Electroluminescent element

Disclosed is an electroluminescent element comprising an anode, a cathode and, disposed therebetween, an organic luminescent layer comprising a mixture of a fluorescent luminescent agent, at least one hole moving and donating agent capable of moving holes and donating the same to the luminescent agent and at least one electron moving and donating agent capable of moving electrons and donating the same to the luminescent agent. In the element, the components of the luminescent layer have specific oxidation potential and reduction potential relationships. The element emits light in response to electrical signals. The element exhibits high luminescence efficiency and brightness even at low voltages, and it can efficiently be produced at low cost.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electroluminescent element. More 
particularly, the present invention is concerned with an 
electroluminescent element comprising an anode, a cathode and, disposed 
therebetween, an organic luminescent layer comprising a mixture of a 
fluorescent luminescent agent, at least one hole moving and donating agent 
capable of moving holes and donating the same to the luminescent agent and 
at least one electron moving and donating agent capable of moving 
electrons and donating the same to the luminescent agent. In the element, 
the components of the luminescent layer have specific oxidation potential 
and reduction potential relationships therebetween. The element emits 
light in response to electrical signals. 
The electroluminescent element of the present invention exhibits high 
luminescence efficiency and brightness, even at low voltages, and it can 
efficiently be produced at low cost. 
2. Discussion of Related Art 
Electroluminescent elements or devices are known, each of which comprises 
opposite electrodes and, disposed therebetween, an organic luminescent 
(light emitting) layer. Electrons are injected from one of the opposite 
electrodes, while holes are injected from the other of the opposite 
electrodes. When the injected electrons are recombined with the injected 
holes in the organic luminescent layer, light is emitted. In such an 
electroluminescent element, single crystalline anthracene and other single 
crystalline materials have been employed as an organic luminescent 
material for constructing the luminescent layer. The employment of single 
crystalline materials is however disadvantageous from the viewpoint of 
manufacturing cost and mechanical strength. Further, single crystalline 
materials inevictably have drawbacks in that a layer having an extremely 
small thickness is not easily formed, only a faint light is emitted with a 
single crystal having a thickness of about 1 mm and a driving voltage as 
high as 100 V or more is frequently required. Due to the above 
disadvantages and drawbacks, the single crystal materials have not yet 
been practically used in an electroluminescent element. 
Attempts have been made to form a film of anthracene or the like having a 
thickness as small as 1 .mu.m or less by vapor deposition techniques (see 
Thin Solid Films, vol. 94, page 171, 1982). For a film to have desired 
performances, it is requisite that a thin film of only several thousand 
Angstroms or so in thickness be prepared under strictly controlled 
film-forming conditions. However, it should be noted that even if a 
luminescent layer is formed of such a thin film, the densities of holes 
and electrons as carriers are so low in the layer that the transportation 
and recombination of the carries cannot be satisfactorily accomplished, 
thereby causing efficient light emission to be unattainable. Especially, 
no satisfactory power consumption and brightness have been attained by 
only the use of such a thin film. 
U.S. Pat. Nos. 4,356,429, 4,539,507 (corresponding to EP-A-120,673) and 
4,720,432 (corresponding to EP-A-278,758) disclose electroluminescent 
elements in which a hole injecting layer is disposed between an anode and 
a luminescent layer in order to increase the density of holes as carriers 
and hence to obtain improved luminescence efficiency. In the 
electroluminescent elements of these patents, a material having excellent 
electron injecting and transporting properties as well as fluorescence 
efficiency must be used as the luminescent layer. However, no material 
disclosed therein is satisfactory in the above-mentioned properties and 
efficiency. 
Moreover, Japanese Patent Application Laid-Open Specification Nos. 
61-37886/1986, 2-250292/1990, 2-291696/1990 and 3-790/1991 disclose the 
use as a luminescent layer of a thin film of a mixture of a compound 
having fluorescence and having the capability of hole transportation and a 
compound having the capability of electron transportation, and also 
disclose the use, as a luminescent layer, of a thin film of a mixture of a 
compound having the capability of hole transportation and a compound 
having fluorescence and having the capability of electron transportation. 
That is, in the electroluminescent elements of these patent documents, a 
single compound serves to accomplish both the transportation of holes or 
electrons and light emission. However, any compound disclosed therein 
cannot satisfactorily perform both of the transportation of holes or 
electrons and the light emission at high efficiency. Accordingly, these 
conventional electroluminescent elements exhibit unsatisfactory brightness 
and power consumption. 
Further, U.S. Pat. No. 4,769,292 discloses an electroluminescent element 
comprising in sequence an anode, an organic hole injecting and 
transporting layer, a luminescent layer and a cathode, in which the 
luminescent layer is formed of a thin film comprised of an organic host 
material forming a layer capable of sustaining both hole and electron 
injection and a small proportion of a fluorescent material. However, no 
material disclosed therein is satisfactory for performing injection of 
both the holes and electrons with high efficiency. Moreover, the 
transportation of holes and electrons to luminescence centers (fluorescent 
material), which is another step which is very important for obtaining 
high luminescence efficiency and brightness in the electroluminescent 
element, cannot satisfactorily be accomplished by any material described 
therein. Therefore, the disclosed electroluminescent element is 
unsatisfactory in respect of brightness and power consumption. 
SUMMARY OF THE INVENTION 
In the current situation as described above, the present inventors have 
conducted extensive and intensive studies with a view toward developing an 
electroluminescent element free from the above-mentioned drawbacks of the 
prior art and capable of exhibiting excellent luminescence efficiency and 
brightness. As a result, it has unexpectedly been found that such a 
desired electroluminescent element can be obtained by employing an organic 
luminescent layer comprised of a mixture of a fluorescent luminescent 
agent, a hole moving and donating agent capable of moving holes and 
donating the same to the fluorescent agent and an electron moving and 
donating agent capable of moving electrons and donating the same to the 
fluorescent agent, wherein the components of the luminescent layer are 
chosen so as to have specific oxidation potential and reduction potential 
relationships therebetween. On the basis of this unexpected finding, the 
present invention has been completed. 
Accordingly, it is an object of the present invention to provide a novel 
electroluminescent element exhibiting excellent luminescence efficiency 
and brightness even at low voltage and low current density, which can 
efficiently be produced at low cost. 
The foregoing and other objects, features and advantages of the present 
invention will be apparent from the following detailed description and 
appended claims taken in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
In one and principal aspect of the present invention, there is provided an 
electroluminescent element comprising: 
an anode for injecting holes, a cathode for injecting electrons and, 
disposed therebetween, an organic luminescent layer, at least one of the 
anode and cathode being transparent, 
the organic luminescent layer comprising a mixture of at least one 
fluorescent luminescent agent, at least one hole moving and donating agent 
capable of moving the holes injected from the anode and donating the holes 
to the luminescent agent, and at least one electron moving and donating 
agent capable of moving the electrons injected from the cathode and 
donating the electrons to the luminescent agent, 
the luminescent agent having a first oxidation potential which is equal to 
or less noble relative to that exhibited by the hole moving and donating 
agent, 
the luminescent agent having a first reduction potential which is equal to 
or noble relative to that exhibited by the electron moving and donating 
agent, 
the first oxidation potential of the respective agent and the first 
reduction potential of the respective agent being measured by cyclic 
voltammetry with respect to a solution of the respective agent in a 
solvent for the agent. 
Hereinbelow, the present invention will be described in greater detail. 
To attain excellent luminescence efficiency and brightness in an organic 
electroluminescent element, it is requisite that both holes and electrons 
be injected at a high efficiency from the electrodes, that both holes and 
electrons be moved to a luminescence center where they are recombined, and 
that the recombination be effected at a high luminescence efficiency at 
the luminescence center. Major conventional means for meeting these 
requirements have resided in disposing a hole injecting and transporting 
layer between an anode and a luminescent layer comprised of a luminescent 
agent having the ability to move electrons injected from a cathode, or 
disposing an electron injecting and transporting layer between a cathode 
and a luminescent layer comprised of a luminescent agent having the 
ability to move holes injected from an anode, so as to form a structure 
comprised of functionally different layers. This prior art has a drawback 
in that in the case of the use of an electron-transporting luminescent 
layer, holes cannot be effectively transported to the luminescence center 
and in the case of the use of a hole-transporting luminescent layer, 
electrons cannot be effectively transported to the luminescence center. By 
contrast, in the present invention, an electroluminescent element having 
excellent luminescence efficiency and brightness is obtained by the use of 
an organic luminescent layer comprising a mixture of a luminescent agent, 
a hole moving and donating agent and an electron moving and donating 
agent. The reason for the above has not yet been elucidated. However, the 
following presumption is possible. Effective transportation of electrons 
and holes to the luminescence center is achieved by a mixture of a hole 
moving and donating agent and an electron moving and donating agent, while 
effective luminescence on the luminescence center is achieved by an 
appropriately chosen luminescent agent having high fluorescence 
efficiency. 
The terminology "hole moving and donating agent" used herein means a 
material which is capable of moving the holes injected from an anode to a 
fluorescent luminescent agent forming a luminescence center, where the 
holes are donated to the fluorescent luminescent agent. The compound for 
use as the hole moving and donating agent has a first oxidation potential, 
as measured with respect to a solution of the compound in a solvent 
therefor, which is not limited but generally less noble as compared to 
+2.00 V. Further, this compound exhibits a hole mobility of at least 
1.times.10.sup.-10 cm.sup.2 /V.multidot.sec at a field strength of 
1.times.10.sup.5 V/cm. The hole mobility of the hole moving and donating 
agent can be measured according to the customary time-of-flight method 
(TOF method) (described in J. Appl Phys., 43, No. 12, PP. 5033-5040 (1972) 
by W. D. Gill et al.). 
Either low molecular weight compounds or high molecular weight polymers can 
be employed as the hole moving and donating agent. 
Preferred examples of low molecular weight compounds include an anthracene 
compound, such as 2, 6, 9, 10-tetraisopropoxyanthracene; an oxadiazole 
compound, such as 2, 5-bis(4-diethylaminophenyl)-1, 3, 4-oxadiazole; a 
triphenyl amine compound, such as N, N'-diphenyl-N, N'-di 
(3-methylphenyl)-1, 1'-biphenyl-4, 4'-diamine; an aromatic tertiary amine 
compound, such as N-phenyl carbazole; N-isopropyl-carbazole and compounds 
described as being suitable as a hole transporting layer in Japanese 
Patent Application Laid-Open Specification No. 63-264692; a pyrazoline 
compound, such as 
1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)-2-pyrazoline; a 
styryl compound, such as 9-(p-diethylaminostyryl)anthracene; a hydrazone 
compound, such as p-diethylminobenzaldehyde-(diphenylhydrazone); a 
triphenylmethane compound, such as 
bis(4-dimethylamino-2-methylphenyl)-phenyl-methane; a stilbene compound, 
such as .alpha.-(4-methoxyphenyl)-4-N, N-diphenylamino(4'methoxy)stilbene; 
an enamine compound, such as 1, 1-(4,4'-diethoxyphenyl)-N, N-(4, 
4'-dimethoxyphenyl)enamine; a metal- or a non-metalphthalocyanine 
compound; and a porphyrin compound. 
Examples of polymers for use as the hole moving and donating agent include 
polymers having a main chain or a side chain containing a low molecular 
weight compound as a hole moving and donating agent. Representative 
examples of such polymers are as follows: 
##STR1## 
wherein A.sup.1 represents a hydrogen atom or an alkyl group having 1 to 8 
carbon atoms, A.sup.2 represents an aromatic residue, x and n are an 
integer of from 0 to 6 and an integer of 3 or more, respectively. 
Examples of aromatic residues represented by A.sup.2 are as follows: 
##STR2## 
wherein Y.sup.1 represents a hydrogen atom, a bromine atom, or a chlorine 
atom, 
##STR3## 
wherein Y.sup.1 is as defined above, and B.sup.1 represents a phenyl 
group, an isopropyl group, or an ethyl group, 
##STR4## 
wherein Y.sup.1 and B.sup.1 are as defined above, 
##STR5## 
wherein B.sup.2 is an alkyl group having 1 to 6 carbon atoms, 
##STR6## 
wherein B.sup.2 is an alkyl group having 1 to 6 carbon atoms, 
##STR7## 
Specific examples of such polymers used as the hole moving and donating 
agent include poly(N-vinylcarbazole), poly(3,6-dibromo-N-vinylcarbazole), 
poly(4-diphenylaminophenylmethyl methacrylate), a polyester produced from 
2,6-dimethoxy-9,10-dihydroxyanthracene and a dicarboxylic acid chloride, a 
condensation polymer produced from 3,3'-diaminobenzidine and 
3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, a condensation 
polymer produced from a triphenylamine compound and a dicarboxylic acid 
chloride, and polysilylenes, such as poly(phenylmethylsilylene) and 
poly(diphenylsilylene). 
These hole moving and donating agents can be used individually or in 
combination. 
The terminology "electron moving and donating agent" used herein means a 
material which is capable of moving electrons injected from a cathode to a 
fluorescent luminescent agent as a luminescence center, where the 
electrons are donated to the fluorescent luminescent agent. 
The electron moving and donating agent exhibits a first reduction 
potential, as measured with respect to a solution of the agent in a 
solvent therefor, which is not limited but generally noble as compared to 
-2.50 V, preferably -2.00 V. This nobility of the first reduction 
potential is preferred from the viewpoint of lowering of 
electron-injection barrier to thereby attain an improved luminescence. 
Either low molecular weight compounds or high molecular weight polymers can 
be employed as the electron moving and donating agent. Preferred examples 
of low molecular weight compounds include various dyes and pigments, such 
as a triphenylmethane having an amino group or a derivative thereof, a 
xanthene, an acridine, an azine, a thiazine, a thiazole, an oxazine, and 
an azo; an indanthrene dye, such as flavanthrone; a perinone pigment; a 
perylene pigment; a cyanine color; an electron acceptor, such as 
2,4,7-trinitrofluorenone, tetracyanoquinodimethane and tetracyanoethylene; 
a metal or non-metal phthalocyanine having an electron attracting 
substituent attached to the ring; a porphyrin having a pyridyl group, a 
quinolyl group or a quinoxaryl group attached to the ring; metal complexes 
of 8-hydroxyquinolines; diarylbutadienes, such as 1,4-diphenylbutadiene 
and 1,1,4,4-tetraphenylbutadiene; stilbenes, such as 
4,4'-bis[5,7-di(tert-pentyl)-2-benzoxazolyl)stilbene, 
4,4'-bis(5-methyl-2-benzoxazolyl)stilbene, and trans-stilbene; thiophenes, 
such as 2,5-bis[5,7-di-(tert-pentyl)-2-benzoxazolyl]thiophene, and 
2,5-bis[5-(.alpha.,.alpha.-dimethylbenzyl)-2-benzoxanolyl]-thiophene, and 
2,5-bis[5,7-di(tert-pentyl)-2-benzoxazolyl]-3,4-diphenylthiophene; 
benzothiazoles, such as 2,2'-(1,4-phenylenedivinylene)bisbenzothiazole and 
2(p-dimethylaminostyryl)benzothiazol; and styryl compounds, such as 
1,4-bis(2-methylstyryl)benzene, 2-(p-dimethylaminostyryl)benzoxazole, 
2-(p-dimethylaminostyryl)quinoline, 4(p-dimethylaminostyryl)quinoline, 
2-(p-dimethylaminostyryl)-3,3'-dimethyl-3H-indole and 
2-(p-dimethylaminostyryl)naphtho[1,2-d]thiazole. 
Other preferred examples of low molecular weight compounds include 
condensed polycyclic, aromatic compounds, such as anthracene, tetracene, 
pentacene, pyrene, chrysene, perylene, coronene, 3,4-benzofluoranthene, 
1,2-benzanthracene, 2,3-benzofluorene, 1,12-benzoperylene, 
3,4-benzopyrene, 4,5-benzopyrene, 9,10-bis(4-methoxyphenyl)anthracene, 
1-chloro-9,10-diphenylanthracene, 9,10-diphenylanthracene, 
9-phenylanthracene, 4,5-methylenephenanthrene, decacyclene, 
1,2:3,4-dibenzanthracene, 1,2:5,6-dibenzanthracene, periflanthene, 
4,7-diphenyl-1,10-phenanthroline, fluoranthene, 3-methylcholanthrene, 
rubrene, triphenylene, benzo[ghi]perylene and 
4H-cyclopenta[def]phenanthrene, and their derivatives having an alkyl 
substituent having 1 to 20 carbon atoms, and also include aromatic 
compounds, such as 1,3-diphenylisobenzofuran, 
1,2,3,4-tetraphenyl-1,3-cyclopentadiene and pentaphenylcyclopentadiene. 
Further examples of low molecular weight compounds for use as the electron 
moving and donating agent include an oxadiazole compound of formula (21), 
and oxazole compounds of formulae (22) and (23), 
##STR8## 
wherein each of R.sup.1 and R.sup.2 independently represents a phenyl 
group, a biphenyl group, a naphthyl group, an anthryl group, a 
phenanthrenyl group, a pyrenyl group, a pyridyl group, a pyrazolyl group, 
a quinolyl group, a thiazolyl group, a benzothiazolyl group, an 
oxadiazolyl group, an oxazolyl group, or a benzoxazolyl group, provided 
that these groups may be substituted with a hydroxy group, a cyano group, 
a halogen atom, an R.sup.4 group, an OR.sup.4 group or an 
##STR9## 
R.sup.4 employed above represents a straight chain or branched alkyl group 
having 1 to 19 carbon atoms, a cycloalkyl group having 5 to 18 carbon 
atoms, an alkenyl group having 2 to 4 carbon atoms, a dialkylamino group 
having 1 to 3 carbon atoms, a phenyl group, a biphenyl group, a naphthyl 
group, an anthryl group, a phenanthrenyl group, a pyrenyl group, a pyridyl 
group, a pyrazolyl group, a quinolyl group, a thiazolyl group, a 
benzothiazolyl group, an oxadiazolyl group, an oxazolyl group or a 
benzoxazolyl group. These groups may have a substituent, such as a hydroxy 
group, a cyano group, a halogen atom, a straight chain or branched alkyl 
group having 1 to 19 carbon atoms, a cycloalkyl group having 5 to 18 
carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkoxy group 
having 1 to 19 carbon atoms, an alkylcarbonyloxy group having 1 to 19 
carbon atoms, a cycloalkylcarbonyloxy group having 6 to 12 carbon atoms or 
an alkenylcarbonyloxy group having 2 to 4 carbon atoms. 
Furthermore, the R.sup.4 group may have a substituent, such as a phenyl 
group, a biphenyl group, a naphthyl group, an anthryl group, a 
phenanthrenyl group, a pyrenyl group, a pyridyl group, a pyrazolyl group, 
a quinolyl group, a thiazolyl group, a benzothiazolyl group, an 
oxathiazolyl goup, an oxazolyl group or a benzoxazolyl group. 
These groups may have a substituent R. The substituent R represents a 
hydroxy group, a cyano group, a halogen atom, a straight chain or branched 
alkyl group having 1 to 19 carbon atoms, a cycloalkyl group having 5 to 18 
carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkoxy group 
having 1 to 19 carbon atoms, an alkylcarbonyloxy group having 1 to 19 
carbon atoms, a cycloalkylcarbonyloxy group having 6 to 12 carbon atoms, 
or an alkenylcarbonyloxy group having 2 to 4 carbon atoms. 
Further, the substituent R represents a phenyl group, a biphenyl group or a 
naphtyl group. These groups may have a substituent, such as a hydroxy 
group, a cyano group, a halogen atom, a straight chain or branched alkyl 
group having 1 to 19 atoms, or an alkoxy group having 1 to 19 carbon 
atoms. R.sup.3 represents hydrogen or a straight chain or branched alkyl 
group having 1 to 8 carbon atoms. 
Still further examples of low molecular weight compounds as the electron 
moving and donating agent include vinylene compounds of formulae (24, (25) 
and (26): 
##STR10## 
wherein each of R.sup.5 and R.sup.7 independently represents a group of 
the formula selected form the following formulae: 
##STR11## 
wherein at least one hydrogen atom of each of these groups may be 
substituted with a hydroxy group, a cyano group, a halogen atom, a 
straight chain or branched alkyl group having 1 to 8 carbon atoms, an 
alkyloxy group having 1 to 8 carbon atoms or alkylcarbonyloxy group having 
1 to 8 carbon atoms, and Z represents O, S, Se, N--R.sup.8 or 
C(R.sup.8)R.sup.9. Each of R.sup.8 and R.sup.9 independently represents a 
straight chain or branched alkyl group having 1 to 8 carbon atoms. 
In formula (24), R.sup.6 represents a phenyl group, a biphenyl group, a 
naphthyl group, an anthryl group, a phenanthrenyl group or a pyrenyl 
group. R.sup.6 may have a substituent, such as a hydroxy group, a cyano 
group, a halogen atom, a straight chain or branched alkyl group having 1 
to 8 carbon atoms, an alkyloxy group having 1 to 8 carbon atoms, an 
alkylcarbonyloxy group having 1 to 19 carbon atoms, an alkenylcarbonyloxy 
group having 2 to 4 carbon atoms, a cycloalkylcarbonyloxy group having 6 
to 12 carbon atoms, a cycloalkyl group having 5 to 18 carbon atoms, a 
dialkylamino group having 1 to 6 carbon atoms, a diphenylamino group, an 
oxazolyl group, or a thiazolyl group. Furthermore, R.sup.6 may have a 
substituent, such as a phenyl group, a phenoxy group, a naphthyl group, a 
naphthyloxy group, an anthryl group or an anthryloxy group. These groups 
may have a substituent such as a cyano group, a nitro group, a halogen 
atom, or a straight chain or branched alkyl group having 1 to 8 carbon 
atoms. 
Representative examples of R.sup.6 and R.sup.7 include nuclei of 
benzothiazoles, such as benzothiazole, 5-methylbenzothiazole, 
6-methylbenzothiazole, 5,6-dimethylbenzothiazole, 
5-tert-butylbenzothiazole, 5-bromobenzothiazole, 5-phenylbenzothiazole, 
4'-methoxy-5-phenylbenzothiazole, 5-methoxybenzothiazole, 
6-methoxybenzothiazole, 5,6-dimethoxybenzothiazole, 
5,6-dioxymethylenebenzothiazole, 5-hydroxybenzothiazole, 
6-hydroxybenzothiazol and dibenzo[e,g]benzothiazole. 
Other examples of R.sup.5 and R.sup.7 include nuclei of naphthothiazoles, 
such as naphtho[2,1-d]thiazole, naphtho[1,2-d]thiazole, 
5-ethylnaphtho[1,2-d]thiazole, 5-tert-butylnaphtho[1,2-d]thiazole, 
5-phenylnaphtho-[1,2-d]thiazole, 5-methoxynaphtho[1,2-d]thiazole, 
5-ethoxynaphtho[1,2-d]thiazole, 5-chloronaphtho[1,2-d]-thiazole, 
8-ethylnaphtho[2,1-d]thiazole, 7-ethylnaphtho-[2,1-d]thiazole, 
8-tert-butylnaphtho[2,1-d]thiazole, 7-tert-butylnaphtho[2,1-d]thiazole, 
8-methoxynaphtho-[2,1-d]thiazole, 7-methoxynaphtho[2,1-d]thiazole, 
8-phenylnaphtho[2,1-d]thiazole, 7-phenylnaphtho[2,1-d]-thiazole, 
8-chloro-naphtho[2,1-d]thiazole and 7-chloronaphtho[2,1-d]thiazole. 
Further examples of R.sup.5 and R.sup.7 include nuclei of 
thionaphthene[7,6-d]thiazoles, such as 
7-methoxythionaphtheno[7,6-d]thiazole, and nuclei of benzoxazoles, such as 
benzoxazole, 5-methylbenzoxazole, 6-methylbenzoxazole, 
5,6-dimethylbenzoxazole, 5-tertbutylbenzoxazole, 5-bromobenzoxazole, 
5-phenylbenzoxazole, 4,-methoxy-5-phenylbenzoxazole, 5-methoxybenzoxazole, 
6-methoxybenzoxazol, 5,6-dimethoxybenzoxazole, 
5,6-dioxymethylenebenzoxazole, 5-hydroxybenzoxazole, 6-hydroxybenzoxazole 
and dibenzo[e,g]benzoxazole. 
Still further examples of R.sup.5 and R.sup.7 include nuclei of 
naphthoxazoles, such as naphtho[2,1-d]oxazole, naphtho[1,2-d]oxazole, 
5-ethylnaphtho[1,2-d]oxazole, 5-tert-butylnaphtho[1,2-d]oxazole, 
5-phenylnaphtho[1,2-d] oxazole, 5-methoxy-naphtho[1,2-d]oxazole, 
5-ethoxynaphtho-[1,2-d]oxazole, 5-chloronaphtho[1,2-d]oxazole, 
8-ethylnaphtho[2,1-d]oxazole, 7-ethylnaphtho[2,1-d]-oxazole, 
8-tert-butylnaphtho[2,1-d]oxazole, 7-tertbutylnaphtho[2,1-d]oxazole, 
8-methoxynaphtho[2,1-d]oxazole, 7-methoxynaphtho[2,1-d]oxazole, 
8-phenylnaphtho[2,1-d]-oxazole, 7-phenylnaphtho[2,1-d]oxazole, 
8-chloronaphtho[2,1-d]oxazole and 7-chloronaphtho[2,1-d]oxazole. 
Still further examples of R.sup.5 and R.sup.7 include nuclei of 
benzoselenazoles, such as benzoselenazole, 5-methylbenzoselenazole, 
6-methylbenzoselenazole, 5,6-dimethylbenzoselenazole, 
5-tert-butylbenzoselenazole, 5-bromobenzoselenazole, 
5-phenylbenzoselenazole, 4'-methoxy-5-phenylbenzoselenazole, 
5-methoxybenzoselenazole, 6-methoxybenzoselenazole, 
5,6dimethoxybenzoselenazole, 5,6-dioxymethylenebenzoselenazole, 
5-hydroxybenzoselenazole, 6-hydroxybenzoselenazole and 
dibenzo[e,g]benzoselenazole. 
Still further examples of R.sup.5 and R.sup.7 include nuclei of 
naphthoselenazoles, such as naphtho[2,1-d]selenazole, 
naphtho[1,2-d]selenazole, 5-ethylnaphtho[1,2-d]selenazole, 
5-tert-butylnaphtho[1,2-d]selenazole, 5-phenylnaphtho[1,2-d]selenazole, 
5-methoxynaphtho[1,2-d]selenazole, 5-ethoxynaphtho[1,2-d]selenazole, 
5-chloronaphtho[1,2-d]selenazole, 8-ethylnaphtho[2,1-d]selenazole, 
7-ethylnaphtho[2,1-d]selenazole, 8-tert-butylnaphtho[2,1-d]selenazole, 
7-tert-butylnaphtho[2,1-d]selenazole, 8-methoxynaphtho[2,1-d]selenazole, 
7-methoxynaphtho[2,1d]selenazole, 8-phenylnaphtho[2,1-d]selenazole, 
7-phenylnaphtho[2,1-d]selenazole, 8-chloronaphtho[2,1-d]selenazole and 
7-chloronaphtho[2,1-d]selenazole. 
Still further examples of R.sup.5 and R.sup.7 include nuclei of 
2-quinolines, such as 2-quinoline, 6-methyl-2-quinoline, 
6-phenyl-2-quinoline, 6-chloro-2-quinoline, 6-methoxy-2-quinoline, 
6-ethoxy-2-quinoline and 6-hydroxy-2-quinoline; nuclei of 4-quinolines, 
such as 4-quinoline, 6-methoxy-4-quinoline, 7-methyl-4-quinoline, 
7-phenyl-4-quinoline and 8-methyl-4-quinoline; nuclei of 1-isoquinolines, 
such as 1-isoquinoline and 3,4-dihydroxy-1-isoquinoline; and nuclei of 
3-isoquinolines, such as 3-isoquinoline. 
Still further examples of R.sup.5 and R.sup.7 include nuclei of 
3,3-dialkylindolenines, such as 3,3-dimethylindolenine, 
3,3-dimethyl-5-chloroindolenine, 3,3,5-trimethylindolenine, 
3,3,7-trimethylindolenine, 3,3-dimethyl-5-phenylindolenine, 
3,3-dimethyl-benzo[e]indolenine, 3,3-dimethyl-benzo[g]indolenine and 
3,3-dimethyl-dibenzo[e,g]indolenine. 
Still further examples of R.sup.5 and R.sup.7 include nuclei of pyridines, 
such as pyridine, 5-methylpyridine, 5-phenylpyridine and 5-chloropyridine; 
nuclei of benzimidazoles, such as 1-ethyl-5,6-dichlorobenzimidazole, 
1-ethyl-5-chlorobenzimidazole, 1-ethyl-5,6-dibromobenzimidazole, 
1-ethyl-5-phenylbenzimidazole, 1-ethyl-5-cyanobenzimidazole, 
1-ethyl(4,-ethyl)-5-phenylbenzimidazole, 1-ethyl-5-acetylbenzimidazole, 
1-ethyl-5-ethoxycarbonylbenzoimidazole, 1-ethylbenzo[e]benzimidazole, 
1-ethylbenzo[g]benzimidazole and 1-ethyldibenzo[e,g]benzimidazole. 
Polymers for use as the electron moving and donating agent may have a main 
chain or a side chain containing a compound selected from the 
above-mentioned low molecular weight compounds for use as the electron 
moving and donating agent. For example, use is made of a polymer having a 
main chain or a side chain having a 1,3,4-oxadiazole unit. 
Representive examples of polymers for use as the electron moving and 
donating agent include polyethers of formula (38), which is obtained from 
a dihalogen derivative of oxadiazole and a bisphenol compound, 
##STR12## 
wherein each of X.sup.1 and X.sup.2 independently represents a phenylene 
group, a biphenylene group, a naphthylene group, an anthracenylene group, 
a phenanthrenylene group, a pyrenylene group or a pyridilene group. These 
groups may be substituted with a group, such as acyano group, a halogen 
atom, a straight chain or branched alkyl group having 1 to 8 carbon atoms 
and analkyloxy group having 1 to 8 carbon atoms, Y represents an aromatic 
group or an alkylene group having 1 to 20 carbon atoms, and n is an 
integer of 3 or more. 
Representative examples of the aromatic group Y are: 
##STR13## 
Other examples of polymers for use as the electron moving and donating 
agent include polyesters of formulae (98) and (99): 
##STR14## 
wherein X.sup.1, X.sup.2, Y and n are as defined above. 
Further examples of polymers include polycarbonates of formula (100): 
##STR15## 
wherein X.sup.1, X.sup.2 and n are as defined above. 
Still further examples of polymers include polyamides of formulae (101) and 
(102): 
##STR16## 
wherein X.sup.1, X.sup.2, Y and n are as defined above, and polyurethanes 
obtained from a bisphenol derivative of oxadiazole and a diisocyanate 
compound. 
These polymers can be prepared according to the conventional condensation 
polymerization method. The prepared polymers may be purified by 
reprecipitation or the like before use. 
Examples of polymers having a side chain having an oxadiazole unit include 
an ethylene polymer having a side chain having an oxadiazole unit, 
represented by formula (103) 
##STR17## 
wherein R.sup.10 represents an alkyl group having 1 to 3 carbon atoms, 
X.sup.1 is as defined above, X.sup.3 represents a phenyl group, a biphenyl 
group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a 
pyrenyl group or a pyridyl group, provided that these groups may have a 
substituent, such as a cyano group, a halogen atom, a straight chain or 
branched alkyl group having 1 to 8 carbon atoms or an alkyloxy group 
having 1 to 8 carbon atoms. 
These polymers can be prepared by polymerizing an ethylene monomer having 
an oxadiazole unit in the side chain thereof, or by reacting an oxadiazole 
compound with an ethylene polymer. 
Still further examples of polymers for use as the electron moving and 
donating agent include polymers having a side chain having a condensed 
polycyclic aromatic residue, represented by the formula selected from the 
following formulae: 
##STR18## 
wherein A.sup.3 represents a hydrogen atom or an alkyl group having 1 to 8 
carbon atoms, A.sup.4 represents an aromatic residue, x is an integer of 
from 0 to 6, and n is an integer of 3 or more. 
Representative examples of aromatic residues represented by A.sup.4 are: 
##STR19## 
The above electron moving and donating agents may be used individually or 
in combination. 
The fluorescent materials for use as the fluorescent luminescent agent in 
the present invention may be chosen from dyes for a dye laser, fluorescent 
brighteners and compounds capable of exhibiting fluorescence upon 
ultra-violet radiation, as described in for example, "Laser Dyes" written 
by M. Maeda (Published by Academic Press, 1984) and "Organic Luminescent 
Materials" written by B. M. Krasovitskii and B. M. Bolotin (Published by 
VCH, 1988). 
Preferred examples of fluorescent materials with a low molecular weight 
include condensed polycyclic aromatic compounds, such as anthracene, 
pyrene, chrysene, perylene, coronene, 3,4-benzofluoranthene, 
1,2-benzanthracene, 2,3-benzofluorene, 1,12-benzoperylene, 
3,4-benzopyrene, 4,5-benzopyrene, 9-phenylanthracene, 
9,10-bis(4-methoxyphenyl)anthracene, 1-chloro-9,10-diphenylanthracene, 
9,10-diphenylanthracene, 4,5-methylenephenanthrene, decacyclene, 
1,2:3,4-dibenzanthracene, 1,2:5,6-dibenzanthracene, periflanthene, 
4,7-diphenyl-1,10-phenanthroline, fluoranthene, 3-methylcholanthrene, 
rubrene, triphenylene, benzo[ghi]perylene and 
4H-cyclopenta[def]phenanthrene; aromatic compounds, such as terphenyl, 
1,3-diphenylisobenzofuran, 1,2,3,4-tetraphenyl-1,3-cyclopentadiene and 
pentaphenylcyclopentadiene; perylene derivatives as disclosed in for 
example, Japanese Patent Application Laid-Open Specification No. 2-189890; 
6-propionyl-2-dimethylaminonaphthalene; and naphthalene derivatives as 
disclosed in Japanese Patent Application Laid-Open Specification No. 
2-255789. 
Other examples of low molecular weight fluorescent materials include 
fluorescent coumarin dyes, such as 7-hydroxy-4-methylcoumarin, 
7-diethylamino-4-methylcoumarin, 7-dimethylaminocyclopenta[c]coumarin, 
1,2,4,5,-3H,6H,10H-tetrahydro-8-methyl[1]benzopyrano[9,9a,1-gh]-quinolizin 
-10-one, 7-amino-4-trifluoromethylcoumarin, 
1,2,4,5,3H,6H,10H-tetrahydro-9-cyano[1]benzopyrano[9,9a,1-gh]quinolizin-10 
-one, 
1,2,4,5,3H,6H,10H-tetrahydro-9carbo-t-butoxy[1]benzopyrano[9,9a,1-gh]quino 
lizin-10-one, 7-ethylamino-6-methyl-4-trifluoromethylcoumarin, 
1,2,4,5,3H,6H,10H-tetrahydro-9-carbethoxy[1]benzopyrano[9,9a,1-gh]quinoliz 
in-10-one, 7-diethylamino-3-(1-methylbenzimidazolyl)coumarin, 
7-dimethylamino-4-trifluoromethylcoumarin, 
1,2,4,5,3H,6H,10H-tetrahydro-9-carboxy[1]benzopyrano[9,9a,1-gh]quinolizin- 
10-one, 
1,2,4,5,3H,6H,10H-tetrahydro-9-acetyl[1]benzopyrano[9,9a,1-gh]quinolizin-1 
0-one, 3(2-benzimidazolyl)-7-N, N-diethylaminocoumarin, 
1,2,4,5,-3H,6H,10H-tetrahydro-8-trifluoromethyl[1]benzopyrano[9,9a,1-gh]qu 
inolizin-10-one, 3-(2-benzothiazolyl)-7-diethylaminocoumarin, 
7-diethylamino-4-trifluoromethylcoumarin, 
2,3,6,7,-tetrahydro-9-(trifluoromethyl)-1H,5H,11H-[1]benzopyrano[6,7,8-ij] 
quinolizin-11-one, 7-amino-4-methylcoumarin and 
4,6-dimethyl-7-etylaminocoumarin. 
Further examples of low molecular weight fluorescent materials include 
xanthene dyes, for example, Rhodamine dyes, such as Rhodamine B, Rhodamine 
6G, Rhodamine 6G perchlorate, Rhodamine 19 perchlorate, Rhodamine 101 
inner salt, Rhodamine 110, Rhodamine 116 perchlorate, Rhodamine 123, 
Sulforhodamine B and Sulforhodamine 101, and fluorescein dyes, such as 
fluorescein and 2', 7'-dichlorofluorescein. 
Still further examples of preferred low molecular weight fluorescent 
materials include styryl pigments, such as 
2-(p-dimethylaminostyryl)quinoline, 2-(p-dimethylaminostyryl)benzoxazole, 
4-(p-dimethylaminostyryl)quinoline, 
2-(p-dimethylaminostyryl)-6-ethoxyquinoline, 
2-(p-dimethylaminostyryl)benzothiazole, 
2-(p-dimethylaminostyryl)naphtho[1,2-d]oxazole, 
2-(p-dimethylaminostyryl)-3,3'-dimethyl-3H-indole, 
2-(p-dimethylaminostyryl)naphtho[1,2-d]thiazole, 
4-dicyanomethylene-6-(p-dimethylaminostyryl)-2-methyl-4H-pyran. 
Still further examples of preferred low molecular weight fluorescent 
materials include pigments, such as those of polymethine type, oxazine 
type, xanthene type and cyanine type; aromatic amines; aromatic imines; 
butadienes, such as 1,1,4,4-tetraphenyl-1,3-butadiene, 
1-(9-anthracenyl)-4-phenyl-1,3-butadiene and 
1-(4-quinolyl)-4-(p-dimethylamino)phenyl-1,3-butadiene; acridines; 
stilbenes, such as 4,4'-bis(5-methyl-2-benzoxazolyl)stilbene; benzofurans, 
such as 1,3-isobenzofuran; compounds capable of exhibiting an excimer or 
exciplex fluorescence, such as 1,3-dipyrenylpropane, disclosed in Japanese 
Patent Application Laid-Open Specification No. 1-242879; benzoxadiazoles, 
such as 7-(p-methoxybenzylamino)-4-nitrobenzoxadiazole; fluorescent 
brighteners, such as an oxazole compound, an oxadiazole compound, a 
benzoimidazole compound and a thiazole compound; a metal complex, a 
ruthenium complex and a rare earth element complex of 8-hydroxyquinolines 
and their derivatives; fluoresent metal and rare earth element complexes, 
as represented by europium complexes, of benzoyltrifluoroacetone, 
furoyltrifluoroacetone and hexafluoroacetone; and a rare earth metal salt, 
such as terbium picolinate. Further, those described as being useful 
fluorescent materials in Japanese Patent Application Laid-Open 
Specification No. 63-264692 can also be employed. 
Examples of high molecular weight fluorescent materials include polymers 
having, at its main chain, side chain or terminals, the above-mentioned 
low molecular weight fluorescent material. 
In the electroluminescent element of the present invention, the organic 
luminescent layer comprises a mixture of at least one fluorescent 
luminescent agent, at least one hole moving and donating agent and at 
least one electron moving and donating agent. To attain a high 
luminescence efficiency, it is required to employ an appropriate 
combination of these component agents. When the combination of these 
component agents is not appropriate, it is likely that only faint 
luminescence results from the hole moving and donating agent and the 
electron moving and donating agent, or no luminescence is obtained at all 
without the luminescence from the luminescent agent. 
In the electroluminescent element of the present invention, luminescence is 
attained by the recombination, at the luminescent agent which serves as 
the hole-electron recombination center, of the holes having been moved and 
donated to the luminescence center by the action of the hole moving and 
donating agent with the electron having been moved and donated to the 
luminescence center by the action of the electron moving and donating 
agent. 
The present inventors have found that the luminescence from the luminescent 
agent is attained at high efficiency when the ionization potential of the 
fluorescent luminescent agent is equal to or less noble relative to the 
ionization potential of the hole moving and donating agent and when the 
electron affinity of the fluorescent luminescent agent for electrons is 
equal to or noble relative to the electron affinity of the electron moving 
and donating agent for electrons. 
For efficiently moving holes, it is desired that the ionization potential 
of the hole moving and donating agent be equal to or less noble relative 
to the ionization potential of the electron moving and donating agent. On 
the other hand, for efficiently moving electrons, it is desired that the 
affinity of the electron moving and donating agent for electrons be equal 
to or noble relative to the affinity of the hole moving and donating agent 
for electrons. When the above-mentioned relationships are not satisfied, 
it is likely that the hole moving and donating agent and the electron 
moving and donating agent act as traps for holes and electrons, 
respectively, thereby lowering the hole mobility and electron mobility. 
The ionization potential and electron affinity (affinity for electrons) of 
each component compound of the mixture of the hole moving and donating 
agent, the electron moving and donating agent and the luminescent agent 
can be, respectively, determined based on the first oxidation potential 
and first reduction potential of each component compound, as measured in a 
solution of the component for a solvent thereof. Using the first oxidation 
potential and the first reduction potential as criteria, the individual 
component compounds can be appropriately selected for combination. 
Thus, a certain compound to be used as a component of the above-mentioned 
mixture, can also be used as another component by appropriately choosing 
types of other component compounds to be combined therewith. For example, 
a fluorescent compound capable of moving electrons is used as the electron 
moving and donating agent in a certain combination of component compounds, 
and also used as the luminescent agent in another combination of component 
compounds. 
The first oxidation potential and the first reduction potential of each 
component compound with respect to a solution thereof in a solvent for the 
component can be determined by the conventional cyclic voltammetry 
technique. Illustratively stated, the measurement of the first oxidation 
potential and the first reduction potential of each component compound is 
performed at 25.degree. C. in a solution of the compound in a solvent for 
the compound, for example, in an acetonitrile solution containing the 
compound at a concentration of 1.times.10.sup.-4 to 1.times.10.sup.-6 
mole/liter, using 0.1 mole/liter tetra-n-butylammonium perchlorate as a 
supporting electrolyte. A silver-silver chloride electrode is used as a 
reference electrode, a platinum electrode is used as an opposite 
electrode, and a glassy carbon electrode is used as a working electrode. 
Using a potentiostat (HA-303 manufactured and sold by HOKUTO DENKO LTD., 
Japan) and a function generator (HB-104 manufactured and sold by HOKUTO 
DENKO LTD., Japan), the working electrode is subjected to potential 
sweeping in the above-mentioned solution at a sweep rate corresponding to 
a triangular wave of 10 mV.multidot.S.sup.-1, thereby determining a 
current-potential curve. In the operation, when a reduction potential is 
to be measured, the potential sweep is conducted between a starting 
potential of 0 V and a turning potential of -2.5 V, and when an oxidation 
potential is to be measured, the potential sweep is conducted between a 
starting potential of 0 V and a turning potential of +2.5. Before the 
measurement, nitrogen gas is blown into the solution for 15 minutes so as 
to remove any oxygen dissolved therein. 
On the potential-current curve obtained by the above-mentioned procedure, 
the potential (half wave potential) corresponding to a half of a peak 
exhibiting a maximum current is taken as an oxidation potential or a 
reduction potential (provided that when the current value at the potential 
at which the current starts to change drastically is not zero, the current 
value is subtracted from the peak current value). When the measurement is 
conducted with respect to a compound which cannot be dissolved in 
acetonitrile, other suitable solvents, such as dimethylformamide, dimethyl 
sulfoxide or the like is used as a solvent instead of acetonitrile. 
In the selection of an appropriate combination of component compounds for 
the luminescent layer, important are not the absolute values of the 
oxidation potential and reduction potential of the compounds, but the 
relative values of the oxidation potential and reduction potential of the 
compounds. Therefore, the method for measuring the oxidation potential and 
the reduction potential is not particularly limited as long as the 
individual component compounds to be used in combination are measured with 
respect to the oxidation potential and the reduction potention under the 
same conditions. 
There is no particular limitation with respect to the amounts of the 
luminescent agent, the hole moving and donating agent and the electron 
moving and donating agent in the luminescent layer. However, in general, 
the amount of the luminescent agent is preferably 0.01 to 20 parts by 
weight, more preferably 0.01 to 10 parts by weight, based on 100 parts by 
weight of the total of the hole moving and donating agent and the electron 
moving and donating agent. The weight ratio of the electron moving and 
donating agent to the hole moving and donating agent is 95:5 to 5:95. When 
the amount of the luminescent agent is less than 0.01 part by weight, 
based on 100 parts by weight of the total of the hole moving and donating 
agent and the electron moving and donating agent, a high luminescence 
efficiency cannot be obtained due to too low a concentration thereof. 
Further, when the amount of the luminescent agent is more than 20 parts by 
weight, also, a high luminescence efficiency cannot be obtained due to 
concentration quenching. 
In addition to the essential components, i.e., the luminescent agent, the 
hole moving and donating agent and the electron moving and donating agent, 
the luminescent layer may further optionally comprise a binder polymer 
when the luminescent layer is formed from a solution by a coating method. 
Examples of binder polymers include solvent-soluble resins, such as 
polyvinyl chloride, a polycarbonate, polystyrene, polymethyl methacrylate, 
polybutyl methacrylate, a polyester, a polysulfone, polyphenylene oxide, 
polybutadiene, a hydrocarbon resin, a ketone resin, a phenoxy resin, a 
polyamide, ethylcellulose, vinyl acetate, ABS resin, and a polyurethane 
resin; and curable resins, such as a phenol resin, a xylene resin, a 
petroleum resin, a urea resin, a melamine resin, an unsaturated polyester 
resin, an alkyd resin, an epoxy resin, and a silicone resin. 
When a binder polymer is used, the amount thereof is preferably up to 1 
part by weight per one part by weight of the total of a fluorescent 
luminescent agent, a hole moving and donating agent and an electron moving 
and donating agent. When the binder polymer is used in an amount of 
greater than 1 part by weight, the ability to move holes and electrons is 
lowered, thereby causing high luminescence efficiency to be unattainable. 
The thickness of the organic luminescent layer is generally in the range of 
from 50 .ANG. to 1 .mu.m. It is preferred however that the thickness do 
not exceed 5000 .ANG.. 
To form the electroluminescent element of the present invention, an organic 
layer as a luminescent layer is formed on an anode, and further a cathode 
is formed thereon, and vice versa. The luminescent layer may be formed by 
vapor deposition of component compounds, or alternatively may be formed by 
coating of a solution of component compounds containing a binder polymer 
if desired, followed by drying. When the luminescent layer is formed by 
coating of a solution, the coating may be performed by the conventional 
coating methods, such as a casting method, a blade coating method, a dip 
coating method, a spin coating method, a spray coating method and a roll 
coating method. Especially, when the luminescent layer is formed by 
coating of a solution followed by drying, it is preferred that after 
coating on an electrode preferably disposed on a supporting body, leveling 
of the coated solution be performed in a solvent vapor at the time of 
drying, in order to obtain an element capable of uniform light emission. 
An electroluminescent element capable of uniform light emission which 
exhibits a statistical brightness dispersion (scatterning of brightness 
values from their average) of 5% or less relative to the average 
brightness in a single element has excellent durability in continuous 
light emission. The brightness dispersion is determined as follows. First, 
brightness is measured on at least two portions of a brightening surface 
of an electroluminescent element whose area is defined by the area of an 
anode or a cathode whichever is smaller, using a brightness meter having a 
measuring area of 0.1 mm in diameter. Second, an arithmetic mean of all 
measured values is calculated. Third, the difference between the maximum 
value and the arithmetic mean and the difference between the minimum value 
and the arithmetic mean are calculated. The differences are compared, and 
the percentage of the larger difference to the arithmetic mean is 
calculated, which is defined as the brightness dispersion. 
It is desired that the organic luminescent layer of the element according 
to the present invention, irrespective of the preparation method as 
described above, exhibit a photoelectric work function of from 5.0 to 6.0 
eV, which work function is determined by means of a low energy electron 
spectrometer after formation of a luminescent layer followed by 
processing, such as drying, if desired. The value of the photoelectric 
work function is an index of the electron state of the luminescent layer. 
If the value of the photoelectric work function changes as much as 0.2 eV 
or more when the luminescent layer is allowed to stand for one or more 
days after the formation of the layer, the number of non-luminescent 
points in the luminescent layer increases, leading to a lowering of the 
quality of the layer as a surface luminescent light source The presumed 
reason is that crystallization, phase separation and/or change of 
compounds occurs in the luminescent layer due to the lapse of time, 
thereby changing the electron state thereof. The measuring of the 
photoelectric work function is effective as a nondestructive testing means 
at the time of manufacturing. 
The photoelectric work function of the luminescent layer is determined as 
follows. Excitation energy is applied to the layer, and the energy is 
increased 0.05 eV from 4.40 eV to 6.2 eV, using a surface analyzer (AC-1; 
manufactured and sold by Riken Keiki Co., Ltd.) in an atmosphere of 
25.degree. C.-50% RH. The number of photoelectrons at each energy level is 
measured. The root of the number of photoelectrons is set on a vertical 
axis and the excitation energy is set on a horizontal axis of Cartesian 
coordinates. The work function is determined as an intercept of the 
straight line drawn according to the least square method with the 
horizontal axis. 
In the present invention, the anode is comprised of a transparent or an 
opaque conductive material formed on an insulating support. When the 
cathode is opaque, the anode must be transparent. Preferred examples of 
conductive materials include conductive oxides, such as tin oxide, indium 
oxide and indium tin oxide (ITO); metals, such as gold, silver and 
chromium; inorganic conductive materials, such as copper iodide and copper 
sulfide; and conductive polymers, such as polythiophene, polypyrrole and 
polyaniline. 
Preferably used as a cathode in the present invention is a transparent, 
semitransparent or opaque electrode comprised of a metal, such as lithium, 
indium, silver, aluminum, lead, magnesium, copper, lanthanum, europium and 
ytterbium, a rare earth element or a complex thereof. 
In the electroluminescent element of the present invention, a hole 
injecting and transporting layer and/or a hole inhibiting layer may be 
provided in addition to the above-mentioned luminescent layer. 
The hole injecting and transporting layer is provided between the anode and 
the luminescent layer so as to facilitate the injection of holes from the 
anode, and further to transport the injected holes to the luminescent 
layer. The layer may be comprised of a compound used as the hole moving 
and donating agent or a P-type inorganic semiconductor, such as Si, 
Si.sub.1-x C.sub.x wherein x is 0.1 to 0.9, CuI and ZnTe each in an 
amorphous or a microcrystalline form. When the anode is transparent, it is 
preferred that the layer be permeable for light generated in the 
luminescent layer. 
The hole inhibiting layer is provided between the organic luminescent layer 
and the cathode, and inhibits passage of holes into the cathode to hold 
the holes within the organic luminescent layer, thereby permitting the 
holes to effectively contribute to luminescence. An arbitrary electron 
transporting compound can be used in the formation of the hole inhibiting 
layer. However, it is preferred that the first oxidation potential of the 
compound used as the hole inhibiting layer be equal to or noble relative 
to the first oxidation potential of the hole transporting and donating 
agent used in the luminescent layer, from the viewpoint of obtaining 
higher performances of the electroluminescent element. 
Examples of electron transporting compounds to be used for formation of the 
hole inhibiting layer include all organic compounds and metal complexes 
which can be used as the electron moving and donating agent in the present 
invention, and further include n-type inorganic semiconductors, such as 
CdS, CdSe, CdTe, znO, ZnS, ZnSe, ZnTe (n-type), Si.sub.1-x C.sub.x wherein 
x is 0.1 to 0.9, monocrystalline silicon and amorphous silicon. 
The hole injecting and transporting layer and the hole inhibiting layer may 
be comprised of an appropriate compound per se or in the form of a 
dispersion of an appropriate compound in a binder resin. The layers may be 
formed by vapor deposition, spattering, or an electrolytic reaction, or 
may be formed by coating. The binder resin is selected from conventional 
polymers, such as a polycarbonate, polyvinyl chloride, polystyrene, a 
polyester, a polysulfone, polyphenylene oxide, a polyurethane, an epoxy 
resin and polysilane. The amount of added binder resin is not particularly 
limited. However, it is generally up to 100 parts by weight per part by 
weight of the compound. 
Each of the hole injecting and transporting layer and the hole inhibiting 
layer does not necessarily consist of one layer, and two or more 
sub-layers may be laminated to constitute each of the layers. The 
thickness of each of the layers is preferably in the range of from 50 
.ANG. to 1 .mu.m. 
The electroluminescent element of the present invention may be driven by a 
direct current power source. Alternatively, in order to ensure light 
emission at high brightness for a prolonged period of time, it may be 
driven by an alternating current. With respect to the waveform of the 
alternating current signal, not only sine waveform but also any arbitrary 
alternating current waveform, such as a rectangular waveform, a triangular 
waveform and waveforms obtained by combining or synthesizing them, can be 
employed in the present invention. 
The electroluminescent element of the present invention finds applications 
in surface luminous light sources, such as a backlight of a liquid crystal 
display, an erasing light source for a copying machine, and a pilot lamp 
of a meter; various types of display devices, such as a flat panel display 
of a flat television and a display mounted on an automobile; and other 
general uses wherein conventional luminescent elements are used, such as a 
direction indicator and a tail lamp for use in a bicycle, a watch dial 
light, a luminescent device of a toy, a surface luminescent light source 
for advertisement, and a night pilot lamp for road construction. 
PREFERRED EMBODIMENTS OF THE INVENTION 
The present invention will now be further illustrated in more detail with 
reference to the following Examples, which should not be construed to be 
limiting the scope of the present invention. 
EXAMPLE 1 
ITO glass (manufactured and sold by HOYA Corp., Japan), which is a glass 
substrate prepared by forming an ITO film having a thickness of 1000 .ANG. 
on a glass plate of 100.times.100.times.1.1 mm in size, is subjected to 
ultrasonic washing in acetone, followed by air-drying, and then washed 
with an ultraviolet washing apparatus [model PL-10-110; manufactured and 
sold by Sen Engineering Co., Ltd., Japan] for 5 minutes. On the ITO glass, 
a luminescent layer is formed in a thickness of 1000 .ANG. by dip coating 
of a 1,2-dichloroethane solution containing 1 part by weight of 
poly(N-vinylcarbazole) (hereinafter simply referred to as PVK, having a 
first oxidation potential of +1.06 V and a first reduction potential which 
is less noble as compared to -2.5; Luvican M170 manufactured and sold by 
BASF A.G., Germany) as a hole moving and donating agent, 1 part by weight 
of 2-(4'-tert-butylphenyl)-5-(4''-biphenyl)-1,3, 4-oxadiazole (hereinafter 
simply referred to as butyl-PBD; having a first oxidation potential of 
+1.76 V and a first reduction potential of -2.04 V; manufactured and sold 
by Dojindo Laboratories, Japan) as an electron moving and donating agent 
and 0.02 part by weight of 3-(2 
-benzimidazolyl)-7-N,N-diethylaminocoumarin (hereinafter simply referred 
to as coumarin 7; having a first oxidation potential of +0.86 V and a 
first reduction potential of -2.01 V) as a fluorescent luminescent agent. 
Further, on the layer, metallic magnesium is vapor-deposited through a 
shadow mask in an area of 0.1 cm.sup.2 to from a cathode defining the area 
of the element. Direct current voltage is applied to the thus prepared 
element using ITO glass as an anode. As a result, green light is emitted. 
Brightness thereof is 200 cd/m.sup.2 at 21 V and 10 mA/cm.sup.2. 
The hole mobility of poly(N-vinylcarbazole) at 1.times.10.sup.5 V/cm is 
1.3.times.10.sup.-7 cm.sup.2 /V.multidot.sec, and the hole mobility of the 
luminescent layer is 7.0.times.10.sup.-8 cm.sup.2 /V.multidot.sec. 
Further, the photoelectric work function of the luminescent layer is 5.66 
eV. 
COMATIVE EXAMPLE 1 
An element having a luminescent layer of 1000 .ANG. in thickness is 
prepared by dip coating a 1,2-dichloroethane solution containing 2 parts 
by weight of PVK and 0.02 parts by weight of coumarin 7 according to 
substantially the same procedure as described in Example 1, except that 
butyl-PBO as an electron moving and donating agent is not used. The 
prepared element needs at least a voltage of 40 V for flowing a current of 
10 mA/cm.sup.2, at which the brightness is only 20 cd/m.sup.2. 
COMATIVE EXAMPLE 2 
An element having a luminescent layer of 1000 .ANG. in thickness is 
prepared using a 1,2-dichloroethane solution containing 1 part by weight 
of polyester resin (Vylon-200, manufactured and sold by Toyobo Co., Ltd., 
Japan) as a binder polymer, 1 part by weight of butyl-PBD as an electron 
moving and donating agent and 0.02 part by weight of coumarin 7 as a 
fluorescent luminescent agent according to substantially the same 
procedure as described in Example 1, except that PVK as a hole moving and 
donating agent is not used. In the prepared element, an electric current 
can flow only at a current density of 1 mA/cm.sup.2 even if a voltage of 
38 V is applied, at which the brightness is only 2 cd/m.sup.2 Applying 
more voltage results in destruction of the element. 
As is apparent from the above results, high luminescence efficiency cannot 
be obtained by the use of a mixture consisting only of a hole moving and 
donating agent and a fluorescent luminescent agent or a mixture consisting 
only of an electron moving and donating agent and a fluorescent 
luminescent agent. 
COMATIVE EXAMPLE 3 
An element is prepared according to substantially the same procedure as 
described in Example 1, except that 0.02 part by weight of 
1,2,3,4,5,3H,6H,10H-tetrahydro-8-methyl[1]benzopyrano-(9,9a,1-gh)quinolizi 
n-10-one (coumarin 102) having a first oxidation potential of +0.65 V and a 
first reduction potential of -2.15 V is used as a fluorescent luminescent 
agent, instead of coumarin 7. The prepared element emits a blue light, the 
brightness of which is only 3 cd/m.sup.2 at a voltage of 30 V and a 
current density of 10 mA/cm.sup.2. 
COMATIVE EXAMPLE 4 
An element is prepared according to substantially the same procedure as 
decribed in Example 1, except that 0.02 part by weight of 
7-amino-4-trifluoromethylcoumarin (coumarin 151) having a first oxidation 
potential of +1.18 V and a first reduction potential of -1.55 V is used as 
a fluorescent luminescent agent, instead of coumarin 7. The prepared 
element emits a blue light, the brightness of which is only 4 cd/m.sup.2 
at a voltage of 20 V and a current density of 10 mA/cm.sup.2. 
As is apparent from the above results, even if an element comprises a 
mixture of a hole moving and donating agent, a fluorescent luminescent 
agent and an electron moving and donating agent, high luminescence 
efficiency cannot be obtained when the first reduction potential of the 
fluorescent lumnescent agent is less noble relative to that of the 
electron moving and donating agent, or when the first oxidation potential 
of the fluorescent luminescent agent is noble relative to that of the hole 
moving and donating agent. 
EXAMPLES 2 TO 16 
Various types of electron moving and donating agents 
In the following Examples, elements are separately prepared according to 
substantially the same procedure as described in Example 1, except that 
poly(N-vinylcarbazole) is used as a hole moving and donating agent, 
3-(2'-benzothiazolyl)-7-diethylaminocoumarin (coumarin 6) having a first 
oxidation potential of 0.95 V and a first reduction potential of -1.67 V 
is used as a flouorescnt luminescent agent and each of the compounds 
indicated below is individually used as an electron moving and donating 
agent. The weight proportions of PVK: the electron moving and donating 
agent: coumarin 6 are 90:10:1 in Examples 2 to 4, and 55:45:1 in Examples 
5 to 16. All of the elements emit a green light. The voltages required to 
drive the elements at a current density of 10 mA/cm.sup.2 and the 
brightnesses at those voltages, as well as the oxidation and reduction 
potentials of the electron moving and donating agents and the 
photoelectric work functions of the luminescent layers, are shown in Table 
1. 
##STR20## 
TABLE 1 
______________________________________ 
1st 1st Photoelectric 
Ex- oxidation 
reduction 
work Bright- 
ample potential 
potential 
function Voltage 
ness 
Nos. (V) (V) (eV) (V) (cd/m.sup.2) 
______________________________________ 
2 +0.92 -1.72 5.57 17 180 
3 +1.50 -1.79 5.48 15 200 
4 +1.17 -1.90 5.52 16 190 
5 +1.64 -1.85 5.66 13 150 
6 +1.60 -1.85 5.66 18 230 
7 +1.50 -1.85 5.64 18 250 
8 +1.44 -1.86 5.65 14 210 
9 +1.66 -1.79 5.48 10 80 
10 +1.27 -1.70 5.46 13 52 
11 +1.12 -1.83 5.52 13 45 
12 +1.02 -1.72 5.68 13 46 
13 +1.64 -1.71 5.57 11 36 
14 +1.27 -1.70 5.48 12 80 
15 +1.32 -1.72 5.75 13 35 
16 +1.10 -1.69 5.85 15 65 
17 +1.40 -1.80 5.68 17 145 
______________________________________ 
EXAMPLES 18 TO 21 
Luminescent layers each having a thickness of 1500 .ANG. are formed onto 
ITO glass treated in the same manner as described in Example 1, by vacuum 
deposition, individually using the compounds indicated below as a hole 
moving and donating agent, 2,5-bis(1-napthyl)-1,3,4-oxadiazole and 
2,5-bis(2-naphthyl)-1,3,4-oxadiazole each having a first oxidation 
potential of +1.64 V and a first reduction potential of -1.85 V as 
electron moving and donating agents and 
2-(p-dimethylaminostyryl)naphtho[1,2-d]thiazole (hereinafter referred to 
as "NK-1886") having a first oxidation potential of +0.51 V and a first 
reduction potential of -1.83 V as a fluorescent luminescent agent. The 
temperatures of the boats of the vacuum deposition apparatus respectively 
containing the above-mentioned agents therein are regulated at a vacuum of 
3.times.10.sup.-6 Torr so that the weight proportions of the hole moving 
and donating agent: one of the electron moving and donating agents: the 
other of the electron moving and donating agents: the fluorescent 
luminescent agent are 50:25:25:1. The respective elements are examined in 
the same manner as described in Example 1. All of these elements emit a 
green light. The voltage values required to drive the elements at a 
current density of 10 mA/cm.sup.2 and the brightnesses thereat, as well as 
the oxidation and reduction potentials of the hole moving and donating 
agents and the photoelectric work functions of the luminescent layers, are 
shown in Table 2. 
Example 18: 
N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine 
Example 19: 
.alpha.-(4-methoxyphenyl)-4-N,N-diphenylamino(4'-methoxy)stilbene 
Example 20: 
1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)-2-pyrazoline 
Example 21: p-diethylamino benzaldehyde diphenylhydrazone 
TABLE 2 
______________________________________ 
1st 1st Photoelectric 
Ex- oxidation 
reduction 
work Bright- 
ample potential 
potential 
function Voltage 
ness 
Nos. (V) (V) (eV) (V) (cd/m.sup.2) 
______________________________________ 
18 +0.65 -1.87 5.48 18 200 
19 +0.75 -- 5.53 18 190 
20 +0.52 -- 5.38 15 170 
21 +0.55 -- 5.79 17 75 
______________________________________ 
EXAMPLE 22 
An electroluminescent element is prepared in substantially the same manner 
as in Example 1 except that a luminescent layer having a thickness of 1000 
.ANG. is formed from a chloroform solution containing 1 part by weight of 
N-isopropylcarbazole (first oxidation potential: +1.06 V, first reduction 
potential: less noble as compared to -2.5 V) as a hole moving and donating 
agent, 1 part by weight of a polyether (first oxidation potential : +1.50 
V, first reduction potential: -1.85 V) obtained from 
2,5-bis(4,4'-difluoro-1-naphthyl)-1,3,4-oxadiazole and 
2,2-bis(4-hydroxyphe nyl)propane (bisphenol A) as an electron moving and 
donating agent, and 0.02 part by weight of coumarin 6 as a luminescent 
agent. The thus obtained element exhibits a green luminescence having a 
brightness of 460 cd/m.sup.2 at 12 V and 10 mA/cm.sup.2. 
EXAMPLE 23 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 1 part by weight of a polyether (first 
oxidation potential: +1.50 V, first reduction potential: -1.85 V) obtained 
from 2,5-bis(4,4'-difluoro-1-naphthyl)-1,3,4-oxadiazole and 
1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), is used as an electron 
moving and donating agent, and 0.02 part by weight of perylene is used as 
a luminescent agent. The thus obtained element exhibits a blue 
luminescence having a brightness of 300 cd/m.sup.2 at 18 V and 40 
mA/cm.sup.2. 
EXAMPLE 24 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 5 parts by weight of 
N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine is used 
as a hole moving and donating agent, 95 parts by weight of a polyether 
(first oxidation potential: +1.78 V, first reduction potential: -1.98 V) 
represented by the formula (127): 
##STR21## 
is used as an electron moving and donating agent, and 5 parts by weight of 
NK-1886 is used as a luminescent agent. The thus obtained element exhibits 
a green luminescence having a brightness of 200 cd/m.sup.2 at 16 V and 12 
mA/cm.sup.2. 
EXAMPLE 25 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 1 part by weight of N-phenylcarbazole is used 
as a hole moving and donating agent, 1 part by weight of a polyester 
(first oxidation potential: +1.98 V, first reduction potential: -1.91 V) 
obtained from 4,4'-dihydroxy-diphenyloxadiazole derivative and 
decanedicarboxyl chloride and represented by the formula (128): 
##STR22## 
is used as an electron moving and donating agent, and 0.01 part by weight 
of coumarin 6 is used as a luminescent agent. The thus obtained element 
exhibits a green luminescence having a brightness of 520 cd/m.sup.2 at 13 
V and 10 mA/cm.sup.2. 
EXAMPLE 26 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 1 part by weight of a polycarbonate (first 
oxidation potential: +1.96 V, first reduction potential: -1.90 V) 
represented by the formula (129): 
##STR23## 
is used as an electron moving and donating agent. The thus obtained 
element exhibits a green luminescence having a brightness of 550 
cd/m.sup.2 at 10 V and 10 mA/cm.sup.2. 
EXAMPLE 27 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 1 part by weight of a polyamide (first 
oxidation potential: +1.71 V, first reduction potential: -1.87 V) 
represented by the formula (130): 
##STR24## 
is used as an electron moving and donating agent. The thus obtained 
element exhibits a green luminescence having a brightness of 200 
cd/m.sup.2 at 13 V and 10 mA/cm.sup.2. 
EXAMPLE 28 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 95 parts by weight of PVK is used as a hole 
moving and donating agent, 5 parts by weight of the polyether which is the 
same as used in Example 22 is used as an electron moving and donating 
agent, and 1 part by weight of coumarin 6 is used as a luminescent agent. 
The thus obtained element exhibits a green luminescence having a 
brightness of 260 cd/m.sup.2 at 17 V and 15 mA/cm.sup.2. 
EXAMPLE 29 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 1 part by weight of a polymer (first 
oxidation potential: +1.69 V, first reduction potential: -1.91 V) 
represented by the formula (131): 
##STR25## 
is used as an electron moving and donating agent. The thus obtained 
element exhibits a green luminescence having a brightness of 450 
cd/m.sup.2 at 12 V and 10 mA/cm.sup.2. 
EXAMPLE 30 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 1 part by weight of 
2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole (first oxidation potential: 
+0.75 V, first reduction potential: -1.58 V) is used as a hole moving and 
donating agent, and 0.02 part by weight of NK-1886 is used as a 
luminescent agent. The thus obtained element exhibits a green luminescence 
having a brightness of 300 cd/m.sup.2 at 15 V and 80 mA/cm.sup.2. 
EXAMPLE 31 
An electroluminescent element is prepared in substantially the same manner 
as in Example 30 except that 
.alpha.-(4-methoxyphenyl)-4-N,N-diphenylamino-(4'-methoxy)stilbene is used 
as a hole moving and donating agent. The thus obtained element exhibits a 
green luminescence having a brightness of 46 cd/m.sup.2 at 17 V and 10 
mA/cm.sup.2. 
EXAMPLE 32 
An electroluminescent element is prepared in substantially the same manner 
as in Example 30 except that 9-(p-diethylaminostyryl)anthracene (first 
oxidation potential: +1.40 V, first reduction potential: -1.77 V) is used 
as a hole moving and donating agent. The thus obtained element exhibits a 
green luminescence having a brightness of 160 cd/m.sup.2 at 18 V and 32 
mA/cm.sup.2. 
EXAMPLE 33 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 1 part by weight of a polymer (first 
reduction potential: -1.93 V) represented by the formula (132): 
##STR26## 
is used as an electron moving and donating agent, and Rhodamine B (first 
oxidation potential: +1.00 V, first reduction potential: -1.19 V) is used 
as a luminescent agent. The thus obtained element exhibits a yellow 
luminescence having a brightness of 80 cd/m.sup.2 at 13 V and 10 
mA/cm.sup.2. 
EXAMPLE 34 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 22.5 parts by weight of 
N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine is used 
as a hole moving and donating agent, 22.5 parts by weight of 
2,5-bis(1-naphthyl)-1,3,4-oxadiazole is used as an electron moving and 
donating agent, 5 parts by weight of NK-1886 is used as a luminescent 
agent and 50 parts by weight of a polyester resin (Vylon-200) is used as a 
binder polymer. The thus obtained element exhibits a green luminescence 
having a brightness of 30 cd/m.sup.2 at 22 V and 20 mA/cm.sup.2. 
EXAMPLE 35 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that a coating layer having a thickness of 500 A 
is formed from a toluene solution containing 35 parts by weight or 
N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine as a hole 
moving and donating agent, 35 parts by weight of 
2-(1-naphthyl)-5-phenyloxazole (first oxidation potential: +1.64 V, first 
reduction potential: -1.85 V) as an electron moving and donating agent, 1 
part by weight of Rhodamine B as a luminescent agent and 30 parts by 
weight of a styrenated alkyd resin (Styresole 4250 manufactured and sold 
by Dainippon Ink & Chemicals, Inc., Japan) as a binder polymer and that 
the coating layer is heated at 100.degree. C. for 30 minutes to effect 
curing, thereby forming a luminescent layer. The thus obtained element 
exhibits a yellow luminescence having a brightness of 50 cd/m.sup.2 at 16 
V and 10 mA/cm.sup.2. 
EXAMPLE 36 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that 50 parts by weight of 
poly(4-diphenylaminophenylmethyl methacrylate) (first oxidation potential: 
+0.68 V, first reduction potential: -1.89 V) is used as a hole moving and 
donating agent, 50 parts by weight of 
1,4-bis[2-(4-methyl-5-phenyloxazolyl)]benzene (first oxidation potential: 
+1.21 V, first reduction potential: -1.86 V) is used as an electron moving 
and donating agent, and 1 part by weight of NK-1886 is used as a 
luminescent agent. The thus obtained element exhibits a green luminescence 
having a brightness of 120 cd/m.sup.2 at 23 V and 10 mA/cm.sup.2. 
EXAMPLES 37 THROUGH 46 
(Use of various luminescent agents) 
An electroluminescent element is prepared in substantially the same manner 
as in Example 1 except that 55 parts by weight of PVK is used as a hole 
moving and donating agent, 45 parts by weight of 
2,5-bis(1-naphthyl)-1,3,4-oxadiazole is used as an electron moving and 
donating agent, and 1 part by weight of each of the below-indicated 
compounds is individually used as a luminescent agent. 
The voltage which is needed for flowing a current of 10 mA/cm.sup.2 through 
each element, and the brightness and color of the obtained luminescence, 
are shown in Table 3, together with the oxidation potential and the 
reduction potential. 
Luminescent agents employed are as follows: 
Example 37: perylene 
Example 38: 7-diethylamino-4-trifluoromethylcoumarin. 
Example 39: 
1,2,4,5,3H,6H,10H-tetrahydro-9-cyano[1]benzopyrano[9,9a,1-gh]quinolizin-10 
-one. 
Example 40: 
1,2,4,5,3H,6H,10H-tetrahydro-8-trifluoromethyl[1]benzopyrano[9,9a,1-gh]qui 
nolizin-10-one. 
Example 41: 7-diethylamino-3-(1-methylbenzimidazolyl)coumarin. 
Example 42: 2-(p-dimethylaminostyryl)naphtho[1,2-d]thiazole. 
Example 43: 2-(p-dimethylaminostyryl)benzothiazole. 
Example 44: Rhodamine B 
Example 45: 4-dicyanomethylene-6-(p-dimethylaminostyryl)-2-methyl-4H-pyran. 
Example 46: Nile Red 
TABLE 3 
______________________________________ 
1st 1st 
oxidation 
reduction 
Ex. potential 
potential 
Voltage 
Brightness 
Color of 
Nos (V) (V) (V) (cd/m.sup.2) 
Luminescence 
______________________________________ 
37 +0.92 -1.72 16 140 Blue 
38 +1.04 -1.67 15 96 Blue 
39 +0.89 -1.49 15 160 Bluish green 
40 +0.81 -1.59 15 110 Bluish green 
41 +0.87 -1.72 17 60 Bluish green 
42 +0.52 -1.85 15 80 Green 
43 +0.53 -1.82 15 52 Green 
44 +1.00 -1.80 15 80 Yellow 
45 +0.7 -1.28 15 84 Orange 
46 +0.76 -1.89 16 64 Red 
______________________________________ 
EXAMPLES 47 THROUGH 52 
(Use of various amounts of hole moving and donating agent and electron 
moving and donating agent) 
An electroluminescent element is prepared in substantially the same manner 
as in Example 5 except that the amounts of the hole moving and donating 
agent and the electron moving and donating agent are varied as indicated 
in Table 4 below. The amount of the luminescent agent is 1 part by weight. 
Voltages which that the amounts of the hole moving and donating agent and 
the electron moving and donating agent are varied as indicated in Table 4 
below. The amount of the luminescent agent is 1 part by weight. Voltages 
which are needed for flowing a current of 10 mA/cm.sup.2 through the 
individual elements and the obtained brightness values are also shown in 
Table 4. 
TABLE 4 
______________________________________ 
Electron 
Hole moving moving and 
and donating donating 
Ex. agent (part agent (part 
Voltage Brightness 
Nos by wt.) by wt.) (V) (cd/m.sup.2) 
______________________________________ 
47 99 1 40 20 
48 95 5 16 72 
49 92.5 7.5 14 93 
50 90 10 14 112 
51 85 15 15 132 
52 70 30 13 180 
5 55 45 13 150 
______________________________________ 
EXAMPLES 53 THROUGH 56 
(Use of various amounts of hole moving and donating agent and electron 
moving and donating agent) 
An electroluminescent element is prepared in substantially the same manner 
as in Example 22 except that the amounts of the hole moving and donating 
agent and the electron moving and donating agent are varied as indicated 
in Table 5 below. The amount of the luminescent agent is 2 parts by 
weight. Voltages which are needed for flowing a current of 10 mA/cm.sup.2 
through the individual elements and the obtained brightness values are 
also shown in Table 5. 
TABLE 5 
______________________________________ 
Electron 
Hole moving moving and 
and donating donating 
Ex. agent (part agent (part 
Voltage Brightness 
Nos by wt.) by wt.) (V) (cd/m.sup.2) 
______________________________________ 
53 1 99 -- -- 
54 5 95 16 75 
55 20 80 14 140 
56 30 70 13 300 
22 50 50 12 460 
______________________________________ 
Note: In Example 53, a current of 10 mA/cm.sup.2 cannot be flowed. 
EXAMPLES 57 THROUGH 61 AND COMATIVE EXAMPLE 5 
(Use of various amounts of luminescent agent) 
An electroluminescent element is prepared in substantially the same manner 
as in Example 2 except that the amount of the luminescent agent is varied 
as indicated in Table 6 below. Voltages which are needed for flowing a 
current of 10 mA/cm.sup.2 through the individual elements are shown in 
Table 6. The obtained brightness values and luminescence colors are also 
shown in Table 6. 
TABLE 6 
______________________________________ 
Luminescent 
Ex. agent (part 
Voltage Brightness 
Color of 
Nos by wt.) (V) (cd/m.sup.2) 
luminescence 
______________________________________ 
Comp. 0 16 2 Blue 
Ex. 5 
57 0.01 16 50 Bluish green 
58 0.1 17 90 Green 
2 1 17 180 Green 
59 5 17 180 Green 
60 20 19 80 Orangish green 
61 30 21 3 Orange 
______________________________________ 
EXAMPLE 62 
An ITO glass is washed in the same manner as in Example 1. A coating film 
having a thickness of 400 .ANG. is formed on the glass by dip coating a 
toluene solution containing 50 parts by weight of 
1,1-(4,4'-diethoxyphenyl)-N,N-(4,4'-dimethoxyphenyl)enamine and 50 parts 
by weight of a styrenated alkyd resin (Styresole 4250 manufactured and 
sold by Dainippon Ink & Chemicals Inc., Japan). Then, the film is heated 
at 100.degree. C. for 30 minutes to effect curing, thereby obtaining a 
hole injecting and transporting layer. The same luminescent layer having a 
thickness of 1000 .ANG. as formed in Example 42, is formed on the 
above-obtained hole injecting and transporting layer by the spin coating 
method, and a cathode is formed in the same manner as in Example 1. Thus, 
an electroluminescent element is prepared. A current of 10 mA/cm.sup.2 is 
flowed at 12 V through this element and a green luminescence having a 
brightness of 85 cd/m.sup.2 is exhibited. Due to the provision of the hole 
injecting and transporting layer, the voltage necessary for luminescence 
is reduced. 
EXAMPLE 63 
An ITO glass is washed in the same manner as in Example 1, and copper 
phthalocyanine (manufactured and sold by Toyo Ink Mfg. Co., Ltd., Japan) 
is vapor-deposited onto this glass in a thickness of 300 .ANG. under a 
vacuum of 3.times.10.sup.-6 Torrs, thereby forming a hole injecting and 
transporting layer. On this layer, a luminescent layer of 500 .ANG. in 
thickness is formed in the same manner as in Example 62. Further, a 
tris(8-quinolinol) aluminum complex is vapor-deposited thereon in a 
thickness of 300 .ANG. under a vacuum of 3.times.10.sup.-6 Torrs, thereby 
forming a hole inhibiting layer, and then a cathode is provided in the 
same manner as in Example 1. Thus, an electroluminescent element is 
prepared. A current of 10 mA/cm.sup.2 is flowed at 11 V through this 
element and a green luminescence having a brightness of 130 cd/m.sup.2 is 
exhibited. Due to the provision of the hole injecting and transporting 
layer and the hole inhibiting layer, the luminescence efficiency is 
improved. 
EXAMPLE 64 
A luminescent layer is formed from the same compounds as in Example 5, 
changing the amount of the hole moving and donating agent to 40 parts by 
weight and the amount of the electron moving and donating agent to 60 
parts by weight. Upon air drying the formed layer for 1 hour, the layer 
exhibits a photoelectric work function of 5.72 eV. A cathode is then 
immediately formed by vapor deposition, and then the obtained element is 
operated so as to exhibit a luminescence. The element exhibits a uniform 
luminescence without non-luminescent portions. 
Separately, the luminescent layer is allowed to stand for 1 day after the 
formation thereof. As a result, the layer exhibits a photoelectric work 
function of 5.46 eV. A cathode is then formed by vapor deposition and the 
element is operated so as to exhibit a luminescence. The element exhibits 
non-uniformity in the luminescence intensity and has 5 non-luminescent 
portions each having a diameter of about 0.1 mm. 
EXAMPLE 65 
A sine wave voltage having an effective voltage of 20 V and a frequency of 
50 Hz is applied to the electroluminescent element obtained in Example 5. 
As a result, the element exhibits a green luminescence having a brightness 
of 300 cd/m.sup.2. After the element is continuously operated for 200 
hours, the brightness is 276 cd/m.sup.2. On the other hand, when a direct 
current voltage of 13 V is applied to the element of Example 5, the 
brightness after a continuous operation for 200 hours is 23 cd/m.sup.2. 
EXAMPLE 66 
ITO glass (manufactured and sold by Hoya Corp., Japan), which is a glass 
substrate prepared by forming an ITO film having a thickness of 1000 .ANG. 
on a glass plate of 100.times.100.times.1.1 mm in size, is washed in the 
same manner as in Example 1. This glass substrate is used as an anode. 
13.6 g of PVK as a hole moving and donating agent, 1.51 g of perylene as an 
electron moving and donating agent and 0.21 g of coumarin 6 as a 
luminescent agent are dissolved in 1000 g of 1,2-dichloroethane, thereby 
obtaining a coating solution for forming a luminescent layer. The thus 
obtained coating solution is placed in dipping bath 6 of FIG. 1. Further, 
50 cc of 1,2-dichloroethane is placed in solvent vessel 3. 
The glass substrate having been washed is held by catching device 5 fixed 
at the end of vertical mover 4, and the vertical mover 4 is lowered so 
that the glass substrate is dipped into the coating solution to a position 
10 mm below the upper edge of the substrate. Then, the glass substrate is 
raised at a rate of 150 mm/minute, and when the lower edge of the 
substrate comes out of the solution, the raising is stopped and the 
substrate is kept at that position, to thereby effect leveling in the 
solvent vapor. Then, the substrate is raised at a rate of 150 mm/minute so 
as to take the substrate out of dipping bath 6, and is immediately 
subjected to drying at 50.degree. C. in a drying apparatus. Thus, a 
luminescent layer is formed on the substrate. 
9 Cathodes (A to I shown in FIG. 2) each having a 1.times.1 mm size are 
formed on the luminescent layer by a vapor deposition of metallic 
magnesium through a shadow mask. Thus, the size of each of the obtained 
elements is 1.times.1 mm. As shown in FIG. 2, cathodes A, B and C are 
formed in alignment at intervals of 25 mm at a distance of 25 mm from the 
upper edge of the substrate. Cathodes D, E and F are formed in alignment 
at intervals of 25 mm at a distance of 50 mm from the upper edge of the 
substrate. Cathodes G, H and I are formed in alignment at intervals of 25 
mm at a distance of 75 mm from the upper edge of the substrate. 
Then, a gold wire as a lead is connected to each electrode (cathode) by 
means of a silver paste. Thus, an electroluminescent element assembly 
containing 9 elements (designated as A-1 to I-1, respectively) is 
prepared. When a direct current voltage of 17 V is applied to each element 
using ITO portion 9 as an anode, a current of about 0.1 mA is flowed 
though each element and each element exhibits a green luminescence. 
An attachment lens (AL-7, attached to the below-mentioned meter BM-7) is 
attached to a color/luminance meter BM-7 (manufactured and sold by TOPCON 
CO., LTD., Japan) and the lens is focused on the luminescent surface of 
the element at a measurement angle of 0.1.degree. and at a distance of 52 
mm between the lens and the luminescent surface (In this instance, the 
measuring area is 0.1 mm.phi.). 
With respect to the sites for measuring brightness for the element of 1 
mm.times.1 mm size, measurement is conducted at 9 points consisting of 3 
points present at a distance of 0.25 mm from one side of the element and 
at intervals of 0.25 mm, 3 points present at a distance of 0.5 mm from the 
side and at intervals of 0.25 mm and 3 points present at a distance of 
0.75 mm from the side and at intervals of 0.25 mm. The results of the 
measurement are shown in Table 7. 
An electroluminescent element assembly containing nine elements (A-2 to 
I-2) is prepared, and the brightnesses of the elements are measured in 
substantially the same manner as described above, except that no solvent 
is placed in solvent vessel 3, that after the glass substrate is dipped in 
the coating solution to a position 10 mm below the upper edge of the 
substrate, the substrate is raised at a rate of 150 mm/minute until it is 
completely taken out of dipping bath 6, and the substrate is kept in the 
atmosphere for 1 minute, immediately followed by drying at 50.degree. C. 
in a drying apparatus. The results are shown in Table 7. 
As apparent from Tables 7 and 8, when the coating for forming a luminescent 
layer is subjected to leveling, a uniform luminescence is obtained with a 
small brightness dispersion relative to the average brightness within a 
single element, whereas when the leveling is not conducted, the brightness 
dispersion within a single element is large and it is possible that the 
obtained element cannot exhibit luminescence due to an electric leak. 
EXAMPLE 67 
The electroluminescent elements A-1 through I-1 and A-2, D-2, E-2, F-2, H-2 
and I-2 obtained in Example 66 are individually subjected to continuous 
operation by applying a direct current of 0.1 mA using a constant current 
power source. After the operation is conducted for 100 hours, the 
brightness is measured at the same measuring sites as those employed in 
Example 66 for measuring the initial brightness. The results are shown in 
Table 9. As apparent from Table 9, elements A-1 through I-1 which are 
small in brightness dispersion within a single element are capable of 
exhibiting a luminescence of high brightness for a long period of time as 
compared to elements A-2, D-2, E-2, F-2, H-2 and I-2 which are large in 
brightness dispersion within a single element. 
TABLE 7 
__________________________________________________________________________ 
Average 
Brightness 
Element 
Brightness (cd/m.sup.2) 
brightness 
dispersion (%) 
__________________________________________________________________________ 
A-1 180, 185, 179, 180, 176, 183, 182, 176, 185 
180.6 2.4 
B-1 185, 182, 187, 180, 185, 178, 187, 180, 179 
182.3 2.6 
C-1 180, 185, 185, 183, 182, 182, 183, 183, 184 
182.9 1.1 
D-1 172, 179, 176, 171, 176, 176, 175, 179, 177 
175.8 2.7 
E-1 172, 175, 176, 179, 176, 171, 174, 176, 176 
175.0 2.3 
F-1 172, 176, 175, 175, 174, 173, 171, 172, 176 
173.9 1.7 
G-1 172, 171, 172, 171, 173, 176, 170, 171, 172 
172.1 2.3 
H-1 172, 171, 172, 174, 175, 177, 179, 171, 172 
172.9 3.5 
I-1 172, 174, 175, 171, 171, 170, 170, 171, 172 
171.7 1.9 
__________________________________________________________________________ 
TABLE 8 
__________________________________________________________________________ 
Average 
Brightness 
Element 
Brightness (cd/m.sup.2) 
brightness 
dispersion (%) 
__________________________________________________________________________ 
A-2 164, 189, 179, 152, 181, 182, 178, 191, 168 
176.0 13.6 
B-2 No luminescence attained 
-- -- 
C-2 No luminescence attained 
-- -- 
D-2 140, 141, 172, 138, 135, 143, 141, 138, 130 
141.9 21.2 
E-2 123, 127, 125, 119, 141, 148, 116, 131, 125 
128.4 15.3 
F-2 131, 133, 130, 121, 138, 140, 130, 135, 141 
133.1 9.1 
G-2 No luminescence attained 
-- -- 
H-2 98, 116, 109, 94, 103, 112, 103, 107, 111 
105.9 11.2 
I-2 115, 103, 116, 113, 116, 119, 116, 104, 113 
112.8 8.7 
__________________________________________________________________________ 
TABLE 9 
______________________________________ 
Average 
Element 
Brightness (cd/m.sup.2) 
brightness 
______________________________________ 
A-1 126, 130, 125, 126, 123, 128, 127, 124, 129 
126.4 
B-1 130, 127, 130, 126, 129, 125, 129, 127, 125 
127.3 
C-1 126, 129, 129, 127, 127, 127, 127, 127, 127 
127.3 
D-1 121, 125, 125, 121, 125, 125, 125, 125, 125 
123.9 
E-1 121, 125, 125, 125, 125, 123, 125, 125, 125 
124.1 
F-1 122, 123, 123, 126, 123, 122, 123, 123, 125 
123.3 
G-1 122, 121, 124, 123, 125, 126, 125, 125, 123 
123.7 
H-1 121, 122, 125, 124, 124, 125, 125, 122, 123 
123.3 
I-1 123, 123, 124, 123, 123, 122, 121, 123, 123 
122.8 
A-2 See Note -- 
D-2 28, 25, 0, 27, 23, 15, 13, 18, 29 
19.7 
E-2 15, 17, 16, 12, 11, 15, 12, 15, 16 
14.4 
F-2 16, 16, 17, 21, 15, 14, 15, 15, 13 
15.7 
H-2 18, 16, 16, 20, 19, 12, 15, 15, 15 
16.2 
I-2 15, 20, 16, 18, 16, 16, 12, 18, 15 
16.3 
______________________________________ 
Note: 
No luminescence is attained after 85 hours of operation.