JPS6155239B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintered electroluminescent device with improved brightness and lifetime.

Currently, liquid crystals, light emitting diodes, fluorescent display tubes, etc. are used as display elements by taking advantage of their respective features, but electroluminescent elements (hereinafter referred to as EL elements) are used in only a small number of automobiles. It is only used for meter panels, etc., and is hardly ever put into practical use as a display. The reason is that the brightness and lifespan have not reached practical levels. However, EL elements are essentially surface light sources;
It has features that are difficult to obtain with other display methods currently in use, such as being able to emit light in each color, having low power consumption, being able to produce relatively large areas at low cost, and having a high degree of freedom in design. There are still strong expectations for its use as a display means for automobile equipment, measuring instruments, etc.

The biggest reason for hindering the practical application of EL devices is the issue of lifespan. Although much research has already been carried out regarding EL deterioration, the deterioration mechanism has not yet been fully elucidated, and in particular, the mechanism of relatively large initial deterioration seen in the early stages of EL element lighting is not understood. There are many.

Currently, the only practical EL phosphor is ZnS-based, but this has the drawback of rapidly decreasing brightness when emitted in the presence of moisture, and when operating as an EL device, the device must be sealed with a moisture-proof seal. It is well known that it is necessary to provide protection. If efforts are made to remove residual moisture in the light-emitting layer by devising the processing temperature, processing time, and moisture-proofing method during moisture-proof sealing, the degree of initial deterioration can be reduced, although the initial deterioration will not be completely eliminated. can. From this, it is thought that the influence of trace amounts of residual moisture at the level of adsorbed water may be a factor in the initial deterioration. Removal of extremely small amounts of water at the level of adsorbed water usually requires heat treatment at several hundred degrees, which cannot be achieved with resin-type EL. On the other hand, enamel-type EL elements have been known in which phosphors are bound together with a glass binder, and because they are manufactured in a high-temperature atmosphere of several hundred degrees, initial deterioration is small and the lifespan is relatively long. The drawback is that the brightness is lower than the resin type EL used.
The reason for this is that the dielectric constant of the enamel frit, which can be used as a binder for ZnS-based phosphors, is 5.
This is thought to be because the phosphor itself is deteriorated and the brightness is lowered because it is small at ~10° C. and requires a high working temperature of 600 to 700° C.
As mentioned above, EL that has practical brightness for display use, can be sealed moisture-proof at high temperatures, and has a long life.
The device has not yet been developed.

The purpose of the present invention is to eliminate the drawbacks of the conventional resin-type EL elements and enamel-type EL elements described above, and to develop a new sintered EL element with improved brightness and service life.
The purpose is to provide elements.

The sintered EL element of the present invention can be produced by sintering the phosphor and other inorganic additives with an inorganic binder that has a relatively high dielectric constant even through heat treatment at around 450°C, which allows the use of a very ordinary Nesa glass substrate. It can be manufactured by tying it together.

The sintered EL element of the present invention is characterized by having a light emitting layer containing a phosphor and a dielectric between the transparent conductive layer on the light emitting side and the back electrode.
In the device, the light-emitting layer has a phosphor layer, and the phosphor layer is a sintered body obtained by thermal decomposition firing at about 450° C. of a compound of a metal organic complex containing the phosphor and which is harmless to the phosphor. The phosphor layer further includes a sintered body impregnated with an organic complex of metal and fired by heating, so that moisture in the phosphor layer is sufficiently removed. That's what happens. In this case, the phosphor in the phosphor layer is a ZnS-based phosphor, and the organic complex of the metal is a ZnS-based phosphor such as titanium, barium, strontium, calcium, zinc, lead, tin, indium, tantalum, silicon, etc. Preferably, the compound is a metal alkoxide that is harmless to the phosphor, and a stabilizer is added to the compound of the organic complex of the metal that is harmless to the phosphor. In addition, the compound of the metal organic complex that is harmless to the phosphor includes a transparent or white filling inorganic fine powder that is harmless to the phosphor and has an average particle size sufficiently smaller than that of the phosphor. In this case, the light emitting layer is a two-layer structure light emitting layer having a reflective high dielectric constant/insulating layer on the back electrode side of the phosphor layer.・
The insulating layer is a sintered body made by heating and firing a metal organic complex compound containing a high dielectric constant such as barium titanate or titanium oxide, and the high dielectric constant insulating layer is further impregnated with a metal organic complex. It also includes a sintered body obtained by heating and firing a sintered body, and it is preferable that moisture in the high dielectric constant/insulating layer is sufficiently removed. In such a sintered EL element of the present invention, the phosphor is sintered in the high dielectric sintered layer at a temperature that does not damage the phosphor.
Since moisture in the luminescent layer is sufficiently removed, the luminance is high and the life is long.

The following steps can be used to manufacture the above-described sintered EL device of the present invention.

Titanium, barium, strontium, calcium, zinc, lead, tin, indium, tantalum,
A phosphor layer is formed on the transparent conductive layer using a phosphor paste or phosphor slurry in which an organic complex of a harmless metal element is blended with a ZnS-based phosphor such as silicon, and then heated and dried. The phosphor layer is additionally impregnated with a stabilizing liquid of a metal complex such as titanium or barium, and after drying, the organic components in the phosphor layer are burned out without leaving any residue by firing at about 450°C. The phosphor is sintered with metal oxides produced by thermal decomposition of metal complexes.
A light-emitting layer made of the phosphor layer is formed by filling the voids in the phosphor layer as much as possible by repeating the process several times if necessary, and at the same time sufficiently removing the moisture in the layer. A back electrode is formed by the means.

In addition, as a more effective means of suppressing the generation of voids in the phosphor layer due to firing, it is possible to use materials other than the phosphor that are harmless to the phosphor and whose particle size is larger than that of the phosphor. A mixture of small, transparent or white inorganic oxide fine powder,
Similarly to the above, a light emitting layer can also be formed by sintering an oxide produced by thermal decomposition of a metal complex.

In addition, a high dielectric constant material such as barium titanate or titanium oxide and an organic complex of the metal described above are formed on a phosphor layer formed by blending the fine powder of the transparent or white inorganic oxide. After forming a high dielectric constant/insulating layer using the blended paste and drying it by heating, it is further impregnated with a metal complex stabilizing liquid, and then sintered by firing at around 450℃ to make it reflective. It is also possible to form a high dielectric constant/insulating layer to form a two-layer light emitting layer, and then form a back electrode.

Hereinafter, the present invention will be specifically explained in detail by referring to the drawings and describing the manufacturing process using examples.

Example 1 This will be explained with reference to the partial cross-sectional view of FIG.

0.4 parts by weight of ethyl cellulose, 0.5 parts by weight of titanium tetraisopropoxide (organic metal complex),
Phosphor paste made by adding 0.5 parts by weight of acrylic ester SA (trade name) (stabilizer), 5.5 parts by weight of barium titanate (inorganic fine powder), 16.8 parts by weight of phosphor, and an appropriate amount of α-terpineol, ethyl alcohol, etc. transparent conductive layer 2 on glass substrate 1 using
A phosphor layer 3 having a thickness of 35 to 40 μm after drying is formed by printing on the transparent conductive layer 2 of the Nesa glass plate on which the phosphor layer 3 is formed. Next, 0.4 parts by weight of ethyl cellulose,
Titanium tetraisopropoxide (organometallic complex)
0.5 parts by weight, 0.5 parts by weight of acrylic ester SA (trade name) (stabilizer), 33 parts by weight of barium titanate (high dielectric), and an appropriate amount of α-terpineol,
Using a high dielectric paste made of ethyl alcohol, a high dielectric constant insulating layer 4 with a thickness of about 15 to 20 μm is formed on the phosphor layer 3, and the total film thickness is 50 to 55 μm.
A light emitting layer 6 having a double structure of m is formed. Next, after heating and drying the light-emitting layer 6, a stabilized titanium complex liquid consisting of 1 part by weight of titanium tetraisopropoxide, 1 part by weight of acrylic ester SA (trade name), and 2 parts by weight of ethanol was added to the luminescent layer 6. Layer 6 is coated and impregnated. Next, the light-emitting layer 6 is heated and dried at 160°C for 30 minutes, and then baked at 450°C for 40 minutes.
While burning out all the organic components in the titanium complex, the titanium oxide 3 produced by thermal decomposition of the titanium complex is
3 and 43 only contain barium titanate as the phosphor 31 in the phosphor layer 3 and the inorganic fine powder 32 for filling, and the barium titanate powder as the inorganic fine particles 42 which are high dielectrics in the high dielectric constant/insulating layer 4. are formed into a sintered light-emitting layer in a bonded form, and moisture in the light-emitting layer is sufficiently removed. Next, a back electrode 5 is formed on the high dielectric constant insulating layer 4 by Al vacuum evaporation. As a result, in the light-emitting layer that has a double structure of a phosphor layer and a high dielectric constant/insulating layer, the phosphor layer and the inorganic fine powder for filling are bound together by sintered titanium oxide. The high dielectric constant/insulating layer is made by bonding barium titanate, which is a high dielectric, with sintered titanium oxide, and the voids in these layers are filled with sintered titanium oxide by impregnation firing. The moisture inside will be sufficiently removed to form a product.

The thus obtained sintered EL device in this example exhibited a luminance of approximately 20 ft-L at 250 Hz and 100 V, which was 20 ft-L brighter than the conventional iron-enamel EL device.
It was more than twice as bright. In addition, the sintered EL element created as described above was subjected to moisture-proof sealing treatment with low-melting glass in a high-temperature atmosphere of 450°C, and the brightness deteriorated by continuously lighting it at room temperature at 250Hz and 100V. As a result of research, its brightness half-life is approximately
3,000 hours, and it was found that a practical level could be obtained.

Embodiment 2 This embodiment will also be explained with reference to the partial sectional view of FIG.

0.5 parts by weight of nitrocellulose, 0.5 parts by weight of titanium tetraisopropoxide (organic metal complex),
Acrylic ester SA (trade name) (stabilizer) 0.5 parts by weight, ZnO-B ₂ O ₃ -SiO ₂ glass fine powder (inorganic fine powder) 6 parts by weight, titanium oxide fine powder (inorganic fine powder) 3.5 parts by weight ZnS for EL with an average particle size of 10μm
A phosphor paste containing 21.0 parts by weight of the phosphor and an appropriate amount of the solvent α-terpineol and ethyl alcohol was printed onto the transparent conductive layer 2 of a Nesa glass plate in which the transparent conductive layer 2 was formed on the glass substrate 1. , heat-dried at 160℃ for 30 minutes to obtain a film thickness of approximately 40μ.
m phosphor layers 3 are formed. Next, 0.3 parts by weight of nitrocellulose, titanium tetraisopropoxide
High dielectric barium titanate consisting of 0.5 parts by weight, 0.5 parts by weight of stabilizer acrylic ester SA (trade name), 33.0 parts by weight of barium titanate fine powder specially calcined at 1200°C, and appropriate amounts of α-terbineol and ethoxyethanol. A paste is used to print on the above phosphor layer 3 to form a high dielectric constant/insulating layer 4, and a light emitting layer 6 having a two-layer structure of the phosphor layer 3 and the high dielectric constant/insulating layer 4 is formed. . Next, after heating and drying at 160℃ for 30 minutes, the acrylic ester
A series of treatment steps consisting of additional impregnation with an ethoxyethanol solution of titanium tetraisopropoxide stabilized by adding SA, then heating drying at 160°C for 20 minutes, followed by calcination at 440°C for 40 minutes. Repeat times.
Next, the back electrode 5 is formed on the fired light emitting layer 6 by Al vacuum evaporation.

Through the above steps, the phosphor layer 3 and the high dielectric constant
A sintered EL element of this example is obtained, which includes a light emitting layer 6 having a two-layer structure with an insulating layer 4. However, in this light-emitting layer 6, the phosphor layer 3 includes a phosphor 31, an inorganic fine powder 32 consisting of a ZnO-B ₂ O ₃ -SiO _2- based glass fine powder and a titanium oxide fine powder, and a sintered titanium oxide 33. The high dielectric constant insulating layer 4 includes high dielectric inorganic fine powder 32 made of barium titanate and titanium oxide bound by sintered titanium oxide 43, and these phosphors The voids in the layer 3 and the high dielectric constant/insulating layer 4 are filled with sintered titanium oxide, and the moisture in the layers is sufficiently removed to form a light-emitting layer 6.

The brightness of the sintered EL element in this example obtained in this way was 25 to 30 ft-250 Hz and 100 V lighting.
It was L. Furthermore, when this was sealed moisture-proof by bonding a glass plate with low-melting point glass in a high-temperature atmosphere of 450°C, the luminance half-life when continuously lit at 250Hz and 100V was approximately 3000 hours.

In Examples 1 and 2 above, a titanium alkoxide is used as an organometallic complex used when compounding the paste for forming a light-emitting layer and when performing additional impregnation after film formation and drying, and the sinter produced by its thermal decomposition is used as an organometallic complex. Although titanium oxide is used to sinter phosphors, filled inorganic fine powders, and high dielectric barium titanate, such organometallic complexes are not limited to titanium alkoxides, but include barium, strontium, calcium, It is possible to manufacture high-performance sintered EL devices in the same manner as in Examples 1 and 2 by using organic complexes of metal elements such as zinc, lead, tin, indium, tantalum, and silicon that are harmless to ZnS-based phosphors. It turns out that it is.

In addition to the above-mentioned barium titanate, titanium oxide, and ZnO-B ₂ O ₃ -SiO ₂ -based glass powder, examples of transparent or white inorganic fine powder for filling in the light-emitting layer include aluminum, magnesium, and calcium. It has been found that oxides or carbonates of barium, strontium, indium, zinc, tin, tantalum, silicon, etc. can be used.

The light-emitting layer in the above example has a two-layer structure consisting of a phosphor layer and a high dielectric constant/insulating layer, but in the same example as the above example, the light-emitting layer may consist only of a phosphor layer, or It was found that the phosphor layer without inorganic fine powder was also effective.

As can be seen from the above explanation, the present invention has extremely large effects.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing a section taken along a plane perpendicular to the light emitting surface of a sintered EL element according to an embodiment of the present invention. 1...Glass substrate, 2...Transparent conductive layer, 3...
Phosphor layer, 4... High dielectric constant/insulating layer, 5... Back electrode, 6... Light emitting layer, 31... Phosphor, 32...
Inorganic fine powder, 33,43...Sintered titanium oxide,
42...Inorganic fine particles.

Claims (1)

[Claims] 1. EL comprising a light emitting layer containing a phosphor and a dielectric between a transparent conductive layer on the light emitting side and a back electrode.
In the device, the light-emitting layer has a phosphor layer, and the phosphor layer is a sintered body obtained by thermal decomposition firing at about 450° C. of a compound of a metal organic complex containing the phosphor and which is harmless to the phosphor. The phosphor layer further includes a sintered body impregnated with an organic complex of metal and fired by heating, and the moisture in the phosphor layer is sufficiently removed. A sintered EL element featuring: 2 The phosphor in the phosphor layer is a ZnS-based phosphor, and the metal organic complex is titanium, barium, strontium, calcium, zinc, lead,
Claim 1: The compound is an alkoxide of a metal such as tin, indium, tantalum, silicon, etc. that is harmless to the ZnS-based phosphor, and a stabilizer is added to the compound of an organic complex of the metal that is harmless to the phosphor. The sintered EL element described in Section 1. 3 The compound of the metal organic complex that is harmless to the phosphor further includes a transparent or white filling inorganic fine powder that is harmless to the phosphor and has an average particle size sufficiently smaller than that of the phosphor. The sintered EL according to claim 1 or 2, which is obtained by blending
element. 4. The light emitting layer is a two-layer structure light emitting layer with a reflective high dielectric constant/insulating layer on the back electrode side of the phosphor layer, and the reflective high dielectric constant/insulating layer is made of barium titanate or oxide. A sintered body is formed by heating and firing a metal organic complex compound containing a high dielectric constant such as titanium, and the high dielectric constant/insulating layer is further impregnated with a metal organic complex, which is then heated and fired. 4. The sintered EL device according to claim 3, which also includes a sintered body, and the moisture in the high dielectric constant/insulating layer is sufficiently removed.