JPS6137860A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To provide the titled element having a high luminescent efficacy even by low-voltage drive, by providing a luminous layer in which an electron-accepting org. compd. layer, electron-donating org. compd. layer, and insulating layer are laminated at least two-folds between two transparent electrode layers. CONSTITUTION:The first layer with a thickness of 500Angstrom or less comprising a relatively electron-accepting org. compd. 5-1, 5-2, the second layer with a thickness of 300Angstrom or less comprising a monomolecular film or monomolecular cumulative film of a relatively electron-donating org. compd. 6-1, 6-2, and the third layer with a thickness of 300Angstrom or less comprising a monomolecular film or monomolecular cumulative film of an insulating compd. 4-1, 4-2, 4-3 are laminated at least two-folds in the order of the third layer 4-1, the first layer 5-1, the second layer 6-1, the third layer 4-2, etc. between two electrode layers 1, 2 at least one of which is transparent, thus forming a luminous layer 3 with a thickness of 1mum or less.

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, unlike traditional light emitting methods, such as incandescent light bulbs where a filament is heated to emit light, or fluorescent light, where electrically excited gas imparts energy to a phosphor and causes it to emit light, thin panels are used. For example, various shapes such as a shape, a belt shape, a cylindrical shape, etc.

It is attracting attention as a component of display media used to display lamps, lines, diagrams, images, etc., and as a material that has the potential to realize light-emitting bodies such as large-area panel lamps.

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: a powder type with layers and a powder type with layers.

In addition, conventionally, as a material having the above-mentioned EL function, M
n, Cu 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 a thin light-emitting layer, which allows the distance between the electrodes to be sufficiently shortened, and a stronger electric field is generated within one light-emitting layer, resulting in improved brightness even when driven at low voltage. 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 forming methods have been used to control the chemical structure and higher-order structure of organic compound materials, which enable the formation of thin films with high precision. As materials for electronics, their application to electrochromic elements, piezoelectric elements, pyroelectric elements, nonlinear optical elements, ferroelectric liquid crystals, etc. is attracting attention. It is expected to be used as a forming 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 $1 layer, the second layer, and the third layer are laminated in this order two or more times on the layer, and the second layer
It is characterized in that the layer and the third layer are composed of a monomolecular film or a monomolecular cumulative film of a compound capable of forming these respective layers.

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 4-2 are alternately stacked.
1.6-2 and the third layers 4-1, 4-2, and 4-3 are formed from a monomolecular film of a compound capable of forming each layer 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 is in direct contact with the first layer 5-1. The second layer 6-1 laminated in this manner 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, 7-2, when a voltage is applied to the electrode 1.2 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 El-1, 8-2 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. The second layer 6-1.6 contains compound molecules having as
-2 is formed from a monomolecular film or a monomolecular cumulative film.

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 8-1.8-
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 ELfi ability are arranged, and compound (ED compound) molecules 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 6-1.8-2
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 layers 5-1 and 5-2, respectively.

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, fI class 10 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. Based on exciplex formation, <EL
Among these compounds, one or more compounds that can relatively become an EA compound and one or more compounds that can become an ED compound are appropriately selected and combined, and the above-mentioned first The composition of the layer and the second layer (a
), for the first layer, a thin coating method, C
For the second layer, using a thin film formation method such as the VD method,
It can be formed using the single molecule accumulation method described later.

Further, compounds that can serve as electron acceptors or electron donors for the above-mentioned compounds having <EL11 based on exciplex formation include heterocyclic compounds other than the above-mentioned compounds and their derivatives, aromatic amines, aromatic Group polyamines, compounds having 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 first layer. A light-emitting layer having two layer configurations (b) or (C) can be formed.

゛ Note that the compounds that can form the functional moieties mentioned above may be compounds that have a function of emitting light that is not based on exciplex formation.The light emission in the EL device of the present invention is Interface 7-1 between first layer and second layer.
The light emission in the first layer 5-1, 5-2 and/or the second layer 8-1,
It may also include a case where light is emitted within 13-2.

In order to form a monomolecular film or a monomolecular cumulative film containing the above-mentioned compound or a compound having at least one of the compound molecules as a functional moiety, it is possible to achieve highly ordered molecular orientation and arrangement, and to easily form an ultra-thin film layer. A so-called single molecule accumulation method, which can be used to form a single molecule, can be suitably applied.

This single molecule accumulation method is based on the following principle. In other words, 1. For example, in a molecule that has a lignophilic part and a hydrophobic part in the molecule, when the balance between the two (balance of amphiphilicity) is maintained appropriately, many of these molecules will be on the water surface. Form a monomolecular layer with the hydrophilic portion 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: nA =
kT (k: Portzmann's constant, T: absolute temperature) holds true, and these molecules form a "gas film." However, when A is made sufficiently small, intermolecular interactions become stronger, and these molecules form a two-dimensional solid "condensation film" ( or a solid film).

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.

According to this method, the molecules forming the monomolecular film are arranged in such a way that, for example, almost all of the tree-philic parts of the constituent molecules are oriented toward the substrate in a highly ordered manner.

It can be made uniform within one monolayer.

Therefore, by forming the second layer of the light-emitting layer of the EL device of the present invention into a monomolecular film or a monomolecular cumulative film, the function consisting of compound molecules directly involved in the formation of an exciplex contained in each second layer can be improved. It becomes possible to arrange the sexual parts with high density at the interface between the first layer and the second layer.

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 solutions for forming a monomolecular film, water or a solution containing water as a main component is preferably used because it is inexpensive, easy to handle, and safe.

The structure of the light-emitting layer of the EL device of the present invention will be described below, taking as an example the case where a single molecule accumulation method using water or a solution containing water as a main component is applied.

Basically, the compound capable of forming the second layer consisting of a monomolecular film or a monomolecular cumulative film included in the light-emitting layer of the EL element of the present invention is a compound capable of forming the above-mentioned functional portion or It is a compound that has at least one molecule of this compound as a functional moiety. Among these compounds, compounds for forming monolayers include, for example, one functional moiety.
Taking as an example a monolayer-forming compound having a functional moiety, depending on the position in the molecule containing the functional moiety, as shown in the schematic diagram of the molecular structure in Figure 2, (a) the t1 functional moiety 21 is located in the parent tree; On the sexual part 22 side,
- Fig. 2 (a) (b) The functional part 21 is located near the hydrophobic part 23 - Fig. 2 (b) (C) The functional part 21 is located between the hydrophobic part 23 and the hydrophilic part 22
- It is broadly classified into the three types shown in Figure 2 (C).

Technique 5 The components of the hydrophilic portion 22 of these compounds are:
For example, carboxyl groups and their metal salts, amine salts and esters, sulfonic acid groups and their metal salts and amine salts, sulfonamide groups, amide groups, amino groups, imino groups,
Examples include hydroxyl group, quaternary amino group, oxyamino group, oximit group, diazonium group, guanidine group, hydrazine group, phosphoric acid group, silicic acid group, aluminic acid group, etc., each of which can be used alone or in combination to form the above compound. A tree-friendly portion 22 inside can be constructed.

Further, as the constituent elements of the hydrophobic portion 23, linear or branched alkyl groups, vinylene, vinylidene,
Examples include olefinic hydrocarbons such as acetylene, fused polycyclic phenyl groups such as phenyl, naphthyl, anthranyl, and groups exhibiting hydrophobic properties such as chain polycyclic phenyl groups such as biphenyl. Alternatively, they can be combined to constitute the hydrophobic portion 23 in the above compound.

On the other hand, the interface between the first layer and the second layer of the light emitting layer of the EL device of the present invention? The orientation and arrangement of the monomolecular film at -1 and 7-2 (parts where light is mainly emitted) are at interface 7-1 in Figure 3.
As shown in the nearby schematic partial cross-sectional view (in this figure, the second layer is formed from a monomolecular film consisting only of a compound having one functional part), (1) the second layer fl The wood-philic portion 32 having the functional portion 31 of the molecule forming the monolayer of -1 is the interface.

7-1.

(2) Is the hydrophobic portion 33 having the functional portion 31 of the molecules forming the monomolecular film of the second layer 6-1 an interface? -1 orientation.

Figure 3 (b) It is basically divided into two patterns.

In order to form such an interface pattern of the light-emitting layer, types a and b of the monolayer-forming compounds mentioned above are used.
Compounds belonging to the above group are preferably used. Further, in order to form the above-mentioned interface pattern (1), it is preferable to use the compound belonging to the type a in the second layer, and in order to form the above-mentioned interface pattern (2), it is preferable to use the compound belonging to the type a in the second layer. It is preferable to use a compound belonging to type b.

The example explained above is a case where the second layer is formed from a monomolecular film, but even when the second layer 8-1.6-2 is formed from a monomolecular cumulative film, the first The interface between the first layer and the second layer so that the interface between the layer and the second layer takes the pattern shown above? What is necessary is to form a monomolecular film constituting -1 and 7-2.

In addition, when the second layer 6-1.6-2 consists of a monomolecular cumulative film, each monomolecular film constituting the cumulative film may be the same, or the monomolecular film One or more of these may be different from other monolayers. Furthermore, the structure based on the orientation state of the molecules forming each monomolecular film of the monomolecular cumulative film is so-called Y-type (between each film, there are a woody part and a woody part, or a hydrophobic part and a hydrophobic part). (structures in which the hydrophobic parts face each other), Y-type (structures in which the hydrophobic part faces the substrate side of each part), Z-type (structure in which the hydrophilic parts face the board side in each part), and modified structures of these. Various structures are possible. Furthermore, the second light-emitting layer of the EL element of the present invention has
The layer may be a multi-component monomolecular film formed of two or more kinds of compounds. In such cases, the second layer may be a combination of two or more compounds having functional moieties, or may increase the strength of the monomolecular layer constituting the light-emitting layer or improve adhesion with other layers. It may also be formed by adding other ingredients.

The structure of such a monomolecular film or a monomolecular cumulative film should be appropriately selected depending on the desired electrochemical properties of the second layer, that is, depending on the compound or combination of compounds forming the second layer. For example, monolayer films made of compounds belonging to types a, b, or C of the monolayer-forming compounds may be combined and accumulated to form a potential curve of π electrons in a direction perpendicular to the surface direction of the monolayer film. It can be controlled, etc.

Compounds that can be used to form the second layer 8-1.6-2 include the above-mentioned compounds capable of forming a functional part, or having one or more of the compounds listed above. Among compounds, those that have a good balance of hydrophilic and hydrophobic parts can be used as is for forming monolayers, and those that do not have hydrophilic and/or hydrophobic groups as mentioned above. A group can be newly introduced into the molecule to form a monomolecular film-forming compound.

Examples of such compounds include compounds represented by the following structural formulas.

In addition, in the structural formula shown below, X and Y represent the parent wood group as mentioned above, but when both of these exist in one molecule, even if either one is the parent wood 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 10 to 25 carbon atoms.

5.6゜6≦m10n 7・8゜9° 10・
1520゜21, 22゜(
CH2) n
YbCl 32゜M=Er, Sm, Eu, Gd, Tb, Dy+Tm+Yb
◎ Pure, -t-Bu 84゜M = Er, Srn! Eu + Gd + T
b+DylTrnlybM-Er,
Sm, Eu, Gd, Tb, Dy, Tm, YbR
1-H, -0H3, -CF3be■ 36, 37. 3
B.

89, 40°48,
44゜H(G!I(2
)nX 54, 55°R1 I Hn.

RR BF4 65, 66°69,
70°71・
-72°7 B, 74
゜77, 7B.

s 4. 85゜88゜89゜Among these compounds, the compound with the structural formula J, 1-positive 35 has the <EL function based on the formation of an exciplex among the compounds that can form the functional moiety listed above. This compound is modified with a hydrophobic group and/or a parent group to form a monolayer-forming compound.

Note that the compounds of the structural formulas //L42 to N654 and /h85 to Positive 86 have a structure in which an alkyl chain is directly bonded to a functional moiety, but the bonding of the alkyl chain to the functional moiety is, for example, It may be an ether bond, a bond via a carbonyl group, or the like.

Note that among the compounds exemplified here, compounds that can be applied to thin film forming methods such as vapor deposition methods can also be used for forming the first layer. Furthermore, the first layer may also be formed of two or more types of compounds, similar to the structure of the second layer described above, and in such a case, two or more types of compounds having one functional moiety may be formed. The first layer can also be formed in combination or with the addition of other components to increase the strength of the first layer or improve adhesion to other layers.

The third layer 4-1.4-2, 4-3, which is another layer of the light-emitting layer of the EL element of the present invention, is a layer having an insulating property, 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. As a material that can form these third layers, the general formula that can form a monomolecular film having accurate and uniform insulation properties is: % formula %) (In the above formula, n is 10 ≦n≦30, and X
is -COOH, -CONH2, -GOOR, -N (
CH3) No. 3 CI-.

Examples include compounds represented by (representing a group such as).

This third layer may also be a monomolecular film or a monomolecular cumulative film, and in the case of a monomolecular cumulative film, each monomolecular film may be the same or one or more of each monomolecular film may be It may be different from other monolayers. Further, the monomolecular film forming the third layer may be a monomolecular film made of one type of compound, or may be a multicomponent monomolecular film made of two or more types of compounds.

Although the uninvented EL element having two interfaces formed by the first layer and the second layer has been described 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,
5008 or less, preferably 2008 or less, for the second layer, 3008 or less, preferably 1008 or less, the third layer
For layers, 30Q A or less, preferably 100A
Hereinafter, it is desirable that the thickness of the entire light emitting layer be less than 1 lu, preferably less than 3,000 lu, in order to obtain a good light emitting state even when driven at a low voltage.

The light-emitting layer of the present invention can be formed, for example, in the following manner by combining the single molecule accumulation method as described above and other thin film formation methods.

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 layer by vapor deposition or the like using a material capable of forming the first layer described above. Further, on this first layer, a second layer consisting of a monomolecular film or a monomolecular cumulative film having a desired configuration is laminated using a material capable of forming the above-described second layer.

Furthermore, a third layer is laminated on the second layer, and the first to third 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, on this third layer, A1. The EL element of the present invention can be formed by laminating metals such as Ag and Au by a vapor deposition method or the like.

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 for forming a transparent electrode layer such as No. 7.0 may be laminated on the light emitting layer by vapor deposition or the like. In addition, if 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.

Furthermore, in the EL element of the present invention, the configurations of the two layers constituting the interfaces are changed for each interface for the plurality of interfaces that mainly emit light, and by combining these layers, the emitted light color can be adjusted as desired. It is now possible to control the

In addition, the light-emitting layer of the EL element of the present invention is mainly formed by combining an organic compound material and a thin film forming method suitable for the material. Although the layer 3 is formed from a monomolecular film or a monomolecular cumulative film, it has a multilayer structure with multiple interfaces that emit light as described above.
Since the overall thickness of the light-emitting layer is thin, an efficient light-emitting state can be obtained even when driven at a low voltage, and sufficient brightness can be obtained.

Furthermore, in the EL device of the present invention, since the second layer directly involved in light emission is formed of a monomolecular film or a monomolecular cumulative film, the functional portion of the compound directly involved in light emission has a high It is possible to emit light based on the formation of exciplexes that are oriented and aligned toward the interface with order and precision, resulting in more efficient transfer of electrons. It is now possible to use heat-sensitive organic compounds, which could not be used in conventional vapor deposition methods, as constituent materials for the second and third layers constituting the light-emitting layer. became.

Furthermore, each layer of the light-emitting layer of the EL device of the present invention can be easily formed as a thin film with high precision using various organic compound materials, and even when formed as a large-area EL device, the light-emitting layer can be formed with high precision. Therefore, the EL device of the present invention has good functionality, is inexpensive, and can be mass-produced.

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

Example 1 A film thickness of 150θ was formed on a 50mm square glass surface by sputtering. A transparent electrode plate was formed by forming a T and 0 layer.・This electrode plate was manufactured by Joyce-Loebe I Co., Ltd. c7
) 4X 1 in Langmuir7Trough 4
It was immersed in an aqueous phase whose pH was adjusted to 6.5 by containing 0'4111 ol/A of CdCl2.

Next, add stearic acid to chloroform. IXIO-3m
ol/j! 0.5+s7 of the solution dissolved at a concentration of 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 in the direction across the water surface at a speed of 2 cm/ml.
forming a monomolecular film of stearic acid molecules as a layer on the electrode layer of the electrode plate and pulling it out of the aqueous phase;
It was left to dry at room temperature for 30 minutes or more. Furthermore, this operation was repeated to form a monomolecular cumulative film in which three monomolecular films made of stearic acid molecules were laminated as a third layer on the electrode layer 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 placed in the resistance heating port, and the temperature inside the tank was first heated to 10”.
After reducing the pressure to a vacuum level of Torr, the deposition rate was 27!
The current flowing through the resistance heating port was adjusted to be 1/see, and the vapor deposited layer consisting of anthracene to
This layer was formed on the insulating layer as the third layer formed previously. In addition, the degree of vacuum in the tank during vapor deposition was set to 9
The temperature of the substrate holder was 10' Torr and 20°C.

After forming the first layer in this way, the electrode substrate is again immersed in the aqueous phase used previously to form the third layer, from which the remaining stearic acid has been completely removed, and then a new layer is added. 0.5 mj! of a chloroform solution containing (OH2)10 CONH2 at a concentration of IX 10"'mal// was spread on this aqueous phase, the surface pressure was adjusted to 30 dyne/am, and a monomolecular film of the above compound was formed. After forming the electrode plate on the water phase, the electrode plate was gently pulled up at a speed of 2 cm/sin in the direction across the water surface, and the electrode plate was immersed and pulled up once each, resulting in a monomolecular film consisting of three layers of the above compound molecules. A molecular accumulation film was formed as a second layer on the previously formed first layer, and then this electrode plate was taken out of the aqueous phase and left to dry at room temperature for 30 minutes or more again.

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: approximately 150OA)
was formed.

The electrode plate on which the light-emitting layer was formed in this manner was placed in a 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.
0A/5ecc7) evaporation rate, 1500A(7)A
One layer was deposited on the last formed third layer to form an EL element of the present invention as a back electrode. This EL element
As shown in the figure, after sealing with a sealing glass 41, an EL cell 43 was formed by injecting silicone oil 42 that had been purified, degassed, and dehydrated according to a conventional method into the seal.

Such an EL cell (7) electrode 44.45 d, 20
V, '400 Hz alternating voltage is applied to emit light,
When the luminance and current density in light emission were measured, a luminance of 28 Ft-L was measured at a current density of 0.12+*A/cm 2 .

[Brief explanation of the drawing]

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 diagram of the molecular structure of the monolayer-forming compound, and Figure 3 is a schematic diagram showing a typical example of the arrangement of molecules at the interface between the first layer and the second layer of the EL device of the present invention. , FIG. 4 is a schematic cross-sectional view of an EL nacelle incorporating the EL element of the present invention. ■, 44 = transparent electrode layer 2.45: electrode layer 3: light emitting layer 4-1.4-2.4-3: third layer 5-1.5-2.5-3: first layer 6 -1.6-2.6-3: Second layer 7-1.7-2=interface 21.31: Functional portion 22, . 32: Wood-loving portion 23. 33: Hydrophobic portion 40: EL element 41 Nigarasu seal 42: Silicone oil 43: EL cell Fig. 1; Fig. 3

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 laminated in this order two or more times on the third layer, and the second layer and the third layer are further stacked on the third layer. An electroluminescent device comprising a monomolecular film or a monomolecular cumulative film of a compound capable of forming each of these layers.