JPH10335066A - Organic electroluminescent element and flat panel display using this organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the hole filling performance and electron filling performance, save the power consumption, and prolong the lifetime by having a hole filling layer between a positive electrode and a hole transport layer, and having an electron injection layer between a negative electrode and an electron transport layer. SOLUTION: In an EL element, direct current voltage is applied between a positive electrode 2 and a positive electrode 4 so that hole, which is filled from the positive electrode 2 through a hole filling layer 11, arrives a light emitting layer 7 through a hole transport layer 6 and so that electron, which is injected from the negative electrode 4 through an electron injecting layer 12, arrives the light emitting layer 7 through an electron transport layer 8. As a result, in the light emitting layer 7, recombination of the electron/hole is generated so as to generate the singlet exciton, and the light emission having the predetermined wavelength is generated. In the case of a layer structure (b), in which the light emitting layer is omitted, the light emission having the predetermined wavelength is generated from an interface of the hole transport layer 6 and the electron transport layer 8. These light emission is observed from a substrate 1 side. In the case of a transmission type EL element expressed with a figure (a), light emission can be observed from a protecting layer 5, besides from the substrate 1 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device and a flat panel display including a luminescent material which emits light by current injection, an organic electron transporting material, and the like as components thereof, and more particularly, from an anode to a hole transport layer. The present invention relates to an organic electroluminescent device characterized by a hole injection means and an electron injection means from a cathode to an electron transport layer, and a flat panel display using the same.

[0002]

2. Description of the Related Art Conventionally, a cathode ray tube has been most widely used as an image display for an information communication terminal device such as a computer and a television, which has features of high luminance and good color reproducibility, but is bulky. It is heavy and has large power consumption. Therefore, there is a great demand for a lightweight, thin, and highly efficient flat panel display. Currently, the most frequently used flat panel display is an active matrix drive type liquid crystal display.However, it has a narrow viewing angle, and when using a backlight because it is not self-luminous, the power consumption of this backlight is large. There is a problem that it does not have a sufficient response to a high-definition and high-speed video signal which is expected to be put to practical use, and there are problems such as uniformity and high cost in manufacturing a large screen display. There is a possibility of light emitting diodes as a candidate for a flat panel display instead of a liquid crystal display, but it is difficult to manufacture a light emitting diode matrix on a single substrate with a large area, and it has not become a low-cost display to replace a cathode ray tube .

As a flat panel display having the potential to solve these problems, a display employing an organic electroluminescent element has recently been receiving attention. This is advantageous in that self-luminous light has a high response speed and has no viewing angle dependence.

An organic electroluminescent device using an organic luminescent material is one in which an organic electroluminescent layer containing an organic luminescent material is sandwiched between a translucent anode and a metal cathode. CWTang
and SAVanSlyke et al. made the organic electroluminescent layer a two-layer structure consisting of a hole transport layer and an electron transport layer, and developed a device structure that emits light when holes and electrons injected from the anode and cathode into the organic electroluminescent layer recombine. First reported (Appl. Phys.
Lett., 51 (12), 913-915 (Sept. 1987)). In this device structure, either the hole transport layer or the electron transport layer also functions as the light emitting layer. Light emission occurs in a wavelength band corresponding to the energy gap between the ground state and the excited state of the light emitting material. By thus forming the organic electroluminescent layer in a two-layer structure, a drastic reduction in driving voltage and an improvement in luminous efficiency are achieved.
Since then, research aimed at application to all solid-state flat panel displays and the like has been advanced. Various metal complexes such as a zinc complex and an aluminum complex have been proposed as light emitting materials for obtaining high luminous efficiency.

[0005] Regarding the device structure, C. Adachi, T.
Tsutsui and S. Saito et al. Described an example of a three-layer structure consisting of a hole transport layer, a light-emitting layer, and an electron transport layer. Jap. J. of App
l. Phys. 27 -2, reported in L269-L271 (1988). Further, a light emitting material is included in the electron transport layer, and a two-layer structure of an electron transport layer also serving as a light emitting layer and a hole transport layer is described in CWTang, S. et al.
J. of Appl. Phy by A. VanSlyke and CHChen et al.
s. 65 -9, 3610-3616 (1989). From these reports, the possibility of high-brightness light emission at a low voltage has been verified, and research and development of organic electroluminescent devices have been very actively performed in recent years.

However, for practical use of the organic EL device, there are some problems to be solved, such as light emission luminance and durability. In order to realize an organic electroluminescent device having high emission luminance and excellent stability over time, in addition to the ability to transport electrons and holes, the barrier at the organic / inorganic interface is small and the injection properties of electrons or holes are excellent. Therefore, it is necessary to develop a durable element structure.

In an early research stage of an organic electroluminescent device, a TPD represented by the following formula (3) was used as a hole transporting material.
(N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-bip
henyl-4,4'-diamine) has been used. However, TPD has a melting point of about 170 ° C. and a glass transition point of about 60.
When used as a hole transporting material in organic electroluminescent devices, the device temperature rises due to the conversion of reactive current consumed during light emission driving other than light emission into heat. In extreme cases, the hole transport layer may be melted to stop the light emission.

[0008]

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In order to eliminate these disadvantages, equation (3)
The N substituent of TPD represented by N, N'-naphthyl phenyl
(US Pat. No. 5,615,695), and T
A compound represented by the following formula (4) in which a bipheny group located at the center of PD is a naphthalene group (for example, see JP-A-8-87
No. 122), a compound having an anthracene group (for example, JP-A-8-53397), or a compound having a phenanthlene group (for example, JP-A-8-20770, JP-A-8-20
No. 771).

[0010]

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On the other hand, as an example of the electron transporting material used for the electron transporting layer, an aluminum quinolinol complex represented by the following formula (5), Tris- (8-hydroxyqu
Inoline) -aluminium (hereinafter abbreviated as Alq3) is often used. Alq3 has an emission wavelength of 529n.
It is a green light-emitting material having a peak at m, and it can be said that a light-emitting material exceeding this material has not yet been obtained in terms of luminous efficiency and luminous life.

[0012]

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[0013]

However, none of the compounds mentioned as the hole transporting materials have been found to be materials having satisfactory hole transporting performance. That is, in addition to the performance improvement of the hole transporting material, it is necessary to enhance the overall hole transporting capacity in consideration of the high efficiency of the hole injection at the stage of the hole injection from the anode to the hole transporting layer.

Further, even in Alq3, which has been evaluated to a certain degree as an electron transporting material, damage to the electron transporting layer containing Alq3 by the incident metal particles during the formation of the cathode by sputtering or the like, and the problem of the cathode metal and the electron transporting layer Due to the presence of a structural defect such as the occurrence of a non-contact portion, a non-light emitting point called a dark spot may occur, or element deterioration may be accelerated. Therefore, in addition to improving the performance of the electron transporting material itself, it is necessary to consider the overall efficiency of electron injection at the stage of injecting electrons from the cathode into the electron transport layer, and to avoid damage during cathode film formation. Transport capacity needs to be improved.

The present invention has been proposed in view of such technical background, and has improved hole injection performance between an anode and a hole transport layer and electron injection performance between a cathode and an electron transport layer, and has excellent hole transport efficiency and electron transport efficiency. An object of the present invention is to provide an organic electroluminescent device and to further improve the luminance and durability of the organic electroluminescent device and a flat panel display using the same.

[0016]

SUMMARY OF THE INVENTION The present invention proposes to achieve the above object. That is, the organic electroluminescent device of the present invention is an organic electroluminescent device having a structure in which an organic electroluminescent layer including a hole transport layer and an electron transport layer is sandwiched between an anode and a cathode. And a hole injection layer between the cathode and the electron transport layer.

A preferred configuration of the organic electroluminescent device of the present invention is such that an organic electroluminescent layer comprising a hole injection layer, at least a hole transport layer, a light emitting layer, and an electron transport layer on an anode, and an electron injection layer. And a cathode are sequentially laminated in this order.

In another preferred configuration of the organic electroluminescent device of the present invention, an organic electroluminescent layer comprising a hole injection layer, at least a hole transport layer, and an electron transport layer, an electron injection layer, The cathode is characterized in that the cathode and the cathode are sequentially laminated. Such an element structure is
One of the hole transport layer and the electron transport layer also serves as the light emitting layer.

The hole injection layer, which is one of the essential components of the present invention, is characterized by having at least one kind of tetraphenyl metal compound represented by the following general formula (1).

[0020]

Embedded image However, in the general formula (1), M represents a metal atom. Preferred metal atoms include Ge, Sn, Pb, As and At.
Etc. are exemplified. Further, these tetraphenyl metal compounds may be salts of halogen such as chlorine and bromine.

In the present invention, the thickness of the hole injection layer is 1
It is desirable that the thickness be 0 nm or less. The lower limit of the thickness of the hole injection layer is not particularly limited as long as it is formed as a uniform continuous film, but from the viewpoint of controlling the film thickness in a film forming apparatus, the thickness is preferably one molecular layer or more, and practically 0.5 nm or more. desirable.

The electron injection layer, which is another essential component of the present invention, preferably has at least one porphyrin derivative represented by the following general formula (2). In the general formula (2), preferred metal atoms are Co, Cu, P
Examples thereof include b, Cd, Zn, Mn, and Ca. The feature of the porphyrin derivative is that the porphyrin derivative has functional groups of a nitrogen-containing heterocyclic ring at positions 5, 10, 15, and 20 of the porphyrin ring.

[0023]

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It is desirable that the thickness of the electron injection layer is also 10 nm or less. The lower limit of the thickness is not particularly limited as long as the film is formed as a uniform continuous film. However, from the viewpoint of controlling the film thickness in a film forming apparatus, the thickness is preferably one molecular layer or more, and practically 0.5 nm or more.

In the organic electroluminescent device of the present invention, since an extremely thin hole injection layer is newly provided between the anode and the hole transport layer, the interface between the anode made of a transparent conductive material such as ITO and the hole transport layer is provided. And the hole injection efficiency is improved. The hole injection layer also functions as a barrier layer for preventing diffusion of oxygen or adsorbed water from a transparent conductive material such as ITO into the hole transport layer at the time of heat generation of the element, thereby preventing deterioration of the hole transport material. In addition, ITO
By inserting a tetraphenyl metal compound layer having an intermediate energy level between the energy level of a metal oxide such as the one described above and the energy level of a hole transport material that is an organic substance,
From this aspect, it is inferred that this contributes to the improvement of the hole injection efficiency. As described above, since the hole injection layer controls the state of the interface between the anode and the hole transport layer, a thin film having a thickness of 10 nm or less is sufficient. Further, this tetraphenyl metal compound is sublimable, and it is possible to easily form a dense film having a controlled film thickness by a means such as a molecular beam evaporation method.

Further, in the organic electroluminescent device of the present invention, an extremely thin electron injection layer is newly provided between the cathode and the electron transport layer. The adhesion at the interface is improved, and the electron injection efficiency is improved. The electron injection layer also functions as a barrier layer for preventing diffusion of oxygen and adsorbed water from the cathode made of a metal material such as aluminum into the electron transport layer when the element generates heat, thereby preventing deterioration of the electron transport material. I do. Further, by inserting a porphyrin derivative layer having an energy level intermediate between the energy level of a metal such as aluminum and the energy level of an electron transporting material that is an organic substance, the electron injection efficiency can be improved from this aspect as well. It is considered to contribute. In addition, when the cathode is formed by sputtering or the like, damage to the electron transport layer can be prevented. As described above, the electron injection layer controls the state of the interface between the cathode and the electron transport layer.
A thin film of nm or less is sufficient. This porphyrin derivative is sublimable, and a dense film with a controlled film thickness can be easily formed by means such as molecular beam evaporation.

Since the hole transporting efficiency and the electron transporting efficiency are both improved by these comprehensive actions, an organic electroluminescent device having high luminance and excellent durability and a flat panel display using the same can be provided by the synergistic effect. Can be made.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. First, the concept of a device configuration in which the organic electroluminescent device of the present invention is applied to an EL device will be described with reference to schematic sectional views shown in FIGS. Among them, FIG. 1A shows the device configuration of a transmission type organic electroluminescent device, and FIG. 1B shows the device configuration of a reflection type organic electroluminescent device. The arrow in the figure indicates the direction in which light is emitted.

In each of the element configurations, reference numeral 1 denotes a substrate made of a transparent material such as glass or plastics, or another suitable material such as silicon. When the organic electroluminescent device is used in combination with another display device, a driving circuit, or the like, the substrate 1 can be shared. Reference numeral 2 denotes an anode, which is made of a transparent conductive material such as Sb-containing SnO ₂ , Al-containing ZnO, or Au thin film in addition to ITO (Indium Tin Oxide) and SnO ₂ . Alternatively, a conductive polymer thin film such as polythiophene or polypyrrole may be used. The electric resistance of the anode is preferably low in order to reduce power consumption and heat generation of the element. The method for forming the anode is not particularly limited, and a vacuum deposition method using an electron beam or the like, a sputtering method, a CVD method, or the like can be appropriately employed.

Reference numeral 3 denotes an organic electroluminescent layer, the structure of which will be described later.

Reference numeral 4 denotes a cathode, and as an electrode material, for example, an active metal having a low work function such as Li, Mg or Ca;
An alloy with Ag, Al, In or the like or a laminated structure can be adopted. The film formation method is not particularly limited, and a vacuum evaporation method such as resistance heating, an ion plating method, a sputtering method, or the like can be employed. In the case of the transmission type organic electroluminescent device shown in FIG. 1A, by adjusting the thickness of the cathode 4, a light transmittance suitable for the intended use can be obtained. To complement the conductivity of the cathode 4, an additional IT
A transparent conductive film such as O or SnO ₂ may be stacked and used.

Reference numeral 5 denotes a protective layer formed as necessary, and any material can be adopted as long as the material satisfies airtightness, optical characteristics, and the like, regardless of an organic material such as plastics or an inorganic material such as SiO _2. .

Reference numerals 11 and 12 are characteristic portions of the organic electroluminescent device of the present invention, and reference numeral 11 is a hole injection layer inserted between the anode 2 and a hole transport layer (not shown) of the organic electroluminescent layer 3. It is. Reference numeral 12 denotes an electron injection layer inserted between the cathode 4 and an electron transport layer (not shown) of the organic electroluminescent layer 3.

The hole injection layer 11 is made of the above-described general formula (1)
And a mixture thereof using a vacuum technique such as vacuum deposition by resistance heating, ion plating, molecular beam deposition, or molecular beam epitaxy. In addition to the membrane method,
Chemical modification method, spin coating method or LB (Langmuir-Br
(odjet) method or the like. Since the hole injection layer 11 is an extremely thin film having a thickness of 10 nm or less, it is desirable to adopt a film formation method having good film thickness controllability.

The electron injection layer 12 is composed of one or a mixture of the porphyrin derivatives represented by the above-mentioned general formula (2), and is formed by a vacuum deposition method such as resistance heating, an ion plating method, or a molecular beam deposition method. In addition to film forming methods using vacuum techniques such as molecular beam epitaxy, chemical modification, spin coating or LB (Langmuir-Brodjet)
It is also possible to use a wet film forming method such as a method. Since the electron injection layer 12 is also an extremely thin film having a thickness of 10 nm or less, it is desirable to adopt a film formation method with good film thickness controllability.

FIGS. 2A and 2B show a more detailed layer structure of the organic electroluminescent layer 3. The basic configuration of the organic electroluminescent layer 3 is a layer configuration capable of obtaining organic electroluminescence,
Any of the conventionally proposed structures can be adopted.
That is, as shown in FIG. 2A, in addition to the three-layer structure in which the hole transport layer 6 / light-emitting layer 7 / electron transport layer 8 are laminated in this order from the anode 2, the hole transport layer 6 and the electron transport layer 8 In the case where any one of the above has a light emitting property, the light emitting layer 7 is also used as these layers, and as shown in FIG. A structure is also possible.

The hole transport layer 6 is made of a hole transport material alone,
Alternatively, it is formed by uniformly dispersing a hole transport material in a matrix such as an organic polymer. As the hole transport material, TPD (N, N'-diphenyl-N, N'-bi) represented by the following formula (3) is used.
s (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine),
Compounds in which the biphenyl skeleton is substituted with condensed rings, tertiary amines such as N-isopropylcarbazole, pyrazoline derivatives, stilbene compounds, hydrazone compounds, heterocyclic compounds represented by oxadiazole derivatives and phthalocyanine derivatives, polymer systems In these, polycarbonate derivatives and polystyrene derivatives having these monomers in the side chain,
Polyvinyl carbazole or polysilane can be preferably used, but is not particularly limited.

[0038]

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As the light emitting material used for the light emitting layer, in addition to Alq3 represented by the above formula (5), anthracene,
Pyrene, bisstyrylanthracene derivative, tetraphenylbutadiene derivative, coumarin derivative, oxadiazole derivative, distyrylbenzene derivative, pyrrolopyridine derivative, perinone derivative, cyclopentadiene derivative, oxadiazole derivative, thiadiazolopyridine derivative, and polymer type For example, a polyphenylenevinylene derivative, a polyparaphenylene derivative, a polythiophene derivative, or the like can be used, but the present invention is not limited thereto.
As a dopant to be added to the light emitting layer, rubrene, a quinacridone derivative, DCM (4-dicyanomethylene-6) is used.
-(P-dimethylaminostyryl) -2-methyl 4H-
Pyran), perinone, perylene, coumarin and the like may be used.

The electron transporting material used for the electron transporting layer may be any substance having a high electron transporting efficiency. For this purpose, the electron transporting material has high electron affinity and electron mobility, high stability, and further has impurities during production and light emission. It is desirable that the material does not generate. As such a material, Alq3 represented by the aforementioned formula (5) is exemplified, but another material may be used.

The various organic electroluminescent layer materials are formed by sequentially laminating the materials themselves, but may be dispersed and laminated in a polymer and sandwiched between an anode and a cathode. Polymer polymers include polyvinyl chloride,
Examples thereof include polycarbonate and polystyrene, but are not limited thereto. The formation method of each of these layers contributing to light emission includes a vapor deposition method using resistance heating, an electron beam, or the like,
Dry film forming methods such as ion plating, molecular beam evaporation, molecular beam epitaxy, and sputtering are preferable, but wet film forming methods such as chemical modification, spin coating, and LB are also used. Is also possible.

In order to improve the hole or electron charge transport performance, one or both of the hole transport layer 6 and the electron transport layer 8 have a structure in which a plurality of types of materials are laminated.
Alternatively, a structure in which a plurality of types of materials are mixed may be used.
Further, in order to improve the light emitting performance, any one or more of the hole transport layer 6, the light emitting layer 7, and the electron transport layer 8 may contain a fluorescent material. The fluorescent material is not particularly limited, and examples thereof include quinacridone and DCM (4-dicyanomethylene-6- (p-dimethylaminostyryl) -2-methyl-4H-pyran) represented by the following structural formula (6). Is done. In these cases,
In order to further improve the luminous efficiency, a thin film for controlling the transport of holes or electrons can be included in the layer structure.

[0043]

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In the EL device shown in FIG.
By applying a DC voltage between the anode 2 and the cathode 4,
Holes injected from the anode 2 through the hole injection layer 11 pass through the hole transport layer 6 and from the cathode 4 to the electron injection layer 1.
The electrons injected through 2 pass through the electron transport layer 8 and reach the light emitting layers 7 respectively. As a result, electron / hole recombination occurs in the light emitting layer 7 to generate singlet excitons, and the singlet excitons emit light of a predetermined wavelength.
In the case of the layer configuration in which the light emitting layer shown in FIG.
Light of a predetermined wavelength is generated from the interface between the hole transport layer 6 and the electron transport layer 8. These light emissions are observed from the substrate 1 side. In the case of the transmission type EL element shown in FIG. 1A, light emission is also observed from the protective layer 5 side.

The current applied to the organic electroluminescent device is usually a direct current, but a pulse current or an alternating current may be used. The current value and the voltage value are not particularly limited as long as they are within a range that does not cause element destruction. However, in consideration of power consumption and life of the organic electroluminescent element, it is desirable to emit light efficiently with as little electric energy as possible.

An example in which the light emitting device of the present invention is applied to an actual organic EL device is shown in a schematic perspective view of FIG. EL of FIG.
The device has a structure in which an electron injection layer 12, an organic electroluminescent layer 3, and a hole injection layer 11 are disposed between a cathode 4 and an anode 2. The layer configuration of the organic electroluminescent layer 3 may be any of the above-described FIG. 2A or FIG. 2B. The cathode 4 and the anode 2 are both patterned in a stripe pattern and are orthogonal to each other in a matrix. The control circuits 9 and 10 having a built-in shift register apply a signal voltage in a time series manner, and emit light at the crossing position. It was done. The EL element having such a configuration is composed of a character
It can be used not only as a display for symbols and the like but also as an image reproducing device. Further, it is possible to arrange a stripe pattern of the cathode 4 and the anode 2 corresponding to each color of red (R), green (G) and blue (B) to constitute a multi-color or full-color all solid-state flat panel display. It becomes possible. The illustrated EL element is a configuration example of a simple matrix display having an 8 × 3 RGB configuration, but any conventionally known drive circuit, electrode configuration, and the like can be adopted.

Hereinafter, preferred examples of the organic electroluminescent device of the present invention will be described in more detail while appropriately adding comparative examples. However, the present invention is not limited to these examples.

Example 1 Fabrication of Organic Electroluminescent Element In this example, among the tetraphenyl metal compounds represented by the general formula (1), tetraphenylgermanium (abbreviated as TPGe) was used as a material for the hole injection layer. Among the porphyrin derivatives of the formula (2), 5, 10, 15,
This is an example in which 20-tetra (4-pyridyl) -21H, 23H-porphyrin nickel (abbreviated as NiTPyP) is employed as an electron injection layer material to produce an organic electroluminescent device.

An anode made of ITO having a thickness of 100 nm was formed on a surface of a 30 mm × 3
A 0 mm glass substrate was set 25 cm above the molecular beam source. As a deposition mask, a plurality of 2.0 mm ×
A metal mask having a unit opening of 2.0 mm is arranged close to the substrate, and TPGe is deposited to a thickness of, for example, 1 nm under an ultra-high vacuum of 10 ⁻⁷ Pa or less by a molecular beam evaporation method to form a hole injection layer. Formed. The film formation rate was controlled to, for example, 0.1 nm / sec or less by a film thickness monitor using a quartz oscillator.

Next, the substrate on which the hole injection layer is formed is transported to a resistance heating type vacuum evaporation apparatus, and the substrate is placed above the evaporation source.
It was set at a position of 5 cm. As a deposition mask,
Similarly, a plurality of metal masks each having a unit opening of 2.0 mm × 2.0 mm are arranged close to the substrate and aligned with the pattern of the hole injection layer formed earlier, and 10 ⁻⁷ Pa is applied by vacuum evaporation. The TPD represented by the above formula (3) was deposited to a thickness of, for example, 50 nm under the following high vacuum to form a hole transport layer. The film formation rate was controlled at, for example, 2 nm / sec by a film thickness monitor using a quartz oscillator.

Further, in the same resistance heating type vacuum deposition apparatus, Alq3 represented by the above-mentioned formula (5) was deposited on the hole transporting layer as a material serving also as the light emitting layer and the electron transporting layer. The layer thickness of Alq3 was also set to, for example, 50 nm, and the film formation rate was also controlled to, for example, 2 nm / sec by a film thickness monitor using a quartz oscillator.

Further, Alq serving as both a light emitting layer and an electron transport layer
The substrate on which the three layers were formed was transported to a molecular beam deposition apparatus, and set at a position 25 cm above the molecular beam source. As a vapor deposition mask, a plurality of 2.0 mm × 2.0 mm
A metal mask having a unit opening is placed in close proximity to the substrate and aligned with the pattern of the previously formed Alq3 layer, and NiTPyP is placed under ultra vacuum of 10 ⁻⁷ Pa or less by molecular beam evaporation. Was formed to a thickness of, for example, 1 nm to form an electron injection layer. The film formation rate was controlled to 0.1 nm / sec or less by a film thickness monitor using a quartz oscillator. The reason why the molecular beam evaporation method was used to form the hole injection layer and the electron injection layer is that the thickness control in the formation of an extremely thin film is easier as compared with a normal resistance heating evaporation method or the like.

As the cathode material, a laminated film of Mg and Ag is employed, which is formed by ordinary resistance heating vacuum evaporation at a deposition rate of 4 nm / sec to a thickness of, for example, 50 nm (Mg) and 150 nm (Ag). Then, a basic form of the organic electroluminescent device according to Example 1 was manufactured.

Evaluation of Light Emitting Characteristics Light emitting characteristics were evaluated by applying a forward bias DC voltage in a nitrogen atmosphere to the organic electroluminescent device of Example 1 thus manufactured. It emitted a green light, which was found by spectrometry to have a peak at 529 nm in FIG. For the spectroscopic measurement, a spectroscope using a photodiode array made by Otsuka Electronics as a detector was used. The spectrum in FIG. 4 matched the emission spectrum of Alq3, and it was confirmed that the emission of the EL element was due to Alq3. When the applied voltage was gradually increased and the luminance was measured by a luminance meter, a luminance of 1000 cd / m ² was obtained at an applied voltage of 9 V. After manufacturing this organic electroluminescent device, it was left indoors for one month, but no device deterioration was observed. In addition, when the applied voltage of 10 V was continuously applied to continuously emit light and forcedly deteriorated, the element life until light emission completely disappeared was 35 days.

Embodiment 2 In this embodiment, NiTPy in which tetraphenyl tin (abbreviated as TPSn) is used as the electron injection layer material instead of TPGe used as the hole injection layer material in the first embodiment.
In place of P, 5,10,15,20-tetra (4-pyridyl) -21H, 23H-porphyrin zinc (ZnTP
yP) was used as the material of the electron injection layer, and the layer structure and the film forming method of each organic electroluminescent layer were the same as those of the first embodiment.
An organic electroluminescent device was produced according to the standard.

The organic electroluminescent device of Example 2 also emitted green light similar to that of Example 1. As a result of the spectroscopic measurement, the spectrum was consistent with the spectrum of the organic electroluminescent device of Example 1, and it was confirmed that the spectrum was due to the emission of Alq3. When the applied voltage was gradually increased and the luminance was measured by a luminance meter, a luminance of 1500 cd / m ² was obtained at an applied voltage of 10 V. After manufacturing this organic electroluminescent device, it was left indoors for one month, but no device deterioration was observed.

Example 3 In this example, tetraphenyl lead (abbreviated as TPPb) was used in place of TPGe used as the hole injection layer material in Example 1 and NiTPyP used as the electron injection layer material. Instead, 5,10,15,20-
Layer structure of each organic electroluminescent layer, except that tetra (4-pyridyl) -21H, 23H-porphyrin titanium (abbreviated as TiTPyP) was used as an electron injection layer material.
An organic electroluminescent device was produced according to the same method as in Example 1 for the film formation method.

The organic electroluminescent device of the third embodiment is the same as that of the first embodiment.
And emitted the same green light emission. As a result of the spectroscopic measurement, the spectrum was consistent with the spectrum of the organic electroluminescent device of Example 1, and it was confirmed that the spectrum was due to the emission of Alq3. When the applied voltage was gradually increased and the luminance was measured by a luminance meter, a luminance of 1200 cd / m ² was obtained at an applied voltage of 10 V. After manufacturing this organic electroluminescent device, it was left indoors for one month, but no device deterioration was observed.

COMPARATIVE EXAMPLE 1 For comparison, the layer configuration and film formation of the electron injection layer and each organic electroluminescent layer, except that a hole injection layer of a tetraphenyl metal compound was not formed between the anode and the hole transport layer. An organic electroluminescent device was produced according to the method described in Example 1 above.

The organic electroluminescent device of Comparative Example 1 also emitted green light similar to that of Example 1. As a result of the spectroscopic measurement, the spectrum was consistent with the spectrum of the organic electroluminescent device of Example 1, and it was confirmed that the spectrum was due to the emission of Alq3. However, the power consumption for obtaining the same luminance as that of the organic electroluminescent device of Example 1 increased by about 32%, and the device life was increased from 35 days of the organic electroluminescent device of Example 1 to 25%.
Days decreased.

Comparative Example 2 For comparison, except that an electron injection layer made of a porphyrin derivative was not formed between the cathode and the electron transport layer, the hole injection layer, the layer structure of each organic electroluminescent layer, and the film formation method were the same. An organic electroluminescent device was manufactured according to Example 1 described above.

The organic electroluminescent device of Comparative Example 2 also emitted green light similar to that of Example 1. As a result of the spectroscopic measurement, the spectrum was consistent with the spectrum of the organic electroluminescent device of Example 1, and it was confirmed that the spectrum was due to the emission of Alq3. However, the power consumption for obtaining the same luminance as that of the organic electroluminescent device of Example 1 is increased by about 25%, and the device life is increased from 35 days of the organic electroluminescent device of Example 1 to 10%.
Days decreased.

Comparative Example 3 For comparison, a hole injection layer of a tetraphenyl metal compound was provided between the anode and the hole transport layer, and an electron injection layer of a porphyrin derivative was provided between the cathode and the electron transport layer.
Except that neither was formed, an organic electroluminescent device was produced in accordance with the same manner as in Example 1 except for the layer structure and the film forming method of each organic electroluminescent layer.

The organic electroluminescent device of Comparative Example 3 also emitted green light similar to that of Example 1. As a result of the spectroscopic measurement, the spectrum was consistent with the spectrum of the organic electroluminescent device of Example 1, and it was confirmed that the spectrum was due to the emission of Alq3. However, the power consumption for obtaining the same luminance as that of the organic electroluminescent device of Example 1 was increased by about 35%, and the device life was also reduced from 35 days of the organic electroluminescent device of Example 1 to 2 days.

Although the organic electroluminescent device of the present invention has been described in detail, the present invention is not limited to these embodiments. For example, T employed as a tetraphenyl metal compound as a material for the hole injection layer
In addition to PGe, TPSn or TPPb, other various metal compounds and their halogen salts may be employed. As the porphyrin derivative used as the material of the electron injection layer, various metal compounds and halogen salts thereof may be used in addition to NiTPyP, ZnTPyP, and TiTPyP described in the embodiments. As the hole transporting material of the hole transporting layer or the electron transporting material of the electron transporting layer, other than the compounds of the examples, other conventionally known hole transporting materials or electron transporting materials may be used. In addition, as for the layer structure and the electrode structure of the organic electroluminescent layer, and the forming method thereof, any of the conventionally known structures can be employed.

[0066]

As is apparent from the above description, according to the present invention, both the hole injection performance and the electron injection performance of the organic electroluminescent device are improved, and the stable organic electroluminescence with low power consumption and long life is obtained. An element and a flat panel display using the element can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a device configuration in which an organic electroluminescent device of the present invention is applied to an EL device.

FIG. 2 is a schematic cross-sectional view showing a device configuration in which the organic electroluminescent device of the present invention is applied to an EL device, and shows a layer configuration of an organic electroluminescent layer.

FIG. 3 is a schematic perspective view showing a device configuration in which an organic electroluminescent element is applied to a flat panel display.

FIG. 4 is an emission spectrum of the organic electroluminescent device of Example 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Anode, 3 ... Organic electroluminescent layer, 4 ... Cathode,
5: protective layer, 6: hole transport layer, 7: light emitting layer, 8: electron transport layer, 9, 10: control circuit, 11: hole injection layer, 1
2 ... Electron injection layer

Claims (10)

[Claims] 1. An organic electroluminescent device having a structure in which an organic electroluminescent layer including a hole transport layer and an electron transport layer is sandwiched between an anode and a cathode. An organic electroluminescent device comprising a hole injection layer, and an electron injection layer between the cathode and the electron transport layer. 2. An organic electroluminescent layer comprising a hole injection layer, at least a hole transport layer, a light emitting layer, and an electron transport layer, an electron injection layer, and a cathode are sequentially laminated on the anode in this order. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device has a bent structure. 3. A structure in which an organic electroluminescent layer including a hole injection layer, at least a hole transport layer, and an electron transport layer, an electron injection layer, and a cathode are sequentially stacked on the anode in this order. The organic electroluminescent device according to claim 1, wherein: 4. The hole injection layer according to the following general formula (1)
The organic electroluminescent device according to claim 1, comprising at least one kind of tetraphenyl metal represented by the following formula: Embedded image (In the general formula (1), M represents a metal atom.) 5. The organic electroluminescent device according to claim 1, wherein the thickness of the hole injection layer is 10 nm or less. 6. The organic electroluminescent device according to claim 1, wherein the electron injection layer contains at least one porphyrin derivative represented by the following general formula (2). Embedded image 7. The organic electroluminescent device according to claim 1, wherein the thickness of the electron injection layer is 10 nm or less. 8. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent layer further contains a fluorescent dye. 9. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is an electroluminescent device. 10. A flat panel display comprising the organic electroluminescent device according to claim 1. Description: