JPS6137870A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To provide an intrinsic electroluminescent element in the form of thin film achieving an excellent luminescence efficacy by low drive voltage, by a construction wherein an insulating layer, electron-accepting layer, and electron- donating layer are laminated repeatedly in this order to form a luminous layer and, furthermore, a particular layer is composed of a monomolecular (cumulative) film. CONSTITUTION:The third layer comprising an insulating material 4-1 (or 4-2, 4-3), the first layer comprising an electron-accepting org. compd. (contg. a relatively electron-donating org. compd.) 5-1 (or 5-2, 5-3), and the second layer comprising an electron-donating org. compd. (contg. a relatively electron-accepting org. compd.) 6-1 (or 6-2) are laminated to form a luminous layer 3 [with the proviso that the first layer is composed of a monomolecular (cumulative) film]. Then, a transparent electrode 1 and an electrode 2 respectively are provided on each side of said luminous layer 3 to yield an electroluminescent element emitting mainly at interfaces 7-1, 7-2.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an electroluminescent device (electroluminescent (E, L) device) that performs electroluminescence, and more particularly, it relates to an electroluminescent (E, L) device that performs electroluminescence, and more specifically, it is a method of using two types of thin films made of organic compounds and having different electrochemical properties. It has a layer with an EL function that combines the
Regarding L elements.

[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 of a thin film type, which has a thin film made of a material with EL function as a light-emitting layer, and those formed by dispersing a material with EL function in a binder. It is broadly classified into two types: a powder type that has a light emitting layer and a powder type that has a light emitting layer.

In addition, as materials having the above-mentioned EL41 ability, conventionally,
Mn, Cu or ReF3 (Re represents rare earth)
Inorganic metal materials such as ZnS containing ZnS as an activator have been mainly used.

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

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

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

On the other hand, recently, various thin film formation methods have been used to control the chemical structure and higher-order structure of organic compound materials that can be used to form thin films with high precision, and optical and As materials for electronics, their use in applications such as electrochromic elements, piezoelectric elements, pyroelectric elements, nonlinear optical elements, and ferroelectric liquid crystals is drawing attention. It is expected that it will be used as a material for

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 electrically insulating properties, and the first layer further contains another compound that can serve as an electron donor to the relatively electron-accepting organic compound. ,
and the second layer contains another compound that can serve as an electron acceptor for the organic compound relatively exhibiting electron donating properties, and these layers.

The first layer, the second layer, and the third layer are repeatedly stacked in this order two or more times on the third layer from one of the electrode layers to the other.

Furthermore, the first layer is characterized in that it consists of a monomolecular film or a monomolecular cumulative film of a compound capable of forming the layer.

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

The light-emitting layer of the EL device of the present invention includes an organic compound (hereinafter abbreviated as EA compound) that exhibits a relatively electron-accepting property;
A compound that can become an electron donor to the EA compound (hereinafter referred to as an EA-d compound) is placed at a position where organic compounds that are relatively electron donating (hereinafter referred to as ED compounds) are in contact with each other and around the EA compound. (abbreviated as E), but also the above E
It has a structure in which compounds (hereinafter referred to as ED-a compounds) that can serve as electron acceptors for the compound are arranged around the D compound, and when these compounds are placed in an electric field, the The main source of light is a luminescence effect based on the formation of an exciplex through the exchange of electrons between the ED compound and the EA compound. It is characterized by having a structure suitable for efficient formation as it occurs.

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

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

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

The first layer 5-1 of the light-emitting layer 3 contains as a main component a compound that can be an EA compound with respect to the above-mentioned ED compound contained in the second layer 6-1, and this first layer 5-1 The second layer 6-1 is laminated in direct contact with the first layer 5-1.
Contains as a main component a compound that can become an ED compound with respect to the EA compound contained in 1, and the interface 7-1 between the first layer 5-1 and the second layer B-1 is the contact between the EA compound and the ED compound. It is a face. First layer 5-2 and second layer 6-2
The relationship between
-2 is uniquely formed.

At these interfaces 7-1 and 7-2, 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.

Furthermore, the first layer 5-1.5-2 contains EA- which can act as an electron donor for the EA compound which is the main component of these layers.
d compound is mixed, and this EA-d compound is E
It mainly has the function of increasing the electric field excitation efficiency of the EA compound through interaction with the EA compound, such as donating electrons to the A compound.

In addition, the second layer 6-1, 6-2 contains ED-, which can act as an electron acceptor for the ED compound that is the main component of these layers.
A compound is mixed therein, and this ED-a compound also mainly has the function of increasing the electric field excitation efficiency of the ED compound through interaction with the ED compound, such as receiving electrons from the ED compound.

The ED-a and EA-d compounds can control the electrochemical properties of the first layer and the second layer as desired, such as controlling the emission color, by interacting with the EA compound and the ED compound. In addition to the above-mentioned functions, the controller may also have a function of controlling the above-mentioned functions.

First layer 5 constituting the light emitting layer of the EL element of the present invention
-1.5-2 and the second layer 6-1.8-2 contain compound molecules directly involved in the formation of the field-excited complex as shown below, or at least one of the compounds as a functional moiety. The first layer 5-
1.5-2 is formed from a monomolecular film or a medium-molecular cumulative film.

Furthermore, the first layer 5-1.5-2 contains EA-4, which can act as an electron donor for the EA compound that is the main component of these layers.
A compound is included as a subcomponent, and the second layer 13-1
．． 6-2 contains as a subcomponent an ED-a compound which can serve as an electron acceptor for the ED compound which is the main component of these layers.

A light emitting layer 3 of a compound molecule directly involved in the formation of an electric field excited complex contained as a main component in the first layer and the second layer.
As for the arrangement within, the following combinations can be cited as typical ones.

(a) First layer 5-1.5-2 and second layer 8-1.8-
A compound molecule having an EL function (mainly emitting light) based on exciplex formation is arranged in each of 2.

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

(c) A compound molecule having <EL function based on exciplex formation is placed in the second fi 8-1.6-2.

Compounds that can act as electron acceptors for these compounds (E
A compound) molecules are arranged in the first layer 5-1, 5-2, respectively.

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

Examples of such compounds include fused polycyclic aromatic hydrocarbons, p-terphenyl, 2,5-diphenyloxazole, 1,4-bis-(2-methylstyryl)-benzene, xanthine, coumarin, acridine, and cyanine. Pigments, benzophenone, phthalocyanine, metal complexes of phthalocyanine, porphyrin, metal complexes of porphyrin, 8-hydroxyquinoline, metal complexes of 8-hydroxyquinoline, ruthenium complexes, rare earth complexes, and derivatives of these compounds, and heterocycles other than those listed above. Based on exciplex formation, <EL
Among these compounds, one or more compounds that can relatively become an EA compound and one or more compounds that can become an ED compound are appropriately selected and combined, and the above-mentioned first The composition of the layer and the second layer (a
) for the first layer using the single molecule accumulation method described later, and for the second layer using the vapor deposition method, CV
It can be formed using a thin film forming method such as the D method.

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

Furthermore, EA which is the main component of the first layer contained in the first layer
an EA-d compound that can serve as an electron donor to the compound;
The ED-a compound that can serve as an electron acceptor for the ED compound that is the main component of the layer @2 contained in the second layer has <EL function (mainly Compounds that emit light), compounds that can act as electron donors or acceptors for the compound, compounds that can become a light emitter through transfer of excitation energy, and compounds that have at least one of these compound molecules as a functional moiety. I can do it. When forming the first layer and the second layer, these EAs are selected depending on the compound used as the main component of the first layer and the second layer.
-d and EII-a compounds may be appropriately selected and used so that they have the above-mentioned functions. Amount of EA-d compound relative to EA compound and ED-a relative to ED compound
The amount of compound will vary depending on the compounds used in the first layer and the second layer - cannot be generally specified, but typically EA
-d compounds, from 10 mol% to 0.0% of the EA compound.
For the ED-a compound, it is about 10 mol% to 0.1 mol% of the ED compound.

Note that the compounds that can be the ED and EA compounds mentioned above may be compounds that have a function of emitting light that is not based on the formation of an exciplex, and furthermore, the compounds that can be used as the ED and EA compounds may be compounds that have a function of emitting light that is not based on the formation of an exciplex.
The compound that can become the -a compound may also have an EL function, and the light emission in the EL element of the wooden invention is the first
The interface between the layer and the second layer? -1, 7-2, but also light emission in the first layer 5-1, 5-2 and/or the second layer 6-1, 6-2. It may also include cases in which it is carried out.

In order to form a monomolecular film or a monomolecular cumulative film containing the above-mentioned compound or a compound having the compound molecule as a functional part, it is necessary to enable highly ordered molecular orientation and arrangement and to easily form an ultra-thin film layer. The so-called single molecule accumulation method 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 woody part facing down.

This monomolecular layer has the characteristics of a two-dimensional system, and when these molecules are sparsely dispersed, the two-dimensional ideal gas equation between the area A per molecule and the surface pressure ■; nA = kT.
(k: Portzmann's constant, T: absolute temperature), and these molecules form a ``gas film.'' However, when A is made sufficiently small, intermolecular interactions become stronger, and these molecules form a ``condensed film'' of a two-dimensional solid (or solid This condensed film can be transferred onto the surface of a substrate such as glass, and an ultra-thin monomolecular film or a cumulative film thereof can be formed on the substrate.

According to this method, the orientation of the molecules forming the monolayer is such 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 making the first layer of the light-emitting layer of the EL device of Wood's invention a monomolecular film or a monomolecular cumulative film, the functionality consisting of compound molecules directly involved in the formation of an exciplex contained in the first layer can be improved. It becomes possible to arrange the portions 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 compounds contained in the first layer and the second layer of the light emitting layer of the EL device of the present invention include the above-mentioned E D ,
It is a compound having at least one of EA, ED-a, and EA-d compounds, or any of these compounds as a functional moiety. Among such compounds, monolayer-forming compounds, for example, take a compound having one functional moiety, depending on the position within the molecule containing the functional moiety, the second V! As shown in the schematic diagram of the molecular structure of J, (a) the functional part 21 is on the side of the hydrophilic part 22, - Figure 2 (a) (b) the functional part 21 is on the side of the hydrophobic part 23 , - FIG. 2(b) (C) The functional part 21 is a hydrophobic part 23 and a hydrophilic part 22
- It is 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, hydroxyl groups, quaternary amine groups, oximino groups, oximino group, diazonium group, guanidine group, hydrazine group, phosphoric acid group, silicate group, aluminate group, etc., and each can constitute the wood-philic moiety 22 in the above compound alone or in combination. .

In addition, the constituent elements of the hydrophobic portion 23 include linear or branched alkyl groups, olefinic hydrocarbons such as vinylene, 'vinylidene, and acetylene, fused polycyclic phenyl groups such as phenyl, naphthyl, and anthranyl,
Hydrophobic groups such as chain polycyclic phenyl groups such as biphenyl can be mentioned, and these can also be used alone or in combination to constitute the hydrophobic moiety 23 in the above compound.

On the other hand, the EA compound contained in 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. The orientation and arrangement are shown in a schematic partial cross-sectional view near the interface 7-1 in Figure 3 (in the case of this figure, the first layer is a single molecule containing a compound molecule each having one functional moiety consisting of an EA compound molecule). As shown in (1) The first layer 5-1 is (E) of molecules forming a monolayer
Is the parent part 32 having the functional part 31 (consisting of compound A) the interface? -1 orientation.

- Figure 3 (a) (2) (E
A hydrophobic portion 33 having a functional portion 31 (composed of compound A) is oriented at the interface 7-1.

Figure 3 (b) It is 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 are preferably used as monolayer-forming compounds containing the above-mentioned EA compound molecules as a functional moiety. . Hereinafter, in order to form the above-mentioned interface pattern (1), it is recommended to use a compound belonging to the above-mentioned type a in the first layer.
In order to form 2), it is preferable to use a compound belonging to the above type b in the first layer.

The types of molecules having a functional portion consisting of the EA-d compound molecules 34 (not shown) include the above-mentioned interface pattern (1), A suitable type may be appropriately selected depending on the EA compound used in '(2).

The example explained above is a case where the first layer is formed from a monomolecular film, but even when the first layer 5-1.5-2 is formed from a monomolecular cumulative film, the first layer 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? -1,? What is necessary is to form a monomolecular film of the first layer constituting -2.

In addition, when the first layer 5-1.5-2 consists of a monomolecular cumulative film, each monomolecular film constituting the cumulative film may be the same, or the monomolecular film One or more of these may be different from other monolayers. Furthermore, the structure based on the orientation state of the molecules forming each monomolecular film of the monomolecular cumulative film is a so-called Y-type structure (between each film, a phyllophilic part and a hydrophilic part or a hydrophobic part and a hydrophobic part are formed). (structures facing each other), x-type (structures with hydrophobic parts facing the substrate side of each side), Z-type (structures with hydrophilic parts facing the substrate side of each side), and various modified structures of these. The structure can be as follows. Furthermore, the monomolecular film forming the first layer constituting the light-emitting layer of the EL device of the present invention contains one or more compounds having an EA compound as a main component as a functional moiety;
A multi-component monomolecular film containing one or more compounds other than one or more compounds having the EA-d compound molecules as a functional part as a subcomponent may also be used. In such cases, other compounds that do not have a single functional moiety but can control the electrochemical properties of the light-emitting layer through interaction with a compound that does have a functional moiety; Compounds that can increase the strength of a monomolecular film or improve adhesion to other layers can be mentioned.

The structure of the monomolecular film or monomolecular cumulative film as described above depends on the desired electrical characteristics of the first layer.
For example, monomolecular films consisting of compounds belonging to type a, b, or type C of the above-mentioned monomolecular film forming compounds may be combined and accumulated to form a monomolecular film. It is possible to control the potential curve of π electrons in the direction perpendicular to the surface direction of the film.

Compounds that can be used to form the first layer 5-1.5-2 include the above-mentioned compounds capable of forming a functional part, or having one or more of these compounds. Among compounds, those that have a good balance of hydrophilic and hydrophobic parts can be used as is for forming monolayers, and those that do not have hydrophilic and/or hydrophobic groups as mentioned above. A group can be newly introduced into the molecule to form a monomolecular film-forming compound.

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

In addition, in the structural formula shown below, X and Y represent the parent wood group as mentioned above, but when both of these exist in one molecule, even if either one is the parent wood group, In such a case, the other one will be hydrogen. Further, R represents a linear or side chain alkyl group having about 4 to 30 carbon atoms, preferably about 10 to 25 carbon atoms.

5.6° 7.8° 21, 22° (CH2
) n
YbCl 32゜M=Er, Sm, Eu, Gd, Tb, Dy, Tm, Yb
84゜M-E r + Sm + Eu + Gd + T
b + Dy + Trn + YbM-Er, Sm,
Eu, Gd, Tb, Dy, Tm, YbR+ -H, -0
H3, CF3, heat 36, 37. 3B.

, 39. 4Q.

48, 44゜■
(mouth 2) X54・
55゜62゜RR 65, 66゜69, 70゜-R 88゜89゜Among these compounds, the compound with the structural formula of Based on the formation of a complex, a compound having an EL function is modified with a hydrophobic group and/or a parent tree group to form a monolayer-forming compound.

In addition, the compounds having the structural formulas of Sutto 42 to N654 and Masu 85 to Sutto 86 have a structure in which an alkyl chain is directly bonded to a functional moiety. It may be a bond, a bond via a carbonyl group, or the like.

Furthermore, among the monolayer-forming compounds exemplified here,
Compounds that can be used in other thin film formation methods such as vapor deposition methods include secondary
It can also be used to form layers. In addition, the second layer also contains one or more compounds having ED-a compound molecules as a main component as a functional part and ED-a compound molecules as a sub-component, as in the first layer. It may also contain one or more other compounds other than one or more of the compounds having it as a functional moiety; in such a case, the other compound may be a compound that does not have a functional moiety but does have a functional moiety. Compounds that can control the electrochemical properties of the light-emitting layer through interaction with the light-emitting layer, as well as compounds that can increase the strength of the second layer and improve adhesion with other layers, etc. can.

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 materials that can form these third layers, the general formula that can form a uniform insulating layer with high precision is as follows: % Formula % (In the above formula, n is 10≦n≦30. ,X
-COOH, -CONH2, -GOOR, -N” (
CH3)3, C1-1, etc.) can be mentioned, and one or more of these materials can be used to form this third compound by a thin film forming method such as a vapor deposition method or a CVD method.
layers can be formed.

Although the EL element of the present invention having two interfaces formed by the first layer and the $2 layer shown in FIG. 1 has been described so far, the EL element of the present invention has two interfaces. The number is not limited to this, and may be three or more.

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,
300A or less, preferably loo A or less, for the second layer, 500A or less, preferably 200A or less,
For the third layer, 500A or less, preferably 200A
A or less, and the layer thickness of the entire light emitting layer is 1u1 or less,
Preferably, it is 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,
ll102.5n02, insium tin oxide (1,7,0), 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 0.3 μ, preferably approximately 0.05 μ to 0.2 μ.

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 and 2 of the device, for example, a 1×1
By applying direct current, alternating current, or pulse voltage so that an electric field of about 0.05 to 3.times.10.sup.6 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 first 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 medium-molecular film-forming compound dissolved or dispersed in a suitable solvent is spread into 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 this precipitate from freely diffusing on the water phase and spreading too much, a partition plate (or float) is provided to limit the development area and create an aggregated 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 first layer of the light emitting layer of the EL element of the present invention by the middle molecule accumulation method.
7. Types of additives and their amounts for adjusting the water phase, etc.
Operating conditions such as M1 degree, substrate raising/lowering speed, or surface pressure may be appropriately selected depending on the type of compound for forming a middle molecular film to be used, the characteristics of the film to be formed, and the like.

The light-emitting layer of the present invention can be formed, for example, in the following manner using the single molecule accumulation method as described above and other thin film forming methods such as vapor deposition.

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

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, gold such as A1, Ag, and Au can be laminated on this third layer by a gold B'e 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 T or O, may be laminated on the light emitting layer by a vapor deposition method 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, for a plurality of interfaces that mainly emit light, the configurations of the two layers constituting the interface are changed for each interface, and these are combined to achieve a desired emission color, etc. It is now possible to control the

In addition, the light-emitting layer of the EL element of the present invention is mainly formed by combining an organic compound material and a thin film formation suitable for the material, and in particular, the first layer of each layer constituting the light-emitting layer is a monomolecular material. Because it is formed from a film or a monomolecular cumulative film, the thickness of the entire 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 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, the first layer that participates in direct light emission of the light emitting layer is formed by the middle molecular film or the monomolecular cumulative film.
layer is formed, so that the functional parts of the compound directly involved in light emission are oriented and arranged toward the interface with high order and accuracy, and the functional parts of the compound directly involved in light emission are oriented and arranged toward the interface, and the functional parts of the compound directly involved in light emission are oriented and arranged toward the interface. Since the light-emitting layer contains a compound that can serve as an electron donor and a compound that can serve as an electron donor, it has become possible to emit light based on the formation of an exciplex that accompanies more efficient transfer of electrons.

In addition, monomolecular films can be formed at room temperature and pressure, and the first layer constituting the light-emitting layer is made of a heat-resistant organic material that could not be used in conventional vapor deposition methods. Compounds can now also be used as building materials.

Furthermore, each layer of the light-emitting layer of the EL device of the present invention can be easily formed as a precise thin film using various organic compound materials, and the EL device of the present invention has become an EL device that 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 film thickness of 1500 A was formed by sputtering on a 50 ff 111 square glass surface to form 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 placed in the resistance heating port, and a catfish was heated to 10" in the tank.
After reducing the pressure to a vacuum level of Torr, the deposition rate was 2A/s.
The current flowing through the resistance heating port was adjusted so that ee was obtained, and a vapor deposited layer consisting of 200 methyl stearate layers was formed as a third layer on the transparent electrode layer of the electrode plate. During vapor deposition, the degree of vacuum in the tank was set to 8×10°6To
rr and the temperature of the substrate holder was 20°C.

The electrode plate was connected to a Lan manufactured by Joyce-Loebe I.
4X 10' in gsu ir-Trough 4
mol/j! By containing CdC:I2 of
It was immersed in an aqueous phase whose H was adjusted to 6.5.

Next, in the ratio of 50 mal: 50 mol: 1 mol, the total amount of these is 1 × 10 ""mol#! 0.5mj of a solution dissolved in chloroform to a concentration of ! was spread on this water phase, the surface pressure was adjusted to 30 dyne/cm, and when a middle molecular film of the above compound was formed on the water phase, the electrode plate was gently moved in the direction across the water surface at a speed of 2 cm/sin. A monomolecular cumulative film, in which four monomolecular films made of the above compound molecules were accumulated by moving up and down twice, was formed as a first layer on the previously formed third layer. 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, this electrode plate is set again in the predetermined position in the vapor deposition tank of the resistance heating vapor deposition apparatus, and 2,5-diphenyloxazole is put into one of the resistance heating ports, and carbazole is put into the other one. After first reducing the pressure in the tank to a vacuum level of 10'Torr, the vapor deposition rate of carbazole was reduced to 0.2 Torr.
The current flowing through the resistive heating port containing carbazole was kept constant so that the current was about A /see, and the deposition rate of the entire vapor deposition layer consisting of a mixture of carbazole and 2,5-diphenylxazole was 2 A/sec. Adjust the current flowing to the port containing carbazole at 20
A vapor deposited layer consisting of a mixture of OA carbazole and 2,5-diphenyloxazole was formed on the insulating layer as the third layer that was previously formed as the first layer. The degree of vacuum in the tank during vapor deposition was maintained at 9 x 10' Torr, and the temperature of the substrate holder was 20°C.

Thereafter, in the same manner as described above, a third layer consisting of two monomolecular films made of stearic acid is laminated on the second layer, and the formation from the first layer to the third layer described above is performed. 4 operations
This was repeated several times to form a light-emitting layer (layer thickness: about 220 OA) having four interfaces between the first layer and the second layer.

The electrode plate on which the light-emitting layer was formed in this way was put back into the vapor deposition tank, and the pressure inside the tank was first reduced to a vacuum level of 104 Torr, and then the vacuum level was further adjusted to 1'O'5 Torr. At a deposition rate of 20A/set, A1 of 1500A
A layer was deposited on the last formed third layer to form the EL device of the present invention 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.

To such an EL nacelle electrode 44.45, 20V, 40
0 [(When an AC voltage of z was applied to emit light and the luminance and current density of the emitted light were measured, the current density was 0.
A luminance of 28 Ft-L was measured at 13 mA/cm2.

[Brief explanation of drawings]

Figure 1 is a schematic sectional view of an example of an uninvented EL element, Figure 2 is a schematic cross-sectional view of an example of an uninvented EL element;
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. l, 44: transparent electrode layer 2.45: electrode layer 3: light emitting layer 4-1.4-2.4-3: third layer 5-1.5-2.5-3 = first layer 6 -1.8-2.8-3: Second layer 7-1.7-2: Interface 21.31: Functional portion 22.32: Hydrophilic portion 23.33: Hydrophobic portion 34: EA-d Compound molecule having a compound as a functional part 40: EL element 41 Nigarasu seal 42: Silicone oil 43: EL cell Fig. 1 Fig. 3

Claims (1)

[Claims] 1) In an electroluminescent device having two electrode layers, at least one of which is transparent, and a light-emitting layer provided between these electrode layers, the light-emitting layer contains an organic compound that relatively exhibits electron-accepting properties. 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 further contains another compound that can serve as an electron donor for the relatively electron-accepting organic compound, and the second layer contains the relatively contains another compound that can serve as an electron acceptor for an organic compound exhibiting electron donating properties, and these layers are arranged on the third layer from one of the electrode layers to the other. The first layer, the second layer, and the third layer are stacked in this order twice or more, and the first layer is a monomolecular film or a monomolecular cumulative film of a compound capable of forming the layer. An electroluminescent device comprising: