JPH08185984A - Organic electroluminescent element - Google Patents

Abstract

PURPOSE: To provide an organic EL element which is transparent as an element and has good emitting efficiency. CONSTITUTION: The thickness of an electron injecting metal layer 6 is set as thin as several nm, and a second transparent conductive layer 7 is laminated on the electron injecting metal layer 6. Since the electron injecting characteristic managing the emitting intensity is ensured by the electron injecting metal layer of several nm, and the absorption of visual light in the electron injecting metal layer can be ignored, an organic EL element haying a high transparency and good emitting efficiency can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of an organic electroluminescence device (hereinafter referred to as "organic EL device").

[0002]

2. Description of the Related Art An electroluminescence (EL) element is useful as a light emitting element for display or illumination, and an organic EL element which can be driven at a low voltage can be said to be a very excellent display element or light emitting element.

FIG. 7 is a sectional view showing a typical organic EL device. The organic EL element is formed on a transparent substrate 1 such as glass by indium tin oxide (ITO) or tin oxide (Sn).
A transparent conductive layer 72 such as O2), a hole transport layer 3 such as a triphenyldiamine derivative, a light emitting layer 4 such as a distyrylbiphenyl derivative, and an aluminum chelate complex (Alq).
Each thin film of the electron transport layer 5 and the metal electrode layer 76 is sequentially laminated.

Here, as the material of the metal electrode layer 76, a metal having a small work function such as magnesium (Mg) or lithium (Li), or Mg-Ag, Mg-Al, Al-L.
Select an alloy with a low work function such as i.

When a direct current voltage is applied to the metal electrode layer 76 so that the transparent conductive layer 72 becomes positive, the light emitting layer 4
EL emission occurs at, and light is emitted to the outside through the transparent substrate 1.

Now, when the light emitting device is obtained as a transparent body,
Various practical effects can be expected. For example, as disclosed in U.S. Pat. No. 4,775,964, when it is used for illuminating a dial for a timepiece, an arrangement under the light emitting element can be seen when the light is not emitted. Can be

In this respect, the general organic EL element described with reference to FIG. 7 is opaque because it has the metal electrode layer 76 with a film thickness of about 100 nm. The transparent organic EL element is described in JP-A-6-151063.

FIG. 8 is a sectional view showing the structure described in the above publication. The transparent conductive layer 72 and the metal electrode layer 76 are both the first transparent conductive layer 82 and the second transparent conductive layer 8 to which a metal is added.
It has been replaced with 6.

The purpose of adding the metal is to add the metal to the first transparent conductive layer 82 and the second transparent conductive layer 86, respectively.
The work function is controlled to increase the injection efficiency of electrons or holes into the organic EL element and further increase the emission intensity.

Here, the light emitting layer 4 and the electron transporting layer 5 in FIG. 7 are replaced with an electron transporting light emitting layer 84 having a one-layer structure.

How to functionally separate the light emitting layer 4 and the electron transporting layer 5 is known as a variation of the organic EL device structure, and is selected in consideration of the light emitting efficiency and the light emitting color. It will be apparent from the following description that the choice can be made freely as far as the invention is concerned.

The black dye layer 87 is provided for the purpose of improving the contrast as a display body.

[0013]

In the conventional organic EL device structure shown in FIG. 8, the inventors of the present invention formed the structure described in the above publication and conducted an experiment. It was difficult to realize the transmittance of the device at the same time.

In the case of adding a trace amount of metal of about 1% or less, the transparency of the transparent conductive layer is hardly affected, but the emission intensity is remarkably reduced, and the transparency is maintained with the addition of metal of several% or more. The present inventors thought that it was not possible.

The present inventors assume that the work function of each transparent conductive layer cannot be sufficiently controlled when a trace amount of metal is added in an amount of about 1% or less as a cause of the decrease in emission intensity.

An object of the present invention is to solve the above-mentioned problems and to make an organic E which is transparent as an element and has a high luminous efficiency.
It is to provide an L element.

[0017]

In order to achieve the above object, the organic EL device of the present invention employs the following means.

In the organic EL device of the present invention, an organic thin film composed of a plurality of layers and first and second electrode layers provided on both sides of the organic thin film are provided in layers on a transparent substrate. An electron-injecting metal layer of a ultra-thin film of a metal with a low work function or an alloy of the metals, which is provided on the organic thin film, and a transparent conductive layer provided on the electron-injecting metal layer. Is characterized in that

In the organic EL device of the present invention, an organic thin film composed of a plurality of layers and first and second electrode layers provided on both sides of the organic thin film are provided in layers on a transparent substrate. An electron-injecting metal layer of a ultra-thin film of a metal with a low work function or an alloy of the metals, which is provided on the organic thin film, and a transparent conductive layer provided on the electron-injecting metal layer. And a colored layer provided on part or all of one side of the structure.

In the organic EL element of the present invention, an organic thin film composed of a plurality of layers and first and second electrode layers provided on both sides of the organic thin film are provided in layers on a transparent substrate. An electron-injecting metal layer of a ultra-thin film of a metal with a low work function or an alloy of the metals, which is provided on the organic thin film, and a transparent conductive layer provided on the electron-injecting metal layer. And the antireflection layer or the light diffusing layer provided on one side of the structure.

In the organic EL device of the present invention, an organic thin film composed of a plurality of layers, and first and second electrode layers provided on both surfaces of the organic thin film are provided in layers on a transparent substrate. An electron-injecting metal layer of a ultra-thin film of a metal with a low work function or an alloy of the metals, which is provided on the organic thin film, and a transparent conductive layer provided on the electron-injecting metal layer. And a colored layer on part or all of one side of the structure, and an antireflection layer or a light diffusion layer on the other side.

The colored layer of the organic EL element in the present invention is
It is characterized in that the color of the colored layer and the emission color of organic electroluminescence have a substantially complementary relationship.

The electron injection metal layer of the organic EL device of the present invention is characterized by having an average thickness of several nm.

[0024]

In the organic EL device of the present invention, the organic thin film composed of a plurality of layers and the first and second electrode layers provided on both sides of the organic thin film are provided in layers on the transparent substrate.

The first electrode layer is composed of a transparent conductive layer, and the second electrode layer is an extremely thin electron injection metal layer of a low work function metal or its alloy provided on the organic thin film, and an electron injection metal layer. It is composed of a transparent conductive layer formed above. The electron injection metal layer is a thin film having an average thickness of several nm.

According to the present invention, an electron injection metal layer having an extremely thin film thickness of several nm is provided. Therefore, the absorption of light is almost negligible, and the characteristic of the work function inherent to the metal material is exhibited, so that electrons can be efficiently injected into the organic thin film.

From this, it is possible to obtain a transparent organic EL element having excellent light emitting characteristics.

[0028]

The structure of an organic EL device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an organic EL device according to the first embodiment of the present invention.

As shown in the sectional view of FIG. 1, a first transparent conductive layer 2, a hole transport layer 3, and a light emitting layer 4 are formed on a transparent substrate 1.
The electron transport layer 5, the electron injection metal layer 6, and the second transparent conductive layer 7 are sequentially laminated.

The point of the structure of the organic EL device in the present invention is the electron injection metal layer 6. That is, as in the conventional example, the material of the electron injection metal layer 6 is selected from a metal having a good work function of electron injection and a small work function or an alloy thereof, but the thickness of the electron injection metal layer 6 is made extremely thin to several nm. Is very important in the present invention.

At this time, it is possible that the electron injection metal layer 6 does not become a perfect film but grows in an island shape. However, even such an imperfect film has an average thickness. Number n
If m, there is no problem.

In the electron injecting metal layer 6 having this thickness, absorption of visible light in the metal layer is several percent at maximum, and the transparency as an organic EL element can be maintained.

Here, the electron injection efficiency from the electron injection electrode layer side is almost the same as in the conventional case where the film thickness of the electron injection metal layer 6 is about 100 nm.

As a component of FIG. 1, the transparent substrate 1 is made of a polymer film such as glass or polyester.

Further, the first transparent conductive layer 2 and the second transparent conductive layer 6 are made of ITO or S having a film thickness of 100 nm to 200 nm.
It is composed of nO2.

Further, the hole transport layer 3 has a film thickness of 50 nm to 1
Light-emitting layer 4 using a 00 nm triphenylamine derivative
Is a distyryl biphenyl derivative having a thickness of about 50 nm, and the electron transport layer 5 is an aluminum chelate complex (Alq) having a thickness of about 50 nm.

Next, a manufacturing method for forming the organic EL device structure shown in FIG. 1 will be described. First of all, 1.1
ITO having a film thickness of 100 nm is formed on a polishing glass having a thickness of mm by a sputtering method.

Further, triphenyldiamine (TPD: N, N'-diphenyl-) having a film thickness of 60 nm is formed by a vacuum deposition method.
N, N'-di (3-methylphenyl) -4,4'-diaminobiphenyl) is formed to give a film thickness of 40 nm of distyrylbiphenyl (DPVBi: 4,4'-bis (2,2-diphenylvinyl) biphenyl). ) Is formed and the film thickness is further increased to 2
A 0 nm aluminum chelate complex (Alq: tris (8-quinolinol) aluminum) is formed.

Furthermore, magnesium (Mg)-
Silver (Ag) is formed in a film thickness of 2 nm by the simultaneous vacuum deposition method.

After that, ITO having a film thickness of 150 nm is formed by the sputtering method to obtain the organic EL element shown in FIG.

When a voltage of 9 V was applied to the organic EL device thus obtained, a light emission luminance of 90 cd / m ² was obtained.

This emission luminance value was the same as that in the case of the conventional structure shown in FIG. 7 where the metal electrode layer 76 is a Mg-Ag element having a film thickness of 100 nm.

Further, the organic EL device of the present invention is
It was almost transparent with a visible light transmittance of 87%.

As described above, in the organic EL device according to the embodiment of the present invention, it is important to provide the extremely thin electron injection metal layer 6 having a thickness of several nm.

Therefore, even if the transparent substrate 1 is arranged on the side of the second transparent conductive layer 7 by integrally considering the laminated structure from the first transparent conductive layer 2 to the second transparent conductive layer 7 in FIG. , Have exactly the same effect.

Further, the organic thin film portion of the hole transport layer 3, the light emitting layer 4, and the electron transport layer 5 relating to the light emission of the organic EL element may be formed by another combination of the hole transport layer and the electron transporting light emitting layer. , Which has exactly the same effect as described above.

FIG. 2 is a sectional view showing an organic EL device according to the second embodiment of the present invention. Organic E with the same structure as in Figure 1
In the L element, the coloring layer 8 is added to the second transparent conductive layer side.

The colored layer 7 is a coating film using a dye or a pigment, but it does not necessarily have to be a single color and includes any pattern.

The thickness of the colored layer 8 may be selected in the range of several μm to several hundreds of μm without any problem. Furthermore, the colored layer 8 does not need to have a structure that is adhered to the second transparent conductive layer 7, and may have a structure that is merely in contact with or separated from each other.

Further, as the coloring layer 8, a plastic plate which is painted or wholly colored is used, and the second transparent conductive layer 7 is used.
Can be stacked on the side of.

The structure of FIG. 2 is similar to the structure of FIG. 8 showing the structure of the conventional example. However, in contrast to FIG. 8 which merely improves the contrast as a display element, according to the present invention, when the organic EL element does not emit light, it is transparent when viewed from the transparent substrate 1 side. The color and pattern of the colored layer 8 can be seen through the organic EL element, and since almost the emission color appears when emitting light, various illumination effects can be realized.

Further, for example, as shown in the optical spectrum of FIG. 3, the red color shown by the reflection spectrum 31 as the colored layer 8 and the blue color shown by the emission spectrum 32 having a complementary color relationship with this red color as the emission color. Consider the case of a combination of. In addition, red lead was used as red pigment, and blue was used as distilyl biphenyl (DPVBi) as a pigment.

When the organic EL does not emit light, the colored layer 8 naturally looks red. On the other hand, when emitting organic EL,
The red color reflected from the colored layer and the blue color of the emission color are mixed, and various hues such as red, bluish, and white colors are obtained depending on the intensity of the external light. Can be produced.

FIG. 4 shows another embodiment of the present invention in which an antireflection layer 9 is further formed on the lower surface of the transparent substrate 1 of FIG. If the lower surface referred to here is more generalized and accurately expressed, it will be the boundary surface with the air on the side where the light emission of the organic EL element is viewed.

As is well known, as the antireflection layer, a layer such as a non-reflection film formed of multilayer interference thin films having different refractive indexes is used.

If the reflection on the surface of the transparent substrate 1 is suppressed in this way, the color and pattern of the colored layer can be seen more clearly when the organic EL element is placed in a bright environment without light emission. .

Further, it is also very effective to provide a layer having a light diffusing property such as frosted glass or semitransparent ceramics in place of the antireflection layer 9 instead.

At this time, since the specular reflection on the lower surface of the transparent substrate 1 can be prevented, not only a soft color tone can be obtained in both non-light emission and light emission, but also
There is an effect of visually blocking a minute non-light emitting portion that becomes a black spot when the element emits light, which occurs when the organic EL element is formed or used, which is a great advantage in practical use.

FIG. 5 and FIG. 6 are sectional views showing the constitution when the organic EL device of the present invention is applied to a timepiece.

FIG. 5 shows an embodiment in which the transparent substrate 1 is arranged on the side of the second transparent conductive layer 7 as described in the description of FIG. 1, and a colored layer 8 similar to that of FIG. 2 is further provided. Transparent substrate 1
Provided on the bottom surface of. Furthermore, a transparent timepiece dial 10
Are arranged as shown in FIG.

In this case, since the dial plate on which the time characters are printed and the organic EL element are provided separately, there is an advantage that the parts can be easily manufactured.

FIG. 6 is a sectional view showing a timepiece incorporating the organic EL element of the embodiment of the present invention. Figure 2 shows the organic EL device
Since the transparent substrate 1 also serves as a dial plate, the time characters are printed on the side of the transparent substrate 1 on which the light emitting layer is not formed.

In FIG. 6, a movement 62 for driving the pointer 61 is provided in an exterior 64 in which a windshield 63 made of transparent glass or sapphire is incorporated.

Although not shown, the movement 62 includes a crystal oscillator, a semiconductor integrated circuit for driving the pulse motor, and a train wheel mechanism for driving the pointer 61. Further, the exterior 64 is sealed with a back cover 65 to form a completed watch.

With such a structure, when a voltage is applied to the organic EL element using a battery and a switch, which are not shown here, as a power source, the organic EL element emits light, and the clock display can be clearly recognized even in a dark place.

On the other hand, in a bright place, the color or pattern of the colored layer 8 is recognized as a dial, and various design characteristics as a timepiece can be pursued.

Furthermore, in FIG. 6, if all or part of the colored layer 8 is omitted, the whole or part of the movement 62 can be seen when the organic EL element is not emitting light. For example, by making the train wheel mechanism visible, a very interesting timepiece can be constructed.

[0068]

As is apparent from the above description, according to the organic EL element of the present invention, the emission color of a normal organic EL is obtained in the light emitting state, and the organic EL element is transparent in the non-light emitting state. You can see the shapes and colors of the objects placed on the back side of.

As a result, when it is used as a timepiece dial, it is possible to provide a timepiece which is rich in designability and can easily see the time display even in a dark place.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an organic EL device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an organic EL element according to a second embodiment of the present invention.

FIG. 3 is a graph showing an optical spectrum of an organic EL element in an example of the present invention.

FIG. 4 is a sectional view showing an organic EL element in a third embodiment of the present invention.

FIG. 5 is a sectional view showing an organic EL device according to a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a timepiece using an organic EL element in an example of the present invention.

FIG. 7 is a cross-sectional view showing an organic EL element in a conventional example.

FIG. 8 is a cross-sectional view showing an organic EL element in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 1st transparent conductive layer 4 Light emitting layer 5 Electron transport layer 6 Electron injection metal layer 7 2nd transparent conductive layer 8 Coloring layer 62 Movement

Continued Front Page (72) Inventor Ayako Kazama 840 Takeno, Shimotomi, Tokorozawa, Saitama Prefecture Citizen Watch Co., Ltd.

Claims (6)

[Claims] 1. An organic thin film composed of a plurality of layers, and first and second electrode layers provided on both surfaces of the organic thin film are provided in layers on a transparent substrate, the first electrode layer comprising a transparent conductive layer, The second electrode layer comprises an electron-injecting metal layer of an ultrathin film of a low work function metal or an alloy of the metal provided on an organic thin film, and a transparent conductive layer provided on the electron-injecting metal layer. Electroluminescent device. 2. An organic thin film composed of a plurality of layers, and first and second electrode layers provided on both surfaces of the organic thin film are provided in layers on a transparent substrate, the first electrode layer comprising a transparent conductive layer, The second electrode layer is a structure comprising an electron injection metal layer of an ultrathin film of a low work function metal or an alloy of the metal provided on an organic thin film, and a transparent conductive layer provided on the electron injection metal layer, and this structure. An organic electroluminescence device, characterized in that a colored layer is provided on a part or all of one side. 3. An organic thin film comprising a plurality of layers, and first and second electrode layers provided on both sides of the organic thin film are provided in layers on a transparent substrate, the first electrode layer comprising a transparent conductive layer, The second electrode layer comprises an electron-injecting metal layer of an ultrathin film of a metal having a low work function or an alloy of the metal provided on the organic thin film, and a transparent conductive layer provided on the electron-injecting metal layer. An organic electroluminescent device, which is provided with either an antireflection layer or a light diffusion layer on one side. 4. An organic thin film composed of a plurality of layers, and first and second electrode layers provided on both sides of the organic thin film are provided in layers on a transparent substrate, the first electrode layer comprising a transparent conductive layer, The second electrode layer is composed of an electron-injecting metal layer of an ultrathin film of a low work function metal or an alloy of the metal provided on the organic thin film, and a transparent conductive layer provided on the electron-injecting metal layer. An organic electroluminescent device, characterized in that a colored layer is provided on a part or all of one side and an antireflection layer or a light diffusion layer is provided on the other side. 5. The organic electroluminescence device according to claim 2, wherein the color of the colored layer and the emission color of the organic electroluminescence have a substantially complementary relationship. 6. The electron injection metal layer has an average thickness of several nanometers.
An organic electroluminescent device according to item 1.