JPS6137863A - 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 having insulating properties 4-1, the first layer contg. a relatively electron-accepting org. compd. (e.g., anthracene) 5-1, and the second layer comprising a monomolecular film or monomolecular cumulative film of a relatively electron-donating org. compd. (e.g., of the formula) 6-1 are formed successively 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 repeatedly 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 applying an electric field and converting electrical energy directly into light. Unlike conventional light emitting methods, in which excited gas imparts energy to a phosphor and causes it to emit light, it can be used in a thin panel, belt, or
It is attracting attention as it has the potential to realize various shapes such as cylindrical shapes, for example, as a component of display media used to display lamps, lines, diagrams, images, etc., or as a material that can realize light-emitting bodies such as large-area panel lamps. has been done.

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. It can be roughly divided into two 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
u, (u 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.

If the layer thickness is thin, defects such as pinholes are likely to occur in the light-emitting layer.There are structural limits to reducing the layer thickness of the light-emitting layer beyond a certain level in order to sufficiently improve the light-emitting characteristics. It is not possible to emit light, especially high brightness, and since the layer thickness is relatively thick, there have been problems such as increased power consumption in order to generate a stronger electric field. 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 laminated in this order two or more times on the layer of
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 a so-called intrinsic EL type, which has two electrode layers, at least one of which is transparent, and a light-emitting layer having EL@ function provided between these electrode layers with an insulating layer interposed therebetween. It is a thin film type EL device, 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. Based on the formation of exciplexes associated with It has characteristics.

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 and 2 are electrodes 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, The second layer e-t, 6-2 and the third layer 4-2 are alternately stacked to form a multilayer structure, and the second layer B-
1 and 8-2 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 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,? -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 8-1.6-2 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. The second layer contains compound molecules having as 8-1.6-
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 6-1.6-
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.
The first layer is formed by vapor deposition, CV
The second layer can be formed using a thin film forming method such as the D method, and a single molecule accumulation method described later.

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 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. 2 layer configuration (b) or (
A light emitting layer having 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, and the light emission in the EL element of the present invention is caused by the Interface between layer 1 and layer 7 7-1.7-
The first layer 5-1.5-2 and/or the second layer 6-1, B
It may also include a case where light is emitted within -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 between the area A per molecule and the surface pressure ■; 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, the intermolecular interaction becomes stronger, and these molecules form a "condensed film" of a two-dimensional solid. (or solid film). This condensed film can be transferred to the surface of a substrate such as glass,
An ultra-thin monomolecular film or a cumulative film thereof can be formed on a substrate.

According to this method, the molecules forming the monolayer are arranged in such a way that, for example, almost all of the tree-like parts of the constituent molecules are oriented toward the substrate in a highly ordered manner. It can be uniform.

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 monomolecular I contained in the light-emitting layer of the EL device of the present invention
The compound that can form II or the second layer consisting of a monomolecular cumulative film is a compound that can form the above-mentioned functional part, or a compound that has at least one molecule of the compound as a functional part. Among these compounds, monolayer-forming compounds have, for example, monolayer-forming compounds that have one functional moiety. As shown in the schematic diagram of the structure, (a) the m-part part 21 is on the hydrophilic part 22 side, -
2(a) (b) The functional portion 21 is on the hydrophobic portion 23 side, - FIG. 2(b) (C) 41e The functional portion 21 is located approximately between the hydrophobic portion 23 and the hydrophilic portion 22 In the middle - Broadly classified into the three types shown in Figure 2 (C).

The components of the hydrophilic portion 22 of these compounds include:
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, oximino 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 of hydrophobic groups include olefinic hydrocarbons such as acetylene, fused polycyclic phenyl groups such as phenyl, naphthyl, and anthracol, and chain polycyclic phenyl groups such as biphenyl. They can constitute the hydrophobic moiety 23 in the above compound either alone or in combination.

On the other hand, the orientation and arrangement of the monomolecular film at the interface 7-1, 7-2 (the part where light emission mainly occurs) between the first layer and the second layer of the light-emitting layer of the EL device of the present invention is as follows: 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 a functional part), (1) Second layer B-1 A tree-philic portion 32 having a functional portion 31 of molecules forming a monolayer is oriented at the interface 7-1.

(2) The hydrophobic portion 33 having the functional portion 31 of the molecules forming the monolayer of the second layer 6-1 is oriented at the interface 7-1.

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

In order to form such an interface pattern of the light-emitting layer, compounds belonging to types a and b of the monomolecular film forming compounds listed above are preferably used. In addition, in order to form the above-mentioned interface pattern (1), it is recommended to use a compound belonging to the type a in the second layer, and to form the above-mentioned interface pattern (2), it is recommended to use the compound in the second layer. It is preferable to use compounds 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 layers El-1 and 6-2 are composed of monomolecular cumulative films, each of the monomolecular films constituting the cumulative film may be the same, or the monomolecular films may be the same. One or more of these may be different from 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), Y-type (structure with hydrophobic parts facing the substrate side of each school), Z-shape (structure with parent wood parts facing the substrate side of each school), and modified structures of these, etc. Various structures are possible. Further, the monomolecular film constituting the second layer of the light-emitting layer of the EL device of the present invention may be a multicomponent monomolecular film formed of two or more kinds of compounds. In such cases, the second layer may be formed by combining two or more compounds having functional moieties, or by increasing the strength of the monomolecular layer constituting the second layer or improving adhesion with other layers. It may also be formed by adding other ingredients for the purpose.

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 6-1.6-2 include the above-mentioned compounds capable of forming a functional part, or having one or more of these compounds. Among the compounds, compounds that have a well-balanced wood-loving part and hydrophobic part can be used as is for forming a monolayer, and those that do not have a parent wood group and/or a hydrophobic part as mentioned above. Alternatively, a hydrophobic group can be newly introduced into the molecule to form a monolayer-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≦m+
n 7・8゜21, 22゜(C!
H2) nX 6≦n≦20 28°R3 27°28°M=H2, Be, Mg, C! a, Cd, 5rAICjl
, YbC1, Sm, Eu, Gd, Tb, Dy+Tm+YbR1, R
2BB-[stock], J70F3+H.

◎D, -t-Bu 84゜M = Er, Sm, Eu, Gci, Tb, D
y, 'rm, ybM-Er, Sm, Eu, G
d, Tb +Dy, 'Il'm, YbR1-H, -
CH31CFs +A 36, ・37.
3B.

43, 44・54・
55゜R1 RR 65, 66゜69, 70゜-R 71・72゜73,
74°77,
78゜88゜Among these compounds, the compounds with the structural formulas 々1 to NfL35 are based on the formation of an exciplex among the compounds that can form the functional moiety listed above. and/or modified with a parent tree group to form a monolayer-forming compound.

In addition, Masaru 42-Sui 54 and Sui 85-. The compound with the structural formula /L88 has a structure in which an alkyl chain is directly bonded to a functional moiety, but the bond of the alkyl chain to the functional moiety is, for example, an ether bond or a bond via a carboxyl group. etc. may be used.

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. Further, 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 functional moieties may be formed. The electrochemical properties of the emissive layer, such as electronegativity, can be controlled in combination or by the interaction of a compound with a functional moiety and a compound without a functional moiety but with a functional moiety. In combination with other compounds, and even a second compound.
The second layer can also be formed by adding other components to increase the strength of the layer or improve adhesion to other layers.

The third layer T1.4-2, 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. 3 has a function of increasing the insulation of the capacitor structure of the EL element of the present invention, and the third layer 4-2 confines the movement of electrons within a necessary minimum area and allows light emission by efficient exchange of electrons. It has a function to make it perform. As for the materials that can form these third layers, the general formula that can form a uniform insulating layer with high precision is: % formula %) (In the above formula, n is 10≦n≦30) Yes, X4
OOH, -CONH2, -GOOR, -N'(
CH3)3・CI.

etc.), and using one or more of these materials, vapor deposition method, CVD method, etc. can be mentioned.
This third layer can be formed by a thin film forming method such as a method.

Although the EL element of the present invention having two interfaces formed by the first layer and the second layer has been described with reference to FIG. 1, the number of interfaces that the EL element of the present invention has 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, 300A or less, preferably 100A; for the third layer, 500A or less, preferably 200A
In order to obtain a good light emitting state even in low voltage driving, it is preferable that the thickness of the entire light emitting layer be less than A, and more preferably less than IJJJI, preferably less than 3000 A.

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 that can form an ordinary electrode with sufficient conductivity, or may be formed by directly applying AI to a suitable substrate or a light emitting layer formed thereon.
, Ag, Au, etc. can be laminated by a vapor deposition method or the like.

The thickness of these electrode layers is approximately 0.01 g to O-3Jl11, preferably 0.05. ~0.2μ approximately.

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, e.g.
By applying direct current, alternating current, or pulse voltage so that an electric field of about 0' to 3 x 10'' is applied, good light emission can be obtained from the light emitting layer 3 through the transparent electrode.

Hereinafter, a typical operation of the single-molecule accumulation method, typified by the Langmuir-Blodgett method (LB method), applied to the formation of the second 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 dipping method described above, there are also horizontal adhesion methods in which the water phase surface of the substrate is kept parallel and in contact with it horizontally, 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 second layer of the light emitting layer of the EL element 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.

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 having a desired structure is formed by vapor deposition or the like using the third layer forming material described above on the substrate provided with the transparent electrode layer as described above, and then the third layer is formed by a vapor deposition method or the like. A first layer having a desired structure is formed using a material capable of forming the above-described first layer on the layer, also by vapor deposition or the like. 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, a metal such as Al, Ag, or Au can be laminated on this third layer by a vapor deposition method or the like to form the EL element of the present invention.

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

Furthermore, 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, and in particular, the second layer of each layer constituting the light-emitting layer is formed by a single layer. Because it is formed from a molecular film or a monomolecular cumulative film, the overall thickness of the light-emitting layer is thin, even though it has a multilayer structure with multiple interfaces that emit light as described above. Even when driven at a low voltage, an efficient light emitting state can be obtained, 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 has become possible to use heat-sensitive organic compounds as constituent materials for this second layer, which could not conventionally be used in vapor deposition methods or the like.

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.

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

Example 1 A 1.7.0 layer with a thickness of 1500 mm was formed on a 50 II 11 square glass surface by sputtering to obtain a transparent electrode plate.

This electrode plate was set at a predetermined position in the vapor deposition tank of the resistance heating vapor deposition apparatus, and methyl stearate (mp, 38°C) was put into the resistance heating port, and the inside of the tank was heated to 10' T.
After reducing the pressure to the vacuum degree of orr, the deposition rate is 2 people/se
Adjust the current flowing through the resistance heating port so that c.
A vapor deposited layer of 200 A methyl stearate was formed as a third layer on the transparent electrode layer of the electrode plate. The degree of vacuum in the tank during vapor deposition was 9 x 10'T.
Orr, the temperature of the substrate holder was set to 20°C.

Next, instead of methyl stearate, anthracene (m
t4. p, 21B '0) except that the temperature of the resistance heating port was made slightly higher than the melting point of anthracene. In the same manner as in the formation of the third layer, a evaporated layer of 200 A of anthracene was formed as the first layer on the insulating layer as the third layer formed earlier.

This electrode plate was attached to a Lang
+suir-Trough 4 in 4 X 10'4
no 1/I (7) It was immersed in an aqueous phase whose pH was adjusted to 6.5 by containing GdC12.

Next, 0.5++/! was spread on the aqueous phase, and the surface pressure was set to 30
dyne/cm, and after a monomolecular film made of the above compound was deposited on the surface of the aqueous phase, the electrode plate was gently pulled up at a speed of 2 cIl/win in the direction across the water surface, and further immersed and pulled up once each. A second monomolecular film consisting of three monomolecular films made of a mixture of the above compounds was formed on the previously formed first layer. here,
This electrode plate was taken out of the aqueous phase and left to dry at room temperature for 30 minutes or more.

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 190OA)
was formed.

The electrode plate on which the luminescent layer was formed in this way 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 10'5 Torr.
At a deposition rate of OA/sec, a 1500A(7)A1 layer was deposited on the last formed third layer to form an EL device of the present invention as a back electrode. As shown in FIG. 4, this EL element is sealed with a sealing glass 41, and then purified, degassed, and dehydrated using silicone oil 4.
2 was injected into the seal to form an EL cell 43.

Ko (7) Yona EL se Jlz (7) pole 44.45 ni,
When an alternating current voltage of 20 V and 400 Hz was applied to cause the light to emit light, and the luminance and current density of the light emission were measured, the brightness was 24 at a current density of 0-0-1 O/cm2.
There was Ft-L 't'.

[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. 1.44: 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 8 -1,6-2.6-3: Second layer 7-1.7-2: Interface 21.31: Functional portion 22.32: Hydrophilic portion 23.33: Hydrophobic portion 40: EL element 41 Nigarasu seal 42: Silicone oil 43: EL cell Figure 1 Figure 2 Figure 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 stacked on the third layer in this order twice or more, and the second 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.