KR100528909B1 - Method for preparing green emitting phosphor - Google Patents

Abstract

The present invention discloses a method of manufacturing a green light emitting phosphor for a plasma display panel having improved afterglow and lifespan characteristics. In order to have excellent afterglow property and not to age easily even after long-term UV irradiation, a predetermined amount or more of an activator should be added. For this purpose, a coprecipitation agent such as oxalic acid, oxalate or phosphate is used in the present invention. When the phosphor is manufactured according to the manufacturing method of the present invention, it is possible to impregnate a larger amount of the activator than the conventional method, thereby maintaining an improved luminance value without rapidly aging the phosphor even when irradiated with ultraviolet light for a long time. Can be.

Description

Method for preparing green light emitting phosphor for plasma display panel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a green light emitting phosphor, and more particularly, to a green light emitting phosphor that can be applied to a plasma display panel (hereinafter, PDP). .

Phosphor is a material having a property of emitting light due to energy stimulation other than temperature radiation, most of the phosphors are practically synthesized by industrial technology rather than natural minerals.

Phosphors are generally for light sources such as fluorescent lamps, fluorescent mercury lamps, radiation lamps and the like; For display elements such as cathode ray tubes, electroluminescent elements, plasma display panels and the like; And X-ray sensitizers, scintillaters, and other detection devices, and the like, and with the development of new multimedia devices, it is expected to be used for various purposes in the future.

Phosphors should be chosen to have the characteristics of excitation in the wavelength range of the light source to which the device employing them is exposed, and the current saturation characteristics, deterioration characteristics, luminance, color purity, afterglow characteristics, driving voltage, and resistance under high current density suitable for each application equipment. And other physical properties should preferably be provided.

In consideration of such conditions, Zn ₂ SiO ₄ : Mn is an example of a preferable green light emitting phosphor for PDP. This phosphor has excellent color coordinate characteristics and luminance, and has the advantage that the particle shape and the particle size are suitable for PDP, which has been spotlighted as a green light emitting phosphor for PDP. However, this phosphor has a problem that the afterglow characteristic is poor compared to the luminance characteristic.

In order to improve the afterglow characteristic of the phosphor to a desired degree, the content of Mn as an activator should be more than a predetermined amount, specifically about 1.2 to 1.5% by weight relative to the total weight of the parent Zn ₂ SiO ₄ .

Usually, the manufacturing method of the fluorescent substance generally used includes a dry mixing method and a wet mixing method.

Dry mixing method is a method of mixing raw materials in powder form and baking, which is simpler than wet mixing method, but is not suitable for preparing phosphors using Mn as activator. . This is because, due to the properties of Mn, Mn is difficult to fully penetrate into the mother body by dry mixing.

Another wet mixing method is a method of preparing Mn in an aqueous solution, and then coprecipitating Mn by adding another raw material powder and a coprecipitation agent to the aqueous solution.

Ammonium hydroxide (NH ₄ OH) has been mainly used as a coprecipitation agent for wet mixing of the phosphor, Zn ₂ SiO ₄ : Mn. However, since the amount of Mn that can be co-precipitated using this coprecipitation agent is only about 0.5% by weight relative to the total weight of the mother body, the luminance characteristic and the color coordinate characteristic are not desirable as desired. It was found to be significantly lowered. A large luminance drop means that the phosphor life is short.

The present invention has been made in an effort to provide a method of manufacturing a green light emitting phosphor for PDP, in which luminance and lifetime characteristics are improved.

Technical problem of the present invention, a) adding a mixture of a zinc compound and a silicon compound to an aqueous solution of a manganese compound to prepare a mixed aqueous solution; And b) adding a coprecipitation agent selected from the group consisting of oxalic acid, oxalate and phosphate to the mixed aqueous solution and then firing at a temperature of 1000 to 1500 ° C. for 90 to 150 minutes. It can be made by a method for producing a phosphor.

In the present invention, the mixed weight ratio of the zinc compound and the silicone compound is preferably 2: 1 to 3: 1.

Furthermore, the oxalate salt is an ammonium oxalate monohydrate _{((NH 4) 2 C 2} O 4 · H 2 O)) to, and be, is in the phosphate, ammonium dihydrogen phosphate ((NH ₄₎ H ₂ PO ₄ ), and the addition amount thereof is preferably 0.5 moles or more based on the total moles of manganese and zinc.

On the other hand, between the step a) and b), may further comprise the step of filtering and drying the mixture with a filter.

In addition, after step b) may further comprise the step of further firing the product of step b) for 20 to 1 hour at a temperature of 600 to 1000 ℃ under a reducing atmosphere. At this time, the reducing atmosphere is preferably a mixed gas atmosphere of 5% H ₂ /95% N ₂ .

In addition, if necessary, the product obtained by further calcining the product of step b) or the product of step b) may be further subjected to the ball milling and drying.

The principle of the present invention is as follows.

Oxalic acid, oxalate or phosphate used as a coprecipitation agent in the present invention acidifies the atmosphere of the mixed aqueous solution. As such, when the mixed aqueous solution forms an acidic atmosphere, a small amount of zinc oxide, which is usually almost insoluble, is dissolved to form a salt form, for example, Zn-Mn-oxalic acid, thereby increasing the amount of Mn impregnation. By this mechanism, when a predetermined amount of Mn is co-precipitated in the phosphor matrix, not only the afterglow property is improved but also a sudden degradation of the phosphor may be prevented even when exposed to UV for a long time.

One preferred embodiment of the manufacturing method according to the present invention will be described.

First, manganese sulfate (MnSO ₄ · H ₂ O) is dissolved in pure water, and then a mixture of zinc oxide and silicon dioxide (mixed weight ratio is 2: 1 to 3: 1) is added to the aqueous solution, followed by stirring for 1 hour. To prepare a mixed aqueous solution.

Subsequently, a coprecipitation agent such as oxalic acid, oxalate or phosphate is added to the mixed aqueous solution and stirred, wherein the addition amount of the coprecipitation agent is preferably 1.5 moles or less while 0.5 moles or more of the total moles of manganese and zinc. If the addition amount of the coprecipitation agent is less than the above range, the impregnation amount of Mn does not increase to the desired extent, while if the coprecipitation amount is more than the above range, an excess coprecipitation agent remains, thereby causing a problem of lowering the luminance.

Next, the product was filtered and dried, then heated to a temperature of 1000 to 1500 ° C. over 2 to 3 hours, and then calcined at this temperature for 2 to 3 hours. Subsequently, the calcined compound was calcined in a reducing atmosphere, and then subjected to a ball mill process to obtain a final product. At this time, as specific ball mill process conditions, the weight ratio of phosphor: ball: water is preferably 1: 4: 2 and is preferably performed at 100 rpm for 1 hour.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1

MnSO ₄ 5H ₂ O After dissolving 3.2 g (0.0133 mole) in 150 mL of water, 35 g (0.42 mole) of ZnO and 15 g (0.25 mole) of SiO ₂ were added, followed by stirring for 30 minutes. After stirring, 54 g (0.43 mol) of oxalic acid was dissolved in water in the mixed aqueous solution, followed by stirring for 1 hour. The product was filtered and dried, then slowly raised to 1225 ° C. over 180 minutes and calcined at this temperature for 120 minutes.

Finally, the resultant was ball milled at 100 rpm for 1 hour using a zirconia ball having a diameter of 3 mm to obtain a green light emitting phosphor for PDP as a final product.

The luminance of the final product obtained was measured, and then the luminance at 24, 48, 72, 96 and 120 hours was measured while irradiating ultraviolet rays to the final product to determine the relative luminance relative to the initial luminance value. Was measured and the results are shown in Table 1 below.

Example 2

A green light emitting phosphor for PDP was obtained in the same manner as in Example 1 except that the amount of oxalic acid added was 82 g (0.65 mol). The luminance was measured in the same manner as in Example 1 with respect to the obtained phosphor, and the results are shown in Table 1.

Example 3

MnSO ₄ 5H ₂ O After dissolving 3.2 g (0.0133 mole) in 150 mL of water, 35 g (0.42 mole) of ZnO and 15 g (0.25 mole) of SiO ₂ were added, followed by stirring for 30 minutes. After stirring, 54 g (0.43 mol) of oxalic acid was dissolved in water in the mixed aqueous solution, stirred for 1 hour, and then filtered and dried.

The product was then slowly warmed to 1225 ° C. over 180 minutes, calcined at this temperature for 120 minutes, and then calcined further at 800 ° C. for 30 minutes under a 5% H ₂ /95% N ₂ gas atmosphere.

Finally, the resultant was ball milled at 100 rpm for 1 hour using a zirconia ball having a diameter of 3 mm to obtain a green light emitting phosphor for PDP as a final product.

The luminance was measured in the same manner as in Example 1 with respect to the obtained phosphor, and the results are shown in Table 1.

Example 4

A green light emitting phosphor for PDP was obtained in the same manner as in Example 3 except that the amount of oxalic acid added was 82 g (0.65 mol). The luminance was measured in the same manner as in Example 1 with respect to the obtained phosphor, and the results are shown in Table 1.

Comparative Example 1

A green light emitting phosphor for PDP was obtained in the same manner as in Example 1 except that 4 ml of ammonia water was added instead of oxalic acid and stirred for at least 90 minutes. The luminance was measured in the same manner as in Example 1 with respect to the obtained phosphor, and the results are shown in Table 1.

UV irradiation time Example 1 Example 2 Example 3 Example 4 Comparative Example 1 24 hours later 99% 99% 96% 97% 95% 48 hours later 99% 99% 96% 97% 92% After 72 hours 99% 99% 96% 95% 91% 96 hours later 98% 99% 95% 95% 91% 120 hours later 98% 98% 95% 95% 90%

As can be seen from the results of Table 1, the phosphor prepared according to the present invention was excellent in luminance even after prolonged ultraviolet irradiation compared to the phosphor prepared by the conventional method (luminance increase rate: 8 to 10%).

When the phosphor is manufactured according to the manufacturing method of the present invention, it is possible to impregnate a larger amount of the activator than the conventional method, thereby maintaining an improved luminance value without rapidly aging the phosphor even when irradiated with ultraviolet light for a long time. Can be.

Claims (8)

a) preparing a mixed aqueous solution by adding a zinc compound and a silicone compound in a mixed weight ratio of 2: 1 to 3: 1 in an aqueous solution of a manganese compound; And b) the above mixed aqueous solution of oxalic acid, ammonium oxalate monohydrate _{((NH 4) 2 C 2} O 4 · H 2 O)) and ammonium dihydrogen phosphate ((NH ₄₎ H _2, selected from the group consisting of PO ₄₎ Method for producing a green light emitting phosphor for PDP comprising the step of firing for 90 to 150 minutes at a temperature of 1000 to 1500 ℃ after adding the coprecipitation agent. delete delete delete The method according to claim 1, wherein the amount of the coprecipitation is 0.5 to 1.5 times molar with respect to the total moles of manganese and zinc. The method of claim 1, further comprising filtering and drying the mixture with a filter between the steps a) and b). The method of claim 1, further comprising, after step b), further firing the resultant of step b) at a temperature of 600 to 1000 ° C. for 20 minutes to 1 hour under a reducing atmosphere. Method for producing a green light emitting phosphor. The method of manufacturing a green light emitting phosphor according to claim 7, wherein the reducing atmosphere is a mixed gas atmosphere of 5% H ₂ /95% N ₂ .