JPS6137864A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To yield an improved luminescence efficacy and high luminance even by low-voltage drive, by a construction wherein two thin films comprising an org. compd. and having electrochemical properties different from each other are combined to yield layers having an EL function, which are laminated to form a luminous layer. CONSTITUTION:A luminous layer 3 comprising a plurality of layers is provided between a transparent electrode 1 and a back electrode 2. In the formation of the luminous layer 3, the third layer comprising a monomolecular film or monomolecular cumulative film of a compd. having insulating properties (e.g., stearic acid) 4-1, the first layer contg. a relatively electron-accepting org. compd. (e.g., anthracene) 5-1, and the second layer contg. a relatively electron-donating org. compd. (e.g., carbazole) 6-1 are successively formed on the transparent electrode 1. Furthermore, the third layer 4-2, the first layer 5-2, the second layer 6-2, and the third layer 4-3 are laminated in this order on the above construction to form the luminous layer 3, thus yielding the intended electroluminescent element.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an electroluminescent (EL) device that performs electroluminescence, and more particularly, it relates to an electroluminescent (EL) device that emits electroluminescence. The present invention relates to an EL element that has layers having a combination of EL functions, can emit light efficiently even when driven at a low voltage, and has sufficient brightness.

[Prior art]

An EL element has a structure in which a light-emitting layer containing a material with an EL function, that is, a material that emits light when placed in an electric field, is placed between two electrodes, and a voltage is applied between these electrodes. A light-emitting element that generates light by generating an electric field and converting electrical energy directly into light.
For example, like an incandescent light bulb, the filament is heated to emit light. Alternatively, unlike conventional light emitting methods such as fluorescent lamps, in which electrically excited gas imparts energy to phosphors and causes them to emit light, they can be used in various shapes such as thin panels, belts, cylinders, etc. For example, lamps, lines, diagrams,
It is attracting attention as a component of a display medium used to display images, etc., or as a material that has the potential to realize a light emitting body such as a large-area panel lamp.

These EL devices differ in their light emission methods; one is an intrinsic EL method that performs field-excited light emission due to the movement of carriers within the light-emitting layer, and the other is an intrinsic EL method that performs field-excited light emission by injecting carriers into the light-emitting layer from an electrode. There are two main types: the carrier injection EL method and the carrier injection EL method.

Furthermore, due to the differences in the structure of the light-emitting layer of the device, EL devices are divided into thin film types, which have a thin film made of a material that has an EL function as a light-emitting layer, and light-emitting devices that have a material that has an EL function dispersed in a binder. It is broadly classified into two types: powder type with layers and powder type.

In addition, conventionally, as a material having the above-mentioned EL function, M
n, Gu or ReF3 (Re represents rare earth)
Inorganic metal materials such as ZnS containing ZnS and the like as activators have been mainly used.

Thin-film EL devices have thin light-emitting layers that allow the distance between the electrodes to be sufficiently shortened, and a stronger electric field is generated within the light-emitting layer, resulting in lower brightness even when driven at low voltages. It has a structure suitable for obtaining high-quality light emission. However, if this type of EL device is manufactured by forming a thin light-emitting layer using the above-mentioned inorganic metal material mainly consisting of ZnS using a thin film forming method such as vapor deposition, the manufacturing cost becomes extremely high. In addition, since it is extremely difficult to form a light-emitting layer made of a uniform thin film over a large area, it has not been possible to mass-produce high-quality, large-area EL elements.

On the other hand, E
As an L element, an intrinsic E in which a light-emitting layer is formed by dispersing the above-mentioned ZnS-based EL inorganic material in an organic binder.
An L-type organic powder type EL element is known.

However, in this powder type EL element, when the layer thickness is formed thin, defects such as pinholes are likely to occur in the light emitting layer. There are structural limits to making it thinner, making it impossible to obtain sufficient light emission, especially high brightness, and because the layer thickness is relatively thick, power consumption increases to generate a stronger electric field. It had the following problems. In order to generate a stronger electric field in the light-emitting layer of this powder-type EL element, an improved powder-type EL element was developed, in which an intermediate dielectric layer made of vinylidene fluoride polymer was provided.
Although it is known from the publication No. 172891, it is currently not possible to obtain satisfactory performance in terms of brightness, power consumption, etc.

On the other hand, recently, various thin film formation methods have been used to control the chemical structure and higher-order structure of organic compound materials, which can form thin films with high precision, and are being used in optical and electronic applications instead of conventionally used metals and inorganic materials. It is attracting attention for its application as a material for electrochromic elements, piezoelectric elements, pyroelectric elements, nonlinear optical elements, ferroelectric liquid crystals, etc. Furthermore, it is also possible to use these materials to form the light emitting layer of EL elements. It is expected to be used as a material.

Among these, anthracene, pyrene, perylene, or their derivatives are known as organic materials for the light-emitting layer of EL devices, and carrier injection using a monomolecular cumulative film of these materials as the light-emitting layer is known. An EL type element is known from Japanese Patent Laid-Open No. 52-35587.

However, in this EL device, although the light-emitting layer is formed as a thin film with high precision, the density of electrons or holes, which are carriers, is very low, and the probability of excitation of functional molecules due to carrier movement or recombination is low. low,
At present, it is not possible to obtain efficient light emission, and the results are not particularly satisfactory in terms of power consumption and brightness.

[Purpose of the invention]

An object of the present invention is to provide a novel EL element that has good luminous efficiency, provides sufficient brightness even when driven at low voltage, is inexpensive, and has a structure that is easy to manufacture.

Another object of the present invention is to enable EL devices to be formed by appropriately selecting various organic compound materials and combining the optimal thin film formation method for the material, and to easily impart desired light emitting characteristics. An object of the present invention is to provide an EL element having a structure that allows for.

[Structure of the invention]

That is, the electroluminescent device of the present invention is an electroluminescent device having two electrode layers, at least one of which is transparent, and a light emitting layer provided between these electrode layers, in which the light emitting layer is relatively free of electrons. A first layer containing an organic compound exhibiting acceptability, and a second layer containing an organic compound relatively exhibiting electron donating property.
and a third layer having electrical insulating properties, and these layers extend from one of the electrode layers to the other toward the third layer.
The first layer, the second layer, and the third layer are stacked in this order two or more times on the calendar, and the third layer is further stacked.
The layer is characterized in that it consists of a monomolecular film or a monomolecular cumulative film of a compound capable of forming the layer.

The light-emitting element of the present invention basically has two electrode layers, at least one of which is transparent, and a light-emitting layer having an EL function provided between these electrode layers with an insulating layer interposed therebetween. It is a thin film type EL element, and its feature lies in the structure of the light emitting layer.

The light-emitting layer of the EL device of the present invention includes an organic compound (hereinafter abbreviated as EA compound) that exhibits a relatively electron-accepting property;
It has a structure in which organic compounds that exhibit relatively electron-donating properties (hereinafter abbreviated as ED compounds) are placed in contact with each other, and when these compounds are placed in an electric field, the exchange of electrons between these compounds occurs. It has a luminescence effect based on the formation of an exciplex associated with the generation of an electric field as its main light source, and is characterized by having a structure suitable for efficiently forming such an exciplex with the generation of an electric field. be.

Hereinafter, the EL element of the present invention will be explained in more detail using the drawings.

FIG. 1 is a schematic cross-sectional view of an example of the EL element of the present invention.

1.2 is an electrode for generating an electric field by applying a voltage, and 1 is a transparent electrode for extracting the generated light. 3 is a light emitting layer having an EL function, and a first layer 5-1.5-2,
It has a multilayer structure in which the second layer 6-1, 6-2 and the third layer R4-2 are alternately stacked.
-1.4-2 and 4-3 are formed from a monomolecular film of a compound capable of forming these respective layers or a cumulative film thereof.

The first layer 5-1 of the light-emitting layer 3 contains a compound that can be an EA compound with respect to the above-mentioned ED compound contained in the second layer 6-1, and a liquid is directly applied to the first layer 5-1. The second layer 6-1 laminated in this way contains a compound that can be an ED compound with respect to the EA compound contained in the first layer 5-1, and the first layer 5-1 and the second layer 6-1 interface 7-
1 is the contact surface between the EA compound and the ED compound.

The relationship between the first layer 5-2 and the second layer 6-2 is similar to this, and an interface 7-2 is uniquely formed by these layers.

These interfaces? -1,? -2, when a voltage is applied to the electrodes 1 and 2 and an electric field is applied to the light emitting layer 3, E
A compound and ED compound form a complex in an excited state,
When this exciplex returns to the ground state, excitation energy is generated as light from the complex, EA compound, and/or ED compound in the excited state. In this way, the EL of the present invention
The main source of light emission in the device is light emission at this interface 7-1, 7-2.

First layer 5 constituting the light emitting layer of the EL element of the present invention
-1.5-2 and the second layer 6-1.6-2 contain compound molecules directly involved in the formation of the field-excited complex as shown below, or at least one of the compound molecules as a functional moiety. Contains compound molecules with as.

As for the arrangement of compound molecules directly involved in the formation of such an electric field excited complex in the light emitting layer 3, the following combinations can be cited as typical examples.

(a) First layer 5-1.5-2 and second layer 8-1.6-
A compound molecule having an EL function (mainly emitting light) based on exciplex formation is arranged in each of 2.

(b) Based on exciplex formation in the first layer 5-1.5-2<
Compound molecules having an EL function are arranged, and molecules of compounds (ED compounds) that can serve as electron donors for these compound molecules are arranged in the second layer 6-1, 6-2, respectively.

(C) Based on exciplex formation in the second layer 6-1.6-2<
Compound molecules having an EL function are arranged, and compound (EA compound) molecules that can serve as electron acceptors for these compounds are arranged in the first layer 5-1, 5-2.

As the compound having the EL function based on the formation of an exciplex, an organic compound that has a high luminescence quantum efficiency, has a π-electron system that is easily susceptible to external perturbation, and is easily excited by an electric field is preferably used.

Examples of such compounds include fused polycyclic aromatic hydrocarbons, P-terphenyl, 2,5-diphenyloxazole, 1,4-bis-(2-methylstyryl)-benzene, xanthine, coumarin, acridine, and cyanine. Pigments, benzophenones, phthalocyanines, metal complexes of phthalocyanines, porphyrins, metal complexes of porphyrins,
8-hydroxyquinoline, metal complexes of 8-hydroxyquinoline, ruthenium complexes, rare earth complexes, and derivatives of these compounds, as well as heterocyclic compounds other than the above and their derivatives, aromatic amines, aromatic polyamines, and quinone structures. Among the compounds, there are compounds that have an EL function based on exciplex formation, and among these compounds, there are one or more compounds that can be relatively EA compounds, and one or more compounds that can be relatively ED compounds. are selected and combined as appropriate to form the structure (a) of the first layer and second layer described above.
A light emitting layer having the above can be formed using a thin film forming method such as a vapor deposition method or a CVD method.

Further, as compounds that can serve as electron acceptors or electron donors for compounds having an EL function based on exciplex formation, examples include heterocyclic compounds other than the above-mentioned compounds, derivatives thereof, aromatic amines, and aromatic amines. Group polyamines, compounds with a quinone structure, tetracyanoquinodimethane, tetracyanoethylene, etc. can be mentioned, and the above-mentioned compounds and these compounds can be appropriately selected and combined to form the first layer and the above-described first layer. Second layer configuration (b) or (
A light emitting layer having Q) can be formed.

On the other hand, examples of derivatives of the above compounds that can be used to form the first layer and the second layer include compounds having the following structural formulas.

In addition, in the structural formula shown below, X and Y represent the parent tree group as mentioned above, but when both of these exist in one molecule, one of them is the parent tree group. In such a case, the other one will be hydrogen. Further, R represents a linear or side chain alkyl group having about 4 to 30 carbon atoms, preferably about IO to 25 carbon atoms.

56゜6≦m+n 7.8゜21・22゜(CH2
)nX 6≦n≦20 28°Hs 28°M=H2+ B e + Mg 20 a + cd
, S rhtct, Ybct M = Er, Sm, Eu, Gd, Tb, Dy,
Tm, YbE+, R2R11-BQ/"?Hfu◎clean, -CH3,-t-Bu M=Er, Sm+Eu, Gd, Tb, DLT'm, Yb
M-Er, Sm, Eu, Gd, Tb +Dy
, Tm, YbR+-T(',-yama,-〇F3.A 87°36,
38°39, 4Q
.

4I3.・４４、■
(Tap 2) X54・
55°R1 56, H57, H 62°RR 69, 70°71, 72°73,
74°7'1.
78゜■ 84・85゜88゜89゜Among these compounds, the compound with the structural formula of 々1-435 is one of the compounds listed above that can directly participate in the formation of an exciplex. Based on the above, a compound having an EL function is modified with a hydrophobic group and/or a parent group. In addition, positive 42~/L54 and positive 85~final 8
The compound of structural formula 6 has a structure in which an alkyl chain is directly bonded to a moiety directly involved in the formation of an exciplex. It may be something.

Note that the compounds listed above may be compounds that have a function of emitting light that is not based on exciplex formation.
Does the EL device of the present invention emit light at the interface between the first layer and the second layer? -1, 7-2, the first layer 5-1, 5-2 and/or the second layer
It may also include a case where light is emitted within the layers B-1 and 8-2.

Furthermore, the first layer and the second layer may each be formed of two or more kinds of compounds, and in such a case,
These layers are made by combining two or more compounds that directly participate in the formation of exciplexes, or by adding other components to increase the strength of these layers or improve adhesion with other layers. It may also be a formed one.

The third layer 4-1.4-2, 4-3, which is another layer of the light-emitting layer of the uninvented EL element, is a layer having insulating properties, and in particular, the third layer 4-1. 4-3 is the EL of the present invention
It has the function of increasing the insulation of the element's capacitor structure,
The third layer 4-2 has the function of confining the movement of electrons within a necessary minimum area and emitting light by efficiently transferring and receiving electrons.

This third layer is formed from a monomolecular film or a monomolecular cumulative film having electrical insulation properties.

To form this third layer, a monomolecular accumulation method is preferably applied, which allows an ultra-thin film to be easily formed at approximately room temperature and pressure.

This single molecule accumulation method is based on the following principle. In other words, for example, in a molecule that has a hydrophilic part and a hydrophobic part, when the balance between the two (amphiphilic balance) is maintained at an appropriate level, many of these molecules have a hydrophilic part and a hydrophobic part on the water surface. Form a monolayer with the woody part facing down. This monomolecular layer has the characteristics of a two-dimensional system, and when these molecules are sparsely dispersed, the two-dimensional ideal gas equation is expressed between the area A per molecule and the surface pressure ■;
= kT (k: Portzmann's constant, T: absolute temperature), and these molecules form a "gas fPJ"'; however, if A is made sufficiently small, the intermolecular interaction becomes stronger, and these molecules become "condensed" into a two-dimensional solid. A film (or solid film)''' is formed. This condensed film can be transferred to the surface of a substrate such as glass, and an ultra-thin monomolecular film or a cumulative film thereof can be formed on the substrate.

Various solutions can be used as the solution for forming a monomolecular film in this monomolecular accumulation method, and depending on the solution used, the solution has a well-balanced portion that has different affinity for the solution. A monomolecular film can be formed by appropriately selecting a compound for forming a monomolecular film. Among such monolayer-forming solutions, it is inexpensive and easy to handle.

Water or a solution containing water as a main component is preferably used from the viewpoint of safety.

The third layer forming material that can be used when applying the monomolecular accumulation method using water or a solution mainly composed of water has the general formula; % formula % (in the above formula, n is 10≦n≦30, and X
is -C001(, -CONH2, -GOOR, -N (
C[(3)3.CI-.

The third layer can be formed using one or more of these materials.

In addition, when the third layers 4-1, 4-2 and 4-3 are composed of monomolecular cumulative films, each monomolecular film constituting the cumulative film is
They may be the same, or one or more of the monolayers may be different from the other monolayers.

Furthermore, the structure of the monomolecular cumulative film due to the orientation state of the molecules forming each monolayer is so-called Y-type (between each film, a hydrophilic part and a lignophilic part or a hydrophobic part and a hydrophobic part are formed). (structures facing each other), The structure can be as follows.

Hereinafter, typical operations of the single-molecule accumulation method, typified by the Langmuir-Blodgett method (LB method), applied to the formation of the third layer of the light-emitting layer of the EL device of the present invention will be explained.

An aqueous phase for forming a monomolecular film is provided in a water tank, and a clean substrate is immersed in the aqueous phase. Next, a predetermined amount of a solution of a monomolecular film-forming compound dissolved or dispersed in a suitable solvent is spread in the aqueous phase, and this compound is deposited in the form of a film on the surface of the aqueous phase. At this time, in order to prevent the precipitates from freely diffusing on the water phase and spreading too much, a partition plate (or float) is provided to limit the area of development and control the aggregation state of the membrane material.
Obtain a surface pressure (■) proportional to the aggregate state. Then, the partition plate is activated to reduce the developed area and gradually increase the surface pressure (2) to set the surface pressure (4) suitable for forming a monomolecular film. Now, when the substrate that has already been immersed is gently moved up and down in a direction perpendicular to the aqueous phase surface while maintaining this surface pressure, a monomolecular film is formed as the substrate moves upward and downward. is transferred onto the substrate to form a monomolecular cumulative film.

To transfer a monomolecular film onto a substrate, in addition to the vertical immersion method mentioned above, there are also horizontal attachment methods in which the substrate is brought into contact with the water phase horizontally while keeping it parallel to the surface, and a cylindrical substrate is rotated on the water surface. Various methods can be applied, such as a rotating cylinder method in which a monomolecular film is transferred to the surface of a substrate using a rotating cylinder method, or a method in which the substrate is extruded from a substrate roll into an aqueous phase. In the vertical dipping method, the orientation of the film-forming molecules is usually reversed between the substrate pulling process and the dipping process, so that a so-called Y-shaped film is formed. Further, according to the horizontal deposition method, a monomolecular film with hydrophobic groups facing the substrate side is formed, and when a cumulative film is formed, a so-called X-type film is formed.

However, the orientation of such parent wood groups and hydrophobic groups can also be changed by surface treatment of the substrate.

Furthermore, the pH of the aqueous phase when forming the third layer of the light emitting layer of the EL device of the present invention by the single molecule accumulation method;
The operating conditions such as the type and amount of additives, the temperature of the aqueous phase, the rate of raising and lowering the substrate, or the surface pressure, etc., are as follows:
It may be selected as appropriate depending on the type of monomolecular film-forming compound used, the characteristics of the film to be formed, etc.

Although the EL element of the present invention having two interfaces formed by the first layer and the second layer has been explained using FIG. 1, the number of interfaces that the EL element of the present invention has is , there may be three or more, without being limited to this.

The thickness of each layer constituting the light-emitting layer of the EL device of the present invention having the above structure varies depending on the number of interfaces the EL device has and the structure of each layer itself, but for the first layer,
500A or less, preferably 200A or less, for the second layer, 500A or less, preferably 200A or less, for the third layer, 300A or less, preferably 100A or less
It is desirable that the thickness of the entire light-emitting layer is 1 g or less, preferably 3000 A or less, in order to obtain a good light-emitting state even when driven at a low voltage.

At least one of the two electrode layers 1 and 2 of the EL element of the present invention is provided as a transparent electrode in order to extract light.

When forming an electrode layer as a transparent electrode, PMMA,
InO2, 5n02, insium tin oxide (1, T, O), etc. are laminated by vapor deposition on a film or sheet of polyester, or a transparent substrate such as a glass plate, or these materials are used as a light emitting layer. It can be formed by direct lamination.

In addition, the non-transparent electrode layer may be a thin plate made of a material capable of forming an ordinary electrode with sufficient conductivity, or may be directly applied to an AI on a suitable substrate or on an ephemeris formed.
, Ag, Au, etc. can be laminated by a vapor deposition method or the like.

The thickness of these electrode layers is about 0.01 u to 0.3 cape, preferably about 0.05 g to 0.2 tile.

Note that the shape and size of the EL element of the present invention can be made into various shapes as desired. For example, when forming a transparent electrode, the substrate is used as a substrate for forming a light emitting layer, and this substrate may be shaped like a plate, a belt, etc. A desired shape and size can be obtained by using, for example, a cylindrical shape. Further, the two electrode layers may be patterned into various shapes as desired.

In the EL element of the present invention having the above configuration, the EL
Between the two electrodes 1.2 of the device, for example, lXI is applied to the light emitting layer 3.
By applying direct current, alternating current, or pulse voltage so that an electric field of about O3 to 3 x 106 is applied, good light emission can be obtained from the light emitting layer 3 through the transparent electrode.

In the EL element of the present invention having the above structure, the light emitting layer of the present invention can be formed, for example, in the following manner.

First, a third layer consisting of a monomolecular film or a monomolecular cumulative film having a desired configuration is formed using the third layer forming material described above on the substrate on which the transparent electrode layer is provided. Next, a first layer having a desired structure is formed on this third calendar by vapor deposition or the like using a material capable of forming the first layer described above. Further, on this first calendar, a second layer having a desired structure is laminated using a material capable of forming the second layer described above, also by vapor deposition or the like.

Furthermore, a third layer is laminated on the second calendar, and the layers are stacked according to the desired number of interfaces between the first layer and the second layer.
Repeat the layer formation operation twice or more.

Finally, the EL element of the present invention can be formed by laminating a metal such as AI, Ag, or Au by vapor deposition or the like on this third calendar.

If a substrate with a non-transparent electrode plate or electrode layer is used as the substrate for forming the first light-emitting layer, the final
．． A material such as T or O for forming a transparent electrode layer may be laminated on the ephemeris by vapor deposition or the like. In addition, when both electrodes are transparent, a transparent electrode layer may be formed using the above-mentioned material on a transparent substrate for forming a light emitting layer, and another transparent electrode layer may be laminated after the formation of the light emitting layer is completed. .

Note that the plurality of first layers included in the light emitting layer of the EL element of the present invention may each have the same structure, and the structure of one or more of the plurality of first layers may be different from each other. The structure of the first layer may be different from that of the other first layers.
The same applies to the layer and the third layer. Further, an adhesive layer may be provided between each layer constituting the EL element of the present invention in order to improve the adhesiveness of each layer. Furthermore, it is desirable that the EL element of the present invention be provided with a protective structure for protecting the element from the effects of moisture and oxygen in the air.

The EL device of the present invention as described above mainly emits light at the interface between two layers having different electrochemical properties, and has a structure in which a plurality of such interfaces are provided in the light extraction direction of the EL device. The amount of light emitted per unit of the light extraction surface is greatly increased compared to conventional EL elements.

In addition, in the EL element of the present invention, with respect to a plurality of interfaces that mainly emit light, the composition of the two layers constituting the interface is changed for each interface, and these are combined to adjust the emitted light color as desired. It is now possible to control the

Furthermore, the light-emitting layer of the EL device of the present invention is mainly formed by combining an organic compound material and forming a thin film suitable for the material, and in particular, the third layer of each layer constituting the light-emitting layer is made of a monomolecular material. Although it has a multilayer structure with multiple interfaces that emit light as described above, because it is formed from a film or a monomolecular cumulative film, the thickness of the entire light emitting layer is thin. Even when driven at a low voltage, an efficient light emitting state can be obtained, and sufficient brightness can be obtained.

Moreover, each layer of the light-emitting layer of the EL device of the present invention can be easily formed as a precise thin film using various organic compound materials, and even when formed as a large-area EL device,
The light-emitting layer is formed with high precision and has good functionality. In addition, the third layer included in the light-emitting layer is formed from a monomolecular film or a monomolecular cumulative film, and this monomolecular film is , can be formed at room temperature and pressure, and for this third layer, heat-sensitive organic compounds that could not be conventionally used in vapor deposition methods can also be used as constituent materials. The EL device of the present invention is an inexpensive and mass-producible EL device.

Hereinafter, the EL device of the present invention will be explained in more detail according to Examples.

Example 1 A film with a thickness of 15QQA was deposited on a 50mm square glass surface by sputtering. A T and 0 layer was formed to obtain a transparent electrode plate. This electrode plate was manufactured by Joyce-Loebe1.
4X 10' in ngmuir-Trough 4
It was immersed in an aqueous phase whose pH was adjusted to 8.5 by containing mol// of CdCl2.

Next, stearic acid was dissolved in chloroform.
0.5+/l of the solution dissolved at a concentration of Ilol/l,
It was developed on the aqueous phase. After chloroform was removed by evaporation from the surface of the aqueous phase, the surface pressure of the aqueous phase was adjusted to 30 dyne/cm, and a film of stearic acid was precipitated on the surface of the aqueous phase.

Furthermore, while keeping the surface pressure constant, the electrode plate was gently pulled up at a speed of 2C/sin in the direction across the water surface, and a monomolecular film made of stearic acid molecules as a third layer was applied to the electrode plate. Formed on top and pulled it out of the aqueous phase for 30 minutes.
It was left to dry at room temperature for more than a minute. Furthermore, this operation was repeated once again to form a monomolecular cumulative film in which two monomolecular films made of stearic acid molecules were laminated as a third layer on the electrode calendar of the electrode plate. Note that the stearic acid remaining on the surface of the water phase was completely removed from the surface of the water phase.

Next, this electrode plate was set at a predetermined position in the vapor deposition tank of the resistance heating vapor deposition apparatus, and anthracene (mp, 218°C) was put into the resistance heating port, and the inside of the tank was heated for 10 minutes.
After reducing the pressure to a vacuum level of Torr, the deposition layer rate is 2 people/s.
The current flowing through the resistance heating port was adjusted so that ee was obtained, and a vapor deposited layer of 200 anthracene was formed on the insulating layer as the third layer formed previously as the first layer. In addition, the degree of vacuum in the tank during vapor deposition is 9X to 4
Torr, and the temperature of the substrate holder was set to 20°C.

Furthermore, carbazole (mp, 2
A vapor-deposited layer consisting of carbazole 200 was used as the second layer in the same manner as in the formation of the first layer, except that the temperature of the resistance heating port was made slightly higher than the melting point of carbazole. It was formed on the first calendar formed earlier.

Thereafter, the above-described formation operation from the third layer to the second layer is repeated four times, and finally the third layer is laminated to form the first layer and the second layer.
A light emitting layer having four layer interfaces (layer thickness: approx. 1800A)
was formed.

The electrode plate on which the light-emitting layer was formed in this manner was put back into the vapor deposition tank, and the pressure inside the tank was first reduced to a vacuum level of 10' Torr, and then the vacuum level was further adjusted to 10' Torr. A1 to 1500, with a deposition rate of
The EL element of the present invention was formed as a back electrode by vapor deposition on the third layer formed last. As shown in FIG. 2, this EL element was sealed with a sealing glass 21, and then silicone oil 22, which had been purified, degassed, and dehydrated according to a conventional method, was injected into the seal to form an EL cell 23.

To such an EL nacelle electrode 24.25, 20V, 40
When an alternating current voltage of 0 Hz was applied to emit light, and the luminance and current density of the emitted light were measured, the current density was 0.1.
A brightness of 32 Ft-L was measured at 3a+A2.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an example of the EL element of the present invention, and FIG.
The figure is a schematic cross-sectional view of an EL nacelle in which the EL element of the present invention is incorporated. l, 24: Transparent electrode layer 2.25: Electrode layer 3: Luminescent layer 4-1.4-2.4-3: Third layer 5-1.5-2.5-3: First layer B -1. B-2.8-3: Second layer 7-1.7-2: Interface 20: EL element 21 Glass seal 22: Silicone oil 23: EL nacelle 1 Figure

Claims (1)

[Claims] 1) In an electroluminescent device having two electrode layers, at least one of which is transparent, and a light-emitting layer provided between these electrode layers, the light-emitting layer contains an organic compound that relatively exhibits electron-accepting properties. It has a first layer, a second layer containing an organic compound that exhibits relatively electron-donating properties, and a third layer that has electrical insulation properties, and these layers extend from one of the electrode layers to the other. The first layer, the second layer, and the third layer are stacked in this order two or more times on the third calendar, and the third layer is further stacked on the third layer. 1. An electroluminescent device comprising a monomolecular film or a monomolecular cumulative film of a compound that can be formed.