JPS6259878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making a distributed EL device.

Powder dispersion type EL elements are low-cost, low-power consumption flat light sources that can be easily expanded to large areas, and are expected to be applied to displays in various devices, flat displays, flat TVs, etc. However, the reason why it has not yet been fully put into practical use is because the brightness and lifespan have not yet reached a practical level.

Currently, the only electroluminescent phosphor that can be expected to have practical brightness is ZnS-based phosphor, and although it is essentially the same as it was 20 years ago, its brightness and
Some improvements have been made in terms of longevity. This ZnS
The electroluminescence intensity of the system phosphor increases approximately in proportion to the frequency of the applied electric field, and increases in proportion to the second to third power of the intensity of the applied electric field. On the other hand, in terms of lifetime, the luminance half-life time is almost inversely proportional to the frequency of the applied electric field. The way to make good use of current phosphors by taking advantage of these characteristics is to drive them with a low-frequency electric field and apply as much electric field strength as possible to the phosphor particles in the light-emitting layer to achieve practical brightness. It can be said to cause There are also problems with film-forming technology to provide a large electric field strength to the phosphor particles in the light-emitting layer.
At least the light-emitting layer dielectric in which the fluorescent material is dispersed should have a dielectric constant as high as possible. Conventionally known organic materials with a high dielectric constant include cyanoethylated saccharose having a dielectric constant of 37 to 39, and cyanoethylated polyhydric alcohols such as cyanoethylated sorbitol having a dielectric constant of about 48. However, these are all liquids and do not have film-forming properties, so these materials include cyanoethylcellulose, which has a relatively high dielectric constant, and cyanoethylated cellulose.
It has been used by adding PVA etc. to impart film-forming properties. As a result, the dielectric constant of the light-emitting layer binder was slightly lowered, and it seemed like a step forward in achieving a desired brightness by applying a low-frequency electric field.

We would like to use cyanoethylated polyhydric alcohols, amides, or nitriles with a high dielectric constant as a binder for the light-emitting layer, but there is no conventional method for creating practical dispersed EL devices using liquid dielectrics. It had not been established. Among the above-mentioned high dielectric constant substances, acetamide and succinonitrile are amides and nitriles that are solid at room temperature and relatively easy to handle. These have relatively high dielectric constants, and it has been experimentally confirmed that high brightness can be obtained when used as a binder for the light-emitting layer of an EL device. The melting points of these two substances are 69.5°C and 57°C, respectively, and they easily become fluid when heated, so they can be uniformly mixed with the phosphor and can be easily formed into a film. but,
Even if an attempt is made to form a back electrode on these layers by vacuum evaporation of aluminum, for example, the high vapor pressure of these substances causes a large amount of volatilization, making it difficult to obtain an Al surface that can be used as a back electrode. be. Additionally, the above two substances tend to absorb moisture very easily, and when applied to the production of EL elements, there is a problem that considerable consideration must be taken in terms of moisture-proof sealing. It was hot.

The purpose of the present invention is to solve the above-mentioned difficulties and problems in the prior art. The object of the present invention is to provide a method for creating a dispersed EL element with excellent brightness and lifetime by using a substance that can be made fluid at temperature as a binder for a light emitting layer.

The feature of the method for producing a distributed EL element of the present invention is that the conductive surface layers of two glass substrates having transparent conductive surface layers are faced to each other, or the conductive surface layers of glass substrates having one transparent conductive surface layer are A glass substrate and a metal plate having a silvery-white reflective surface are placed so that the transparent conductive surface layer and the silvery-white reflective surface face each other, and the periphery is separated by a certain distance, except for a part. Using a spacer, a container with a flat plate-like space is formed by welding with low melting point glass or adhesion with epoxy resin, etc., and a part of the periphery is used as an injection port. Injecting a fluid mixture consisting of a mamid or a nitrile, which is a substance with a high melting point and a high dielectric constant, preferably succinonitrile, and an electroluminescent phosphor, into the flat space of the container through the injection port,
Next, the injection port is closed and sealed. According to the method of the present invention, a high-brightness light-emitting layer of an electroluminescent phosphor can be easily created using a high-permittivity substance that is solid at room temperature, which has been difficult to use in the past, as a binder. Therefore, there is no problem even if the high dielectric constant material is hygroscopic.

Hereinafter, the present invention will be explained in more detail by way of examples with reference to the drawings.

Example 1 First, the plan view of FIG. 1, FIG. 2 which is a sectional view taken along line AA of FIG. 1, and the line BB of FIG. 1.
This will be explained with reference to FIG. 3, which is a cross-sectional view according to FIG.

As shown in FIGS. 1 to 3, two glass substrates 1 and 2 having a predetermined transparent conductive pattern portion are placed so that the transparent conductive surface layers forming the electrodes face each other to a predetermined thickness (20 ~50μm) spacer 3
While maintaining a predetermined electrode spacing using A flat container was produced by welding or gluing, having an injection port 5 on one edge, and having both electrode surfaces facing each other (electrode spacing: 20 to 50 μm) to form a plate space 4.

Next, 1 part by weight of succinonitrile was mixed with 2 parts by weight of ZnS:Cu,Cl-based phosphor powder, which is an electroluminescent phosphor, and heated to about 100°C. A fluid composition in which the phosphor powder was homogeneously dispersed was prepared by melting the phosphor powder.

This fluid composition is injected into the plate space 4 from the injection port 5 into the flat container in a dry nitrogen gas atmosphere heated to about 120°C, and at this time, the flat container is inverted. Alternatively, the phosphor particles were homogeneously dispersed in the succinonitrile by means of tilting.

Subsequently, after cleaning the injection port 5 with acetone in a dry atmosphere, the injection port 5 was closed and sealed using an ultraviolet curing epoxy resin.

The fluid composition filled in the plate-like space 4 was then cooled to room temperature, the succinonitrile solidified, and a dispersed EL element with complete moisture-proof sealing could be obtained.

This state is shown in FIGS. 4, 5, and 6.
4 is a plan view, FIG. 5 is a sectional view taken along line CC in FIG. 4, and FIG. 6 is a sectional view taken along line DD in FIG. 4. In FIGS. 4, 5, and 6, reference numeral 8 indicates a luminescent layer filled in the plate-like space 4, in which fluorescent powder is uniformly dispersed in succinonitrile, and reference numeral 6 indicates the luminescent layer filled in the plate-like space 4, in which fluorescent powder is uniformly dispersed in succinonitrile. This is an epoxy resin with which the injection port 5 is closed and sealed.

The luminance on both surfaces of the thus obtained distributed EL element was approximately 10 footlamberts (fL) when lit at 50 Hz and 100 V, and could be used as a practical display element.

Note that the above-mentioned device is a double-sided light-emitting type, but for a device that requires only one side to emit light,
I was able to create it as follows.

This will be explained with reference to FIG. 7, which is a sectional view corresponding to FIG. 5, and FIG. 8, which is a sectional view corresponding to FIG. 6.

On one side of the EL element obtained above, for example, on the outside of the substrate 2, a white or silvery white reflective film as shown by reference numeral 7 is formed, or a similar white or silvery white reflective film is formed. A reflective layer was formed by applying .

One-sided emitting distributed type created in this way
The brightness at the light emitting surface 1 of the EL element was 20 to 30% higher than the brightness in the double-sided light emitting type.

As described above, according to the present invention, a practical distributed EL element can be obtained.

Example 2 Dispersed EL was fabricated in exactly the same manner as described in the previous part of Example 1, except that one of the substrates, for example, the substrate indicated by reference numeral 2 in FIGS. 1 to 6, was an aluminum plate. The element was created.

The product thus created is one in which aluminum foil is pasted on the outside of one of the transparent conductive substrates in the latter stage of Example 1, for example, aluminum foil 7 is pasted on the outside of the transparent conductive substrate 2 in FIGS. 7 and 8. Dispersed type created by pasting and forming a reflective layer.
The performance was comparable to that of EL elements.

Example 3 On the transparent conductive film of the other transparent conductive substrate facing one transparent conductive substrate, for example, on the inner surface of the substrate 2 shown in FIGS. A distributed EL device was produced in exactly the same manner as described in the previous section of Example 1, except that a thick or thin reflective layer was formed.

The thus manufactured device had higher luminance than the dispersion type EL device manufactured in the latter stage of Example 1 or in Example 2.

As can be seen from the above explanation, according to the method of the present invention, a high dielectric constant liquid, which has conventionally been difficult to use as a material for a light emitting layer of a practical distributed EL element,
Alternatively, high-permittivity substances that are solid at room temperature but have a relatively high vapor pressure can be used as binders, and high brightness can be easily obtained at low frequency and low voltage, making it possible to create practical distributed EL elements. has become easier to obtain. Further, according to the method of the present invention, a dangerous moisture-proofing treatment step is omitted, and a high-permittivity material with high hygroscopicity can be used, which has an extremely large industrial effect.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a flat container having a flat space according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line A--A in FIG. 1, and FIG. 3 is a cross-sectional view along line B-- in FIG. 1.
FIG. FIG. 4 shows a flowable composition in a heated state in which particles of electroluminescent phosphor powder are homogeneously dispersed in succinonitrile within the flat space of the container shown in FIGS. After filling, the inlet is closed and sealed. Figure 5 is a sectional view taken along line CC in Figure 4. Figure 6 is line D in Figure 4.
-D is a cross-sectional view. Figures 7 and 8 show a distributed EL element prepared by providing a white or silvery white reflective layer on the outside of one of two transparent conductive substrates with their transparent conductive surfaces facing each other. , is a sectional view corresponding to FIGS. 5 and 6 above. DESCRIPTION OF SYMBOLS 1...Transparent conductive substrate, 2...Transparent conductive substrate, or a metal substrate having a white or silvery white reflective surface, 3...Spacer, 4...Planar space, 5...Injection port, 6...Occluded sealant, 7 ...white or silvery white reflective layer, 8...light emitting layer.

Claims (1)

[Scope of Claims] 1. A glass substrate having a transparent conductive surface layer and a glass substrate also having a transparent conductive surface layer or a metal substrate such as aluminum having a silvery white reflective surface are combined with each other or with a conductive surface layer. A conductive surface layer and a reflective surface face each other at a predetermined interval, and the peripheral edge other than the injection port is adhered via a spacer to create a container having a flat space with an injection port,
Next, in a dry atmosphere heated to a temperature of 60 to 120°C, a fluidity consisting of a low melting point high dielectric constant material and an electroluminescent phosphor, which is solid at room temperature and fluid in the above temperature range, is produced. A method for producing a distributed EL element, comprising filling the mixture into the flat space through the injection port, and then closing and sealing the injection port in a dry atmosphere. 2. The bonding via the spacer is achieved by welding with low melting point glass or bonding with epoxy resin, etc.
Method for creating a distributed EL device as described in Section 1. 3. The method for producing a distributed EL element according to claim 1 or 2, wherein the drying atmosphere is a reduced pressure drying atmosphere or a dry inert gas atmosphere. 4. The method for producing a dispersed EL device according to any one of claims 1 to 3, wherein the low melting point, high dielectric constant substance is an amide or a nitrile, preferably succinonitrile. . 5. The method for producing a distributed EL element according to any one of claims 1 to 4, wherein the injection port is closed and sealed using an epoxy resin, an ultraviolet curable resin, or the like. .