JPH04335087A - Organic electroluminescent element - Google Patents

Abstract

PURPOSE:To improve luminescence performance and efficiency by laminating an anode, a hole injecting and transporting organic layer and an electron injecting and transporting org. layer on a base sheet. CONSTITUTION:An anode 2a with a visible light transmittance of 60% or more and a thickness of 50-10,000Angstrom , a hole injecting and transporting org. layer 3 consisting of a naphthacene derive. of formula [ wherein R<1> to R<4> are each H, an alkyl, an aralkyl, an alkenyl, an allyl, an arom. hydrocarbon cyclic group which may have a substd. group, an arom. heterocyclic group, a halogen, an amide, an alkoxy(carbonyl), a nitro or an amino which may have a substd. group; R<5> and R<6> are each H, a halogen, an alkoxy(carbonyl) or an alkyl] and with a thickness of 100-3,000Angstrom , an electron injecting and transporting org. layer 4 consisting of the naphthacene deriv. and with a thickness of 100-2,000Angstrom and a cathode 2b with a visible light transmittance of 60% or higher and a thickness of 50-10,000Angstrom are laminated.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an organic electroluminescent device, and more specifically, a thin film that emits light by applying an electric field through a combination of a hole injection transport layer and an electron injection transport layer made of organic compounds. It concerns type devices.

0002

[Prior Art] Conventionally, thin film type electroluminescent devices include:
ZnS, which is a II-VI group compound semiconductor of inorganic material, C
aS, SrS, etc., include Mn, which is the luminescent center, and rare earth elements (
(Eu, Ce, Tb, Sm, etc.), but electroluminescent devices made from the above inorganic materials: ■ Requires AC drive (50 to 1000 Hz); ■
It has the following problems: the driving voltage is high (~200V), (1) it is difficult to make it full color (blue is a particular problem), and (2) the cost of the peripheral drive circuit is high.

On the other hand, in recent years, in order to improve the above-mentioned problems, electroluminescent elements using organic materials have been developed. In addition to anthracene and pyrene, which have long been known as materials for organic light-emitting layers, cyanine dyes (
J. Chem. Soc. , Chem. Commun. ，
557 pages, 1985), pyrazoline (Mol.Cry
s. Liq. Cryst. , vol. 135, p. 355, 19
1986), perylene (Jpn.J.Appl.Phys
．． , Vol. 25, p. L773, 1986), or coumarin-based compounds and tetraphenylbutadiene (Japanese Patent Application Laid-open No.
In order to improve the efficiency of carrier injection from the electrode in order to increase the luminous efficiency, optimization of the electrode type and the combination of the hole injection transport layer and the organic phosphor have been reported. (Japanese Unexamined Patent Publication Nos. 57-51781, 1983-194393, 63-295695, Appl.P.
hys. Lett. , vol. 51, p. 913, 1987)
etc. are being carried out.

[0004] Furthermore, in order to improve the luminous efficiency of the device and change the luminescent color, an aluminum complex of 8-hydroxyquinoline is used as a host material and is doped with a fluorescent dye for lasers such as coumarin (J. Appl. Phys.
s. , Vol. 65, p. 3610, 1989), but the problem is that the emission wavelength changes depending on the amount of doping, so strict control of the amount of doping is required.

[0005] Furthermore, using anthracene as a host material,
Perylene (N
1) or naphthacene (N2) to emit light (Jpn. J. Appl. Ph.
ys. , vol. 10, p. 527, 1971; Mol. Cr
yst. Liq. Cryst. , vol. 72, p. 113, 1
981; Institute of Electronics and Communication Engineers Technical Research Report, OME89-4
8, 1989), the driving voltage is high, and only a low value of luminance can be obtained.

[0006]

[Case 2]

[0007]

[Chemical formula 3]

[0008]

[Problems to be Solved by the Invention] As mentioned above, the organic electroluminescent devices disclosed so far have
In particular, the luminous efficiency was still insufficient, and further improvement studies were desired.

The present invention has been made in view of the above-mentioned conventional situation, and an object of the present invention is to provide an organic electroluminescent device that can be driven with high luminous efficiency.

0010

[Means for Solving the Problems] The organic electroluminescent device of the present invention is an organic electroluminescent device in which an anode, an organic hole injection/transport layer, an organic electron injection/transport layer, and a cathode are sequentially laminated. The hole injection transport layer and/or the organic electron injection transport layer are characterized in that they contain a naphthacene derivative represented by the following general formula (I).

[0011]

[C4]

(In the formula, R1, R2, R3 and R4 are a hydrogen atom, an alkyl group, an aralkyl group, an alkenyl group, an allyl group, an aromatic hydrocarbon ring group which may have a substituent, or an aromatic heterocycle) group, a halogen atom, an amide group, an alkoxy group, an alkoxycarbonyl group, a nitro group, an amino group that may have a substituent, R5 and R6 are a hydrogen atom, a halogen atom, an alkoxy group, an alkoxycarbonyl group,
Indicates an alkyl group. ) That is, the present inventors have developed an organic electroluminescent device that can be driven with high luminous efficiency.
As a result of extensive studies, the present invention was completed by discovering that it is preferable for the organic hole injection transport layer and/or the organic electron injection transport layer to contain a specific compound. Below, the organic electroluminescent device of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a structural example of an organic electroluminescent device of the present invention, in which 1 is a substrate, 2a and 2b are conductive layers, 3 is an organic hole injection transport layer, and 4 is an organic electron injection transport layer. Each represents a layer.

[0013] The substrate 1 serves as a support for the organic electroluminescent device of the present invention, and usually includes a quartz or glass plate, a metal plate or metal foil, a plastic film or sheet, etc. A glass plate or a transparent synthetic resin substrate such as polyester, polymethyl methacrylate, polycarbonate, or polysulfone is preferable.

A conductive layer 2a is provided on the substrate 1. This conductive layer 2a is usually made of metals such as aluminum, gold, silver, nickel, palladium, and tellurium, metal oxides such as indium and/or tin oxides, copper iodide, carbon black, or poly(3- It is made of conductive resin such as methylthiophene).

In the example shown in FIG. 1, the conductive layer 2a serves as an anode to inject holes. On the other hand, the conductive layer 2b plays a role of injecting electrons into the organic electron injection transport layer 4 as a cathode. As the constituent material of the conductive layer 2b, it is possible to use the constituent material of the conductive layer 2a, but in order to efficiently inject electrons, a metal with a low work function is preferable, such as tin, magnesium, etc. , indium, aluminum, silver, or alloys thereof.

The formation of the conductive layers 2a and 2b is usually carried out by sputtering, vacuum evaporation, etc.; however, metal fine particles such as silver, copper iodide, carbon black, conductive metal oxide fine particles, In the case of conductive resin fine powder, it can also be formed by dispersing these powders in a suitable binder resin solution and coating it on the substrate. Furthermore, in the case of conductive resin, a thin film can be directly formed on the substrate by electric field polymerization. Note that the conductive layers 2a and 2b may be a composite layer formed by laminating two or more materials.

The thickness of the conductive layer 2a varies depending on the required transparency, but if 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 10,
000 Å, preferably about 100 to 5,000 Å. Note that if the conductive layer 2a is opaque, the conductive layer 2a
The material may be the same as that of the substrate 1, or it is also possible to laminate the conductive layer with another substance different from the material constituting the conductive layer. On the other hand, the thickness of the conductive layer 2b is usually as follows:
The thickness is approximately the same as that of the conductive layer 2a.

Although not shown in FIG. 1, this conductive layer 2
A substrate similar to substrate 1 can also be provided on top of b. However, as an electroluminescent device, it is necessary that at least one of the conductive layers 2a and 2b has good transparency. From this, at least one of the conductive layers 2a and 2b has a 100-
The film thickness is preferably 5,000 Å, and good transparency is desired.

The organic hole injecting and transporting layer 3 provided on the conductive layer 2a can efficiently transport holes from the anode toward the organic electron injecting and transporting layer 4 between the electrodes to which an electric field is applied. is required to be formed from a compound that can. Therefore, the organic hole injection/transport compound needs to be a compound that has high hole injection efficiency from the conductive layer 2a and can efficiently transport the injected holes. For this purpose, the ionization potential is small, the hole mobility is large, and the stability is excellent.
It is required that the impurity that becomes a trap is a compound that is unlikely to be generated during manufacturing or use.

Examples of such hole injection and transport compounds include those described in pages 5 to 6 of Japanese Patent Application Laid-open No. 194393/1983 and columns 13 to 14 of US Pat. No. 4,175,960. . Preferred specific examples of these compounds include N,N'-diphenyl-N,N'-(3-
methylphenyl)-1,1'-biphenyl-4,4'-
Examples include aromatic amine compounds such as diamine: 1,1'-bis(4-di-p-tolylaminophenyl)cyclohexane: 4,4'-bis(diphenylamino)quadrophenyl. In addition to aromatic amine compounds, hydrazone compounds disclosed in JP-A-2-311591 may be mentioned. These aromatic amine compounds or hydrazone compounds may be used alone or as a mixture, if necessary.

The organic electron injection and transport layer 4 provided on the organic hole injection and transport layer 3 efficiently transports electrons from the cathode toward the organic hole injection and transport layer between the electrodes to which an electric field is applied. is required to be formed from a compound that can be used. Therefore, the organic electron injection/transport compound needs to be a compound that has high electron injection efficiency from the conductive layer 2b and can efficiently transport the injected electrons. To this end, it is required that the compound has high electron affinity, high electron mobility, excellent stability, and does not easily generate trapping impurities during production or use.

Materials that meet these conditions include aromatic compounds such as tetraphenylbutadiene (Japanese Unexamined Patent Application Publication No. 1989-1999).
7-51781), metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Application Laid-open No. 59-1943)
93), cyclopentadiene derivatives (JP-A No. 2-
289675), perinone derivatives (JP-A-2-2
89676), oxadiazole derivatives (JP-A-2-216791), bisstyrylbenzene derivatives (JP-A-1-245087, JP-A-2-22248)
4), perylene derivatives (JP-A-2-189890)
Publications No. 191694, No. 3-791), coumarin compounds (Japanese Unexamined Patent Publication No. 2-191694, No. 3-792), rare earth complexes (Japanese Unexamined Patent Publication No. 1-256584), distyrylpyrazine derivatives (Unexamined Japanese Patent Publication No. 2003-256584), -252793). When these compounds are used, the organic electron injection and transport layer simultaneously plays the role of transporting electrons and the role of producing light emission upon recombination of holes and electrons.

In the organic electroluminescent device of the present invention, the naphthacene derivative represented by the general formula (I) is contained in the organic hole injecting and transporting layer and/or the organic electron injecting and transporting layer made of such materials. , in the normal case, the general formula (
The naphthacene derivative represented by I) is doped in a region near the interface between the organic hole injection transport layer 3 and the organic electron injection transport layer 4. The layer to be doped may be one or both of the organic hole injection transport layer 3 and the organic electron injection transport layer 4, or even a partial region of each layer. For example, as shown in FIG.
It may be the layer 4a near the interface on the organic hole injection transport layer 3 side. Furthermore, as shown in FIG. 3, it may be a layer 3a near the interface of the organic hole injection and transport layer 3 on the organic electron injection and transport layer 4 side, and as shown in FIG.
4a) and organic electron injection transport layer 4 of organic hole injection transport layer 3
It may be both the layer 3a near the side interface (Fig. 2,
In FIGS. 3 and 4, 3a and 4a are doped regions, 3b and 4b are undoped regions, and numerals 1, 2a, 2b, 3, and 4 refer to the same ones as in FIG. 1. . ). The amount of the above-mentioned naphthacene derivative doped with respect to the host material is preferably 10-3 to 10 mol%. Note that the host material is, for example, the organic electron injection transport layer 4
When the organic hole injection transport layer 3 plays the role of a host material, examples include the above-mentioned organic electron injection transport compounds, and when the organic hole injection transport layer 3 plays a role as a host material, the above-mentioned aromatic amine compounds and hydrazone compounds can be used.

In the general formula (I), R1, R2,
As R3 and R4, hydrogen atom; alkyl group having 1 to 6 carbon atoms such as methyl group and ethyl group; alkoxyalkyl group such as methoxyethyl group and ethoxyethyl group; methoxy-
Alkoxyalkoxyalkyl groups such as ethoxyethyl group and n-butoxyethoxyethyl group; Aryloxyalkyl groups such as phenyloxyethyl group, naphthyloxyethyl group and p-chlorophenyloxyethyl group; benzyl group, phenethyl group, p-chlorobenzyl group arylalkyl groups such as p-nitrobenzyl groups; cycloalkylalkyl groups such as cyclohexylmethyl, cyclohexylethyl, and cyclopentylethyl groups; alkenyloxyalkyl groups such as allyloxyethyl and 3-bromoallyloxyethyl groups; Cyanoalkyl groups such as cyanoethyl group and cyanomethyl group; Hydroxyalkyl groups such as hydroxyethyl group and hydroxymethyl group; Substituted or unsubstituted alkyl groups such as tetrahydrofuryl alkyl groups such as tetrahydrofuryl group and tetrahydrofurylethyl group, allyl groups ; Substituted or unsubstituted alkenyl groups such as 2-chloroallyl group; Substituted or unsubstituted aryl groups such as phenyl group, p-methylphenyl group, naphthyl group, m-methoxyphenyl group; cycloalkyl group such as cyclohexyl group, cyclopentyl group Group; Halogen atoms such as chlorine atom and bromine atom; Amide group; Alkoxy group having 1 to 6 carbon atoms such as methoxy group and ethoxy group; Alkoxycarbonyl group having 1 to 6 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group; Nitro group: includes an amino group which may have a substituent, but is preferably selected from a substituted or unsubstituted aryl group, a halogen atom, and a hydrogen atom.

R5 and R6 are hydrogen atoms; chlorine atoms, halogen atoms; 1 carbon atoms such as methoxy groups and ethoxy groups;
~6 alkoxy groups; alkoxycarbonyl groups having 1 to 6 carbon atoms such as methoxycarbonyl groups and ethoxycarbonyl groups; alkyl groups having 1 to 6 carbon atoms such as methyl groups and ethyl groups; benzyl groups, phenethyl groups, p-chloro benzyl group,
Aryl alkyl groups such as p-nitrobenzyl group; cycloalkylalkyl groups such as cyclohexylmethyl group, cyclohexylethyl group, cyclopentylethyl group; alkenyloxyalkyl groups such as allyloxyethyl group, 3-bromoallyloxyethyl group; cyclopentyl group Preferably, the cycloalkyl group is selected from a hydrogen atom, an alkoxy group having 1 to 6 carbon atoms, and an alkyl group having 1 to 6 carbon atoms.

The method for synthesizing the naphthacene derivative according to the present invention is described, for example, in Copmt. Rend. , vol. 207, 585
Page (1938); Vol. 240, p. 1113 (1955)
239, p. 1101 (1954); Bul
l. Soc. Chim. France, page 418 (19
48); p. 155 (1952); Compt. R
end. , vol. 231, p. 5 (1950); vol. 246, p. 661 (1958); vol. 237, p. 621 (1958);
953); vol. 232, p. 2233 (1951);
J. Chem. Soc. , 3151 pages (1954);
Ann. Chim. , vol. 4, p. 365 (1959);
Tetrahedron Lett. , vol. 29, 13
59 (1988), etc.

Specific examples of the naphthacene derivative represented by the general formula (I) are shown in the following structural formulas (1) to (14), but the invention is not limited to these.

[0028]

[C5]

[0029]

[C6]

In the present invention, the organic hole injecting and transporting layer 3 and the organic electron injecting and transporting layer 4 are formed by, for example, being laminated on the conductive layer 2a by a coating method or a vacuum evaporation method. In the case of coating, an organic hole injecting and transporting compound or an organic electron injecting and transporting compound, a naphthacene derivative represented by the above general formula (I), and, if necessary, a binder that does not act as a trap for electrons or holes or a quencher for light emission. A coating solution is prepared by adding and dissolving additives such as a resin and a coating property improver such as a leveling agent, and the coating solution is coated on the organic hole injection transport layer 3 by a method such as a spin coating method, and dried to form an organic hole injection transport layer 3. A hole injection transport layer 3 or an organic electron injection transport layer 4 is formed. Examples of the binder resin include polycarbonate, polyarylate, polyester, and the like. If the binder resin is added in a large amount, it will reduce the electron mobility, so a small amount is desirable, and the amount is preferably 50% by weight or less based on the coating solution.

In the case of the vacuum evaporation method, an organic hole injecting and transporting material or an organic electron injecting and transporting material is placed in a crucible placed in a vacuum container, and the naphthacene derivative represented by the general formula (I) is added to another crucible. After placing it in a crucible and evacuating the inside of the vacuum container to about 10-6 Torr with an appropriate vacuum pump, each crucible is heated at the same time to evaporate the contents, and organic holes are created in the substrate 1 placed facing the crucible. A layer is formed on the injection transport layer 3 or further on the organic electron injection transport layer 4 . Alternatively, the above materials may be mixed in advance at a predetermined ratio and then evaporated using the same crucible.

The film thickness of the organic hole injection transport layer 3 thus formed is usually 100 to 3000 Å, preferably 300 to 1000 Å, and the film thickness of the organic electron injection transport layer 4 is usually 100 to 3000 Å, preferably 300 to 1000 Å. , 100-2000 Å, preferably 300-1000 Å. In order to uniformly form such a thin film, a vacuum evaporation method is normally preferably used.

The above method is for doping with the naphthacene derivative represented by the general formula (I), but when doping is not performed, the method is performed without using the naphthacene derivative.
It can be formed in a similar manner.

In addition, in order to further improve the luminous efficiency of the organic electroluminescent device, another organic electron injection transport layer 4, as shown in FIG. It is conceivable to laminate the transport layer 5. The compound used for this organic electron injection and transport layer 5 is required to be able to easily inject electrons from the cathode and to have a large electron transport ability. Examples of such organic electron injection transport materials include diphenylquinone derivatives such as the compound shown in Chemical Formula 7, and perylenetetracarboxylic acid derivatives such as the compound shown in Chemical Formula 8 (Jpn. J. Appl. Phys. Vol. 27, L
269, 1988), oxadiazole derivatives such as the compound shown in Chemical Formula 9 (Appl. Phys. Lett.
55, p. 1489, 1989).

[0035]

[C7]

[0036]

[Chemical formula 8]

[0037]

[Chemical formula 9]

The thickness of the organic electron injection and transport layer 5 is usually 100 to 2000 Å, preferably 300 to 100 Å.
00 Å.

In the present invention, the structure is opposite to that shown in FIG.
It is also possible to adopt a configuration in which the organic hole injection transport layer 3 and the conductive layer 2a are laminated in this order, and as described above, the organic electric field of the present invention is formed between two substrates, at least one of which is highly transparent. It is also possible to provide a light emitting element. Also, similarly,
Regarding FIGS. 2, 3, 4, and 5, it is also possible to stack the layers in the reverse structure.

[0040]

[Function] Excellent luminescent properties can be achieved by using the naphthacene derivative represented by the general formula (I) as a doping material for the organic hole injection transport layer and/or organic electron injection transport layer of the organic electroluminescent device. It is believed that it is possible to bring about

By the way, for the purpose of improving the luminous efficiency of organic electroluminescent devices and changing the luminescent color, various fluorescent dyes are doped using an aluminum complex of 8-hydroxyquinoline as a host material (
U.S. Pat. No. 4,769,292). The advantages of this method include: ■ Improved luminous efficiency due to highly efficient fluorescent dyes;
■ Emission wavelength can be varied by selecting the fluorescent dye; ■ Fluorescent dyes that cause concentration quenching can also be used; ■ Fluorescent dyes with poor film properties can also be used.

In the organic electroluminescent device of the present invention, the holes and electrons injected from the anode and cathode recombine to generate excitons, and the fluorescent dye present in the region where the excitons diffuse collide with the excitons. It is thought that light emission occurs due to excitation. The region where holes and electrons recombine is considered to be near the interface between the organic hole injection and transport layer 3 and the organic electron injection and transport layer 4. Therefore, the general formula (
The naphthacene derivative represented by I) is preferably applied to a region near the interface between the organic hole injection transport layer 3 and the organic electron injection transport layer 4.

[0043]

[Examples] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the description of the following Examples unless it exceeds the gist thereof. Examples 1 to 3 Organic electroluminescent devices having the structure shown in FIG. 1 were manufactured by the following method. Indium tin oxide (IT
O) After washing the transparent conductive film deposited to a thickness of 1200 Å with water and ultrasonic cleaning with isopropyl alcohol,
Installed in a vacuum evaporation device, the degree of vacuum inside the device is 2×10
It was evacuated using an oil diffusion pump until the temperature became -6 Torr or less. As an organic hole injection transport layer material, the following hydrazone compounds (H1) and (H2) were used in a molar ratio (H1):
A mixture of (H2)=1:0.3 was placed in a ceramic crucible, heated with a tantalum wire heater around the crucible, and evaporated in a vacuum container. The temperature of the crucible is 150~
In the range of 170℃, the degree of vacuum during vapor deposition is 7×10-7To
It was rr. In this way, the organic hole injection transport layer is formed into 5
The film was deposited to a thickness of 30 Å. The deposition time was 8 minutes.

[0044]

[Chemical formula 10]

Next, as the material for the organic electron injection transport layer,
The 8-hydroxyquinoline complex of aluminum Al(C9H6NO)3 shown in the following structural formula and the naphthacene derivative (Rublene) shown in Chemical Formula 5 above as a doping fluorescent dye were heated simultaneously using separate crucibles. evaporation was performed.

[0046]

[Chemical formula 11]

At this time, the temperature of each crucible was 240 to 2
80℃, 165-175 for naphthacene derivative ■
Controlled at °C. The degree of vacuum during deposition was 9 x 10-7 Torr.
The deposition time was 2 minutes. As a result, the film thickness was 770
An organic electron injecting and transporting layer doped with 3.7 mol % of naphthacene derivative (1) based on the above complex was obtained.

Finally, as a cathode, an alloy electrode of magnesium and silver was deposited to a thickness of 1500 Å using a binary simultaneous deposition method. A molybdenum boat was used for vapor deposition, the degree of vacuum was 8 x 10-6 Torr, and the vapor deposition time was 8 minutes, and as a result, a glossy film was obtained. The atomic ratio of magnesium to silver was in the range of 10:1-2. In this way, organic electroluminescent device A (Example 1) was produced.

In the same manner, organic electroluminescent devices B and C (Examples 2 and 3) in which the organic electron injection transport layer was doped with 2.2 mol % or 7.5 mol % of the naphthacene derivative (1) were prepared. Table 1 shows the results of the luminescence 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 elements A to C. The peak wavelengths of the emission spectra of these devices A to C were all 570 nm, and they exhibited uniform yellow light emission. In Table 1, Vth is the voltage at which the luminance becomes 1 cd/m2, and the luminous efficiency is the efficiency at V100.

Comparative Example 1 An organic electroluminescent device D was prepared in the same manner as in Example 1, except that the organic electron injection transport layer was not doped with the naphthacene derivative (2).
was created. Table 1 shows the measurement results of the light emitting characteristics of this device. The peak wavelength of the emission spectrum of this element D is 530
It exhibited green uniform luminescence at 100 nm.

[0051]

[Table 1]

Comparative Examples 2 and 3 Devices E and F were prepared in the same manner as in Example 1, except that 0.9 mol % and 3.9 mol % of the compounds shown in Table 2 were doped as doping dyes in the organic electron injection transport layer. was created. Table 2 shows the measurement results of the emission wavelengths of these elements E and F.

[0053]

[Table 2]

Example 4 An organic electroluminescent device having the structure shown in FIG. 2 was produced by the following method. In the same manner as in Example 1, an organic hole injection transport layer made of the hydrazone mixture was deposited to a thickness of 610 Å on a cleaned ITO glass substrate. Next, in the same manner as in Example 1, an organic electron injecting and transporting layer made of an 8-hydroxyquinoline complex of aluminum containing 4.5 mol % of the naphthacene derivative (1) was deposited to a thickness of 410 Å. Furthermore, an organic electron injecting and transporting layer consisting of only an 8-hydroxyquinoline complex of aluminum without the above derivative was deposited in the same manner to a thickness of 420 Å. Finally, a cathode was deposited in the same manner as in Example 1 to obtain element G.

Table 3 shows the emission characteristics of this element G. The peak wavelength of the emission spectrum of this element G is 570 nm,
It showed uniform yellow luminescence.

Example 5 An organic electroluminescent device having the structure shown in FIG. 4 was produced by the following method. In the same manner as in Example 1, an organic hole injection transport layer made of the hydrazone mixture was deposited to a thickness of 300 Å on a cleaned ITO glass substrate. Next, the above-mentioned naphthacene derivative (1) was vapor-deposited using a different crucible than that for the hydrazone mixture and heated simultaneously with the hydrazone mixture. In this manner, an organic hole injection transport layer containing 8.0 mol % of the naphthacene derivative (1) was deposited to a thickness of 200 Å. Furthermore, an organic electron injecting and transporting layer consisting only of an 8-hydroxyquinoline complex of aluminum was deposited to a thickness of 720 Å. Finally, a cathode was deposited in the same manner as in Example 1 to obtain element H.

Table 3 shows the emission characteristics of this element H. The peak wavelength of the emission spectrum of this element H is 570 nm,
It showed uniform yellow luminescence.

Example 6 An organic electroluminescent device having the structure shown in FIG. 4 was produced by the following method. In the same manner as in Example 1, an organic hole injection transport layer made of the hydrazone mixture was deposited to a thickness of 300 Å on a cleaned ITO glass substrate. Next, in the same manner as in Example 3, an organic hole injection transport layer containing 8.0 mol % of the naphthacene derivative (1) was deposited to a thickness of 200 Å. Furthermore, in the same manner as in Example 1, an organic electron injecting and transporting layer was prepared from an aluminum 8-hydroxyquinoline complex containing 3.9 mol% of the naphthacene derivative (1).
The film was deposited to a film thickness of 1.5 Å. Finally, a cathode was deposited in the same manner as in Example 1 to obtain device I.

Table 3 shows the emission characteristics of this device I. The peak wavelength of the emission spectrum of this element I is 570 nm,
It showed uniform yellow luminescence.

[0060]

[Table 3]

Example 7 Element C containing 7.5 mol % of the naphthacene derivative (1) in the organic electron injection transport layer prepared in Example 3 was heated to 1.
Table 4 shows the results of measuring the luminescence properties after storage for 18 days. As is clear from Table 4, the reduction in luminance and luminous efficiency was not a practical problem, and long-term stability was demonstrated.

[0062]

[Table 4]

Comparative Example 3 When the device D produced in Comparative Example 1 was stored in vacuum in the same manner as in Example 7, the maximum luminance was 10 after 14 days.
It decreased to 0 [cd/m2] or less.

[0064]

As described in detail above, according to the organic electroluminescent device of the present invention, an anode, an organic hole injection transport layer, an organic electron injection transport layer, and a cathode are sequentially provided on a substrate. Since the hole injection transport layer and/or the organic electron injection transport layer, or a portion thereof, is doped with a specific naphthacene derivative, when a voltage is applied to both poles, luminescence with sufficient luminance for practical use can be obtained with a low driving voltage. Moreover, the initial luminescent properties can be maintained even after long-term storage. The electroluminescent device of the present invention can be used in the field of flat panel displays (e.g., wall-mounted televisions), light sources (e.g., light sources for copying machines, backlight sources for liquid crystal displays, instruments), display boards, etc. , its application to marker lights is considered, and its industrial usefulness is extremely large.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the organic electroluminescent device of the present invention.

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

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

FIG. 4 is a sectional view showing still another embodiment of the organic electroluminescent device of the present invention.

FIG. 5 is a sectional view showing different embodiments of the organic electroluminescent device of the present invention.

[Explanation of symbols]

1 Board 2a, 2b Conductive layer 3 Organic hole injection transport layer 4 Organic electron injection transport layer

Claims (1)

[Claims] Claim 1: Sequentially an anode, an organic hole injection transport layer,
In an organic electroluminescent device in which an organic electron injection transport layer and a cathode are laminated, the organic hole injection transport layer and/or the organic electron injection transport layer contains a naphthacene derivative represented by the following general formula (I). Characteristic organic electroluminescent device. [Formula 1] (wherein R1, R2, R3 and R4 are a hydrogen atom, an alkyl group, an aralkyl group, an alkenyl group, an allyl group, an aromatic hydrocarbon ring group which may have a substituent, or an aromatic heterocyclic group) cyclic group, halogen atom, amide group, alkoxy group, alkoxycarbonyl group, nitro group, amino group which may have a substituent, R5 and R6 are hydrogen atom, halogen atom,
Indicates an alkoxy group, an alkoxycarbonyl group, and an alkyl group. )