JPH0790261A - Production of fluorescent material for electroluminescence element - Google Patents

Abstract

PURPOSE:To obtain the fluorescent material narrow in particle size distribution, uniform in particle diameter and particle shape, improved in brightness, and useful for organic dispersion type electroluminescence lamps, etc., by adding an activating agent and a coactivating and particle growth-accelerating agent to a fluorescent parent material and subsequently burning the mixture under specific conditions. CONSTITUTION:A method for producing a fluorescent material for electroluminescence elements comprises adding an activating agent such as a copper compound and a coactivating and particle growth-accelerating agent such as a halide compound containing magnesium chloride, subjecting the mixture to the primary burning at a high temperature for allowing the particles of the fluorescent parent material to grow into a specific diameter, adding 0.01-3mol.% of an aluminum compound excluding its halide compounds, such as aluminum nitrate, to 1mol of the produced intermediate fluorescent material, and subsequently subjecting the mixture to the secondary burning.

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 chlorinated compounds (MgCl ₂ , Na
It is obtained by firing a mixed powder to which a co-activator and grain growth promoter (flux) composed of Cl and 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, CuSO _{4 is} added to 1 mol of ZnS (fluorescent matrix).
0.1 to 0.2 mol% of (activator) is added and dried. Next, as shown in FIG. ₂ (d), MgCl 2 of 3
mol%, 3 mol% of NaCl, and 3 of SrCl ₂
A flux (12a) obtained by mixing with a 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 calcination, the flux (12a) (melting point 700 ° C) is first melted and turned into a liquid, which is accumulated in the vicinity of the bottom of the crucible and successively becomes vapor. 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, and further excess impurities other than the copper compound on the phosphor surface by etching cleaning with an acid (HCl), for example, zinc oxide deposited on the surface or ungrown Then, the excess copper compound on the phosphor surface is removed by cyan (KCN) cleaning. Then, it is washed with water to remove the cyan component, dried and classified (sieved) to obtain a desired phosphor for an electroluminescent device.

[0006]

The problem to be solved by the present invention is that ungrown grains or insufficiently grown grains are generated during firing, and the grown grain sizes become uneven, resulting in a wide grain size distribution.
In the next step, especially with an acid, the surface of the particles is not sufficiently cleaned by etching, and the particles are evenly ground as they are, and the particle size and shape cannot be made uniform. There are problems that the brightness and life are reduced, the yield is reduced, and the grain shape becomes unstable and it is difficult to apply an electric field.

[0007]

Means for Solving the Problems According to the present invention, a mixture obtained by adding an activator and a co-activator / granular growth accelerator to a fluorescent base material is primarily fired at a high temperature to grow the fluorescent base material grain to a predetermined diameter. In order to form a phosphor by second-baking the intermediate phosphor after obtaining an intermediate phosphor, an aluminum compound other than a halide is added in an amount of 0.01 to 3 per 1 mol of the phosphor host during the second-baking.
It is characterized by adding mol%.

[0008]

According to the above technical means, when the aluminum compound is added during the secondary firing during the grain growth reaction of the phosphor matrix, the etching effect by the subsequent acid cleaning is remarkably improved and the grain size and shape are uniform. Turn into.

[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 a phosphor for an electroluminescent device is formed by two-step firing, an aluminum compound other than a halide such as aluminum nitrate {A
l (NO3) 3}, or aluminum sulfate {Al ₂ (S
O _{4) 3}} 0.01~3mo to fluorescent matrix 1mol etc.
1% is added. As the above-mentioned flux, plural kinds of halides of alkali metals or alkaline earth metals may be selectively used.

The present invention will be described based on the above means. First, CuSO ₄ (activator) is added in an amount of 0.1 to 0.2 mol% with respect to 1 mol of ZnS (fluorescent matrix), and a drying treatment is performed. Next, as in the case of FIG. 2D, a chlorinated compound (MgC
A flux (co-activator and grain growth promoter) (12a) consisting of l ₂ , NaCl, SrCl ₂ ) is supplied into the crucible (13) together with fine powder of the fluorescent matrix (12b) containing an aluminum compound. Then, in the crucible (13), the mixed powder is heated and stirred in an air atmosphere at 1100 ° C. for 3 hours to perform primary firing. After the above primary firing, the residual flux is removed by washing with water, and after heating and drying at 120 ° C. for 12 hours to form an intermediate phosphor, it is dynamically pressed by a ball mill or the like to apply an external force. Next, the above aluminum compound was added to the intermediate phosphor in an amount of 0.01 to 3 mol% with respect to 1 mol of the phosphor base, and the mixture was annealed (secondarily fired) at 750 ° C. for 3 hours, and then acid (HCl) and cyan (KCN) were added. ) Wash. Then, after removing the cyan component by washing with water, it is heated at 120 ° C. for 12 hours, dried, and classified to obtain a desired phosphor for an electroluminescent device.

According to the above-mentioned embodiment, even if ungrown or undergrown grains are generated during the grain growth reaction of the phosphor matrix (12b) during the primary firing, if the aluminum compound is added during the secondary firing, as in the conventional case, Anomalous minute impurities (zinc oxide, oxygen compounds, etc.) are generated on the surface of the fluorescent host particles, but the aluminum compound is smashed into fine particles by striking the surface of the fluorescent host particles so that the aluminum compound tries to enter the fluorescent host particles during firing. Then, the impurities are easily dissolved in the subsequent washing step with acid, and are easily polished and removed, so that the etching effect is remarkably improved. Therefore, the grain surface of the phosphor matrix becomes smooth, and the grain size and shape are made smaller and uniform. Here, it has been confirmed from the observation photograph of the surface of the fluorescent base particles that the above-mentioned surface state remarkably changes before and after the acid cleaning.

Further, according to the particle size distribution measurement graph shown in FIG. 1 (a), the particle size distribution diagram (dashed line) when the aluminum compound of the present invention is added is the particle size distribution diagram (solid line) when the conventional aluminum compound is not added. It is known that the particle size slightly shifts in the direction of smaller particle size, and becomes sharper, resulting in a narrow distribution. Further, according to the luminance measurement graph shown in FIG. 1B, the luminance in the example of the present invention is 10 to 10 as compared with the conventional case.
It is known to improve by 25%.

[0013]

EFFECTS OF THE INVENTION According to the present invention, when a phosphor for an electroluminescence device is formed by two-step firing, an aluminum compound is added in an amount of 0.01 to 3 mol% with respect to 1 mol of the phosphor matrix during the second firing.
Even if the particle size and shape are not uniform in the grain growth reaction of the phosphor matrix during firing, the etching effect by the next acid cleaning is improved and the particle size and shape are evenly arranged to improve the brightness. In addition, the particle size distribution is narrowed and the yield is improved.

[Brief description of drawings]

FIG. 1A is a particle size distribution graph according to a method for manufacturing a phosphor for an electroluminescent device according to the present invention. (B) is a luminance distribution graph with respect to electric power according to the method for manufacturing a phosphor for an electroluminescent device according to the present invention.

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]

 12a Grain growth promoter 12b Fluorescent matrix

Claims (2)

[Claims] 1. A mixture obtained by adding an activator and a co-activator / granular growth accelerator 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 a phosphor, an aluminum compound other than a halide is added in an amount of 0.01 to 3 mol% with respect to 1 mol of the phosphor base during the second firing. Body manufacturing method. 2. The phosphor for an electroluminescent device according to claim 1, wherein the phosphor matrix is zinc sulfide, the activator is a copper compound, and the grain growth promoter is a halide containing magnesium chloride. Method.