KR20060133788A - Preparation method of high efficient thiogallate green phosphors - Google Patents

Abstract

Provided is a method for preparing a thiogallate-based green phosphor which is lowered in heat treatment temperature, does not use additional flux or toxic component and improves the efficiency of a phosphor. The method comprises the steps of mixing 0.5-1.1 mol of an alkaline earth metal precursor, 1.8-2.2 mol of a gallium precursor and 0.001-0.5 mol of an activator precursor to prepare a metal mixture, adding sulfur to the metal mixture, and ball milling the obtained mixture to prepare a thiogallate-based green phosphor precursor; and heat treating the obtained thiogallate-based green phosphor precursor at a temperature of 700-1,000 deg.C under the atmosphere of a mixture gas comprising nitrogen and hydrogen. Preferably the alkaline earth metal precursor is a sulfide or nitride of a metal selected from Ca, Sr and Ba; the gallium precursor is an oxide or nitride; and the activator precursor is a compound of Eu or Ce.

Description

Preparation method of high efficient thiogallate green phosphor

Figure 1 shows the X-ray diffraction diagram of the SrGa ₂ S ₄ : Eu phosphor prepared in Example 1 according to the present invention.

Figure 2 shows the emission and excitation spectrum of the SrGa ₂ S ₄ : Eu phosphor prepared in Example 1 according to the present invention.

Figure 3 shows the emission spectrum of the phosphor prepared by Example 1 and Comparative Example 1 according to the present invention.

The present invention relates to a method for producing a high-efficiency thiogallate-based green phosphor, and more particularly, to a metal mixture in which alkaline earth metals, gallium, and activators are mixed in a certain component ratio, by adding excessive sulfur, and ball milling under specific conditions By introducing a novel mechanochemical process for preparing a phosphor precursor and heat-treating the prepared precursor under a reaction gas in which nitrogen and hydrogen are mixed at a constant component ratio, heat treatment can be performed at a lower temperature than in the prior art to reduce the temperature. The present invention relates to a method for producing a high efficiency thiogallate-based green phosphor having excellent luminescence under the condition that separate flux and toxic components are excluded.

In general, sulfide-based phosphors are well known for display industry materials such as cathode ray tube (CRT) and low voltage display (LED or VFD) because of their excellent luminous efficiency.

Among them, ZnS: Cu, Al, and Y ₂ O ₂ S: Eu are well known green and red phosphors, and in particular, alkaline earth metal sulfide-based phosphors are phosphorescent phosphors in the 1980s and 1990s. It has a long afterglow property by making a trap by using an activator other than the active agent, and many studies have been conducted on it as a phosphor.

Recently, there is a growing interest in luminaires and displays using light emitting diodes (LEDs), and there is a demand for phosphors excited in the long wavelength region, and alkaline earth metal sulfide-based phosphors are very suitable as phosphors satisfying such conditions.

To date, alkaline earth metal sulfide-based phosphors are prepared by using oxides or carbonates, H ₂ S or CS ₂ gases, which are toxic gases, and alkaline earth metal sulfides using sulfates, and then impregnating an activator with precursors. After the preparation, a method of heat treatment using a toxic gas H ₂ S or CS ₂ gas and hydrocarbon gas and a large amount of sulfur together is widely used. In addition, the active agent was mixed well with the alkaline earth metal sulfide, and then prepared by heat treatment in an atmosphere where nitrogen and hydrogen gas were mixed.

This method is manufactured using toxic H ₂ S or CS ₂ gas, and has been using a separate flux to lower the firing temperature because the firing temperature is higher than 1,200 ℃ when heat treatment.

In addition, it has been proposed to introduce a method using a metal complex designed to use no toxic gas. However, it excludes toxic gases but uses a lot of activated carbon and sulfur as well as using a flux such as a solid phase reaction method to lower the firing temperature.

Accordingly, the present inventors have tried to solve the problems of the reaction conditions, such as the toxic gas, the economic and environmental problems due to the use of sulfur, the firing temperature in the conventional thiogallate-based phosphor manufacturing process. As a result, an excess of sulfur is mixed with a metal mixture of alkaline earth metals, gallium, and an activator, and ball milling is carried out under specific conditions to prepare a phosphor precursor, and the prepared precursor is prepared under a reaction gas in which nitrogen and hydrogen are mixed in a constant component ratio. By introducing the method of synthesizing the mechanochemical to be heat-treated, it is possible to manufacture a thiogallate-based green phosphor at a low temperature without using a separate flux for reducing the conventional firing temperature, and toxic components such as H ₂ S, CS ₂ gas, and sulfur It has been found that the use of can be eliminated to complete the present invention.

Accordingly, an object of the present invention is to provide a method for producing a thiogallate-based green phosphor by the synthesis of mechanochemical at a low reaction temperature without the use of toxic components and reaction flux.

According to the present invention, a metal mixture is prepared by mixing 0.5 to 1.1 moles of alkaline earth metal precursors, 1.8 to 2.2 moles of gallium precursors and 0.001 to 0.5 moles of activator precursors, and then ball milling by mixing sulfur to form a thigallate green phosphor precursor. Manufacturing step,

There is a feature of the method for producing a thiogallate-based green phosphor comprising the step of heat-treating the prepared thiogallate-based green phosphor precursor in a temperature range of 700 ~ 1000 ℃ under a mixed gas atmosphere of nitrogen and hydrogen.

Hereinafter, the present invention will be described in detail.

The present invention is a physical method of producing a phosphor precursor by ball milling by mixing an excess of sulfur to a metal mixture of alkaline earth metal, gallium and activator in a certain component ratio, and the precursor prepared by mixing nitrogen and hydrogen in a constant component ratio The present invention relates to a novel method of preparing a thiogallate-based green phosphor of Formula 1 by introducing a method of synthesizing a mechanochemical using a chemical method of heat treatment and calcining under a reaction gas.

[Formula 1]

AGa ₂ S ₄ : D

In Formula 1, A is calcium, strontium and barium metal, D represents europium or cerium.

In general, sulfide-based phosphors are mostly synthesized by a solid phase reaction method, but the use of toxic gases such as H ₂ S or CS ₂ and a high firing temperature have required a flux to lower them. The method using the metal complex introduced as an alternative to the solid phase reaction method uses a large amount of activated carbon and sulfur instead of the harmful gas, but the flux for lowering the firing temperature has the disadvantage that it is invariably required.

On the other hand, the present invention is uniformly distributed through the mechanochemical, that is, physicochemical operation to form a fine particle size, so that the heat treatment at a temperature of more than 1200 ℃ actual firing temperature in the conventional solid-phase reaction method In comparison, the reaction is possible even in a relatively low temperature range, and no separate flux is required to lower the reaction temperature. In general, since the type and physical properties of the manufactured phosphor are greatly changed by the minute difference in the firing temperature during the manufacturing process of the phosphor, the firing temperature not only acts as an important factor but it is also an innovative method to lower the firing temperature range. have.

In addition, the present invention reacts with hydrogen gas during the precursor heat treatment process to decompose the precursor of sulfate-based to form sulfide and water vapor, and the formed water vapor is vaporized during heat treatment to form only sulfide H ₂ S or It is possible to exclude toxic components such as CS ₂ gas and sulfur.

Looking at the method for producing a thioglate green phosphor according to the present invention in more detail as follows.

According to the present invention, a metal mixture is prepared by mixing an alkaline earth metal precursor, a gallium precursor, and an activator precursor, followed by ball milling by mixing an excess of sulfur to prepare a thiogallate green phosphor precursor. The ball mill can generally be produced by both dry and wet milling methods, but more preferably, wet milling is more effective for the production of uniform precursors. When wet milling, milling is performed using a small amount of a solvent such as distilled water, alcohol, acetone, etc. in order to form a slurry to improve fluidity. At this time, it is more preferable to use mixed solvents, such as distilled water and alcohol, distilled water, acetone, rather than using each solution independently. The amount of the solvent may be used in the range of 1 to 5% by volume relative to the powder volume in an amount capable of wet milling in the art. If the range is out of the above range, it is preferable to maintain the above range because a large amount of solution decreases productivity, takes a long reaction time, and decreases luminous efficiency.

The ball introduced during the ball milling generally depends on the raw material, but 5 mm or less, preferably 1 to 5 mm size ball is used, when the ball size exceeds 5 mm of the ball compared to the powder It is preferable to maintain the above range because the size is very large, which causes a problem of pulverization and chemical reaction of the powder.

The ball is added at least 1 weight ratio, preferably at least 5 weight ratios, more preferably at least 10 weight ratios, based on the total mixture used in the manufacture of the phosphor, if the input amount is less than 1 weight ratio to sufficiently form the kinetic energy required for the reaction There is a problem that does not make enough reactions.

Phosphors are an important variable because their properties vary significantly with the time of milling. Therefore, the present invention is carried out for 1 to 168 hours using the ball at a speed of 300 to 1,800 rpm. If the range is out of the range, it is very important to maintain the range because the reaction may not be performed properly or the reaction time may be too long to be applied to the actual process.

The alkaline earth metal precursor is generally used in the art, and specifically, a compound of a metal such as calcium (Ca), strontium (Sr), and barium (Ba) may be used. The alkaline earth metal precursor may be used in any form used in the art as the compound containing the metal, but more preferably, a compound in the form of sulfide or nitrate, and sulfide in the case of strontium (Sr) Good to do.

The alkaline earth metal precursor is used in the range of 0.5 to 1.1 moles, and when the amount is less than 0.5 moles, a second phase is additionally formed to reduce the luminous efficiency, and when it exceeds 1.1 moles, an undesirable new compound is formed to improve the luminous efficiency. There is a decreasing problem.

The gallium precursor may be used in any form of compound used in the art, more preferably in the form of oxide or nitrate. When the gallium precursor is used in the range of 1.8 to 2.2 moles, when the amount of the gallium precursor is less than 1.8 moles, a sulfide system composed solely of alkaline earth metals is formed, and thus the luminous efficiency is reduced. This causes a problem that the luminous efficiency is reduced.

In addition, the activator precursor is generally used in the art, and specifically, for example, a compound of a metal such as europium (Eu) or cerium (Ce) may be used. Such an activator precursor may contain any type of compound used in the art as containing the metal, but more preferably, a compound in the form of an oxide, nitrate or sulfide is used. When the activator precursor is used in 0.001 to 0.5 mole, when the amount is less than 0.001 mole, light emission is very weak, and when the amount exceeds 0.5 mole, the luminous efficiency is not good and the amount of the activator increases, leading to a problem that the manufacturing cost increases.

The sulfur is added in an amount of 100 to 500% by weight based on the metal mixture of alkaline earth metals, gallium and europium, and when the amount is less than 100% by weight, the amount of sulfur volatilized during heat treatment is not formed when the amount of sulfur is more than 500% by weight. It is desirable to maintain the above range because there is a problem that the amount is accumulated in the gas exhaust pipe and the heat treatment operation is not easily performed.

Next, the thiogallate-based green phosphor precursor is heat-treated under a mixed gas atmosphere of nitrogen and hydrogen to prepare a thiogallate-based green phosphor.

The mixed gas is introduced in order to reduce the activator by reacting the precursor with hydrogen gas and to form a sulfide-based phase, and nitrogen and hydrogen may maintain a volume ratio of 60 to 95: 5 to 40. If the volume of the nitrogen exceeds the range of the active agent is not reduced well because the light of the desired color is not good, if the volume of the hydrogen exceeds the range, the hydrogen gas reacts with the external oxygen to explode Therefore, it is preferable to maintain the above range.

The temperature during the heat treatment is preferably maintained at a temperature range of 700 to 1000 ℃, preferably 850 to 950 ℃. If the temperature is less than 700 ℃ it is not possible to obtain a sulfide crystal phase, the light emission does not occur, and if it exceeds 1000 ℃ it is preferable to maintain the above range because the problem of coarse particles and light emission efficiency decreases.

The thiogallate-based green phosphor prepared as described above can be heat-treated at a low temperature, and thus it is possible to prepare a phosphor having excellent luminescence properties even under conditions in which a flux and a toxic component used for temperature reduction are excluded.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Example 1

Eu ₂ O ₃ was dissolved in 15 mL of nitric acid, and then dispersed in distilled water to prepare a 1M solution to prepare a europium stock solution.

3.9982 g of Ga (NO ₃ ) ₃ H ₂ O, 0.5685 g of SrS and the europium stock solution were taken out of a 0.25 mL solution so that the europium had a doping atom concentration of 0.05 mol and placed in a ball milling vessel. 1 mL of distilled water was added to the solution to dissolve gallium nitrate, and then 10 mL of acetone was added thereto. 5.25 g of sulfur, 300% by weight, was added to the weight of the SrGa ₂ S ₄ : Eu phosphor to be prepared.

The ball mill was milled for 24 hours at a rotational speed of 600 rpm using 40 g of 5 mm zirconia balls. After milling and drying for 12 hours at a temperature of 50 ℃ in a dryer and put into alumina ceramics and heat-treated at 900 ℃ 2 hours. At this time, the SrGa ₂ S ₄ : Eu green phosphor was prepared by firing in a mixed gas atmosphere supplied with 140 cc / min nitrogen gas and 60 cc / min hydrogen gas.

The crystallinity (X-ray diffraction pattern) and emission intensity (465 nm) of the SrGa ₂ S ₄ : Eu green phosphor prepared above are shown in FIGS. 1 and 2.

Example 2

In the same manner as in Example 1, SrGa ₂ S ₄ : Eu phosphor was prepared using 0.7012 g of SrCO ₃ instead of 0.5685 g of the SrS.

Example 3

In the same manner as in Example 1, SrGa ₂ S ₄ : Eu phosphor was prepared by performing the rotation time of the ball milling for 3 hours instead of 24 hours.

Example 4

Ga ₂ O ₃ was dissolved in 35 mL of nitric acid and then dispersed in distilled water to prepare a 1.2 M gallium stock solution.

8.05 mL of the gallium stock solution prepared above and 0.5685 g of SrS and 0.25 mL of the europium stock solution prepared in Example 1 were collected and placed in a ball milling vessel. To the solution was added 10 mL of acetone and 5.25 g of sulfur, 300% by weight, based on the weight of the SrGa ₂ S ₄ : Eu phosphor to be prepared. The ball mill was milled for 24 hours at a rotational speed of 600 rpm using 40 g of 5 mm zirconia balls. After milling and drying for 12 hours at a temperature of 50 ℃ in a dryer and put into an alumina crucible was heat-treated at 900 ℃ 2 hours. At this time, the SrGa ₂ S ₄ : Eu green phosphor was prepared by firing in a mixed gas atmosphere supplied with 140 cc / min nitrogen gas and 60 cc / min hydrogen gas.

Example 5

In the same manner as in Example 1, except for 3.9982 g of Ga (NO ₃ ) ₃ H ₂ O

SrGa ₂ S ₄ : Eu green phosphor was prepared using 0.9372 g of Ga ₂ O ₃ .

Comparative Example 1

Compared to the commercial SrGa ₂ S ₄ : Eu phosphor (Phosphor tech Co., UK), the emission spectrum was measured and the results are shown in FIG.

The relative emission intensity of the phosphors prepared in Examples 1 to 5 and Comparative Example 1 was measured, and the results are shown in Table 1 below.

division Relative emission intensity (%) Example 1 121 Example 2 97 Example 3 105 Example 4 103 Example 5 99 Comparative Example 1 100

As shown in Table 1, it was confirmed that the phosphors of Examples 1 to 5 according to the present invention had a luminescence intensity equal to or higher than that of the phosphor prepared by the conventional solid phase method.

As described above, the thiogallate-based green phosphor prepared by the method of synthesizing the ball milling and calcining mechanochemical under certain conditions in accordance with the present invention can be heat-treated at a lower temperature than conventional, thereby lowering the temperature. The use of a separate flux for the purpose of elimination and the use of a mixture of hydrogen and nitrogen instead of toxic gases such as H ₂ S or CS ₂ gas is expected to excellence in terms of environmental and economic.

Claims (9)

0.5 to 1.1 mole of alkaline earth metal precursor, 1.8 to 2.2 mole of gallium precursor and 0.001 to 0.5 mole of activator precursor are mixed to prepare a metal mixture, and then sulfur is mixed, followed by ball milling to prepare a thiogallate green phosphor precursor. Steps, Heat treating the prepared thiogallate-based green phosphor precursor to a temperature range of 700 to 1000 ° C. under a mixed gas atmosphere of nitrogen and hydrogen; Method for producing a thiogallate-based green phosphor, characterized in that made. The method of claim 1, wherein the alkaline earth metal precursor is a compound of a metal selected from calcium (Ca), strontium (Sr), and barium (Ba). 3. The method of claim 1 or 2, wherein the alkaline earth metal precursor is a sulfide or nitrate compound. The method of claim 1, wherein the gallium precursor is a compound in the form of an oxide or nitrate. The method of claim 1, wherein the activator precursor is a compound of a metal selected from europium (Eu) or cerium (Ce). 6. The method of claim 1 or 5, wherein the activator precursor is a compound in the form of an oxide, nitrate or sulfide. The method of claim 1, wherein the sulfur is added in an amount of 100 to 500% by weight based on the metal mixture. The method of claim 1, wherein the ball milling is a method for producing a thigallate-based green phosphor, characterized in that for 1 to 200 hours at a speed of 300 to 1,800 rpm by inserting a ball of 1 to 5 mm size. The method of claim 1, wherein the nitrogen and hydrogen are mixed and used in a volume ratio of 60 to 95: 5 to 40 by volume.

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