KR100390775B1 - Preparation of red phosphor particles for PDP by spray pyrolysis - Google Patents

Abstract

The present invention relates to a method for manufacturing a red phosphor for plasma display (hereinafter referred to as 'PDP') by spray pyrolysis, and more particularly, to an ultrasonic spray device for generating a large amount of droplets in the characteristics of the conventional spray pyrolysis. By adding a flux as an additive in the reaction solution, it is possible to adjust the combination of flux and precursor materials to be added to improve the morphology and luminescence brightness of the phosphor powder and to perform the milling process in one heat treatment at a lower temperature than the conventional solid phase method. Since it can be omitted, the process is simple and mass production of phosphor powder is possible, and it has economical and uniform shape and high brightness, so it can be applied as a red light emitting phosphor of PDP. It relates to a method for producing a red phosphor.

(Y _x Gd _1-xy ) BO ₃ : Eu _y

In Chemical Formula 1, 0 ≦ x ≦ 1, and 0.01 ≦ y ≦ 0.1.

Description

Preparation method of red phosphor for PD by spray pyrolysis {Preparation of red phosphor particles for PDP by spray pyrolysis}

The present invention relates to a method for manufacturing a red phosphor for plasma display (hereinafter referred to as 'PDP') by spray pyrolysis, and more particularly, to an ultrasonic spray device for generating a large amount of droplets in the characteristics of the conventional spray pyrolysis. By adding a flux as an additive in the reaction solution, it is possible to adjust the combination of flux and precursor materials to be added to improve the morphology and luminescence brightness of the phosphor powder and to perform the milling process in one heat treatment at a lower temperature than the conventional solid phase method. Since it can be omitted, the process is simple and mass production of phosphor powder is possible, and it has economical and uniform shape and high brightness, so it can be applied as a red light emitting phosphor of PDP. It relates to a method for producing a red phosphor.

Formula 1

(Y _x Gd _1-xy ) BO ₃ : Eu _y

In Chemical Formula 1, 0 ≦ x ≦ 1, and 0.01 ≦ y ≦ 0.1.

As phosphors for displays and lamps, sulfide phosphors doped with precious metals in a matrix such as ZnS, CdS, ZnCdS and the like have been mainly used. These sulfide phosphors have been studied for decades and have evolved to the point where efficiency is now improved to the point where no further increase in efficiency is possible. Thus, a few years ago, research on these phosphors had been done by very few research groups.

However, as interest in high definition television (HDTV) has recently increased, the development of displays has been invigorating. Representative displays are plasma displays (PDP) and field emission displays (FED), which are recently popular flat panel displays. Unlike conventional displays, due to their lightness and thinness, these displays have many applications, such as wall-mounted TVs, computers, camcorders, and auto navigation devices.

On the other hand, in a conventional cathode ray tube (CRT) display, there is no problem because sulfide phosphors have excellent luminescence properties, but it is difficult to use conventional sulfide phosphors in flat panel displays and field emission displays. That is, in the flat panel display and the field emission display, since the phosphors emit light under high vacuum, when the conventional sulfide phosphor is used, problems such as deterioration of vacuum degree and deterioration due to decomposition of the sulfide occur.

Accordingly, in order to solve the problem of the sulfide phosphor, research on an oxide phosphor has recently been conducted.

Unlike the sulfide phosphors, the oxide phosphors are very stable to ultraviolet rays or electron beams, which are energy sources for emitting light in displays, and thus are used as flat panel phosphors. Representative examples are aluminates, silicates, titanates, borates and the like.

Among the various oxide-based phosphors, the (YGd) BO ₃ : Eu phosphor is a phosphor that emits red light and is a very important phosphor as a red light-emitting phosphor in a flat panel display plasma display. At present, such a phosphor is mainly produced by a solid phase method.

In addition to the solid phase method, spray pyrolysis has been actively studied as a process for producing spherical phosphor powders. However, while phosphor powders exhibit good luminescence properties when the specific surface area is small and the surface defects are small, the phosphor powders produced by conventional spray pyrolysis methods have been pointed out as a problem because they have a hollow and porous form. . As a method for eliminating the disadvantages of the spray pyrolysis method, a technique has been developed to improve the characteristics of the phosphor powder by applying a colloidal solution to obtain a solid phosphor powder or by applying a flux to remove surface defects. _{However, (YGd) BO 3: (} YGd) BO 3 having a spherical shape of the in the spray pyrolysis method because the large amount use of the boron compound to be used as a flux in a typical phosphor powder manufacturing process in the case of Eu phosphor: Eu phosphor powder Is difficult to manufacture. Therefore, a study was required to uniformly control the form of the (YGd) BO ₃ : Eu phosphor powder in spray pyrolysis.

Thus, the present inventors have studied to optimize the shape and luminescence properties of the powder obtained by using a flux in preparing (YGd) BO ₃ : Eu phosphor powder by spray pyrolysis. As a result, the (YGd) BO ₃ : Eu phosphor powders obtained by spray pyrolysis without the use of conventional flux have spherical shapes and irregular shapes during high temperature heat treatment, while the powders have a uniform shape and optimum Luminescent properties were shown.

After all, the main object of the present invention is to develop a process for preparing (YGd) BO ₃ : Eu phosphor powders represented by Formula 1, which emits red light by optimizing the type and amount of flux and the combination of precursor materials in spray pyrolysis. In addition, to provide a method for producing a red phosphor for PDP represented by the formula (1) to enable the mass production of phosphor powder through an ultrasonic spray device for generating a large amount of fine droplets.

1 is an electron micrograph of the (YGd) BO ₃ : Eu phosphor powder obtained when no flux is used.

2 is an electron micrograph of the (YGd) BO ₃ : Eu phosphor powder obtained when 2% potassium chloride (KCl) flux is used.

3 is an electron micrograph of (YGd) BO ₃ : Eu phosphor powder obtained when 4% KCl flux is used.

4 is an electron micrograph of (YGd) BO ₃ : Eu phosphor powder obtained when 8% KCl flux is used.

5 is an electron micrograph of the (YGd) BO ₃ : Eu phosphor powder obtained when 6% KCl flux is used.

FIG. 6 shows the luminescence properties of (YGd) BO ₃ : Eu phosphor powders obtained by adding KCl flux according to the present invention and commercial products.

7 is an electron micrograph of (YGd) BO ₃ : Eu phosphor powder obtained by using lithium chloride (LiCl) as a flux.

The present invention relates to 1) a precursor material constituting a phosphor matrix dissolved in a water-soluble alcohol, an activator precursor material for doping the matrix, and a flux having a weight ratio of metal halide and carbonate compound of 1 / 0.1 to 40 in distilled water, respectively. Preparing a phosphor particle precursor solution of ˜2 M;

2) injecting the precursor solution into a spray device to generate droplets of 0.1 to 100 ㎛ diameter; And

3) A method of preparing a red phosphor for PDP represented by the following Chemical Formula 1 by spray pyrolysis, which comprises a process of preparing the phosphor powder by introducing the generated droplets into a reactor (200 to 1500 ° C.).

Formula 1

(Y _x Gd _1-xy ) BO ₃ : Eu _y

In Chemical Formula 1, 0 ≦ x ≦ 1, and 0.01 ≦ y ≦ 0.1.

The present invention will be described in more detail as follows.

(Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 Phosphor powders obtained by spray pyrolysis without addition of flux have a porous irregular shape during the heat treatment process, while fluxes such as potassium chloride (KCl) or lithium chloride (LiCl) are added. In this case, powders having a uniform shape may be obtained if recrystallization is performed during the heat treatment of the powders.

Hereinafter, the (YGd) BO ₃ : Eu phosphor represented by Chemical Formula 1 according to the spray pyrolysis method of the present invention will be described in more detail by dividing by each step based on the preparation method thereof.

1) First step: obtaining a phosphor particle precursor solution

In order to obtain the phosphor represented by the formula (1), the present invention is used by dissolving each precursor material constituting the parent of the phosphor powder and the activator doping the parent, water or alcohol or the like. The precursor materials of yttrium, gadolinium, and europium metals constituting the matrix of the phosphor powder and the active agent doping the matrix are widely used in the art, and acetates easily dissolve in a solvent such as water or alcohol. ), Salts such as nitrate, chloride, and hydride are used to derive the optimal composition combination by combining with each other. In addition, the boron precursor material constituting the matrix of the phosphor powder is also well known in the art, using boric acid (boric acid) easily dissolved in a solvent such as water or alcohol.

In particular, in the present invention, by adding a flux to the precursor solution and changing the type of flux, it is possible to obtain powders having a uniform form while recrystallization occurs during the heat treatment of the powders. As the flux, compounds selected from KCl, LiCl, NaCl, Li ₂ CO ₃ , Na ₂ CO ₃ and K ₂ CO ₃ which are used in a general powder manufacturing process may be used in combination as one kind or a mixture of two or more kinds. That is, at least one of each flux is used to control the shape and luminescence properties of the (YGd) BO ₃ : Eu phosphor powders. The flux is added in an amount of 0.1 to 40% by weight based on the finally obtained phosphor powder.

In addition, since the size of the phosphor particles to be prepared is determined according to the concentration of the precursor solution, the concentration of the precursor solution should be appropriate in order to produce particles of a desired size, and the total concentration of the precursor solution is preferably in the range of 0.02 to 2 M. The higher the better In this case, when the total concentration of the precursor solution is less than 0.02 M, there is a problem in that the productivity of the powder is lowered.

2) second process: spraying of droplets

Next, a process of spraying the precursor solution of the phosphor particles into the droplets using a spray device is performed.

In this case, in order to spray the precursor droplets, an ultrasonic atomizer, an air nozzle atomizer, an ultrasonic nozzle atomizer, a filter expansion aerosol generator (FEAG), or the like may be used. Here, in the case of the ultrasonic nozzle sprayer and the FEAG sprayer, it is possible to produce a submicron-sized fine phosphor powder at a high concentration, and the air nozzle and the ultrasonic nozzle can produce a large amount of particles of the submicron size in the micron.

In addition, the sprayed droplets have a diameter of 0.1 to 100 μm, and when the diameter of the droplets does not reach 0.1 μm, there is a problem in that the size of the resulting particles is too small, and the diameter of the droplets exceeds 100 μm. On the contrary, a problem arises in that the size of generated particles is too large.

In particular, in order to control the shape of the powder obtained, a device for generating fine droplets of several microns in size is required. An ultrasonic droplet generator is more suitable for this. To this end, in the present invention, a large amount of droplets are generated by connecting six or more vibrators, which are the portions that generate droplets, side by side, and by connecting the droplet generators in parallel to generate several tens of droplets per hour, thereby spraying the phosphor by spray pyrolysis. Commercial production of the powder was made possible. In addition, the conventional ultrasonic droplet generators are in direct contact with the vibrator and the solution, while the present invention prevents contact between the solution and the vibrator using a polyacetal film. In other words, the container in which the solution is put is separately made of glass or acrylic and a polyacetal film is attached to the bottom of the container. Polyacetal film is good at spraying the droplets, and is very stable to the vibration of the ultrasonic wave can be used permanently.

3) 3rd process: production of phosphor powder

The droplets are converted into precursors of the phosphor particles in a hot tubular reactor. At this time, the temperature of the electric furnace is preferably 200 to 1500 ℃ for drying the precursor materials. Since (YGd) BO ₃ : Eu phosphor powders are crystals obtained by a reaction of several hours or more at a high temperature of 1100 ° C. or more in a general solid phase method, a desired crystal phase cannot be obtained in a spray pyrolysis process having a residence time of several seconds. Therefore, precursor materials obtained by spray pyrolysis require post-treatment processes for crystal growth. The post-heat treatment temperature varies depending on the type and amount of flux used, and generally sufficient crystal growth occurs above 900 ° C. In addition to the brightness and crystallinity of the (YGd) BO ₃ : Eu phosphor powder, the shape of the powder becomes an important parameter. It is important to find an optimal heat treatment temperature that satisfies all these variables.

4) 4th process: the emission characteristics of the phosphor powder

The (YGd) BO ₃ : Eu phosphor powders obtained were compared and analyzed for light emission characteristics in a vacuum UV (VUV) region in order to examine application characteristics of the plasma display.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are only intended to explain the present invention more specifically, and the scope of the present invention according to the gist of the present invention to these examples. It will be apparent to one of ordinary skill in the art that the present invention is not limited thereto.

Comparative Example 1: Preparation of Phosphor Without Flux

In each starting material, nitrate was used as a precursor material of yttrium, gadolinium, and europium, and boric acid (HBO ₃ ) was used as a precursor material of boron. The total concentration of the solution was 0.5M and the composition of the precursor solution was adjusted so that the resulting phosphor powder had a composition of (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 . The prepared precursor solutions were generated by droplets of several microns in size using an ultrasonic atomizer that generates a large amount of droplets, and dried and pyrolyzed in a reactor to obtain a powder. At this time, the temperature of the reactor was maintained at 900 ℃. Ultrasonic nebulizer is a device capable of generating a large amount of droplets, and used six oscillators connected in series with a frequency of 1.7 MHz. The device is a large capacity that sprays 3 liters of solution per hour and is the capacity available in the actual production process. In other words, in the actual production process, several devices may be connected in parallel to increase generation capacity, or six or more vibrators may be connected in the device.

The powders obtained by the above spray pyrolysis method had a crystallinity of (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 but did not sufficiently crystallize because the reactor temperature was low. Therefore, it went through a post heat treatment process. 1 is an electron micrograph of powders obtained by subjecting the obtained powders to heat treatment at 1000 ° C. for 3 hours. The precursor powders obtained by spray pyrolysis had a perfect spherical shape, but the powder form after heat treatment disappeared. In the process of crystallization of the powder, as the particle structure was densified, a spherical shape having a hollow shape was broken and a powder having an irregular shape was obtained. Even when the heat treatment temperature was 1100 ° C. or more, the particles had a spherical shape and had an aggregate of submicron-sized primary particles. That is, the powders obtained can be said to have a form in which primary particles having a submicron size are severely agglomerated to have a micron size. The powders obtained at this time showed a brightness of 5% or more than commercial use. In particular, if the manufacturing conditions or post-treatment process is optimized, it is expected to have better emission luminance.

Example 1 When Using KCl Flux

Prepared in the same manner as in Comparative Example 1, but only up to 40% by weight relative to the powder obtained by the flux in the preparation of the spray solution. In the case where no flux was added, the spherical shape was broken during the heat treatment process, resulting in an irregular shape. On the other hand, in the case of adding KCl flux, spherical morphology disappeared during the heat treatment, and recrystallization was performed into fine particles having little aggregation between the particles. That is, the powders obtained by adding the flux have a very uniform form similar to the spherical shape, whereas very powdery irregular powders are obtained when the flux is not added. The addition amount of the KCl flux influenced the properties of the obtained powder even at about 2% in the mass ratio of the obtained (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 phosphor powder. In addition, as the amount of KCl increased to 2% or more, the aggregation between particles disappeared. At 4% or more, the aggregation between particles was small, so that the milling process was unnecessary. In other words, in the spray pyrolysis method using flux, it is possible to synthesize (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 phosphor powder having a fine size and no agglomeration between particles even with a simple heat treatment without a milling process. Because it is very economical.

2, 3 and 4 are electron micrographs of (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 phosphor powders obtained when the amount of KCl flux added is 2, 4, or 8 by mass ratio. From the electron micrographs, it can be seen that as the amount of KCl added increases, the powder size increases and the aggregation between particles decreases. The heat treatment temperature also greatly influenced the form of the powders obtained when the flux was added. Even at relatively low heat treatment temperatures of 900 ° C., smooth powders with less agglomeration between the particles were obtained when the flux was used. The average size of the powders increased with increasing heat treatment temperature. However, agglomeration of powders did not occur even when the heat treatment temperature was raised to 1250 ° C. FIG. 5 is an electron micrograph of powders obtained when the heat treatment temperature is 1150 ° C. when 6% of KCl flux is added in a mass ratio. FIG. It can be seen that the average size of the powders is about 2 microns.

6 shows the luminescence properties in the vacuum ultraviolet region of the powders obtained with and without KCl flux. Even when the flux is added, it can be seen that the light emission luminance is similar to that of commercial products. That is, it was possible to have a light emission luminance of sufficient brightness while controlling the shape of the (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 phosphor powders obtained by adding KCl flux. The luminescence properties of the powders obtained at this time will show better luminescence brightness if the composition of the powder, heat treatment conditions, spraying properties, etc. are optimized.

Example 2 When Using LiCl Flux

In the case of using LiCl as a flux, the powder had more effect than in the case of using KCl. In the case of LiCl, even if a small amount was added than in the case of KCl, when the flux was not added, the porous powder characteristics obtained were lost. However, when more than a reasonable amount of LiCl was added, the particles grew excessively and had an irregular shape. Therefore, in the case of LiCl, 6% or less was appropriate in the mass ratio of the powder obtained. On the other hand, in the case of using KCl as a flux, even when the amount of the flux was added in excess of 40%, no excessive growth of the particles occurred and no aggregation between the particles occurred. On the other hand, when the potassium chloride (KCl) flux is added in excess, the crystallinity of the powder is lowered and the luminescence brightness is decreased.

In the case of using lithium chloride (LiCl), the properties of the (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 phosphor powders obtained by the heat treatment temperature were different from those of potassium chloride (KCl). The powders subjected to heat treatment at 1000 ° C. had very uniform properties, but at temperatures below and above, the powders grew excessively and exhibited irregular morphology. 7 is an electron micrograph of (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 phosphor powders obtained when the 4% LiCl is added and subjected to a heat treatment at 1000 ° C. FIG. The powders have very uniform properties of 1 micron in size.

Example 3: In case of using other flux

In addition to the above KCl or LiCl, fluxes such as NaCl, Li ₂ CO ₃ , K ₂ CO ₃ , Na ₂ CO ₃ , which are used in the general phosphor powder manufacturing process, are used. It has also been used in a mixed form. In addition, the characteristics of the powders according to the droplet size and manufacturing conditions were adjusted using an air nozzle. In the case of changing the droplet generating device, it was easier to adjust the characteristics such as the shape of the powder and the luminance of light as the device for generating fine droplets was used.

As described and demonstrated in detail above, the present invention uses an ultrasonic spraying device for uniformizing the properties of the powders obtained by adding a flux to the reaction solution and generating a large amount of droplets by spray pyrolysis (Y _0.6 Gd _0.35 ). Mass production of BO ₃ : Eu _0.05 phosphor powders was made possible. In particular, while (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 phosphor powders obtained in the conventional spray pyrolysis process without adding a flux have a porous irregular shape during the heat treatment process, a flux such as KCl or LiCl is added. As a result of recrystallization during the heat treatment of the powders, powders having a uniform form can be obtained. In the spray pyrolysis process using a flux, a simple heat treatment is performed at a lower temperature than a conventional solid phase method and a milling process is not required. Because it goes through, its economy is very high. Since the (Y _0.6 Gd _0.35 ) BO ₃ : Eu _0.05 phosphor powders obtained by spray pyrolysis using flux have a uniform shape and high brightness, they are suitable for application as a red light emitting phosphor of PDP.

Claims (9)

1) a flux material selected from the precursor materials of yttrium (Y), gadolinium (Ga) and boron (B) constituting the phosphor matrix, the precursor materials of activator europium (Eu) doping the matrix, and metal halides and carbonate compounds Dissolving each in distilled water to prepare a phosphor particle precursor solution of 0.02 to 2 M; 2) injecting the precursor solution into a spray device to generate droplets of 0.1 to 100 ㎛ diameter; And 3) the red phosphor for plasma display (PDP) represented by the following Chemical Formula 1 by spray pyrolysis method comprising the step of preparing the phosphor powder by introducing the generated droplets into the reactor (200 ~ 1500 ℃) Manufacturing method. Formula 1 (Y _x Gd _1-xy ) BO ₃ : Eu _y In Chemical Formula 1, 0 ≦ x ≦ 1, and 0.01 ≦ y ≦ 0.1. The method according to claim 1, further comprising post-treating the phosphor particles obtained after the step 3) at a temperature of 800 to 1500 ° C. for 1 to 5 hours. The manufacturing method of the red phosphor for PDP shown. The material constituting the phosphor matrix is selected from yttrium nitrate, yttrium acetate and yttrium chloride as the precursor material of yttrium (Y), and gadolinium nitrate, gadolinium acetate as the precursor material of gadolinium (Ga). And gadolinium chloride, and boric acid is used as a precursor material of boron (B). The method of manufacturing a red phosphor for PDP represented by Chemical Formula 1 by spray pyrolysis method. According to claim 1, wherein the precursor material of the active agent europium (Eu) of the red phosphor for PDP represented by the formula (1) by the spray pyrolysis method, characterized in that selected from europium nitrate, europium acetate and europium chloride Manufacturing method. The method according to claim 1, wherein the flux is added in an amount of 0.1 to 40% by weight based on the finally obtained phosphor powder. The method of claim 1, wherein the metal halide is selected from lithium chloride (LiCl), potassium chloride (KCl), and sodium chloride (NaCl). . The method according to claim 1, wherein the carbonate compound is selected from lithium carbonate (Li ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ) and potassium carbonate (K ₂ CO ₃ ). The manufacturing method of the red phosphor for PDP shown. The method of claim 1, wherein the spraying apparatus includes an ultrasonic wave, an air nozzle, an ultrasonic nozzle, and a filter expansion droplet generator. The method of manufacturing a red phosphor for PDP represented by Chemical Formula 1 by the spray pyrolysis method. Red phosphor represented by the following formula (1), characterized in that prepared by the spray pyrolysis method selected from claims 1 to 8. Formula 1 (Y _x Gd _1-xy ) BO ₃ : Eu _y In Chemical Formula 1, 0 ≦ x ≦ 1, and 0.01 ≦ y ≦ 0.1.