JP4409066B2 - Blue light emitting electroluminescent phosphor and organic dispersion type electroluminescent device using the same - Google Patents

Description

表１から明らかなように、蛍光体粒子の表面に青色顔料を付着させた実施例では、付着させない比較例に比べ、いずれも発光色が青色側にシフトしており、また、寿命も向上していた。
【００５０】
なお、ここで、青色顔料の付着量を変化させたときのＣＩＥ色度の変化を調べるために行なった実験およびその結果について記載する。
【００５１】
まず、実験は、上記実施例１と同様にして、実施例１と同一組成の蛍光体粒子の表面にコバルトブルーが蛍光体粒子重量に対して0〜4.5重量％の割合で付着している硫化亜鉛系電場発光蛍光体を調製した。次いで、これらの各電場発光蛍光体を用いて、実施例１と同様にしてＥＬパネルを作製し、ＣＩＥ色度を測定した。
【００５２】
図２は、このような測定結果に基づいて作成した、青色顔料（コバルトブルー）の付着量とＣＩＥ色度（ＣＩＥｙ値）の関係を示すグラフで、青色顔料の付着量が蛍光体粒子重量に対して2重量％までは、付着量の増大にともないＣＩＥｙ値は徐々に下がり、2重量％で付着による効果がほぼ飽和に達していることがわかる。
【００５３】
【発明の効果】
以上説明したように、本発明によれば、蛍光体粒子の表面に青色顔料を付着するようにしたので、青色発光させることが可能となり、かつ輝度および寿命特性を向上させることができる。したがって、青色発光で、かつ輝度および寿命特性が良好な電場発光蛍光体、およびそのような電場発光蛍光体を用いた有機分散型の電場発光素子を得ることができる。
【図面の簡単な説明】
【図１】 本発明の有機分散型電場発光素子の一実施形態の要部構造を示す断面図。
【図２】 青色顔料の付着量とＣＩＥｙ値の関係を示すグラフ。
【符号の説明】
１……有機分散型電場発光素子
２……発光体層
３……反射絶縁層
４……背面電極層
５……透明電極層
６……パッケージングフィルム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a blue light emitting electroluminescent phosphor and an organic dispersion type electroluminescent device using the same.
[0002]
[Prior art]
The organic dispersion type electroluminescent device has a structure in which electrodes are arranged on both sides of a phosphor layer in which an electroluminescent phosphor is dispersed in a dielectric, and at least one of them is a transparent electrode. And it is an element made to light-emit by applying an alternating voltage between these electrodes. Main applications of such an organic dispersion type electroluminescent device include display devices and backlights of display devices.
[0003]
As the electroluminescent phosphor used in the organic dispersion type electroluminescent device, zinc sulfide is used as a base, copper is included as an activator, and at least one selected from chlorine, bromine, iodine and aluminum as a coactivator. In general, a material containing bismuth is used. That is, the electroluminescent phosphor emits blue-green light and is usually used by mixing a red organic dye and emitting white light.
[0004]
By the way, recently, there is a demand for an electroluminescent phosphor having a higher blueness emission color for use as a backlight in a display unit of a mobile phone or the like. On the other hand, it is known that the electroluminescent phosphor changes its emission color depending on the copper content, and the emission color shifts from blue-green to blue as the copper content decreases.
[0005]
For this reason, it has been studied to obtain blue light emission by reducing the copper content in the electroluminescent phosphor.
[0006]
However, there has been a problem that luminance and life characteristics are lowered by reducing the copper content.
[0007]
[Problems to be solved by the invention]
As described above, recently, there is a demand for electroluminescent phosphors with high emission color with high blueness, which is known as blue-green phosphor, based on zinc sulfide, containing copper as an activator, In an electroluminescent phosphor containing at least one selected from chlorine, bromine, iodine and aluminum as a coactivator, it has been studied to obtain blue light emission by reducing the copper content. However, in this case, there is a problem that luminance and life characteristics are deteriorated. For this reason, the development of electroluminescent phosphors that emit blue light and have good luminance and lifetime characteristics has been a challenge.
[0008]
The present invention has been made to cope with such problems. An electroluminescent phosphor that emits blue light and has good luminance and lifetime characteristics, and an organic dispersed electric field using such an electroluminescent phosphor. It is an object to provide a light emitting element.
[0009]
[Means for Solving the Problems]
As described in claim 1, the blue light emitting electroluminescent phosphor of the present invention is based on zinc sulfide as a base, copper as an activator, and chlorine, bromine, iodine and aluminum as a coactivator. In a blue light-emitting electroluminescent phosphor comprising phosphor particles containing at least one selected, a blue pigment is attached to the surface of the phosphor particles.
[0010]
In the electroluminescent phosphor of the present invention, as described in claim 2, the chromaticity of the emission color is preferably such that the X value in the CIE chromaticity diagram is less than 0.3 and the Y value is less than 0.4, As described in claim 3, the phosphor particles preferably have a copper content of 0.09% by weight or more based on the weight of the phosphor matrix.
[0011]
In the electroluminescent phosphor of the present invention, as described in claim 4, the blue pigment is preferably at least one selected from the group consisting of cobalt blue, ultramarine blue, cerulean blue, and blue-green pigment. As described in 5, it is more preferable that it is cobalt blue.
[0012]
Further, as described in claim 6, the amount of blue pigment attached is preferably 0.05 to 2% by weight with respect to the weight of the phosphor particles. If the amount of blue pigment attached is less than 0.05% by weight with respect to the phosphor particle weight, the effect due to adhesion cannot be obtained sufficiently. If the amount exceeds 2% by weight, the amount attached is too much and the phosphor emits insufficiently. There is a risk of becoming.
[0013]
As described in claim 7, the organic dispersion type electroluminescent device of the present invention is characterized in that it comprises a light emitting layer containing the above-described electroluminescent phosphor of the present invention.
[0014]
As a specific configuration of the organic dispersion type electroluminescent device of the present invention, as described in claim 8, the phosphor layer including the electroluminescent phosphor of the present invention and one main surface of the phosphor layer are arranged. And a back electrode layer that is integrally disposed through a reflective insulating layer and a transparent electrode layer that is integrally disposed to face the other main surface of the light emitting layer.
[0015]
In the electroluminescent phosphor of the present invention, the emission color can be shifted to blue by the filter effect of the blue pigment attached to the surface of the phosphor particles, and the luminance and lifetime characteristics of the phosphor are improved. be able to. Therefore, it is possible to obtain an electroluminescent phosphor that emits blue light and has high luminance and long life. The electroluminescent element of the present invention including such an electroluminescent phosphor has a bluish luminescent color and excellent luminance and lifetime characteristics.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, modes for carrying out the present invention will be described.
[0017]
The electroluminescent phosphor of the present invention is a phosphor containing zinc sulfide as a base, copper as an activator, and at least one selected from the group of chlorine, bromine, iodine and aluminum as a coactivator. An electroluminescent phosphor composed of particles, which is configured by attaching a blue pigment to the surface of the phosphor particles.
[0018]
Copper as an activator is preferably contained in an amount of 0.09% by weight or more based on the phosphor matrix made of zinc sulfide. If it is less than 0.09% by weight, the luminance and life characteristics may be insufficient. A more preferable range of the copper content is 0.10 to 0.15% by weight. Further, the coactivator selected from chlorine, bromine, iodine and aluminum is preferably contained in the range of 0.001 to 0.1% by weight with respect to the phosphor matrix made of zinc sulfide, and if less than 0.001% by weight, the luminous efficiency And the brightness decreases. A more preferable range of the content of the coactivator is 0.03 to 0.08% by weight.
[0019]
As the blue pigment, ultramarine _{(Na x Al x Si (12x} ) O 24 Na y S z), cobalt blue _{(CoO · nAl 2 O 3)} , cerulean blue _{(CoO · SnO 2 · MgO ·} Al 2 O 3) And at least one selected from the group of blue-green pigments (TiO ₂ · CoO · NiO · Li ₂ O, TiO ₂ · CoO · Al ₂ O ₃ · Li ₂ O) is preferred. Of these, the use of cobalt blue is preferred.
[0020]
The amount of blue pigment attached is preferably in the range of 0.05 to 2% by weight with respect to the weight of the phosphor particles. By adhering such an amount, it is possible to emit light with emission colors having an x value and a y value in the CIE chromaticity diagram, that is, a CIEx value and a CIEy value of 0.3 or less and 0.4 or less, respectively, without reducing the light emission luminance. In addition, the life characteristics can be improved. The more preferable range of the blue pigment adhesion amount is 1 to 2% by weight, and more preferably 1 to 1.5% by weight, based on the weight of the phosphor particles.
[0021]
The electroluminescent phosphor of the present invention is produced by the following method.
[0022]
That is, first, a predetermined amount of pure water is added to a zinc sulfide powder having a particle size of about 1 to 3 μm to form a slurry, and this is added to a predetermined amount of an activator raw material such as copper sulfate, magnesium chloride, barium chloride, sodium chloride. Add a crystal growth agent such as and mix thoroughly.
[0023]
The above chloride also serves as a starting material for chlorine as a coactivator. When bromine other than chlorine, iodine, or aluminum is used as a coactivator, potassium bromide, sodium bromide, barium iodide, aluminum fluoride, or the like is added.
[0024]
Next, after drying such a slurry-like mixture, it is filled in a quartz crucible and baked at a temperature of 600 to 800 ° C. for 1 to 3 hours in a reducing atmosphere. This fired product is dispersed in pure water and washed by repeating stirring, sedimentation and supernatant drainage several times. To this, a blue pigment previously dispersed in water is added and mixed thoroughly.
Thereafter, a drying process is performed.
[0025]
As a result, the blue pigment adheres to the surface of the phosphor particles containing zinc sulfide as a base, copper as an activator, and at least one selected from chlorine, bromine, iodine and aluminum as a coactivator. The electroluminescent phosphor of the present invention is obtained.
[0026]
The electroluminescent phosphor of the present invention is used for a light emitter layer 2 of an organic dispersion type electroluminescent element 1 as shown in FIG. The organic dispersion type electroluminescent device 1 shown in FIG. 1 is a light emission in which the above-described electroluminescent phosphor of the present invention is dispersed and contained in an organic polymer binder (organic dielectric) having a high dielectric constant such as cyanoethyl cellulose. It has a body layer 2.
[0027]
On one main surface of the phosphor layer 2, a reflective insulating material in which a highly reflective inorganic oxide powder such as TiO ₂ or BaTiO ₃ is dispersed and contained in an organic polymer binder having a high dielectric constant such as cyanoethyl cellulose. Layer 3 is laminated. The back electrode layer 4 made of a metal foil such as an Al foil or a metal film is integrally disposed on one main surface of the light emitting layer 2 with the reflective insulating layer 3 interposed therebetween.
[0028]
On the other main surface of the luminous body layer 2, a transparent electrode layer (transparent electrode sheet) 5 in which an ITO film or the like is formed on a transparent insulating film such as a polyester (PET) film is integrally disposed. Yes. The transparent electrode sheet 5 is disposed so that the electrode film (ITO film) faces the light emitter layer 2.
[0029]
The organic dispersed electroluminescent device 1 is configured by, for example, thermocompression bonding the transparent electrode layer 5, the light emitting layer 2, the reflective insulating layer 3, and the back electrode layer 4. Although not shown, electrodes are drawn from the back electrode layer 4 and the transparent electrode layer 5, respectively, and an alternating voltage is applied to the light emitter layer 2 from these electrodes.
[0030]
The organic dispersion type electroluminescent element 1 composed of the above-described laminate (thermocompression bonded body) is covered with transparent packaging films 6 and 6. For the packaging film 6, for example, a moisture-proof film such as a polychlorotrifluoroethylene (PCTFE) film having a low water permeability is used. If necessary, a hygroscopic film (not shown) such as a 6-nylon film is disposed on the transparent electrode layer 3 side. And the electroluminescent panel (EL panel) is comprised by carrying out the thermocompression bonding of the protruding part of these packaging films 6, and sealing the organic dispersion type electroluminescent element 1. FIG.
[0031]
According to such an organic dispersion type electroluminescent device 1 and an EL panel using the same, a bluish luminescent color is obtained and excellent luminance and lifetime are obtained by the luminescent characteristics of the electroluminescent phosphor in the luminescent layer 2. Characteristics can be provided.
[0032]
【Example】
Next, specific examples of the present invention and evaluation results thereof will be described.
[0033]
Example 1
1 L (liter) of pure water was added to 100 g of zinc sulfide powder having a particle size of about 2 μm to form a slurry. Thereto, 0.35 g of copper sulfate (pentahydrate), 4 g of magnesium chloride, 4 g of barium chloride and 1 g of sodium chloride were added and mixed thoroughly. The slurry-like mixture was dried at 700 ° C. for 2 hours, filled in a quartz crucible, and baked at 800 ° C. for 40 minutes in a reducing atmosphere (hydrogen sulfide gas).
[0034]
This fired product was dispersed in 100 g of pure water, and stirring, sedimentation, and supernatant drainage were repeated 5 times, and then 1 g of cobalt blue was dispersed in 1000 g of pure water and added. Then, it filtered and dried and obtained the electroluminescent fluorescent substance (ZnS: Cu, Cl) of this invention.
[0035]
As a result of chemical analysis of the zinc sulfide-based electroluminescent phosphor thus obtained, the copper content was 700 ppm, and cobalt blue on the phosphor particle surface was 1 wt.% With respect to the phosphor particle weight. % Was confirmed to adhere.
[0036]
Next, using the obtained zinc sulfide-based electroluminescent phosphor, the EL panel shown in FIG. 1 was prepared, and CIE chromaticity and lifetime were measured. That is, on the upper surface of the back electrode layer 4 made of Al foil, the reflective insulating layer 3 in which TiBaO 3 is dispersed in cyanoethyl cellulose as an organic binder, the light emitter layer 2 having a thickness of 50 μm, and the transparent electrode layer 5 made of InO 3 And the packaging films 6 and 6 were disposed on both sides of the laminate. The phosphor layer 2 was formed by blending so that the weight ratio of the phosphor and the epoxy resin as the organic binder was 7: 3. Then, an alternating voltage of 100 V and 4 kHz is applied between the transparent electrode layer 5 and the back electrode layer 4 under the conditions of 20 ° C. and 60% RT, and the electric field of the phosphor layer 2 is 2 × 10 ⁴ V / CIE chromaticity at cm was measured. In addition, the lifetime is 20 ° C. and 60% RT, and an alternating voltage of 100 V and 400 Hz is applied between the transparent electrode layer 5 and the back electrode layer 4 to emit light, and the luminance becomes 1/2 of the initial luminance. It was evaluated by the time until. These measurement results are shown in Table 1.
[0037]
Examples 2-5
The electroluminescent phosphor of the present invention was prepared in the same manner as in Example 1 except that the type of pigment and the amount added were changed as shown in Table 1.
[0038]
As a result of chemical analysis of each zinc sulfide-based electroluminescent phosphor thus obtained, the copper content was 700 ppm, and the ratio of the pigment adhering to the phosphor particle surface was In Example 2, cobalt blue was 2% by weight, in Example 3, ultramarine blue was 1% by weight, in Example 4, ultramarine blue was 2% by weight, and in Example 5, cerulean blue was 2% by weight of body particles. It was confirmed that the weight was%.
[0039]
Further, using each of the obtained zinc sulfide-based electroluminescent phosphors, an EL panel was produced in the same manner as in Example 1, and CIE chromaticity and lifetime were measured. These measurement results are also shown in Table 1.
[0040]
Comparative Example 1
An electroluminescent phosphor was prepared in the same manner as in Example 1 except that cobalt aluminate was not used and the fired body was washed and then dried as it was.
[0041]
As a result of chemical analysis of the thus obtained zinc sulfide-based electroluminescent phosphor, the copper content was 700 ppm.
[0042]
In addition, using the obtained zinc sulfide-based electroluminescent phosphor, an EL panel was produced in the same manner as in Example 1, and CIE chromaticity and lifetime were measured. These measurement results are also shown in Table 1.
[0043]
Example 6
The electroluminescent phosphor of the present invention was prepared in the same manner as in Example 1 except that the amount of copper sulfate (pentahydrate) added was 0.45 g.
[0044]
As a result of the chemical analysis of the zinc sulfide-based electroluminescent phosphor thus obtained, the copper content is 900 ppm, and the ratio of the pigment adhering to the phosphor particle surface is the weight of the phosphor particle 1% by weight was confirmed.
[0045]
In addition, using the obtained zinc sulfide-based electroluminescent phosphor, an EL panel was produced in the same manner as in Example 1, and CIE chromaticity and lifetime were measured. These measurement results are also shown in Table 1.
[0046]
Comparative Example 2
An electroluminescent phosphor was prepared in the same manner as in Example 6 except that cobalt aluminate was not used and the fired body was washed and then dried and sieved.
[0047]
As a result of the chemical analysis of the zinc sulfide-based electroluminescent phosphor thus obtained, the copper content was 900 ppm.
[0048]
In addition, using the obtained zinc sulfide-based electroluminescent phosphor, an EL panel was produced in the same manner as in Example 1, and CIE chromaticity and lifetime were measured. These measurement results are also shown in Table 1.
[0049]
[Table 1]

As is clear from Table 1, in the examples in which the blue pigment was adhered to the surface of the phosphor particles, the emission color was shifted to the blue side and the lifetime was improved compared to the comparative example in which the phosphor pigment was not adhered. It was.
[0050]
Here, an experiment conducted to examine the change in CIE chromaticity when the amount of blue pigment attached is changed and the result thereof will be described.
[0051]
First, the experiment was performed in the same manner as in Example 1 above. Sulfurization in which cobalt blue adhered to the surface of the phosphor particles having the same composition as in Example 1 at a ratio of 0 to 4.5% by weight with respect to the weight of the phosphor particles. A zinc-based electroluminescent phosphor was prepared. Next, using each of these electroluminescent phosphors, an EL panel was produced in the same manner as in Example 1, and CIE chromaticity was measured.
[0052]
FIG. 2 is a graph showing the relationship between the adhesion amount of blue pigment (cobalt blue) and CIE chromaticity (CIEy value) created based on such measurement results. The adhesion amount of blue pigment represents the weight of the phosphor particles. On the other hand, up to 2% by weight, the CIEy value gradually decreases as the amount of adhesion increases, and it can be seen that the effect of adhesion reaches almost saturation at 2% by weight.
[0053]
【The invention's effect】
As described above, according to the present invention, since the blue pigment is attached to the surface of the phosphor particles, it is possible to emit blue light and improve the luminance and life characteristics. Therefore, it is possible to obtain an electroluminescent phosphor that emits blue light and has good luminance and lifetime characteristics, and an organic dispersion type electroluminescent device using such an electroluminescent phosphor.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the main structure of an embodiment of an organic dispersed electroluminescent device of the present invention.
FIG. 2 is a graph showing the relationship between the amount of blue pigment deposited and the CIEy value.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Organic dispersion type electroluminescent element 2 ... Light emitter layer 3 ... Reflective insulating layer 4 ... Back electrode layer 5 ... Transparent electrode layer 6 ... Packaging film

Claims (8)

Blue light- emitting electroluminescent phosphor comprising zinc sulfide as a base, phosphor particles containing copper as an activator and at least one selected from the group of chlorine, bromine, iodine and aluminum as a coactivator In
A blue light- emitting electroluminescent phosphor, wherein a blue pigment is attached to the surface of the phosphor particles. In the blue-emitting electroluminescent phosphor of claim 1 wherein the chromaticity of the emission color is less than X value in the CIE chromaticity diagram is 0.3, the blue-emitting electroluminescent phosphor Y value is equal to or less than 0.4. In the blue-emitting electroluminescent phosphor of claim 1 or 2, wherein said phosphor particles, electroluminescent phosphor, wherein the content of copper is 0.09 wt% or more of the phosphor host weight. The blue light-emitting electroluminescent phosphor according to any one of claims 1 to 3, wherein the blue pigment is at least one selected from the group consisting of cobalt blue, ultramarine blue, cerulean blue, and blue-green pigment. An electroluminescent phosphor. In electroluminescent phosphor of any one of claims 1 to 3, wherein the blue pigment, the blue-emitting electroluminescent phosphor, which is a cobalt blue. In the blue-emitting electroluminescent phosphor of any one of claims 1 to 5, the adhesion amount of the blue pigment, the blue light emitting field, which is a 0.05 to 2% by weight of the phosphor particles by weight Luminescent phosphor. An organic dispersion type electroluminescent device comprising a light emitting layer comprising the blue light emitting electroluminescent phosphor according to any one of claims 1 to 6.   8. The organic dispersed electroluminescent device according to claim 7, further comprising a back electrode layer integrally disposed through a reflective insulating layer along one main surface of the light emitter layer, and the other of the light emitter layers. An organic dispersion type electroluminescent device comprising: a transparent electrode layer integrally disposed opposite to the main surface of the organic electroluminescent device.

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