Organic electroluminescence device

An organic electroluminescence device which comprises laminating layers in the order of anode/light emitting layer/adhesive layer/cathode, or anode/hole-injecting layer/light emitting layer/adhesive layer/cathode, the energy gap of the light emitting layer being larger than that of 8-hydroxyquinoline or metal complex thereof and contained in the adhesive layer, the light emitting layer comprising a compound which emits a blue, greenish blue or bluish green light in CIE chromaticity coordinates, and the adhesive layer including a metal complex of 8-hydroxyquinoline or a derivative thereof and at least one organic compound in an arbitrary region in the direction of the thickness of the layer, the thickness of which is smaller than that of the above-mentioned light emitting layer. According to the above organic electroluminescence device, improvements in uniformity in light emission and emission efficiency are realized.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an organic electroluminescence device, and 
more particularly, to an organic electroluminescence device capable of 
improving the uniformity of light emission and retarding the lowering in 
initial luminances. 
2. Description of the Relates Arts 
Since an electroluminescence device (hereinafter referred to as EL device) 
has features in a high self-distinguishability because of its 
self-emission, and having a high impact resistance because it is a 
completely solid device, various devices using inorganic and organic 
compounds are proposed at present and attempts to put them into practice 
use have been made. Among these devices, organic EL devices permit 
drastically low voltage to be applied, and therefore developments of 
various materials for these devices as well as devices have been 
undertaken. 
The above organic EL device basically comprises anode/light emitting 
layer/cathode, and those which are provided with a hole injecting layer or 
electron-injecting layer at need for improving the light emitting 
property. In this structure of the device, the cathode must be 
sufficiently adhered to the light emitting layer. If the adhesivity is not 
sufficient, the mechanical strength of the device becomes low, causing 
ununiform light emission, and in the worst case non-emission regions. 
Furthermore, ununiformity of the load in the light emitting face is 
caused, which accelerates the deterioration to shorten the lifetime of the 
device, and this is an obstacle to practical use of the device. 
Heretofore, it has been known that an electron-injecting layer or a hole 
barrierer layer is provided, at need, between the light emitting layer and 
the cathode. In these techniques, particularly when the latter layer is 
provided, the material is selected depending on the difference from the 
light emitting layer in the energy level, and the material must fit to 
this concept. An example of them is a technique of "providing a hole 
blocking layer (hole barrier layer) having a first oxidation voltage 0.1 V 
higher than that of the light emitting layer, between the light emitting 
layer and the cathode" (Japanese Patent Application Laid-Open No. 
195683/1990). Also in Japanese Patent Application Nos. 195683/1990 and 
255788/1990, 8-hydroxyquinoline derivative is used as the hole barrier 
layer basing on the above concept, but the emission efficiency of blue 
lights in these arts are still so low as 0.3 (1 m.W.sup.-1). On the other 
hand, when the materials described in Japanese Patent Application 
Laid-Open No. 231070/1991 and Japanese Patent Application No. 279304/1990 
are used for the light emitting layer, an emission of blue light in a high 
brightness can be obtained. These materials are mentioned as effective 
materials for full-colorization of flat panel displays and the like in 
future. However, when these materials are formed to devices in the 
structure of anode/light emitting layer/cathode/, or anode/hole injecting 
layer/light emitting layer/cathode as described before, ununiform emission 
or non-emission region are sometimes caused, which have brought about 
problems in analyzing the practical use of the devices concerning lifetime 
of the device, minute processing of the device. 
On the other hand, as the means to dissolve the above-mentioned problems, 
the doping technique (Japanese Patent Application Laid-Open No. 
255190/1991, The Institute of Electronics, Information and Communication 
Engineers(IEICE) Technical Report (vol. 91, No. 406(1991), p47), Polymer 
Preprints Japan (vol. 40, No. 10 (1991))) and the like have been 
disclosed. 
These aim at improving the properties by contaminating a second component 
into the light emitting layer. However, when the second component is 
contaminated into the light emitting layer, a possible fall in emission 
efficiency or change in the color of the emitting light have had to be 
considered sufficiently. 
SUMMARY OF THE INVENTION 
Under these circumstances, after intensively studying the adhesivity 
between the light emitting layer and the cathode, the present inventors 
found that an EL device having an improved uniformity of light emission 
and an improved emission efficiency can be obtained by contaminating a 
second component into the layer (adhesive layer) to improve the adhesivity 
between the light emitting layer and the cathode, without changing the 
color of the emission light, while the characteristics of EL devices 
maintained. 
The present invention has been accomplished on the basis of such a 
knowledge. 
That is, the present invention provides an organic electroluminescence 
device which comprises laminating layers in the order of anode/light 
emitting layer/adhesive layer/cathode, or anode/hole injecting layer/light 
emitting layer/adhesive layer/cathode, the energy gap of the light 
emitting layer being larger than that of 8-hydroxyquinoline or metal 
complex thereof and contained in the adhesive layer, and the adhesive 
layer including a metal complex of 8-hydroxyquinoline or a derivative 
thereof and at least one organic compound in an arbitrary region in the 
direction of the thickness of the layer, the thickness of which is smaller 
than that of the above-mentioned light emitting layer. 
The present invention also provides an organic electroluminescence device 
which comprises laminating layers in the order of anode/light emitting 
layer/adhesive layer/cathode, or anode/hole-injecting layer/light emitting 
layer/adhesive layer/cathode, the light emitting layer comprising a 
compound which emits a blue, greenish blue or bluish green light in CIE 
chromaticity coordinates, the adhesive layer including a metal complex of 
8-hydroxyquinoline or a derivative thereof and at least one organic 
compound in an arbitrary region in the direction of the thickness of the 
layer, the thickness of which is smaller than that of the above-mentioned 
light emitting layer. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The organic EL device of the present invention comprises laminating layers 
in the order of anode/light emitting layer/adhesive layer/cathode, or 
anode/hole injecting layer/light emitting layer/adhesive layer/cathode. 
As to the anode in the organic EL device of the present invention, a metal, 
an alloy, an electro-conducting compound or a mixture thereof, all having 
a large work function (not less than 4 eV), is preferably used as an 
electrode material. Specific examples of these electrode materials are 
metals such as Au, and a dielectric transparent materials such as Cul, 
ITO, SnO.sub.2, and ZnO. Said anode can be prepared by forming said 
electrode material into thin film by vapor deposition or sputtering. To 
obtain light emission from said electrode, it is preferable that the 
transmittance of the electrode is more than 10% and the resistance of the 
sheet as an electrode is not more than several hundred 
.OMEGA./.quadrature.. 
The film thickness of the anode is usually in the range of 10 nm to 1 
.mu.m, preferably 10 to 200 nm, depending upon the material. 
On the other hand, as the cathode, a metal, an alloy, an electroconducting 
compound or a mixture thereof, all having a small work function (not more 
than 4 eV) is preferably used as an electrode material. Specific examples 
of such electrode materials are sodium, a sodium-potassium alloy, 
magnesium, lithium, a mixture of magnesium and copper, Al/AlO.sub.2, 
indium, and rare earth metals. Said cathode can be prepared by forming 
said electrode material into thin film by vapor deposition or sputtering. 
The resistance of the sheet as an electrode is preferably not more than 
several hundred .OMEGA./.quadrature.. The film thickness is usually in the 
range of 10 nm to 1 .mu.m, preferably 50 to 200 nm. In the EL device of 
the present invention, it is preferable that either anode or cathode be 
transparent or translucent because light emission is transmitted and 
obtained with a high efficiency. 
Next, the light emitting layer in the above-mentioned device possesses, 
similarly to the conventional light emitting layer, (i) injecting function 
(at application of voltage, holes can be injected from the anode or the 
hole-injecting layer, and electrons can be injected from the cathode or 
the electron-injecting layer), (ii) transporting function (positive holes 
and electrons can be moved by the power of electric field), and (iii) 
light emitting function (to provide a place for recombination of holes and 
electrons, permitting light emission). The thickness of said layer is not 
particularly limited, but can be appropriately selected depending on 
circumstances, and it is preferably 1 nm to 10 .mu.m, and particularly 
preferably 5 nm to 5 .mu.m. 
The light emitting layer of the present invention is characterized by 
having an energy gap larger than that of 8-hydroxyquinoline or metal 
complex thereof contained in the adhesive layer, and comprising a compound 
which emits blue, greenish blue, or bluish green light in CIE chromaticity 
coordinates. 
Therein, energy gap means a value of energy corresponding to the wavelength 
of absorption ends of the absorption spectrum of thin film, indicating the 
value corresponding to the difference in energy between the maximum 
population level and the minimum population level of electron orbit. Said 
value of energy gap can be determined from the absorption ends of the 
absorption spectrum of thin film to be used, or the measurement by 
internal photoelectric effect using a material of known work function as 
the electrode. 
Specific examples of the material of this light emitting layer are 
tetraphenylbutadiene compounds (see Japanese Patent Application No. 
96990/1992) and compounds represented by general formula (I), (II) and 
(III) as follows. 
##STR1## 
wherein R.sup.1 to R.sup.4 indicate each a hydrogen atom, an alkyl group 
having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, 
an aralkyl group having 7 to 8 carbon atoms, a substituted or 
unsubstituted aryl group having 6 to 18 carbon atoms, a substituted or 
unsubstituted cyclohexyl group, a substituted or unsubstituted aryloxyl 
group having 6 to 18 carbon atoms, or an alkoxyl group having 1 to 6 
carbon atoms; therein, the substituent is an alkyl group having 1 to 6 
carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, an aralkyl 
group having 7 to 8 carbon atoms, an aryloxyl group having 6 to 18 carbon 
atoms, an aryl group having 1 to 6 carbon atoms, an acyloxyl group having 
1 to 6 carbon atoms, a carboxyl group, a styryl group, an arylcarbonyl 
group having 6 to 20 carbon atoms, an aryloxycarbonyl group having 6 to 20 
carbon atoms, an alkoxycarbonyl group having 1 to 6 carbon atoms, a vinyl 
group, an anilinocarbonyl group, a carbamoyl group, a phenyl group, a 
nitro group, a hydroxyl group or a halogen; these substituents may be used 
solely or in plural; R.sup.1 to R.sup.4 may be identical to or different 
from one another, and R.sup.1 and R.sup.2 and R.sup.3 and R.sup.4 may 
combine with groups substituting each other to form a substituted or 
unsubstituted saturated five-membered ring or a substituted or 
unsubstituted saturated six-membered ring; Ar indicates a substituted or 
unsubstituted arylene group having 6 to 20 carbon atoms, a single bond, or 
a conjugated polyene 2 to 6 carbon atoms; an arylene group therein may be 
mono-substituted or poly-substituted, and its position may be any of 
ortho-, para- and meta-; however, when Ar is an unsubstituted phenylene, 
R.sup.1 to R.sup.4 is each selected from the group consisting of an 
alkoxyl group having 1 to 6 carbon atoms, an aralkyl group having 7 to 8 
carbon atoms, a substituted or unsubstituted naphthyl group, a biphenyl 
group, a cyclohexyl group, and an aryloxyl group, general formula (II): 
EQU A--Q--B (II) 
wherein A and B indicate each a monovalent group which is obtained by 
removing a hydrogen atom from the compound represented by the above 
general formula (I), and may be identical to or different from each other; 
Q indicates a divalent group breaking the conjugation, or general formula 
(III) 
##STR2## 
wherein A.sup.1 indicates a substituted or unsubstituted arylene group 
having 6 to 20 carbon atoms or a divalent aromatic heterocyclic group; its 
position may be any of ortho-, meta- and para-; A.sup.2 is a substituted 
or unsubstituted aryl group having 6 to 20 carbon atoms or a monovalent 
aromatic heterocyclic group; R.sup.5 and R.sup.6 indicate each a hydrogen 
atom, a substituted or unsubstituted aryl group having 6 to 20 carbon 
atoms, a cyclohexyl group, a monovalent aromatic heterocyclic group, an 
alkyl group having 1 to 10 carbon atoms, an aralkyl group having 7 to 20 
carbon atoms or an alkoxyl group having 1 to 10 carbon atoms; R.sup.5 and 
R.sup.6 may be identical to or different from each other; the 
mono-substituent therein is an alkyl group, an aryloxyl group, an amino 
group or a phenyl group with or without a substituent; each substituent of 
R.sup.5 may combine with A.sup.1 to form a saturated or unsaturated 
five-membered ring or six-membered ring, and similarly each substituent of 
R.sup.6 may combine with A.sup.2 to form a saturated or unsaturated 
five-membered ring or six-membered ring; Q indicates a divalent group 
breaking a conjugation, and emits a blue, greenish blue or bluish green 
light in CIE chromaticity coordinates, said adhesive layer being a layer 
including a metal complex of 8-hydroxyquinoline or its derivative and at 
least one of organic compound in an arbitrary region in the direction of 
the thickness of the layer, the thickness of which is smaller than that of 
the above-mentioned light emitting layer. 
Herein, R.sup.1 to R.sup.4 in general formula (I) may be identical to or 
different from one another as described before, and each indicates a 
hydrogen atom, an alkyl group having 1 to 6 carbon atoms (such as a methyl 
group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl 
group, an i-butyl group, a sec-butyl group, a tert-butyl group, an 
isopentyl group, a t-pentyl group, a neopentyl group, and an isohexyl 
group), an alkoxyl group having 1 to 6 carbon atoms (such as a methoxyl 
group, an ethoxyl group, a propoxyl group, and a butoxyl group), an 
aralkyl group having 7 to 8 carbon atoms (such as a benzyl group, and a 
phenethyl group), an aryl group having 6 to 18 carbon atoms (such as a 
phenyl group, a biphenyl group, and a naphthyl group), a cyclohexyl group, 
or an aryloxyl group having 6 to 18 carbon atoms (such as a phenoxyl 
group, a biphenyloxyl group, and a naphthyloxyl group). 
R.sup.1 to R.sup.4 may be groups resulted by combining the above with 
substituents. Specifically, R.sup.1 to R.sup.4 indicate each a 
substituent-containing phenyl group, a substituent-containing aralkyl 
group, a substituent-containing cyclohexyl group, a substituent-containing 
biphenyl group, or a substituent-containing naphthyl group. The 
substituent therein includes an alkyl group having 1 to 6 carbon atoms, an 
alkoxyl group having 1 to 6 carbon atoms, an aralkyl group having 7 to 8 
carbon atoms, an aryloxyl group having 6 to 18 carbon atoms, an acyl group 
having 1 to 6 carbon atoms, an acyloxyl group having 1 to 6 carbon atoms, 
an aryloxycarbonyl group having 6 to 20 carbon atoms, a carboxyl group, a 
styryl group, an arylcarbonyl group having 6 to 20 carbon atoms, an 
alkoxycarbonyl group having 1 to 6 carbon atoms, a vinyl group, an 
anilinocarbonyl group, a carbamoyl group, a phenyl group, a nitro group, a 
hydroxyl group or a halogen, and may be poly-substituted. Accordingly, for 
example, a substituent-containing aralkyl group includes alkyl 
group-substituted aralkyl groups (such as methylbenzyl group, and 
methylphenethyl group), alkoxyl group-substituted aralkyl groups (such as 
methoxybenzyl group and an ethoxyphenethyl group), aryloxyl 
group-substituted aralkyl groups (such as phenoxybenzyl group, and 
naphthyloxyphenethyl group), phenyl group-substituted aralkyl group (such 
as phenylphenethyl group); above-mentioned substituent-containing phenyl 
groups include alkyl group-substituted phenyl groups (such as tolyl group, 
dimethylphenyl group, and ethylphenyl group), alkoxyl group-substituted 
phenyl groups (such as methoxyphenyl group, and ethoxyphenyl group), 
aryloxyl group-substituted phenyl groups (such as phenoxyphenyl group, and 
naphtyloxyphenyl group) and phenyl group-substituted phenyl group (that 
is, biphenylyl group). Substituent-containing cyclohexyl groups include 
alkyl group-substituted cyclohexyl group (such as methylcyclohexyl group, 
dimethylcyclohexyl group, and ethylcyclohexyl group), alkoxy 
group-subsituted cyclohexyl groups (such as methoxycyclohexyl group, and 
ethoxycyclohexyl group), aryloxyl group-substituted cyclohexyl groups 
(such as phenoxycyclohexyl group, and naphthyloxycyclohexyl group), and 
phenyl group-substituted cyclohexyl groups (such as phenylcyclohexyl 
group). Substituent-containing naphthyl groups include alkyl 
group-substituted naphthyl groups (such as methylnaphtyl group, and 
dimethylnaphthyl group), alkoxyl group-substituted naphthyl group (such as 
methoxynaphthyl group, and ethoxynaphthyl group), aryloxyl 
group-substituted naphthyl group (such as phenoxynaphthyl group and 
naphthyl oxylnaphthyl group), and phenyl group-substituted naphthyl group. 
As R.sup.1 to R.sup.4, among the above, each an alkyl group having 1 to 6 
carbon atoms, an aryloxyl group, a phenyl group, a naphthyl group, a 
biphenyl group, or a cyclohexyl group is preferable. They may be 
substituted or unsubstituted. R.sup.1 to R.sup.4 may be identical to or 
different from one another, and R1 and R.sup.2 and R.sup.3 and R.sup.4 may 
combine with the substituents one another to form a substituted or 
unsubstituted saturated five-membered ring or substituted or unsubstituted 
saturated six-membered ring. 
On the other hand, Ar in general formula (I) indicates a substituted or 
unsubstituted aryl group having 6 to 20 carbon atoms, that is, an arylene 
group such as a substituted or unsubstituted phenylene group, a 
biphenylene group, p-terphenylene group, a naphthylene group, a 
terphenylene group, a naphthalenediyl group, an anthracenediyl group, 
phenanthrenediyl group, and a phenalenediyl group, and may be 
unsubstituted or substituted. The position of methylidine 
(.dbd.C.dbd.CH--) may be any of ortho-, meta-, and para-. However, when Ar 
is an unsubstituted phenylene, R.sup.1 to R.sup.4 are each selected from 
the group consisting of an alkoxyl group having 1 to 6 carbon atoms, an 
aralkyl group having 7 to 8 carbon atoms, a substituted or unsubstituted 
naphthyl group, a biphenyl group, a cyclohexyl group, and an aryloxyl 
group. The substituent includes an alkyl group (such as a methyl group, an 
ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, an 
i-butyl group, a sec-butyl group, a t-butyl group, an isopentyl group, a 
t-pentyl group, a neopentyl group, and an isohexyl group), an alkoxyl 
group (such as a methoxyl group, an ethoxyl group, a propoxyl group, an 
i-propoxyl group, a butyloxyl group, an i-butyloxyl group, a sec-butyloxyl 
group, a t-butyloxyl group, an isopentyloxyl group, and a t-pentyloxyl 
group), an aryloxyl group (such as a phenoxyl group, and a naphthyloxyl 
group), an acyl group (such as a formyl group, an acetyl group, a 
propionyl group, and a butylyl group), an acyloxyl group, an aralkyl group 
(such as a benzyl group, and a phenethyl group), a phenyl group, a 
hydroxyl group, a carboxyl group, an anilinocarbonyl group, a carbamoyl 
group, an aryloxycarbonyl group, a methoxycarbonyl group, an 
ethoxycarbonyl group, a butoxycarbonyl group, a nitro group, and a 
halogen, and may be mono-substituted or poly-substituted. 
Dimethylidine aromatic compound represented by the above-mentioned formula 
(I) contains two methylidine units (.dbd.C.dbd.CH--) in one molecule, 
varying in four combinations according to the geometrical isomerism of 
said methylidine unit, that is, cis-cis, trans-cis, cis-trans and 
trans-trans. The light emitting layer of the present invention may be any 
of them, or may be mixtures of geometrical isomers. Particularly preferred 
one comprises trans isomer only. 
The above-mentioned substituent may combine among substituents to form a 
substituted or unsubstituted saturated five-membered ring or six-membered 
ring. 
A and B in general formula (II) indicate each a monovalent group resulted 
by removing one hydrogen atom from the compounds represented by the 
above-mentioned general formula (I), and may be identical to or different 
from each other. Therein Q indicates a divalent group breaking the 
conjugation. 
The conjugation therein is attributed to the delocalization of 
.pi.-electron, and includes a conjugated double bond or a conjugation due 
to an unpaired electron or a lone electron-pair. Q indicates specifically 
a divalent group which results from removing each one hydrogen atom from a 
straight chain alkane, such as: 
##STR3## 
The divalent group breaking the conjugation is thus used for the purpose 
that EL emission light obtained when A or B shown in above (that is, the 
compound of general formula (I)) is used solely as the organic EL device 
of the present invention and the EL emission light obtained when the 
compound represented by general formula (II) is used as the organic EL 
device of the present invention may be identical in color. In other words, 
said divalent group is used so that the wavelength of the light emitting 
layer represented by general formula (I) or general formula (II) may not 
be changed to shortened or lengthened. By combining with a divalent group 
to break conjugation, it is confirmed that the glass transition 
temperature (Tg) rises, and uniform pinhole free minute crystal or 
amorphous thin film can be obtained, improving the uniformity of light 
emission. Further, combining with a divalent group breaking the 
conjugation brings about advantages that EL emission is not long-wavened, 
and synthesis or purification can be easily effected. 
Moreover, A.sup.1 in general formula (III) indicates an arylene group 
having 6 to 20 carbon atoms, and a divalent aromatic heterocyclic group, 
and A.sup.2 indicates an aryl group having 6 to 20 carbon atoms (such as a 
phenyl group, a biphenyl group, and a naphthyl group), or a monovalent 
aromatic heterocyclic group. R.sup.5 and R.sup.6 indicates each a hydrogen 
atom, a substituted or unsubstituted aryl group having 6 to 20 carbon 
atoms, a cyclohexyl group, a monovalent aromatic heterocyclic group, an 
alkyl group having 1 to 10 carbon atoms (such as a methyl group, an ethyl 
group, a n-propyl group, an i-propyl group, a n-butyl group, an i-butyl 
group, a sec-butyl group, a tert-butyl group, an isopentyl group, 
at-pentyl group, a neopentyl group, and an isohexyl group), an aralkyl 
group having 7 to 20 carbon atoms (such as a benzyl group, and a phenethyl 
group), or an alkoxyl group having 1 to 10 carbon atoms (such as a 
methoxyl group, an ethoxyl group, a propoxyl group, and a buthoxyl group). 
R.sup.5 and R.sup.6 may be identical to or different from each other. A 
substituent therein is, in mono-substitution, an alkyl group, an aryloxyl 
group, an amino group or a substituted or unsubstituted phenyl group. Each 
substituent in R.sup.5 may combine with A.sup.1 to form a saturated or 
unsaturated five-membered ring or six-membered ring, and similarly each 
substituent in R.sup.6 may combine with A.sup.2 to form a saturated or 
unsaturated five-membered ring or six-membered ring. Q indicates a 
divalent group breaking conjugation as described above. 
Further, in the present invention, the light emitting layer represented by 
general formula (I), general formula (II) or general formula (III) must be 
a compound providing an emission of blue, greenish blue or bluish green 
light in CIE chromaticity coordinates. 
The above-mentioned light emitting layer can be prepared by forming the 
above compound into thin film by a known method such as the vapor 
deposition method, the spin-coating method, the casting method or the LB 
method, but particularly, a molecular accumulated film is preferable. A 
molecular accumulated film therein is a thin film formed by depositing 
said compound from a gaseous state, or a thin film formed by 
solidification of said compound from a solution or liquid state. Usually, 
said molecular accumulated film is distinguished from a thin film 
(molecular built-up film) formed by the LB method, by the difference in 
the aggregation structure or the higher-order structure, or the functional 
difference resulting therefrom. 
Said light emitting layer, as disclosed in Japanese Patent Application 
Laid-Open No. 194393/1984, can be formed by dissolving a binding agent 
such as a resin and said compound in a solvent to prepare solution, which 
is formed into thin film by the spin-coating method and the like. 
The film thickness of the light emitting layer thus formed is not 
particularly limited, and can be determined appropriately according to the 
circumstances. Usually, it is preferably in the range of 1 nm to 10 .mu.m, 
particularly preferably 5 nm to 5 .mu.m. 
As described above, the light emiting layer of the present invention has an 
injection function of injecting holes from the anode or the hole-injecting 
layer, and electrons from the cathode or the adhesive and transporting 
layer upon application of an electric field, a transport function of 
transporting injected charges (holes and electrons) by the action of an 
electric field, and a light emitting function of providing a field for 
recombination of electrons and holes, thereby emitting light. There may be 
a difference in between injectability of holes and electrons, and a 
difference in transporting ability represented by mobilities of holes and 
electrons, but it is preferable to move either one. 
Herein examples of compounds to be used as the above-mentioned light 
emitting layer are shown as follows. 
##STR4## 
Next, the hole injecting layer in the present invention is not necessarily 
required for the present device, but is preferably used for the purpose of 
improving the emission ability. The preferable material of said 
hole-injecting layer is one which transports holes to the light emitting 
layer at a lower electric field, and still more preferably the 
transportation of holes is made at least 10.sup.-6 cm.sup.2 /volt.sec in 
an electric field of 10.sup.4 to 10.sup.6 volt/cm. For example, arbitrary 
material can be selected and used from the conventionally used ones as the 
electric charges injecting and transporting material for holes and the 
known ones to be used for the hole-injecting layer of EL devices in 
conventional photo-conducting materials. 
Examples of materials for hole-injecting layer are triazole derivatives 
(described in the specification of U.S. Pat. No. 3,112,197, etc.), 
oxadiazole derivatives (described in the specification of U.S. Pat. No. 
3,189,447, etc.), imidazole derivatives (described in Japanese Patent 
Publication No. 16096/1962, etc.), polyarylalkane derivatives (described 
in the specifications of U.S. Pat. Nos. 3,615,402, 3,820,989 and 
3,542,544, and in Japanese Patent Publication Nos. 555/1970 and 
10983/1976, and further in Japanese Patent Application Laid-Open Nos. 
93224/1976, 17105/1980, 4148/1981, 108667/1980, 156953/1980 and 
36656/1981, etc.), pyrazoline derivatives or pyrazolone derivatives 
(described in the specifications of U.S. Pat. Nos. 3,180,729 and 
4,278,746, and in Japanese Patent Application Laid-Open Nos. 88064/1980, 
88065/1980, 105537/1974, 51086/1980, 80051/1981, 88141/1981, 45545/1982, 
112637/1979 and 74546/1970, etc.), phenylenediamine derivatives (described 
in the specification of U.S. Pat. No. 3,615,404, and in Japanese Patent 
Publication Nos. 10105/1976, 3712/1971 and 25336/1972, and further in 
Japanese Patent Application Laid-Open Nos. 53435/1979, 110536/1979 and 
119925/1979, etc.), arylamine derivatives (described in the specification 
of U.S. Pat. Nos. 3,567,450, 3,180,703, 3,240,597, 3,658,520, 4,232,103, 
4,175,961 and 4,012,376, and in Japanese Patent Publication Nos. 
35702/1974 and 27577/1964, and further in Japanese Patent Application 
Laid-Open Nos. 144250/1980, 119132/1981 and 22437/1981, and German Patent 
No. 1,110,518, etc.), amino-substituted chalcone derivatives (described in 
the specification of U.S. Pat. No. 3,526,501, etc.), oxazole derivatives 
(described in the specification of U.S. Pat. No. 3,257,203, etc.), 
styrylanthracene derivatives (described in Japanese Patent Application 
Laid-Open No. 46234/1981, etc.), fluorenone derivatives (described in 
Japanese Patent Application Laid-Open No. 110837/1979, etc.), hydrazone 
derivatives (described in the specification of U.S. Pat. No. 3,717,462, 
and in Japanese Patent Application Laid-Open Nos. 59143/1979, 52063/1980, 
52064/1980, 46760/1980, 85495/1980, 11350/1982, 148749/1982, and 
311591/1990, etc.), and stilbene derivatives (described in Japanese Patent 
Application Laid-Open Nos. 210363/1986, 228451/1986, 14642/1986, 
72255/1986, 47646/1987, 36674/1987, 10652/1987, 30255/1987, 93445/1985, 
94462/1985, 174749/1985, and 175052/1985, etc.) 
Further, examples of hole-injecting and transporting materials are silazane 
derivatives (described in the specification of U.S. Pat. No. 4,950,950), 
polysilane based material (described in Japanese Patent Application 
Laid-Open No. 204996/1990), aniline-based copolymer (described in Japanese 
Patent Application Laid-Open No. 282263/1990), and electrically conductive 
high molecular oligomer disclosed in the specification of Japanese Patent 
Application No. 211399/1989, among them, thiophene oligomer. 
In the present invention, the above compounds can be used as a 
hole-injecting compound, but it is preferred to use porphyrin compounds 
(described in Japanese Patent Application Laid-Open No. 2956965/1988, 
etc.), aromatic tertiary amine compounds or styrylamine compounds 
(described in the specification of U.S. Pat. No. 4,127,412, and Japanese 
Patent Application Laid-Open Nos. 27033/1978, 58445/1979, 149634/1979, 
64299/1979, 79450/1980, 144250/1980, 119132/1981, 295558/1986, 98353/1986 
and 295695/1988), and most preferably, said aromatic tertiary amine 
compounds are used. 
Representative examples of said porphyrin compounds are porphin; 
1,10,15,20-tetraphenyl-21H,23H-porphin copper (II), 
1,10,15,20-tetraphenyl-21H,23H-porphin zinc (II), 
5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphin, sil 
iconphthalocyanine oxide, aluminum phthalocyanine chloride, phthalocyanine 
(nonmetal), dilithium phthalocyanine, copper tetramethylphthalocyanine, 
copper phthalocyanine, chrome phthalocyanine, zinc phthalocyanine, lead 
phthalocyanine, titanium phthalocyanine oxide, magnesium phthalocyanine, 
and copper octamethylphthalocyanine. 
Representative examples of said aromatic tertiary amine compounds or 
styrylamine compounds are N,N,N',N'-tetraphenyl-4,4'-diaminophenyl, 
N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diaminobiphenyl (TPDA), 
2,2-bis(4-di-p-tolylaminophenyl)propane, 
1,1-bis(4-di-p-tolylaminophenyl)-cyclohexane, 
N,N,N',N'-tetra-p-tolyl-4,4'-diaminobiphenyl, 
1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane, 
bis(4-dimethylamino-2-methylphenyl)phenylmethane, 
bis(4-di-p-tolylaminophenyl)phenylmethane, 
N,N'-diphenyl-N,N'-di(4-methoxyphenyl)-4,4'-diaminobiphenyl, 
N,N,N',N'-tetraphenyl-4,4'-diaminodiphenylether, 
4,4'-bis(diphenylamino)quadriphenyl, N,N,N-tri(p-tolyl)amine, 
4-(di-p-tolylamino)-4'-[4(di-p-tolylamino)styryl]stilbene, 
4-N,N-diphenylamino-(2-diphenylvinyl)benzene, 
3-methoxy-4'-N,N-diphenylaminostilbene, N-phenylcarbazole, and aromatic 
dimethylidine-based compounds. 
The hole injecting layer in the EL device of the present invention can be 
obtained by forming the above compound into a film by the known method of 
film forming such as the vacuum deposition method, the spin coating 
method, the casting method, and the LB method. The film thickness as said 
hole injecting layer is not particularly limited, but usually 5 nm to 5 
.mu.m. 
The hole injecting layer may consist of one layer comprising one or two or 
more of these hole-injecting and transporting materials, or may be a 
laminate of hole injecting layer comprising other compounds than the 
before-mentioned hole injecting layer. 
As the structure of the organic EL device to be obtained according to the 
present invention, the layer (adhesive layer) newly added to improve the 
adhesivity betweeen the light emitting layer and the cathode is desired to 
contain a material having a high adhesivity to the light emitting layer 
and the cathode. As the material having such an adhesivity, metal 
complexes of 8-hydroxyquinoline or derivative thereof are mentioned. 
Specific example of them are metal chelated oxinoide compound containing 
chelates of oxine (generally, 8-quinolinol or 8-hydroxyquinoline). These 
compounds exhibits high level properties, and are easy to be formed into 
thin film. Examples of the oxinoide compounds satisfy the structural 
formula as under. 
##STR5## 
wherein Mt indicates a metal, n is an integer of 1 to 3, and Z indicates 
an atom required to complete at least two condensed aromatic ring, being 
located independently. 
Therein metals represented by Mt are those which can be monovalent, 
divalent or trivalent metals, that is, alkali metals such as lithium, 
sodium and potassium, alkaline earth metals such as magnesium and calcium, 
and earth metals such as boron and aluminum. 
Generally any of monovalent, divalent and trivalent metals which are known 
to be useful chelated compounds can be used therein. 
Z indicates an atom to form a hetero ring comprising azole or azine as one 
of at least two condensed aromatic rings. Herein, if necessary, another 
ring can be added to the above-mentioned condensed aromatic ring. 
Moreover, in order to avoid adding bulky molecules without improvement in 
function, the number of the atoms shown by Z is preferably kept to not 
more than 18. 
Further, specific examples of the chelated oxinoide compounds are 
tris(8-quinolinol)aluminum, bis(8-quinolinol)magnesium, 
bis(benzo-8-quinolinol)zinc, bis(2-methyl-8-quinolato)aluminumoxide, 
tris(8-quinolinol)indium, tris(5-methyl-8-quinolinol)aluminum, 
8-quinolinol lithium, tris(5-chloro-8-quinolinol)gallium, 
bis(5-chloro-8-quinolinol)calcium, 
tris(5,7-dichloro-8-quinolinol)aluminum, tris(5,7-dibromo-8-hydroxyquinoli 
nol)aluminum, bis(8-quinolinol)beryllium, 
bis(2-methyl-8-quinolinol)beryllium, bis(8-quinolinol)zinc, 
bis(2-methyl-8-quinolinol)zinc, bis(8-quinolinol)tin, and 
tris(7-propyl-8-quinolinol)aluminum. 
The adhesive layer in the present invention comprises preferably, in 
addition to the above compound, further one or more compounds. Said one or 
more compounds are sufficient if they are soluble in the same solvents of 
metal complexes of 8-hydroxyquinoline or derivative thereof, or 
depositable without being decomposed under appropriate conditions. Such 
compounds are sufficient if contaminated in an arbitrary region in the 
direction of the thickness of the adhesive layer. If the contamination of 
these additional compounds are 0.01 mol % or more, the film is kept from 
crystallization, allowing a constant driving of the device. 
Further, it is desired that the metal complex of 8-hydroquinoline or its 
derivative is the largest in the ratio of molecule number in the adhesive 
layer. It is to maintain a stable adhesivity with metal electrode 
contaminated with any compound. Therein, if the metal complex of 
8-hydroquinoline or its derivative is smaller than other compounds in the 
ratio of molecule number in the adhesive layer, the adhesive layer is easy 
to be removed from the metal electrode. 
It is further preferred that the device is adjusted so that the voltage 
required to emit the initial luminaries after 100 hours of continuous 
driving is not more than 1.1 times the initial voltage. Since the voltage 
during the initial continuous 100 hours of driving usually fluctuates 
widely, keeping the fluctuation in the voltage constant can reduce the 
burden on the driving system. 
Specific examples of the compounds contained in the adhesive layer in 
addition to metal complexes of 8-hydroquinoline or its derivative are 
pentacene, tetracene, rubrene, tetrabenzoperylene, benzoperylene, 
coronene, perylene, benzotetracene, dibenzoanthracene, and quinacridone, 
and the compounds given in the aforegoing description of hole-injecting 
layer. Particularly preferred are aromatic tertiary amine compounds and 
styryl amine compounds. 
The thickness of the above-mentioned layer should be smaller than that of 
the light emitting layer, and is preferably 1 to 50 nm, particularly 
preferably 5 to 30 nm. Such limitation of film thickness (controlling the 
light emission region) is for the purpose of keeping the color of emission 
light blue. 
Moreover, it is still preferable that in the ratio of molecular number in 
the adhesive layer, the ratio of metal complexes of 8-hydroxyquinoline or 
its derivative is the largest. More preferably, the ratio in molecule 
number of the metal complexes of 8-hydroxyquinoline or its derivative is 
50% or more. 
Similarly, preferred is a structure wherein the ratio of molecule number is 
adjusted so as to the voltage required to emit the initial luminance after 
100 hours of continuous light emission of the resulting device is 1.1 
times the initial voltage. 
The adhesive layer is formed by, for instance, the spin-coating method, the 
casting method, or the deposition method. Preferably, the deposition 
method is used as in the forming of the light emitting layer and the hole 
injecting layer as described before. 
According to the organic EL device of the present invention, it is realized 
that the uniformity in light emitting face is improved, and the lowering 
in the initial luminance can be prevented. Accordingly, the minute 
processing, the improvement in productivity, and further the longer 
lifetime of the device has come to be obtained. 
Consequently, the organic EL device of the present invention is expected to 
be effectively used as various light-emitting materials.

The present invention will be described in greater detail with reference to 
the reference examples, the examples and the comparative examples as 
follows. 
REFERENCE EXAMPLE 1 
[Preparation of 4,4'-bis(2,2-diphenylvinyl)biphenyl] 
(1) Production of Arylene Group-Containing Phosphonate 
9.0 g of 4,4'-bis(bromomethyl)biphenyl and 11 g of triethyl phosphite were 
stirred on oil bath in a stream of argon for 6 hours while heated at 
140.degree. C. Then, the excessive triethyl phosphite and by-produced 
ethyl bromide were vacuum distilled away. The residue was allowed to stand 
overnight to obtain 9.5 g of a white crystal (yield: 80%). The results of 
analyzing the product are as follows. 
Melting point: 97.0.degree. to 100.0.degree. C. 
Determination by proton nuclear magnetic resonance (.sup.1 
H-NMRCDCl.sub.3): .delta.=7.0 to 7.6 ppm (m; 8H, biphenylene ring-H) 
.delta.=3.1 ppm (d; 4H, J=20 Hz (.sup.31 P-.sup.1 H coupling) P-CH.sub.2) 
.delta.=4.0 ppm (q; 8H, ethoxymethylene-CH.sub.2) .delta.=1.3 ppm (t; 12H, 
ethoxymethyl-CH.sub.3) 
The results as above were confirmed that the above-mentioned product was an 
arylene group-containing phosphonate (phosphonate: Mw=454.5) represented 
by the formula: 
##STR6## 
(2) Preparation of Aromatic Dimethylidine Compound 
4.5 g of phosphonate as obtained in Reference Example 1 (1) and 5.5 g of 
benzophenone were dissolved into 100 ml of dimethylsulfoxide, and 2.2 g of 
potassium-t-butoxide was added thereto, and the mixture was stirred for 4 
hours in an argon stream at room temperature, then allowed to stand 
overnight. 
To the resulting mixture, 100 ml of methanol was added, and the crystal 
precipitated was filtered. The remainder was sufficiently washed three 
times with 100 ml of water, then three times with 100 ml of methanol, and 
purified on column to obtain 2.0 g of a yellowish orange powder (yield: 
26%). 
Analytical data of the product ape as follows. 
Melting point: 204.5.degree. to 206.5.degree. C. 
Determination by .sup.1 H-NMR (CDCl.sub.3): .delta.=6.7 to 7.3 ppm (m; 30H, 
terminal phenyl ring-H, central biphenylene and methylidine 
.dbd.C.dbd.CH--) 
The result of an elementary analysis providing the composition formula as 
C.sub.40 H.sub.30 was as follows. The values in the parentheses are 
theoretical. 
C: 94.23% (94.08%) 
H: 5.84% (5.92%) 
N: 0.00% (0%) 
The infrared ray (IR) absorption spectrum (by KBr pellet method) is as 
follows. 
EQU .nu..sub.C.dbd.C 1520, 1620 cm.sup.-1 
By Mass Spectrum analysis, the molecular ion peak of the objective product, 
that is, m/Z=510 was detected out. 
Above confirmed that the powder as the above-mentioned product was 
4,4'-bis(2,2-diphenylvinyl)biphenyl represented by the formula: 
##STR7## 
Examples 1 to 11 
Indium tin oxide (ITO) was provided on a 25 mm.times.75 mm.times.1.1 mm 
glass substrate in a 100 nm thick film formed by the vapor deposition 
method to obtain a transparent supporting substrate. Said substrate was 
ultrasonically washed with isopropylalcohol for 5 minutes and further five 
minutes in pure water, then subjected to UV ozone washing for 10 minutes 
in an apparatus manufactured by Samco International Institute Inc. Said 
transparent supporting substrate was attached to a substrate holder of a 
commercially available vapor deposition system (manufactured by ULVAC Co., 
Ltd.), 200 mg of 
N,N'-bis(3-methylphenyl)-N,N'-diphenyl[1,1'-biphenyl]-4,4'-diamine(TPD) 
was placed in an electrically-heated boat made of molybdenum, and 200 mg 
of 4,4'-bis(2,2-diphenylvinyl)biphenyl (DPVBi) obtained in Reference 
Example 1 was placed in another boat made of molybdenum, and the pressure 
in the vacuum chamber was decreased to 1.times.10.sup.-4 Pa. After that, 
said boat containing TPD was heated to 215.degree. to 220.degree. C., and 
TPD was vapor-deposited on the transparent supporting substrate at a 
deposition rate of 0.1 to 0.3 nm/sec to obtain a hole injection layer of 
60 nm in film thickness. In this deposition process, the substrate was at 
room temperature. 
Without taking the substrate out of the vacuum chamber, DPVBi from another 
boat was laminate-deposited in thickness of 40 nm on the hole injection 
layer to form the light emitting layer. The deposition was performed with 
a boat temperature of 240.degree. C. at a deposition rate of 0.1 to 0.3 
nm/sec, and the substrate was at room temperature. 
Subsequently, the pressure in the vacuum chamber was raised to the 
atmospheric pressure, and 200 g of metal complexes of 8-hydroxyquinoline 
or its derivative as the material of the adhesive layer ((A) in Table 1) 
was newly placed in an electrically-heated boat made of molybdenum, and 
further 50 mg of an organic compound ((B) in Table 1) was added thereto, 
then the pressure of vacuum chamber was reduced to 1.times.10.sup.-4 Pa. 
Then, the boat containing (A) was heated ((C) in Table 1) with a 
deposition rate of 1.2 to 1.5 nm/sec, and the boat containing (B) was 
heated ((D) in Table 1) with a deposition rate of 0.01 to 0.03 nm/sec, 
thus they were deposited simultaneously to form an adhesive layer with a 
film thickness of 20 nm. 
Then, the pressure of the vacuum chamber was raised to the atmospheric 
pressure, and a stainless steel mask was placed on said layer film, which 
was fixed on the substrate holder. In the electrically-heated boat made of 
molybdenum, 1 g of magnesium ribbon was placed, and 500 mg of silver wire 
was placed in a tungsten basket, and the pressure was reduced. After the 
pressure in the vacuum chamber was reduced to 1.times.10.sup.-4 Pa, silver 
was deposited at the deposition rate of 0.1 nm/sec, and simultaneously 
magnesium was deposited at a deposition rate of 1.4 nm/sec to form a 
counter electrode with a film thickness of 150 nm. 
Examples 12 
A device was produced in the same manner as in Example except that 
1,1,4,4,-tetraphenyl-1,3-butadiene (energy gap: 2.80 eV) was used in place 
of DPVBi. 
Herein, energy gaps of (A) in Examples are shown as follows. 
______________________________________ 
(A) energy gap 
______________________________________ 
tris(8-quinolinol)aluminum 
2.50 eV 
bis(8-quinolinol)aluminum 
2.43 eV 
tris(8-quinolinol)indium 
2.33 eV 
bis(8-quinolinol)zinc 
2.30 eV 
bis(8-quinolinol)zinc 
2.20 eV 
______________________________________ 
TABLE 1 
______________________________________ 
(C) (D) 
(A) (B) .degree.C. 
.degree.C. 
______________________________________ 
Example 1 
tris(8-quinolinol)aluminum 
rubrene*.sup.1 
230 310 
Example 2 
tris(8-quinolinol)aluminum 
TPD*.sup.2 
230 215 
Example 3 
tris(8-quinolinol)aluminum 
Fastogen 230 350 
Super Red 
7094Y*.sup.3 
Example 4 
bis(8-quinolinol)magnesium 
rubrene*.sup.1 
410 310 
Example 5 
bis(8-quinolinol)magnesium 
TPD*.sup.2 
410 215 
Example 6 
tris(8-quinolinol)indium 
rubrene*.sup.1 
315 310 
Example 7 
tris(8-quinolinol)indium 
TPD*.sup.2 
315 215 
Example 8 
bis(8-quinolinol)zinc 
rubrene*.sup.1 
315 310 
Example 9 
bis(8-quinolinol)zinc 
TPD*.sup.2 
315 215 
Example 10 
bis(8-quinolinol)zinc 
Fastogen 315 350 
Super Red 
7094Y*.sup.3 
Example 11 
bis(8-quinolinol)tin 
TPD*.sup.2 
220 215 
Example 12 
tris(8-quinolinol)aluminum 
rubrene*.sup.1 
230 310 
______________________________________ 
*.sup.1 produced by Aldrich Chemical Company, Inc. 
The structural formula is as follows. 
##STR8## 
*.sup.2 N,N'-bis(3methylphenyl)-N,N'-diphenyl[1,1'-biphenyl]-4,4'-diamine 
*.sup.3 produced by Dainippon Ink. & Chemical Incorp. 
The structural formula is as follows. 
##STR9## 
Comparative Example 1 
On a 25 mm.times.75 mm.times.1.1 mm glass substrate, ITO was provided in a 
100 nm thick film formed by the vapor deposition method to obtain a 
transparent supporting substrate. Said substrate was ultrasonically washed 
with isopropyl alcohol for 5 minutes and further five minutes in pure 
water, then subjected to UV ozone washing for 10 minutes in an apparatus 
manufactured by Samco International Institute Inc. Said transparent 
supporting substrate was attached to a substrate holder of a commercially 
available vapor deposition system (manufactured by ULVAC Co., Ltd.), 200 
mg of TPD was placed in an electrically-heated boat made of molybdenum, 
and 200 mg of DPVBi obtained in Reference Example 1 was placed in another 
boat made of molybdenum, and the pressure in the vacuum chamber was 
decreased to 1.times.10.sup.-4 Pa. After that, said boat containing TPD 
was heated to 215.degree. to 220.degree. C., and TPD was vapor-deposited 
on the transparent supporting substrate at a deposition rate of 0.1 to 0.3 
nm/sec to obtain a hole injecting layer of 60 nm in film thickness. In 
this deposition process, the substrate was at room temperature. Without 
taking the substrate out of the vacuum chamber, DPVBi from another boat 
was laminate-deposited in thickness of 40 nm on the hole injection layer 
to form the light emitting layer. The deposition was performed with a boat 
temperature of 240.degree. C. at a deposition rate of 0.1 to 0.3 nm/sec, 
and the substrate was at room temperature. 
The substrate was taken out from the vacuum chamber, a stainless steel mask 
was placed on said light emitting layer, which was fixed again on the 
substrate holder. Subsequently, in a boat made of molybdenum, 200 mg of 
tris(8-quinolinol)aluminum (Alq.sub.3) was placed and deposited in the 
vacuum chamber. Further, in the electrically-heated boat made of 
molybdenum, 1 g of magnesium ribbon was placed, and 500 mg of silver wire 
was placed in a tungsten basket, and deposited. After the pressure in the 
vacuum chamber was reduced to 1.times.10.sup.-4 Pa, the boat containing 
Alq.sub.3 was heated to 230.degree. C., and deposited in a thickness of 20 
nm at a deposition rate of 0.01 to 0.03 nm/sec. Further, silver was 
deposited at the deposition rate of 0.1 nm/sec, and simultaneously, by the 
electrically heating method, magnesium was deposited at a deposition rate 
of 1.4 nm/sec from another molybdenum boat to form a counter electrode 
with a film thickness of 150 nm. 
Comparative Example 2 
On a 25 mm.times.75 mm.times.1.1 mm glass substrate, ITO was provided in a 
100 nm thick film formed by the vapor deposition method to obtain a 
transparent supporting substrate. Said substrate was ultrasonically washed 
with isopropyl alcohol for 5 minutes and further 5 minutes in pure water, 
then subjected to UV ozone washing for 10 minutes in an apparatus 
manufactured by Samco International Institute Inc. Said transparent 
supporting substrate was attached to a substrate holder of a commercially 
available vapor deposition system (manufactured by ULVAC Co., Ltd.), 200 
mg of TPD was placed in an electrically-heated boat made of molybdenum, 
and 200 mg of DPVBi obtained in Reference Example 1 was placed in another 
boat made of molybdenum, and the pressure in the vacuum chamber was 
decreased to 1.times.10.sup.-4 Pa. After that, said boat containing TPD 
was heated to 215.degree. to 220.degree. C., and TPD was vapor-deposited 
on the transparent supporting substrate at a deposition rate of 0.1 to 0.3 
nm/sec to obtain a hole injecting layer of 60 nm in film thickness. In 
this deposition process, the substrate was at room temperature. Without 
taking the substrate out of the vacuum chamber, DPVBi from another boat 
was laminate-deposited in thickness of 40 nm on the hole injection layer 
to form the emitting layer. The deposition was performed with a boat 
temperature of 240.degree. C. at a deposition rate of 0.1 to 0.3 nm/sec, 
and the substrate was at room temperature. 
The substrate was taken out from the vacuum chamber, a stainless steel mask 
was placed on said emitting layer, which was fixed again on the substrate 
holder. Subsequently, in a boat made of molybdenum, 200 mg of 
bis(8-quinolinol)magnesium (Mgq.sub.2) was placed and deposited on the 
vacuum chamber. Further, in the electrically-heated boat made of 
molybdenum, 1 g of magnesium ribbon was placed, and 500 mg of silver wire 
was placed in a tungsten basket, and deposited. After the pressure in the 
vacuum chamber was reduced to 1.times.10.sup.-4 Pa, the boat containing 
Mgq.sub.3 was heated to 410.degree. C., and deposited in a thickness of 20 
nm at a deposition rate of 0.01 to 0.03 nm/sec. Further, silver was 
deposited at the deposition rate of 0.1 nm/sec, and simultaneously, by the 
electrically heating method, magnesium was deposited at a deposition rate 
of 1.4 nm/sec from another molybdenum boat to form a counter electrode 
with a film thickness of 150 nm. 
Comparative Example 3 
On a 25 mm.times.75 mm.times.1.1 mm glass substrate, ITO was provided in a 
100 nm thick film formed by the vapor deposition method to obtain a 
transparent supporting substrate. Said substrate was ultrasonically washed 
with isopropyl alcohol for 5 minutes and further five minutes in pure 
water, then subjected to UV ozone washing for 10 minutes in an apparatus 
manufactured by Samco International Institute Inc. Said transparent 
supporting substrate was attached to a substrate holder of a commercially 
available vapor deposition system (manufactured by ULVAC Co., Ltd.), 200 
mg of TPD was placed in an electrically-heated boat made of molybdenum, 
and 200 mg of DPVBi obtained in Reference Example 1 was placed in another 
boat made of molybdenum, and the pressure in the vacuum chamber was 
decreased to 1.times.10.sup.-4 Pa. After that, said boat containing TPD 
was heated to 215.degree. to 220.degree. C., and TPD was vapor-deposited 
on the transparent supporting substrate at a deposition rate of 0.1 to 0.3 
nm/sec to obtain a hole injection layer of 60 nm in film thickness. In 
this deposition process, the substrate was at room temperature. Without 
taking the substrate out of the vacuum chamber, DPVBi from another boat 
was laminate-deposited in thickness of 40 nm on the hole injecting layer 
to form the light emitting layer. The deposition was performed with a boat 
temperature of 240.degree. C. at a deposition rate of 0.1 to 0.3 nm/sec, 
and the substrate was at room temperature. 
The substrate was taken out from the vacuum chamber, a stainless steel mask 
was placed on said light emitting layer, which was fixed again on the 
substrate holder. Subsequently, in a boat made of molybdenum, 200 mg of 
tris(8-quinolinol)indium (Inq.sub.3) was placed and deposited on the 
vacuum chamber. Further, in the electrically-heated boat made of 
molybdenum, 1 g of magnesium ribbon was placed, and 500 mg of silver wire 
was placed in a tungsten basket, and deposited. After the pressure in the 
vacuum chamber was reduced to 1.times.10.sup.-4 Pa, the boat containing 
Inq.sub.3 was heated to 315.degree. C., and deposited in a thickness of 20 
nm at a deposition rate of 0.01 to 0.03 nm/sec. Further, silver was 
deposited at the deposition rate of 0.1 nm/sec, and simultaneously, by the 
electrically heating method, magnesium was deposited at a deposition rate 
of 1.4 nm/sec from another molybdenum boat to form a counter electrode 
with a film thickness of 150 nm. 
The devices obtained in Examples 1 to 12 and Comparative Examples 1 to 3 
were subjected to aging by applying DC electric field every two seconds 
with an interval of 4.2.times.10.sup.4 V/cm up to 1 to 1.3.times.10.sup.6 
V/cm with ITO as the anode and metal electrodes as the cathodes in the 
atmosphere. Further, in Fluorinert.RTM. (FC-70, produced by Sumitomo 3M 
Ltd.), aging was conducted for 10 minutes with an initial luminance of 100 
cd/m.sup.2. 
The devices thus obtained were made to emit light continuously by driving 
by DC in Fluorinert.RTM. with setting an initial luminance of 100 
cd/m.sup.2. After 50 hours of the continuous light emitting, the devices 
were evaluated on brightness and its uniformity under the conditions 
below. The results are shown in Table 2. 
Uniformity: The devices were made to emit light at a brightness of 100 
cd/m.sup.2, the emitting surfaces were observed by the use of a luminance 
meter (CS-100, manufactured by Minolta Camera Co.), and evaluation was 
made as follows. 
X: The region observed has non-emission region with a diameter of 10 .mu.m 
or more, or has ununiformity in color. 
.smallcircle.: The region observed is uniformly emitted (without 
non-emission region or ununiformity in color) 
Further, after 100 hours of continuous light emitting, the luminance and 
the voltage of the device were measured to find the ratio to the initial 
voltage (the voltage after 100 hours/the initial voltage). The result is 
shown in Table 2. 
TABLE 2 
______________________________________ 
After 50 hours 
After 100 hours 
of driving of driving 
Luminance Luminance Voltage 
(cd/m.sup.2) 
Uniformity 
(cd/m.sup.2) 
ratio 
______________________________________ 
Example 1 100 .largecircle. 
95 1.03 
Example 2 100 .largecircle. 
93 1.03 
Example 3 98 .largecircle. 
92 1.01 
Example 4 100 .largecircle. 
94 1.05 
Example 5 100 .largecircle. 
93 1.06 
Example 6 95 .largecircle. 
91 1.05 
Example 7 95 .largecircle. 
90 1.07 
Example 8 98 .largecircle. 
92 1.03 
Example 9 98 .largecircle. 
92 1.03 
Example 10 
95 .largecircle. 
90 1.05 
Example 11 
92 .largecircle. 
90 1.06 
Example 12 
92 .largecircle. 
90 1.09 
Comparative 
75 x 69 1.23 
Example 1 
Comparative 
70 x 67 1.30 
Example 2 
Comparative 
65 x 60 1.28 
Example 3 
______________________________________