JPS6143687A - El element - Google Patents

Abstract

PURPOSE:To provide an EL element emitting luminescence in high luminance even at a low voltage, and producible easily at a low cost, by using a double- layered luminescent layer, wherein each of the first and the second luminescent layers is made of a thin film of an electroluminescent organic compound having different electronegativity from each other. CONSTITUTION:The first luminescent layer placed opposite to the transparent electrode layer 1 is made of a mixed molecular built-up film composed of a mixture of an electroluminescent organic compound 5 having higher electron affinity than the second luminescent layer and an organic compound having higher electron donative property than the compound 5. The second luminescent layer is placed opposite to the back electrode layer 3, and is made of a mixed monomolecular film or its built-up film composed of a mixture of an electroluminescent organic compound 4 having higher electron donative property than the first luminescent layer and an organic compound 4' having higher electron affinity than the organic compound 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an EL device using electrical light emitting, that is, EL, and more specifically, it is composed of one light emitting structure, and each layer is connected to an adjacent layer of another light emitting structure. The present invention relates to an EL device comprising a thin film of at least one electroluminescent organic compound having a different electronegativity relative to the electroluminescent organic compound.

(Prior art) Conventional EL elements are made of Mu, Cu or ReF.
It consists of a luminescent layer whose luminescent base material is ZnS containing 3 (R e ; rare earth ion) etc. as an activator,
Due to the difference in the basic structure of the light emitting layer, there are two types: powder type EL and thin film type E.
It is structurally classified into L.

Among devices that have been put into practical use, thin @ELs generally have higher brightness than powder-type ELs, but thin-film ELs have a large area because the light-emitting layer is formed by vapor-depositing a light-emitting base material on the substrate. This method has drawbacks such as difficulty in manufacturing the device and extremely high manufacturing cost.

Therefore, the most Ii! High productivity and low cost111
2! ! Powder-type EL, in which a light-emitting base material, ie, ZnS, is dispersed in an organic binder, which requires only a few tenths of the amount of an element, has started to attract attention. In general.

In full EL light emission, the thinner the light emitting layer is, the better the light emitting characteristics will be. B1: In the case of powder type EL, the luminescent base material is discontinuous powder, so if one luminescent layer is made thin, pinholes are likely to occur in one luminescent layer, making it difficult to reduce the layer thickness. Therefore, it has a major drawback in that sufficient brightness characteristics cannot be obtained. Recently, the powder type E
An improved device in which an intermediate dielectric layer made of a vinylidene fluoride polymer is disposed within the light-emitting layer of L is disclosed in Japanese Patent Application Laid-Open No. 58-172.
Although it is disclosed in Publication No. 891, it has not yet achieved sufficient performance in terms of luminance brightness, power consumption, etc.
Recently, research and development has been actively conducted to control the chemical structure and higher-order structure of organic materials to create core optical and electronic materials. Elements, ferroelectric liquid products, etc., metals, SM
Organic materials that are comparable to or superior to these materials have been published. In this way, as there is a demand for the development of functional organic materials as new functional materials that surpass inorganic materials, the cumulative Jll of a monomolecular layer of anthracene derivatives and pyrene derivatives, which have a parent group and a hydrophobic group in one molecule, has been developed as an electrode. An EL element formed on a "substrate" is proposed in Japanese Patent Application Laid-Open No. 52-35587. However, these EL elements have not yet achieved sufficient performance as a real EL element, such as brightness and extinction, and furthermore, in the case of 4'l EL elements, carrier electrons, 1, and holes are The density is very low, and the probability of excitation of functional molecules due to carrier recombination is very small, so efficient light emission cannot be expected.

(Disclosure of the Invention) Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide an EL element that can emit light with sufficiently high brightness even when driven at a low voltage, is inexpensive, and is easy to manufacture. It is to provide.

The above object of the present invention has been achieved by forming a light emitting layer of an EL element by combining specific materials and having a specific configuration.

That is, the present invention provides an EL device comprising a two-layered light-emitting layer, a transparent electrode layer and a back electrode layer sandwiching the light-emitting layer, wherein the first light-emitting layer faces the transparent electrode layer,
and a mixed molecule deposited film consisting of a mixture of an electroluminescent organic compound that is electron-accepting relative to the second emitting layer and an organic compound that is electron-donating relative to the compound. A light-emitting layer faces the above-mentioned back-type a-layer and comprises an electroluminescent organic compound relatively electron-donating to the first light-emitting layer and an electroluminescent organic compound relatively electron-accepting to the first light-emitting layer. The above EL device is characterized in that it is made of a mixed monomolecular film made of a mixture with an organic compound or a cumulative film thereof.

To explain the present invention in detail, the electroluminescent organic compound used in the present invention and which mainly characterizes the present invention has a high luminous quantum efficiency and also has a π-electron system that easily accepts external donations. It is a compound that can be electrically excited and has 1
For example, basically fused polycyclic aromatic hydrocarbons, p-
Terphenyl.

2,5-diphenyloxazole, 1,4-bis(2-
methylstyryl) - benzene, xanthine, coumarin,
Examples include acridine, cyanine dye, benzophenone, phthalocyanine and its metal complex, porphyrin and its gold FS complex, 8-hydroxyquinoline and its metal complex, organic ruthenium complex, organic rare earth complex, and derivatives of these compounds9. Furthermore, compounds that can act as electron acceptors or electron donors for the above compounds include heterocyclic compounds other than those mentioned above and their derivatives, aromatic amines and aromatic polyamines, compounds with a quinone structure, and tetracyanquinodine. Methane, tetracyanoethylene, etc. can be mentioned.

In the present invention, compounds useful for forming the first light-emitting layer are selected from the above-mentioned compounds.

In addition, in the present invention, the organic compound useful for forming the second light-emitting layer can be obtained by chemically modifying the electroluminescent compound as described above by a known method as necessary, so that the organic compound has a structure that is A compound having at least one hydrophobic moiety and at least one hydrophilic moiety (both of which are in a relative sense), for example, the compound having the following general formula (I). It includes the compound represented by and other compounds.

[(X-R1), Z], -φ-R, (I) X in the above formula is a hydrogen atom, a halogen atom, an alkoxy group, an alkyl ether group, a nitro group; a carboxyl group, a sulfonic acid group, a phosphorus Acid group, silicic acid group, 1st to 3rd amino group;
These metal salts, primary to tertiary amine salts, acetic acid salts; ester groups, sulfamide groups, amide groups, imino groups, quaternary amino groups and their salts, hydroxyl groups, etc.; R2 has 4 to 4 carbon atoms;
30, preferably 10 to 25 alkyl groups, preferably linear alkyl groups; m is 1 or a group (R, is an arbitrary substituent such as a hydrogen atom, an alkyl group, aryl, etc.); φ is a residue of an electroluminescent compound as exemplified later; R2, like X, is a hydrogen atom or any other substituent; one or more of X, φ and R
At least one of 2 is a hydrophilic part, and at least one is a hydrophobic part.

Preferred examples of the basic skeleton of the compound useful for forming the first layer and φ of the compound of general formula (I) include:
It is as follows. (However, φ (basic skeleton) illustrated below is an alkyl group having 1 to 4 carbon atoms, an alkoxy group, an alkyl ether group, a halogen atom, a nitro group,
It may have general substituents such as a class amino group, a hydrophobic group, a carboxamide group, and a sulfoamide group. ) (Margin below) Z=NH, 0, S Z=CO, NHZ=CO%N
H,01SZ=NH,O,5 Z=NH1O,S Z=NH,01
SZ=S%Se z:s%Se
Z=S&SeZ=NH,0,S Z=NH,α
S Z=NH10%SM=Mg,ZnbSn%AtC
4M=Hz%Be+M4Ca%CdSn,ALCt,Y
bCI M = E rlTm Smi Eu h Tb,
Z=Os Nau M=A4 Ga, Ir, Ta, a=3 M=
Er, Sm, Eu distance Znx Cd %Mg %p
b %a=2 Gd s Tb * D yT
m, Yb M=Er* Sm, Eu, Gd M=Erh
Sm, EuTb, Dy %T+n, Yb
Gd, Tb%D) ITm, Yb Z:0, S, Se OGp≦2 The above luminescent compounds can be used alone or as a mixture in each luminescent layer in the present invention. In addition,
These compounds are examples of preferred compounds, and it goes without saying that other derivatives or other compounds may be used as long as the same purpose is achieved.

The present invention is characterized in that the luminescent compounds as described above are used separately in the first luminescent layer and the second luminescent layer of the EL device of the present invention, depending on their electronegativity. That is, since the above-mentioned luminescent compounds have different electronegativities, among them, the compound that is relatively electron-accepting is selected as the luminescent compound for forming the first luminescent layer. However, the light-emitting compound that is relatively electron-donating to these compounds may be selected as the second light-emitting layer forming compound.

Among such light-emitting compounds, particularly preferable electron-donating compounds include those having electron-donating groups such as ff11 to tertiary amino groups, hydroxyl groups, alkoxy groups, and alkyl ether groups, or those having electron-donating groups such as ff11 to tertiary amino groups, hydroxyl groups, alkoxy groups, and alkyl ether groups; The main ones are terocyclic compounds, and the main ones having electron-accepting properties are compounds having electron-withdrawing groups such as carbonyl group, sulfonyl group, nitro group, and quaternary amine 7 group.

In the present invention, such luminescent compounds can be used alone or in combination in each luminescent layer.

The present invention further provides an organic compound (hereinafter referred to as a donor) that is relatively more electron-donating than the luminescent compound forming the wS1 layer as described above.

Preferably, about 1/100 to 1/1 mole of the former
In addition, in order to adjust the electron-accepting property of the first layer, and to adjust the electron-accepting property of the first layer, an organic compound (which is relatively more electron-accepting than the luminescent compound forming the second group)
(hereinafter referred to as acceptor) is preferably added at a ratio of about 1/1O to 1/Zoo mole per 1 mole of the former,
It is characterized by adjusting the electron donating property of the second layer.

゛The acceptor as described above may be selected from the above-mentioned luminescent compounds, or may be selected from other organic compounds with high electron-withdrawing properties other than the above-mentioned, and the donor may also be selected from the above-mentioned luminescent compounds. For example, as the acceptor, the acceptor may be selected from various organic compounds having a large electron-donating property such as those mentioned above. The donor can also be selected from various organic compounds having large electron-donating substituents as described above.

The other elements forming the EL element of the present invention, namely the transparent electrode layer and the back electrode layer, sandwich one light emitting layer,
Any conventionally known material can be used, but at least one layer thereof must be transparent. As the transparent electrode layer, any desired transparent electrode layer can be used as in the past, and preferred examples include polymethyl methacrylate,
A transparent conductive material such as indium oxide, tin oxide, or indium tin oxide coated entirely or in a pattern on the surface of a transparent film or sheet such as transparent synthetic resin such as polyester or glass. It is. If an opaque back electrode layer is used on one side, these opaque IJ] electrode layers may also be of conventional type, and typically and preferably have a thickness of about 0.1-0.
It is a 34 m long vapor-deposited film of aluminum, silver, gold, etc. Tooru again! The shape of the first electrode layer or the back electrode layer may be any shape such as a plate, a belt, or a cylinder, and can be selected depending on the purpose of use. Further, the thickness of the transparent electrode layer is preferably about 0.01 to 0.21 Lm; if the thickness is less than this range, the physical strength and electrical properties of the element itself will be insufficient; The thickness may cause problems in transparency, lightness, compactness, etc.

In the EL element of the present invention, between the two electrode layers as described above,
It is obtained by forming a luminescent layer consisting of two layers using separately the electroluminescent compounds (containing an acceptor or a donor) having relatively different electronegativities as described above, and the formed two The first layer constituting the light-emitting layer of the layered structure faces the transparent electrode layer and is a mixed molecule stack consisting of a relatively electron-accepting compound containing a donor with respect to the second layer; The scrap is a mixed monomolecular film or a cumulative film thereof, which faces the back electrode layer and is composed of a compound that is relatively electron-donating and includes an acceptor to the first layer, and is arranged with a highly ordered molecular orientation. It is characterized by

In the present invention, particularly preferred methods for forming the mixed molecule deposited film constituting the first light emitting layer are resistance heating evaporation method and CVD method. For example, in the evaporation method, tI
As a light emitting layer of Sl, a thin film of about 500 Å can be formed.

For example, when using the resistance heating vapor deposition method, the material is placed in a tungsten board placed in a vacuum chamber, and the material is placed 30 cm from the substrate.
Otherwise, resistance heating is performed, and sublimable materials are set at the sublimation temperature, and meltable materials are vapor deposited at a temperature higher than the melting point. The pre-vacuum level was set to 2 x 10 Torr or less, the port was closed with a shutter, the port was heated, and the air was left open for 2 minutes.

Open the shutter and deposit.

The speed during vapor deposition is measured with a film thickness monitor using a crystal oscillator, but a suitable speed is 08IA/aec~
The vacuum is maintained at 100 A/sec at a rate of 10 to 5 Torr or less, preferably about 1O-↑art, in order to prevent oxidation.

In this method, a particularly preferred method for forming the second layer of mixed monolayer or a cumulative film thereof is the Langmuir-Projet method (LB method). When the balance between the two (amphiphilic balance) is properly maintained in a molecule with a structure that has a lignophilic group and a hydrophobic group, one molecule is formed on the water surface with the hydrophilic group facing downward. This method utilizes the layering of molecules to form a monomolecular film or its cumulative layer 11Q. Specifically, to prevent the monomolecular film spread on the water layer from spreading too much on the water phase, a partition plate (or float) is installed to limit the spread area and allow the film material to gather. control the state,
By gradually increasing the surface pressure, a monomolecular film or its cumulative 1
1. Set the surface pressure suitable for manufacturing. By gently raising or lowering the clean substrate vertically while maintaining this surface pressure, the monomolecular film is transferred onto the substrate.

Although a monomolecular film is manufactured in the above manner, a cumulative film of a monomolecular film is formed by repeating the above-described operations as a cumulative film having a desired degree of accumulation.

In addition to the above-mentioned vertical dipping method, the monomolecular film can be transferred onto the substrate by methods such as a horizontal deposition method and a rotating cylinder method. The horizontal deposition method is a method in which the substrate is brought into horizontal contact with the water surface and transferred, and the rotating cylinder method is a method in which a cylindrical substrate is rotated on the water surface to transfer the monomolecular film onto the surface of the substrate. In the vertical immersion method described above, when a substrate with a hydrophilic surface is lifted out of water in a direction transverse to the water surface, a monomolecular film is formed on the substrate with the tree-philic groups of the molecules facing toward the substrate. As mentioned above, when the substrate is moved up and down, one monomolecular film is overlapped in each process.The direction of the film-forming molecules is reversed between the lifting process and the dipping process, so according to this method, the molecules between each layer are A Y-shaped film is formed in which the hydrophilic group and the wood-philic group of the molecule face each other, and the hydrophobic group and the hydrophobic group of the molecule face each other. On the other hand, in the horizontal adhesion method, a substrate is attached horizontally to the water surface and transferred, and a monomolecular film with one molecule of hydrophobic group facing the substrate is formed on the substrate. In this method, even if monomolecular films are accumulated, there is no change in the direction of the film-forming molecules, and an X-shaped film is formed in which the hydrophobic groups face the substrate in all layers. The cumulative film with the wood-philic group facing the substrate is zJj! The 0-rotation cylinder method, called L-membrane, is a method in which a monomolecular film is transferred onto the surface of the substrate by rotating the cylinder above the water surface of the substrate. The method of transferring the monomolecular film onto the substrate is not limited to these methods; in other words, when using a large-area substrate, a method of extruding the substrate from a substrate roll into a water layer may also be used. Furthermore, the directions of the above-mentioned woodphilic groups and hydrophobic groups toward the substrate are in principle, and can be changed by surface treatment of the substrate, etc.

The E L of the present invention is composed of, as the first layer facing the transparent electrode layer of the two electrode layers as described above, a compound that is relatively electron-accepting from the above-mentioned compound and a suitable donor. A mixed molecular mass 81M is formed by the molecular deposition method as described above, and as a second layer facing the back electrode layer, a compound which is relatively electron-donating from the above-mentioned compounds and a suitable one are selected. This can be obtained by selecting a mixture of acceptors, forming a mixed monomolecular film or a cumulative film thereof by, for example, the LB method, and forming a light-emitting layer into a two-layer structure.

As described in the section of the prior art, it is known to form an EL element by the LB method, but with this known method, an EL element with sufficient performance cannot be obtained.

As a result of various studies, the present inventor made the light emitting layer a two-layer structure,
The first light-emitting layer is formed as a mixed molecule deposited film using a relatively electron-accepting compound containing a donor as described above, and the second layer is formed as a relative electron-accepting compound containing an acceptor with respect to the first layer. It has been discovered that the performance of conventional EL devices can be significantly improved by forming a mixed monomolecular film or a cumulative film thereof from a compound that is electron-donating.

One embodiment of the present invention is an embodiment in which the first layer is a mixed molecule deposited film as described above, and the luminescent layer of FF52 is a mixed monomolecular film made of the luminescent material containing an acceptor.

This ilj-like EL element is manufactured by first forming the 19th layer, and then adding a mixture consisting of a material that is relatively electron-donating to the first layer and an acceptor using a suitable organic solvent. 1. For example, dissolve the solution in chloroform, dichloromethane, dichloroethane, etc. to a concentration of about 10 to 10 μm, and adjust the solution to an appropriate pH that may contain various metal ions.
(for example, pi about 1 to 8), and the solvent is evaporated to form a mixed monomolecular film.
In Method B, the mixed molecule deposited film was transferred onto a transparent substrate on which it had already been formed to form a second layer, dried thoroughly, and then
The back electrode layer is obtained by depositing an electrode material such as aluminum, *, gold, etc., preferably by vapor deposition, on the surface of this second layer.

The thickness of the two-layer light-emitting layer of the EL device thus obtained varies depending on the type of material used, but is generally about 0.05 mm thick. A thickness of 01 to 17 zm is preferred.

Another important aspect is that the second layer constituting the light emitting layer of the EL device of the present invention is a cumulative film of the above-mentioned mixed monomolecular film. In this embodiment, by using the above-mentioned LB method, the above-described integrated monomolecular film is formed by various methods to accumulate up to the required number of layers on a transparent substrate on which a mixed molecule deposited film has already been formed. obtained by doing.

The thickness of the light-emitting layer of the EL device of the present invention obtained in this way can be arbitrarily changed, but in the present invention, the thickness of the first layer of the mixed molecule deposited film is approximately 0.01-0.5. le m
It is preferable that the cumulative number of mixed monolayers in the second layer is about 4 to 200, and the total thickness of one light emitting layer is about 0.02 to lILm.

Note that the adhesion between one electrode layer used as a substrate, or both electrode layers, and the light-emitting layer is sufficiently strong in the molecular deposition method and the LB method, and there is no possibility that the light-emitting layer will peel or peel off. However, in order to strengthen the adhesive strength, the surface of the substrate may be treated in advance, or a suitable adhesive layer may be provided between the substrate and the light emitting layer.

Furthermore.

In the LB method, various conditions such as the type of material for forming the light-emitting layer, the pH of the water layer used, the ion species, the water temperature, the transfer rate of the monomolecular film, or the surface pressure of the monomolecular film can be adjusted by changing the adhesive strength by 7A. The performance of the EL element formed in the above manner may deteriorate due to the influence of moisture and ugliness in the air, so the moisture resistance and oxygen resistance can be improved by conventionally known means. It is desirable to have a v:M structure.

In the EL device of the present invention as described above, the structure of the light emitting layer is as follows:
It is a super S film, and the second M has a high degree of molecular order and function necessary for the operation of the EL device, and the first layer and the second layer have various electrical interactions. By doing so, excellent light emitting performance can be achieved.

Furthermore, as shown schematically in FIG. 1, the light-emitting layer of the EL 2 device of the present invention is different from the light-emitting layer consisting of a single layer in the prior art, as shown schematically in FIG. light emitting layer and second
Since the light-emitting layer has a uniform interface, various interactions between these two layers with different electronegativity are extremely easy, and it exhibits excellent light-emitting performance that cannot be achieved with conventional technology. It is something to do. That is, by variously changing the difference in electronegativity between the first light-emitting layer and the second light-emitting layer, the light emission intensity can be improved or the light emission color can be changed arbitrarily, and the service life can also be changed. It can be significantly extended.

Furthermore, in the conventional technology, it was virtually impossible to use materials that had excellent luminescence but insufficient film formability or film strength; however, in the present invention, materials with poor film formability or film strength could not be used. but,
Even if a material has excellent luminescence properties, by using a material with excellent film-forming properties for one of the layers, a light-emitting layer with excellent luminescence properties, film-forming properties, and film strength can be obtained.

The EL device of the present invention described above can achieve excellent EL emission by applying electrical energy such as alternating current, pulse, or direct current between the electrode layers so that electrical energy such as a suitable electric field acts on the light emitting layer. This shows that.

Next, the present invention will be explained in more detail with reference to Examples. Note that the words in the middle of the text are based on weight.

Example 1 ITO was deposited to a thickness of 1500 Å on the surface of a 50 mm square glass plate by sputtering to form a transparent electrode.

Next, triphenylamine (A) (mp, 127°C
) and anthraquinone (B) (mp.

286°C) was deposited to a thickness of 500A II2. This vapor deposition is carried out by first reducing the pressure in the vapor deposition tank to a vacuum level of 10 Torr, and gradually increasing the temperature of the resistance heating board (Mo) so that the anthraquinone vapor deposition rate is approximately 1^/Sec. A vapor deposited film was formed by keeping the current flowing through the board containing triphenylamine constant at node A such that the total vapor deposition rate was 5 A/sec. The degree of vacuum during vapor deposition was 9XlOTorr. Also.

The temperature of the substrate holder was kept constant by circulating 20°C water.

next.

A chloroform solution in which CD was dissolved in a molar ratio of 100:l was
Contains 4 x 10-4sol CdCIJ, pH 6,
Joyce adjusted to 5 - La manufactured by Loebe1
Developed in the aqueous phase of ngmuir-Trough4.

After removing the solvent chloroform by evaporation, the surface pressure was increased (3
0 dyne/am), the above-mentioned mixed molecules were deposited in the form of a film. Then, while keeping the surface pressure constant, the film-forming substrate is gently moved up and down in the direction across the water surface (vertical speed 2
cra/sin), the mixed monomolecular film was transferred onto a substrate to create a mixed monomolecular cumulative film that was accumulated over 6 days.

In this accumulation process, each time the substrate was pulled out of the water tank, it was left to stand for 30 minutes or more to evaporate and remove the water adhering to the substrate.

Finally, the substrate with the thin film formed as described above was placed in a vapor deposition tank, and the nuclide was once reduced to a vacuum level of 10 Torr, and then the vacuum level was adjusted to 10 Torr, and the vapor deposition rate was increased to 2.
At 0λ/scc, a 1,500-thick film of TeAI was deposited on the thin film to serve as a back electrode.The fabricated EL element was sealed with a sealing glass as shown in FIG. , purified, degassed, and dehydrated silicone oil was injected into the seal to form the EL light emitting cell of the present invention. IOV, 400H for these (7) EL light emitting cells
When an AC voltage of z was applied, the current density was 0.09 mA.
/ C♂ exhibited EL emission with a brightness of 22 ft-L.

The above-mentioned EL element of the present invention had a lower driving voltage and better luminance characteristics than the conventional EL element using ZnS as a light emitting matrix.

Comparative Example 1 A comparative EL element was obtained in the same manner as in Example 1 except that the first W was not carved,
Moreover, when evaluated in the same manner as in Example 1, the current density was 0.1
The brightness was 1 ft-L or less at 0 mA/c♂.

Example 2 In place of compounds A, B, C and D in Example 1,
Using the following compounds E, F, G and H.

E F GH and others obtained the EL device of the present invention (however, the cumulative number was 6) in the same manner as in Example 1, and evaluated it under the same conditions as in Example 1. At a current density of 0 and 12 mA/c♂ , the brightness (Ft-L) is 2
It was 1.

[Brief explanation of the drawing]

FIG. 1 diagrammatically shows an EL device using the conventional LB method, FIG. 2 diagrammatically shows an EL device using unreleased 15I, and FIG. FIG. 2 schematically shows a cross section of an EL element.

Claims (1)

[Claims] In an EL device consisting of a two-layered light-emitting layer, a transparent electrode layer and a back electrode layer sandwiching the light-emitting layer, the first light-emitting layer faces the transparent electrode layer and the second light-emitting layer faces the second light-emitting layer. The second light-emitting layer is composed of a mixed molecule deposited film consisting of a mixture of an electroluminescent organic compound that is relatively electron-accepting to the organic compound and an organic compound that is electron-donative to the compound, and the second light-emitting layer is A mixed unit facing the back electrode layer and comprising a mixture of an electroluminescent organic compound that is electron-donating relative to the first light-emitting layer and an organic compound that is electron-accepting relative to the compound; The above-mentioned EL device is composed of a molecular film or a cumulative film thereof.