JPS6137858A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To provide the titled element having a high luminescence 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:A luminous layer 3 with a thickness of 1mum or less is formed in which the first layer with a thickness of 300Angstrom or less comprising a monomolecular film or monomolecular cumulative film of 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 500Angstrom 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.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an electroluminescent (EL) device that emits electroluminescence, and more particularly, it relates to an electroluminescent (EL) device that emits electroluminescence, and more specifically, it is a device that uses two types of thin films made of organic compounds with different electrochemical properties. The present invention relates to an EL element having a layer having an EL function in combination with EL elements, which 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. Possibility of realizing light-emitting bodies such as lamps, lines, diagrams, images, etc., or as components of display media such as lamps, lines, diagrams, images, etc., or as light-emitting bodies such as large-area panel lamps. It is attracting attention as having the following.

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 one light-emitting layer that is thin and the distance between the electrodes can be sufficiently shortened, and a stronger electric field can be generated within the light-emitting layer, allowing for even low-voltage operation. It has a structure suitable for obtaining high brightness and good 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. As a material for electroluminescence, it is attracting attention for its application to electrochromic elements, piezoelectric elements, electroless elements, nonlinear optical elements, ferroelectric liquid crystals, and other applications. It is expected that it will be applied as

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, can provide sufficiently high luminance 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 twice or more on the layer, and the first layer, the second layer, and the third layer are , is characterized in that it consists of a monomolecular film or a monomolecular cumulative film of a compound capable of forming each of these 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 type 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. 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.

2 and 2 are electrodes for generating an electric field by applying a voltage, and 2 is a transparent electrode for extracting the generated light. 3 is a light emitting layer having an EL type function, and a first layer 5-1.5-2, It has a multilayer structure in which the second layer 8-1, 6-2 and the third layer 4-2 are alternately stacked, and each layer is made of a compound that can form the respective layer. It is formed from a monomolecular film 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 8-1, and is in direct contact with the first layer 5-1. The second layer e-t 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? -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.

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

The first layer 5-1.5-2 and the second layer 8-1.6-2 constituting the light-emitting layer of the EL element of the present invention directly contribute to the formation of the field-excited complex as shown below. It is formed from a monomolecular film or a monomolecular cumulative film containing the participating compound molecules or compound molecules having at least one of the compound molecules as a functional moiety.

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 (7) layer 5-! , 5-2 and the second layer 6-1.
A compound molecule having an EL function (mainly emitting light) based on exciplex formation is arranged in each of 8-2.

(b) Based on exciplex formation in the first layer 5-1.5-2<
Compound molecules having ELM ability are arranged, and compound (ED compound) molecules that can serve as electron donors for these compound molecules are arranged in the second layer 6-1.8-2.

(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 1, for example, fused polycyclic aromatic hydrocarbons, p-terphenyl, 2,5-diphenyloxazole, 1,4-bis-(2-methystyryl)-
Benzene, xanthine, coumarin, acridine, cyanine dye, benzophenone, phthalocyanine, metal complex of 2-thalocyanine, porphyrin, metal complex of porphyrin, 8-hydroxyquinoline, metal complex of 8-hydroxyquinoline, ruthenium complex, rare earth complex, and these Based on exciplex formation among derivatives of compounds, heterocyclic compounds and their derivatives other than those listed above, aromatic amines, aromatic polyamines, and compounds having a quinone structure.
Compounds having an EL function can be mentioned, and from 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 A light-emitting layer having the structure (a) of the layer and the second layer can be formed using 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-
2, the first layer 5-1.5-2 and/or the second layer 8-1, 8-
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, for example, in a molecule that has a lignophilic part and a hydrophobic part in the molecule, when the balance between the two (amphiphilic balance) 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, 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 "condensed film" (or form a solid film)''.

This condensed film can be transferred to the surface of a substrate such as glass, and an ultra-thin film portion/preparation or its cumulative M film 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 making the interface between the first layer and the second layer of the EL element of the present invention an interface formed by a monomolecular film, the exciplex contained in the first layer and the second layer, respectively, is directly involved in the formation of the exciplex. It becomes possible to arrange functional parts made of compound molecules at high density at the interface between the first layer and the second layer.

Various solutions can be used as a solution for forming a single molecule in this single molecule accumulation method, and depending on the solution used, a well-balanced number of molecules having different affinity for the solution can be used. A monomolecular film can be formed by appropriately selecting a compound for forming a molecular 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 that can form the first layer and the second layer of the light-emitting layer of the EL device of the present invention is a compound that can form the above-mentioned functional part or a compound that can function as a compound molecule. These compounds have at least one functional moiety, for example, one functional moiety.
Taking as an example a monolayer-forming compound having a functional moiety, depending on the position within the molecule, as shown in the schematic diagram of the molecular structure in FIG. 2, (a) the functional moiety 21 is a hydrophilic moiety; 22 side - Fig. 2(a) (b) The functional part 21 is on the hydrophobic part 23 side - Fig. 2(b) (C) 41! The functional part 21 is located approximately midway between the hydrophobic part 23 and the hydrophilic part 22. - They are broadly classified into three types as shown in FIG. 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, amine groups, imino groups,
Examples include hydroxyl group, quaternary amine group, oxyamine group, oxyimino group, diazonium group, guanidine group, hydrazine group, phosphoric acid group, silicate group, aluminate group, etc., and each of them 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 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: Figures 3a and 3b
As shown in the schematic cross-sectional partial view near interface 7-1 in the figure (in this figure, the layer of node 1 and the second layer are formed from a monomolecular film consisting only of a compound having a functional moiety). (1) A hydrophilic portion 32 having a functional portion 31 of molecules forming a monomolecular film of the first layer 5-1, and a second layer B-1.
A hydrophilic portion 32' having a functional portion 31' of molecules forming a monomolecular film 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 first layer 5-1 and the second layer B-1
A hydrophobic part 33' having a functional part 31' of a molecule forming a monomolecular film is oriented at the interface 7-1.

(3) A hydrophobic portion 33 having a functional portion 31 of molecules forming a monomolecular film of the first layer 5-1, and a second layer 6-1.
The hydrophilic part 32' having the functional part 31' of the molecule forming the monomolecular film is an interface? -1 orientation.

(4) The hydrophilic portion 32 having the functional portion 31 of the molecules forming the monolayer of the first layer 5-1, and the second layer 8-1 of FIG.
The hydrophobic part 33' having the functional part 33' of the molecule forming the monomolecular film is an interface? -1 orientation.

Figure 3b (b) It is basically divided into four 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 a compound belonging to the above-mentioned type a in the first layer and the second layer, and to form the above-mentioned interface pattern (2), It is preferable to use a compound belonging to type b in the first layer and the second layer. Further, in order to form the above-mentioned interface pattern (3), it is preferable to use the compound belonging to the type a in the first layer and the compound belonging to the type b in the second layer, and form the above-mentioned interface pattern (3). 4), it is preferable to use a compound belonging to type b in the first layer and a compound belonging to type a in the second layer.

In the example explained above, the first layer and the second layer are formed from a monomolecular film, but the first layer 5-1.5-
2 and/or the second layer 6-1.6-2 is composed of a monomolecular cumulative film, so that the interface between the first layer and the second layer takes the above pattern, Interface 7-1 between the first layer and the second layer, ? A monomolecular film constituting -2 may be formed.

Note that the first layer 5-1.5-2 and/or the second layer θ
-1 and 8-2 are composed of monomolecular cumulative films.

Each of the monomolecular films constituting the cumulative film may be the same, or one or more of the monomolecular films may be different from the other monomolecular films. Furthermore, the structure of the monomolecular cumulative film due to the orientation state of the molecules forming each monolayer is the so-called Y type (between each film, a hydrophilic part and a hydrophilic part or a hydrophobic part and a hydrophobic part are mutually separated). x-type (structure with the hydrophobic part facing the substrate side of each film),
Various structures can be used, such as a Z-type (a structure in which the hydrophilic portion of each film faces the substrate side) and modified structures thereof. Furthermore, the monomolecular film constituting the light-emitting layer of the present invention may be a multicomponent monomolecular film formed of two or more kinds of compounds.

In such a case, the first layer and the second layer may be a combination of two or more compounds having functional moieties to increase the strength of the monomolecular layer constituting the emissive layer or to improve the adhesion between each layer. It may also be formed by adding other ingredients to improve its properties.

The structure of such a monomolecular film or a monomolecular cumulative film is determined depending on the desired electrical characteristics of the first layer or the second layer.
That is, it may be selected as appropriate depending on the compound or combination of compounds forming the first layer or the second layer, for example, type a, b or type C of the monolayer-forming compound.
It is possible to control the potential curve of π electrons in the direction perpendicular to the surface direction of the monomolecular film by combining and accumulating monomolecular films made of compounds belonging to the monomolecular film.

The above first layer 5-1.5-2 and second layer 6-1.6
Compounds that can be used to form -2 include the above-mentioned compounds capable of forming a functional moiety, or compounds containing one or more of these compounds:
Compounds that have a good balance of hydrophilic and hydrophobic parts can be used as they are for forming monolayers,
If this is not the case, a parent tree group and/or a hydrophobic group such as those mentioned above can be newly introduced into the molecule to form a compound for forming a monomolecular film. 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 an alkyl group having a linear or side chain having about 4 to 30 carbon atoms, preferably about 10 to 25 carbon atoms.

5・6゜7・8゜9, 10
゜18゜15. 16°19, 20°2
1, 22
゜(CH2)nX 6≦n≦20 28゜Hs 24゜0≦n≦2 25゜M=H2, Be, Mg, Oa, Cd, 5rAICI, Y
bC1 M = Er, Sm, Eu, Gd, Tb, Dy
, Tm, Yb ◎ Acceptable, -CH3, -tBu 84゜M=Er, Sm, Eu, Gd, Tb, Dy, Tm, Yb
M −hr + Srn, Eu HGd + T
b + D'I + 'I'rn + Y bR+-'
H, -mountain, -cps4 36, 37. 3B.

89, 40°4 &
44゜Hα1H2)
X 62°RR 65, 66°69, 7α71,
-72°73,
74°77, 7
B.

■ 82° 83 B 4. 8
5゜88゜R Among these compounds, the compound with the structural formula N61-AIllL35 is 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, notification 42~AI6.54 and positive 85~. The compound with the structural formula /18B has a structure in which an alkyl chain is directly bonded to a functional moiety, but the alkyl chain is bonded to the functional moiety by, for example, an ether bond, a bond via a carbonyl group, etc. 1. X.

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 for the material that can form these third layers, the general formula that can form a monomolecular film with accurate and uniform insulation properties is: % Formula % (In the above formula, n is IO≦ n≦30, and X
1i-000H,-111:0NH2,-GOOR,-
N+(OH3)3- represents a group such as CI-), etc. can be mentioned.

This third layer may also be a monomolecular film or a monomolecular cumulative film, and in the case of a monomolecular cumulative film, even if each monomolecular film is the same, at least one of each monomolecular film is 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 EL element of the present invention 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,
300 Å or less, preferably 100 Å or less, the second layer: 300 Å or less, preferably 100 Å or less, the third layer: 500 Å or less, preferably 200 Å or less, and the thickness of the entire light emitting layer: , 1JIj1 or less, preferably 30008 or less, in order to obtain a good light emission state even in low voltage driving.

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 such as 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 0. It is about O1 to 0.3 scales, preferably about 0.05 to 0.2 scales.

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 monomolecular film, and this substrate may be in the form of a plate, a belt, etc. A desired shape and size can be obtained by using a cylindrical shape or 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 l, 2 of the device, for example, lXI in 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.

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

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 light-emitting layer of the EL device of the present invention by the single molecule accumulation method, the type and amount of additives for adjusting the pH of the aqueous phase, the temperature of the aqueous phase, and the raising and lowering of the substrate. Operating conditions such as speed and surface pressure may be appropriately selected depending on the type of monomolecular film-forming compound used, the characteristics of the film to be formed, and the like.

By the single molecule accumulation method as described above, 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 and a second layer consisting of a monomolecular film or a monomolecular cumulative film having a desired configuration are formed in this order using a material capable of forming the first layer and second layer described above. Laminated on the previously formed third 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 initial monolayer formation, 1. Materials such as T and O for forming a transparent electrode layer may be laminated by a vapor deposition method or the like.

In addition, if the two electrodes are both transparent, the transparent electrode layer may be formed using the above-mentioned material on the transparent substrate for monomolecular film formation, and the transparent electrode layer may be laminated after the formation of the light emitting layer is completed. .

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 first layers among the plurality of $1 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, although the light-emitting layer of the EL element of the present invention is composed of a plurality of monomolecular films and has a multilayer structure with a plurality of interfaces that emit light as described above, the entire light-emitting layer is The thickness is extremely thin, and even when driven at low voltage, an efficient light emitting state can be obtained, and sufficient brightness can be obtained.

Moreover, in the EL device of the present invention, each layer of the light emitting layer is formed of a monomolecular film, so the functional parts of the compound directly involved in light emission are directed toward the interface with high order and precision. It becomes possible to emit light based on the formation of an exciplex that is oriented and arranged and receives and transfers electrons more efficiently, and each layer can be formed at room temperature and pressure, which is different from conventional methods such as vapor deposition. Even heat-sensitive organic compounds that could not be used can now be used as constituent materials, and the EL device of the present invention has become an inexpensive and mass-producible EL device.

Furthermore, even when the EL device of the present invention is formed as a large-area EL device, the large-area light-emitting layer is formed with high precision by the single-molecule accumulation method, and it has good functionality.

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 1,500 mm was formed on a 50 mm 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 10'4 in ngmuir-Trough 4
mol/l (7) It was immersed in an aqueous phase whose PFI was adjusted to 6.5 by containing CdCI2.

Next, araxic acid was converted to chlorophor Ak: IXIQ=m
ol/j! 0.5 mj of a solution dissolved at a concentration of! , and 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/c, and a film of araxic 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 2 cm/inch in the direction across the water surface, and the third layer, a monomolecular film insulating layer made of araxic acid molecules, was applied to the electrode plate. form on a layer, pull this out of the aqueous phase, 3
It was left to dry at room temperature for 0 minutes or more.

Here, the alexic acid remaining on the surface of the aqueous phase is completely removed from the surface of the aqueous phase, and the electrode plate on which the monomolecular insulating layer made of alexic acid is formed is immersed again in the aqueous phase.
0.5 ml of a chloroform solution containing fresh LX 10-" mol/A was spread on this aqueous phase, and the surface pressure was adjusted to 30 dyne/cm. Then, the electrode plate was moved 2 cm across the water surface. /win to form a monomolecular film made of the above compound molecules on the insulating layer as a second layer.Next, this electrode plate was pulled out of the water phase and left at room temperature for at least 30 minutes again. and dried.

Furthermore, the above compound left on the surface of the aqueous phase is completely removed by LX
0.5 +/! of a chloroform solution containing at a concentration of 10-3 mal//! was developed on this water phase, and the surface pressure was set to 30c.
jyne/cm, the electrode plate was gently pulled up at a speed of 2 cm/win in the direction across the water surface, and a monomolecular film made of the above compound molecules was formed as a first layer on the $2 layer.

Thereafter, the above-described formation operation from the third layer to the first 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 (layer thickness: about 400 layers) having four interfaces of layers was formed.

The electrode plate on which the light-emitting 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" Torr, and the vacuum level was adjusted to 20A
An EL device of the present invention was formed by depositing an A1 layer of 1500 A on the last formed third layer at a deposition rate of /sec as a back electrode. As shown in FIG. 4, this EL element was sealed with a sealing glass 41, and then silicone oil 42, which had been purified, degassed, and dehydrated according to a conventional method, was injected into the seal to form an EL nacelle 3.

Konoyo Una EL SE J1z electrode 44.45N, 10V,
An AC voltage of 400 Hz was applied to emit light, and the luminance and current density of the emitted light were measured. The results are shown in Table 1.

Examples 2 to 4 The formation operation from the third layer to the first layer was performed 8 times (Example 2
), 12 times (Example 3) or 16 times (Example 4). (Example 3) or 16 (Example 4) EL elements of the present invention were respectively formed, and these were used to create an EL nacelle.

Each EL nacelle was caused to emit light in the same manner as in Example 1, and the brightness and current density at that time were measured. The results are shown in Table 1.

Example 5 A film with a thickness of 1500A was deposited on a 50+w+w glass surface by sputtering. A T and 0 layer was formed to obtain a transparent electrode plate. This electrode plate was placed in a 4x1
It was immersed in an aqueous phase whose pH was adjusted to 6.5 by containing 0' mol/jl of CdCl2.

Next, add araxic acid to chloroform.IX10-3m
0.5 ■ of a solution dissolved at a concentration of ol/jl! 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 3 Qdyne/cm, and a film of araxic acid was precipitated on the surface of the aqueous phase.

Furthermore, while keeping the surface pressure constant, the electrode plate was gently reciprocated vertically twice at a speed of 2 cm/sin in the direction across the water surface to form an insulating layer consisting of four accumulated monomolecular films of alexic acid. A third layer was formed on the electrode layer of the electrode plate, pulled out of the aqueous phase, and left to dry at room temperature for 30 minutes or more.

Here, the alexic acid remaining on the surface of the aqueous phase is completely removed from the surface of the aqueous phase, and the electrode plate on which the monomolecular insulating layer made of alexic acid is formed is immersed again in the aqueous phase.
0.5 mj! of a chloroform solution containing a fresh IX l (1" mol #!) was spread on the water phase, and the surface pressure was adjusted to 30 dyne/cm. Then, the electrode plate was moved 2 cm in the direction across the water surface. A first layer consisting of three monomolecular films made of the above compound was formed on the insulating layer 2 by gently pulling and pulling at a speed of 1/min, and then pulling and pulling once. Next, this electrode plate was taken out of the aqueous phase and left to dry again at room temperature for 30 minutes or more.

Next, the above compound left on the surface of the aqueous phase is completely removed, the electrode plate is immersed in the aqueous phase, and a new IX 10-"
mol#! 0.5 m of chloroform solution containing at a concentration of
A was developed on the aqueous phase, and the surface pressure was set to 30 dyne/Cl.
After adjusting the electrode plate to 11, move the electrode plate 2 in the direction across the water surface.
The layer was gently pulled up at a speed of cm/+*in, and then lowered and pulled up once each to form a second layer of 3M of the above-mentioned compound on the first layer.

Thereafter, the above-described formation operation from the third layer to the second layer is repeated four times, and finally the third layer is further laminated to form a light-emitting layer having four interfaces between the first layer and the second layer. (Layer thickness: approx. 1000
people) 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 to' Torr.
At a deposition rate of OA/sec, an A1 layer of 1,500 mL was evaporated onto the last formed third layer to form an EL device of the present invention as a back electrode. As shown in FIG. 4, after this EL element is sealed with a sealing glass 41, a silicone oil 42 is purified, degassed, and dehydrated according to a conventional method.
was injected into the seal to form the EL nacelle 3.

To such an EL nacelle electrode 44.45, lO■, 40
An AC voltage of 0 Hz was applied to emit light, and the luminance and current density of the emitted light were measured. The results are shown in Table 1.

Table 1

[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 diagram of the molecular structure of a monolayer-forming compound, 3a.
Figures 3 and 3b are schematic diagrams showing typical examples of the arrangement of molecules at the interface between the first layer and the second layer of the EL device of the present invention, and Figure 4 is a schematic diagram showing a typical arrangement of molecules at the interface between the first layer and the second layer of the EL device of the present invention. FIG. 2 is a schematic cross-sectional view of an EL nacelle. 1.44: Transparent electrode layer 2.45: Electrode layer 3: Light emitting layer 4-1.4-2.4-3: Third layer 5-1, j-2, 5-3: First layer 6 -1;8'-
2.8-3: Second layer 7-1.7-2: Interface 21.31.31': Functional part 22.32.32': Hydrophilic part 23.33.33': Hydrophobic part 40 :EL element 4! Nigarasu Seal 42: Silicone Oil 43: EL Nacelle Applicant Canon Co., Ltd. Figure 1 Figure 2 (a) (b) Figure 38 (a) Figure 3b

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. a first layer, a second layer containing an organic compound relatively exhibiting electron-donating properties, and a third layer having electrical insulation properties.
The first layer, the second layer, and the third layer are formed on the third layer from one of the electrode layers to the other two or more times in this order. The first layer, the second layer, and the third layer are made of a monomolecular film or a monomolecular cumulative film of a compound capable of forming each of these layers. An electroluminescent device characterized by: