JPH04174995A - Light-emitting element - Google Patents

Abstract

PURPOSE:To realize a stable element having reproducibility and enhance the emission intensity of the element by employing a combination of voltages applied to predeter mined layers of conductive material when each layer of fluorescent material emits light. CONSTITUTION:A thin film of Al is formed as a layer 5 of a conductive material on a base 1 and an organic fluorescent material is formed into a layer 6 of fluorescent material using deposition method. Next, another thin film of Al is formed as a layer 7 of conductive material and a layer of films of a naturally oxidized surface is formed as a layer 8 of insulating material and a film of Au is formed as a layer 9 of conductive material and an organic fluorescent material is formed into a layer 10 of fluorescent material using deposition method and another thin film of Al is formed as a layer 11 of conductive material. In this element, the thin film 7 is used as reference potential for excitation of the layer 6 and positive and negative potentials are applied to the films 5,9, respectively. Next, the film 9 is used as reference potential for excitation of the layer 10 and negative and positive potentials are applied to the films 7,11, respectively. This voltage applications are alternately carried out at a fixed cycle whereby good light emission of the organic fluorescent material is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention relates to light emitting devices, particularly light emitting devices that utilize MIM and phosphors, and can be used in all application fields of light emitting devices such as flat panel displays. be.

[Conventional technology] 2. Description of the Related Art Light emitting elements having an MIM structure are conventionally known.

This structure is shown in FIG. A first metal layer such as AI is formed on the substrate, an insulating layer is formed on this surface, and a second metal layer such as Au is further formed on this surface.
Light emission is obtained by applying a voltage between the metal layer and the second metal layer.

However, the emission spectrum of this light emitting element is 400-10
This light-emitting element emits very broad light in the range of 00 nm, and therefore cannot be used in display devices and the like that require elements of three primary colors with high brightness. As a way to solve these problems,
There is 3-232295. According to this, by inserting a phosphor layer between the second electrode and the insulator layer as shown in Figure 1, a specific wavelength determined by the phosphor is emitted and at the same time tunnels through the insulator layer. It is said that it can also be directly excited by electrons, producing strong light emission.

However, in this configuration, the thickness of the formed insulator layer is 20
Since it is extremely thin at ~30X, damage during formation of the phosphor layer cannot be ignored, resulting in problems with the stability and reproducibility of the device. Also, the thickness of the phosphor layer is very thin at 10-20s.
Considering that in order to obtain sufficient properties as a phosphor, the particle size must be on the order of several microns, it can be predicted that sufficient luminous intensity will not be obtained with this film thickness. Furthermore, when considering excitation by tunneled electrons, the energy of the electrons is determined by the applied voltage; on the other hand, the energy of tunneled electrons is several eV.
Therefore, depending on the characteristics of the phosphor material used, it may not emit light.

[Problems to be Solved by the Invention] An object of the present invention is to provide a light emitting element that has high luminance and can be produced stably and with good reproducibility.

[Means for Solving the Problems] The structure of the present invention for solving the above problems is a light emitting device as described in the claims.

FIG. 1 shows the structure of a device according to the present invention. In the present invention, by forming the phosphor layer in the position shown in the figure, damage to the insulator layer, which was a drawback of the conventional technology, can be avoided, and a stable and reproducible device can be realized. Emission intensity also improves. In addition, by combining each phosphor layer, a multicolor light emitting device can be realized by controlling the voltage by additively mixing the emission colors of each phosphor and adjusting the emission intensity of each phosphor by applying voltage. .

Basically, when driving the device according to the present invention, when the first phosphor layer is made to emit light, a voltage is applied to the first, second and third conductor layers, and when the second phosphor layer is made to emit light, a voltage is applied to the first, second and third conductor layers. , 2. A combination of applying a voltage to the third and fourth conductor layers is used.

There are two possible ways to excite the phosphor: excitation by light emission from the MIM element and excitation by tunnel electrons.
In order to excite each phosphor layer with tunneling electrons, each of the insulator layer and the first and second conductor layers must be extremely thin.

In particular, since electrons need to tunnel through the insulator layer, the film thickness ranges from several to several hundred layers, preferably from 20 to 200 mm.
For humans, the optimal number is between 20 and 100. Furthermore, it goes without saying that it is necessary to exhibit insulation properties with a film thickness within the above range. Furthermore, each layer must also have translucency.

Furthermore, in the present invention, a first conductor layer is provided for the first phosphor layer, and a fourth conductor layer is provided for the second phosphor layer, and each phosphor layer is By applying a bias of 10 to each conductive layer when excited by tunneling electrons, the tunneled electrons are accelerated, the excitation intensity of the phosphor is increased, and the emission intensity is improved. Furthermore, charging of electrons on the surface of the phosphor is avoided. There is no particular restriction on the accelerating voltage, but in consideration of practicality, it is desirable to set it to about several +V.

There are no particular restrictions on the organic material phosphor, but a phosphor that can be used as a material for the light-emitting layer of organic thin film electroluminescence is desirable.

There are no particular restrictions on the method for producing the first phosphor layer, but a method that causes little damage to the organic phosphor material itself is desirable. That is, a vapor deposition method, an LB method, or a coating method is preferable.

Further, as a method for producing the second phosphor layer, it is desirable that damage to the underlying layer is small, and therefore a coating method or a vacuum evaporation method is preferable.

There are no particular restrictions on the material or manufacturing method for the 2.4th conductor layer, but a manufacturing method that does not cause much damage to the underlying phosphor layer is preferred.

There are no particular restrictions on the substrate, but if the direction in which light is extracted is from the substrate side, it must be translucent. In this case, it is necessary that the first conductor layer and the first phosphor layer each have translucency. Furthermore, when emitting light from the film forming side, the second phosphor layer and the fourth conductor layer each need to have light-transmitting properties.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Here, a light emitting device having a device structure as shown in FIG. 1 was manufactured. As the substrate 1, a glass substrate was used. An A1 thin film was formed as the first conductor layer 5 on the substrate by heating with a resistance wire of about 1μ11. Next, as the first phosphor layer 6,
An organic phosphor material having the structure shown below was formed by vapor deposition.

H3 Next, an Al thin film was formed as the second conductive layer 7 by heating with a resistance wire of about 100 A%. Next, the insulator layer 8 was left in the air for about 10 days to form a surface natural oxide film layer of about 50λ. Furthermore, about 100 people formed an Au thin film as the third conductor layer 9 by heating with a resistance wire. And the second
As the phosphor layer IO, an organic phosphor similar to that of the first phosphor layer was formed by vapor deposition. Finally, as a fourth conductor layer 11, a thin Al film of about 1 μm was formed by heating with a resistance wire.

In the device thus manufactured, first, the first phosphor layer is excited by applying a positive potential to the Al thin film serving as the second electrode, using the Al thin film serving as the second electrode as a reference potential, and applying a positive potential to the Al thin film serving as the third electrode.
A negative potential is applied to each of the U thin films, and then, to excite the second phosphor layer, the third electrode, the Au thin film, is set as a reference potential, the second electrode, the Al thin film, is applied with a negative potential, and the fourth electrode is applied with a negative potential. A positive potential was applied to each of the Al thin films.

By applying this voltage alternately at a certain period, good luminescence of the organic material phosphor was obtained based on this period.

Note that the effects of the present invention are not limited to the organic phosphor material used in this example, but similar effects were obtained with other organic phosphor materials.

Example 2 In this case as well, a light emitting device having the device structure shown in FIG. 1 was manufactured. A glass substrate was used as the substrate l. An A1 thin film was formed as the first conductor layer 5 on the substrate to a thickness of approximately 1 μm by heating with a resistance wire. Next, as the first phosphor layer 6,
ZnO: Zn, which is a phosphor material for low-speed electron beams, was formed by a coating method. Next, as the second conductive layer 7, an A1 thin film having a thickness of approximately 100 mm was formed by heating with a resistance wire.

Next, as an insulator layer 8, the temperature is about 150-200"C in air.
Heating was performed for 140 minutes to form a surface oxide layer of approximately 30-5OA on the surface of AI. Further, as the third conductor layer 9, A
A u thin film was formed by resistance wire heating at about 100X. Then, as the second phosphor layer 1o, ZnO:Zn was formed in the same manner as the first phosphor layer, and finally, as the fourth conductor layer 11, an Al thin film of about 1 μm was formed by resistance wire heating. .

The device thus prepared was first excited by applying a positive potential to the A1 thin film of the first electrode, and applying a positive potential to the A1 thin film of the third electrode, with the A1 thin film serving as the second electrode as a reference potential. A negative potential is applied to each of the Au thin films, and then to excite the second phosphor layer, the Au thin film that is the third electrode is set as a reference potential, the negative potential is applied to the Al thin film that is the second electrode, and the negative potential is applied to the Al thin film that is the second electrode. A positive potential was applied to each of the Al thin films.

By applying this voltage alternately at a certain period,
Based on this period, good luminescence of the ZnO:Zn phosphor was obtained.

In this example, Al2O3, which is the surface oxidation of the A1 thin film that is the second conductor layer, was used as the material for the insulator layer, but the effects of the present invention are not limited to these, and other materials may be used. Similar effects were obtained using different manufacturing methods.

[Effects of the Invention] As described above, the light emitting element of the present invention is stable, has good reproducibility, and can emit light with high brightness.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of a light-emitting element of the present invention, and FIG. 2 is a schematic cross-sectional view showing the structure of a light-emitting element having a conventional MIM structure. DESCRIPTION OF SYMBOLS 1... Substrate, 2... First metal layer, 3... Insulator layer, 4... Second metal layer, 5... First conductor layer,
6... First phosphor layer, 7... Second conductor layer, 8
...Insulator layer, 9...Third conductor layer, lOo...
- Second phosphor layer, 11... fourth conductor layer.

Claims (2)

[Claims] (1) A first conductor layer is provided on the substrate, and a first conductor layer is provided on the surface of the substrate.
a phosphor layer of an organic material, a second conductor layer on the surface thereof, an insulator layer formed on the surface of the second conductor layer, a third conductor layer on the surface of the insulator layer, and a third conductor layer formed on the surface of the insulator layer; 1. A light-emitting device, characterized in that it has a second organic material phosphor layer on its surface, and finally a fourth conductive layer, and a voltage is applied to each of the conductive layers. (2) Having a first conductor layer on the substrate, and having a first conductor layer on the surface thereof.
a phosphor layer, a second conductor layer on the surface thereof, an insulator layer made of an inorganic material formed on the surface thereof, and a third conductor layer on the surface of the insulator layer. , further having a second phosphor layer on its surface, and finally a fourth conductor layer,
A light emitting device characterized in that a voltage is applied to each of the conductor layers.