JPH11329734A - Organic electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white organic electroluminescent element having high luminous efficiency and improved stability. SOLUTION: This light emitting element comprises at least: a hole transport layer sandwiched between a positive electrode and a negative electrode, a light emitting layer, and a hole blocking layer on a substrate, wherein the light emitting layer contains an aromatic amine compound having a maximum fluorescence wavelength in a range of 400 to 500 nm, the ionization potential of the hole transport layer is larger than that of the light emitting layer by 0.1 eV or more, the ionization potential, of the hole blocking layer is larger than that of the light emitting layer by 0.2 eV or more, and at least the light emitting layer contains a fluorochrome whose maximum fluorescent wavelength is in a range of 550 to 650 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an organic electroluminescent device. More specifically, the present invention relates to an organic electroluminescent device in which a light emitting layer containing a specific aromatic amine is doped with a specific fluorescent dye. Since the organic electroluminescent device of the present invention can achieve white light emission with high luminous efficiency and has improved stability,
It is expected to be applied to a flat panel display, a multi-color display element, or a light source utilizing the characteristics of a surface light emitter.

[0002]

2. Description of the Related Art Conventionally, as a thin film type electroluminescent (EL) element, Zn, which is a group II-VI compound semiconductor of an inorganic material, is used.
In general, S, CaS, SrS, and the like are doped with Mn or a rare earth element (Eu, Ce, Tb, Sm, or the like) which is a luminescence center. However, EL devices manufactured from the above inorganic materials include: 1) AC drive is required (50 to 1000 Hz), 2) High drive voltage (up to 200 V), 3) It is difficult to achieve full color (especially blue), and 4) Peripheral drive circuit is expensive. .

However, in recent years, in order to improve the above problems,
Development of EL devices using organic thin films has been started. In particular, in order to enhance the luminous efficiency, the type of the electrode was optimized for the purpose of improving the efficiency of carrier injection from the electrode, and a hole transport layer composed of an aromatic diamine and a luminescent layer composed of an aluminum complex of 8-hydroxyquinoline were used. Of an organic electroluminescent device provided with a device (Appl. Phys. Le)
tt. , Vol. 51, p. 913, 1987), the luminous efficiency has been greatly improved as compared with a conventional EL device using a single crystal such as anthracene. Also, for example,
Doping with a fluorescent dye for laser such as coumarin using an aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. Phys., 65, 3610).
1989), the emission efficiency has been improved, the emission wavelength has been converted, and the like.

In addition to the electroluminescent device using a low molecular material as described above, poly (p-phenylenevinylene) (Nature, 347, 539, 1) may be used as a material for the light emitting layer.
990), poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene] (Ap
pl. Phys. Lett. 58, 1982, 1
991 et al.), Poly (3-alkylthiophene) (J
pn. J. Appl. Phys, Volume 30, L1938
1991), and the development of electroluminescent devices using polymer materials, and devices in which a low molecular light emitting material and an electron transfer material are mixed with a polymer such as polyvinyl carbazole (Applied Physics,
61, p. 1044, 1992).

[0005]

To produce a display element capable of multicolor or full-color display using an organic electroluminescent element, two methods have been considered. one,
A method using fluorescence conversion with green and red fluorescent materials using an organic electroluminescent element capable of emitting blue light as an excitation light source (Proc. 15th Int. Di).
spray Research Conference
e, p. 269, 1995). The other is a method of combining an organic electroluminescent element capable of emitting white light and a color filter (Japanese Patent Application Laid-Open No. 7-142169).

In the former multi-color and full-color system using a combination of blue light emission and fluorescence conversion, the performance of the blue organic electroluminescent device, particularly, the life during driving is a problem.
So far, the initial luminance of the blue light emitting element is 1
A life of 8000 hours was reported at 00 cd / m ² (Inorganic and Organic E).
electroluminescence / EL 96
Berlin. ed. R. H. Mauch and
H. E. FIG. Gumlich, p. 95, Wissensc
haft und Technik Verlag,
Berlin), considering the loss due to the fluorescence conversion and the required practical luminance of 300 cd / m ² , the current life is insufficient.

In the latter method of combining a white organic electroluminescent device and a color filter, the luminous efficiency of white light emission is a problem (Preprints of the 55th Annual Conference of the Japan Society of Applied Physics, 19p-H-6, p. 992). Proceedings of the 56th Japan Society of Applied Physics, 28p-V-7,
1028, 1995). With respect to white light emission, in addition to the demand for multicolor and full-color emission, there is also a need to use white light emission itself as display light or to use it for a backlight of a liquid crystal display or the like, and the ripple effect can be said to be great. Therefore, further improvement studies are desired for white light emission, which can be said to be the basis of a display element.

In order to achieve white light emission, a system in which a blue light-emitting layer, a green light-emitting layer and a red light-emitting layer are stacked (JP-A-6-207170; JP-A-7-14216)
No. 9), there is a problem that the color shift due to a change in the white EL spectrum due to driving and the luminous efficiency is low because the recrystallization zone extends over a plurality of layers. In order to solve this problem, it is conceivable that blue, green, and red fluorescent dyes are simultaneously doped into the light-emitting layer. In the case of a coating type polymer, it is easy to mix the fluorescent dyes of each color at the stage of adjusting the coating liquid. Is obtained (Appl.P
hys. Lett. 64, 815, 1994.
In the case of a polymer, the luminous efficiency and the driving stability are far from practical use because it is difficult to control impurities. Although it is possible to dope the fluorescent dye of each color into the luminescent layer host by vacuum evaporation using a low molecule, the doping amount of each fluorescent dye is adjusted by controlling the deposition rate of many evaporation sources at the same time. I have to say that it is very difficult considering the actual production.

As described above, for a white light-emitting element, the layer structure is as simple as possible, for example, the light-emitting layer is a single layer, has high luminous efficiency, is unlikely to cause white color shift, and has a high driving efficiency. Sometimes stable characteristics are required. The present invention
An object of the present invention is to provide a white organic electroluminescent device having high luminous efficiency and improved stability.

[0010]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies in view of the above situation, and as a result, doped a specific fluorescent dye into a light emitting layer containing a specific aromatic amine, The inventors have found that the above problem can be solved by specifying the relative relationship between the ionization potentials of the layer and the hole blocking layer, and have completed the present invention.

[0011]

That is, the gist of the present invention is as follows.
On the substrate, a hole transport layer sandwiched by an anode and a cathode,
An organic electroluminescent device including at least a light emitting layer and a hole blocking layer, wherein the light emitting layer contains an aromatic amine compound having a fluorescence maximum wavelength in a range of 400 to 500 nm, and the ionization potential of the hole transport layer is light emission. The ionization potential of the layer is 0.1 eV or more, the ionization potential of the hole blocking layer is 0.2 eV or more than the ionization potential of the light-emitting layer, and at least the light-emitting layer contains a fluorescent dye having a maximum fluorescence wavelength in the range of 550 to 650 nm. The organic electroluminescent device.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an organic electroluminescent device according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing an example of the structure of a general organic electroluminescent device used in the present invention, wherein 1 is a substrate, 2 is an anode, 4 is a hole transport layer, 5 is a light emitting layer, and 6 is The hole blocking layers, 8 each represent a cathode. The substrate 1 serves as a support for the organic electroluminescent element, and is made of a quartz or glass plate, a metal plate or metal foil, a plastic film or sheet, or the like. Particularly, a glass plate or a plate of a transparent synthetic resin such as polyester, polymethacrylate, polycarbonate, and polysulfone is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent device may be deteriorated by the outside air passing through the substrate, which is not preferable. For this reason, a method of providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate to secure gas barrier properties is also a preferable method.

An anode 2 is provided on a substrate 1. The anode 2 plays a role of injecting holes into a hole transport layer. This anode is usually made of a metal such as aluminum, gold, silver, nickel, palladium and platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or poly. (3-methylthiophene), conductive polymers such as polypyrrole and polyaniline. Usually, the formation of the anode 2 is often performed by a sputtering method, a vacuum evaporation method, or the like.
In the case of fine particles of metal such as silver, fine particles of copper iodide or the like, carbon black, fine particles of conductive metal oxide, fine particles of conductive polymer, etc., they are dispersed in an appropriate binder resin solution and To form the anode 2. Further, in the case of a conductive polymer, a thin film can be formed directly on the substrate 1 by electrolytic polymerization, or the conductive polymer can be applied on the substrate 1 to form the anode 2 (Ap).
pl. Phys. Lett. 60, 2711, 1
992). The anode 2 can be formed by laminating different materials. The thickness of the anode 2 depends on the required transparency. When transparency is required, it is desirable that the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness is usually 5 to 10%.
00 nm, preferably about 10 to 500 nm. If opaque, the anode 2 may be the same as the substrate 1. Further, it is also possible to laminate a different conductive material on the anode 2.

On the anode 2, a hole transport layer 4 is provided. As a condition required for the material of the hole transport layer, it is necessary that the material has a high hole injection efficiency from the anode and can efficiently transport the injected holes. Therefore, the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is further improved, and impurities serving as traps are hardly generated at the time of manufacture or use. Required. In addition to the above general requirements, when considering applications for in-vehicle display, the element is required to have further heat resistance. Therefore, Tg is 85
A material having a value of at least C is desirable.

As such a hole transport material, for example, an aromatic diamine compound having a tertiary aromatic amine unit linked thereto such as 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane (particularly, Kaisho 59-194393
Publication), 4,4'-bis [N- (1-naphthyl) -N
[Phenylamino] biphenyl, aromatic amines containing two or more tertiary amines and two or more condensed aromatic rings substituted with nitrogen atoms (JP-A-5-234681); Aromatic triamines having a starburst structure in derivatives (US Pat. No. 4,92
3,774), N, N'-diphenyl-N,
N'-bis (3-methylphenyl) biphenyl-4,
Aromatic diamines such as 4'-diamine (U.S. Pat.
No. 64,625), a triphenylamine derivative which is sterically asymmetric as a whole molecule (JP-A-4-12927).
No. 1), a compound in which a pyrenyl group is substituted with a plurality of aromatic diamino groups (JP-A-4-175395), and an aromatic diamine in which a tertiary aromatic amine unit is linked by an ethylene group (JP-A-4-264189). Japanese Patent Application Laid-Open No. 4-290466), aromatic diamines having a styryl structure (Japanese Patent Application Laid-Open No. Hei 4-290851), those obtained by linking aromatic tertiary amine units with thiophene groups (Japanese Patent Application Laid-Open No. 4-304466), starburst type aromatics Triamines (JP-A-4-308688) and benzylphenyl compounds (JP-A-4-36415)
No. 3), a compound in which a tertiary amine is linked by a fluorene group (Japanese Patent Application Laid-Open No. 5-25473), a triamine compound (Japanese Patent Application Laid-Open No. 5-239455), and a bisdipyridylaminobiphenyl (Japanese Patent Application Laid-Open No. 5-320634). ),
N, N, N-triphenylamine derivatives (Japanese Unexamined Patent Publication No.
No. 972), aromatic diamines having a phenoxazine structure (JP-A-7-138562), diaminophenylphenanthridine derivatives (JP-A-7-25247).
No. 4), silazane compounds (US Pat. No. 4,950,
950), silanamine derivatives (JP-A-6-49)
079), phosphamine derivatives (JP-A-6-25)
659) and quinacridone compounds.
These compounds may be used alone, or may be used as a mixture as necessary.

In addition to the above compounds, as a material of the hole transport layer, polyvinyl carbazole or polysilane (App
l. Phys. Lett. 59, 2760, 19
1991), polyphosphazene (JP-A-5-31094)
No. 9), polyamide (JP-A-5-310949), polyvinyl triphenylamine (JP-A-7-53).
No. 953), a polymer having a triphenylamine skeleton (Japanese Patent Laid-Open No. 4-133065), and a polymer in which triphenylamine units are linked by a methylene group (Synth
etic Metals, 55-57, 4163,
1993), polymethacrylates containing aromatic amines (J. Polym. Sci., Polym. Che.
m. Ed. , 21, 969, 1983).

The hole transport layer 4 is formed by laminating the above hole transport material on the anode 2 by a coating method or a vacuum evaporation method. In the case of the coating method, one or two or more hole transport materials and, if necessary, an additive such as a binder resin or a coatability improver that does not trap holes are added,
The solution is dissolved to prepare a coating solution, applied to the anode 2 by a method such as spin coating, and dried to form the hole transport layer 4. Examples of the binder resin include polycarbonate, polyarylate, and polyester. If the amount of the binder resin is large, the hole mobility is reduced, so that a small amount is desirable, and usually 50% by weight or less is preferable.

In the case of the vacuum evaporation method, the hole transporting material is put into a crucible placed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ^-4 Pa by a suitable vacuum pump, and then the crucible is heated. Then, the hole transport material is evaporated to form the hole transport layer 4 on the anode 2 on the substrate 1 placed facing the crucible. When the hole transport layer 4 is formed, a metal complex and / or a metal salt of an aromatic carboxylic acid (JP-A-4-320484), a benzophenone derivative, and a thiobenzophenone derivative (JP-A-Hei.
295361), fullerenes (JP-A-5-33)
1458) or the like at a concentration of 10 ⁻³ to 10% by weight to generate holes as free carriers, thereby enabling low-voltage driving. The thickness of the hole transport layer 4 is usually 10 to 300 nm, preferably 30 to 100 nm. In order to uniformly form such a thin film, generally, a vacuum deposition method is often used.

In order to improve the contact between the anode 2 and the hole transport layer 4, it is conceivable to provide an anode buffer layer 3 as shown in FIG. The conditions required for the material used for the anode buffer layer are that a uniform thin film can be formed with good contact with the anode and thermally stable, that is, the melting point and the glass transition temperature are high, and the melting point is 300 ° C. or more, A glass transition temperature of 100 ° C. or higher is required. In addition, the ionization potential is low, holes can be easily injected from the anode, and the hole mobility is high. To this end, porphyrin derivatives and phthalocyanine compounds (JP-A-63-29569) and star-burst-type aromatic triamines (JP-A-Hei.
308688), hydrazone compounds (Japanese Unexamined Patent Publication No.
No. 320483), an alkoxy-substituted aromatic diamine derivative (Japanese Patent Application Laid-Open No. 4-220995), p- (9
-Anthryl) -N, N-di-p-tolylaniline (JP-A-3-111485), polythienylenevinylene and poly-p-phenylenevinylene (JP-A-4-145)
192), polyaniline (Appl. Phys.
Lett. 64, p. 1245, 1994), and sputtered carbon films (JP-A-8-3).
No. 1573) and metal oxides such as vanadium oxide, ruthenium oxide and molybdenum oxide (the 43rd Joint Lecture on Applied Physics, 27a-SY-9, 1996).
Year) has been reported.

Examples of the compound often used as the material of the anode buffer layer include a porphyrin compound and a phthalocyanine compound. These compounds may have a central metal or may be non-metallic. Specific examples of preferred such compounds include the following compounds: porphine 5,10,15,20-tetraphenyl-21H, 23H-porphine 5,10,15,20-tetraphenyl-21H, 23H-porphine Cobalt (II) 5,10,15,20-Tetraphenyl-21H, 23H-porphine Copper (II) 5,10,15,20-Tetraphenyl-21H, 23H-porphine Zinc (II) 5,10,15, 20-tetraphenyl-21H, 23H-porphine vanadium (IV) oxide 5,10,15,20-tetra (4-pyridyl) -21H, 23H-porphine 29H, 31H-phthalocyanine Copper (II) phthalocyanine Zinc (II) phthalocyanine Titanium phthalocyanine oxide Magnesium phthalocyanine Lead phthalocyanine Copper (II) 4,4 ', 4 ", 4"'-tetraaza-29H,
31H-phthalocyanine

In the case of the anode buffer layer, a thin film can be formed in the same manner as in the case of the hole transport layer. However, in the case of an inorganic substance, a sputtering method, an electron beam evaporation method, or a plasma CVD method is used. The thickness of the anode buffer layer 3 formed as described above is usually 3 to 100 nm, preferably 10 to 100 nm.
５０50 nm.

The light emitting layer 5 is provided on the hole transport layer 4. The light-emitting layer 5 passes between the electrodes to which an electric field is applied, holes transported through the hole transport layer injected from the anode 2, and holes transported through the hole blocking layer 6 injected from the cathode 8. It is formed from a compound that emits white light by efficiently recombining the transported electrons. Therefore, it is a compound that has both hole transporting properties and electron transporting properties, has high hole mobility and electron mobility, and has excellent stability and is less likely to generate impurities that become traps during production or use. Is required.

In the present invention, the light-emitting layer is formed by using an aromatic amine compound having a fluorescent maximum wavelength in a thin film state in the range of 400 to 500 nm as a host material and having a fluorescent maximum wavelength in a dispersed state or a dilute solution state of 550 to 650 nm. In the range of 0.1 to 0.1 with respect to the host material.
By containing 10 to 10% by weight, highly efficient white light emission can be achieved. This is shown in FIG.
This will be described with reference to an E chromaticity coordinate diagram (JISZ8701).
White light emission is represented by a region centered on a white point (x = y = 1/3) indicated by W in the figure. The emission of the blue host material having the maximum fluorescence wavelength at 400 to 500 nm is located in the blue-green, blue, and blue-violet regions in FIG. On the other hand, the emission of the fluorescent dye for doping having a maximum fluorescence wavelength of 550 to 650 nm corresponds to the yellow-green, yellow, orange, and red regions in the figure. For example, when a point a is used as a host material for blue-violet emission, when a point b is combined as a doping dye, a color represented by the ab line is achieved by additive color mixing, and the white region can be adjusted by adjusting the doping amount. Is obtained. Similarly, by selecting a blue host material having a point c and a doping dye having a point d, a cd line which widely crosses a white region can be obtained, and a white light emitting element which is gently dependent on the doping concentration can be achieved. The same applies to the ef line and the ef 'line.

In the present invention, a fluorescent aromatic amine compound is used as a blue host material satisfying the above conditions. Conventionally, attempts have been made to use an aromatic amine compound as a light-emitting layer having a hole-transport property. However, a hole-transport layer is not provided between the anode and the anode (Jpn. J. Appl. Ph.
ys. 32, L917, 1993), the ionization potential of the light emitting layer is higher than the ionization potential of the hole transport layer (Jpn. J. Appl. Phy.
s. 35, 4819, 1996).
The light emitting efficiency of the device was low, and only a blue light emitting device with low stability was obtained. In the present invention, in order to effectively use a hole transporting aromatic amine compound as a light emitting layer, the ionization potential of the hole transporting layer is 0.1%.
It has been found that it is preferable to use a fluorescent aromatic amine having an ionization potential smaller than eV.
With this element structure, it is possible to simultaneously increase the hole concentration in the light emitting layer when the element is energized, and to prevent extinction of the exciton at the anode due to recombination in the light emitting layer.

As the material of the light emitting layer in the organic electroluminescent device of the present invention, there is no further limitation on the aromatic amine compound as long as it satisfies the relation of ionization potential with the hole transport layer. Considering stability, it is desirable to have a high glass transition temperature (Tg). As an aromatic amine compound having a high Tg, it is useful to contain a tertiary nitrogen atom having at least one fused aromatic ring group as a substituent. From this, the aromatic amine contained in the light emitting layer is represented by the following general formula (I)
Alternatively, it is more preferable to be selected from the aromatic amine compounds represented by (II).

[0026]

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In the general formula (I), preferably,
X is a divalent optionally substituted benzene ring, naphthalene ring, anthracene ring, binaphthyl, fluorene ring, phenanthrene ring, pyrene ring, acridine ring, phenazine ring, phenanthridine ring, phenanthroline ring , A bipyridyl ring or a biphenyl, wherein the substituent is a halogen atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group; an alkenyl group such as a vinyl group; and a carbon number such as a methoxycarbonyl group and an ethoxycarbonyl group. 1
6 to 6 alkoxycarbonyl groups; alkoxy groups having 1 to 6 carbon atoms such as methoxy group and ethoxy group; aryloxy groups such as phenoxy group and benzyloxy group; and dialkylamino groups such as diethylamino group and diisopropylamino group. Particularly preferred examples of the substituent include a methyl group, a phenyl group and a methoxy group.

Ar ¹ to Ar ⁴ are preferably each independently a phenyl group, a biphenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a pyrenyl group, a viridyl group, each of which may have a substituent. Triazyl group,
A pyrazyl group, a quinoxalyl group or a thienyl group, wherein the substituent is a halogen atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group; an alkenyl group such as a vinyl group; a methoxycarbonyl group or an ethoxycarbonyl group A methoxy group having 1 to 6 carbon atoms;
An alkoxy group having 1 to 6 carbon atoms such as an ethoxy group; an aryloxy group such as a phenoxy group and a benzyloxy group; a dialkylamino group such as a diethylamino group and a diisopropylamino group. As the substituent, particularly preferably,
Examples include a methyl group, a phenyl group, and a methoxy group.

[0029]

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In the general formula (II), Y is selected from a nitrogen atom or a trivalent benzene ring substituted at the 1,3,5-position. Ar ⁵ and Ar ⁶ are preferably each independently a phenyl group, a biphenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a pyrenyl group, a pyridyl group, a triazyl group, each of which may have a substituent. A pyrazyl group, a quinoxalyl group, or a thienyl group, wherein the substituent is a halogen atom;
Alkyl groups of 6 to 6; alkenyl groups such as vinyl groups; and 1 to 1 carbon atoms such as methoxycarbonyl groups and ethoxycarbonyl groups.
6 alkoxycarbonyl group; C1-C6 alkoxy group such as methoxy group and ethoxy group; aryloxy group such as phenoxy group and benzyloxy group; diethylamino group; dialkylamino group such as diisopropylamino group. Particularly preferred examples of the substituent include a methyl group, a phenyl group and a methoxy group.

In the present invention, the molecular structure represented by the general formula (I) or the general formula (II) allows the Tg to be 85 ° C. or higher, and the improved heat resistance makes it difficult to crystallize easily. It is possible to provide a crystalline thin film, and it is possible to sufficiently suppress the interdiffusion of molecules between a hole transport layer, an electron transport layer, and the like even at a high temperature of 85 ° C. or higher.
Further, the ionization potential can be made 0.1 eV or more lower than that of the hole transport layer.
A light emitting layer having a fluorescence maximum in a wavelength region of 500 nm can be designed. Preferred specific examples of the aromatic amine compounds represented by the general formulas (I) and (II) are shown in Tables 1 to 5, but are not limited thereto.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

[Table 5]

These compounds may be used alone or, if necessary, in combination. The fluorescent dye doped into the light emitting layer using the aromatic amine compound as a host material may be a fluorescent dye having a maximum fluorescence wavelength in a dispersion state or a dilute solution state in a range of 550 to 650 nm. Here, the dispersed state or the dilute solution state means a concentration range in which concentration quenching of the fluorescent dye does not occur, and is usually 10% by weight or less. Examples of dyes having yellow-green to yellow fluorescence include naphthacene derivatives represented by rubrene (JP-A-4-335087).
Perimidone derivatives (JP-A-4-320485),
Examples of orange fluorescent dyes include benzothioxanthene derivatives (JP-A-5-222362), DCM dyes (JP-A-63-264892), rhodamine dyes, and the like.
Examples of red fluorescent dyes include azabenzothioxanthene derivatives (Japanese Patent Application No. 9-88172), phenoxazone, and DCJ dyes (Chem. Funct.
rc. Int. Symp. , 2nd 1992, 5
36) and perylene pigments such as Lumogen F Red. 0.1 to 1 of the above fluorescent dye is added to the blue host material.
By doping in a concentration range of 0% by weight, desired white light emission can be obtained by adding light emission from the doped dye to light emission from the host material.

It is also effective to further dope and add a fluorescent dye having a fluorescent maximum wavelength in a dilute state at 400 to 500 nm in order to balance the white color and improve the luminous efficiency. Examples of the doped dye used for this purpose include condensed polycyclic aromatic rings such as perylene (JP-A-5-198377), coumarin derivatives,
Examples thereof include naphthalic acid imide derivatives (JP-A-4-320486) and aromatic amine derivatives (JP-A-8-199162). The content of these doped dyes in the host material is preferably in the range of 0.1 to 10% by weight. The 400 to 500 nm fluorescent dye may be uniformly doped in the light emitting layer or may be partially doped. As a method of performing the above-mentioned doping by a vacuum evaporation method, there are a method of co-evaporation and a method of previously mixing an evaporation source at a predetermined concentration. Note that the ionization potential of the host material does not change due to doping within the above doping concentration range.

When the above dopants are doped in the light emitting layer, they are uniformly doped in the thickness direction of the light emitting layer. However, even if there is a concentration distribution in the thickness direction or the light emitting layer is partially doped. I do not care. For example, doping may be performed only near the interface with the hole transport layer, or conversely, near the interface with the hole blocking layer. The light emitting layer 5 is formed by a coating method or a vacuum evaporation method in the same manner as the hole transport layer 4.
It is formed by laminating on top. However, in the case of the coating method, it is necessary to use a solvent that does not dissolve the hole transport layer already formed as a thin film. The thickness of the light emitting layer 5 is usually 5 to 300 nm, preferably 10 to 100 nm. In order to uniformly form such a thin film, generally, a vacuum deposition method is often used.

On the light emitting layer 5, a hole blocking layer 6 is provided. The hole blocking layer 6 has a role of preventing holes moving from the light emitting layer from reaching the cathode, and a compound capable of efficiently transporting electrons injected from the cathode toward the light emitting layer 5. It is formed. The physical properties required for the material constituting the hole blocking layer are that the electron mobility is high and the hole mobility is low, and in order to efficiently confine holes in the light emitting layer, the ionization potential of the light emitting layer is 0.2 eV
It is necessary to have a large value of the ionization potential. Since the hole transporting layer is made of a material having no electron transporting ability, the hole blocking layer has a function of confining holes and electrons in the light emitting layer and improving luminous efficiency. As a hole blocking layer material satisfying such conditions, a mixed ligand complex represented by the following general formula (III):

[0041]

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(Wherein R ¹ to R ⁶ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, an allyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, Carboxyl group, alkoxy group, alkylsulfonyl group, α-haloalkyl group, hydroxyl group, amide group optionally having substituent (s), aromatic hydrocarbon group optionally having substituent (s) or substituent (s) Represents an aromatic heterocyclic group which may be represented by the following formula: M represents an Al atom or a Ga atom; L represents a general formula (IIIa) shown below;
(Indicates any group of (IIIb) or (IIIc))

[0043]

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(Wherein, Z represents any atom of Si, Ge or Sn, and Ar ⁹ or Ar ¹⁰ are each independently an aromatic hydrocarbon group which may have a substituent. Or an aromatic heterocyclic group) a binuclear metal complex represented by the following general formula (IV):

[0045]

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(Wherein R ¹ to R ⁶ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, an allyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, Carboxyl group, alkoxy group, alkylsulfonyl group, α-haloalkyl group, hydroxyl group, amide group optionally having substituent (s), aromatic hydrocarbon group optionally having substituent (s) or substituent (s) Represents an aromatic heterocyclic group which may be represented by M, and M represents an Al atom or a Ga atom.) A compound having at least one 1,2,4-triazole ring represented by the following structural formula (IV),

[0047]

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A styryl compound represented by the following general formula (V) is exemplified.

[0049]

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(In the formula, Ar ¹² represents a divalent aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and Ar ¹³ to Ar ¹⁶ each independently represent Represents an aromatic hydrocarbon group or an aromatic hydrocarbon group, each of which may have a substituent.) As a specific example of the mixed ligand complex represented by the general formula (III), bis (2-methyl -8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato (ortho-cresolato) aluminum, bis (2-
Methyl-8-quinolinolato) (meta-cresolato) aluminum, bis (2-methyl-8-quinolinolato) (para-cresolato) aluminum, bis (2-methyl-8)
-Quinolinolato) (ortho-phenylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (meta-phenylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (para-phenylphenolato) aluminum, Bis (2-methyl-8-quinolinolato) (2,3-dimethylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (2,6-dimethylphenolato) aluminum, bis (2-methyl-8-amino)
Quinolinolato) (3,4-dimethylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (3
5-dimethylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (3,5-di-tert-butylphenolato) aluminum, bis (2-methyl-8)
-Quinolinolato) (2,6-diphenylphenolato) aluminum, bis (2-methyl-8-quinolinolato)
(2,4,6-triphenylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (2,4
6-trimethylphenolato) aluminum, bis (2-
Methyl-8-quinolinolato) (2,3,6-trimethylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (2,3,5,6-tetramethylphenolato) aluminum, bis (2-methyl -8-quinolinolato) (1-naphtolat) aluminum, bis (2-methyl-8-quinolinolato) (2-naphtolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, bis (2 -Methyl-8
-Quinolinolato) (triphenylgermanolato) aluminum, bis (2-methyl-8-quinolinolato) (tris (4,4, -biphenyl) silanolato) aluminum, bis (2,4-dimethyl-8-quinolinolato) (ortho -Phenylphenolato) aluminum, bis (2,
4-dimethyl-8-quinolinolato) (para-phenylphenolato) aluminum, bis (2,4-dimethyl-8)
-Quinolinolato) (meta-phenylphenolato) aluminum, bis (2,4-dimethyl-8-quinolinolato)
(3,5-dimethylphenolato) aluminum, bis (2,4-dimethyl-8-quinolinolato) (3,5-di-tert-butylphenolato) aluminum, bis (2-methyl-4-ethyl-8-) Quinolinolato) (para-cresolato) aluminum, bis (2-methyl-4-)
Methoxy-8-quinolinolato) (para-phenylphenolato) aluminum, bis (2-methyl-5-cyano-)
8-quinolinolato) (ortho-cresolato) aluminum, bis (2-methyl-6-trifluoromethyl-8-
Quinolinolato) (2-naphtolat) aluminum, bis (2-methyl-8-quinolinolato) (phenolato) gallium, bis (2-methyl-8-quinolinolato) (ortho-cresolato) gallium, bis (2-methyl-8-quinolinolato) ) (Para-phenylphenolato) gallium, bis (2-methyl-8-quinolinolato) (1-naphthrat) gallium, bis (2-methyl-8-quinolinolato)
(2-Naphthrat) gallium, bis (2-methyl-8-
Quinolinolato) (triphenylsilanolato) gallium,
Bis (2-methyl-8-quinolinolato) (Tris (4,
4-biphenyl) silanolato) gallium and the like. Particularly preferably, bis (2-methyl-8-quinolinolato) (2-naphthrat) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato)
Aluminum.

As a specific example of the binuclear metal complex represented by the general formula (IV), bis (2-methyl-8-quinolato)
Aluminum-μ-oxo-bis- (2-methyl-8-
Quinolinolato) aluminum, bis (2,4-dimethyl-8-quinolinolato) aluminum-μ-oxo-bis- (2,4-dimethyl-8-quinolinolato) aluminum, bis (4-ethyl-2-methyl-8-quinolinolato) ) Aluminum-μ-oxo-bis- (4-ethyl-
2-methyl-8-quinolinolato) aluminum, bis (2-methyl-4-methoxyquinolinolato) aluminum-μ-oxo-bis- (2-methyl-4-methoxyquinolinolato) aluminum, bis (5-cyano -2-Methyl-8-quinolinolato) aluminum-μ-oxo-
Bis- (5-cyano-2-methyl-8-quinolinolato)
Aluminum, bis (5-chloro-2-methyl-8-quinolinolato) aluminum-μ-oxo-bis- (5-
Chloro-2-methyl-8-quinolinolato) aluminum, bis (2-methyl-5-trifluoromethyl-8-)
Quinolinolato) aluminum-μ-oxo-bis- (2
-Methyl-5-trifluoromethyl-8-quinolinolato) aluminum and the like. Particularly preferably, bis (2-methyl-8-quinolinolato) aluminum-μ
-Oxo-bis- (2-methyl-8-quinolinolato) aluminum. Specific examples of the compound having at least one 1,2,4-triazole ring represented by the structural formula (V) are shown below.

[0052]

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Specific examples of the styryl compound represented by the general formula (VI) include, for example, a distyrylbiphenyl derivative represented by the following structural formula.

[0054]

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The thickness of the hole blocking layer 6 is usually 0.3 to 1
00 nm, preferably 0.5 to 30 nm. The hole blocking layer can be formed in the same manner as the hole transporting layer, but usually, a vacuum evaporation method is used. It is conceivable to provide an electron transport layer 7 between the hole blocking layer 6 and the cathode 8 for the purpose of further improving the luminous efficiency of the device. The electron transport layer 7 is formed of a compound capable of efficiently transporting electrons injected from the cathode between the electrodes to which an electric field is applied in the direction of the hole blocking layer 6. The electron transport layer
This has an effect of preventing excitons generated by recombination in the light emitting layer from being diffused and quenched by the cathode 8. The electron transporting compound used in the electron transporting layer 7 is preferably a compound having high electron injection efficiency from the cathode 8 and having high electron mobility and capable of efficiently transporting injected electrons. is necessary.

Materials satisfying such conditions include 8
Metal complexes such as aluminum complexes of 10-hydroxyquinoline (JP-A-59-194393) and metal complexes of 10-hydroxybenzo [h] quinoline (JP-A-6-322)
362), oxadiazole derivatives (Japanese Unexamined Patent Publication No.
No. 216791), distyrylbiphenyl derivatives (JP-A-3-231970), silole derivatives (JP-A-9-87616), and 3- or 5-hydroxyflavone metal complexes (Appl. Phys. Let).
t. , 71, 3338, 1997), benzoxazole metal complexes (JP-A-6-336586),
Benzothiazole metal complex (JP-A-9-279134), trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compound (JP-A-6-207169), phenanthroline derivative (JP-A-5-279169) No. 3,314,459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine (Phys. Stat. Sol. (A), 142).
Vol., P. 489, 1994), n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide and the like. The thickness of the electron transport layer 7 is usually 5 to 200 nm, preferably 10 to 100 nm.

The cathode 8 plays a role of injecting electrons into the electron transport layer 7. As the material used for the cathode 8, the material used for the anode 2 can be used, but for efficient electron injection, a metal having a low work function is preferable, and tin, magnesium, indium, calcium,
A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include a low work function alloy electrode such as a magnesium-silver alloy, a magnesium-indium alloy, and an aluminum-lithium alloy.

Furthermore, inserting an ultrathin film (0.1 to 5 nm) of an alkali metal compound such as LiF or Li ₂ O or an alkaline earth halide at the interface between the cathode and the light emitting layer or the electron transporting layer can be used. (Appl. Phys. Lett., 70, 152).
P. 1997; IEEE Trans. Electr
on. Devices, 44, 1245, 1997.
Year; Japanese Patent Application No. 9-86662). The thickness of the cathode 8 is usually the same as that of the anode 2. In order to protect the cathode made of a low work function metal, further laminating a metal layer having a high work function and being stable to the atmosphere increases the stability of the device. For this purpose, metals such as copper, aluminum, silver, nickel, chromium, gold, platinum and the like are used.

Incidentally, the structure reverse to that of FIG. 1, that is, the cathode 8, the electron transport layer 7, the light emitting layer 5, the hole transport layer 4, the anode 2
And the organic electroluminescent device of the present invention can be provided between two substrates, at least one of which has high transparency, as described above. Similarly, it is also possible to laminate in a structure opposite to the above-mentioned respective layer constitutions shown in FIGS. According to the organic electroluminescent device of the present invention, high luminous efficiency, white light emission with excellent stability is obtained, not only useful as a direct-view display device,
It also functions as a backlight light source, and can be used in combination with a color filter to produce a full-color display element.

[0060]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the description of the following examples unless it exceeds the gist. Reference Example 1 A glass substrate was ultrasonically washed with acetone, washed with pure water, ultrasonically washed with isopropyl alcohol, dried with dry nitrogen, and dried.
After performing the V / ozone cleaning, the apparatus was set in a vacuum evaporation apparatus, and evacuated using an oil diffusion pump until the degree of vacuum in the apparatus became 2 × 10 ⁻⁶ Torr or less. Exemplary compound (I-
3) was placed in a ceramic crucible and heated by a tantalum wire heater around the crucible to perform vapor deposition. At this time, the temperature of the crucible was controlled in the range of 200 to 260 ° C. The degree of vacuum at the time of vapor deposition is 1.8 × 10 ⁻⁶ Torr (about 2.3 × 10 ⁻⁴ Pa).
Thus, a uniform and transparent film having a thickness of 82 nm was obtained at a deposition rate of 0.3 nm / sec. When the ionization potential of this thin film sample was measured using an ultraviolet electron analyzer (AC-1) manufactured by Riken Keiki Co., Ltd., a value of 5.06 eV was shown. The maximum of the fluorescence wavelength measured by exciting this vapor-deposited film with a mercury lamp (wavelength 350 nm) was 465 nm, which was blue fluorescence. Further, the powder sample of the exemplified compound was subjected to differential thermal analysis measurement using DSC-20 manufactured by Seiko Electronics Co., Ltd., and as a result, Tg showed a high value of 93 ° C. Similarly, the results of measuring the ionization potential, the fluorescence maximum wavelength, and Tg of the other exemplified compounds are shown in Table-6.

[0061]

[Table 6]

Reference Example 2 As a material for the hole transport layer, the following compound, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, was used instead of compound (I-3). (H-1) as an evaporation source

[0063]

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A vapor deposition film was prepared in the same manner as in Reference Example 1 except for the above. When the ionization potential of this thin film sample was measured, it showed a value of 5.25 eV. Reference Example 3 As a material for the hole blocking layer, bis (2-methyl-8-quinolinolato) shown below was used in place of the exemplary compound (I-3).
(Triphenylsilanolato) aluminum complex (HB-
A deposited film was prepared in the same manner as in Reference Example 1 except that 1) was used as the deposition source.

[0065]

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The measured ionization potential of this thin film sample was 5.51 eV. Example 1 An organic electroluminescent device having a structure shown in FIG. 2 was produced by the following method. Indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 120 nm (Geomatec; electron beam filmed product; sheet resistance 15Ω)
Was patterned into 2 mm-wide stripes using ordinary photolithography and hydrochloric acid etching to form an anode. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with acetone, water cleaning with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally cleaned with ultraviolet and ozone, and placed in a vacuum evaporation apparatus. installed. After the rough exhaust of the above apparatus is performed by an oil rotary pump, the degree of vacuum in the apparatus is 2 × 10 ⁻⁶ Torr (about ^2.10 Torr).
Evacuation was performed using an oil diffusion pump equipped with a liquid nitrogen trap until the pressure became 7 × 10 ⁻⁴ Pa) or less.

As a hole transport layer material, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (H-1) was put in a ceramic crucible, and a tantalum wire heater around the crucible was used. Heating was performed for vapor deposition. The temperature of the crucible at this time was controlled in the range of 275 to 280 ° C. The degree of vacuum at the time of vapor deposition is 1.1 × 10 ⁻⁶ Torr (about 1.5 × 1 Torr).
0 ^-4 Pa) at a deposition rate of 0.3 nm / sec and a film thickness of 60 nm.
Was obtained. Next, the above-described hole transport layer was formed by a dual simultaneous vapor deposition method using the exemplified compound (I-10) as a host material and rubrene (D-1) represented by the following structural formula as a doped fluorescent dye. 4 was deposited.

[0068]

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At this time, the crucible temperature of Exemplified Compound (I-10) was controlled in the range of 320 to 330 ° C., and the crucible temperature of rubrene was controlled at 200 ° C. The degree of vacuum during vapor deposition is 1.1 × 10 ^-6
At Torr (about 1.5 × 10 ⁻⁴ Pa), the deposition rate of the host material was 0.2 nm / sec, and the film thickness was 30 nm. At this time, the first 15 nm-thick region was set as an undoped region without opening the shutter of the rubrene crucible.
In the region of m, rubrene was set to be 0.4% by weight with respect to the host material. Subsequently, as a material for the hole blocking layer 6, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum complex (HB-1) was deposited on the light emitting layer 5 in the same manner. . At this time, the temperature of the crucible was controlled in the range of 180 to 190 ° C. The degree of vacuum during vapor deposition is 8.0 × 10 ⁻⁷ Torr (about 1.1 × 10 ⁻⁴ P
In a), the deposition rate was 0.5 nm / sec, and the film thickness was 20 nm. Further, an 8-hydroxyquinoline complex of aluminum (E-1) shown below as a material for the electron transport layer 7 was deposited on the hole blocking layer 6 in the same manner.

[0070]

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At this time, the temperature of the crucible was controlled in the range of 300 to 310 ° C. The degree of vacuum during deposition is 8.0 × 10 ⁻⁷ To
rr (approximately 1.1 × 10 ⁻⁴ Pa) at a deposition rate of 0.3 nm
/ S and the film thickness was 25 nm. The above hole transport layer 4
The substrate temperature at the time of vacuum-depositing the electron transport layer 7 was kept at room temperature.

Here, the element on which the electron transport layer 7 was deposited was once taken out of the vacuum deposition apparatus into the atmosphere, and a 2 mm-wide striped shadow mask was used as a cathode deposition mask. It is closely attached to the element so as to be orthogonal to the stripe, and is placed in another vacuum evaporation apparatus, and the degree of vacuum in the apparatus is 2 × 10 ⁻⁶ as in the case of the organic layer.
Evacuation was performed until the pressure became Torr (about 2.7 × 10 ⁻⁴ Pa) or less. As the cathode 8, first, magnesium fluoride (Mg)
F ₂ ) was deposited on a molybdenum boat at a deposition rate of 0.04.
nm / sec, vacuum degree 5.0 × 10 ⁻⁶ Torr (about 6.7 ×
At 10 ⁻⁴ Pa), a film was formed on the electron transport layer 7 to a thickness of 0.5 nm. Next, the aluminum layer was similarly heated by a molybdenum boat to form a 40 nm-thick aluminum layer at a deposition rate of 0.5 nm / sec, a degree of vacuum of 1.2 × 10 ⁻⁵ Torr (about 1.6 × 10 ⁻³ Pa). Was formed. Further, copper is further heated thereon using a molybdenum boat in order to increase the conductivity of the cathode, and a deposition rate of 0.4 nm / sec.
The degree of vacuum is 1.2 × 10 ⁻⁵ Torr (about 1.6 × 10 ⁻³ P)
A cathode 8 was completed by forming a copper layer having a thickness of 40 nm in a). The substrate temperature during the deposition of the above three-layer cathode 8 was kept at room temperature.

As described above, an organic electroluminescent device having a light emitting area of 2 mm × 2 mm was obtained.
Table 7 shows the light emission characteristics of this device. In Table-7,
The emission luminance indicates a value at a current density of 250 mA / cm ² , the luminous efficiency indicates a value at 100 cd / m ² , the luminance / current indicates a slope of the luminance-current density characteristic, and the voltage indicates a value at 100 cd / m ^2. . The CIE chromaticity coordinate values (JIS Z8701) are also shown. The EL spectrum is shown in FIG. The emission color was white. Even after storage for a long time, this element does not show a remarkable increase in drive voltage, there is no decrease in luminous efficiency and luminance,
Stable storage stability of the device was obtained.

[0074]

[Table 7]

Example 2 The exemplified compound (I-27) was used as a host material for the light emitting layer.
Same as Example 1 except that the doped fluorescent dye was a benzothioxanthene derivative (D-2) represented by the following structural formula

[0076]

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Thus, an element was manufactured. Table 7 shows the emission characteristics of the device. The EL spectrum is shown in FIG. The emission color was white. Example 3 Exemplified compound (I-3) as a host material of a light emitting layer, perylene as a doped fluorescent dye in a region with a film thickness of 15 nm on the hole transport layer side, and doping in a region with a film thickness of 15 nm on the hole blocking layer side An element was prepared in the same manner as in Example 1 except that the fluorescent dye was an azabenzothioxanthene derivative (D-3) represented by the following structural formula.

[0078]

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Table 7 shows the emission characteristics of the device. Example 4 The results obtained by measuring the emission spectrum of the device manufactured in Example 1 while changing the luminance level by changing the voltage and obtaining the chromaticity coordinates are shown in Table-8. Although the chromaticity coordinate values slightly fluctuated, all of them were in the white light emitting region, and were practically no problem.

[0080]

[Table 8]

Reference Example 4 A device was prepared in the same manner as in Example 1 except that the exemplified compounds (I-10), (I-27) and (I-3) were used as the light emitting layer material and the light emitting layer was not doped. . Table 7 shows the light emission characteristics of these devices. All emitted blue and blue-green light. Chromaticity coordinates of these undoped elements and Examples 1 to
FIG. 7 shows chromaticity coordinate values obtained from the fluorescence spectrum of the solution of the doped dye used in No. 3.

Comparative Example 1 An element was produced in the same manner as in Example 2 except that the hole blocking layer was not provided and the thickness of the electron transport layer was changed to 45 nm. Table 7 shows the light emission characteristics of this device. Blue light emission was not obtained, and yellow-green light emission in which a doped dye was added to light emission from the 8-hydroxyquinoline complex of aluminum used as the electron transport layer was observed. Comparative Example 2 A light-emitting layer material was prepared using the exemplified compound (I-
As 3), an element was produced in the same manner as in Example 1 except that the film thickness was 60 nm and azabenzothioxanthene (D-3) was used as a dope dye. Table 7 shows the light emission characteristics of this device. Although white light emission was obtained, the light emission efficiency was low.

Comparative Example 3 The above compound (HB-1) was used as a host material for a blue light emitting layer, and perylene and benzothioxanthene (D-2) were doped at 1.0 and 0.4% by weight, respectively. Was prepared in the same manner as in Example 1 except that 45 nm (E-1) was used as the electron transporting layer without providing the element. Table 7 shows the light emission characteristics of this device. Although white light emission was obtained, the light emission efficiency was low.

[0084]

According to the organic electroluminescent device of the present invention, since a specific luminescent dye is contained in the luminescent layer composed of a specific aromatic amine, white luminescence with high luminous efficiency can be achieved.
Further, an element with improved stability can be obtained. Therefore, the organic electroluminescent device according to the present invention can
Light sources (e.g., light sources for copiers, backlight sources for liquid crystal displays and instruments, etc.), display boards, signs, and the like (e.g., light sources for displays (e.g., OA computers and wall-mounted televisions), multi-color display elements, or surface light emitters) The technical value is great as an in-vehicle or outdoor display element that requires high heat resistance.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an organic electroluminescent device.

FIG. 2 is a schematic sectional view showing another example of the organic electroluminescent device.

FIG. 3 is a schematic sectional view showing another example of the organic electroluminescent device.

FIG. 4 is a CIE chromaticity coordinate diagram showing the concept of additive color mixture.

FIG. 5 is an emission spectrum from the organic electroluminescent device of Example 1.

FIG. 6 is an emission spectrum from the organic electroluminescent device of Example 2.

FIG. 7 is a CIE chromaticity coordinate diagram of light emission from a host and a doped dye used in Examples 1 to 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Anode buffer layer 4 Hole transport layer 5 Emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Cathode

Claims (7)

[Claims] An organic electroluminescent device comprising at least a hole transport layer, a light emitting layer, and a hole blocking layer sandwiched between an anode and a cathode on a substrate, wherein the light emitting layer is 400 to 500
The compound contains an aromatic amine compound having a fluorescence maximum wavelength in the range of nm, the ionization potential of the hole transport layer is 0.1 eV or more larger than the ionization potential of the light emitting layer, and the ionization potential of the hole blocking layer is the ionization potential of the light emitting layer. An organic electroluminescent device characterized by containing a fluorescent dye having a maximum fluorescence wavelength in the range of 550 to 650 nm at least in the light emitting layer by 0.2 eV or more. 2. The aromatic amine compound contained in the light emitting layer
The aromatic compound represented by the following general formula (I) or (II)
2. The compound according to claim 1, wherein the compound is a mine compound.
Electroluminescent device. Embedded image(Wherein X is a divalent group which may have a substituent,
Represents an aromatic hydrocarbon group or an aromatic heterocyclic group, and represents Ar¹
Or Ar^FourEach independently has a substituent
May represent an aromatic hydrocarbon group or an aromatic heterocyclic group.
X and Ar¹Or Ar^FourAt least one of the
(This is a condensed aromatic ring group.)(In the formula, Y is a nitrogen atom or a group substituted at the 1,3,5-position.
Represents a Zensen ring, Ar ^FiveAnd Ar⁶Are independent
An aromatic hydrocarbon group which may have a substituent
Or represents an aromatic heterocyclic group) 3. The organic electroluminescent device according to claim 1, wherein the amount of the fluorescent dye contained in the light emitting layer is in the range of 0.1 to 10% by weight. 4. A metal complex represented by the following general formula (III) or (IV), a triazole derivative containing at least one of the following structural formulas (V) or styryl represented by the following general formula (VI): The organic electroluminescent device according to any one of claims 1 to 3, wherein the organic electroluminescent device is composed of at least one compound. Embedded image (Wherein, R ¹ to R ⁶ are each independently a hydrogen atom,
Having a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, an allyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, an alkoxy group, an alkylsulfonyl group, an α-haloalkyl group, a hydroxyl group, and a substituent. Represents an amide group which may be substituted, an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent, M represents an Al atom or a Ga atom, Is represented by the following general formula (IIIa), (IIIb) or (III
c) represents any group of the formula) (Wherein, Z represents an atom of any of Si, Ge and Sn, and Ar ⁹ and Ar ¹⁰ each independently represent an aromatic hydrocarbon group or an aromatic group which may have a substituent. Represents a heterocyclic group) (Wherein, R ¹ to R ⁶ are each independently a hydrogen atom,
Having a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, an allyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, an alkoxy group, an alkylsulfonyl group, an α-haloalkyl group, a hydroxyl group, and a substituent. Represents an amide group which may be substituted, an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent, and M represents an Al atom or a Ga atom. Formula 6 Embedded image (In the formula, Ar ¹² represents a divalent aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent,
Ar ¹³ to Ar ¹⁶ each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.) 5. The organic electroluminescent device according to claim 1, wherein an electron transporting layer is provided between the hole blocking layer and the cathode. 6. The film thickness of the hole blocking layer is 0.5 to 30 nm.
The organic electroluminescent device according to any one of claims 1 to 5, wherein 7. The organic electroluminescent device according to claim 1, wherein the hole transport layer is formed of an aromatic amine compound.