JPH05295361A - Organic electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain the objective element which provides luminescence with a practically enough luminance at a low driving voltage and retains the initial luminescence characteristics even after a long-storage. CONSTITUTION:This element comprises an anode 2a, an org. hole transport layer 3, an org. electron transport layer 4, and a cathode 2b laminated sequentially in this order. The hole transport layer contains a compd. of the general formula: (Ar<1>) (Ar<2>)C=X (wherein Ar<1> and Ar<2> are each independently an optionally substd. arom. hydrocarbon or arom. heterocyclic group; and X is an oxygen or sulfur atom).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device, and more specifically, it is a thin film type device which emits light by applying an electric field by a combination of a hole transport layer and an electron transport layer made of an organic compound. It is about devices.

[0002]

2. Description of the Related Art Conventionally, as a thin film type electroluminescent device,
ZnS, Ca which are II-VI group compound semiconductors of inorganic materials
In S, SrS, etc., Mn, which is the emission center, and rare earth elements (E
(u, Ce, Tb, Sm, etc.) is generally doped, but the electroluminescent device made of the above inorganic material is: 1) AC drive is required (50 to 1000 Hz), 2) High drive voltage (Up to 200 V), 3) full colorization is difficult (especially blue color is a problem), and 4) peripheral drive circuit cost is high.

However, in recent years, in order to improve the above problems,
Development of electroluminescent devices using organic materials has started. In addition to the previously known anthracene and pyrene as the light emitting layer material, cyanine dyes (J. Chem. S
oc., Chem. Commun., 557, p. 1985, pyrazoline (Mol. Crys. Liq. Cryst., 135, 355,
1986), Perylene (Jpn. J. Appl. Phys., 25)
Vol., L773, 1986) or coumarin compounds and tetraphenyl butadiene (JP-A-57-5178).
No. 1) has been reported.

Further, in order to improve the efficiency of carrier injection from the electrode in order to increase the luminous efficiency, the kind of the electrode is optimized and a light emitting layer comprising a hole transport layer and an organic phosphor is provided. 57-51781, JP-A-59-59
-194393, JP-A-63-295695, Appl. Phys. Lett., 51, 913, 1987.
Years) etc. Furthermore, for the purpose of improving the light emission efficiency of the device and changing the light emission color, dope a fluorescent dye for laser such as coumarin using aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. P.
hys., 65, 3610, 1989).

However, in the organic electroluminescent elements disclosed so far, the luminous performance (driving voltage and luminous efficiency)
But it's not enough. In particular, in order to lower the driving voltage, it is necessary to use an organic hole transport material having a small ionization potential for facilitating hole injection from the anode in the organic hole transport layer. Therefore, for example, Japanese Patent Laid-Open No. 63-2
Japanese Patent Publication No. 95695 discloses that a phthalocyanine compound is inserted as an organic hole injection layer between the organic hole transport layer and the anode for the purpose of promoting hole injection from the anode. However, since these compounds have large absorption in the visible light region, the emission efficiency is lowered and the emission spectrum itself is changed.

Therefore, when considering the application of the organic electroluminescent device to full-color display, it is not a preferable method to use a phthalocyanine compound or a porphyrin compound as the organic hole transport layer. In addition, in the organic electroluminescent devices disclosed so far, electroluminescence is brought about by recombination of injected holes and electrons. However, in general, the injection of carriers, for example, the injection of holes, must be carried out over the injection barrier at the interface between the anode and the organic hole transport layer, and this injection barrier requires a high electric field. As a result, the driving voltage of the device becomes high, so that the light emission performance, especially the light emission efficiency becomes insufficient, and the instability of the operation due to the instability of the interface is also observed, and further improvement studies are desired.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, the present inventors have made earnest studies as a result of providing an organic electroluminescence device that can be driven at a low voltage, and as a result,
The present invention has been completed by finding that it is suitable to contain a specific compound in the organic hole transport layer.

[0008]

That is, the gist of the present invention is as follows.
In an organic electroluminescent device in which an anode, an organic hole transporting layer, an organic electron transporting layer, and a cathode are sequentially laminated, the organic hole transporting layer has the following general formula (I) (Ar ¹ ) (Ar ² ) C = X (I) (In the formula, Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and X represents an oxygen atom or a sulfur atom. The organic electroluminescent device is characterized by containing a compound represented by the formula (1).

The organic electroluminescent device of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view schematically showing an example of the structure of the organic electroluminescent device of the present invention, in which 1 is a substrate, 2a and 2b are conductive layers, and 3 contains a compound represented by the general formula (I). Organic hole transport layers and 4 represent organic electron transport layers, respectively. The substrate 1 serves as a support for the organic electroluminescent element of the present invention, and a plate of quartz or glass, a metal plate or metal foil, a plastic film or sheet, or the like can be used, but a glass plate, polyester, A transparent synthetic resin substrate such as polymethacrylate, polycarbonate or polysulfone is preferable.

A conductive layer 2a is provided on the substrate 1,
This conductive layer 2a is usually a metal such as aluminum, gold, silver, nickel, palladium, tellurium, a metal oxide such as an oxide of indium and / or tin, copper iodide, carbon black or poly (3-methylthiophene). )
It is composed of a conductive resin or the like. The conductive layer 2a is usually formed by a sputtering method, a vacuum deposition method, or the like, but metal fine particles such as silver, copper iodide, carbon black, conductive metal oxide fine particles,
In the case of a conductive resin fine powder or the like, it can also be formed by dispersing it in an appropriate binder resin solution and applying it on a substrate. Further, in the case of a conductive resin, a thin film can be directly formed on the substrate by electrolytic polymerization. Conductive layer 2
It is also possible to form a by laminating different materials.

The thickness of the conductive layer 2a varies depending on the required transparency, but when the transparency is required, it is desirable that the visible light transmittance is 60% or more, preferably 80% or more, In this case, the thickness is usually 50 to 1000.
It is 0Å, preferably about 100 to 5000Å. The conductive layer 2a may be the same as the substrate 1 if it is opaque. Further, the conductive layer 2a can be laminated with different materials.

In the example of FIG. 1, the conductive layer 2a plays a role of hole injection as an anode. on the other hand,
The conductive layer 2b is a cathode (cathode) and serves as an organic electron transport layer 4
Plays a role of injecting electrons into. The material used for the conductive layer 2b can be the material for the conductive layer 2a, but a metal having a low work function is preferable for efficient electron injection, and tin, magnesium,
Metals such as indium, aluminum and silver or alloys thereof are used. The thickness of the conductive layer 2b is usually about the same as that of the conductive layer 2a, and the conductive layer 2b can be formed by the same method.

Although not shown in FIG. 1, a substrate similar to the substrate 1 may be further provided on the conductive layer 2b. However, in the electroluminescent element, at least one of the conductive layer 2a and the conductive layer 2b needs to have good transparency. From this, one of the conductive layers 2a and 2b is
A film thickness of 100 to 5000Å is preferable, and good transparency is desired.

The organic hole transporting layer 3 is provided on the conductive layer 2a. The organic hole transporting layer 3 efficiently transports holes from the anode between the electrodes to which an electric field is applied. Formed of a compound that can be transported in the direction of. The organic hole transport compound needs to be a compound having a high hole injection efficiency from the conductive layer 2a and capable of efficiently transporting the injected holes. For that purpose, it is required that the compound has a small ionization potential, a large hole mobility, and a stable and excellent trapping impurity that does not easily occur during manufacturing or use.

Examples of such hole transport compounds include those described in JP-A-59-194393, pages 5 to 6 and US Pat. No. 4,175,960, columns 13 to 14. Be done. Preferred specific examples of these compounds include N, N'-diphenyl-N, N'-
(3-methylphenyl) -1,1'-biphenyl-4,
Aromatic amine compounds such as 4'-diamine, 1,1'-bis (4-di-p-tolylaminophenyl) cyclohexane and 4,4'-bis (diphenylamino) quadrophenyl are mentioned. Other than aromatic amine compounds,
Examples thereof include hydrazone compounds disclosed in JP-A-2-311591, and silazane compounds disclosed in US Pat. No. 4,950,950. These compounds may be used alone or as a mixture if necessary.
In addition to the above compounds, polyvinylcarbazole and Appl. Ph
ys. Lett., Vol. 59, p. 2760 (1991), and high molecular compounds such as polysilane.

The organic hole transport layer 3 is formed by laminating on the conductive layer 2a by a coating method or a vacuum deposition method. For example, in the case of the coating method, one or more organic hole transport compounds are added and dissolved by adding a binder resin that does not become a hole trap if necessary, and an additive such as a coating property improving agent such as a repelling agent. The applied coating solution is prepared, coated on the conductive layer 2a by a method such as spin coating, and dried to form the organic hole transport layer 3. Examples of the binder resin include polycarbonate, polyacrylate, polyester and the like. If the addition amount of the binder resin is large, the hole mobility is lowered.

In the case of the vacuum deposition method, the organic hole transporting material is placed in a crucible installed in a vacuum container, the interior of the vacuum container is evacuated to 10 ⁻⁶ Torr by an appropriate vacuum pump, and then the crucible is placed. Is heated to evaporate the hole transport material and form a layer on the substrate placed facing the crucible. The thickness of the organic hole transport layer 3 is usually 100 to 3000Å, preferably 300 to 1000Å. In order to uniformly form such a thin film, the vacuum vapor deposition method is often used.

An organic electron transporting layer 4 is provided on the organic hole transporting layer 3, and the organic electron transporting layer 4 efficiently transfers electrons from the cathode between the electrodes to which an electric field is applied. It is formed from a compound that can be transported in three directions. The organic electron transport compound needs to be a compound that has a high electron injection efficiency from the conductive layer 2b and can efficiently transport the injected electrons. For that purpose, it is required that the compound has a high electron affinity, a high electron mobility, excellent stability, and an impurity that becomes a trap and is unlikely to be generated at the time of production or use.

As a material satisfying such a condition, an aromatic compound such as tetraphenyl butadiene (Japanese Patent Application Laid-Open No. 57-57157)
No. 51781), aluminum complexes of 8-hydroxyquinoline, and other metal complexes (JP-A-59-194393).
JP-A-2-28).
9675), perinone derivatives (JP-A-2-289)
676), an oxadiazole derivative (JP-A-2-
No. 216791), and bisstyrylbenzene derivatives (JP-A Nos. 1-245087 and 2-222484).
No.), perylene derivatives (JP-A-2-189890 and JP-A-3-791), coumarin compounds (JP-A-2-191694 and JP-A-3-792), and rare earth complexes (JP-A-1-256584). No.), a distyrylpyrazine derivative (JP-A-2-252793), a thiadiazolopyridine derivative (JP-A-3-37292), a pyrrolopyridine derivative (JP-A-3-37293), a naphthyridine derivative (special Kaihei 3-203982
Gazette) and the like. When these compounds are used, the organic electron transport layer 4 has a role of transporting electrons and a role of causing light emission upon recombination of holes and electrons, and also serves as a light emitting layer. When the organic hole transport compound has a light emitting function, that is, when the organic hole transport layer 3 also serves as a light emitting layer, the organic electron transport layer 4 serves only to transport electrons.

The thickness of the organic electron transport layer 4 is usually 100.
˜2000 Å, preferably 300 to 1000 Å.
The organic electron transport layer 4 can also be formed by the same method as the organic hole transport layer 3, but a vacuum deposition method is usually used. Hitherto, various fluorescent dyes have been doped with an aluminum complex of 8-hydroxyquinoline as a host material for the purpose of improving the luminous efficiency of an organic light emitting device and changing the color of emitted light (US Pat. 76
9, 292), the advantages of this dope method are that the highly efficient fluorescent dye improves the emission efficiency, the emission wavelength can be examined by selecting the fluorescent dye, and the fluorescent dye that causes concentration quenching can also be used. A poor fluorescent dye can also be used, and the like.

Also in the present invention, various fluorescent dyes are used as the host material in the organic electron transport material, and various fluorescent dyes are added in an amount of 10 ⁻³ to 10 mol%.
By doping, the luminous efficiency of the device can be further improved. Further, in order to further improve the luminous efficiency of the organic electroluminescent device, another organic electron transport layer 5 may be laminated on the organic electron transport layer 4 as shown in FIG. The compound used for the organic electron transport layer 5 is required to be capable of easily injecting electrons from the cathode and further having an electron transporting ability. Examples of such an organic electron transport compound include nitro-substituted fluorenone derivatives such as compounds represented by the following structural formula (D9), thiopyran dioxide derivatives such as compounds represented by the following structural formula (D10), and structural formula (D11) below. A diphenylquinone derivative such as a compound represented by the following structural formula (D1
2) Perylene tetracarboxylic acid derivative such as a compound (Jpn. J. Appl. Phys. 27, L269,
1988), an oxadiazole derivative such as a compound represented by the following structural formula (D13) (Appl. Phys. Lett.
55, p. 1489, 1989).

[0022]

[Chemical 1]

The film thickness of the organic electron transport layer 5 is
Usually, 100 to 2000Å, preferably 300 to 100
It is 0Å. In addition, it is also possible to stack the conductive layer 2b, the organic electron transporting layer 4, the organic hole transporting layer 3, and the conductive layer 2a in this order on the substrate in the opposite structure to that of FIG. It is also possible to provide the electroluminescent element of the present invention between two substrates, one of which is highly transparent. Also,
Similarly, the structure opposite to that of FIG. 2 can be adopted.

In the present invention, by doping the organic hole transporting layer 3 with the compound represented by the general formula (I), carriers can be easily injected from the electrode, and excellent light emission characteristics, especially driving voltage can be obtained. A drop can be achieved. The region doped with the compound represented by the general formula (I) is
It may be the whole organic hole transport layer 3 or a part thereof, and for example, it may be doped on the anode side 3a of the organic hole transport layer as shown in FIG. The amount of the compound represented by the general formula (I) doped with respect to the host material is
It is preferably 10 ⁻³ to 10 mol%.

As a method for doping the organic hole transport layer 3 with the compound represented by the general formula (I), for example, in the case of a coating method, the organic hole transport compound and the general formula (I) are used.
In addition, a coating solution prepared by adding and dissolving a compound such as a binder resin that does not trap holes or electrons, and an additive such as a coating improver such as a leveling agent is prepared by a spin coating method. The organic hole transport layer 3 is formed by coating the conductive layer 2a on the conductive layer 2a and drying it. Examples of the binder resin include polycarbonate, polyarylate, polyester and the like. The binder resin lowers the mobility of holes or electrons when it is added in a large amount, and therefore it is preferable that the binder resin be added in a small amount, preferably 50% by weight or less. In the case of the vacuum vapor deposition method, the organic hole transport compound is placed in a crucible installed in a vacuum container, and the compound represented by the general formula (I) is used.
The compound represented by was placed in another crucible, the inside of the vacuum vessel was evacuated to about 10 ^-6 Torr by an appropriate vacuum pump, and then each crucible was heated and evaporated at the same time, and placed facing the crucible. Form a layer on the substrate. Further, as another method, a mixture of the above materials in a predetermined ratio may be evaporated using the same crucible.

In the general formula (I), Ar ¹ and A
Each r ² independently represents an aromatic hydrocarbon group such as benzene, naphthalene, or anthracene which may have a substituent, or an aromatic heterocyclic group such as carbazole which may have a substituent. As the substituent, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group which may have a substituent; a hydroxyl group; a halogen atom; a nitro group; a cyano group; a methoxy group, an ethoxy group , Butoxy group, and other alkoxy groups; dimethylamino group, diethylamino group, and other dialkylamino groups; alkyl group, alkoxy group, halogen atom, amino group, phenyl group which may have a substituent such as aryl group, naphthyl Groups such as aryl groups; aralkyl groups such as benzyl group, naphthylmethyl group, phenethyl group; diaries such as dibenzylamino group, diphenylamino group Arylamino group Ne methoxycarbonyl group, such alkoxycarbonyl groups such as ethoxycarbonyl group. X represents an oxygen atom or a sulfur atom.

Specific examples of the compound represented by the general formula (I) are shown below, but the invention is not limited thereto.

[0028]

[Chemical 2]

[0029]

[Chemical 3]

[0030]

The organic hole transport material described above is an insulator itself without injection of carriers from the electrodes, and is considered to have almost no carriers. Generally, a hole injection barrier exists between the conductive layer 2a and the organic hole transport layer 3, and this injection barrier is the difference between the ionization potential of the organic hole injection transport layer 3 and the work function of the conductive layer 2a. Can be considered. Therefore, it is preferable that the ionization potential of the organic hole transport layer 3 be as small as possible for a given anode (conductive layer 2a) material. Indium tin oxide (hereinafter abbreviated as "ITO") is usually used for the anode, but the work of commercially available ITO glass (HOYA Co., Ltd. glass is NA-40 and ITO film thickness is 1200Å) The function is about 4.70 eV. In the present invention, the work function (ionization potential) was measured with an ultraviolet photoelectron analyzer (AC-1 type) manufactured by Riken Keiki Co., Ltd.

On the other hand, as the organic hole transport layer 3, for example,
The above-mentioned N, N′-diphenyl-N, N ′-(3-methylphenyl) -1, which is a conventionally used aromatic diamine,
1'-biphenyl-4,4'-diamine (Jpn.J.
Appl. Phys. , 27, L269, 1988
Was formed by vacuum vapor deposition, and its ionization potential was similarly measured with AC-1.
It was V. Therefore, the hole injection barrier in this case is 0.5.
It is estimated to be 3 eV.

From the above results, from the anode to the organic hole transport layer 3
A high electric field is required to overcome the hole injection barrier to the. In addition, since a voltage drop occurs at the interface between the anode and the organic hole transport layer, Joule heat is concentrated on the interface when the device is driven, which causes instability and deterioration of the device operation.
If the hole injection barrier is reduced, the driving voltage of the device can be lowered. As one method for achieving this, it is conceivable to insert a material having a smaller ionization potential as an organic hole injection layer between the organic hole transport layer 3 and the anode. Examples of the organic hole injecting layer material of the organic electroluminescent device having this structure include, for example, JP-A-63 / 63
And phthalocyanine compounds as disclosed in No. 295695. However, these compounds have large absorption in the visible light region (5 on the glass substrate).
FIG. 5 shows absorption spectra of the metal-free phthalocyanine [H ₂ -Pc] vapor-deposited film and the copper phthalocyanine [CuPc] vapor-deposited film which were vacuum-deposited to a film thickness of about 00Å, respectively. ).

The light from the organic electron transporting layer 4 which also serves as a light emitting layer is usually taken out from the glass substrate side through the organic electron transporting layer 4, and therefore, as shown in the embodiment of JP-A-63-295695. When the phthalocyanine hole injection layer having a film thickness of about 350 Å is provided, the output light is absorbed up to 90% in the wavelength region of 400 nm to 500 nm, and the emission spectrum itself changes.
Therefore, when considering the application of the organic electroluminescence device to full-color display, it is not a preferable method to use a phthalocyanine or porphyrin compound as the organic hole injection layer.

In the present invention, when the compound represented by the general formula (I) is doped into the organic hole injection layer, it is considered that the hole injection barrier is reduced at the interface with the anode, and as a result, it is excellent. It is possible to achieve a reduction in light emission characteristics, particularly a driving voltage.

[0035]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the description of the following examples unless it exceeds the gist thereof. Example 1 An organic electroluminescent device having the structure shown in FIG. 1 was produced by the following method.

A 1200 Å transparent conductive film of indium tin oxide (ITO) deposited on a glass substrate was ultrasonically washed with an organic alkali, washed with water, and ultrasonically washed with isopropyl alcohol, and then placed in a vacuum deposition apparatus. The apparatus was evacuated using an oil diffusion pump until the degree of vacuum in the apparatus became 2 × 10 ⁻⁶ Torr or less. As an organic hole transport layer material,
A mixture of hydrazone compounds represented by the following structural formulas (H1) and (H2) at a molar ratio of (H1) :( H2) = 1: 0.6,

[0037]

[Chemical 4]

The above-exemplified compound (1) as a compound to be doped was put in each of different ceramic crucibles, and simultaneously heated by a tantalum wire heater around the crucible for vapor deposition. The temperature of each crucible at this time was controlled in the range of 160 to 170 ° C. for the hydrazone compound and at 82 to 86 ° C. for the exemplified compound (1). The degree of vacuum during evaporation was 2 × 10 ⁻⁶ Torr, and the vapor deposition time was 1 minute. As a result, an organic hole transport layer having a film thickness of 530 Å doped with 2.2 mol% of the exemplified compound (1) was formed.

Next, an aluminum 8-hydroxyquinoline complex represented by the following structural formula (E1) was used as a material for the organic electron transport layer.

[0040]

[Chemical 5]

Was vapor-deposited on the above organic hole transport layer in the same manner to form an organic electron transport layer. The temperature of the crucible at this time was controlled in the range of 230 to 270 ° C. The degree of vacuum during vapor deposition was 8 to 9 × 10 ⁻⁷ Torr, the vapor deposition time was 1 minute, and the film thickness was 760 Å. This layer serves as a light emitting layer. Finally, as a cathode, an alloy electrode of magnesium and silver was vapor-deposited to a film thickness of 1200 Å by a two-source simultaneous vapor deposition method. Vapor deposition uses a molybdenum boat and the degree of vacuum is 7-8.
The vapor deposition time was 5 minutes at × 10 ^-6 Torr. A glossy film was obtained. The atomic ratio of magnesium to silver is 10:
It was 2.4.

Table 1 shows the results of the emission characteristics measured by applying a positive DC voltage to the ITO electrode (anode) and a negative DC voltage to the magnesium / silver electrode (cathode) of the organic electroluminescent device thus produced. This device showed uniform emission of yellow-green, and the peak wavelength of emission was 560 nm.

Example 2 An organic electroluminescent device having the structure shown in FIG. 3 was produced by the following method. In the same manner as in Example 1, a mixture of the hydrazone compounds (H1) and (H2) on an ITO glass substrate in a molar ratio of (H1) :( H2) = 1: 0.6 was added to the above exemplified compound (1). ) Was doped at a concentration of 1.7 mol% to form an organic hole transport layer having a film thickness of 100 Å by vapor deposition.

Next, a film thickness 415 made of only the hydrazone compound mixture without doping the exemplified compound (1).
The organic hole transport layer of Å was formed by vapor deposition. Next, as a material for the organic electron transporting layer also serving as the light emitting layer, the aluminum 8-hydroxyquinoline complex was vapor-deposited on the organic hole transporting layer in the same manner as in Example 1.

Finally, as a cathode, an alloy electrode of magnesium and silver was vapor-deposited in the same manner as in Example 1 to produce an organic electroluminescence device. Table 1 shows the measurement results of the emission characteristics of the obtained organic electroluminescent device. This device showed uniform emission of green light, and the emission peak wavelength was 560 nm.

Example 3 An organic electroluminescence device was produced in the same manner as in Example 2 except that the concentration of the exemplified compound (1) with which the organic hole transport layer was doped was 9.8 mol%. Table 1 shows the measurement results of the emission characteristics of this device. Example 4 Organic compound was prepared in the same manner as in Example 2 except that the exemplified compound (10) was doped at a concentration of 2.0 mol% instead of the exemplified compound (1) as a compound to be doped into the organic hole transport layer. An electroluminescent device was produced. Table 1 shows the measurement results of the emission characteristics of this device.

Comparative Example 1 An organic electroluminescent device was prepared in the same manner as in Example 1 except that the organic hole transport layer was not doped with the exemplified compound (1). Table 1 shows the measurement results of the emission characteristics of this device. This device had a peak wavelength of light emission at 560 nm and showed uniform green light emission.

[0048]

[Table 1]

Example 5 As a material for the organic hole transport layer, the hydrazone compound (H
Instead of the mixture of 1) and (H2), the following structural formula (H
Using the aromatic diamine compound represented by 3),

[0050]

[Chemical 6]

An organic electroluminescence device was produced in the same manner as in Example 2 except that the concentration of the exemplified compound (1) doped in the organic hole transport layer was 2.6 mol%. Table 2 shows the measurement results of the light emission characteristics of this device. Moreover, the light emission luminance-voltage characteristic of this element is shown in FIG. This element is 560
It had a peak wavelength of light emission at nm and showed uniform green light emission.

Comparative Example 2 An organic electroluminescent device was produced in the same manner as in Example 5, except that the organic hole transport layer was not doped with the exemplified compound (1). Table 2 shows the measurement results of the light emission characteristics of this device. Moreover, the light emission luminance-voltage characteristic of this element is shown in FIG. This device had a peak wavelength of light emission at 560 nm and showed uniform green light emission.

[0053]

[Table 2]

Example 6 The device produced in Example 1 was stored in a vacuum for 30 days, and the emission characteristics were measured. Emission brightness,
The decrease in luminous efficiency was not a problem for practical use, and showed stability over a long period of time.

[0055]

[Table 3]

[0056]

In the organic electroluminescent device of the present invention, an anode (anode), an organic hole injecting and transporting layer, an organic electron injecting and transporting layer and a cathode (cathode) are sequentially provided on a substrate,
Since the organic hole transport layer is doped with a specific compound,
When a voltage is applied using both conductive layers as electrodes, it is possible to obtain light emission with practically sufficient brightness at a low driving voltage and achieve high light emission efficiency.

Therefore, the electroluminescent element of the present invention is used in the field of flat panel displays (for example, OA computers and wall-mounted televisions) and light sources (for example, light sources for copiers, liquid crystal displays and measuring instruments) which make the best use of the characteristics as a surface light emitter. It can be applied to various types of backlight sources, display boards, and marker lights, and its technical value is great.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of the organic electroluminescent device of the present invention.

FIG. 2 is a cross-sectional view of another embodiment of the organic electroluminescent device of the present invention.

FIG. 3 is a cross-sectional view of another embodiment of the organic electroluminescent device of the present invention.

FIG. 4 is a diagram showing emission luminance-voltage characteristics of the organic electroluminescent elements produced in Example 5 of the present invention and Comparative Example 2.

FIG. 5 is a diagram showing an absorption spectrum of a vapor-deposited thin film of a phthalocyanine compound in a visible light region.

[Explanation of symbols]

1 Substrate 2a, 2b Conductive Layer 3, 3a Organic Hole Transport Layer Containing Compound Represented by General Formula (I) 3b Organic Hole Transport Layer Not Containing Compound Represented by General Formula (I) 4 Organic Electron Organic electron transport layer composed of a compound different from transport layer 54

Claims (1)

[Claims] 1. In an organic electroluminescent device in which an anode, an organic hole transport layer, an organic electron transport layer, and a cathode are sequentially laminated, the organic hole transport layer has the following general formula (I) (Ar ¹ ) ( Ar ² ) C = X (I) (In the formula, Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and X is An organic electroluminescent device containing a compound represented by an oxygen atom or a sulfur atom.