , Ar ³ and Ar ⁴ are shown below. First, a hydrogen atom, a cyano group, and a nitro group are exemplified. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The substituted or unsubstituted amino group includes
Examples include amino groups and substituted amino groups such as dimethylamino, diethylamino, diphenylamino, and dibenzylamino groups.

Examples of the substituted or unsubstituted ester group include a methyl ester group, an ethyl ester group, a phenyl ester group, a 3-methylphenyl ester group, and a 4-cyanophenyl group.

Examples of the substituted or unsubstituted alkyl group include a methyl group, an ethyl group, an n-propyl group, an iso-propyl 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.

The substituted or unsubstituted aromatic heterocyclic group includes a pyridyl group, a bipyridyl group, a methylpyridyl group,
Examples thereof include a thienyl group, a terthienyl group, a propylthienyl group, a furyl group, a quinolyl group, a carbazolyl group, and an N-ethylcarbazolyl group. Ar ¹ , Ar ² , A
As r ³ and Ar ^4, a substituted or unsubstituted polyphenylene or a substituted or unsubstituted aromatic condensed polycyclic ring is preferable.

Next, Tables 1 to 10 show typical examples of the pyrazine compound represented by the general formula [1]. However, it is not limited to these compounds.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

[Table 6]

[0031]

[Table 7]

[0032]

[Table 8]

[0033]

[Table 9]

[0034]

[Table 10]

In the organic light emitting device of the present invention, the pyrazine compound represented by the above general formula [1] is formed between the anode and the cathode by a vacuum deposition method or a solution coating method. The thickness of the organic layer is less than 10 μm, preferably 0.5 μm.
m 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 luminous performance, or when a compound having each property is used as a mixture.

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, when the luminescent material has either the hole transporting property or the electron transporting property or a material having both functions in each layer, and is used in combination with a mere hole transporting substance having no luminescent property or an electron transporting substance Useful for In this case, the light emitting layer 3 is made 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 luminescence, and is used in a timely combination with a compound having each property of hole transport, electron transport, and luminescence.
The degree of freedom in material selection is greatly increased, and various compounds having different emission wavelengths can be used, so that the emission hue can be diversified. Furthermore, it is possible to effectively confine each carrier or exciton in the central light emitting layer to improve the light emission efficiency.

However, FIGS. 1 to 3 show only a very basic device structure, and the structure of an organic light emitting device using a layer made of an organic compound containing a pyrazine compound represented by the general formula [1] of the present invention is as follows. It is not limited to these.
For example, various layer configurations such as providing an insulating layer at an interface between an electrode and an organic layer, providing an adhesive layer or an interference layer, and forming a hole transport layer from two layers having different ionization potentials can be employed.

The pyrazine compound represented by the general formula [1] used in the present invention is a compound which is far superior in electron injecting property, electron injecting layer, electron transporting property and light emitting property as compared with conventional compounds. Any of the forms shown in FIGS. 1 to 3 can be used.

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 an electron transport layer, and is also useful as a light emitting layer.

In the present invention, the pyrazine compound represented by the above general formula [1] is used as a component of the electron transporting layer and the light emitting layer. For example, Table 11 below
To 14) or a luminescent compound (for example, a compound shown in Table 19 below) or an electron transporting compound (for example, a compound shown in Tables 15 to 18 below) as necessary. They can be used together.

[0043]

[Table 11]

[0044]

[Table 12]

[0045]

[Table 13]

[0046]

[Table 14]

[0047]

[Table 15]

[0048]

[Table 16]

[0049]

[Table 17]

[0050]

[Table 18]

[0051]

[Table 19]

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 by a vacuum deposition method or a coating method after dissolving in a suitable solvent. Form a thin film. 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, a single metal such as gold, platinum, nickel, palladium, cobalt, selenium, and vanadium or an alloy 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, the cathode material preferably 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 or a ceramic substrate, or a transparent substrate such as glass, quartz, or a plastic sheet is 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 manufactured 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 fluororesin, 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.

[0058]

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

Example 1 Indium tin oxide (ITO) having a thickness of 120 nm formed on a glass substrate by a sputtering method was used as a transparent conductive support substrate. This was ultrasonically washed with acetone and isopropyl alcohol (IPA) sequentially, washed with boiling IPA, and dried. Further, the substrate subjected to UV / ozone cleaning was used as a transparent conductive support substrate.

The above-mentioned Compound No. 0.050 g of 29
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
(00 rpm) to form an organic layer film having a thickness of 120 nm.

Next, a metal layer film having a thickness of 150 nm was formed on the above-mentioned organic layer by a vacuum evaporation method using a vapor deposition material composed of aluminum and lithium (lithium concentration: 1 atomic%). An element having the structure shown was prepared. The degree of vacuum at the time of deposition is 1.0 × 10 ⁻⁴ Pa, and the film formation rate is 1.0 to
The film was formed under the condition of 1.2 nm / sec.

When a DC voltage of 8 V is 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 flows at a current density of 2.3 mA / cm ² , and the initial luminance Blue light emission of 145 cd / m ² was observed.

Example 2 Indium tin oxide (ITO) formed on a glass substrate by sputtering to a thickness of 120 nm was used as a transparent conductive support substrate. This was ultrasonically washed with acetone and isopropyl alcohol (IPA) sequentially, washed with boiling IPA, and dried. Further, the substrate subjected to UV / ozone cleaning was used as a transparent conductive support substrate.

On a transparent conductive support substrate, the following structural formula [2]
Is formed into a film having a thickness of 70 nm by a vacuum evaporation method. A pyrazoline compound represented by No. 14 was formed into a film with a thickness of 50 nm by a vacuum evaporation method. The film was formed under the conditions of a vacuum degree of 1.0 × 10 ⁻⁴ Pa and a film formation rate of 0.2 to 0.3 nm / sec during the vapor deposition.

Next, a metal layer film having a thickness of 150 nm was formed on the above-mentioned organic layer by a vacuum vapor deposition method using a vapor deposition material composed of aluminum and lithium (lithium concentration 1 atomic%). An element having the structure shown was prepared. The degree of vacuum at the time of deposition is 1.0 × 10 ⁻⁴ Pa, and the film formation rate is 1.0 to
The film was formed under the condition of 1.2 nm / sec.

When a DC voltage of 8 V was applied to the device thus obtained with the ITO electrode serving as a positive electrode and the Al-Li electrode serving as a negative electrode, A current flowed at a current density of 1 mA / cm ² , and blue-green light emission with an initial luminance of 320 cd / m ² was observed.

[0067]

Embedded image

Example 3 Indium tin oxide (ITO) formed on a glass substrate by sputtering with a thickness of 120 nm was used as a transparent conductive support substrate. This was ultrasonically washed with acetone and isopropyl alcohol (IPA) sequentially, washed with boiling IPA, and dried. Further, the substrate subjected to UV / ozone cleaning was used as a transparent conductive support substrate.

On a transparent conductive support substrate, the following structural formula [3]
Was formed into a film having a thickness of 70 nm by a vacuum evaporation method to form a hole transport layer. Aluminum trisquinolinol was used as the light emitting layer, and 25
The film was formed with a thickness of nm. Further, the exemplified compound No. 35
Of the pyrazoline compound represented by
The electron transport layer was formed by forming a film having a thickness of m. 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, a metal layer film having a thickness of 150 nm was formed on the above-mentioned organic layer by a vacuum evaporation method using an evaporation material composed of aluminum and lithium (lithium concentration: 1 atomic%). An element having the structure shown was prepared. The degree of vacuum at the time of deposition is 1.0 × 10 ⁻⁴ Pa, and the film formation rate is 1.0 to
The film was formed under the condition of 1.2 nm / sec.

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 5.4 mA / cm ² , resulting in an initial luminance. Green light emission of 570 cd / m ² was observed.

[0072]

Embedded image

Further, this device was placed in 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 The device of Comparative Example 1 was completely identical to the device of Example 3 except that the compound used for the electron transporting layer of Example 3 was changed to a comparative compound represented by the following structural formula [4]. It was created.

[0075]

Embedded image

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

Further, this device was placed under 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.

[0078]

As described above, the organic light-emitting device having a layer containing the pyrazine compound represented by the general formula [1] of the present invention can be used at a low applied voltage and at a high applied voltage, as shown in Examples and Comparative Examples. Bright light emission is obtained and the durability is excellent.

In particular, the organic layer containing the pyrazine compound represented by the general formula [1] of the present invention 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 and large-area device 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

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiji Mashimo 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yuichi Hashimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Non-corporation F term (reference) 3K007 AB00 AB02 AB03 AB04 AB06 AB18 BB00 BB02 BB06 CA01 CA02 CA04 CA05 CA06 CB01 DA00 DB03 EB00 FA01

Claims (3)

[Claims] 1. An organic light-emitting element having at least a pair of electrodes comprising an anode and a cathode and one or more layers containing an organic compound sandwiched between the pair of electrodes, wherein at least one of the layers comprising the organic compound is provided. An organic light-emitting device wherein one layer contains a pyrazine compound represented by the following general formula [1]. Embedded image (Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a halogen atom, a cyano group, a nitro group, a substituted or unsubstituted ester group, a substituted or unsubstituted amino group,
Represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group or a substituted or unsubstituted aromatic heterocyclic group, Ar ¹ ,
Ar ² , Ar ³ , and Ar ⁴ each independently represent a substituted or unsubstituted aryl group or a substituted or unsubstituted aromatic heterocyclic group. ) 2. The organic light-emitting device according to claim ¹ , wherein Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ are a substituted or unsubstituted polyphenylene or a substituted or unsubstituted fused aromatic polycyclic. 3. The layer comprising the organic compound, wherein at least the electron injecting / transporting layer and the light emitting layer have the general formula [1].
The organic light-emitting device according to claim 1, comprising a pyrazine compound represented by the following formula: