JPH0325893A - Electroluminescent display element and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce bleeding of emission around a luminous area and obtain a minute image by forming a non-luminous area having turbulent crystallinity which encloses the luminous area of an EL layer on the same EL layer. CONSTITUTION:In an EL display element, a plurality of luminous areas 15 are partitioned on an EL layer 4, and the EL layer is provided with a plurality of non-luminous areas 10 formed to enclose the individual luminous areas therein. The non-luminous area 10 is an area in which lots of crystal defects and crystal grains are caused by the ion implantation of impurities into the EL layer 4 of one layer or their explosion into plasma to make diffusion and trap of electrons frequently existent therein. Therefore, in the non-luminous area, the average free stroke of the electrons is shortened, so that the electrons can not be sufficiently accelerated, the generation of hot electrons is suppressed, and no emission occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an electroluminescent display element that emits light in response to an electrical signal and a method for manufacturing the same.

BACKGROUND ART Braun tubes are widely used as color display devices that display multiple colors in response to electrical signals. Liquid crystal display elements have also been developed to make devices thinner. Furthermore, display elements using electroluminescence (hereinafter referred to as EL), which are completely solid-state and can emit high-intensity light, have also been developed.

Such EL display elements are classified by structure into DC type, which does not have an insulating layer or dielectric layer between the electrode and the EL layer, and AC type, which has an insulating layer between the electrode and the EL layer. The AC type is suitable as a dot matrix EL display element.

Furthermore, when classifying EL display elements by the EL layer that emits light, E
There are two types: a dispersed type in which fine particles of the L layer material are bonded with a binder and formed by coating, and a thin film type in which the EL layer material is formed by a thin film forming method such as vapor deposition or sputtering.

FIG. 3 shows a schematic cross section of an X,Y matrix type double insulation type AC EL display element. The EL display element has a plurality of transparent electrodes 2 such as ITO, a first insulating film 3, an EL layer 4, a second insulating film 5, and a plurality of back electrodes 6 crossing the transparent electrodes 2 on a glass transparent substrate 1. They are laminated and formed in order. EL
@4 is II-V such as ZnS, ZnSe, CaS, SrS, etc.
This is a layer containing several percent of a luminescent center material using a semiconductor material of a group I metal compound as a host material.

In the light emitting mechanism of such an EL display element, a voltage is applied between the back electrode 6 and the transparent electrode 2, and an electric field is applied to the EL layer 4 via the first and second insulating films 5.

The applied electric field generates free electrons in the host material of the EL layer 4, and the free electrons in the electric field are accelerated to become hot electrons in a high energy state.

These hot electrons excite the luminescent center substance of the EL layer 4, and the excited state is relaxed to emit light having a predetermined spectral distribution. The color of the emitted light is determined by the combination of the host material of the EL layer 4 and the luminescent center material.

For example, when using ZnS as a host material, when the luminescence center substance is Sm, it emits red light, and similarly, when the luminescence center substance is Sm, it emits yellow light, and when it is Mn, it emits yellow light and T
At b, green light is emitted, and at Tm, blue light is emitted.

As shown in the plan view seen from the rear electrode 6 side in FIG. 4, since such an EL display element has an X, Y matrix structure, an EL layer 41 between the intersecting electrodes 2 and 6; a pixel, that is, a light emitting area A is formed. be done.

However, because of the single EL layer, crosstalk and "bleeding" of light emission occur around the pixels. In other words, in the mesh line part C of FIG. 4, from the green part of each electrode
With a width of 3 μm, a crosstalk light emitting region corresponding to the width of the electrode is generated. For this reason, the resolution of the EL display element as a whole decreases, making it impossible to obtain fine images.

SUMMARY OF THE INVENTION An object of the present invention is to provide an EL display element capable of obtaining fine images and a method for manufacturing the same.

The EL display element of the present invention is an EL display element having at least one pair of electrodes facing each other and an EL layer disposed between the electrodes, and in which a portion of the EL layer sandwiched by the electrodes serves as a light emitting region, The EL layer is a crystalline EL layer consisting of a host substance and a luminescent center substance, and is characterized by having a non-luminescent region with disordered crystallinity surrounding a luminescent region.

The method for manufacturing an EL display element of the present invention includes at least one pair of electrodes facing each other and an EL layer disposed between the electrodes, and a light emitting region is a portion of the EL layer sandwiched between the electrodes. A manufacturing method, comprising: a first electrode layer forming step of forming a first electrode layer on a substrate; and a crystalline E consisting of a host substance and a luminescent center substance on the substrate.
An EL layer forming step for forming an L layer, and a step of partially covering the EL layer to expose the periphery of a portion of the EL layer that is to be a light emitting region, and implanting an impurity into the exposed portion to improve the crystallinity of the EL layer. a non-light-emitting region forming step of forming a non-light-emitting region with disordered crystallinity surrounding the light-emitting region by partially disturbing the light-emitting region; and a second electrode forming a second electrode layer on the EL layer corresponding to the light-emitting region. This includes a layer forming step. It is characterized by.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the EL display element of the example has a plurality of light emitting regions 15 defined in the EL layer 4, and a plurality of non-light emitting regions 10 formed so as to surround each light emitting region. It is provided in the EL layer. The non-light emitting region 10 is 1
This is a region in which many crystal defects and crystal grains are generated by ion-implanting impurities into the EL layer 4 or by exposing it to plasma, resulting in the existence of many electron scattering and traps.

In order to manufacture such an EL display element, first, the method shown in FIG.
), a plurality of transparent electrodes 2 are laminated in stripes on the surface of a glass substrate 1 so that they are parallel to each other.

Next, as shown in FIG. 2(b), a first insulator layer 3 is laminated on the plurality of transparent electrodes 2.

Next, as shown in FIG. 2(c), an EL layer 4 containing a luminescent center substance is uniformly formed on the first insulating layer 3 on the substrate surface by, for example, a sputtering method. EL
The layer 4 is preferably formed to a thickness of 0.3 to 1.0 μm. The EL layer 4 is made of, for example, zinc sulfide Zn as a host material.
S, as a luminescent center substance, for example, the above-mentioned Sm, Mn%T
Selected from bSTm, etc. It is desirable that the EL layer 4 has a well-developed crystal structure in order to obtain good light emitting characteristics. Alternatively, an EL layer containing a short-wavelength luminescent center substance may be formed by forming a ZnS matrix layer in advance, depositing a luminescent center substance thereon, and using a thermal diffusion method.

Next, as shown in FIG. 2(d), the EL layer 4 is masked to expose only the intended non-emissive region, and atoms such as N are ionized as impurities into one EL layer. This implantation causes crystal defects and many crystal grains. Alternatively, the EL layer 4 with a predetermined masking may be exposed to plasma and atoms such as O may be implanted to cause crystal defects. In this way, a light emitting region 15 surrounded by a non-light emitting region 10 is formed.

Next, as shown in FIG. 2(e), a second insulating layer 5 is deposited on the EL layer 4 in which the non-light-emitting region 10 is formed, and then the light-emitting region 15 surrounded by the non-light-emitting region 10 is A second electrode layer 6 corresponding to each of the above is deposited and deposited thereon.

In this way, the EL display element of the present invention shown in FIG. 1 is obtained. In such an EL display element, only a portion adjacent to a pixel sandwiched between opposing electrode pairs and which should not emit light is set as a non-emissive region 10 to increase crystal grain boundaries and disturb crystallinity. Therefore, the mean free path of electrons becomes short in the non-emissive region, and the electrons are no longer sufficiently accelerated, the generation of hot electrons is suppressed, and no light is emitted.

Furthermore, although the EL display elements of the above embodiments are AC type having an insulating layer or dielectric layer between the electrodes and the EL layer, it is also a DC type having no insulating layer between the electrodes and the EL layer. It can also be applied to EL display elements.

Effects of the Invention As described above, according to the EL display element of the present invention, since the non-light emitting region with disordered crystallinity surrounding the light emitting region of the EL layer is formed in the same EL layer, only the light emitting region emits light. , the "bleeding" of the light emission around the light emitting area is suppressed, and a finer image can be obtained.

FIG. 2 is an enlarged partial perspective sectional view of an element substrate during manufacture of an EL display element according to the present invention, FIG. 3 is a partial sectional view of a conventional EL display element, and FIG. 4 is a partial plan view of a conventional EL display element. be.

Explanation of symbols of main parts 1... Board 2...Transparent electrode 3.5...Insulator layer 4...EL layer 6... Electrode 10...Non-luminous area 15... Light emitting area

Claims (4)

[Claims] (1) having at least a pair of electrodes facing each other and an electroluminescent layer disposed between the electrodes;
An electroluminescent display element whose light emitting region is a portion of the electroluminescent layer sandwiched by the electrodes, wherein the electroluminescent layer is made of a crystalline electroluminescent material consisting of a host substance and a luminescent center substance; An electroluminescent display element characterized by having a non-light-emitting region with disordered crystallinity surrounding a light-emitting region. (2) The host material is ZnS, the luminescent center material is a material selected from the group consisting of Sm, Mn, Tb, and Tm, and the non-luminescent region further contains impurities. The electroluminescent display element described above. (3) having at least a pair of electrodes facing each other and an electroluminescent layer disposed between the electrodes;
A method for manufacturing an electroluminescent display element in which a portion of the electroluminescent layer sandwiched by the electrodes is a light emitting region, comprising: a first electrode layer forming step of forming a first electrode layer on the substrate; an electroluminescent layer forming step of forming a crystalline electroluminescent layer consisting of a host substance and a luminescent center substance on a substrate; and the electroluminescent layer that partially covers the electroluminescent layer to form the light emitting region. Expose the area around the
a non-light-emitting region forming step of injecting an impurity into the exposed portion to partially disrupt the crystallinity of the electroluminescent layer to form a non-light-emitting region with disordered crystallinity surrounding the light-emitting region; a second electrode layer forming step of forming a second electrode layer on the electroluminescent layer in accordance with the method of manufacturing an electroluminescent display element. (4) A first insulating layer is formed between the first electrode layer forming step and the electroluminescent layer forming step.
Claim 3, further comprising an insulating layer forming step, and a second insulating layer forming step of forming a second insulating layer between the non-light emitting region forming step and the second electrode layer forming step. A method of manufacturing the electroluminescent display element described above.