JPH02265193A - Multicolored electroluminescence display element and its manufacture - Google Patents

Abstract

PURPOSE:To facilitate process control for the manufacture in the title and higher densification of a luminous-region pattern by constituting electroluminescence(EL) strata of a matrix layer containing a matrix material and at least one kind of emission center material, and the emission center material of each different luminous color mixedly included in a specified region corresponding to at least one out of luminous regions. CONSTITUTION:A matrix layer 10 containing a matrix material and an emission center material which mainly emits light having the shortest wavelength in plural luminous regions of EL strata scheduled is formed uniformly on a first dielectric layer 3 out of the laminates upon the face of a substrate 1 by a method of, e.g. chemical vapor deposition, such physical vapor deposition as sputtering or the like, or the like. By the method of vacuum deposition, emission center materials 11a, 12a are subsequently deposited respectively onto the matrix layer 10 to form their corresponding films two-dimensionally in stratiform fashion so that respectively different luminous regions are formed. This readily achieves process control for the manufacture in the title and higher densification of a luminous region pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to multicolor electroluminescent display elements that emit light in response to electrical signals.

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. 5 shows a schematic cross section of a double-insulated AC EL display element. The EL display element includes a glass transparent substrate 1, a transparent electrode 2 such as ITO, a first insulating film 3. An EL layer 5, a second insulating film 3, and a back electrode 9 are laminated and formed in this order. E
The L layer 5 is made of II- such as ZnS, Zn5e, CaS, SrS, etc.
This is a layer containing several percent of a luminescent center material using a Vll gold metal compound semiconductor material as a host material.

In the light emitting mechanism of such an EL display element, a voltage is applied between the back electrode 9 and the transparent electrode 2, and an electric field is applied to the EL layer 5 via the first and second insulating films 3.

The applied electric field generates free electrons in the host material of the EL layer 5, 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 5, 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 5 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 a method of making such an EL display element multicolored, there is a method of constructing the element by sequentially stacking a plurality of types of EL layers on a flat substrate. However, in this case, there are problems in that the brightness of the entire EL display element is insufficient and defects are likely to occur in the EL layer.

Therefore, a method has been developed in which an EL display element is constructed by two-dimensionally arranging multicolored light emitting regions forming an EL layer on a flat substrate. A method for manufacturing such a flat multicolor EL display element involves depositing an EL layer material on a glass substrate, and using photolithography to leave a thin film of the EL layer material only on a desired portion and peeling off the rest along with a photoresist film from the substrate. There is a method of repeating the process of removing and forming a light emitting region to create light emitting region thin films of multiple types of EL layer materials two-dimensionally adjacent to each other (Monthly Semiconductor World, 1987, (8), 156- 157 pages).

This method of creating multiple types of light emitting regions is performed through the steps shown in FIG. First, a transparent electrode 2 and a dielectric layer 3 are sequentially laminated on a glass substrate 1, a photoresist 4 is applied thereon, and the photoresist is removed at a portion where a first light emitting region is to be provided by a photolithography method ( 6th
Diagram a). Subsequently, a first light emitting region material 5 is deposited thereon (FIG. 6b). By peeling off the first light-emitting region material 5 together with the photoresist 4, the first light-emitting region material 5 is left only in a desired portion (FIG. 6C).

Next, a photoresist 4 is applied, and the photoresist in the area where the second light emitting region is to be provided is removed by photolithography (FIG. 6d). Subsequently, a second light emitting region material 6 is deposited thereon (FIG. 6e). Next, the second light-emitting region material 6 is peeled off together with the photoresist 4, leaving the second light-emitting region material 6 only in desired areas, and the first light-emitting region material 5 and the second light-emitting region material 6 are separated. A substrate is obtained in which each of the substrates is disposed at a desired portion (FIG. 6f).

Next, the above steps are repeated for the third light-emitting region material 7 to obtain a substrate body in which all the predetermined light-emitting regions are arranged in predetermined portions (FIG. 6g). This is covered with a dielectric layer 8.
6h), an EL display element is manufactured by providing corresponding electrodes 9 on each light emitting region at respective positions according to a known process (FIG. 6i).

In the conventional manufacturing method as described above, the light emitting region layer deposited in the hole formed in the photoresist layer is left behind, and the other light emitting region layers on the photoresist layer are peeled off and removed together with the photoresist layer. , it is necessary to precisely form the pattern shape of the resist layer over the entire surface of the substrate.

It is also necessary to accurately control the deposition thickness of the light emitting region layer.

In such an EL element manufacturing method, there is a limit to increasing the density of the light emitting region pattern because it requires finer patterns and stricter process control.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multicolor EL display element and a method for manufacturing the same, which can easily achieve process control and increase the density of a light emitting region pattern.

The multicolor electroluminescent display element of the present invention is an electroluminescent display element having an electroluminescent layer including a plurality of light emitting regions having different emission colors, the electroluminescent layer comprising a host substance and at least one type of luminescent center substance. and luminescent center substances of different luminescent colors mixed in a predetermined region corresponding to at least one of the luminescent regions.

The method for manufacturing a multicolor electroluminescent display element of the present invention is a method for manufacturing an electroluminescent element having an electroluminescent layer including light emitting regions of different emission colors, the method comprising: a base substance and at least one type of luminescent center substance; a film-forming step of forming a base layer containing a luminescent center substance having a longer wavelength than the luminescent color of the at least one type of luminescent center substance, and diffusing a luminescent center substance having a longer wavelength than the luminescent color of the at least one type of luminescent center substance into a predetermined region corresponding to at least one of the light emitting regions of the base layer. The method is characterized in that it includes a diffusion step.

Example Embodiments of the present invention will be described below with reference to the drawings.

First, a transparent electrode 2 and a first dielectric layer 3 are placed on the surface of a glass substrate 1.
Prepare a layered layer in this order. Next, Figure 1(a)
As shown in FIG. 1, a matrix is formed on the first dielectric layer 3 on the substrate surface, which includes a matrix material and a luminescent center substance that mainly emits light with the shortest wavelength among the plurality of luminescent regions of the planned EL layer. layer 10
is uniformly formed, for example, by a method such as chemical vapor deposition or physical vapor deposition such as sputtering.

The base layer 10 is preferably formed to a thickness of 0.3 to 1.0 μm by a physical vapor deposition method such as a vacuum deposition method. For the matrix layer 10, a matrix composition common to a plurality of light emitting regions of the planned EL layer, such as zinc sulfide ZnS, is selected. It is desirable that such a base layer 10 has a well-developed crystal structure in order to obtain good light-emitting characteristics. Alternatively, a matrix layer of ZnS may be formed in advance, and a luminescence center substance with a short wavelength may be deposited thereon to form a matrix layer containing the luminescence center substance with a short wavelength by thermal diffusion.

Next, as shown in FIG. 1(b), the luminescent center substances 11a and 12a are two-dimensionally formed into a layered film by vacuum evaporation so as to form different luminescent regions on the base layer 10. At this time, since the base layer 10 is already in a state of emitting light, the entire surface of the base layer 10 is not covered with the thin film of the luminescent center substances 11a and 12a.

As a method for attaching the thin film, for example, a method such as printing on the base layer 10 as a water-based paint, or a physical vapor deposition method such as sputter deposition can be used. When particularly high precision is not required, it is preferable to use conventional printing methods. When a fine pattern is required, a combination of printing or vapor deposition and a photoetching process can be used.

Next, the substrate 1 on which the luminescent center substances 11a and 12a are attached in a thin film form is heated to diffuse the luminescent center substances into the base layer 10, as shown in FIG. 1(c). Light emitting regions 11 and 12 that emit different light are formed. The conditions for such thermal diffusion are 400 to 800°C in vacuum and 5 to 50°C.
It takes about an hour.

In these light-emitting regions 11 and 12, a short-wavelength light-emitting center substance previously included in the base layer 10 and a longer-wavelength light-emitting center substance 11a, 12a coexist. In this way, on the first dielectric layer 3, a short wavelength light emitting region, which is the base layer 10, and a long wavelength light emitting region 11, 12 are formed.

Next, as shown in FIG. 1(d), a second dielectric layer 8 is deposited on the first dielectric layer 3 carrying short wavelength and long wavelength light emitting regions 10, 11, 12, and then each color By depositing a second electrode layer 5 on top of the second electrode layer 5 corresponding to each of the light emitting regions, the EL of the present invention can be formed as shown in FIG. 1(e).
A display element is obtained.

Specifically, the light emission of the EL display element of this example was investigated. Second
The graph in the figure shows that a long-wavelength luminescent center substance Mn is added to the base layer consisting of a base material ZnS and a short-wavelength luminescent center substance TbF3.
The spectral distribution of light emitted from the long wavelength light emitting region 11 shown in FIG. The graph in FIG. 3 shows the short wavelength light emitting region 1 shown in FIG.
It shows the spectral distribution of light emitted from zero.

As a comparative example, the light emission of a conventional EL display element was investigated. Fourth
The graph in the figure shows the base material ZnS formed by thermal diffusion.
The spectral distribution of light emitted from the long-wavelength light-emitting region of a conventional base layer consisting of a long-wavelength light-emitting center substance Mn and a long-wavelength light-emitting center substance Mn is shown.

The film forming conditions are as shown in the table below, and the diffusion conditions are all 550° C. and 8 hours.

In this way, from the above results, even if the base layer contains a short wavelength (green) luminescent center substance, the long wavelength luminescent center can be activated by the long wavelength luminescent center substance when the base layer is activated by the long wavelength luminescent center substance. It can be seen that the substance becomes dominant and the region changes to a luminescent region that emits light of a long wavelength (yellow).

In addition, here, a double insulation type AC voltage application system was explained as an example of a multicolor EL display element.
The dielectric layer may be omitted or a conductive layer may be used to apply a DC voltage. Alternatively, the electrode may be formed of a transparent electrode material and then a multicolor light emitting region layer may be stacked thereon.

Effects of the Invention According to the EL display element of the present invention, the multicolor EL layer includes a matrix layer containing a matrix substance and at least one kind of luminescent center substance;
Since it consists of luminescent center substances of different luminescent colors coexisting within a predetermined region corresponding to at least one of the luminescent regions,
Even in an EL layer in which long-wavelength and short-wavelength light-emitting regions are dually mixed depending on the type of luminescent center substance, long-wavelength light is emitted preferentially, so the design of multiple light-emitting regions and their boundaries is difficult. becomes easier.

According to the method for manufacturing an EL display element of the present invention, on a matrix layer containing a matrix substance common to the luminescent regions of each color and a luminescent center substance that emits the shortest wavelength, a matrix is formed by converting the matrix into the luminescent regions of each color. A multicolor EL layer is formed by depositing a thin layer of long-wavelength emission center substances and then heat-treating this to diffuse each emission center substance into the base layer at once.
There are fewer steps than traditional manufacturing methods. And conventionally,
Since the light-emitting region layer is formed on a photoresist, high-temperature conditions cannot be used, and film-forming conditions that determine the composition, crystal structure, etc. of the light-emitting region cannot be freely selected. There are no restrictions at all, and there is an advantage that any film forming conditions can be selected.

Furthermore, the method for depositing the luminescent center substance layer on the base layer can be appropriately selected to satisfy both accuracy and economy, and in particular, a printing process can be used, so it has the advantage of being mass-producible.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a substrate in the manufacturing process of the EL display element of the present invention, and FIGS. 2 and 3 are distribution graphs of emission spectra in the long wavelength and short wavelength emission regions of the EL display element of the present invention. , FIG. 4 is a distribution graph of the emission spectrum in the long wavelength emission region of a conventional EL display element.
FIG. 5 is a cross-sectional view of a conventional EL display element, and FIG. 6 is a schematic cross-sectional view of a substrate in the process of manufacturing a conventional multicolor EL display element. Explanation of symbols of main parts

Claims (8)

[Claims] (1) An electroluminescent display element having an electroluminescent layer including a plurality of light emitting regions having different emission colors, the electroluminescent layer comprising a host layer containing a host substance and at least one kind of luminescent center substance, A multicolor electroluminescent display element characterized by comprising luminescent center substances of different luminescent colors coexisting in a predetermined region corresponding to at least one of the luminescent regions. (2) The host material is ZnS, and the at least one
2. The multicolor electroluminescent display device according to claim 1, wherein the type of luminescent center substance is TbF_3, and the luminescent center substance of the different luminescent color is Mn. (3) A method for manufacturing an electroluminescent display element having an electroluminescent layer including light-emitting regions of different emission colors, the method comprising: a film-forming step of forming a host layer containing a host substance and at least one type of luminescent center substance; , comprising a step of diffusing a luminescent center substance having a longer wavelength than the luminescent color of the at least one type of luminescent center substance into a predetermined region corresponding to at least one of the light emitting regions of the base layer. A method for manufacturing a multicolor electroluminescent display element. (4) The host material is ZnS, and the at least one
4. The method according to claim 3, wherein the type of luminescent center substance is TbF_3, and the luminescent center substance of the long wavelength emission color is Mn. (5) The method according to claim 3, wherein in the film forming step, the base layer is formed by a physical vapor deposition method. (6) In the diffusion step, the luminescence center substance of the long wavelength luminescent color is formed as a thin film layer on the base layer,
4. The method according to claim 3, wherein the luminescent center substance emitting the long-wavelength luminescent color is diffused into the base layer by solid phase/solid phase direct thermal diffusion method. (7) The method according to claim 6, wherein the thin film layer is formed by physical vapor deposition. (8) The method according to claim 6, wherein the thin film layer is formed by printing.