JPH0762342A - Production of fluorescencer for electroluminescent element - Google Patents

Abstract

PURPOSE:To produce a fluorescencer for electroluminescent element which can realize the improvement of luminance and the prolongation of lifetime by stably accelerating the growth of parent fluorescencer particles during the primary growth to thereby make the particle diameters and shapes uniform in the formation of the fluorescencer by two-stage firing. CONSTITUTION:The process comprises a primary firing step wherein a mixture comprising parent fluorescencer particles 14b, an activator and a coactivator/ grain growth accelerator 14a is fired at a high temperature to grow the particles into intermediate fluorescencer particles of a specified particle diameter and a secondary firing step wherein the intermediate fluorescencer particles are fired. The total amount of the accelerator 14a used in the primary step is 15-30mol%, based on the particles 14b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a phosphor used in a light emitting layer of a dispersion type electroluminescent device.

[0002]

2. Description of the Related Art An organic dispersion type electroluminescent lamp (hereinafter referred to as an EL panel) used for a backlight of a liquid crystal display panel or the like is shown below with reference to FIGS.
The EL panel (1) comprises an electroluminescent device (6) formed by laminating a back electrode (2), a reflective insulating layer (3), a light emitting layer (4) and a transparent electrode (5) in this order. A hygroscopic film (7) such as a polyamide resin is arranged on the back surface, and the entire electroluminescent element (6) including the hygroscopic film (7) is hermetically sealed with an outer skin film (8) made of a fluororesin or the like, The leads (9) and (10) are led out from the electrode (2) and the transparent electrode (5) through the sealing portion of the outer cover film (8).

As shown in FIG. 2 (c), the light emitting layer (4) is formed by dispersing a phosphor (12) such as zinc sulfide (ZnS) activated by copper in an organic binder (11). Reflective insulation layer (3) formed by organic binder (11)
Is glued to. In the EL panel (1), the electrodes (2) and (5) were sandwiched between the electrodes (2) and (5) by applying a high voltage from the leads (9) and (10) between the back electrode (2) and the transparent electrode (5). The phosphor (12) of the light emitting layer (4) is caused to emit light and is driven at a desired emission brightness.

The above phosphor (12) is generally made of granular zinc sulfide (ZnS) as a phosphor matrix, and a copper compound (CuS) is added thereto.
O ₄ ) activator and chlorine compound (MgCl ₂ , N
It is obtained by firing a mixed powder to which a co-activator and grain growth promoter (flux) composed of aCl, SrCl ₂ ) is added. Then, a fluorescent host material having a diameter of 1 to 3 μm is grain-grown with a flux to a diameter of 20 to 30 μm to prolong the life, and at the same time, copper and chlorine are doped as emission centers to achieve high brightness.

Therefore, when forming the phosphor (1),
First, ZnS (fluorescent matrix) is CuSO ₄ for 1 mol.
0.1 to 0.2 mol% of (activator) is added and dried. Next, as shown in FIG. ₂ (d), MgCl 2 3
A flux (12a) formed by mixing mol%, NaCl 3 mol%, and SrCl ₂ 3 mol% is supplied into the crucible (13) together with the fine powder of the fluorescent matrix (12b).
Then, in the crucible (13), mix the above-mentioned powder at 1150 ° C.
When heated for 6 hours to perform primary firing, the flux (12a) (melting point 700 ° C.) is first melted and turned into a liquid, which is successively vaporized in the crucible. Then, when the inside of the crucible is stirred, the flux (12a) is dispersed, and the phosphor base particles are fused and bonded to each other through the melt or vapor, and the particle size gradually grows. After the primary firing, the flux is removed by washing with water and drying to form an intermediate phosphor, which is statically pressed by a rubber press or the like.
Next, secondary baking (annealing) is performed at 700 ° C. for 1 hour,
Furthermore, after washing with acid (HCl) and cyan (KCN), drying, and then classification (sieving), a desired phosphor for an electroluminescence device is obtained.

[0006]

The problem to be solved is that the amount of flux during the primary firing is 10 mol% or less with respect to 1 mol of the phosphor matrix, so the flux (12a)
When melted, it becomes vapor sequentially in the crucible, and as a result, when the phosphor matrix (12b) grows grains, mainly the flux steam is bonded and covering the grains of the phosphor matrix (12b) to grow the flux. The main point is solid-state reaction by steam. Then, even if the inside of the crucible is stirred, the flux vapor is dispersed sparsely and is not evenly distributed throughout the whole. Therefore, in the region where the flux vapor exists, the grains grow sufficiently, but the flux vapor is insufficient. If there,
Ungrown grains or insufficiently grown grains also occur, the grown grains become uneven and the grain size distribution becomes wider, the brightness and life characteristics deteriorate, the yield decreases, and the grain shape is unstable. Therefore, there arises a problem that it is difficult to apply an electric field. or,
According to the solid-state reaction, grains having different crystal axes are bonded to each other and the grains are likely to grow as they are, so that the electric field is applied differently depending on each crystal axis direction of the grains, and the brightness as a fluorescent matrix (12b) is reduced. There is also a problem. In this case, if firing is performed at a high temperature for a long time, the crystal axis directions of the grains are easily aligned, but the firing conditions cannot be changed indiscriminately, which is practically difficult to carry out.

[0007]

Means for Solving the Problems According to the present invention, a mixture obtained by adding an activator and a co-activator / granular growth promoter to a fluorescent matrix is primarily fired at a high temperature for a long time to bring the fluorescent matrix particles into a predetermined size. After growing to obtain an intermediate phosphor, and secondarily firing it to form a phosphor, the total amount of the grain growth promoter used in the first firing is 15 to 30 with respect to 1 mol of the phosphor host.
It is characterized in that it is set to a ratio of mol%.

[0008]

According to the above technical means, the phosphor matrix can be uniformly grown during the primary firing.

[0009]

EXAMPLE An example of a method for manufacturing a phosphor for an electroluminescent device according to the present invention will be described below with reference to FIGS. 1 (a) and 1 (b). The feature of the present invention is that when forming a phosphor for an electroluminescent device by two-step firing, the total amount of flux used in the primary firing is increased as compared with the conventional one, and 1 mol of the phosphor host is used.
On the other hand, the total amount of flux is set to a ratio of 15 to 30 mol%. As the flux, plural kinds of halogen compounds of alkali metals or alkaline earth metals may be selectively used within the above set amount range.

According to the above-mentioned means, CuS ₄ (activator) is added in an amount of 0.1 to 0.
Add 2 mol% and dry. Next, as shown in FIG. 1A, MgCl ₂ is 15 mol% and NaCl is 3
a crucible (13) together with a fine powder of the fluorescent matrix (14b) by mixing a flux (a co-activator and grain growth promoter) (14a), which is a mixture of ₂ mol% of BaCl ₂ and ₂ mol% of BaCl _2.
Supply in. Then, when the mixed powder is heated in the crucible (13) at 1100 ° C. for 3 hours to perform the primary firing, the flux (14b) is first melted into a liquid state, and the liquid flux (14b) causes the phosphor base particles to be formed. Grains grow gradually as they bond to each other. At this time, since the fluorescent base material (14b) is covered with the liquid flux (14a) and grows grains, the grain growth is sufficiently promoted to make the grain sizes uniform, and at the same time, the grain size distribution is narrowed and the grain shape is It is also stable. Further, since the crystal axes of the particles to be bonded are aligned in the same direction in accordance with the growth, a sufficient electric field is applied and the electroluminescence becomes stable. In order to promote the liquid phase reaction, it is better to increase the amount of flux, but if it is too large, the concentration of the luminescence center to be doped becomes large and the brightness decreases, so the amount of flux is set within the above range. To do.

After the primary firing, the residual flux is washed with water to remove the residual flux, and the intermediate phosphor is heated at 120 ° C. for 12 hours and dried to form an intermediate phosphor. The intermediate phosphor is dynamically formed by a ball mill or the like. Pressurize and apply external force. Then, distortion occurs inside the intermediate phosphor particles, and further, 750 °
When annealed (secondary firing) at C for 3 hours, the copper that had been uniformly dispersed in the grains moved and gathered in the strained portions, and a conductive layer was formed (segregation) in the grains, causing emission centers (copper, chlorine). ) Efficiently electroluminescent. At this time, a slight excess of copper (0.1mo
1%) contributes to the formation of the conductive layer and realizes high brightness. Furthermore, since the particle size and the shape are uniform, the stress is evenly applied to the particles one by one by the application of an external force, and the above-mentioned strains are evenly formed, which contributes to the improvement of brightness. Next, acid (HCl) and cyan (KC
N) After washing, heating at 120 ° C. for 12 hours to dry, and then classifying to obtain a desired phosphor for electroluminescent device.

As the flux (14a) at the time of primary firing, in addition to the above embodiment, 20 mol% of MgCl ₂ and NaC are used.
Two kinds of 1 may be 1 mol%. According to the measurement
In FIG. 1B, a solid line (first embodiment) and a dotted line (second embodiment)
2) and the chain line (conventional example), the luminance is significantly higher than that of the conventional example in both examples.

[0013]

According to the present invention, when a phosphor for an electroluminescence device is formed by two-step firing, the total amount of the grain growth promoter (flux) used in the primary firing is increased to make it uniform in the crucible. Since the grains are grown in a stable manner, the grain growth is stably promoted, the grain size and the shape are uniformly aligned, brightness can be improved and the life can be extended, and the grain size distribution can be narrowed to improve the yield.

[Brief description of drawings]

FIG. 1A is a side sectional view of a crucible showing one step of an embodiment of a method for manufacturing a phosphor for an electroluminescent element according to the present invention. (B) is a graph showing the luminance of the phosphor in the example according to the present invention and the conventional example.

FIG. 2A is a side sectional view showing an example of an organic dispersion type electroluminescent lamp. (B) is a top view which shows an example of an organic dispersion type electroluminescent lamp. (C) is a partial side sectional view of a light emitting layer. FIG. 3D is a side sectional view of the crucible showing a step of an example of a conventional method for manufacturing a phosphor for an electroluminescence device.

[Explanation of symbols]

 14a Grain growth promoter 14b Fluorescent matrix

Claims (3)

[Claims] 1. A mixture obtained by adding an activator and a co-activator / granular growth accelerating agent to a phosphor matrix is primarily fired at a high temperature to grow the phosphor matrix particles to a predetermined diameter to obtain an intermediate phosphor. When the second firing is performed to form the phosphor, the total amount of the grain growth promoter used in the first firing is set to the phosphor base 1.
A method for producing a phosphor for an electroluminescent device, characterized in that the ratio is set to 15 to 30 mol% with respect to mol. 2. The method for producing a phosphor for an electroluminescent device according to claim 1, wherein an external force is statically or dynamically applied to the intermediate phosphor after the primary firing, and then the secondary firing is performed. 3. The method for producing a phosphor for an electroluminescent device according to claim 1, wherein the phosphor base is zinc sulfide, the activator is a copper compound, and the grain growth promoter is a halogen compound.