JPH01220394A - High-intensity el element - Google Patents

Abstract

PURPOSE:To efficiently extract the illuminated light and improve the intensity of a luminous layer by providing a lower electrode, an insulating layer, a luminous layer and an upper electrode in sequence on a substrate and providing a mirror reflecting the light on one face of the luminous layer. CONSTITUTION:A lower electrode 2 is formed in a stripe shape on a glass substrate 1. A Ta2O3 film with the thickness of 1mum is formed as the first insulating layer 3 on the electrode 2, then the surface is formed in a wave shape. The Ta2O3 film is formed by the spattering method, the wave shape is formed by the chemical etching method. A mirror 7 is formed on the insulating layer 3. A metal aluminum film with the thickness of 0.005mum, for example, is used for the mirror 7, the mirror 7 suppresses the luster at the cone-shaped bottom portion and prevents the reflection of the external light. A luminous layer 4 is formed on the mirror 7, the second insulating layer 2 is formed on the luminous layer 4, a back electrode 6 is formed on it. The illuminated light is efficiently extracted, thereby the intensity of the luminous layer can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a thin film type KL element that is expected to be used as a flat display with excellent space factor and display quality, and particularly relates to the increase in the height of 4 degrees.

[Conventional technology]

The III-film model L element has vague characteristics such as being completely solid-state, self-luminous, thin, and having high quality display, so it is suitable as a display for information terminal equipment.

III display (II, D) which is already monochrome yellow-orange
) has been on the market, and research into multi-color and full-color ELDs is currently active. In the field of multicolor and full color, research on increasing brightness is particularly active.

As shown in Figure 2, the structure of the KL element is a double insulating film structure in which the upper and lower surfaces of the light emitting layer are covered with dielectric thin films, which has the longest life and excellent long-term stability, and is the most common. It is.

The basic structure of a variable light drive type double insulating film EL device will be explained with reference to FIG. That is, FIG. 2 is a schematic cross-sectional view showing the structure of a conventional thin -mr, + element, where 1 is a glass substrate, 2 is a lower electrode, 3 is a first insulating layer, 4 is a light emitting layer, and 5 is a second Insulation No. 6 means back electrode. Glass substrate 1
A transparent electrode 2 as a lower electrode, a first insulating layer 5, a light emitting layer 4, a second insulating layer 5, and a back electrode 6 made of a transparent electrode or a metal #film are sequentially formed on top. Naturally, light is emitted from the light emitting layer 4, but in order to extract this light, it is necessary to make either the lower electrode or the back electrode a transparent IC electrode.

In the above EL element, when an alternating current electric field (approximately 10' V/3) is applied between the lower electrode 2 and the back electrode 6, electrons emitted from the interface between the insulating layer and the light-emitting layer are moved inside the light-emitting layer 4 by the electric field. It is excited into the conduction band and accelerated to obtain sufficient energy to collide and excite the luminescent center. EL light emission is said to occur when the excited light-emitting center returns to its ground state.

As the luminescent center, Mn, 06% l1fu,
Tb.

A small amount of Bm or the like is doped into a base material such as OehB, ar8, or ZnB. Colors with different emission wavelengths can be obtained depending on the combination of the host material and the luminescent center. For example, doping with Oe8 ic mu gives a deep red color, doping 8r8 with Oe gives a dark green color, doping with ZnB Ic Tb gives a green color, and doping with Zn8 KMn gives a yellow-orange color.

[Problems to be Solved by the Invention] The conventional EIJ element structure has the disadvantage that light cannot be extracted efficiently because the nine rays of light are scattered in directions other than the required directions. In other words, in the conventional device structure, only about a portion of the amount of light obtained in the light emitting layer is utilized.

An object of the present invention is to provide a BL element that efficiently extracts emitted light and increases the brightness of a light emitting layer.

[Means for solving the problem]

To summarize the present invention, the present invention relates to a high 14 degree BL element, which has a lower 'ti, an insulating layer, a light emitting layer, and an upper electrode on a substrate, and has a voltage between both 'ti' electrodes. An ML element that emits light by applying a ray of light is characterized in that a mirror that reflects light is provided on one side of the light emitting layer.

In the present invention, by forming a film having a mirror effect on one side of the light-emitting layer of the 11iL element (1IIIl opposite to the surface from which light is extracted as information), light emitted from the surroundings of the light-emitting layer is prevented and reflected. , collects light on a surface where it is extracted as optical information. As a result, the light obtained in the light emitting layer is extracted efficiently, so that the brightness of the KL element is increased. In the conventional ZL element structure without a mirror, only about 1000 liters of light is utilized, and most of it is emitted in directions other than necessary.

Furthermore, by forming the mirror in the shape of a bowl, it is possible to eliminate light loss to the surroundings of the light emitting layer.

In the present invention, the mirror is preferably provided at a position of 1 fM between the substrate and the polarization layer, between the electrode and the insulating layer, and between the insulating layer and the light emitting layer.

Naturally, depending on the location of the mirror, it is necessary to decide whether to use transparent polarization at the bottom or at the back.

Any metal material may be used as the mirror material, but
Among them, chromium and aluminum are good.

Alternatively, an insulating reflective layer may be coated on the metal layer, and the reflective layer is preferably one that can be mirror-finished. An example of this is a metal foil coated with an oxide film, such as a silica film, and then mirror-finished.

[Actual example]

The present invention will be explained below using actual examples! 1! However, the present invention is not limited to these Examples.

Embodiment 1 Hereinafter, one actual m-series f of the present invention will be explained with reference to FIG. That is, FIG. 1 is a schematic cross-sectional view 69 showing the structure of one row of the thin film EL device of the present invention, where numerals 1 to 6 have the same meanings as in FIG. 2, and 7 means a mirror.

Figure 1 shows an l1iIl element structure model, with a glass substrate 1
On top, a metal aluminum film (with a thickness of approx.
12 μm) using resistance heating method to reduce line width 2-1 electrode spacing α
It was formed into a 2- stripe shape.

In this case, the striped pattern was formed using a metal mask. On top of this, as the first insulating layer 3? After forming alO,@ to a thickness of 1 μm, the surface was formed into a wavy shape as seen in FIG. TEL! The OB film is formed by sputtering, and the wavy pattern is formed by chemical etching. A mirror 7 was formed on the first insulating layer 3.

Any material may be selected for the mirror as long as it has a glossy surface. Here, a 1005 μm thick metal aluminum membrane was used. In addition, the mirror can prevent reflection of external light by reducing the gloss on the bottom of the mirror.

Further, even if the mirror is formed flat, it is effective.

A red light-emitting layer of CaS: mu was formed on the mirror 7 by a 4-ta beam evaporation method. In forming this light-emitting layer, first, a metal mask is used to form it only in the grooves in the shape of a forest, and when the surface is flat, the chamber is opened and the metal mask is removed. (
! a8: A mu light emitting layer was formed and its thickness was increased. The thickness from the bottom of the forest to the surface of the luminescent layer is approximately 1.5μ
It was formed into m. T is formed as a second insulating layer 5 on the light emitting layer 4.
The films a, o, and CL were formed to a thickness of 5 μm by sputtering. On top of this, a back electrode pattern was formed. Here, an ITO (indium tin oxide) film (4 width 2 mm, interval α2 rhyme, thickness CL 2 μm), which is a transparent conductive film, was formed into a stripe shape by electron beam evaporation. Note that the back electrode 6 was formed in a direction perpendicular to the lower electrode.

In the above element configuration, the mirror 7r! between the glass substrate 1 and the lower electrode 2, between the lower electrode 2 and the first insulating layer 3, between the light emitting layer 4 and the second insulating layer 5, between the second insulating layer 5 and the back electrode, etc. It may be placed somewhere in one place. However, in this case, it is necessary to select an insulating mirror material when it comes into contact with the electrode. Furthermore, depending on the position of the mirror, it is of course necessary to decide whether to use the transparent electrode at the bottom or at the back.

FIG. 3 shows the brightness measured by applying an alternating current electric field between the lower polarization 2 and the back electrode 6 of a KL element fabricated using a method similar to the method described above. 1! This is a graph comparing the brightness of iL1g, the vertical axis is 4FIf, II
(Cd/m3).

Figure 3 a% b and C are of the conventional element structure, a', b'
and a' are those of the device structure of the present invention. Here, a
and a' are red light-emitting devices whose light-emitting layer is composed of Ca8:mu, b and b' are green light-emitting devices whose light-emitting layer is composed of Zn8:Tb, and C and a' are Sr8:Co.
This represents the brightness of a blue-green light emitting element consisting of:

As is clear from the third prisoner, the red glow has a; 760
067 m", a'=+1100 cd/m", green brightness is b=3950 a67 m", 1)'=
6070c d/@”, blue-green t4glL is a =
980 ad/yB", 0' = 15500 dl m snow. From these results, it is clear that the element according to the present invention can obtain a 4-turn value that is about 1.5 times higher than the conventional element. On the other hand, in the case of a flat mirror with no steps, the brightness was about 1.2 times higher than that of a normal mirror.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to effectively draw out the luminance of the light emitted, so it has a great effect on increasing the luminance of ML, especially in multi-color and full-color 1
This will have a great effect on the practical application of 1iLD.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of an example of a thin film 11ili element of the present invention, and FIG. 2 is a conventional thin film 11! FIG. 3 is a cross-sectional schematic diagram showing the structure of the IKL element, and is a complete comparison graph of the BLfp degree between the conventional product and the product of the present invention. 1 glass substrate, 2: lower electrode, 3: first insulation layer, 4:
Light emitting layer, 5: second insulating layer 0.6: back electrode, 7: mirror

Claims (2)

[Claims] 1. In an EL element that has a lower electrode, an insulating layer, a light-emitting layer, and an upper electrode on a substrate and emits light by applying a voltage between both electrodes, light is reflected on one side of the light-emitting layer. A high-brightness EL element characterized by being equipped with a mirror. 2. 2. The high-brightness EL device according to claim 1, wherein the mirror is provided at one of the locations between the substrate and the electrode, between the electrode and the insulating layer, and between the insulating layer and the light emitting layer.