JPS6137859A - 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: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 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 with a thickness of 0.01-0.3mum at least one of which is transparent, thus forming a luminous layer 3 with a thickness of 1mum or less.

Description

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

[Prior art]

An EL element has a structure in which a light-emitting layer containing a material with an EL function, that is, a material that emits light when placed in an electric field, is placed between two electrodes, and a voltage is applied between these electrodes. A light-emitting element that generates light by generating an electric field and converting electrical energy directly into light.
For example, unlike traditional light emitting methods, such as incandescent light bulbs where a filament is heated to emit light, or fluorescent light, where electrically excited gas imparts energy to a phosphor and causes it to emit light, thin panels are used. For example, various shapes such as a shape, a belt shape, a cylindrical shape, etc.

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

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

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

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

Thin-film EL devices have a thin light-emitting layer that allows the distance between the electrodes to be sufficiently shortened, and a stronger electric field can be generated within the light-emitting layer, allowing for 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 a thin film forming method such as vapor deposition using the above-described ZnS-based metal material, the manufacturing cost becomes extremely high. In addition, it is very difficult to form a light-emitting layer made of a uniform thin film over a large area, so 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 laminated in this order two or more times on the layer of
The layer and the second layer are characterized in that they are made of a monomolecular film or a monomolecular cumulative film of a compound capable of forming these respective layers.

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

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

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

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

1.2 is an electrode for generating an electric field by applying a voltage, and 1 is a transparent electrode for extracting the generated light. 3 is a light-emitting layer having an EL function, and a first layer 5-1.5-2 is placed between a third layer 4-1.4-3 which functions as an insulating layer laminated on both ends of the bottom. It has a multilayer structure in which the second layer 8-1.6-2 and the third layer 4-2 are alternately stacked, and the first layer 5-1.5-2 and the third layer 4-2 are stacked alternately. The second layer 8-1, 6-2 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 a compound that can be an EA compound with respect to the above-mentioned ED compound contained in the second layer 6-1, and is in direct contact with the first layer 5-1. The second layer 6-1 laminated in this manner contains a compound that can be an ED compound with respect to the EA compound contained in the first layer 5-1, and the first layer 5-1 and the second layer 8 -1 interface 7-1
is the contact surface between the EA compound and the ED compound. The relationship between the first layer 5-2 and the second layer 6-2 is similar to this, and the interfaces 7-2 are uniquely formed by these layers.

These interfaces? -1, 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.

First layer 5 constituting the light emitting layer of the EL element of the present invention
-1.5-2 and the second layer 6-1.6-2 contain compound molecules directly involved in the formation of the field-excited complex as shown below, or at least one of the compound molecules as a functional moiety. It is formed from a monomolecular film or a monomolecular cumulative film containing compound molecules having as.

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

(a) First layer 5-1.5-2 and second layer 6-1.8-
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 compounds (ED compounds) that can serve as electron donors for these compound molecules are arranged in the second layer 6-1, 6-2, respectively.

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

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

Examples of such compounds include fused polycyclic aromatic hydrocarbons, p-terphenyl, 2,5-diphenyloxazole, 1,4-bis-(2-methylstyryl)-benzene, xanthine, coumarin, acridine, and cyanine. Pigments, benzophenones, phthalocyanines, metal complexes of phthalocyanines, porphyrins, metal complexes of porphyrins,
8-hydroxyquinoline, metal complexes of 8-hydroxyquinoline, ruthenium complexes, rare earth complexes, and derivatives of these compounds, as well as heterocyclic compounds other than the above and their derivatives, aromatic amines, aromatic polyamines, and quinone structures. Among the compounds, there are compounds that have an EL function based on exciplex formation, and among these compounds, there are one or more compounds that can be relatively EA compounds, and one or more compounds that can be relatively ED compounds. are selected and combined as appropriate to form the structure (a) of the first layer and second layer described above.
A light-emitting layer having the following 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 Interface 7-1 between first layer and second layer.
The light emission in the first layer 5-1, 5-2 and/or the second layer 8-1,
It may also include a case where light is emitted within B-2.

In order to form a monomolecular film or a monomolecular cumulative film containing a compound described in A so-called single molecule accumulation method, which can be easily formed, 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 hydrophilic part and a hydrophobic part, when the balance between the two (amphiphilic balance) is maintained at an appropriate level, many of these molecules have a hydrophilic part and a hydrophobic part on the water surface. Form a monolayer with the woody part facing down. This monomolecular layer has the characteristics of a two-dimensional system, and when these molecules are sparsely dispersed, the two-dimensional ideal gas equation: rTA
= kT (k: Portzmann's constant, T: absolute temperature), and these molecules form a "gas film", but A
When S is made sufficiently small, intermolecular interactions become stronger and these molecules form a two-dimensional solid "condensed film (or solid film)". This condensed film can be transferred to the surface of a substrate such as glass. An ultra-thin monomolecular film or a cumulative film thereof can be formed on a substrate.

According to this method, the molecules forming the monolayer are arranged in the same direction within one monolayer, for example, almost all of the hydrophilic parts of the constituent molecules are oriented toward the substrate in a highly ordered manner. It can be done as follows.

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. It is a compound that has at least one sexual moiety. Among these compounds, monolayer-forming compounds have, for example, monolayer-forming compounds that have one functional moiety. As shown in the schematic diagram of the structure, (a) the functional part 21 is on the side of the woody part 22, - Figure 2 (a), (b) the functional part 21 is on the side of the hydrophobic part 23, -Figure 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).

15 - Constituent elements of the hydrophilic portion 22 of these compounds include:
For example, carboxyl groups and their metal salts, amine salts and esters, sulfonic acid groups and their metal salts and amine salts, sulfonamide groups, amide groups, amino groups, imino groups,
Examples include a hydroxyl group, a quaternary amino group, an oxyamino group, an oxyamino group, a diazonium group, a guanidine group, a hydrazine group, a phosphoric acid group, a silicate group, an aluminate group, and each may be used alone or in combination. The hydrophilic portion 22 in the above compound can be constituted by the above compound.

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
A schematic cross-sectional partial view near interface 7-1 in the figure (in this figure, the layer of tube 1 and the second layer are formed from a monomolecular film consisting only of a compound having one functional part) is shown. (1) The wood-loving portion 32 having the functional portion 31 of the molecules forming the monolayer of the first layer 5-1, and the second layer 6-1.
A hydrophilic portion 32' having a functional portion 31' of molecules forming a monomolecular film is oriented at the interface 7-1.

(2) 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 hydrophobic part 33' having the functional part 31' of the molecule forming the monolayer is an interface? -1 orientation.

(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.
A functional portion 31' of molecules forming a monolayer and a tree-philic portion 32' are oriented at the interface 7-1.

- Figure 3b (D-) (4) 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 8-1.
The hydrophobic part 33' having the functional part 33' of the molecule forming the monomolecular film is an interface? -1 orientation.

Figure 3b ζb) 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 /Mata are such that even when the second layers B-1 and e-2 are composed of monomolecular cumulative films, the interface between the first layer and the second layer takes the above pattern. , the interface between the first layer and the second layer? What is necessary is to form a monomolecular film constituting -1 and 7-2.

Note that the first layer 5-1.5-2 and/or the second layer 6
-1.6-2 is composed of a monomolecular cumulative film, each of the monomolecular films constituting the cumulative film may be the same, and one or more of the monomolecular films may be different from other monomolecular films. It may be different from a monomolecular film. 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). structure facing each other), X
type (structure with the hydrophobic part facing the substrate side of each school), Z type (
Various structures can be used, such as a structure in which the parent tree portion faces the substrate side of each school) and modified structures thereof. Furthermore, the monomolecular film included in the first layer and the second layer of the light emitting layer of the EL device of the present invention may be a multicomponent monomolecular film formed of two or more kinds of compounds. In such cases, these layers may be formed by combining two or more types of compounds having functional moieties, or by adding other materials to increase the strength of the monomolecular layer constituting the light-emitting layer or to improve adhesion between each layer. It may be formed by adding the ingredients.

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 well-balanced lignophilic part and hydrophobic part can be used as they are for forming a monomolecular film,
If this is not the case, a monomolecular film-forming compound can be obtained by newly introducing a parent tree group and/or a hydrophobic group as mentioned above into the molecule. 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. Also,
゛ -←=td, R represents an alkyl group having about 4 to 30 carbon atoms, preferably about 10 to 25 carbon atoms, and having a linear or side chain.

5・6゜7.8・21・22゜(C
H2) nX 6≦n≦20 23°CH3! 24゜0≦n≦2 25゜26゜28゜htct, ybcl M=Er+Sm+Eu+Gd+Tb+DLTm+Yb◎
D, -0Hs, -t-Bu 34゜M = Er, Sm + Eu l Gd + Tb
+ Dy l 'I'rn I ybM-Er, Sm
, Eu, Gd, Tb, 'Dy, Tm+YbR+-H,-
Mountain, -CF3. 86, 87as of H.

39, 40°48.
44°H (G!Hz) X 62°RR 69・70°-R 71, 72°78, 74°77,
7B.

84, 85゜88゜(CI(2) <A compound having an EL function is modified with a hydrophobic group and/or a parent tree group to form a monolayer-forming compound.

The compounds of the structural formulas N642 to N654 and Sui 85 to Makoto 86 have structures in which an alkyl chain is directly bonded to the functional moiety, but the bond of the alkyl chain to the functional moiety is, for example, an ether bond. , a bond via a carbonyl group, etc. may be used.

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. The materials that can form these third layers include the general formula that can form a uniform insulating layer with high precision: CH2 leak-CH5CH20CO-
+CH2 circle, □CH3 (In the above formula, n is 10≦n≦30, and X
is -COOH, -CONH2, -GOOR, -N (C
:H3):+, CI-.

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

Although the EL element of the present invention having two interfaces formed by the first layer and the second layer has been described 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 Q of the EL device and the structure of each layer itself. A or less, preferably 1008 or less, for the second layer, 3008 or less, preferably 1
00 A or less, the third layer is 500 Å or less, preferably 200 Å or less, and the thickness of the entire light emitting layer is 13 ua or less, preferably 3000 Å or less, which is good for low voltage driving. This is desirable in order to obtain a light-emitting state.

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, 51102, 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 0.01. gm to about 0.3u1, preferably about 0.05u1 to 0.2 tiles.

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

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

The following is a typical operation of the single molecule accumulation method represented by the Langmuir-Blodgett method (LB method) applied to the formation of the first layer and the second layer of the light emitting layer of the EL device of the present invention. explain.

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.
A surface pressure n proportional to the aggregate state is obtained. Then, the partition plate is operated to reduce the developed area and gradually increase the surface pressure (2) to set the surface pressure (H) to a value 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.

In order to transfer a monomolecular film onto a substrate, in addition to the vertical immersion method described above, there is also a horizontal adhesion method in which the substrate is brought into contact with the water phase horizontally while keeping it parallel to the surface.1 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 above-mentioned vertical dipping method, the orientation of the film-forming molecules is reversed between the pulling step and the dipping step of one normal substrate, 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 and the second layer of the light emitting layer of the EL device of the present invention by the single molecule accumulation method.
The operating conditions, such as the type and amount of additives used to adjust the pH of the aqueous phase, the temperature of the aqueous phase, the lowering rate or surface pressure of the substrate, etc., depend on the monolayer-forming compound used. It may be selected appropriately depending on the type, characteristics of the film to be formed, etc.

At least one of the two electrodes M1.2 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, 5J102, insium tin oxide (1,7,0), 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 a normal electrode with sufficient conductivity, or a thin plate made of a material that can form an ordinary electrode with sufficient conductivity, or an Al layer directly formed on a suitable substrate or on a light emitting layer formed.
, Ag, Au, etc. can be laminated by a vapor deposition method or the like.

The thickness of these electrode layers is about 0.01 g to 0.3 tiles,
Preferably 0.05. It is said to be about 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 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 1X1
By applying a direct current, alternating current, or pulse voltage so that an electric field of about 0.05 to 3.0 x to'' is applied, good light emission can be obtained from the light emitting layer 3 through the transparent electrode.

Hereinafter, typical single-molecule accumulation methods such as the Langmuir-Prodgett method (LB method) applied to the formation of the first layer and the second layer of the light-emitting layer of the E and L elements of the present invention will be described. Explain the operation.

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.
A surface pressure n proportional to the aggregate state is obtained. Then, the partition plate is operated to reduce the developed area and gradually increase the surface pressure (2) to set the surface pressure (H) to a value suitable for forming a monomolecular film. Now, when the substrate that has already been immersed is gently moved up and down in the direction perpendicular to the aqueous phase surface while maintaining this surface pressure n, the monomolecular film is formed as the substrate moves upward and downward. is transferred to substrate-L 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 single molecule H'J is transferred to the surface of the 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 above-mentioned vertical dipping method, the orientation of the film-forming molecules is usually reversed between the substrate removal step and the dipping step, 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 groups and hydrophobic groups can also be changed by surface treatment of the substrate, etc. 6 Furthermore, by a single molecule accumulation method, the first layer and pH of water phase when forming second layer
2. The type and amount of additives for adjusting the pn, etc. of the aqueous phase, the temperature of the aqueous phase, the operating conditions such as the rate of raising and lowering the substrate, or the surface pressure, etc., are determined by the type of monomolecular film forming compound used,
It may be selected appropriately depending on the characteristics of III to be formed.

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 desired third layer is formed on the substrate on which the transparent electrode layer as described above is provided, using the above-mentioned third layer forming material by vapor deposition or the like, and then the above-mentioned first layer is formed. A first layer consisting of a monomolecular film or a monomolecular cumulative film of a desired configuration using a material capable of forming a second layer,
The second layer is laminated in this order 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 forming the first light-emitting layer, the final
．． A material for forming a transparent electrode layer such as No. 7.0 may be laminated on the light emitting layer by vapor deposition or the like. In addition, when the two electrodes are both transparent, a transparent electrode layer may be formed using the above-mentioned material on a transparent substrate for forming a light emitting layer, and the transparent electrode layer may be laminated after the formation of the light emitting layer is completed.

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

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

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

In addition, the first
Although the layer and the second layer are formed from a monomolecular film or a monomolecular cumulative film, and have a multilayer structure with multiple interfaces that emit light as described above, the overall layer thickness of the light emitting layer is It has become extremely thin, and even when driven at a low voltage, an efficient light emitting state can be obtained, and sufficiently high brightness can be obtained.

Moreover, in the EL device of the present invention, the first layer directly involved in the light emission of the light emitting layer is formed by the monomolecular film or the monomolecular cumulative film.
layer and the second layer are formed, the functional parts of the compound that are directly involved in light emission are oriented and arranged toward the interface with high order and accuracy, resulting in more efficient transfer and reception of electrons. It is now possible to emit light based on the formation of an exciplex, and the first and second layers can be formed at almost normal temperature and pressure, which could not previously be used in vapor deposition methods. Heat-sensitive organic compounds can also be used as constituent materials, and the EL device of the present invention is an inexpensive and mass-producible EL device.
It became Motoko.

Furthermore, even when the EL device of the present invention is formed as a large-area EL device, the light-emitting layer is formed with high precision, resulting in an EL device with good functionality.

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

Example 5 A 1.7.0 layer with a thickness of 1500 was formed on a 50 mm square glass surface by sputtering to obtain a transparent electrode plate.

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

This electrode plate was attached to a Lang
4X 10' mo in muir-Trough 4
l/j! By containing CdCl2, the pH is 6.
It was immersed in an aqueous phase adjusted to 5.

Next, at a ratio of 1 mol: 1 mol, the total amount of these is 1 x 10-3 mol/j! 0.5 mj of a solution dissolved in chloroform so that! was developed on the aqueous phase, and the surface pressure was set to 30 dY? After the multi-component monomolecular film consisting of the above two compounds was deposited on the surface of the aqueous phase, the electrode plate was gently moved up and down in the direction across the water surface at a speed of 2 cm/inch. By reciprocating, a monomolecular cumulative film as a second layer consisting of four monomolecular films made of the mixture of the above compounds was formed on the previously formed third layer. here,
This electrode plate was taken out of the aqueous phase and left to dry at room temperature for 30 minutes or more.

Furthermore, the above compound left on the surface of the aqueous phase was completely removed, the electrode plate was immersed in the aqueous phase, and a new (OH2) 10 C
0.5 mj+ of a chloroform solution containing 0NI(2) at a concentration of l x 10' mol/j! is developed on this aqueous phase,
The surface pressure was adjusted to 30 dyne/cm, a monomolecular film made of this compound was deposited on the aqueous phase, and the electrode plate was gently pulled up at a speed of 2 cm/min in a direction across the water surface, followed by further immersion and pulling. A monomolecular film formed by stacking three monomolecular films composed of the above compound molecules was formed as a first layer on the previously formed second 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 and second layers.
Luminescent layer with 4 layer interfaces (layer thickness: approx. 1700 layers)
was formed.

The electrode plate on which the luminescent layer was formed in this manner was placed in a vapor deposition tank, and the pressure inside the tank was first reduced to a vacuum level of 10' Torr, and then the vacuum level was further adjusted to 10' Torr. At a deposition rate of 1,500 sec, an A1 layer of the present invention was deposited on the last formed third layer to form the back electrode.
An L element was formed. 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 cell 43.

For such an EL nacelle electrode 44.45, 10■, 40
When an AC voltage of 0 Hz was applied to cause light to emit light and the brightness and current density of the light emission were measured, the current density was 0.0.
At 8 mAIcm2, the brightness was 20 Ft-L.

[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.
Figure 311I shows the EI of the present invention, the $1 that the device has
FIG. 4 is a schematic diagram showing a typical example of the arrangement of molecules at the interface between the first layer and the second layer.
FIG. 3 is a schematic cross-sectional view of the nacelle. 1.44: Transparent electrode layer 2.45: Electrode layer 3: Light emitting layer 4-1.4-2.4-3: Third layer 5-1.542, 5-3: First layer 13-1 .6-
2.6-3: Second layer? -1.7-2: Interface 21.31.31 ” : Functional part 22.32.32 ” : Hydrophilic part 23.33.33 ” : Hydrophobic part 40 : EL element 41 Glass seal 42 : Silicone oil 43: EL cell Fig. 1 Fig. 2 (a) Fig. 3a (a) Fig. 3b Cow 5 Fig. 4 ゛

Claims (1)

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